1
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Tambay V, Raymond VA, Voisin L, Meloche S, Bilodeau M. Reprogramming of Glutamine Amino Acid Transporters Expression and Prognostic Significance in Hepatocellular Carcinoma. Int J Mol Sci 2024; 25:7558. [PMID: 39062801 PMCID: PMC11277143 DOI: 10.3390/ijms25147558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2024] [Revised: 07/05/2024] [Accepted: 07/07/2024] [Indexed: 07/28/2024] Open
Abstract
Hepatocellular carcinoma (HCC) is the most prevalent primary liver malignancy and is a major cause of cancer-related mortality in the world. This study aimed to characterize glutamine amino acid transporter expression profiles in HCC compared to those of normal liver cells. In vitro and in vivo models of HCC were studied using qPCR, whereas the prognostic significance of glutamine transporter expression levels within patient tumors was analyzed through RNAseq. Solute carrier (SLC) 1A5 and SLC38A2 were targeted through siRNA or gamma-p-nitroanilide (GPNA). HCC cells depended on exogenous glutamine for optimal survival and growth. Murine HCC cells showed superior glutamine uptake rate than normal hepatocytes (p < 0.0001). HCC manifested a global reprogramming of glutamine transporters compared to normal liver: SLC38A3 levels decreased, whereas SLC38A1, SLC7A6, and SLC1A5 levels increased. Also, decreased SLC6A14 and SLC38A3 levels or increased SLC38A1, SLC7A6, and SLC1A5 levels predicted worse survival outcomes (all p < 0.05). Knockdown of SLC1A5 and/or SLC38A2 expression in human Huh7 and Hep3B HCC cells, as well as GPNA-mediated inhibition, significantly decreased the uptake of glutamine; combined SLC1A5 and SLC38A2 targeting had the most considerable impact (all p < 0.05). This study revealed glutamine transporter reprogramming as a novel hallmark of HCC and that such expression profiles are clinically significant.
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Affiliation(s)
- Vincent Tambay
- Laboratoire d’Hépatologie cellulaire, Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Montréal, QC H2X 0A9, Canada
| | - Valérie-Ann Raymond
- Laboratoire d’Hépatologie cellulaire, Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Montréal, QC H2X 0A9, Canada
| | - Laure Voisin
- Institut de Recherche en Immunologie et en Cancérologie de l’Université de Montréal, Montréal, QC H3T 1J4, Canada
| | - Sylvain Meloche
- Institut de Recherche en Immunologie et en Cancérologie de l’Université de Montréal, Montréal, QC H3T 1J4, Canada
- Département de Pharmacologie et Physiologie, Université de Montréal, Montréal, QC H3C 3J7, Canada
| | - Marc Bilodeau
- Laboratoire d’Hépatologie cellulaire, Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Montréal, QC H2X 0A9, Canada
- Département de Médecine, Université de Montréal, Montréal, QC H3T 1J4, Canada
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2
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Dong Y, Wang J, Grewer C. Transient kinetics reveal the mechanism of competitive inhibition of the neutral amino acid transporter ASCT2. J Biol Chem 2024; 300:107382. [PMID: 38763337 PMCID: PMC11193019 DOI: 10.1016/j.jbc.2024.107382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 04/23/2024] [Accepted: 05/10/2024] [Indexed: 05/21/2024] Open
Abstract
ASCT2 (alanine serine cysteine transporter 2), a member of the solute carrier 1 family, mediates Na+-dependent exchange of small neutral amino acids across cell membranes. ASCT2 was shown to be highly expressed in tumor cells, making it a promising target for anticancer therapies. In this study, we explored the binding mechanism of the high-affinity competitive inhibitor L-cis hydroxyproline biphenyl ester (Lc-BPE) with ASCT2, using electrophysiological and rapid kinetic methods. Our investigations reveal that Lc-BPE binding requires one or two Na+ ions initially bound to the apo-transporter with high affinity, with Na1 site occupancy being more critical for inhibitor binding. In contrast to the amino acid substrate bound form, the final, third Na+ ion cannot bind, due to distortion of its binding site (Na2), thus preventing the formation of a translocation-competent complex. Based on the rapid kinetic analysis, the application of Lc-BPE generated outward transient currents, indicating that despite its net neutral nature, the binding of Lc-BPE in ASCT2 is weakly electrogenic, most likely because of asymmetric charge distribution within the amino acid moiety of the inhibitor. The preincubation with Lc-BPE also led to a decrease of the turnover rate of substrate exchange and a delay in the activation of substrate-induced anion current, indicating relatively slow Lc-BPE dissociation kinetics. Overall, our results provide new insight into the mechanism of binding of a prototypical competitive inhibitor to the ASCT transporters.
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Affiliation(s)
- Yang Dong
- Department of Chemistry, Binghamton University, Binghamton, New York, USA
| | - Jiali Wang
- Department of Chemistry, Binghamton University, Binghamton, New York, USA
| | - Christof Grewer
- Department of Chemistry, Binghamton University, Binghamton, New York, USA.
