Chou An-Hsun, Yeh Tu-Hsueh, Kuo Yu-Li, Kao Yu-Cheng, Jou Mei-Jie, Hsu Chia-Yu, Tsai Shu-Ru, Kakizuka Akira, Wang Hung-Li
Department of Anesthesiology, Chang Gung Memorial Hospital, Taiwan, ROC.
Neurobiol Dis. 2006 Feb;21(2):333-45. doi: 10.1016/j.nbd.2005.07.011. Epub 2005 Aug 19.
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-x(L) 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.
3型脊髓小脑共济失调（SCA3）是一种由多聚谷氨酰胺扩增的ataxin-3引起的常染色体显性神经退行性疾病。在本研究中，我们通过使用重组腺病毒在小脑、纹状体和黑质的神经元培养物中表达致病突变体ataxin-3-Q79。随后，利用SCA3细胞模型研究ataxin-3-Q79导致神经元死亡的分子机制。TUNEL染色研究表明，ataxin-3-Q79诱导小脑、纹状体或黑质神经元的凋亡性死亡。ataxin-3-Q79激活了caspase-3和caspase-9，但未诱导活性caspase-8的形成。ataxin-3-Q79促进了细胞色素c和Smac从线粒体的释放，这之前Bax蛋白表达上调，Bcl-x(L)蛋白表达下调。实时TaqMan RT-PCR分析表明，ataxin-3-Q79上调了纹状体、小脑和黑质神经元中Bax mRNA水平，下调了Bcl-xL mRNA表达。我们的结果表明，多聚谷氨酰胺扩增的ataxin-3-Q79激活线粒体凋亡途径，并通过上调Bax表达和下调Bcl-xL表达诱导神经元死亡。
