Protein kinase C (PKC) isoforms translocate to triton-insoluble fractions in stimulated human neutrophils: Correlation of conventional PKC with activation of NADPH oxidase

The responses of human neutrophils (PMN) involve reorganization and phospho rylation of cytoskeletal components. We investigated the translocation of p rotein kinase C (PKC) isoforms to PMN cytoskeletal (Triton-insoluble) fract ions, in conjunction with activation of the respiratory burst enzyme NADPH oxidase. In resting PMN, PKC-delta (29%) and small amounts of PKC-alpha (0. 6%), but not PKC-beta II, were present in cytoskeletal fractions. Upon stim ulation with the PKC agonist PMA, the levels of PKC-alpha, PKC-beta II, and PKC-delta increased in the cytoskeletal fraction, concomitant with a decre ase in the noncytoskeletal (Triton-soluble) fractions. PKC-delta maximally associated with cytoskeletal fractions at 160 nM PMA and then declined, whi le PKC-alpha and PKC-beta II plateaued at 300 nM PMA. Translocation of PKC- delta was maximal by 2 min and sustained for at least 10 min. Translocation of PKC-alpha and PKC-beta II was biphasic, plateauing at 2-3 min and then increasing up to 10 min. Under maximal stimulation conditions, PKC isoforms were entirely cytoskeletal associated. Translocation of the NADPH oxidase component p47(phox) to the cytoskeletal fraction correlated with translocat ion of PKC-alpha and PKC-beta II, but not with translocation of PKC-delta. Oxidase activity in cytoskeletal fractions paralleled translocation of PKC- alpha, PKC-beta II, and p47(phox). Stimulation with 1,2-dioctanoylglycerol resulted in little translocation of PKC isoforms or p47(phox), and in minim al oxidase activity. We conclude that conventional PKC isoforms (PKC-alpha and/or PKC-beta II) may regulate PMA-stimulated cytoskeletal association an d activation of NADPH oxidase, PKC-delta may modulate other PMN responses t hat involve cytoskeletal components.