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，细菌保持一个几乎恒定的比例主要膜甘油磷脂。然而，环境信号可以诱导阴离子两性离子磷脂的摩尔比的变化，提出了关于头基组成的调节变化的生理作用的问题。这项拟议的研究的具体目的是调查磷脂头基组成的调节变化是否会影响活动，涉及大分子与磷脂的革兰氏阴性病原体沙门氏菌肠道使用遗传和生化方法的相互作用。目的1是工程化具有可调节的磷脂头基组成的沙门氏菌菌株。目的2是检查磷脂组成是否影响PhoQ的生物化学性质和传感能力，PhoQ是一种整合的膜传感器激酶，其利用配体介导的与阴离子磷脂的相互作用来检测信号并响应于低的胞质外Mg 2+、抗菌肽的存在和酸性pH。目的3是研究磷脂组成的调节变化是否介导对爪蟾抗菌肽2的抗性，一种破坏细胞膜杀死细菌的阳离子抗菌肽。将采用独立和平行的方法来解决目标2和3：目标1中构建的菌株将用于体内实验，重构的生化脂质体系统将用于体外实验。从这些拟议的实验结果将表明是否调节磷脂头基组合物的变化调节的活动的一个完整的膜传感器激酶或介导的耐药性的阳离子抗菌肽。这些目标的实现将使人类病原体中磷脂头基组成的改变的遗传学研究成为可能，并将阐明一种重要细胞成分的新生理功能。 公共卫生相关性：生物膜在细胞周围形成屏障，封闭隔间，并包含具有生命基本功能的分子。该提案旨在了解导致人类胃肠炎和伤寒的致病菌肠道沙门氏菌的内膜组成的变化是否影响沙门氏菌适应新环境和抵抗抗菌肽杀死的能力。这项拟议研究的结果将提供对调节细胞变化的理解，这些变化使沙门氏菌能够在不同的地方繁荣并导致疾病。

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.