Phosphate-Dependent Regulation of MGP in Osteoblasts: Role of ERK1/2 and Fra-1
Phosphate-Dependent Regulation of MGP in Osteoblasts: Role of ERK1/2 and Fra-1
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DOI：
10.1359/jbmr.090508
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发表时间：
2009-11-01
影响因子：
6.2
通讯作者：
Guicheux, Jerome
中科院分区：
文献类型：
--
作者：
Julien, Marion;Khoshniat, Solmaz;Guicheux, Jerome
无机磷酸盐（Pi）和基质玻璃蛋白（MGP）是骨形成的关键调节因子。我们最近表明，Pi上调生长板软骨细胞中的MGP，这可能代表了矿化控制的负反馈回路。来自Fra-1缺失小鼠的成骨细胞表达低水平的MGP，而在Fra-1转基因成骨细胞中，MGP的表达升高，这表明Fra-1在MGP表达和骨形成中起作用。在这项研究中，我们旨在破译成骨细胞中Pi和MGP之间的关系，以确定Pi依赖性调节MGP的分子机制。在MC3T3-E1细胞和原代骨源性成骨细胞中，Pi在mRNA和蛋白水平上增加了MGP和fr -1的表达。我们还发现Pi增强了ERK1/2的磷酸化。U0126 （MEK1/2抑制剂）抑制pi刺激的MGP和fr -1表达，表明ERK1/2是pi依赖性调控MGP和fr -1所必需的。此外，通过体外DNA结合和染色质免疫沉淀实验，我们发现Fra-1在MC3T3-E1细胞中与MGP启动子相互作用以响应Pi。最后，我们发现在fra-1敲除MC3T3-E1的成骨细胞中，Pi不再显著上调MGP的表达水平。我们进一步发现，来自fra -1缺陷小鼠的原代成骨细胞未能表现出pi依赖性的MGP表达刺激。这些数据首次表明，Pi通过ERK1/2-Fra-1通路调节成骨细胞中MGP的表达。[J]中华骨科学杂志，2009;24(2):556 - 568。2009年5月4日在线发布；doi: 10.1359 / JBMR.090508
Inorganic phosphate (Pi) and the matrix Gla protein (MGP) are key regulators of bone formation. We have recently shown that Pi upregulates MGP in growth plate chondrocytes, which may represent a negative feedback loop for the control of mineralization. Osteoblasts from Fra-1-deleted mice express low levels of MGP, whereas the expression of MGP is elevated in Fra-1 transgenic osteoblasts, suggesting a role for Fra-1 in MGP expression and bone formation. In this study, we aimed at deciphering the relationships between Pi and MGP in osteoblasts to determine the molecular mechanisms involved in the Pi-dependent regulation of MGP. In MC3T3-E1 cells and primary calvaria-derived osteoblasts, Pi increased MGP and Fra-1 expression at both the mRNA and protein levels. We also found that Pi enhanced the phosphorylation of ERK1/2. U0126 (MEK1/2 inhibitor) suppressed Pi-stimulated MGP and Fra-1 expression, indicating that ERK1/2 is required for Pi-dependent regulation of MGP and Fra-1. In addition, using in vitro DNA binding and chromatin immunoprecipitation assays, we showed that Fra-1 interacts with the MGP promoter in response to Pi in MC3T3-E1 cells. Finally, we found that in fra-1 knockdown MC3T3-E1 osteoblasts, the level of MGP expression is no more significantly upregulated by Pi. We further showed that primary osteoblasts from Fra-1-deficient mice failed to exhibit a Pi-dependent stimulation of MGP expression. These data show, for the first time, that Pi regulates MGP expression in osteoblasts through the ERK1/2-Fra-1 pathway. J Bone Miner Res 2009;24:1856-1868. Published online on May 4, 2009; doi: 10.1359/JBMR.090508