EPITHELIAL CXCR4 IN A MUCOSAL COMMUNICATION NETWORK

描述(申请人提供)：肠上皮细胞是粘膜免疫的活跃伙伴，并包括一种自我更新的物理屏障，这对于最大限度地减少暴露在外部环境的外来和有毒刺激中是必不可少的。趋化因子是无处不在的调节因子，参与白细胞的激活和定向转运，是生理性黏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，趋化因子受体刺激特定靶细胞的迁移、增殖和分化。肠上皮细胞表达一对一夫一妻制的趋化因子/趋化因子受体对，已被证明是体内必不可少的。这项建议的总体目标是探索趋化因子受体CXCR4在通过调节上皮屏障完整性来建立固有粘膜宿主防御中的作用。到目前为止，CXCR4基因缺陷小鼠的胚胎致死性阻止了对CXCR4在胃肠道粘膜中的生理作用的研究。我们将使用肠上皮细胞的组织培养模型和条件性基因敲除小鼠来机械地定义CXCR4对粘膜屏障的管理。Aim 1的研究将使用人和大鼠肠道上皮细胞培养模型来验证CXCR4信号通过偶联G蛋白和PI3K调节上皮修复和建立安全的上皮屏障的假设。在目标2中，我们将扩展我们的研究，验证CXCR4间接调节屏障维持的假设；通过G蛋白阻断cAMP，以及直接通过Rho激活的对肌动蛋白细胞骨架和细胞-细胞连接的调节。在目标3中，我们将使用条件性基因敲除小鼠来验证CXCR4是体内肠道上皮迁移和屏障形态形成的关键效应因子的假设。这些研究将首次详细说明趋化因子受体CXCR4作为粘膜屏障动态平衡和伤口修复调节因子的功能。阐明调控这一过程的生化和细胞机制将对设计治疗策略以管理因传染病或慢性炎症性疾病造成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.