Structure function studies in intestinal epithelial JAM

描述（由申请方提供）：胃肠道的上皮衬里形成重要的保护屏障，将管腔抗原和毒素与下层组织隔室隔开。患有炎症性肠病（IBD）（包括克罗恩病和溃疡性结肠炎）的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。在急性炎症和慢性损伤的肠区域的上皮衬里中，都记录了细胞旁通透性的增加。上皮屏障功能在很大程度上由称为紧密连接（TJ）的顶端最细胞间连接调节。TJ不仅将管腔区室与组织空间分开，而且已经显示在不同的生理和病理状态下调节溶质穿过细胞旁空间的运动。上皮TJ中的跨膜蛋白包括封闭蛋白、封闭蛋白家族的成员、连接粘附分子（JAM）-A和科萨基和腺病毒受体（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。在这个提议中，我们继续基于结构-功能的方法来研究人类JAM-A。该提案的具体目标集中在确定介导JAM-A功能的细胞内事件和负责此的JAM-A的细胞外嗜同性相互作用的结构基础上。我们将主要利用体外细胞培养系统，该系统适于解剖出肠上皮细胞系中的生化和分子事件，并与小鼠体内研究相结合，以突出相关性。长期目标是将我们关于JAM-A功能的分子调节的发现与IBD的病理生理学相关联。了解调节细胞间连接和液体和溶质的细胞旁运动的基本机制可能为粘膜疾病（如IBD）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.