Molecular Signals for Trafficking Surfactant Protein B

描述（由申请方提供）：表面活性剂蛋白B（SP-B）在肺泡II型细胞生理学中起核心作用。作为肺表面活性物质的一种成分，它促进磷脂转移到气液界面，降低单层表面张力，改变单层组成。SP-B对II型细胞的分化，特别是板层体的形成至关重要。我们一直在探索SP-B产生的翻译后调节。这是因为观察到尽管SP-B RNA增加，但成熟的SP-B蛋白直到妊娠后期才在胎肺中积累，从而允许SP-B产生的爆发，促进LB生成和表面活性剂分泌到胎肺液中。我们已经表明，SP-B生物合成中的翻译后事件在调节肺泡II型细胞中SP-B的产生和转运中是重要的。当表面活性剂的从头合成是必要的时，如在肺成熟的最后阶段过渡到空气呼吸（如在RDS中），以及当细胞外和/或细胞内表面活性剂储存耗尽时（如在ARDS中），这些事件尤其关键。上一个资助期的工作表明，参与proSP-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分子伴侣如ERp 29的翻译后事件是至关重要的调节SP-B的生产，因此板层体的发生和II型细胞生理学。我们将在3个具体目标中检验这一假设：1）表征PGC在SP-B蛋白水解加工中的作用，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，3）证明伴侣相互作用，特别是ERp 29：proSP-B相互作用，促进proSP-B从ER的输出。我们将使用体外系统的人II型细胞分化，以检查板层体的生成过程中，由于中断SP-B的加工/贩运。项目叙述：表面活性剂治疗对患有呼吸窘迫的早产儿是成功的，但在成人中并不成功。成人呼吸窘迫综合征与功能障碍或表面活性蛋白B（SP-B）减少有关。这些研究将提高我们对控制SP-B产生的因素的理解，并将为新的治疗策略提供基础，以提高SP-B的产生和表面活性剂的功能。

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.