Water channel required to promote glycerol permeability and water transport across cell membranes (PubMed:12239222, PubMed:30420639). Acts as a glycerol transporter in skin and plays an important role in regulating SC (stratum corneum) and epidermal glycerol content. Involved in skin hydration, wound healing, and tumorigenesis. Provides kidney medullary collecting duct with high permeability to water, thereby permitting water to move in the direction of an osmotic gradient. Slightly permeable to urea and may function as a water and urea exit mechanism in antidiuresis in collecting duct cells. It may play an important role in gastrointestinal tract water transport and in glycerol metabolism (By similarity). Widely expressed in epithelial cells of kidney (collecting ducts) and airways, in keratinocytes, immature dendritic cells and erythrocytes. Isoform 2 is not detectable in erythrocytes at the protein level. Up-regulated by magnesium. Aquaporins contain two tandem repeats each containing three membrane-spanning domains and a pore-forming loop with the signature motif Asn-Pro-Ala (NPA). AQP3 is responsible for the GIL blood group system. Isoform 2 is detected in GIL-negative individuals that lack functional AQP3. Due to a polymorphism at the 5'-splice donor site of intron 5, leading to exon 5 skipping and premature termination of translation. This is the molecular basis of the GIL blood group. Belongs to the MIP/aquaporin (TC 1.A.8) family. Blood group antigen gene mutation database