Cellular protein maturation and degradation

细胞蛋白质的成熟和降解

• 批准号: 6731821
• 负责人: Daniel N. Hebert
• 金额: $ 25.77万
• 依托单位: UNIVERSITY OF MASSACHUSETTS AMHERST
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-04-01 至 2009-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6731821
• 关键词: albinism; calnexin; calreticulin; crosslink; endoplasmic reticulum; glycoproteins; immunoprecipitation; laboratory rabbit; lectin; melanoma; molecular chaperones; monophenol monooxygenase; mutant; posttranslational modifications; protease inhibitor; protein biosynthesis; protein degradation; protein folding; protein structure function; protein transport

DESCRIPTION (provided by applicant): The overall goal of this proposal is to elucidate the role of N-linked glycans in the maturation and quality control of proteins that traverse the secretory pathway. Carbohydrates play a pivotal role in maturation and degradation of proteins in the cell. The addition of the large hydrophilic and flexible structures to the polypeptide backbone modifies the solubility and stability of proteins. In recent years, N-linked glycans have emerged as the lumenal tags within the secretory pathway that direct the folding, quality control and degradation of nascent glycoproteins by providing attachment sites for resident ER proteins possessing carbohydrate-binding properties. We hypothesize that the position of N-linked glycans on a protein plays an important role in the efficient maturation of glycoproteins in the cell by mediating the timing and location of interactions between the nascent chain and resident ER proteins that assist in the maturation process. Resident ER proteins can protect problematic regions of a maturing protein from premature folding or aggregation, aid in the recruitment of folding catalysts, or the joining of distal domains. Therefore, by controlling the binding of the lectin chaperones calnexin and calreticulin, and the subsequent recruitment of their associated oxidoreductase ERp57, glycans can direct the co- and post-translational maturation of glycoproteins. In addition, N-linked glycans also act as quality control sorting signals within the ER- a type of 'lumenal ubiquitin' that targets aberrant proteins for ER associated-protein degradation (ERAD). Thus, enzymes that regulate the structures of glycans and carbohydrate-binding proteins that recognize specific glycan structures play key roles in directing the protein quality control traffic in the secretory pathway. The specific aims of this proposal are: (l) to investigate the interplay between glycans and problematic folding regions focusing on the relationship between glycans and vulnerable Cys residues during the folding process; (2) to elucidate the mechanisms by which the lectin ER chaperones calnexin and calreticulin, and their associated foldase ERp57 aid in the maturation of glycoproteins; (3) to characterize the structure and ER maturation pathway of tyrosinase, a model ERAD substrate whose misfolding is associated with albinism and melanoma, by using novel cell biological approaches; (4) to uncover the mechanism by which N-linked glycans direct proteins to the degradative pathway; and (5) to determine the role of he ER resident and putative quality control receptor EDEM in the degradation of aberrant glycoproteins. These studies will provide insights into how proteins are able to fold with high efficiencies in the cell and how the cell degrades aberrant proteins associated with disease states.

描述(由申请人提供)：本提案的总体目标是阐明N-连接的多聚糖在穿越分泌途径的蛋白质的成熟和质量控制中的作用。碳水化合物在细胞内蛋白质的成熟和降解中起着关键作用。在多肽骨架上增加了大的亲水性和柔性结构，改变了蛋白质的溶解性和稳定性。近年来，N-连接的葡聚糖作为分泌途径中的管腔标签出现，通过为具有碳水化合物结合特性的内质网蛋白提供附着位点来指导新生糖蛋白的折叠、质量控制和降解。 我们假设，N-连接的糖链在蛋白质上的位置通过调节初生链和帮助成熟过程的驻留ER蛋白之间相互作用的时间和位置，在细胞中糖蛋白的有效成熟中发挥重要作用。驻留的ER蛋白可以保护成熟蛋白质的问题区域，防止过早折叠或聚集，帮助折叠催化剂的招募，或远端结构域的连接。因此，通过控制凝集素伴侣钙粘蛋白和钙网网蛋白的结合，以及随后与之相关的氧化还原酶ERp57的募集，多糖可以指导糖蛋白的共翻译和翻译后成熟。此外，N-连接的多糖还作为内质网内信号的质量控制分选--内质网泛素的一种类型，以ER相关蛋白降解(ERAD)的异常蛋白为靶标。因此，调节多糖结构的酶和识别特定糖链结构的碳水化合物结合蛋白在指导分泌途径中的蛋白质质量控制交通中发挥着关键作用。 这项建议的具体目的是：(L)研究折叠过程中糖和有问题的折叠区域之间的相互作用，重点关注糖和脆弱的Cys残基之间的关系；(2)阐明凝集素ER伴侣钙粘蛋白和钙网蛋白及其相关的折叠酶ERp57帮助糖蛋白成熟的机制；(3)用新的细胞生物学方法表征酪氨酸酶的结构和ER成熟途径，酪氨酸酶是ERAD的模型底物，其错误折叠与白化和黑色素瘤有关；(4)揭示N-连接的糖聚糖引导蛋白质进入降解途径的机制；以及(5)确定内质网驻留和可能的质量控制受体EDEM在异常糖蛋白降解中的作用。这些研究将提供关于蛋白质如何能够在细胞内高效折叠以及细胞如何降解与疾病状态相关的异常蛋白质的见解。