BIOCHEMISTRY OF UBIQUITIN-CONJUGATING ENZYMES

描述(改编自申请人的摘要)：ER相关的退化 指的是细胞膜和管腔蛋白在细胞内 胞浆26S降解内质网(ER)室 蛋白酶体。进入这种降解途径的蛋白质包括 蛋白质的水平受到调节的蛋白质降解以及新的 合成的蛋白质进入内质网，但未能正确折叠或 与它们的组成蛋白质伙伴组装。在几个人类中 遗传性疾病，特定等位基因变异的广泛退化结果 在它们的目的地隔间中减少或不存在这样的蛋白质时， 导致功能不足和疾病症状。这样的例子 在囊性纤维化中发现了CFTR蛋白的等位基因变体， α1-抗胰蛋白酶在儿童肝病和成人肺气肿中的应用 A型胰岛素抵抗中的受体、家族性低密度脂蛋白受体 高胆固醇血症和髓过氧化物酶缺乏症。 而泛素介导的蛋白降解在蛋白质降解中的作用 ER相关蛋白是公认的，几乎没有任何关于 这一途径在哺乳动物细胞中的泛素化过程。这样的信息是 对于了解该通路如何被调控以及评估 这一通路在治疗干预方面的潜力。校长 研究人员在这里提出，哺乳动物细胞中内质网相关的降解 利用与酵母中类似的级联反应 Cerevisiae，它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得到了证实。目标将是 用一个模型底物系统来检验这个假设，它提供了 易于进行生化分析的显著优势。为此， 首席研究人员已经确定了一组人类泛素偶联 可能参与这一过程的酶和泛素-蛋白连接酶 路径。他预计生化分析将提供重要的 机械洞察力和评估的前提信息 这一途径为潜在的治疗干预提供了可能。

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.