A polarized localization of amino acid/carnitine transporter B0,+ (ATB0,+) in the blood-brain barrier

International audience; Brain capillary endothelial cells control the uptake and efflux from the brain of many hydrophilic compounds due to highly specialized transporters often localized in a polarized way. Localization of Na+- and Cl--dependent amino acid and carnitine transporter B0,+ (ATB0,+) was studied in a co-culture of bovine brain capillary endothelial cells (BBCEC) grown on filters above astrocytes (an in vitro blood-brain barrier model). Immunoblotting and three-dimensional immunocytochemistry analysis with anti- B0,+antibodies demonstrated the presence of this transporter and its prevalent co-localization with P-glycoprotein i.e. at the apical side. The sensitivity of leucine uptake through the apical membrane to 2-aminobicyclo-[2.2.1]-heptane-2-carboxylic acid (BCH), D-serine as well as sodium and chloride replacement confirm the functioning of ATB0,+ and suggests an important physiological role of ATB0,+ in controlling the delivery of amino acids and carnitine to the brain.