Capability of Polyunsaturated Phosphatidylcholine for Non-raft Domain Formation in Cholesterol-containing Lipid Bilayers

Polyunsaturated lipids are one of major components in cell membranes, but have attracted less interests compared to lipids with saturated or monosaturated acyl chains. A recent study reported that polyunsaturated phosphatidylethanolamine (PE) induces the non-raft domain formation in lipid bilayers comprising fluid phosphatidylcholine (PC) and cholesterol (Chol) via the segregation of polyunsaturated PE. In this study, we investigated the effects of polyunsaturated PC on the non-raft domain formation. We prepared supported lipid bilayers (SLBs) comprising polyunsaturated PC, monounsaturated PC (POPC), and Chol. Observation by fluorescence microscopy and atomic force microscopy showed that polyunsaturated PCs caused the domain formation, depending on their concentration and the degree of unsaturation. However, their effectivity was less than polyunsaturated PEs. Intermolecular interaction at the hydrophobic part induced the segregation of polyunsaturated PC from the Chol-containing region, although competing with the umbrella effect due to the hydrophilic headgroup of PC which favors the association with Chol.