Surfactant protein C mutations and interstitial lung diease

描述（由申请人提供）： 表面活性剂蛋白C（SP-C）是一种由35个氨基酸组成的肺特异性疏水肽，其增强表面活性剂磷脂的生物物理活性。SP-C对肺部健康和疾病的重要性已经通过以下观察结果得到强调：人类SP-C基因中超过20种不同突变的杂合表达与慢性间质性肺病（ILD）相关，并且通过证明聚集倾向proSP-C COOH末端与家族性阿尔茨海默样痴呆（称为BRICHOS）相关蛋白之间的结构同源性。该项目的总体目标是进一步了解BRICHOS突变SP-C表达作为间质性肺病病理生理学相关上皮功能障碍的病因学和模型的分子机制。我们假设SP-C基因突变诱导异常蛋白产物的发展，这些蛋白产物采用非天然构象，导致聚集和产生毒性功能增益。肺泡上皮细胞（AEC）最初通过激活未折叠蛋白反应（UPR）来响应易于聚集的SP-C BRICHOS蛋白，目的是纠正错误折叠。UPR未能实现重折叠导致细胞处置程序的激活，包括ER相关降解（ERAD）和大自噬以增加突变蛋白的清除。在处理失败的情况下，延长的UPR激活（即“ER应激”）导致危险信号的产生，从而影响细胞因子的产生和细胞凋亡，这有助于ILD中观察到的异常伤口愈合和纤维化重塑。我们的实验方法利用遗传学和药理学技术来剖析与ILD相关的SP-C基因折叠突变的细胞应答的分子途径。我们实验室开发的突变SP-C expresson的体外细胞模型将与设计用于interrogate蛋白质稳定途径的工具和试剂相结合，如UPR [特异性目的1]以及ERAD和自噬[特异性目的2]，它们参与AEC处理异常蛋白质客户的稳态反应。此外，这些模型系统将用于评价在其他蛋白质抑制性疾病中显示有效的新兴治疗策略[特定目标3]，从而为治疗这种毁灭性肺部疾病提供快速从实验室到床边转化的可能性。 公共卫生相关性： 肺纤维化是一种破坏性的间质性肺病（ILD），其特征是持续的呼吸衰竭和死亡。越来越多的人认识到肺上皮细胞功能障碍在ILD的发病机制中起重要作用。人类表面活性蛋白C（SP-C）基因中超过20种不同的突变与肺纤维化有关。由于SP-C是由肺泡2型细胞合成的，因此SP-C突变可用作理解ILD发病机制中上皮细胞功能障碍的模型系统。该项目的总体目标是表征响应于突变SP-C表达的调节蛋白质稳态（“蛋白稳态”）的分子机制。该项目资助的结果将定义所使用的蛋白质抑制反应（未折叠蛋白质反应，蛋白酶体降解，自噬）的作用。 上皮细胞的细胞保护作用，它们的失败如何有助于ILD发病机制，并将允许快速评估ILD治疗的新治疗靶点。

DESCRIPTION (provided by applicant): Surfactant protein C (SP-C) is a 35 amino acid lung-specific hydrophobic peptide that enhances the biophysical activity of surfactant phospholipid. The importance of SP-C to lung health and disease has been underscored by the observations that heterozygous expression of over 20 different mutations in the SP-C gene in humans is associated with chronic interstitial lung disease (ILD) and by the demonstration of structural homology between the aggregation-prone proSP-C COOH terminus and a protein associated with familial Alzheimer-like dementia (termed BRICHOS). The overall goal of this project is to further understand the molecular mechanisms underlying the consequences of BRICHOS mutant SP-C expression as both an etiology for and a model of the epithelial dysfunction associated with the pathophysiology of interstitial lung disease. We hypothesize that mutations in the SP-C gene induce the development of aberrant protein products that adopt non-native conformations that lead to aggregation and production of a toxic gain of function. Alveolar epithelial cells (AEC) initially respond to aggregation-prone SP-C BRICHOS protein by activating the unfolded protein response (UPR) aimed at correcting misfolding. Failure of the UPR to effect refolding results in activation of cellular disposal programs including ER- Associated Degradation (ERAD) and macroautophagy to augment mutant protein clearance. In the face of failed disposal, prolonged UPR activation (i.e. "ER Stress") results in elaboration of danger signals to effect cytokine elaboration and apoptosis which contribute to the abnormal wound healing and fibrotic remodeling seen in ILD. Our experimental approach utilizes genetic and pharmacologic techniques to dissect out molecular pathways underlying the cellular response to folding mutations in the SP-C gene associated with ILD. In vitro cellular models of mutant SP-C expresson developed in our laboratory will be combined with tools and reagents designed to interogate proteostatic pathways such as the UPR [Specific Aim 1] as well as ERAD and autophagy [Specific Aim 2] that participate in the homeostatic response used by AEC to handle abnormal protein clients. In addition, these model systems will be used to evaluate emerging therapeutic strategies shown to be effective in other proteostatic diseases [Specific Aim 3] thus offering the possibilty of rapid bench to bedside translation for the treatment of this devastating lung disease. PUBLIC HEALTH RELEVANCE: Pulmonary fibrosis is a devastating interstitial lung disease (ILD) marked by unrelenting respiratory failure and death. It is increasingly recognized that lung epithelial cell dysfunction plays an important role in the pathogenesis of ILD. Over 20 different mutations in the Surfactant Protein C (SP-C) gene in humans are associated with lung fibrosis. Since SP-C is synthesized by alveolar type 2 cells, SP- C mutations can be used as a model system to understand epithelial cell dysfunction in ILD pathogenesis. The overall goal of this project is to characterize molecular mechanisms regulating protein homeostasis ("proteostasis") in response to mutant SP-C expression. Results funded by this project will define the role of proteostatic responses (unfolded protein response, proteasomal degradation, autophagy) used by epithelial cells for cytoprotection, how their failure contributes to ILD pathogenesis and will permit rapid assessment of new therapeutic targets for ILD treatment.