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β -2家族中整合素的核心作用。中性粒细胞利用这些整合素附着在感染附近的内皮细胞上，随后附着在细胞外基质上，以引导它们走向病原体。β -2整合素CR3 （CD11b/CD18）是一种独特的受体，它具有两个不同的配体结合位点，即识别细胞粘附分子、补体成分和细胞外基质的i结构域；凝集素结构域结合碳水化合物，如-葡聚糖和糖基磷脂酰肌醇锚定受体上表达的碳水化合物。葡聚糖是（1,3）(1,6)- β - d键中葡萄糖部分的聚合物，通常是真菌细胞壁的结构成分，是CR3凝集素位点的功能激动剂。在目前的资助期内，我们发现许多依赖cr3的中性粒细胞功能受到不同的调节，以响应i结构域、凝集素位点或两者的连接。在本续中提出了实验，以确定解释单个受体在其不同的结合位点连接时如何转导如此不同的细胞影响的机制。本提案的具体目的是：(1)确定I结构域和凝集素位点差异激活时CR3的动态调控和空间定位；（II）确定在CR3凝集素位点激活后介导人类中性粒细胞从随机迁移到定向迁移的信号转导途径；（三）确定CR3凝集素位点激活在体内宿主防御中的作用。考虑到CR3在白细胞功能的各个方面的重要性，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由其失调引起的病理状况。过度活跃会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愈合失败。针对CR3的治疗方法可能会被开发出来，以安全有效地增强手术前或癌症患者或创伤、败血症、受伤、衰老或免疫抑制患者的白细胞功能。该建议的基本前提是，更好地了解白细胞整合素调节可能揭示整合素代表安全有效地调节先天免疫系统的治疗靶点。公共卫生相关性：炎症是对损伤或感染的基本反应，因为它可以防止感染广泛传播并开始愈合过程。白细胞在血液中不断循环，但为了应对局部损伤，它们必须从血液中迁移到受损组织中开始愈合。这项提议的重点是帮助确定循环白细胞如何感知组织损伤的位置并直接迁移到准确的位置。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，也是本提案的主题。

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.