title: Reduced net charge and heterogeneity of pI isoforms in familial amyotrophic lateral sclerosis mutants of copper/zinc superoxide dismutase.
abstract: Familial cases of amyotrophic lateral sclerosis (fALS) are related to mutations of copper/zinc superoxide dismutase 1 (SOD1). Aggregation of SOD1 plays a central role in the pathogenesis of fALS and altered metallation of SOD1 mutants could be involved in this process. Using IEF gel electrophoresis under non-denaturating conditions and particle induced X-ray emission (PIXE) analysis, we studied the pI distribution and metallation status of fALS SOD1 mutants (A4V, G93A, D125H) compared to human wild-type (hWT). SOD1 fALS mutants are characterized by a variable number of isoforms and higher pI compared to hWT, reflecting a reduced net charge that might explain their greater propensity to precipitation and aggregation. Cu/Zn ratios were slightly different for the predominant expressed isoforms of A4V, G93A, and D125H mutants compared to hWT. Differences in metallation were observed within each genotype, the more basic isoforms exhibiting lower Cu/Zn ratios. Moreover, we revealed the existence of a pool of fALS mutants SOD1 pI isoforms, slightly expressed (<10%), with a low Cu/Zn ratio and high pI values. Overall, IEF-PIXE results suggest that the toxicity of SOD1 mutants should be studied at the pI isoform level with a particular attention to the species with the lowest charges.
authors.affiliation: University of Bordeaux, CENBG, UMR 5797, Gradignan, France.|CNRS, IN2P3, CENBG, UMR 5797, Gradignan, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Roudeau
authors.affiliation: University of Bordeaux, CENBG, UMR 5797, Gradignan, France.|CNRS, IN2P3, CENBG, UMR 5797, Gradignan, France.
authors.forename: Sylviane
authors.initials: S
authors.lastname: Chevreux
authors.affiliation: University of Bordeaux, CENBG, UMR 5797, Gradignan, France.|CNRS, IN2P3, CENBG, UMR 5797, Gradignan, France.
authors.forename: Asuncion
authors.initials: A
authors.lastname: Carmona
authors.affiliation: University of Bordeaux, CENBG, UMR 5797, Gradignan, France.|CNRS, IN2P3, CENBG, UMR 5797, Gradignan, France.
authors.forename: Richard
authors.initials: R
authors.lastname: Ortega
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics*; D006801:Humans; D007525:Isoelectric Focusing; D009154:Mutation / Q000235:genetics*; D013482:Superoxide Dismutase / Q000235:genetics*; D000072105:Superoxide Dismutase-1
chemical_list: C000606290:SOD1 protein, human; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1
keywords: Amyotrophic lateral sclerosis; IEF; Metalloproteins; Particle-induced X-ray emission; Superoxide dismutase