The Role And Molecular Mechanism Of CGAS In Chicken Innate Immunity And Viral Infection

Innate immunity is the animal's first line of defense against invading pathogenic microorganisms and plays a key role in the regulation of mammalian immune response.It is available at the time of birth and has no antigen specificity.It recognizes different pathogen-associated molecular patterns(PAMP)through a series of pattern recognition receptors(PRR),and then activates the autoimmune system to clear the corresponding PAPM.Cyclic GMP-AMP(cGAMP)synthase(cGAS)is a predominant DNA sensor inducing the activation of the innate immune responses that produce proinflammatory cytokines and type I interferons,which has been well investigated in mammals.However,chicken cGAS(chcGAS),which participates in avian innate immunity,has not been well-investigated.Here,we cloned the complete open reading frame sequence of chcGAS.Multiple sequence alignment and phylogenetic analysis revealed that chcGAS was homologous to mammalian cGAS.The chcGAS mRNA was highly expressed in the bone marrow and ileum.The subcellular localization of chcGAS was mainly in the cytoplasm,and partial co-localization was observed in the endoplasmic reticulum.Through overexpression and RNA interference,we demonstrated that chcGAS responded to exogenous dsDNA,HS-DNA,and poly(dA:dT),and to self dsDNA from the DNA damage response,thereby triggering the activation of STING/TBK1/IRF7-mediated innate immunity in both chicken embryonic fibroblasts and chicken liver cancer cells.Furthermore,downregulation of chcGAS enhanced the infection of fowl adenovirus serotype 4 in LMH cells.Our results demonstrated that chcGAS was an important cytosolic DNA sensor activating innate immune responses and may shed light on a strategy for preventing infectious diseases in the poultry industry.