Zheng Nai Q, Zheng Zi H, Xu Hai X, Huang Ming X, Peng Xiao M
Department of Infectious Diseases, the Third Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China.
Jinan University Clinic, the First Affiliated Hospital of Jinan University, Guangzhou, China.
Virol J. 2017 Apr 13;14(1):77. doi: 10.1186/s12985-017-0747-z.
Hepatitis B virus (HBV) is the leading cause of liver cirrhosis and hepatocellular carcinoma in Asia and Africa. Existing antivirals cannot cure HBV or eliminate risk of hepatocellular carcinoma. Glucose-regulated protein 78 (GRP78) can inhibit HBV replication, but promote virion secretion and hepatocellular cancer cell invasion. For these reasons, the overall effect of GRP78 on HBV production and whether to utilize the HBV replication-inhibitory effect of GRP78 up-regulation or the hepatocellular cancer cell invasion-inhibitory effect of its down-regulation were further investigated in order to improve the efficacy of current antiviral therapy.
GRP78 regulations in HepG2.2.15 cells were conducted by transfections of expressing vector and small interfering RNA, respectively. The changes in HBV replication, hepatitis B e antigen (HBeAg) synthesis and hepatoma cell motility were monitored.
GRP78 overall decreased HBV production due to its HBV replication-inhibitory effect time-dependently overwhelming virion secretion-promoting effect in HepG2.2.15 cells. Unlike the parental cells (HepG2), HepG2.2.15 cells demonstrated decreased expressions of the major genes in the interferon-β1-dependent pathway. Moreover, the expressions of these genes were not affected by GRP78 regulations. However, GRP78 was found to inhibit HBeAg secretion and to increase the retro-transportation of capsid assembly-interfering HBeAg precursor from the endoplasmic reticulum into the cytosol where new viral nucleocapsids formed. Furthermore, GRP78 overexpression promoted wound healing process (the motility) of HepG2.2.15 cells. In contrast, GRP78 knockdown enhanced HBV replication and HBeAg secretion, but they were abolished by entecavir and furin inhibitor, respectively.
GRP78 mainly demonstrates anti-HBV effects, reducing HBV production and HBeAg secretion. With due regard to the hepatocellular cancer invasion risk of the overexpression and the rectifiability of the unpleasant effects of the knockdown, GRP78 down-regulation may be more suitable to serve as an additive strategy to cover the hepatocellular cancer prevention shortage of current antiviral therapy in the future.
乙型肝炎病毒（HBV）是亚洲和非洲肝硬化和肝细胞癌的主要病因。现有的抗病毒药物无法治愈HBV或消除肝细胞癌风险。葡萄糖调节蛋白78（GRP78）可抑制HBV复制，但会促进病毒粒子分泌和肝癌细胞侵袭。基于这些原因，为提高当前抗病毒治疗的疗效，进一步研究了GRP78对HBV产生的总体影响，以及是利用上调GRP78的HBV复制抑制作用还是下调其肝癌细胞侵袭抑制作用。
分别通过转染表达载体和小干扰RNA对HepG2.2.15细胞中的GRP78进行调控。监测HBV复制、乙型肝炎e抗原（HBeAg）合成及肝癌细胞运动性的变化。
在HepG2.2.15细胞中，GRP78因其HBV复制抑制作用在时间上压倒病毒粒子分泌促进作用，从而总体上降低了HBV产生。与亲代细胞（HepG2）不同，HepG2.2.15细胞中干扰素-β1依赖途径的主要基因表达降低。此外，这些基因的表达不受GRP78调控的影响。然而，发现GRP78可抑制HBeAg分泌，并增加衣壳组装干扰性HBeAg前体从内质网向内质网的逆向转运，在内质网中形成新的病毒核衣壳。此外，GRP78过表达促进了HepG2.2.15细胞的伤口愈合过程（运动性）。相反，GRP78敲低增强了HBV复制和HBeAg分泌，但分别被恩替卡韦和弗林蛋白酶抑制剂消除。
GRP78主要表现出抗HBV作用，减少HBV产生和HBeAg分泌。考虑到过表达的肝癌侵袭风险以及敲低不良效应的可纠正性，下调GRP78可能更适合作为一种附加策略，以弥补未来当前抗病毒治疗在肝癌预防方面的不足。
