title: Vesicular stomatitis virus G protein acquires pH-independent fusion activity during transport in a polarized endometrial cell line.
abstract: Entry of vesicular stomatitis virus (VSV), the prototype member of the rhabdovirus family, occurs by receptor-mediated endocytosis. Subsequently, during traversal through the endosomal compartments, the VSV G protein acquires a low-pH-induced fusion-competent form, allowing for fusion of the viral membrane with endosomal and lysosomal membranes. This fusion event releases genomic RNA into the cytoplasm of the cell. Here we provide evidence that the VSV G protein acquires a fusion-competent form during exocytosis in a polarized endometrial cell line, HEC-1A. VSV infection of HEC-1A cells results in high viral yields and giant cell formation. Syncytium formation is blocked in a concentration-dependent manner by treatment with the lysosomotropic weak base ammonium chloride, which raises intravesicular pH. Virus release is somewhat delayed by treatment with ammonium chloride, but virus yields gradually reach those of control cells. In addition, inhibition of vacuolar H(+)-ATPases by treatment with bafilomycin A1 also inhibited cell to cell fusion without altering virus yields. Virions released from infected HEC cells were themselves not fusion competent, since viral entry required an active H(+)-ATPase and a low-pH-induced conformational change in the viral G protein. Thus, the conformation change leading to fusion competence during exocytotic transport is reversible and reverts during or after release of the virion from the infected cell.
authors.affiliation: Department of Microbiology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: P C
authors.initials: PC
authors.lastname: Roberts
authors.forename: T
authors.initials: T
authors.lastname: Kipperman
authors.forename: R W
authors.initials: RW
authors.lastname: Compans
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001692:Biological Transport; D002460:Cell Line; D016764:Cell Polarity; D002522:Chlorocebus aethiops; D006224:Cricetinae; D004285:Dogs; D004717:Endometrium / Q000166:cytology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015726:Giant Cells; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D018942:Macrolides; D008561:Membrane Fusion / Q000502:physiology*; D008562:Membrane Glycoproteins; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014407:Tumor Cells, Cultured; D025262:Vacuolar Proton-Translocating ATPases; D014709:Vero Cells; D014721:Vesicular stomatitis Indiana virus / Q000378:metabolism*; D014759:Viral Envelope Proteins / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D004791:Enzyme Inhibitors; C028391:G protein, vesicular stomatitis virus; D018942:Macrolides; D008562:Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; D014759:Viral Envelope Proteins; C040929:bafilomycin A1; D025262:Vacuolar Proton-Translocating ATPases; D006180:Proton-Translocating ATPases