Studies of polyQ diseases : possible mechanisms of cell death and its prevention by molecular chaperone

我们利用脊髓和延髓肌萎缩症(SBMA)的细胞模型，分析了含有扩展多聚体(97或24)的蛋白诱导的细胞凋亡途径。当含有与GFP融合的多Q区(tAR24和tAR97)或与GFP融合的多Q区(PolyQ24和PolyQ97)的截短ARs的表达载体导入COS-7细胞时，tAR97和PolyQ97，而不是tAR24和PolyQ24，可诱导有核聚集的细胞明显聚集和凋亡。在凋亡细胞中，伴随着多聚Q97的表达，Bax向线粒体的转变，细胞色素c的释放和caspase 3的激活。然而，在这些细胞中没有观察到未折叠的蛋白反应。因此，多聚Q97诱导的细胞凋亡可能部分是通过Bax途径通过线粒体途径发生的。由于热休克蛋白(HSP)的过度表达抑制了多聚Q通路扩张引起的细胞死亡，因此HSP的增强表达可能为多聚Q疾病提供一种有效的治疗途径。我们发现，非类固醇抗炎药水杨酸钠和消炎痛通过激活热休克因子上调了37℃处的热休克蛋白启动子，并诱导哺乳动物细胞中热休克蛋白的积累增加，同时还发现水杨酸钠和消炎痛抑制了多聚Q链扩张引起的多聚Q97的聚集和细胞凋亡。因此，非甾体抗炎药似乎被用来保护细胞免受有害应激源和神经退行性疾病的影响。

We analyzed the apoptotic pathway induced by proteins containing expanded polyQ tract (97 or 24) using cellular model of Spinal and bulbar muscular atrophy (SBMA). When expression plasmids of truncated ARs containing polyQ tracts fused to GFP (tAR24 and tAR97) or polyQ tracts fused to GFP (polyQ24 and polyQ97) were transfected into COS-7 cells, tAR97 and polyQ97, but not tAR24 and polyQ24, induced marked formation of the aggregates and apoptosis in the cells with nuclear aggregates.To examine the apoptotic pathway induced by the polyQ proteins, we next esatablished HeLa-tet cell lines in which expression of PolyQ proteins was regulated by doxycycline. In apoptotic cells, the transition of Bax to mitochondria, release of cytochrome c and activation of caspase 3 were observed concomitantly with the expression of polyQ97. However, unfolded protein response was not observed in these cells. Thus, polyQ97-induced apoptosis seemed to be in part occurred through the mitochondrial pathway via Bax.As the over-expression of heat shock proteins (hsp) suppresses cell death caused by expansion of the polyQ tract, the enhanced expression of hsp may provide an effective therapeutic approach for polyQ diseases. We found that non-steroid anti-inflamatory drugs such as sodium salicylate and indomethacin up-regulated the hsp promoter at 37℃ through the activation of heat shock factor and induced the increased accumulation of hsp in mammalian cells, and also revealed that sodium salicylate and indomethacin suppressed the aggregation of polyQ97 and apoptosis caused by an expanded polyQ tract. Thus, NSAIDs seemed to be used for the protection of cells against deleterious stressors and neurodegenerative diseases.