title: Effect of CCS on the accumulation of FALS SOD1 mutant-containing aggregates and on mitochondrial translocation of SOD1 mutants: implication of a free radical hypothesis.
abstract: Missense mutations of SOD1 are linked to familial amyotrophic lateral sclerosis (FALS) through a yet-to-be identified toxic-gain-of-function. One of the proposed mechanisms involves enhanced aggregate formation. However, a recent study showed that dual transgenic mice overexpressing both G93A and CCS copper chaperone (G93A/CCS) exhibit no SOD1-positive aggregates yet show accelerated FALS symptoms with enhanced mitochondrial pathology compared to G93A mice. Using a dicistronic mRNA to simultaneously generate hSOD1 mutants, G93A, A4V and G85R, and hCCS in AAV293 cells, we revealed: (i) CCS is degraded primarily via a macroautophagy pathway. It forms a stable heterodimer with inactive G85R, and via its novel copper chaperone-independent molecular chaperone activity facilitates G85R degradation via a macroautophagy-mediated pathway. For active G93A and A4V, CCS catalyzes their maturation to form active and soluble homodimers. (ii) CCS reduces, under non-oxidative conditions, yet facilitates in the presence of H(2)O(2), mitochondrial translocation of inactive SOD1 mutants. These results, together with previous reports showing FALS SOD1 mutants enhanced free radical-generating activity, provide a mechanistic explanation for the observations with G93A/CCS dual transgenic mice and suggest that free radical generation by FALS SOD1, enhanced by CCS, may, in part, be responsible for the FALS SOD1 mutant-linked aggregation, mitochondrial translocation, and degradation.
authors.affiliation: Laboratory of Biochemistry, NHLBI, National Institutes of Health, Bethesda, MD 20892-8012, USA.
authors.forename: Ha Kun
authors.initials: HK
authors.lastname: Kim
authors.forename: Youn Wook
authors.initials: YW
authors.lastname: Chung
authors.forename: P Boon
authors.initials: PB
authors.lastname: Chock
authors.forename: Moon B
authors.initials: MB
authors.lastname: Yim
mesh_terms: D002460:Cell Line; D005609:Free Radicals / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D018832:Molecular Chaperones / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D018384:Oxidative Stress; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics; D013482:Superoxide Dismutase / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D000072105:Superoxide Dismutase-1
chemical_list: C114678:CCS protein, human; D005609:Free Radicals; D018832:Molecular Chaperones; D012333:RNA, Messenger; C000606290:SOD1 protein, human; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1