title: The effects of glutaredoxin and copper activation pathways on the disulfide and stability of Cu,Zn superoxide dismutase.
abstract: Mutations in Cu,Zn superoxide dismutase (SOD1) can cause amyotrophic lateral sclerosis (ALS) through mechanisms proposed to involve SOD1 misfolding, but the intracellular factors that modulate folding and stability of SOD1 are largely unknown. By using yeast and mammalian expression systems, we demonstrate here that SOD1 stability is governed by post-translational modification factors that target the SOD1 disulfide. Oxidation of the human SOD1 disulfide in vivo was found to involve both the copper chaperone for SOD1 (CCS) and the CCS-independent pathway for copper activation. When both copper pathways were blocked, wild type SOD1 stably accumulated in yeast cells with a reduced disulfide, whereas ALS SOD1 mutants A4V, G93A, and G37R were degraded. We describe here an unprecedented role for the thiol oxidoreductase glutaredoxin in reducing the SOD1 disulfide and destabilizing ALS mutants. Specifically, the major cytosolic glutaredoxin of yeast was seen to reduce the intramolecular disulfide of ALS SOD1 mutant A4V SOD1 in vivo and in vitro. By comparison, glutaredoxin was less reactive toward the disulfide of wild type SOD1. The apo-form of A4V SOD1 was highly reactive with glutaredoxin but not SOD1 containing both copper and zinc. Glutaredoxin therefore preferentially targets the immature form of ALS mutant SOD1 lacking metal co-factors. Overall, these studies implicate a critical balance between cellular reductants such as glutaredoxin and copper activation pathways in controlling the disulfide and stability of SOD1 in vivo.
authors.affiliation: Department of Environmental Health Sciences, The Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland 21205, USA.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Carroll
authors.forename: Caryn E
authors.initials: CE
authors.lastname: Outten
authors.forename: Jody B
authors.initials: JB
authors.lastname: Proescher
authors.forename: Leah
authors.initials: L
authors.lastname: Rosenfeld
authors.forename: Walter H
authors.initials: WH
authors.lastname: Watson
authors.forename: Lisa J
authors.initials: LJ
authors.lastname: Whitson
authors.forename: P John
authors.initials: PJ
authors.lastname: Hart
authors.forename: Laran T
authors.initials: LT
authors.lastname: Jensen
authors.forename: Valeria
authors.initials: V
authors.lastname: Cizewski Culotta
mesh_terms: D003300:Copper / Q000737:chemistry / Q000378:metabolism*; D004220:Disulfides / Q000737:chemistry*; D005347:Fibroblasts / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D005786:Gene Expression Regulation; D054477:Glutaredoxins; D006801:Humans; D009154:Mutation; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013482:Superoxide Dismutase / Q000378:metabolism*
chemical_list: D004220:Disulfides; D005656:Fungal Proteins; D054477:Glutaredoxins; D013438:Sulfhydryl Compounds; D003300:Copper; D010088:Oxidoreductases; D013482:Superoxide Dismutase; D010100:Oxygen