Polyglutamine-expanded ataxin-3 activates mitochondrial apoptotic pathway by upregulating Bax and downregulating Bcl-xL

An Hsun Chou, Tu Hsueh Yeh, Yu Li Kuo, Yu Cheng Kao, Mei Jie Jou, Chia Yu Hsu, Shu Ru Tsai, Akira Kakizuka, Hung Li Wang

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73 Citations (Scopus)


Spinocerebellar ataxia type 3 (SCA3) is an autosomal dominant neurodegenerative disease caused by polyglutamine-expanded ataxin-3. In the present study, we expressed disease-causing mutant ataxin-3-Q79 in neuronal cultures of cerebellum, striatum and substantia nigra by using recombinant adenoviruses. Subsequently, SCA3 cellular model was used to investigate the molecular mechanism by which ataxin-3-Q79 causes neuronal death. TUNEL staining studies showed that ataxin-3-Q79 induced apoptotic death of cerebellar, striatal or substantia nigra neurons. Ataxin-3-Q79 activated caspase-3 and caspase-9 without inducing the formation of active caspase-8. Ataxin-3-Q79 promoted mitochondrial release of cytochrome c and Smac, which was preceded by the upregulation of Bax protein and downregulation of Bcl-xL protein expression. Real-time TaqMan RT-PCR assays demonstrated that ataxin-3-Q79 upregulated Bax mRNA level and downregulated Bcl-xL mRNA expression in striatal, cerebellar and substantia nigra neurons. Our results suggest that polyglutamine-expanded ataxin-3-Q79 activates mitochondrial apoptotic pathway and induces neuronal death by upregulating Bax expression and downregulating Bcl-xL expression.

Original languageEnglish
Pages (from-to)333-345
Number of pages13
JournalNeurobiology of Disease
Issue number2
Publication statusPublished - Feb 2006
Externally publishedYes


  • Apoptosis
  • Ataxin-3
  • Bax
  • Bcl-x
  • Polyglutamine neurodegenerative disorders
  • Polyglutamine-expanded ataxin-3
  • Spinocerebellar ataxia type 3

ASJC Scopus subject areas

  • Neurology


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