Acidic Lipid, NBD-PG has Crucial Effect on the Voltage-Dependence of Virus Fusion

Abstract

Previously we have shown that cell-cell fusion mediated by Class II and Class III proteins is voltage-dependent, whereas fusion of cells expressing Class I fusion protein is not affected by voltage. Moreover, by testing chimeras consisting of the ectodomain of a Class I protein and the transmembrane domain (TMD) of a Class III protein, we found that TMD was the candidate for the voltage sensor in fusion mediated by Class II and Class III viral proteins.We hypothesized that, since flip-flop of acidic lipids inherently potential-dependent, incorporation of these lipids into a target membrane should facilitate the fusion at trans-positive membrane potential through affecting the TMD.To test this hypothesis we incorporated a fluorescent acidic lipid (NBD-PG) into target cells membrane and allowed fusion with VSV-G effector cells maintained at negative (−40mV) or positive potential (+40mV) created by the ionophore, SQI-Pr.We determined that when NPD-PG was present in the target (or effector) cell membranes, the extent of fusion was the same at negative and positive potentials, whereas fusion with untreated cells was inhibited in the presence of ionophore.Our result show that accumulation of acidic lipids in membranes during fusion directly affects to potential-dependence of fusion.