Influenza Virus Down-Modulates G6PD Expression and Activity to Induce Oxidative Stress and Promote Its Replication.

Marta De Angelis,Giovanna De Chiara,Alessandra Fraternale,Lucia Nencioni,Mauro Magnani,Alessandra Zevini,Anna Teresa Palamara,Donatella Amatore,Paola Checconi,John Hiscott

doi:10.3389/fcimb.2021.804976

Abstract

Influenza virus infection induces oxidative stress in host cells by decreasing the intracellular content of glutathione (GSH) and increasing reactive oxygen species (ROS) level. Glucose-6-phosphate dehydrogenase (G6PD) is responsible for the production of reducing equivalents of nicotinamide adenine dinucleotide phosphate (NADPH) that is used to regenerate the reduced form of GSH, thus restoring redox homeostasis. Cells deficient in G6PD display elevated levels of ROS and an increased susceptibility to viral infection, although the consequences of G6PD modulation during viral infection remain to be elucidated. In this study, we demonstrated that influenza virus infection decreases G6PD expression and activity, resulting in an increase in oxidative stress and virus replication. Moreover, the down regulation of G6PD correlated with a decrease in the expression of nuclear factor erythroid 2-related factor 2 (NRF2), a key transcription factor that regulates the expression of the antioxidant response gene network. Also down-regulated in influenza virus infected cells was sirtuin 2 (SIRT2), a NADPH-dependent deacetylase involved in the regulation of G6PD activity. Acetylation of G6PD increased during influenza virus infection in a manner that was strictly dependent on SIRT2 expression. Furthermore, the use of a pharmacological activator of SIRT2 rescued GSH production and NRF2 expression, leading to decreased influenza virus replication. Overall, these data identify a novel strategy used by influenza virus to induce oxidative stress and to favor its replication in host cells. These observations furthermore suggest that manipulation of metabolic and oxidative stress pathways could define new therapeutic strategies to interfere with influenza virus infection.

Highlights

Viral infection is associated with alterations in the intracellular redox balance which are important for the activation of redoxsensitive pathways required for viral replication (Checconi et al, 2020)
To determine whether inhibition of Glucose-6-phosphate dehydrogenase (G6PD) activity by influenza virus infection involved post-translational mechanisms other than antioxidant gene regulation, we evaluated the role of sirtuin 2 (SIRT2) in regulating G6PD dimer formation, based on previous studies demonstrating that deacetylation of G6PD at Lys403 stimulated dimer formation and the G6PD activity (Wang et al, 2014)
We identify a novel mechanism used by influenza virus to tip the intracellular redox balance towards increased oxidative stress for its own replicative advantage (Figure 7)

Summary

Introduction

Viral infection is associated with alterations in the intracellular redox balance which are important for the activation of redoxsensitive pathways required for viral replication (Checconi et al, 2020). In G6PD-knockdown cells, higher ROS production correlated with increased human coronavirus (HCoV) 229E replication (Wu et al, 2008), and it was recently suggested that individuals affected by G6PD deficiency may be more susceptible to SARS-CoV-2 infection (Buinitskaya et al, 2020; Jain et al, 2020; Vick, 2020). Overall, these data indicate that G6PD levels play an important role in regulating the susceptibility to viral infection and the extent of viral replication. How G6PD expression and enzymatic activity may be modulated during influenza virus infection remains unexplored, as does its role in virus-induced oxidative stress and viral replication

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Conclusion