Inhibition of the transmembrane protein tyrosine phosphatase lar by 3S-peptide-I enhances insulin receptor phosphorylation in intact cells

Discrete region of the insulin receptor carboxyl terminus plays key role in insulin action

In the present study, we attempted to determine the importance of a 23-amino-acid sequence within the carboxyl terminus of the human insulin receptor (IR) molecule in modulating insulin action in Chinese hamster ovary cells. Stable expression of a minigene encoding the receptor fragment led to an increase in insulin-induced IR autophosphorylation that was 2.4-fold higher when compared to that of IR-expressing cells transfected with empty vector. Insulin-stimulated downstream signaling was also significantly elevated in cells expressing the minigene. It was found that expression of the minigene had no effect toward insulin-like growth factor I receptor kinase activity and function. These results indicate that the IR carboxyl terminus contains a motif that acts as a physiologic modulator of insulin signaling. J. Cell. Biochem. 78:160-169, 2000. Published 2000 Wiley-Liss, Inc.