Cholesterol Modulates Membrane Properties and the Interaction of gp41 Fusion Peptide To Promote Membrane Fusion

Abstract

An envelope glycoprotein, gp41, is crucial for the entry of human immunodeficiency virus (HIV) into the host cell. The 20−23 N-terminal amino acid sequence of gp41 plays an important role in promoting fusion between viral and host cells. Interestingly, the structure and function of the fusion peptide are extremely sensitive to the characteristics of the lipid environment. In this present work, we have extensively utilized steady-state and time-resolved fluorescence spectroscopy in tandem with molecular dynamics simulation to elucidate peptide binding and peptide-induced perturbation to the membrane. We have used two depth-dependent fluorescence probes, 1,6-diphenyl-1,3,5-hexatriene (DPH) and its trimethylammonium derivative (TMA-DPH), to monitor the effect of peptide binding along the bilayer normal and have reconciled the experimental observation with the insights from the simulated molecular events. We have further monitored the effect of membrane cholesterol on peptide-induced membrane perturbation. The molecular dynamics simulation data show that the peptide alters the membrane properties in the vicinity of the peptide and it penetrates to a larger extent into the bilayer when the membrane contains cholesterol. Our results clearly elucidate that cholesterol alters the membrane physical properties in favor of membrane fusion and interaction pattern of the fusion peptide with the membrane in a concentration-dependent fashion. The role of cholesterol is specifically important as the host eukaryotic cells contain a decent amount of cholesterol that might be critical for the entry of HIV into the host cells.

Single-virus content mixing assay reveals cholesterol-enhanced influenza membrane fusion efficiency

“…These simplified membranes enable researchers to control target membrane compositions to systematically study the impact of various membrane components on viral fusion. Cholesterol is one membrane component that is of significant interest as it is hypothesized that the cholesterol-rich regions of host membranes facilitate viral fusion peptide engagement, which can promote membrane fusion (9)(10)(11), and vesicle fusion studies have found that cholesterol enhances fusion and pore formation (12)(13)(14). In bulk studies, where fusion between virions and vesicles is observed by fluorescence dequenching and an overall increase in fluorescence signal, cholesterol speeds the rates of IAV lipid mixing (hemifusion) and content mixing (pore formation) (15).…”

Target membrane cholesterol modulates single influenza virus membrane fusion efficiency but not rate

“…It has also been demonstrated in bulk studies that cholesterol in target vesicles speeds the rates of IAV hemifusion and fusion pore formation (8), which may be facilitated by the negative spontaneous curvature of cholesterol (9). For other enveloped viruses like human immunodeficiency virus (HIV), fusion peptide insertion is facilitated by cholesterol in the target membrane, which has led to speculation that cholesterol may play some role in facilitating HA engagement for IAV (10)(11)(12). Given that cholesterol may stabilize each fusion intermediate, bulk measurements cannot deconvolve the mechanistic details of cholesterol's influence on IAV fusion.…”

Entry Inhibitors: Efficient Means to Block Viral Infection

“…2 Schematic representation of the fusion reaction profile considering the lipid-stalk model of membrane fusion. The figure has been adapted from reference Meher et al ( 2019b ) with permission …”

“…6 . Initially, gp160 undergoes receptor-mediated proteolytic cleavage into two subunits viz., gp120 (the surface protein) and gp41 (the transmembrane protein) (Meher et al 2019b ; Skehel and Wiley 2000 ; White et al 2008 ). The heterodimer, gp120 and gp41 organize on the viral membrane as a trimer of three gp41 subunits and three gp120 subunit through non-covalent interaction (Berkhout et al 2012 ).…”