Cholesterol Mediates Gp41 Linear Aggregation and Enhanced Membrane Curvature during HIV-1 Infection

The envelope glycoprotein gp41 of HIV-1 plays a critical role in mediating viral entry through membrane fusion. Although the viral membrane is highly enriched in cholesterol, which is essential for infectivity, the molecular mechanisms by which cholesterol regulates gp41 behavior and membrane remodeling remain poorly understood. Here, we employ molecular dynamics simulations to investigate the dynamics of gp41 in membranes with varying cholesterol concentrations. We demonstrate that cholesterol induces a conformational change in gp41, promoting an umbrella-like structure that facilitates linear, one-dimensional aggregation, in contrast to the compact, disc-shaped clusters formed in cholesterol-free bilayers. Furthermore, we reveal that cholesterol amplifies the local membrane curvature near gp41 clusters. Strikingly, at cholesterol molar fractions ≥30%, gp41-enriched sites undergo a transition to form highly curved membrane structures. These structures drive further accumulation of gp41 in the region of maximal curvature, significantly increasing local protein density and fostering the formation of larger, more stable clusters. These effects are attributed to cholesterol's modulation of intermolecular interactions of gp41 and membrane thickness, and the subsequent increase in local membrane curvature. Our findings provide a comprehensive molecular-level framework for cholesterol-mediated facilitation of HIV-1 entry, linking lipid composition to protein clustering and membrane curvature generation, and suggest novel strategies for inhibiting viral fusion.