No abstract

Our laboratory is interested in understanding the regulation of NADPH oxidase activity in human monocyte/macrophages. Protein kinase C (PKC) is reported to be involved in regulating the phosphorylation of NADPH oxidase components in human neutrophils; however, the regulatory roles of specific isoforms of PKC in phosphorylating particular oxidase components have not been determined. In this study calphostin C, an inhibitor for both novel PKC (including PKCδ, -ε, -θ, and -η) and conventional PKC (including PKCα and -β), inhibited both phosphorylation and translocation of p47phox, an essential component of the monocyte NADPH oxidase. In contrast, GF109203X, a selective inhibitor of classical PKC and PKCε, did not affect the phosphorylation or translocation of p47phox, suggesting that PKCδ, -θ, or -η is required. Furthermore, rottlerin (at doses that inhibit PKCδ activity) inhibited the phosphorylation and translocation of p47phox. Rottlerin also inhibited O⨪2 production at similar doses. In addition to pharmacological inhibitors, PKCδ-specific antisense oligodeoxyribonucleotides were used. PKCδ antisense oligodeoxyribonucleotides inhibited the phosphorylation and translocation of p47phox in activated human monocytes. We also show, using the recombinant p47phox-GST fusion protein, that p47phox can serve as a substrate for PKCδ in vitro. Furthermore, lysate-derived PKCδ from activated monocytes phosphorylated p47phox in a rottlerin-sensitive manner. Together, these data suggest that PKCδ plays a pivotal role in stimulating monocyte NADPH oxidase activity through its regulation of the phosphorylation and translocation of p47phox.