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3
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Lyda BR, Leary GP, Farnsworth J, Seaver B, Silvius D, Kavanaugh MP, Esslinger CS, Natale NR. Discovery and Synthesis of Hydroxy-l-Proline Blockers of the Neutral Amino Acid Transporters SLC1A4 (ASCT1) and SLC1A5 (ASCT2). Molecules 2024; 29:2330. [PMID: 38792190 PMCID: PMC11123841 DOI: 10.3390/molecules29102330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Revised: 04/29/2024] [Accepted: 05/03/2024] [Indexed: 05/26/2024] Open
Abstract
As a conformationally restricted amino acid, hydroxy-l-proline is a versatile scaffold for the synthesis of diverse multi-functionalized pyrrolidines for probing the ligand binding sites of biological targets. With the goal to develop new inhibitors of the widely expressed amino acid transporters SLC1A4 and SLC1A5 (also known as ASCT1 and ASCT2), we synthesized and functionally screened synthetic hydroxy-l-proline derivatives using electrophysiological and radiolabeled uptake methods against amino acid transporters from the SLC1, SLC7, and SLC38 solute carrier families. We have discovered a novel class of alkoxy hydroxy-pyrrolidine carboxylic acids (AHPCs) that act as selective high-affinity inhibitors of the SLC1 family neutral amino acid transporters SLC1A4 and SLC1A5. AHPCs were computationally docked into a homology model and assessed with respect to predicted molecular orientation and functional activity. The series of hydroxyproline analogs identified here represent promising new agents to pharmacologically modulate SLC1A4 and SLC1A5 amino acid exchangers which are implicated in numerous pathophysiological processes such as cancer and neurological diseases.
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Affiliation(s)
- Brent R. Lyda
- Division of Biological Sciences, University of Montana, 32 Campus Dr., Missoula, MT 59812, USA
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, 32 Campus Dr., Missoula, MT 59812, USA (B.S.); (D.S.)
| | - Gregory P. Leary
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, 32 Campus Dr., Missoula, MT 59812, USA (B.S.); (D.S.)
| | - Jill Farnsworth
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, 32 Campus Dr., Missoula, MT 59812, USA (B.S.); (D.S.)
| | - Benjamin Seaver
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, 32 Campus Dr., Missoula, MT 59812, USA (B.S.); (D.S.)
| | - Derek Silvius
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, 32 Campus Dr., Missoula, MT 59812, USA (B.S.); (D.S.)
| | - Michael P. Kavanaugh
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, 32 Campus Dr., Missoula, MT 59812, USA (B.S.); (D.S.)
| | - C. Sean Esslinger
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, 32 Campus Dr., Missoula, MT 59812, USA (B.S.); (D.S.)
| | - Nicholas R. Natale
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, 32 Campus Dr., Missoula, MT 59812, USA (B.S.); (D.S.)
- Medicinal Chemistry Graduate Program, University of Montana, 32 Campus Dr., Missoula, MT 59812, USA
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4
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Fan Y, Xue H, Li Z, Huo M, Gao H, Guan X. Exploiting the Achilles' heel of cancer: disrupting glutamine metabolism for effective cancer treatment. Front Pharmacol 2024; 15:1345522. [PMID: 38510646 PMCID: PMC10952006 DOI: 10.3389/fphar.2024.1345522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 02/23/2024] [Indexed: 03/22/2024] Open
Abstract
Cancer cells have adapted to rapid tumor growth and evade immune attack by reprogramming their metabolic pathways. Glutamine is an important nitrogen resource for synthesizing amino acids and nucleotides and an important carbon source in the tricarboxylic acid (TCA) cycle and lipid biosynthesis pathway. In this review, we summarize the significant role of glutamine metabolism in tumor development and highlight the vulnerabilities of targeting glutamine metabolism for effective therapy. In particular, we review the reported drugs targeting glutaminase and glutamine uptake for efficient cancer treatment. Moreover, we discuss the current clinical test about targeting glutamine metabolism and the prospective direction of drug development.
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Affiliation(s)
- Yuxin Fan
- Department of Clinical Laboratory Diagnostics, School of Medical Technology, Beihua University, Jilin City, China
- Department of Basic Medicine, Medical School, Taizhou University, Taizhou, Zhejiang Province, China
| | - Han Xue
- Department of Clinical Laboratory Diagnostics, School of Medical Technology, Beihua University, Jilin City, China
- Department of Basic Medicine, Medical School, Taizhou University, Taizhou, Zhejiang Province, China
| | - Zhimin Li
- Department of Clinical Laboratory Diagnostics, School of Medical Technology, Beihua University, Jilin City, China
- Department of Basic Medicine, Medical School, Taizhou University, Taizhou, Zhejiang Province, China
| | - Mingge Huo
- Department of Clinical Laboratory Diagnostics, School of Medical Technology, Beihua University, Jilin City, China
- Department of Basic Medicine, Medical School, Taizhou University, Taizhou, Zhejiang Province, China
| | - Hongxia Gao
- Department of Clinical Laboratory Diagnostics, School of Medical Technology, Beihua University, Jilin City, China
| | - Xingang Guan
- Department of Basic Medicine, Medical School, Taizhou University, Taizhou, Zhejiang Province, China
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5
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Cheng X, Wang Y, Gong G, Shen P, Li Z, Bian J. Design strategies and recent development of bioactive modulators for glutamine transporters. Drug Discov Today 2024; 29:103880. [PMID: 38216118 DOI: 10.1016/j.drudis.2024.103880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 12/25/2023] [Accepted: 01/08/2024] [Indexed: 01/14/2024]
Abstract
Glutamine transporters are integral to the metabolism of glutamine in both healthy tissues and cancerous cells, playing a pivotal role in maintaining amino acid balance, synthesizing biomolecules, and regulating redox equilibrium. Their critical functions in cellular metabolism make them promising targets for oncological therapies. Recent years have witnessed substantial progress in the field of glutamine transporters, marked by breakthroughs in understanding of their protein structures and the discovery of novel inhibitors, prodrugs, and radiotracers. This review provides a comprehensive update on the latest advancements in modulators targeting the glutamine transporter, with special attention given to LAT1 and ASCT2. It also discusses innovative approaches in drug design aimed at these transporters.
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Affiliation(s)
- Xinying Cheng
- School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Yezhi Wang
- School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Guangyue Gong
- School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Pei Shen
- School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Zhiyu Li
- School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China.
| | - Jinlei Bian
- School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China.
