1
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Conger KO, Chidley C, Ozgurses ME, Zhao H, Kim Y, Semina SE, Burns P, Rawat V, Lietuvninkas L, Sheldon R, Ben-Sahra I, Frasor J, Sorger PK, DeNicola GM, Coloff JL. ASCT2 is a major contributor to serine uptake in cancer cells. Cell Rep 2024; 43:114552. [PMID: 39068660 PMCID: PMC11406281 DOI: 10.1016/j.celrep.2024.114552] [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: 10/06/2023] [Revised: 05/23/2024] [Accepted: 07/12/2024] [Indexed: 07/30/2024] Open
Abstract
The non-essential amino acid serine is a critical nutrient for cancer cells due to its diverse biosynthetic functions. While some tumors can synthesize serine de novo, others are auxotrophic and therefore reliant on serine uptake. Importantly, despite several transporters being known to be capable of transporting serine, the transporters that mediate serine uptake in cancer cells are not known. Here, we characterize the amino acid transporter ASCT2 (SLC1A5) as a major contributor to serine uptake in cancer cells. ASCT2 is well known as a glutamine transporter in cancer, and our work demonstrates that serine and glutamine compete for uptake through ASCT2. We further show that ASCT2-mediated serine uptake is essential for purine nucleotide biosynthesis and that estrogen receptor α (ERα) promotes serine uptake by directly activating SLC1A5 transcription. Collectively, our work defines an additional important role for ASCT2 as a serine transporter in cancer and evaluates ASCT2 as a potential therapeutic target.
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Affiliation(s)
- Kelly O Conger
- Department of Physiology and Biophysics, University of Illinois Cancer Center, University of Illinois College of Medicine, Chicago, IL, USA
| | - Christopher Chidley
- Laboratory of Systems Pharmacology, Harvard Program in Therapeutic Science, Harvard Medical School, Boston, MA, USA
| | - Mete Emir Ozgurses
- Department of Physiology and Biophysics, University of Illinois Cancer Center, University of Illinois College of Medicine, Chicago, IL, USA
| | - Huiping Zhao
- Department of Physiology and Biophysics, University of Illinois Cancer Center, University of Illinois College of Medicine, Chicago, IL, USA
| | - Yumi Kim
- Department of Cancer Metabolism and Physiology, H. Lee. Moffitt Cancer Center, Tampa, FL, USA
| | - Svetlana E Semina
- Department of Physiology and Biophysics, University of Illinois Cancer Center, University of Illinois College of Medicine, Chicago, IL, USA
| | - Philippa Burns
- Department of Physiology and Biophysics, University of Illinois Cancer Center, University of Illinois College of Medicine, Chicago, IL, USA
| | - Vipin Rawat
- Department of Physiology and Biophysics, University of Illinois Cancer Center, University of Illinois College of Medicine, Chicago, IL, USA
| | - Lina Lietuvninkas
- Department of Physiology and Biophysics, University of Illinois Cancer Center, University of Illinois College of Medicine, Chicago, IL, USA
| | - Ryan Sheldon
- Metabolic and Nutritional Programming, Center for Cancer and Cell Biology, Van Andel Institute, Grand Rapids, MI, USA
| | - Issam Ben-Sahra
- Robert H. Lurie Cancer Center, Department of Biochemistry and Molecular Genetics, Northwestern University, Chicago, IL, USA
| | - Jonna Frasor
- Department of Physiology and Biophysics, University of Illinois Cancer Center, University of Illinois College of Medicine, Chicago, IL, USA
| | - Peter K Sorger
- Laboratory of Systems Pharmacology, Harvard Program in Therapeutic Science, Harvard Medical School, Boston, MA, USA; Department of Systems Biology, Harvard Medical School, Boston, MA, USA
| | - Gina M DeNicola
- Department of Cancer Metabolism and Physiology, H. Lee. Moffitt Cancer Center, Tampa, FL, USA
| | - Jonathan L Coloff
- Department of Physiology and Biophysics, University of Illinois Cancer Center, University of Illinois College of Medicine, Chicago, IL, USA.
