Regulation of the phagocyte NADPH oxidase activity: phosphorylation of gp91phox/NOX2 by protein kinase C enhances its diaphorase activity and binding to Rac2, p67phox, and p47phox

Neutrophils generate microbicidal oxidants through activation of a multicomponent enzyme called NADPH oxidase. During activation, the cytosolic NADPH oxidase components (p47phox, p67phox, p40phox, and Rac2) translocate to the membranes, where they associate with flavocytochrome b558, which is composed of gp91phox/NOX2 and p22phox, to form the active system. During neutrophil stimulation, p47phox, p67phox, p40phox, and p22phox are phosphorylated; however, the phosphorylation of gp91phox/NOX2 and its potential role have not been defined. In this study, we show that gp91phox is phosphorylated in stimulated neutrophils. The gp91phox phosphoprotein is absent in neutrophils from chronic granulomatous disease patients deficient in gp91phox, which confirms that this phosphoprotein is gp91phox. The protein kinase C inhibitor GF109203X inhibited phorbol 12-myristate 13-acetate-induced phosphorylation of gp91phox, and protein kinase C (PKC) phosphorylated the recombinant gp91phox- cytosolic carboxy-terminal flavopro...