Interaction between the Grb10 SH2 domain and the insulin receptor carboxyl terminus

Abstract

Grb10 is a member of a recently identified family of adapter proteins that are thought to play a role in receptor tyrosine kinase-mediated signal transduction. We identified and isolated the Grb10 SH2 domain based on its interaction with the intracellular domain of the insulin receptor β-subunit using the yeast two-hybrid system. The interaction was specific for the insulin receptor and the insulin-like growth factor-1 receptor, and it required a catalytically active receptor kinase domain and an intact Grb10 SH2 domain. Glutathione S-transferase fusion proteins containing the Grb10 SH2 domain associated in an insulin-dependent manner with insulin receptors from cell lysates and with purified insulin receptors. Co-precipitation experiments revealed the association of cellular Grb10 with hormone- stimulated insulin receptors in cell extracts. The Grb10 SH2 domain did not bind to an insulin receptor lacking 43 amino acids at the carboxyl terminus, and it exhibited highest affinity for a phosphopeptide containing Tyr(P)- 1322. Unlike p85 and Syp, which also bind to Tyr(P)-1322, Grb10 was not found to associate with insulin receptor substrate-1. These results suggest that Grb10 is a novel insulin receptor interactive protein and provide direct evidence for an insulin receptor substrate-1-independent function of the insulin receptor carboxyl terminus in protein binding.