Adherens junction: molecular architecture and regulation

Abstract

The adherens junction (AJ) is an element of the cell-cell junction in which cadherin receptors bridge the neighboring plasma membranes via their homophilic interactions. Cadherins associate with cytoplasmic proteins, called catenins, which in turn bind to cytoskeletal components, such as actin filaments and microtubules. These molecular complexes further interact with other proteins, including signaling molecules, rendering the AJs into highly dynamic and regulatable structures. The AJs of such nature contribute to the physical linking of cells, as well as to the regulation of cell-cell contacts, which is essential for morphogenesis and remodeling of tissues and organs. Thus, elucidating the molecular architecture of the AJs and their regulatory mechanisms are crucial for understanding how the multicellular system is organized.

Figure 1.

Morphological variations of the adherens junction. In Caco2 cells (colonic carcinoma line), E-cadherin is localized along the actin circumferential belt to organize the zonula adherens (arrow). At the lateral portions of cell junction (arrowheads), E-cadherin signals are punctate, only occasionally overlapping with actin signals in this specific sample. The lateral patterns of cadherin and actin distribution, however, vary with cellular conditions. In MCF10A cells (mammary epithelial line), spotty adherens junctions are seen, where actin filaments perpendicularly terminate at E-cadherin puncta.

Figure 2.

Representative molecular constituents of the zonula adherens. These constituents vary with the types of adherens junction.