About the journal   Subscriptions   Authors   Users   Librarians   FAQs 



Medline/PubMed Citation | Related Articles in PubMed | Download to Citation Matcher  

Biochem. J. (2002) 368 (377–396) (Printed in Great Britain)

Review article
Transglutaminases: Nature's biological glues
Martin GRIFFIN* , Rita CASADIO† and Carlo M. BERGAMINI‡1

*Department of Life Sciences, Nottingham Trent University, Nottingham, U.K., †Department of Biology, University of Bologna, Bologna, Italy, and ‡Department of Biochemistry and Molecular Biology and ICSI (Interdisciplinary Centre for Study of Inflammation), University of Ferrara, Ferrara, Italy

Key words: biotechnology, diseases, extracellular matrix, enzymes, protein cross-links.

Abbreviations used: AD, Alzheimer disease; DN, diabetic nephropathy; LTBP-1, latent TGF (transforming growth factor)-b binding protein-1; PDB, SWISS-PROT Protein Knowledgebase; Tgase, transglutaminase; tTgase, type 2 tissue transglutaminase.

1To whom correspondence should be addressed (e-mail bgc@dns.unife.it).


Transglutaminases (Tgases) are a widely distributed group of enzymes that catalyse the post-translational modification of proteins by the formation of isopeptide bonds. This occurs either through protein cross-linking via e-(g-glutamyl)lysine bonds or through incorporation of primary amines at selected peptide-bound glutamine residues. The cross-linked products, often of high molecular mass, are highly resistant to mechanical challenge and proteolytic degradation, and their accumulation is found in a number of tissues and processes where such properties are important, including skin, hair, blood clotting and wound healing. However, deregulation of enzyme activity generally associated with major disruptions in cellular homoeostatic mechanisms has resulted in these enzymes contributing to a number of human diseases, including chronic neurodegeneration, neoplastic diseases, autoimmune diseases, diseases involving progressive tissue fibrosis and diseases related to the epidermis of the skin. In the present review we detail the structural and regulatory features important in mammalian Tgases, with particular focus on the ubiquitous type 2 tissue enzyme. Physiological roles and substrates are discussed with a view to increasing and understanding the pathogenesis of the diseases associated with transglutaminases. Moreover the ability of these enzymes to modify proteins and act as biological glues has not gone unnoticed by the commercial sector. As a consequence, we have included some of the present and future biotechnological applications of this increasingly important group of enzymes.


INTRODUCTION

The term transglutaminase (Tgase) was first introduced by Clarke et al. in 1957 [ 1] to describe the transamidating activity observed in guinea-pig liver. Later studies undertaken by Pisano et al. [ 2], on the stabilization of fibrin monomers during blood clotting, demonstrated that transamidation is brought about by enzymes which cross-link proteins through an acyl-transfer reaction between the g-carboxamide group of peptide-bound glutamine and the e-amino group of peptide-bound lysine, resulting in a e-(g-glutamyl)lysine isopeptide bond ( Figure 1, Cross-link I).

Since this finding, proteins showing Tgase activity have now been found in micro-organisms [ 3], plants [ 4], invertebrates [ 5], amphibians [ 6], fish [ 7] and birds [ 8]. However, the subject of this review will be confined to the multiple distinct forms of Tgases that are found in mammals. In common with many other important cellular functions found in mammalian cells, Tgases require the binding of Ca2+ for their activity, but at concentrations normally in the supraphysiological, not the physiological, range associated with most intracellular processes [ 9]. Moreover their Ca2+ activation is also modulated by further regulatory processes, which in essence means that they are virtually inactive under normal conditions and only activated following major disruptions in physiological homoeostatic mechanisms. Once activated, Tgases can catalyse a number of reactions, leading to post-translational modification of proteins through acyl- transfer reactions, involving peptidyl glutamine residues as acyl donors and a variety of primary amines as acyl acceptors, with the generation of proteinase resistant isopeptide bonds ( Figure 1). Tgases display strict specificity in recognition of glutamine protein substrates (however, the rules which govern selection of only a few peptidyl glutamine residues are still unclear [ 10]), and poor specificity for the acyl-acceptor amine group, which can either be the e-amino group of peptidyl lysine or a low-molecular-mass primary amine (frequently a polyamine) [ 11]. In the former instance, the reaction products are often cross-linked high-molecular-mass protein aggregates, while in the latter, protein–polyamine conjugates are generated, which can also be further polymerized [ Figure 1, 'Crosslink (II)'] [ 12]. Biochemical and cell-biological studies indicate that both reactions involving protein cross-linking and polyamidation are relevant in vivo, and competition between these amine substrates may take place within cells in a number of important physiological functions where they act as a 'biological glue', including that of cell death [ 13], cell-matrix interactions [ 14, 15] in the stabilization of the epidermis and of hair and in the general maintenance of tissue integrity [ 16]. The interest in these enzymes is further stimulated by their involvement in a number of human disease states (e.g. certain neurodegenerative diseases [ 17], autoimmune conditions such as coeliac disease [ 18], cancer [ 19, 20] and tissue fibrosis [ 21]) and this represents a growing area of Tgase research. The aim of this review is to analyse the structural features of mammalian Tgases with particular focus on the ubiquitous type 2 tissue Tgase (tTgase), which is a multifunctional protein and a bifunctional enzyme with both protein-cross-linking and GTP-hydrolysing activities [ 22]. We will detail the conformational changes induced by the interaction with ligands and antibodies, the regulation of expression and the physiological roles of tTgase with a view to increasing our understanding of the disruption of the functional properties of the enzyme in human pathologies. Reference to other Tgase isoenzymes will be made for comparative purposes. Readers interested in other aspects of Tgase research might fruitfully consult other recent excellent reviews [ 23–25].

Tgases, A FAMILY OF ENZYMES

In mammals, eight distinct Tgase isoenzymes have been identified at the genomic level [ 26]; however, only six have so far been isolated and characterized at the protein level, after purification either from natural sources or as recombinant proteins. As summarized in Table 1, the fully characterized enzymes include (a) the circulating zymogen Factor XIII, which is converted, by a thrombin-dependent proteolysis, into the active Tgase Factor XIIIa, (plasma Tgase) involved in stabilization of fibrin clots and in wound healing; (b) the keratinocyte Tgase (type 1 Tgase) which exists in membrane-bound and soluble forms, is activated severalfold by proteolysis and is involved in the terminal differentiation of keratinocytes; (c) the ubiquitous tissue Tgase (tTgase; type 2 Tgase), whose role is still debated and is the main topic of this review; (d) the epidermal/hair follicle Tgase (type 3 Tgase), which also requires proteolysis to become active and, like type 1, is involved in the terminal differentiation of the keratinocyte; (e) the prostatic secretory Tgase (type 4 Tgase) [ 27], essential for fertility in rodents; and (f) the recently characterized type 5 Tgase [ 28]. The evolutionary tree presented in Figure 2(A) might help one to recognize the relationships among these different forms. A bacterial Tgase available among Tgase sequences deposited in the SWISS-PROT Protein Knowledgebase PDB (PDB) is that from Streptoverticillium sp. (entry TGL STRSS), which is shorter (331 AA) than those from lower animals (the filarial worm Dirofilaria immitis, 076191, 407 AA; the nematode worm Caenorhabditis elegans, 017908, 488 AA). From these ancient Tgases, others have evolved. All mammalian forms have appreciable structural homology, are the products of different genes arising from duplication, rearrangement and chromosomal shifts [ 26], and are members of the papain-like superfamily of cysteine proteases [ 29]. All members of this superfamily possess a catalytic triad of Cys-His-Asp or Cys-His-Asn. A few clusters are easily identifiable on the basis of sequence homology, which include the non- enzymic erythrocyte band 4.2 proteins, TGM4, Factor XIII, TGM5, TGM7, TGM3 and, finally, TGM2 (TGMs are gene names). The tissue content of the different isoenzymes is tightly regulated at the transcriptional level [ 28, 30–32]. This is particularly true for type 1 and type 2 Tgase: tissue levels of Tgase 1 are regulated, in a concerted way with involucrin, with a mechanism involving a number of transcriptional factors, notably the cellular concentration of Ca2+ [ 32]. In the case of tTgase, several transcriptional activators (e.g. cytokines, retinoids, vitamin D and steroid hormones) also regulate expression of this enzyme in a tissue-dependent manner [ 33–36], by transcriptional effects at the promoter region [ 37], the structure of which is summarized in Figure 2(B). Additional regulatory effects arise, at least for tTgase, from methylation of the promoter itself, while other poorly identified tissue factors may confine activation of Tgase expression to those tissues engaged in the induction of apoptosis [ 38, 39]. Several studies have dealt with the chromosomal distribution of the gene for tTgase, which maps to chromosome 20q12 [ 40], and on the effects of its inactivation in vivo and in vitro [ 15], as a means for further understanding its physiological function. Studies on knockout tTgase in type 2 (-/-) transgenic mice demonstrated initially an apparently normal phenotype in the mutant animals, possibly through compensation by other expressed isoenzymes (e.g. type 5 and type 7 Tgases) [ 41, 42]. The first detectable pathophysiological effects so far noted include a diabetic-type response to glucose overload [ 43] and an increased apoptotic cell death rate in cultured islets of Langerhans. However, more recent results have also indicated an altered response in dermal wound healing which appears to be related to altered cell motility and cytoskeletal changes [ 44]. In contrast, analysis of transgenic mice specifically overexpressing type 2 tTgase in the heart display cardiac interstitial fibrosis and a hypertrophic phenotype with disrupted cardiac performance, related to increased cross-linking rather than G-protein signal-transduction activity [ 45]. Further results are awaited before we shall be able to understand fully the pathophysiological consequences of disrupted enzyme expression.


Table 1 Tgases characterized at the protein level

In addition to the eight different enzymes listed below, a further Tgase-like protein has been characterized from red blood cells. This protein, named erythrocyte-bound 4.2, has strong sequence identity with the Tgase family of proteins, but is inactive because of a substitution of alanine for the active-site cysteine: it forms a major component of the erythrocyte membrane skeleton [ 251].

Identified forms of Tgase Synonyms Residues (molecular mass in kDa) Gene Gene map locus Prevalent function
Factor XIII A Catalytic A subunit of Factor XIII found associated with B subunit in plasma as A2B2 heterotetramer. Fibrin stabilizing factor 732(83) F13A1 6p24-25 Blood clotting and wound healing
Type 1 Tgase Keratinocyte Tgase 814(90) TGM1 14q11.2 Cell envelope formation in the differentiation of keratinocytes
Type 2 Tgase Tissue Tgase 686(80) TGM2 20q11-12 Cell death and cell differentiation, matrix stabilization, adhesion protein
Type 3 Tgase Epidermal Tgase 692(77) TGM3 20q11-12 Cell envelope formation during terminal differentiation of keratinocytes
Type 4 Tgase Prostate Tgase 683(77) TGM4 3q21-22 Reproductive function involving semen coagulation particularly in rodents
Type 5 Tgase Tgase X 719(81) TGM5 15q15.2 Epidermal differentiation
Type 6 Tgase Tgase Y TGM6 20q11 15 Not characterized
Type 7 Tgase Tgase Z 710(80) TGM7 15q15.2 Not characterized

Once expressed, type 2 Tgase is mainly localized in the cytosolic cell compartment, with a small fraction of the enzyme in the membrane and extracellular fraction. However, in some cell types, e.g. neuroblastoma cells, the enzyme is also be found in the nuclear compartment [ 46].

STRUCTURAL FEATURES OF Tgase

Early structural studies on Tgases, performed by high-resolution crystallography on the zymogenic A subunit of plasma Factor XIII (which requires proteolytic processing by thrombin to generate the active dimeric enzyme) [ 47–49] revealed that each Factor XIIIA subunit is composed of four domains [termed N-terminal b-sandwich, core domain (containing the catalytic and the regulatory sites), and C-terminal b-barrels 1 and 2] and that two monomers assemble into the native dimer through the surfaces in domains 1 and 2, in opposite orientation. This organization in four domains is highly conserved during evolution among Tgase isoforms {type 1, keratinocyte, Tgase [ 50], type 2, tTgase, from human [ 51] and fish sources [ 52] (available in the PDB at the accession codes 1FAU and 1GOD respectively) and type 3, epidermal, Tgase [ 53]}, with minor variations related to the specialized functions of each isoenzyme. Typically, in human type 2 tTgase [ 51], domains 1–4 span amino acids 1–139, 140–454, 479–585 and 586–687 respectively, with different secondary-structure arrangements, since domains 1, 3 and 4 are folded in b-structures and domain 2 presents prevalently a-helical secondary structure ( Figure 3). Furthermore, the 13 tryptophan residues of the protein are all present within domains 1 and 2. These features have provided domain-specific intrinsic spectroscopic probes, useful in studies of protein unfolding by chemical and thermal [ 54] denaturation.

Domain 1 consists of an initial flexible loop, a short 310 helix, an isolated b-strand (B1), five additional tightly packed antiparallel strands (B2–B6) in b-sandwich motif and a further short strand, B7, close to, and interactive with, the B1 strand, covering the lower end of the b-sandwich. In domain 2 the peptide chain folds in two additional b-strands (B8 and B9) which move downwards and upwards along the surface of the core domain, containing Ser171 and Lys173, involved in GTP binding, four additional b strands, B 10–B13, and four a-helixes. The first three helixes (H1, H2 and H3) are triangularly arranged, pointing towards the active-site triad involving Cys277, His335 and Asp358. The last helix (H4) is close to the very end of the core domain and harbours the amino acids involved in the main Ca2+-binding region (Ser449, Glu451 and Glu452). The following loop (amino acids 454–478) is the site of major variation in the amino acid sequence of type 2 tTgases. This loop is well exposed to the solvent (see Figure 3A) and is crucial for regulation of type 2 tTgase activity, since it acts as the hinge across which the three-dimensional position of the protein domains is varied (see below). In other Tgases (Tgase 1 and Tgase 3, as well as Factor XIII) similar loops appear to play different roles. The C-terminal domains 3 and 4 of type 2 tTgase are arranged as antiparallel b-barrels and are composed of six b strands and one b turn (domain 3), and of seven antiparallel b-strands (domain 4). These C-terminal domains are important in regulating both transamidating activity and GTPase (and ATPase) activity, since C-terminal deletion mutants display increased kcat without changes in Km [ 55].

tTgase interacts with other macromolecules. Interaction with phospholipase Cd [ 56], which is dependent on the last C-terminal amino acids in domain 4, is strongly specific for the transamidation-inactive GTP-bound state and is crucial to the role of the enzyme as a GTP- binding effector protein in the transduction of extracellular a1-adrenergic signals, coupled with phosphatidylinositide metabolism [ 57, 58]. Further characterization of this signalling complex has revealed the association of tTgase with a 50kDa protein thought to be responsible for down-regulation of the GTP binding as a function of the enzyme. This protein has now been identified as the Ca2+-binding protein calreticulin [ 59]. Tgases also display a strong binding affinity for heparin and heparan sulphates, but the functional role of this effect (useful in devising pseudoaffinity procedures for purification of type 2 [ 60] and type 3 Tgase and of Factor XIII) has not been explored until now. Further scrutiny for location of putative heparin-binding regions (usually clusters of arginine residues [ 61]) has not been carried out, although this might be relevant for interaction of Tgases with extracellular-matrix protein components and membrane proteins such as integrins [ 62, 63]. The interaction with fibronectin involves the N-terminal region [ 64], probably amino acids 1–4, and is believed to play a role in localizing Tgase in regions of tissue damage [ 65], where it acts as a matrix-associated membrane-bound exoenzyme [ 20, 66] able to polymerize fibrinogen and fibronectin on the cell surface [ 67], and is cleavable by membrane-bound matrix metalloproteinases [ 68]. This is particularly true for transformed cells and might be relevant in relation to the involvement of tTgase in the stabilization of the extracellular matrix, since loss of tTgase by proteolytic cleavage would facilitate increased cell migration and invasion in the metastatic process [ 69, 70].

REGULATION OF THE CATALYTIC ACTIVITY OF TYPE 2 tTgase

Recent structural studies have given a fine picture of the regulatory mechanism of the transamidating activity. The arrangement of the amino acids of the catalytic centre (Cys277, His 335 and Asp358) in a charge-relay catalytic triad, analogous to that of thiol proteinases such as papain [ 71], confers high reactivity on Cys277 to form thioesters with peptidylglutamine moieties in the protein substrate or to react with relatively mild chemicals such as acrylamide [ 72]. Reaction with acrylamide, in the presence of Ca2+, provokes a rapid suicide-like inactivation, which is probably the basis of the high in vivo toxicity of acrylamide towards nervous tissues [ 73]. The high reactivity of Cys277 has been employed to develop a wide range of active-site-directed irreversible inhibitors of the enzyme. In the absence of Ca2+, the enzyme assumes the basic latent conformation and the reactivity of Cys277 is decreased either by hydrogen-bonding with the phenolic hydroxy group of Tyr516 or by formation of a disulphide with a neighbouring cysteine residue, namely Cys336, as fully discussed by Noguchi et al. [ 52].

