Department of Anesthesiology, Chang Gung Memorial Hospital, Kwei-San, Tao-Yuan, Taiwan, ROC.
Neurochem Int. 2011 Feb;58(2):145-52. doi: 10.1016/j.neuint.2010.11.005. Epub 2010 Nov 16.
Spinocerebellar ataxia type 3 (SCA3) is an autosomal dominant neurodegenerative disorder caused by polyglutamine-expanded ataxin-3. SCA3 neurodegeneration is found in the pontine nuclei and cerebellum. Polyglutamine-expanded ataxin-3-Q79 caused apoptotic death of cerebellar and pontine nuclei neurons by upregulating mRNA expression of pro-apoptotic Bax and activating mitochondria-mediated apoptotic cascade. Following various cellular stresses, transcription factor p53 promotes apoptotic neuronal death by enhancing the transcription of pro-apoptotic genes including Bax and PUMA. In the present study, cellular and animal models of SCA3 were used to test the hypothesis that mutant polyglutamine ataxin-3 upregulates Bax expression of cerebellar and pontine nuclei neurons by augmenting transcriptional activity of p53. Electrophoretic mobility shift assay (EMSA) indicated that p53 binding activity to Bax promoter sequence was significantly enhanced in cultured cerebellar neurons expressing mutant ataxin-3-Q79 and pontine nuclei and cerebellum of SCA3 transgenic mice expressing ataxin-3-Q79. The mRNA level of PUMA, a p53-inducible pro-apoptotic gene, was increased in the cerebellum and pontine nuclei of SCA3 transgenic mice and cultured cerebellar neurons expressing ataxin-3-Q79. Mutant polyglutamine ataxin-3 increased the protein level of active phospho-p53(Ser15) in cerebellar and pontine nuclei neurons without affecting mRNA or protein level of p53. Intraperitoneal administration of p53 inhibitor pifithrin-α significantly ameliorated neuronal death in the pontine nuclei of SCA3 transgenic mice. Our results suggest that polyglutamine-expanded ataxin-3 upregulates mRNA expression of Bax and PUMA and causes apoptotic death of affected neurons by enhancing phosphorylation and transcriptional activity of p53.
脊髓小脑共济失调 3 型（SCA3）是一种常染色体显性遗传的神经退行性疾病，由多聚谷氨酰胺扩展的ataxin-3 引起。SCA3 神经退行性变发生在脑桥核和小脑。多聚谷氨酰胺扩展的 ataxin-3-Q79 通过上调促凋亡 Bax 的 mRNA 表达并激活线粒体介导的凋亡级联反应，导致小脑和脑桥核神经元凋亡死亡。在各种细胞应激下，转录因子 p53 通过增强包括 Bax 和 PUMA 在内的促凋亡基因的转录，促进凋亡性神经元死亡。在本研究中，使用 SCA3 的细胞和动物模型来检验假设，即突变的多聚谷氨酰胺 ataxin-3 通过增强 p53 的转录活性来上调小脑和脑桥核神经元 Bax 的表达。电泳迁移率变动分析（EMSA）表明，在表达突变型 ataxin-3-Q79 的培养小脑神经元以及表达 ataxin-3-Q79 的 SCA3 转基因小鼠的脑桥核和小脑中，p53 与 Bax 启动子序列的结合活性显著增强。PUMA，一种 p53 诱导的促凋亡基因的 mRNA 水平在 SCA3 转基因小鼠的小脑和脑桥核以及表达 ataxin-3-Q79 的培养小脑神经元中增加。突变的多聚谷氨酰胺 ataxin-3 增加了小脑和脑桥核神经元中活性磷酸化 p53(Ser15)的蛋白水平，而不影响 p53 的 mRNA 或蛋白水平。腹腔内给予 p53 抑制剂 pifithrin-α 可显著改善 SCA3 转基因小鼠脑桥核中的神经元死亡。我们的结果表明，多聚谷氨酰胺扩展的 ataxin-3 通过增强 p53 的磷酸化和转录活性，上调 Bax 和 PUMA 的 mRNA 表达，并导致受影响神经元的凋亡死亡。
