Grass carp (Ctenopharyngodon idella) IRAK1 and STAT3 up-regulate synergistically the transcription of IL-10.

In vertebrates, IL-10 is an anti-inflammatory factor that serves as a key inhibitory role in a wide range of immune responses. IRAK1 (IL-1 receptor-associated kinase 1), a key molecule in the inflammatory signal of IL-1R/TLR, plays an important pivotal role in regulating the autoimmunity of body. STAT3 (Signal transducer and activator of transcription 3) activated by IRAK1 participates in inflammation, tumorigenesis, metabolic disorders and immune response. Under the stimulation of LPS, IRAK1 enters the nucleus to form a dimer with STAT3 and regulates the expression of IL-10. However, the relationship between fish IRAK1 and STAT3 has not been reported. To explain the anti-inflammation in fish, we amplified and identified the complete open reading frame of grass carp IRAK1 (CiIRAK1) and STAT3 (CiSTAT3) based on the existing sequences. The expression of CiIRAK1 and CiSTAT3 were up-regulated significantly under the stimulation of LPS. This result suggests that both Ci IRAK1 and Ci STAT3 may be involved in LPS-induced TLR4 pathway. The subcellular localization experiment revealed that Ci IRAK1 is distributed in cytoplasm and enters nucleus after LPS stimulation. Ci STAT3 is distributed in both cytoplasm and nucleus with or without LPS stimulation. Immunoprecipitation assay revealed that Ci IRAK1 interacted with Ci STAT3 under LPS stimulation. However in absence of LPS stimulation, Ci IRAK1 and Ci STAT3 cannot interact with each other. Subsequently, immunofluorescence colocalization experiment further proved the interaction of Ci IRAK1 and Ci STAT3 in nucleus under LPS stimulation. The dual luciferase reporter assays indicated that the binding of Ci IRAK1 and Ci STAT3 synergistically enhanced the activity of CiIL-10 promoter. • Grass carp IRAK1 and STAT3 can respond to LPS stimulation. • LPS promotes grass carp IRAK1 nuclear translocation. • Grass carp IRAK1 interacts with STAT3 in nuclear. • Grass carp IRAK1 and STAT3 up-regulates synergistically the promoter activity of IL-10. [ABSTRACT FROM AUTHOR]