Adherens junctions connect adjacent cells and consist of transmembrane cell adhesion proteins, such as N-cadherin, and their intracellular binding partners, such as p120-catenin. Peglion et al. used various imaging techniques to investigate the regulation of adherens junctions during collective cell migration (see also Hirata et al.). After scratch wounding of a confluent monolayer of primary rat astrocytes expressing GFP-tagged N-cadherin, adherens junctions continuously flowed in a retrograde manner along the lateral sides of cells at the leading edge of the wound, from the front to the rear of the cells, but stayed mostly stationary in follower cells. In migrating astrocytes, N-cadherin accumulated in clusters at the leading edge, a phenomenon that was disrupted by siRNA-mediated knockdown of p120-catenin. Vesicles containing GFP-tagged N-cadherin formed near adherens junctions at the back of migrating astrocytes and moved toward the front to the cells, suggesting endocytosis and recycling of N-cadherin, which was prevented by various manipulations that inhibit clathrin-mediated endocytosis. p120-catenin colocalized with N-cadherin at adherens junctions throughout nonmigrating cells; however, in migrating cells, it showed stronger colocalization with N-cadherin in adherens junctions at the front than at the rear. Phosphorylation of Thr310 on p120-catenin increased in cells subjected to scratch wounding, and this phosphorylated form of p120-catenin localized to adherens junctions located toward the rear of migrating cells. The interaction of a nonphosphorylatable form of p120-catenin (T310A) with N-cadherin was greater than that of wild-type p120-catenin. Endocytosis of cadherin is inhibited by binding to p120-catenin. In cells depleted of endogenous p120-catenin and expressing the T310A mutant of p120-catenin, the mutant localized to adherens junctions throughout the cells, and N-cadherin did not colocalize with clathrin. GSK-3 can phosphorylate Thr310 on p120-catenin, and pharmacological inhibition of GSK-3 in migrating cells prevented phosphorylation of Thr310, increased the colocalization of N-cadherin with p120-catenin toward the rear, and decreased the accumulation of N-cadherin and formation of adherens junctions at the leading edge. Depletion of p120-catenin decreased intercellular adhesion between leader cells, as suggested by the increased amount of free space between leader cells, and increased the mean velocity of migration. Expression of the T310A mutant of p120-catenin in these cells increased intercellular adhesion (an effect phenocopied by GSK-3 inhibition in control cells) and reduced cell migration. Thus, polarized regulation of the interaction of p120-catenin with N-cadherin by GSK-3 enables the retrograde movement and recycling of adherens junctions to enable cells to maintain cohesion during collective migration.
F. Peglion, F. Llense, S. Etienne-Manneville, Adherens junction treadmilling during collective migration. Nat. Cell Biol. 16, 639–651 (2014).[PubMed]
E. Hirata, D. Park, E. Sahai, Retrograde flow of cadherins in collective cell migration. Nat. Cell Biol. 16, 621–623 (2014). [PubMed]