Effects of molecular chaperones on polyQ-mediated cell death and toxicity using cellular model of SBMA

1. 我们使用 SBMA 细胞模型检查了 Hsp105α 对聚 Q 束扩张引起的聚集体形成和细胞毒性的影响。含有扩展的polyQ束的截短雄激素受体（tAR）的瞬时表达诱导COS-7和SK-N-SH细胞中聚集体的形成，并伴随着这些具有核聚集体的细胞的凋亡细胞死亡。当Hsp105α在细胞中与tAR97一起过表达时，由polyQ束扩张引起的聚集体形成和细胞毒性显着减少。 Hsp105α 的 β-折叠结构域和 α-螺旋结构域（而非 ATPase 结构域）对于体内和体外聚集体形成的抑制是必需的。此外，在患有 SBMA 的患者和转基因小鼠的组织中，发现 Hsp105α 定位于由 Ars 形成的核包涵体中，该核包涵体含有扩展的 PolyQ 束。这些结果表明，Hsp105α的过表达可以抑制无伴侣活性的polyQ束扩张引起的细胞死亡，脑中Hsp105α必需结构域表达的增强可能为CAG重复疾病提供有效的治疗手段。 2．我们检查了载体蛋白对聚 Q 束扩张引起的聚集体形成和细胞毒性的影响。当包含与 GFP 融合的扩展 PolyQ 束（tAR24 和 tAR97）或与 GFP 融合的扩展 PolyQ 束（polyQ24 和 polyQ97）的截短 Ars 在 COS-7 细胞中表达时，polyQ97 比 tAR97 引起显着的聚集体形成和细胞凋亡。此外，虽然tAR24和polyQ24都没有引起它们的聚集，但polyQ24而不是tAR24诱导细胞凋亡。由此推测携带polyQ束的蛋白会影响polyQ束的细胞毒性。 3．蛋白质组分析目前正在寻找负责表达含有扩展的polyQ束的tAR的细胞的细胞毒性和凋亡的蛋白质。

1. We examined the effects of Hsp105α on the aggregate formation and cytotoxicity caused by expansion of polyQ tracts using cellular model of SBMA. The transient expression of truncated androgen receptors (tARs) containing expanded polyQ tracts induced aggregate formation in COS-7 and SK-N-SH cells and concomitantly apoptotic cell death in these cells with nuclear aggregates. When Hsp105α was over-expressed with tAR97 in cells, the aggregate formation and cytotoxicity caused by expansion of polyQ tracts were markedly reduced. Both β-sheet and α-helix domains, but not ATPase domain, of Hsp105α were necessary for the suppression of the aggregate formation in vivo and in vitro. Furthermore, Hsp105α was found to localize in nuclear inclusions formed by Ars containing expanded polyQ tracts in tissues of patients and transgenic mice with SBMA. These findings suggest that over-expression of Hsp105α suppresses cell death caused by expansion of polyQ tracts without chaperone activity, and the enhanced expression of the essential domains of Hsp105α in brain may provide an effective therapeutic mean for CAG repeat diseases.2. We examined the effect of carrier protein on the aggregate formation and cytotoxicity caused by expansion of polyQ tracts. When truncated Ars containing expanded polyQ tracts fused to GFP (tAR24 and tAR97) or expanded polyQ tracts fused to GFP (polyQ24 and polyQ97) were expressed in COS-7 cells, polyQ97 caused marked aggregate formation and apoptosis than tAR97 did. Furthermore, although both tAR24 and polyQ24 did not cause their aggregation, polyQ24 but not tAR24 induced apoptosis. Thus, it was suggested that protein carrying polyQ tracts affects the cytotoxicity of polyQ tract.3. Proteome analysis is now progress to find proteins which are responsible for cytotoxicity and apoptosis of cells expressing tARs containing expanded polyQ tracts.