Membrane Order Regulates SNARE Mediated Vesicle Fusion in Insulin-Secreting Cells

Recently, a model has been proposed for how Ca2+ influx into the cell triggers fusion of secretory vesicles with the plasma membrane (Kiessling et al., NSMB 25:911[2018]). In this model, Ca2+ mediated binding of synaptotagmin-1's C2 domains to the membrane causes a disordering of the acyl chains in the membrane, which shifts the membrane-anchored SNARE Syx1 to a more fusogenic, stiffer conformation. In model membranes, lipid order and its effect on SNARE conformation and SNARE-mediated fusion efficiencies were previously observed by changing the acyl-chain saturation of the employed lipids.