Investigations of the structural basis for the activation of the enzyme by Ca2+ by small-angle scattering [ 74], protein dynamics [ 51], site-directed mutagenesis [ 75] and crystallography [ 76] strongly suggest that switching on of the transamidating (i.e. cross-linking) activity of tTgase involves movement of protein domains, with influences on the reactivity of the active site and its accessibility to the substrates. As stated above, the active centre of the enzyme is located deeply within domain 2, hidden from contact with peptidylglutamine substrates by the overlayering of domains 3 and 4, under 'resting' conditions. During activation, the interactions between domain 2 (the active-site domain) and domains 3 and 4 break down, following binding of Ca2+, the essential activator of the transamidating activity, at the main binding site located at the terminal a-helix (H4) in domain 2. Other Ca2+-binding regions are certainly present, but they have not been definitely identified [ 77]. Upon Ca2+ binding to a-helix H4, this structure unfolds, perturbing the structure of the neighbouring loop 455–478, which connects domains 2 and 3, and also the spatial location of domains 3 and 4, which move from each other and from domain 2, opening access to the active site for the transamidating activity (see Figure 3Biii). The presence of non-proline cis peptide bonds in Tgases is also relevant in this respect in Tgases investigated so far [ 78]. In type 2 tTgase, a few tryptophan residues are also crucial, such as Trp241, which is close to the newly formed substrate channel to the active site and appears to stabilize the transition-state intermediate. It is noteworthy that these effects are altered by limited proteolysis of the 455–474 loop, leading to inactive derivatives in the case of tTgase and of Factor XIII, but not in the case of the epidermal Tgase, which is instead activated by proteolytic cleavage of its homologous loop via the binding of additional Ca2+. A detailed comparison between the structure of the interacting regions in these isoenzymes is now underway in several laboratories.

The activation by Ca2+ is thus crucial for the transamidating activity. In vitro studies on the sensitivity of tTgase to activation by Ca2+ (by the usual primary-amine incorporation; e.g. the [14C]putrescine-incorporation-into-N,N´-dimethylcasein assay) indicate Km (app) values in the region of 20–100µ M [ 79] and in some cases even larger. However, it should be remembered that casein in its phosphorylated form is prone to sequester free Ca2+, so that the amount of free Ca2+ present is likely to be much lower than that calculated. Assays carried out in the presence of casein (previously dephosphorylated with alkaline phosphatase [ 80] and Ca2+/EGTA buffers to clamp the free Ca2+), yielded a Km (app) for Ca2+ for the tTgase enzyme of 2–3µM, thus within the physiological concentrations for a Ca2+ receptor protein. However, other important regulators, such as GTP/GDP, can further modulate the activation of tTgase by Ca2+ [ 81, 82].

The mechanism of activation of tTgase by Ca2+, mediated through the dislocation of the Tgase inhibitory domains, can be counteracted by the 'allosteric' inhibitor GTP. The nucleotide binds at Lys173 and is finally hydrolysed in a process also involving serine 171, leading to a reversible, GTPase-dependent regulatory mechanism. Trp332 is also relevant in the regulation by GTP [ 75]. It is noteworthy that type 3 Tgase is also inhibited by GTP, which is bound by the protein but is not hydrolysed. Mutated forms of tTgase at Ser171 and Lys173 retain transamidating activity, but are devoid of GTPase activity. The mechanism of inhibition by GTP probably involves both local and long-spanning events: the GTP pocket is located in a long b-structure segment, which is distant from the active-site Cys277 in the amino acid sequence, but it is very close in the spatial location, so that a direct action of the nucleotide on the cysteine reactivity is feasible [ 83], through strengthening of the hydrogen-bonding of the active-site Cys277 to the phenolic hydroxy group of Tyr516, which occurs already in the Ca2+-free state [ 84], as referred to above. However, crystallographic studies on tTgase complexed with GDP gave unexpected results, including the existence of tTgase dimers (never postulated earlier) and the absence of serine residues from the GDP-binding region. The question arises as to whether the GDP form investigated by Clardy and associates [ 76] is a physiologically relevant one. Inhibition of tTgase by GTP is nevertheless limited to conditions of suboptimal activation by Ca2+ ions [ 81] and involves: (i) modulation of Ca2+ binding affinity; (ii) interference with the conformational changes induced by Ca2+; (iii) local alteration in domain flexibility; and (iv) an increased strength of interaction between domain 4 and the flexure between domain 1 and domain 2, thus contributing to hinder the access of substrate to the active site. It is noteworthy that derivatives of type 2 tTgase isolated from mammalian brain, which are cleaved by endogenous proteinases within domain 4, display reduced sensitivity to inhibition by GTP. This effect might be understood in terms of interference in the interaction between the proteolysed domain 4 and the flexure between domains 1 and 2 [ 74, 81]. The interaction between the core domain and the C-terminal b-barrels is also relevant in the inhibition of Factor XIIIa activity by a fibrinogen-directed antibody that displays cross-reactivity with the C-terminal moiety of Factor XIIIa, confirming the relevance of these contacts in the overall regulation of catalytic activity of Tgases [ 85]. Large conformational changes are thus crucial in ligand-induced modulation and they can be further appreciated by image reconstruction from Monte Carlo analysis of small-angle-scattering experiments [ 74]. The experimentally determined gyration radius varied consistently from 3.14nm, in absence of ligands, to 2.96 and to 3.83nm in the presence of GTP and of Ca2+ respectively [ 51]. It is thus confirmed that the physiologically opposite effects of these ligands depend on opposite structural perturbations to tighten and to relax the protein structure.

Potential regulatory effects might also occur through the interaction of type 2 Tgase with phospholipids [ 86] and following nitrosylation of cysteine residues by NO donors. It is particularly interesting that lysophosphatidylcholine, a relatively minor membrane phospholipid component, has the ability to increase the sensitivity of the enzyme to Ca2+, so that Tgase acquires appreciable activity at near physiological levels of Ca2+ [ 79], thus broadening the cellular conditions under which Tgase is active. These effects are carried out through relatively weak association between tTgase and lipid materials, while keratinocyte (type 1) Tgase is covalently modified by lipids through thioesterification by fatty acids of a cysteine residue at the N-terminal region [ 87]. Another potentially relevant regulatory effect on tTgase activity stems from the easy nitrosylation of the enzyme by NO releasing agents [ 88]. This results in a marked inhibition of activity and an increased sensitivity to the inhibitory effects of GTP. Different sets of cysteine residues are nitrated in the absence or presence of Ca2+, but only the modification taking place in the presence of Ca2+ is apparently relevant in regulating the transamidating activity of cellular Tgases. Likewise Factor XIII is also inactivated by S-nitrosylation of cysteine residues [ 89]. These effects have been examined mainly in relation to the transamidation reaction, not taking into account the GTPase activity of type 2 tTgase. These regulatory phenomena, mainly investigated in vitro, are possibly physiologically relevant in vivo. Thus Smethurst and Griffin [ 90] reported the combined effects of 'physiological' levels of Ca2+ and nucleotide di- and tri-phosphates on Tgase activity in electroporated ECV 304 human endothelial-like cells, concluding that both ligands are likely to contribute to regulation of the transamidating activity. In a previous study on digitonin permeabilized Yoshida tumour cells, the same conclusion was recorded, i.e. that the enzyme is kept latent largely because of the inhibitory action of GTP [ 91]. Additional studies have dealt more closely with regulation of activity in the intracellular compartment, taking advantage of specific procedures to alter the intracellular levels of GTP (through incubation with tiazofurin) and of Ca2+ (with maitotoxin) [ 92]. The results, beyond confirming the physiological relevance of the ligand-dependent regulatory mechanisms, indicate further possible modulation of intracellular tTgase activity through the action of proteinases, since the enzyme is a substrate for both calpain and for caspase 3 [ 93, 94].

In addition to their pivotal role in controlling activity of tTGase, Ca2+ and GTP also appear to affect stability to other denaturing stimuli such as heat treatment [ 95] and chemical denaturants [ 54], in addition to proteinases [ 93, 94]. For instance, treatment with guanidine (or with urea at concentrations close to those expected to occur in renal medulla) leads to unfolding of tTgase through initial disruption of the structure of domains 1 and 2, yielding an intermediate which can be refolded with recovery of catalytic activity, in the presence of GTP. Ca2+ promotes, and GTP protects from, inactivation, while osmolytes, e.g. trimethyl-N-oxide, known to protect proteins from chemical denaturation and to favour correct refolding [ 96], counteract the effects of urea (C.M. Bergamini, unpublished work). It is therefore possible that unfolding intermediates of Tgase are also encountered in vivo, and may eventually be immunogenic (see also below).

TURNOVER AND STABILITY OF Tgases

Tgases are believed to be relatively short-lived proteins, with the half-life of type 2 tTgase calculated to be around 11h [ 97]. Very little, however, is known about the regulation of their turnover, besides the observation that type 1 and type 2 Tgases are subjected to transcriptional regulation by retinoids, steroid hormones and a number of peptide growth factors (see above).

Proteolysed forms of type 2 Tgase have been detected in tissue extracts, for instance, in apoptotic thymocytes [ 94], through cleavage by caspase 3. Studies by one of us (M. Griffin, unpublished work) have indicated similar findings in Swiss 3T3 fibroblast cells stimulated to undergo apoptosis using staurosporine. In these cells, loss of tTgase activity due to caspase cleavage appears to take place prior to total loss of cell ATP. Enzyme fragments are easily detectable by immunoblotting and likely represent forms of tTgase undergoing breakdown. In vitro, type 2 tTgase can be either resistant or sensitive to proteolysis, depending on the specificity of the proteinase. For instance, the enzyme is highly sensitive to the pancreatic proteinases trypsin, chymotrypsin and elastase (cleaving predominantly at the loop between domain 2 and domain 3), while it is completely resistant to proteinases specific for acidic residues (e.g. staphylococcal V8 proteinase). The ligands Ca2+ and GTP respectively augment and protect from proteolysis by the pancreatic proteinases (but do not affect cleavage by the V8 proteinase). Once again, this sensitivity to ligands is also physiologically linked to the intracellular concentrations of Ca2+ and GTP [ 90–92]; in these instances, Ca2+ promoted proteolysis of type 2 tTgase via activation of the calpain system [ 93]. Extracellular modulation of cell-surface tTgase by membrane-bound metalloproteinase has also been reported, as previously mentioned [ 68].

While detection of processed forms of type 2 Tgase in tissues might suggest enzyme breakdown and deregulation of Ca2+-mediated activity, the presence of partially proteolysed forms of type 1 and type 3 Tgases, which are present in tissues as zymogens with low catalytic activity [ 98, 99], indicates in situ formation of active mature enzyme. Activation of Tgase 3 is accomplished through a single cleavage at the loop connecting domain 2 and 3, yielding two complementary peptides, which remain tightly associated. In contrast, the process of activation of Tgase 1 is more complex, requiring cleavage of the zymogen at two distinct sites, to remove an N-terminal extension and to nick the homologous loop. It is noteworthy that the zymogen is largely membrane-bound through modification by fatty acids at the N-terminal extension. In this way Tgase 1 is activated about 10–20-fold to yield a group of soluble enzymes depending on the type of peptides which are associated in the final protein.

In relation to cellular processing of Tgases, it is important to mention the report that rodent intestinal mucosa contains both a high-molecular-mass (90kDa) and a low-molecular-mass (55kDa) form of Tgase which does not require Ca2+ to display transamidating activity [ 100, 101]. However, the significance of this finding and its relationship to the involvement of the enzyme in different disease states, e.g. coeliac disease, needs further explanation.

Tgase-CATALYSED MODIFICATION OF TISSUE PROTEINS

Despite extensive investigations, the question of the identification of substrate proteins of physiological relevance acted upon by type 2 tTgase remains an open one, largely because the products which accumulate in vivo or in situ in cells and tissues following activation of the enzyme are predominatly highly cross-linked insoluble polymers, formed by either direct or polyamine- dependent linkage ( Figure 1, Crosslinks I and II). Their structure is complicated, so that the identification of the proteins involved in the polymerization process has been very problematic. Furthermore, when experiments are carried out by modulating Ca2+ levels in tissue homogenates, in permeabilized cells or in cells induced to die by Ca2+ overload, two distinct processes usually take place: the protein modification catalysed by Tgase and the proteolytic processing by Ca2+-activated proteases (e.g. the well known calpains), despite attempts to inhibit these proteases [ 102]. It is also noteworthy that prior phosphorylation [ 103] or proteolytic cleavage of proteins can frequently influence their subsequent transamidation. Clarification with respect to identification of Tgase substrate proteins has been attempted on several occasions either by performing incubations in vitro using cell extracts, or in situ using whole cells or tissues which are incubated in the presence of high concentrations of labelled primary amines (e.g. radiolabelled putrescine [ 104], monodansylcadaverine, monofluorescein cadaverine [ 105], 3-{Na-[Ne-(2´,4´-dinitrophenyl)amino-n-hexanoyl]- L-lysylamido}propane-1-ol ('DALP') [ 106] and 5-biotinamidopentylamine [ 107], or glutamine-rich peptides, e.g. biotinylated TVQQEL [ 108]) to force the reaction towards the simple incorporation of amines or reaction with the glutamine-rich peptide rather than polymerization. Labelled lysine donor proteins or amine acceptor proteins can then be identified either by decreased band intensities of substrates in electrophoretograms, direct immunological detection using fluorescent microscopy or identification of the modified protein by MS [ 109], depending on the method used. A few guidelines have emerged from these studies: (i) different Tgase enzymes display selective labelling of glutamine residues even in the same substrate protein [ 110]; (ii) distinct proteins are acted upon in different tissues, acting as either acyl donors or acceptors or both. Probably the best example of (i) and (ii) is the way in which the different Tgase enzymes cross-link the a-, b- and g-chains of fibrin or its precursor fibrinogen (first illustrated by Chung et al. in 1974 [ 111]). Conditions under which the reaction is carried out also markedly affect the results. In relation to the last point, as previously mentioned, the ability of some proteins to act as Tgase substrates, can be affected by prior proteolytic processing, post-translational modification or loss of the native compact structure, all or some of which may be important in the physiological and pathological roles of these enzymes. The effect of loss of native compact structure is exemplified by studies on the labelling of a-lactoalbumin by bacterial (Ca2+ -independent) Tgase [ 112]; in this case, incorporation of labelled amines was prevalent for the molten-globule form in comparison with the native protein.

An overview of endogenous substrate proteins for mammalian type 2 tTgase is given in Table 2. They are classified according to their cellular distribution and function. In many instances, studies were carried out following incorporation of radioactive polyamines into protein glutamine residues and, eventually, protein polymerization. In some cases the direct study of lysine residues was carried out, although protein cross-linking is indirect proof of the presence of both lysine and glutamine reactive residues in a single substrate protein. For space limitation we do not comment further on this list, although it is evident that a huge number of tTgase substrate proteins are those involved in cell motility, in the interaction of cells with extracellular matrix structures, and in key steps of energetic intermediate metabolism. Despite their great functional relevance, attempts to relate tTgase-catalysed protein modification to changes in physiological functions have so far been deceiving and are limited depending on the experimental system. Examples include those involving gain of function, e.g. stimulation of phospholipase A2 activity [ 113], biological effects of midkine protein (a member of the heparin-binding neurotrophic factor family) [ 114] and activation of transforming growth factor-b1 (TGFb1) via cross-linking of the latent TGF b- binding protein-1 (LTBP-1) [ 115] or loss of function, e.g. loss of myosin in vitro contractile activity upon addition of tTgase-polymerized actin [ 116], blockage of protein synthesis upon glutamidation of translation initiation factor 5A ('IF5A') at its unique hypusine residue [ 117], inactivation of glyceraldehyde-3-phosphate dehydrogenase and a-oxoglutarate dehydrogenase [ 118].


