RuvB-Like Protein 2 Interacts with the NS1 Protein of Influenza A Virus and Affects Apoptosis That Is Counterbalanced by Type I Interferons.

Yimeng Wang,Jianhong Zhou,Samuel G Mackintosh,Yuchun Du

doi:10.3390/v13061038

Yimeng Wang, Jianhong Zhou + Show 2 more

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https://doi.org/10.3390/v13061038

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Abstract

The NS1 protein of influenza A virus (IAV) plays important roles in viral pathogenesis and host immune response. Through a proteomic approach, we have identified RuvB-like proteins 1 and 2 (RuvBL1 and RuvBL2) as interacting partners of the NS1 protein of IAVs. Infection of human lung A549 cells with A/PR/8/34 (PR8) virus resulted in reductions in the protein levels of RuvBL2 but not RuvBL1. Further studies with RuvBL2 demonstrated that the NS1-RuvBL2 interaction is RNA-independent, and RuvBL2 binds the RNA-binding domain of the NS1. Infection of interferon (IFN)-deficient Vero cells with wild-type or delNS1 PR8 virus reduced RuvBL2 protein levels and induced apoptosis; delNS1 virus caused more reductions in RuvBL2 protein levels and induced more apoptosis than did wild-type virus. Knockdown of RuvBL2 by siRNAs induced apoptosis and overexpression of RuvBL2 resulted in increased resistance to infection-induced apoptosis in Vero cells. These results suggest that a non-NS1 viral element or elements induce apoptosis by suppressing RuvBL2 protein levels, and the NS1 inhibits the non-NS1 viral element-induced apoptosis by maintaining RuvBL2 abundance in infected cells in the absence of IFN influence. In contrast to Vero cells, infection of IFN-competent A549 cells with PR8 virus caused reductions in RuvBL2 protein levels but did not induce apoptosis. Concomitantly, pretreatment of Vero cells with a recombinant IFN resulted in resistance to infection-induced apoptosis. These results demonstrate that the infection-induced, RuvBL2-regulated apoptosis in infected cells is counterbalanced by IFN survival signals. Our results reveal a novel mechanism underlying the infection-induced apoptosis that can be modulated by the NS1 and type I IFN signaling in IAV-infected cells.

Highlights

Introduction iationsHost cells have developed various defenses against influenza A virus (IAV) infection.The most important defense mechanism is the innate response of production of typeI interferons (IFNs), which induce an antiviral state in infected cells and neighboring uninfected cells by triggering the expression of IFN-inducible genes or IFN-stimulated genes [1,2,3]
The results demonstrated that RuvBL2 bound the RNA-binding domain (RBD) domain but not the effector domain (ED) domain of the nonstructural protein 1 (NS1) of PR8 virus (Figure 4B, upper panel)
The results demonstrated that knockdown of RuvBL2 in Vero cellshad hadno nosignificant significanteffect effecton on the the NS1

Summary

Introduction

Host cells have developed various defenses against influenza A virus (IAV) infection. I interferons (IFNs), which induce an antiviral state in infected cells and neighboring uninfected cells by triggering the expression of IFN-inducible genes or IFN-stimulated genes [1,2,3]. Host cells can limit IAV replication by inducing apoptosis of infected cells [4,5]. The nonstructural protein 1 (NS1) of IAVs is a master in this regard and facilitates IAV replication by inhibiting both IFN induction and apoptosis in infected cells [2,3,6]. The NS1 protein suppresses IFN expression through the inhibition of retinoic acid-inducible gene (RIGI)-mediated activation of the transcription factors interferon regulatory factor-3 (IRF-3), Licensee MDPI, Basel, Switzerland

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