title: Alsin and SOD1(G93A) proteins regulate endosomal reactive oxygen species production by glial cells and proinflammatory pathways responsible for neurotoxicity.
abstract: Recent studies have implicated enhanced Nox2-mediated reactive oxygen species (ROS) by microglia in the pathogenesis of motor neuron death observed in familial amyotrophic lateral sclerosis (ALS). In this context, ALS mutant forms of SOD1 enhance Rac1 activation, leading to increased Nox2-dependent microglial ROS production and neuron cell death in mice. It remains unclear if other genetic mutations that cause ALS also function through similar Nox-dependent pathways to enhance ROS-mediate motor neuron death. In the present study, we sought to understand whether alsin, which is mutated in an inherited juvenile form of ALS, functionally converges on Rac1-dependent pathways acted upon by SOD1(G93A) to regulate Nox-dependent ROS production. Our studies demonstrate that glial cell expression of SOD1(G93A) or wild type alsin induces ROS production, Rac1 activation, secretion of TNFα, and activation of NFκB, leading to decreased motor neuron survival in co-culture. Interestingly, coexpression of alsin, or shRNA against Nox2, with SOD1(G93A) in glial cells attenuated these proinflammatory indicators and protected motor neurons in co-culture, although shRNAs against Nox1 and Nox4 had little effect. SOD1(G93A) expression dramatically enhanced TNFα-mediated endosomal ROS in glial cells in a Rac1-dependent manner and alsin overexpression inhibited SOD1(G93A)-induced endosomal ROS and Rac1 activation. SOD1(G93A) expression enhanced recruitment of alsin to the endomembrane compartment in glial cells, suggesting that these two proteins act to modulate Nox2-dependent endosomal ROS and proinflammatory signals that modulate NFκB. These studies suggest that glial proinflammatory signals regulated by endosomal ROS are influenced by two gene products known to cause ALS.
authors.affiliation: Department of Anatomy and Cell Biology, The University of Iowa Carver College of Medicine, 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: Nicholas J
authors.initials: NJ
authors.lastname: Pantazis
authors.forename: John F
authors.initials: JF
authors.lastname: Engelhardt
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D000818:Animals; D002460:Cell Line; D011992:Endosomes / Q000201:enzymology* / Q000235:genetics; D004789:Enzyme Activation / Q000235:genetics; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009154:Mutation; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000074624:NADPH Oxidase 1; D000074662:NADPH Oxidase 2; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009457:Neuroglia / Q000201:enzymology* / Q000473:pathology; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D000072105:Superoxide Dismutase-1; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020830:rac1 GTP-Binding Protein
chemical_list: C512358:Als2 protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D009479:Neuropeptides; C484602:Rac1 protein, mouse; D017382:Reactive Oxygen Species; C000606290:SOD1 protein, human; D014409:Tumor Necrosis Factor-alpha; C109415:SOD1 G93A protein; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D009247:NADH, NADPH Oxidoreductases; C488842:Cybb protein, mouse; D000074624:NADPH Oxidase 1; D000074662:NADPH Oxidase 2; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C000614711:NOX1 protein, mouse; C422943:Nox4 protein, mouse; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein