NADPH oxidase activity controls phagosomal proteolysis in macrophages through modulation of the lumenal redox environment of phagosomes.
The phagosomal lumen in macrophages is the site of numerous interacting chemistries that mediate microbial killing, macromolecular degradation, and antigen processing. Using a non-hypothesis-based screen to explore the interconnectivity of phagosomal functions, we found that NADPH oxidase (NOX2) negatively regulates levels of proteolysis within the maturing phagosome of macrophages. Unlike the NOX2 mechanism of proteolytic control reported in dendritic cells, this phenomenon in macrophages is independent of changes to lumenal pH and is also independent of hydrolase delivery to the phagosome. We found that NOX2 mediates the inhibition of phagosomal proteolysis in macrophages through reversible oxidative inactivation of local cysteine cathepsins. We also show that NOX2 activity significantly compromises the phagosome's ability to reduce disulfides. These findings indicate that NOX2 oxidatively inactivates cysteine cathepsins through sustained ablation of the reductive capacity of the phagosomal lumen. This constitutes a unique mechanism of spatiotemporal control of phagosomal chemistries through the modulation of the local redox environment. In addition, this work further implicates the microbicidal effector NOX2 as a global modulator of phagosomal physiologies, particularly of those pertinent to antigen processing.
Rybicka
Joanna M
JM
Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada.
Balce
Dale R
DR
Khan
Morgan F
MF
Krohn
Regina M
RM
Yates
Robin M
RM
D000818:Animals; D055162:Biocatalysis; D002403:Cathepsins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008247:Lysosomes / Q000201:enzymology; D008264:Macrophages / Q000166:cytology / Q000201:enzymology*; D008562:Membrane Glycoproteins / Q000172:deficiency / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000172:deficiency / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000172:deficiency / Q000378:metabolism; D010084:Oxidation-Reduction; D010588:Phagosomes / Q000201:enzymology*; D017382:Reactive Oxygen Species / Q000378:metabolism
D008562:Membrane Glycoproteins; D017382:Reactive Oxygen Species; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D002403:Cathepsins