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6
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Jakobsen S, Nielsen CU. Exploring Amino Acid Transporters as Therapeutic Targets for Cancer: An Examination of Inhibitor Structures, Selectivity Issues, and Discovery Approaches. Pharmaceutics 2024; 16:197. [PMID: 38399253 PMCID: PMC10893028 DOI: 10.3390/pharmaceutics16020197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 01/18/2024] [Accepted: 01/28/2024] [Indexed: 02/25/2024] Open
Abstract
Amino acid transporters are abundant amongst the solute carrier family and have an important role in facilitating the transfer of amino acids across cell membranes. Because of their impact on cell nutrient distribution, they also appear to have an important role in the growth and development of cancer. Naturally, this has made amino acid transporters a novel target of interest for the development of new anticancer drugs. Many attempts have been made to develop inhibitors of amino acid transporters to slow down cancer cell growth, and some have even reached clinical trials. The purpose of this review is to help organize the available information on the efforts to discover amino acid transporter inhibitors by focusing on the amino acid transporters ASCT2 (SLC1A5), LAT1 (SLC7A5), xCT (SLC7A11), SNAT1 (SLC38A1), SNAT2 (SLC38A2), and PAT1 (SLC36A1). We discuss the function of the transporters, their implication in cancer, their known inhibitors, issues regarding selective inhibitors, and the efforts and strategies of discovering inhibitors. The goal is to encourage researchers to continue the search and development within the field of cancer treatment research targeting amino acid transporters.
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Affiliation(s)
- Sebastian Jakobsen
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense, Denmark
| | - Carsten Uhd Nielsen
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense, Denmark
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7
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Dong Y, Wang J, Garibsingh RA, Hutchinson K, Shi Y, Eisenberg G, Yu X, Schlessinger A, Grewer C. Conserved allosteric inhibition mechanism in SLC1 transporters. eLife 2023; 12:e83464. [PMID: 36856089 PMCID: PMC10017108 DOI: 10.7554/elife.83464] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 02/27/2023] [Indexed: 03/02/2023] Open
Abstract
Excitatory amino acid transporter 1 (EAAT1) is a glutamate transporter belonging to the SLC1 family of solute carriers. It plays a key role in the regulation of the extracellular glutamate concentration in the mammalian brain. The structure of EAAT1 was determined in complex with UCPH-101, apotent, non-competitive inhibitor of EAAT1. Alanine serine cysteine transporter 2 (ASCT2) is a neutral amino acid transporter, which regulates pools of amino acids such as glutamine between intracellular and extracellular compartments . ASCT2 also belongs to the SLC1 family and shares 58% sequence similarity with EAAT1. However, allosteric modulation of ASCT2 via non-competitive inhibitors is unknown. Here, we explore the UCPH-101 inhibitory mechanisms of EAAT1 and ASCT2 by using rapid kinetic experiments. Our results show that UCPH-101 slows substrate translocation rather than substrate or Na+ binding, confirming a non-competitive inhibitory mechanism, but only partially inhibits wild-type ASCT2. Guided by computational modeling using ligand docking and molecular dynamics simulations, we selected two residues involved in UCPH-101/EAAT1 interaction, which were mutated in ASCT2 (F136Y, I237M, F136Y/I237M) in the corresponding positions. We show that in the F136Y/I237M double-mutant transporter, 100% of the inhibitory effect of UCPH-101 could be restored, and the apparent affinity was increased (Ki = 4.3 μM), much closer to the EAAT1 value of 0.6 μM. Finally, we identify a novel non-competitive ASCT2 inhibitor, through virtual screening and experimental testing against the allosteric site, further supporting its localization. Together, these data indicate that the mechanism of allosteric modulation is conserved between EAAT1 and ASCT2. Due to the difference in binding site residues between ASCT2 and EAAT1, these results raise the possibility that more potent, and potentially selective ASCT2 allosteric inhibitors can be designed .
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Affiliation(s)
- Yang Dong
- Department of Chemistry, Binghamton UniversityBinghamtonUnited States
| | - Jiali Wang
- Department of Chemistry, Binghamton UniversityBinghamtonUnited States
| | - Rachel-Ann Garibsingh
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount SinaiNew YorkUnited States
| | - Keino Hutchinson
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount SinaiNew YorkUnited States
| | - Yueyue Shi
- Department of Chemistry, Binghamton UniversityBinghamtonUnited States
| | - Gilad Eisenberg
- Department of Chemistry, Binghamton UniversityBinghamtonUnited States
| | - Xiaozhen Yu
- Department of Chemistry, Binghamton UniversityBinghamtonUnited States
| | - Avner Schlessinger
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount SinaiNew YorkUnited States
| | - Christof Grewer
- Department of Chemistry, Binghamton UniversityBinghamtonUnited States
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8
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Ndaru E, Zielewicz L, Shi Y, Hutchinson K, Garibsingh RAA, Schlessinger A, Grewer C. Alanine serine cysteine transporter (ASCT) substrate binding site properties probed with hydroxyhomoserine esters. J PHYS ORG CHEM 2022; 35:e4347. [PMID: 36568026 PMCID: PMC9786560 DOI: 10.1002/poc.4347] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 03/18/2022] [Indexed: 02/06/2023]
Abstract
The glutamine transporter ASCT2 is highly overexpressed in cancer cells. Block of glutamine uptake by ASCT2 is a potential strategy to inhibit growth of cancer cells. However, pharmacology of the ASCT2 binding site is not well established. In this work, we report the computational docking to the binding site, and the synthesis of a new class of ASCT2 inhibitors based on the novel L-hydroxyhomoserine scaffold. While these compounds inhibit the ASCT2 leak anion conductance, as expected for competitive inhibitors, they did not block leak conductance in glutamate transporters (EAAT1-3 and EAAT5). They were also ineffective with respect to subtype ASCT1, which has >57% amino acid sequence similarity to ASCT2. Molecular docking studies agree very well with the experimental results and suggest specific polar interactions in the ASCT2 binding site. Our findings add to the repertoire of ASCT2 inhibitors and will aid in further studies of ASCT2 pharmacology.
