Neutrophils play a key role in host-defence mechanisms against invading pathogens, using their capacity to migrate, engulf micro-organisms and produce toxic radicals. Protein kinase C (PKC) isotypes are important intracellular regulators of these processes in neutrophils. PKC isotypes themselves are controlled by interactions with lipids, Ca2+ and proteins. The C2-like domain of PKC-δ (δC2) has been identified as a protein-interaction domain in this PKC isotype. In the present paper we have investigated the contribution of protein interactions at this domain to the regulation/function of PKC-δ in neutrophils. Using affinity chromatography we identified actin as a δC2 binding partner in these cells. Fluorescein-labelled δC2, microinjected into immobilized neutrophils, interacts with filamentous actin (F-actin) inside the cell. PKC-δ co-localizes with F-actin in neutrophils, in lamellipodia at the leading edge of the cell. Stimulation with phorbol ester or IgG-opsonized Staphylococcus aureus results in co-ordinated redistribution of PKC-δ and F-actin, and a PKC-δ inhibitor inhibits these changes. Microinjection of δC2 also inhibits F-actin redistribution. Thus PKC-δ binds to F-actin through its C2 domain, and these interactions are important in regulating actin redistribution in neutrophils.
Abbreviations used: δC2, C2-like domain of PKC-δ; F-actin, filamentous actin; G-actin, globular actin; his-δC2, histidine-tagged δC2; MALDI–TOF, matrix-assisted laser-desorption ionization–time-of-flight; Ni-NTA, Ni2+-nitrilotriacetate; PKC, protein kinase C; TLCK, tosyl-lysylchloromethane; TRITC, tetramethylrhodamine β-isothiocyanate.