title: Palmitoylation of superoxide dismutase 1 (SOD1) is increased for familial amyotrophic lateral sclerosis-linked SOD1 mutants.
abstract: Mutations in Cu,Zn-superoxide dismutase (mtSOD1) cause familial amyotrophic lateral sclerosis (FALS), a neurodegenerative disease resulting from motor neuron degeneration. Here, we demonstrate that wild type SOD1 (wtSOD1) undergoes palmitoylation, a reversible post-translational modification that can regulate protein structure, function, and localization. SOD1 palmitoylation was confirmed by multiple techniques, including acyl-biotin exchange, click chemistry, cysteine mutagenesis, and mass spectrometry. Mass spectrometry and cysteine mutagenesis demonstrated that cysteine residue 6 was the primary site of palmitoylation. The palmitoylation of FALS-linked mtSOD1s (A4V and G93A) was significantly increased relative to that of wtSOD1 expressed in HEK cells and a motor neuron cell line. The palmitoylation of FALS-linked mtSOD1s (G93A and G85R) was also increased relative to that of wtSOD1 when assayed from transgenic mouse spinal cords. We found that the level of SOD1 palmitoylation correlated with the level of membrane-associated SOD1, suggesting a role for palmitoylation in targeting SOD1 to membranes. We further observed that palmitoylation occurred predominantly on disulfide-reduced as opposed to disulfide-bonded SOD1, suggesting that immature SOD1 is the primarily palmitoylated species. Increases in SOD1 disulfide bonding and maturation with increased copper chaperone for SOD1 expression caused a decrease in wtSOD1 palmitoylation. Copper chaperone for SOD1 overexpression decreased A4V palmitoylation less than wtSOD1 and had little effect on G93A mtSOD1 palmitoylation. These findings suggest that SOD1 palmitoylation occurs prior to disulfide bonding during SOD1 maturation and that palmitoylation is increased when disulfide bonding is delayed or decreased as observed for several mtSOD1s.
authors.affiliation: Department of Neurobiology, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Antinone
authors.forename: Ghanashyam D
authors.initials: GD
authors.lastname: Ghadge
authors.forename: Tukiet T
authors.initials: TT
authors.lastname: Lam
authors.forename: Lijun
authors.initials: L
authors.lastname: Wang
authors.forename: Raymond P
authors.initials: RP
authors.lastname: Roos
authors.forename: William N
authors.initials: WN
authors.lastname: Green
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D054878:Lipoylation; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D013058:Mass Spectrometry; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D010084:Oxidation-Reduction; D011499:Protein Processing, Post-Translational; D013116:Spinal Cord / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics* / Q000378:metabolism; D000072105:Superoxide Dismutase-1
chemical_list: D004220:Disulfides; D008164:Luminescent Proteins; C000606290:SOD1 protein, human; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D003545:Cysteine
keywords: Amyotrophic Lateral Sclerosis (Lou Gehrig Disease); Neurodegenerative Diseases; Post-translational Modification; Protein Palmitoylation; Superoxide Dismutase (SOD)