title: Relationship between mutant Cu/Zn superoxide dismutase 1 maturation and inclusion formation in cell models.
abstract: A common property of Cu/Zn superoxide dismutase 1 (SOD1), harboring mutations associated with amyotrophic lateral sclerosis, is a high propensity to misfold and form abnormal aggregates. The aggregation of mutant SOD1 has been demonstrated in vitro, with purified proteins, in mouse models, in human tissues, and in cultured cell models. In vitro translation studies have determined that SOD1 with amyotrophic lateral sclerosis mutations is slower to mature, and thus perhaps vulnerable to off-pathway folding that could generate aggregates. The aggregation of mutant SOD1 in living cells can be monitored by tagging the protein with fluorescent fluorophores. In this study, we have taken advantage of the Dendra2 fluorophore technology in which excitation can be used to switch the output color from green to red, thereby clearly creating a time stamp that distinguishes pre-existing and newly made proteins. In cells that transiently over-express the Ala 4 to Val variant of SOD1-Dendra2, we observed that newly made mutant SOD1 was rapidly captured by pathologic intracellular inclusions. In cell models of mutant SOD1 aggregation over-expressing untagged A4V-SOD1, we observed that immature forms of the protein, lacking a Cu co-factor and a normal intramolecular disulfide, persist for extended periods. Our findings fit with a model in which immature forms of mutant A4V-SOD1, including newly made protein, are prone to misfolding and aggregation.
authors.affiliation: Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA.
authors.forename: Jacob I
authors.initials: JI
authors.lastname: Ayers
authors.affiliation: Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA.
authors.forename: Benjamin
authors.initials: B
authors.lastname: McMahon
authors.affiliation: Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Gill
authors.affiliation: Department of Chemistry and Biochemistry, UCLA, Los Angeles, California, USA.
authors.forename: Herman L
authors.initials: HL
authors.lastname: Lelie
authors.affiliation: Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Fromholt
authors.affiliation: Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA.
authors.forename: Hilda
authors.initials: H
authors.lastname: Brown
authors.affiliation: Department of Chemistry and Biochemistry, UCLA, Los Angeles, California, USA.
authors.forename: Joan Selverstone
authors.initials: JS
authors.lastname: Valentine
authors.affiliation: The Pasarow Mass Spectrometry Laboratory, NPI-Semel Institute, David Geffen School of Medicine, UCLA, Los Angeles, California, USA.
authors.forename: Julian P
authors.initials: JP
authors.lastname: Whitelegge
authors.affiliation: Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Borchelt
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D057809:HEK293 Cells; D006801:Humans; D002479:Inclusion Bodies / Q000201:enzymology* / Q000235:genetics*; D009154:Mutation / Q000502:physiology*; D066329:Protein Aggregates / Q000502:physiology; D017510:Protein Folding; D000072105:Superoxide Dismutase-1 / Q000096:biosynthesis* / Q000235:genetics*
chemical_list: D066329:Protein Aggregates; C000606290:SOD1 protein, human; D000072105:Superoxide Dismutase-1
keywords: aggregation; amyotrophic lateral sclerosis; live imaging; oxidation; superoxide dismutase 1