The Role of TamAB in Salmonella Pathogenesis

TamAB 在沙门氏菌发病机制中的作用

基本信息

批准号：
10415194
负责人：
JAMES M. SLAUCH
金额：
$ 22.67万
依托单位：
UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN
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：
2021-06-01 至 2024-05-31
项目状态：
已结题

项目摘要

ABSTRACT Salmonella Typhimurium is a major food-borne pathogen that propagates within macrophages, leading to life-threatening disease. The long-term objectives of our research are to understand the molecular mechanisms by which Salmonella circumvents the host immune system to cause disease. The outer membrane of the bacterium is the interface with the immune system. Outer membrane beta- barrel proteins are normally assembled by the Bam complex. A homolog of Bam, the TamAB translocation module is highly conserved in the Gammaproteobacteria. Originally proposed as a system for assembly of a subset of beta-barrel proteins, the so-called autotransporter proteins, the actual function of TamAB is unknown. We have discovered that tamAB is a previously unrecognized member of the PhoPQ regulon and is induced when Salmonella is replicating in macrophages, suggesting that this system is important for virulence. Indeed, our preliminary data strongly support our primary hypothesis that TamAB is induced to assist Bam function under the stressful conditions in the phagosome. Our secondary hypothesis is that TamAB is required for proper assembly of particular proteins in the outer membrane under the conditions in the phagosome, and that decreases or loss of these proteins attenuate Salmonella virulence. In Aim 1, we will determine outer membrane composition using mass spectrometry, and monitor expression of envelope stress response systems, to determine the biochemical and regulatory effects caused by loss of TamAB, thereby identifying proteins that directly or indirectly require TamAB for proper assembly. We will also isolate mutations that suppress in vitro defects in outer membrane permeability conferred or exacerbated by loss of TamAB. In Aim 2, we will characterize identified loci and their role in macrophage survival and virulence. The overall role of the identified factors in macrophage survival will be revealed by genetic interactions with tamAB. Understanding the roles of TamAB will inform us about the conditions in the phagosome leading to outer membrane assembly stress and the mechanisms used by Salmonella to combat them. Identifying the specific proteins affected by loss of TamAB also identifies additional virulence factors critical for Salmonella pathogenesis.

抽象的鼠伤寒沙门氏菌是一种主要的食源性病原体，在巨噬细胞内繁殖，导致危及生命的疾病。我们研究的长期目标是了解沙门氏菌规避宿主免疫系统引起疾病的分子机制。细菌的外膜是与免疫系统的界面。外膜β- 桶状蛋白通常由 Bam 复合体组装。 Bam 的同源物 TamAB 易位模块在伽马变形菌中高度保守。最初建议作为一个系统用于组装β-桶蛋白的子集，即所谓的自转运蛋白，实际 TamAB 的功能尚不清楚。我们发现 tamAB 是一个以前未被识别的成员 PhoPQ 调节子的作用，当沙门氏菌在巨噬细胞中复制时被诱导，这表明该系统对于毒力很重要。事实上，我们的初步数据有力地支持了我们的主要观点假设 TamAB 在压力条件下被诱导以协助 Bam 功能吞噬体。我们的第二个假设是 TamAB 是正确组装在吞噬体的条件下外膜中的特定蛋白质，并且这些蛋白质的减少或丢失会减弱沙门氏菌的毒力。在目标 1 中，我们将确定使用质谱分析外膜组成，并监测包膜应力的表达响应系统，以确定 TamAB 损失引起的生化和调节效应，从而识别直接或间接需要 TamAB 才能正确组装的蛋白质。我们也会分离抑制体外膜通透性缺陷的突变，或 TamAB 的缺失会加剧这种情况。在目标 2 中，我们将描述已识别的位点及其在巨噬细胞的存活和毒力。已确定因素在巨噬细胞存活中的总体作用将通过与 tamAB 的遗传相互作用来揭示。了解 TamAB 的角色将为我们提供帮助关于吞噬体中导致外膜组装应力的条件以及沙门氏菌用来对抗它们的机制。识别受缺失影响的特定蛋白质 TamAB 还确定了对沙门氏菌发病机制至关重要的其他毒力因子。