Molecular Chaperones and Protein Degradation

分子伴侣和蛋白质降解

• 批准号: 6876429
• 负责人: ALFRED L GOLDBERG
• 金额: $ 52.01万
• 依托单位: HARVARD MEDICAL SCHOOL
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-08-01 至 2008-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6876429
• 关键词: Archaea; Escherichia coli; RNA interference; adenosinetriphosphatase; bacterial proteins; cell line; chromatin immunoprecipitation; conformation; electron microscopy; enzyme activity; fungal proteins; heat shock proteins; mass spectrometry; molecular chaperones; proteasome; protein degradation; protein folding; protein structure function; proteolysis; stress proteins; ubiquitin; yeasts

DESCRIPTION (provided by applicant): One important function of intracellular proiein degradation is to selectively destroy proteins with abnormal conformations, whose accumulation can be toxic. Molecular chaperones, in addition to catalyzing protein folding and translocation, play several essential functions in this degradative process, which we hope to understand. Most protein breakdown in mammalian cells is catalyzed by the 26S proteasome, whose 19S regulatory particle contains six ATPases that function as molecular chaperones. To elucidate their roles in protein degradation, we are studying the simpler homologous ATPase complex, PAN, which supports proteolysis by 20S proteasomes in archaebacteria. We hope to clarify its mode of substrate recognition and how it catalyzes the unfolding of globular proteins and their translocation into the 20S proteasome. In eukaryotic cells, the chaperones hsp70 and hsp40 are required for the degradation of abnormal proteins by the ubiquitin-proteasome pathway, and recently a Ub ligase, CHIP, was discovered that functions with Hsp70 in the ubiquitination of unfolded proteins. We hope to define the precise roles of chaperones in ubiquitination by CHIP and to learn how additional factors, in particular, the ubiquitin-binding protein, S5a, may function to facilitate the degradation of the Ub-conjugated proteins by 26S proteasomes. In E. coli, the rapid degradation of certain polypeptides requires the chaperones, GroEL and GroES, which facilitate the unfolding of domains that resist degradation by ATP-dependent proteases. We shall test whether in eukaryotes there is a similar collaboration between the related chaperones (CCT/TriC) and proteasomes in catalyzing the complete degradation of "hard-to-unfold" domains in proteins. In harsh conditions which favor protein denaturation (e.g., heat-shock or oxidative stress), microorganisms produce hsps and large amounts of the "chemical chaperone," trehalose, which enhances cellular resistance to these stresses. We recently discovered that trehalose is also produced in high amounts upon shift to low temperatures (0-10 degrees C) in yeast, and its accumulation protects cells against freezing. We hope to learn how this disaccharide protects cell proteins against cold-induced denaturation, whether trehalose influences protein degradation, and whether higher eukaryotes show similar adaptations to near-freezing temperatures.

描述（由申请人提供）：细胞内PROIEIN降解的一个重要功能是选择性破坏具有异常构象的蛋白质，其积累可能是有毒的。除了催化蛋白质折叠和易位，分子伴侣在此降解过程中起着几种基本功能，我们希望能理解。 26S蛋白酶体催化哺乳动物细胞中的大多数蛋白质分解，其19S调节粒子包含六个充当分子伴侣的ATP酶。为了阐明它们在蛋白质降解中的作用，我们正在研究较简单的同源ATPase复合物PAN，该复合物在古细菌中支持20S蛋白酶体的蛋白水解。我们希望阐明其底物识别方式，以及它如何催化球状蛋白的展开及其易位到20S蛋白酶体。在真核细胞中，泛素HSP70和HSP40是通过泛素 - 蛋白酶体途径降解异常蛋白所必需的，最近发现了一个UB连接酶ChIP，发现该蛋白质在泛蛋白的泛素化中与HSP70起作用。我们希望定义伴侣通过芯片泛素化的精确作用，并了解其他因素，尤其是泛素结合蛋白S5A的其他因素如何起作用，以促进26S蛋白酶蛋白酶促进UB结合的蛋白质的降解。在大肠杆菌中，某些多肽的快速降解需要伴侣，凹槽和凹槽，这有助于抗ATP依赖性蛋白酶抗降解的域的展开。我们应测试在真核生物中，相关伴侣（CCT/Tric）与蛋白酶体之间是否存在类似的合作，从而催化蛋白质中“难以毫无用说”的域的完全降解。在有利于蛋白质变性的恶劣条件下（例如，热休克或氧化应激），微生物会产生HSP和大量的“化学伴侣蛋白”，Treehalose，从而增强了对这些应激的细胞抗性。我们最近发现，在酵母中转移到低温（0-10摄氏度）时，海藻糖也很高，其积累可保护细胞免受冷冻的冻结。我们希望了解这种二糖如何保护细胞蛋白免受冷诱导的变性，是否会影响蛋白质降解，以及较高的真核生物是否表现出与近冻结温度相似的适应性。