The GID Ubiquitin Ligase and the Pro/N-End Rule Pathway in Yeast and Mammals

项目摘要/摘要 由泛素-蛋白酶体系统(泛素系统)调节的蛋白分解在 多种生物过程，对人类健康和疾病有重大影响，包括 疾病范围从癌症和神经退行性变到心血管综合征和 豁免权。我们对泛素-蛋白酶体系统和泛素依赖的N-端规则通路的研究 在很大程度上是由于目前的赠款(DK039520-30)， 目前处于其支持的第31个年头。N-末端规则通路识别含有N-末端的蛋白质 被称为N-降解子的降解信号，多泛素化这些蛋白质，从而导致它们 蛋白酶体的降解。N-端规则通路的识别组件称为N-识别素。 在真核生物中，N-识别素是可以靶向N-降解子的E3泛素连接酶。真核生物的N末端规则 路径由三个分支组成。第一个分支称为Arg/N-end规则途径，针对特定的 蛋白质底物的非乙酰化N-末端残基。这个分支是我们实验室在1986年发现的， 仍然是生物学洞察力的源泉。第二个分支称为Ac/N末端规则通路，是 是我们实验室在2010年发现的。该途径识别N-末端乙酰化的蛋白质 残留物。N-端规则通路的第三个分支，称为Pro/N-端规则通路，已经出现 通过我们实验室在过去两年中未发表的研究。这种蛋白分解途径是 由已知的泛素连接酶GID介导，识别N-末端的Pro 蛋白质的残基和相邻的序列基序。 目前(DK039520)的续展申请主要集中在这些(最新的)进展和大部分 在酵母和哺乳动物中，未探索的Pro/N末端规则通路。其生物学功能包括 调节需要从头合成的细胞状态之间的重要生理转变 葡萄糖(例如，饥饿或半饥饿状态)和充足的葡萄糖供应条件。这个 Pro/N-End规则途径还有其他功能，这些功能正在开始出现，部分是通过我们的 Pro/N-端靶向或与Pro/N-端相互作用的非糖异生蛋白的最新鉴定 规则途径，在酵母和哺乳动物中。这些以及相关的酵母菌和哺乳动物研究，在 目前更新应用的具体目标，将促进对蛋白质降解和 普遍存在的N-端规则通路。

Project Summary/Abstract Regulated proteolysis by the ubiquitin-proteasome system (ubiquitin system) plays essential roles in a multitude of biological processes and has major ramifications for human health and disease, including illnesses that range from cancer and neurodegeneration to cardiovascular syndromes and defects of immunity. Our studies of the ubiquitin-proteasome system and the ubiquitin-dependent N-end rule pathway over the last three decades were made possible, to a large extent, by the present grant (DK039520-30), currently in its 31st year of support. The N-end rule pathway recognizes proteins containing N-terminal degradation signals called N-degrons, polyubiquitylates these proteins and thereby causes their degradation by the proteasome. Recognition components of the N-end rule pathway are called N-recognins. In eukaryotes, N-recognins are E3 ubiquitin ligases that can target N-degrons. The eukaryotic N-end rule pathway consists of three branches. The first branch, called the Arg/N-end rule pathway, targets specific unacetylated N-terminal residues of protein substrates. This branch, discovered by our laboratory in 1986, continues to be a fount of biological insights. The second branch, called the Ac/N-end rule pathway, was discovered by our laboratory in 2010. This pathway recognizes proteins that bear N-terminally acetylated residues. The third branch of the N-end rule pathway, termed the Pro/N-end rule pathway, has emerged through unpublished studies, over the last two years, by our laboratory. This proteolytic pathway is mediated by the previously known ubiquitin ligase called GID and recognizes the N-terminal proline (Pro) residue of a protein and an adjoining sequence motif. The present (DK039520) renewal application focuses on these (latest) advances and the largely unexplored Pro/N-end rule pathway, in both yeast and mammals. Its biological functions include the regulation of physiologically important transitions between cellular states that require de novo synthesis of glucose (for example, starvation or semi-starvation states) and conditions of ample glucose availability. The Pro/N-end rule pathway has other functions as well, which are beginning to emerge, in part through our recent identification of non-gluconeogenic proteins that are either targeted by or interact with the Pro/N-end rule pathway, in both yeast and mammals. These and related yeast and mammalian studies, described in Specific Aims of the present renewal application, will advance the understanding of protein degradation and the universally present N-end rule pathway.