Hepatocyte growth factor suppresses profibrogenic signal transduction via nuclear export of Smad3 with galectin-7
Hepatocyte growth factor suppresses profibrogenic signal transduction via nuclear export of Smad3 with galectin-7
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DOI：
10.1053/j.gastro.2008.01.014
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发表时间：
2008-04-01
期刊：
影响因子：
29.4
通讯作者：
Okazaki, Isao
中科院分区：
文献类型：
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作者：
Inagaki, Yutaka;Higashi, Kiyoshi;Okazaki, Isao
背景和目标：肝细胞生长因子（HGF）和转化生长因子-β（TGF-β）调节多种细胞功能，并且通常相互拮抗。例如，TGF-β是加速肝纤维化的最有效因素，而HGF治疗可阻止其进展。在这里，我们提出了一种新的分子机制，HGF反抑制TGF-β刺激的促纤维化信号转导。研究方法：采用体外培养的肝星状细胞（HSC）和携带α 2（I）胶原基因（COL 1A 2）启动子的转基因小鼠，研究了HGF对I型胶原（纤维化肝的主要基质成分）TGF-β反应基因转录的影响。免疫印迹法和免疫荧光染色法分别检测Smad 3的表达和亚细胞定位。质谱分析，以确定免疫沉淀蛋白与antiphospho-Smad 2/3抗体。结果如下：HGF过表达可抑制HSC中COL 1A 2的转录，并抑制四氯化碳诱导的肝组织中COL 1A 2启动子的激活。质谱分析鉴定半乳糖凝集素-7作为HGF处理后抗磷酸化Smad 2/3抗体的免疫沉淀蛋白之一。HGF通过增强Smad 3与galectin-7的相互作用加速Smad 3的核输出。用galectin-7小干扰RNA转染细胞抑制Smad 3的核输出，并消除HGF对TGF-β反应基因如COL 1A 2和纤溶酶原激活物抑制剂-1表达的抑制作用。另一方面，半乳糖凝集素-7的过度表达抑制了TGF-β刺激的这些靶基因的表达。结论：这些结果揭示了细胞内galectin-7通过与Smad 3相互作用作为转录调节因子的新功能，并为HGF的抗纤维化作用提供了分子基础。
Background & Aims: Hepatocyte growth factor (HGF) and transforming growth factor-beta (TGF-beta) regulate diversified cellular functions and often act antagonistically against each other. For example, TGF-beta is the most potent factor accelerating liver fibrosis, whereas HGF treatment prevents its progression. Here, we propose a novel molecular mechanism by which HGF counter represses TGF-beta-stimulated profibrogenic signal transduction. Methods: Effects of HGF on TGF-beta-responsive gene transcription of type I collagen, the major matrix component of fibrotic liver, were examined by using cultured hepatic stellate cells (HSC) and transgenic mice harboring alpha 2(I) collagen gene (COL1A2) promoter. Expression and subcellular localization of Smad3 were determined by Western blot analyses and immunofluorescence staining, respectively. A mass spectrometric analysis was employed to identify immunoprecipitated proteins with antiphospho-Smad2/3 antibodies. Results: Over expression of HGF inhibited COL1A2 transcription in cultured HSC and suppressed activation of COL1A2 promoter in liver tissue induced by carbon tetrachloride administration. A mass spectrometric analysis identified galectin-7 as one of the immunoprecipitated proteins with antiphospho-Smad2/3 antibodies following HGF treatment. HGF accelerated nuclear export of Smad3 by enhancing its interaction with galectin-7. Transfection of cells with galectin-7 small interfering RNA inhibited nuclear export of Smad3 and abolished suppressive effect of HGF on expression of TGF-beta-responsive genes such as COL1A2 and plasminogen activator inhibitor-1. on the other hand, over expression of galectin-7 suppressed TGF-beta-stimulated expression of those target genes. Conclusions: These results reveal a novel function of intracellular galectin-7 as a transcriptional regulator via its interaction with Smad3 and provide a molecular basis for the antifibrotic effect of HGF.