Table 2 Endogenous and exogenous substrates of mammalian tTgase

Endogenous substrates
Cellular proteins
Cytosolic proteins
Aldolase A [ 228]
Glyceraldehyde-3-phosphate dehydrogenase [ 229]
Phosphorylase kinase [ 230]
Crystallins [ 108, 231]
Glutathione S-transferase [ 107]
Cytoskeletal proteins
Actin [ 106, 232]
Myosin [ 232]
Troponin [ 233]
b-Tubulin [ 234]
Tau [ 182]
Rho A [ 235]
Organelle proteins
Histone H2B [ 236]
a-Oxoglutarate dehydrogenase [ 185]
Cytochromes [ 237]
Erythrocyte band III [ 238]
CD38 [ 239]
Acetylcholine esterase [ 240]
Extracellular proteins
Matrix-associated proteins
Collagen [ 241]
Fibronectin [ 15, 242]
Fibrinogen [ 243]
Vitronectin [ 244]
Osteopontin [ 245]
Nidogen [ 203]
Laminin [ 203]
LTBP-1 [ 173]
Osteonectin [ 246]
Osteocalcin [ 245]
Signalling proteins and peptides
Substance P [ 247]
Phospholipase A2 [ 113]
Midkine [ 248]
Exogenous proteins
Alimentary proteins
Wheat gliadin ([ 175] and references therein)
Whey proteins [ 249]
Soy protein [ 250]
Pea legumin [ 251]
Yeast proteins
Candida albicans surface proteins [ 213]
Viral proteins
HIV envelope glycoproteins gp120 and gp41 [ 222, 221]
HIV aspartyl proteinase [ 223]
Hepatitis C virus core protein [ 225]

It is also pertinent to mention that tTgase can modify a number of exogenous proteins, including alimentary proteins, like wheat and soya-bean proteins, milk casein and whey proteins (see, for instance, the discusion on pathogenesis of coeliac disease) and proteins from pathogenic micro-organisms (e.g. Candida albicans surface proteins, envelope proteins and aspartyl-proteinase from HIV and the hepatitis-C-virus core protein) (see Table 2).

IMMUNOREACTIVITY OF tTgase

Interaction of Tgases with antisera has been the subject of continuous study since an early report demonstrating distinct epitopes on the type 2 enzyme when exposed to Ca2+ [ 119]. Polyclonal antibodies, raised in several laboratories, usually display prominent enzyme selectivity towards type 1, type 2 and type 3 Tgase [ 120]. Thus specific epitopes are present on each isoenzyme, but they have not been adequately mapped. The antibodies available at the University of Ferrara, produced either in rabbit or chickens, are directed against epitopes in the large chymotryptic fragment of type 2 Tgase, including domains 1 and 2. They do not affect the transamidating activity, but they have not been tested for effects on the GTP-ase activity (C.M. Bergamini, unpublished work). The most widely employed monoclonal antibody against Tgase is CUB 74, which was originally produced by Birckbichler and associates and is specific for type 2 Tgase [ 121]. This antibody reacts with both native and unfolded Tgase by binding at sites of the protein which partially overlap the Ca2+- and nucleotide-binding sites, i.e. in the N-terminal region of the protein [ 122], and has been extremely useful in studying both tissue distribution of the enzyme and physiological function (see [ 123] and references cited therein).

Interest in type 2 tTgase immunoreactivity has grown explosively during the last few years in relation to the pathogenesis and diagnosis of coeliac disease (see below for a more extensive discussion). In the intestinal mucosa of gliadin-sensitive individuals, tTgase is apparently involved in deamidation of glutamine residues in gliadin and in formation of aggregates of Tgase itself and of gliadin, which are highly immunogenic through local activation of T-lymphocytes [ 124, 125]. It should be noted that deamidation of glutamine-containing peptides, whereby water rather than a primary amine acts as the acceptor substrate (see Figure 1, reaction B), only normally occurs under acidic conditions or when a suitable amine donor is absent [ 126]. The autoantibodies produced usually belong to the IgA class [ 127]. Evidence suggests they can exert effects in tTgase function, although evidence for their effects on transamidating activity seems to be controversial [ 128]. In any case it appears that different regions in the N- and C-terminal moieties are recognized as epitopes by the autoantibodies [ 129] and that the reactivity of antisera against tissue Tgase is more prominent in the case of the Ca2+-stabilized conformation [ 130]. Other autoimmune diseases where anti-tTgase antibodies have been found include diabetes mellitus Type 1 and, more recently, in systemic lupus erythematosus and Sjögren syndrome [ 131].

PHYSIOLOGICAL FUNCTIONS OF tTgase

The search for a physiological function of type 2 tTgase is certainly not yet over. Most studies dedicated to this issue have tried to extend and attribute general meanings to experiments carried out on relatively narrow and specialized fields. Early investigations suggested that tTgase may have a role in cell proliferation [ 132, 133]. Others generated the impression that the enzyme was involved in receptor-mediated endocytosis [ 134]. A further role was postulated for the enzyme in the Ca2+-mediated exocytotic events involved in the stimulus–secretion coupling involved in insulin release [ 135, 136]. Interestingly the tTgase knockout mice (-/-) do show symptoms of mild onset diabetes as they age, which is thought to be related to perturbations in insulin release from their pancreatic b-cells [ 43]. Early techniques used to study tTgase function involved stimulation of cells with known inducers of the enzyme, e.g. differentiating agents such as retinoids and others. However, relating phenotypic changes to Tgase activity using agents that cause a host of pleiotropic responses must now be treated with caution. The first cell-transfection studies used to investigate the function of the enzyme by increasing its expression in NIH3T3 fibroblasts suggested a role for the enzyme in cell adhesion, since many cells appeared very flat and showed increased resistance to detachment by trypsin. A further morphological feature noted in the transfected cells was an apparent increased rate of cell death [ 14].

CELL DEATH AND tTgase

The initial report indicating that tTgase might be involved in apoptosis came from Fesus et al. [ 137], who noted that the levels of tTgase expression and activity correlated with maximum cellular regression found in the livers of rats following induction of hyperplasia. It was suggested that tTgase was important in stabilizing the apoptotic cells by intracellular cross-linking [ 70], thus preventing loss of intracellular components prior to clearance by phagocytosis. Prior to the acceptance of apoptosis as a distinct form of cell death, involvement of tTgase in cell death had been reported for the human erythrocyte by Lorand and Conrad [ 138]. Since these initial observations, the involvement of tTgase with apoptosis has been more widely reported [ 139–141]. There is also widespread evidence for the up-regulation of the tTgase gene during cell death [ 142–145]. However, it is also becoming apparent that the occurence of apoptosis and tTgase expression do not always completely overlap. Moreover, overexpression of tTgase in stably transfected Swiss 3T3 fibroblasts under the tight control of the inducible tet regulatory system did not lead to increased endogenous rates of apoptosis or cell death in these cells [ 95]. However, recent studies have indicated that, by a mechanism thought to involve hyperpolarization of the mitochondrial membrane, tTgase might act as a sensitizer of death stimuli [ 146]. Probably the most confirmatory evidence indicating that tTgase is not obligatory for the apoptotic mechanism comes from the type 2 tTgase (-/-) knockout mice, which do not show any phenotype indicating perturbations in apoptosis from loss of type 2 tTgase [ 41, 42]. However, it cannot be ruled out that loss of the enzyme in mice may be compensated for by the other isoforms. Interestingly, more recent work has suggested that increased expression of tTgase prolongs cell survival by preventing apoptosis via a GTP-binding mechanism [ 147, 148]. What is becoming apparent is that expression of tTgase in cells can lead to massive intracellular (both nuclear and cytoplasmic) cross-linking, resulting in cell death if Ca2+ homoeostasis in these cells is suddenly perturbed [ 95, 149] (see Figure 4). This form of cell death is not inhibited by Bcl2 (B-cell leukaemia/lymphoma 2) [ 150] and is caspase-independent [ 138]. Both up-regulation of the enzyme in cells and its ability to induce Ca2+-mediated intracellular cross-linking is likely to be related to its proposed role in wound healing and maintenance of tissue integrity [ 151, 152] when its interaction with the extracellular matrix also becomes a key event. However, a role for tTgase in the later stages of some forms of apoptosis cannot still be ruled out. For a review on tTgase and cell death, readers should see Griffin and Verderio [ 149].

tTgase and the extracellular matrix

Despite the lack of a leader sequence, which would facilitate export of tTgase to the cell surface by the conventional endoplasmic reticulum/Golgi route, the enzyme appears to be secreted from cells in a controlled manner [ 64, 65, 96, 153]. Other proteins thought to fall into this category include fibroblast growth factor-1 [ 154], interleukin-1b [ 155], thioredoxin [ 156], muscle lectin [ 157], the A subunit of Factor XIII [ 158] and the prostate Tgase [ 159]. Our own studies with tTgase indicate that a number of criteria are important for the enzyme to be externalized. The first includes a fibronectin-binding site in its N-terminal b-sandwich domain [ 64]. The second is the presence of a non-proline cis peptide bond at Tyr274, since mutation of this bond leads to both loss of transamidating activity and loss of secretion of the enzyme [ 153]. The presence of an intact site, Cys277, is also important for deposition of the enzyme into the matrix [ 153]. As previously referred to, the presence of non-proline cis peptide bonds appears to be a conserved feature in a number of Tgases [ 48] and was first recognized in Factor XIII, which has two non-proline cis peptide bonds, one of which is close to the active site between Arg310 and Tyr311 and the other between Gln425 and Phe426, which is close to the dimerization interface. Like tTgase, loss of the cis peptide bond close to the active site leads to loss in transamidating activity [ 160].

Once externalized from the cell, tTgase has been shown to bind and cross-link a number of extracellular proteins, in particular fibronectin, for which it has a high binding affinity [ 64, 95, 122]. Other extracellular proteins found both at the cell surface and in the surrounding matrix which have been reported to be substrates for tTgase are shown in Table 2.

The physiological implications related to matrix protein cross-linking indicate that its function is not only to stabilize these proteins, i.e. increasing their proteolytic, chemical and mechanical resistance, but also to facilitate cell adhesion and cell motility [ 153, 161]. For example, reduced expression of tTgase in ECV 304 endothelial-like cells by antisense silencing leads to the reduced ability of these cells to spread and adhere [ 15]. Similarly, preincubation of these cells or others, e.g. Swiss 3T3 fibroblasts with anti-tTgase antibody CUB 74, which binds to tTgase at the cell surface, leads to a comparable loss in cell adhesion [ 15, 95].

We and others have demonstrated a close association of the cell-surface-related tTgase with the b1 and b3 integrins [ 62, 63], in particular at focal adhesion sites where fibronectin fibril assembly is taking place [ 62, 63, 95] (see Figure 5). A new role for tTgase has been proposed whereby the enzyme acts as an integrin-binding adhesion co-receptor for fibronectin [ 63], a function thought to be not only important in cell adhesion, but also in fibronectin assembly [ 162]. Of particular importance was the finding that transamidating activity did not need to be intact for the enzyme to undertake these cell-adhesion roles [ 63]. It has also been demonstrated that over expression of the active (Cys277) or the inactive mutant (Ser277) form of the enzyme in Swiss 3T3 fibroblasts leads to a lowered rate of cell migration on fibronectin–a feature that is dependent on the presence of the enzyme at the cell surface–but not its transamidating activity [ 153].

Recent results have also indicated that, when tTgase is immobilized on fibronectin, either in its active or inactive form, it can support cell adhesion in what appears to be an integrin- independent manner. These studies indicate that the RGD-related binding peptides, which block integrin binding to fibronectin, although able to inhibit cell adhesion to fibronectin alone cannot block cell adhesion to the tTgase–fibronectin complex. Similar results were obtained when a5- and b1-integrin-blocking antibodies were used. This tTgase–fibronectin-mediated cell adhesion in the presence of RGD-containing peptides elicits a series of intracellular signals involving focal adhesion kinase ('FAK'), and the GTP-binding proteins raf-1 and rho [ 163, 164], which are able to increase cell survival when the cells' fibronectin-binding sites are blocked by the presence of RGD-containing peptides.

Such a role for the enzyme, like its function in cell death, could be related to its importance in the maintenance of tissue integrity following damage whereby cells under stress/insult release the enzyme into the matrix. The end result is maintenance of tissue integrity via protein cross-linking and matrix deposition and a reduction in cell death by prevention of anoikis – an apoptotic cell death common in many cell types from loss of adherence [ 165, 166]. As previously mentioned, a survival function for tTgase has also been related to its intracellular GTP-binding activity [ 147, 148]. tTgase-mediated cell death involving massive intracellular cross-linking may therefore only represent the end result when its survival function fails. ( Scheme 1 details a possible scenario whereby tTgase becomes involved in cell survival/cell death and maintenance of tissue integrity following cell stress or damage.)



Scheme 1 Importance of tTgase in the maintenance of tissue integrity following cell stress/injury

Tissue Tgase is normally secreted into the extracellular matrix in relatively low amounts depending on the tissue. Following stress or insult, up-regulation of tTgase often occurs, resulting in further enzyme externalized into the matrix. Insult leading to cell damage can also lead to increased tTgase leaking into the matrix. This is accompanied by the massive intracellular cross-linking of the tTgase containing dying cells following loss of Ca2+ homoeostasis. Once increased in the matrix, the enzyme has both direct and indirect effects on the matrix, either through direct protein cross-linking leading to matrix stabilization or indirectly via the activation of matrix-bound TGFb1 leading to matrix deposition. Matrix-bound tTgase can also act as an independent cell-adhesion protein when bound to fibronectin preventing cell death by anoikis. The end result is wound healing and maintenance of tissue integrity. Abbreviations: tTG, tTgase; ECM, extracellular matrix.


TYPE 2 tTgase–A KEY PLAYER IN A NUMBER OF MAMMALIAN PATHOLOGICAL STATES

This topic has attracted much interest, and in very recent years has yielded interesting new data with respect to the relevance of Tgases in chronic diseases, in particular in (a) inflammatory diseases, including wound healing, tissue repair and fibrosis, and autoimmune conditions; (b) chronic degenerative diseases (e.g. arthritis, atherosclerosis and neurodegenerative pathologies); and (c) tumour biology. In the majority of these diseases the prevalent role of tTgase appears to be related to its interaction with, and stabilization of, the cell matrix, rather than as a major player in apoptosis.

Wound healing requires the involvement of several distinct Tgases, which co-operate with each other to finally reconstitute tissue integrity damaged by traumatic or other pathological injuries. Factor XIIIa is clearly involved in the control of blood loss after the traumatic injury of blood vessels, through the stabilization of fibrin during blood clotting, in the activation of platelets, and in the deposition of granulation tissues, which represents the first stable repair to a local lesion. Tgases 1 and 3 are particularly involved in repair of the epidermal teguments, in conjunction with Tgase 2, which is probably involved in the angiogenic phase of wound repair as well as in its interaction with and stabilization of the extracellular matrix, possibly through its role as an independent cell-adhesion protein or as an integrin co-receptor, as previously outlined [ 13, 14, 15, 62, 63, 161]. While this is an example of physiologically oriented involvement of Tgases in repair mechanisms, it is also likely that Tgases, particularly the type 2 tTgase, are as a consequence also involved in tissue fibrosis and scarring. Examples include the severe chronic inflammatory states found in liver diseases (cirrhosis and fibrosis, alcoholic hepatopathy and type C hepatitis) [ 167, 168], and in renal and lung fibrosis [ 21, 169, 152, 170], the latter ultimately leading to renal and pulmonary failure via deposition of excessive scar tissue (see Figure 6). In addition, involvement of tTgase in the pathogenesis of the chronic inflammatory diseases of the joints, including rheumatoid arthritis and osteoarthritis, has been reported [ 171]. A major role of the enzyme in many of these conditions is apparently linked to its involvement in the activation of pro-inflammatory cytokines such as TGFb1 [ 171, 172]. In the latter case, tTgase is thought to be important in both the matrix storage and activation of TGFb1 via a mechanism that involves the cross- linking of the LTBP-1 complex to the matrix, which is a pre-requisite for the release and activation of this fibrogenic cytokine [ 173, 174] (see Scheme 1). Activated cytokines such as TGFb1 can stimulate pyrophosphate release in diseased joints, leading to mineralization and progression of diseases such as arthritis. Activation of growth factors such as TGFb1 and cytokines such as interleukin-6 and tumour necrosis factor- a in their turn can lead to further induction and expression of tTgase, leading to an effective, but vicious, autocrine loop. It is also noteworthy that Factor XIII is frequently present and active in the synovial fluids of inflamed joints, catalysing stabilization of fibrin, further complicating the biological clinical picture [ 175]. It must also be noted that several autoimmune diseases are characterized by the production of autoantibodies reactive against tTgase (see also the discussion in section 'Immunoreactivity of tTgase' above). Data in this perspective have been collected mostly for coeliac disease [ 124], Type 1 diabetes [insulin-dependent diabetes, ('IDD')] [ 176], thyroid diseases, and, more recently, systemic lupus erythematosus and Sjögren syndrome [ 131]. In all these instances the documentation of serum immunoreactivity against tTgase can be a valuable aid for diagnostic purposes and in evaluating the progression of the disease [ 177]. It has also been suggested that, at least in coeliac disease, the autoantibodies have a pathogenic role, since they interfere with the normal development and differentiation of the intestinal mucosa [ 178]. It is likely that these effects depend, at least partially, on interference with the functional role of the surface-exposed tTgase, i.e. cell adhesion and survival, and in the activation of matrix-associated TGFb1 and/or other important cytokines [ 173, 174] required in the repair process of the gut (see Scheme 2). Probably quite different are the mechanisms whereby Tgases are involved in the pathogenesis of several chronic neurodegenerative diseases, which are characterized by the accumulation of highly cross-linked insoluble protein materials. These include senile dementia of the Alzheimer type (Alzheimer disease, AD) and the polyglutamine (polyQ) tail diseases, such as Huntington's disease, rubropallidal atrophy and spinocerebellar palsy. In AD, the expression of tTgase is increased [ 179] and is also qualitatively altered such that shorter forms of the enzyme are expressed (by a misreading of an exon/intron boundary) [ 180], lacking portions of domain 4. In the diseased brain, the elevated tTgase activity is manifested by polymerization of a number of proteins, including Ab peptide, b-amyloid precursor protein [ 181] and the microtubule-associated tau protein, with formation of neurofibrillary tangles [ 181, 182], as well as deposition of amyloid-like materials in the extracellular compartments. These abnormal protein polymers might be relevant to the pathogenesis of AD brains, and their formation has been ascribed to increased tTgase activity and to an altered distribution of the truncated protein.



