Fig. 1. Schematic model. (A) Wnt-off condition. In the absence of Wnt or below a certain threshold of Wnt, active merlin bind to LRP6 and inhibits Wnt/β-catenin signaling. (B) In the presence of Wnt, the level of PIP2 is increased, which could be used as a docking site for PAK1. Active PAK1 phosphorylates Merlin on Ser518, resulting in detachment of Merlin from LRP6 and allowing activation of LRP6 for the initiation of Wnt/β-catenin signaling.
