Fig. 3. Discrimination of amino acid transport activities in A549 lung carcinoma cells.

The transport of [¹⁴C]amino acids is shown for a leucine (100 µM, 2 min, n = 9), b glutamine (100 µM, 2 min, n = 9), c alanine (300 µM, 2 min, n = 9), d proline (100 µM, 6 min, n = 9), e glycine (100 µM, 6 min, n = 9), f glutamate (100 µM, 6 min, n = 9), and g arginine (100 µM, 6 min, n = 9). AA uptake was measured in Na⁺-based buffer (white squares above the bars), NMDG⁺-based buffer (black squares above the bars), or Li⁺-based buffer (gray squares above the bars). In the control experiments, no inhibitor or competitor was added. Except for NEM (10 min preincubation), inhibitors and competitors were added together with the substrate at the concentrations given in Table S1. To facilitate analysis, blocked transporters relevant to the cell line are shown above the bars, the active transporters are shown inside the bar. The transporters are color coded, white gaps indicate an unresolved discrepancy. Nonspecific uptake/binding was evaluated by addition of 10 mM unlabeled substrate and was subtracted from all experiments. The mean and 95% confidence intervals are shown for all data. All samples were derived from e = 3 experiments. A one-way ANOVA with Tukey’s multiple comparison test was used to analyze differences between groups. Groups that were not considered different from each other were assigned the same letter, p values for all comparisons are listed in Table S15. Amino acids are shown in three-letter code; BCH 2-amino-2-norbornane-carboxylic acid, DHK dihydrokainate, JPH JPH203, Lora, loratadine, MeAIB N-methyl-aminoisobutyric acid, NEM N-ethylmaleimide, Org ORG25543, SAS sulfasalazine, TBOA dl-threo-β-benzyloxyaspartate, UCPH UCPH-101.