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

基本信息

批准号：
10636626
负责人：
Naeha Subramanian
金额：
$ 56.45万
依托单位：
INSTITUTE FOR SYSTEMS BIOLOGY
依托单位国家：
美国
项目类别：
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

项目摘要

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.

项目概要炎症小体是多蛋白复合物，可感知微生物感染并通过诱导半胱天冬酶做出反应 1 介导的炎症细胞死亡形式称为细胞焦亡。炎症小体与检测并清除多种细菌病原体，但对于是否存在活性物质知之甚少宿主传感机制与病原体刺激配体表达之间的串扰。我们发现炎性体激活可调节沙门氏菌 NLRC4 配体鞭毛蛋白的表达。一个 NLRC4介导的巨噬细胞焦亡后释放的宿主脂质刺激通过以下方式增加鞭毛蛋白的表达细胞外细菌在内化时增强细胞焦亡，建立正反馈循环增强沙门氏菌的检测和清除。随着感染的进展，天然 I 型干扰素依赖性宿主负反馈反应关闭 NLRC4 和溶血磷脂生物合成的表达酶 iPLA2 低于基线水平，将沙门氏菌转变为巨噬细胞内鞭毛蛋白低的表型。基于这些发现，我们假设沙门氏菌已经进化到选择 NLRC4 激活和脂质最初增强细胞外鞭毛蛋白的产生，从而促进病原体的全身传播面临 NLRC4 介导的清除的风险，然后利用 NLRC4 和脂质产生减少的优势（一种宿主策略，可能旨在限制过度的 NLRC4 介导的免疫病理学）下调鞭毛蛋白细胞内巨噬细胞内。在本提案中，我们将研究宿主细胞内在的先天调节涉及调节沙门氏菌时间开关的 I 型 IFN 信号传导、NLRC4 和 iPLA2 活性的电路巨噬细胞内从高鞭毛蛋白到低鞭毛蛋白表型。我们将在以下具体目标：1) 确定巨噬细胞焦亡如何促进鞭毛蛋白产量的早期增加由细胞外沙门氏菌引起； 2）剖析天然I型干扰素依赖性宿主负反馈建立低 NLRC4 和低 iPLA2 细胞内环境的反应，促使沙门氏菌转换巨噬细胞内鞭毛蛋白低的表型。我们的调查将确定时间和双相通过炎症小体激活的过程来调节病原体衍生的炎症小体配体宿主与病原体相互作用的新模式，揭示了沙门氏菌利用的宿主机制巨噬细胞内鞭毛蛋白下调和免疫逃逸。这些研究也将有更广泛的对理解宿主先天免疫如何促进微生物效应子调节的影响影响感染的发展和解决。