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Affiliation(s)
- Elias Ndaru
- Department of Chemistry, Binghamton University, Binghamton, NY 13902
| | - Laura Zielewicz
- Department of Chemistry, Binghamton University, Binghamton, NY 13902
| | - Yueyue Shi
- Department of Chemistry, Binghamton University, Binghamton, NY 13902
| | - Keino Hutchinson
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | - Rachel-Ann A Garibsingh
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | - Avner Schlessinger
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | - Christof Grewer
- Department of Chemistry, Binghamton University, Binghamton, NY 13902
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9
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Huttunen J, Adla SK, Markowicz-Piasecka M, Huttunen KM. Increased/Targeted Brain (Pro)Drug Delivery via Utilization of Solute Carriers (SLCs). Pharmaceutics 2022; 14:pharmaceutics14061234. [PMID: 35745806 PMCID: PMC9228667 DOI: 10.3390/pharmaceutics14061234] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 06/06/2022] [Accepted: 06/07/2022] [Indexed: 02/04/2023] Open
Abstract
Membrane transporters have a crucial role in compounds’ brain drug delivery. They allow not only the penetration of a wide variety of different compounds to cross the endothelial cells of the blood–brain barrier (BBB), but also the accumulation of them into the brain parenchymal cells. Solute carriers (SLCs), with nearly 500 family members, are the largest group of membrane transporters. Unfortunately, not all SLCs are fully characterized and used in rational drug design. However, if the structural features for transporter interactions (binding and translocation) are known, a prodrug approach can be utilized to temporarily change the pharmacokinetics and brain delivery properties of almost any compound. In this review, main transporter subtypes that are participating in brain drug disposition or have been used to improve brain drug delivery across the BBB via the prodrug approach, are introduced. Moreover, the ability of selected transporters to be utilized in intrabrain drug delivery is discussed. Thus, this comprehensive review will give insights into the methods, such as computational drug design, that should be utilized more effectively to understand the detailed transport mechanisms. Moreover, factors, such as transporter expression modulation pathways in diseases that should be taken into account in rational (pro)drug development, are considered to achieve successful clinical applications in the future.
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Affiliation(s)
- Johanna Huttunen
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland; (J.H.); (S.K.A.)
| | - Santosh Kumar Adla
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland; (J.H.); (S.K.A.)
- Institute of Organic Chemistry and Biochemistry (IOCB), Czech Academy of Sciences, Flemingovo Namesti 542/2, 160 00 Prague, Czech Republic
| | - Magdalena Markowicz-Piasecka
- Department of Pharmaceutical Chemistry, Drug Analysis and Radiopharmacy, Medical University of Lodz, ul. Muszyńskiego 1, 90-151 Lodz, Poland;
| | - Kristiina M. Huttunen
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland; (J.H.); (S.K.A.)
- Correspondence:
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10
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Functional and Kinetic Comparison of Alanine Cysteine Serine Transporters ASCT1 and ASCT2. Biomolecules 2022; 12:biom12010113. [PMID: 35053261 PMCID: PMC8773628 DOI: 10.3390/biom12010113] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/05/2022] [Accepted: 01/07/2022] [Indexed: 02/01/2023] Open
Abstract
Neutral amino acid transporters ASCT1 and ASCT2 are two SLC1 (solute carrier 1) family subtypes, which are specific for neutral amino acids. The other members of the SLC1 family are acidic amino acid transporters (EAATs 1–5). While the functional similarities and differences between the EAATs have been well studied, less is known about how the subtypes ASCT1 and 2 differ in kinetics and function. Here, by performing comprehensive electrophysiological analysis, we identified similarities and differences between these subtypes, as well as novel functional properties, such as apparent substrate affinities of the inward-facing conformation (in the range of 70 μM for L-serine as the substrate). Key findings were: ASCT1 has a higher apparent affinity for Na+, as well as a larger [Na+] dependence of substrate affinity compared to ASCT2. However, the general sequential Na+/substrate binding mechanism with at least one Na+ binding first, followed by amino acid substrate, followed by at least one more Na+ ion, appears to be conserved between the two subtypes. In addition, the first Na+ binding step, presumably to the Na3 site, occurs with high apparent affinity (<1 mM) in both transporters. In addition, ASCT1 and 2 show different substrate selectivities, where ASCT1 does not respond to extracellular glutamine. Finally, in both transporters, we measured rapid, capacitive charge movements upon application and removal of amino acid, due to rearrangement of the translocation equilibrium. This charge movement decays rapidly, with a time constant of 4–5 ms and recovers with a time constant in the 15 ms range after substrate removal. This places a lower limit on the turnover rate of amino acid exchange by these two transporters of 60–80 s−1.
