Relationship between mutant Cu/Zn superoxide dismutase 1 maturation and inclusion formation in cell models. Issue 1 (25th November 2016)

• Record Type: Journal Article
• Authors: Ayers, Jacob I.; McMahon, Benjamin; Gill, Sabrina; Lelie, Herman L.; Fromholt, Susan; Brown, Hilda; Valentine, Joan Selverstone; Whitelegge, Julian P.; Borchelt, David R.
• Is Part Of: Journal of neurochemistry. Volume 140:Issue 1(2017)
• Page Start: 140
• Page End: 150
• Publication Date: 2016-11-25
• Subjects: aggregation -- amyotrophic lateral sclerosis -- live imaging -- oxidation -- superoxide dismutase 1; Neurochemistry -- Periodicals; 616.8042
• DOI: 10.1111/jnc.13864
• Languages: English
• ISSNs: 0022-3042

Abstract

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. Abstract : Mutations in Cu/Zn superoxide dismutase 1 (SOD1) may cause amyotrophic lateral sclerosis by causing the protein to misfold and aggregate. Here, we demonstrate that newly made mutant SOD1 is rapidly incorporated into growing pathologic intracellular inclusions. Furthermore, we link incomplete post‐translational maturation (metal binding and intramolecular disulfide oxidation) of mutant SOD1 to aggregation. These findings suggest that promoting the maturation of mutant SOD1 could produce therapeutic benefits.