Figure 8.

Mixed heterotrimers consisting of WT and R501C EAAT4 exhibit functional properties that are intermediate to WT and R501C homotrimers. A, Representative current responses to voltage steps to −95 and +125 mV, respectively, from a cell cotransfected with WT and R501C EAAT4 in the presence of 1 mm serine (dotted line), 1 mm glutamate (dashed line), and both together (solid line). The bold solid line gives the sum of the current amplitudes observed after application of individual substrates. B, Voltage dependence of current amplitudes from the experiment shown in A. C, Voltage dependence of normalized mean current amplitudes during the application of both substrates (filled triangles) compared with the predicted value assuming independence of individual subunits forming an anion conduction pathway (open inverted triangles). Means ± SEM from 10 cells. *p < 0.05 and **p < 0.01 indicate a significant difference between measured and predicted values.