ROLE OF SURFACTANT PROTEIN D IN SURFACTANT HOMEOSTASIS

这是一项为期五年的支持研究SP-D的分子机制的应用，SP-D是钙依赖凝集素家族的成员，它在表面活性物质磷脂稳态中发挥关键作用。在健康的肺、肺泡和组织中，表面活性物质池的大小受到严格的调节，然而，调节表面活性物质动态平衡的确切分子机制仍然不清楚。在转基因小鼠中靶向缺失SP-D(-/-)，导致肺泡和组织表面活性物质磷脂显著增加。在SP-D(-/-)小鼠中，表面活性物质磷脂的增加与表面活性蛋白的增加无关，但与肺泡巨噬细胞的大小和外观的改变、小管髓鞘减少和肺泡内异常致密的脂质形式有关。SP-D基因打靶实验已经确定了一条以前未知的途径，通过它可以选择性地调节表面活性物质磷脂池的大小。我们将确定SP-D(+/+)和SP-D(-/-)小鼠sat PC池大小变化的个体发生，并相对于SP-D(+1+)小鼠表征SP-D(-/-)小鼠表面活性物质磷脂的合成、分泌和清除。我们还将回答以下问题：1)SP-D是否直接改变空气中表面活性物质的脂质结构，进而改变表面活性物质的功能和分解代谢；2)SP-D是否直接与II型细胞和肺泡巨噬细胞相互作用，以信号转导影响表面活性物质脂质摄取、分解代谢或循环的细胞事件；以及3)SP-D对表面活性物质磷脂代谢的影响是否通过SP-D分子中特定的结构域来调节。我们的目标是了解SP-D在细胞和/或结构机制中的作用，这些机制涉及磷脂和表面活性物质蛋白稳态的独立调节。

This is an application for five years of support to study the molecular mechanisms by which SP-D, a member of the collectin family of calcium-dependent lectins, plays a critical role in surfactant phospholipid homeostasis. In the healthy lung, alveolar and tissue surfactant pool sizes are tightly regulated, however, the precise molecular mechanisms mediating surfactant homeostasis remain poorly clarified. Targeted deletion of SP-D in transgenic mice, SP-D (-/-), resulted in a marked increase in alveolar and tissue surfactant phospholipid. In SP-D (-/-) mice, the increased surfactant phospholipid was not associated with Increased surfactant proteins, but was associated with alterations in the size and appearance of alveolar macrophages, decreased tubular myelin and abnormally dense lipid forms In the alveoli. The SP-D gene targeting experiments have identified a previously unknown pathway by which the surfactant phospholipid pool sizes are selectively regulated. We will determine the ontogenesis of changes In Sat PC pool size in SP-D (+/+) and SP-D (-/-) mice and characterize surfactant phospholipid synthesis, secretion, and clearance In SP-D (-/-) mice relative to SP-D (+1+) mice. We also will answer the following questions: 1) Whether SP-D directly alters surfactant lipid structures in the airspaces, in turn, altering surfactant function and catabolism; 2) Whether SP-D interacts directly with type II cells and alveolar macrophages to signal cellular events which influence surfactant lipid uptake, catabolism, or recycling; and 3) Whether the effects of SP-D on surfactant phospholipid metabolism are mediated by specific structural domains within the SP-D molecule. The goal is to understand the role of SP-D in the cellular and/or structural mechanisms involved in independent regulation of phospholipid and surfactant protein homeostasis.