Mechanism Research Of KCTD1in Sup-Pressesing Canonical Wnt Signaling Pathway

The canonical Wnt signaling pathway controls normal embryonic development, cellular proliferation and growth, and its aberrant activity results in human carcinogenesis. The core component in regulation of this pathway is β-catenin, but molecular regulation mechanisms of p-catenin stability are not completely known. Here, our recent studies have shown that KCTD1strongly inhibits TCF/LEF reporter activity. Moreover, KCTD1interacted with β-catenin both in vivo by co-immunoprecipitation as well as in vitro through GST pull-down assays. We further mapped the interaction regions to the1-9armadillo repeats of P-catenin and the BTB domain of KCTD1, especially Position Ala-30and His-33. Immunofluorescence analysis indicated that KCTDl promotes the cytoplasmic accumulation of P-catenin. Furthermore, protein stability assays revealed that KCTD1enhances the ubiquitination/degradation of P-catenin in a concentration-dependent manner in HeLa cells. And the degradation of β-catenin mediated by KCTD1was alleviated by the proteasome inhibitor, MG132. In addition, KCTD1-mediated P-catenin degradation was dependent on dependent on casein kinase1(CK1) and glycogen synthase kinase-3β (GSK-3β)-mediated phosphorylation and enhanced by the E3ubiquitin ligase β-transducin repeat-containing protein (β-TrCP). Moreover, KCTD1suppressed the expression of endogenous Wnt downstream genes and transcription factor AP-2a. Finally, we found that Wnt pathway member APC and tumor suppressor p53influence KCTD1-mediated downregulation of P-catenin. These results suggest that KCTD1functions as a novel inhibitor of Wnt signaling pathway.