Irs-2 coordinates Igf-1 receptor-mediated beta-cell development and peripheral insulin signalling

Insulin receptor substrates (Irs proteins) mediate the pleiotropic effects of insulin and Igf-l (insulin-like growth factor-1), including regulation o f glucose homeostasis and cell growth and survival. We intercrossed mice he terozygous for two null alleles (Irs1(+/-) and Irs2(+/-)) and investigated growth and glucose metabolism in mice with viable genotypes. Our experiment s revealed that Irs-1 and Irs-2 are critical for embryonic and post-natal g rowth, with Irs-l having the predominant role. By contrast, both Irs-l and Irs-2 function in peripheral carbohydrate metabolism, but Irs-2 has the maj or role in beta-cell development and compensation for peripheral insulin re sistance. To establish a role for the Igf-l receptor in beta-cells, we inte rcrossed mice heterozygous for null alleles of Igf1r and Irs2. Our results reveal that Igf-l receptors promote beta-cell development and survival thro ugh the Irs-2 signalling pathway. Thus, Irs-2 integrates the effects of ins ulin in peripheral target tissues with Igf-l in pancreatic beta-cells to ma intain glucose homeostasis.