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11
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Rational design of ASCT2 inhibitors using an integrated experimental-computational approach. Proc Natl Acad Sci U S A 2021; 118:2104093118. [PMID: 34507995 PMCID: PMC8449414 DOI: 10.1073/pnas.2104093118] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/28/2021] [Indexed: 12/04/2022] Open
Abstract
The glutamine transporter ASCT2 is an emerging therapeutic target for various cancer types. Here, we use an integrated computational and experimental approach to develop unique ASCT2 inhibitors targeting a conformational state useful for rational drug design. We apply computational chemistry tools such as molecular docking and molecular dynamics simulations, in combination with structure determination with cryo-electron microscopy and synthetic chemistry, to design multiple ASCT2 inhibitors. Our results reveal a unique mechanism of stereospecific inhibition of ASCT2 and highlight the utility of combining state-of-the-art computational and experimental approaches in characterizing challenging human membrane protein targets. ASCT2 (SLC1A5) is a sodium-dependent neutral amino acid transporter that controls amino acid homeostasis in peripheral tissues. In cancer, ASCT2 is up-regulated where it modulates intracellular glutamine levels, fueling cell proliferation. Nutrient deprivation via ASCT2 inhibition provides a potential strategy for cancer therapy. Here, we rationally designed stereospecific inhibitors exploiting specific subpockets in the substrate binding site using computational modeling and cryo-electron microscopy (cryo-EM). The final structures combined with molecular dynamics simulations reveal multiple pharmacologically relevant conformations in the ASCT2 binding site as well as a previously unknown mechanism of stereospecific inhibition. Furthermore, this integrated analysis guided the design of a series of unique ASCT2 inhibitors. Our results provide a framework for future development of cancer therapeutics targeting nutrient transport via ASCT2, as well as demonstrate the utility of combining computational modeling and cryo-EM for solute carrier ligand discovery.
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12
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Lopes C, Pereira C, Medeiros R. ASCT2 and LAT1 Contribution to the Hallmarks of Cancer: From a Molecular Perspective to Clinical Translation. Cancers (Basel) 2021; 13:E203. [PMID: 33429909 PMCID: PMC7828050 DOI: 10.3390/cancers13020203] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 12/31/2020] [Accepted: 01/07/2021] [Indexed: 02/06/2023] Open
Abstract
The role of the amino acid transporters ASCT2 and LAT1 in cancer has been explored throughout the years. In this review, we report their impact on the hallmarks of cancer, as well as their clinical significance. Overall, both proteins have been associated with cell death resistance through dysregulation of caspases and sustainment of proliferative signaling through mTOR activation. Furthermore, ASCT2 appears to play an important role in cellular energetics regulation, whereas LAT1 expression is associated with angiogenesis and invasion and metastasis activation. The molecular impact of these proteins on the hallmarks of cancer translates into various clinical applications and both transporters have been identified as prognostic factors in many types of cancer. Concerning their role as therapeutic targets, efforts have been undertaken to synthesize competitive or irreversible ASCT2 and LAT1 inhibitors. However, JHP203, a selective inhibitor of the latter, is, to the best of our knowledge, the only compound included in a Phase 1 clinical trial. In conclusion, considering the usefulness of ASCT2 and LAT1 in a variety of cancer-related pathways and cancer therapy/diagnosis, the development and testing of novel inhibitors for these transporters that could be evaluated in clinical trials represents a promising approach to cancer prognosis improvement.
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Affiliation(s)
- Catarina Lopes
- Molecular Oncology and Viral Pathology Group, IPO Porto Research Center (CI-IPOP), Portuguese Oncology Institute of Porto (IPO-Porto), Rua Dr. António Bernardino de Almeida, 4200-072 Porto, Portugal; (C.L.); (R.M.)
| | - Carina Pereira
- Molecular Oncology and Viral Pathology Group, IPO Porto Research Center (CI-IPOP), Portuguese Oncology Institute of Porto (IPO-Porto), Rua Dr. António Bernardino de Almeida, 4200-072 Porto, Portugal; (C.L.); (R.M.)
- CINTESIS—Center for Health Technology and Services Research, University of Porto, Rua Dr. Plácido da Costa, 4200-450 Porto, Portugal
| | - Rui Medeiros
- Molecular Oncology and Viral Pathology Group, IPO Porto Research Center (CI-IPOP), Portuguese Oncology Institute of Porto (IPO-Porto), Rua Dr. António Bernardino de Almeida, 4200-072 Porto, Portugal; (C.L.); (R.M.)
- Research Department of the Portuguese League Against Cancer—North (LPCC-NRNorte), Estrada da Circunvalação, 4200-177 Porto, Portugal
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13
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Interaction of the neutral amino acid transporter ASCT2 with basic amino acids. Biochem J 2020; 477:1443-1457. [PMID: 32242892 DOI: 10.1042/bcj20190859] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 03/16/2020] [Accepted: 04/03/2020] [Indexed: 12/20/2022]
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 µM 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. Furthermore, the pH dependence of the L-DAP response showed that the compound can bind in several protonation states. Together, these results suggest that the ASCT2 binding site is able to recognize L-amino acids with short, basic side chains, such as the L-DAP derivative β-N-methylamino-l-Alanine (BMAA), a well-studied neurotoxin. Our results expand the substrate specificity of ASCT2 to include amino acid substrates with positively charged side chains.
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14
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Bröer S. Amino Acid Transporters as Targets for Cancer Therapy: Why, Where, When, and How. Int J Mol Sci 2020; 21:ijms21176156. [PMID: 32859034 PMCID: PMC7503255 DOI: 10.3390/ijms21176156] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 08/23/2020] [Accepted: 08/24/2020] [Indexed: 12/14/2022] Open
Abstract
Amino acids are indispensable for the growth of cancer cells. This includes essential amino acids, the carbon skeleton of which cannot be synthesized, and conditionally essential amino acids, for which the metabolic demands exceed the capacity to synthesize them. Moreover, amino acids are important signaling molecules regulating metabolic pathways, protein translation, autophagy, defense against reactive oxygen species, and many other functions. Blocking uptake of amino acids into cancer cells is therefore a viable strategy to reduce growth. A number of studies have used genome-wide silencing or knock-out approaches, which cover all known amino acid transporters in a large variety of cancer cell lines. In this review, these studies are interrogated together with other databases to identify vulnerabilities with regard to amino acid transport. Several themes emerge, such as synthetic lethality, reduced redundancy, and selective vulnerability, which can be exploited to stop cancer cell growth.
