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（如过敏性反应， 过敏性鼻炎和特应性哮喘，它们在美国造成了非常大的疾病负担和经济成本， 发达世界。MC对于某些先天免疫应答的最佳表达也是至关重要的。而 许多注意力集中在积极调节IgE和特异性抗原的元件上 （Ag）依赖性的促炎介质和细胞因子从MCs分泌， 对能够抑制这种反应的幅度和/或持续时间的机制的研究较少。 我们最近报道了RabGEFI（Rajb鸟嘌呤核苷酸交换因子1。）可以负调节 Ras依赖的信号通路，以及所有三类介质（预形成的，脂质和 细胞因子），在用IgE和特异性Ag刺激的MC中。最近，我们发现RabGEFI还 重要的是调节MCs的反应，这些反应是由主要的生存，发育和 MCs增殖因子，SCF（干细胞因子，c-Kit配体）。值得注意的是，我们的Rabgefl小鼠表现出 与MC数量增加相关的严重皮肤炎症，真皮MC证据 脱粒（即，"活化"），以及血清中组胺和IgE水平的增加。中央 我们现在希望解决的问题是：RabGEFI通过什么分子机制影响MC 发展，激活和功能，以及RabGEFI对MCs的这些行动在多大程度上可能起作用 在Rabgefl小鼠中观察到的一些显著的表型异常？在目标1中。我们将调查 RabGEFI及其单个功能结构域如何负调节小鼠MC激活诱导 通过在体外或体内经由FceRI或c-Kit（SCF受体）的信号传导，并且将鉴定和表征 RabGEFI相互作用蛋白及其在MC中的下游效应物， 受体。在目标2中。我们将定义RabGEFI可以调节存活的机制， 体外和体内MC的发育、表型和增殖。体内研究将利用 我们将缺乏RabGEFI或表达RabGEFI突变形式的wfro衍生的MC转移到组织中的能力 c-kit突变体、Kitw/w~v或Kit "-3/'*"遗传MC缺陷小鼠（表达野生型RabGEFI）的免疫反应。我们 因此，可以研究RabGEFI对小鼠MC的影响，其中只有MC缺乏或表达突变形式 ，Rabgefi。阐明RabGEFI如何负调节MC中的FceRI或c-Kit依赖性信号传导 将增加我们对MC激活和发育的调节的理解，这是长期的， 这个项目的目标。这些工作也可能有助于开发新的治疗方法， 缓解与IgE依赖性MC相关的疾病，如哮喘和特应性皮炎 活化，并且在许多患者中，受影响组织中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.