title: Absence of ataxin-3 leads to cytoskeletal disorganization and increased cell death.
abstract: 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.
authors.affiliation: Life and Health Sciences Research Institute, University of Minho, Braga, Portugal.
authors.forename: Ana-João
authors.initials: AJ
authors.lastname: Rodrigues
authors.forename: Maria
authors.initials: M
authors.lastname: do Carmo Costa
authors.forename: Teresa-Luísa
authors.initials: TL
authors.lastname: Silva
authors.forename: Daniela
authors.initials: D
authors.lastname: Ferreira
authors.forename: Fernanda
authors.initials: F
authors.lastname: Bajanca
authors.forename: Elsa
authors.initials: E
authors.lastname: Logarinho
authors.forename: Patrícia
authors.initials: P
authors.lastname: Maciel
mesh_terms: D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D000067699:Ataxin-3; D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology; D003599:Cytoskeleton / Q000378:metabolism*; D022001:Focal Adhesions / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D020287:In Situ Nick-End Labeling; D039423:Integrin alpha1 / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D034622:RNA Interference; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology
chemical_list: D039423:Integrin alpha1; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C092341:ATXN3 protein, human; D000067699:Ataxin-3; C511594:Atxn3 protein, mouse