title: Superoxide dismutase 1 mutants related to amyotrophic lateral sclerosis induce endoplasmic stress in neuro2a cells.
abstract: One of the common features of damaged neurons in many neurodegenerative diseases is the presence of abnormal aggregates of the disease-related proteins. In amyotrophic lateral sclerosis (ALS) of both sporadic and familial forms, protein aggregates are found in the affected spinal cords. In familial ALS with mutations in copper-zinc superoxide dismutase 1 (SOD1), the propensity of SOD1 for aggregation is known to increase with the mutation. In the present study, we examined whether the aggregate-prone SOD1 mutants induce endoplasmic reticulum (ER) stress and the inhibition of the ER stress protects the cells. The ALS-related mutant G85R SOD1 and G93A SOD1 formed visible aggregates and caused cell death possibly by apoptosis when over-expressed in neuro2a cells. Interestingly, the rate of the mutant SOD1-induced cell death was greater than that of the visible aggregate formation. Expression of the mutant SOD1 caused signs of both early and late ER stress responses, namely, RNA-dependent protein kinase-like ER kinase and eukaryotic initiation factor alpha phosphorylation, Jun amino-terminal kinase activation, activating transcription factor 6-translocation, X-box binding protein 1 mRNA splicing, and caspase 12 activation. The X-box binding protein 1 mRNA splicing activation was also detected in the mutant SOD1-expressing cells even without the visible aggregates. The cell death induced by the mutant SOD1 over-expression looked like apoptosis as evidenced by nuclear morphology and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end labeling. Importantly, an ER stress inhibitor, salubrinal delayed the formation of insoluble aggregates of the mutant SOD1 and suppressed the mutant-induced cell death. In addition, over-expression of the ER-targeted Bcl-xL protected the cells from the mutant SOD1-induced cytotoxicity. These results suggest that the misfolding of ALS-related mutant SOD1 induces ER stress possibly prior to the formation of visible aggregates, which may contribute to the motor neuron degeneration in ALS pathogenesis.
authors.affiliation: Department of Molecular Biology, Sejong University, Seoul, Korea.
authors.forename: Yeo Kyoung
authors.initials: YK
authors.lastname: Oh
authors.forename: Ki Soon
authors.initials: KS
authors.lastname: Shin
authors.forename: Junying
authors.initials: J
authors.lastname: Yuan
authors.forename: Shin Jung
authors.initials: SJ
authors.lastname: Kang
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D000818:Animals; D045744:Cell Line, Tumor; D004721:Endoplasmic Reticulum / Q000201:enzymology* / Q000473:pathology; D006801:Humans; D051379:Mice; D009154:Mutation; D017510:Protein Folding; D013482:Superoxide Dismutase / Q000235:genetics* / Q000502:physiology; D000072105:Superoxide Dismutase-1
chemical_list: C000606290:SOD1 protein, human; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1