Aquaglyceroporins

Aquaglyceroporins are a subfamily of the aquaporin family of membrane channels that allow rapid passage of water and small solutes, most notably glycerol, across cell membranes. Like other aquaporins, they are integral membrane proteins that assemble as tetramers in the plasma membrane. Each monomer forms a water-conducting pore, and a constriction formed by the aromatic/arginine (ar/R) filter and the NPA motifs determines permeability to glycerol and other solutes. Gating and regulation can modulate their activity in response to cellular needs.

In humans, the best-characterized aquaglyceroporins are AQP3, AQP7, AQP9 and AQP10. AQP3 is expressed in skin and mucosa and transports water and glycerol, influencing skin hydration and elasticity. AQP7 is found in adipose tissue and mediates glycerol efflux during lipolysis. AQP9, abundant in liver and some immune cells, transports glycerol and other small solutes; AQP10 is expressed in the intestinal epithelium and can facilitate glycerol transport under certain conditions.

Beyond humans, aquaglyceroporins are widespread in animals, plants and microorganisms and participate in osmoregulation, metabolism and stress responses. In plants, glycerol-permeable aquaporins contribute to glycerol fluxes during development and in response to drought. The physiological roles of aquaglyceroporins reflect the need to balance water movement with the transport of compatible solutes like glycerol for energy production and redox balance.

Regulation and research: They can be regulated by phosphorylation, pH, and interactions with cytosolic factors; structural analyses have revealed details of the pore and selectivity filter that underlie glycerol transport. Because of their roles in metabolism, skin physiology and stress responses, aquaglyceroporins are active areas of study for metabolic and dermatological conditions.