Distinct Roles for Extracellular Signal-Regulated Kinase 1 (ERK1) and ERK2 in the Structure and Production of a Primate Gammaherpesvirus

Abstract

<jats:p>During their progression from intranuclear capsids to mature trilaminar virions, herpesviruses incorporate an extensive array of viral as well as a smaller subset of cellular proteins. Our laboratory previously reported that rhesus monkey rhadinovirus (RRV), a close homolog of the human pathogen Kaposi's sarcoma-associated herpesvirus (KSHV), is comprised of at least 33 different virally encoded proteins. In the current study, we found that RRV infection activated the extracellular signal-regulated kinase (ERK) pathway and nascent virions preferentially incorporated the activated form of ERK2 (pERK2) into the tegument. This was evident even in the face of greatly diminished stores of intracellular ERK2, suggesting a clear bias toward the incorporation of pERK2 into the RRV particle. Similar to earlier findings with KSHV, activation of ERK was essential for the production of lytic viral proteins and virions. Knockdown of intracellular ERK, however, failed to inhibit virus production, likely due to maintenance of residual pools of intracellular pERK2. Paradoxically, selective knockdown of ERK1 enhanced virion production nearly 5-fold and viral titers more than 10-fold. These data are the first to implicate ERK1 as a negative regulator of lytic replication in a herpesvirus and the first to demonstrate the incorporation of an activated signaling molecule within a herpesvirus. Together, the results further our understanding of how herpesviruses interact with host cells during infection and demonstrate how this family of viruses can exploit cellular signal transduction pathways to modulate their own replication.</jats:p>

Activation of p90 Ribosomal S6 Kinases by ORF45 of Kaposi's Sarcoma-Associated Herpesvirus Is Critical for Optimal Production of Infectious Viruses

“…Although this small region is conserved among ␥2 herpesviruses, ORF45 homologues seem to differ in their abilities to activate RSK and ERK (E. Kuang and F. Zhu, unpublished data), suggesting additional regions are involved. Recent studies by other groups have confirmed critical roles of the ERK pathway in MHV-68 and RRV lytic infection cycles that are at least partially dependent on ORF45 (43)(44)(45). More studies are needed to elucidate the molecular mechanisms by which ORF45 causes persistent activation of RSK and ERK.…”

Maturation and Vesicle-Mediated Egress of Primate Gammaherpesvirus Rhesus Monkey Rhadinovirus Require Inner Tegument Protein ORF52

“…Following purification and cleavage of GST, the proteins were used by the University of Virginia Lymphocyte Culture Center to produce mouse monoclonal antibodies to ORF52 and ORF65/SCIP. Rabbit polyclonal anti-RRV ORF45 was generated by Open Biosystems, Inc. (28). Mouse monoclonal anti-RRV major capsid protein (MCP) and anti-glycoprotein B (gB) were kindly provided by Scott Wong at Oregon Health and Science University.…”

“…Though the process of tegumentation remains poorly defined, previous studies have found both cellular and viral proteins within the layer (22)(23)(24)(25)(26)(27). This gives rise to a proteomic tegument profile that is distinct for each viral species and possibly even within the same species grown in different cell types or under different conditions (28). Until recently, structural data for the tegument were limited to images from electron microscopy (EM) that suggested that the layer was comprised of an amorphous collection of proteins; however, more recent studies with human cytomegalovirus (HCMV) (29), herpes simplex virus 1 (HSV-1) (30,31), murine gammaherpesvirus 68 (MHV-68) (32), RRV (33), and KSHV (34) indicate the presence of ordered tegument structures (30).…”

Network Architecture Predisposes an Enzyme to Either Pharmacologic or Genetic Targeting

“…Perturbation responses can diverge with the addition of one regulatory edge, which we demonstrate by using simple and detailed kinetic models complemented with experiments. In the MAPK literature, there are reports of surprising discrepancies between inhibitor and knockdown responses (Beliveau et al, 2010; Woodson and Kedes, 2012). As with the other wiring motifs, we believe that these discrepancies could be reconciled with the strength of ERK –| Raf feedback, which varies depending on cellular context (Pratilas et al, 2009).…”