3
|
Novel Functions of Hendra Virus G N-Glycans and Comparisons to Nipah Virus. J Virol 2015; 89:7235-47. [PMID: 25948743 DOI: 10.1128/jvi.00773-15] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Accepted: 04/27/2015] [Indexed: 12/21/2022] Open
Abstract
UNLABELLED Hendra virus (HeV) and Nipah virus (NiV) are reportedly the most deadly pathogens within the Paramyxoviridae family. These two viruses bind the cellular entry receptors ephrin B2 and/or ephrin B3 via the viral attachment glycoprotein G, and the concerted efforts of G and the viral fusion glycoprotein F result in membrane fusion. Membrane fusion is essential for viral entry into host cells and for cell-cell fusion, a hallmark of the disease pathobiology. HeV G is heavily N-glycosylated, but the functions of the N-glycans remain unknown. We disrupted eight predicted N-glycosylation sites in HeV G by conservative mutations (Asn to Gln) and found that six out of eight sites were actually glycosylated (G2 to G7); one in the stalk (G2) and five in the globular head domain (G3 to G7). We then tested the roles of individual and combined HeV G N-glycan mutants and found functions in the modulation of shielding against neutralizing antibodies, intracellular transport, G-F interactions, cell-cell fusion, and viral entry. Between the highly conserved HeV and NiV G glycoproteins, similar trends in the effects of N-glycans on protein functions were observed, with differences in the levels at which some N-glycan mutants affected such functions. While the N-glycan in the stalk domain (G2) had roles that were highly conserved between HeV and NiV G, individual N-glycans in the head affected the levels of several protein functions differently. Our findings are discussed in the context of their contributions to our understanding of HeV and NiV pathogenesis and immune responses. IMPORTANCE Viral envelope glycoproteins are important for viral pathogenicity and immune evasion. N-glycan shielding is one mechanism by which immune evasion can be achieved. In paramyxoviruses, viral attachment and membrane fusion are governed by the close interaction of the attachment proteins H/HN/G and the fusion protein F. In this study, we show that the attachment glycoprotein G of Hendra virus (HeV), a deadly paramyxovirus, is N-glycosylated at six sites (G2 to G7) and that most of these sites have important roles in viral entry, cell-cell fusion, G-F interactions, G oligomerization, and immune evasion. Overall, we found that the N-glycan in the stalk domain (G2) had roles that were very conserved between HeV G and the closely related Nipah virus G, whereas individual N-glycans in the head quantitatively modulated several protein functions differently between the two viruses.
Collapse
|
10
|
Helle F, Vieyres G, Elkrief L, Popescu CI, Wychowski C, Descamps V, Castelain S, Roingeard P, Duverlie G, Dubuisson J. Role of N-linked glycans in the functions of hepatitis C virus envelope proteins incorporated into infectious virions. J Virol 2010; 84:11905-15. [PMID: 20844034 PMCID: PMC2977866 DOI: 10.1128/jvi.01548-10] [Citation(s) in RCA: 171] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Accepted: 09/03/2010] [Indexed: 12/12/2022] Open
Abstract
Hepatitis C virus (HCV) envelope glycoproteins are highly glycosylated, with generally 4 and 11 N-linked glycans on E1 and E2, respectively. Studies using mutated recombinant HCV envelope glycoproteins incorporated into retroviral pseudoparticles (HCVpp) suggest that some glycans play a role in protein folding, virus entry, and protection against neutralization. The development of a cell culture system producing infectious particles (HCVcc) in hepatoma cells provides an opportunity to characterize the role of these glycans in the context of authentic infectious virions. Here, we used HCVcc in which point mutations were engineered at N-linked glycosylation sites to determine the role of these glycans in the functions of HCV envelope proteins. The mutants were characterized for their effects on virus replication and envelope protein expression as well as on viral particle secretion, infectivity, and sensitivity to neutralizing antibodies. Our results indicate that several glycans play an important role in HCVcc assembly and/or infectivity. Furthermore, our data demonstrate that at least five glycans on E2 (denoted E2N1, E2N2, E2N4, E2N6, and E2N11) strongly reduce the sensitivity of HCVcc to antibody neutralization, with four of them surrounding the CD81 binding site. Altogether, these data indicate that the glycans associated with HCV envelope glycoproteins play roles at different steps of the viral life cycle. They also highlight differences in the effects of glycosylation mutations between the HCVpp and HCVcc systems. Furthermore, these carbohydrates form a "glycan shield" at the surface of the virion, which contributes to the evasion of HCV from the humoral immune response.
