Pertussis toxin inhibits fMet-Leu-Phe- but not phorbol ester-stimulated changes in rabbit neutrophils: role of G proteins in excitation response coupling

Abstract

Addition of pertussis toxin to rabbit neutrophils inhibits the fMet-Leu-Phe- induced increases in Na+ influx and in intracellular pH. In addition, pretreatment of the cells with the toxin inhibits the decrease in the levels of phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 4-phosphate and the enhanced production of phosphatidic acid produced by the chemotactic factor fMet-Leu-Phe. Furthermore, the fMet-Leu-Phe-induced changes in the phosphorylation of a 46-kDa protein and of several other proteins are also inhibited by the toxin. On the other hand, the phorbol 12-myristate 13-acetate (PMA)-induced increases in the phosphorylation of several proteins are not inhibited by the toxin. PMA, but not its inactive analogue 4 alpha-phorbol 12,13-didecanoate, was also found to stimulate Na+ influx and to increase the intracellular pH in rabbit neutrophils. These ionic effects, like those produced by fMet-Leu-Phe, are inhibited by amiloride. The stimulated Na+ influx and H+ efflux produced by the phorbol ester, on the other hand, are not inhibited by pertussis toxin. The results reported here suggest that the activity of the Na+/H+ antiport in neutrophils is regulated by protein kinase C; that the G-protein system, either directly or indirectly, is involved in the stimulus-response coupling sequence in these cells; and that the toxin acts at, or prior to, the steps responsible for the activation of phospholipase C, and it does not affect the sequence of reactions initiated by the activation of the protein kinase C.