Cross-talk between Wnt and bone morphogenetic protein 2 (BMP-2) signaling in differentiation pathway of C2C12 myoblasts
Cross-talk between Wnt and bone morphogenetic protein 2 (BMP-2) signaling in differentiation pathway of C2C12 myoblasts
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DOI：
10.1074/jbc.m504612200
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发表时间：
2005-11-11
影响因子：
4.8
通讯作者：
Tamura, M
中科院分区：
文献类型：
--
作者：
Nakashima, A;Katagiri, T;Tamura, M
Wnt辅助受体（脂蛋白受体相关蛋白5）功能的丧失会降低骨形成，该基因的点突变会导致高骨量，表明该信号通路在骨形成中的重要性。然而，确切的机制目前尚不清楚。我们研究了Wnt信号和骨形态发生蛋白2（BMP-2）在成骨细胞分化中的潜在作用。为了评估Wnt的贡献，我们产生了过表达Wnt 3a或Wnt 5a的C2 C12细胞，并用BMP-2处理这些细胞。我们发现，在Wnt 3a过表达的C2 C12细胞中，BMP-2诱导基质细胞外磷酸糖蛋白的表达，但在Wnt 5a过表达的C2 C12细胞中不诱导。在C2 C12细胞中，当切换到低促分裂原培养基时，Wnt 3a的过表达阻断了BMP-2诱导的肌管形成抑制。在这些培养物中，DNA结合/分化抑制剂（Id）1（BMP-2诱导的螺旋-环-螺旋蛋白）的表达在稳定的Wnt 3a-表达细胞中降低，但在Wnt 5a-表达细胞中不降低。这种抑制是由Id 1基因启动子的BMP-2响应元件的富含GC的区域介导的，并且Smad 1/4和β-连环蛋白之间的相互作用对于Wnt介导的C2 C12细胞中BMP-2响应的抑制至关重要。经典Wnt信号传导抑制剂Dickkopf的过表达抑制了这种抑制。相反，BMP-2或Smad 1/4上调Wnt 3a或激活β-连环蛋白诱导的淋巴增强因子1/T细胞因子依赖性转录活性。这些发现确定了Wnt和BMP信号之间Id 1表达的功能性串扰，并证明了Wnt调节BMP-2反应的新机制，将Id 1表达与Wnt/β-连环蛋白信号联系起来。
Loss of function of the Wnt co-receptor, lipoprotein receptor-related protein 5, decreases bone formation, and a point mutation in this gene results in high bone mass, indicating the importance of this signaling pathway in bone formation. However, the exact mechanism is currently unknown. We examined a potential role for Wnt signaling and functional cross-talk of bone morphogenetic protein 2 (BMP-2) in osteoblast differentiation. To assess the contribution of Wnt, we generated C2C12 cells over-expressing Wnt3a or Wnt5a and treated these with BMP-2. We showed that expression of matrix extracellular phosphoglycoprotein was induced by BMP-2 in Wnt3a over-expressing C2C12 cells but not in Wnt5a over-expressing C2C12 cells. Over-expression of Wnt3a blocked BMP-2-induced inhibition of myotube formation in C2C12 cells when switched to low mitogen medium. In these cultures, expression of inhibitor of DNA binding/differentiation ( Id) 1, a helix-loop-helix protein induced by BMP-2, decreased in stable Wnt3a- but not in Wnt5a-expressing cells. This suppression is mediated by a GC-rich region of the BMP-2-responsive element of the Id1 gene promoter, and interaction between Smad1/4 and beta-catenin is crucial for Wnt-mediated suppression of the BMP-2 response in C2C12 cells. Overexpression of the inhibitor of canonical Wnt signaling, Dickkopf, inhibits this suppression. In contrast, BMP-2 or Smad1/4 up-regulated Wnt3a or activated beta-catenin-induced lymphoid-enhancing factor 1/T cell factor-dependent transcriptional activity. These findings identify functional cross-talk of Id1 expression between Wnt and BMP signaling and demonstrate a novel mechanism for Wnt regulation of the BMP-2 response, linking Id1 expression to Wnt/beta-catenin signaling.