Figure 1.

Reduced function and trafficking of the mutant GABA transporter 1 encoded by SLC6A1 variants associated with epilepsy, autism, ADHD and intellectual delay. (A) Schematic presentation of mutant GABA transporter 1 (GAT-1) protein topology and locations of representative variants in human SLC6A1 associated with various epilepsy syndromes and neurodevelopmental disorders as described in our previous work. These variants are distributed in various locations and domains of the encoded GAT-1 protein peptide. The large dots represent the eight variants evaluated in the study. (B–D) HEK293T cells were transfected with the wildtype or the mutant GAT-1^YFP for 48 h. (B) The graph represents the altered GABA reuptake function of the mutant GAT-1 encoded by eight different SLC6A1 variants in HEK293T cells measured by the high-throughput ³H radio-labelling GABA uptake on a liquid scintillator with QuantaSmart. Around 966 stands for the wildtype treated with GAT-1 inhibitor Cl-966 (50 µM) and NNC-711 for the wildtype treated with NNC-711 (35 µM) for 30 min before preincubation. (C, D) The flow cytometry histograms depict the relative surface (C) or total (D) expression of the wildtype and the mutant GAT-1. The relative total expression level of GAT-1 in each mutant transporter was normalized to that obtained from cells with transfection of the wildtypes. N = 4–5 different transfections, δδδ P < 0.001 overall mutations versus wt, *P < 0.05, **P < 0.01, ***P < 0.001 versus wt, one-way analysis of variance and Newman–Keuls test. Values were expressed as mean ± SEM.