Looking beyond the Wnt pathway for the deep nature of β-catenin.

After two decades of stardom, one would think that β-catenin has revealed all of its most intimate details. Yet the essence of its duality has remained mysterious--how can a single protein both be the core link between cadherins and the cytoskeleton, and the nuclear messenger for Wnt signalling? On the basis of the available evidence and on molecular and evolutionary considerations, I propose that β-catenin was a born nuclear transport receptor, which by interacting with adhesion molecules acquired the property to coordinate nuclear functions with cell-cell adhesion. While Wnt signalling diverted this activity, the original pathway might still function in modern eukaryotes.