Ctenopharyngodon idella Tollip regulates MyD88-induced NF-κB activation

Toll-interacting protein (Tollip) and MyD88 are key components of the TLR/IL-1R signaling pathway in mammals. MyD88 is known as a universal adaptor protein involving in TLR/IL-1R-induced NF-kappa B activation. Tollip is a crucial negative regulator of TLR-mediated innate immune responses. Previous studies have demonstrated that teleost Tollip served as a negative regulator of MyD88-dependent TLR signaling pathway. However, the mechanism is still unclear. In particular, the effect of TBD, C2, and CUE domains of Tollip on MyD88-NF-kappa B signaling pathway remains to be elucidated. In this study, we found that the response of grass carp Tollip (CiTollip) to LPS stimulation was faster and stronger than that of poly I:C treatment, and CiTollip diminished the expression of tnf-alpha induced by LPS. Further assays indicated that except for the truncated mutant of Delta CUE2 (1-173 aa), wild type CiTollip and other truncated mutants (Delta N-(52-276 aa), Delta C2-(173-276 aa) and Delta CUE1-(1-231 aa)) could associate with MyD88 and negatively regulate MyD88-induced NF-kappa B activation. It suggested that the C-terminal (173-276 aa), in particular the connection section between C2 and CUE domains (173-231 aa), played a pivotal role in suppressing MyD88-induced activation of NF-kappa B.

Automated summary

In this study, grass carp Tollip (CiTollip) showed a faster and stronger response to LPS stimulation compared to poly I:C treatment, reducing the expression of tnf-alpha induced by LPS. Except for the truncated mutant of Delta CUE2 (1-173 aa), wild type CiTollip and other truncated mutants were able to associate with MyD88 and negatively regulate its induced NF-kappa B activation, indicating the crucial role of the C-terminal region, especially the connection between the C2 and CUE domains, in suppressing MyD88-induced NF-kappa B activation.