Abstract：
Heat stress strongly triggers the nuclear localization of the molecular chaperone HSP70. Hikeshi functions as a unique nuclear import carrier of HSP70. However, how the nuclear import of HSP70 is activated in response to heat stress remains unclear. Here, we investigated the effects of heat on the nuclear import of HSP70. In vitro transport assays revealed that pretreatment of the test samples with heat facilitated the nuclear import of HSP70. Furthermore, binding of Hikeshi to HSP70 increased when temperatures rose. These results indicated that heat is one of the factors that activates the nuclear import of HSP70. Previous studies showed that the F97A mutation in Hikeshi in an extended loop induced an opening in the hydrophobic pocket and facilitated the translocation of Hikeshi through the nuclear pore complex. We found that nuclear accumulation of HSP70 occurred at a lower temperature in cells expressing the Hikeshi-F97A mutant than in cells expressing wild-type Hikeshi. Collectively, our results show that the movement of the extended loop may play an important role in the interaction of Hikeshi with both FG (phenylalanine-glycine)-nucleoporins and HSP70 in a temperature-dependent manner, resulting in the activation of nuclear import of HSP70 in response to heat stress.
摘要：
热应力强烈触发分子伴侣HSP70的核定位。Hikeshi是HSP70的独特核进口载体。然而,热应激如何激活HSP70的核输入尚不清楚.这里,我们研究了热对HSP70核输入的影响。体外转运测定表明，用热预处理测试样品有助于HSP70的核输入。此外，当温度升高时，Hikeshi与HSP70的结合增加。这些结果表明，热量是激活HSP70核输入的因素之一。先前的研究表明，Hikeshi在扩展环中的F97A突变诱导了疏水口袋的开口，并促进了Hikeshi通过核孔复合物的易位。我们发现，与表达野生型Hikeshi的细胞相比，表达Hikeshi-F97A突变体的细胞在较低的温度下发生HSP70的核积累。总的来说，我们的结果表明，延伸环的运动可能在Hikeshi与FG（苯丙氨酸-甘氨酸）-核孔蛋白和HSP70以温度依赖性方式相互作用中起重要作用，导致响应热应激的HSP70核输入的激活。
