Interaction of the neutral amino acid transporter ASCT2 with basic amino acids.

Interaction of the neutral amino acid transporter ASCT2 with basic amino acids. Biochem J. 2020 Apr 03;: Authors: Ndaru E, Garibsingh RA, Zielewicz L, Schlessinger A, Grewer C Abstract Glutamine transport across cell membranes is performed by a variety of transporters, including the alanine serine cysteine transporter 2 (ASCT2). The substrate binding site of ASCT2 was proposed to be specific for small amino acids with neutral side chains, excluding basic substrates such as lysine. A series of competitive inhibitors of ASCT2 with low mM affinity were developed previously, on the basis of the 2,4-diaminobutyric acid (DAB) scaffold with a potential positive charge in the side chain. Therefore, we tested whether basic amino acids with side chains shorter than lysine can interact with the ASCT2 binding site. Molecular docking of L-1,3-diaminopropionic acid (L-DAP) and L-DAB suggested that these compounds bind to ASCT2. Consistent with this prediction, L-DAP and L-DAB, but not ornithine, lysine or D-DAP, elicited currents when applied to ASCT2-expressing cells. The currents were carried by anions and showed the hallmark properties of ASCT2 currents induced by transported substrates. The L-DAP response could be eliminated by a competitive ASCT2 inhibitor, suggesting that binding occurs at the substrate binding site. The Km for L-DAP was weakly voltage dependent. Further, the pH dependence of the L-DAP response showed that the compound can b...
Source: The Biochemical Journal - Category: Biochemistry Authors: Tags: Biochem J Source Type: research