Our research focuses on elucidating virus-host membrane interactions, with a particular emphasis on the role of fusion peptides (FPs). Enveloped viruses employ spike proteins to initiate infection, and in influenza, the highly conserved 23-amino acid FP of the hemagglutinin (HA) protein drives fusion of the viral and host membranes. We are investigating if the influenza FP clustering observed on in silico bilayers (Rice et al., Nat. Comm 2022; Rice et al, JPCB 2025) can be detected on supported lipid bilayers (SLB), and how lipid composition modulates this process. Our recent findings reveal a novel cholesterol-dependent localization in which FP added uniformly to a SLB patch exhibits in time, a segregation of FP to the edge of the bilayer. Specifically, when FP covalently labeled with rhodamine is incorporated into bilayers containing 50% cholesterol in POPC, it preferentially localizes to bilayer edges. FRAP experiments indicate diminished mobility of edge FP, consistent with the formation of higher order oligomers that may cross-link. Edge localization is absent in bilayers composed solely of POPC. We hypothesize that cholesterol lowers the energetic barrier for FP clustering, while curvature preference increases local FP concentration, together facilitating clustering through a mass-action mechanism. To further define the molecular determinants of this process, and the relationship of these processes to the membrane fusion of viral entry, we are conducting experiments on FP with altered amino acids known to alter fusion phenotypes to compare the potentials of mean force (from molecular dynamic simulations), and the edge-preference and mobility (from the experiments described earlier) to identify residues within the FP that drive curvature-associated clustering.
Sardar et al. (Sun,) studied this question.