Figure 2.

The effect of MB on ASP⁺ uptake in EM4 cells transiently transfected with GFP-hSERT. Confocal images presented in panel A show an image of cells expressing GFP-hSERT. GFP-hSERT is indicated by green fluorescence and ASP⁺ by red fluorescence. Co-localization of the two fluorophores is indicated by the merged images (yellow). GFP-hSERT and ASP⁺ localization before time 0 (top panel) or 5 s (middle panel) and 40 s (lower panel) after ASP⁺ addition are shown. These images show that ASP⁺ rapidly binds to hSERT located on the cell surface followed by a slower phase of intracellular ASP⁺ accumulation. (B) Time course of mean ASP⁺ uptake in control and MB-treated cells (n= 8–9 cells per treatment) is shown. Note the initial rapid binding phase after ASP⁺ addition followed by the linear uptake phase. Addition of MB (3 µM) decreases the rate of ASP⁺ uptake relative to vehicle (distilled water) values. The change in hSERT function is presented as the change in the slope of uptake measured for 1 min immediately before and 5 min after MB addition. Each data point represents the mean ± SEM fluorescent intensity, which was calculated as AFU. (C) The bar graph compares the changes in ASP⁺ accumulation rates calculated after 5 min application of vehicle (0.1% distilled water) or MB. The data are from three different experiments. The numbers of cells are presented below each bar. *P < 0.01, significantly different.