INSULIN INDUCES TYROSINE PHOSPHORYLATION OF SHC AND STIMULATES SHC GRB2 ASSOCIATION IN INSULIN-SENSITIVE TISSUES OF THE INTACT RAT/

Shc is a novel type of tyrosine-phosphorylated protein activated in re sponse to a wide variety of polypeptide ligands. In this study, we use d immunoprecipitation and immunoblotting to examine the effect of insu lin on Shc tyrosine phosphorylation and Shc/GRB2 association in insuli n-sensitive tissues of the intact rat. Following an infusion of insuli n, Shc was tyrosine-phosphorylated in the liver, skeletal muscle, and adipose tissue in a time- and dose-dependent fashion, which peaked 5 m in after exposure to the hormone and, except in the case of adipose ti ssue, returned to basal values after 15 min. There was coimmunoprecipi tation of Shc and the insulin receptor after stimulation with insulin. Receptor tyrosine kinase activity toward Shc was also observed. Follo wing an infusion of insulin, Shc was found to associate with GRB2. The se results demonstrate that after stimulation of rat tissues with insu lin, Shc binds to the insulin receptor, is tyrosine-phosphorylated, an d subsequently associates with GRB2.