Polyglutamine-expanded ataxin-7 activates mitochondrial apoptotic pathway of cerebellar neurons by upregulating Bax and downregulating Bcl-xL

Hung Li Wang, Tu Hsueh Yeh, An Hsun Chou, Yu Li Kuo, Li Jean Luo, Cai Ying He, Pei Chen Huang, Allen Hon Lun Li

Research output: Contribution to journalArticle

46 Citations (Scopus)

Abstract

Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant neurodegenerative disorder caused by polyglutamine-expanded ataxin-7. In the present investigation, we expressed disease-causing mutant ataxin-7-Q75 in the primary neuronal culture of cerebellum with the aid of recombinant adenoviruses. Subsequently, this in vitro cellular model of SCA7 was used to study the molecular mechanism by which mutant ataxin-7-Q75 induces neuronal death. TUNEL staining studies indicated that polyglutamine-expanded ataxin-7-Q75 caused apoptotic cell death of cultured cerebellar neurons. Mutant ataxin-7-Q75 induced the formation of active caspase-3 and caspase-9 without activating caspase-8. Polyglutamine-expanded ataxin-7-Q75 promoted the release of apoptogenic cytochrome-c and Smac from mitochondria, which was preceded by the downregulation of Bcl-xL protein and upregulation of Bax protein expression in cultured cerebellar neurons. Further real-time TaqMan RT-PCR assays showed that mutant ataxin-7-Q75 upregulated Bax mRNA level and downregulated Bcl-xL mRNA expression in the primary neuronal culture of cerebellum. The present study provides the evidence that polyglutamine- expanded ataxin-7-Q75 activates mitochondria-mediated apoptotic cascade and induces neuronal death by upregulating Bax expression and downregulating Bcl-xL expression of cerebellar neurons.

Original languageEnglish
Pages (from-to)541-552
Number of pages12
JournalCellular Signalling
Volume18
Issue number4
DOIs
Publication statusPublished - Apr 2006
Externally publishedYes

Fingerprint

Down-Regulation
Neurons
Spinocerebellar Ataxias
Cerebellum
Mitochondria
bcl-2-Associated X Protein
Messenger RNA
Ataxin-7
polyglutamine
Caspase 9
Caspase 8
In Situ Nick-End Labeling
Cytochromes c
Adenoviridae
Caspase 3
Neurodegenerative Diseases
Cell Death
Up-Regulation
Staining and Labeling
Polymerase Chain Reaction

Keywords

  • Apoptosis
  • Ataxin-7
  • Cerebellum
  • Polyglutamine neurodegenerative disorders
  • Polyglutamine-expanded ataxin-7
  • Spinocerebellar ataxia type 7

ASJC Scopus subject areas

  • Cell Biology

Cite this

Polyglutamine-expanded ataxin-7 activates mitochondrial apoptotic pathway of cerebellar neurons by upregulating Bax and downregulating Bcl-xL. / Wang, Hung Li; Yeh, Tu Hsueh; Chou, An Hsun; Kuo, Yu Li; Luo, Li Jean; He, Cai Ying; Huang, Pei Chen; Li, Allen Hon Lun.

In: Cellular Signalling, Vol. 18, No. 4, 04.2006, p. 541-552.

Research output: Contribution to journalArticle

Wang, Hung Li ; Yeh, Tu Hsueh ; Chou, An Hsun ; Kuo, Yu Li ; Luo, Li Jean ; He, Cai Ying ; Huang, Pei Chen ; Li, Allen Hon Lun. / Polyglutamine-expanded ataxin-7 activates mitochondrial apoptotic pathway of cerebellar neurons by upregulating Bax and downregulating Bcl-xL. In: Cellular Signalling. 2006 ; Vol. 18, No. 4. pp. 541-552.
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AB - Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant neurodegenerative disorder caused by polyglutamine-expanded ataxin-7. In the present investigation, we expressed disease-causing mutant ataxin-7-Q75 in the primary neuronal culture of cerebellum with the aid of recombinant adenoviruses. Subsequently, this in vitro cellular model of SCA7 was used to study the molecular mechanism by which mutant ataxin-7-Q75 induces neuronal death. TUNEL staining studies indicated that polyglutamine-expanded ataxin-7-Q75 caused apoptotic cell death of cultured cerebellar neurons. Mutant ataxin-7-Q75 induced the formation of active caspase-3 and caspase-9 without activating caspase-8. Polyglutamine-expanded ataxin-7-Q75 promoted the release of apoptogenic cytochrome-c and Smac from mitochondria, which was preceded by the downregulation of Bcl-xL protein and upregulation of Bax protein expression in cultured cerebellar neurons. Further real-time TaqMan RT-PCR assays showed that mutant ataxin-7-Q75 upregulated Bax mRNA level and downregulated Bcl-xL mRNA expression in the primary neuronal culture of cerebellum. The present study provides the evidence that polyglutamine- expanded ataxin-7-Q75 activates mitochondria-mediated apoptotic cascade and induces neuronal death by upregulating Bax expression and downregulating Bcl-xL expression of cerebellar neurons.

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