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A cellular function is required for pseudorabies virus envelope glycoprotein processing and virus egress
M E Whealy1, A K Robbins, F Tufaro
1Du Pont Merck Pharmaceutical Company, Viral Diseases Research, Wilmington, Delaware 19880-0328.
Abstract:
The mouse L-cell mutant gro29 is defective for egress of herpes simplex virus type 1 (HSV-1) virions and is significantly reduced in HSV-1 glycoprotein export (B. W. Banfield and F. Tufaro, J. Virol. 64:5716-5729, 1990). In this report, we demonstrate that pseudorabies virus (PRV), a distantly related alphaherpesvirus, shows a distinctive set of defects after infection of gro29 cells. Specifically, we identify defects in the rate and extent of viral glycoprotein export, infectious particle formation, plaque formation, and virus egress. The initial rate of viral glycoprotein synthesis was unaffected in gro29 cells, but the extent of export from the endoplasmic reticulum to the Golgi apparatus was impaired and export through the Golgi apparatus became essentially blocked late in infection. Moreover, by using a secreted variant of a viral membrane protein, we found that export from the Golgi apparatus out of the cell was also defective in gro29 cells. PRV does not form plaques on gro29 monolayers. A low level of infectious virus is formed and released early after infection, but further virus egress is blocked. Taken together, these observations suggest that the gro29 phenotype involves either multiple proteins or a single protein used at multiple steps in viral glycoprotein export and virus egress from cells. Moreover, this host cell protein is required by both HSV and PRV for efficient propagation in infected cells.
Insights
The gro29 mouse cell mutant impairs herpes simplex virus type 1 (HSV-1) and pseudorabies virus (PRV) glycoprotein export and virus egress. This suggests a critical host protein is essential for efficient viral propagation.
Area of Science:
- Virology
- Cell Biology
- Molecular Biology
Background:
- The mouse L-cell mutant gro29 exhibits defects in herpes simplex virus type 1 (HSV-1) virion egress and glycoprotein export.
- Alphaherpesviruses, including HSV-1 and pseudorabies virus (PRV), rely on host cell machinery for replication and egress.
Purpose of the Study:
- To investigate the role of the gro29 mutation in pseudorabies virus (PRV) infection.
- To determine if the cellular defect in gro29 cells affects other alphaherpesviruses.
- To elucidate the specific steps in viral glycoprotein export and egress impacted by the gro29 mutation.
Main Methods:
- Infection of gro29 cells with PRV.
- Analysis of viral glycoprotein synthesis and export kinetics.
- Assessment of infectious particle formation and release.
- Use of a secreted viral membrane protein variant to study Golgi export.
Main Results:
- PRV-infected gro29 cells displayed defects in glycoprotein export, infectious particle formation, plaque formation, and virus egress.
- Export of viral glycoproteins from the endoplasmic reticulum to the Golgi was impaired, and Golgi export was blocked late in infection.
- Export of a secreted viral protein from the Golgi out of the cell was also defective.
- PRV formed plaques poorly on gro29 cells, with limited early virus release followed by blocked egress.
Conclusions:
- The gro29 mutation affects multiple steps in viral glycoprotein export and virus egress, suggesting involvement of a single protein utilized at various stages or multiple proteins.
- The identified host cell protein is crucial for the efficient propagation of both HSV-1 and PRV.
- The gro29 cell line serves as a valuable tool for studying host-pathogen interactions in alphaherpesvirus replication.