Aquaporins (AQPs) are a large family of integral membrane water transport channel proteins that facilitate the transport of water through the cell membrane. Aquaporin 5 (AQP5) is a water channel protein. Aquaporin 5 plays a role in the generation of saliva, tears and pulmonary secretions. In the lung, AQP5 is responsible for the majority of water transport across the apical membrane of type I alveolar epithelial cells.
