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Published on: October 4, 2017

Impaired post-translational folding of familial ALS-linked Cu, Zn superoxide dismutase mutants

Cami K Bruns1, Ron R Kopito

  • 1Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020, USA.

The EMBO Journal
|January 27, 2007
PubMed

Insights

Familial ALS mutations in superoxide dismutase (SOD1) impair its folding. This suggests misfolded SOD1 intermediates contribute to cytotoxicity and offer a unifying mechanism for SOD1-linked ALS.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Neuroscience

Background:

  • Over 110 missense mutations in the superoxide dismutase (SOD1) gene are linked to familial amyotrophic lateral sclerosis (FALS).
  • The precise mechanism by which these SOD1 mutations cause cytotoxicity remains largely unknown.
  • Understanding SOD1 protein folding is crucial for elucidating FALS pathogenesis.

Purpose of the Study:

  • To investigate the post-translational folding mechanism of wild-type and mutant human SOD1.
  • To determine the role of molecular chaperones and metal binding in SOD1 folding.
  • To explore how FALS-associated SOD1 mutations affect protein folding kinetics and stability.

Main Methods:

  • Synthesis of wild-type and mutant SOD1 in cell-free reticulocyte extracts.
  • Analysis of SOD1 folding kinetics and conformational states.
  • Assessment of the requirement for ATP-dependent molecular chaperones and metal ions (Zn2+, Cu2+) during folding.

Main Results:

  • Human SOD1 folds post-translationally into a hyperstable, native-like conformation without requiring ATP-dependent chaperones.
  • SOD1 folding is dependent on tight zinc binding but not copper binding.
  • All 11 FALS-associated SOD1 mutants examined exhibited delayed folding kinetics.
  • Mutant SOD1 proteins could still form native-like states, albeit with altered kinetics.

Conclusions:

  • Impaired post-translational folding of SOD1 mutants leads to increased populations of folding intermediates.
  • These aberrant SOD1 folding intermediates may represent a source of proteotoxicity in FALS.
  • Altered SOD1 folding kinetics provide a unifying mechanism for the pathogenesis of SOD1-linked FALS.

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