Proteolytic cleavage of bovine herpesvirus 1 (BHV-1) glycoprotein gB is not necessary for its function in BHV-1 or pseudorabies virus

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Item Type:	Article
Title:	Proteolytic cleavage of bovine herpesvirus 1 (BHV-1) glycoprotein gB is not necessary for its function in BHV-1 or pseudorabies virus
Creators Name:	Kopp, A., Blewett, E., Misra, V. and Mettenleiter, T.C.
Abstract:	Glycoprotein B homologs represent the most highly conserved group of herpesvirus glycoproteins. They exist in oligomeric forms based on a dimeric structure. Despite the high degree of sequence and structural conservation, differences in posttranslational processing are observed. Whereas gB of herpes simplex virus is not proteolytically processed after oligomerization, most other gB homologs are cleaved by a cellular protease into subunits that remain linked via disulfide bonds. Proteolytic cleavage is common for activation of viral fusion proteins, and it has been shown that herpesvirus gB homologs are essential for membrane fusion events during infection, e.g., virus penetration and direct viral cell-to-cell spread. To analyze the importance of proteolytic cleavage for the function of gB homologs, we isolated a mutant bovine herpesvirus 1 (BHV-1) expressing a BHV-1 gB that is no longer proteolytically processed because of a deletion of the proteolytic cleavage site and analyzed its phenotype in cell culture. We showed previously that BHV-1 gB can functionally substitute for the homologous glycoprotein in pseudorabies virus (PrV), based on the isolation of a PrV gB-negative PrV recombinant that expresses BHV-1 gB (A. Kopp and T. C. Mettenleiter, J. Virol, 66:2754-2762, 1992). Therefore, we also isolated a mutant PrV lacking PrV gB but expressing a noncleavable BHV-1 gB. Our results show that cleavage of BHV-1 gB is not essential for its function in either a BHV-1 or a PrV background. Compared with the PrV recombinant expressing cleavable BHV-1 gB, deletion of the cleavage site in the recombinant PrV did not detectably alter the viral phenotype, as analyzed by plaque assays, one-step growth kinetics, and penetration kinetics. In the BHV-1 mutant, the uncleaved BHV-1 gB was functionally equivalent to the wild-type protein with regard to penetration and showed only slightly delayed one-step growth kinetics compared with parental wild-type BHV-1. However, the resulting plaques were significantly smaller, indicating a role for proteolytic cleavage of BHV-1 gB in cell-to-cell spread of BHV-1.
Keywords:	Amino Acid Sequence, Base Sequence, Bovine Herpesvirus 1, Cultured Cells, Kidney, Membrane Fusion, Molecular Sequence Data, Mutation, Plaque Assay, Post-Translational Protein Processing, Sequence Deletion, Structure-Activity Relationship, Suid Herpesvirus 1, Viral Genome, Viral Proteins, Virus Replication, Animals, Cattle
Source:	Journal of Virology
ISSN:	0022-538X
Publisher:	American Society for Microbiology
Volume:	68
Number:	3
Page Range:	1667-1674
Date:	March 1994
Official Publication:	http://jvi.asm.org/cgi/content/abstract/68/3/1667
PubMed:	View item in PubMed

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