Fig. 2. Serotonin uptake function of CHO-QQ and Lec4-SERT cells.
The uptake of serotonin by CHO-QQ cells or Lec4-SERT cells was greatly reduced compared with wild-type SERT in CHO cells. [3H]Serotonin uptake was measured in intact cells transiently expressing the transporters as described under “Experimental Procedures.” Background accumulation of [3H]serotonin was measured in the same experiment using mock-transfected cells and subtracted from each experimental value. Maximum background accumulation was 0.01 pmol/mg of protein/min. White bars represent CHO cells; hatched bars represent Lec4 cells (Origin plotting program, MicroCal Software). Mutation of both potential glycosylation sites caused a 70% decrease in the serotonin uptake function in CHO cells, but only 37% decrease in Lec4 cells. No difference was observed with Q1 or Q2.