CPE-mediated enhancement of [3H] DA uptake. A, Representative saturation plots of [3H]DA uptake in HEK-293 cells expressing the DAT alone or coexpressing-CPE revealed an increase in the Vmax for [3H] DA uptake accumulation (n = 9, P < 0.01) with no significant alteration in estimated Km values (listed in the text). B, CPE-mediated increase in [3H] DA uptake by DAT was blocked with the coexpression of a minigene encoding the DAT-CT583–620 peptide but did not alter the uptake of cells expressing DAT alone (n = 4, P < 0.01). C, Representative curves of the dose-dependent inhibition of [3H] WIN (4 nM) binding by dopamine to DAT. Coexpression of CPE and DAT did not alter the estimated affinity value of dopamine for DAT (IC50 values listed in the text). D, Estimated IC50 values in control or CPE coexpressing cells. Values represent the means ± SEM of 3–9 independent experiments, each conducted in duplicate. Data were analyzed by ANOVA, followed by post hoc Student-Newman-Keuls test. **, P < 0.01 compared with the group cotransfected with DAT and pcDNA3; ##, P < 0.01 compared with the group cotransfected with DAT and CPE.