Membrane Fusion between a Giant Vesicle and Small Enveloped Particles: Possibilities for the Application to Construct Model Cells

Giant unilamellar vesicles (GUVs) are biochemical compartments enclosed with phospholipid bilayers. GUVs are expected to be materials for construction and investigation of artificial cell models. There, fusion phenomena between GUVs and smaller vesicles (referred to as "asymmetric fusion" here) seem to have some potential for utilization of the transporters bringing reagents and membrane proteins to GUVs. In the present work, by using microscopic observation on individual GUVs, we demonstrate asymmetric fusions in the two simple systems: GUVs vs. large unilamellar vesicles (LUVs), and GUVs vs. enveloped virus particles. In the former, the fusion is caused by amphipathic peptides, and we found the condition in which the asymmetric fusion was preferred; the fusion is controllable by having a difference in content ratios of acid lipids between GUVs and LUVs. In the latter, the fusion between GUVs and enveloped virus particles was induced by pH-sensitive fusogenic glycoproteins. The confocal microscopic observation of the asymmetric fusion of GUVs and the particles showed that the particle fused with artificial GUV membranes in naturally preferable conditions: occurring pH and acid lipid contents. The possibilities to preparation giant proteoliposomes by using these systems will be suggested, leading to an application for constructing cell models