of work: Apoptosis is a natural phenomenon that plays a major role in normal turnover of cells. In recent years, evidence accumulated to indicate that insulin has antiapoptotic properties, in part, by activating transcription factors that are known to be involved in the control of the apoptotic process. Using cells transfected with various insulin receptor mutants, we established the important role played by the insulin receptor kinase function but observed that tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) and the subsequent activation of phosphatidylinositol 3'-kinase do not contribute to the survival properties of the insulin receptor. However, we found that farnesylation of Ras-related small GTP-binding proteins may be involved in the antiapoptotic protection by insulin. Under the same experimental conditions, triggering of the GLP-1 receptor also confers resistance against apoptotic death. Whether protein farnesylation is a required step in GLP-1 action is unclear. The importance of Dr. Lee-Kwon?s work was highlighted by receiving the 1998 Glenn Foundation Endocrinology and Aging Award. The results of these studies are now in press in Biochemistry. There are only three members of the Ras family that are known to be farnesylated and targeted at the plasma membrane. We are currently establishing whether any of these three members play an essential role in the transduction of the insulin's antiapoptotic signals. Transfection of cells with wild-type and dominant-negative mutant of these small GTP-binding proteins is underway. Because the interaction between some members of the Ras superfamily and Raf-1 serine/threonine kinase represents a regulated integrative point for cross talk between tyrosine kinase receptor- and cyclic AMP-dependent signaling cascades, we plan to investigate the role of insulin and GLP-1 on Raf-1 activation, a possible trigger for survival in several cell types. It is widely believed that the devastating complications of diabetes are the results of prolonged periods of hyperglycemia. Byproducts of cellular respiration as well as high glucose concentrations found in diabetic conditions can result in cell death. We plan to characterize the mechanism by which glucose and its metabolites functions as a progression factor for apoptosis in some tissues but not in others.
