부산대학교 도서관

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cellsig.2006.07.007 Byline: Qing Li (a), Venkita Subbulakshmi (a), Claudine M. Oldfield (a), Rozina Aamir (a), Crystal M. Weyman (b), Alan Wolfman (a)(b), Martha K. Cathcart (a)(b) Keywords: Human monocyte; Superoxide anion; Protein kinase C; Phospholipase; NADPH oxidase; Arachidonic acid; Chronic inflammation; Atherosclerosis Abstract: Phospholipases A.sub.2 (PLA.sub.2) are potent regulators of the inflammatory response. We have observed that Group IV cPLA.sub.2 activity is required for the production of superoxide anion (O.sub.2.sup.-) in human monocytes [Li Q., Cathcart M.K. J. Biol. Chem. 272 (4) (1997) 2404-2411.]. We have previously identified PKC[alpha] as a kinase pathway required for monocyte O.sub.2.sup.- production [Li Q., Cathcart M.K. J. Biol. Chem. 269 (26) (1994) 17508-17515.]. We therefore investigated the potential interaction between PKC[alpha] and cPLA.sub.2 by evaluating the requirement for specific PKC isoenzymes in the process of activating cPLA.sub.2 enzymatic activity and protein phosphorylation upon monocyte activation. We first showed that general PKC inhibitors and antisense oligodeoxyribonucleotides (ODN) to the cPKC group of PKC enzymes inhibited cPLA.sub.2 activity. To distinguish between PKC[alpha] and PKC[beta] isoenzymes in regulating cPLA.sub.2 protein phosphorylation and enzymatic activity, we employed our previously characterized PKC[alpha] or PKC[beta] isoenzyme-specific antisense ODN [Li Q., Subbulakshmi V., Fields A.P., Murray, N.R., Cathcart M.K., J. Biol. Chem. 274 (6) (1999) 3764-3771]. Suppression of PKC[alpha] expression, but not PKC[beta] expression, inhibited cPLA.sub.2 protein phosphorylation and enzymatic activity. Additional studies ruled out a contribution by Erk1/2 to cPLA.sub.2 phosphorylation and activation. We also found that cPLA.sub.2 co-immunoprecipitated with PKC[alpha] and vice versa. In vitro studies demonstrated that PKC[alpha] could directly phosphorylate cPLA.sub.2.and enhance enzymatic activity. Finally, we showed that addition of arachidonic acid restored the production of O.sub.2.sup.- in monocytes defective in either PKC[alpha] or cPLA.sub.2 expression. Taken together, our data suggest that PKC[alpha], but not PKC[beta], is the predominant cPKC isoenzyme required for cPLA.sub.2 protein phosphorylation and maximal induction of cPLA.sub.2 enzymatic activity upon activation of human monocytes. Our data also support the concept that the requirements for PKC[alpha] and cPLA.sub.2 in O.sub.2.sup.- generation are solely due to their seminal role in generating arachidonic acid. Author Affiliation: (a) Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, United States (b) Department of Biology, Geology and Environmental Sciences, Cleveland State University, Cleveland, OH 44115, United States Article History: Received 14 July 2006; Accepted 18 July 2006