Cholesterol and Ceramide Facilitate Membrane Fusion Mediated by the Fusion Peptide of the SARS-CoV-2 Spike Protein

Abstract

SARS-CoV-2 entry into host cells is mediated by the Spike (S) protein of the viral envelope. The S protein is composed of two subunits: S1 that induces binding to the host cell via its interaction with the ACE2 receptor of the cell surface and S2 that triggers fusion between viral and cellular membranes. Fusion by S2 depends on its heptad repeat domains that bring membranes close together and its fusion peptide (FP) that interacts with and perturbs the membrane structure to trigger fusion. Recent studies have suggested that cholesterol and ceramide lipids from the cell surface may facilitate SARS-CoV-2 entry into host cells, but their exact mode of action remains unknown. We have used a combination of in vitro liposome–liposome and in situ cell–cell fusion assays to study the lipid determinants of S-mediated membrane fusion. Our findings reveal that both cholesterol and ceramide lipids facilitate fusion, suggesting that targeting these lipids could be effective against SARS-CoV-2. As a proof of concept, we examined the effect of chlorpromazine (CPZ), an antipsychotic drug known to perturb membrane structure. Our results show that CPZ effectively inhibits S-mediated membrane fusion, thereby potentially impeding SARS-CoV-2 entry into the host cell.

Bis(Monoacylglycero)Phosphate Promotes Membrane Fusion Facilitated by the SARS-CoV-2 Fusion Domain

“…Alongside anionic lipids, both POPE and CHOL have been implicated in viral fusion previously with the lipids found to impact membrane curvature and fluidity, respectively. − Unexpectedly, neither POPE nor CHOL displayed any positive impact on the ability of the FD to elicit fusion (Figure S3). This was a particular surprise as in vivo -based studies have shown cholesterol to positively influence SARS-CoV-2 fusion. , The discrepancy in results could be due to a greater complexity of membrane lipid compositions involved in such studies or the more likely scenario by where the formation of lipid rafts results in the localization of the ACE2 receptor on the cell surface. Hence, rather than direct protein–lipid interactions between the SARS-CoV-2 spike protein and the target cell membrane, it is in fact the membranes’ impact on the ACE2 receptor that may promote fusion in such cases.…”

Link Between the G Protein-Coupled Receptor (GPCR), SARS-CoV-2 Spike Protein, ACE2, Vaccines, and Long COVID

“…Niort et al also elucidate that the repeated heptad domains of the S2 subunit bring the viral and cellular membranes close together while the fusion peptide interacts with and perturbs the membrane structure. This is facilitated by cholesterol and ceramide lipids from the cell surface, which aid in the membrane fusion process [15]. Furthermore, the formation of a six-helical bundle via the two-heptad repeat domain in the S2 subunit, as described by Huang et al, indicates significant structural rearrangements during the fusion process [16].…”