Defining the mechanism of substrate binding by the Hsp110 molecular chaperone

 描述（由申请方提供）：分子伴侣在蛋白质合成、递送、损伤修复和降解过程中确保蛋白质质量。普遍存在的和高度保守的分子伴侣70-kDa热休克蛋白（Hsp 70）在维持蛋白质稳态中发挥重要作用，通过循环通过高和低亲和力结合未折叠的蛋白质客户端，以促进折叠。热休克蛋白110是热休克蛋白70的不同亲属，在防止蛋白质聚集方面非常有效，但缺乏热休克蛋白70中所见的标志性折叠活性。Hsp 110作为Hsp 70核苷酸交换因子（NEF），通过诱导蛋白质底物从Hsp 70释放来促进Hsp 70折叠循环，从而回收分子伴侣用于连续一轮折叠，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（Saccharomyces cerevisiae）中，热休克蛋白110由蛋白质Sse 1和Sse 2代表，它们具有像热休克蛋白70一样的底物结合结构域（SBD），使它们在其他功能相似但结构不同的NEFs中独一无二。对Hsp 110和Sse 1的研究表明，伴侣蛋白/NEF家族可以结合多肽并阻止蛋白质在体外聚集，这种能力是由SBD赋予的。然而，在体内研究Hsp 110蛋白结合的尝试并不成功。迄今为止，Hsp 110对肽结合的影响尚不清楚。在这里，我建议（1）阐明和定义底物结合酵母HSP 110和（2）定义这种活动对蛋白质和细胞内稳态的贡献。Hsp 110作为Hsp 70的主要伴侣，其在细胞中的活性测定是全面了解分子伴侣介导的蛋白质稳态的前提。通过研究酵母中的伴侣蛋白功能和活性，我们可以了解人类细胞蛋白质质量控制系统，然后可以将其作为靶点来对抗蛋白质构象障碍，包括阿尔茨海默氏症，亨廷顿氏症和帕金森氏症。

 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.