aquaporiner

Aquaporiner is not a standard term in mainstream biology. In most literature, a similar-sounding word refers to aquaporins, a family of integral membrane proteins that form channels selective for water and, in some cases, small solutes. When encountered, aquaporiner typically denotes aquaporin-related proteins or may result from a spelling variant or translation difference. The rest of this article summarizes the established concept of aquaporins.

Aquaporins are part of the major intrinsic protein (MIP) family and function as channels that enable rapid, bidirectional water movement across cell membranes in response to osmotic gradients. Each aquaporin monomer typically contains six transmembrane alpha-helices and assembles as a tetramer in the membrane; within each monomer, a pore conducts water. Many aquaporins contain conserved NPA (asparagine–proline–alanine) motifs that contribute to selectivity and pore structure, and a second region, the aromatic/arginine (ar/R) filter, helps determine which molecules can pass.

Diversity among aquaporins includes water-selective channels and aquaglyceroporins, which also permit glycerol and some other small solutes. Tissue distribution is broad: for example, AQP2 in kidney collecting ducts is regulated by vasopressin to control water reabsorption; AQP4 supports water homeostasis in the brain; AQP0 functions in the lens. Regulation occurs through trafficking to and from the membrane, phosphorylation, pH, and interacting partners.

Clinical relevance includes disorders from impaired water balance, such as nephrogenic diabetes insipidus due to AQP2 mutations, and potential roles in edema, brain injury, and cancer. The discovery of aquaporins by Peter Agre in 1991 led to the 2003 Nobel Prize in Chemistry. See also aquaporin and membrane transport proteins.