Connexin43 Potentiates Osteoblast Responsiveness to Fibroblast Growth Factor 2 via a Protein Kinase C-Delta/Runx2-dependent Mechanism
Connexin43 Potentiates Osteoblast Responsiveness to Fibroblast Growth Factor 2 via a Protein Kinase C-Delta/Runx2-dependent Mechanism
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DOI：
10.1091/mbc.e08-10-1079
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发表时间：
2009-06-01
影响因子：
3.3
通讯作者：
Stains, Joseph P.
中科院分区：
文献类型：
--
作者：
Lima, Florence;Niger, Corinne;Stains, Joseph P.
在这项研究中，我们研究的作用，差距连接蛋白，连接蛋白43（Cx43），骨钙素成纤维细胞生长因子2（FGF 2）在MC 3 T3成骨细胞的转录反应。通过荧光素酶报告基因检测，我们发现骨钙素对FGF 2的转录反应通过Cx43的过表达而显著增加，这种作用是由Runx 2通过其OSE 2同源元件介导的，而不是由先前确定的连接蛋白反应性Sp1/Sp3结合元件介导的。此外，用Cx43 siRNA或连接蛋白45的过表达破坏Cx43功能显著减弱对FGF 2的应答。用rottlerin或siRNA介导的敲低抑制蛋白激酶C δ（PKC δ）消除了骨钙素对FGF 2的反应。此外，我们发现，在用FGF 2治疗后，PKC δ易位到细胞核，PKC δ和Runx 2被磷酸化，并且这些事件通过Cx43过表达而增强，这表明激活程度通过增加Cx43水平而增强。实际上，骨钙蛋白近端启动子与针对Runx 2的抗体的染色质免疫沉淀证明响应于FGF 2处理的Runx 2向骨钙蛋白启动子的募集通过Cx43过表达显著增强。因此，Cx43通过影响PKC delta和Runx 2功能，在调节成骨细胞对FGF 2反应的能力方面发挥着关键作用。
In this study, we examine the role of the gap junction protein, connexin43 (Cx43), in the transcriptional response of osteocalcin to fibroblast growth factor 2 (FGF2) in MC3T3 osteoblasts. By luciferase reporter assays, we identify that the osteocalcin transcriptional response to FGF2 is markedly increased by overexpression of Cx43, an effect that is mediated by Runx2 via its OSE2 cognate element, but not by a previously identified connexin-responsive Sp1/Sp3-binding element. Furthermore, disruption of Cx43 function with Cx43 siRNAs or overexpression of connexin45 markedly attenuates the response to FGF2. Inhibition of protein kinase C delta (PKC delta) with rottlerin or siRNA-mediated knockdown abrogates the osteocalcin response to FGF2. Additionally, we show that upon treatment with FGF2, PKC delta translocates to the nucleus, PKC delta and Runx2 are phosphorylated and these events are enhanced by Cx43 overexpression, suggesting that the degree of activation is enhanced by increased Cx43 levels. Indeed, chromatin immunoprecipitations of the osteocalcin proximal promoter with antibodies against Runx2 demonstrate that the recruitment of Runx2 to the osteocalcin promoter in response to FGF2 treatment is dramatically enhanced by Cx43 overexpression. Thus, Cx43 plays a critical role in regulating the ability of osteoblasts to respond to FGF2 by impacting PKC delta and Runx2 function.