Activation of protein kinase C in neutrophil cytoplasts

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Abstract
Treatment of enucleated, granule‐free neutrophil cytoplasts with the protein kinase C activator phorbol 12O‐myristate‐13‐acetate (PMA) causes an increased ‐32P‐incorporation into a variety of polypeptides. Permeabilization of PMA‐stimulated, 32P‐labeled cytoplasts by 0.01% digitonin fully releases the majority of these phosphorylated proteins. A statistically significant correlation is found between the extent of PMA‐induced activation of generation of Superoxide anion (O− 2) and the phosphorylation of a cytosolic polypeptide with an apparent M r, of 46000, whose ‐32P‐labeling is also enhanced by the treatment of cytoplasts with 1‐oleyl‐2‐acetylglycerol, the Ca2+ ionophore ionomycin or latex beads. Furthermore, treatment of cytoplasts with the protein kinase C inhibitor trifluoperazine markedly inhibits the 32P‐labeling of proteins in the 40000 M r range, including the 46 kDa polypeptide, and almost totally abolishes the activation of O− 2 production by PMA.