Structure function studies in intestinal epithelial JAM

描述(申请人提供)：胃肠道的上皮衬里形成一个重要的保护性屏障，将管腔抗原和毒素与下面的组织隔间隔开。炎症性肠病(IBD)患者包括克罗恩病和溃疡性结肠炎，临床表现为复发的肠炎和腹泻。许多机制已经被提出来解释这些临床症状，包括肠上皮屏障功能缺陷。在急性炎症和慢性肠损伤区的上皮衬里中，细胞旁通透性增加。上皮屏障功能在很大程度上由顶端最紧密的细胞间连接(TJ)调节。TJ不仅将腔室与组织间隙分开，而且已被证明在不同的生理和病理状态下调节溶质在细胞旁间隙中的移动。上皮性TJ的跨膜蛋白包括Occludin，Claudin家族成员，JAM-A，Coxsackie和腺病毒受体(CAR)。我们的研究表明，JAM-A是一种关键的TJ蛋白，在调节肠上皮屏障、细胞形态和细胞-基质黏附方面具有重要功能。在这个建议中，我们继续采用基于结构功能的方法来研究人类JAM-A。这项建议的具体目标集中在确定介导JAM-A功能的细胞内事件以及导致这一点的JAM-A胞外亲水性相互作用的结构基础。我们将主要利用体外细胞培养系统，结合小鼠体内研究，剖析肠上皮细胞系中的生化和分子事件，以突出相关性。长期目标是将我们关于JAM-A功能的分子调控的发现与IBD的病理生理学联系起来。了解调节细胞间连接和细胞外液体和溶质运动的基本机制可能为IBD等粘膜疾病的病理生理学提供线索，并有助于开发新的治疗策略，旨在减少与这些疾病相关的通透性增强和粘膜损伤。

DESCRIPTION (provided by applicant): The epithelial lining of the gastrointestinal tract forms a vital protective barrier that separates luminal antigens and toxins from the underlying tissue compartments. Patients with inflammatory bowel disease (IBD) encompassing both Crohn's disease and ulcerative colitis present clinically with relapsing intestinal inflammation and diarrhea. Numerous mechanisms have been proposed to explain these clinical symptoms and include defective intestinal epithelial barrier function. Increased paracellular permeability has been documented in the epithelial lining from both the acutely inflamed and chronically damaged areas of the intestine. Epithelial barrier function is regulated to a large extent by the apical most intercellular junction referred to as the tight junction (TJ). The TJ not only separates the lumenal compartment from the tissue space, but has been shown to regulate movement of solutes across the paracellular space in diverse physiologic and pathologic states. The transmembrane proteins in epithelial TJs include occludin, members of the claudin family, junctional adhesion molecule (JAM)-A and coxsackie and adenovirus receptor (CAR). Our studies indicate that JAM-A is a key TJ protein with several functions important in regulating intestinal epithelial barrier, cell shape and cell-matrix adhesion. In this proposal, we continue a structure-function based approach to study human JAM-A. The specific aims of this proposal are focused on determining intracellular events that mediate JAM-A function and the structural basis of extracellular homophilic interactions of JAM-A responsible for this. We will primarily utilize in vitro cell culture systems amenable to dissecting out biochemical and molecular events in intestinal epithelial cell lines in concert with in vivo studies in mice to highlight relevance. The long term goal is to correlate our findings on the molecular regulation of JAM-A function with pathophysiology in IBD. Understanding basic mechanisms regulating intercellular junctions and paracellular movement of fluids and solutes may provide clues to the pathophysiology of mucosal diseases such as IBD and aid in the development of new therapeutic strategies aimed at diminishing enhanced permeability and mucosal injury associated with these conditions.