Smad5 and DPC4 are key molecules in mediating BMP-2-induced osteoblastic differentiation of the pluripotent mesenchymal precursor cell fine C2C12
Smad5 and DPC4 are key molecules in mediating BMP-2-induced osteoblastic differentiation of the pluripotent mesenchymal precursor cell fine C2C12
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DOI：
10.1074/jbc.273.4.1872
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发表时间：
1998-01-23
影响因子：
4.8
通讯作者：
Yoneda, T
中科院分区：
文献类型：
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作者：
Nishimura, R;Kato, Y;Yoneda, T
由于骨形态发生蛋白（BRSPs）是转化生长因子-β（TGF-β）超家族的成员，诱导间充质前体细胞分化为成骨细胞，我们确定了相关的信号分子负责介导BMP-2对间充质前体细胞的影响。BMP-2通过增加碱性磷酸酶活性和骨钙素产生诱导多能间充质细胞系C2 C12的成骨分化。由于最近的研究表明，细胞质Smad蛋白参与TGF-β超家族信号转导，我们计划分离相关的Smad家族成员参与成骨细胞分化。我鉴定了人Smad 5，其与Smad 1高度同源。BMP-2引起Smad 5和Smad 1的丝氨酸磷酸化。相反，TGF-β不能引起Smad 1和Smad 5的丝氨酸磷酸化。我们发现Smad 5通过与BMP Ia或Ib型受体的物理结合而被这些受体直接激活。磷酸化后，Smad 5与另一个Smad家族成员DPC 4结合，复合物被转移到细胞核。点突变的Smad 5：（G419 S）或C末端缺失突变体DPC 4（DPC 4 Delta C）的过表达阻断了C2 C12细胞中BMP-2处理后碱性磷酸酶活性骨钙蛋白产生的诱导以及Smad 5-DPC 4信号级联反应。这些数据表明，Smad 5的激活和随后的Smad 5-DPC 4复合物的形成是BMP信号通路中的关键步骤，其介导BMP-2诱导的C2 C12间充质细胞的成骨分化。
Since the bone morphogenetic proteins (BRSPs) are members of the transforming growth factor-beta (TGF-beta) superfamily that induce the differentiation of-mesenchymal precursor cells into the osteogenic cells, we identified the relevant signaling molecules responsible for mediating BMP-2 effects on mesenchymal precursor cells. BMP-2 induces osteoblastic differentiation of the pluripotent mesenchymal cell line C2C12 by increasing alkaline phosphatase activity and osteocalcin production. As recent studies have demonstrated that cytoplasmic Smad proteins are involved in TGF-beta superfamily signaling, we plan to isolate the relevant Smad family members involved in osteoblastic differentiation. me identified human Smad5, which is highly homologous to Smad1. BMP-2 caused serine phosphorylation of Smad5 as well as Smad1. In contrast, TGF-beta failed to cause serine phosphorylation of Smad1 and Smad5. We found Smad5 is directly activated by BMP type Ia or Ib receptors through physical association with these receptors. Following phosphorylation, Smad5 bound to DPC4, another Smad family member, and the complex was translocated to the nucleus. Overexpression of point-mutated Smad5: (G419S) or a C-terminal deletion mutant DPC4 (DPC4 Delta C) blocked the induction of alkaline phosphatase activity osteocalcin production, and Smad5-DPC4 signaling cascades upon BMP-2 treatment in C2C12 cells. These data suggest that activation of Smad5 and subsequent Smad5-DPC4 complex formation are key steps in the BMP signaling pathway, which mediates BMP-2-induced osteoblastic differentiation of the C2C12 mesenchymal cells.