COMBINATION OF INSULINOMIMETIC AGENTS H2O2 AND VANADATE ENHANCES INSULIN-RECEPTOR MEDIATED TYROSINE PHOSPHORYLATION OF IRS-1 LEADING TO IRS-1 ASSOCIATION WITH THE PHOSPHATIDYLINOSITOL 3-KINASE

To analyze the mechanism of action of the insulinomimetic agents H2O2, vanadate, and pervanadate (H2O2 and vanadate), CHO cells or CHO cells that overexpress wild-type or mutant insulin receptor and/or the insulin receptor substrate (IRS-1) were used. H2O2 or vanadate treatment alone had little or no effect on tyrosine phosphorylation of eel lu lar protei ns; however, pervanadate treatment dramatically enhanced tyrosine phosphorylation of a number of proteins including the insulin receptor and IRS-1. However, the insulin receptor and IRS-1 coimmunoprecipitate from insulin-treated but not from pervanadate-treated cells. Pervanadate-induced tyrosine phosphorylation of the insulin receptor led to an increase in insulin receptor tyrosine kinase activity toward IRS-1 in vivo and IRS-1 peptides in vitro equal to that induced by insulin treatment. Pervanadate-enhanced phosphorylation of IRS-1 led to a fifteenfold increase in IRS-1-associated phosphatidylinositol (Ptdlns) 3-kinase activity. However, insulin receptor-associated Ptdlns 3-kinase activity from pervanadate-treated cells was not detectable, while insulin receptor-associated Ptdlns 3-kinase activity from insulin-treated cells was 20% of the IRS-1-associated activity. Thus, pervanadate but not H2O2 or vanadate alone under these conditions mimics many of insulin actions, but pervanadate treatment does not induce insulin receptor/IRS-1 association. (C) 1995 Wiley-Liss, Inc.