ERK acts in parallel to PKCδ to mediate the connexin43-dependent potentiation of Runx2 activity by FGF2 in MC3T3 osteoblasts
ERK acts in parallel to PKCδ to mediate the connexin43-dependent potentiation of Runx2 activity by FGF2 in MC3T3 osteoblasts
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DOI：
10.1152/ajpcell.00262.2011
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发表时间：
2012-04-01
影响因子：
5.5
通讯作者：
Stains, Joseph P.
中科院分区：
文献类型：
--
作者：
Niger, Corinne;Buo, Atum M.;Stains, Joseph P.
尼日尔C，Buo AM，Hebert C，Duggan BT，威廉姆斯MS，染色JP. ERK与PKC δ平行作用，介导MC 3 T3成骨细胞中FGF 2对Runx 2活性的连接蛋白43依赖性增强。美国生理学杂志细胞生理学302：C1035-C1044，2012年。首次发表于2012年1月25日; doi：10.1152/ajpcell.00262.2011。差距连接蛋白43（connexin 43，Cx43）在骨骼生物学中起着重要作用。以前，我们已经表明，Cx43可以通过增加蛋白激酶C-δ（PKC δ）的激活来影响Runx 2的活性，从而增强成骨细胞对成纤维细胞生长因子2（FGF 2）的信号传导和转录反应。在本研究中，我们通过荧光素酶报告基因分析表明，ERK信号级联与PKC δ平行作用，调节FGF 2信号转导的Cx43依赖性扩增下游的Runx 2活性。通过蛋白质印迹证实了FGF 2对ERK的PKC δ非依赖性激活，以及ERK激活的Cx43依赖性增强。与我们先前对PKC δ的观察一致，流式细胞术分析显示Cx43过表达增强了响应于FGF 2的磷酸化ERK阳性细胞的百分比，支持间隙连接偶联细胞之间共享信号导致对FGF 2的响应增强的观点。在低密度和高密度条件下培养的成骨细胞上进行的蛋白质印迹和荧光素酶报告基因测定显示，Cx43需要细胞-细胞接触来放大ERK激活和基因转录。类似地，用通道阻断剂18 β-大黄酸抑制间隙连接通讯减弱了Runx 2转录活性的Cx43依赖性增强。总之，这些数据强调了细胞间通讯和ERK和PKC δ通路的激活在成骨细胞群体中成骨细胞对FGF 2反应的协调中的重要性。
Niger C, Buo AM, Hebert C, Duggan BT, Williams MS, Stains JP. ERK acts in parallel to PKC delta to mediate the connexin43-dependent potentiation of Runx2 activity by FGF2 in MC3T3 osteoblasts. Am J Physiol Cell Physiol 302: C1035-C1044, 2012. First published January 25, 2012; doi:10.1152/ajpcell.00262.2011.-The gap junction protein, connexin43 (Cx43), plays an important role in skeletal biology. Previously, we have shown that Cx43 can enhance the signaling and transcriptional response to fibroblast growth factor 2 (FGF2) in osteoblasts by increasing protein kinase C-delta (PKC delta) activation to affect Runx2 activity. In the present study, we show by luciferase reporter assays that the ERK signaling cascade acts in parallel to PKC delta to modulate Runx2 activity downstream of the Cx43-dependent amplification of FGF2 signaling. The PKC delta-independent activation of ERK by FGF2 was confirmed by Western blotting, as was the Cx43-dependent enhancement of ERK activation. Consistent with our prior observations for PKC delta, flow cytometry analyses show that Cx43 overexpression enhances the percentage of phospho-ERK-positive cells in response to FGF2, supporting the notion that shared signals among gap junction-coupled cells result in the enhanced response to FGF2. Western blots and luciferase reporter assays performed on osteoblasts cultured under low-density and high-density conditions revealed that cell-cell contacts are required for Cx43 to amplify ERK activation and gene transcription. Similarly, inhibition of gap junctional communication with the channel blocker 18 beta-glycyrrhetinic acid attenuates the Cx43-dependent enhancement of Runx2-transcriptional activity. In total, these data underscore the importance of cell-cell communication and activation of the ERK and PKC delta pathways in the coordination of the osteoblast response to FGF2 among populations of osteoblasts.