Scheme 2 Possible roles of Tgase in the pathogenesis of intestinal mucosal atrophy in coeliac disease

Intestinal tTgase can modify glutamine residues in proteolytic fragments of alimentary gliadin, through deamidation or cross-linkage to the enzyme itself. In the first instance, the appearence of glutamine residues favours complex formation between gliadin peptides and MHC to activate intestinal T lymphocytes. In turn, this affects secretion of local cytokines, thereby leading to alterations in enterocyte proliferation and differentiation. In the second instance, autoantibodies produced against the gliadin–tTgase complex (the tTgase moiety is the major autoreactive component) might affect the enzymes cellular function, e.g. cell adhesion, cell survival, matrix stabilization, activation of TGFb1 (see Scheme 1). Both mechanisms might contribute to mucosal atrophy and overt clinical manifestations of coeliac disease. The framed panels are those where a direct involvement of tTgase is postulated.


In contrast, the polyQ diseases are primarily characterized by transcriptional defects in the substrates, rather than in the enzyme, with the synthesis of proteins with abnormal tail extensions that represent the sites of Tgase-mediated protein cross-linking [ 25]. This issue is still controversial, since the presence of multiple glutamine repeats directly promotes stickiness in the altered proteins [ 183], which tend to rapidly polymerize. This phenomenon would, however, be further favoured by covalent cross-linking by tTgase [ 184]. PolyQ extensions could be present in a number of proteins in the diseased brains, including several enzymes associated with energy metabolism [ 185]. Recent studies have demonstrated that administration of the Tgase inhibitor cystamine to transgenic mice (expressing exon 1 of huntingtin containing an expanded polyglutamine repeat) was found to alter the course of the disease in a favourable way, thus providing further evidence for the involvement of tTgase in this disease [ 186].

An additional field of active research on the importance of tTgases in human pathology is that of neoplastic diseases. Numerous reports have dealt with these issues, and the general feeling is that tumour cells, when observed in vitro, generally have a lower tTgase content than their normal counterparts [ 20, 187, 188], contain forms of Tgase which are identical with those found in normal cells, together with modified forms, which are sometimes inactive [ 69, 189], and may differ in their subcellular localization. Tumours usually display a definitively larger proportion of Tgase activity in the cell particulate fraction when compared with normal cells [ 69, 187, 188, 190–192], although the absolute amount of enzyme present in this fraction is normally not altered. The decline of Tgase activity in tumours is potentially a bad prognostic biomarker [ 20, 188] and is possibly related to tumour metastatic potential, dictating the ability of the cells to cross basal membranes and to invade the bloodstream [ 189, 190]. Given the proposed functions of tTgase, reduced enzyme ex-pression and activity in tumours would indeed lead to reduced cell adhesion, increased migration and a less stable extracellular matrix, thus facilitating the initial invasive stage of the tumour. However, reports of increased tTgase expression in highly invasive tumours have also been reported, e.g. in the breast [ 193, 194], and increased tTgase expression has been found in secondary metastatic tumours [ 189]. Other intriguing issues arise from the reported decreased rates of apoptosis in tumours [ 195] and the still-debated relationships between Tgases and apoptosis. It is also noteworthy that successful induction of tTgase by powerful inducers such as retinoids (e.g. 9-cis-retinoic acid or all-trans-retinoic) provide an effective switch to cell differentiation and apoptotic death, as observed with squamous-cell carcinoma in vitro and in promyelocytic leukaemia in vivo [ 196–198]. The observation that other synthetic retinoids can be even more active than retinoic acid in inducing tTgase activity and apoptosis in cell lines which are insensitive to the therapeutic effects of retinoic acid [ 199] has stimulated further research on the application of modified retinoids [ 200]. It is also now clear that other chemotherapeutic agents of different structure might be as effective as antineoplastic drugs, but their relationships to Tgase-related pathways are still controversial [ 201]. Conversely, host tissues frequently display higher tTgase expression and activity in peritumoral regions, possibly as a local wound-healing mechanism [ 202], related to the rearrangement of the extracellular matrix [ 203], which may even promote angiogenesis and further spreading of the cancerous cells.

THERAPEUTIC, DIAGNOSTIC AND INDUSTRIAL APPLICATIONS OF Tgases

This brief updating on Tgase research cannot go unfinished without some mention of the application of Tgases as applied biocatalysts in the biomedical and biotechnology fields. This is probably one of the fastest-growing areas in Tgase research, as reflected by an increasing number of patent applications filed on Tgases. Among the early therapeutic applications of Tgases, was the use of Factor XIII substitutive therapy [ 204] in the rare genetic defects of blood clotting related to loss of the plasma Tgase. Most recently the local administration of purified enzymes (usually placental Factor XIII, but more recently tTgase) have been used as an exogenous biological 'glue' to aid in the repair of surgical wounds, fractures and cartilage lesions [ 205]. This practice, employing recombinant rather than extracted enzymes, is still being explored in surgical practice and in the treatment of certain intestinal diseases [ 206].

A recent alternative and useful approach is to modulate endogenous tTgase expression, rather than to administer purified enzyme, by means of specific inducers such as the retinoids. This approach is now a recognized strategy in dermatological conditions such as acne [ 207], and, as stated above, in the therapy of selected malignancies in vivo [ 196, 208]. Although studies are still at the experimental stage, additional encouraging results have been obtained in some animal tumours, e.g. melanomas, in which metastatic spread is greatly limited by inducing tTgase activity in either the invading tumour or the host [ 208, 209]. Earlier studies showing that cell transfection leading to overexpression of tTgase in fibrosarcoma cells results in the reduction in tumour growth may have a future application as a tool for gene therapy [ 210]. The great advantage of such selective therapy, as compared with classic chemotherapy, is its reduced toxicity to normal cells.

Commercial applications of Tgase appear continuously at an increasing rate in the Tgase research field, for example, in the pathogenesis of infectious diseases and in the development of new strategies in vaccination for bacterial and viral infections. For instance, it is known that some bacterial toxins, e.g. the Escherichia coli toxin cytotoxic factor 1, act as a Tgase, although with an absolute substrate specificity (in this case) for the GTP-binding protein Rho [ 211], which clearly differentiates this bacterial Tgase from other prokaryotic enzymes. Furthermore, development of bacterial and yeast biofilms frequently involve Tgase-like modification of surface proteins [ 212]. From this perspective we must stress that several bacterial and fungal Tgases have been identified, although only one has been extensively purified and characterized. This is the Streptoverticillum morabiense Tgase, which does not require Ca2+ for activity [ 213, 214]. This enzyme is commercially available and has found several applications as a biocatalyst in the food, cosmetic and textile industries [ 215–219]. In the case of viral diseases, considerable interest has been attracted by reports on HIV infection describing Tgase-mediated modification of the viral surface glycoproteins gp41 and gp120 [ 220, 221], which mediate HIV entry into target cells. Curiously this promising issue has not been the subject of further investigations. Furthermore, it was reported that Tgase-mediated polyamidation brought about inhibition of HIV aspartyl-proteinase [ 222] and that Tgase was crucial in apoptotic clearance of infected T-lymphocytes in the establishment of HIV-associated lymphopenia [ 223]. It has also been reported that Tgase-dependent post-translational modification of viral core protein is involved in hepatitis-C-virus cellular replication [ 224]. This body of information is suggestive of the potential usefulness of pharmacological modulation of Tgase activity in these severe viral diseases.

Classic applications of Tgase in biotechnology research further include its diagnostic applications for autoimmune diseases (as exemplified by the large body of information available on coeliac disease, as referred to above), their use in food processing (reviewed in [ 225, 226]) and, more recently, rapid methods of detecting the free e-(g-glutamyl)lysine isodipeptide in body fluids, which has the potential to be used as a marker in a number of diseases in which Tgases are involved [ 227].

CONCLUSIONS

In this short review we have tried to summarize the rapidly increasing body of knowledge that is accumulating on Tgases. Although the emphasis has been on the Type 2 tissue Tgase, we hope we have provided enough information to the reader to justify the loose terminology of 'biological glues' to this group of enzymes.

The physiological functions ascribed to tTgase are now becoming more focused and the cause–effect relationships are starting to become established. As a consequence, its role in tissue repair and cell death as a response to loss in tissue homoeostasis following trauma has now become accepted. It is in this respect that this multifunctional protein expresses the characteristics of a true 'superglue', acting as an independent cell-adhesion protein, a cross-linker of matrix proteins and intracellular proteins and as a GTP-binding protein in its bid to maintain tissue integrity.

Note added in proof (received 31 October 2002)

Since this review was originally submitted in August 2002, several other interesting papers have appeared in scientific journals. We would like to call to the attention of readers the first report of the crystal structure of a bacterial Tgase, namely that from Streptoverticillium mobaraense [ 254]. This protein is quite different from the mammalian enzyme, displaying as it does a single disk-like structure with a central groove to accommodate the active-centre region and with a similar triad-like organization. The Streptoverticillium Tgase is notably characterized by elevated transamidating activity and minimal peptidylglutamine hydrolase activity. Another interesting report, from Sblattero et al. [ 255], describes the careful analysis of the interaction between specific coeliac-disease antibodies, expressed as an ScV phage-display library, and cloned fragments of human tTgase. The data demonstrate that the epitopes recognized by the antibodies are largely conformational and are restricted to the core domain in the region spanning amino acids 140–376. Additional reactive regions are probably present at the conformational loop between domains 2 and 3. It can be anticipated that this kind of approach will help our understanding of the autoimmune reactivity of tTgase in defining clearly the different effects of circulating antibodies on enzyme activity.

M.G. wishes to acknowledge the Wellcome Trust, the National Kidney Research Fund (NKRF), Diabetes UK, Cancer Research UK, The Engineering and Physical Sciences Research Council (EPSRC) and The Biotechnology and Biological Sciences Research Council (BBSRC), and the Alan MacDonald Foundation for support of his research work on Tgases. Thanks also go to Mary Stevenson for patience and diligence in the preparation of the manuscript. C.M.B. wishes to acknowledge the continuous financial support of his research by grants from the Italian Consiglio Nazionale delle Ricerche (CNR) and Il Ministero dell'Università e della Ricerca Scientifica e Tecnologica (MURST). He is also personally grateful to the late Professor Mario Rippa, who introduced him to this interesting protein (this review is largely dedicated to his memory), and to Monica Squerzanti, for continous, competent technical help. We thank T. Johnson and J. Skill (Nottingham Trent University) for their help in the work producing Figure 6.

REFERENCES

1 Clarke, D.D., Mycek, M.J., Neidle, A. and Waelsch, H. (1957) The incorporation of amines into proteins. Arch. Biochem. Biophys. 79, 338–354
1st Citation

2 Pisano, J.J., Finlayson, J.S. and Peyton, M.P. (1968) Cross-link in fibrin polymerized by factor 13: e-(g- glutamyl)lysine. Science 160, 892–893
Medline   1st Citation

3 Kanaji, T., Ozaki, H., Takao, T., Kawajiri, H., Ide, H., Motok, M. and Shimonishi, Y. (1993) Primary structure of microbial transglutaminase from Streptoverticilium sp. strain S-8112, J. Biol. Chem. 268, 11565–11572
1st Citation

4 Del Duca, S., Beninati, S. and Serafini-Fracassini, D. (1995) Polyamines in chloroplasts: identification of their glutamyl and acetyl derivatives. Biochem. J. 305, 233–237
Medline   1st Citation

5 Singh, R.N. and Mehta, K. (1994) Purification and characterisation of a novel transglutaminase from filarial nematode Brugia Malayi. Eur. J. Biochem. 225, 625–634
Medline   1st Citation

6 Zhang, J. and Masui, Y. (1997) Role of amphibian egg transglutaminase in the development of secondary cytostatic factor in vitro. Mol. Reprod. Dev. 47, 302–311
Medline   1st Citation

7 Yasueda, H., Kumazawa, Y. and Motoki, M. (1994) Purification and characterization of a tissue-type transglutaminase from red sea bream (Pagrus major). Biosci. Biotechnol. Biochem. 58, 2041–2045
Medline   1st Citation

8 Puszkin, E.G. and Raghuraman, V. (1985) Catalytic properties of a calmodulin-regulated transglutaminase from human platelet and chicken gizzard. J. Biol. Chem. 260, 16012–16020
Medline   1st Citation

9 Burgoyne, R.D. and Weiss, J.L. (2001) The neuronal Ca2+ sensor family of Ca2+-binding proteins. Biochem. J. 353, 1–12
Medline   1st Citation

10 Coussons, P.J., Price, N.C., Kelly, S.M., Smith, B. and Sawyer, L. (1992) Factors that govern the specificity of transglutaminase-catalysed modification of proteins and peptides. Biochem. J. 282, 929–930
Medline   1st Citation

11 Folk, J.E., Park, M.H., Chung, S.I., Schrode, J., Lester, E.P. and Cooper, H.L. (1980) Polyamines as physiologicalal substrates for transglutaminases. J. Biol. Chem. 255 , 3695–3700
Medline   1st Citation

12 Martinet, N., Beninati, S., Nigra, T.P. and Folk, J.E. (1990) N1,N8-bis(g-glutamyl)spermidine cross- linking in epidermal-cell envelopes. Comparison of cross-link levels in normal and psoriatic cell envelopes. Biochem. J. 271, 305–308
Medline   1st Citation

13 Fesus, L., Madi, A., Balajthy, Z., Nemes, Z. and Szondy, Z. (1996) Transglutaminase induction by various cell death and apoptosis pathways. Experientia 52, 942–949
Medline   1st Citation  2nd

14 Gentile, V., Thomazy, V., Piacentini, M., Fesus, L. and Davies, P.J. (1992) Expression of tissue transglutaminase in Balb-C 3T3 fibroblasts: effects on cellular morphology and adhesion. J. Cell Biol. 119, 463–474
Medline   1st Citation  2nd  3rd

15 Jones, R.A., Nicholas, B., Mian, S., Davies, P.J. and Griffin, M. (1997) Reduced expression of tissue transglutaminase in a human endothelial cell line leads to changes in cell spreading, cell adhesion and reduced polymerisation of fibronectin. J. Cell Sci. 110, 2461–2472
Medline   1st Citation  2nd  3rd  4th  5th  6th

16 Greenberg, C.S., Birckbichler, P.J. and Rice, R.H. (1991) Transglutaminases: multifunctional cross-linking enzymes that stabilize tissues. FASEB J. 5, 3071–3077
Medline   1st Citation

17 Lesort, M., Tucholski, J., Miller, M.L. and Johnson, G.V. (2000) Tissue transglutaminase: a possible role in neurodegenerative diseases. Prog. Neurobiol. 61, 439–463
Medline   1st Citation

18 Dieterich, W., Ehnis, T., Bauer, M., Donner, P., Volta, U., Riecken, E.O. and Schuppan, D. (1997) Identification of tissue transglutaminase as the autoantigen of coeliac disease. Nat. Med. 3, 797–801
Medline   1st Citation

19 Birckbichler, P.J., Orr, G.R., Conway, E. and Patterson, Jr, M.K. (1977) Transglutaminase activity in normal and transformed cells. Cancer Res. 37, 1340–1344
Medline   1st Citation

20 Barnes, R.N., Bungay, P.J., Elliott, B.M., Walton, P.L. and Griffin, M. (1985) Alterations in the distribution and activity of transglutaminase during tumour growth and metastasis. Carcinogenesis 6, 459–463
Medline   1st Citation  2nd  3rd  4th

