Fig. 3: RA-V represses NF-κB activation upstream of the IKK protein complex.

a RA-V inhibited the TRAF2- and MyD88-induced expression of the NF-κB reporter in a dose-dependent manner. The indicated plasmids were transfected into HEK293T cells together with the 5 × κB-luciferase and pTK-Renilla reporters. Twenty-four hours after transfection, the cells were incubated with various concentrations of RA-V for 48 h before luciferase assays were performed. b RA-V inhibited TRAF2- and MyD88-induced p65 phosphorylation and IκBα phosphorylation in a dose-dependent manner. HEK293T cells were transfected with TRAF2, MyD88, IKKβ, or p65 for 24 h and then treated with various concentrations of RA-V for 48 h. The cell lysates were immunoblotted with the indicated antibodies. c RA-V likely exerts its inhibitory activity on the NF-κB pathway by acting on the TRAF6-TAK1–TAB1/2 complex. Using drugCIPHER, ARRB1 is a potential target of RA-V, as ARRB1 ranks 44th of 13388 genome-wide candidates. TRAF6-TAK1–TAB1/2 complex is a key link that connects ARRB1 and the NF-κB signaling pathway by searching the STRING database. The data in a and b are presented as the means ± S.D. from three independent experiments. *, p < 0.05; **, p < 0.01