Aquaporin channel protein (AQP)

Aquaporins are a family of integral membrane channel proteins that facilitate the rapid and highly selective transport of water (and, in some subtypes, glycerol and small solutes) across cell membranes[1][4][7]. Each aquaporin assembles as a homotetramer in the membrane, with each monomer forming its own water channel lined by six α-helical transmembrane segments and highly conserved NPA (Asn-Pro-Ala) motifs that help establish water selectivity[1][2][3][4][7]. Aquaporins are found in virtually all forms of life, including bacteria, plants, and animals, and play diverse roles in osmoregulation, renal water reabsorption, secretion in exocrine glands, and maintenance of central nervous system water balance[1][7]. Genetic mutations or antibody-mediated targeting of specific aquaporins (notably AQP2, AQP4) are implicated in human diseases such as nephrogenic diabetes insipidus and neuromyelitis optica[1]. Despite their fundamental importance, there are few selective small-molecule aquaporin modulators in clinical use; targeting remains challenging due to the ubiquity of these channels and the potential for systemic side effects[7]. *The aquaporin family includes many members, primarily distinguished by their tissue distribution and permeability to solutes beyond water. Classic examples include AQP1 (erythrocytes and kidney), AQP2 (kidney collecting duct), AQP4 (brain astrocytes), and the aquaglyceroporins (e.g., AQP3, AQP7, AQP9), which are also permeable to glycerol and other small molecules[4][7].*

Other names

water channel proteinmajor intrinsic protein (MIP)aquaglyceroporin (for specific subtypes)

Channel blockade (direct or indirect inhibition of water permeation); Alteration of protein trafficking (regulating surface abundance, e.g., vasopressin-induced AQP2 trafficking); Modulation of expression (steroid and non-steroidal regulation)