Mechanism and pathophysiological significance of mast cell regulated exocytosis

描述（由申请人提供）：肥大细胞在炎症和先天免疫反应中发挥重要作用。活化的肥大细胞释放许多炎症介质。其中一些是预先形成的，储存在它们的分泌颗粒中，并通过脱粒（一种受调节的胞吐作用）释放。与其他肥大细胞反应不同，脱粒在炎症发展和演变中的重要性尚不清楚。人们普遍认为肥大细胞脱粒在早期过敏反应中是重要的，因为组胺和5-羟色胺是通过这种机制分泌的。然而，我们最近发现肥大细胞在脱颗粒过程中释放的类胰蛋白酶在炎症性关节炎和抵抗细菌感染中起重要作用。脱粒对过敏性和非过敏性炎症慢性阶段的影响尚不清楚。胞吐是一个高度调节的过程，Syntaxins和Munc 18蛋白是胞吐机制的重要组成部分。虽然Syntaxins在胞吐中的确切作用是众所周知的，但由Munc 18蛋白控制的胞吐步骤的身份仍然存在争议。突触融合蛋白3和4以及Munc 18 -2和3是肥大细胞中表达的主要同种型。Munc 18 -3调节Syntaxin-4，Munc 18 -2调节Syntaxin-3。我们已经创造了基因修饰小鼠，在它们的肥大细胞中特异性删除了这四个基因。对这些突变小鼠的初步研究指出，肥大细胞调节的胞吐作用存在严重的选择性缺陷。我们计划以高分辨率研究这些独特小鼠的单个肥大细胞，以揭示由这些突触融合蛋白介导并由这些Munc 18蛋白调节的特定胞吐步骤。此外，我们将能够描述两种不同的Syntaxin/Munc 18对如何控制相同的囊泡运输事件。然后，从单细胞研究转向整体动物研究，我们将通过研究我们的肥大细胞脱颗粒缺陷小鼠在慢性过敏性哮喘、炎性关节炎和细菌性肺炎模型中的作用，试图结束关于肥大细胞脱颗粒作用的程度和多样性的争议。我们的转基因小鼠可能揭示肥大细胞脱颗粒是否是某些炎症性疾病的一个有吸引力和安全的治疗靶点。

DESCRIPTION (provided by applicant): Mast cells play important roles in inflammation and innate immune reactions. Activated mast cells release many inflammatory mediators. Some of them are preformed, stored in their secretory granules, and released via degranulation, a form of regulated exocytosis. The importance of degranulation, different to other mast cell responses, in the development and evolution of inflammation is not known. It is accepted that mast cell degranulation should be important in the early allergic response because histamine and serotonin are secreted through this mechanism. However, we have recently shown that mast cell tryptases released during degranulation play important roles in inflammatory arthritis and defense against bacterial infections. The effects of degranulation on the chronic stages of allergic and non-allergic inflammation are not known. Exocytosis is a highly regulated process, and Syntaxins and Munc18 proteins are essential components of the exocytic machinery. Although the precise role of Syntaxins in exocytosis is well known, the identity of the exocytic step controlled by Munc18 proteins remains controversial. Syntaxins-3 and -4, and Munc18-2 and -3 are the main isoforms expressed in mast cells. Munc18-3 regulates Syntaxin-4 and Munc18-2 regulates Syntaxin-3. We have created genetically-modified mice with specific deletions of each of these four genes in their mast cells. Preliminary studies in these mutant mice point to a severe and selective defect in mast cell regulated exocytosis. We plan to study single mast cells from these unique mice at high resolution to uncover the specific exocytic step mediated by each of these Syntaxins and regulated by each of these Munc18 proteins. Additionally, we will be able to describe how two different Syntaxin/Munc18 pairs control the same vesicular trafficking event. Then, moving from single cell to whole animal studies, we will try to end the controversy about the extent and versatility of the effects of mast cell degranulation by studying our mast cell degranulation- deficient mice in models of chronic allergic asthma, inflammatory arthritis, and bacterial pneumonia. Our genetically modified mice may reveal if mast cell degranulation is an attractive and safe therapeutic target for some inflammatory diseases.