Aquaporins selectively conduct water molecules in and out of the cell, while preventing the passage of ions and
other solutes. Known as water channels, they are
integral membrane pore proteins (1, 2).
Aquaporin 2 is the vasopressin-regulated water channel
of the apical membrane of collecting duct cells. It is
located in kidney epithelial cells and usually lies dormant
in intracellular vesicle membranes. When it is needed
vasopressin binds to the cell surface vasopressin
receptor, activating a signaling pathway that cause AQP2
containing vesicles to fuse with the plasma membrane so
the AQP2 can be used by the cell (3). Defects in AQP2
area cause of an autosomal dominant form of
nephrogenic diabetes insipidus (NDI) (4).