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Functional study of the C-terminal part of the hepatitis C virus E1 ectodomain

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Abstract
In the hepatitis C virus (HCV) envelope glycoproteins E1 and E2, which form a heterodimer, E2 is the receptor binding protein and the major target of neutralizing antibodies, whereas the function of E1 remains less characterized. To investigate E1 functions, we generated a series of mutants in the conserved residues of the C-terminal region of the E1 ectodomain in the context of an infectious clone. We focused our analyses on two regions of interest. The first region is located in the middle of the E1 glycoprotein (between amino acid [aa] 270 and aa 291), which contains a conserved hydrophobic sequence and was proposed to constitute a putative fusion peptide. The second series of mutants was generated in the region from aa 314 to aa 342 (the aa314-342 region), which has been shown to contain two alpha helices (alpha 2 and alpha 3) by nuclear magnetic resonance studies. Of the 22 generated mutants, 20 were either attenuated or noninfectious. Several mutations modulated the virus's dependence on claudin-1 and the scavenger receptor BI coreceptors for entry. Most of the mutations in the putative fusion peptide region affected virus assembly. Conversely, mutations in the alpha-helix aa 315 to 324 (315-324) residues M318, W320, D321, and M322 resulted in a complete loss of infectivity without any impact on E1E2 folding and on viral assembly. Further characterization of the W320A mutant in the HCVpp model indicated that the loss of infectivity was due to a defect in viral entry. Together, these results support a role for E1 in modulating HCV interaction with its coreceptors and in HCV assembly. They also highlight the involvement of alpha-helix 315-324 in a late step of HCV entry. IMPORTANCE: HCV is a major public health problem worldwide. The virion harbors two envelope proteins, E1 and E2, which are involved at different steps of the viral life cycle. Whereas E2 has been extensively characterized, the function of E1 remains poorly defined. We characterized here the function of the putative fusion peptide and the region containing alpha helices of the E1 ectodomain, which had been previously suggested to be important for virus entry. We could confirm the importance of these regions for the virus infectivity. Interestingly, we found several residues modulating the virus's dependence on several HCV receptors, thus highlighting the role of E1 in the interaction of the virus with cellular receptors. Whereas mutations in the putative fusion peptide affected HCV infectivity and morphogenesis, several mutations in the alpha 2-helix region led to a loss of infectivity with no effect on assembly, indicating a role of this region in virus entry.
Keywords
hepatitis C virus, glycoprotein, envelope proteins, viral entry, viral assembly, ENVELOPE GLYCOPROTEIN E1, MEMBRANE-FUSION PROTEINS, SEMLIKI-FOREST-VIRUS, E2 GLYCOPROTEIN, CELL-CULTURE, SUBCELLULAR-LOCALIZATION, NEUTRALIZING ANTIBODIES, STRUCTURAL PROTEINS, APOLIPOPROTEIN-E, ENTRY

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Chicago
Moustafa, Rehab I, Juliano G Haddad, Lydia Linna, Xavier Hanoulle, Véronique Descamps, Ahmed Atef Ahmed Abouzeid Mesalam, Thomas F Baumert, et al. 2018. “Functional Study of the C-terminal Part of the Hepatitis C Virus E1 Ectodomain.” Journal of Virology 92 (20).
APA
Moustafa, R. I., Haddad, J. G., Linna, L., Hanoulle, X., Descamps, V., Mesalam, A. A. A. A., Baumert, T. F., et al. (2018). Functional study of the C-terminal part of the hepatitis C virus E1 ectodomain. JOURNAL OF VIROLOGY, 92(20).
Vancouver
1.
Moustafa RI, Haddad JG, Linna L, Hanoulle X, Descamps V, Mesalam AAAA, et al. Functional study of the C-terminal part of the hepatitis C virus E1 ectodomain. JOURNAL OF VIROLOGY. 2018;92(20).
MLA
Moustafa, Rehab I, Juliano G Haddad, Lydia Linna, et al. “Functional Study of the C-terminal Part of the Hepatitis C Virus E1 Ectodomain.” JOURNAL OF VIROLOGY 92.20 (2018): n. pag. Print.
@article{8576096,
  abstract     = {In the hepatitis C virus (HCV) envelope glycoproteins E1 and E2, which form a heterodimer, E2 is the receptor binding protein and the major target of neutralizing antibodies, whereas the function of E1 remains less characterized. To investigate E1 functions, we generated a series of mutants in the conserved residues of the C-terminal region of the E1 ectodomain in the context of an infectious clone. We focused our analyses on two regions of interest. The first region is located in the middle of the E1 glycoprotein (between amino acid [aa] 270 and aa 291), which contains a conserved hydrophobic sequence and was proposed to constitute a putative fusion peptide. The second series of mutants was generated in the region from aa 314 to aa 342 (the aa314-342 region), which has been shown to contain two alpha helices (alpha 2 and alpha 3) by nuclear magnetic resonance studies. Of the 22 generated mutants, 20 were either attenuated or noninfectious. Several mutations modulated the virus's dependence on claudin-1 and the scavenger receptor BI coreceptors for entry. Most of the mutations in the putative fusion peptide region affected virus assembly. Conversely, mutations in the alpha-helix aa 315 to 324 (315-324) residues M318, W320, D321, and M322 resulted in a complete loss of infectivity without any impact on E1E2 folding and on viral assembly. Further characterization of the W320A mutant in the HCVpp model indicated that the loss of infectivity was due to a defect in viral entry. Together, these results support a role for E1 in modulating HCV interaction with its coreceptors and in HCV assembly. They also highlight the involvement of alpha-helix 315-324 in a late step of HCV entry. 
IMPORTANCE: HCV is a major public health problem worldwide. The virion harbors two envelope proteins, E1 and E2, which are involved at different steps of the viral life cycle. Whereas E2 has been extensively characterized, the function of E1 remains poorly defined. We characterized here the function of the putative fusion peptide and the region containing alpha helices of the E1 ectodomain, which had been previously suggested to be important for virus entry. We could confirm the importance of these regions for the virus infectivity. Interestingly, we found several residues modulating the virus's dependence on several HCV receptors, thus highlighting the role of E1 in the interaction of the virus with cellular receptors. Whereas mutations in the putative fusion peptide affected HCV infectivity and morphogenesis, several mutations in the alpha 2-helix region led to a loss of infectivity with no effect on assembly, indicating a role of this region in virus entry.},
  articleno    = {e00939-18},
  author       = {Moustafa, Rehab I and Haddad, Juliano G and Linna, Lydia and Hanoulle, Xavier and Descamps, V{\'e}ronique and Mesalam, Ahmed Atef Ahmed Abouzeid and Baumert, Thomas F and Duverlie, Gilles and Meuleman, Philip and Dubuisson, Jean and Lavie, Muriel},
  issn         = {0022-538X},
  journal      = {JOURNAL OF VIROLOGY},
  language     = {eng},
  number       = {20},
  pages        = {19},
  title        = {Functional study of the C-terminal part of the hepatitis C virus E1 ectodomain},
  url          = {http://dx.doi.org/10.1128/jvi.00939-18},
  volume       = {92},
  year         = {2018},
}

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