Molecular Signals for Trafficking Surfactant Protein B

描述（由申请人提供）：表面活性剂蛋白B （SP-B）在肺泡II型细胞生理中起核心作用。作为肺表面活性剂的组成部分，促进磷脂向气液界面转移，降低单层表面张力，改变单层组成。SP-B对II型细胞的分化，特别是板层体的发生至关重要。我们一直在探索翻译后对SP-B产生的调控。这源于观察，尽管SP-B RNA增加，成熟的SP-B蛋白直到妊娠后期才在胎儿肺中积累，从而允许SP-B生产的爆发，促进LB的发生和表面活性剂分泌到胎儿肺液中。我们已经证明SP-B生物发生中的翻译后事件在调节II型肺泡细胞SP-B的产生和转运中是重要的。当表面活性剂的重新合成是必需的，如在肺成熟过渡到空气呼吸的最后阶段（如RDS），以及当细胞外和/或细胞内表面活性剂储存耗尽（如ARDS）时，这些事件尤为关键。先前资助期的工作表明，参与pro - b翻译后加工的酶对II型细胞生理学很重要。基于新的初步数据，我们现在假设涉及蛋白酶胃蛋白酶原C （PGC）和ER伴侣（如ERp29）的翻译后事件对调节SP-B的产生，从而调节板层体发生和II型细胞生理至关重要。我们将从三个方面验证这一假设：1)表征PGC在SP-B蛋白水解过程中的作用，2)建立指导PGC表达的发育和细胞类型特异性的关键转录元件，以及3)证明伴侣蛋白相互作用，特别是ERp29:pro - b相互作用，促进了ER中pro - b的输出。我们将使用人类II型细胞分化的体外系统来检查由于SP-B加工/运输中断而导致的板层体形成过程。表面活性剂治疗对于患有呼吸窘迫的早产儿来说是成功的，但是对于成人来说却没有那么成功。成人呼吸窘迫综合征与表面活性蛋白B （SP-B）功能障碍或降低有关。这些研究将提高我们对控制SP-B产生的因素的理解，并将为提高SP-B产生和表面活性剂功能的新治疗策略提供基础。

DESCRIPTION (provided by applicant): Surfactant Protein B (SP-B) plays a central role in alveolar type II cell physiology. As a component of pulmonary surfactant, it facilitates transfer of phospholipids to the air-liquid interface, lowering of monolayer surface tension, and altering of monolayer composition. SP-B is critical to the differentiation of type II cells, specifically lamellar body genesis. We have been exploring the post-translational regulation of SP-B production. This stems from observations that despite increasing SP-B RNA, mature SP-B protein does not accumulate in the fetal lung until late in gestation, thereby allowing for a burst of SP-B production that facilitates LB genesis and surfactant secretion into fetal lung fluid. We have shown that post-translational events in SP-B biogenesis are important in regulating the production and transit of SP-B in the alveolar type II cell. These events are especially critical when de novo synthesis of surfactant is essential, as in the final phase of lung maturation for the transition to air breathing (as in RDS), and when extracellular and/or intracellular surfactant stores are depleted (as in ARDS). Work from the previous funding period demonstrated that enzymes involved in proSP-B post-translational processing are important to type II cell physiology. Based on new preliminary data, we hypothesize now that post-translational events involving the protease Pepsinogen C (PGC) and ER chaperones such as ERp29 are critical for regulating SP-B production, and consequently lamellar body genesis and type II cell physiology. We will test this hypothesis in 3 specific aims: 1) Characterize the role of PGC in SP-B proteolytic processing, 2) Establish key transcriptional elements directing the developmental and cell-type specificity of PGC expression, and 3) Demonstrate that chaperone interactions, specifically ERp29:proSP-B interactions, facilitate export of proSP-B from the ER. We will use an in vitro system of human type II cell differentiation to examine the process of lamellar body genesis as a result of disrupted SP-B processing/trafficking. Project Narrative: Surfactant therapy has been a success for premature infants with respiratory distress, but has not been as successful in adults. Adult respiratory distress syndrome is associated with dysfunction or decreased Surfactant Protein B (SP-B). These studies will improve our understanding of factors that control SP-B production and will provide a foundation for novel therapeutic strategies to enhance SP-B production and surfactant function.