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

我们利用脊髓和球性肌萎缩（SBMA）细胞模型，分析了含有扩展多q束（97或24）的蛋白诱导的细胞凋亡途径。将含有与GFP融合的多q束（tAR24和tAR97）或与GFP融合的多q束（polyQ24和polyQ97）的截断ar表达质粒转染到COS-7细胞中，tAR97和polyQ97，而不是tAR24和polyQ24，诱导细胞核聚集的细胞明显形成聚集体和凋亡。为了研究polyQ蛋白诱导的凋亡途径，我们建立了polyQ蛋白表达受强力霉素调控的HeLa-tet细胞系。在凋亡细胞中，随着polyQ97的表达，Bax向线粒体的转移、细胞色素c的释放和caspase 3的激活也随之发生。然而，在这些细胞中未观察到未折叠蛋白的反应。因此，polyq97诱导的细胞凋亡似乎部分是通过线粒体途径通过Bax发生的。由于热休克蛋白（hsp）的过表达可抑制多q通道扩张引起的细胞死亡，因此增强热休克蛋白的表达可能为多q疾病的治疗提供有效的途径。我们发现水杨酸钠和吲哚美辛等非甾体类抗炎药物在37℃时通过激活热休克因子上调hsp启动子，诱导hsp在哺乳动物细胞中积累增加，同时发现水杨酸钠和吲哚美辛抑制polyQ97的聚集和polyQ通道扩张引起的细胞凋亡。因此，非甾体抗炎药似乎可用于保护细胞免受有害压力源和神经退行性疾病的侵害。

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.