FIGURE 6.
Sodium dependence of WT and E500X EAAT2 anion currents. A and C, representative current traces at −185 mV from tsA201 cells expressing WT or E500X EAAT2 with standard internal solution containing KNO3 (A) or NaNO3 (C) and external solution containing Cl−. Dotted lines represent 0 nA. Cells were perfused with 140 mm cholineCl (gray) or 140 mm NaCl in the absence (black) or in the presence (white) of 0.5 mm l-glutamate. B and D, late current amplitudes at −185 mV of WT (●) or E500X (■) in the absence (black) or in the presence (white) of 0.5 mm l-glutamate with internal K+ (B) or Na+ (D). Currents are normalized to the current in the presence of 140 mm NaCl and 0.5 mm l-glutamate. Each data point gives means ± S.E. with n ≥ 3. Data were fitted with Michaelis-Menten equation providing the following apparent Km values: WT with internal K+: Km Na = 11 ± 6 mm without glutamate, Km Na = 27 ± 6 mm with glutamate; E500X with internal K+: Km Na = 109 ± 68 mm without glutamate, Km Na = 264 ± 62 mm with glutamate. WT with internal Na+: Km Na = 15 ± 6 mm without glutamate, Km Na = 52 ± 11 mm with glutamate; E500X with internal Na+: Km Na = 31 ± 14 mm without glutamate, Km Na = 68 ± 27 mm with glutamate.