MEK inhibition drives anti-viral defence in RV but not RSV challenged human airway epithelial cells through AKT/p70S6K/4E-BP1 signalling

Abstract

Background The airway epithelium is a major target tissue in respiratory infections, and its antiviral response is mainly orchestrated by the interferon regulatory factor-3 (IRF3), which subsequently induces type I (β) and III (λ) interferon (IFN) signalling. Dual specificity mitogen-activated protein kinase kinase (MEK) pathway contributes to epithelial defence, but its role in the regulation of IFN response in human primary airway epithelial cells (AECs) is not fully understood. Here, we studied the impact of a small-molecule inhibitor (MEKi) on the IFN response following challenge with two major respiratory viruses rhinovirus (RV2) and respiratory syncytial virus (RSVA2) and a TLR3 agonist, poly(I:C). Methods The impact of MEKi on viral load and IFN response was evaluated in primary AECs with or without a neutralising antibody against IFN-β. Quantification of viral load was determined by live virus assay and absolute quantification using qRT-PCR. Secretion of cytokines was determined by AlphaLISA/ELISA and expression of interferon-stimulated genes (ISGs) was examined by qRT-PCR and immunoblotting. A poly(I:C) model was also used to further understand the molecular mechanism by which MEK controls IFN response. AlphaLISA, siRNA-interference, immunoblotting, and confocal microscopy was used to investigate the effect of MEKi on IRF3 activation and signalling. The impact of MEKi on ERK and AKT signalling was evaluated by immunoblotting and AlphaLISA. Results Here, we report that pharmacological inhibition of MEK pathway augments IRF3-driven type I and III IFN response in primary human AECs. MEKi induced activation of PI3K-AKT pathway, which was associated with phosphorylation/inactivation of the translational repressor 4E-BP1 and activation of the protein synthesis regulator p70 S6 kinase, two critical translational effectors. Elevated IFN-β response due to MEKi was also attributed to decreased STAT3 activation, which consequently dampened expression of the transcriptional repressor of IFNB1 gene, PRDI-BF1. Augmented IFN response translated into inhibition of rhinovirus 2 replication in primary AECs but not respiratory syncytial virus A2. Conclusions Our findings unveil MEK as a key molecular mechanism by which rhinovirus dampens the epithelial cell’s antiviral response. Our study provides a better understanding of the role of signalling pathways in shaping the antiviral response and suggests the use of MEK inhibitors in anti-viral therapy against RV. Electronic supplementary material The online version of this article (10.1186/s12964-019-0378-7) contains supplementary material, which is available to authorized users.

Growth factor receptor signaling inhibition prevents SARS-CoV-2 replication

“…While monitoring signaling changes in host cells, we observed activation of GFR signaling cascades after infection, consistent with other viruses relying on the receptors themselves or elicited signal transduction (Eierhoff et al, 2010;Kung et al, 2011;Lupberger et al, 2011;Ueki et al, 2013;Wu et al, 2017;Zhu et al, 2009). From our data we could not clearly conclude which GFR might be activated and thus tested whether GFR 235 downstream signaling inhibition can prevent SARS-CoV-2 replication, as reported for some other viruses (Baturcam et al, 2019;Pleschka et al, 2001).Previously, temporal kinome analysis identified antiviral potential of RAS/RAF/MEK and PI3K/AKT/ for MERS-CoV (Kindrachuk et al, 2015). By targeting the RAS/RAF/MEK and PI3K/AKT/mTOR downstream axes of GFR signaling, we found efficient inhibition of cytopathic effects and cell destruction (Figure 4).…”

<p>Dual Role For A MEK Inhibitor As A Modulator Of Inflammation And Host Defense Mechanisms With Potential Therapeutic Application In COPD</p>

“…The beneficial effect of MEK inhibitors on host defense may not be limited to bacterial infections as several reports suggest a direct or indirect antiviral effect on different respiratory viruses, including influenza 58,59 and rhinovirus. 60 The completion of the life cycle of influenza is dependent on the MEK pathway as it facilitates the nuclear export of the viral ribonucleoprotein. 61 We recently identified MEK as a key regulator of interferon response in airway epithelial cells and inhibition of MEK led to enhanced IFN response, which translated into a reduction of rhinovirus replication.…”

“…61 We recently identified MEK as a key regulator of interferon response in airway epithelial cells and inhibition of MEK led to enhanced IFN response, which translated into a reduction of rhinovirus replication. 60 Since these viruses are commonly associated with COPD exacerbations, the inhibition of MEK1/2 pathway may represent a new strategy for treating virus-induced exacerbations in COPD.…”

Interleukin-22 Inhibits Respiratory Syncytial Virus Production by Blocking Virus-Mediated Subversion of Cellular Autophagy

“…Downstream of IL-22 signaling, IL-22 primarily activates STAT3 (Baturcam et al, 2019;Edsbacker et al, 2019;Gimeno Brias et al, 2016;Mahony et al, 2017;Wolk et al, 2010) with STAT1 involvement in certain instances (Lejeune et al, 2002). To determine which of these pathways is involved in the inhibition of virus production by IL-22, we examined STAT1 and STAT3 activation status in the IL-22-treated A549 cells and observed that IL-22 triggered phosphorylation of both STAT1 and STAT3 to similar degrees (Figures 2A and 2B).…”

“…Type I IFNs play a crucial role in host defense against viruses and upregulate several IFN-stimulated genes (ISGs) that play important roles in eliminating the virus from infected cells (Baturcam et al, 2019;Edsbacker et al, 2019;Mahony et al, 2017). In addition, type III IFNs (IFN-l) have been also implicated in anti-viral host defense (Kotenko, 2011).…”