β-Catenin is a key downstream effector in the Wnt signaling pathway. It is implicated in two major biological processes in vertebrates: early embryonic development and tumorigenesis. CK1 phosphorylates β-catenin at Ser45. This phosphorylation event primes β-catenin for subsequent phosphorylation by GSK-3β. GSK-3β destabilizes β-catenin by phosphorylating it at Ser33, Ser37, and Thr41. Mutations at these sites result in the stabilization of β-catenin protein levels and have been found in many tumor cell lines.
