The function of AQP6 (aquaporin 6, Ensembl gene identifier ENSG00000086159) is as follows. Aquaporins form homotetrameric transmembrane channels, with each monomer independently mediating water transport across the plasma membrane along its osmotic gradient (PubMed:8812490). Unlike classical aquaporins, AQP6 is an intracellular channel with selective anion permeability, particularly for nitrate, and exhibits very low water permeability (By similarity). It may also facilitate the transport of gases, such as CO2 and NH4(+), as demonstrated in vitro (By similarity). {ECO:0000250|UniProtKB:Q9WTY0, ECO:0000269|PubMed:8812490}.