1 Comprehensive Pneumology Center (CPC), University Hospital of the Ludwig-Maximilians University (LMU), LMU, Helmholtz Zentrum München, Member of the German Center for Lung Research (DZL), Munich, Germany.
2 Department of Internal Medicine, Universities of Giessen and Marburg Lung Center (UGMLC), Justus-Liebig-University Giessen, Member of the DZL, Giessen, Germany.
Am J Respir Crit Care Med. 2015 Nov 1;192(9):1089-101. doi: 10.1164/rccm.201412-2270OC.
The ubiquitin-proteasome system is critical for maintenance of protein homeostasis by degrading polyubiquitinated proteins in a spatially and temporally controlled manner. Cell and protein homeostasis are altered upon pathological tissue remodeling. Dysregulation of the proteasome has been reported for several chronic diseases of the heart, brain, and lung. We hypothesized that proteasome function is altered upon fibrotic lung remodeling, thereby contributing to the pathogenesis of idiopathic pulmonary fibrosis (IPF).
To investigate proteasome function during myofibroblast differentiation.
We treated lung fibroblasts with transforming growth factor (TGF)-β and examined proteasome composition and activity. For in vivo analysis, we used mouse models of lung fibrosis and fibrotic human lung tissue.
We demonstrate that induction of myofibroblast differentiation by TGF-β involves activation of the 26S proteasome, which is critically dependent on the regulatory subunit Rpn6. Silencing of Rpn6 in primary human lung fibroblasts counteracted TGF-β-induced myofibroblast differentiation. Activation of the 26S proteasome and increased expression of Rpn6 were detected during bleomycin-induced lung remodeling and fibrosis. Importantly, Rpn6 is overexpressed in myofibroblasts and basal cells of the bronchiolar epithelium in lungs of patients with IPF, which is accompanied by enhanced protein polyubiquitination.
We identified Rpn6-dependent 26S proteasome activation as an essential feature of myofibroblast differentiation in vitro and in vivo, and our results suggest it has an important role in IPF pathogenesis.
泛素-蛋白酶体系统通过时空控制方式降解多泛素化蛋白，对于维持蛋白质内稳态至关重要。细胞和蛋白质内稳态在病理性组织重塑时会发生改变。几种心脏、大脑和肺部的慢性疾病已报道存在蛋白酶体失调。我们假设在纤维化性肺重塑时，蛋白酶体功能发生改变，从而导致特发性肺纤维化（IPF）的发病机制。
研究成肌纤维细胞分化过程中的蛋白酶体功能。
我们用转化生长因子（TGF）-β处理肺成纤维细胞，并检测蛋白酶体组成和活性。为了进行体内分析，我们使用了肺纤维化的小鼠模型和纤维化的人肺组织。
我们证明 TGF-β诱导的成肌纤维细胞分化涉及 26S 蛋白酶体的激活，这严重依赖于调节亚基 Rpn6。在原代人肺成纤维细胞中沉默 Rpn6 可拮抗 TGF-β诱导的成肌纤维细胞分化。在博来霉素诱导的肺重塑和纤维化过程中，检测到 26S 蛋白酶体的激活和 Rpn6 的表达增加。重要的是，在 IPF 患者的肺中，Rpn6 在肌成纤维细胞和小支气管上皮的基底细胞中过度表达，伴随着蛋白多泛素化的增强。
我们确定了 Rpn6 依赖性 26S 蛋白酶体激活是体外和体内成肌纤维细胞分化的一个重要特征，并且我们的结果表明它在 IPF 发病机制中具有重要作用。
