AQP5

Aquaporin 5 (AQP5) is a protein that in humans is encoded by the AQP5 gene. AQP5 is a member of the aquaporin family, a group of small, integral membrane proteins related to the transport of water across cell membranes. AQP5 plays a critical role in the generation of saliva, tears, and pulmonary secretions.

Function

AQP5 is predominantly expressed in the salivary glands, airways of the lungs, and the eye's cornea and lacrimal gland, where it facilitates the transport of water. In the salivary glands, AQP5 is crucial for the production of saliva, affecting both its volume and composition. In the lungs, AQP5 helps maintain the moisture of the airway surfaces and is involved in the production of pulmonary secretions. In the eye, AQP5 plays a role in maintaining the moisture and transparency of the cornea and is involved in tear production.

Clinical Significance

Alterations in AQP5 expression or function have been associated with several diseases. In Sjögren's syndrome, an autoimmune disease that primarily affects the salivary and lacrimal glands, reduced expression of AQP5 has been observed, which contributes to the dry mouth and dry eyes symptoms characteristic of the disease. In pulmonary edema, the inappropriate accumulation of AQP5 in the lung airspaces has been implicated in the excessive fluid retention. Furthermore, AQP5 has been studied in the context of cancer, where its overexpression in certain tumors has been linked to tumor progression and metastasis.

Genetics

The AQP5 gene is located on the long (q) arm of chromosome 12 at position 13.12, designated as 12q13.12. Variants within or near the AQP5 gene have been associated with susceptibility to certain diseases, including Sjögren's syndrome and other disorders affecting the salivary and lacrimal glands.

Research Directions

Research on AQP5 continues to explore its potential as a therapeutic target. For diseases characterized by dryness, such as Sjögren's syndrome, strategies to upregulate AQP5 expression or function are being investigated. Conversely, in conditions where fluid retention is problematic, such as in pulmonary edema, approaches to downregulate AQP5 are being studied. Additionally, given the role of AQP5 in cancer, it is being explored as a potential target for cancer therapy.