Calpastatin-mediated inhibition of calpains in the mouse brain prevents mutant ataxin 3 proteolysis, nuclear localization and aggregation, relieving Machado-Joseph disease

Brain. 2012 Aug;135(Pt 8):2428-39. doi: 10.1093/brain/aws177.

Abstract

Machado-Joseph disease is the most frequently found dominantly-inherited cerebellar ataxia. Over-repetition of a CAG trinucleotide in the MJD1 gene translates into a polyglutamine tract within the ataxin 3 protein, which upon proteolysis may trigger Machado-Joseph disease. We investigated the role of calpains in the generation of toxic ataxin 3 fragments and pathogenesis of Machado-Joseph disease. For this purpose, we inhibited calpain activity in mouse models of Machado-Joseph disease by overexpressing the endogenous calpain-inhibitor calpastatin. Calpain blockage reduced the size and number of mutant ataxin 3 inclusions, neuronal dysfunction and neurodegeneration. By reducing fragmentation of ataxin 3, calpastatin overexpression modified the subcellular localization of mutant ataxin 3 restraining the protein in the cytoplasm, reducing aggregation and nuclear toxicity and overcoming calpastatin depletion observed upon mutant ataxin 3 expression. Our findings are the first in vivo proof that mutant ataxin 3 proteolysis by calpains mediates its translocation to the nucleus, aggregation and toxicity and that inhibition of calpains may provide an effective therapy for Machado-Joseph disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus / genetics*
  • Adult
  • Animals
  • Ataxin-3
  • Brain Chemistry / genetics*
  • Calcium-Binding Proteins / physiology*
  • Calpain / antagonists & inhibitors*
  • Calpain / genetics
  • Calpain / metabolism*
  • Female
  • Glycoproteins / antagonists & inhibitors*
  • Glycoproteins / biosynthesis
  • Glycoproteins / physiology
  • Humans
  • Machado-Joseph Disease / enzymology
  • Machado-Joseph Disease / metabolism*
  • Machado-Joseph Disease / prevention & control*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Middle Aged
  • Mutation / physiology
  • Neuroprotective Agents / pharmacology
  • Neuroprotective Agents / therapeutic use
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Proteolysis
  • Transcription Factors / genetics
  • Transcription Factors / metabolism

Substances

  • Calcium-Binding Proteins
  • Glycoproteins
  • Neuroprotective Agents
  • Nuclear Proteins
  • Transcription Factors
  • calpain inhibitors
  • calpastatin
  • Ataxin-3
  • Atxn3 protein, mouse
  • Calpain