21 Griffin, M., Smith, L.L. and Wynne, J. (1979) Changes in transglutaminase activity in an experimental model of pulmonary fibrosis induced by paraquat. Br. J. Exp. Pathol. 60, 653–661
Medline   1st Citation  2nd

22 Lee, K.N., Birckbichler, P.J. and Patterson, Jr, M.K. (1989) GTP hydrolysis by guinea pig liver transglutaminase. Biochem. Biophys. Res. Commun. 162, 1370–1375
Medline   1st Citation

23 Melino, G., Thiele, C.J., Knight, R.A. and Piacentini, M. (1997) Retinoids and the control of growth/death decisions in human neuroblastoma cell lines. J. Neurooncol. 31 , 65–83
Medline   1st Citation

24 Chen, J.S. and Mehta, K. (1999) Tissue transglutaminase: an enzyme with a split personality. Int. J. Biochem. Cell Biol. 31, 817–836
Medline   1st Citation

25 Cooper, A.J., Sheu, K.F., Burke, J.R., Strittmatter, W.J., Gentile, V., Peluso, G. and Blass, J.P. (1999) Pathogenesis of inclusion bodies in (CAG)n/Q n-expansion diseases with special reference to the role of tissue transglutaminase and to selective vulnerability. J. Neurochem. 72, 889–899
Medline   1st Citation  2nd

26 Grenard, P., Bates, M.K. and Aeschlimann, D. (2001) Evolution of transglutaminase genes: identification of a transglutaminase gene cluster on human chromosome 15q15. Structure of the gene encoding transglutaminase x and a novel gene family member, transglutaminase z. J. Biol. Chem. 276, 33066–33078
Medline   1st Citation  2nd

27 Dubbink, H.J., de Waal, L., van Haperen, R., Verkaik, N.S., Trapman, J. and Romijn, J.C. (1998) The human prostate-specific transglutaminase gene (TGM4): genomic organization, tissue-specific expression and promoter characterization. Genomics 51, 434–444
Medline   1st Citation

28 Candi, E., Oddi, S., Terrinoni, A., Paradisi, A., Ranalli, M., Finazzi-Agrò, A. and Melino, G. (2001) Transglutaminase 5 cross-links loricrin, involucrin and small proline-rich proteins in vitro. J. Biol. Chem. 276, 35014–35023
Medline   1st Citation  2nd

29 Makarov, K.S., Aravind, L. and Koonin, E.U. (1999) A superfamily of archael, bacterial and eukaryotic proteins homologous to animal transglutaminases. Protein Science 8 , 1714–1719
Medline   1st Citation

30 Polakowska, R.R., Graf, B.A., Falciano, V. and LaCelle, P. (1999) Transcription regulatory elements of the first intron control human transglutaminase type I gene expression in epidermal keratinocytes. J. Cell. Biochem. 73, 355–369
Medline   1st Citation

31 Lee, J.H., Jang, S.I., Yang, J.M., Markova, N.G. and Steinert, P.M. (1996) The proximal promoter of the human transglutaminase 3 gene. Stratified squamous epithelial- specific expression in cultured cells is mediated by binding of Sp1 and ets transcription factors to a proximal promoter element. J. Biol. Chem. 271, 4561–4568
Medline   1st Citation

32 Eckert, R.L. and Welter, J.F. (1996) Transcription factor regulation of epidermal keratinocyte gene expression. Mol. Biol. Rep. 23, 59–70
Medline   1st Citation  2nd

33 Kuncio, G.S., Tsyganskaya, M., Zhu, J., Liu, S.L., Nagy, L., Thomazy, V., Davies, P.J. and Zern, M.A. (1998) TNF-a modulates expression of the tissue transglutaminase gene in liver cells. Am. J. Physiol. 274, G240–G245
Medline   1st Citation

34 Ou, H., Haendeler, J., Aebly, M.R., Kelly, L.A., Cholewa, B.C., Kwitek-Black, A., Jacob, H.J., Berk, B.C. and Miano, J.M. (2000) Retinoic acid-induced tissue transglutaminase and apoptosis in vascular smooth muscle cells. Circ. Res. 87, 881–887
Medline   1st Citation

35 Ishii, I. and Ui, M. (1994) Possible involvement of GTP-binding proteins in 1a,25-dihydroxyvitamin D3 induction of tissue transglutaminase in mouse peritoneal macrophages. Biochem. Biophys. Res. Commun. 203, 1773–1780
Medline   1st Citation

36 Fujimoto, M., Kanzaki, H., Nakayama, H., Higuchi, T., Hatayama, H., Iwai, M., Kaneko, Y., Mori, T. and Fujita, J. (1996) Requirement for transglutaminase in progesterone- induce decidualization of human endometrial stromal cells. Endocrinology (Baltimore) 137, 1096–1101
1st Citation

37 Yan, Z.H., Noonan, S., Nagy, L., Davies, P.J. and Stein, J.P. (1996) Retinoic acid induction of the tissue transglutaminase promoter is mediated by a novel response element. Mol. Cell. Endocrinol. 120, 203–212
Medline   1st Citation

38 Lu, S. and Davies, P.J. (1997) Regulation of the expression of the tissue transglutaminase gene by DNA methylation. Proc. Natl. Acad. Sci. U.S.A. 94, 4692–4697
Medline   1st Citation

39 Szegezdi, E., Szondy, Z., Nagy, L., Nemes, Z., Friis, R.R., Davies, P.J. and Fesus, L. (2000) Apoptosis-linked in vivo regulation of the tissue transglutaminase gene promoter. Cell Death Differ. 7, 1225–1233
Medline   1st Citation

40 Gentile, V., Davies, P.J. and Baldini, A. (1994) The human tissue transglutaminase gene maps on chromosome 20q12 by in situ fluorescence hybridization. Genomics 20 , 295–297
Medline   1st Citation

41 De Laurenzi, V. and Melino, G. (2001) Gene disruption of tissue transglutaminase. Mol. Cell Biol. 21, 148–155
Medline   1st Citation  2nd

42 Nanda, N., Iismaa, S.E., Owens, W.A., Husain, A., Mackay, F. and Graham, R.M. (2001) Targeted inactivation of Gh/tissue transglutaminase II. J. Biol. Chem. 276, 20673–20678
Medline   1st Citation  2nd

43 Melino, G., De Laurenzi, V., Bernassola, F. and Candi, E. (2001) Transglutaminases in cell death. 9th Euroconference on Apoptosis, October 13–16, Vienna, Austria
1st Citation  2nd

44 Mearns, B., Nanda, N., Michalicek, J., Iismaa, S. and Graham, R. (2002) Impaired wound healing and altered fibroblast cytoskeletal dynamics in Gh knockout mice. 7th International Conference on Transglutaminase and Protein Crosslinking Reactions, September 14–17, 2002, Ferrara, Italy
1st Citation

45 Small, K., Feng, J.-F., Lorenz, J., Donnelly, E.T., Yu, A., Im, M.-J., Dorn, II, G.W. and Liggett, S.B. (1999) Cardiac specific overexpression of transglutaminase II (G h) results in a unique hypertrophy phenotype independent of phospholipase C activation. J. Biol. Chem. 274, 21291–21296
Medline   1st Citation

46 Lesort, M., Attanavanish, K., Zhang, J.W. and Johnson, G.V.W. (1998) Distinct nuclear localization and activity of tissue transglutaminase. J. Biol. Chem. 273, 11991–11994
Medline   1st Citation

47 Yee, V.C., Pedersen, L.C., Le Trong, I., Bishop, P.D., Stenkamp, R.E. and Teller, D.C. (1994) Three-dimensional structure of a transglutaminase: human blood coagulation factor XIII. Proc. Natl. Acad. Sci. U.S.A. 91, 7296–7300
Medline   1st Citation

48 Weiss, M.S., Metzner, H.J. and Hilgenfeld, R. (1998) Two non-proline cis peptide bonds may be important for Factor XIII function. FEBS Lett. 423, 291–296
Medline   1st Citation  2nd

49 Fox, B.A., Yee, V.C., Pedersen, L.C., Le Trong, I., Bishop, P.D., Stenkamp, R.E. and Teller, D.C. (1999) Identification of the Ca2+ binding site and a novel ytterbium site in blood coagulation Factor XIII by x-ray crystallography. J. Biol. Chem. 274, 4917–4923
Medline   1st Citation

50 Candi, E., Melino, G., Lahm, A., Ceci, R., Rossi, A., Kim, I.G., Ciani, B. and Steinert, P.M. (1998) Transglutaminase 1 mutations in lamellar ichthyosis. Loss of activity due to failure of activation by proteolytic processing. J. Biol. Chem. 273, 13693–13702
Medline   1st Citation

51 Casadio, R., Polverini, E., Mariani, P., Spinozzi, F., Carsughi, F., Fontana, A., Polverino de Laureto, P., Matteucci, G. and Bergamini, C.M. (1999) The structural basis for the regulation of tissue transglutaminase by Ca2+ ions. Eur. J. Biochem. 262, 672–679
Medline   1st Citation  2nd  3rd  4th

52 Noguchi, K., Ishikawa, K., Yokoyama, K.i., Ohtsuka, T., Nio, N. and Suzuki, E. (2001) Crystal structure of red sea bream transglutaminase. J. Biol. Chem. 276, 12055–12059
Medline   1st Citation  2nd

53 Kim, H.C., Nemes, Z., Idler, W.W., Hyde, C.C., Steinert, P.M. and Ahvazi, B. (2001) Crytallization and preliminary x-ray analysis of human transglutaminase 3 from zymogen to active form. J. Struct. Biol. 135, 73–77
Medline   1st Citation

54 Bergamini, C.M., Dean, M., Matteucci, G., Hanau, S., Tanfani, F., Ferrari, C., Boggian, M. and Scatturin, A. (1999) Conformational stability of human erythrocyte transglutaminase: Patterns of thermal unfolding at acid and alkaline pH. Eur. J. Biochem. 266, 575–582
Medline   1st Citation  2nd

55 Lai, T.S., Slaughter, T.F., Koropchak, C.M., Haroon, Z.A. and Greenberg, C.S. (1996) C-terminal deletion of human tissue transglutaminase enhances magnesium-dependent GTP/ATPase activity. J. Biol. Chem. 271, 31191–31195
Medline   1st Citation

56 Hwang, K.C., Gray, C.D., Sivasubramanian, N. and Im, M.J. (1995) Interaction site of GTP binding Gh (transglutaminase II) with phospholipase C. Biol. Chem. 270 , 27058–27062
1st Citation

57 Nakaoka, H., Perez, D.M., Baek, K.J., Das, T., Husain, A., Misono, K., In, M.J. and Graham, R.M. (1994) Gh: a GTP-binding protein with transglutaminase activity and receptor signaling function. Science 264, 1593–1596
Medline   1st Citation

58 Im, M.J., Russell, M.A. and Feng, J.F. (1997) Transglutaminase II: a new class of GTP-binding protein with new biological functions. Cell Signal. 7, 477–482
1st Citation

59 Feng, J.F., Readon, M., Yadav, S.P. and Im, M.J. (1999) Calreticulin down-regulates both GTP binding and transglutaminase activities of transglutaminase II. Biochemistry 38, 10743–10749
Medline   1st Citation

60 Signorini, M., Bortolotti, F., Poltronieri, L. and Bergamini, C.M. (1988) Human erythrocyte transglutaminase: purification and preliminary characterisation. Biol. Chem. Hoppe Seyler 369, 275–281
Medline   1st Citation

61 Fromm, J.R., Hileman, R.E., Caldwell, E.E.O., Weiler, J.M. and Linhardt, R.J. (1995) Differences in the interaction with arginine and lysine and the importance of these basic amino acids in the binding of heparin to the acidic fibroblast growth factor. Arch. Biochem. Biophys. 323, 279–285
Medline   1st Citation

62 Gaudry, C.A., Verderio, E., Jones, R.A., Smith, C. and Griffin, M. (1999) Tissue transglutaminase is an important player at the surface of human endothelial cells: evidence for its externalisation and its colocalization with the b1 integrin. Exp. Cell Res. 252, 104–113
Medline   1st Citation  2nd  3rd  4th

63 Akimov, S.S., Krylov, D., Fleischman, L.F. and Belkin, A.M. (2000) Tissue transglutaminase is an integrin-binding adhesion coreceptor for fibronectin. J. Cell Biol. 148 , 825–838
Medline   1st Citation  2nd  3rd  4th  5th  6th

64 Gaudry, C.A., Verderio, E., Aeschlimann, D., Cox, A., Smith, C. and Griffin, M. (1999) Cell surface localisation of tissue transglutaminase is dependent on a fibronectin- binding site in its N-terminal b-sandwich domain. J. Biol. Chem. 274, 30707–30714
Medline   1st Citation  2nd  3rd  4th  5th  6th

65 Upchurch, H.F., Conway, E., Patterson, Jr, M.K., Birkbichler, P.I. and Maxwell, M.D. (1987) Cellular transglutaminase has affinity for extracellular matrix. In vitro . Cell. Dev. Biol. 23, 795–800
1st Citation  2nd

66 Tyrrell, D.J., Sale, W.S. and Slife, C.W. (1988) Fibronectin is a component of the sodium dodecyl sulfate-insoluble transglutaminase substrate. J. Biol. Chem. 263, 8464–8469
Medline   1st Citation

67 Martinez, J., Chalupowicz, D.G., Roush, R.K., Sheth, A. and Barsigian, C. (1994) Transglutaminase-mediated processing of fibronectin by endothelial cell monolayers. Biochemistry 33, 2538–2545
Medline   1st Citation

68 Belkin, A.M., Akimov, S.S., Zaritskaya, L.S., Ratnikov, B.I., Deryugina, E.I. and Strongin, A.Y. (2001) Matrix-dependent proteolysis of surface transglutaminase by membrane- type metalloproteinase regulates cancer cell adhesion and locomotion. J. Biol. Chem. 276, 18415–18422
Medline   1st Citation  2nd

69 Zirvi, K.A., Keogh, J.P., Slomiany, A. and Slomiany, B.L. (1993) Effects of exogenous transglutaminase on spreading of human colorectal carcinoma cells. Cancer Biochem. Biophys. 13, 283–294
Medline   1st Citation  2nd  3rd

70 Knight, C.R., Rees, R.C. and Griffin, M. (1991) Apoptosis: a potential role for cytosolic transglutaminase and its importance in tumour progression. Biochim. Biophys. Acta 1096, 312–318
Medline   1st Citation  2nd

71 Pedersen, L.C., Yee, V.C., Bishop, P.D., Le Trong, I., Teller, D.C. and Stenkamp, R.E. (1994) Transglutaminase factor XIII uses proteinase-like catalytic triad to crosslink macromolecules. Protein Sci. 3, 1131–1135
Medline   1st Citation

72 Bergamini, C.M. and Signorini, M. (1988) Ca2+ dependent reversible inactivation of erythrocyte transglutaminase by acrylamide. Biochem. Int. 17, 855–862
Medline   1st Citation

73 Bergamini, C.M. and Signorini, M. (1990) In vivo inactivation of transglutaminase during the acute acrylamide toxic syndrome in the rat. Experientia 46, 278–281
Medline   1st Citation

74 Mariani, P., Carsughi, F., Spinozzi, F., Romanzetti, S., Meier, G., Casadio, R. and Bergamini, C.M. (2000) Ligand-induced conformational changes in tissue transglutaminase: Monte Carlo analysis of small-angle scattering data. Biophys. J. 78, 3240–3251
Medline   1st Citation  2nd  3rd  4th

75 Murthy, S.N.P., Iismaa, S., Begg, G., Freymann, D.M., Graham, R.M. and Lorand, L. (2002) Conserved tryptophan in the core domain of transglutaminase is essential for catalytic activity. Proc. Natl. Acad. Sci. U.S.A. 99, 2738–2742
Medline   1st Citation  2nd

76 Liu, S., Cerione, R.A. and Clardy, J. (2002) Structural basis for the guanine nucleotide-binding activity of tissue transglutaminase and its regulation of transamidation activity. Proc. Natl. Acad. Sci. U.S.A. 99, 2743–2747
Medline   1st Citation  2nd

77 Ambrus, A., Banyai, I., Weiss, M.S., Hilgenfeld, R., Keresztessy, Z., Musbek, L. and Fesus, L. (2001) Ca2+ binding of transglutaminases: a 43Ca NMR study combined with surface polarity analysis. J. Biomol. Struct. Dyn. 19, 59–74
Medline   1st Citation

78 Weiss, M.S., Metzner, H.J. and Hilgenfeld, R. (1998) Two non-proline cis peptide bonds may be important for Factor XIII function. FEBS Lett. 423, 291–296
Medline   1st Citation

79 Lai, T.S., Bielawska, A., Peoples, K.A., Hannun, Y.A. and Greenberg, C.S. (1997) Sphingosylphosphocholine reduces the Ca2+ ion requirement for activating tissue transglutaminase. J. Biol. Chem. 272, 16295–16300
Medline   1st Citation  2nd

