We have analysed the involvement of the β isotype of the protein kinase C (PKC) family in the activation of NADPH oxidase in primary neutrophils. Using immunofluorescence and cell fractionation, PKC-β is shown to be recruited to the plasma membrane upon stimulation with phorbol ester and to the phagosomal membrane upon phagocytosis of IgG-coated particles (Fcγ-receptor stimulus). The time course of recruitment is similar to that of NADPH oxidase activation by these stimuli. The PKC-β specific inhibitor 379196 inhibits the response to PMA as well as to IgG-coated bacteria. Partial inhibition occurs between 10 and 100 nM of inhibitor, the concentration at which PKC-β, but not other PKC isotypes, is targeted. Neutrophils isolated from a mouse that lacks PKC-β also showed an inhibition of NADPH oxidase activation by PMA and IgG-coated particles. The level of inhibition is comparable to that achieved with 379196 in human neutrophils. Thus the PKC-β isotype mediates activation of NADPH oxidase by PMA and by stimulation of Fcγ receptors in neutrophils.

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