乙型肝炎病毒小包膜蛋白的推测两亲性α螺旋在亚病毒颗粒

StephenW

A putative amphipathic alpha helix in hepatitis B virus small envelope protein plays a critical role in the morphogenesis of subviral particles
Sisi Yang  1   2 , Zhongliang Shen  1 , Yaoyue Kang  1 , Liren Sun  2 , Usha Viswanathan  2 , Hongying Guo  1 , Tianlun Zhou  2 , Xinghong Dai  3 , Jinhong Chang  2 , Jiming Zhang  4 , Ju-Tao Guo  5
Affiliations
Affiliations

    1
    Department of Infectious Diseases, Huashan Hospital, Fudan University, Shanghai, China.
    2
    Baruch S. Blumberg Institute, Hepatitis B Foundation, Doylestown, Pennsylvania, USA.
    3
    Department of Physiology and Biophysics, Case Western Reserve University, School of Medicine, Cleveland, Ohio, USA.
    4
    Department of Infectious Diseases, Huashan Hospital, Fudan University, Shanghai, China [email protected] [email protected].
    5
    Baruch S. Blumberg Institute, Hepatitis B Foundation, Doylestown, Pennsylvania, USA [email protected] [email protected].

    PMID: 33536177 DOI: 10.1128/JVI.02399-20

Abstract

Hepatitis B virus (HBV) small (S) envelope protein has the intrinsic ability to direct the formation of small spherical subviral particles (SVPs) in eukaryotic cells. However, the molecular mechanism underlying the morphogenesis of SVPs from the monomeric S protein initially synthesized at the endoplasmic reticulum (ER) membrane remains largely elusive. Structure prediction and extensive mutagenesis analysis suggested that the amino acid residues spanning W156 to R169 of S protein form an amphipathic alpha helix and play essential roles in SVP production and S protein metabolic stability. Further biochemical analyses showed that the putative amphipathic alpha helix was not required for the disulfide-linked S protein oligomerization, but was essential for SVP morphogenesis. Pharmacological disruption of vesicle trafficking between the ER and Golgi complex in SVP producing cells supported the hypothesis that S protein-directed SVP morphogenesis takes place at the ER-Golgi intermediate compartment (ERGIC). Moreover, it was demonstrated that S protein is degraded in hepatocytes via a 20S proteasome-dependent, but ubiquitination-independent non-classic ER-associated degradation (ERAD) pathway. Taken together, the results reported herein favor a model in which the amphipathic alpha helix at the antigenic loop of S protein attaches to the lumen leaflet to facilitate SVP budding from the ERGIC compartment, whereas the failure of budding process may result in S protein degradation by 20S proteasome in an ubiquitination-independent manner.Importance Subviral particles are the predominant viral product produced by HBV-infected hepatocytes. Their levels exceed the virion particles by 10,000 to 100,000-fold in the blood of HBV infected individuals. The high levels of SVPs, or HBV surface antigen (HBsAg), in the circulation induces immune tolerance and contributes to the establishment of persistent HBV infection. The loss of HBsAg, often accompanied by appearance of anti-HBs antibodies, is the hallmark of durable immune control of HBV infection. Therapeutic induction of HBsAg loss is, therefore, considered to be essential for the restoration of host antiviral immune response and functional cure of chronic hepatitis B. Our findings on the mechanism of SVP morphogenesis and S protein metabolism will facilitate the rational discovery and development of antiviral drugs to achieve this therapeutic goal.

Copyright © 2021 American Society for Microbiology.

StephenW

乙型肝炎病毒小包膜蛋白的推测两亲性α螺旋在亚病毒颗粒的形态发生中起关键作用
杨思思1 2，沉忠良1，康耀跃1，孙立人2，乌沙·维斯瓦纳坦2，郭宏英1，周天伦2，邢兴岱3，张金宏2，张继明4，郭聚涛5
隶属关系
隶属关系

    1个
    复旦大学附属华山医院传染病科，上海。
    2
    美国宾夕法尼亚州Doylestown的乙型肝炎基金会Baruch S.Blumberg研究所。
    3
    凯斯西储大学生理学和生物物理学系，美国俄亥俄州克利夫兰医学院。
    4
    复旦大学附属华山医院传染病科，上海[email protected] [email protected]。
    5
    美国宾夕法尼亚州Doylestown的乙型肝炎基金会Baruch S. Blumberg研究所[email protected] [email protected]。

    PMID：33536177 DOI：10.1128 / JVI.02399-20

抽象

乙型肝炎病毒（HBV）小（S）包膜蛋白具有指导真核细胞中小的球形亚病毒颗粒（SVP）形成的内在能力。但是，从最初在内质网（ER）膜上合成的单体S蛋白形成SVP的分子机制尚不清楚。结构预测和广泛的诱变分析表明，跨越S蛋白的W156至R169的氨基酸残基形成两亲性α螺旋，并在SVP产生和S蛋白代谢稳定性中起重要作用。进一步的生化分析表明，二硫键连接的S蛋白寡聚化不需要假定的两亲性α螺旋，但对于SVP形态发生是必不可少的。 SVP产生细胞中ER和高尔基体之间的小泡运输的药理学破坏支持了S蛋白指导的SVP形态发生在ER-高尔基体中隔室（ERGIC）的假设。此外，已证明S蛋白通过20S蛋白酶体依赖性但不依赖泛素化的非经典ER相关降解（ERAD）途径在肝细胞中降解。综上所述，本文报道的结果支持这样一种模型，其中S蛋白的抗原环处的两亲性α螺旋附着在管腔小叶上，以促进SVP从ERGIC区室出芽，而出芽过程的失败可能导致S蛋白降解。 20S蛋白酶体以不依赖泛素化的方式发生。重要亚病毒颗粒是HBV感染的肝细胞产生的主要病毒产物。在乙肝病毒感染者的血液中，它们的含量超过病毒颗粒的10,000到100,000倍。循环中高水平的SVP或HBV表面抗原（HBsAg）诱导免疫耐受并有助于建立持久性HBV感染。 HBsAg的丢失通常伴随着抗HBs抗体的出现，是对HBV感染进行持久免疫控制的标志。因此，治疗性诱导HBsAg丢失被认为对于恢复宿主抗病毒免疫应答和慢性乙型肝炎的功能治愈至关重要。我们对SVP形态发生和S蛋白代谢机制的发现将有助于抗病毒药物的合理发现和发展。药物来达到这个治疗目的。

版权所有©2021美国微生物学会。