乙型肝炎e抗原通过中断K63连接的NEMO泛素化来抑制NF-κB活性

StephenW

Hepatitis B e Antigen Inhibits NF-κB Activity by Interrupting K63-Linked Ubiquitination of NEMO
Yuan Wang, Lei Cui, Guifang Yang, Jianbo Zhan, Liang Guo, Yu Chen, Chengpeng Fan, Dan Liu, Deyin Guo
J.-H. James Ou, Editor
DOI: 10.1128/JVI.00667-18

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ABSTRACT

Viruses have adopted diverse strategies to suppress antiviral responses. Hepatitis B virus (HBV), a virus that is prevalent worldwide, manipulates the host’s innate immune system to evade scavenging. It is reported that the hepatitis B e antigen (HBeAg) can interfere with NF-κB activity, which then leads to high viral loads, while HBV with the G1896A mutation remains infectious without the production of HBeAg but can induce more severe proinflammatory response and liver damage. The aim of current work was to study the molecular mechanism by which HBeAg suppresses interleukin-1β (IL-1β)-stimulated NF-κB activity, which leads to the suppression of the innate immune responses to HBV infection. Our study revealed that HBeAg could interact with NEMO, a regulatory subunit associated with IκB kinase, which regulates the activation of NF-κB. HBeAg suppressed the IL-1β-induced tumor necrosis factor (TNF)-associated factor 6 (TRAF6)-dependent K63-linked ubiquitination of NEMO, thereby downregulating NF-κB activity and promoting virus replication. We further demonstrated the inhibitory effect of HBeAg on the NF-κB signaling pathway using primary human hepatocytes, HBV-infected HepG2-NTCP cells, and clinical liver samples. Our study reveals a molecular mechanism whereby HBeAg suppresses IL-1β-induced NF-κB activation by decreasing the TRAF6-dependent K63-linked ubiquitination of NEMO, which may thereby enhance HBV replication and promote a persistent infection.

IMPORTANCE The role of HBeAg in inflammatory responses during the infection of hepatitis B virus (HBV) is not fully understood, and several previous reports with regard to the NF-κB pathway are controversial. In this study, we showed that HBeAg could suppress both Toll-like receptor 2 (TLR2)- and IL-1β-induced activation of NF-κB in cells and clinical samples, and we further revealed novel molecular mechanisms. We found that HBeAg can associate with NEMO, the regulatory subunit for IκB kinase (IKK) that controls the NF-κB signaling pathway, and thereby inhibits TRAF6-mediated K63-linked ubiquitination of NEMO, resulting in downregulation of NF-κB activity and promotion of virus replication. In contrast, the HBeAg-negative HBV mutant can induce higher levels of NF-κB activity. These results are important for understanding the HBV-induced pathogenesis of chronic hepatitis and indicate that different clinical measures should be considered to treat HBeAg-positive and HBeAg-negative infections. Our findings represent a conceptual advance in HBV-related suppression of NF-κB signaling.

StephenW

乙型肝炎e抗原通过中断K63连接的NEMO泛素化来抑制NF-κB活性
王远，崔磊，杨桂芳，詹建波，梁国，陈宇，范承鹏，刘丹，郭德胤
J.-H. James Ou，编辑
DOI：10.1128 / JVI.00667-18

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抽象

病毒采用多种策略来抑制抗病毒反应。乙型肝炎病毒（HBV）是一种在世界范围内流行的病毒，它操纵宿主的先天免疫系统以逃避清除。据报道，乙型肝炎e抗原（HBeAg）可以干扰NF-κB活性，从而导致高病毒载量，而具有G1896A突变的HBV仍然具有感染性而不产生HBeAg但可诱导更严重的促炎反应和肝脏损伤。目前的工作目的是研究HBeAg抑制白细胞介素-1β（IL-1β）刺激的NF-κB活性的分子机制，从而抑制对HBV感染的先天免疫反应。我们的研究表明，HBeAg可以与NEMO相互作用，NEMO是一种与IκB激酶相关的调节亚基，可调节NF-κB的活化。 HBeAg抑制IL-1β诱导的肿瘤坏死因子（TNF）相关因子6（TRAF6）依赖性K63连锁的NEMO泛素化，从而下调NF-κB活性并促进病毒复制。我们进一步证实了HBeAg对原代人肝细胞，HBV感染的HepG2-NTCP细胞和临床肝脏样品的NF-κB信号传导途径的抑制作用。我们的研究揭示了一种分子机制，即HBeAg通过减少TRAF6依赖性K63连接的NEMO泛素化来抑制IL-1β诱导的NF-κB活化，从而可以增强HBV复制并促进持续感染。

重要性HBeAg在乙型肝炎病毒（HBV）感染过程中的炎症反应中的作用尚不完全清楚，之前有关NF-κB途径的一些报道存在争议。在这项研究中，我们发现HBeAg可以抑制细胞和临床样本中Toll样受体2（TLR2）和IL-1β诱导的NF-κB活化，我们进一步揭示了新的分子机制。我们发现HBeAg可与NEMO结合，NEMO是控制NF-κB信号通路的IκB激酶（IKK）的调节亚基，从而抑制TRAF6介导的K63连接的NEMO泛素化，导致NF-κB活性下调和促进病毒复制。相反，HBeAg阴性HBV突变体可以诱导更高水平的NF-κB活性。这些结果对于了解HBV诱导的慢性肝炎发病机制非常重要，并表明应考虑采用不同的临床措施来治疗HBeAg阳性和HBeAg阴性感染。我们的研究结果代表了HBV相关的NF-κB信号抑制的概念进展。