aquaporin-3; AQP-3 (AQP3)

Function

• forms a water-specific channel that provide kidney medullary collecting duct with high permeability to water, permitting water to move in the direction of an osmotic gradient
• may function as a water & urea exit mechanism in antidiuresis in collecting duct cells
• slightly permeable to urea & glycerol
• may play an important role in gastrointestinal tract water transport & in glycerol metabolism (putative)

Structure

• aquaporins contain two tandem repeats each containing 3 membrane-spanning domains & a pore-forming loop with the signature motif Asn-Pro-Ala (NPA)
• belongs to the MIP/aquaporin (TC 1.A.8) family

Compartment

• basolateral cell membrane in collecting ducts of kidney

Alternative splicing

named isoforms=2

Expression

• widely expressed in epithelial cells of kidney (collecting ducts) & airways, in keratinocytes, immature dendritic cells & erythrocytes
• isoform 2 is not detectable in erythrocytes at the protein level

Polymorphism

• AQP3 is responsible for the GIL blood group system
• polymorphism at the 5'-splice donor site of intron 5, leading to exon 5 skipping & premature termination of translation
• isoform 2 is detected in GIL-negative individuals that lack functional AQP3

More general terms

• transmembrane 6 protein
• aquaporin
• glycoprotein

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=360
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:360
• OMIM: https://mirror.omim.org/entry/600170
• OMIM: https://mirror.omim.org/entry/607457
• UniProt: http://www.uniprot.org/uniprot/Q92482.html