Fusogenic properties of uncleaved spike protein of murine coronavirus JHMV.
We have tested the fusogenic properties of cleaved and uncleaved spike (S) protein of murine coronavirus (MCV) JHMV variant cl-2 by expressing the S protein by recombinant vaccinia viruses (RVVs). The amino acid sequence of the putative cleavage site of cl-2 S protein, Arg-Arg-Ala-Arg-Arg, was replaced by Arg-Thr-Ala-Leu-Glu by in vitro mutagenesis of cl-2 S gene. The RVVs having cl-2 S gene [RVV t(+)] or mutated cl-2 S gene [RVV t(-)] were tested for their ability to induce fusion as well as cleavability in DBT cells. After inoculation with RVV t(+) onto DBT cells, the fusion formation was first observed at 8 h postinoculation (p.i.) and spread throughout the whole culture by 24 h. In cells infected with RVV t(-), fusion appeared by 2 h and most of cells were fused by 30 h p.i. The S protein and its cleavage products were detected in DBT cells expressing wild type S protein. However, no cleavage products of the S protein were detected in RVV t(-) infected cells producing mutated S protein, even though fusion was clearly visible. These results suggest that the cleavage event of JHMV-S protein of MCV is not a prerequisite for fusion formation, but that it enhances fusion.
Taguchi
F
F
National Institute of Neuroscience, NCNP, Tokyo, Japan.
Ikeda
T
T
Saeki
K
K
Kubo
H
H
Kikuchi
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001254:Astrocytoma; D001483:Base Sequence; D002459:Cell Fusion; D003588:Cytopathogenic Effect, Viral; D010450:Endopeptidases / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D006517:Murine hepatitis virus / Q000235:genetics / Q000502:physiology*; D016297:Mutagenesis, Site-Directed; D011499:Protein Processing, Post-Translational; D064370:Spike Glycoprotein, Coronavirus; D014407:Tumor Cells, Cultured / Q000382:microbiology; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism*
D008562:Membrane Glycoproteins; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; C578557:spike glycoprotein, SARS-CoV; C578553:spike protein, mouse hepatitis virus; D010450:Endopeptidases