Huntley Raphael, Davydova Julia, Petryk Anna, Billington Charles J, Jensen Eric D, Mansky Kim C, Gopalakrishnan Rajaram
Department of Diagnostic and Biological Sciences, University of Minnesota, Minneapolis, 55455, Minnesota.
Department of Surgery, University of Minnesota, Minneapolis, 55455, Minnesota.
J Cell Biochem. 2015 Oct;116(10):2239-46. doi: 10.1002/jcb.25174.
Proper regulation of osteoclast (OCL) function is critical for normal bone homeostasis. Bone morphogenetic protein (BMP) signaling and its regulation have been shown to have direct effects on OCL differentiation and activity. One of the major modulators of BMP signaling in the extracellular space is the secreted protein twisted gastrulation (TWSG1), which can inhibit BMP signaling and OCL differentiation. In this study we examine specific N-terminal regions of TWSG1 protein that have been previously proposed as BMP binding sites to determine whether TWSG1 binding to BMPs is required for its inhibitory effects on OCLs. We demonstrate that overexpression of wild type TWSG1 suppresses osteoclastogenesis, while overexpression of mutant TWSG1 proteins (W66A and N80Q/N146Q mutants), which cannot bind BMPs, leads to increased BMP signaling, enhanced osteoclastogenesis, increased resorptive activity, and expression of OCL-specific genes. Our results show that BMP binding is required for TWSG1-mediated inhibition of OCL formation and function, and validate the critical functional regions within the TWSG1 protein for these interactions.
破骨细胞（OCL）功能的适当调节对于正常的骨稳态至关重要。骨形态发生蛋白（BMP）信号传导及其调节已被证明对破骨细胞分化和活性有直接影响。细胞外空间中BMP信号传导的主要调节因子之一是分泌蛋白扭曲原肠胚形成蛋白（TWSG1），它可以抑制BMP信号传导和破骨细胞分化。在本研究中，我们研究了TWSG1蛋白先前被认为是BMP结合位点的特定N端区域，以确定TWSG1与BMPs的结合是否是其对破骨细胞抑制作用所必需的。我们证明野生型TWSG1的过表达抑制破骨细胞生成，而不能结合BMPs的突变型TWSG1蛋白（W66A和N80Q/N146Q突变体）的过表达导致BMP信号传导增加、破骨细胞生成增强、吸收活性增加以及破骨细胞特异性基因的表达。我们的结果表明，BMP结合是TWSG1介导的破骨细胞形成和功能抑制所必需的，并验证了TWSG1蛋白内这些相互作用的关键功能区域。
