G Protein Coupled Receptor Signaling in Mast Cells

描述(由申请人提供)： 补体系统是先天免疫的核心，也是多种炎症性疾病的媒介。最近在人体和动物模型上的研究表明，补体成分C3a在哮喘的发病机制中发挥着新的重要作用。然而，C3a调节哮喘的细胞和分子机制仍不清楚。我们的初步研究表明，C3a的G蛋白偶联受体(GPCR)在人肥大细胞中表达，C3a可引起肥大细胞快速脱颗粒/白三烯C4的产生和延迟的核因子-β激活/趋化因子的产生，这些途径协调调节哮喘的两个主要特征--气道高反应性(AHR)和肺部炎症。我们的初步研究还提出了肥大细胞C3aR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。G蛋白偶联受体激酶(GRKs)的受体磷酸化和随后的arrestin募集为GPCRs的脱敏提供了重要的机制。我们进行了新的观察，发现抑制肥大细胞脱颗粒的C3aR磷酸化为趋化因子基因的表达提供了刺激信号。基于这些发现，我们假设不同GRK的C3aR磷酸化通过抑制肥大细胞脱颗粒但刺激趋化因子基因表达来不同地调节AHR和肺部炎症。为了检验这一假说，本文提出了三个具体目标。在目标1中，我们将验证不同GRK对C3aR不同位点的磷酸化抑制肥大细胞脱颗粒，但促进核因子-β激活/趋化因子产生的假设。在目标2中，我们将检验这样的假设，即磷酸化的C3aR与含有2-arrestin和PSD-95/DLG/Zo1(PDZ)结构域的蛋白质结合，分别抑制和刺激NF-β活性。在目标3中，我们将通过靶向肥大细胞中的C3aR磷酸化来调节体内变应原诱导的AHR和肺部炎症。总的来说，这些研究将产生关于C3aR信号如何调节哮喘的重要新信息，并可能为哮喘和呼吸道炎症的治疗提供新的治疗方法。 简介：哮喘是一种复杂的呼吸道炎症性疾病，以支气管收缩、呼吸道高反应性(AHR)和炎症为特征。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全球范围内急剧上升。肥大细胞存在于导致哮喘症状的肺释放介质中。这一建议是基于发现了一种调节哮喘中肥大细胞功能的新分子。我们相信，拟议的研究将在肥大细胞的调节方面产生重要的新信息，并可能为哮喘的治疗提供新的治疗方法。

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.