SP-A Receptor Regulation in Lung Innate Defense

描述（由申请人提供）：本申请将检验以下假设：表面活性蛋白-A（SP-A），一种肺聚集蛋白，通过调节肺泡巨噬细胞上的表面受体在保护肺免受细菌感染中起关键作用。 本申请中提供的初步数据提供了SP-A和补体受体3型（CR 3）之间的明确关系，从而提供了SP-A作用通过CR 3介导的强有力的推断。 我们认为SP-A在肺中起着复杂的调节作用，与肺泡巨噬细胞上存在的细胞表面受体结合，影响微生物的结合、摄取和杀灭。 CR 3是识别微生物病原体的重要吞噬细胞受体，并负责介导吞噬细胞的吞噬作用、脱粒和呼吸爆发。 CR 3介导的吞噬作用在清除B族链球菌（GBS）和流感嗜血杆菌（两者都是儿童疾病中的重要病原体）中是重要的。 本申请将利用SP-A的合成被遗传改变的模型，使用SP-A-/-和SP-A+/+小鼠来确定在SP-A不存在的情况下肺泡巨噬细胞上的CR 3表达是否改变。 本申请将测试SP-A通过调节介导这些事件的表面受体来增强吞噬作用并激活肺泡巨噬细胞的中心假设。 具体目标1将检验SP-A通过动员细胞内CR 3库来调节肺泡巨噬细胞上CR 3表达的假设。 特异性目标2将检验SP-A与肺泡巨噬细胞上的CR 3结合的假设，并将确定增强CR 3表达的特异性SP-A结构域。 具体目标3将检验SP-A调理GBS或H的假设。流感激活CR 3以增强巨噬细胞吞噬作用和氧自由基产生。 将使用CR 3转染的细胞在体外和使用来自SP-A-/-、CR 3-/-、SP-A-/-CR 3-/-和野生型小鼠的肺泡巨噬细胞在体内研究SP-A增强CR 3介导的吞噬作用中重要的信号传导途径。 这些研究将有助于阐明SP-A在肺先天防御中的作用，并为未来维持内源性或提供外源性SP-A以预防细菌感染发病的治疗提供基础。

DESCRIPTION (provided by applicant): This application will test the hypothesis that surfactant protein-A (SP-A), a pulmonary collectin, plays a critical role in protecting the lung from bacterial infection by modulating surface receptors on alveolar macrophages. Preliminary data presented in this application provides a clear relationship between SP-A and complement receptor type 3 (CR3) providing a strong inference that SP-A effects are mediated through CR3. We propose that SP-A serves complex regulatory roles in the lung, binding to cell surface receptors present on alveolar macrophages influencing binding, uptake, and killing of microorganisms. CR3 is an important phagocyte receptor for recognition of microbial pathogens and is responsible for mediating phagocytosis, degranulation, and respiratory bursts by phagocytic cells. CR3 mediated phagocytosis is important in clearance of group B streptococcus (GBS) and Haemophilus influenza, both important pathogens in childhood disease. This application will utilize models in which the synthesis of SP-A is altered genetically, using SP-A-/- and SP-A+/+ mice to determine if CR3 expression on alveolar macrophages is altered in the absence of SP-A. This application will test the central hypothesis that SP-A enhances phagocytosis and activates alveolar macrophages by modulating surface receptors mediating these events. Specific Aim 1 will test the hypothesis that SP-A regulates expression of CR3 on alveolar macrophages by mobilizing intracellular CR3 pools. Specific Aim 2 will test the hypothesis that SP-A binds to CR3 on alveolar macrophages and will determine the specific SP-A domain that enhances CR3 expression. Specific Aim 3 will test the hypothesis that SP-A opsonized GBS or H. influenza activate CR3 to enhance macrophage phagocytosis and oxygen radical production. Signaling pathways important in SP-A enhanced CR3 mediated phagocytosis will be studied in vitro using CR3 transfected cells and in vivo with alveolar macrophages from SP-A-/-, CR3-/-, SP-A-/-CR3-/- and wild type mice. These studies will help clarify the role of SP-A in innate defense of the lung and provide the basis for future therapies to maintain endogenous or supply exogenous SP-A to prevent morbidity from bacterial infection.