DA-Raf-Mediated Suppression of the Ras--ERK Pathway Is Essential for TGF-β1-Induced Epithelial-Mesenchymal Transition in Alveolar Epithelial Type 2 Cells.
DA-Raf-Mediated Suppression of the Ras--ERK Pathway Is Essential for TGF-β1-Induced Epithelial-Mesenchymal Transition in Alveolar Epithelial Type 2 Cells.
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DOI：
10.1371/journal.pone.0127888
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Endo T
中科院分区：
文献类型：
--
作者：
Watanabe-Takano H;Takano K;Hatano M;Tokuhisa T;Endo T
肌成纤维细胞通过沉积细胞外基质成分在特发性肺纤维化的发展中起关键作用。肺肌成纤维细胞的一个来源被认为是经历上皮-间充质转化（EMT）的肺泡上皮2型细胞。转化生长因子-β1（TGF-β1）处理的大鼠RLE-6 TN肺泡上皮2型细胞通过EMT转化为肌成纤维细胞。TGF-β诱导经典Smad信号传导和非经典信号传导，包括Ras诱导的ERK途径（Raf-MEK-ERK）。然而，TGF-β1诱导EMT的信号转导机制尚不完全清楚。在此，我们发现Ras-ERK通路负调控TGF-β1诱导的RLE-6 TN细胞EMT，而A-Raf的剪接异构体DA-Raf 1（DA-Raf）和Ras-ERK通路的显性负拮抗剂在EMT中起着重要作用。用激活ERK通路的成纤维细胞生长因子2（FGF 2）刺激细胞，显著抑制TGF-β1诱导的EMT。MEK的抑制剂，但不是磷脂酰肌醇3-激酶的抑制剂，从FGF 2对EMT的抑制中拯救TGF-β1处理的细胞。Ras-ERK途径组分的组成型活性突变体的过表达，即，H-Ras、B-Raf或MEK 1干扰EMT。用siRNA敲低DA-Raf表达促进了MEK和ERK的活性，它们仅被TGF-β1微弱且短暂地激活。尽管DA-Raf敲低消除了TGF-β1诱导的EMT，但加入MEK抑制剂可逆转EMT的消除。此外，DA-Raf基因敲低可抑制TGF-β1诱导的Smad 2的核转位，而Smad 2介导EMT所需的转录。这些结果表明，内源性DA-Raf通过拮抗TGF-β1诱导的Ras-ERK通路在RLE-6 TN细胞中发挥重要作用。
Myofibroblasts play critical roles in the development of idiopathic pulmonary fibrosis by depositing components of extracellular matrix. One source of lung myofibroblasts is thought to be alveolar epithelial type 2 cells that undergo epithelial–mesenchymal transition (EMT). Rat RLE-6TN alveolar epithelial type 2 cells treated with transforming growth factor-β1 (TGF-β1) are converted into myofibroblasts through EMT. TGF-β induces both canonical Smad signaling and non-canonical signaling, including the Ras-induced ERK pathway (Raf–MEK–ERK). However, the signaling mechanisms regulating TGF-β1-induced EMT are not fully understood. Here, we show that the Ras–ERK pathway negatively regulates TGF-β1-induced EMT in RLE-6TN cells and that DA-Raf1 (DA-Raf), a splicing isoform of A-Raf and a dominant-negative antagonist of the Ras–ERK pathway, plays an essential role in EMT. Stimulation of the cells with fibroblast growth factor 2 (FGF2), which activated the ERK pathway, prominently suppressed TGF-β1-induced EMT. An inhibitor of MEK, but not an inhibitor of phosphatidylinositol 3-kinase, rescued the TGF-β1-treated cells from the suppression of EMT by FGF2. Overexpression of a constitutively active mutant of a component of the Ras–ERK pathway, i.e., H-Ras, B-Raf, or MEK1, interfered with EMT. Knockdown of DA-Raf expression with siRNAs facilitated the activity of MEK and ERK, which were only weakly and transiently activated by TGF-β1. Although DA-Raf knockdown abrogated TGF-β1-induced EMT, the abrogation of EMT was reversed by the addition of the MEK inhibitor. Furthermore, DA-Raf knockdown impaired the TGF-β1-induced nuclear translocation of Smad2, which mediates the transcription required for EMT. These results imply that intrinsic DA-Raf exerts essential functions for EMT by antagonizing the TGF-β1-induced Ras–ERK pathway in RLE-6TN cells.
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DOI：
10.3109/08977194.2011.595714
发表时间：
2011-10
期刊：
Growth factors (Chur, Switzerland)
影响因子：
--
作者：
Biernacka A;Dobaczewski M;Frangogiannis NG
通讯作者：
Frangogiannis NG
影响因子：
64.8
作者：
Matheny, SA;Chen, CY;White, MA
通讯作者：
White, MA
影响因子：
2.5
作者：
Fujimura, Lisa;Watanabe-Takano, Haruko;Hatano, Masahiko
通讯作者：
Hatano, Masahiko
影响因子：
--
作者：
Matallanas, David;Birtwistle, Marc;Kolch, Walter
通讯作者：
Kolch, Walter
TGFβ 信号的背景
DOI：
10.1038/nrm3434
发表时间：
2012-10
期刊：
Nature reviews. Molecular cell biology
影响因子：
--
作者：
通讯作者：
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