Defining Siglec-6 and Siglec-8 function on effector cells of allergic diseases

摘要 在食物和药物过敏、过敏反应、过敏性鼻炎、哮喘和其他形式的急性和慢性过敏 疾病，嗜酸性粒细胞和肥大细胞，通过释放预先形成的和新产生的介质颗粒 蛋白质、细胞因子和其他介质被认为是关键的效应细胞。嗜酸性粒细胞和肥大细胞也是 与其他2型免疫疾病有关，包括慢性鼻-鼻窦炎、嗜酸性食管炎和 特应性皮炎。对于许多过敏性疾病，抑制肥大细胞脱颗粒的药物会减少嗜酸性粒细胞 数字，或抵消其释放的介体是有用的疗法，但所有仍然不完全有效。 Siglec-6和Siglec-8是CD33相关的唾液酸结合免疫球蛋白样亚家族的成员 凝集素(Siglecs)。Siglec-6在人的肥大细胞、一些B细胞、细胞滋养层细胞和合体滋养层细胞上发现。 胎盘表达Siglec-8，而Siglec-8表达于人嗜酸性粒细胞、肥大细胞和嗜碱性粒细胞。这些 跨膜蛋白含有N端胞外凝集素结合域，可识别不同的糖链 配体，以及C-末端的胞内结构域，包括可能的ITIM和ITSM信号基序。两个Siglec-6 (无鼠标对应物)和Siglec-8(其中Siglec-F是其最接近的鼠标对应物)和 独一无二地识别特定的多糖配体结构。Siglec-8/-F与抗体或人工结合 配体会导致嗜酸性粒细胞死亡。Siglec-F缺乏或呼吸道粘蛋白MUC5B缺乏的小鼠， 携带Siglec-F的唾液酸苷配体，表现为夸张的过敏性嗜酸性肺部炎症。 相反，肥大细胞上的Siglec-8并不影响细胞的存活，而是抑制IgE介导的功能 激活。人们对Siglec-6知之甚少，Siglec-6是一种显著表达的人类肥大细胞蛋白。可用数据 提示Siglec-6也可能作为抑制性受体发挥作用，Siglec-6和Siglec-8似乎都 对IgE和非IgE介导的肥大细胞反应均具有抑制活性。项目的总体目标 一是利用特定的嗜酸性粒细胞和肥大细胞信号来预防或治疗即时过敏反应和 慢性过敏性炎症。特别是，Siglec-6和Siglec-8提供了用于操纵的选择性目标 肥大细胞和/或嗜酸性粒细胞反应。这些概念将在三个具体的目标中使用小说来探索 Siglec-6和Siglec-8敲入小鼠和人源化小鼠与其他项目高度整合的研究 描述Siglec-6和Siglec-8在嗜酸性粒细胞和肥大细胞中的功能和信号特性(目标1，与 项目2和核心B)，定义和开发Siglec-8及其配体在 慢性嗜酸性炎症模型(目标2，项目2)，以及利用Siglec-6的特定配体 和Siglec-8，用于其抗肥大细胞和嗜酸性粒细胞效应(目标3，项目2、项目3和核心B)。

ABSTRACT In food and drug allergy, anaphylaxis, allergic rhinitis, asthma and other forms of acute and chronic allergic diseases, eosinophils and mast cells, through release of preformed and newly generated mediators, granule proteins, cytokines and other mediators are felt to be key effector cells. Eosinophils and mast cells are also implicated in other type 2 immunologic diseases including chronic rhinosinusitis, eosinophilic esophagitis and atopic dermatitis. For many allergic diseases, drugs that inhibit mast cell degranulation, reduce eosinophil numbers, or counteract their released mediators are useful therapies, but all remain incompletely effective. Siglec-6 and Siglec-8 are members of the CD33-related subfamily of sialic acid-binding immunoglobulin-like lectins (siglecs). Siglec-6 is found on human mast cells, some B cells and cyto- and syncytiotrophoblasts of the placenta, while Siglec-8 is expressed on human eosinophils, mast cells and weakly on basophils. These transmembrane proteins contain N-terminal extracellular lectin binding domains that recognize distinct glycan ligands, and c-terminal intracellular domains including putative ITIM and ITSM signaling motifs. Both Siglec-6 (no mouse counterpart) and Siglec-8 (with Siglec-F being its closest mouse counterpart) preferentially and uniquely recognize specific glycan ligand structures. Engagement of Siglec-8/-F with antibodies or artificial ligands causes eosinophil death. Mice deficient in Siglec-F, or deficient in the airway mucin Muc5b, which carries sialoside ligands for Siglec-F, display exaggerated allergic eosinophilic pulmonary inflammation. Siglec-8 on mast cells, in contrast, does not influence cell survival, but instead functions to inhibit IgE-mediated activation. Less is known about Siglec-6, a prominently expressed human mast cell protein. Available data suggest that Siglec-6 may also function as an inhibitory receptor, and both Siglec-6 and Siglec-8 appear to possess inhibitory activity for both IgE- and non-IgE-mediated mast cell responses. The overall goal of Project 1 is to exploit specific eosinophil and mast cell Siglecs to prevent or treat immediate allergic reactions and chronic allergic inflammation. In particular, Siglec-6 and Siglec-8 provide selective targets for manipulating mast cell and/or eosinophil responses. These concepts will be explored in three specific aims using novel Siglec-6 and Siglec-8 knock-in mice and humanized mice in studies highly integrated with other projects by delineating Siglec-6 and Siglec-8 function and signaling properties in eosinophils and mast cells (Aim 1, with Project 2 and Core B), defining and exploiting Siglec-8 and its ligands for their anti-eosinophil properties in models of chronic eosinophilic inflammation (Aim 2, with Project 2), and exploiting specific ligands of Siglec-6 and Siglec-8 for their anti-mast cell and eosinophil effects (Aim 3, , with Project 2, Project 3 and Core B).