The Roles Of Yellow Catfish CGAS,cGASl,IRF1,IRF2 And IRF8 In Innate Immune Response

Pattern recognition receptor-mediated immune recognition is the initial stage of immune response,and effective recognition and response to “self” and “different” is the basis and key of innate immune defense.CyclicGMP-AMP synthase(cGAS)is an important pattern recognition receptor that can recognize a special “different” component——DNA,and then initiate a signal cascade reaction to induce the expression of type I interferon and proinflammatory cytokines,which can produces innate immunity and adaptive immune response.Interferon regulatory factor(IRF)is a kind of multifunctional transcription factor that can regulate the expression of interferon(IFN)gene.It plays an important role in innate immunity,blood cell development,and the development and regulation of the immune system.As the lowest vertebrates,fish have a certain similarity to mammals in their innate immune recognition and response mode,and they also have their own uniqueness.The in-depth study of fish cGAS and IRF genes can expand people’s understanding of vertebrate cGAS signaling pathways and interferon regulation mechanisms,and provide references for the immune prevention and control of fish diseases.We have identified two cGAS genes from important economic fish,Pelteobagrus fulvidraco,including the cGAS gene that has an orthologous evolutionary relationship with mammals and the cGAS-like(cGASL)gene unique to lower vertebrates.In this paper,a series of studies have been carried out on their expression patterns,subcellular localization,induction and activation of interferon and disease resistance effects.At the same time,based on the preliminary identification of the IRF family genes of yellow catfish,this article conducted a preliminary exploration of the role of IRF1,IRF2 and IRF8 in fish antiviral immunity.The results are as follows:PfcGAS and PfcGASL have similar structural features to the cGAS genes of other vertebrates,but the C-terminus of PfcGASL also contains a transmembrane domain.Similar to the subcellular localization of human cGAS,PfcGAS is distributed in cells in three situations:only in the cytoplasm,only in the nucleus,and both cytoplasm and nucleus.PfcGASL is located in the endoplasmic reticulum.PfcGAS and PfcGASL are widely distributed in yellow catfish tissues,and can be up-regulated by Edwardsiella catfish,poly I:C and LPS.Both can activate fish type I IFN promoters and ISRE elements to varying degrees,suggesting that they play a role in the induced activation of interferon.cGAS-like can also inhibit the induction of IFN promoter by poly I:C、polyd A:d T,it may be involved in the regulation of innate immunity.Overexpression of PfcGAS gene can induce the expression of IFN and interferon-stimulated genes(ISGs),and inhibit the proliferation of carp spring viremia virus(SVCV)and Edwardsiella ictaluri.Combining deletion mutations and point mutations,studies have found that amino acids 1-206 and amino acids 398,404,407,and 414 of PfcGAS play an important role in Pf GAS-induced IFN disease resistance.Pf IRF1,Pf IRF2 A,and Pf IRF2 B are located in the cytoplasm and nucleus,and Pf IRF8 is located in the nucleus.Preliminary functional studies have shown that Pf IRF1 can activate fish type I IFN promoter and ISRE elements,induce IFN system gene expression,and inhibit SVCV proliferation.Pf IRF2A、Pf IRF2B、Pf IRF8 repress fish NF-k B,IFN promoter,and ISRE elements.This paper focuses on the expression characteristics and functional characteristics of the pattern recognition receptors cGAS and cGASL of the yellow catfish and the interferon regulatory factors IRF1,IRF2 and IRF8.The research results help to clarify the immunity of the yellow catfish in response to pathogenic microorganisms.The recognition and response mechanism lays the foundation for the development of drugs and breeding for disease resistance.