The Outer Surface of Vibrio Cholerae

描述(申请人提供)：细菌细胞包膜是一种特殊而复杂的结构，可以保护细菌免受周围环境的影响。革兰氏阴性细菌的一个决定性特征是存在一层外膜，包裹着这些生物体的肽聚糖层。内膜由甘油磷脂组成，外膜是一个独特的、不对称的双层，甘油磷脂局限于内叶，而脂A，一种独特的糖脂，定位于外叶。脂类A是脂多糖(LPS)的脂类部分，将脂多糖锚定在细菌表面。细菌已经进化出各种机制来适应他们不可预测的和往往是敌对的环境，包括重塑他们的膜结构的策略。通常，这些修饰提供对哺乳动物先天免疫系统组成部分的抵抗力，并调节宿主对入侵微生物的识别。脂多糖的脂质A结构域通过TLR4-MD2的识别，对人类有毒，是天然免疫系统的有力刺激因子。许多革兰氏阴性病原体通过改变其脂类A结构来逃避宿主的检测。此外，脂类A和甘油磷脂的结构变化可以直接影响细菌对宿主抗菌肽等天然免疫效应的抵抗力。这项应用的总体目标是解开霍乱弧菌重塑其膜结构的分子机制，以及这种重塑在毒力中所起的作用。目前应用的具体目标是：(1)霍乱弧菌内毒素甘氨酸修饰的生化和遗传学分析；(2)霍乱弧菌内毒素磷乙醇胺修饰的生化和遗传学分析；(3)阐明霍乱弧菌磷脂重塑所需的机制；(4)霍乱弧菌膜重塑对宿主天然免疫反应的影响。这些目标的完成将直接有助于我们理解脂质重塑/修饰机制如何影响发病机制。最后，这项工作不仅将带来对霍乱疾病的更好了解，还将为疫苗开发和产生可用作潜在佐剂和/或内毒素拮抗剂的工程内毒素结构的能力提供新的途径。

DESCRIPTION (provided by applicant): The bacterial cell envelope is a remarkable and complex structure that guards bacteria from their surrounding environment. A defining feature of Gram-negative bacteria is the presence of an outer membrane that encapsulates the peptidoglycan layer of these organisms. While the inner membrane is composed of glycerophospholipids, the outer membrane is a unique, asymmetric bilayer with glycerophospholipids confined to the inner leaflet and lipid A, a unique saccharolipid, localized to the outer leaflet. Lipid A is the lipid moiety of lipopolysaccharide (LPS) and anchors LPS to the bacterial surface. Bacteria have evolved various mechanisms to adapt to their unpredictable and often hostile surroundings, including strategies for remodeling their membrane architecture. Often these modifications provide resistance to components of the mammalian innate immune system and modulate host recognition of the invading microorganism. The lipid A domain of LPS is toxic to humans and potent stimulator of the innate immune system through via recognition by TLR4- MD2. A number of Gram-negative pathogens modify their lipid A structure to evade host detection. Additionally, structural alteration of lipid A and glycerophospholipids can directly impact bacterial resistance to innate immune effectors such as host antimicrobial peptides. The overall objective of this application is to unravel the molecular mechanisms by which Vibrio cholerae, the causative agent of the disease cholera, remodels it membrane architecture and the role this remodeling plays in virulence. The Specific Aims of the current application are: (1) biochemical and genetic analysis of glycine modification of V. cholerae LPS; (2) Biochemical and genetic analysis of phosphoethanolamine modification of V. cholerae LPS; (3) elucidation of machinery required for phospholipid remodeling in V. cholerae; and (4) impact of V. cholerae membrane remodeling on the host innate immune response. The completion of these Aims will directly contribute to our understanding of how lipid remodeling/modification machinery impacts pathogenesis. Finally, from this work will come not only a better understanding of the disease cholera, but new avenues for vaccine development and the ability to generate engineered LPS structures that could serve as potential adjuvants and/or LPS antagonists.