Adherens

Adherens junctions, or adherens, are cell–cell junctions that mechanically couple the actin cytoskeleton of adjacent cells. In epithelial tissues they form a belt-like structure called the zonula adherens just below tight junctions and help maintain tissue integrity and coordinate cell movements during morphogenesis.

Classical adherens junctions are defined by transmembrane cadherins, most notably E-cadherin in epithelia, which engage in homophilic, calcium-dependent adhesion. The cadherin cytoplasmic tails bind catenins (beta-catenin and p120-catenin), which link to the actin cytoskeleton through alpha-catenin and other actin-binding proteins such as vinculin. The complex is dynamic and regulated by calcium levels, phosphorylation, endocytosis, and remodeling of the actin network.

Functions include providing tensile strength, enabling cell sorting, and facilitating tissue remodeling during development and wound healing. Adherens junctions work with tight junctions to establish epithelial polarity and are involved in morphogenetic movements. They are dynamic structures that undergo turnover and recycling of cadherins in response to mechanical and signaling cues.

Adherens junctions are distinct from desmosomes, which connect cells via intermediate filaments through desmosomal cadherins. However, both types contribute to tissue cohesion. Downregulation or loss of E-cadherin is associated with epithelial-to-mesenchymal transition, enabling cells to detach and migrate during development and cancer progression.

In addition to their adhesive role, beta-catenin can participate in Wnt signaling when released from cadherin complexes, linking cell–cell adhesion to transcriptional regulation and development.