Functional Diversity of J-protein Components of Hsp70 Chaperone Machinery

描述(申请人提供)：蛋白质如何折叠，即获得其三维结构，是一个对人类健康具有重要影响的基本生物学过程。错误折叠的蛋白质通常是有毒的，被称为“蛋白质折叠疾病”的神经退行性疾病的数量就说明了这一点。分子伴侣在重塑蛋白质结构中起着至关重要的作用--帮助蛋白质从头开始折叠，防止蛋白质聚集和分解蛋白质复合体。以热休克蛋白70为基础的机器，以J-蛋白为必需成分，是最保守的分子伴侣系统之一。J-蛋白是一组非常多样化的蛋白质，只有70个氨基酸的J-结构域是共同的。所有J-蛋白都有能力刺激其伴侣Hsp70的ATPase活性，使它们能够捕获客户蛋白。但正是它们的功能多样性使它们能够协调HSP70的S能力，以参与广泛的复杂和多样化的生物功能。这一建议侧重于了解J-蛋白功能的特异性基础。选择酵母胞浆中的两个J-蛋白：Sis1和Zuo1进行了深入的分析。这种选择是基于它们的关键重要性和高度的序列保守性。它们的人类同源物能够替代酵母蛋白，因此这项工作的结果将为理解J-蛋白在其他生物中的功能提供一个范例。为了了解SIS1的特异性，我们将利用它在酵母蛋白繁殖中的作用，因为它是分离蛋白复合体所必需的。因此，结果还将提供有关这些自我复制的淀粉样蛋白聚集体的生物发生和繁殖的重要信息。Zuo1是一种高度保守的核糖体相关伴侣蛋白，当HSP70离开核糖体时，它能促进HSP70与新生多肽的相互作用。核糖体相关的伴侣蛋白是蛋白质合成和蛋白质折叠之间的纽带，因此是细胞生产功能蛋白质的关键。此外，我们还将研究分子伴侣在细胞核中的作用，重点是独立于伴侣活性和可与伴侣活性分离的新的调节功能。与公共健康相关：本提案中描述的研究重点是了解活细胞内蛋白质折叠和成熟的过程，以及分子伴侣在其中的重要作用。高效的蛋白质折叠对正常细胞功能至关重要；蛋白质错误折叠是许多人类疾病的主要原因，包括囊性纤维化和神经退行性疾病，如阿尔茨海默病。

DESCRIPTION (provided by applicant): How proteins fold, that is attain their three-dimensional structure, is a fundamental biological process with important implications for human health. Misfolded proteins are often toxic, as illustrated by the number of neurodegenerative diseases referred to as "protein folding diseases". Molecular chaperones play vital roles in remodeling protein structure -- assisting de novo protein folding, preventing protein aggregation and disassembling protein complexes. Hsp70-based machineries, having J-proteins as obligate components, are amongst the most highly conserved molecular chaperone systems. J-proteins are a very diverse set of proteins, having only the 70 amino acid J-domain in common. All J-proteins share the ability to stimulate the ATPase activity of their partner Hsp70s, allowing them to capture client proteins. But it is their functional diversity that enables them to orchestrate Hsp70's capacity to participate in a wide array of complex and diverse biological functions. This proposal focuses on understanding the basis of the specificity of J-proteins function. Two J-proteins of the yeast cytosol have been chosen for in depth analysis: Sis1 and Zuo1. This choice is based on their critical importance and their high degree of sequence conservation. Their human homologs are able to substitute for the yeast proteins, thus the outcome of this work will serve as a paradigm for understanding J-protein function in other organisms. To understand the specificity of Sis1, its function in the propagation of yeast prions will be exploited, as it is specifically required for fragmentation of prion complexes. Thus, results will also yield important information about the biogenesis and propagation of these self-replicating amyloid protein aggregates. Zuo1 is a highly conserved ribosome-associated chaperone that facilitates interaction of Hsp70 with nascent polypeptides as they exit the ribosome. Ribosome-associated chaperones serve as a link between protein synthesis and protein folding and are thus a key to the cell<s production of functional proteins. In addition, we will investigate roles of molecular chaperones in the nucleus, focusing on novel regulatory functions independent of and separable from chaperone activity. PUBLIC HEALTH RELEVANCE: The research described in this proposal focuses on understanding the processes of protein folding and maturation within living cells and the important roles of molecular chaperones in them. Productive protein folding is critical to normal cell function; protein misfolding is the primary cause of many human diseases, including cystic fibrosis and neurodegenerative diseases such as Alzheimer's disease.