THE MECHANISM OF A NOVEL FAMILY OF BACTERIAL UBIQUITIN E3 LIGASES IMPORTANT FOR PHAGOSOME REMODELING

项目摘要/摘要 泛素的翻译后修饰是改变蛋白质功能的重要机制 真核生物。泛素是一种由76个氨基酸组成的蛋白质，它通过一系列泛素与特定的蛋白质结合 激活酶E1、结合酶E2和泛素连接酶E3。泛素化起着至关重要的作用 在广泛的细胞过程中发挥作用，包括转录，DNA修复，信号转导， 自噬、细胞周期、免疫反应和膜运输。泛素化过程中的像差 该系统会导致许多人类疾病，如神经退行性疾病和癌症。 值得注意的是，尽管原核生物中没有泛素，但编码E3泛素连接酶的细菌病原体 (BELs)被发现被运送到真核宿主细胞中，以操纵宿主泛素系统 成功感染。我们最近发现了一个新的BEL家族，命名为SIDC，来自细胞内 细菌病原体嗜肺军团菌。SIDC在序列和结构上与任何 已知的真核环型或类Hect泛素连接酶。我们的初步数据引起了人们的兴趣 诸如这个新的泛素E3连接酶家族的独特分子机制是什么 考虑到它们在初级和第三级与经典Hect或无名指E3连接酶的明显差异 结构层次？SIDC的具体底物是什么？以及这些宿主的泛素化是如何 潜在的宿主因素在膜转运调控中起作用吗？这项提案的首要目标是 是阐明这个独特的泛素连接酶家族的分子机制及其在开发利用中的作用 主体膜追踪。具体来说，我们会达致以下目标：目标1：划定 SidC/SDCA连接泛素的分子机制目的2：阐明肌动蛋白的活性调节 SIDC/SDCA。目的3：鉴定SidC/SDCA在宿主膜转运中的作用 它们特定的底物。我们期望这项提议的成功实施将产生重大意义 有助于理解这两种酶的级联反应的分子机制 泛素化和宿主泛素途径在细菌病原体发病机制中的作用。

PROJECT SUMMARY/ABSTRACT Post-translational modification by ubiquitin is an essential mechanism to alter protein function in eukaryotes. Ubiquitin, a 76 amino acid protein, is attached to specific proteins via a cascade of ubiquitin activating enzyme E1, conjugating enzyme E2, and ubiquitin ligase E3. Ubiquitination plays an essential role in a broad aspect of cellular processes, including transcription, DNA repair, signal transduction, autophagy, cell cycle, immune response, and membrane trafficking. Aberration in the ubiquitination system lead to a number of human diseases, such as neurodegenerative diseases and cancers. Remarkably, although ubiquitin is absent in prokaryotes, Bacterial pathogen encoded E3 ubiquitin Ligase (BELs) are found to be delivered into eukaryotic host cells to manipulate the host ubiquitin system for successful infection. We recently discovered a novel family of BELs, named SidC, from the intracellular bacterial pathogen Legionella pneumophila. SidC have no sequence and structure resemblance to any known eukaryotic RING-type or HECT-like ubiquitin ligases. Our preliminary data raised intriguing questions such as what is the unique molecular mechanism of this novel family of ubiquitin E3 ligases given their apparent disparities to canonic HECT or RING-finger E3 ligases at both primary and tertiary structure levels? What are the specific substrates of SidC? And how the ubiquitination of these host potential host factors play a role in membrane trafficking regulation? The overarching goal of this proposal is to elucidate the molecular mechanism of this distinct family of ubiquitin ligases and their role in exploiting host membrane tracking. Specifically, we will pursuing the following aims: Aim 1: To delineate the molecular mechanism of ubiquitin ligation by SidC/SdcA. Aim 2: To elucidate the activity regulation of SidC/SdcA. Aim 3: To characterize the role of SidC/SdcA in host membrane trafficking and to identify their specific substrates. We expect the successful implementation of this proposal will make significant contributions to the understanding of both the molecular mechanisms of the enzymatic cascade of ubiquitination and the role of host ubiquitin pathway in the pathogenesis of bacterial pathogens.