Sphingomyelin and cholesterol promote HIV-1 gp41 pretransmembrane sequence surface aggregation and membrane...

Area of Science:

• Structural biology
• Virology
• Biochemistry

Background:

• The gp41 glycoprotein subunit's interfacial sequence is crucial for human immunodeficiency virus type 1 (HIV-1) fusion and virion incorporation.
• Understanding the role of this sequence in membrane interaction is key to deciphering HIV-1 entry mechanisms.

Purpose of the Study:

• To investigate the function of the HIV-1 gp41 interfacial sequence (HIV(c) peptide) in membrane destabilization and fusion.
• To elucidate the impact of specific lipid components (sphingomyelin and cholesterol) on peptide-lipid interactions and viral fusion.

Main Methods:

• Liposome pore formation and lipid mixing assays using model membranes mimicking the HIV-1 envelope lipid composition.
• Surface aggregation assays with fluorescently labeled peptides.
• Studies using planar supported lipid bilayers with fluorescent phospholipid analogs.

Main Results:

• The HIV(c) peptide formed lytic pores in mixed lipid vesicles (POPC:SPM:Chol) and promoted lipid mixing at low peptide concentrations.
• Sphingomyelin (SPM) sustained pore formation, while cholesterol (Chol) specifically promoted fusion activity.
• SPM and Chol facilitated HIV(c) self-aggregation within membranes, with peptides observed in ordered lipid domains.

Conclusions:

• The HIV-1 gp41 pretransmembrane sequence plays a significant role in destabilizing lipid bilayers at fusion sites.
• Lipid composition, particularly SPM and Chol, modulates the peptide's aggregation and its effects on membrane fusion and pore formation.
• Findings suggest the pretransmembrane sequence contributes to gp41 clustering and membrane fusion initiation during HIV-1 entry.