Junctional Tension, Mechanosensing and Epithelial Homeostasis

Cell-cell adhesion physically couples epithelial cells together, contributing to the mechanical coherence that allows epithelia to resist and transmit forces and, ultimately, maintain their physiological integrity. Further, we have come to appreciate that many forces experienced at cell-cell junctions are exerted by neighbouring cells. In other words, adhesive apparatuses, notably the classical cadherin cell-cell adhesion system, serve to couple the contractile cortices of cells together. The contribution of cadherins to the mechanical coherence of epithelia thus extends beyond passive mechanical coupling. I will discuss recent evidence demonstrating that cadherin adhesion plays an active role in generating mechanically coherent tissues. 1) Cadherin adhesion contributes to establishing cellular contractility at junctions, both through generation of actin cytoskeletal networks and through the recruitment and activation of Myosin II. 2) Mechanosensitive pathways allow cadherin junctions to sense and respond to alterations in mechanical forces. These include responses to altered mechanical force, exemplified by tension-sensitive actin assembly and cell signaling.