Research

This group is concerned with the mechanisms involved in the intracellular transmission of hormone and growth factor signals. Of particular interest are mechanisms that involve the phosphorylation and dephosphorylation of proteins. One specific area of research addresses the question of how growth factor receptors possessing protein tyrosine kinase activity, e.g., the insulin, epidermal growth factor, and the platelet-derived growth factor receptors, regulate the phosphorylation of cellular proteins on serine or threonine residues. For example, can it be shown that protein serine/threonine kinases or phosphatases are direct targets for the receptors and undergo changes in enzymic activity as a result of phosphorylation on tyrosine residues or are indirect mechanisms involved? The group is also interested in the action of oncogene-encoded protein tyrosine kinases, and many of the same questions that are posed with respect to receptor-type kinases are also being asked with respect to these enzymes. Cells that are overexpressing "oncoproteins" with tyrosine kinase activity often display elevated protein serine/threonine kinase activity. Through identification of the specific enzymes involved it is hoped that some light can be shed on the oncogenic process. More than a hundred different protein kinases have been identified in eukaryotic cells; and although it has been assumed that all of these enzymes are involved in regulatory processes, the functions of some of them remain obscure. One kinase in this category is casein kinase II, which is being investigated in this group. Its functions and regulation are being studied by overexpression, through an examination of its biochemical properties, and by measuring its enzymic activity after treating cells with various drugs and hormones.