Claudins are tetraspan transmembrane proteins of tight junctions. They determine the barrier properties of this type of cell-cell contact existing between the plasma membranes of two neighbouring cells, such as occurring in endothelia or epithelia.
Where are claudin protein found in?
The claudin family consists of 24 known transmembrane proteins exhibiting distinct tissue- and development-specific distribution patterns [37, 38]. They are detected in both epithelial and endothelial cells and form a complex with occludin and/or JAMs [32, 39].
What is occludin and claudin?
Claudin and occludin are major transmembrane proteins of the tight junction that provide tight control over paracellular diffusion within an epithelium. Interestingly, claudin and occludin are often targeted and misplaced by viruses,1, 6 bacteria,7, 8 and inflammatory cytokines.
What are tight junctions for?
Tight junctions form the continuous intercellular barrier between epithelial cells, which is required to separate tissue spaces and regulate selective movement of solutes across the epithelium.
How can I improve my intestinal tight junctions?
Vitamin D and zinc also have a protective effect on tight junctions. Zinc specifically can help against damaged caused by chronic alcohol exposure, diarrhea, colitis, and other gastrointestinal ailments. Diets that are high in sugar can damage your intestinal wall and causes diseases such as Type II diabetes.
What do Occludins do?
Function. Occludin is an important protein in tight junction function. Studies have shown that rather than being important in tight junction assembly, occludin is important in tight junction stability and barrier function.
What is paracellular reabsorption?
Paracellular reabsorption of Cl− is driven by a lumen negative potential through the tight junction in the collecting duct of the kidney. Two claudin proteins – claudin-4 and claudin-8 make the paracellular pathway for Cl− permeation.
Where is occludin made?
Occludin was the first integral tight junction membrane protein to be identified. It has four transmembrane domains with intracellular N- and C-termini. Occludin is ubiquitously expressed in epithelial cells, localizing predominantly at bicellular junctions (junctions where two cells meet).
Is claudin a glycoprotein?
There were also three samples of normal human mammary epithelial cells (HMEC) grown in primary culture and two from cell lines established from benign tumors (MCF10A, MCF12A). Claudin proteins are not N-linked glycoproteins and are not present in the data set.
What proteins are involved in tight junctions?
Tight junction complex is composed of occludin and claudin proteins, adhesion junctions (integral membrane-bound cadherins and cytoplasmic accessory proteins, i.e., α and β catenin), JAM-1, and accessory proteins (ZO-1, ZO-2, ZO-3).
What is the function of the claudin family of proteins?
Although the exact roles of these proteins are not completely clear, it seems that the claudins form the backbone of the tight junction strands. The claudin family of proteins is comprised of 23 members of closely related transmembrane proteins (see Fig. 1 ).
What is the structure of a Claudin?
Structure of claudins. Claudin proteins are a family of proteins containing four transmembrane domains. The extracellular loops represent promising targets for therapy using monoclonal antibodies or, in the case of claudin-3 and claudin-4, the CPE.
What is the role of claudin-3 and Claudin 4 in cancer?
In particular, claudin-3 and claudin-4 are frequently overexpressed in several neoplasias, including ovarian, breast, pancreatic, and prostate cancers. Although the exact roles of these proteins in tumorigenesis are still being uncovered, it is clear that they represent promising targets for cancer detection, diagnosis, and therapy.
How do claudins affect tight junction function in cancer?
In addition to the down-regulation of protein levels, phosphorylation of tight junction proteins, including claudins, may affect tight junction function in cancer ( 14 ).
