SP-A Receptor Regulation in Lung Innate Defense

描述（由申请人提供）：本申请将测试表面活性剂蛋白a (SP-A)，一种肺集合，通过调节肺泡巨噬细胞表面受体在保护肺部免受细菌感染方面发挥关键作用的假设。本应用程序中提供的初步数据提供了SP-A与补体受体3型（CR3）之间的明确关系，从而有力地推断SP-A的作用是通过CR3介导的。我们认为SP-A在肺中起着复杂的调节作用，与肺泡巨噬细胞上的细胞表面受体结合，影响微生物的结合、摄取和杀死。CR3是一种重要的吞噬细胞受体，用于识别微生物病原体，并负责介导吞噬细胞的吞噬、脱颗粒和呼吸爆发。CR3介导的吞噬作用在清除B族链球菌（GBS）和流感嗜血杆菌（Haemophilus influenza）这两种儿童疾病的重要病原体中起着重要作用。该应用将利用SP-A合成被基因改变的模型，使用SP-A-/-和SP-A+/+小鼠来确定在SP-A缺失的情况下，肺泡巨噬细胞上的CR3表达是否会改变。该应用程序将验证SP-A通过调节介导这些事件的表面受体来增强吞噬和激活肺泡巨噬细胞的中心假设。特异性目的1将验证SP-A通过动员细胞内CR3池调节肺泡巨噬细胞CR3表达的假设。特异性目的2将验证SP-A在肺泡巨噬细胞上与CR3结合的假设，并确定SP-A特异性结构域增强CR3表达。特异性目的3将验证SP-A活化的GBS或流感嗜血杆菌激活CR3以增强巨噬细胞吞噬和氧自由基产生的假设。在体外研究SP-A增强CR3介导的吞噬作用的重要信号通路时，将使用CR3转染细胞和体内SP-A-/-、CR3-/-、SP-A-/-CR3-/-和野生型小鼠的肺泡巨噬细胞进行研究。这些研究将有助于阐明SP-A在肺部先天防御中的作用，并为未来维持内源性或供应外源性SP-A以预防细菌感染发病率的治疗提供基础。

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.