PP2A Facilitates Porcine Reproductive and Respiratory Syndrome Virus Replication by Deactivating irf3 and Limiting Type I Interferon Production.

Jiayu Xu,Zhijun Tian,Lu Zhang,Yunfei Xu,Hongyan Chen,Junxin Gao,Yue Wang,Lv Xuan,Qian Wang,He Zhang

doi:10.3390/v11100948

Abstract

Protein phosphatase 2A (PP2A), a major serine/threonine phosphatase in mammalian cells, is known to regulate the kinase-driven intracellular signaling pathways. Emerging evidences have shown that the PP2A phosphatase functions as a bona-fide therapeutic target for anticancer therapy, but it is unclear whether PP2A affects a porcine reproductive and respiratory syndrome virus infection. In the present study, we demonstrated for the first time that inhibition of PP2A activity by either inhibitor or small interfering RNA duplexes in target cells significantly reduced their susceptibility to porcine reproductive and respiratory syndrome virus (PRRSV) infection. Further analysis revealed that inhibition of PP2A function resulted in augmented production of type I interferon (IFN). The mechanism is that inhibition of PP2A activity enhances the levels of phosphorylated interferon regulatory factor 3, which activates the transcription of IFN-stimulated genes. Moreover, inhibition of PP2A activity mainly blocked PRRSV replication in the early stage of viral life cycle, after virus entry but before virus release. Using type I IFN receptor 2 specific siRNA in combination with PP2A inhibitor, we confirmed that the effect of PP2A on viral replication within target cells was an interferon-dependent manner. Taken together, these findings demonstrate that PP2A serves as a negative regulator of host cells antiviral responses and provides a novel therapeutic target for virus infection.

Highlights

The porcine reproductive and respiratory syndrome virus (PRRSV) is an enveloped, positive-stranded RNA virus, classified in the family Arteriviridae of the order Nidovirales [1,2].PRRSV is the causative agent of porcine reproductive and respiratory syndrome (PRRS), characterized by respiratory problems in growing pigs and reproductive failure in pregnant sows
We used the TCID50 assay to evaluate the effect of the inhibitor on PRRSV yield, and the results again showed that that okadaic acid treatment decreased the levels of virus titers (Figure 1F)
Examined for virus infection by Immunofluorescence assay (IFA) with an anti-PRRSV N protein mAb. (D) Viral RNA levels were determined by quantitative RT-PCR. (E) Detergent lysates collected from Marc-145 cells were subjected to immunoblotting with antibodies as indicated, and densitometric data for PRRSV M

Summary

Introduction

PRRSV is the causative agent of porcine reproductive and respiratory syndrome (PRRS), characterized by respiratory problems in growing pigs and reproductive failure in pregnant sows. Host cells can trigger signaling events that lead to the activation of the innate immune responses. This antiviral response is initiated by the pathogen-associated molecular patterns (PAMPs) through cellular pattern recognition receptors. This induces the production of antiviral molecules such as interferons (IFNs), a broad range of interferon-stimulated genes (ISGs), and inflammatory cytokines [6,7,8]. Interferon regulatory factor 3 (IRF3), a member of the interferon regulatory factors family, plays a central role in type I IFNs induction and antiviral responses [9]

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Results

Conclusion