Glutamate uptake assay

Human iPSC-derived astrocytes and HEK 293FT cells were treated with HBSS containing 20 μM glutamate for 10 min or 30 min at 37 °C, and the remaining glutamate in the medium was measured using the Glutamate Colorimetric Assay kit (Abcam) (25). The absorbance of the product was measured at 492 nm using a microplate reader (Biotek). Cellular glutamate uptake was calculated by subtracting the remaining glutamate in the medium after incubation with the cells. Cellular glutamate uptake measurements were normalized by protein concentration of cell lysates of each sample.