Heterotrimeric G Protein Signaling In Allergic Inflammation

过敏性炎症中的异三聚体 G 蛋白信号传导

基本信息

批准号：
10692050
负责人：
Kirk m Druey
金额：
$ 6.85万
依托单位：
NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
依托单位国家：
美国
项目类别：
财政年份：
资助国家：
美国
起止时间：
至
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10692050
关键词：
Allergens Allergic Allergic inflammation Area Asthma Basophils Biochemical Biological Cells Congenital Abnormality Coupled Development Dissociation Effector Cell Extrinsic asthma Family G Protein-Coupled Receptor Signaling G(q) Alpha G-Protein-Coupled Receptors GNAI2 gene GTP Binding GTP-Binding Protein Regulators GTP-Binding Protein alpha Subunits GTP-Binding Protein alpha Subunits, Gs GTP-Binding Proteins Gene Deletion Goals Guanosine Triphosphate Guanosine Triphosphate Phosphohydrolases Heterotrimeric GTP-Binding Proteins Human Hydrolysis Immune Immunologic Deficiency Syndromes Infection Inflammation Inflammatory Investigation Knowledge Laboratories Leukocyte Trafficking Leukocytes Ligands Lung Lymphocyte Mediating Modeling Mus Mutation Pathway interactions Patients Phenotype Physiological Predisposition Process Property Proteins Pulmonary Inflammation RGS Proteins Receptor Activation Role Signal Pathway Signal Transduction Signaling Protein Site Time Tissues allergic response base cell motility chemokine desensitization genetic approach granulocyte human subject kindred leukocyte activation mast cell neutrophil novel receptor recruit release of sequestered calcium ion into cytoplasm response trafficking

项目摘要

Mast cells (MCs), granulocytes, and lymphocytes are integral to the development of an allergic response. Allergic inflammation may also be generated through activation of receptors coupled to heterotrimeric G proteins (GPCRs). The purpose of this study is to understand mechanisms of G protein-mediated signal transduction in immune cells, with a focus on GPCR-mediated trafficking of leukocytes to sites of allergic inflammation. GPCRs activate a core pathway of heterotrimeric G proteins. G protein alpha subunits oscillate between GDP- (inactive) and GTP- (active) bound forms based on ligand occupancy of the associated receptor. The GTP-bound form of the G protein alpha subunit induces downstream signaling cascades, including intracellular calcium flux responsible for MC/basophil degranulation. This project focuses on a family of regulators of G protein signaling (RGS proteins), which inhibit the function of G alpha-i and G alpha-q, but not G alpha-s, proteins by increasing their intrinsic GTPase activity, a property that promotes deactivation of the signaling pathway. The GTPase accelerating (GAP) activity of RGS proteins limits the time of interaction of active G-alpha and its effectors, resulting in desensitization of GPCR signaling. Despite a growing body of knowledge concerning the biochemical mechanisms of RGS action, relatively little is known about the physiological role of these proteins in allergic inflammation. A major area of investigation is the recruitment of inflammatory leukocytes to sites of inflammation. Chemokines are a major class of compounds acting on leukocyte GPCRs, which orchestrate immune cell trafficking, and RGS proteins including RGS10, RGS13, and RGS16 inhibit chemokine signaling by desensitizing GPCR signals. In Fiscal Year (FY) 22, we characterized the phenotype of patients with undefined immunodeficiencies and novel mutations in G proteins in collaborative studies with Dr. Su. During G-protein coupled receptor (GPCR) signaling, heterotrimeric G-proteins undergo cycles of GDP/GTP exchange and hydrolysis with activation or deactivation of downstream effector signals, coordinated with dissociation and reassembly of their subunits with GPCR. We described 17 patients from 16 kindreds with rare heterozygous mutations in GNAI2 that impeded GTP hydrolysis by Galphai2, thereby augmenting Glaphai2s inhibitory signaling. The patients had congenital malformations in diverse tissues and infection susceptibility with immunodyregulation caused by defective cell migration. More potent activating mutations also impeded G-protein reassembly to block subsequent GPCR responses to chemokines. Our findings explain the paradoxical biological effects that result from inhibiting the cycling of Gi between its active and inactive forms for Gi association with GPCR in humans.

肥大细胞 (MC)、粒细胞和淋巴细胞是过敏反应发生过程中不可或缺的一部分。过敏性炎症也可能通过与异三聚体 G 蛋白 (GPCR) 偶联的受体的激活而产生。本研究的目的是了解免疫细胞中 G 蛋白介导的信号转导机制，重点是 GPCR 介导的白细胞向过敏性炎症部位的运输。 GPCR 激活异源三聚体 G 蛋白的核心途径。 G 蛋白 α 亚基根据相关受体的配体占据情况在 GDP-（无活性）和 GTP-（活性）结合形式之间振荡。 G 蛋白 α 亚基的 GTP 结合形式诱导下游信号级联，包括负责 MC/嗜碱性粒细胞脱粒的细胞内钙流。该项目重点关注 G 蛋白信号传导调节因子（RGS 蛋白）家族，该家族通过增加其内在 GTP 酶活性来抑制 G α-i 和 G α-q 蛋白的功能，但不抑制 G α-s 蛋白的功能。促进信号通路失活。 RGS 蛋白的 GTP 酶加速 (GAP) 活性限制了活性 G-α 及其效应物相互作用的时间，导致 GPCR 信号转导脱敏。尽管人们对 RGS 作用的生化机制的了解越来越多，但对这些蛋白质在过敏性炎症中的生理作用知之甚少。研究的一个主要领域是炎症白细胞向炎症部位的募集。趋化因子是作用于白细胞 GPCR 的一类主要化合物，白细胞 GPCR 协调免疫细胞运输，而 RGS 蛋白（包括 RGS10、RGS13 和 RGS16）通过使 GPCR 信号脱敏来抑制趋化因子信号传导。在第 22 财年 (FY)，我们与 Su 博士合作研究了患有不明免疫缺陷和 G 蛋白新突变的患者的表型。在 G 蛋白偶联受体 (GPCR) 信号传导过程中，异三聚体 G 蛋白经历 GDP/GTP 交换和水解循环，并激活或失活下游效应信号，并与 GPCR 亚基的解离和重新组装相协调。我们描述了来自 16 个家族的 17 名患者，这些患者的 GNAI2 存在罕见的杂合突变，这些突变阻碍了 Galphai2 的 GTP 水解，从而增强了 Glaphai2s 抑制信号传导。患者的多种组织存在先天性畸形，且细胞迁移缺陷导致免疫失调，易受感染。更有效的激活突变也会阻碍 G 蛋白重新组装，从而阻止随后的 GPCR 对趋化因子的反应。我们的研究结果解释了由于抑制 Gi 在其活性和非活性形式之间的循环而导致的矛盾的生物效应，因为 Gi 与人类 GPCR 相关。