title: Aberrant association of misfolded SOD1 with Na(+)/K(+)ATPase-α3 impairs its activity and contributes to motor neuron vulnerability in ALS.
abstract: Amyotrophic lateral sclerosis (ALS) is an adult onset progressive motor neuron disease with no cure. Transgenic mice overexpressing familial ALS associated human mutant SOD1 are a commonly used model for examining disease mechanisms. Presently, it is well accepted that alterations in motor neuron excitability and spinal circuits are pathological hallmarks of ALS, but the underlying molecular mechanisms remain unresolved. Here, we sought to understand whether the expression of mutant SOD1 protein could contribute to altering processes governing motor neuron excitability. We used the conformation specific antibody B8H10 which recognizes a misfolded state of SOD1 (misfSOD1) to longitudinally identify its interactome during early disease stage in SOD1G93A mice. This strategy identified a direct isozyme-specific association of misfSOD1 with Na(+)/K(+)ATPase-α3 leading to the premature impairment of its ATPase activity. Pharmacological inhibition of Na(+)/K(+)ATPase-α3 altered glutamate receptor 2 expression, modified cholinergic inputs and accelerated disease pathology. After mapping the site of direct association of misfSOD1 with Na(+)/K(+)ATPase-α3 onto a 10 amino acid stretch that is unique to Na(+)/K(+)ATPase-α3 but not found in the closely related Na(+)/K(+)ATPase-α1 isozyme, we generated a misfSOD1 binding deficient, but fully functional Na(+)/K(+)ATPase-α3 pump. Adeno associated virus (AAV)-mediated expression of this chimeric Na(+)/K(+)ATPase-α3 restored Na(+)/K(+)ATPase-α3 activity in the spinal cord, delayed pathological alterations and prolonged survival of SOD1G93A mice. Additionally, altered Na(+)/K(+)ATPase-α3 expression was observed in the spinal cord of individuals with sporadic and familial ALS. A fraction of sporadic ALS cases also presented B8H10 positive misfSOD1 immunoreactivity, suggesting that similar mechanism might contribute to the pathology.
authors.affiliation: Institute of Cell Biology, University of Bern, Bern, Switzerland.|Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland.
authors.forename: Céline
authors.initials: C
authors.lastname: Ruegsegger
authors.affiliation: Institute of Cell Biology, University of Bern, Bern, Switzerland.|Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland.
authors.forename: Niran
authors.initials: N
authors.lastname: Maharjan
authors.affiliation: Institute of Neuropathology, Rheinisch-Westfälische Technische Hochschule, Aachen University Hospital, Aachen, Germany.
authors.forename: Anand
authors.initials: A
authors.lastname: Goswami
authors.affiliation: Institute of Cell Biology, University of Bern, Bern, Switzerland.|Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland.|Department of Neuroscience, Genentech, Inc., South San Francisco, California, USA.
authors.forename: Audrey
authors.initials: A
authors.lastname: Filézac de L'Etang
authors.affiliation: Institute of Neuropathology, Rheinisch-Westfälische Technische Hochschule, Aachen University Hospital, Aachen, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Weis
authors.affiliation: Division of Neuropathology, Department of Pathology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Dirk
authors.initials: D
authors.lastname: Troost
authors.affiliation: Department of Clinical Research, Inselspital, University of Bern, Bern, Switzerland.
authors.forename: Manfred
authors.initials: M
authors.lastname: Heller
authors.affiliation: Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland.
authors.forename: Heinz
authors.initials: H
authors.lastname: Gut
authors.affiliation: Institute of Cell Biology, University of Bern, Bern, Switzerland. smita.saxena@izb.unibe.ch.
authors.forename: Smita
authors.identifier: http://orcid.org/0000-0003-4574-4591
authors.initials: S
authors.lastname: Saxena
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000378:metabolism / Q000503:physiopathology*; D000818:Animals; D015153:Blotting, Western; D004195:Disease Models, Animal; D006801:Humans; D047468:Immunoprecipitation; D013058:Mass Spectrometry; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D009046:Motor Neurons / Q000473:pathology*; D017510:Protein Folding; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000737:chemistry / Q000378:metabolism*; D000072105:Superoxide Dismutase-1; D014162:Transfection
chemical_list: D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D000254:Sodium-Potassium-Exchanging ATPase
keywords: ALS; Motor neuron excitability; Na+/K+ATPase-α3; SOD1 interactome; Sporadic and familial ALS