Dr. Vulliet's research will investigate the biochemical mechanisms controlling cellular responses to growth factors. Previous work has demonstrated that PC12 cells respond to treatment with nerve growth factor (NGF) and epidermal growth factor (EGF) by altering the phosphorylation of specific proteins. Dr. Vulliet has identified a unique site distinct from other known phosphorylation sites on tyrosine hydroxylase that is phosphorylated following NGF and EGF treatment. The amino acid sequence around this site suggests that it may be phosphorylated by a novel protein kinase. Screening of other known kinases for their ability to phosphorylate tyrosine hydroxylase has failed to demonstrate any phosphorylation of this specific site. Using a synthetic peptide identical with the first 19 amino acids of tyrosine hydroxylase, Dr. Vulliet has developed an assay for this kinase activity and succeeded in obtaining a partial purification and characterization of this protein kinase. Dr. Vulliet now proposes to further isolate, purify and characterize this novel kinase activity by employing a combination of traditional biochemical techniques and FPLC methods to develop a rapid purification of this kinase from pheochromocytoma tissue. Other embryonic and neoplastic tissues will be examined for the presence of this particular kinase activity. The biochemical and kinetic properties of this enzyme will be investigated. In addition, the physiological function of this kinase will be investigated in PC12 cells treated with a variety of growth factors. Dr. Vulliet anticipates that this novel protein kinase may play an important role in mediating the biochemical responses of the PC12 cells to NGF and EGF.
