ROLE OF SURFACTANT PROTEIN D IN SURFACTANT HOMEOSTASIS

这是一项为期五年的支持申请，旨在研究SP-D（钙依赖性凝集素聚集蛋白家族的成员）在表面活性剂磷脂动态平衡中发挥关键作用的分子机制。 在健康的肺，肺泡和组织表面活性物质池的大小受到严格的管制，然而，精确的分子机制介导的表面活性物质的稳态仍然不清楚。 在转基因小鼠SP-D（-/-）中靶向缺失SP-D导致肺泡和组织表面活性剂磷脂显著增加。 在SP-D（-/-）小鼠中，增加的表面活性剂磷脂与增加的表面活性剂蛋白无关，但与肺泡巨噬细胞的大小和外观改变、小管髓鞘减少和肺泡中异常致密的脂质形式有关。SP-D基因靶向实验已经确定了一种以前未知的途径，通过该途径选择性地调节表面活性剂磷脂池的大小。我们将确定SP-D（+/+）和SP-D（-/-）小鼠中Sat PC池大小变化的个体发生，并表征SP-D（-/-）小鼠相对于SP-D（+1+）小鼠的表面活性剂磷脂合成、分泌和清除。 我们还将回答以下问题：1）SP-D是否直接改变了空气中的表面活性剂脂质结构，进而改变了表面活性剂的功能和催化作用; 2）SP-D是否直接与II型细胞和肺泡巨噬细胞相互作用，以发出影响表面活性剂脂质摄取、催化作用或再循环的细胞事件的信号;以及3）SP-D对表面活性剂磷脂代谢的影响是否由SP-D分子内的特定结构域介导。 目的是了解SP-D在磷脂和表面活性蛋白稳态独立调节中所涉及的细胞和/或结构机制中的作用。

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.