Role of conserved E2 residue W420 in receptor binding and hepatitis C virus infection

Cowton, V. M., Angus, A. G.N., Cole, S. J., Markopoulou, C. K., Owsianka, A., Dunlop, J. I., Gardner, D., Krey, T. and Patel, A. H. (2016) Role of conserved E2 residue W420 in receptor binding and hepatitis C virus infection. Journal of Virology, 90(16), pp. 7456-7468. (doi: 10.1128/JVI.00685-16) (PMID:27279607) (PMCID:PMC4984626)

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Hepatitis C virus (HCV) enters cells via interactions with several host factors, a key one being that between the viral E2 envelope glycoprotein and the CD81 receptor. We previously identified the E2 tryptophan 420 (W420) as an essential CD81-binding residue. However, the importance of W420 in the context of the native virion is unknown as these earlier studies predate the infectious HCV cell-culture (HCVcc) system. Here, we introduced four separate mutations (F, Y, A or R) at position 420 within the infectious JFH-1 HCVcc genome and characterized their effects on the viral cycle. Whilst all mutations reduced E2-CD81 binding, only two (W420A and W420R) reduced HCVcc infectivity. Further analyses of mutants with hydrophobic residues (F or Y) found that interactions with receptors SR-BI as well as CD81 were modulated which in-turn determined the viral uptake route. Both mutant viruses were significantly less dependent on SR-BI, and its lipid-transfer activity, for virus entry. Furthermore, they were resistant to the drug erlotinib that targets EGFR (a host co-factor for HCV entry) and also blocks SR-BI dependent HDL-mediated enhancement of virus entry. Together, our data indicate a model where alteration at position 420 causes a subtle change in E2 conformation that prevents interaction with SR-BI and increases accessibility to the CD81 binding site in-turn favoring a particular internalization route. They further show that a hydrophobic residue with a strong preference for tryptophan at position 420 is important, both functionally and structurally, to provide an additional hydrophobic anchor to stabilize the E2-CD81 interaction. IMPORTANCE Hepatitis C virus (HCV) is a leading cause of liver disease causing up to 500000 deaths annually. The first step in the viral life-cycle is the entry process. This study investigates the role of a highly conserved residue, tryptophan 420 of the viral glycoprotein E2 in this process. We analyzed the effect of changing this residue in the virus and confirmed that this region is important for binding to the CD81 receptor. Furthermore, alteration of this residue modulated the interaction with the SR-BI receptor and changes to these key interactions were found to affect the virus internalization route involving the host co-factor, EGFR. Our results also show that the nature of the amino acid at this position is important functionally and structurally to provide an anchor-point to stabilize the E2-CD81 interaction.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Cowton, Dr Vanessa and Dunlop, Dr James and Angus, Dr Allan and Cole, Mrs Sarah and Owsianka, Dr Anna and Gardner, Miss Deborah and Patel, Professor Arvind
Authors: Cowton, V. M., Angus, A. G.N., Cole, S. J., Markopoulou, C. K., Owsianka, A., Dunlop, J. I., Gardner, D., Krey, T., and Patel, A. H.
College/School:College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
Journal Name:Journal of Virology
Publisher:American Society for Microbiology
ISSN (Online):1098-5514
Published Online:08 June 2016
Copyright Holders:Copyright © 2016 American Society for Microbiology
First Published:First published in Journal of Virology 90(16): 7456-7468
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
656491Basis of the host range and tissue tropism for hepatitis C virusArvind PatelMedical Research Council (MRC)MC_UU_12014/2MVLS III - CENTRE FOR VIRUS RESEARCH