Potential nectin-1 binding site on herpes simplex virus glycoprotein d

Area of Science:

• Virology
• Structural Biology
• Molecular Biology

Background:

• Herpes simplex virus (HSV) entry into host cells is a critical step in infection.
• Four glycoproteins (gD, gB, gH, and gL) are essential for HSV-mediated cell fusion.
• Glycoprotein D (gD) initiates fusion by binding to cellular receptors like nectin-1 or herpesvirus entry mediator (HVEM).

Purpose of the Study:

• To investigate the role of conformational changes in gD upon receptor binding in triggering HSV cell fusion.
• To determine if the transition of the gD N terminus to a hairpin loop upon HVEM binding is sufficient to mediate fusion.
• To identify regions of gD involved in nectin-1 and HVEM interactions.

Main Methods:

• Comparative structural analysis of gD alone and bound to HVEM.
• Engineering a disulfide bond in gD to "lock" the N-terminal loop conformation.
• Assessing fusion-triggering capabilities of the engineered gD mutant.
• Mutating residues surrounding Y38 in gD to analyze receptor binding and function.

Main Results:

• The engineered gD mutant (gD-A3C/Y38C) with a locked N-terminal loop did not trigger fusion independently.
• This mutant bound HVEM but failed to bind nectin-1, highlighting Y38's importance for nectin-1 interaction.
• Mutations in the region surrounding Y38 affected nectin-1 binding, suggesting this area is critical for nectin-1 interaction and distinct from HVEM binding sites.

Conclusions:

• The conformational change of the gD N terminus to a loop is necessary but not sufficient for triggering HSV fusion.
• Specific residues, like Y38, play critical roles in mediating interactions with distinct receptors (nectin-1).
• The study generated novel gD mutants with altered receptor usage, valuable for further dissecting HSV entry mechanisms.