Hepatitis B Virus Core Protein Sensitizes Hepatocytes to Tumor Necrosis Factor-Induced Apoptosis by Suppression of the Phosphorylation of Mitogen-Activated Protein Kinase Kinase 7
Hepatitis B Virus Core Protein Sensitizes Hepatocytes to Tumor Necrosis Factor-Induced Apoptosis by Suppression of the Phosphorylation of Mitogen-Activated Protein Kinase Kinase 7
复制标题
乙型肝炎病毒核心蛋白通过抑制丝裂原激活蛋白激酶激酶 7 的磷酸化使肝细胞对肿瘤坏死因子诱导的细胞凋亡敏感
DOI：
10.1128/jvi.03106-14
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发表时间：
2015-02-01
影响因子：
5.4
通讯作者：
Deng, Qiang
中科院分区：
文献类型：
--
作者：
Jia, Baosen;Guo, Minggao;Deng, Qiang
摘要由乙型肝炎病毒(乙肝病毒)感染引起的乙型肝炎仍然是世界范围内的主要健康威胁。肝损伤和慢性炎症再生是慢性乙型病毒性肝炎肝纤维化和肝硬变的主要驱动因素，促炎症肿瘤坏死因子-α(α)被认为是病毒性肝炎时肝细胞死亡的主要诱因。在此，我们报道了在肝癌细胞系以及原代小鼠和人肝细胞中，乙肝病毒核心蛋白的表达使细胞对肿瘤坏死因子-α诱导的细胞凋亡敏感。通过串联亲和纯化和质谱分析，发现活化蛋白激酶C1受体(RACK1)与HBC相互作用。RACK1是最近报道的一种支架蛋白，促进其上游激活物对丝裂原活化蛋白激酶7(MKK7)的磷酸化。我们的研究表明，HBc通过竞争性地与RACK1结合来阻断MKK7与RACK1之间的相互作用，从而下调肿瘤坏死因子-α诱导的MKK7的磷酸化和c-jun氨基末端激酶的激活。与这一发现一致的是，MKK7的特异性敲除增加了肝细胞对肿瘤坏死因子-α诱导的凋亡的敏感性，而RACK1的过表达则抵消了HBc的促凋亡活性。衣壳颗粒的形成对HBC促凋亡活性不是必需的，正如使用装配缺陷的HBC突变体所分析的那样。总之，HBc的表达通过破坏MKK7和α之间的相互作用而使肝细胞对肿瘤坏死因子-RACK1诱导的细胞凋亡敏感。因此，我们的研究是第一个表明HBc在乙肝期间肝脏损伤中的致病作用的指标。重要的是，我们的研究揭示了HBc在肿瘤坏死因子-α介导的细胞凋亡中先前未被认识到的作用。HBC的促凋亡活性对了解乙肝的发病机制具有重要意义。特别是，与重型肝炎相关的乙肝病毒变异株可能通过增强HBC的表达上调肝细胞的凋亡。我们的研究还发现，MKK7在肿瘤坏死因子-α诱导的肝细胞凋亡中起中心作用，并揭示了JNK信号在这一过程中的多方面作用。
ABSTRACT Hepatitis B, which caused by hepatitis B virus (HBV) infection, remains a major health threat worldwide. Hepatic injury and regeneration from chronic inflammation are the main driving factors of liver fibrosis and cirrhosis in chronic hepatitis B. Proinflammatory tumor necrosis factor alpha (TNF-α) has been implicated as a major inducer of liver cell death during viral hepatitis. Here, we report that in hepatoma cell lines and in primary mouse and human hepatocytes, expression of hepatitis B virus core (HBc) protein made cells susceptible to TNF-α-induced apoptosis. We found by tandem affinity purification and mass spectrometry that receptor of activated protein kinase C 1 (RACK1) interacted with HBc. RACK1 was recently reported as a scaffold protein that facilitates the phosphorylation of mitogen-activated protein kinase kinase 7 (MKK7) by its upstream activators. Our study showed that HBc abrogated the interaction between MKK7 and RACK1 by competitively binding to RACK1, thereby downregulating TNF-α-induced phosphorylation of MKK7 and the activation of c-Jun N-terminal kinase (JNK). In line with this finding, specific knockdown of MKK7 increased the sensitivity of hepatocytes to TNF-α-induced apoptosis, while overexpression of RACK1 counteracted the proapoptotic activity of HBc. Capsid particle formation was not obligatory for HBc proapoptotic activity, as analyzed using an assembly-defective HBc mutant. In conclusion, the expression of HBc sensitized hepatocytes to TNF-α-induced apoptosis by disrupting the interaction between MKK7 and RACK1. Our study is thus the first indication of the pathogenic effects of HBc in liver injury during hepatitis B. IMPORTANCE Our study revealed a previously unappreciated role of HBc in TNF-α-mediated apoptosis. The proapoptotic activity of HBc is important for understanding hepatitis B pathogenesis. In particular, HBV variants associated with severe hepatitis may upregulate apoptosis of hepatocytes through enhanced HBc expression. Our study also found that MKK7 is centrally involved in TNF-α-induced hepatocyte apoptosis and revealed a multifaceted role for JNK signaling in this process.