Effect of Neutrophil Priming on Chemotaxis and Signaling

描述(由申请人提供)：外周血中性粒细胞向感染部位的迁移包括整合素在β-2家族中的核心作用。中性粒细胞利用这些整合素与感染附近的内皮细胞黏附，然后黏附到细胞外基质上，以引导它们导航至病原体。β-2整合素CR3(CD11b/CD18)是一种独特的受体，它有两个不同的配体结合部位，一个是识别细胞黏附分子、补体成分和细胞外基质的I区，另一个是与糖基磷脂酰肌醇锚定受体上表达的糖结合的凝集素结构域。β-葡聚糖是以(1，3)(1，6)-β-D-键连接的葡萄糖部分的聚合物，通常被发现作为真菌细胞壁的结构成分，是CR3凝集素位点的功能激动剂。在目前的资助期间，我们发现许多依赖CR3的中性粒细胞功能在I-结构域、凝集素位点或两者同时连接时受到不同的调节。在本续篇中，建议进行实验以确定机制/S，解释当单个受体连接在其不同的结合位置时，如何转导如此不同的细胞影响。本研究的具体目的是：(I)确定CR3在I结构域和凝集素位点差异激活时的动态调节和空间定位；(Ii)确定在CR3凝集素位点激活时，介导中性粒细胞从随机迁移到定向迁移的信号转导途径；(Iii)确定CR3凝集素位点激活在体内宿主防御中的作用。鉴于CR3在白细胞功能各个方面的重要性，更好地了解控制其功能的复杂调节机制可能会导致更好地治疗因其调节失调而导致的病理情况。多动症可导致自身免疫性疾病、多发性硬化症、炎症性肠病、牛皮癣和关节炎等疾病。功能不足会导致反复感染和伤口无法愈合。可以开发以CR3为靶点的治疗方法，以安全有效地增强手术前或癌症患者或创伤、脓毒症、创伤、衰老或免疫抑制患者的白细胞功能。这一建议的基本前提是，对白细胞整合素调节的更好理解可能揭示整合素是安全和有效调节天然免疫系统的治疗靶点。与公共卫生相关：炎症是对伤害或感染的一种基本反应，因为它防止感染蔓延并开始愈合过程。白细胞在血液中持续循环，但作为对局部损伤部位的反应，它们必须从血液中迁移到受损组织中才能开始愈合。这项建议的重点是帮助确定循环中的白细胞如何感知组织损伤的位置并直接迁移到确切的位置。被称为整合素的细胞表面受体是白细胞正确导航所必需的，也是这项提议的主题。

DESCRIPTION (provided by applicant): The emigration of peripheral blood neutrophils to a site of infection includes a central role of integrins within the beta-2 family. Neutrophils use these integrins to adhere to endothelial cells located in the vicinity of infection and subsequently to extracellular matrix in order to guide their navigation towards the pathogen. The beta-2 integrin CR3 (CD11b/CD18) is a unique receptor in that it has two distinct ligand binding sites, the I-domain which recognizes cell adhesion molecules, complement components and extracellular matrix; and the lectin domain which binds carbohydrate such as beta-glucan and those expressed on glycosylphosphatidyl inositol-anchored receptors. Beta-glucan is a polymer of glucose moieties in (1,3)(1,6)-beta-D-linkages found normally as a structural component of the fungal cell wall and is a functional agonist of the CR3 lectin site. During the current funding period we found than a number of CR3-dependent neutrophil functions are regulated differently in response to ligation of the I-domain, the lectin site, or both together. Experiments are proposed in this continuation to determine the mechanism/s that explain how a single receptor can transduce such different cellular affects when ligated at its distinct binding sites. The specific aims of this proposal are: (I) to determine the dynamic regulation and spatial localization of CR3 upon differential activation of the I-domain and the lectin site; (II) to determine the signal transduction pathways that mediate the conversion of random to directed migration of human neutrophils upon activation of the CR3 lectin site; (III) to determine the role of CR3 lectin site activation on host defense in vivo. Given the importance of CR3 in every aspect of leukocyte function, a better understanding of the complex regulatory mechanisms that control its function may lead to better treatment of the pathological conditions that result from its dysregulation. Hyperactivity can lead to pathologies such as autoimmune diseases, multiple sclerosis, inflammatory bowel disease, psoriasis, and arthritis. Insufficient function can result in recurrent infection and failure to heal wounds. Therapies that target CR3 may be developed to safely and effectively enhance leukocyte function in presurgical or cancer patients or those following trauma, sepsis, wounding, aging or immunosuppression. The underlying premise of this proposal is that a better understanding of leukocyte integrin regulation may reveal that integrins represent therapeutic targets for safe and effective regulation of the innate immune system. PUBLIC HEALTH RELEVANCE: Inflammation is an essential response to injury or infection as it prevents infections from becoming widespread and begins the process of healing. White blood cells (leukocytes) circulate continuously in the bloodstream but in response to a local site of injury, they must emigrate from the blood into the damaged tissue to begin healing. The focus of this proposal is to help determine how circulating white blood cells sense the location of a tissue injury and migrate directly to the exact spot. Cell surface receptors known as integrins are necessary for leukocytes to navigate properly and are the subject of this proposal.