title: Nonnative SOD1 trimer is toxic to motor neurons in a model of amyotrophic lateral sclerosis.
abstract: Since the linking of mutations in the Cu,Zn superoxide dismutase gene (sod1) to amyotrophic lateral sclerosis (ALS) in 1993, researchers have sought the connection between SOD1 and motor neuron death. Disease-linked mutations tend to destabilize the native dimeric structure of SOD1, and plaques containing misfolded and aggregated SOD1 have been found in the motor neurons of patients with ALS. Despite advances in understanding of ALS disease progression and SOD1 folding and stability, cytotoxic species and mechanisms remain unknown, greatly impeding the search for and design of therapeutic interventions. Here, we definitively link cytotoxicity associated with SOD1 aggregation in ALS to a nonnative trimeric SOD1 species. We develop methodology for the incorporation of low-resolution experimental data into simulations toward the structural modeling of metastable, multidomain aggregation intermediates. We apply this methodology to derive the structure of a SOD1 trimer, which we validate in vitro and in hybridized motor neurons. We show that SOD1 mutants designed to promote trimerization increase cell death. Further, we demonstrate that the cytotoxicity of the designed mutants correlates with trimer stability, providing a direct link between the presence of misfolded oligomers and neuron death. Identification of cytotoxic species is the first and critical step in elucidating the molecular etiology of ALS, and the ability to manipulate formation of these species will provide an avenue for the development of future therapeutic strategies.
authors.affiliation: Curriculum in Bioinformatics and Computational Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599; Program in Molecular and Cellular Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599; Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599;
authors.forename: Elizabeth A
authors.identifier: http://orcid.org/0000-0002-7627-2198
authors.initials: EA
authors.lastname: Proctor
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599;
authors.forename: Lanette
authors.initials: L
authors.lastname: Fee
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599;
authors.forename: Yazhong
authors.initials: Y
authors.lastname: Tao
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599;
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Redler
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599;
authors.forename: James M
authors.initials: JM
authors.lastname: Fay
authors.affiliation: Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, NE 68198;
authors.forename: Yuliang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, NE 68198;
authors.forename: Zhengjian
authors.initials: Z
authors.lastname: Lv
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599;
authors.forename: Ian P
authors.initials: IP
authors.lastname: Mercer
authors.affiliation: Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599.
authors.forename: Mohanish
authors.initials: M
authors.lastname: Deshmukh
authors.affiliation: Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, NE 68198;
authors.forename: Yuri L
authors.initials: YL
authors.lastname: Lyubchenko
authors.affiliation: Curriculum in Bioinformatics and Computational Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599; Program in Molecular and Cellular Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599; Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599; dokh@unc.edu.
authors.forename: Nikolay V
authors.initials: NV
authors.lastname: Dokholyan
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000473:pathology*; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D004795:Enzyme Stability / Q000187:drug effects; D006801:Humans; D008954:Models, Biological; D008958:Models, Molecular; D009046:Motor Neurons / Q000187:drug effects / Q000473:pathology*; D050505:Mutant Proteins / Q000633:toxicity; D009154:Mutation / Q000235:genetics; D066329:Protein Aggregates / Q000187:drug effects; D011487:Protein Conformation; D017510:Protein Folding / Q000187:drug effects; D055503:Protein Multimerization / Q000187:drug effects; D013482:Superoxide Dismutase / Q000737:chemistry / Q000633:toxicity*
chemical_list: D050505:Mutant Proteins; D066329:Protein Aggregates; D013482:Superoxide Dismutase
keywords: ALS; neurodegeneration; protein aggregation; protein misfolding; structural modeling