Aquaporin-5

Aquaporin-5 (AQP5) is a water channel protein that is part of the aquaporin family. It is encoded in humans by the AQP5 gene. AQP5 plays a crucial role in the production of saliva, tears, and pulmonary secretions.

Structure

AQP5 is a membrane protein that forms a pore in the cell membrane, allowing water molecules to pass through. It is composed of six transmembrane domains, with both the amino and carboxy termini located on the cytoplasmic side of the membrane. The protein also has two asparagine-proline-alanine (NPA) motifs, which are characteristic of the aquaporin family.

Function

AQP5 is primarily expressed in the salivary gland, lung, and cornea, where it facilitates water transport. In the salivary gland, AQP5 is involved in the production of saliva. In the lung, it contributes to the thinness of the alveolar fluid, which is essential for normal gas exchange. In the cornea, AQP5 helps maintain the transparency of the cornea by regulating water content.

Clinical significance

Mutations in the AQP5 gene have been associated with various diseases. For example, a mutation in AQP5 can cause Sjögren's syndrome, a condition characterized by dry mouth and dry eyes. In addition, overexpression of AQP5 has been observed in several types of cancer, including lung cancer and breast cancer, suggesting that AQP5 may play a role in tumor progression.

See also

• Aquaporin
• Sjögren's syndrome
• Lung cancer
• Breast cancer