Physiological roles of regulated changes in membrane phospholipid composition

描述（由申请人提供）：膜的关键生物学功能取决于其磷脂组成。因此，细菌的主要膜甘油磷脂保持几乎恒定的比例。然而，环境信号可以诱导阴离子与两性离子磷脂的摩尔比的变化，这就提出了头基团组成调节变化的生理作用的问题。本研究的具体目的是利用遗传和生化方法研究革兰氏阴性病原体肠沙门氏菌中磷脂头群组成的调节变化是否影响与磷脂的大分子相互作用的活性。目的1：设计具有可调节磷脂基团组成的沙门氏菌菌株。目的2是研究磷脂成分是否会影响PhoQ的生化特性和传感能力，PhoQ是一种整体膜传感器激酶，利用配体介导的与阴离子磷脂的相互作用来检测信号，并对低胞外质Mg2+、抗菌肽的存在和酸性ph做出反应。目的3是研究磷脂成分的调节变化是否介导对magainin 2的抗性。一种阳离子抗菌肽，可破坏膜以杀死细菌。目标2和目标3将采用独立和平行的方法：在目标1中构建的菌株将用于体内实验，重组的生化脂质体系统将用于体外实验。这些实验的结果将表明磷脂头群组成的调节变化是否会调节整体膜传感器激酶的活性或介导对阳离子抗菌肽的抗性。这些目标的实现将使对人类病原体中磷脂头群组成变化的遗传研究成为可能，并将阐明一种基本细胞成分的新生理功能。

DESCRIPTION (provided by applicant): The critical biological functions of membranes depend on their phospholipid composition. Consequently, bacteria maintain a nearly constant ratio of major membrane glycerophospholipids. Nevertheless, environmental signals can induce changes in the molar ratio of anionic to zwitterionic phospholipids, raising questions about the physiological roles of regulated changes in headgroup composition. The specific aims of this proposed research investigate whether regulated changes in phospholipid headgroup composition affect activities that involve macromolecular interactions with phospholipids in the Gram-negative pathogen Salmonella enterica using genetic and biochemical approaches. Aim 1 is to engineer Salmonella strains with adjustable phospholipid headgroup compositions. Aim 2 is to examine whether phospholipid composition affects the biochemical properties and sensing capabilities of PhoQ, an integral membrane sensor kinase that utilizes ligand-mediated interactions with anionic phospholipids to detect signals and to respond to low extracytoplasmic Mg2+, the presence of antimicrobial peptides, and acidic pH. Aim 3 is to investigate whether regulated changes in phospholipid composition mediate resistance to magainin 2, a cationic antimicrobial peptide that disrupts membranes to kill bacteria. Independent and parallel approaches will be adopted to address Aims 2 and 3: strains constructed in Aim 1 will be utilized for in vivo experiments, and reconstituted biochemical liposome systems will be utilized for in vitro experiments. Results from these proposed experiments will indicate whether regulated changes in phospholipid headgroup composition modulate the activities of an integral membrane sensor kinase or mediate resistance to a cationic antimicrobial peptide. Accomplishment of these aims will enable genetic investigations of alterations in phospholipid headgroup composition in a human pathogen and will illuminate novel physiological functions for an essential cellular component. PUBLIC HEALTH RELEVANCE: Biological membranes form barriers around cells, enclose compartments, and contain molecules that have essential functions for life. This proposal aims to understand whether changes in the composition of the inner membrane of the pathogenic bacterium Salmonella enterica, which causes gastroenteritis and typhoid fever in humans, affect the ability of Salmonella to adapt to new environments and to resist killing by antimicrobial peptides. Results from this proposed research will provide an understanding of the regulated cellular changes that enable Salmonella to prosper in different locales and to cause disease.