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Journal of Virology, December 1999, p. 10447-10457, Vol. 73, No. 12
Department of Microbiology and Immunology,
Emory University School of Medicine, Atlanta, Georgia 30322
Received 28 May 1999/Accepted 19 August 1999
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.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Vesicular Stomatitis Virus G Protein Acquires pH-Independent
Fusion Activity during Transport in a Polarized Endometrial Cell
Line
*
Corresponding author. Present address: Department of
Immunology and Microbiology, Wayne State University School of Medicine, Detroit, MI 48201. Phone: (313) 577-6494. Fax: (313) 577-1155. E-mail:
proberts{at}med.wayne.edu.
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