Which epithelial junction is primarily linked to the actin cytoskeleton and mediates cell–cell adhesion?

• A. Tight junctions
• B. Adherens junctions
• C. Desmosomes
• D. Gap junctions

Answer: (B)

The junctions that directly connect the cell–cell boundary to the actin cytoskeleton to hold neighboring epithelial cells together are the adherens junctions. They use transmembrane cadherins on one cell that bind to cadherins on a neighboring cell in a calcium-dependent, homophilic manner. Inside the cell, these cadherins link to actin filaments through catenins and other actin-binding proteins like vinculin, anchoring the junction to the actin network and allowing mechanical forces to be transmitted across the cell sheet. This creates a belt-like structure around cells, known as the zonula adherens, which is essential for maintaining tissue integrity and coordinating movement during morphogenesis. In contrast, tight junctions sit at the apex and mainly regulate paracellular permeability and polarity, not the main adhesive link to actin. Desmosomes provide adhesion by connecting to intermediate filaments, not actin, while gap junctions form channels for intercellular communication rather than adhesion.