Rujano M A, Kampinga H H, Salomons F A
Department of Cell Biology, Section of Radiation & Stress Cell Biology, University Medical Center Groningen, University of Groningen, The Netherlands.
Exp Cell Res. 2007 Oct 1;313(16):3568-78. doi: 10.1016/j.yexcr.2007.07.034. Epub 2007 Aug 8.
Components of the Hsp70 chaperone machine have been implied in protection against polyglutamine (poly-Q) pathologies. Yet, little is known about specific mechanisms and the rate-limiting components that account for this protective effect. Here, we examined the effects of an Hsp70 chaperone family member (HspA1A) and its cofactors Hsp40 (DnaJB1), Bag-1 and CHIP on poly-Q protein inclusion formation and SDS-insolubilization. Overexpression of HspA1A alone did not suppress inclusion formation, while overexpression of DnaJB1 reduced poly-Q inclusion formation and insolubilization. The reducing effect of DnaJB1 on inclusion formation was enhanced by coexpressing HspA1A, and was dependent on the interaction of DnaJB1 with Hsp70/Hsc70 chaperones. Additionally, two factors connecting Hsp70 activity with protein degradation by the ubiquitin-proteasome system Bag-1 and CHIP slightly decreased the levels of soluble poly-Q protein, but the amount of aggregated protein and fraction of cells with inclusions remained unaltered. Our data suggest that the HspA1A chaperone machine can modulate poly-Q inclusion formation depending on the ratio of its components and that DnaJB1 is the rate-limiting step.
热休克蛋白70（Hsp70）伴侣机制的组成部分已被认为具有抵御多聚谷氨酰胺（poly-Q）病变的作用。然而，对于产生这种保护作用的具体机制以及限速成分，我们却知之甚少。在此，我们研究了Hsp70伴侣家族成员（HspA1A）及其辅助因子Hsp40（DnaJB1）、Bag-1和CHIP对多聚谷氨酰胺蛋白包涵体形成和SDS不溶性的影响。单独过表达HspA1A并不能抑制包涵体的形成，而过表达DnaJB1则可减少多聚谷氨酰胺包涵体的形成和不溶性。共表达HspA1A可增强DnaJB1对包涵体形成的减少作用，且该作用依赖于DnaJB1与Hsp70/Hsc70伴侣蛋白的相互作用。此外，将Hsp70活性与泛素-蛋白酶体系统介导的蛋白质降解联系起来的两个因子Bag-1和CHIP，可略微降低可溶性多聚谷氨酰胺蛋白的水平，但聚集蛋白的量以及含有包涵体的细胞比例并未改变。我们的数据表明，HspA1A伴侣机制可根据其各组分的比例调节多聚谷氨酰胺包涵体的形成，且DnaJB1是限速步骤。
