Cholesterol and ceramide facilitate SARS-CoV-2 Spike protein-mediated membrane fusion

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 perturb the membrane structure to trigger fusion. Recent studies suggest 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. We found that cholesterol and ceramide both facilitated fusion, suggesting that targeting lipids could be effective against SARS-CoV-2. As proof of concept, we examined the effect of chlorpromazine (CPZ), an antipsychotic drug known to perturb membrane structure. We found that CPZ inhibited S-mediated membrane fusion and thus potentially SARS-CoV-2 entry.