Collapse
Affiliation(s)
- François Helle
- Institut Pasteur de Lille, Center of Infection and Immunity of Lille (CIIL), and Inserm U1019, F-59019 Lille, CNRS UMR8204, F-59021 Lille, and Université Lille Nord de France, F-59000 Lille, France, Laboratoire de Virologie, Centre Hospitalier Universitaire, Amiens, France, Institute of Biochemistry, Bucharest, Romania, Inserm U966, Université François Rabelais and CHRU de Tours, Tours, France
| | - Gabrielle Vieyres
- Institut Pasteur de Lille, Center of Infection and Immunity of Lille (CIIL), and Inserm U1019, F-59019 Lille, CNRS UMR8204, F-59021 Lille, and Université Lille Nord de France, F-59000 Lille, France, Laboratoire de Virologie, Centre Hospitalier Universitaire, Amiens, France, Institute of Biochemistry, Bucharest, Romania, Inserm U966, Université François Rabelais and CHRU de Tours, Tours, France
| | - Laure Elkrief
- Institut Pasteur de Lille, Center of Infection and Immunity of Lille (CIIL), and Inserm U1019, F-59019 Lille, CNRS UMR8204, F-59021 Lille, and Université Lille Nord de France, F-59000 Lille, France, Laboratoire de Virologie, Centre Hospitalier Universitaire, Amiens, France, Institute of Biochemistry, Bucharest, Romania, Inserm U966, Université François Rabelais and CHRU de Tours, Tours, France
| | - Costin-Ioan Popescu
- Institut Pasteur de Lille, Center of Infection and Immunity of Lille (CIIL), and Inserm U1019, F-59019 Lille, CNRS UMR8204, F-59021 Lille, and Université Lille Nord de France, F-59000 Lille, France, Laboratoire de Virologie, Centre Hospitalier Universitaire, Amiens, France, Institute of Biochemistry, Bucharest, Romania, Inserm U966, Université François Rabelais and CHRU de Tours, Tours, France
| | - Czeslaw Wychowski
- Institut Pasteur de Lille, Center of Infection and Immunity of Lille (CIIL), and Inserm U1019, F-59019 Lille, CNRS UMR8204, F-59021 Lille, and Université Lille Nord de France, F-59000 Lille, France, Laboratoire de Virologie, Centre Hospitalier Universitaire, Amiens, France, Institute of Biochemistry, Bucharest, Romania, Inserm U966, Université François Rabelais and CHRU de Tours, Tours, France
| | - Véronique Descamps
- Institut Pasteur de Lille, Center of Infection and Immunity of Lille (CIIL), and Inserm U1019, F-59019 Lille, CNRS UMR8204, F-59021 Lille, and Université Lille Nord de France, F-59000 Lille, France, Laboratoire de Virologie, Centre Hospitalier Universitaire, Amiens, France, Institute of Biochemistry, Bucharest, Romania, Inserm U966, Université François Rabelais and CHRU de Tours, Tours, France
| | - Sandrine Castelain
- Institut Pasteur de Lille, Center of Infection and Immunity of Lille (CIIL), and Inserm U1019, F-59019 Lille, CNRS UMR8204, F-59021 Lille, and Université Lille Nord de France, F-59000 Lille, France, Laboratoire de Virologie, Centre Hospitalier Universitaire, Amiens, France, Institute of Biochemistry, Bucharest, Romania, Inserm U966, Université François Rabelais and CHRU de Tours, Tours, France
| | - Philippe Roingeard
- Institut Pasteur de Lille, Center of Infection and Immunity of Lille (CIIL), and Inserm U1019, F-59019 Lille, CNRS UMR8204, F-59021 Lille, and Université Lille Nord de France, F-59000 Lille, France, Laboratoire de Virologie, Centre Hospitalier Universitaire, Amiens, France, Institute of Biochemistry, Bucharest, Romania, Inserm U966, Université François Rabelais and CHRU de Tours, Tours, France
| | - Gilles Duverlie
- Institut Pasteur de Lille, Center of Infection and Immunity of Lille (CIIL), and Inserm U1019, F-59019 Lille, CNRS UMR8204, F-59021 Lille, and Université Lille Nord de France, F-59000 Lille, France, Laboratoire de Virologie, Centre Hospitalier Universitaire, Amiens, France, Institute of Biochemistry, Bucharest, Romania, Inserm U966, Université François Rabelais and CHRU de Tours, Tours, France
| | - Jean Dubuisson
- Institut Pasteur de Lille, Center of Infection and Immunity of Lille (CIIL), and Inserm U1019, F-59019 Lille, CNRS UMR8204, F-59021 Lille, and Université Lille Nord de France, F-59000 Lille, France, Laboratoire de Virologie, Centre Hospitalier Universitaire, Amiens, France, Institute of Biochemistry, Bucharest, Romania, Inserm U966, Université François Rabelais and CHRU de Tours, Tours, France
| |
Collapse
|