101. Hepatocyte growth factor suppresses profibrogenic signal transduction via nuclear export of Smad3 with galectin-7
- Author
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Johbu Itoh, Ichiro Kuwabara, Isao Okazaki, Kiyoshi Higashi, Tadashi Moro, Toshiyuki Mikami, Goshi Shiota, Miwa Kushida, Toru Kimura, Yun Yu Hong, Sachie Nakao, Yutaka Inagaki, and Reiichi Higashiyama
- Subjects
Small interfering RNA ,Transcription, Genetic ,Galectins ,Blotting, Western ,Fluorescent Antibody Technique ,Gene Expression ,Mice, Transgenic ,Biology ,Liver Cirrhosis, Experimental ,Antibodies ,Collagen Type I ,Mass Spectrometry ,Mice ,Western blot ,Plasminogen Activator Inhibitor 1 ,medicine ,Animals ,Immunoprecipitation ,Smad3 Protein ,Nuclear export signal ,Promoter Regions, Genetic ,Cells, Cultured ,Flavonoids ,Microscopy, Confocal ,Mitogen-Activated Protein Kinase 3 ,Hepatology ,medicine.diagnostic_test ,Hepatocyte Growth Factor ,Reverse Transcriptase Polymerase Chain Reaction ,Gastroenterology ,Transfection ,Molecular biology ,Enzyme Activation ,Calcium-Calmodulin-Dependent Protein Kinases ,Hepatic stellate cell ,Disease Progression ,RNA ,Hepatocyte growth factor ,Collagen ,Signal transduction ,medicine.drug ,Transforming growth factor ,Signal Transduction - Abstract
Background & Aims: Hepatocyte growth factor (HGF) and transforming growth factor-β (TGF-β) regulate diversified cellular functions and often act antagonistically against each other. For example, TGF-β 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-β-stimulated profibrogenic signal transduction. Methods: Effects of HGF on TGF-β-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 α2(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-β-responsive genes such as COL1A2 and plasminogen activator inhibitor-1. On the other hand, over expression of galectin-7 suppressed TGF-β-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.
- Published
- 2007