MAPK inhibitors modulate Smad2/3/4 complex cyto-nuclear translocation in myofibroblasts via Imp7/8 mediation
MAPK inhibitors modulate Smad2/3/4 complex cyto-nuclear translocation in myofibroblasts via Imp7/8 mediation
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MAPK 抑制剂通过 Imp7/8 介导调节肌成纤维细胞中的 Smad2/3/4 复杂细胞核转位
DOI：
10.1007/s11010-015-2443-x
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发表时间：
2015-08-01
影响因子：
4.3
通讯作者：
Yang, Yan
中科院分区：
文献类型：
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作者：
Jiang, Yufeng;Wu, Chao;Yang, Yan
丝裂原活化蛋白激酶（MAPK）途径依赖的Smad 2/3连接子磷酸化和随后的Smad 2/3/4复合物的形成及其核转位在肝纤维化中转化生长因子β（TGF）-β/Smad信号转导失调中至关重要。消除TGF-β/Smad信号传导导致肝纤维化的这一关键步骤可以为未来的治疗提供新的见解，但其机制仍不完全清楚。接下来，我们使用三种MAPK特异性抑制剂研究了外源性TGF-β1刺激的肌成纤维细胞（MFB）中限速Smad 2/3/4复合物的亚细胞表达和核运输。结果表明，外源性TGF-β 1刺激MFB后，Smad 7蛋白表达降低，Smad 2C/L、Smad 3L、Smad 4、Importin 7/8（Imp 7/8）和PAI-1蛋白表达增加，Smad 2C/L、Smad 3L、Smad 4和派-1蛋白表达增加，Smad 4蛋白表达增加，Smad 7蛋白表达减少。然而，MAPK特异性抑制剂不同地逆转了这些观察结果;例如，ERK特异性抑制剂阻断了pSmad 2C/L的表达和核转位，而JNK和p38特异性抑制剂均阻断了pSmad 2C/L和致癌pSmad 3L的表达和核转位。MAPK特异性抑制剂对Smad 4的总蛋白表达没有显著影响，但显著阻断了其核转位。所有MAPK特异性抑制剂恢复Smad 7表达，并降低Imp 7/8和派-1（蛋白质和mRNA）表达。MAPK特异性抑制剂通过抑制Smad 7的表达和阻断Smad 3L的磷酸化来阻断Smad 2/3/4复合物的形成，同时通过抑制Imp 7/8来阻断Smad 2/3/4复合物的核转位，从而降低派-1（蛋白和mRNA）的表达。
Mitogen-activated protein kinase (MAPK) pathway-dependent linker phosphorylation of Smad2/3 and subsequent formation of Smad2/3/4 complex and its nuclear translocation are crucial for dysregulated transforming growth factor beta (TGF)-β/Smad signaling in liver fibrosis. Abrogation of this critical step of TGF-β/Smad signaling leading to liver fibrosis could provide new insights for future therapy, but the mechanisms remain incompletely understood. In pursuit, we investigated the subcellular expression and nuclear trafficking of the rate limiting Smad2/3/4 complex in exogenous TGF-β1-stimulated myofibroblasts (MFBs) using three MAPK-specific inhibitors. Our results showed that exogenous TGF-β1stimulation of MFBs produced both increased protein expression and nuclear translocation of phosphorylated (p)-Smad2C/L, oncogenic pSmad3L, Smad4, importin7/8 (Imp7/8), and plasminogen activator inhibitor (PAI)-1 (Protein and mRNA), while decreased Smad7 protein expression. However, the MAPK-specific inhibitors differentially reversed these observations; for instance, ERK-specific inhibitor blocked the expression and nuclear translocation of pSmad2C/L, while both JNK and p38-specific inhibitors blocked the expression and nuclear translocation of pSmad2C/L and oncogenic pSmad3L. The MAPK-specific inhibitors had no significant effect on the total protein expression of Smad4, but rather significantly blocked its nuclear translocation. All the MAPK-specific inhibitors restored Smad7 expression and also decreased Imp7/8 and PAI-1 (Protein and mRNA) expression. Evidently, the MAPK-specific inhibitors blocked Smad2/3/4 complex formation via restoration of inhibitory Smad7 expression and blockade of Smad3L phosphorylation, while they blocked nuclear translocation of Smad2/3/4 complex through inhibition of Imp7/8 leading to decreased PAI-1 (Protein and mRNA) expression.