Functional analysis of cell surface-expressed hepatitis C virus E2 glycoprotein

Area of Science:

• Virology
• Cell Biology
• Protein Biochemistry

Background:

• Hepatitis C virus (HCV) glycoproteins E1 and E2 are typically retained in the endoplasmic reticulum (ER).
• Secretion of E2 can be achieved by C-terminal truncation, suggesting the involvement of a transmembrane anchor sequence.
• Understanding E1 and E2 function is crucial for developing antiviral strategies.

Purpose of the Study:

• To investigate the cell surface expression and functional properties of a modified HCV E2 glycoprotein.
• To explore the role of E2 in viral entry and potential fusion mechanisms.
• To identify the HCV fusion peptide and its contribution to viral entry.

Main Methods:

• Construction and expression of a chimeric glycoprotein (E2661-HATMCT) fusing HCV E2 residues to influenza A virus hemagglutinin (HA) domains.
• Assessment of E2661-HATMCT cell surface expression and binding to antibodies and CD81.
• Analysis of pH-dependent conformational changes and cell fusion assays with CD81-positive cells.
• Investigation of potential HCV fusion peptide within the E1 glycoprotein.

Main Results:

• The chimeric E2661-HATMCT glycoprotein was successfully expressed on the cell surface.
• E2661-HATMCT exhibited proper folding, binding to conformation-dependent antibodies and soluble CD81.
• pH-dependent conformational changes were observed, suggesting acid-mediated fusion, but cell fusion was not induced.
• A conserved hydrophobic region in E1 was proposed as the HCV fusion peptide.

Conclusions:

• The E2 ectodomain can be correctly folded and targeted to the cell surface when fused to appropriate domains.
• The E2-CD81 interaction is important but insufficient for mediating cell fusion, indicating other factors are involved.
• A hydrophobic region in E1 likely functions as the HCV fusion peptide, crucial for viral entry.