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Affiliation(s)
- Stefan Bröer
- Research School of Biology, Australian National University, Canberra ACT 2600, Australia
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15
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Target the human Alanine/Serine/Cysteine Transporter 2(ASCT2): Achievement and Future for Novel Cancer Therapy. Pharmacol Res 2020; 158:104844. [DOI: 10.1016/j.phrs.2020.104844] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 04/12/2020] [Accepted: 04/13/2020] [Indexed: 12/11/2022]
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16
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Scalise M, Pochini L, Galluccio M, Console L, Indiveri C. Glutamine transporters as pharmacological targets: From function to drug design. Asian J Pharm Sci 2020; 15:207-219. [PMID: 32373200 PMCID: PMC7193454 DOI: 10.1016/j.ajps.2020.02.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 02/18/2020] [Accepted: 02/29/2020] [Indexed: 12/17/2022] Open
Abstract
Among the different targets of administered drugs, there are membrane transporters that play also a role in drug delivery and disposition. Moreover, drug-transporter interactions are responsible for off-target effects of drugs underlying their toxicity. The improvement of the drug design process is subjected to the identification of those membrane transporters mostly relevant for drug absorption, delivery and side effect production. A peculiar group of proteins with great relevance to pharmacology is constituted by the membrane transporters responsible for managing glutamine traffic in different body districts. The interest around glutamine metabolism lies in its physio-pathological role; glutamine is considered a conditionally essential amino acid because highly proliferative cells have an increased request of glutamine that cannot be satisfied only by endogenous synthesis. Then, glutamine transporters provide cells with this special nutrient. Among the glutamine transporters, SLC1A5, SLC6A14, SLC6A19, SLC7A5, SLC7A8 and some members of SLC38 family are the best characterized, so far, in both physiological and pathological conditions. Few 3D structures have been solved by CryoEM; other structural data on these transporters have been obtained by computational analysis. Interactions with drugs have been described for several transporters of this group. For some of them, the studies are at an advanced stage, for others, the studies are still in nuce and novel biochemical findings open intriguing perspectives.
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Affiliation(s)
- Mariafrancesca Scalise
- Department of DiBEST (Biologia, Ecologia e Scienze della Terra), University of Calabria, Arcavacata di Rende (CS) 87036, Italy
| | - Lorena Pochini
- Department of DiBEST (Biologia, Ecologia e Scienze della Terra), University of Calabria, Arcavacata di Rende (CS) 87036, Italy
| | - Michele Galluccio
- Department of DiBEST (Biologia, Ecologia e Scienze della Terra), University of Calabria, Arcavacata di Rende (CS) 87036, Italy
| | - Lara Console
- Department of DiBEST (Biologia, Ecologia e Scienze della Terra), University of Calabria, Arcavacata di Rende (CS) 87036, Italy
| | - Cesare Indiveri
- Department of DiBEST (Biologia, Ecologia e Scienze della Terra), University of Calabria, Arcavacata di Rende (CS) 87036, Italy
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17
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Amino Acid Transporters and Exchangers from the SLC1A Family: Structure, Mechanism and Roles in Physiology and Cancer. Neurochem Res 2020; 45:1268-1286. [DOI: 10.1007/s11064-019-02934-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 12/10/2019] [Accepted: 12/13/2019] [Indexed: 12/13/2022]
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18
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Abstract
The transport of materials across membranes is a vital process for all aspects of cellular function, including growth, metabolism, and communication. Protein transporters are the molecular gates that control this movement and serve as key points of regulation for these processes, thus representing an attractive class of therapeutic targets. With more than 400 members, the solute carrier (SLC) membrane transport proteins are the largest family of transporters, yet, they are pharmacologically underexploited relative to other protein families and many of the available chemical tools possess suboptimal selectivity and efficacy. Fortuitously, there is increased interest in elucidating the physiological roles of SLCs as well as growing recognition of their therapeutic potential. This Perspective provides an overview of the SLC superfamily, including their biochemical and functional features, as well as their roles in various human diseases. In particular, we explore efforts and associated challenges toward drugging SLCs, as well as highlight opportunities for future drug discovery.
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Affiliation(s)
- Wesley Wei Wang
- Department of Chemistry, The Scripps Research Institute, Jupiter, Florida 33458, United States
| | - Leandro Gallo
- Department of Chemistry, The Scripps Research Institute, Jupiter, Florida 33458, United States
| | - Appaso Jadhav
- Department of Chemistry, The Scripps Research Institute, Jupiter, Florida 33458, United States
| | - Richard Hawkins
- Department of Chemistry, The Scripps Research Institute, Jupiter, Florida 33458, United States
| | - Christopher G Parker
- Department of Chemistry, The Scripps Research Institute, Jupiter, Florida 33458, United States.,Department of Chemistry, The Scripps Research Institute, La Jolla, California 92037, United States
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19
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Yu X, Plotnikova O, Bonin PD, Subashi TA, McLellan TJ, Dumlao D, Che Y, Dong YY, Carpenter EP, West GM, Qiu X, Culp JS, Han S. Cryo-EM structures of the human glutamine transporter SLC1A5 (ASCT2) in the outward-facing conformation. eLife 2019; 8:e48120. [PMID: 31580259 PMCID: PMC6800002 DOI: 10.7554/elife.48120] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 10/02/2019] [Indexed: 12/17/2022] Open
Abstract
Alanine-serine-cysteine transporter 2 (ASCT2, SLC1A5) is the primary transporter of glutamine in cancer cells and regulates the mTORC1 signaling pathway. The SLC1A5 function involves finely tuned orchestration of two domain movements that include the substrate-binding transport domain and the scaffold domain. Here, we present cryo-EM structures of human SLC1A5 and its complex with the substrate, L-glutamine in an outward-facing conformation. These structures reveal insights into the conformation of the critical ECL2a loop which connects the two domains, thus allowing rigid body movement of the transport domain throughout the transport cycle. Furthermore, the structures provide new insights into substrate recognition, which involves conformational changes in the HP2 loop. A putative cholesterol binding site was observed near the domain interface in the outward-facing state. Comparison with the previously determined inward-facing structure of SCL1A5 provides a basis for a more integrated understanding of substrate recognition and transport mechanism in the SLC1 family.
