Proteolytic processing of procollagens is a central step during collagen fibril formation. Bone morphogenic protein 1 (BMP1) is a metalloprotease which plays an important role in the cleavage of carboxyterminal (C-terminal) propeptides from procollagens. Although the removal of propeptides is required to generate mature collagen fibrils, the contribution of BMP1 to this proteolytic process and its action site remain to be fully determined. In this study, using postnatal lung fibroblasts as a model system, we showed that genetic ablation of Bmp1 in primary murine lung fibroblasts abrogated C-terminal cleavage from type I procollagen as measured by C-terminal propeptide of type I procollagen (CICP) production. We also showed that inhibition of BMP1 by siRNA-mediated knockdown or small-molecule inhibitor reduced the vast majority of CICP production and collagen deposition in primary human lung fibroblasts. Furthermore, we discovered and characterized two antibody inhibitors for BMP1. In both postnatal lung fibroblast and organoid cultures, BMP1 blockade prevented CICP production. Together, these findings reveal a non-redundant role of extracellular BMP1 to process CICP in lung fibroblasts and suggest that development of antibody inhibitors is a viable pharmacological approach to target BMP1 proteinase activity in fibrotic diseases.

中文翻译：

---

细胞外BMP1是肺成纤维细胞中I型胶原蛋白C端蛋白水解的主要蛋白酶

前胶原蛋白水解加工是胶原原纤维形成过程中的中心步骤。骨形态发生蛋白1（BMP1）是一种金属蛋白酶，在从前胶原中裂解羧基端（C端）前肽方面发挥着重要作用。尽管需要除去前肽才能生成成熟的胶原蛋白原纤维，但是BMP1对这种蛋白水解过程及其作用部位的贡献仍有待完全确定。在这项研究中，使用出生后的肺成纤维细胞作为模型系统，我们证明了原发性鼠肺成纤维细胞中Bmp1的基因消融消除了I型胶原蛋白的C末端前肽（CICP）生产，从而消除了I型胶原蛋白的C末端裂解。我们还表明，通过siRNA介导的敲除或小分子抑制剂抑制BMP1可以减少绝大多数CICP产生和原代人肺成纤维细胞中胶原沉积。此外，我们发现并鉴定了BMP1的两种抗体抑制剂。在产后肺成纤维细胞和类器官培养物中，BMP1阻滞均阻止了CICP的产生。在一起，这些发现揭示了胞外BMP1处理肺成纤维细胞中CICP的非冗余作用，并表明抗体抑制剂的开发是在纤维化疾病中靶向BMP1蛋白酶活性的可行药理方法。BMP1封锁阻止了CICP的产生。在一起，这些发现揭示了胞外BMP1处理肺成纤维细胞中CICP的非冗余作用，并表明抗体抑制剂的开发是在纤维化疾病中靶向BMP1蛋白酶活性的可行药理方法。BMP1封锁阻止了CICP的产生。在一起，这些发现揭示了胞外BMP1处理肺成纤维细胞中CICP的非冗余作用，并表明抗体抑制剂的开发是在纤维化疾病中靶向BMP1蛋白酶活性的可行药理方法。