Apolipoprotein H drives hepatitis B surface antigen retention and endoplasmic reticulum stress during hepatitis B virus infection,The International Journal of Biochemistry & Cell Biology

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Apolipoprotein H drives hepatitis B surface antigen retention and endoplasmic reticulum stress during hepatitis B virus infection
The International Journal of Biochemistry & Cell Biology ( IF 3.4 ) Pub Date : 2020-12-26 , DOI: 10.1016/j.biocel.2020.105906
Yaming Liu ₁ , Jessica L Maiers ₂ , Yajuan Rui ₃ , Xiaoming Jiang ₃ , Bayasi Guleng ₁ , Jianlin Ren ₁

Affiliation

Background

Apolipoprotein H (APOH), also known as beta2-glycoprotein I (beta2-GPI), is an acute phase protein in hepatitis B virus (HBV) infection and binds to hepatitis B surface antigen (HBsAg) with high-affinity. APOH expression is upregulated by HBV and the large surface protein (LHBs), but also elevated in HBV-related hepatoma cells. Previous studies show that intracellular retention of HBsAg induces endoplasmic reticulum (ER) stress, a key driver of hepatocyte damage during chronic liver injury, but the mechanisms are unclear. We hypothesize that APOH mediates HBV-induced ER stress through increased retention of HBsAg.

Methods

VR-APOH-myc and VR-LHBs-flag plasmids were constructed by PCR using pcDNA3.1(-)-APOH or an HBV expression vector, respectively. APOH and ER stress markers were examined at protein and mRNA levels by Western Blot or RT-qPCR. HBsAg titer was assayed by ELISA. RNA-seq was performed to elucidate the transcriptional impact of APOH manipulation in HBV-producing cells (HepG2.2.15 cells).

Results

We found that HBV upregulates APOH expression in 293 T cells, and APOH overexpression subsequently inhibits secretion of HBsAg. Next, we show that LHBs overexpression in conjunction with APOH leads to ER stress in 293 T cells, as evidenced by production of the binding immunoglobulin protein (BiP) and C/EBP homologous protein (CHOP), as well as increased splicing of X-box binding protein 1 (XBP1). We further observed that loss of beta2-GPI reduced CHOP expression in HepG2.2.15 cells, while beta2-GPI overexpression enhanced CHOP production.

Conclusion

The interaction of beta2-GPI and HBV initiates ER stress through driving intracellular retention of HBsAg and activates the UPR.

中文翻译：

载脂蛋白H驱动乙型肝炎病毒感染期间乙型肝炎表面抗原保留和内质网应激

背景

载脂蛋白H（APOH）又称β2-糖蛋白I（beta2-GPI），是乙型肝炎病毒（HBV）感染的急性期蛋白，与乙型肝炎表面抗原（HBsAg）具有高亲和力。APOH 表达被 HBV 和大表面蛋白 (LHBs) 上调，但在 HBV 相关的肝癌细胞中也升高。先前的研究表明，HBsAg 的细胞内滞留诱导内质网 (ER) 应激，这是慢性肝损伤期间肝细胞损伤的关键驱动因素，但机制尚不清楚。我们假设 APOH 通过增加 HBsAg 的保留来介导 HBV 诱导的内质网应激。

方法

VR-APOH-myc 和 VR-LHBs-flag 质粒分别使用 pcDNA3.1(-)-APOH 或 HBV 表达载体通过 PCR 构建。通过蛋白质印迹或 RT-qPCR 在蛋白质和 mRNA 水平上检查 APOH 和 ER 应激标记。通过ELISA测定HBsAg滴度。进行 RNA-seq 以阐明 APOH 操作对 HBV 产生细胞（HepG2.2.15 细胞）的转录影响。

结果

我们发现 HBV 上调了 293 T 细胞中 APOH 的表达，APOH 过表达随后抑制了 HBsAg 的分泌。接下来，我们表明 LHBs 过表达与 APOH 一起导致 293 T 细胞中的 ER 应激，这可以通过结合免疫球蛋白 (BiP) 和 C/EBP 同源蛋白 (CHOP) 的产生以及 X-框结合蛋白 1 (XBP1)。我们进一步观察到 beta2-GPI 的损失减少了 HepG2.2.15 细胞中的 CHOP 表达，而 beta2-GPI 过度表达增强了 CHOP 生产。

结论

beta2-GPI 和 HBV 的相互作用通过驱动 HBsAg 的细胞内滞留启动 ER 应激并激活 UPR。

更新日期：2020-12-31

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