Wnt/β-catenin signaling induces the expression and activity of βTrCP ubiquitin ligase receptor

beta-transducing repeat-containing protein (beta TrCP) targets the ubiquitination and subsequent degradation of both beta-catenin and I kappa B, thereby playing an important role in beta-catenin/Tcf and NF-kappa B-dependent signaling. Here evidence is presented that beta-catenin/Tcf signaling elevates the expression of beta TrCP mRNA and protein in a Tcf-dependent manner, which does not require beta TrCP transcription. Induction of beta TrCP expression by the beta-catenin/Tcf pathway results in an accelerated degradation of the wild-type beta-catenin, suggesting that the negative feedback loop regulation may control the beta-catenin/Tcf pathway. This signaling also upregulated NF-kappa B transactivation without affecting the activity of I kappa B kinase, thereby establishing that the maintenance of the beta TrCP level is important for coordination between beta-catenin/Tcf and NF-kappa B signaling.