The Journal of Experimental Medicine
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Published online 31 July 2006 doi:10.1084/jem.20052085
Rockefeller University Press, 0022-1007 $8.00
JEM, Volume 203, Number 8, 1915-1925
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ARTICLE

 The phosphoinositide-binding protein p40phox activates the NADPH oxidase during Fc{gamma}IIA receptor–induced phagocytosis

Chang-Il Suh1, Natalie D. Stull1, Xing Jun Li1, Wei Tian1, Marianne O. Price1,3, Sergio Grinstein5, Michael B. Yaffe6, Simon Atkinson4, and Mary C. Dinauer1,2,3

1 Department of Pediatrics (Hematology/Oncology), Herman B Wells Center for Pediatric Research, Riley Hospital for Children, 2 Department of Microbiology/Immunology, 3 Department of Medical and Molecular Genetics, and 4 Department of Medicine (Nephrology), Indiana University School of Medicine, Indianapolis, IN 46202
5 Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
6 Department of Biology, Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139

CORRESPONDENCE Mary C. Dinauer: mdinauer{at}iupui.edu

Superoxide produced by the phagocyte reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is essential for host defense. Enzyme activation requires translocation of p67phox, p47phox, and Rac-GTP to flavocytochrome b558 in phagocyte membranes. To examine the regulation of phagocytosis-induced superoxide production, flavocytochrome b558, p47phox, p67phox, and the Fc{gamma}IIA receptor were expressed from stable transgenes in COS7 cells. The resulting COSphoxFc{gamma}R cells produce high levels of superoxide when stimulated with phorbol ester and efficiently ingest immunoglobulin (Ig)G-coated erythrocytes, but phagocytosis did not activate the NADPH oxidase. COS7 cells lack p40phox, whose role in the NADPH oxidase is poorly understood. p40phox contains SH3 and phagocyte oxidase and Bem1p (PB1) domains that can mediate binding to p47phox and p67phox, respectively, along with a PX domain that binds to phosphatidylinositol-3-phosphate (PI(3)P), which is generated in phagosomal membranes. Expression of p40phox was sufficient to activate superoxide production in COSphoxFc{gamma}R phagosomes. Fc{gamma}IIA-stimulated NADPH oxidase activity was abrogated by point mutations in p40phox that disrupt PI(3)P binding, or by simultaneous mutations in the SH3 and PB1 domains. Consistent with an essential role for PI(3)P in regulating the oxidase complex, phagosome NADPH oxidase activation in primary macrophages ingesting IgG-coated beads was inhibited by phosphatidylinositol 3 kinase inhibitors to a much greater extent than phagocytosis itself. Hence, this study identifies a role for p40phox and PI(3)P in coupling Fc{gamma}R-mediated phagocytosis to activation of the NADPH oxidase.

Abbreviations used: EYFP, enhanced yellow fluorescence protein; NADPH, reduced nicotinamide adenine dinucleotide phosphate; NBT, nitroblue tetrazolium; PB1, phagocyte oxidase and Bem1p; PEM, peritoneal exudate macrophage; PI3, phosphoinositide 3; PI(3)P, phosphatidylinositol-3-phosphate; PRR, proline-rich region.


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