Fig. 5. Comparison of GSK-3/ß-catenin signalling in Dictyostelium and animals. (A) Extracellular cAMP activates GskA through cAR3/ZAK1 and inhibits it through cAR4. GskA positively regulates the ß-catenin homologue, Aar. (B) The extracellular ligand Wnt-1 stimulates the co-receptors Frizzled (Fz) and LRP5 (or LRP6) to inhibit GSK-3 function through Dishevelled (Dsh). GSK-3 negatively regulates ß-catenin. (C) In nematodes, the Wnt homologue, MOM-2, acts positively on GSK-3 function via the Fz protein MOM-5. GSK-3 appears to positively regulate the ß-catenin homologue WRM-1.
