Host innate immune mechanisms control temporal expression of flagellin by pathogenic Salmonella

宿主先天免疫机制控制致病性沙门氏菌鞭毛蛋白的瞬时表达

• 批准号: 10426346
• 负责人: Naeha Subramanian
• 金额: $ 54.4万
• 依托单位: INSTITUTE FOR SYSTEMS BIOLOGY
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-10 至 2026-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10426346
• 关键词: Bacteria; CASP1 gene; Cell Death; Cells; Complex; Detection; Development; Down-Regulation; Environment; Enzymes; Event; Feedback; Flagellin; Host Defense; IFNAR1 gene; Immune; Immune Evasion; Immune system; Infection; Inflammasome; Inflammatory; Interferon Type I; Interferon-beta; Interferons; Interleukin-1; Investigation; Left; Ligands; Link; Lipids; Lysophosphatidylcholines; Lysophospholipids; Mediating; Microbe; Modeling; Molecular; Multiprotein Complexes; Natural Immunity; Pathogenicity; Phenotype; Play; Population; Process; Production; Refractory; Regulation; Resolution; Risk; Role; Salmonella; Signal Transduction; Stimulus; TLR5 gene; base; cell motility; extracellular; immunopathology; innate immune mechanisms; lipid biosynthesis; macrophage; microbial; neutrophil; novel; pathogen; pathogenic bacteria; response

Project Summary Inflammasomes are multiprotein complexes that sense microbial infections and respond by inducing a caspase- 1-mediated form of inflammatory cell death called pyroptosis. Inflammasomes have been implicated in the detection and clearance of a variety of bacterial pathogens, but little is known about whether there is active cross-talk between the host sensing mechanism and the expression of stimulatory ligands by the pathogen. We have found that inflammasome activation regulates expression of the NLRC4 ligand, flagellin, by Salmonella. A host lipid stimulus released upon NLRC4-mediated macrophage pyroptosis increases expression of flagellin by extracellular bacteria that enhances pyroptosis upon internalization, establishing a positive feedback loop that potentiates Salmonella detection and clearance. As infection progresses, a natural type I interferon-dependent host negative feedback response shuts down expression of NLRC4 and the lysophospholipid biosynthetic enzyme iPLA2 to sub-baseline levels, switching Salmonella to a flagellin-low phenotype inside macrophages. Based on these findings we hypothesize that Salmonella has evolved to co-opt NLRC4 activation and lipid production to initially enhance production of extracellular flagellin that promotes systemic spread of the pathogen at the risk of NLRC4-mediated clearance, and later on take advantage of decreased NLRC4 and lipid production (a host strategy likely aimed at limiting excessive NLRC4-mediated immunopathology) to downregulate flagellin intracellularly within macrophages. In this proposal we will investigate the host cell-intrinsic innate regulatory circuit involving type I IFN signaling, NLRC4 and iPLA2 activity that regulates the temporal switch of Salmonella from a flagellin-high to a flagellin-low phenotype inside macrophages. We will conduct these investigations in the following specific aims: 1) To identify how macrophage pyroptosis promotes early increase in flagellin production by extracellular Salmonella; 2) To dissect the natural type I interferon-dependent host negative feedback response that establishes a NLRC4-low and iPLA2-low intracellular environment prompting Salmonella to switch to a flagellin-low phenotype inside macrophages. Our investigations will identify the temporal and biphasic regulation of a pathogen-derived inflammasome ligand by the very process of inflammasome activation as a novel mode of host-pathogen cross-talk and reveal a host mechanism that Salmonella takes advantage of for flagellin downregulation and immune escape within macrophages. These studies will also have broader implications for understanding how host innate immunity contributes to modulation of microbial effectors impacting the development and resolution of infections.

项目摘要 炎性小体是一种多蛋白复合物，它能感知微生物感染，并通过诱导半胱天冬酶- 1-介导的炎性细胞死亡形式，称为焦亡。炎性小体与 检测和清除各种细菌病原体，但很少有人知道是否有活性 宿主传感机制和病原体刺激配体表达之间的串扰。我们 已经发现炎性小体激活调节沙门氏菌NLRC 4配体鞭毛蛋白的表达。一 在NLRC 4介导的巨噬细胞焦亡时释放的宿主脂质刺激物通过以下途径增加鞭毛蛋白的表达： 细胞外细菌，增强细胞内化后的焦亡，建立正反馈回路， 加强沙门氏菌的检测和清除。随着感染的进展，一种天然的I型干扰素依赖性 宿主负反馈反应关闭NLRC 4的表达， 酶iPLA 2降低到亚基线水平，将沙门氏菌在巨噬细胞内转变为鞭毛蛋白低表型。 基于这些发现，我们假设沙门氏菌已经进化为协同NLRC 4活化和脂质 产生以最初增强促进病原体的系统性传播的细胞外鞭毛蛋白的产生 在NLRC 4介导的清除的风险，并随后利用减少的NLRC 4和脂质产生 （可能旨在限制过度NLRC 4介导的免疫病理学的宿主策略）下调鞭毛蛋白 在巨噬细胞内。在这个建议中，我们将研究宿主细胞内在的先天调节 涉及I型IFN信号传导、NLRC 4和iPLA 2活性的回路，其调节沙门氏菌的时间开关 从鞭毛蛋白高到鞭毛蛋白低的表型。我们将在下列地点进行这些调查： 以下具体目标：1）确定巨噬细胞焦亡如何促进鞭毛蛋白产生的早期增加 2）剖析天然I型干扰素依赖性宿主负反馈 建立低NLRC 4和低iPLA 2细胞内环境的应答，促使沙门氏菌转换 在巨噬细胞内形成鞭毛蛋白低的表型。我们的调查会找出 病原体衍生的炎性体配体的调节是通过炎性体活化的过程来实现的， 宿主-病原体相互作用的新模式，并揭示了沙门氏菌利用宿主机制， 鞭毛蛋白下调和巨噬细胞内的免疫逃逸。这些研究也将有更广泛的 对理解宿主先天免疫如何调节微生物效应物的意义 影响感染的发展和解决。