Cytosolic Phospholipase A sub(2) (cPLA sub(2)) Regulation of Human Monocyte NADPH Oxidase Activity: cPLA sub(2) affects translocation but not phosphorylation of p67 super(phox) and p47 super(phox)

• Published in: The Journal of biological chemistry 2002-07, Vol.277 (28), p.25385-25392
• Main Authors: Zhao, X, Bey, E A, Wientjes, F B, Cathcart, M K
• Format: Article
• Language: English
• Subjects: NADPH oxidase; p47phox protein; p67phox protein; superoxide
• ISSN: 0021-9258

The NADPH oxidase of human monocytes is activated upon exposure to opsonized zymosan and a variety of other stimuli to catalyze the formation of superoxide anion. Assembly of the NADPH oxidase complex is believed to be a highly regulated process, and molecular mechanisms responsible for this regulation have yet to be fully elucidated. We have previously reported that cytosolic phospholipase A sub(2) (cPLA sub(2)) expression and activity are essential for superoxide anion production in activated human monocytes. In this study, we investigated the mechanisms involved in cPLA sub(2) regulation of NADPH oxidase activation by evaluating the effects of cPLA sub(2) on translocation and phosphorylation of p67 super(phox) and p47 super(hox). We report that translocation and phosphorylation of p67 super(phox), as well as p47 super(phox), occur upon activation of human monocytes and that decreased cPLA sub(2) protein expression, mediated by antisense oligodeoxyribonucleotides (AS-ODN) specific for cPLA sub(2) mRNA, blocked the stimulation-induced translocation of p47 super(phox) and p67 super(phox) from the cytosol to the membrane fraction. Inhibition of translocation of both p47 super(phox) and p67 super(phox) by cPLA sub(2) AS-ODN was above 85%. Arachidonic acid (AA), a product of cPLA sub(2) enzymatic activity, completely restored translocation of both of these oxidase components in the AS-ODN-treated, cPLA sub(2)-deficient human monocytes. These results represent the first report that cPLA sub(2) activity or AA is required for p67 super(phox) and p47 super(phox) translocation in human monocytes. Although cPLA sub(2) was required for translocation of p47 super(phox) and p67 super(phox), it did not influence phosphorylation of these components. These results suggest that one mechanism of cPLA sub(2) regulation of NADPH oxidase activity is to control the arachidonate-sensitive assembly of the complete oxidase complex through modulating the translocation of both p47 super(phox) and p67 super(phox). These studies provide insight into the mechanisms by which activation signals are transduced to allow the induction of superoxide anion production in human monocytes.