Deficit of heat shock transcription factor 1-heat shock 70 kDa protein 1A axis determines the cell death vulnerability in a model of spinocerebellar ataxia type 6
Deficit of heat shock transcription factor 1-heat shock 70 kDa protein 1A axis determines the cell death vulnerability in a model of spinocerebellar ataxia type 6
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DOI：
10.1111/j.1365-2443.2009.01348.x
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发表时间：
2009-11-01
期刊：
影响因子：
2.1
通讯作者：
Tanabe, Tsutomu
中科院分区：
文献类型：
--
作者：
Li, Li;Saegusa, Hironao;Tanabe, Tsutomu
脊髓小脑性共济失调6型（SCA6）是由Ca(v)2.1钙通道基因中编码CAG重复序列的聚谷氨酰胺（polyQ）小扩增引起的。为了深入了解SCA6的致病机制，我们利用表达增强绿色荧光蛋白与Ca(v)2.1羧基末端片段（EGFP-Ca(v)2.1 ct）融合蛋白的HEK293细胞[L24和S13细胞分别含有24个polyQ（疾病范围）和13个polyQ（正常范围）]，研究了它们对一些应激源的反应。暴露于CdCl2时，L24细胞的活力低于对照S13细胞，caspase依赖性凋亡在L24细胞中增强。EGFP-Ca(v)2.1CT的定位几乎局限于细胞核内，以斑点状结构存在。有趣的是，CdCl2治疗导致L24细胞中比S13细胞中更多的早幼粒细胞白血病核体（PML-NBs）被破坏，并且在PML-NBs被破坏的细胞中，EGFP-Ca(v)2.1CT的聚集体变得更大。L24细胞比S13细胞形成了更多的聚集体。RNAi实验结果表明HSPA1A决定了CdCl2毒性的差异。此外，激活HSPA1A表达的热休克转录因子1 （HSF1）蛋白表达在L24细胞中下调。因此，HSF1-HSPA1A轴对L24细胞的易损性至关重要。
Spinocerebellar ataxia type 6 (SCA6) is caused by a small expansion of polyglutamine (polyQ)-encoding CAG repeat in Ca(v)2.1 calcium channel gene. To gain insights into pathogenic mechanism of SCA6, we used HEK293 cells expressing fusion protein of enhanced green fluorescent protein and Ca(v)2.1 carboxyl terminal fragment (EGFP-Ca(v)2.1CT) [L24 and S13 cells containing 24 polyQ (disease range) and 13 polyQ (normal range), respectively] and examined their responses to some stressors. When exposed to CdCl2, L24 cells showed lower viability than the control S13 cells and caspase-dependent apoptosis was enhanced more in L24 cells. Localization of EGFP-Ca(v)2.1CT was almost confined to the nucleus, where it existed as speckle-like structures. Interestingly, CdCl2 treatment resulted in disruption of more promyelocytic leukemia nuclear bodies (PML-NBs) in L24 cells than in S13 cells and in cells where PML-NBs were disrupted, aggregates of EGFP-Ca(v)2.1CT became larger. Furthermore, a large number of aggregates were formed in L24 cells than in S13 cells. Results of RNAi experiments indicated that HSPA1A determined the difference against CdCl2 toxicity. Furthermore, protein expression of heat shock transcription factor 1 (HSF1), which activates HSPA1A expression, was down-regulated in L24 cells. Therefore, HSF1-HSPA1A axis is critical for the vulnerability in L24 cells.