title: A phosphatidic acid-activated protein kinase and conventional protein kinase C isoforms phosphorylate p22(phox), an NADPH oxidase component.
abstract: Using a phosphorylation-dependent cell-free system to study NADPH oxidase activation (McPhail, L. C., Qualliotine-Mann, D., and Waite, K. A. (1995) Proc. Natl. Acad. Sci. U. S. A. 92, 7931-7935), we previously showed that p47(phox), a cytosolic NADPH oxidase component, is phosphorylated. Now, we show that p22(phox), a subunit of the NADPH oxidase component flavocytochrome b(558), also is phosphorylated. Phosphorylation is selectively activated by phosphatidic acid (PA) versus other lipids and occurs on a threonine residue in p22(phox). We identified two protein kinase families capable of phosphorylating p22(phox): 1) a potentially novel, partially purified PA-activated protein kinase(s) known to phosphorylate p47(phox) and postulated to mediate the phosphorylation-dependent activation of NADPH oxidase by PA and 2) conventional, but not novel or atypical, isoforms of protein kinase C (PKC). In contrast, all classes of PKC isoforms could phosphorylate p47(phox). In a gel retardation assay both the phosphatidic acid-dependent kinase and conventional PKC isoforms phosphorylated all molecules of p22(phox). These findings suggest that phosphorylation of p22(phox) by conventional PKC and/or a novel PA-activated protein kinase regulates the activation/assembly of NADPH oxidase.
authors.affiliation: Department of Biochemistry and Medicine, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
authors.forename: D S
authors.initials: DS
authors.lastname: Regier
authors.forename: K A
authors.initials: KA
authors.lastname: Waite
authors.forename: R
authors.initials: R
authors.lastname: Wallin
authors.forename: L C
authors.initials: LC
authors.lastname: McPhail
mesh_terms: D002474:Cell-Free System; D004789:Enzyme Activation; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D026901:Membrane Transport Proteins; D009252:NADPH Dehydrogenase / Q000737:chemistry / Q000378:metabolism*; D019255:NADPH Oxidases / Q000737:chemistry / Q000378:metabolism*; D010712:Phosphatidic Acids / Q000737:chemistry / Q000378:metabolism*; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000737:chemistry / Q000378:metabolism*
chemical_list: D007527:Isoenzymes; D026901:Membrane Transport Proteins; D010712:Phosphatidic Acids; D010750:Phosphoproteins; D019255:NADPH Oxidases; C086986:CYBA protein, human; D009252:NADPH Dehydrogenase; D011493:Protein Kinase C