Abstract：
Osteoclasts are multinucleated cells with bone resorption activity. Excessive osteoclast activity has been implicated in osteoporosis, rheumatoid arthritis, and bone destruction due to bone metastases from cancer, making osteoclasts essential target cells in bone and joint diseases. C-terminal domain nuclear envelope phosphatase 1 (Ctdnep1, formerly Dullard) is a negative regulator of transforming growth factor (TGF)-β superfamily signaling and regulates endochondral ossification in mesenchymal cells during skeletal development. In this study, we investigated the role of Ctdnep1 in the Receptor activator of nuclear factor-kappa B ligand (RANKL)-induced RAW264.7 osteoclast differentiation. Expression of Ctdnep1 did not change during osteoclast differentiation; Ctdnep1 protein localized to the cytoplasm before and after osteoclast differentiation. Small interfering RNA-mediated knockdown of Ctdnep1 increased tartrate-resistant acid phosphatase-positive multinucleated osteoclasts and the expression of osteoclast marker genes, including Acp5, Ctsk, and Nfatc1. Interestingly, the knockdown of Ctdnep1 increased the protein level of Nfatc1 in cells unstimulated with RANKL. Knockdown of Ctdnep1 also enhanced calcium-resorbing activity. Mechanistically, the knockdown of Ctdnep1 increased the phosphorylation of RANKL signaling components. These results suggest that Ctdnep1 negatively regulates osteoclast differentiation by suppressing the RANKL signaling pathway.
摘要：
破骨细胞是具有骨吸收活性的多核细胞。过度的破骨细胞活性与骨质疏松症有关，类风湿性关节炎,以及癌症骨转移引起的骨破坏，使破骨细胞成为骨关节疾病中必不可少的靶细胞。C末端结构域核包膜磷酸酶1（Ctdnep1，前身为Dullard）是转化生长因子（TGF）-β超家族信号传导的负调节因子，并在骨骼发育过程中调节间充质细胞的软骨内骨化。在这项研究中,我们研究了Ctdnep1在核因子-κB受体激活剂配体（RANKL）诱导的RAW264.7破骨细胞分化中的作用。Ctdnep1的表达在破骨细胞分化过程中没有变化；Ctdnep1蛋白在破骨细胞分化前后定位于细胞质。小干扰RNA介导的Ctdnep1敲除增加抗酒石酸酸性磷酸酶阳性多核破骨细胞和破骨细胞标记基因的表达，包括Acp5，Ctsk，和Nfatc1。有趣的是,Ctdnep1的敲除增加了未经RANKL刺激的细胞中Nfatc1的蛋白水平。敲除Ctdnep1还增强了钙吸收活性。机械上,Ctdnep1的敲除增加了RANKL信号组件的磷酸化。这些结果表明Ctdnep1通过抑制RANKL信号通路负调控破骨细胞分化。
