Regulation of Mast Cell Development and Function

肥大细胞(MC)是IgE抗体依赖性变态反应性疾病的主要效应细胞，如过敏反应， 过敏性鼻炎和特应性哮喘，这在世界上造成了非常大的疾病负担和经济成本 发达国家。MC对于某些先天免疫反应的最佳表达也是至关重要的。而当 许多注意力集中在积极调节免疫球蛋白E和特异性抗原的元件上。 (AG)依赖于MCs分泌促炎介质和细胞因子，分子 抑制这种反应的幅度和/或持续时间的机制研究较少。 我们最近报道了RabGEFI(Rajb鸟嘌呤核苷酸交换因子1)。可以负向调节 依赖RAS的信号通路，以及所有三类介质(预形成、脂质和 细胞因子)，在IgE和特异性抗原刺激的MC中。最近，我们发现RabGEFI还 重要地调节MC的反应，这些反应由主要的生存、发育和 MC增殖因子，SCF(干细胞因子，c-Kit配体)。值得注意的是，我们的Rabgefl^‘老鼠展示了 皮肤严重炎症与MC数量增加有关，真皮MC的证据 脱颗粒(即“激活”)，以及血清中组胺和IgE水平的增加。中环 我们现在想要解决的问题是：RabGEFI通过什么分子机制影响MC RabGEFI的发展、激活和功能，以及这些行动可能在多大程度上影响MC 对于在目标1中在Rabgefl^的小鼠身上观察到的一些戏剧性的表型异常，我们将进行调查。 RabGEFI及其单个功能域如何负性调节小鼠MC的激活 通过FceRI或c-Kit(SCF受体)在体外或体内发出信号，并将鉴定和表征 MCs中的RabGEFI相互作用蛋白及其下游效应物已被激活 感受器。在目标2中，我们将定义RabGEFI调节生存的机制， 巨噬细胞在体外和体内的发育、表型和增殖。体内研究将利用 我们将缺乏或表达突变形式的RabGEFI的WFRO来源的MC转移到组织中的能力 C-kit突变体Kitw/w~v或Kit“-3”‘*“基因缺陷小鼠(表达野生型RabGEFI)。 因此可以研究RabGEFI对只有MCs缺乏或表达突变形式的小鼠MCs的影响 ，RabGEFI.RabGEFI如何负性调节MCs中FceRI或c-Kit依赖的信号转导 将增加我们对MC激活和发育的调节的认识，这是长期的 这个项目的目标。这项工作还可能有助于开发新的治疗方法 缓解与依赖IgE的MC有关的疾病，如哮喘和特应性皮炎 在许多患者中，受影响组织中的MC数量增加。

Mast cells (MCs) are major effector cells in IgE antibody-dependent allergic disorders, such as anaphylaxis, allergic rhinitis and atopic asthma, which account for a very large burden of illness and economic costs in the developed world. MCsare also critical for the optimal expression of certain innate immune responses. While much attention has been focused on the elements which positively regulate the IgE- and specific antigen (Ag)-dependent secretion of pro-inflammatory mediators and cytokines from MCs, the molecular mechanisms which can suppress the magnitude and/or duration of such responses have been less studied. We recently reported that RabGEFI (Rajb guanine nucleotide exchange factor 1.) can negatively regulate Ras-dependent signaling pathways, and the secretion of all three classes of mediators (pre-formed, lipid and cytokine), in MCs stimulated with IgE and specific Ag. More recently, we found that RabGEFI also importantly regulates responses in MCs which are elicited by the major survival, developmental and proliferation factor for MCs, SCF (stem cell factor, the c-Kit ligand). Notably, our Rabgefl^' mice exhibit severe inflammation of the skin associated with increased numbers of MCs, evidence of dermal MC degranulation (i.e., "activation"), and increased levels of histamine and IgE in the serum. The central questions which we now wish to address are: By what molecular mechanisms does RabGEFI influence MC development, activation and function, and to what extent might these actions of RabGEFI on MCs account for some of the dramatic phenotypic abnormalities observed in Rabgefl^'mice? In Aim 1. we will investigate how RabGEFI, and its individual functional domains, can negatively regulate mouse MC activation induced by signaling via FceRI or c-Kit (the SCF receptor) in vitro or in vivo, and will identify and characterize RabGEFI-interacting proteins and their downstream effectors in MCswhich have been activated via these receptors. In Aim 2. we will define the mechanisms by which RabGEFI can regulate the survival, development, phenotype & proliferation of MCs in vitro and in vivo. The in vivo studies will take advantage of our ability to transfer in wfro-derived MCs which lack, or express mutant forms of, RabGEFI into the tissues of c-kit mutant, Kitw/w~v or Kit"-3¿"'*" genetically MC-deficient mice (which express wild type RabGEFI). We thus can study the effects of RabGEFI on MCs in mice in which only the MCs lack, or express mutant forms of, RabGEFI. Elucidating how RabGEFI negatively regulates FceRI- or c-Kit-dependent signaling in MCs will increase our understanding of the regulation of MC activation and development, which is the long-term goal of this project. Such work also may help in the development of new therapeutic approaches for the alleviation of diseases, such as asthma and atopic dermatitis, which are associated with IgE-dependent MC activation and, in many patients, with increased numbers of MCs in the affected tissues.