Figure 1.

Localization of EAAT2a and EAAT2b in MDCK cells. A, Confocal images of single horizontal sections through the middle of MDCK cells stably expressing EGFP-EAAT2a or EAAT2b. Scale bars: 50 μm. B, Density measurements were taken across the cells and used to quantify cell-surface expression of the isoforms (see Materials and Methods). *p < 0.005 by paired t test (n = 4). Error bars indicate SEM. C, EAAT2 isoforms from polarized MDCK cells that were biotinylated from the apical (A) or basolateral (B) membrane surface show membrane expression of the two carriers. EAAT2a expression is found in both the apical and basolateral membranes as described previously (Cheng et al., 2002); however, EAAT2b is found only in the basolateral membrane. Furthermore, the overall surface expression of EAAT2b is greater than that of EAAT2a.