Figure 3
Comparison of Wnt activation of β-catenin signaling vs formation of β-catenin destruction complex. (Left panel) In the presence of Wnt, β-catenin is stabilized and can induce gene transcription. Various proteins that interact with the transcription factor complexes are indicated in pink circles. The Rac-1 exchange factor is indicated in a purple circle. When Wnt is absent, β-catenin is targeted for proteasomal degradation. GMP, indicated in a yellow oval, is displaced from GSK-3 and GSK-3 is able to phosphorylate β-catenin that results in its ubiquitination by the β-TrCP complex, indicated in a yellow oval. Ubiquitination is indicated by Ub in purple circles. Axin is also poly-ADP-ribosylated TNKS that is linked by PAR indicated by a purple circle that subsequently leads to its proteasomal degradation. TCF/LEF interacts with various proteins including the transcriptional regulators histone deacetylases (HDACs) and Grg/TLE, indicated in black ovals, that prevent it from inducing gene transcription. This figure is presented to provide the reader an idea of how β-catenin turnover can be regulated by GSK-3 and CK1 phosphorylation.
