The cGAS/STING-TBK1-IRF Regulatory Axis Orchestrates a Primitive Interferon-Like Antiviral Mechanism in Oyster.

Xue Qiao,Lingling Wang,Zhaojun Wu,Linsheng Song,Yuanmei Li,Zhaoqun Liu,Yanan Zong

doi:10.3389/fimmu.2021.689783

Abstract

Interferon (IFN) system is considered as the first defense line against viral infection, and it has been extensively studied in vertebrates from fish to mammals. In invertebrates, Vagos from arthropod and IFN-like protein (CgIFNLP) from Crassostrea gigas appeared to function as IFN-like antiviral cytokines. In the present study, the CgIFNLP protein in hemocytes was observed to increase after Poly (I:C) stimulation. After CgIFNLP was knocked down by RNAi, the mRNA expression of IFN-stimulated genes (CgISGs) was significantly inhibited. Both cyclic GMP-AMP synthase (CgcGAS) and stimulator of interferon gene (CgSTING) identified from oyster were able to recognize the double-stranded nucleic acid [Poly (I:C) and dsDNA] and expressed at high level after Poly (I:C) stimulation. The expression of CgIFNLP and interferon regulatory factors (CgIRF1/8) and the nuclear translocation of CgIRF8 were all suppressed in CgcGAS-RNAi or CgSTING-RNAi oysters after Poly (I:C) stimulation. The expression level of CgSTING and TANK binding kinase1 (CgTBK1) did not decrease in CgcGAS-RNAi oysters. After CgSTING was knocked down, the high expression of CgTBK1 induced by Poly (I:C) was prevented significantly. These results indicated that there was a primitive IFN-like antiviral mechanism dependent on the cGAS/STING–TBK1–IRFs regulatory axis in mollusks, which was different from the classic cGAS–STING–TBK1 signal pathway in mammals.

Highlights

Interferon (IFN) system is the vital component of immune response in mammal, and it is recognized as the first line of defense against viral infection
The specificity of polyclonal antibody against CgIFNLP and the abundance of CgIFNLP in hemolymph were examined by Western blot
A single band about 15 kDa with the high specificity was observed, which was consistent with the predicted molecular mass of CgIFNLP (Figure 1A)

Summary

Introduction

Interferon (IFN) system is the vital component of immune response in mammal, and it is recognized as the first line of defense against viral infection. The reaction cascade to regulate the production of IFNs can be initiated by the specific binding of pathogenassociated molecular patterns (PAMPs) to pattern recognition receptors (PRRs), such as Toll like receptors (TLRs), retinoic acid-inducible gene I (RIG-I), melanoma differentiation associated protein 5 (MDA5), cyclic GMP-AMP (cGAMP) synthase (cGAS), and nucleotide binding oligomerization domain-like receptors (NLRs) [5,6,7,8,9]. The IRF-3 and IRF-7 are essential for the regulated expression of IFNs, and IRF-9 is indispensable for gene transcription of ISGs by combining the STAT1 and STAT2 [15]

Methods

Results

Conclusion