Claudin, conserved site
IPR017974
Definition
This entry represents a conserved region located in an extracellular loop between the first and second transmembrane regions. Zona occludens (ZO), or tight junctions (TJ), are specialised membrane domains found at the most apical region of polarised epithelial and endothelial cells. They create a primary barrier, preventing paracellular transport of solutes, and restricting the lateral diffusion of membrane lipids and proteins, thus maintaining cellular polarity PMID:9647647. They also act as diffusion barriers within plasma membranes, creating and maintaining apical and basolateral membrane domains. Under freeze-fracture electron microscopy, TJs appear as a network of continuous anastomosing intramembranous strands. These strands consist mainly of claudins and occludin ([interpro:IPR005417]), which are transmembrane proteins that polymerise within plasma membranes to form fibrils PMID:11283726. Recently, the molecular architecture of tight junctions has begun to be elucidated. One group of proteins thought to be major components of TJs is the claudin family PMID:10370242. Immunofluorescence studies have shown that claudins are targeted to and incorporated into tight junctions PMID:9647647. Furthermore, when claudins are introduced into cells that lack tight junctions, networks of strands and grooves form at cell-cell contact sites that closely resemble native TJs PMID:9786950. The claudin protein family is encoded by at least 17 human genes, with many homologues cloned from other species. Tissue distribution patterns for the claudin family members are distinct. Claudin-1 and -2, for example, are expressed at high levels in the liver and kidney, whereas claudin-3 mRNA is detected mainly in the lung and liver [[cite:PMID:9647647], [cite:PMID:9892664]]. This suggests that multiple claudin family members may be involved in tight junction strand formation in a tissue-dependent manner.
22 human proteins with this domain
Each is a reviewed human protein in the Seroatlas serome and a potential autoantibody target; this domain groups them into one antibody-relevant category. Every entry links to its own record.
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