80 Hand, D., Bungay, P.J., Elliott, B.M. and Griffin, M. (1985) Activation of transglutaminase at Ca2+ levels consistent with a role for this enzyme as a Ca2+ receptor protein. Biosci. Rep. 5, 1079–1086
Medline   1st Citation

81 Bergamini, C.M. (1988) GTP modulates Ca2+ binding and cation-induced conformational changes in erythrocyte transglutaminase. FEBS Lett. 239, 255–258
Medline   1st Citation  2nd  3rd

82 Achyuthan, K.E. and Greenberg, C.S. (1987) Identification of a guanosine triphosphate binding site on guinea pig liver transglutaminase. Role of GTP and Ca2+ ions in modulating activity. J. Biol. Chem. 262, 1901–1906
Medline   1st Citation

83 Iismaa, S.E., Wu, M.J., Nanda, N., Church, W.B. and Graham, R.M. (2000) GTP binding and signaling by Gh/transglutaminase II involves distinct residues in a unique GTP- binding pocket. J. Biol. Chem. 275, 18259–18265
Medline   1st Citation

84 Monsonego, A., Friedmann, I., Shani, Y., Eisenstein, M. and Schwartz, M. (1998) GTP-dependent conformational changes associated with the functional switch between G a and cross-linking activities in brain-derived tissue transglutaminase. J. Mol. Biol. 282, 713–720
Medline   1st Citation

85 Mitkevich, O.V., Shainoff, J.R., DiBello, P.M., Yee, V.C., Teller, D.C., Smejkal, G.B., Bishop, P.D., Kolotushkina, I.S., Fickenscher, K. and Samokhin, G.P. (1998) Coagulation factor XIIIa undergoes a conformational change evoked by glutamine substrate. Studies on kinetics of inhibition and binding of XIIIA by a cross-reacting antifibrinogen antibody. J. Biol. Chem. 273, 14387–14391
Medline   1st Citation

86 Fesus, L., Horvath, A. and Harsfalvi, J. (1983) Interaction between tissue transglutaminase and phospholipid vesicles. FEBS Lett. 155, 1–5
Medline   1st Citation

87 Chakravarty, R. and Rice, R.H. (1989) Acylation of keratinocyte transglutaminase by palmitic and myristic acids in the membrane anchorage region. J. Biol. Chem. 264, 625–629
Medline   1st Citation

88 Lai, T.S., Hausladen, A., Slaughter, T.F., Eu, J.P., Stamler, J.S. and Greenberg, C.S. (2001) Ca2+ regulates S-nitrosylation, denitrosylation and activity of tissue transglutaminase. Biochemistry 40, 4904–4910
Medline   1st Citation

89 Catani, M.V., Bernassola, F., Rossi, A. and Melino, G. (1998) Inhibition of clotting factor XIII activity by nitric oxide. Biochem. Biophys. Res. Commun. 249, 275–278
Medline   1st Citation

90 Smethurst, P.A. and Griffin, M. (1996) Measurement of tissue transglutaminase activity in a permeabilized cell system: its regulation by Ca2+ and nucleotides. Biochem. J. 313, 803–808
Medline   1st Citation  2nd

91 Bergamini, C.M., Signorini, M., Caselli, L. and Melandri, P. (1993) Regulation of transglutaminase activity by GTP in digitonin permeabilized Yoshida tumor cells. Biochem. Mol. Biol. Int. 30, 727–732
Medline   1st Citation  2nd

92 Zhang, J., Lesort, M., Guttmann, R.P. and Johnson, G.V. (1998) Modulation of the in situ activity of tissue transglutaminase by Ca2+ and GTP. J. Biol. Chem. 273, 2288–2295
Medline   1st Citation  2nd

93 Zhang, J., Guttmann, R.P. and Johnson, G.V. (1998) Tissue transglutaminase is an in situ substrate of calpain: regulation of activity. J. Neurochem. 71, 240–247
Medline   1st Citation  2nd  3rd

94 Fabbi, M., Marimpietri, D., Martini, S., Brancolini, C., Amoresano, A., Scaloni, A., Bargellesi, A. and Cosulich, E. (1999) Tissue transglutaminase is a caspase substrate during apoptosis. Cleavage causes loss of transamidating function and is a biochemical marker of caspase 3 activation. Cell Death Differ. 6, 992–1001
Medline   1st Citation  2nd  3rd

95 Baskakov, I. and Bolen, D.W. (1998) Forcing thermodynamically unfolded proteins to fold. J. Biol. Chem. 273, 4831–4834
Medline   1st Citation  2nd  3rd  4th  5th  6th

96 Di Venere, A., Rossi, A., De Matteis, F., Rosato, N., Finazzi-Agrò, A. and Mei, G. (2000) Opposite effects of Ca2+ and GTP binding on tissue transglutaminase tertiary structure. J. Biol. Chem. 275, 3915–3921
Medline   1st Citation  2nd

97 Verderio, E., Nicholas, B., Gross, S. and Griffin, M. (1998) Regulated expression of tissue transglutaminase in Swiss 3T3 fibroblasts: effects on the processing of fibronectin, cell attachement and cell death. Exp. Cell Res. 239, 119–138
Medline   1st Citation  2nd  3rd  4th

98 Steinert, P.M., Chung, S.I. and Kim, S.Y. (1996) Inactive zymogen and highly active proteolytically processed membrane-bound forms of the transglutaminase 1 enzyme in human epidermal keratinocytes. Biochem. Biophys. Res. Commun. 221, 101–106
Medline   1st Citation

99 Kim, I.G., Gorman, J.J., Park, S.C., Chung, S.I. and Steinert, P.M. (1993) The deduced sequence of the novel protransglutaminase E (TGase3) of human and mouse. J. Biol. Chem. 268, 12682–12690
Medline   1st Citation

100 Tsai, Y.H., Lai, W.F., Chen, S.H. and Johnson, L.R. (1998) A novel Ca2+-independent enzyme capable of incorporating putrescine into proteins. Biochem. Biophys. Res. Commun. 244, 161–166
Medline   1st Citation

101 Tsai, Y.H., Lai, W.F., Wu, Y.W. and Johnson, L.R. (1998) Two distinct classes of rat intestinal mucosal enzymes incorporating putrescine into protein. FEBS Lett. 435 , 251–256
Medline   1st Citation

102 Velasco, P.T., Murthy, P., Goll, D.E. and Lorand, L. (1990) Cross-linking and proteolysis in Ca2+-treated lens homogenates. Biochim. Biophys. Acta 1040, 187–191
Medline   1st Citation

103 Owen, R.A., Bungay, P.J., Hussain, M. and Griffin, M. (1988) Transglutaminase catalysed crosslinking of proteins phosphorylated in the pancreatic b-cell during glucose stimulated insulin release. Biochem. Biophys. Acta 968, 220–230
1st Citation

104 Hand, D., Elliott, B.M. and Griffin, M. (1990) Characterisation of endogenous transglutaminase substrates in normal liver and hepatocellular carcinomas. Biochem. Biophys. Acta 1033, 57–64
1st Citation

105 Layemi, M., Demignot, S., Borge, L., Thenet-Gauci, S. and Adolphe, M. (1997) The use of fluorescein cadaverine for detecting amine acceptor protein substrates accessible to active transglutaminase in living cells. Histochem. J. 29, 593–606
Medline   1st Citation

106 Nemes, Z., Ádány, R., Balázs, M., Boross, P. and Fesus, L. (1997) Identification of cytoplasmic actin as an abundant glutaminyl substrate for tissue transglutaminase in HL-60 and U937 cells undergoing apoptosis. J. Biol. Chem. 272, 20577–20583
Medline   1st Citation  2nd

107 Ikura, K., Kita, K., Fujita, I., Hashimoto, H. and Kawabata, N. (1998) Identification of amine acceptor protein substrates of transglutaminase in liver extracts: use of 5- (biotinamido)pentylamine as a probe. Arch. Biochem. Biophys. 356, 280–286
Medline   1st Citation  2nd

108 Groenen, P.J.T.A., Bleomendal, H. and de Jong, W.W. (1992) The carboxy-terminal lysine of aB-crystallin is an amine-donor substrate for tissue transglutaminase. Eur. J. Biochem. 205, 671–674
Medline   1st Citation  2nd

109 Shimizu, T., Takao, T., Hozumi, K., Nunomura, K., Ohta, S., Shimonishi, Y. and Ikegami, S. (1997) Structure of a covalently cross-linked form of core histones present in the starfish sperm. Biochemistry 36, 12071–12079
Medline   1st Citation

110 Fesus, L., Metsis, M.L., Muszbek, L. and Koteliansky, V.E. (1986) Transglutaminase-sensitive glutamine residues of human plasma fibronectin revealed by studying its proteolytic fragments. Eur. J. Biochem. 154, 371–374
Medline   1st Citation

111 Chung, S.I., Lewis, M.S. and Folk, J.E. (1974) Relationships of the catalytic properties of human plasma and platelet transglutaminases (activated blood coagulation factor XIII) to their subunit structures. J. Biol. Chem. 249, 940–950
Medline   1st Citation

112 Matsumura, Y., Chanyongvorakul, Y., Kumazawa, Y., Ohtsuka, T. and Mori, T. (1996) Enhanced susceptibility to transglutaminase reaction of a- lactalbumin in the molten globule state. Biochim. Biophys. Acta 1292, 69–76
Medline   1st Citation

113 Cordella-Miele, E., Miele, L. and Mukherjee, A.B. (1990) A novel transglutaminase-mediated post-translational modification of phospholipase A2 dramatically increases its catalytic activity. J. Biol. Chem. 265, 17180–17188
Medline   1st Citation  2nd

114 Kojima, S., Inui, T., Maramatsu, H., Suzuki, Y., Kadomatsu, K., Yoshizawa, M., Hirose, S., Kimura, T., Sakakibara, S. and Maramatsu, T. (1997) Dimerization of midkine by tissue transglutaminase and its functional implication. J. Biol. Chem. 272, 9410–9416
Medline   1st Citation

115 Kojima, S., Nara, K. and Rifkin, D.B. (1993) Requirement for transglutaminase in the activation of latent transforming growth factor-b in bovine endothelial cells. J. Cell Biol. 121, 439–448
Medline   1st Citation

116 Kim, E., Bobkova, E., Hegyi, G., Muhlrad, A. and Reisler, E. (2002) Actin cross-linking and inhibition of the actomyosin motor. Biochemistry 41, 86–93
Medline   1st Citation

117 Beninati, S., Nicolini, L., Jakus, J., Passeggio, A. and Abbruzzese, A. (1995) Identification of a substrate site for transglutaminases on the human protein synthesis initiation factor 5A. Biochem. J. 305, 325–328
1st Citation

118 Cooper, A.J., Sheu, K.R., Burke, J.R., Onodera, O., Strittmatter, W.J., Roses, A.D. and Blass, J.P. (1997) Transglutaminase-catalyzed inactivation of glyceraldehyde 3- phosphate dehydrogenase and a-ketoglutarate dehydrogenase complex by polyglutamine domains of pathological length. Proc. Natl. Acad. Sci. U.S.A. 94, 12604–12609
Medline   1st Citation

119 Fesus, L. and Laki, K. (1977) Two antigenic sites of tissue transglutaminase. Biochemistry 16, 4061–4066
Medline   1st Citation

120 Kim, S.Y., Chung, S.I. and Steinert, P.M. (1995) Highly active soluble processed forms of the transglutaminase 1 enzyme in epidermal keratinocytes. J. Biol. Chem. 270 , 18026–18035
Medline   1st Citation

121 Birckbichler, P.J., Upchurch, H.F., Patterson, Jr, M.K. and Conway, E. (1985) A monoclonal antibody to cellular transglutaminase. Hybridoma 4, 179–186
Medline   1st Citation

122 Achyuthan, K.E., Goodell, R.J., Kennedy, J.R., Lee, K.N., Henley, A., Stiefer, J.R. and Birckbichler, P.J. (1995) Immunochemical analyses of human plasma fibronectin- cytosolic transglutaminase interactions. J. Immunol. Methods 180, 69–79
Medline   1st Citation  2nd

123 Thomazy, V. and Fesus, L. (1989) Differential expression of tissue transglutaminase in human cells. Cell Tissue Res. 255, 215–224
Medline   1st Citation

124 Arentz-Hansen, H., Korner, R., Molberg, O., Quarsten, H., Vader, W., Kooy, Y.M., Lundin, K.E., Koning, F., Roepstorff, P., Sollid, L.M. and McAdam, S.N. (2000) The intestinal T cell response to alpha-gliadin in adult celiac disease is focused on a single deamidated glutamine targeted by tissue transglutaminase. J. Exp. Med. 191, 603–612
Medline   1st Citation  2nd

125 Marzari, R., Sblattero, D., Florian, F., Tongiorgi, E., Not, T., Tommasini, A., Ventura, A. and Bradbury, A. (2001) Molecular dissection of the tissue transglutaminase autoantibody response in celiac disease. J. Immunol. 166, 4170–4176
Medline   1st Citation

126 Folk, J.E. and Finlayson, J.S. (1977) The e(g-glutamyl)lysine crosslink and the catalytic role of transglutaminase. Adv. Prot. Chem. 31, 1–133
1st Citation

127 Schuppan, D. and Hahn, E.G. (2001) IgA anti-tissue transglutaminase: setting the stage for coeliac disease screening. Eur. J. Gastroenterol. Hepatol. 13, 635–637
Medline   1st Citation

128 Keaveny, A.P., Offner, G.D., Bootle, E. and Nunes, D.P. (2000) No significant difference in antigenicity or tissue transglutaminase substrate specificity of Irish and US wheat gliadins. Dig. Dis. Sci. 45, 755–762
Medline   1st Citation

129 Seissler, J., Wohlraub, U., Wuensche, C., Scherbaum, W.A. and Boehm, B.O. (2001) Autoantibodies from patients with coeliac disease recognize different structural domains of the autoantigen tissue transglutaminase. Clin. Exp. Immunol. 125, 216–221
Medline   1st Citation

130 Zauli, D., Grassi, A., Granito, A., Foderaro, S., De Franceschi, L., Ballardini, G., Bianchi, F.B. and Volta, U. (2000) Prevalence of silent coeliac disease in atopics. Dig. Liver Dis. 32, 775–779
Medline   1st Citation

131 Villalta, D., Bizzaro, N., Tonutti, E. and Tozzoli, R. (2002) IgG anti-transglutaminase autoantibodies in systemic lupus erythematosus and Sjögren syndrome. Clin. Chem. 48, 1133
Medline   1st Citation  2nd

132 Birckbichler, P.J. and Patterson, Jr, M.K. (1978) Cellular transglutaminase, growth and transformation. Ann. N.Y. Acad. Sci. 312, 354–365
Medline   1st Citation

133 Birchbichler, P.J., Orr, G.R., Patterson, Jr, M.K., Conway, E. and Carter, H.A. (1981) Increase in proliferative markers after inhibition of transglutaminase. Proc. Natl. Acad. Sci. U.S.A. 78, 5005–5008
Medline   1st Citation

134 Levitzki, A., Willingham, M. and Pastan, I. (1980) Evidence for participation of transglutaminase in receptor-mediated endocytosis. Proc. Natl. Acad. Sci. U.S.A. 77 , 706–710
1st Citation

135 Bungay, P., Potter, J. and Griffin, M. (1984) Inhibition of insulin secretion by primary amines: a role for transglutaminase in the secretory mechanism. Biochem. J. 219 , 819–827
Medline   1st Citation

136 Sener, A., Dunlop, M.E., Gomis, R., Mathias, P.C., Malaisse-Lagae, F. and Malaisse, W.J. (1985) Role of transglutaminase in insulin release. Study with glycine and sarcosine methylesters. Endocrinology (Baltimore) 117, 237–242
1st Citation

137 Fesus, L., Thomazy, V. and Falus, A. (1987) Induction and activation of tissue transglutaminase during programmed cell death. FEBS Lett. 224, 104–108
Medline   1st Citation

138 Lorand, L. and Conrad, S.M. (1984) Transglutaminases. Mol. Cell Biochem. 58, 9–35
1st Citation  2nd

139 Melino, G., Annichiarico-Petruzzelli, M., Piredda, L., Candi, E., Gentile, V., Davies, P.J. and Piacentini, M. (1994) Tissue transglutaminase and apoptosis: sense and antisense transfection studies with human neuroblastoma cells. Mol. Cell. Biol. 14, 6584–6596
Medline   1st Citation

140 Piredda, L., Farrace, M.G., Lo Bello, M., Malorni, W., Melino, G., Petruzzelli, R. and Piacentini, M. (1999) Identification of 'tissue' transglutaminase binding protein in neuronal cells committed to apoptosis. FASEB J. 13, 355–364
Medline   1st Citation

