Intestinal epithelial apical junctional complex proteins (AJC proteins)

The intestinal epithelial apical junctional complex (AJC) is a specialized structure composed of tight junctions (TJs) and adherens junctions (AJs) that regulates the paracellular barrier between epithelial cells (Lee, 2015, PubMed: 25647722). Tight junctions, which include proteins such as claudins, occludin, and zonula occludens (ZO-1), act as a gatekeeper for the passage of ions, water, and solutes while preventing the entry of pathogens and toxins (Groschwitz & Hogan, 2009, PubMed: 19586907). Adherens junctions, primarily formed by E-cadherin and catenins, provide the mechanical adhesive force necessary to hold cells together and serve as a foundation for TJ assembly (Buckley & Turner, 2018, PubMed: 29146450). Disruption of these junctional proteins is a key pathological feature in diseases like inflammatory bowel disease (IBD), celiac disease, and irritable bowel syndrome (IBS), leading to increased intestinal permeability or "leaky gut" (Chelakkot et al., 2018, PubMed: 30013308). Therapeutic interventions aim to restore barrier integrity by modulating these proteins or inhibiting the signaling pathways that cause their internalization or degradation. For example, larazotide acetate is a peptide that inhibits zonulin-induced tight junction disassembly, while other agents like lubiprostone promote the assembly of these complexes through chloride channel activation (Khaleghi et al., 2021, PubMed: 33440475; Cuppoletti et al., 2012, PubMed: 22403571). Understanding the dynamics of the AJC is crucial for developing targeted therapies that can repair the intestinal barrier and mitigate chronic inflammation.

Other names

Tight junction proteinsAdherens junction proteinsIntestinal barrier proteinsApical junctional complex

Modulation of paracellular permeability through the stabilization or assembly of tight junction and adherens junction proteins, often by antagonizing zonulin or activating chloride channels (Khaleghi et al., 2021, PubMed: 33440475; Cuppoletti et al., 2012, PubMed: 22403571).