SARS-CoV-2 Nsp14 protein associates with IMPDH2 and activates NF-κB signaling

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection leads to NF-κB activation and induction of pro-inflammatory cytokines, though the underlying mechanism for this activation is not fully understood. Our results reveal that the SARS-CoV-2 Nsp14 protein contributes to the viral activation of NF-κB signaling. Nsp14 caused the nuclear translocation of NF-κB p65. Nsp14 induced the upregulation of IL-6 and IL-8, which also occurred in SARS-CoV-2 infected cells. IL-8 upregulation was further confirmed in lung tissue samples from COVID-19 patients. A previous proteomic screen identified the putative interaction of Nsp14 with host Inosine-5’-monophosphate dehydrogenase 2 (IMPDH2), which is known to regulate NF-κB signaling. We confirmed the Nsp14-IMPDH2 protein interaction and identified that IMPDH2 knockdown or chemical inhibition using ribavirin (RIB) and mycophenolic acid (MPA) abolishes Nsp14- mediated NF-κB activation and cytokine induction. Furthermore, IMPDH2 inhibitors (RIB, MPA) or NF-κB inhibitors (bortezomib, BAY 11-7082) restricted SARS-CoV-2 infection, indicating that IMPDH2-mediated activation of NF-κB signaling is beneficial to viral replication. Overall, our results identify a novel role of SARS-CoV-2 Nsp14 in inducing NF-κB activation through IMPDH2 to promote viral infection.

SARS-CoV-2 NSP14 MTase activity is critical for inducing canonical NF-κB activation

“…In addition to the central role of NSP14 methyltransferase activity, we show that p65 is essential for NSP14-induced NF-κB activity, whereas it is not dependent on the NSP14-binding factor c-Rel. This is consistent with other studies showing activation of p65 upon in vitro SARS-CoV-2 infection [ 31 ] and expression of NSP14 [ 27 ]. However, even though NEMO is critical for NSP14-triggered NF-κB activation, NSP14 overexpression is unable to induce upstream canonical IKK/NF-κB signaling.…”

“…Indeed, we could demonstrate the induction of transcriptional NF-κB activity in a dose dependent manner by overexpressing NSP14. This finding is consistent with other publications establishing NSP14 as a viral factor that activates NF-κB [ 27 , 28 ].…”

Aesculus hippocastanum extract and the main bioactive constituent β-escin as antivirals agents against coronaviruses, including SARS-CoV-2

“…NF-κB activation induced by coronavirus infection not only affects viral multiplication, but also elicits the expression of pro-inflammatory cytokines, including IL-6 and TNF-α, that contribute to inflammation and the pathology of the infection 11 – 17 . The expression of these cytokines promotes activation and recruitment of immune cells such as macrophages, which resulted in increased secretion of inflammatory cytokines 12 , 16 , 17 . Thus, considering the role of macrophages in the inflammatory response against coronaviruses, we decided to analyze the effect of β-escin and AH in macrophages infected with coronaviruses.…”

“…SARS-CoV-2 and other coronaviruses trigger NF-κB signaling in epithelial cells and macrophages, which is required for viral replication and cytokine production 11 – 17 . In consequence of that, NF-κB plays a very important role in the progression of SARS-CoV-2 infection as well as in exacerbating the production of proinflammatory cytokines in the “cytokine storm” observed in patients with severe COVID-19.…”

Anthracyclines inhibit SARS-CoV-2 infection

“…Anisomycin has been shown to inhibit hCoV-OC43 (55) and hCoV-229E in this study, suggesting a pan-coronavirus activity of this compound. A second example is mycophenolic acid which is an inhibitor of inosine-5’-monophosphate dehydrogenase 2 (IMPDH2) and inhibits SARS-CoV-2 at least partially through suppressing viral protein NSP14-mediated activation of NF-κB (56, 57). We also observed the anti-SARS-CoV-2 activity of cyclosporin A which was evaluated in clinical trials as a potential treatment for COVID-19 (58).…”