Inefficient degradation of truncated polyglutamine proteins by the proteasome
Inefficient degradation of truncated polyglutamine proteins by the proteasome
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DOI：
10.1038/sj.emboj.7600426
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发表时间：
2004-10-27
期刊：
影响因子：
11.4
通讯作者：
Morimoto, RI
中科院分区：
文献类型：
--
作者：
Holmberg, CI;Staniszewski, KE;Morimoto, RI
突变蛋白聚集成错误折叠的物种和聚集体是包括多谷氨酰胺疾病在内的多种神经退行性疾病的特征。虽然一些研究表明，聚谷氨酰胺蛋白聚集损害泛素-蛋白酶体系统，但聚谷氨酰胺蛋白和蛋白酶体之间相互作用的分子机制仍然难以捉摸。在这项研究中，我们使用荧光活细胞成像来证明蛋白酶体被不可逆地隔离在过表达的n端突变亨廷顿蛋白片段或简单的聚谷氨酰胺扩增蛋白的聚集体中。此外，通过直接靶向聚谷氨酰胺蛋白进行蛋白酶体降解，我们观察到这些底物在体外和体内都不完全降解。因此，我们的数据揭示了聚谷氨酰胺蛋白的内在特性阻止了它们的有效降解和清除。此外，在蛋白酶体和聚集的聚谷氨酰胺蛋白之间检测到荧光共振能量转移，表明密切而稳定的相互作用。我们提出含有聚谷氨酰胺的蛋白质在蛋白酶体中被动态捕获，这可以解释它们随着时间的推移对细胞功能的有害影响。
Accumulation of mutant proteins into misfolded species and aggregates is characteristic for diverse neurodegenerative diseases including the polyglutamine diseases. While several studies have suggested that polyglutamine protein aggregates impair the ubiquitin - proteasome system, the molecular mechanisms underlying the interaction between polyglutamine proteins and the proteasome have remained elusive. In this study, we use fluorescence live-cell imaging to demonstrate that the proteasome is sequestered irreversibly within aggregates of overexpressed N-terminal mutant Huntingtin fragment or simple polyglutamine expansion proteins. Moreover, by direct targeting of polyglutamine proteins for proteasomal degradation, we observe incomplete degradation of these substrates both in vitro and in vivo. Thus, our data reveal that intrinsic properties of the polyglutamine proteins prevent their efficient degradation and clearance. Additionally, fluorescence resonance energy transfer is detected between the proteasome and aggregated polyglutamine proteins indicative of a close and stable interaction. We propose that polyglutamine-containing proteins are kinetically trapped within proteasomes, which could explain their deleterious effects on cellular function over time.