Abstract
Transforming growth factor-β (TGF-β) is considered to be a major factor contributing to liver fibrosis. We have previously shown that nuclear translocation of YB-1 antagonizes the TGF-β/Smad3 signaling in regulating collagen gene expression. More recently, we have demonstrated that the novel small compound HSc025 promotes nuclear translocation of YB-1, resulting in the improvement of skin and pulmonary fibrosis. Here, we presented evidence as to the mechanism by which HSc025 stimulates nuclear translocation of YB-1 and the pharmacological effects of HSc025 on a murine model of hepatic fibrosis. A proteomics approach and binding assays using HSc025-immobilized resin showed that HSc025 binds to the amino acid sequence within the C-tail region of YB-1. In addition, immunoprecipitation experiments and glutathione S-transferase pulldown assays identified poly(A)-binding protein (PABP) as one of the cytoplasmic anchor proteins of YB-1. HSc025 directly binds to YB-1 and interrupts its interaction with PABP, resulting in accelerated nuclear translocation of YB-1. Transfection of cells with PABP siRNA promoted nuclear translocation of YB-1 and subsequently inhibited basal and TGF-β-stimulated collagen gene expression. Moreover, HSc025 significantly suppressed collagen gene expression in cultured activated hepatic stellate cells. Oral administration of HSc025 to mice with carbon tetrachloride-induced hepatic fibrosis improved liver injury as well as the degree of hepatic fibrosis. Altogether, the results provide a novel insight into therapy for organ fibrosis using YB-1 modulators.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Active Transport, Cell Nucleus / drug effects
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Active Transport, Cell Nucleus / genetics
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Alkadienes / pharmacology*
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Animals
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Carbon Tetrachloride / toxicity
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Carbon Tetrachloride Poisoning / drug therapy
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Carbon Tetrachloride Poisoning / genetics
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Carbon Tetrachloride Poisoning / metabolism
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Cell Nucleus / genetics
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Cell Nucleus / metabolism*
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Collagen / biosynthesis*
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Collagen / genetics
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism
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Gene Expression Regulation / drug effects*
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Gene Expression Regulation / genetics
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Humans
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Liver Cirrhosis, Experimental / drug therapy*
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Liver Cirrhosis, Experimental / genetics
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Liver Cirrhosis, Experimental / metabolism*
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Mice
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Poly(A)-Binding Proteins / genetics
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Poly(A)-Binding Proteins / metabolism
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Protein Binding / drug effects
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Protein Binding / genetics
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Protein Structure, Tertiary
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Rats
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Signal Transduction / drug effects
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Signal Transduction / genetics
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Smad3 Protein / genetics
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Smad3 Protein / metabolism
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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Transforming Growth Factor beta / antagonists & inhibitors
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Transforming Growth Factor beta / genetics
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Transforming Growth Factor beta / metabolism
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Y-Box-Binding Protein 1
Substances
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Alkadienes
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DNA-Binding Proteins
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HSc025
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Nuclear Proteins
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Poly(A)-Binding Proteins
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SMAD3 protein, human
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Smad3 Protein
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Smad3 protein, mouse
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Smad3 protein, rat
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Transcription Factors
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Transforming Growth Factor beta
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Y-Box-Binding Protein 1
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YB-1 protein, mouse
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YBX1 protein, human
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Collagen
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Carbon Tetrachloride