Immunochemical identification and translocation of protein kinase C zeta in human neutrophils

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Abstract
Western blots of human polymorphonuclear leukocyte (PMN) extracts were immunostained with antibodies specific for various protein kinase C (PKC) isoforms. Two bands corresponding to PKC type ξ with apparent molecular masses of 81 kDa and 76 kDa were identified in the cytosolic fraction of resting cells, in addition to PKC types α and β. PKCξ was apparently abundant, like PKCβ, whereas PKCδ, ‐ε, and ‐γ were not detectable. Following short stimulation (5 min) of PMN with phorbol‐12‐myristate‐13‐acetate (1 μ/ml), physical translocation of PKCξ from the cytosol to the plasma membrane fraction occurred, although this isoform does not bind phorbol esters. These data show that, in addition to the two calcium‐dependent isoenzymes α and β, human PMN express a calcium‐independent isoenzyme ξ which translocates in stimulated cells, suggesting a role in the regulation of antibacterial activities.