PHOSPHATIDYLINOSITOL-DEPENDENT MEMBRANE-FUSION INDUCED BY A PUTATIVE FUSOGENIC SEQUENCE OF EBOLA-VIRUS

The membrane-interacting abilities of three sequences representing the putative fusogenic subdomain of the Ebola virus transmembrane protein have been investigated, In the presence of calcium, the sequence EBOG E (GAAIGLAWIPYFGPAAE) efficiently fused unilamellar vesicles composed of phosphatidylcholine, phosphatidylethanolamine, cholesterol, and pho sphatidylinositol (molar ratio, 2:1:1:0.5), a mixture that roughly res embles the lipid composition of the hepatocyte plasma membrane. Analys is of the lipid dependence of the process demonstrated that the fusion activity of EBO,, was promoted by phosphatidylinositol but not by oth er acidic phospholipids. In comparison, EBOEA (EGAAIGLAWIPYFGPAA) and EBOEE (EGAAIGLAWIPYFGPAAE) sequences, which are similar to EBOGE excep t that they bear the negatively charged glutamate residue at the N ter minus and at both the N and C termini, respectively, induced fusion to a lesser extent. As revealed by binding experiments, the glutamate re sidue at the N terminus severely impaired peptide-vesicle interaction. In addition, the fusion-competent EBOGE sequence did not associate si gnificantly with vesicles lacking phosphatidylinositol. Tryptophan flu orescence quenching by vesicles containing brominated phospholipids in dicated that the EBO,, peptide penetrated to the acyl chain level only when the membranes contained phosphatidylinositol. We conclude that b inding and further penetration bf the Ebola virus putative fusion pept ide into membranes might be governed by the nature of the N-terminal r esidue and by the presence of phosphatidylinositol in the target membr ane. Moreover, since insertion of such a peptide Leads to membrane des tabilization and fusion, the present data would be compatible with the involvement of this sequence in Ebola virus fusion.