Tight junction protein complex (TJ) (TJ)

The tight junction protein complex is a multi-protein structure located at the apical-most part of the lateral cell membrane in epithelial and endothelial cells. It serves as a primary regulator of the paracellular barrier, controlling the flow of ions and solutes while preventing the translocation of pathogens and toxins (StatPearls, NBK532240). The complex is composed of transmembrane proteins such as claudins, occludin, and junctional adhesion molecules (JAMs), which interact with intracellular scaffolding proteins like zonula occludens (ZO-1) to link the junction to the actin cytoskeleton (UniProt, Q16625). Dysfunction of these proteins is linked to various pathologies, including inflammatory bowel disease and celiac disease, where leaky barriers allow for chronic immune activation (Nature Reviews, 10.1038/nrgastro.2014.182). In oncology, specific proteins like Claudin-18.2 are targeted by monoclonal antibodies such as zolbetuximab to treat gastric cancers. Therapeutic interventions aim to either reinforce the barrier to treat inflammatory conditions or selectively open it to facilitate drug delivery across the blood-brain barrier or intestinal epithelium. Additionally, the complex plays a vital role in maintaining cell polarity, which is often lost during epithelial-mesenchymal transition in metastatic cancer.

Other names

Zonula occludensOccluding junctionsEpithelial barrierParacellular barrierTight junction proteins

Antagonism of zonulin-mediated tight junction disassembly; Monoclonal antibody-mediated targeting of specific claudin isoforms; Activation of chloride channels to promote junctional assembly; GLP-2 receptor agonism to promote mucosal growth and barrier integrity.