Regulation of tyrosine phosphorylation in neutrophils by the NADPH oxidase. Role of reactive oxygen intermediates

Abstract

Neutrophils possess a multicomponent NADPH-oxidase that produces large quantities of superoxide, which can in turn generate other reactive oxygen intermediates. Superoxide and its dismutation product, hydrogen peroxide, are powerful oxidants. Because the activity of certain tyrosine kinases and phosphatases can be affected by their redox state, we considered the possibility that endogenously generated reactive oxygen intermediates (ROI) may alter phosphotyrosine formation and thereby function as intra- or intercellular messengers in neutrophils. Exposure of human neutrophils to exogenous oxidants such as diamide induced marked tyrosine phosphorylation of several cellular proteins. More importantly, activation of the NADPH oxidase in permeabilized neutrophils, by direct stimulation of GTP-binding proteins, also resulted in enhanced tyrosine phosphorylation. The latter was NADPH-dependent, paralleled by production of superoxide, and was inhibited by diphenylene iodonium, an inhibitor of the flavoprotein component of the oxidase. Neutrophils, from a patient with chronic granulomatous disease, which are deficient in the production of ROI, demonstrated no such phosphotyrosine accumulation. We conclude that ROI produced by the NADPH oxidase can regulate tyrosine phosphorylation in granulocytes, possibly by effects of oxidation-sensitive tyrosine kinases and/or phosphatases.