PKACα negatively regulates TAK1/IRF7 signaling in black carp Mylopharyngodon piceus

Protein Kinase A catalytic subunit alpha (PKAC alpha), plays an important role in the PKA and NF-kappa B signaling pathway in mammals. However, the function of PKAC alpha in teleost fish remains largely unknown. In this study, PKAC alpha from black carp (bcPKAC alpha) has been cloned and its role in the innate immune antiviral signaling pathway was investigated. The open reading frame of bcPKAC alpha gene contains 1056 nucleotides and the immunofluorescence assay verified that PKAC alpha was mainly distributed in the cytoplasm. The reporter assay showed that bcPKAC alpha expression and co-expression of bcPKAC alpha and black carp TAK1 (bcTAK1) could activate the transcription of NF-kappa B. However, bcTAK1/bcIRF7-mediated IFN transcription was inhibited by bcPKAC alpha. Knockdown of bcPKAC alpha showed slightly enhanced antiviral activity against spring viremia of carp virus (SVCV) compared with control group. Accordingly, the antiviral activity against SVCV and grass carp reovirus (GCRV) of EPC cells co-expressing bcPKAC alpha, bcTAK1 and bcIRF7 was obviously lower than that of EPC cells co-expressing bcTAK1 and bcIRF7. The similar subcellular distribution and interaction between bcPKAC alpha and bcTAK1 were detected by immunofluo-rescent staining and co-immunoprecipitation assay separately. The data generated in this study demonstrates that bcPKAC alpha associates with bcTAK1 and positively regulates NF-kappa B signaling, however, negatively regulates TAK1/IRF7 signaling pathway.

Automated summary

The study cloned bcPKAC alpha from black carp and investigated its role in the innate immune antiviral signaling pathway. It was found that bcPKAC alpha positively regulates NF-kappa B signaling but negatively regulates TAK1/IRF7 signaling pathway. Knockdown of bcPKAC alpha slightly enhanced antiviral activity against SVCV, indicating its involvement in the antiviral response.