特发性肺纤维化(IPF)是一种病死率极高的间质性肺疾病。活化的肺成纤维细胞转变为肌成纤维细胞是引起IPF发生发展的关键途径，然而其中的机制尚未明确。TGFβ-1及其下游信号分子参与调控肺成纤维细胞活化从而影响IPF进展。申请人前期发现TGFβ-1/Raf-1通路可调控E3泛素连接酶Nedd4L表达，后者的下调可增加TβRII蛋白稳定性进而促进肺成纤维细胞活化，最终加速IPF进展。本课题拟通过挽救实验阐明Raf-1下调Nedd4L表达进而促进TGFβ-1信号通路的分子机制，通过位点突变实验证明Nedd4L调控TβRII泛素化的泛素结合位点。同时，结合肺纤维化动物模型和临床数据验证三者的关系及其在IPF中的作用。本课题旨在从临床、动物、细胞、分子水平，揭示Raf-1/Nedd4L/TβRII信号轴在IPF中的作用及机制，为IPF预后的早期判读提供实验基础、为靶向治疗IPF新策略提供理论依据。

Idiopathic pulmonary fibrosis (IPF) is fatal fibrotic lung disease. Activation of fibroblasts to myofibroblasts is a key event in fibrosis and precise mechanisms remain unknown. TGFβ-1 signaling leads to myofibroblast differentiation, play central roles in the pathogenesis of pulmonary fibrosis. In our preliminary data, Raf-1 regulates TGFβ-1-suppressed Nedd4L expression, and downregulation of Nedd4L increases TβRII stability, resulting in fibroblast activation and IPF. The current proposal is to utilize the rescue experiments to investigate the mechanisms of suppression of Nedd4L expression by Raf-1 contributes to the pathogenesis of pulmonary fibrosis through promoting TGFβ-1 pathways. We will extend the preliminary data to characterize the molecular signature of Nedd4L ubiquitination of TβRII, including ubiquitination sites and determine the role of Raf-1, Nedd4L, and TβRII in human and animal tissues. In summary, the achievement of this application will reveal the role of the Raf-1/Nedd4L/TβRII axis in the pathogenesis of IPF, which is important for early diagnosis and development of a new therapeutic strategy for treating IPF.