G Protein Coupled Receptor Signaling in Mast Cells

描述（由申请人提供）： 补体系统形成先天免疫的中心核心，但也介导各种炎性疾病。最近的研究表明，补体成分C3 a在哮喘的发病机制中起着新的和重要的作用。然而，C3 a调节哮喘的细胞和分子机制仍然未知。我们的初步研究表明，G蛋白偶联受体（GPCR）的C3 a（C3 aR）表达在人肥大细胞和C3 a导致快速肥大细胞脱粒/白三烯C4的产生和延迟NF-？B活化/趋化因子产生;协调调节气道高反应性（AHR）和肺部炎症（哮喘的两个主要特征）的途径。我们的初步研究还提出了肥大细胞中C3 aR功能调节的新概念，这可能为AHR和肺部炎症的差异调节提供新的靶点。通过G蛋白偶联受体激酶（GRKs）的受体磷酸化和随后的抑制蛋白的募集提供了GPCR脱敏的重要机制。我们进行了新的观察，C3 aR磷酸化，抑制肥大细胞脱粒，提供了一个刺激信号的趋化因子基因表达。基于这些发现，我们假设不同GRKs的C3 aR磷酸化通过抑制肥大细胞脱粒但刺激趋化因子基因表达来差异调节AHR和肺部炎症。提出了三个具体目标来检验这一假设。在目标#1，我们将测试的假设，在不同的网站由不同的GRKs磷酸化C3 aR抑制肥大细胞脱粒，但促进NF-？B活化/趋化因子产生。在目标#2中，我们将测试磷酸化C3 aR与2-arrestin和PSD-95/Dlg/Zo 1（PDZ）结构域包含的蛋白质结合以抑制和刺激NF-κ B的假说。B活性。在目标#3中，我们将通过靶向肥大细胞中的C3 aR磷酸化来调节过敏原诱导的AHR和肺部炎症。总的来说，这些研究将产生关于C3 aR信号如何调节哮喘的重要新信息，并可能为治疗哮喘和气道炎症提供新的治疗方法。 叙述：哮喘是一种以支气管收缩、气道高反应性（AHR）和炎症为特征的复杂气道炎症性疾病。据估计，大约有1700万美国人患有哮喘，其中三分之一是儿童。近年来，哮喘的患病率和严重程度在世界范围内急剧增加。肥大细胞存在于肺释放介质，导致哮喘的症状。这项建议是基于一个新的分子，调节肥大细胞功能的哮喘的鉴定。我们相信，拟议的研究将产生重要的肥大细胞的调节新的信息，并可能提供新的治疗方法治疗哮喘。

DESCRIPTION (provided by applicant): The complement system forms the central core of innate immunity but also mediates a variety of inflammatory diseases. Recent studies with human subjects and animal models demonstrated that complement component C3a plays a novel and important role in the pathogenesis of asthma. The cellular and molecular mechanism by which C3a modulates asthma, however, remains unknown. Our preliminary studies demonstrated that G protein coupled receptor (GPCR) for C3a (C3aR) are expressed in human mast cells and that C3a causes rapid mast cell degranulation/leukotriene C4 generation and delayed NF-?B activation/chemokine generation; pathways that coordinately regulate airway hyperresponsiveness (AHR) and lung inflammation, two major features of asthma. Our preliminary studies also suggest new concepts in the regulation of C3aR function in mast cells, which may provide novel targets for differential regulation of AHR and lung inflammation. Receptor phosphorylation by G protein coupled receptor kinases (GRKs) and the subsequent recruitment of ¿-arrestin provides an important mechanism for desensitization of GPCRs. We made the novel observation that C3aR phosphorylation, which inhibits mast cell degranulation, provides a stimulatory signal for chemokine gene expression. Based on these findings, we hypothesize that C3aR phosphorylation by distinct GRKs differentially regulates AHR and lung inflammation by inhibiting mast cell degranulation but stimulating chemokine gene expression. Three specific aims are proposed to test this hypothesis. In aim #1, we will test the hypothesis that phosphorylation of C3aR at distinct site by different GRKs inhibits mast cell degranulation but promotes NF-?B activation/chemokine generation. In aim #2, we will test the hypothesis that phosphorylated C3aR associates with both 2-arrestin and PSD-95/Dlg/Zo1 (PDZ) domain containing proteins to inhibit and stimulate NF-?B activity, respectively. In aim #3, we will modulate allergen-induced AHR and lung inflammation in vivo by targeting C3aR phosphorylation in mast cells. Collectively, these studies will generate significant new information on how C3aR signaling modulates asthma and may offer novel therapeutic approaches for the treatment of asthma and airway inflammation. Narrative: Asthma is a complex airway inflammatory disease characterized by bronchoconstriction, airway hyperresponsiveness (AHR) and inflammation. Approximately 17 million Americans are estimated to have asthma, one third of them children. In recent years, asthma prevalence and severity have been increasing dramatically world-wide. Mast cells present in the lung release mediators that cause the symptoms of asthma. This proposal is based on the identification of a new molecule that regulates mast cell function in asthma. We believe that proposed studies will generate significant new information on the regulation of mast cells and may offer novel therapeutic approaches for the treatment of asthma.