Porcine reproductive and respiratory syndrome virus nonstructural protein 2 contributes to NF-κB activation

Abstract

BackgroundNuclear factor-kappaB (NF-κB) is an inducible transcription factor that plays a key role in inflammation and immune responses, as well as in the regulation of cell proliferation and survival. Previous studies by our group and others have demonstrated that porcine reproductive and respiratory syndrome virus (PRRSV) infection could activate NF-κB in MARC-145 cells and alveolar macrophages. The nucleocapsid (N) protein was identified as an NF-κB activator among the structural proteins encoded by PRRSV; however, it remains unclear whether the nonstructural proteins (Nsps) contribute to NF-κB activation. In this study, we identified which Nsps can activate NF-κB and investigated the potential mechanism(s) by which they act.ResultsBy screening the individual Nsps of PRRSV strain WUH3, Nsp2 exhibited great potential to activate NF-κB in MARC-145 and HeLa cells. Overexpression of Nsp2 induced IκBα degradation and nuclear translocation of NF-κB. Furthermore, Nsp2 also induced NF-κB-dependent inflammatory factors, including interleukin (IL)-6, IL-8, COX-2, and RANTES. Compared with the Nsp2 of the classical PRRSV strain, the Nsp2 of highly pathogenic PRRSV (HP-PRRSV) strains that possess a 30 amino acid (aa) deletion in Nsp2 displayed greater NF-κB activation. However, the 30-aa deletion was demonstrated to not be associated with NF-κB activation. Further functional domain analyses revealed that the hypervariable region (HV) of Nsp2 was essential for NF-κB activation.ConclusionsTaken together, these data indicate that PRRSV Nsp2 is a multifunctional protein participating in the modulation of host inflammatory response, which suggests an important role of Nsp2 in pathogenesis and disease outcomes.

Porcine epidemic diarrhea virus infection induces NF-κB activation through the TLR2, TLR3 and TLR9 pathways in porcine intestinal epithelial cells

“…Examples of such viral proteins include the PRRSV structural protein N and the non-structural protein 2 (NSP2) (Fang et al, 2012;Fu et al, 2012;Luo et al, 2008), herpes simplex virus glycoproteins gH/gL and gB (Leoni et al, 2012), Epstein-Barr virus latent membrane protein 1 (Smirnova et al, 2011), HIV envelope glycoprotein gp120 (Bren et al, 2009), SARS-CoV proteins S and N (Dosch et al, 2009;Liao et al, 2005), and hepatitis C virus protein NSP2 (Oem et al, 2008). Virion envelope proteins could initiate NF-kB activation by binding to cellular surface receptors.…”

Mycobacterium tuberculosis Rv2185c contributes to nuclear factor-κB activation

“…Procedure for confocal fluorescence microscopy was described previously (Fang et al, 2012). Briefly, HeLa cells were seeded on glass coverslips (NEST Biotechnology) that had been placed in 24-well plates until cultures were 70-80% confluent.…”

Quantitative interactome reveals that porcine reproductive and respiratory syndrome virus nonstructural protein 2 forms a complex with viral nucleocapsid protein and cellular vimentin

“…Previous studies have demonstrated that nsp2 uses its DUB activity to inhibit NF-κB activation by suppressing the polyubiquitination process of IκBα and nuclear translocation of NF-κB [29], and to inhibit type I IFN production by blocking the ubiquitination of RIG-I [25]. Among the identified cellular proteins interacting with nsp2, some of them are involved in innate immune regulation.…”

“…Gene fragments of a series of PRRSV WUH3 nonstructural and structural genes were cloned into the pCAGGS-HA vector in-frame as previously described [29]. Gene fragments encoding PRRSV nsp2 and N proteins were inserted into the pCAGGS-Flag vector to construct pCAGGS-Flag nsp2 and pCAGGS-Flag-N, respectively.…”