Figure 3. Mutations in SLC1A1 from subjects with DA affect its function.

(A) Representative oocytes expressing WT, R445W, or I395del cRNA or noninjected oocytes (control) were clamped at –60 mV and perfused with ND96 buffer containing 100 μM (for WT and R445W) or 1 mM (for I395del and control) l-glutamate. Black scale bars represent the time (s, x axis) that l-glutamate was applied and the current size (nA, y axis). Scale is shown for time versus current. (B) The l-glutamate dose response for WT (filled circles) and R445W (open circles). Current (I_norm) was normalized to the maximal current, defined as unit I_max (WT, K_0.5 = 30 ± 4 μM and I_max = 424 ± 13 nA; R445W, K_0.5 = 2 ± 0.3 μM and I_max 53 ± 7 nA). (C) Radiolabeled l-glutamate uptake at K_0.5. (D) The l-cysteine dose response for WT (filled circles) and R445W (open circles). Current was normalized to the maximal current (WT, K_0.5 = 115 ± 13 μM and I_max = 590 ± 19 nA; R445W, K_0.5 = 3.3 ± 0.1 μM and I_max = 54 ± 20 nA). (E) Radiolabeled l-cysteine uptake at K_0.5. ³H-l-glutamate and ³⁵S-l-cysteine uptake in noninjected oocytes was subtracted from the data presented (C and E, respectively). All data represent the mean ± SEM of at least 3 oocytes (in B–E). (F–H) Representative oocytes expressing EGFP-tagged SLC1A1 cRNA. (F) WT oocytes. (G) R445W oocytes. (H) Noninjected control oocytes. Scale bar: 200 μm.