Insulin-stimulated hydrogen peroxide reversibly inhibits protein-tyrosine phosphatase 1B in vivo and enhances the early insulin action cascade

The insulin signaling pathway is activated by tyrosine phosphorylation of the insulin receptor and key postreceptor substrate proteins and balanced by the action of specific protein-tyrosine phosphatases (PTPases), PTPase activity, in turn, is highly regulated in vivo by oxidation/reduction reactions involving the cysteine thiol moiety required for catalysis, Here we show that insulin stimulation generates a burst of intracellular H2O2 in insulin-sensitive hepatoma and adipose cells that is associated with reversible oxidative inhibition of up to 62% of overall cellular PTPase activity, as measured by a novel method using strictly anaerobic conditions. The specific activity of immunoprecipitated PTP1B, a PTPase homolog implicated in the regulation of insulin signaling, was also strongly inhibited by up to 88% following insulin stimulation, Catalase pretreatment abolished the insulin-stimulated production of H2O2 as well as the inhibition of cellular PTPases, including PTP1B, and was associated with reduced insulin-stimulated tyrosine phosphorylation of its receptor and high M-r insulin receptor substrate (IRS) proteins. These data provide compelling new evidence for a redox signal that enhances the early insulin-stimulated cascade of tyrosine phosphorylation by oxidative inactivation of PTP1B and possibly other tyrosine phosphatases.