I love it when worlds collide. I love the movies where a country boy falls for a city girl. Or a robot develops a friendship with a wookie. Hilarity typically ensues in the movies, but fantastic new ideas and questions result from the discovery of biological processes colliding. So, when I came across a recent paper that revealed new results on the relationship between endocytosis and adhesion, I was all over it.
Cell-cell adhesion is constantly adjusted throughout development, wound healing, and cancer metastasis. E-cadherin is the major adhesion molecule that functions in epithelial cell adhesion and polarity, and is linked to the actin skeleton (via α-catenin) and p120. The level of E-cadherin at the cell surface influences the adhesive strength between two cells, and this strength can be adjusted by internalization (endocytosis) of E-cadherin away from the cell surface. A recent paper discusses results showing how internalization of E-cadherin is regulated by Numb, a protein that interacts with endocytosis adaptor proteins and is important throughout development. Sato and colleagues found that Numb interacts directly with p120, and showed that impairment of Numb prevents E-cadherin internalization. The images above show cysts of epithelial cells. In control cysts (top rows), E-cadherin and p120 (red) were found at the basolateral cell-cell junctions. In cysts with reduced levels of Numb (bottom rows), both E-cadherin and p120 localized to the apical membrane region (blue) too.
Sato, K., Watanabe, T., Wang, S., Kakeno, M., Matsuzawa, K., Matsui, T., Yokoi, K., Murase, K., Sugiyama, I., Ozawa, M., & Kaibuchi, K. (2011). Numb controls E-cadherin endocytosis through p120 catenin with aPKC Molecular Biology of the Cell, 22 (17), 3103-3119 DOI: 10.1091/mbc.E11-03-0274