Defining the mechanism of substrate binding by the Hsp110 molecular chaperone

 描述(申请人提供)：分子伴侣确保蛋白质合成、传递、损伤修复和降解过程中的蛋白质质量。热休克蛋白(Hsp70)是一种普遍存在且高度保守的分子伴侣蛋白，它通过与未折叠蛋白的高、低亲和力结合来促进折叠，从而在维持蛋白质动态平衡方面发挥重要作用。Hsp110是Hsp70的不同亲缘关系，在防止蛋白质聚集方面非常有效，但缺乏Hsp70中看到的标志性折叠活性。Hsp110作为Hsp70核苷酸交换因子(NEF)，通过诱导Hsp70释放蛋白质底物来促进Hsp70的折叠循环，从而循环伴侣进行一轮连续的折叠，并允许成功折叠的底物退出折叠循环。在模式生物酿酒酵母中，Hsp110由蛋白质Sse1和SSE2代表，它们具有与Hsp70类似的底物结合结构域(SBD)，这使得它们在其他功能相似但结构不同的NEF中是独一无二的。对Hsp110和Sse1的研究表明，伴侣/NEF家族在体外可以结合多肽并阻止蛋白质聚集，这一能力是由SBD赋予的。然而，在体内研究Hsp110蛋白结合的尝试并不成功。到目前为止，Hsp110结合多肽的影响尚不清楚。在这里，我建议(1)阐明和定义酵母Hsp110结合的底物和(2)定义这种活性对蛋白质和细胞动态平衡的贡献。作为Hsp70的主要合作伙伴，细胞内Hsp110活性的测定是全面了解伴侣蛋白介导的蛋白质动态平衡的前提。通过研究酵母中的伴侣功能和活性，我们可以了解人类细胞蛋白质质量控制系统，然后可以通过药物靶向对抗蛋白质构象紊乱，包括阿尔茨海默病、亨廷顿病和帕金森病。

 DESCRIPTION (provided by applicant): Molecular chaperones ensure protein quality during protein synthesis, delivery, damage repair, and degradation. The ubiquitous and highly conserved molecular chaperone 70-kDa heat-shock proteins (Hsp70s) play essential roles in maintaining protein homeostasis by cycling through high and low affinity binding of unfolded protein clients to facilitate folding. Hsp110s are divergent relatives of Hsp70s that are highly efficient in preventing protein aggregation but lack the hallmark folding activity seen in Hsp70s. Hsp110s serve as Hsp70 nucleotide exchange factors (NEF) and facilitate the Hsp70 folding cycle by inducing release of protein substrate from Hsp70, thus recycling the chaperone for a sequential round of folding and allowing successfully folded substrates to exit the folding cycle. In the model organism Saccharomyces cerevisiae, Hsp110 is represented by the proteins Sse1 and Sse2, which possess a substrate binding domain (SBD) like the Hsp70s, making them unique among other functionally similar, but structurally distinct, NEFs. Studies of Hsp110 and Sse1 have demonstrated that the chaperone/NEF family can bind polypeptides and prevent proteins from aggregating in vitro and this ability is conferred by the SBD. However, attempts to study Hsp110 protein binding in vivo have not been successful. To date, the impact of peptide binding by Hsp110 is unknown. Here, I propose to (1) elucidate and define substrate binding by yeast Hsp110 and (2) define the contributions of this activity toward protein and cellular homeostasis. As a major partner of Hsp70, determining Hsp110 activities in the cell is a prerequisite to full understanding of chaperone-mediated protein homeostasis. By studying chaperone functions and activities in yeast, we can understand human cellular protein quality control systems which can then be pharmacologically targeted to combat protein conformational disorders, including Alzheimer's, Huntington's and Parkinson's diseases.