A Highly Conserved gp120 Inner Domain Residue Modulates Env Conformation and Trimer Stability

Area of Science:

• Virology
• Structural Biology
• Immunology

Background:

• HIV-1 envelope glycoprotein (Env) conformational changes are essential for viral entry.
• Highly conserved residues in the gp120 inner domain regulate these transitions.
• Residue W69 is critical for Env processing, CD4 binding, and CD4-induced antibody recognition.

Purpose of the Study:

• To investigate the role of W69 hydrophobicity in HIV-1 Env conformational changes.
• To determine how alterations in W69 affect Env processing, CD4 binding, and CD4-induced antibody recognition.
• To explore compensatory mutations that restore Env function.

Main Methods:

• Site-directed mutagenesis of W69 with residues of varying hydrophobicity.
• Assessment of Env processing and CD4 binding.
• Structural analysis of wild-type and mutant Env proteins using X-ray crystallography and cryo-electron microscopy.
• Evaluation of antibody binding and neutralization.

Main Results:

• W69 hydrophobicity is vital for Env processing, CD4 binding, and the transition to the CD4-bound conformation.
• Mutations at W69, particularly to alanine or glycine, severely impaired these functions.
• Restoration of function was observed with increasing aliphatic chain length and aromatic residues.
• A compensatory mutation (S115W) restored CD4 binding in the W69A mutant.
• Structural studies revealed increased mobility in key regions of the W69A/S115W double mutant.

Conclusions:

• W69 plays a critical role in mediating HIV-1 Env conformational changes upon CD4 binding.
• The hydrophobicity of W69 is a key determinant for Env function and viral entry.
• Understanding W69's role provides insights for designing novel immunogens targeting HIV-1 Env.