Structural basis for stereospecific inhibition of ASCT2 from rational design

Abstract

Abbreviations: SLC, solute carrier; ASCT2, alanine serine cysteine transporter 2. EAAT, excitatory amino acid transporter.ABSTRACT ASCT2 (SLC1A5) is a sodium-dependent neutral amino acid transporter that controls amino acid homeostasis in peripheral tissues. ASCT2 is upregulated in cancer, where it modulates intracellular glutamine levels, fueling cell proliferation. Nutrient deprivation via ASCT2 inhibition provides an emerging strategy for cancer therapy. Here, guided by a homology model of ASCT2 in an outward-facing conformation, we rationally designed novel inhibitors exploiting stereospecific pockets in the substrate binding site. A cryo-EM structure of ASCT2 in complex with inhibitor (Lc-BPE) validated our predictions and was subsequently refined based on computational analysis. The final structures, combined with MD simulations, show that the inhibitor samples multiple conformations in the ASCT2 binding site. Our results demonstrate the utility of combining computational modeling and cryo-EM for SLC ligand discovery, and a viable strategy for structure determination of druggable conformational states for challenging membrane protein targets.

Exploiting the Achilles’ heel of cancer: disrupting glutamine metabolism for effective cancer treatment

“…This inhibitor targets a stereo-specific pocket in the substrate binding site of ASCT2 and demonstrates submicromolar potency and stereoselectivity. It has been shown to inhibit cell proliferation in various cancer cells, such as MCF-7, LnCaP, and MDA-MB-231 in vitro (Garibsingh et al, 2020).…”