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

 描述（由申请人提供）：主题领域和基本原理：炎症性肠病（IBD）是一种慢性免疫性疾病，影响数百万美国人，并具有显著的健康和经济负担。虽然IBD的病因仍然未知，但疾病发病机制部分归因于肠固有层中效应CD 4 + T细胞的浸润增加和异常炎症反应。阻断白细胞运输已被证明是有效的治疗策略。然而，控制CD 4 + T细胞迁移到结肠的机制已经排除了结肠炎选择性治疗，因为结肠特异性运输分子的定义很差。背景与假设：我们最近发现GPR 15是一种T细胞表达的结肠特异性转运受体，在实验性结肠炎中起着重要作用。我们发现GPR 15在溃疡性结肠炎（UC）患者的结肠Th 2细胞上高表达，但在小鼠Th 2细胞中不表达。与小鼠相反，IBD和非IBD患者中的人结肠TCR 4似乎不表达GPR 15。对小鼠与人结肠中GPR 15表达的详细分析使我们鉴定了Th 2与Treg表达的物种差异，其与Th 2相关的GATA 3与Treg相关的Foxp 3转录因子分别与人和小鼠GPR 15增强子的优先结合相关。除了UC的结肠Th 2细胞上的GPR 15表达之外，IBD和非IBD结肠中显著比例的GPR 15 + CD 4+效应T细胞缺乏Th 1或Th 17细胞因子表达。因此，该项目的目标之一是进一步表征非Th 2结肠GPR 15 + CD 4+效应T细胞并了解其功能意义。与GATA 3结合基序不同，GPR 15增强子中存在两个保守的芳烃受体（AHR）结合位点。因此，我们的总体目标是确定GPR 15的调节，并定义人结肠中的T细胞运输分子，并与小鼠进行比较。在目标1中，我们将表征和定义正常和发炎的人结肠中的CD 4 + T效应细胞，并测试GPR 15 + CD 4 + T效应细胞代表稳态和结肠炎下结肠中的特化功能亚群的假设。在目标2中，我们将确定调节GPR 15在小鼠和人中表达的机制，并测试GPR 15是AHR调节的蛋白质的假设，该蛋白质在响应于AH配体的效应T细胞的肠道运输中起作用。在目标3下，我们将定义调节结肠中CD 4 + T效应细胞上的GPR 15表达的树突状细胞，并测试结肠树突状细胞亚群在引发结肠归巢CD 4 + T效应细胞中有效的假设。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，必须阐明效应T细胞进入结肠的细胞机制。了解结肠T细胞运输的短期影响将是确定结肠特异性T细胞运输受体的作用和调节。潜在的长期影响具有重大的临床意义，因为我们的研究可能导致结肠T细胞特异性靶点的发展， 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.