Hepatitis C virus RNA replication is regulated by Ras-Erk signalling

Abstract

The hepatitis C virus NS5A protein has been previously demonstrated to partially attenuate activation of the Ras-Erk signalling pathway, via a conserved class II polyproline motif located towards the C terminus of the protein. However, the role of Ras-Erk signalling in the virus life cycle remains undetermined. To investigate this, levels of RNA replication were measured in genotypes 1 and 2 transient luciferase subgenomic replicon systems in the context of either pharmacological or genetic (dominant-negative) inhibition of MEK1, a kinase in the Ras-Erk signalling cascade. Incubation in the presence of two inhibitors (U0126 and PD184352) resulted in a decrease in the levels of RNA replication, conversely incubation with inhibitor PD98059 resulted in a modest increase in replication. The results obtained with PD98059 could not be explained by an off-target effect on Cox-2, stability of replicon RNA or stimulation of global translation levels, suggesting stimulation by a yet uncharacterized mechanism. To verify data obtained using pharmacological inhibitors the transient replicon RNA was co-electroporated with a dominant-negative mutant of MEK1. This resulted in a reduction in replication, confirming data seen with U0126 and PD184352. Our data are consistent with the hypothesis that a low level Ras-Erk signalling activity is required for RNA replication. However, complete inhibition of Ras-Erk signalling is inhibitory. These results suggest that perturbation of this signalling pathway by NS5A may be a mechanism to regulate levels of genomic RNA replication.

Activation of the Ras/Raf/MEK Pathway Facilitates Hepatitis C Virus Replication via Attenuation of the Interferon-JAK-STAT Pathway

“…This was consistent with the work of Gretton and colleagues, who used SGR-luc-JFH-1, a genotype 2a HCV replicon encoding firefly luciferase, to represent HCV replication (24). They used two types of Ras/Raf/MEK pathway inhibitors and a MEK1 dominant mutant to inhibit this pathway and found a reduction in HCV replication after inhibition (24). However, another study has shown that inhibition of the Ras/Raf/MEK pathway enhances the replication of the HCV subgenomic replicon (29).…”

“…According to the results, we concluded that the Ras/Raf/MEK pathway facilitates HCV replication. This was consistent with the work of Gretton and colleagues, who used SGR-luc-JFH-1, a genotype 2a HCV replicon encoding firefly luciferase, to represent HCV replication (24). They used two types of Ras/Raf/MEK pathway inhibitors and a MEK1 dominant mutant to inhibit this pathway and found a reduction in HCV replication after inhibition (24).…”

Human heme oxygenase 1 is a potential host cell factor against dengue virus replication

“…NF-κB and MAPKs act as major inflammatory transcriptional factors that bind to consensus sequences on pro-inflammatory genes such as COX-2 and promote their expression48. Previous studies indicate that NF-κB- and MAPKs-mediated COX-2 activation may be used by some viruses such as HCV to promote viral replication49. In our previous study, we observed that potential agents inhibited HCV replication by inhibiting COX-2 expression or activation5051.…”

Hepatitis C Virus Nonstructural 5A Protein Interacts with Abelson Interactor 1 and Modulates Epidermal Growth Factor-mediated MEK/ERK Signaling Pathway

“…activity is required for HCV RNA replication, but complete inhibition of the Ras-ERK signaling is inhibitory (25). Other groups also reported that inhibition of MEK/ERK signaling enhanced HCV propagation (26).…”