All epithelial cells express the transmembrane adhesion molecule E-cadherin, a cadherin which localises most prominently to the junction between the apical and lateral membranes. The extra-cellular domains of E-cadherin molecules from neighbouring cells bind to one another via a homotypic interaction. The intra-cellular domains of E-cadherin molecules bind to the actin cytoskeleton via the adaptor proteins alpha-catenin and beta-catenin. Thus, E-cadherin forms adherens junctions that connect the actin cytoskeletons of neighbouring cells. Adherens junctions are the primary force-bearing junctions between epithelial cells and are fundamentally important for maintaining epithelial cell shape and for dynamic changes in shape during tissue development. How E-cadherin localizes to the boundary between apical and lateral membranes is not known, but polarized membranes are essential for maintaining E-cadherin at adherens junctions.
