Identification of the interaction between TAB2 and TAK1 proteins from Ctenopharyngodon idella and effect of their interaction on the expression of two antimicrobial peptides genes

To investigate whether grass carp (Ctenopharyngodon idella) TAB2 (CiTAB2) can interact with CiTAK1 and the effect of their interaction on the expression of two antimicrobial peptides (AMPs) genes Cihepcidin and Ciβ-defensin1, the temporal and spatial expression patterns of Citab2 and Citak1 in the immune-related tissues of grass carp after Vibrio mimicus infection were firstly analyzed by qPCR in the present study. Subsequently, fluorescence co-localization, co-immunoprecipitation and Western blot were used to identify the intracellular co-localization and interaction between CiTAB2 and CiTAK1 proteins. Finally, the mRNA expression levels of Cihepcidin and Ciβ-defensin1 were examined after the overexpression plasmids pEGFP-N1-Citak1 and pEGFP-N1-Citab2 were co-transfected into CIK cells. The results showed that V. mimicus infection significantly altered the relative mRNA expression levels of Citab2 and Citak1. Among them, the former showed different spatio-temporal expression patterns in each examined tissue at different time points post-infection, while the expression pattern of the latter was up-regulated then down-regulated in all examined tissues. CiTAB2 and CiTAK1 were co-localized in the cytoplasm of both HEK293T and CIK cells observed under a fluorescence microscope, and the CiTAB2-CiTAK1 protein complex could be formed in HEK293T cells post-transfection. After co-overexpression of CiTAB2 and CiTAK1, the mRNA expression levels of Cihepcidin and Ciβ-defensin1 were significantly up-regulated in the CIK cells at each test time point. These results indicated that CiTAB2 could interact with CiTAK1 and their interaction was able to promote the transcriptional expression of these two AMPs, which provides a new strategy for the control of fish vibriosis from the perspective of protein interaction.