Structure function studies in intestinal epithelial JAM

描述（由申请人提供）：胃肠道上皮形成重要的保护屏障，将腔内抗原和毒素与底层组织隔室分开。包括克罗恩病和溃疡性结肠炎在内的炎症性肠病（IBD）患者在临床上表现为复发性肠道炎症和腹泻。已经提出了许多机制来解释这些临床症状，包括肠上皮屏障功能缺陷。在肠急性炎症和慢性损伤区域的上皮内，细胞旁通透性增加已被证实。上皮屏障功能在很大程度上是由最顶端的细胞间连接紧密连接（TJ）调节的。TJ不仅将管腔室与组织空间分离，而且在不同的生理和病理状态下调节溶质在细胞旁空间的运动。上皮性TJs中的跨膜蛋白包括occludin、claudin家族成员、连接粘附分子(JAM)-A和柯萨奇和腺病毒受体（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、细胞形状和细胞-基质粘附方面具有重要的功能。在本文中，我们继续采用基于结构功能的方法来研究人类JAM-A。本提案的具体目的集中在确定介导JAM-A功能的细胞内事件以及负责此功能的JAM-A的细胞外亲同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来解剖肠上皮细胞系的生化和分子事件，并与小鼠体内研究相结合，以突出相关性。长期目标是将JAM-A功能的分子调控与IBD的病理生理联系起来。了解调节细胞间连接和细胞旁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渗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.