TABLE 1
[3H]GABA uptake by the WT and mutants in HeLa cells
Uptake of [3H]GABA in HeLa cells expressing wild-type GAT-4 and the indicated mutants was done in NaCl-containing medium as described under Materials and Methods at an [3H]GABA concentration of 20 nM. The 100% uptake value for GAT-4 was 88,236 ± 4103 cpm/10 min/well (∼0.18 ± 0.01 pmol/min/well). The background levels of [3H]GABA transport, determined as the uptake by HeLa cells transfected with an empty SK(−) vector, was in the range of 800 to 3200 cpm/10 min/well (∼1%-4% of WT uptake). All values are presented as mean (±S.E.) of at least three experiments.