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

项目概要/摘要 泛素-蛋白酶体系统（泛素系统）调节的蛋白水解作用在 多种生物过程，对人类健康和疾病具有重大影响，包括 疾病范围从癌症和神经退行性疾病到心血管综合征和缺陷 免疫力。我们对泛素-蛋白酶体系统和泛素依赖的N端规则途径的研究 在过去的三十年里，这在很大程度上是通过目前的赠款（DK039520-30）实现的， 目前已进入第 31 个支持年头。 N端规则途径识别含有N端的蛋白质 称为 N-降解决定子的降解信号使这些蛋白质多泛素化，从而导致其 被蛋白酶体降解。 N端规则路径的识别组件称为N端识别。 在真核生物中，N-识别蛋白是可以靶向 N-降解决定子的 E3 泛素连接酶。真核生物的N端规则 路径由三个分支组成。第一个分支称为 Arg/N 端规则路径，针对特定的 蛋白质底物的未乙酰化的 N 末端残基。这个分支是我们实验室在1986年发现的， 仍然是生物学见解的源泉。第二个分支，称为 Ac/N 端规则路径，是 我们的实验室于 2010 年发现。该通路可识别 N 末端乙酰化的蛋白质 残留物。 N端规则路径的第三个分支，称为Pro/N端规则路径，已经出现 通过我们实验室过去两年未发表的研究。该蛋白水解途径是 由先前已知的称为 GID 的泛素连接酶介导并识别 N 端脯氨酸 (Pro) 蛋白质的残基和相邻的序列基序。 目前的 (DK039520) 续展申请重点关注这些（最新）进展以及很大程度上 在酵母和哺乳动物中，未探索的 Pro/N 末端规则途径。其生物学功能包括 调节细胞状态之间生理上重要的转变，需要从头合成 葡萄糖（例如，饥饿或半饥饿状态）和充足葡萄糖可用性的条件。的 Pro/N 端规则路径还有其他功能，这些功能正在开始出现，部分是通过我们的 最近鉴定出由 Pro/N 端靶向或与 Pro/N 端相互作用的非糖异生蛋白 酵母和哺乳动物中的规则途径。这些以及相关的酵母和哺乳动物研究，描述于 本更新申请的具体目标将促进对蛋白质降解和 普遍存在的N端规则路径。

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 The third branch of the N-end rule pathway, termed the Pro/N-end rule pathway, has emerged through unpublished studies, over the last two years, by our laboratory.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.