Molecular mechanism of lung discases by analysis of surfactant protein A and its receptor.

肺表面活性物质在肺磷脂稳态和宿主防御机制中起着重要作用。本课题主要研究具有碳水化合物识别结构域的聚类表面活性剂磷酸腺苷A （ptein A, SP-A）及其受体。本项目旨在探讨sp - a - 1与肺部疾病的分子机制。我们检测了SP-A对从肺泡II型细胞分离的质膜磷脂脂质体相互作用的影响。SP-A显著促进脂质体与II型细胞源性膜的结合，而不是与肝质膜的结合。结果表明，SP-A受体可能参与了SP-A促进脂质体与膜结合的作用。甘露糖结合蛋白A （MBP-A）也属于c型凝集素的集合亚群，在结构上与SP-A同源。我们构建了SP-A区Glu^<195>-P…的嵌合分子，其中he^<228>被MBP-A区Glu^<185>-Ala^<221>取代。该嵌合体保留了结合双棕榈酰磷脂酰胆碱和与肺泡II型细胞相互作用的能力，而从大鼠血清中分离的MBP-A则不能表达这些SP-A功能。结果表明，SP-A区Glu^<195>-Phe^<228>和MBP-A区Glu^<185>-Ala^<221>是可互换的，而SP-A功能没有损失。点突变重组蛋白的结果也表明，人SP-A的Arg^<199>和Lys^<201>以及大鼠SP-A的Lys^<201>和Lys^<203>对SP-A的功能并不是至关重要的，SP-A介导脂质体聚集的关键机制与SP-A介导II型细胞脂质摄取的关键机制不同。来自肺泡II型细胞患者的SP-A寡聚物的异常聚集体与II型细胞的相互作用效果较差，并表现出异常的磷脂膜组织。发现IgG与SP-A寡聚物的异常大聚集体相关，而与正常大小的SP-A - 4无关。通过对肺腺癌患者胸膜积液中SP-A基因和蛋白表达的分析发现，超过四分之三的腺癌细胞表达SP-A，这是一种外周气道细胞标志物。少

Pulmonary surfactant plays important roles in phospholipid homeostasis and in host deffence mechanism of the lung. In this research project, we focussed on surfactant ptotein A (SP-A) that belongs to collectin family which possesses the carbohydrate recognition domain, and on SP-A receptor. The purpose of this project was to investigate the molecular mechanisms of the lung discases in relation to SP-A.1. We examined the effect of SP-A on the interaction of phospholipid liposomes with plasma membrane isolated from alveolar type II cells. SP-A significantly facilitated the binding of liposomes to type II cell-derived membrane but not to liver plasma membrane. The results suggest that SP-A receptor on type II cells may be involved in facilitated effect of SP-A on liposome binding to membrane.2. Mannose-binding protein A (MBP-A) also belongs to the collectin subgroup of C-type lectins and structurally homologous to SP-A.We constructed chimeric molecules in which the SP-A region Glu^<195>-P … More he^<228> was substituted with the MBP-A region Glu^<185>-Ala^<221>. This chimera retained the ability to bind dipalmitoylphosphatidylcholine and interact with alveolar type II cells, while MBP-A isolated from rat sera failed to express these SP-A function. The results indicate that the SP-A region Glu^<195>-Phe^<228> and the MBP-A region Glu^<185>-Ala^<221> are interchangeable without loss of SP-A functions. The results from the recombinant proteins with point mutations also indicate that Arg^<199> and Lys^<201> of human SP-A and Lys^<201> and Lys^<203> of rat SP-A are not critical for the SP-A functions and that the crucial mechanism of SP-A-mediated liposome aggregation is distinct from that of SP-A-mediated lipid uptake by type II cells.3. The abnormal aggregates of SP-A oligomer derived from patients with alveolar type II cells was less effective in interaction with type II cells and exhibited abnormal phospholipid membrane organization. IgG was found to associate with the abnormal larger aggregates of SP-A oligomer but not with normal-sized SP-A.4. The analysis of SP-A gene and protein expression in cancer cells from pleural effusions of patients with lung adenocarcinomas revealed that more than three quaters of adenocarcinoma cells express SP-A,one of peripheral airway cell markers. Less