BIOCHEMISTRY OF UBIQUITIN-CONJUGATING ENZYMES

描述（改编自申请人摘要）：ER相关降解 是指膜以及腔蛋白在细胞中的过程， 内质网（ER）区室被胞质26 S降解 蛋白酶体进入这一降解途径的蛋白质包括 蛋白质，其水平受到调节的蛋白水解以及新的 合成蛋白质进入内质网，但未能正确折叠， 与它们的组成蛋白质伴侣组装。几种人 遗传性疾病，特定等位基因变体的广泛降解导致 在这些蛋白质在其指定区室中减少或不存在时， 导致功能缺陷和疾病症状。的例子 在囊性纤维化中发现CFTR蛋白的等位基因变体， α 1-抗胰蛋白酶在儿童肝病和成人肺气肿，胰岛素 A型胰岛素抵抗的LDL受体，家族性胰岛素抵抗的LDL受体， 高胆固醇血症和髓过氧化物酶缺乏。 虽然泛素介导的蛋白水解在降解中的作用， ER相关蛋白是公认的，实际上对ER相关蛋白还一无所知。 在哺乳动物细胞中这一途径的泛素化过程。该等资料不 关键是要了解如何调节途径，并评估 这一途径的潜在治疗干预。校长 研究者在此提出，哺乳动物细胞中ER相关降解 利用类似的级联反应，如在酵母 酿酒酵母，其中的几个蛋白质参与者的身份， 泛素化过程已经通过遗传分析鉴定。进球会 是要测试这个假设与模型基板系统，提供了 这是易于进行生化分析的显著优点。为此，委员会建议， 主要研究者已经确定了一组人类泛素结合 酶和泛素-蛋白质连接酶可能参与了这一过程， 通路他预计生化分析将提供重要的 机械的见解和先决条件的信息，为评价 这一途径的潜在治疗干预。

DESCRIPTION (adapted from applicant's abstract): ER-associated degradation refers to the process whereby membrane as well as lumenal proteins in the endoplasmic reticulum (ER) compartment are degraded by the cytosolic 26S proteasome. Proteins that are routed into this degradative pathway include proteins whose levels are subjected to regulated proteolysis as well as newly synthesized proteins that entered the ER but failed either to fold properly or to be assembled with their constituent protein partners. In several human hereditary diseases, extensive degradation of specific allelic variants results in the reduction or absence of such proteins in their destined compartment, leading to deficiency in function and disease symptoms. Examples of such allelic variants have been found with the CFTR protein in cystic fibrosis, alpha1-antitrypsin in childhood liver disease and adult emphysema, insulin receptor in type A insulin resistance, LDL receptor in familial hypercholesterolemia and in myeloperoxidase deficiency. While the role of ubiquitin-mediated proteolysis in the degradation of ER-associated proteins is well recognized, virtually nothing is known on the ubiquitination process of this pathway in mammalian cells. Such information is crucial to understand how the pathway could be regulated and to evaluate the potential of this pathway for therapeutic intervention. The principal investigator proposes here that ER-associated degradation in mammalian cells utilizes a similar cascade of reactions as in the yeast Saccharomyces cerevisiae, for which the identity of several protein participants of the ubiquitination process have been identified by genetic analysis. The goal will be to test this hypothesis with a model substrate system that offers the significant advantage of being amenable to biochemical analysis. To this end, the principal investigator has identified a set of human ubiquitin-conjugating enzymes and ubiquitin-protein ligases that are likely participants in this pathway. He expects that the biochemical analysis will provide important mechanistic insights and the prerequisite information for the evaluation of this pathway for potential therapeutic intervention.