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、肉和农产品的细菌污染进行了昂贵的尝试，但产滋贺毒素的E.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）引起食源性腹泻病的日益频繁的爆发，从而构成巨大的健康负担。这些病原体中的每一种都使用III型分泌系统（T3 SS）将毒力蛋白（效应子）注入宿主细胞。虽然T3 SS效应子在细菌毒力中发挥重要作用，但其生化机制尚不完全。 我们正在表征STEC效应子靶向的哺乳动物信号转导途径。我们最近描述了一种名为NleH 1的STEC效应蛋白，其通过使用独特的机制靶向NF-κ B转录因子来抑制宿主对感染的先天免疫应答。 转录因子的NF-κ B家族调节许多关键的促炎宿主防御微生物病原体的激活。参与对细菌感染的先天性应答的关键基因处的NF-κ B活性受核糖体蛋白S3（RPS 3）调节，RPS 3作为NF-κ B亚基具有辅助核功能。我们发现NleH 1抑制RPS 3的核输入，导致NF-κ B活性的选择性丧失。我们发现NleH 1通过抑制Ik）磷酸化RPS 3来阻止RPS 3的核转位，这是其核转位所必需的。 STEC血清型最常参与引起人类出血性结肠炎的致命爆发，也编码一种名为NleH 2的同源效应子。尽管与NleHl共享84%的同一性，但NleH 2刺激而不是抑制RPS 3/NF-κ B依赖性转录。这项研究的中心假设是STEC NleH 1和NleH 2效应子通过颠覆由RPS 3/NF-κ B控制的对感染的炎症反应的调节来促进细菌存活。以下具体目标被设计来定义这些新蛋白质的分子机制：目标1。表征NleH 1抑制RPS 3的IKK？磷酸化以阻止其核输入的分子机制。目标2.阐明NleH 1和NleH 2之间的机制差异及其在调节RPS 3/NF-κ B依赖性信号传导中的病理生理学意义。目标3.使用细菌性结肠炎动物模型量化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）揭示这组新的细菌效应子如何选择性地调节先天免疫; 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）表征细菌如何将其毒力蛋白整合到破坏宿主信号转导级联中。