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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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Tu G, Fu T, Zheng G, Xu B, Gou R, Luo D, Wang P, Xue W. Computational Chemistry in Structure-Based Solute Carrier Transporter Drug Design: Recent Advances and Future Perspectives. J Chem Inf Model 2024; 64:1433-1455. [PMID: 38294194 DOI: 10.1021/acs.jcim.3c01736] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
Solute carrier transporters (SLCs) are a class of important transmembrane proteins that are involved in the transportation of diverse solute ions and small molecules into cells. There are approximately 450 SLCs within the human body, and more than a quarter of them are emerging as attractive therapeutic targets for multiple complex diseases, e.g., depression, cancer, and diabetes. However, only 44 unique transporters (∼9.8% of the SLC superfamily) with 3D structures and specific binding sites have been reported. To design innovative and effective drugs targeting diverse SLCs, there are a number of obstacles that need to be overcome. However, computational chemistry, including physics-based molecular modeling and machine learning- and deep learning-based artificial intelligence (AI), provides an alternative and complementary way to the classical drug discovery approach. Here, we present a comprehensive overview on recent advances and existing challenges of the computational techniques in structure-based drug design of SLCs from three main aspects: (i) characterizing multiple conformations of the proteins during the functional process of transportation, (ii) identifying druggability sites especially the cryptic allosteric ones on the transporters for substrates and drugs binding, and (iii) discovering diverse small molecules or synthetic protein binders targeting the binding sites. This work is expected to provide guidelines for a deep understanding of the structure and function of the SLC superfamily to facilitate rational design of novel modulators of the transporters with the aid of state-of-the-art computational chemistry technologies including artificial intelligence.
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Affiliation(s)
- Gao Tu
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical Sciences, Chongqing University, Chongqing 401331, China
| | - Tingting Fu
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | | | - Binbin Xu
- Chengdu Sintanovo Biotechnology Co., Ltd., Chengdu 610200, China
| | - Rongpei Gou
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical Sciences, Chongqing University, Chongqing 401331, China
| | - Ding Luo
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical Sciences, Chongqing University, Chongqing 401331, China
| | - Panpan Wang
- College of Chemistry and Pharmaceutical Engineering, Huanghuai University, Zhumadian 463000, China
| | - Weiwei Xue
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical Sciences, Chongqing University, Chongqing 401331, China
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5
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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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6
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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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7
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Gauthier-Coles G, Bröer A, McLeod MD, George AJ, Hannan RD, Bröer S. Identification and characterization of a novel SNAT2 (SLC38A2) inhibitor reveals synergy with glucose transport inhibition in cancer cells. Front Pharmacol 2022; 13:963066. [PMID: 36210829 PMCID: PMC9532951 DOI: 10.3389/fphar.2022.963066] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 08/30/2022] [Indexed: 11/18/2022] Open
Abstract
SNAT2 (SLC38A2) is a sodium-dependent neutral amino acid transporter, which is important for the accumulation of amino acids as nutrients, the maintenance of cellular osmolarity, and the activation of mTORC1. It also provides net glutamine for glutaminolysis and consequently presents as a potential target to treat cancer. A high-throughput screening assay was developed to identify new inhibitors of SNAT2 making use of the inducible nature of SNAT2 and its electrogenic mechanism. Using an optimized FLIPR membrane potential (FMP) assay, a curated scaffold library of 33934 compounds was screened to identify 3-(N-methyl (4-methylphenyl)sulfonamido)-N-(2-trifluoromethylbenzyl)thiophene-2-carboxamide as a potent inhibitor of SNAT2. In two different assays an IC50 of 0.8–3 µM was determined. The compound discriminated against the close transporter homologue SNAT1. MDA-MB-231 breast cancer and HPAFII pancreatic cancer cell lines tolerated the SNAT2 inhibitor up to a concentration of 100 µM but in combination with tolerable doses of the glucose transport inhibitor Bay-876, proliferative growth of both cell lines was halted. This points to synergy between inhibition of glycolysis and glutaminolysis in cancer cells.
