Starvation-increased Insulin-dependent Tyrosine Phosphorylation of the 195-kDa Protein in Intact Rat Liver

Abstract

Insulin stimulates tyrosine phosphorylation of 175-195 kDa proteins including insulin receptor substrate-1 (IRS-1) in various tissues and cell types. In intact rat livers, starvation increased the insulin-dependent tyrosine phosphorylation of the insulin receptor and IRS-1 as has been described by others. Surprisingly, starvation greatly increased the tyrosine phosphorylation of the 195-kDa protein induced by insulin, indicating that this protein may be a new substrate of the insulin receptor kinase. The marked increase in tyrosine phosphorylation of the 195-kDa protein may have a physiological role in signal transmission in response to insulin under starvation conditions.