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J. Biol. Chem., Vol. 282, Issue 41, 30273-30284, October 12, 2007
Characterization of a Mutation in the Phox Homology Domain of the NADPH Oxidase Component p40phox Identifies A Mechanism for Negative Regulation of Superoxide Production* 1![]() ![]() ![]() 2
From the
The phagocyte oxidase (Phox) protein p40phox contains a Phox homology (PX) domain which, when expressed alone, interacts with phosphatidylinositol 3-phosphate (PtdIns (3)P). The functions of the PX domain in p40phox localization, association with the cytoskeleton, and superoxide production were examined in transgenic COS-7 cells expressing gp91phox, p22phox, p67phox, and p47phox (COSphox cells). Full-length p40phox exhibited a cytoplasmic localization pattern in resting cells. Upon stimulation with phorbol 12-myristate 13-acetate or fMet-Leu-Phe, p40phox translocated to plasma membrane in a p67phox- and p47phox-dependent manner. Heterologous expression of p40phox markedly enhanced superoxide production in phorbol 12-myristate 13-acetate - and fMet-Leu-Phe-stimulated COSphox cells. Unexpectedly, mutation of Arg-57 in the PX domain to Gln, which abrogated PtdIns (3)P binding, produced a dominant inhibitory effect on agonist-induced superoxide production and membrane translocation of p47phox and p67phox. The mutant p40phox (p40R57Q) displayed increased association with actin and moesin and was found enriched in the Triton X-100-insoluble fraction along with p67phox and p47phox. The enhanced cytoskeleton association of p67phox and p47phox and the dominant inhibitory effect produced by the p40R57Q were alleviated when a second mutation at Asp-289, which eliminated p40phox interaction with p67phox, was introduced. Likewise, cytochalasin B treatment abolished the dominant inhibitory effect of p40R57Q on superoxide production. These findings suggest a dual regulatory mechanism through the PX domain of p40phox; its interaction with the actin cytoskeleton may stabilize NADPH oxidase in resting cells, and its binding of PtdIns (3)P potentiates superoxide production upon agonist stimulation. Both functions require the association of p40phox with p67phox.
Received for publication, May 30, 2007 , and in revised form, August 7, 2007. * This work was supported by National Institutes of Health Grants HL077806 and AI033503 (to R. D. Y.) and HL045635 (to M. C. D.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 Recipient of an American Heart Association Predoctoral Fellowship. 2 To whom correspondence should be addressed: Pharmacology, University of Illinois, 835 South Wolcott Ave., MC868, Chicago, IL 60612. Tel.: 312-996-5087; Fax: 312-996-7857; E-mail: yer{at}uic.edu.
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