141 Zhang, L.X., Millis, K.J., Dawson, M.I., Collins, S.J. and Jetten, A.M. (1995) Evidence for the involvement of retinoic acid receptor RARa- dependent signalling pathway in the induction of tissue transglutaminase and apoptosis by retinoids. J. Biol. Chem. 270, 6022–6029
Medline   1st Citation

142 Nagy, L., Thomazy, V.A., Heuman, R.A. and Davies, P.J.A. (1998) Retinoid-induced apoptosis in normal and neoplastic tissue. Cell Death Differ. 5, 11–19
Medline   1st Citation

143 Nagy, L., Thomazy, V.A., Saydak, M.M., Stein, J. and Davies, P.J.A. (1997) The promoter of the mouse tissue transglutaminase gene directs tissue-specific, retinoid- regulated and apoptosis-linked expression. Cell Death Differ. 4, 534–547
1st Citation

144 Nemes, Z., Friis, R.R., Aeschlimann, D., Saurer, S., Paulsson, M. and Fesus, L. (1996) Expression and activation of tissue transglutaminase in apoptotic cells of involuting rodent mammary tissue. Eur. J. Cell. Biol. 70, 125–133
Medline   1st Citation

145 Nagy, L., Saydak, M., Shipley, N., Lu, S., Basilion, J.P., Yan, Z.H., Syka, P., Chandraratna, R.A.S., Stein, J.P., Heyman, R.A. and Davies, P.J.A. (1996) Identification and characterisation of a versatile retinoid response element (retinoic acid receptor response element-retinoid X receptor response element) in the mouse tissue transglutaminase gene promoter. J. Biol. Chem. 271, 4355–4365
Medline   1st Citation

146 Piacentini, M., Farrace, M.G., Matarrese, P., Ciccosanti, F., Falasca, L., Rodolfo, C., Giammarioli, A.M., Verderio, E., Griffin, M. and Malorni, W. (2002) Transglutaminase overexpression sensitises neuronal cell lines to apoptosis by increasing mitochondrial membrane potential and cellular oxidative stress. J. Neurochem. 81, 1061–1072
Medline   1st Citation

147 Antonyak, M.A., Singh, V.S., Lee, D.A., Boehm, J.E., Combs, C., Zgola, M.M., Page, R.L. and Cerione, R.A. (2001) Effects of tissue transglutaminase on retinoic acid induced cellular differentiation and protection against apoptosis. J. Biol. Chem. 276, 33582–33587
Medline   1st Citation  2nd

148 Antonyak, M.A., Boehm, J.E. and Cerione, R.A. (2002) Phosphoinositide 3-kinase activity is required for retinoic acid-induced expression and activation of the tissue transglutaminase. J. Biol. Chem., 277, 14712–14716
1st Citation  2nd

149 Griffin, M. and Verderio, E. (2000) Tissue transglutaminase in cell death. In Programmed Cell Death in Animals and Plants (Bryant, J.A., Hughes, S.G. and Garland, J.M., eds.), pp. 223–240, BIOS Scientific Publishers, Oxford
1st Citation  2nd

150 Johnson, T.S., Scholfield, C.I., Parry, J. and Griffin, M. (1998) Induction of tissue transglutaminase by dexamethasone: its correlation to receptor number and transglutaminase-mediated cell death in a series of malignant hamster fibrosarcomas. Biochem. J. 331, 105–112
Medline   1st Citation

151 Haroon, Z.A., Hettasch, J.M., Lai, T.S., Dewhirst, M.W. and Greenberg, C.S. (1999) Tissue transglutaminase is expressed, active and directly involved in rat dermal wound healing and angiogenesis. FASEB J. 13, 1787–1795
Medline   1st Citation

152 Johnson, T.S., Skill, N.J., El Nahas, A.M., Oldroyd, S.D., Thomas, G.L., Douthwaite, J.A., Haylor, J.L. and Griffin, M. (1999) Transglutaminase transcription and antigen translocation in experimental renal scarring. J. Am. Soc. Nephrol. 10, 2146–2157
Medline   1st Citation  2nd  3rd

153 Balklava, Z., Verderio, E., Collighan, R., Gross, S., Adams, J. and Griffin, M. (2002) Analysis of tissue transglutaminase function in the migration of Swiss 3T3 fibroblasts. J. Biol. Chem. 277, 16567–16575
Medline   1st Citation  2nd  3rd  4th  5th

154 Tarantini, F., LaVallee, T., Jackson, A., Gamble, S., Carreira, C.M., Garfinkel, S., Burgess, W.H. and Maciag, T. (1998) The extravesicular domain of synaptotagmin-1 is released with the latent fibroblast growth factor-1 homodimer in response to heat shock. J. Biol. Chem. 273, 22209–22216
Medline   1st Citation

155 Rubartelli, A., Cozzolino, F., Talio, M. and Sitia, R. (1990) A novel secretory pathway for interleukin-1b, a protein lacking a signal sequence. EMBO J. 9, 1503–1510
Medline   1st Citation

156 Rubartelli, A., Bajetto, A., Allavena, G., Wollman, E. and Sitia, R. (1992) Secretion of thioredoxin by normal and neoplastic cells through a leaderless secretory pathway. J. Biol. Chem. 267, 24161–24164
Medline   1st Citation

157 Muesch, A., Hartinann, E., Rolide, K., Rubartelli, A., Sitia, R. and Rapoport, T.A. (1990) A novel pathway for secretory proteins?. Trends Biochem. Sci. 15, 86–88
Medline   1st Citation

158 Kaetsu, H., Hashiguchi, T., Foster, D. and Ichinose, A. (1996) Expression and release of the a and b subunits for human coagulation factor XIII in baby hamster kidney (BHK) cells. J. Biochem. (Tokyo) 119, 961–969
Medline   1st Citation

159 Seitz, J., Keppler, C., Huntemann, S., Rausch, U. and Aumuller, G. (1991) Purification and molecular characterisation of a secretory transglutaminase from coagulating gland of the rat. Biochim. Biophys. Acta 1078, 139–146
Medline   1st Citation

160 Hettasch, J.M. and Greenberg, C.S. (1994) Analysis of human factor XIII by site-directed mutagenesis. J. Biol. Chem. 269, 28309–28313
Medline   1st Citation

161 Akimov, S.S. and Belkin, A.M. (2001) Cell surface tissue transglutaminase is involved in adhesion and migration of monocytic cells on fibronectin. Blood 98, 1567–1576
Medline   1st Citation  2nd

162 Akimov, S.S. and Belkin, A.M. (2001) Cell surface tissue transglutaminase promotes fibronectin assembly via interaction with the gelatin-binding domain of fibronectin: a role in TGFb-dependent matrix deposition. J. Cell Sci. 114, 2989–3000
Medline   1st Citation

163 Verderio, E., Telci, D., Okoye, A., Melino, G. and Griffin, M. (2002) Fibronectin bound tissue transglutaminase rescues cells from anoikis. Minerva Biotecnol. 14, 206
1st Citation

164 Telci, D., Verderio, E., Baccarini, M. and Griffin, M. (2002) Importance of tissue transglutaminase cell adhesion complex in signalling pathways. Minerva Biotecnol. 14 , 206
1st Citation

165 Grossmann, J., Walther, K., Artinger, M., Kiessling, S. and Schölmerich, J. (2001) Apoptotic signalling during initiation of detachment-induced apoptosis (''anoikis'') of primary human intestinal epithelial cells. Cell Growth Differ. 12, 147–155
Medline   1st Citation

166 Aoudjit, F. and Vuori, K. (2001) Matrix attachment regulates Fas-induced apoptosis in endothelial cells: a role for c-Flip and implications for anoikis. J. Cell Biol. 152, 633–644
Medline   1st Citation

167 Mirza, A., Liu, S.L., Frizell, E., Zhu, J., Maddukuri, S., Martinez, J., Davies, P., Schwarting, R., Norton, P. and Zern, M.A. (1997) A role for tissue transglutaminase in hepatic injury and fibrogenesis and its regulation by NF-kB. Am. J. Physiol. 272, G281–G288
Medline   1st Citation

168 Grenard, P., Bresson-Hadni, S., El Alaoui, S., Chevallier, M., Vuitton, D.A. and Ricard-Blum, S. (2001) Transglutaminase-mediated cross-linking is involved in the stabilization of extracellular matrix in human liver fibrosis. J. Hepatol. 35, 367–375
Medline   1st Citation

169 Richards, R.J., Masek, L.C. and Brown, R.F. (1991) Biochemical and cellular mechanisms of pulmonary fibrosis. Toxicol. Pathol. 19, 526–539
Medline   1st Citation

170 Johnson, T.S., Griffin, M., Thomas, G.L., Skill, J., Cox, A., Yang, B., Nicholas, B., Birckbichler, P.J., Muchaneta-Kubara, C. and Meguid El Nahas, A. (1997) The role of transglutaminase in the rat subtotal nephrectomy model of renal fibrosis. J. Clin. Invest. 99, 2950–2960
Medline   1st Citation

171 Johnson, K., Hashimoto, S., Lotz, M., Pritzker, K. and Terkeltaub, R. (2001) Interleukin-1 induces pro-mineralizing activity of cartilage tissue transglutaminase and Factor XIIIa. Am. J. Pathol. 159, 149–163
Medline   1st Citation  2nd

172 Rosenthal, A.K., Gohr, C.M., Henry, L.A. and Le, M. (2000) Participation of transglutaminase in the activation of latent Transforming Growth Factor b1 in aging articular cartilage. Arthritis Rheum. 43, 1729–1733
Medline   1st Citation

173 Verderio, E., Gaudry, C.A., Gross, S., Smith, C., Downes, S. and Griffin, M. (1999) Regulation of cell surface tissue transglutaminase: effects on matrix storage of latent transforming growth factor b-binding protein-1. J. Histochem. Cytochem. 47, 1417–1432
Medline   1st Citation  2nd  3rd

174 Kojima, S., Narak, K. and Rifkin, D.B. (1993) Requirement for transglutaminase in the activation of latent TGFb1 in bovine endothelial cells. J. Cell Biol. 121, 439–448
Medline   1st Citation  2nd

175 Plenz, A., Fritz, P., Konig, G., Laschner, W. and Saal, J.G. (1996) Immunohistochemical detection of factor XIIIa and factor XIIIs in synovial membranes of patients with rheumatoid arthritis or osteoarthritis. Rheumatol. Int. 16, 29–36
Medline   1st Citation  2nd

176 Seissler, J., Schott, M., Boms, S., Wohlrab, U., Ostendorf, B., Morgenthaler, N.G. and Scherbaum, W.A. (1999) Autoantibodies to human tissue transglutaminase identify silent coeliac disease in Type I diabetes. Diabetologia 42, 1440–1441
Medline   1st Citation

177 Schuppan, D., Dieterich, W., Ehnis, T., Bauer, M., Donner, P., Volta, U. and Riecken, E.O. (1998) Identification of the autoantigen of celiac disease. Ann. N.Y. Acad. Sci. 859, 121–126
Medline   1st Citation

178 Halttunen, T. and Maki, M. (1999) Serum immunoglobulin A from patients with celiac disease inhibits human T84 intestinal crypt epithelial cell differentiation. Gastroenterology 116, 566–572
Medline   1st Citation

179 Johnson, G.V., Cox, T.M., Lockhart, J.P., Zinnerman, M.D., Miller, M.L. and Powers, R.E. (1997) Transglutaminase activity is increased in Alzheimer's disease brain. Brain Res. 751, 323–329
Medline   1st Citation

180 Citron, B.A., SantaCruz, K.S., Davies, P.J. and Festoff, B.W. (2001) Intron–exon swapping of transglutaminase mRNA and neuronal Tau aggregation in Alzheimer disease. J. Biol. Chem. 276, 3295–3301
Medline   1st Citation

181 Rasmussen, L.K., Sorensen, E.S., Petersen, T.E., Gliemann, J. and Jensen, P.H. (1994) Identification of glutamine and lysine residues in Alzheimer amyloid b A4 peptide responsible for transglutaminase-catalysed homopolymerization and cross-linking to alpha 2M receptor. FEBS Lett. 338, 161–166
Medline   1st Citation  2nd

182 Tucholski, J., Kuret, J. and Johnson, G.V. (1999) Tau is modified by tissue transglutaminase in situ: possible functional and metabolic effects of polyamination. J. Neurochem. 73, 1871–1880
Medline   1st Citation  2nd

183 Chen, S., Berthelier, V., Yang, W. and Wetzel, R. (2001) Polyglutamine aggregation behavior in vitro supports a recruitment mechanism of cytotoxicity. J. Mol. Biol. 311, 173–182
Medline   1st Citation

184 Gentile, V., Sepe, C., Calvani, M., Melone, M.A., Cotrufo, R., Cooper, A.J., Blass, J.P. and Peluso, G. (1998) Tissue transglutaminase-catalyzed formation of high- molecular-weight aggregates in vitro is favored with long polyglutamine domains: a possible mechanism contributing to CAG-triplet diseases. Arch. Biochem. Biophys. 352, 314–321
Medline   1st Citation

185 Cooper, A.J., Sheu, K.R., Burke, J.R., Onodera, O., Strittmatter, W.J., Roses, A.D. and Blass, J.P. (1997) Transglutaminase-catalyzed inactivation of glyceraldehyde 3- phosphate dehydrogenase an a-ketoglutarate dehydrogenase complex by polyglutamine domains of pathological length. Proc. Natl. Acad. Sci. U.S.A. 94, 12604–12609
Medline   1st Citation  2nd

186 Karpuj, M.V., Becher, M.W., Springer, J.E., Chabas, D., Youssef, S., Pedotti, R., Mitchell, D. and Steinman, L. (2002) Prolonged survival and decreased abnormal movements in transgenic model of Huntington disease, with administration of the transglutaminase inhibitor cystamine. Nat. Med. 8, 143–149
Medline   1st Citation

187 Hand, D., Elliott, B.M. and Griffin, M. (1988) Expression of the cytosolic and particulate forms of transglutaminase during chemically induced rat liver carcinogenesis. Biochim. Biophys. Acta 970, 137–145
Medline   1st Citation  2nd

188 Birckbichler, P.J., Bonnerm, R.B., Hurst, R.E., Bane, B.L., Pitha, J.V. and Hemstreet, 3rd, G.P. (2000) Loss of tissue transglutaminase as a biomarker for prostate adenocarcinoma. Cancer 89, 412–423
Medline   1st Citation  2nd  3rd

189 Knight, C.R., Rees, R.C., Elliott, B.M. and Griffin, M. (1990) The existence of an inactive form of transglutaminase within metastasising tumours. Biochim. Biophys. Acta 1053, 13–20
Medline   1st Citation  2nd  3rd

190 Chang, S.K. and Chung, S.I. (1986) Cellular transglutaminase. The particulate-associated transglutaminase from chondrosarcoma and liver: partial purification and characterization. J. Biol. Chem. 261, 8112–8121
Medline   1st Citation  2nd

191 Signorini, M., Caselli, L., Lanzara, V., Ferrari, C., Melandri, P. and Bergamini, C.M. (1996) Properties of particulate transglutaminase from Yoshida tumor cells. Biol. Chem. Hoppe Seyler 377, 167–173
Medline   1st Citation

192 Hand, D., Elliott, B.M. and Griffin, M. (1990) Characterisation of the cellular substrates for transglutaminase in normal liver and hepatocellular carcinoma. Biochim. Biophys. Acta 1033, 57–64
Medline   1st Citation

193 van Groningen, J.J., Klink, S.L., Bloemers, H.P. and Swart, G.W. (1995) Expression of tissue-type transglutaminase correlates positively with metastatic properties of human melanoma cell lines. Int. J. Cancer 60, 383–387
Medline   1st Citation

194 Hettasch, J.M., Bandarenko, N., Burchette, J.L., Lai, T.S., Marks, J.R., Haroon, Z.A., Peters, K., Dewhirst, M.D., Iglehart, J.D. and Greenberg, C.S. (1996) Tissue transglutaminase expression in human breast cancer. Lab. Invest. 75, 637–645
Medline   1st Citation

195 Stambolic, V., Mak, T.W. and Woodgett, J.R. (1999) Modulation of cellular apoptotic potentials: contributions to oncogenesis. Oncogene 18, 6094–6103
Medline   1st Citation

196 Jetten, A.M., Kim, J.S., Sacks, P.G., Rearick, J.I., Lotan, D., Hong, W.K. and Lotan, R. (1990) Inhibition of growth and squamous-cell differentiation markers in cultured human head and neck squamous carcinoma cells by b-all-trans-retinoic acid. Int. J. Cancer 45, 195–202
Medline   1st Citation  2nd