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Affiliation(s)
- Gregory Gauthier-Coles
- Research School of Biological Sciences, Australian National University, Canberra, ACT, Australia
| | - Angelika Bröer
- Research School of Biological Sciences, Australian National University, Canberra, ACT, Australia
| | - Malcolm Donald McLeod
- Research School of Chemistry, Australian National University, Canberra, ACT, Australia
| | - Amee J. George
- The John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Ross D. Hannan
- The John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Stefan Bröer
- Research School of Biological Sciences, Australian National University, Canberra, ACT, Australia
- *Correspondence: Stefan Bröer,
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8
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Duan Z, Zhou Z, Lu F, Zhang Y, Guo X, Gui C, Zhang H. Antitumor activity of mianserin (a tetracyclic antidepressant) primarily driven by the inhibition of SLC1A5-mediated glutamine transport. Invest New Drugs 2022; 40:977-989. [PMID: 35834041 DOI: 10.1007/s10637-022-01284-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 07/06/2022] [Indexed: 11/28/2022]
Abstract
Targeting tumor metabolic vulnerabilities such as "glutamine addiction" has become an attractive approach for the discovery of novel antitumor agents. Among various mechanisms explored, SLC1A5, a membrane transporter that plays an important role in glutamine cellular uptake, represents a viable target to interfere with tumor's ability to acquire critical nutrients during proliferation. In the present study, a stably transfected HEK293 cell line with human SLC1A5 (HEK293-SLC1A5) was established for the screening and identification of small molecule SLC1A5 inhibitors. This in vitro system, in conjunction with direct measurement of SLC1A5-mediated L-glutamine-2,3,3,4,4-D5 (substrate) uptake, was practical and efficient in ensuring the specificity of SLC1A5 inhibition. Among a group of diverse compounds tested, mianserin (a tetracyclic antidepressant) demonstrated a marked inhibition of SLC1A5-mediated glutamine uptake. Subsequent investigations using SW480 cells demonstrated that mianserin was capable of inhibiting SW480 tumor growth both in vitro and in vivo, and the in vivo antitumor efficacy was correlated to the reduction of glutamine concentrations in tumor tissues. Computational analysis revealed that hydrophobic interactions between SLC1A5 and its inhibitors could be a critical factor in drug design. Taken together, the current findings confirmed the feasibility of targeting SLC1A5-mediated glutamine uptake as a novel approach for antitumor intervention. It is anticipated that structural insights obtained based on homology modeling would lead to the discovery of more potent and specific SLC1A5 inhibitors for clinical development.
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Affiliation(s)
- Zelin Duan
- College of Pharmaceutical Sciences, Soochow University, Suzhou, 215123, China
| | - Zhiyun Zhou
- College of Pharmaceutical Sciences, Soochow University, Suzhou, 215123, China
| | - Feifei Lu
- College of Pharmaceutical Sciences, Soochow University, Suzhou, 215123, China
| | - Yawen Zhang
- College of Pharmaceutical Sciences, Soochow University, Suzhou, 215123, China
| | - Xvqin Guo
- College of Pharmaceutical Sciences, Soochow University, Suzhou, 215123, China
| | - Chunshan Gui
- College of Pharmaceutical Sciences, Soochow University, Suzhou, 215123, China
| | - Hongjian Zhang
- College of Pharmaceutical Sciences, Soochow University, Suzhou, 215123, China.
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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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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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11
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Scalise M, Console L, Cosco J, Pochini L, Galluccio M, Indiveri C. ASCT1 and ASCT2: Brother and Sister? SLAS DISCOVERY 2021; 26:1148-1163. [PMID: 34269129 DOI: 10.1177/24725552211030288] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The SLC1 family includes seven members divided into two groups, namely, EAATs and ASCTs, that share similar 3D architecture; the first one includes high-affinity glutamate transporters, and the second one includes SLC1A4 and SLC1A5, known as ASCT1 and ASCT2, respectively, responsible for the traffic of neutral amino acids across the cell plasma membrane. The physiological role of ASCT1 and ASCT2 has been investigated over the years, revealing different properties in terms of substrate specificities, affinities, and regulation by physiological effectors and posttranslational modifications. Furthermore, ASCT1 and ASCT2 are involved in pathological conditions, such as neurodegenerative disorders and cancer. This has driven research in the pharmaceutical field aimed to find drugs able to target the two proteins.This review focuses on structural, functional, and regulatory aspects of ASCT1 and ASCT2, highlighting similarities and differences.
