Furin is involved in baculovirus envelope fusion protein activation.
The Spodoptera exigua multicapsid nucleopolyhedrovirus (SeMNPV) Se8 gene was recently shown to encode the viral envelope fusion (F) protein. A 60-kDa C-terminal subunit (F1) of the 76-kDa primary translation product of this gene was found to be the major envelope protein of SeMNPV budded virus (BV) (W. F. J. IJkel, M. Westenberg, R. W. Goldbach, G. W. Blissard, J. M. Vlak, and D. Zuidema, Virology 275:30-41, 2000). A specific inhibitor was used to show that furin is involved in cleavage of the precursor envelope fusion (F0) protein. BV produced in the presence of the inhibitor possesses the uncleaved F0 protein, while an F protein with a mutation in the furin cleavage site was translocated to the plasma membrane but lost its fusogenic activity. These results indicate that cleavage of F0 is required to activate the SeMNPV F protein and is necessary for BV infectivity. Specific antibodies against F1 and against the putative N terminus (F2) of the primary translation product were used to show that the F protein is BV specific and that BVs contain both the 60- (F1) and 21-kDa (F2) cleavage products. In nonreducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis both subunits migrate as a single 80-kDa protein, indicating that the subunits remain associated by a disulfide linkage. In addition, the presence of the F protein predominantly as a monomer suggests that disulfide links are not involved in oligomerization. Thus, the envelope fusion protein from group II nucleopolyhedroviruses of baculoviruses has properties similar to those of proteins from a number of vertebrate viruses.
Westenberg
Marcel
M
Laboratory of Virology, Wageningen University and Research Center, 6709 PD Wageningen, The Netherlands.
Wang
Hualin
H
IJkel
Wilfred F J
WF
Goldbach
Rob W
RW
Vlak
Just M
JM
Zuidema
Douwe
D
D000818:Animals; D016367:Baculoviridae / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D002460:Cell Line; D045683:Furin; D009154:Mutation; D011498:Protein Precursors / Q000378:metabolism; D018411:Spodoptera; D013381:Subtilisins / Q000378:metabolism*; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism*; D014760:Viral Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication
D011498:Protein Precursors; D014759:Viral Envelope Proteins; D014760:Viral Fusion Proteins; D013381:Subtilisins; D045683:Furin