EPITHELIAL CXCR4 IN A MUCOSAL COMMUNICATION NETWORK

描述（由申请人提供）：肠上皮细胞是粘膜免疫的积极伙伴，包括自我更新的物理屏障，对于最小化外部环境的外来和有毒刺激至关重要。趋化因子是普遍存在的调节因子，参与白细胞的激活和定向运输，是生理性粘膜免疫反应的重要组成部分。这些分子的生物学功能是通过趋化因子受体介导的，它们刺激特定靶细胞的迁移、增殖和分化。肠上皮细胞表达一夫一妻制的趋化因子/趋化因子受体对，这在体内已被证明是必不可少的。本提案的总体目标是探讨趋化因子受体CXCR4通过调节上皮屏障完整性在建立先天粘膜宿主防御中的作用。迄今为止，CXCR4基因缺陷小鼠的胚胎致死性阻碍了对CXCR4在胃肠道粘膜中的生理作用的研究。我们将使用肠上皮组织培养模型和条件敲除小鼠来机制地确定CXCR4对粘膜屏障的管理。Aim 1的研究将采用人类和大鼠肠上皮培养模型来验证CXCR4信号通过g蛋白和PI3K偶联调节上皮恢复并建立安全上皮屏障的假设。在Aim 2中，我们将通过测试CXCR4间接调节屏障维持的假设来扩展我们的研究；通过g蛋白阻断cAMP，直接通过rho激活的肌动蛋白骨架和细胞-细胞连接的调节。在Aim 3中，我们将使用条件敲除小鼠来验证CXCR4是体内肠上皮迁移和屏障形态发生的关键效应者的假设。这些研究将首次详细介绍趋化因子受体CXCR4作为粘膜屏障稳态和伤口修复的调节因子的功能。阐明调节这一过程的生化和细胞机制将对设计治疗策略以管理由传染病或慢性炎症性疾病引起的肠道损伤具有重要意义。

DESCRIPTION (provided by applicant): The cells of the intestinal epithelium are an active partner in mucosal immunity and comprise a self renewing physical barrier that is essential to minimizing exposure to foreign and toxic stimuli from the external environment. Chemokines are ubiquitous regulatory factors that participate in the activation and directional trafficking of leukocytes, and are a significant component of the physiologic mucosal immune response. The biologic function of these molecules is mediated through chemokine receptors, which stimulate migration, proliferation and differentiation in specific target cells. Intestinal epithelial cells express a monogamous chemokine/chemokine receptor pair that has been shown to be essential in vivo. The overall objective of this proposal is to explore the role of the chemokine receptor CXCR4 in establishing innate mucosal host defense though the regulation of epithelial barrier integrity. To date, investigations into the physiologic role of CXCR4 in the gastrointestinal mucosa have been prevented by the embryonic lethality of CXCR4 gene deficient mice. We will use both tissue culture models of intestinal epithelia and conditional knockout mice to mechanistically define CXCR4 management of the mucosal barrier. Studies in Aim 1 will employ human and rat intestinal epithelial culture models to test the hypothesis that CXCR4 signals via coupled G-proteins and PI3K to regulate epithelial restitution and establish a secure epithelial barrier. In Aim 2, we will extend our studies by testing the hypothesis that CXCR4 regulates barrier maintenance indirectly; through G-protein blockade of cAMP, and directly, through Rho-activated modulation of the actin cytoskeleton and cell-cell junctions. In Aim 3 we will use conditional knockout mice to test the hypothesis that CXCR4 is a critical effector of intestinal epithelial migration and barrier morphogenesis in vivo. These studies will be the first to detail functions for the chemokine receptor CXCR4 as a regulator of mucosal barrier homeostasis and wound repair. Elucidation of the biochemical and cellular mechanisms regulating this process will have great relevance to the design of therapeutic strategies to manage intestinal damage sustained as a result of infectious disease or chronic inflammatory disorders.