Popiel Helena A, Nagai Yoshitaka, Onodera Osamu, Inui Takashi, Fujikake Nobuhiro, Urade Yoshihiro, Strittmatter Warren J, Burke James R, Ichikawa Atsushi, Toda Tatsushi
Division of Functional Genomics, Department of Post-Genomics and Diseases, Osaka University Graduate School of Medicine, 2-2-B9 Yamadaoka, Suita, Osaka, Japan.
Biochem Biophys Res Commun. 2004 May 14;317(4):1200-6. doi: 10.1016/j.bbrc.2004.03.161.
The polyglutamine (polyQ) diseases are a class of inherited neurodegenerative diseases including Huntington's disease, caused by the expansion of a polyQ stretch within each disease protein. This expansion is thought to cause a conformational change in the protein leading to aggregation of the protein, resulting in cytotoxicity. To analyze whether disrupting the toxic conformation of the polyQ protein can alter its aggregation propensity and cytotoxicity, we examined the effect of interruption of the expanded polyQ stretch by proline insertion, since prolines cause great alterations in protein conformation. Here, we show that insertion of prolines into the expanded polyQ stretch indeed disrupts its ordered secondary structure, leading to suppression of polyQ protein aggregation both in vitro and in cell culture, and reduction of cytotoxicity in correlation with the number of proline interruptions. Furthermore, we found that a short polyQ stretch with a proline interruption is able to inhibit aggregation of the expanded polyQ protein in trans. These results show that a gain in toxic conformation of the expanded polyQ protein is essential for aggregation and cytotoxicity, providing insight into establishing therapies against the polyQ diseases.
多聚谷氨酰胺（polyQ）疾病是一类遗传性神经退行性疾病，包括亨廷顿舞蹈症，由每种疾病蛋白内多聚谷氨酰胺片段的扩增引起。这种扩增被认为会导致蛋白质构象改变，进而导致蛋白质聚集，产生细胞毒性。为了分析破坏多聚谷氨酰胺蛋白的毒性构象是否能改变其聚集倾向和细胞毒性，我们研究了通过脯氨酸插入来中断扩增的多聚谷氨酰胺片段的效果，因为脯氨酸会引起蛋白质构象的巨大改变。在此，我们表明将脯氨酸插入扩增的多聚谷氨酰胺片段确实会破坏其有序二级结构，导致体外和细胞培养中多聚谷氨酰胺蛋白聚集受到抑制，并与脯氨酸插入的数量相关地降低细胞毒性。此外，我们发现带有脯氨酸插入的短多聚谷氨酰胺片段能够反式抑制扩增的多聚谷氨酰胺蛋白的聚集。这些结果表明，扩增的多聚谷氨酰胺蛋白毒性构象的增加对于聚集和细胞毒性至关重要，为建立针对多聚谷氨酰胺疾病的治疗方法提供了思路。
