Protein kinase C-alpha participates in FcgammaR-mediated phagocytosis in macrophages.

Phagocytosis of IgG-opsonized particles by macrophages requires the activation of protein kinase C (PKC), a family of protein serine/threonine kinases. In the present study, we have investigated the role of the PKC-alpha isoenzyme in FcgammaR-mediated phagocytosis using clones of the mouse macrophage cell line RAW 264. 7 overexpressing a dominant-negative (DN) mutant of PKC-alpha. Overexpression of DN PKC-alpha had no effect on the attachment of IgG-opsonized sheep red blood cells, but inhibited their internalization. Further analysis of the signaling events induced by IgG-opsonized sheep red blood cells revealed that whereas tyrosine phosphorylation of Syk was normal, phosphorylation of ERK 1/2 (p42/44) was impaired in DN PKC-alpha-overexpressing macrophages. These observations suggest a role for PKC-alpha in the regulation of FcgammaR-induced phagocytosis and signal transduction. Copyright 2000 Academic Press.