Fig. 3: Junctional network involved in intestinal paracellular transport.

TJs are classified into transmembrane and cytoplasmatic proteins. Transmembrane proteins include TAMP (TJ-associated MARVEL proteins), such as occludins, tricellulin and marvelD3, and claudins, that monitor the movement across the barrier establishing its semipermeable properties; Junctional adhesion molecules (JAMs), that sustain the TJs actively involved in paracellular pathways; and angulins, that act as regulators. Cytoplasmatic proteins include the zonula occludens (ZO) family protein, which anchors transmembrane proteins to cytoskeletal components [46]. A similar role is dictated by desmosomes and adherens junctions—belonging to the Cadherins family—that provide interaction sites and mechanical strength. In addition, gap junctions allow cell communication by releasing proteins, such as Connexin. A comprehensive description of TJs and their relation to inflammatory signalling pathways has been previously reviewed by [135]. Created with BioRender.com.