APASL2013 乙肝病毒表面抗原抑制干扰素诱导的信号通路上调PP2A

StephenW

Hepatitis B Virus Surface Antigen Inhibits IFN-induced Signaling Pathway by Upregulation of PP2A Protein   

Pu Wang1, Rui Zhang2, Jinming Li2
1Beihua University, Jilin, 2National Center for Clinical Laboratories, Beijing Hospital, Beijing, China

Background: There is an excess (100 000-fold) of noninfectious subviral particles in the sera of patients with hepatitis B virus (HBV). These subviral particles are composed of hepatitis B surface antigen (HBsAg) in the form of small spheres and filaments. Why HBV secretes an overabundance of such noninfectious envelope protein particles and whether the free HBsAg can affect alpha interferon ( IFN-α) treatment has been a longstanding enigma. Studies have demonstrated that protein phosphatase 2A (PP2A) physically interacts with and inhibits protein arginine methyltransferase 1 (PRMT1) in cells resulted in hypomethylation of STAT1 and inhibition of IFN-α-induced signaling. Hepatitis B immunoglobulin (HBIG) can be endocytosed into hepatocyte-derived cell lines, and it inhibits the secretion of HBsAg and the intracellular accumulation of HBsAg. Thus the aim of the study was to analyze the influence of subviral particles on protein phosphatase 2A expression and the activation of IFN-α signaling in vitro.
Methods: HepG2.2.15 cells were stimulated with various concentrations of HBIG in the presence or absence of IFN-α. And the HBsAg gene expression is inhibited with the siRNA in HepG2.2.15 cells. Then culture supernatants were assessed by enzyme-linked immune sorbent assay. We analyze the expression level of HBsAg, PP2A and PRMT1 protein using western blot and RT-PCR.
Results: An up-regulation of PP2A was observed in the cells cultured with HBIG and stimulated with or without IFN-α. However, the expression of PP2A protein is significantly inhibited in IFN-αstimulated cells. And PP2A can effectively inhibit PRMT1 production in cells. Moreover, we showed that the PP2A expression was dramaticly decreased when the HBsAg is inhibited by siRNA in HepG2.2.15 cells.
Conclusions: Our research indicated that increased HBsAg in HepG2.2.15 would up-regulate the expression of PP2A. Thus we propose that HBsAg may be the very essential protein through which HBV inhibits the activation of IFN-αsignaling.


Assigned speakers:
Dr. Pu Wang, Beihua University , Jilin , China

Assigned in sessions:
07.06.2013, 08:30-17:30, PT-3, HEP B Basic, Exhibition Hall

StephenW

背景：有B型肝炎病毒（HBV）患者血清中的非感染性亚病毒颗粒过量（100 000倍）。这些亚病毒颗粒是由B型肝炎表面抗原（HBsAg）的小球和长丝的形式。为什么HBV分泌过多的非传染性包膜蛋白颗粒和免费乙肝表面抗原是否能影响α-干扰素（IFN-α）治疗是一个长期存在的谜团。有研究表明，蛋白磷酸酶2A（PP2A）的物理相互作用，并抑制蛋白质精氨酸甲基转移酶1（PRMT1）甲基化的STAT1和抑制IFN-α诱导的信号导致细胞。乙型肝炎免疫球蛋白（HBIG）可被胞吞作用进入肝细胞衍生的细胞系，抑制分泌的HBsAg和乙肝表面抗原的细胞内的积累。因此，本研究的目的是分析蛋白磷酸酶2A的表达和IFN-α的信号在体外激活的亚病毒颗粒的影响。
方法：HepG2.2.15细胞与各种浓度的HBIG在存在或不存在IFN-α的刺激。和HBsAg基因的表达被抑制HepG2.2.15细胞中的siRNA。培养上清液用酶联免疫吸附法进行了评估。我们分析使用免疫印迹和RT-PCR检测乙肝表面抗原，PP2A和PRMT1蛋白的表达水平。
结果：PP2A的上调和乙肝免疫球蛋白的细胞，并观察到IFN-α的有或没有刺激。然而，PP2A蛋白的表达被显着抑制在IFN-αstimulated的细胞。和PP2A可以有效地抑制细胞的的PRMT1生产中。此外，我们发现，PP2A表达乙肝表面抗原时dramaticly下降HepG2.2.15细胞中的siRNA抑制。
结论：我们的研究表明，增加乙肝表面抗原HepG2.2.15细胞上调表达PP2A。因此，我们建议，HBsAg的可能是非常重要的蛋白质，通过抑制HBV的IFN-αsignaling的激活。