Integral membrane proteins that serve as the main water channels that are universally expressed in different cell types of organisms.
Aquaporin 4 is located in the basolateral cell membrane of principal collecting duct cells that offer pathway for water to exit the cells. It is mapped to chromosome 18q11.2-q12.1 that contains four exons encoding 127,55,27 and 92 amino acids with introns of 0.8, 0.3, and 5.2 kb where it is expressed in astrocytes and upregulated directly to the nervous system. The assemblage of four molecules structure embrace the central pore through which the water cations and gases flows.
Aquaporin 4 is the main water channel in the brain that has a vital role in brain water homeostasis. It is abundant in mammalian brain and central collecting duct in the kidney as well as in strenuous astrocytic foot route at the blood-brain barrier. It has been associated with neuroinflammation in acute and chronic brain diseases since it is expressed in astrocytes and characterized by both phenotypic changes and microglial activation.
Aquaporin 4 is the chief autoimmune target in some diseases like neuromyelitis optica wherein antibodies marked astrocytic aquaporin 4 ensuing balance activation and swelling. It also functions in potassium homeostasis in assisting water diffusion along the potassium gradient during brain activity and contributes in cell migration and adhesion.
Gene name: AQP4
Protein name: Aquaporin-4
• Mercurial-insensitive water channel