197 Benedetti, L., Grignani, F., Scicchitano, B.M., Jetten, A.M., Diverio, D., Lo Coco, F., Avvisati, G., Gambacorti-Passerini, C., Adamo, S., Levin, A.A. (1996) Retinoid- induced differentiation of acute promyelocytic leukemia involves PML-RARa-mediated increase of type II transglutaminase. Blood 87, 1939–1950
Medline   1st Citation

198 Davies, P.J., Murtaugh, M.P., Moore, Jr, W.T., Johnson, G.S. and Lucas, D. (1985) Retinoic acid-induced expression of tissue transglutaminase in human promyelocytic leukemia (HL-60) cells. J. Biol. Chem. 260, 5166–5174
Medline   1st Citation

199 Chiantore, M.V., Giandomenico, V. and De Luca, L.M. (1999) Carcinoma cell lines resistant for growth inhibition and apoptosis to retinoic acid are responsive to 4- hydroxyphenylretinamide: correlation with tissue transglutaminase. Biochem. Biophys. Res. Commun. 254, 636–641
Medline   1st Citation

200 Dhar, A., Liu, S., Klucik, J., Berlin, K.D., Madler, M.M., Lu, S., Ivey, R.T., Zacheis, D., Brown, C.W., Nelson, E.C., Birckbichler, P.J. and Benbrook, D.M. (1999) Synthesis, structure–activity relationships and RARg–ligand interactions of nitrogen heteroarotinoids. J. Med. Chem. 42, 3602–3614
Medline   1st Citation

201 Uray, I.P., Davies, P.J. and Fesus, L. (2001) Pharmacological separation of the expression of tissue transglutaminase and apoptosis after chemotherapeutic treatment of HepG2 cells. Mol. Pharmacol. 59, 1388–1394
Medline   1st Citation

202 Haroon, Z.A., Li, T.S., Hettasch, J.M., Lindberg, R.A., Dewhirst, M.W. and Greenberg, C.S. (1999) Tissue transglutaminase is expressed as a host response to tumor invasion and inhibits tumor growth. Lab. Invest. 79, 1679–1686
Medline   1st Citation

203 Aeschlimann, D. and Thomazy, V. (2000) Protein crosslinking in assembly and remodelling of extracellular matrices: the role of transglutaminases. Connect. Tissue Res. 41, 1–27
Medline   1st Citation  2nd  3rd

204 Gootenberg, J.E. (1998) Factor concentrates for the treatment of factor XIII deficiency. Curr. Opin. Hematol. 5, 372–375
Medline   1st Citation

205 Jurgensen, K., Aeschlimann, D., Cavin, V., Genge, M. and Hunziker, E.B. (1997) A new biological glue for cartilage–cartilage interfaces: tissue transglutaminase. J. Bone Joint Surg. Am. 79, 185–193
Medline   1st Citation

206 D'Argenio, G., Grossman, A., Cosenza, V., Valle, N.D., Mazzacca, G. and Bishop, P.D. (2000) Recombinant factor XIII improves established experimental colitis in rats. Dig. Dis. Sci. 45, 987–997
Medline   1st Citation

207 Bershad, S. (2001) Developments in topical retinoid therapy for acne. Semin. Cutan. Med. Surg. 20, 154–161
Medline   1st Citation

208 Lentini, A., Kleinman, H.K., Mattioli, P., Autuori-Pezzoli, V., Nicolini, L., Pietrini, A., Abbruzzese, A., Cardinali, M. and Beninati, S. (1998) Inhibition of melanoma pulmonary metastasis by methylxanthines due to decreased invasion and proliferation. Melanoma Res. 8, 131–137
Medline   1st Citation  2nd

209 Leszczyniecka, M., Roberts, T., Dent, P., Grant, S. and Fisher, P.B. (2001) Differentiation therapy of human cancer: basic science and clinical applications. Pharmacol. Ther. 90, 105–156
Medline   1st Citation

210 Johnson, T.S., Knight, C.R., El-Alaoui, S., Mian, S., Rees, R.C., Gentile, V., Davies, P.J. and Griffin, M. (1994) Transfection of tissue transglutaminase into a highly malignant hamster fibrosarcoma leads to a reduced incidence of primary tumour growth. Oncogene 9, 2935–2942
Medline   1st Citation

211 Schmidt, G., Selzer, J., Lerm, M. and Aktories, K. (1998) The Rho-deamidating cytotoxic necrotizing factor 1 from Escherichia coli possesses transglutaminase activity. Cysteine 866 and histidine 881 are essential for enzyme activity. J. Biol. Chem. 273, 13669–13674
Medline   1st Citation

212 Staab, J.F., Bradway, S.D., Fidel, P.L. and Sundstrom, P. (1999) Adhesive and mammalian transglutaminase substrate properties of Candida albicans Hwp1. Science 283, 1535–1538
Medline   1st Citation

213 Gerber, U., Jucknischke, U., Putzien, S. and Fuchsbauer, H.L. (1994) A rapid and simple method for the purification of transglutaminase from Streptoverticillium mobaraense. Biochem. J. 299, 825–829
Medline   1st Citation  2nd

214 Pasternak, R., Dorsch, S., Otterbach, J.T., Robenek, I.R., Wolf, S. and Fuchsbauer, H.L. (1998) Bacterial pro-transglutaminase from Streptoverticillium mobaraense –purification, characterisation and sequence of the zymogen. Eur. J. Biochem. 257, 570–576
Medline   1st Citation

215 Kuraishi, C., Sakamoto, J., Yamazaki, K., Susa, Y., Kuhara, C. and Soeda, T. (1997) Production of restructured meat using microbial transglutaminase without salt or cooking. J. Food Sci. 62, 488
1st Citation

216 Ishii, C., Soeda, T. and Yamakazi, K. (1994) Method for the production of yoghurt. Eur. Patent EP0610649
1st Citation

217 Bailey, P., Richardson, N.K., Pocalyko, D.J. and Schilling, K.M. (1996) Covalent bonding of active agents to skin, hair or nails. U.S. Patent US5490980
1st Citation

218 Cortez, J.M., Bonner, P. and Griffin, M. (2002) A method for enzymatic treatment of textiles such as wool. World Patent WO0204739
1st Citation

219 Rasmussen, L., Mollgaard, A., Petersen, B.R. and Sorensen, N.H. (1996) Method for casein finishing of leather. World Patent WO9413839
1st Citation

220 Mariniello, L., Esposito, C., DiPierro, P., Cozzolino, A., Pucci, P. and Porta, R. (1993) Human-immunodeficiency-virus transmembrane glycoprotein gp41 is an amino acceptor and donor substrate for transglutaminase in vitro. Eur. J. Biochem. 215, 99–104
Medline   1st Citation

221 Mariniello, L., Esposito, C., Gentile, V. and Porta, R. (1993) Transglutaminase covalently incorporates amines into human immunodeficiency virus envelope glycoprotein gp120 in vitro. Int. J. Pept. Protein Res. 42, 204–206
Medline   1st Citation  2nd

222 Beninati, S. and Mukherjee, A.B. (1992) A novel transglutaminase-catalyzed posttranslational modification of HIV-1 aspartyl protease. Biochem. Biophys. Res. Commun. 187 , 1211–1218
Medline   1st Citation  2nd

223 Amendola, A., Gougeon, M.L., Poccia, F., Bondurand, A., Fesus, L. and Piacentini, M. (1996) Induction of 'tissue' transglutaminase in HIV pathogenesis: evidence for high rate of apoptosis of CD4+ T lymphocytes and accessory cells in lymphoid tissues. Proc. Natl. Acad. Sci. U.S.A. 93, 11057–11062
Medline   1st Citation  2nd

224 Lu, W., Strohecker, A. and Ou, J.H. (2001) Post-translational modification of the hepatitis C virus core protein by tissue transglutaminase. J. Biol. Chem. 276, 47993–47999
Medline   1st Citation

225 Nielsen, P.M. (1995) Reactions and potential industrial applications of transglutaminase. A review of literature and patents. Food Biotecnol. 9, 119–156
1st Citation  2nd

226 Collighan, R., Cortez, J. and Griffin, M. (2002) The biotechnological applications of transglutaminases. Minerva Biotecnol. 14, 143–148
1st Citation

227 Nemes, Z., Sarvari, M., Karpati, L., Muszbek, L. and Fesus, L. (2002) A rapid immunoassay for Ne( g-glutamyl) lysine in body fluids and biological samples. Minerva Biotecnol. 14, 183
1st Citation

228 Lee, K.N., Maxwell, M.D., Patterson, Jr, M.K., Birckbichler, P.J. and Conway, W. (1992) Identification of transglutaminase substrates in HT29 colon cancer cells: use of 5- (biotinamido)pentylamine as a transglutaminase-specfic probe. Biochem. Biophys. Acta 1136, 12–16
1st Citation

229 Orru, S., Ruoppolo, M., Francese, S., Vitagliano, L., Marino, G. and Esposito, C. (2002) Identification of tissue transglutaminase-reactive lysine residues in glyceraldehyde-3-phosphate dehydrogenase. Protein Sci. 11, 137–146
Medline   1st Citation

230 Nadeau, O.W., Traxler, K.W. and Carlson, G.M. (1998) Zero-length crosslinking of the beta subunit of phosphorylase kinase to the N-terminal half of its regulatory alpha subunit. Biochem. Biophys. Res. Commun. 251, 637–641
Medline   1st Citation

231 Lorand, L., Parameswaran, K.N. and Velasco, P.T. (1991) Sorting-out of acceptor–donor relationships in the transglutaminase-catalyzed cross-linking of crystallins by the enzyme-directed labelling of potential sites. Proc. Natl. Acad. Sci. U.S.A. 88, 82–83
Medline   1st Citation

232 Eligula, L., Chuang, L., Phillips, M.L., Seguro, K. and Muhlrad, A. (1998) Transglutaminase-induced cross-linking between subdomain 2 of G-actin and the 636–642 lysine-rich loop of myosin subfragment 1. J. Biophys. 74, 953–963
1st Citation  2nd

233 Bergamini, C.M., Signorini, M., Barbato, R., Menabo, R., DiLisa, F., Gorza, L. and Beninati, S. (1995) Transglutaminase-catalyzed polymerisation of troponin in vitro. Biochem. Biophys. Res. Commun. 206, 201–206
Medline   1st Citation

234 Cohen, I. and Anderson, B. (1987) Immunochemical characterisation of the transglutaminase-catalysed polymer of activated platelets. Thromb. Res. 47, 409–416
Medline   1st Citation

235 Singh, U.S., Kunar, M.T., Kao, Y.L. and Baker, K.M. (2001) Role of transglutaminase 2 in retinoic acid induced activation of Rho A associated kinase 2. EMBO J. 20, 2413–2423
Medline   1st Citation

236 Ballestar, E. and Franco, L. (1997) Use of the transglutaminase reaction to study the dissociation of histone N-terminal tails from DNA in nucleosome core particules. Biochemistry 36, 5963–5969
Medline   1st Citation

237 Butler, S.J. and Landon, M. (1981) Transglutaminase-catalysed incorporation of putrescine into denatured cytochrome. Preparation of a mono-substituted derivative reactive with cytochrome c oxidase. Biochem. Biophys. Acta 670, 214–221
1st Citation

238 Murthy, S.N., Wilson, J., Zhang, Y. and Lorand, L. (1994) Residue Gln-30 of human erythocyte anion transporter is a prime site for reaction with intrinsic transglutaminase. J. Biol. Chem. 269, 22907–22911
Medline   1st Citation

239 Umar, S., Malavasi, F. and Mehta, K. (1996) Post-translational modification of CD38 protein into a high molecular weight form alters its catalytic properties. J. Biol. Chem. 271, 15922–15927
Medline   1st Citation

240 Hand, D., Dias, D. and Haynes, L. (2000) Stabilization of collagen-tailed acetylcholinesterase in muscle cells through extracellular anchorage of transglutaminase- catalyzed cross-linking. Mol. Cell Biochem. 204, 65–76
Medline   1st Citation

241 Kleman, J.P., Aeschlimann, D., Paulsson, M. and van der Rest, M. (1995) Transglutaminase-catalyzed cross-linking of fibrils of collagen V/XI in A204 rhabdomyosarcoma cells. Biochemistry 34, 13768–13775
Medline   1st Citation

242 Mosher, D.F. (1984) Cross-linking of fibronectin to collagenous proteins. Mol. Cell Biochem. 58, 63–68
Medline   1st Citation

243 Martinez, J., Rich, E. and Barsigian, C. (1989) Transglutaminase-mediated cross-linking of fibrinogen by human umbilical vein endothelial cells. J. Biol. Chem. 264 , 20502–20508
Medline   1st Citation

244 Sane, D.C., Moser, T.L., Pippen, A.M., Parker, C.J., Achyuthan, K.E. and Greenberg, C.S. (1988) Vitronectin is a substrate for transglutaminases. Biochem. Biophys. Res. Commun. 157, 115–120
Medline   1st Citation

245 Kaartinen, M.T., Pirhonen, A., Linnala-Kankkunen, A. and Maenpaa, P.H. (1997) Transglutaminase catalyzed cross-linking of osteopontin is inhibited by osteocalcin. J. Biol. Chem. 272, 22736–22741
Medline   1st Citation  2nd

246 Aeschlimann, D., Kaupp, O. and Paulsson, M. (1995) Transglutaminase catalysed matrix crosslinking in differentiating cartilage: identification of osteonectin as a major glutaminyl substrate. J. Cell Biol. 129, 881–892
Medline   1st Citation

247 Pastor, M.T., Diez, A., Perez Paya, E. and Abad, C. (1999) Addressing substrate glutamine requirements for tissue transglutaminase using substance P analogues. FEBS Lett. 451, 231–234
Medline   1st Citation

248 Kojima, S., Inui, T., Muramatsu, H., Suzuki, Y., Kadomatsu, K., Yoshizawa, M., Hirose, S., Kimura, T., Sakakibara, S. and Muramatsu, T. (1997) Dimerization of midkine by tissue transglutaminase and its functional implications. J. Biol. Chem. 272, 9410–9416
Medline   1st Citation

249 Aboumahmoud, R. and Savello, P. (1990) Crosslinking of whey protein by transglutaminase. J. Dairy Sci. 73, 256–263
Medline   1st Citation

250 Ikura, K., Kometani, T., Sasaki, K. and Chiba, H. (1980) Crosslinking of soybean 7S and 11S proteins by transglutaminase. Agric. Biol. Chem. 44, 2979–2984
1st Citation

251 Larrè, C., Chiarello, M., Dudek, S., Chenu, M. and Gueguen, J. (1993) Action of transglutaminase on the constitutive polypeptides of pea legumin. J. Agric. Food Chem. 41, 1816–1820
1st Citation  2nd

252 Peters, L.L., Jindel, H.K., Gwynn, B., Korsgren, C., John, K.M., Lux, S.E., Mohandas, N., Cohen, C.M., Cho, M.R., Golan, D.E. and Brugnara, C. (1999) Mild spherocytosis and altered red cell ion transport in protein 4.2-null mice. J. Clin. Invest. 103, 1527–1537
Medline

253 Shimada, J., Suzuki, Y., Kim, S.-J., Wang, P.-C., Matsumura, M. and Kojima, S. (2001) Transactivation via RAR/RXR–Sp1 interaction: characterisation of binding between Sp1 and GC box motif. Mol. Endocrinol. 15, 1677–1692
Medline   1st Citation

254 Kashiwagi, T., Yokoyama, K.I., Ishikawa, K., Ono, K., Ejima, D., Matsui, H. and Suzuki, E.I. (2002) Crystal structure of microbial transglutaminase from Streptoverticillium mobaraense. J. Biol. Chem. DOI: 10.74/jbc.M203933200
1st Citation

255 Sblattero, D., Florian, F., Azzoni, E., Zyla, T., Park, M., Baldas, V., Not, T., Ventura, A., Bradbury, A. and Marzari, R. (2002) The analysis of the fine specificity of celiac disease antibodies using tissue transglutaminase fragments. Eur. J. Biochem. 269, 5175–5181
Medline   1st Citation


Received 6 August 2002/12 September 2002; accepted 4 October 2002

Published as BJ Immediate Publication 4 October 2002, DOI 10.1042/BJ20021234


The Biochemical Society, London © 2002








PDF
Abstract

Email this article to a friend



Figure 1 Reactions catalysed by Tgases



Figure 2 Gene structure of type 2 tTgase and of its promoter



Figure 3 Schematic structure and ligand-dependent regulation of tTgase



Figure 4 Cell death involving massive intracellular cross-linking following loss of Ca2+ homoeostasis



Figure 5 Extracellular localization of tissue Tgase



Figure 6 Immunolocalization of tTgase in control and diabetic nephropathy (DN) human biopsies