Mutant Surfactant - Induced TGF-beta Secretion in Lung Fibrosis

描述（由申请人提供）：编码表面活性剂蛋白A2 （SP-A2）的基因突变导致家族性特发性肺纤维化（IPF）和肺癌，这两种致命疾病的治疗方案有限。表面活性剂蛋白突变的分子机制尚不清楚，是影响儿童和成人的一系列肺部疾病的基础。我们最近发现，在肺上皮细胞中表达某些突变的表面活性剂蛋白会导致潜在的TGF-ß的表达和分泌增加，TGF-ß是一种强效的促纤维化和促癌细胞因子。需要验证的具体假设是，肺泡上皮细胞中表面活性物质突变蛋白的表达通过TGF-ß的自分泌和旁分泌作用导致肺纤维化，TGF-ß的分泌通过内质网应激依赖性和内质网应激非依赖性途径诱导。我们提出这项工作的基本原理是，它将增强对突变表面活性剂蛋白在引起进行性肺纤维化中的功能获得效应的理解。第一个目标将集中在体外研究这一机制，通过确定：哪些变体表面活性剂蛋白具有诱导潜在TGF-ß分泌增加的功能获得效应，内质网应激信号介导这一机制的相对贡献是什么？潜在途径的分子机制将通过结合蛋白质组学和转录组学方法以及化学抑制剂来探索。第二个目标是确定II型肺泡上皮的损伤或“重编程”

DESCRIPTION (provided by applicant): Mutations in the gene encoding surfactant protein A2 (SP-A2) cause familial idiopathic pulmonary fibrosis (IPF) and lung cancer, both lethal diseases with limited treatment options. The molecular mechanism of mutant surfactant proteins are not well understood and underlie a spectrum of lung diseases affecting children and adults. We have recently discovered that expression of certain mutant surfactant proteins in lung epithelial cells leads to increased expression and secretion of latent TGF-ß, a potent pro-fibrotic and pro-oncogenic cytokine. The specific hypothesis to be tested is that expression of mutant surfactant proteins in alveolar epithelial cells leads to pulmonary fibrosis through the autocrine and paracrine effects of TGF-ß, whose secretion is induced through ER stress-dependent and ER stress-independent pathways. Our rationale for the proposed work is that it will provide enhanced understanding of the gain-of-function effects of mutant surfactant proteins in causing progressive pulmonary fibrosis. The first aim will focus on studying this mechanism in vitro by determining: Which variant surfactant proteins have a gain-of-function effect of inducing increased latent TGF-ß secretion and what is the relative contribution of ER stress signaling that mediates this mechanism? The molecular mechanism of the underlying pathways will be probed using a combination of proteomic and transcriptomic approaches as well as chemical inhibitors. The second aim will define the injury or "reprogramming" of type II alveolar epithelial cells caused by acute or chronic expression of mutant surfactant proteins and the involvement of various pathways that affect the cellular context of TGF-ß signaling. In the third and last aim, we will elucidate the in vivo molecular mechanism of mutant SP-A2 protein-mediated disease using a novel transgenic mouse model. We will specifically explore the genetic contributions of the TGF-ß signaling and telomerase pathways in contributing to bleomycin-induced lung fibrosis. While the signaling pathways downstream of TGF-ß are well characterized, the inciting events that lead to its expression and secretion are not. Successful completion of these aims will elucidate this novel pathway of mutant surfactant induced latent TGF-ß secretion. This work will generate insight into the pathways linking protein misfolding, ER stress, EMT, cellular differentiation and proliferation in lung fibrosis and will assist in the identification of unique targets for drug development.