In metazoan adherens junctions, β-catenin links thecytoplasmic tail of classical cadherins to the F-actin-binding protein α-catenin. Phosphorylation of a Ser/Thr-rich region in the cadherin tail dramatically enhances affinity for β-catenin and promotes cell-cell adhesion in cell culture systems, but its importance has not been demonstrated invivo. Here, we identify a critical phosphorylated serine in the C.elegans cadherin HMR-1 required for strong binding to the β-catenin homolog HMP-2. Ablation of this phosphoserine interaction produces developmental defects that resemble full loss-of-function (Hammerhead and Humpback) phenotypes. Most metazoans possess a single gene for β-catenin, which is also a transcriptional coactivator in Wnt signaling. Nematodes and planaria, however, have a set of paralogous β-catenins; for example, C.elegans HMP-2 functions only in cell-cell adhesion, whereas SYS-1 mediates transcriptional activation through interactions with POP-1/Tcf. Our structural data define critical sequence differences responsible for the unique ligand specificities of these two proteins.
Choi, H. J., Loveless, T., Lynch, A. M., Bang, I., Hardin, J., & Weis, W. I. (2015). A conserved phosphorylation switch controls the interaction between cadherin and β-Catenin in vitro and in vivo. Developmental Cell, 33(1), 82–93. https://doi.org/10.1016/j.devcel.2015.02.005