Apoptotic T Cell Clearance From Murine Lungs

描述(申请人提供)：意义：细胞凋亡是肺气肿发病机制的核心，在急性肺损伤、败血症和病毒性肺炎中广泛存在。必须有效清除凋亡细胞(AC)，以限制肺部炎症和维持免疫耐受。当肺部感染得到成功治疗时，白细胞通过凋亡而死亡，它们被肺泡巨噬细胞(AMO)清除，通过分泌转化生长因子-β(TGF-β)、前列腺素E_2(PGE2)和IL-10来加速肺修复，这些免疫抑制介质也可以破坏对病原体的防御，促进纤维化。因此，了解AMO对AC的反应的机制和后果，这是该项目的长期目标，可能会影响肺部医学的许多领域。该项目研究了一种名为MerTK的受体酪氨酸激酶，它是AC摄取MO所必需的。新的初步数据显示，暴露于AC诱导MerTK与两个先前与AC摄取有关的MO分子相互作用，即A型清道夫受体(SR-A)和脂蛋白受体相关蛋白(LRP)。与SR-A的结合先于MerTK的激活，而与LRP的结合之后是LRP信号转导所必需的特异性丝氨酸磷酸化。阻断MerTK可阻断AC诱导的ERK激活，而ERK是α趋化因子诱导所必需的。这一提议将检验MerTK与SR-A、LRP和特定的细胞内分子顺序相互作用的假设，以诱导MO识别、摄取和产生趋化因子以响应AC。实验将分析来自正常小鼠的AMO细胞系MH-S和常驻AMO，或者来自缺乏SR-A或MO谱系上缺乏LRP的基因靶向小鼠。技术将包括吞噬和黏附分析；免疫沉淀和Western分析；实时聚合酶链式反应；共聚焦显微镜；瞬时转基因；以及使用慢病毒感染和小干扰RNA的基因沉默。相关性：肺细胞死亡是肺气肿、一些肺炎和其他肺损伤的一个特征。这些死亡细胞必须被正确清除，以防止恶化的肺损伤、疤痕形成或免疫损害。该项目研究一种名为MerTK的分子，它似乎控制着清除。了解MerTK可能会导致新的治疗方法，以预防多种类型的肺损伤的并发症。

DESCRIPTION (provided by applicant): Significance: Apoptosis is central to the pathogenesis of emphysema, and is widespread in acute lung injury, sepsis, and viral pneumonias. Apoptotic cells (AC) must be cleared efficiently to limit lung inflammation and to maintain immunologic tolerance. When lung infections are handled successfully, leukocytes die by apoptosis and their clearance by alveolar macrophages (AMO) hastens lung repair via secretion of TGF-beta, PGE2 and IL-10, immunosuppressive mediators that can also compromise defenses against pathogens and promote fibrosis. Thus, understanding the mechanisms and consequences of the AMO response to AC, the Long-Term Goals of this project, could impact many areas of pulmonary medicine. This project has studied a receptor tyrosine kinase called MerTK, which is essential for MO uptake of AC. Novel preliminary data are presented showing that exposure to AC induces MerTK to interact with two MO molecules previously implicated in AC uptake, the type A scavenger receptor (SR-A) and the lipoprotein receptor-related protein (LRP). Association with SR-A precedes MerTK activation, whereas association with LRP is followed by specific serine phosphorylation essential for LRP signaling. Blocking MerTK ablates AC- induced activation of ERK, which is required for alpha chemokine induction. This proposal will test the hypothesis that MerTK interacts sequentially with SR-A, LRP and specific intracellular molecules to induce MO to recognize, ingest and produce chemokines in response to AC. Experiments will analyze the AMO cell line MH-S and resident AMO from normal mice, or from gene-targeted mice lacking SR-A, or lacking LRP specifically on the MO lineage. Techniques will include assays of phagocytosis and adhesion; immunoprecipitation and Western analysis; real-time PCR; confocal microscopy; transient transfections; and gene silencing using lentiviral infection with small interfering RNAs. Relevance: Death of lung cells is a feature of emphysema, some pneumonias, and other lung injuries. These dead cells must be cleared correctly to prevent worsened lung injury, scarring, or immune compromise. This project studies a molecule called MerTK that appears to control clearance. Understanding MerTK could lead to new treatments to prevent complications of many types of lung damage.