Figure 2. An illustration of the Wnt signaling pathway. Without Wnt ligand stimulation, β-cat is trapped within the “destruction complex,” phosphorylated by the protein kinase GSK-3 and CK-1α at Ser33 and adjacent Ser positions, and subsequently degraded by proteasome (left). Following Wnt ligand stimulation and Dishvelled (Dvl) activation, β-cat escapes the trapping, enters the nucleus and forms the bipartite transcription factor cat/TCF, which leads to the stimulation of Wnt target gene expression (middle). GLP-1 was shown to activate cAMP-dependent protein kinase A (PKA), and stimulate β-cat Ser675 phosphorylation, which is positively associated with its nuclear translocation and Wnt target gene expression (right).