Revisit the Correlation between the Elastic Mechanics and Fusion of Lipid Membranes

Membrane fusion is a vital process in key cellular events. The fusion capability of a membrane depends on its elastic properties and varies with its lipid composition. It is believed that as the composition varies, the consequent change in C0 (monolayer spontaneous curvature) is the major factor dictating fusion, owing to the associated variation in GEs (elastic energies) of the fusion intermediates (e.g. stalk). By exploring the correlations among fusion, C0 and Kcp (monolayer bending modulus), we revisit this long-held belief and re-examine the fusogenic contributions of some relevant factors. We observe that not only C0 but also Kcp variations affect fusion, with depression in Kcp leading to suppression in fusion. Variations in GEs and inter-membrane interactions cannot account for the Kcp-fusion correlation; fusion is suppressed even as the GEs decrease with Kcp, indicating the presence of factor(s) with fusogenic importance overtaking that of GE. Furthermore, analyses find that the C0 influence on fusion is effected via modulating GE of the pre-fusion planar membrane, rather than stalk. The results support a recent proposition calling for a paradigm shift from the conventional view of fusion and may reshape our understanding to the roles of fusogenic proteins in regulating cellular fusion machineries.