Discovery of Novel Small Molecule Activators of beta-Catenin Signaling

Wnt/beta-catenin signaling plays a major role in embryonic development and adult stem cell maintenance. Reduced activation of the Wnt/beta-catenin pathway underlies neurodegenerative disorders and aberrations in bone formation. Screening of a small molecule compound library with a beta-galactosidase fragment complementation assay measuring beta-catenin nuclear entry revealed bona fide activators of beta-catenin signaling. The compounds stabilized cytoplasmic beta-catenin and activated beta-catenin-dependent reporter gene activity. Although the mechanism through which the compounds activate beta-catenin signaling has yet to be determined, several key regulators of Wnt/beta-catenin signaling, including glycogen synthase kinase 3 and Frizzled receptors, were excluded as the molecular target. The compounds displayed remarkable selectivity, as they only induced beta-catenin signaling in a human osteosarcoma U2OS cell line and not in a variety of other cell lines examined. Our data indicate that differences in cellular Wnt/beta-catenin signaling machinery can be exploited to identify cell type-specific activators of Wnt/beta-catenin signaling.