Proteasomal Inhibition by Misfolded Mutant Superoxide Dismutase 1 Induces Selective Motor Neuron Death in Familial Amyotrophic Lateral Sclerosis

J Neurochem. 2002 Dec;83(5):1030-42. doi: 10.1046/j.1471-4159.2002.01211.x.

Abstract

Accumulating evidence indicates that abnormal conformation of mutant superoxide dismutase 1 (SOD1) is an essential feature underlying the pathogenesis of mutant SOD1-linked familial amyotrophic lateral sclerosis (ALS). Here we investigated the role of ubiquitin-proteasome pathway in the mutant SOD1-related cell death and the effect of oxidative stress on the misfolding of mutant SOD1. Transient overexpression of ubiquitin with human SOD1 (wild-type, ala4val, gly85arg, gly93ala) in Neuro2A cells decreased the amount of mutant SOD1, but not of wild-type, while only mutants were co-immunoprecipitated with poly-ubiquitin. Proteasome inhibition by lactacystin augmented accumulation of mutant SOD1 in the non-ionic detergent-insoluble fraction. The spinal cord lysates from mutant SOD1 transgenic mice showed multiple carbonylated proteins, including mutant SOD1 with SDS-resistant dimer formation. Furthermore, the treatment of hSOD1-expressing cells with hydrogen peroxide promoted the oligomerization, and detergent-insolubility of mutant SOD1 alone, and the oxidized mutant SOD1 proteins were more heavily poly-ubiquitinated. In Neuro2A cells stably expressing human SOD1 protein, the proteasome function measured by chymotrypsin-like activity, was decreased over time without a quantitative alteration of the 20S proteasomal component. Finally, primary motor neurons from the mouse embryonic spinal cord were more vulnerable to lactacystin than non-motor neurons. These results indicate that the sustained expression of mutant SOD1 leads to proteasomal inhibition and motor neuronal death, which in part explains the pathogenesis of mutant SOD1-linked ALS.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • Amyotrophic Lateral Sclerosis / enzymology*
  • Amyotrophic Lateral Sclerosis / etiology
  • Animals
  • Cell Death
  • Cells, Cultured
  • Cysteine Endopeptidases / metabolism
  • Disease Models, Animal
  • Enzyme Activation
  • Gene Expression
  • Humans
  • Kidney / cytology
  • Kidney / metabolism
  • Macromolecular Substances
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Motor Neurons / cytology
  • Motor Neurons / metabolism*
  • Multienzyme Complexes / antagonists & inhibitors*
  • Multienzyme Complexes / metabolism
  • Neuroblastoma / metabolism
  • Oxidative Stress
  • Proteasome Endopeptidase Complex
  • Protein Denaturation
  • Protein Folding*
  • Solubility
  • Superoxide Dismutase / genetics
  • Superoxide Dismutase / metabolism*
  • Superoxide Dismutase-1
  • Ubiquitin / metabolism

Substances

  • Macromolecular Substances
  • Multienzyme Complexes
  • SOD1 protein, human
  • Ubiquitin
  • SOD1 G93A protein
  • Sod1 protein, mouse
  • Superoxide Dismutase
  • Superoxide Dismutase-1
  • Cysteine Endopeptidases
  • Proteasome Endopeptidase Complex