Staphylococcus albus-induced protein kinase C translocation in human neutrophils: the effect of opsonization, cytochalasin B, pertussis toxin, intra- and extracellular calcium, and R59022

Abstract

Membrane-associated protein kinase C has been proposed to be essential in transmembrane signalling systems activating neutrophils. A main function of the neutrophil is phagocytosis and killing of microorganisms. Nevertheless, previously published reports mainly have described the effect of artificial or soluble stimulators upon neutrophil protein kinase C activity. Therefore, membrane-associated protein kinase C was studied in neutrophils stimulated by Staphylococcus albus. The bacteria were found to induce a striking increase in membrane-associated protein kinase C, an effect which depended upon a previous opsonization of the bacteria. Cytochalasin B, which inhibits phagocytosis, was shown to abrogate S. albus-induced protein kinase C translocation. Chelation of intracellular calcium totally abolished S. albus-induced protein kinase C translocation, a phenomenon that could not exclusively be ascribed to chelation of extracellular calcium. The diacylglycerol kinase inhibitor R59022, which has been reported to increase endogenous diacylglycerol accumulation, nearly doubled the effect of S. albus upon membrane-associated protein kinase C. Pertussis toxin in concentrations which completely inhibited fLMP-induced superoxide generation did not affect S. albus-induced protein kinase C translocation. It is concluded that phagocytosis of S. albus is accompanied by a translocation of protein kinase C to the cell membrane, a phenomenon that relies upon enhanced diacylglycerol production and calcium transients and occurs independently of pertussis toxin-inhibitable G-proteins.