Identification of SHC as a substrate of the insulin receptor kinase distinct from the GAP-associated 62 kDa tyrosine phosphoprotein.

Insulin stimulated tyrosine phosphorylation of SHC, a SH2 containing protein, was demonstrated in Chinese hamster ovary cells overexpressing the insulin receptor by immunoblotting with antiphosphotyrosine antibodies and in vivo labeling. Insulin induced tyrosine phosphorylation of SHC occurred very rapidly (within 1 min) with a dose curve which paralleled the autophosphorylation of the insulin receptor. Phosphorylation of SHC appeared to occur to a high stoichiometry since insulin induced the majority of SHC to shift to a higher molecular weight. The tyrosine phosphorylated SHC was not bound by the GTPase activating protein of Ras although a distinct 62 kDa tyrosine phosphorylated protein was found to be associated in the same experiments. It also was not bound to the insulin receptor, phosphatidylinositol 3-kinase or insulin receptor substrate-1.