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Affiliation(s)
- Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia e Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Lara Console
- Department DiBEST (Biologia, Ecologia e Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Jessica Cosco
- Department DiBEST (Biologia, Ecologia e Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Lorena Pochini
- Department DiBEST (Biologia, Ecologia e Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Michele Galluccio
- Department DiBEST (Biologia, Ecologia e Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia e Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy.,CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnology (IBIOM), Bari, Italy
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12
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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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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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14
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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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15
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Baguet T, Verhoeven J, Pauwelyn G, Hu J, Lambe P, De Lombaerde S, Piron S, Donche S, Descamps B, Goethals I, Vanhove C, De Vos F, Beyzavi MH. Radiosynthesis, in vitro and preliminary in vivo evaluation of the novel glutamine derived PET tracers [ 18F]fluorophenylglutamine and [ 18F]fluorobiphenylglutamine. Nucl Med Biol 2020; 86-87:20-29. [PMID: 32447069 DOI: 10.1016/j.nucmedbio.2020.03.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Revised: 03/13/2020] [Accepted: 03/31/2020] [Indexed: 12/13/2022]
Abstract
INTRODUCTION Glucose has been deemed the driving force of tumor growth for decades. However, research has shown that several tumors metabolically shift towards glutaminolysis. The development of radiolabeled glutamine derivatives could be a useful molecular imaging tool for visualizing these tumors. We elaborated on the glutamine-derived PET tracers by developing two novel probes, namely [18F]fluorophenylglutamine and [18F]fluorobiphenylglutamine. MATERIALS AND METHODS Both tracers were labelled with fluorine-18 using our recently reported ruthenium-based direct aromatic fluorination method. Their affinity was evaluated with a [3H]glutamine inhibition experiment in a human PC-3 and a rat F98 cell line. The imaging potential of [18F]fluorophenylglutamine and [18F]fluorobiphenylglutamine was tested using a mouse PC-3 and a rat F98 tumor model. RESULTS The radiosynthesis of both tracers was successful with overall non-decay corrected yields of 18.46 ± 4.18% (n = 10) ([18F]fluorophenylglutamine) and 8.05 ± 3.25% (n = 5) ([18F]fluorobiphenylglutamine). In vitro inhibition experiments showed a moderate and low affinity of fluorophenylglutamine and fluorobiphenylglutamine, respectively, towards the human ASCT-2 transporter. Both compounds had a low affinity towards the rat ASCT-2 transporter. These results were endorsed by the in vivo experiments with low uptake of both tracers in the F98 rat xenograft, low uptake of [18F]FBPG in the mice PC-3 xenograft and a moderate uptake of [18F]FPG in the PC-3 tumors. CONCLUSION We investigated the imaging potential of two novel PET radiotracers [18F]FPG and [18F]FBPG. [18F]FPG is the first example of a glutamine radiotracer derivatized with a phenyl group which enables the exploration of further derivatization of the phenyl group to increase the affinity and imaging qualities. We hypothesize that increasing the affinity of [18F]FPG by optimizing the substituents of the arene ring can result in a high-quality glutamine-based PET radiotracer. Advances in Knowledge and Implications for patient care: We hereby report novel glutamine-based PET-tracers. These tracers are tagged on the arene group with fluorine-18, hereby preventing in vivo defluorination, which can occur with alkyl labelled tracers (e.g. (2S,4R)4-[18F]fluoroglutamine). [18F]FPG shows clear tumor uptake in vivo, has no in vivo defluorination and has a straightforward production. We believe this tracer is a good starting point for the development of a high-quality tracer which is useful for the clinical visualization of the glutamine transport.
