FIGURE 4.

Transport activity of N-terminal KCC2 mutants. HEK-293 cells were transfected with KCC2^WT and KCC2 mutant constructs, and transport activity was determined by performing Tl⁺ flux measurements. Compared with KCC2^WT, the N-terminal single mutants KCC2^S25A, KCC2^S25D, KCC2^S26A, and KCC2^S26D and the double mutants KCC2^S25A/S26A and KCC2^S25D/S26D showed no significant differences in transport activity. Confirming previous studies, KCC2^T906A and KCC2^T1007A displayed a significantly higher transport activity compared with KCC2^WT. In the presence of furosemide, the Tl⁺ flux was blocked. Graphs represent mean ± S.E. of at least three independent measurements, normalized to KCC2^WT. Statistical analysis is presented in Table 3.