The Role Of Fatty Acid-Binding Protein FABP5 In Regulation Of CGAS-STING Signaling Pathway

Cyclic GMP-AMP synthase(cGAS)is a cytoplasmic DNA sensor that belongs to the nucleotidyl transferase family and catalyzes the synthesis of cyclic GMP-AMP(c GAMP)from GTP and ATP,thereby activating downstream adaptor protein STING and TBK1 to induce the production of type I interferon.The regulatory mechanisms of human and mouse cGAS activation have been extensively studied,but the regulatory mechanisms of porcine cGAS activation remain largely unclear.Fatty acid-binding protein 5(FABP5)belongs to the fatty acid-binding protein family with multiple biological functions and is highly expressed in various cells including epidermal cells and macrophages.Recent studies have found that FABP5 also plays important roles in inflammation and viral infection.We have previously found that pFABP5 could interact with porcine cGAS.However,it is not clear whether pFABP5 can regulate host antiviral immune responses by targeting cGAS.To clarify the role of pFABP5 in the cGAS-STING signaling pathway,we knockdown the expression of pFABP5 in PK-15 cell and 3D4/21 cells by transfection of specific si RNA oligoes.We found that knockdown of pFABP5 significantly inhibited the expression of type I interferon and ISGs induced by ds DNA and DNA virus infection and promoted HSV-1replication.Knockdown of pFABP5 did not affect the expression of type I interferon and ISGs induced by c GAMP,indicating that pFABP5 may regulate cGAS-STING signaling pathway activation by acting on cGAS.To confirm the above observation,we generated stable pFABP5 knockdown cell lines by lentiviral infection.Similarly,stable knockdown of pFABP5 also significantly inhibited the expression of type I interferon and ISGs induced by ds DNA.In addition,knockdown of pFABP5 also suppressed phosphorylation of TBK1 and IRF3 in response to Poly(d A:d T)stimulation but not that of c GAMP stimulation.These data suggest that pFABP5 regulates STING-mediated antiviral immune response by acting on cGAS.Finally,we found that pFABP5 is mainly expressed in the nucleus of cells and that DNA stimulation does not affect the subcellular localization of pFABP5.However,the specific molecular mechanisms by which pFABP5 regulates porcine cGAS activation need to be further investigated.In summary,our results show that pFABP5 is a novel positive regulator of cGAS activation and host antiviral immune response.This data provide valuable information for understanding of the regulatory mechanisms of porcine cGAS activation and host antiviral immune responses.