Molecular Signals for Trafficking Surfactant Protein B

描述（由申请人提供）：SP-B在2型细胞中功能性表面活性剂系统发展中的核心作用得到了对遗传性SP-B缺乏症的公开描述、先前资助期关于SP-B加工的个体发生的工作以及我们使用SP-B反义的初步数据的支持。SP-B的表达和加工是2型细胞表型的组成部分，与2型细胞的分化密切相关。SP-B缺乏症是发育性肺病（RDS）、遗传性SP-B缺乏症（遗传性SP-B缺乏症）致死性呼吸衰竭以及成人和儿童表面活性剂功能障碍疾病（ARDS）的一个组成部分。虽然最终的共同途径通常包括肺泡表面活性剂中成熟SP-B的减少导致表面张力异常，但其机制是多种多样的。我们已经证明SP-B的表达在翻译后水平受发育调控和激素反应。因此，SP-B加工酶在人类肺部疾病中发挥作用是合乎逻辑的。SP-B加工酶的表征将为制备外源表面活性剂的重组成熟SP-B开辟新的途径，从而提供更生理的配方。此外，随着蛋白酶抑制剂治疗用途的扩大，提高对SP-B加工蛋白酶的理解对于评估新一代蛋白酶抑制剂将是必要的。因此，我们假设pro - b的加工需要与SP-B相似的发育和激素调节的2型细胞特异性蛋白酶来促进底物和酶的协调表达。此外，特定亚细胞器中酶和底物的空间调控导致propro - b的逐步蛋白水解，这是暴露运输信号并最终在多泡体中释放成熟SP-B所必需的。建议的研究将：1。确定pro - b的n -侧翼结构域的身份及其在SP-B贩运中的作用；2. 2 .组织蛋白酶H、Napsin A和胃泌素在胎儿肺发育中的发育和激素调节的特征；建立组织蛋白酶H、Napsin A和胃蛋白酶在propro - b加工中的作用

DESCRIPTION (provided by applicant): A central role for SP-B in the development of a functional surfactant system in type 2 cells is supported by published descriptions of inherited SP-B deficiency, work from the previous funding period regarding ontogeny of SP-B processing, and our preliminary data using SP-B antisense. SP-B expression and processing are integral components of type 2 cell phenotype and are intimately related to type 2 cell differentiation. SP-B deficiency is a component of the developmental lung disease (RDS), of fatal respiratory failure from genetic deficiency (inherited SP-B deficiency), and of diseases of surfactant dysfunction in adults and children (ARDS). Although the final common pathway often includes a reduction of mature SP-B in alveolar surfactant resulting in abnormal surface tension, the mechanisms are diverse. We have shown that SP-B expression is developmentally regulated and hormonally responsive at the post-translational level. It is therefore logical that SP-B processing enzymes would have a role in human lung diseases. Characterization of SP-B processing enzymes will open new avenues into preparing recombinant mature SP-B for exogenous surfactant, thus providing a more physiologic formulation. Also, as therapeutic uses of protease inhibitors expand, improved understanding of the SP-B processing proteases will be necessary to evaluate new generation protease inhibitors. We therefore hypothesize that proSP-B processing requires type 2 cell specific proteases which are developmentally and hormonally regulated similarly to SP-B to facilitate the coordinated expression of substrate and enzyme. Furthermore, spatial regulation of enzyme and substrate in specific subcellular organelles results in stepwise proteolysis of proSP-B which is required for exposing trafficking signals and finally in liberating mature SP-B in the multivesicular body. The proposed studies will: 1. Determine the identity of the N-Flanking domain of proSP-B and its role in SP-B trafficking; 2. Characterize the developmental and hormonal regulation of Cathepsin H, Napsin A and Gastricsin in developing fetal lung: and 3. Establish the roles of Cathepsin H, Napsin A and Gastricsin in proSP-B processing