Induction of Cell-Cell Fusion by Ebola Virus Glycoprotein: Low pH Is Not a Trigger

• DOI: 10.1371/journal.ppat.1005373
• Publication Date: 2016-01-05T18:52:33Z
• Authors: Ruben M. Markosyan; Chunhui Miao; Yi-Min Zheng; Gregory B. Melikyan; Shan-Lu Liu; Fredric S. Cohen
• Keywords: Cell fusion; Cathepsin L

Ebola virus (EBOV) is a highly pathogenic filovirus that causes hemorrhagic fever in humans and animals. Currently, how EBOV fuses its envelope membrane within an endosomal to cause infection poorly understood. We successfully measure cell-cell fusion mediated by the protein, GP, assayed transfer of both cytoplasmic dyes. A small molecule inhibitor, neutralizing antibody, as well mutations GP known reduce viral infection, all greatly fusion. By monitoring redistribution aqueous dyes between cells electrical capacitance measurements, we discovered GP-mediated pores do not readily enlarge—a marked difference from behavior other proteins. must be cleaved late endosome-resident cathepsins B or L order become fusion-competent. Cleavage cell surface-expressed appears occur endosomes, evidenced block imposed cathepsin inhibitors, agents raise pH, inhibitor anterograde trafficking. Treating effector with recombinant soluble thermolysin, which cleaves into active form, increases extent fusion, suggesting fraction cleaved. Whereas rate increased brief exposure acidic does at neutral pH. Importantly, independent external pH experiments activity blocked thermolysin. These results imply low promotes through well-known pH-dependent cathepsins; induced process fundamentally The system has revealed some previously unappreciated features entry, could elucidated context entry.