Yang Hailin, Dong Jinbo, Xiong Wei, Fang Zhong, Guan Hanfeng, Li Feng
Department of Orthopaedics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, P.R. China.
Department of Orthopaedics, People's Hospital of Jieshou City, Jieshou, Anhui, P.R. China.
Ann N Y Acad Sci. 2016 Dec;1385(1):41-52. doi: 10.1111/nyas.13221. Epub 2016 Oct 10.
Sclerostin/SOST is a robust negative regulator of bone formation. Loss-of-function mutations of the sclerostin gene (SOST) cause sclerosteosis and Van Buchem disease characterized by bone overgrowth. Mediated by myocyte enhancer factor 2 (MEF2) transcription factors, parathyroid hormone (PTH) suppresses SOST expression through formation of complexes of parathyroid hormone-parathyroid hormone-related peptide receptor 1 (PTH1R) and lipoprotein receptor-related protein 6 (LRP6). N-cadherin has been shown to negatively regulate Wnt/β-catenin and PTH induced, protein kinase-dependent β-catenin signaling. Here, we investigated whether N-cadherin mediates the inhibitory effects of PTH on sclerostin/SOST. In vitro, overexpression of N-cadherin resulted in blunted PTH suppressive effects on sclerostin/SOST expression, as detected by immunoblot and qPCR analysis; PTH-induced downregulation of MEF2A, C, and D was impaired by N-cadherin; and N-cadherin reduced LRP6-PTHR1 interaction and endocytosis in response to PTH. In vivo, intermittent PTH (iPTH)-induced suppression of sclerostin/SOST was accentuated in Dmp1-cre; Cdh2 (Cdh2 ) mice, compared with Cdh2 mice. Additionally, iPTH had greater bone anabolic effects in Cdh2 mice compared to Cdh2 mice. These data indicate that N-cadherin negatively mediates PTH suppressive effects on sclerostin/SOST by regulating LRP6-PTHR1 interaction, ultimately influencing PTH anabolic effects on bone.
硬化蛋白/ SOST是一种强大的骨形成负调节因子。硬化蛋白基因（SOST）的功能丧失突变会导致以骨过度生长为特征的骨硬化症和范布赫姆病。甲状旁腺激素（PTH）由肌细胞增强因子2（MEF2）转录因子介导，通过形成甲状旁腺激素 - 甲状旁腺激素相关肽受体1（PTH1R）和脂蛋白受体相关蛋白6（LRP6）的复合物来抑制SOST表达。已表明N-钙黏蛋白对Wnt/β-连环蛋白以及PTH诱导的、蛋白激酶依赖性β-连环蛋白信号传导起负调节作用。在此，我们研究了N-钙黏蛋白是否介导PTH对硬化蛋白/ SOST的抑制作用。在体外，通过免疫印迹和qPCR分析检测到，N-钙黏蛋白的过表达导致PTH对硬化蛋白/ SOST表达的抑制作用减弱；N-钙黏蛋白损害了PTH诱导的MEF2A、C和D的下调；并且N-钙黏蛋白减少了LRP6 - PTHR1相互作用以及对PTH的内吞作用。在体内，与Cdh2小鼠相比，Dmp1-cre; Cdh2（Cdh2）小鼠中，间歇性PTH（iPTH）诱导的硬化蛋白/ SOST抑制作用增强。此外，与Cdh2小鼠相比，iPTH在Cdh2小鼠中具有更大的骨合成代谢作用。这些数据表明，N-钙黏蛋白通过调节LRP6 - PTHR1相互作用，负向介导PTH对硬化蛋白/ SOST的抑制作用，最终影响PTH对骨的合成代谢作用。
