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活性伴侣，并构成自我更新的物理屏障，这对于最大限度地减少暴露于来自外部环境的外来和毒性刺激至关重要。趋化因子是参与白细胞活化和定向运输的普遍存在的调节因子，并且是生理性粘膜免疫应答的重要组分。这些分子的生物学功能通过趋化因子受体介导，其刺激特定靶细胞的迁移、增殖和分化。肠上皮细胞表达一对已被证明在体内是必不可少的一夫一妻制的趋化因子/趋化因子受体。该提案的总体目标是探索趋化因子受体CXCR 4通过调节上皮屏障完整性在建立先天性粘膜宿主防御中的作用。迄今为止，研究CXCR 4在胃肠道粘膜中的生理作用已经被CXCR 4基因缺陷小鼠的胚胎致死性所阻止。我们将使用肠上皮细胞和条件性基因敲除小鼠的组织培养模型来机械地定义CXCR 4对粘膜屏障的管理。目的1中的研究将采用人和大鼠肠上皮培养模型来测试CXCR 4通过偶联的G蛋白和PI 3 K信号传导来调节上皮恢复并建立安全的上皮屏障的假设。在目标2中，我们将通过测试CXCR 4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测试CXCR 4是体内肠上皮迁移和屏障形态发生的关键效应子的假设。这些研究将是第一个详细说明趋化因子受体CXCR 4作为粘膜屏障稳态和伤口修复调节剂的功能。阐明调节这一过程的生化和细胞机制将与设计治疗策略以管理由于感染性疾病或慢性炎症性疾病而持续的肠损伤具有很大的相关性。

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.