title: Ligation of FcγR Alters Phagosomal Processing of Protein via Augmentation of NADPH Oxidase Activity.
abstract: Proteolysis and the reduction of disulfides, both major components of protein degradation, are profoundly influenced by phagosomal redox conditions in macrophages. We evaluated the activation of phagocytic receptors that are known to influence activation of the phagocyte NADPH oxidase (NOX2), and its effect on phagosomal protein degradation. Population-based and single phagosome analyses of phagosomal chemistries in murine macrophages revealed that activation of NOX2 via the Fcγ receptor (FcγR) during phagocytosis decreased rates of proteolysis and disulfide reduction. Immunoglobulin G (IgG)-stimulated reactive oxygen species (ROS) production and the inhibition of phagosomal proteolysis and disulfide reduction were dependent on NOX2, FcγR and protein kinase C (PKC)/spleen tyrosine kinase (Syk) signaling. In contrast, low levels of ROS production were observed following the phagocytosis of unopsonized beads, which resulted in higher rates of phagosomal proteolysis and disulfide reduction. Phagosomes displayed autonomy with respect to FcγR-mediated differences in NOX2 activation and proteolysis, as phagosomes containing unopsonized cargo retained low NOX2 activation and high proteolysis even in the presence of phagosomes containing IgG-opsonized cargo in the same macrophage. These results show that opsonization of phagocytic cargo results in vastly different phagosomal processing of proteins through the FcγR-triggered, PKC/Syk-dependent local assembly and activation of NOX2.
authors.affiliation: Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, Calgary, Canada.
authors.forename: Dale R
authors.initials: DR
authors.lastname: Balce
authors.affiliation: Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, Calgary, Canada.
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Rybicka
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Calgary, Calgary, Canada.
authors.forename: Catherine J
authors.initials: CJ
authors.lastname: Greene
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Calgary, Calgary, Canada.
authors.forename: Benjamin W
authors.initials: BW
authors.lastname: Ewanchuk
authors.affiliation: Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, Calgary, Canada.|Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Calgary, Calgary, Canada.
authors.forename: Robin M
authors.identifier: 0000-0003-3122-1845
authors.initials: RM
authors.lastname: Yates
mesh_terms: D000818:Animals; D004220:Disulfides / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D008264:Macrophages / Q000201:enzymology / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D010587:Phagocytosis / Q000502:physiology*; D010588:Phagosomes / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D059748:Proteolysis; D017382:Reactive Oxygen Species / Q000378:metabolism; D017452:Receptors, IgG / Q000235:genetics / Q000378:metabolism*
chemical_list: D004220:Disulfides; D008562:Membrane Glycoproteins; D017382:Reactive Oxygen Species; D017452:Receptors, IgG; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases
keywords: Fc receptor; NADPH oxidase; antigen processing; disulfide reduction; endosome; lysosome; macrophage; phagosome; proteolysis; reactive oxygen species; redox