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Affiliation(s)
- Xiaodi Yu
- Medicine DesignPfizer IncGrotonUnited States
| | | | | | | | | | | | - Ye Che
- Medicine DesignPfizer IncGrotonUnited States
| | - Yin Yao Dong
- Structural Genomics ConsortiumUniversity of OxfordOxfordUnited Kingdom
| | | | | | - Xiayang Qiu
- Medicine DesignPfizer IncGrotonUnited States
| | | | - Seungil Han
- Medicine DesignPfizer IncGrotonUnited States
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20
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Garibsingh RAA, Schlessinger A. Advances and Challenges in Rational Drug Design for SLCs. Trends Pharmacol Sci 2019; 40:790-800. [PMID: 31519459 DOI: 10.1016/j.tips.2019.08.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 08/09/2019] [Accepted: 08/13/2019] [Indexed: 01/25/2023]
Abstract
There are over 420 human solute carrier (SLC) transporters from 65 families that are expressed ubiquitously in the body. The SLCs mediate the movement of ions, drugs, and metabolites across membranes and their dysfunction has been associated with a variety of diseases, such as diabetes, cancer, and central nervous system (CNS) disorders. Thus, SLCs are emerging as important targets for therapeutic intervention. Recent technological advances in experimental and computational biology allow better characterization of SLC pharmacology. Here we describe recent approaches to modulate SLC transporter function, with an emphasis on the use of computational approaches and computer-aided drug design (CADD) to study nutrient transporters. Finally, we discuss future perspectives in the rational design of SLC drugs.
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Affiliation(s)
- Rachel-Ann A Garibsingh
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Avner Schlessinger
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
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21
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Ndaru E, Garibsingh RAA, Shi Y, Wallace E, Zakrepine P, Wang J, Schlessinger A, Grewer C. Novel alanine serine cysteine transporter 2 (ASCT2) inhibitors based on sulfonamide and sulfonic acid ester scaffolds. J Gen Physiol 2019; 151:357-368. [PMID: 30718375 PMCID: PMC6400523 DOI: 10.1085/jgp.201812276] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 12/26/2018] [Accepted: 01/10/2019] [Indexed: 01/11/2023] Open
Abstract
The neutral amino acid transporter alanine serine cysteine transporter 2 (ASCT2) belongs to the solute carrier 1 (SLC1) family of transport proteins and transports neutral amino acids, such as alanine and glutamine, into the cell in exchange with intracellular amino acids. This amino acid transport is sodium dependent, but not driven by the transmembrane Na+ concentration gradient. Glutamine transport by ASCT2 is proposed to be important for glutamine homoeostasis in rapidly growing cancer cells to fulfill the energy and nitrogen demands of these cells. Thus, ASCT2 is thought to be a potential anticancer drug target. However, the pharmacology of the amino acid binding site is not well established. Here, we report on the synthesis and characterization of a novel class of ASCT2 inhibitors based on an amino acid scaffold with a sulfonamide/sulfonic acid ester linker to a hydrophobic group. The compounds were designed based on an improved ASCT2 homology model using the human glutamate transporter hEAAT1 crystal structure as a modeling template. The compounds were shown to inhibit with a competitive mechanism and a potency that scales with the hydrophobicity of the side chain. The most potent compound binds with an apparent affinity, K i, of 8 ± 4 µM and can block the alanine response with a K i of 40 ± 23 µM at 200 µM alanine concentration. Computational analysis predicts inhibitor interactions with the binding site through molecular docking. In conclusion, the sulfonamide/sulfonic acid ester scaffold provides facile synthetic access to ASCT2 inhibitors with a potentially large variability in chemical space of the hydrophobic side chain. These inhibitors will be useful chemical tools to further characterize the role of ASCT2 in disease as well as improve our understanding of inhibition mechanisms of this transporter.
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Affiliation(s)
- Elias Ndaru
- Department of Chemistry, Binghamton University, Binghamton, NY
| | - Rachel-Ann A Garibsingh
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - YueYue Shi
- Department of Chemistry, Binghamton University, Binghamton, NY
| | - Evan Wallace
- Department of Chemistry, Binghamton University, Binghamton, NY
| | - Paul Zakrepine
- Department of Chemistry, Binghamton University, Binghamton, NY
| | - Jiali Wang
- Department of Chemistry, Binghamton University, Binghamton, NY
| | - Avner Schlessinger
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Christof Grewer
- Department of Chemistry, Binghamton University, Binghamton, NY
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22
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Scalise M, Pochini L, Console L, Losso MA, Indiveri C. The Human SLC1A5 (ASCT2) Amino Acid Transporter: From Function to Structure and Role in Cell Biology. Front Cell Dev Biol 2018; 6:96. [PMID: 30234109 PMCID: PMC6131531 DOI: 10.3389/fcell.2018.00096] [Citation(s) in RCA: 161] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 08/08/2018] [Indexed: 12/30/2022] Open
Abstract
SLC1A5, known as ASCT2, is a neutral amino acid transporter belonging to the SLC1 family and localized in the plasma membrane of several body districts. ASCT2 is an acronym standing for Alanine, Serine, Cysteine Transporter 2 even if the preferred substrate is the conditionally essential amino acid glutamine, with cysteine being a modulator and not a substrate. The studies around amino acid transport in cells and tissues began in the '60s by using radiolabeled compounds and competition assays. After identification of murine and human genes, the function of the coded protein has been studied in cell system and in proteoliposomes revealing that this transporter is a Na+ dependent antiporter of neutral amino acids, some of which are only inwardly transported and others are bi-directionally exchanged. The functional asymmetry merged with the kinetic asymmetry in line with the physiological role of amino acid pool harmonization. An intriguing function has been described for ASCT2 that is exploited as a receptor by a group of retroviruses to infect human cells. Interactions with scaffold proteins and post-translational modifications regulate ASCT2 stability, trafficking and transport activity. Two asparagine residues, namely N163 and N212, are the sites of glycosylation that is responsible for the definitive localization into the plasma membrane. ASCT2 expression increases in highly proliferative cells such as inflammatory and stem cells to fulfill the augmented glutamine demand. Interestingly, for the same reason, the expression of ASCT2 is greatly enhanced in many human cancers. This finding has generated interest in its candidacy as a pharmacological target for new anticancer drugs. The recently solved 3D structure of ASCT2 will aid in the rational design of such therapeutic compounds.
