Aquaporin 7 (AQP-7) belongs to a family of membrane proteins that allow passage of water and certain other solutes through biological membranes. The family is composed of 13 members (AQP-0 to AQP-12). Little is known about the function of the two newest members, AQP-11 and AQP-12.
The aquaporins can be divided into two functional groups based on their permeability characteristics: the aquaporins that are only permeated by water and the aquaglyceroporins that are permeated by water and other small solutes such as glycerol. This last group includes AQP-7, AQP-3, AQP-9 and AQP-10.
The proteins present a conserved structure of six transmembrane domains with intracellular N- and C-termini. The functional channel is a tetramer but each subunit has a separate pore and therefore the functional channel unit, contains four pores.
AQP-7 is expressed in ovary, testis, kidney and adipose tissue.
The function of AQP-7 in adipose tissue attracted much interest as mice deficient in AQP-7 developed adult-onset obesity and type 2 diabetes. AQP-7 modulates adipocyte glycerol permeability thereby controlling triglyceride accumulation and fat cell size
