Absence of ataxin-3 leads to cytoskeletal disorganization and increased cell death

Biochim Biophys Acta. 2010 Oct;1803(10):1154-63. doi: 10.1016/j.bbamcr.2010.07.004. Epub 2010 Jul 15.


Ataxin-3 (ATXN3) is a widely expressed protein that binds to ubiquitylated proteins, has deubiquitylating activity in vitro and is thought to modulate substrate degradation through the ubiquitin-proteasome pathway. Expansion of a polyglutamine tract in ATXN3 causes Machado-Joseph disease, a late-onset neurodegenerative disorder characterized by ubiquitin-positive aggregate formation and specific neuronal death. Although ATXN3 has been involved in transcriptional repression and in the ubiquitin-proteasome pathway, its biological function is still unknown. In this work, we show that depletion of ATXN3 using small-interference RNA (siRNA) causes a prominent phenotype in both human and mouse cell lines. A mild increase in ubiquitylation occurs and cells exhibit ubiquitin-positive foci, which is consistent with ATXN3 putative function as a deubiquitylating enzyme. In addition, siATXN3-silenced cells exhibit marked morphological changes such as rounder shape and loss of adhesion protrusions. At a structural level, the microtubule, microfilament and intermediate filament networks are severely compromised and disorganized. This cytoskeletal phenotype is reversible and dependent on ATXN3 levels. Cell-extracellular matrix connection is also affected in ATXN3-depleted cells as talin expression is reduced in the focal adhesions and lower levels of alpha-1 integrin subunit are expressed at their surface. Although the cytoskeletal and adhesion problems do not originate any major change in the cell cycle of siATXN3-depleted cells, cell death is increased in siATXN3 cultures compared to controls. In summary, in this work we show that the absence of ATXN3 leads to an overt cytoskeletal/adhesion defect raising the possibility that this protein may play a role in the cytoskeleton.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Animals
  • Apoptosis / physiology*
  • Ataxin-3
  • Blotting, Western
  • Cell Cycle / physiology
  • Cytoskeleton / metabolism*
  • Focal Adhesions / physiology
  • HeLa Cells
  • Humans
  • In Situ Nick-End Labeling
  • Integrin alpha1 / metabolism
  • Mice
  • Microscopy, Confocal
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • Nerve Tissue Proteins / physiology*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Nuclear Proteins / physiology*
  • RNA Interference
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism
  • Repressor Proteins / physiology*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcription Factors / physiology


  • Integrin alpha1
  • Nerve Tissue Proteins
  • Nuclear Proteins
  • Repressor Proteins
  • Transcription Factors
  • ATXN3 protein, human
  • Ataxin-3
  • Atxn3 protein, mouse