2-Substituted Nγ-glutamylanilides as novel probes of ASCT2 with improved potency

Abstract

Herein, we report the discovery and structure-activity relationships (SAR) of 2-substituted glutamylanilides as novel probes of the steric environment comprising the amino acid binding domain of alanine-serine-cysteine transporter subtype 2 (ASCT2). Focused library development led to three novel, highly potent ASCT2 inhibitors, with N-(2-(morpholinomethyl)phenyl)-L-glutamine exhibiting the greatest potency in a live-cell glutamine uptake assay. This level of potency represents a three-fold improvement over the most potent, previously reported inhibitor in this series, GPNA. Furthermore, this and other compounds in the series exhibit tractable chemical properties for further development as potential therapeutic leads.

Keywords: ASCT2; Cancer; Glutamine; Metabolism; SLC1A5.

Figure 1

Synthetic route towards 2-substituted N_γ-glutamylanilides.

Figure 2. Docking of potential leads into ASCT2 homology model

The most potent lead, compound 5 (brown all atom colored, capped sticks) fits the homology model (protein ribbons) generated for the open form of human ASCT2 and is consistent with the displacement of a key loop region (grey, right). The docked pose shown represents the best scoring SurflexDock conformation for compound 5 (IC₅₀ = ~312μM) that contains a morpholino moiety occupying the hydrophobic pocket adjacent to the amino acid zwitterion binding site. One of the two reported sodium binding sites in the SLC1A5 family (purple van der Waals dotted surface) is shown centered beneath the amino acid binding site. A potential weak hydrogen bond between the morpholine oxygen of compound 5 to ASCT2 residue Cys 467 sulfhydryl side chain (yellow dashed line) is highlighted.