Bacterial effectors targeting the IKK/NF-kB pathway

针对 IKK/NF-kB 通路的细菌效应子

• 批准号: 8589734
• 负责人: Philip Ross Hardwidge
• 金额: $ 37.5万
• 依托单位: KANSAS STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-04 至 2013-01-10
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8589734
• 关键词: Bacterial; effectors; targeting; IKK; NF

DESCRIPTION (provided by applicant): Despite costly attempts to reduce bacterial contamination of water, meat, and produce, Shiga toxin-producing E. coli (STEC) and related enteric pathogens (e.g. Salmonella, Shigella, Yersinia) are causing increasingly frequent outbreaks of food borne diarrheal disease, thus constituting enormous health burdens. Each of these pathogens uses a type III secretion system (T3SS) to inject virulence proteins (effectors) into host cells. While T3SS effectors clearly play essential roles in bacterial virulence, their biochemical mechanisms are incompletely characterized. We are characterizing mammalian signal transduction pathways targeted by STEC effectors. We have recently described an STEC effector protein named NleH1 that inhibits the host innate immune response to infection by targeting the NF-KB transcription factor using a unique mechanism. The NF-KB family of transcription factors regulates the activation of many crucial pro-inflammatory host defenses to microbial pathogens. The activity of NF-KB at key genes involved in the innate response to bacterial infection is regulated by ribosomal protein S3 (RPS3), which possesses an accessory nuclear function as an NF-KB subunit. We discovered that NleH1 inhibits the nuclear import of RPS3, leading to the selective loss of NF-KB activity. We found that NleH1 prevents the nuclear translocation of RPS3 by inhibiting the Ik¿ kinase complex (IKK¿) from phosphorylating RPS3, which is required for its nuclear translocation. The STEC serotypes that are most commonly implicated in causing deadly outbreaks of hemorrhagic colitis in humans also encode a homologous effector named NleH2. Despite sharing 84 % identity with NleH1, NleH2 stimulates rather than inhibits RPS3/NF-KB-dependent transcription. The central hypothesis for the proposed research is that the STEC NleH1 and NleH2 effectors promote bacterial survival by subverting the regulation of inflammatory responses to infection controlled by RPS3/NF-KB. The following specific aims are designed to define the molecular mechanism of these novel proteins: Aim 1. Characterize the molecular mechanism by which NleH1 inhibits IKK¿ phosphorylation of RPS3 to prevent its nuclear import. Aim 2. Elucidate mechanistic differences between NleH1 and NleH2 and their pathophysiological significance in regulating RPS3/ NF-KB-dependent signaling. Aim 3. Quantify the importance of NleH effectors to bacterial virulence and transmission using animal models of bacterial diarrheal disease. Successful completion of the proposed research will 1) reveal how this novel group of bacterial effectors selectively modulates innate immunity; 2) clarify how pathogens have evolved to co-opt the accessory nuclear functions of ribosomal proteins; and 3) characterize how bacteria have integrated their virulence proteins into subverting host signal transduction cascades.

描述（由申请人提供）：尽管为减少水、肉类和农产品的细菌污染付出了高昂的代价，但产志贺毒素的大肠杆菌（STEC）和相关肠道病原体（例如沙门氏菌、志贺氏菌、耶尔森氏菌）正在导致食源性腹泻病的爆发日益频繁，从而构成巨大的健康负担。这些病原体均使用 III 型分泌系统 (T3SS) 将毒力蛋白（效应物）注入宿主细胞。虽然 T3SS 效应子显然在细菌毒力中发挥着重要作用，但其生化机制尚未完全表征。 我们正在表征 STEC 效应器针对的哺乳动物信号转导途径。我们最近描述了一种名为 NleH1 的 STEC 效应蛋白，它通过使用独特的机制靶向 NF-KB 转录因子来抑制宿主对感染的先天免疫反应。 转录因子 NF-KB 家族调节许多重要的促炎宿主对微生物病原体防御的激活。 NF-KB 在参与细菌感染先天反应的关键基因上的活性受到核糖体蛋白 S3 (RPS3) 的调节，该蛋白具有作为 NF-KB 亚基的辅助核功能。我们发现 NleH1 抑制 RPS3 的核输入，导致 NF-KB 活性选择性丧失。我们发现 NleH1 通过抑制 Ik¿ 激酶复合物 (IKK¿) 磷酸化 RPS3 来阻止 RPS3 的核转位，而 RPS3 是其核转位所必需的。 最常引起人类出血性结肠炎致命爆发的 STEC 血清型也编码一种名为 NleH2 的同源效应子。尽管与 NleH1 具有 84% 的同一性，但 NleH2 会刺激而不是抑制 RPS3/NF-KB 依赖性转录。本研究的中心假设是，STEC NleH1 和 NleH2 效应子通过破坏 RPS3/NF-KB 控制的感染炎症反应调节来促进细菌存活。以下具体目标旨在定义这些新型蛋白质的分子机制： 目标 1. 表征 NleH1 抑制 RPS3 IKK 磷酸化以阻止其入核的分子机制。目标 2. 阐明 NleH1 和 NleH2 之间的机制差异及其在调节 RPS3/NF-KB 依赖性信号传导中的病理生理学意义。目标 3. 使用细菌性腹泻病动物模型量化 NleH 效应子对细菌毒力和传播的重要性。 成功完成拟议的研究将1）揭示这组新型细菌效应物如何选择性调节先天免疫； 2）阐明病原体如何进化以选择核糖体蛋白的辅助核功能； 3) 描述细菌如何将其毒力蛋白整合到颠覆宿主信号转导级联中。