Fig. 1.

Critical intra- and intercellular forces acting within a polarized epithelium and key molecular structures. a The illustration shows the working model for polarized epithelium tension and intercellular adhesion forces. Cell–cell contacts transmit mechanical tension through a dynamic coupling between adherens and tight junctions and the perijunctional actomyosin cytoskeleton. The epithelium contractility generates an isotropic tension balanced by the intercellular normal and shear adhesive forces. The free body diagram presents the variables used in our theoretical model where; f is the pulling force acting at tricellular junctions, F _NA is the intercellular normal adhesive force, F _SA is the intercellular shear adhesive force, and l _i is the cell edge length. b Diagram illustrating the localization and molecular structural composition of the actomyosin cytoskeleton belt interacting with tight and adherens junctions. In the tight junctions the ZO-1, ZO-2, and ZO-3 proteins bind to the transmembrane receptor proteins claudins and occludins and to the perijunctional actin cytoskeleton plaque. In the adherens junctions catenin proteins bind to the transmembrane cadherins and to the actomyosin belt with large F-actin bundles and bipolar myosin II bipolar minifilaments motors