Reconstructing a Missing Link of HIV-1 Assembly: HIV-1 Envelope-Matrix Interactions in a Native Viral Context

Area of Science:

• Virology
• Structural Biology
• Molecular Biology

Background:

• The HIV-1 envelope glycoprotein (Env) mediates viral entry and fusion.
• Env incorporation into virions is regulated by its cytoplasmic tail (Env-CT) and the Gag matrix (MA) domain.
• Controlling Env copy number is crucial for reducing viral antigenicity.

Purpose of the Study:

• To elucidate the molecular mechanisms governing Env incorporation onto HIV-1 virions.
• To investigate the role of Env-CT and MA interactions in Env recruitment and copy number regulation.
• To understand how Gag maturation affects Env association and subsequent fusion activity.

Main Methods:

• Cryo-electron tomography (cryo-ET) and subtomogram averaging were employed to visualize Env-MA complexes in intact viral particles.
• Molecular dynamics simulations were used to analyze the Env-MA association.
• Mutational analysis was performed to confirm the impact of specific interactions on Env incorporation.

Main Results:

• Full-length Env-CT was resolved over MA trimers, particularly in regions of lattice discontinuity.
• The conserved Kennedy-sequence motif in Env-CT was identified as a critical linker between Env and MA.
• Specific Env-CT and MA interactions were confirmed to influence Env incorporation levels.
• Gag maturation was shown to release MA lattice restraints, promoting Env clustering and enhancing fusion.

Conclusions:

• The Kennedy-sequence motif is essential for linking Env to the MA lattice during HIV-1 assembly.
• Env incorporation and subsequent fusion activity are modulated by Env-MA interactions and Gag maturation.
• Understanding these interactions provides insights into HIV-1 assembly and potential therapeutic targets.