Inhibition of Microtubule Assembly in Osteoblasts Stimulates Bone Morphogenetic Protein 2 Expression and Bone Formation through Transcription Factor Gli2
Inhibition of Microtubule Assembly in Osteoblasts Stimulates Bone Morphogenetic Protein 2 Expression and Bone Formation through Transcription Factor Gli2
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DOI：
10.1128/mcb.01566-08
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发表时间：
2009-03-01
影响因子：
5.3
通讯作者：
Mundy, Gregory R.
中科院分区：
文献类型：
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作者：
Zhao, Ming;Ko, Seon-Yle;Mundy, Gregory R.
骨形态发生蛋白2 （BMP-2）对出生后骨形成和骨折修复至关重要。通过使用基于细胞的试验筛选BMP-2模拟物的化学文库，我们确定了微管组装抑制剂是BMP-2转录的刺激物。这些微管抑制剂在体外增加成骨细胞分化，在小鼠颅骨局部注射时刺激骨膜骨形成，在体内全身注射时增强小梁骨形成。为了探索介导这些反应的分子机制，我们研究了微管抑制剂对hedgehog （Hh）通路的影响，因为已知该通路调节成骨细胞中BMP-2的转录，并且微管已被证明参与果蝇的Hh信号传导。在这里，我们发现在成骨细胞中，抑制微管组装增加了细胞质水平和Gli2的转录活性，Gli2是Hh信号的转录介质，我们之前已经证明它可以增强成骨细胞中BMP-2的表达（M. Zhao等人，Mol. Cell.）。生物学报，26:6197- 6208,2006)。微管抑制可阻断β - trcp介导的成骨细胞中Gli2的蛋白酶体加工。总之，抑制微管组装可以增强BMP-2基因转录和随后的骨形成，部分原因是通过抑制Gli2的蛋白酶体加工和增加细胞内Gli2浓度。
Bone morphogenetic protein 2 (BMP-2) is essential for postnatal bone formation and fracture repair. By screening chemical libraries for BMP-2 mimics using a cell-based assay, we identified inhibitors of microtubule assembly as stimulators of BMP-2 transcription. These microtubule inhibitors increased osteoblast differentiation in vitro, stimulated periosteal bone formation when injected locally over murine calvaria, and enhanced trabecular bone formation when administered systemically in vivo. To explore molecular mechanisms mediating these responses, we examined effects of microtubule inhibitors on the hedgehog (Hh) pathway, since this pathway is known to regulate BMP-2 transcription in osteoblasts and microtubules have been shown to be involved in Hh signaling in Drosophila. Here we show that in osteoblasts, inhibition of microtubule assembly increased cytoplasmic levels and transcriptional activity of Gli2, a transcriptional mediator of Hh signaling that we have previously shown to enhance BMP-2 expression in osteoblasts (M. Zhao et al., Mol. Cell. Biol. 26: 6197- 6208, 2006). Microtubule inhibition blocked beta-TrCP-mediated proteasomal processing of Gli2 in osteoblasts. In summary, inhibition of microtubule assembly enhances BMP-2 gene transcription and subsequent bone formation, in part, through inhibiting proteasomal processing of Gli2 and increasing intracellular Gli2 concentrations.