Porcine deltacoronavirus nucleocapsid protein antagonizes IFN-β production by impairing dsRNA and PACT binding to RIG-I

Abstract

Porcine deltacoronavirus (PDCoV) is an emerging swine enteropathogenic coronavirus that causes watery diarrhea, vomiting and mortality in newborn piglets. Previous studies have suggested that PDCoV infection antagonizes RIG-I-like receptor (RLR)-mediated IFN-β production to evade host innate immune defense, and PDCoV-encoded nonstructural protein nsp5 and accessory protein NS6 are associated with this process. However, whether the structural protein(s) of PDCoV also antagonize IFN-β production remains unclear. In this study, we found that PDCoV nucleocapsid (N) protein, the most abundant viral structural protein, suppressed Sendai virus (SEV)-induced IFN-β production and transcription factor IRF3 activation, but did not block IFN-β production induced by overexpressing RIG-I/MDA5. Furthermore, study revealed that PDCoV N protein interacted with RIG-I and MDA5 in an in vitro overexpression system and evident interactions between N protein and RIG-I could be detected in the context of PDCoV infection, which interfered with the binding of dsRNA and protein activator of protein kinase R (PACT) to RIG-I. Together, our results demonstrate that PDCoV N protein is an IFN antagonist and utilizes diverse strategies to attenuate RIG-I recognition and activation.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Genetic characterization and phylogenetic analysis of porcine deltacoronavirus (PDCoV) in Shandong Province, China

“…SARS-CoV N protein not only modulates the host cell cycle by regulating cyclin-CDK activity but also inhibits the synthesis of type-1 interferon (1 F N) (Chang et al, 2014;Liao et al, 2005). PDCoV N protein suppressed Sendai virus (SEV)-induced IFN-β production and transcription factor IRF3 activation (Chen et al, 2019a). Furthermore, the N-terminal region (1-246 aa) interacts with pRIG-I and interferes with its function (Chen et al, 2019a).…”

“…PDCoV N protein suppressed Sendai virus (SEV)-induced IFN-β production and transcription factor IRF3 activation (Chen et al, 2019a). Furthermore, the N-terminal region (1-246 aa) interacts with pRIG-I and interferes with its function (Chen et al, 2019a). The N protein analysed showed few differences among the three lineage strains.…”

Subcellular localization of the porcine deltacoronavirus nucleocapsid protein

“…Coronavirus N proteins show low amino acid homology, but they share several conserved functions, including immune regulation. Like the N proteins from α-coronavirus or β-coronavirus, the PDCoV N protein also possesses an IFN-inhibition function via interfering dsRNA and PACT binding to RIG-I or RIG-I K63-linked polyubiquitination [ 14 , 24 – 26 ]. Little research into the function of PDCoV N protein has been conducted, but a recent study showed that PDCoV N could upregulate two HSP70 family members, glucose-regulated protein 78 (GRP78) and heat shock cognate 70-kDa protein (HSC70), which may facilitate virus infection.…”

“…Additionally, the N protein is the most abundant and ubiquitous viral protein in the context of CoV infection or assembled virions, and has roles in multifarious activities throughout the life cycle of a CoV [12]. In addition to promoting viral genome transcription or replication, the N protein also modulates the processes of inflammatory cytokine productions, RNA interference and apoptosis, and counteracting the host innate immune defense [13][14][15][16]. Interestingly, based on studies of representative CoVs, a cytoplasmic nucleolar location pattern is common for the N proteins of several CoVs, including porcine epidemic diarrhea virus (PEDV), mouse hepatitis virus (MHV) and infectious bronchitis virus (IBV) [17][18][19].…”

The current landscape of coronavirus-host protein–protein interactions

“…Interestingly, several host factors involved in viral RNA sensing (DDX58, IFIH1, PRKRA), DNA sensing (STING1) or downstream signalling to activate the innate immune response (TRAF3, TBK1, IKBKE, IKBKB, ISG15, IRF3) were targeted by unrelated viral proteins ( Fig. 1e) [3,28,29,[31][32][33][34][35][36][37][38][39][40][41][42][43][44]. This highlights the importance of these interactions for coronaviruses, but is puzzling from an evolutionary perspective.…”