Bidirectional uniporter involved in the facilitative transport of nucleosides and nucleobases, and contributes to maintaining their cellular homeostasis (   ). Functions as a Na(+)-independent, passive transporter . Involved in the transport of nucleosides such as inosine, adenosine, uridine, thymidine, cytidine and guanosine (   ). Also able to transport purine nucleobases (hypoxanthine, adenine, guanine) and pyrimidine nucleobases (thymine, uracil) (, ). Involved in nucleoside transport at basolateral membrane of kidney cells, allowing liver absorption of nucleoside metabolites . Mediates apical nucleoside uptake into Sertoli cells, thereby regulating the transport of nucleosides in testis across the blood-testis-barrier . Mediates both the influx and efflux of hypoxanthine in skeletal muscle microvascular endothelial cells to control the amount of intracellular hypoxanthine available for xanthine oxidase-mediated ROS production (By similarity).
Non functional nucleoside transporter protein for adenosine or thymidine transport. Does not express on cell membrane.
Subcellular locations: Apical cell membrane, Basolateral cell membrane
Localized to the apical membrane of Sertoli cells.
Highly expressed in skeletal muscle . Expressed in liver, lung, placenta, brain, heart, kidney and ovarian tissues . Expressed in testis at the blood-brain-barrier .