An Arginine-Rich Motif in the ORF2 capsid protein regulates the hepatitis E virus lifecycle and interactions with the host cell

PLoS Pathog. 2022 Aug 25;18(8):e1010798. doi: 10.1371/journal.ppat.1010798. eCollection 2022 Aug.

Abstract

Hepatitis E virus (HEV) infection is the most common cause of acute viral hepatitis worldwide. Hepatitis E is usually asymptomatic and self-limiting but it can become chronic in immunocompromised patients and is associated with increased fulminant hepatic failure and mortality rates in pregnant women. HEV genome encodes three proteins including the ORF2 protein that is the viral capsid protein. Interestingly, HEV produces 3 isoforms of the ORF2 capsid protein which are partitioned in different subcellular compartments and perform distinct functions in the HEV lifecycle. Notably, the infectious ORF2 (ORF2i) protein is the structural component of virions, whereas the genome-free secreted and glycosylated ORF2 proteins likely act as a humoral immune decoy. Here, by using a series of ORF2 capsid protein mutants expressed in the infectious genotype 3 p6 HEV strain as well as chimeras between ORF2 and the CD4 glycoprotein, we demonstrated how an Arginine-Rich Motif (ARM) located in the ORF2 N-terminal region controls the fate and functions of ORF2 isoforms. We showed that the ARM controls ORF2 nuclear translocation likely to promote regulation of host antiviral responses. This motif also regulates the dual topology and functionality of ORF2 signal peptide, leading to the production of either cytosolic infectious ORF2i or reticular non-infectious glycosylated ORF2 forms. It serves as maturation site of glycosylated ORF2 by furin, and promotes ORF2-host cell membrane interactions. The identification of ORF2 ARM as a unique central regulator of the HEV lifecycle uncovers how viruses settle strategies to condense their genetic information and hijack cellular processes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Capsid Proteins / chemistry
  • Capsid Proteins / metabolism
  • Female
  • Glycosylation
  • Hepatitis E virus* / growth & development
  • Hepatitis E* / genetics
  • Hepatitis E* / metabolism
  • Humans
  • Pregnancy

Substances

  • Capsid Proteins

Grants and funding

This work was supported by grants from the French agency ANRS-Maladies infectieuses émergentes (ECTZ61515, AAP2015-2 CSS4), Pasteur Institute of Lille (#Diag-HepE), Région Hauts-de-France (#Diag-HepE) and Inserm-transfert (#actiVHE). The PLBS platform used in this work was supported by the ANR (ANR-10-EQPX-04-01) and Feder (12001407 [D-AL] EquipEx ImagInEx BioMed). K.H., M.A. and T.V. were supported by a fellowship from the ANRS-Maladies infectieuses émergentes (ECTZ61515, AAP2015-2 CSS4). M.F. was supported by a fellowship from the Pasteur Institute of Lille and Région Hauts-de-France. M.A. is currently supported by the Fonds National Suisse (FNS). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.