title: Endosomal Nox2 facilitates redox-dependent induction of NF-kappaB by TNF-alpha.
abstract: Growing evidence suggests that NADPH oxidase (Nox)-derived reactive oxygen species (ROS) play important roles in regulating cytokine signaling. We have explored how TNF-alpha induction of Nox-dependent ROS influences NF-kappaB activation. Cellular stimulation by TNF-alpha induced NADPH-dependent superoxide production in the endosomal compartment, and this ROS was required for IKK-mediated activation of NF-kappaB. Inhibiting endocytosis reduced the ability of TNF-alpha to induce both NADPH-dependent endosomal superoxide and NF-kappaB, supporting the notion that redox-dependent signaling of the receptor occurs in the endosome. Molecular analyses demonstrated that endosomal H(2)O(2) was critical for the recruitment of TRAF2 to the TNFR1/TRADD complex after endocytosis. Studies using both Nox2 siRNA and Nox2-knockout primary fibroblasts indicated that Nox2 was critical for TNF-alpha-mediated induction of endosomal superoxide. Redox-active endosomes that form after TNF-alpha or IL-1 beta induction recruit several common proteins (Rac1, Nox2, p67(phox), SOD1), while also retaining specificity for ligand-activated receptor effectors. Our studies suggest that TNF-alpha and IL-1 beta signaling pathways both can use Nox2 to facilitate redox activation of their respective receptors at the endosomal level by promoting the redox-dependent recruitment of TRAFs. These studies help to explain how cellular compartmentalization of redox signals can be used to direct receptor activation from the plasma membrane.
authors.affiliation: Department of Anatomy and Cell Biology, Carver College of Medicine, The University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
authors.forename: Netanya Y
authors.initials: NY
authors.lastname: Spencer
authors.forename: Fredrick D
authors.initials: FD
authors.lastname: Oakley
authors.forename: Garry R
authors.initials: GR
authors.lastname: Buettner
authors.forename: John F
authors.initials: JF
authors.lastname: Engelhardt
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002374:Catalase / Q000494:pharmacology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D034281:Dynamins / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology; D011992:Endosomes / Q000201:enzymology / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000235:genetics / Q000502:physiology; D006801:Humans; D047468:Immunoprecipitation; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000494:pharmacology; D000072105:Superoxide Dismutase-1; D013481:Superoxides / Q000378:metabolism; D047992:TNF Receptor-Associated Factor 2 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D000094765:Glutathione Peroxidase GPX1
chemical_list: D016328:NF-kappa B; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C000606290:SOD1 protein, human; D047992:TNF Receptor-Associated Factor 2; D014409:Tumor Necrosis Factor-alpha; D013481:Superoxides; D002374:Catalase; D005979:Glutathione Peroxidase; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D019255:NADPH Oxidases; D034281:Dynamins; D000094765:Glutathione Peroxidase GPX1