title: Mitochondrial ubiquitin ligase MITOL ubiquitinates mutant SOD1 and attenuates mutant SOD1-induced reactive oxygen species generation.
abstract: We have previously identified a novel mitochondrial ubiquitin ligase, MITOL, which is localized in the mitochondrial outer membrane and is involved in the control of mitochondrial dynamics. In this study, we examined whether MITOL eliminates misfolded proteins localized to mitochondria. Mutant superoxide dismutase1 (mSOD1), one of misfolded proteins, has been shown to localize in mitochondria and induce mitochondrial dysfunction, possibly involving in the onset and progression of amyotrophic lateral sclerosis. We found that in the mitochondria, MITOL interacted with and ubiquitinated mSOD1 but not wild-type SOD1. In vitro ubiquitination assay revealed that MITOL directly ubiquitinates mSOD1. Cycloheximide-chase assay in the Neuro2a cells indicated that MITOL overexpression promoted mSOD1 degradation and suppressed both the mitochondrial accumulation of mSOD1 and mSOD1-induced reactive oxygen species (ROS) generation. Conversely, the overexpression of MITOL CS mutant and MITOL knockdown by specific siRNAs resulted in increased accumulation of mSOD1 in mitochondria, which enhanced mSOD1-induced ROS generation and cell death. Thus, our findings indicate that MITOL plays a protective role against mitochondrial dysfunction caused by the mitochondrial accumulation of mSOD1 via the ubiquitin-proteasome pathway.
authors.affiliation: Laboratory of Molecular Biochemistry, School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Yonashiro
authors.forename: Ayumu
authors.initials: A
authors.lastname: Sugiura
authors.forename: Misako
authors.initials: M
authors.lastname: Miyachi
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Fukuda
authors.forename: Nobuko
authors.initials: N
authors.lastname: Matsushita
authors.forename: Ryoko
authors.initials: R
authors.lastname: Inatome
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Ogata
authors.forename: Takehiro
authors.initials: T
authors.lastname: Suzuki
authors.forename: Naoshi
authors.initials: N
authors.lastname: Dohmae
authors.forename: Shigeru
authors.initials: S
authors.lastname: Yanagi
mesh_terms: D000818:Animals; D002460:Cell Line; D006801:Humans; D008565:Membrane Proteins; D051379:Mice; D008928:Mitochondria / Q000201:enzymology*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D000072105:Superoxide Dismutase-1; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D017382:Reactive Oxygen Species; C000606290:SOD1 protein, human; D025801:Ubiquitin; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; C515578:MARCHF5 protein, human; D044767:Ubiquitin-Protein Ligases