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（适用提供）：尽管试图减少水，肉类和农产品的细菌污染的昂贵尝试，但产生志贺毒素的大肠杆菌（STEC）和相关的促进病原体（例如沙门氏菌，志贺氏菌，耶尔森氏菌，耶尔森氏菌）越来越经常导致食物疾病的疾病爆发，因此bern earrheal疾病的疾病疾病，因此构成了良好的健康。这些病原体中的每一个都使用III型分泌系统（T3SS）将病毒蛋白（效应子）注入宿主细胞。尽管T3SS效应显然在细菌病毒中起着重要作用，但它们的生化机制并未完全表征。我们正在表征由STEC效应器靶向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，该蛋白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。 NF-KB转录因子家族调节许多关键的促炎宿主防御能力对微生物病原体的激活。 NF-KB在与细菌感染的先天反应有关的关键基因上的活性由核糖体蛋白S3（RPS3）调节，后者具有辅助核功能作为NF-KB亚基。我们发现NLEH1抑制了RPS3的核进口，从而导致NF-KB活性的选择性损失。我们发现，NLEH1通过抑制IK？激酶复合物（IKK®）的磷酸化RPS3来防止RPS3的核转运，这是其核转运所需的。最常用的STEC血清型在引起人类出血性结肠炎致命爆发时也编码了一种名为NLEH2的同源效应子。尽管与NLEH1共享84％的身份，但NLEH2刺激而不是抑制RPS3/NF-KB依赖性转录。拟议研究的中心假设是，通过颠覆了由RPS3/NF-KB控制的感染的炎症反应，STEC NLEH1和NLEH2效应促进了细菌存活。以下特定目的旨在定义这些新蛋白的分子机制：目标1。表征NLEH1抑制ikk？k的分子机制，以防止RPS3的磷酸化以防止其核进口。 AIM 2。阐明NLEH1和NLEH2之间的机械差异及其在确定RPS3/ NF-KB依赖性信号传导方面的病理生理意义。目标3。使用细菌腹泻疾病的动物模型来量化NLEH效应对细菌病毒的重要性。拟议的研究成功完成1）揭示了这种新型细菌的影响。有选择地调节先天免疫力； 2）构成病原体如何进化以选择核糖体蛋白的辅助核功能； 3）表征细菌如何将其病毒蛋白整合到颠覆宿主信号转导级联反应中。