CCN2 is required for the TGF-β induced activation of Smad1-Erk1/2 signaling network.
CCN2 is required for the TGF-β induced activation of Smad1-Erk1/2 signaling network.
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DOI：
10.1371/journal.pone.0021911
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发表时间：
2011
期刊：
影响因子：
3.7
通讯作者：
Trojanowska M
中科院分区：
文献类型：
--
作者：
Nakerakanti SS;Bujor AM;Trojanowska M
结缔组织生长因子（CCN 2）是一种多功能的基质细胞蛋白，在器官纤维化过程中经常过度表达。CCN 2是TGF-β在培养细胞中的促纤维化作用的介体，但CCN 2在纤维化过程中的具体功能尚未阐明。在这项研究中，我们表征了TGF-β诱导的纤维化反应所需的CCN 2依赖性信号通路。通过消耗内源性CCN 2，我们发现CCN 2对于TGF-β诱导的Smad 1和Erk 1/2的磷酸化是必不可少的，但对于Smad 3的激活是不必要的。TGF-β刺激触发CCN 2/β3整合素蛋白复合物的形成和Src信号传导的激活。此外，我们证明了通过αvβ3整合素受体和Src的信号传导是TGF-β诱导Smad 1磷酸化所必需的。重组CCN 2激活Src和Erk 1/2信号，并诱导Fli 1磷酸化，但不能刺激Smad 1或Smad 3磷酸化。进行另外的实验以研究CCN 2在胶原蛋白产生中的作用。与先前的研究一致，阻断CCN 2消除了TGF-β诱导的胶原mRNA和蛋白水平。重组CCN 2有效地刺激胶原mRNA水平和上调COL 1A 2启动子的活性，然而CCN 2是胶原蛋白水平的弱诱导剂。CCN 2对胶原蛋白的刺激是剂量依赖性的，较低剂量（<50 ng/ml）对胶原蛋白基因表达具有刺激作用，较高剂量对胶原蛋白基因表达具有抑制作用。总之，我们的研究定义了一种新的CCN 2/αvβ3整合素/Src/Smad 1轴，该轴有助于促纤维化TGF-β信号传导，并表明阻断该途径可能有利于治疗纤维化。
Connective tissue growth factor (CCN2) is a multifunctional matricellular protein, which is frequently overexpressed during organ fibrosis. CCN2 is a mediator of the pro-fibrotic effects of TGF-β in cultured cells, but the specific function of CCN2 in the fibrotic process has not been elucidated. In this study we characterized the CCN2-dependent signaling pathways that are required for the TGF-β induced fibrogenic response. By depleting endogenous CCN2 we show that CCN2 is indispensable for the TGF-β-induced phosphorylation of Smad1 and Erk1/2, but it is unnecessary for the activation of Smad3. TGF-β stimulation triggered formation of the CCN2/β3 integrin protein complexes and activation of Src signaling. Furthermore, we demonstrated that signaling through the αvβ3 integrin receptor and Src was required for the TGF-β induced Smad1 phosphorylation. Recombinant CCN2 activated Src and Erk1/2 signaling, and induced phosphorylation of Fli1, but was unable to stimulate Smad1 or Smad3 phosphorylation. Additional experiments were performed to investigate the role of CCN2 in collagen production. Consistent with the previous studies, blockade of CCN2 abrogated TGF-β-induced collagen mRNA and protein levels. Recombinant CCN2 potently stimulated collagen mRNA levels and upregulated activity of the COL1A2 promoter, however CCN2 was a weak inducer of collagen protein levels. CCN2 stimulation of collagen was dose-dependent with the lower doses (<50 ng/ml) having a stimulatory effect and higher doses having an inhibitory effect on collagen gene expression. In conclusion, our study defines a novel CCN2/αvβ3 integrin/Src/Smad1 axis that contributes to the pro-fibrotic TGF-β signaling and suggests that blockade of this pathway may be beneficial for the treatment of fibrosis.