Membrane Deformation Switching of an Endocytic Protein by Membrane Electrostatic Charge and Packing

Bin-Amphiphysin-Rvs (BAR) domain proteins, including endophilin, deform membrane into tubules or vesicles for cellular processes, including endocytosis. The endophilin BAR domain has amphipathic helices, and degrees of insertion of these helices by mutations or phosphorylation cause a switch between tubule and vesicle formation. However, the membrane phospholipid properties causing switching remains unclear. We examined membrane deformation by endophilin using liposomes from various sources, including the plasma membrane, and found that endophilin vesiculated plasma membrane-derived liposomes. Endophilin vesiculated the plasma membrane-inspired reconstituted liposomes, which contained a small amount of charged phospholipids that resulted in uneven binding of endophilin. In contrast, the increase of charged phospholipids including phosphatidylinositol 4,5-bisphosphate resulted in tubulation by the increased binding of endophilin. Either tubulation or vesiculation required certain packing defects by the unsaturated acyl chains of phospholipids. Therefore, endophilin binding to membrane based on membrane charge density was the switch between tubulation and vesiculation, suggesting the importance of charge density in membrane deformation.