ASSOCIATION OF INSULIN-RECEPTOR SUBSTRATE-3 WITH SH2 DOMAIN-CONTAINING PROTEINS IN RAT ADIPOCYTES

We have recently purified and cloned a new member of the insulin recep tor substrate family, designated insulin receptor substrate 3 (IRS-3), from rat adipocytes. The amino acid sequence of IRS-3 shows multiple potential sites for tyrosine phosphorylation in motifs which engage sp ecific SH2 domain-containing proteins. In order to determine which SH2 domain proteins complex with IRS-3, we have searched for coimmunoprec ipitation from lysates of untreated and insulin-stimulated adipocytes, Phosphatidylinositol 3-kinase and the tyrosine phosphatase SHP-2 comp lexed with the tyrosine phosphorylated form of IRS-3, whereas the phos pholipase C gamma did not, and the adaptor Grb2 did so to a much lesse r extent. These findings complete the survey of SH2 domain proteins as sociated with each of the four known members of the IRS family and pro vide the framework for further analysis of the role of IRS-3 in insuli n signaling. (C) 1998 Academic Press.