Figure 1.

Wnt signaling On–Off. A schematic model portraying Wnt signaling On–Off states. (a) OFF status. When Wnt ligands are absent, the “destruction complex” actively acts to tag β-catenin (e.g., phosphorylation) for degradation via the proteasomal compartment. FZDs are ubiquitinated, internalized, and degraded in the endosome. (b) ON status. In the presence of Wnt ligands, the “destruction complex is dismantled and recruited to the cell membrane, and β-catenin is accumulated. In the presence of RSPO, no ubiquitination of FZDs takes place.