Figure 3

Solute carrier transporters (SLCs) in the BECs (A) and in the CP epithelial cells (B). Only SLC involved in transport of monosaccharides, amino-acids, monocarboxylic acids and peptides are shown. A. A proposed model of SLCs distribution in BECs. A question mark with MCT8 transporter indicates that in BECs this transporter is detected at the transcript level, but its cellular localization is not clear. Also, there are conflicting data on LAT2 expression, also indicated by a question mark. Members of the peptide transporters family (PTR) are not present in BECs. B. A proposed model of SLCs distribution in CPE cells. A question mark indicates that there is conflicting data about presence of SGLT1 in CPE cells. Symbols in superscript indicate: ^a -GLUT1 is present in the apical membrane of the CPE cells, but it is much less abundant in that membrane than in the basolateral membrane; ^b - System y⁺ was detected at the transcript level in CPE cells and functional uptake studies indicated that it was located in the basolateral membrane; ^c - Uptake studies in the rat in vivo indicated that EAAT1 substrates aspartate and glutamate were taken by CPE from CSF side by a saturable and stereospecific mechanism that did not show cross-inhibition with neutral amino acid. However, EAAT1 is not expressed in normal CPE in humans and is expressed in dedifferentiated CPE cells in CP tumors; ^d-CPE cells express MCT 1, but at much lower level than BECs and cellular localization of this isoform includes both basolateral and apical membranes. CPE cells also express a lysosomal AA transporter LYAAT1, which is located intracellularly.