title: Autophagy in spinal motor neurons of conditional ADAR2-knockout mice: An implication for a role of calcium in increased autophagy flux in ALS.
abstract: In the motor neurons of amyotrophic lateral sclerosis (ALS) patients, an RNA editing enzyme called adenosine deaminase acting on RNA 2 (ADAR2) is down-regulated and consequently GluA2 mRNAs unedited at the Q/R site is expressed in contrast to normal motor neurons that express only GluA2 edited at this site. Motor neurons of the mice lacking ADAR2 undergo Ca(2+)-permeable AMPA receptor-mediated slow death. We investigated the spinal cords of conditional ADAR2-knockout mice modeling ALS for the involvement of autophagy. In the motor neurons of the early- and late-symptomatic-stage mice, LC3-immunopositivity or immunoreactivity for both LC3- and p62 was observed, whereas the presymptomatic-stage mice showed no LC3- or p62-immunoreactivity. Western blot analyses showed increased expression of autophagy associated proteins in the anterior horn of the early symptomatic-stage mice. Electron-microscopically, autophagy was observed in the motor neurons most frequently in the early-symptomatic-stage mice which showed the severest motor neuron degeneration. Increased autophagy flux was not recognized in the wild-type mice or AR2res (ADAR2(flox/flox)/VAChT-Cre. Fast/GluR-B(R)(/)(R)) mice having motor neurons genetically engineered to express normally edited GluA2 in the absence of ADAR2, which show normal Ca(2+)-permeability of the AMPA receptors in motor neurons. Significantly increased autophagy flux in the degenerating motor neurons of ADAR2-knockout mice likely resulted from Ca(2+) overload.
authors.affiliation: Department of Neurology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan. Electronic address: ssasaki@nij.twmu.ac.jp.
authors.forename: Shoichi
authors.initials: S
authors.lastname: Sasaki
authors.affiliation: Department of Neurology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan. Electronic address: ssasaki@nij.twmu.ac.jp.
authors.forename: Soichi
authors.initials: S
authors.lastname: Sasaki
authors.affiliation: Department of Neurology, Graduate School of Medicine, University of Tokyo, Japan; Division of Clinical Biotechnology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, University of Tokyo, Japan.
authors.forename: Takenari
authors.initials: T
authors.lastname: Yamashita
authors.affiliation: Department of Neurology, Graduate School of Medicine, University of Tokyo, Japan; Division of Clinical Biotechnology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, University of Tokyo, Japan; Clinical Research Center for Medicine, International University of Health and Welfare, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Kwak
authors.affiliation: Department of Neurology, Graduate School of Medicine, University of Tokyo, Japan; Division of Clinical Biotechnology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, University of Tokyo, Japan; Clinical Research Center for Medicine, International University of Health and Welfare, Japan.
authors.forename: Kwak
authors.initials: K
authors.lastname: Shin
mesh_terms: D000243:Adenosine Deaminase / Q000235:genetics / Q000378:metabolism*; D000690:Amyotrophic Lateral Sclerosis / Q000378:metabolism / Q000473:pathology*; D000818:Animals; D001343:Autophagy; D002118:Calcium / Q000378:metabolism*; D018450:Disease Progression; D015536:Down-Regulation; D018345:Mice, Knockout; D009046:Motor Neurons / Q000378:metabolism / Q000473:pathology*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018091:Receptors, AMPA / Q000378:metabolism; D013116:Spinal Cord / Q000378:metabolism / Q000473:pathology*
chemical_list: D016601:RNA-Binding Proteins; D018091:Receptors, AMPA; C000595151:ADAR2 protein, mouse; D000243:Adenosine Deaminase; D002118:Calcium
keywords: ADAR2-knockout mice; AMPA receptor; Amyotrophic lateral sclerosis; Autophagy; Calcium; LC3