CXCR4 Chemokine Receptor Regulation of ERK MAP Kinase

描述（由申请人提供）：据报道，介导T细胞免疫活化的T淋巴细胞抗原受体（TCR）与刺激细胞迁移和基因表达的趋化因子受体CXCR 4之间存在广泛的免疫功能交叉调节。然而，负责整合CXCR 4和TCR信号转导通路的分子机制仍然是未知的。CXCR 4配体SDF-1在许多组织中组成型表达，包括淋巴结和肠道。CXCR 4广泛表达并重要调节多种疾病，包括HIV-1/AIDS和癌症。在上一个资助周期开始时，我们发现SDF-1通过诱导CXCR 4-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Ca 2+和激活ERK MAP激酶途径和基因表达所必需的。在该资助的最后一个周期中，我们发现CXCR 4-TCR复合物在调节性T细胞（TCR 4）中发出信号，通过特异性需要特定磷脂酶亚型PLC-23的信号传导途径有效地增加IL-10分泌。我们还发现，即使在不存在SDF-1的情况下，通过PLC-23的CXCR 4-TCR信号传导也响应于TCR的连接而严重交叉调节和拮抗初始T细胞活化。IL-10是T细胞介导的自身免疫包括炎症性肠病（IBD）的免疫调节剂和抑制剂。因此，我们的结果表明，通过PLC-23的CXCR 4-TCR信号传导是免疫耐受的有效促进剂，其在调节初始T细胞的活化的同时增强了TcR的功能。评估这些观察结果的生理意义是重要的，然而，到目前为止，这一直是困难的，因为靶向CXCR 4或TCR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PLC-23是CXCR 4-TCR复合物的许多免疫作用所必需的，但不是T细胞迁移所必需的，因此我们在此提出通过研究PLC-23-/-小鼠来解决CXCR 4-TCR信号转导的分子机制和体内免疫影响。我们的中心假设是CXCR 4-TCR异二聚体的信号传导依赖于PLC-23以激活Ras-ERK途径来促进Treg功能，并拮抗TCR信号传导，从而抑制自身免疫。我们的具体目标是：1）表征CXCR 4-TCR异二聚体使用PLC-23进行信号传导的分子机制，2）确定CXCR 4-TCR异二聚体通过PLC-23进行信号传导在体内调节TCR和预防自身免疫性疾病中的作用，和3）表征CXCR 4-TCR异二聚体和PLC-23在体内调节TCR信号传导和T细胞免疫应答中的作用。总之，拟议的研究将解决关于CXCR 4-TCR异二聚体和PLC-23的体内免疫影响的关键问题。这些研究也有可能将PLC-23表征为一种新的药理学靶点，可用于选择性增强CXCR 4-TCR异二聚体信号传导，从而增强Treg功能和耐受性，而不破坏免疫细胞的正常体内迁移模式。

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.