title: Ligand Discovery for the Alanine-Serine-Cysteine Transporter (ASCT2, SLC1A5) from Homology Modeling and Virtual Screening.
abstract: The Alanine-Serine-Cysteine transporter ASCT2 (SLC1A5) is a membrane protein that transports neutral amino acids into cells in exchange for outward movement of intracellular amino acids. ASCT2 is highly expressed in peripheral tissues such as the lung and intestines where it contributes to the homeostasis of intracellular concentrations of neutral amino acids. ASCT2 also plays an important role in the development of a variety of cancers such as melanoma by transporting amino acid nutrients such as glutamine into the proliferating tumors. Therefore, ASCT2 is a key drug target with potentially great pharmacological importance. Here, we identify seven ASCT2 ligands by computational modeling and experimental testing. In particular, we construct homology models based on crystallographic structures of the aspartate transporter GltPh in two different conformations. Optimization of the models' binding sites for protein-ligand complementarity reveals new putative pockets that can be targeted via structure-based drug design. Virtual screening of drugs, metabolites, fragments-like, and lead-like molecules from the ZINC database, followed by experimental testing of 14 top hits with functional measurements using electrophysiological methods reveals seven ligands, including five activators and two inhibitors. For example, aminooxetane-3-carboxylate is a more efficient activator than any other known ASCT2 natural or unnatural substrate. Furthermore, two of the hits inhibited ASCT2 mediated glutamine uptake and proliferation of a melanoma cancer cell line. Our results improve our understanding of how substrate specificity is determined in amino acid transporters, as well as provide novel scaffolds for developing chemical tools targeting ASCT2, an emerging therapeutic target for cancer and neurological disorders.
authors.affiliation: Department of Pharmacology and Systems Therapeutics, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America.
authors.forename: Claire
authors.initials: C
authors.lastname: Colas
authors.affiliation: Department of Chemistry, Binghamton University, Binghamton, New York, United States of America.
authors.forename: Christof
authors.initials: C
authors.lastname: Grewer
authors.affiliation: Origins of Cancer Laboratory Centenary Program, Camperdown, Australia; Sydney Medical School, University of Sydney, Sydney, Australia.
authors.forename: Nicholas James
authors.initials: NJ
authors.lastname: Otte
authors.affiliation: Department of Chemistry, Binghamton University, Binghamton, New York, United States of America.
authors.forename: Armanda
authors.initials: A
authors.lastname: Gameiro
authors.affiliation: Department of Chemistry, Binghamton University, Binghamton, New York, United States of America.
authors.forename: Thomas
authors.initials: T
authors.lastname: Albers
authors.affiliation: Department of Chemistry, Binghamton University, Binghamton, New York, United States of America.
authors.forename: Kurnvir
authors.initials: K
authors.lastname: Singh
authors.affiliation: Department of Pharmacology and Systems Therapeutics, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America.
authors.forename: Helen
authors.initials: H
authors.lastname: Shere
authors.affiliation: Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Bonomi
authors.affiliation: Origins of Cancer Laboratory Centenary Program, Camperdown, Australia; Sydney Medical School, University of Sydney, Sydney, Australia.
authors.forename: Jeff
authors.initials: J
authors.lastname: Holst
authors.affiliation: Department of Pharmacology and Systems Therapeutics, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America.
authors.forename: Avner
authors.initials: A
authors.lastname: Schlessinger
mesh_terms: D000465:Algorithms; D000595:Amino Acid Sequence; D026962:Amino Acid Transport System ASC / Q000737:chemistry* / Q000648:ultrastructure*; D001665:Binding Sites; D004353:Drug Evaluation, Preclinical / Q000379:methods*; D015778:Minor Histocompatibility Antigens; D008956:Models, Chemical; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D011485:Protein Binding; D025941:Protein Interaction Mapping / Q000379:methods*; D020539:Sequence Analysis, Protein / Q000379:methods; D017386:Sequence Homology, Amino Acid
chemical_list: D026962:Amino Acid Transport System ASC; D015778:Minor Histocompatibility Antigens; C420506:SLC1A5 protein, human