Modulation of the transforming growth factor-β signal transduction pathway by hepatitis C virus nonstructural 5A protein
Modulation of the transforming growth factor-β signal transduction pathway by hepatitis C virus nonstructural 5A protein
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DOI：
10.1074/jbc.m512438200
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发表时间：
2006-03-17
影响因子：
4.8
通讯作者：
Hwang, SB
中科院分区：
文献类型：
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作者：
Choi, SH;Hwang, SB
转化生长因子-β（TGF-β）与肝脏疾病的发病机制有关。TGF-β参与肝再生和肝炎病毒感染的纤维化和硬化转化。丙型肝炎病毒（HCV）感染常导致肝硬化和肝细胞癌。HCV非结构蛋白5A（NS 5A）是一种多功能蛋白，可调节丝氨酸介导的信号转导途径。为了阐明HCV致病的分子机制，我们检测了NS 5A蛋白对TGF-β刺激的信号级联的影响。我们发现，NS 5A蛋白抑制TGF-β介导的信号通路在肝癌细胞系报告基因测定。为了进一步研究NS 5A的作用，我们检测了NS 5A和TGF-β信号转导子之间的蛋白质/蛋白质相互作用。体外和体内结合数据均显示，NS 5A蛋白在肝癌细胞系中与TGF-β受体I（T β R-I）直接相互作用。这种相互作用定位于NS 5A的氨基酸148 - 238。我们还发现NS 5A蛋白与T β R-I共定位于Huh 7细胞的细胞质中，并抑制TGF-β介导的Smad 2核转位。此外，我们证明NS 5A蛋白废除了Smad 2的磷酸化和Smad 3和Smad 4的异二聚化。为了进一步探索与病毒感染的相关性，我们研究了HCV亚基因组复制子对TGF-β信号通路的影响。我们发现，HCV亚基因组复制子也抑制TGF-β诱导的信号级联反应。这些结果表明，HCV NS 5A通过与T β R-I相互作用调节TGF-β信号传导，并且NS 5A可能是HCV相关肝脏发病机制中的重要危险因素。
Transforming growth factor-beta (TGF-beta) is implicated in the pathogenesis of liver disease. TGF-beta is involved both in liver regeneration and in the fibrotic and cirrhotic transformation with hepatitis viral infection. Hepatitis C virus (HCV) infection often leads to cirrhosis and hepatocellular carcinoma. HCV nonstructural 5A (NS5A) protein is a multifunctional protein that modulates cytokine-mediated signal transduction pathways. To elucidate the molecular mechanism of HCV pathogenesis, we examined the effect of NS5A protein on TGF-beta-stimulated signaling cascades. We show that NS5A protein inhibited the TGF-beta-mediated signaling pathway in hepatoma cell lines as determined by reporter gene assay. To further investigate the role of NS5A, we examined the protein/protein interaction between NS5A and TGF-beta signal transducers. Both in vitro and in vivo binding data showed that NS5A protein directly interacted with TGF-beta receptor I (T beta R-I) in hepatoma cell lines. This interaction was mapped to amino acids 148 - 238 of NS5A. We also found that NS5A protein co-localized with T beta R-I in the cytoplasm of Huh7 cells and inhibited TGF-beta-mediated nuclear translocation of Smad2. Furthermore, we demonstrate that NS5A protein abrogated the phosphorylation of Smad2 and the heterodimerization of Smad3 and Smad4. To further explore the relevance to viral infection, we examined the effect of the HCV subgenomic replicon on the TGF-beta signaling pathway. We show that the HCV subgenomic replicon also inhibited TGF-beta-induced signaling cascades. These results indicate that HCV NS5A modulates TGF-beta signaling through interaction with T beta R-I and that NS5A may be an important risk factor in HCV-associated liver pathogenesis.