Hsp110 protein chaperone function in yeast

热休克蛋白（Hsps）在细胞生物学中起着双重作用，它们是抵抗细胞凋亡的第一道防线。 细胞毒性应激，并紧密整合到正常生长下的信号和调节途径中 条件包括Hsp70和HspQ0在内的Hsps的一个子集充当分子伴侣，并且可以是 在底物蛋白的生命周期中的多个阶段需要，从生物发生，定位， 稳定性、活化和降解。蛋白伴侣在许多病理生理过程中被诱导， 在某些疾病包括局部缺血和肿瘤发生的情况下， 癌蛋白如v-src激酶和p53肿瘤抑制因子。Hsp110类分子伴侣是一种 Hsp70是一种相对知之甚少的热休克蛋白，存在于所有真核生物中，具有未知的组织特异性同种型。 在人类中的功能。我们的长期目标是阐明这个分子伴侣家族的细胞作用。的 面包酵母Hsp110同源物是由SSE 1和SSE 2基因编码的，关于它们的功能知之甚少。 功能我们已经发现Sse 1在体内以异二聚体的形式与胞质Hsp 70 s Ssa一起存在， Ssb，和Sse1所需的Hsp90分子伴侣系统的信号转导活性。因此， 假设Sse 1，并通过扩展哺乳动物Hsp 110分子伴侣，可能主要作为一种 Hsp70活性的调节剂。该建议旨在获得对细胞作用的机械理解， Hsp110伴侣通过提出两个具体问题：1）Sse1如何与Hsp110伴侣合作， 酵母Hsp70 Ssa 1和2）Sse 1如何参与Hsp90的信号转导？在第一个目标中， 将使用纯化的分子伴侣确定Sse 1对Hsp70的相互作用位点和调节， Sse 1对体外蛋白质折叠的影响。我们将补充这些实验与体内 测定Sse 1对Ssa 1依赖性过程的贡献。第二个目标，我们将 确定Sse 1在Hsp90底物折叠周期中起作用的阶段，以及Sse 1对Hsp90底物折叠周期的具体影响。 使用模型客户蛋白糖皮质激素受体的底物成熟。最后，我们将应用这些 研究结果旨在了解Sse1如何与Hsp90合作， 通过细胞完整性途径中的Slt2 MAP激酶调节信号传导。这些调查路线， 酵母将作为预测Hsp 110在哺乳动物细胞中可能促进的过程的模型。

Heat shock proteins (Hsps) play dual roles in cellular biology; they are the first line of defense against cytotoxic stresses, and are tightly integrated into signaling and regulatory pathways under normal growth conditions. A subset of Hsps, including Hsp70 and HspQO, act as molecular chaperones, and may be required at multiple stages during a substrate protein's lifetime, ranging from biogenesis, localization, and stability, to activation and degradation. Protein chaperones are induced during numerous pathophysiological conditions including ischemia and tumorigenesis, and are known to facilitate stability and activity of oncoproteins such as v-src kinase and the p53 tumor suppressor. The Hsp110 class of chaperones is a poorly understood Hsp70 relative and is present in all eukaryotes, with tissue-specific isoforms of unknown function in humans. Our long-term objective is to elucidate the cellular roles of this chaperone family. The baker's yeast Hsp110 homolog is encoded by the SSE1 and SSE2 genes, and little is known about their function. We have discovered that Sse1 exists as a heterodimer in vivo with the cytosolic Hsp70s Ssa and Ssb, and that Sse1 is required for signal transduction activity of the Hsp90 chaperone system. Wetherefore hypothesize that Sse1, and by extension the mammalian Hsp110 chaperone, may function primarily as a modulator of Hsp70 activity. This proposal seeks to gain a mechanistic understanding of the cellular roles of Hsp110 chaperones by asking two specific questions: 1) How does Sse1 operate in partnership with the yeast Hsp70 Ssa1 and 2) How does Sse1 participate in signal transduction with Hsp90? In the first aim we will determine interaction sites and regulation of Hsp70 by Sse1 using purified chaperones, ultimately deciphering effects of Sse1 on protein folding in vitro. We will complement these experiments with in vivo assays to determine the contribution of Sse1 to Ssa1-dependent processes. In the second aim, we will determine both the stage at which Sse1 acts in the Hsp90 substrate folding cycle, and specific effects on substrate maturation using the model client protein glucocorticoid receptor. Finally we will apply these findings to understand how Sse1 in collaboration with Hsp90 is required for heat shock survival by modulating signaling through the Slt2 MAP kinase in the cell integrity pathway. These lines of investigation in yeast will serve as a model for predicting which processes Hsp110 may facilitate in mammalian cells.