INSULIN RECEPTOR SUBSTRATE -1 AND FLUID SHEAR STRESS

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(Adapted from applicant's abstract) The goals of the proposed research project are: 1) to prepare and train the candidate for a career in cardiovascular research by providing him with the necessary education, environment, and support, and to 2) to gain insight into the potential role of IRS-1 (insulin receptor substrate) in signal transduction of shear stress induced stimulation of NO production and the modulation of IRS-1 signaling by TNF-alpha. The candidate will be provided with extensive education in cardiovascular biochemistry, signal transduction, biophysics, research methods, and statistics. The candidate will be supported and mentored by Marshall Corson and Ruedi Aebersold who with the research advisory committee will monitor the candidate's progress. Finally, the Department of Medicine and Division of Cardiology will provide full commitment and support to developing the candidate's career as an independent investigator. The proposed research project is the foundation of attaining these goals. IRS-1 is a multi domain cytosolic protein that plays an important role in insulin signal transmission and has recently been shown to be used by multiple receptors for cytokines, growth hormones, interleukin and inteferons. We have obtained preliminary data implicating IRS-1 in mechanotranduction of FSS (fluid shear stress) in endothelial cell NO production. The major goal of the research proposal is to determine the molecular mechanisms regulating IRS-1 in this context. Type II diabetes is prevalent in the United States, affecting over 5 percent of the population. Type II diabetes involves defects in insulin action as well as insulin secretion. Insulin resistance is a state in which target cells fail to respond to ordinary levels of circulating insulin; at the molecular level, modifications in the insulin receptor (IR) or IRS-1 can lead to insulin resistance. TNF-alpha, which increases the serine phosphorylation of IRS-1, diminishes insulin induced tyrosine phosphorylation of IRS-1 and this modification of IRS-1 has recently been proposed as an important mediator of insulin resistance. Endothelial cells are not known to play a significant role in glucose metabolism and the role of IRS-1 in FSS endothelial NO signaling has not been previously studied. Our laboratory has recently reported that mechanotransduction of FSS in No production utilizes a P13-Kinase dependent pathway to phosphorylate eNOS. We hypothesize that shear stress induced NO production and insulin signaling share overlapping elements of the same signaling pathway and the same docking protein IRS-1 and that both pathways are modulated by TNF-alpha which increases the serine phosphorylation of IRS- 1. To further characterize this potential link between insulin and NO signaling. Specific Aim 3: Characterize FSS dependent signaling elements which associate with IRS-1.