Role and Regulation of colon Trafficking Novel G-Protein Coupled Receptors

 描述(申请人提供)：主题范围和基本原理：炎症性肠病(IBD)是一种慢性免疫性疾病，影响数百万美国人，并有重大的健康和经济负担。虽然IBD的病因尚不清楚，但疾病的发病机制部分归因于肠道固有层中效应分子CD4+T细胞的浸润增加和异常炎症反应。阻断白细胞转运已被证明是有效的治疗策略。然而，控制CD4+T细胞迁移到结肠的机制已经排除了结肠炎的选择性治疗，因为结肠特异性转运分子的定义很差。背景与假设：我们最近发现GPR15是一种T细胞表达的结肠特异性运输受体，在实验性结肠炎中发挥重要作用。我们发现溃疡性结肠炎(UC)患者结肠Th2细胞高表达GPR15，而小鼠Th2细胞不表达GPR15。与小鼠不同，人结肠Tregs在IBD和非IBD患者中似乎都不表达GPR15。对小鼠和人结肠中GPR15表达的详细分析使我们确定了Th2和Treg表达的物种差异，这些差异与Th2相关的GATA3和Treg相关的Foxp3转录因子分别与人和小鼠GPR15增强子的优先结合有关。除UC结肠Th2细胞表达GPR15外，IBD和非IBD结肠中有相当比例的GPR15+CD4+效应T细胞缺乏Th1或Th17细胞因子表达。因此，该项目的目标之一是进一步鉴定非Th2结肠GPR15+CD4+效应T细胞，并了解它们的功能意义。与GATA3结合基序不同，GPR15增强子中存在两个与芳烃受体(AHR)保守的结合位点。因此，我们的总体目标是确定GPR15的调节，并确定人类结肠中的T细胞运输分子，并与小鼠进行比较。在目标1中，我们将描述和定义正常人和炎症性结肠中的CD_4~+T效应细胞，并验证GPR15~+CD_4~+T效应细胞代表稳态和结肠炎状态下结肠中的特殊功能亚群(S)的假设。在目标2中，我们将确定GPR15在小鼠和人类中表达的调节机制，并检验GPR15是AHR调节的蛋白，在AH配体反应的效应T细胞的肠道运输中发挥作用。在目标3中，我们将定义树突状细胞来调节结肠中CD 4+T效应细胞上GPR15的表达，并测试结肠树突状细胞亚群(S)在启动结肠归巢CD 4+T效应细胞方面是有效的假设。意义和影响：为了开发新的特异性治疗靶点并了解IBD/结肠炎的发病机制，阐明效应性T细胞进入结肠的细胞机制是至关重要的。了解结肠T细胞贩运的短期影响将是确定结肠特异性T细胞贩运受体的作用和调节。潜在的长期影响具有GRET临床意义，因为我们的研究可能导致结肠T细胞特异性靶点的开发，如 有效的IBD新疗法。

 DESCRIPTION (provided by applicant): Topic Area and rationale: Inflammatory bowel disease (IBD) is a chronic immune disease that affects millions of Americans and has significant health and economic burden. Although the etiology of IBD remains unknown, disease pathogenesis is attributed in part to the increased infiltration and aberrant inflammatory responses of effector CD4+ T cells in the intestine lamina propria. Blocking of leukocyte trafficking has proved to be effective therapeutic strategy. However, mechanisms that govern CD4+ T cell migration to the colon have precluded colitis-selective treatment, as colon-specific trafficking molecules are poorly defined. Background & Hypothesis: We recently identified GPR15 as a T cell-expressed colon-specific trafficking receptor that plays a significant role in experimental colitis. We found high expression of GPR15 on colon Th2 cells of ulcerative colitis (UC) patients but is absent in mouse Th2 cells. In contrast to the mouse, human colon Tregs in both IBD and non-IBD patients do not seem to express GPR15. Detailed analysis of GPR15 expression in mouse versus human colon led us to identify species differences in Th2 versus Treg expression that correlated with preferential binding of Th2-associated GATA3 vs. Treg-associated Foxp3 transcription factor binding to human and mouse GPR15 enhancers, respectively. In addition to GPR15 expression on colon Th2 cells of UC, significant proportion of the GPR15+ CD4+ effector T cells in the IBD and non-IBD colons lack Th1 or Th17 cytokine expression. As a result, one of the project's goals is to further characterize the non-Th2 colon GPR15+ CD4+ effector T cells and understand their functional significance. Unlike the GATA3 binding motif, there exist two conserved binding sites for the aryl hydrocarbon receptor (AHR) in the GPR15 enhancer. Thus, our overall goal is to determine regulation of GPR15 and define T cell trafficking molecules in the human colon and compare to the mouse. In aim 1 we will characterize and define CD4+ T effector cells in the normal and inflamed human colon and test the hypothesis that GPR15+ CD4+ T effector cells represent specialized functional subset(s) in the colon under homeostasis and colitis. In aim 2 we will determine mechanisms that regulate GPR15 expression in the mouse and human, and test the hypothesis that GPR15 is AHR-regulated protein that plays a role in intestinal trafficking of effector T cells in response to AH ligands. Under aim 3 we will define dendritic cells that regulate GPR15 expression on CD4+ T effector cells in the colon and test the hypothesis that subset(s) of colon dendritic cells are efficient in priming colon homing CD4+ T effector cells. Significance & Impact: In order to develop new specific therapeutic targets and understand the pathogenesis of IBD/colitis, it is essential to elucidate the cellular mechanisms by which effector T cells gain access to the colon. The short-term impact of understanding colon T cell trafficking will be to define role and regulation of colon specific T cell trafficking receptors. The potential long-term impact is of gret clinical significance, as our studies could lead to development of colon T cell specific targets as potent new IBD therapeutics.