title: Activation of the human neutrophil nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase by protein kinase C.
abstract: A variety of phagocytosable and soluble agonists stimulate the human neutrophil respiratory burst enzyme, NADPH-oxidase, an activity required for normal microbicidal function. Of these agonists, the phorbol esters, which stimulate diverse systems by their ability to substitute for diacylglycerol to activate protein kinase C (the major phorbol ester receptor), have now been shown to directly stimulate NADPH-oxidase through this same receptor. Almost 90% of the specific receptors for phorbol 12,13-dibutyrate (PDBu) were found in the cytosol upon subcellular fractionation. The dissociation constant for [3H]PDBu was 1.2 nM. No significant difference was found in the distribution of the receptor between subcellular fractions from resting as compared with phorbol 12-myristate 13-acetate (PMA)-stimulated neutrophils. On the basis of these binding studies, we were able to establish a reconstituted system in which PMA activated dormant NADPH-oxidase in a light membrane fraction when cytosol, NADPH, phosphatidylserine, or phosphatidylinositol and ATP were added. The calcium chelator, EGTA, inhibited the activation, which suggested a requirement for calcium at low concentrations. The half-maximally effective PMA dose was 1.1 nM, as predicted from the receptor content in these preparations. Reconstitution of oxidase activity was rapid, peaking within 1 min of incubation. Purified protein kinase C was able to substitute for the cytosol fraction, and accounted for 80% of the cytosol activity. These studies demonstrate that phorbol esters stimulate the neutrophil respiratory burst through activation of cytosolic protein kinase C, which in turn activates either a regulatory constituent or the NADPH-oxidase directly in the plasma membrane to generate an active O-2-generating system.
mesh_terms: D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D006801:Humans; D009247:NADH, NADPH Oxidoreductases / Q000097:blood*; D019255:NADPH Oxidases; D009504:Neutrophils / Q000201:enzymology*; D010743:Phospholipids / Q000502:physiology; D011493:Protein Kinase C / Q000097:blood*; D011955:Receptors, Drug; D011971:Receptors, Immunologic / Q000502:physiology; D013481:Superoxides / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D010743:Phospholipids; D011955:Receptors, Drug; D011971:Receptors, Immunologic; C083141:phorbol ester binding protein; C027776:phorbol ester receptor; D013481:Superoxides; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate