Pseudorabies Virus Triggers Glycoprotein gE-Mediated ERK1/2 Activation and ERK1/2-Dependent Migratory Behavior in T Cells

Abstract

The interaction between viruses and immune cells of the host may lead to modulation of intracellular signaling pathways and to subsequent changes in cellular behavior that are of benefit for either virus or host. ERK1/2 (extracellular signal regulated kinase 1/2) signaling represents one of the key cellular signaling axes. Here, using wild-type and gE null virus, recombinant gE, and gEtransfected cells, we show that the gE glycoprotein of the porcine Varicellovirus pseudorabies virus (PRV) triggers ERK1/2 phosphorylation in Jurkat T cells and primary porcine T lymphocytes. PRV-induced ERK1/2 signaling resulted in homotypic T cell aggregation and increased motility of T lymphocytes. Our study reveals a new function of the gE glycoprotein of PRV and suggests that PRV, through activation of ERK1/2 signaling, has a substantial impact on T cell behavior. IMPORTANCEHerpesviruses are known to be highly successful in evading the immune system of their hosts, subverting signaling pathways of the host to their own advantage. The ERK1/2 signaling pathway, being involved in many cellular processes, represents a particularly attractive target for viral manipulation. Glycoprotein E (gE) is an important virulence factor of alphaherpesviruses, involved in viral spread. In this study, we show that gE has the previously uncharacterized ability to trigger ERK1/2 phosphorylation in T lymphocytes. We also show that virus-induced ERK1/2 signaling leads to increased migratory behavior of T cells and that migratory T cells can spread the infection to susceptible cells. In conclusion, our results point to a novel function for gE and suggest that virus-induced ERK1/2 activation may trigger PRV-carrying T lymphocytes to migrate and infect other cells susceptible to PRV replication.A lphaherpesviruses constitute the largest subfamily of the herpesviruses. This subfamily contains closely related pathogens, including herpes simplex virus 1 (HSV-1), HSV-2, and varicellazoster virus (VZV) in humans. Another member of the alphaherpesvirus subfamily is the porcine pseudorabies virus (PRV), which is often used as a model to study general features of alphaherpesvirus biology (1).PRV encodes 11 glycoproteins (2) incorporated in the viral envelope, which are embedded in different host membranes of the infected cell, including the plasma membrane. One of these glycoproteins is glycoprotein E (gE), which is important for virulence and viral (neuronal) spread (3-10). For both PRV and HSV-1, there are indications that gE may have a signaling function in immune cells, as it drives signaling-dependent processes like cell surface antigen capping (11-13). However, to date, there are no reports that gE indeed triggers any particular signaling pathway.The extracellular signal-regulated kinase 1/2 (ERK1/2) mitogen-activated protein kinase (MAPK) signaling pathway is an evolutionarily conserved pathway, controlling many fundamental cellular events, such as cell proliferation, survival, differentiation, migration, apoptosis, and metabolism (14-16). It ma...

The Pseudorabies Virus Glycoprotein gE/gI Complex Suppresses Type I Interferon Production by Plasmacytoid Dendritic Cells

“…The above data indicate that expression of gE in PRV-infected cells suppresses the TI-IFN response by pDC. We found earlier that PRV gE modulates phosphorylation of the ERK1/2 signaling molecule in different cell types, including primary isolated porcine T cells, Jurkat cells, and epithelial PK-15 cells (20,21). Since in human pDC, increased ERK1/2 activation has been linked with increased TI-IFN production (22), we investigated whether gE modulates ERK1/2 phosphorylation in pDC and whether this correlates with its ability to suppress TI-IFN production by these cells.…”

“…These differences in ERK1/2 phosphorylation correlated with the observed differences in TI-IFN production and therefore indicate that ERK1/2 signaling also plays a role in TI-IFN responses in porcine pDC. Besides gE, the US2 tegument protein of PRV, which is also absent in Bartha, is also known to interact with the ERK signaling pathway (20,21,46,47). Although ΔUS2 PRV did not trigger significantly higher pDC-mediated IFN-␣ production, results with this strain showed substantial pig variability (Fig.…”

“…Our data suggest a mechanism for how the gE/gI protein complex affects the TI-IFN response by pDC. The gE/gI complex has been reported before to modulate signaling of the mitogen-activated protein kinase (MAPK) ERK1/2 in different cell types (20,21). MAPK signaling, particularly ERK1/2 signaling, plays an important role in IFN-␣ production by human pDC (22,38,44,45).…”

Equine Herpesvirus Type 1 Enhances Viral Replication in CD172a + Monocytic Cells upon Adhesion to Endothelial Cells

“…Together, these data show that integrin engagement and the activation of integrin-mediated signaling pathways are essential in the induction of EHV-1-infected CD172a ϩ adhesion to EC. Several herpesviruses, such as pseudorabies virus (PRV), herpes simplex virus 1 (HSV-1), human herpesvirus 8 (HHV-8), and HCMV, have been reported to activate integrin-mediated ERK-MAPK and PI3K signaling pathways through the interactions of viral glycoproteins with putative receptors present at the plasma membranes of host cells (23,28,(33)(34)(35). To date, the EHV-1 envelope glycoprotein D (gD) has been shown to interact with ␣V integrins present on PBMC and to be critical for viral entry via endocytosis (36).…”

“…Then, samples were boiled for 10 min. SDS-PAGE and Western blotting were performed as described previously (23). Protein concentrations of 20 to 30 g/ml were used for all experiments.…”