Claudin 25

Claudin 25 is a protein that in humans is encoded by the CLDN25 gene. It is a member of the claudin family, integral membrane proteins that are components of the epithelial cell tight junctions, which regulate movement of solutes and ions through the paracellular space. These proteins are expressed in different patterns in different organ systems, but their function is not fully understood. Claudin 25 is known to be expressed in the gastrointestinal tract and kidney.

Structure

Claudin 25, like all claudins, is a small (20-27 kDa) protein with four transmembrane domains and two extracellular loops. The N- and C-termini of the protein are both located in the cytoplasm. The first extracellular loop contains charged amino acids that are thought to form the ion selectivity filter of the tight junction.

Function

The exact function of Claudin 25 is not yet fully understood. However, it is known that claudins play a crucial role in tight junction formation and function. They are involved in maintaining cell polarity and signal transduction. In the gastrointestinal tract and kidney, Claudin 25 may be involved in regulating the paracellular transport of small ions, including sodium and potassium.

Clinical significance

Alterations in the expression or function of claudins can disrupt tight junctions and lead to disease. For example, mutations in claudin genes have been associated with several human diseases, including inflammatory bowel disease, deafness, and cancer. However, the role of Claudin 25 in human disease is not yet clear and is a topic of ongoing research.

See also

• Claudin
• Tight junction
• Epithelial cell

References

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