CXCR4 Chemokine Receptor Regulation of ERK MAP Kinase

描述（由申请人提供）：已经报道了介导T细胞免疫激活的T淋巴细胞抗原受体（TCR）和刺激细胞迁移和基因表达的趋化因子受体CXCR4之间广泛的免疫功能交叉调节。然而，负责CXCR4和TCR信号转导通路整合的分子机制仍然是未知的。CXCR4配体SDF-1在许多组织中组成性表达，包括淋巴结和肠道。CXCR4广泛表达并对多种疾病（包括HIV-1/AIDS和癌症）起关键调控作用。在上一个资助周期开始时，我们发现SDF-1通过诱导CXCR4-TCR异二聚体复合物的形成在T细胞中发出信号，这是SDF-1刺激迁移、增加胞质Ca2+、激活ERK MAP激酶途径和基因表达所必需的。在本研究的最后一个周期中，我们发现CXCR4-TCR复合物在调节性T细胞（Tregs）中发出信号，通过特定磷脂酶异构体PLC-23的信号通路有效地增加IL-10的分泌。我们还发现，即使在没有SDF-1的情况下，通过PLC-23传递的CXCR4-TCR信号也能在TCR连接时严重交叉调节和拮抗幼稚T细胞激活。IL-10是包括炎症性肠病（IBD）在内的T细胞介导的自身免疫的免疫调节剂和抑制剂。因此，我们的研究结果表明，通过PLC-23传递的CXCR4-TCR信号是免疫耐受的有效启动子，既增强Tregs的功能，又调节幼稚T细胞的激活。评估这些观察结果的生理意义很重要，然而，到目前为止，这一直很困难，因为靶向CXCR4或TCR都会破坏多种免疫功能，包括T细胞发育和稳态T细胞迁移模式。由于CXCR4-TCR复合物的许多免疫作用需要PLC-23，但T细胞迁移不需要PLC-23，因此我们建议通过研究PLC-23-/-小鼠来解决CXCR4-TCR信号通过PLC-23传递的分子机制和体内免疫影响。我们的中心假设是CXCR4-TCR异源二聚体的信号通路依赖于PLC-23，以激活Ras- ERK通路以促进Treg功能，并拮抗TCR信号，从而抑制自身免疫。我们的具体目标是：1)表征CXCR4-TCR异二聚体通过PLC-23信号传导的分子机制；2)确定CXCR4-TCR异二聚体通过PLC-23信号传导在体内调节Tregs和预防自身免疫性疾病中的作用；3)表征CXCR4-TCR异二聚体和PLC-23在体内调节TCR信号传导和T细胞免疫反应中的作用。总之，拟议的研究将解决有关CXCR4-TCR异源二聚体和PLC-23的体内免疫影响的关键问题。这些研究也有可能表征PLC-23作为一种新的药理学靶点，可用于选择性地增强CXCR4-TCR异源二聚体信号，从而在不破坏免疫细胞正常体内迁移模式的情况下增强Treg功能和耐受性。

DESCRIPTION (provided by applicant): Extensive cross-regulation of immune function has been reported between the T lymphocyte antigen receptor (TCR) that mediates T cell immune activation, and CXCR4, a chemokine receptor that stimulates cell migration and gene expression. Yet the molecular mechanisms responsible for the integration of CXCR4 and TCR signal transduction pathways are still mostly unknown. The CXCR4 ligand, SDF-1, is constitutively expressed in many tissues, including lymph nodes and gut. CXCR4 is widely expressed and critically regulates multiple diseases, including HIV-1/AIDS and cancer. At the beginning of the last funding cycle, we showed that SDF-1 signals in T cells by inducing the formation of CXCR4-TCR heterodimeric complexes, which are required for SDF-1 to stimulate migration, increase cytosolic Ca2+, and activate the ERK MAP kinase pathway and gene expression. During the last cycle of this grant, we found that CXCR4-TCR complexes signal in regulatory T cells (Tregs) to potently increase IL-10 secretion via a signaling pathway that specifically requires a particular phospholipase isoform, PLC-23. We also found that CXCR4-TCR signaling via PLC-23 critically cross- regulates and antagonizes naive T cell activation in response to ligation of the TCR, even in the absence of SDF-1. IL-10 is an immune modulator and inhibitor of T cell-mediated autoimmunity including inflammatory bowel disease (IBD). Thus, our results indicate that CXCR4-TCR signaling via PLC-23 is a potent promoter of immune tolerance that both enhances functions of Tregs while modulating activation of naive T cells. Assessing the physiological significance of these observations is important, however, until now this has been difficult since targeting either CXCR4 or the TCR disrupts multiple immune functions including T cell development and homeostatic T cell migration patterns. Since PLC-23 is required for many immune effects of CXCR4-TCR complexes but not for T cell migration, we here propose to address the molecular mechanisms and in vivo immune impact of CXCR4-TCR signaling via PLC-23 by studying PLC-23-/- mice. Our Central Hypothesis is that signaling by the CXCR4-TCR heterodimer depends on PLC-23 in order to activate the Ras- ERK pathway to promote Treg functions, and to antagonize TCR signaling, thereby inhibiting autoimmunity. Our Specific Aims are to: 1) Characterize the molecular mechanisms by which the CXCR4-TCR heterodimer uses PLC-23 for signaling, 2) Determine the role of CXCR4-TCR heterodimer signaling via PLC-23 in regulating Tregs and preventing autoimmune disease in vivo, and 3) Characterize the role of the CXCR4-TCR heterodimer and PLC-23 in modulating TCR signaling and T cell immune responses in vivo. Together, the proposed studies will address key questions regarding the in vivo immune impact of CXCR4-TCR heterodimers and PLC-23. These studies also have the potential to characterize PLC-23 as a novel pharmacologic target that could be used to selectively enhance CXCR4-TCR heterodimer signaling and thereby Treg function and tolerance without disrupting the normal in vivo migration patterns of immune cells.