Bilayer Mechanics of Protein-Induced Lipid Phase Separation

Recent experiments on the mechanosensitive channel of large conductance (MscL), as well as other membrane proteins, have suggested that membrane protein function can be mechanically modulated, in the highly heterogeneous membrane environments typically found in vivo, through the formation of lipid "platforms" of defined lipid composition around membrane proteins. We show here that the interplay of lipid bilayer mechanics and protein-induced lipid phase separation provides one possible physical origin of such lipid platforms. At the mean-field level, the lipid platforms surrounding MscL can be captured by coupling the energetics of protein-induced lipid bilayer thickness deformations to the Ginzburg-Landau model of phase separation. We find that protein-induced lipid phase separation can yield a rich dependence of bilayer-thickness-mediated interactions between membrane proteins on lipid bilayer composition. Our work provides a theoretical framework describing how the heterogeneous lipid compositions found in living cells affect the mechanics of bilayer-proteins interactions.