title: SOD1 mutations disrupt redox-sensitive Rac regulation of NADPH oxidase in a familial ALS model.
abstract: Neurodegeneration in familial amyotrophic lateral sclerosis (ALS) is associated with enhanced redox stress caused by dominant mutations in superoxide dismutase-1 (SOD1). SOD1 is a cytosolic enzyme that facilitates the conversion of superoxide (O(2)(*-)) to H(2)O(2). Here we demonstrate that SOD1 is not just a catabolic enzyme, but can also directly regulate NADPH oxidase-dependent (Nox-dependent) O(2)(*-) production by binding Rac1 and inhibiting its GTPase activity. Oxidation of Rac1 by H(2)O(2) uncoupled SOD1 binding in a reversible fashion, producing a self-regulating redox sensor for Nox-derived O(2)(*-) production. This process of redox-sensitive uncoupling of SOD1 from Rac1 was defective in SOD1 ALS mutants, leading to enhanced Rac1/Nox activation in transgenic mouse tissues and cell lines expressing ALS SOD1 mutants. Glial cell toxicity associated with expression of SOD1 mutants in culture was significantly attenuated by treatment with the Nox inhibitor apocynin. Treatment of ALS mice with apocynin also significantly increased their average life span. This redox sensor mechanism may explain the gain-of-function seen with certain SOD1 mutations associated with ALS and defines new therapeutic targets.
authors.affiliation: Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA.
authors.forename: Maged M
authors.initials: MM
authors.lastname: Harraz
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Marden
authors.forename: Weihong
authors.initials: W
authors.lastname: Zhou
authors.forename: Yulong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Aislinn
authors.initials: A
authors.lastname: Williams
authors.forename: Victor S
authors.initials: VS
authors.lastname: Sharov
authors.forename: Kathryn
authors.initials: K
authors.lastname: Nelson
authors.forename: Meihui
authors.initials: M
authors.lastname: Luo
authors.forename: Henry
authors.initials: H
authors.lastname: Paulson
authors.forename: Christian
authors.initials: C
authors.lastname: Schöneich
authors.forename: John F
authors.initials: JF
authors.lastname: Engelhardt
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D000690:Amyotrophic Lateral Sclerosis / Q000201:enzymology* / Q000235:genetics; D000818:Animals; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000633:toxicity; D008136:Longevity / Q000187:drug effects; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D010084:Oxidation-Reduction; D013482:Superoxide Dismutase / Q000235:genetics / Q000502:physiology*; D000072105:Superoxide Dismutase-1; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein
chemical_list: D000098:Acetophenones; D004791:Enzyme Inhibitors; D008562:Membrane Glycoproteins; D009479:Neuropeptides; C484602:Rac1 protein, mouse; C056165:acetovanillone; D006861:Hydrogen Peroxide; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein