CHEMOKINE RECEPTOR EXPRESSION ON INTESTINAL EPITHELIUM

肠上皮细胞表达一系列细胞因子和趋化因子受体，使这些细胞成为免疫介质的靶标。人肠上皮细胞调节营养物质和电解质运输，维持屏障完整性，并在炎症介质或微生物感染的反应中释放促炎细胞因子和趋化因子，这与这些细胞在启动和调节粘膜先天免疫和获得性免疫中的整体作用是一致的。该建议的总体假设是，人类肠上皮细胞组成性表达的确定的趋化因子受体阵列激活了g蛋白偶联信号通路，使这些细胞成为趋化因子信号传导的功能靶点。Aim 1的研究将表征人肠上皮细胞表达的趋化因子受体的细胞定位、配体结合和受体内化。肠上皮细胞分化为根尖和基底外侧结构域，主要表现为专门用于营养吸收和离子分泌的根尖表面蛋白和专门用于维持电化学梯度的基底外侧膜蛋白。这些研究将使用分子和免疫细胞化学技术来确定体外肠上皮细胞组成表达的趋化因子受体的根尖和基底外侧细胞定位、配体结合特性和受体内化/脱敏。Aim 2的研究将采用逐步的方法来定义由人肠上皮细胞表达的趋化因子受体激活的g蛋白连接的细胞内信号通路。趋化因子受体与特定的g蛋白偶联，在不同的细胞类型中激活几种细胞内信号通路。这些研究将侧重于确定肠上皮细胞组成性表达的趋化因子受体所激活的特异性g蛋白和细胞内信号通路。总之，这些研究将提供潜在的免疫介导的上皮细胞功能调节的见解，如离子分泌，通过趋化因子受体表达肠上皮细胞的细胞内调节信号通路的收敛。人肠上皮细胞对趋化因子受体的表达和信号传导表明，这些细胞可能以自分泌或旁分泌的方式对肠趋化因子受体配体作出反应，这与这些细胞在粘膜炎症反应中起重要作用的观点是一致的。

Intestinal epithelial cells express an array of cytokine and chemokine receptors allowing these cells to be targets for immune mediators. Human intestinal epithelial cells regulate nutrient and elctrolyte transport, maintain barrier integrity, and can release proinflammatory cytokines and chemokines in response to inflammatory mediators or microbial infection, consistent with an integral role for these cells in initiating and regulating mucosal innate and acquired immunity. The overall hypothesis of this proposal is that the defined array of chemokine receptors constitutively expressed by human intestinal epithelial cells activates G-protein-coupled signaling pathways permitting these cells to be functional targets of chemokine signaling. Studies in Aim 1 will characterize the cellular localization, ligand binding, and receptor internalization of chemokine receptors expressed by human intestinal epithelial cells. Intestinal epithelial cells are polarized into apical and basolateral domains, typically reflected in apical surface proteins specialized for nutrient absorption and ion secretion and basolateral membrane proteins specialized for maintenance of the electrochemical gradient. These studies will use molecular and immunocytochemical techniques to define the apical and basolateral cellular localization, ligand binding characteristics, and receptor internalization/desensitization of chemokine receptors constitutively expressed by intestinal epithelial cells in vitro. Studies in Aim 2 will use a step-wise approach to define the G-protein linked intracellular signaling pathways activated by chemokine receptors expressed by human intestinal epithelial cells. Chemokine receptors are coupled to specific G-proteins and activate several intracellular signaling pathways in varying cell types. These studies will focus on defining the specific G-protein activated and the intracellular signaling pathways utilized by chemokine receptors constitutively expressed by intestinal epithelial cells. Together these studies will provide insights into the potential immune mediated regulation of epithelial cell functions, e.g. ion secretion, through the convergence of intracellular regulatory signaling pathways in chemokine receptor expressing intestinal epithelial cells. The expression and signaling of chemokine receptors by human intestinal epithelial cells indicates these cells may respond in an autocrine or paracrine manner to enteric chemokine receptor ligangs and is consistent with the notion that these cells have an essential role in the mucosal response to inflammation.