Insulin receptor substrate–1 (IRS-1) is pivotal in mediating the actions of insulin and growth factors in most tissues of the body, but its role in insulin-producing β islet cells is unclear. Freshly isolated islets from IRS-1 knockout mice and SV40-transformed IRS-1–deficient β-cell lines exhibit marked insulin secretory defects in response to glucose and arginine. Furthermore, insulin expression is reduced by about 2-fold in the IRS-1–null islets and β-cell lines, and this defect can be partially restored by transfecting the cells with IRS-1. These data provide evidence for an important role of IRS-1 in islet function and provide a novel functional link between the insulin signaling and insulin secretion pathways.
Rohit N. Kulkarni, Jonathon N. Winnay, Molly Daniels, Jens C. Brüning, Sarah N. Flier, Douglas Hanahan, C. Ronald Kahn