Shigella repression of innate immunity early during infection

志贺氏菌在感染早期抑制先天免疫

• 批准号: 8853815
• 负责人: Marcia B Goldberg
• 金额: $ 21.75万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-06-01 至 2018-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8853815
• 关键词: Autophagocytosis; Bacteria; Binding; Caspase; Cell membrane; Cells; Clear Cell; Complex; Coupled; Data; Dependency; Deposition; Enzymes; Face; Galactose Binding Lectin; Galactosides; Human; Immune; Immune response; Infection; Inflammatory; Interleukin-1; Interleukin-18; Invaded; Investigation; Lead; Lectin; Location; Mammalian Cell; Mediating; Membrane; Mitogen-Activated Protein Kinases; Modeling; NF-kappa B; Natural Immunity; Organism; OspC protein; Polyubiquitin; Process; Production; Proteins; Publishing; Recruitment Activity; Repression; Salmonella; Salmonella infections; Shigella; Shigella flexneri; Site; TRAF6 gene; Testing; Time; Ubiquitin; Up-Regulation; Vacuole; Vesicle; base; cytokine; human CASP4 protein; insight; microorganism; particle; protein aggregate; protein complex; public health relevance; receptor; response; scaffold; sensor; ubiquitin-protein ligase; uptake

DESCRIPTION (provided by applicant): Mammalian cells employ a variety of innate immune mechanisms to recognize and eliminate invading microorganisms, including autophagy of intracellular particles and pro-inflammatory cytokine mediated recruitment of inflammatory cells to the site of infection. Within minutes of Shigella spp. or Salmonella spp. entry into cells, autophagy is activated and inflammasome receptors and adaptors are recruited around intracellular bacteria. A substantial subpopulation of intracellular bacteria avoids association with autophagy markers. How this subpopulation of bacteria evades recognition by these markers has been unclear. Our preliminary data suggest a model in which S. flexneri actively protects itself from autophagy markers. We find that the subpopulation of S. flexneri not associated with certain autophagy markers is universally associated with the host multifunctional protein Toca-1. Based on our findings and on published data, we hypothesize that in the setting of vacuolar membrane remnants, which normally induce innate immune responses, Toca-1 serves as a scaffold that (1) is anchored to membrane fragments through IcsB and IpaB, and (2) coordinates repression of autophagy and restriction of pro-inflammatory cytokine production. Specifically, we hypothesize that (i) IpaB, IcsB, OspC2/3 proteins, and Toca-1 form a complex associated with vacuolar membrane remnants; (ii) the complex assembles on IpaB that has been inserted into the plasma membrane soon after contact of bacteria with the membrane; and, (iii) the IpaB-IcsB-Toca-1-OspC2/3 protein complex per se interferes with pro- inflammatory cytokine production by promoting OspC3-mediated inhibition of caspase activation. The exploratory investigations proposed in this R21 application will test aspects of this hypothesis. Aim 1: Investigate whether IcsB, OspC2/3 proteins, IpgD, and/or Toca-1 form a complex associated with vacuolar membrane, and if they do, characterize how. Aim 2: Investigate whether the IpaB-IcsB-Toca-1-OspC2/3 protein complex promotes interference with caspase activation. The proposed investigations are highly likely to lead to new insights into mechanisms of S. flexneri manipulation of innate immune responses early during infection. The results obtained from these investigations are likely to have important implications for infection by all intracellular microorganisms and for modulation of innate immune responses more generally.

描述（由申请人提供）：哺乳动物细胞采用多种先天免疫机制来识别和消除入侵的微生物，包括细胞内颗粒的自噬和促炎细胞因子介导的炎症细胞募集到感染部位。志贺氏菌在几分钟内。或沙门氏菌属。进入细胞后，自噬被激活，炎性体受体和接头在细胞内细菌周围募集。细胞内细菌的大量亚群避免与自噬标记物相关。这种细菌亚群如何逃避这些标记的识别尚不清楚。我们的初步数据表明，福氏链霉菌主动保护自身免受自噬标记的影响。我们发现福氏链霉菌亚群与某些自噬标记物不相关，但普遍与宿主多功能蛋白 Toca-1 相关。根据我们的发现和已发表的数据，我们假设在通常诱导先天免疫反应的液泡膜残余物中，Toca-1 充当支架，(1) 通过 IcsB 和 IpaB 锚定到膜片段上，并且 ( 2)协调自噬的抑制和促炎细胞因子产生的限制。具体来说，我们假设 (i) IpaB、IcsB、OspC2/3 蛋白和 Toca-1 形成与液泡膜残余物相关的复合物； (ii) 复合物在细菌与质膜接触后不久就被插入到质膜中的 IpaB 上组装； (iii)IpaB-IcsB-Toca-1-OspC2/3蛋白复合物本身通过促进OspC3介导的半胱天冬酶激活抑制来干扰促炎细胞因子的产生。此 R21 应用程序中提出的探索性研究将测试该假设的各个方面。目标 1：研究 IcsB、OspC2/3 蛋白、IpgD 和/或 Toca-1 是否形成与液泡膜相关的复合物，如果形成，请描述其形成方式。目标 2：研究 IpaB-IcsB-Toca-1-OspC2/3 蛋白复合物是否会促进干扰 caspase 激活。拟议的研究很可能对福氏链球菌在感染早期操纵先天免疫反应的机制产生新的见解。这些调查获得的结果可能具有重要意义 用于所有细胞内微生物的感染以及更广泛地调节先天免疫反应。