Inhibition of Membrane Fusion by Lysophosphatidylcholine

The ability of lysophosphatidylcholine to inhibit membrane fusion at subsolubilizing concentrations (between 1 and 9 mol % with respect to the membrane lipids) was examined. Fusion between N-methyldioleoylphosphatidylethanolamine (DOPE) large unilamellar vesicles (LUV) and fusion between Sendai virus and N-methyl-DOPE LUV were measured. A contents mixing fusion assay was used for LUV fusion (ANTS/DPX), and a lipid mixing assay (octadecylrhodamine B) was used for the virus fusion experiments. Lysophosphatidylcholine was effective at inhibiting both LUV fusion and Sendai virus/LUV fusion. Lysophosphatidylcholine also inhibited leakage from N-methyl-DOPE LUV, 31P nuclear magnetic resonance data were obtained of N-methyl-DOPE in the presence of lysophosphatidylcholine. Lysophosphatidylcholine stabilized the lamellar phase and reduced the incidence of nonlamellar structures at all temperatures. The destabilization of nonlamellar structures with a negative radius of curvature may be a mechanism for inhibition of fusion by lysophosphatidylcholine in these systems.