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Affiliation(s)
- Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy
| | - Lorena Pochini
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy
| | - Lara Console
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy
| | - Maria A Losso
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy.,CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnology, Bari, Italy
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23
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Garibsingh RAA, Otte NJ, Ndaru E, Colas C, Grewer C, Holst J, Schlessinger A. Homology Modeling Informs Ligand Discovery for the Glutamine Transporter ASCT2. Front Chem 2018; 6:279. [PMID: 30137742 PMCID: PMC6066518 DOI: 10.3389/fchem.2018.00279] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Accepted: 06/20/2018] [Indexed: 12/12/2022] Open
Abstract
The Alanine-Serine-Cysteine transporter (SLC1A5, ASCT2), is a neutral amino acid exchanger involved in the intracellular homeostasis of amino acids in peripheral tissues. Given its role in supplying glutamine to rapidly proliferating cancer cells in several tumor types such as triple-negative breast cancer and melanoma, ASCT2 has been identified as a key drug target. Here we use a range of computational methods, including homology modeling and ligand docking, in combination with cell-based assays, to develop hypotheses for structure-function relationships in ASCT2. We perform a phylogenetic analysis of the SLC1 family and its prokaryotic homologs to develop a useful multiple sequence alignment for this protein family. We then generate homology models of ASCT2 in two different conformations, based on the human EAAT1 structures. Using ligand enrichment calculations, the ASCT2 models are then compared to crystal structures of various homologs for their utility in discovering ASCT2 inhibitors. We use virtual screening, cellular uptake and electrophysiology experiments to identify a non-amino acid ASCT2 inhibitor that is predicted to interact with the ASCT2 substrate binding site. Our results provide insights into the structural basis of substrate specificity in the SLC1 family, as well as a framework for the design of future selective and potent ASCT2 inhibitors as cancer therapeutics.
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Affiliation(s)
- Rachel-Ann A Garibsingh
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Nicholas J Otte
- Origins of Cancer Program, Centenary Institute, University of Sydney, Sydney, NSW, Australia.,Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - Elias Ndaru
- Department of Chemistry, Binghamton University, Binghamton, NY, United States
| | - Claire Colas
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Christof Grewer
- Department of Chemistry, Binghamton University, Binghamton, NY, United States
| | - Jeff Holst
- Origins of Cancer Program, Centenary Institute, University of Sydney, Sydney, NSW, Australia.,Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - Avner Schlessinger
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, United States
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24
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Scopelliti AJ, Font J, Vandenberg RJ, Boudker O, Ryan RM. Structural characterisation reveals insights into substrate recognition by the glutamine transporter ASCT2/SLC1A5. Nat Commun 2018; 9:38. [PMID: 29295993 PMCID: PMC5750217 DOI: 10.1038/s41467-017-02444-w] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 11/30/2017] [Indexed: 12/21/2022] Open
Abstract
Cancer cells undergo a shift in metabolism where they become reliant on nutrients such as the amino-acid glutamine. Glutamine enters the cell via the alanine/serine/cysteine transporter 2 (ASCT2) that is upregulated in several cancers to maintain an increased supply of this nutrient and are therefore an attractive target in cancer therapeutic development. ASCT2 belongs to the glutamate transporter (SLC1A) family but is the only transporter in this family able to transport glutamine. The structural basis for glutamine selectivity of ASCT2 is unknown. Here, we identify two amino-acid residues in the substrate-binding site that are responsible for conferring glutamine selectivity. We introduce corresponding mutations into a prokaryotic homologue of ASCT2 and solve four crystal structures, which reveal the structural basis for neutral amino acid and inhibitor binding in this family. This structural model of ASCT2 may provide a basis for future development of selective ASCT2 inhibitors to treat glutamine-dependent cancers. Cancer cells are reliant on nutrients such as glutamine, which enter the cell via the alanine/serine/cysteine transporter 2 (ASCT2). Here, authors use crystallography to show which amino-acid residues in the substrate-binding site are responsible for conferring glutamine selectivity to ASCT2.
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Affiliation(s)
- Amanda J Scopelliti
- Transporter Biology Group, Discipline of Pharmacology, Sydney Medical School, University of Sydney, Sydney, NSW, 2006, Australia.,Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Josep Font
- Transporter Biology Group, Discipline of Pharmacology, Sydney Medical School, University of Sydney, Sydney, NSW, 2006, Australia
| | - Robert J Vandenberg
- Transporter Biology Group, Discipline of Pharmacology, Sydney Medical School, University of Sydney, Sydney, NSW, 2006, Australia
| | - Olga Boudker
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA. .,Howard Hughes Medical Institute, Weill Cornell Medicine, New York, NY, 10065, USA.
| | - Renae M Ryan
- Transporter Biology Group, Discipline of Pharmacology, Sydney Medical School, University of Sydney, Sydney, NSW, 2006, Australia.
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