Department of Gastroenterology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266003, P.R. China.
Department of Gastroenterology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266003, P.R. China.
Oncol Rep. 2018 Aug;40(2):1035-1045. doi: 10.3892/or.2018.6507. Epub 2018 Jun 19.
Chronic hepatitis B virus (HBV) infection remains one of the leading causes of hepatocellular carcinoma (HCC) globally. However, the mechanism underlying the mediation by HBV surface proteins (HBsAgs) of the early steps in the virus life cycle and following HCC development is unclear. β‑2‑glycoprotein I (β2GPI) specifically interacts with HBsAg and demonstrates high expression during the earliest stages of hepatitis B virus infection. In the present study, the assessment of HCC and adjacent tissues revealed that the levels of mRNA and protein of β2GPI were highly expressed in HBV‑related HCC. Previous studies have reported that HBsAg activates the nuclear factor (NF)‑κB pathway via interaction with β2GPI in HCC. However, the underlying mechanism of how the interaction between HBsAg and β2GPI confers activation of the NF‑κB pathway is still unclear. The HBsAg is comprised of three carboxyl‑co‑terminal HB proteins. In the present study, immunofluorescence assay and EMSA consistently revealed that a combination of recombinant small HBV surface antigen (rSHB) and β2GPI can significantly activate the NF‑κB signaling pathway. Another study from our team revealed that high expression of β2GPI enhanced HBsAg binding to cell surfaces and its interaction with Annexin II. However, Annexin II is not a transmembrane protein. Therefore, by a knockdown experiment with TLR2, TLR4 or MyD88 siRNAs using cells with co‑incubated HBsAg/β2GPI, certain aspects of the mechanism through which the HBsAg/β2GPI complex activates the NF‑κB pathway through the Toll‑like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)/IκBα axis were explained. In the present study, we identified the functional domain of HBsAg co‑interaction with β2GPI for the activation of NF‑κB and revealed the mechanism of the HBsAg/β2GPI‑activated NF‑κB pathway which could contribute to the treatment of HBV‑related HCC. A novel finding of the present study is that HBsAg can bind to β2GPI. We first identified the functional domain of HBsAg with β2GPI to activate NF‑κB. Second, by siRNA knockout experiments, we identified the downstream molecules involved in the activation of NF‑κB induced by β2GPI/HBsAg. In addition, we found that HBsAg/β2GPI activated the NF‑κB pathway through the phosphorylation of Ser32/36 by IκBα.
慢性乙型肝炎病毒（HBV）感染仍然是全球肝细胞癌（HCC）的主要病因之一。然而，HBV 表面蛋白（HBsAg）介导病毒生命周期早期步骤以及随后 HCC 发展的机制尚不清楚。β-2-糖蛋白 I（β2GPI）特异性地与 HBsAg 相互作用，并在乙型肝炎病毒感染的最早阶段表现出高表达。在本研究中，对 HCC 及相邻组织的评估显示，HBV 相关 HCC 中β2GPI 的 mRNA 和蛋白水平高度表达。先前的研究报道称，HBsAg 通过与 HCC 中的β2GPI 相互作用激活核因子（NF）-κB 途径。然而，HBsAg 与 β2GPI 相互作用如何赋予 NF-κB 途径激活的潜在机制仍不清楚。HBsAg 由三个羧基末端 HB 蛋白组成。在本研究中，免疫荧光测定和 EMSA 一致表明，重组小 HBV 表面抗原（rSHB）和β2GPI 的组合可显著激活 NF-κB 信号通路。本研究小组的另一项研究表明，β2GPI 的高表达增强了 HBsAg 与细胞表面的结合及其与 Annexin II 的相互作用。然而，Annexin II 不是跨膜蛋白。因此，通过使用共孵育 HBsAg/β2GPI 的细胞用 TLR2、TLR4 或 MyD88 siRNA 进行的敲低实验，解释了 HBsAg/β2GPI 复合物通过 Toll 样受体 4 (TLR4)/髓样分化因子 88 (MyD88)/IκBα 轴激活 NF-κB 途径的部分机制。在本研究中，我们鉴定了 HBsAg 与 β2GPI 相互作用的功能域，用于激活 NF-κB，并揭示了 HBsAg/β2GPI 激活的 NF-κB 途径的机制，这可能有助于治疗 HBV 相关 HCC。本研究的一个新发现是 HBsAg 可以与 β2GPI 结合。我们首先鉴定了 HBsAg 与 β2GPI 相互作用的功能域以激活 NF-κB。其次，通过 siRNA 敲除实验，我们鉴定了β2GPI/HBsAg 诱导的 NF-κB 激活所涉及的下游分子。此外，我们发现 HBsAg/β2GPI 通过 IκBα 的丝氨酸 32/36 磷酸化激活 NF-κB 途径。
