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 t he insulin receptor and key postreceptor substrate proteins and balanced by the action of specific protein-tyrosine phosphatases (PTPases), PTPase act ivity, in turn, is highly regulated in vivo by oxidation/reduction reaction s 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 ox idative inhibition of up to 62% of overall cellular PTPase activity, as mea sured by a novel method using strictly anaerobic conditions. The specific a ctivity of immunoprecipitated PTP1B, a PTPase homolog implicated in the reg ulation of insulin signaling, was also strongly inhibited by up to 88% foll owing insulin stimulation, Catalase pretreatment abolished the insulin-stim ulated production of H2O2 as well as the inhibition of cellular PTPases, in cluding PTP1B, and was associated with reduced insulin-stimulated tyrosine phosphorylation of its receptor and high M-r insulin receptor substrate (IR S) proteins. These data provide compelling new evidence for a redox signal that enhances the early insulin-stimulated cascade of tyrosine phosphorylat ion by oxidative inactivation of PTP1B and possibly other tyrosine phosphat ases.