Structural coupling of smad and Runx2 for execution of the BMP2 osteogenic signal
Structural coupling of smad and Runx2 for execution of the BMP2 osteogenic signal
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DOI：
10.1074/jbc.m705578200
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发表时间：
2008-03-28
影响因子：
4.8
通讯作者：
Lian, Jane B.
中科院分区：
文献类型：
--
作者：
Javed, Amjad;Bae, Jong-Sup;Lian, Jane B.
体内骨形成需要两种调节途径，骨形态发生蛋白（BMP）/转化生长因子-β（TGF β）和转录因子RUNX 2。在这里，我们展示了这些途径诱导成骨程序的相互依赖的要求。使用一组Runx 2缺失和点突变体来检查RUNX 2-SMAD蛋白-蛋白相互作用和在Runx 2缺失细胞中测定的BMP 2诱导的成骨信号传导的生物学后果。这些细胞在不存在Runx 2的情况下不响应BMP 2信号。我们确定RUNX 2 C-末端结构域中的三重突变HTY（426 - 428）破坏了RUNX 2-SMAD相互作用，在启动子报告基因测定中缺乏整合BMP 2/TGF β信号的能力，并且在促进成骨细胞分化的早期阶段中仅具有边缘功能。此外，HTY突变与Runx因子的独特核基质靶向信号重叠，并表现出减少的亚核靶向。因此，RUNX 2-SMAD成骨复合物的形成和亚核靶向在结构和功能上是不可分割的。我们的研究结果建立了RUNX 2的关键残基，通过需要RUNX 2-SMAD转录活性的机制，执行和完成BMP 2信号传导成骨细胞。
Two regulatory pathways, bone morphogenetic protein (BMP)/transforming growth factor-beta(TGF beta) and the transcription factor RUNX2, are required for bone formation in vivo. Here we show the interdependent requirement of these pathways to induce an osteogenic program. A panel of Runx2 deletion and point mutants was used to examine RUNX2-SMAD protein-protein interaction and the biological consequences on BMP2-induced osteogenic signaling determined in Runx2 null cells. These cells do not respond to BMP2 signal in the absence of Runx2. We established that a triple mutation in the C-terminal domain of RUNX2, HTY (426 - 428), disrupts the RUNX2-SMAD interaction, is deficient in its ability to integrate the BMP2/TGF beta signal on promoter reporter assays, and is only marginally functional in promoting early stages of osteoblast differentiation. Furthermore, the HTY mutation overlaps the unique nuclear matrix targeting signal of Runx factors and exhibits reduced subnuclear targeting. Thus, formation of a RUNX2-SMAD osteogenic complex and subnuclear targeting are structurally and functionally inseparable. Our results establish the critical residues of RUNX2 for execution and completion of BMP2 signaling for osteoblastogenesis through a mechanism that requires RUNX2-SMAD transcriptional activity.