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Affiliation(s)
- Tristan Baguet
- Laboratory of Radiopharmacy, Ghent University, Ghent, Belgium.
| | | | - Glenn Pauwelyn
- Laboratory of Radiopharmacy, Ghent University, Ghent, Belgium
| | - Jiyun Hu
- Department of Chemistry and Biochemistry, University of Arkansas, AR, USA
| | - Patricia Lambe
- Department of Chemistry and Biochemistry, University of Arkansas, AR, USA
| | | | - Sarah Piron
- Laboratory of Radiopharmacy, Ghent University, Ghent, Belgium
| | - Sam Donche
- Ghent University Hospital, Department of Nuclear Medicine, Ghent, Belgium
| | - Benedicte Descamps
- IBiTech-MEDISIP Ghent University, Department of Electronics and Information Systems, Ghent, Belgium
| | - Ingeborg Goethals
- Ghent University Hospital, Department of Nuclear Medicine, Ghent, Belgium
| | - Christian Vanhove
- IBiTech-MEDISIP Ghent University, Department of Electronics and Information Systems, Ghent, Belgium
| | - Filip De Vos
- Laboratory of Radiopharmacy, Ghent University, Ghent, Belgium
| | - M Hassan Beyzavi
- Department of Chemistry and Biochemistry, University of Arkansas, AR, USA.
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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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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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19
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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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20
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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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21
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Wang C, Wu J, Wang Z, Yang Z, Li Z, Deng H, Li L, Peng X, Feng M. Glutamine addiction activates polyglutamine-based nanocarriers delivering therapeutic siRNAs to orthotopic lung tumor mediated by glutamine transporter SLC1A5. Biomaterials 2018; 183:77-92. [PMID: 30149232 DOI: 10.1016/j.biomaterials.2018.08.035] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 08/03/2018] [Accepted: 08/18/2018] [Indexed: 01/09/2023]
Abstract
Many human cancer cells exhibit an oncogenetic-driven addiction to glutamine (Gln) as rapidly proliferating cancer cells consume Gln at a dramatically increased rate compared to normal cells. Tumor cells, therefore, compete with host cells for Gln, which causes Gln to flux from normal tissues to the tumor. We have developed and characterized a Gln macromolecular analog polyglutamine (PGS) for the delivery of gene regulators, such as siRNAs, in our previous works. Here, we hypothesize that PGS can utilize the Gln transporter SLC1A5 to specifically deliver therapeutic compounds to Gln-addicted cancer cells. Compared to human lung fibroblast HLF cells, cisplatin-resistant human lung adenocarcinoma A549/DDP cells significantly overexpress SLC1A5, which has a high binding affinity to PGS, as confirmed through molecular docking analysis. Due to the differences in Gln metabolism between malignant and normal cells, PGS/siRNA complexes were remarkably increased in cancer cells, especially when cells were deprived of Gln, which mirrors the conditions that are commonly found in a tumor microenvironment. Furthermore, we identified that chemical and genetic inhibition of Gln transporter SLC1A5 reduced the cellular internalization of PGS/siRNA complexes, suggesting a critical role for SLC1A5 in PGS uptake in cells. In turn, PGS upregulated SLC1A5 expression. Increased uptake of PGS complexes profoundly decreased intracellular Gln levels. Decreased Gln caused a moderate reduction in cell growth. To restore drug sensitivity and further enhance anti-tumor effects, the hybrid siRNAs anti-Survivin and anti-MDR1 (siSM), as model therapeutics, were administered through the PGS delivery system, which resulted in knockdown of Survivin and MDR1 and further sensitized cancer cells to the drug cisplatin (DDP). Since PGS complexes administered i.v. mostly accumulated in the lung parenchyma, a lung orthotopic tumor model was established to evaluate their inhibitory effects on tumors in the lungs. PGS/siSM comparably decreased the rate of tumor growth, while concurrent administration of PGS/siSM and DDP enhanced this effect and insignificantly improved life span. Consistent with our hypothesis, this study demonstrated that PGS mimicked Gln in the SLC1A5 pathway and selectively ferried therapeutics to Gln-addicted cancer cells. Our findings identified a new lung cancer targeting strategy based on Gln metabolism and can be used as a drug/gene delivery system.
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Affiliation(s)
- Cuifeng Wang
- School of Pharmaceutical Sciences, Sun Yat-sen University, University Town, Guangzhou 510006, PR China.
| | - Jiamin Wu
- School of Pharmaceutical Sciences, Sun Yat-sen University, University Town, Guangzhou 510006, PR China; School of Pharmacy, Guangdong Medical University, Dongguan 523808, PR China
| | - Zhongjuan Wang
- School of Pharmaceutical Sciences, Sun Yat-sen University, University Town, Guangzhou 510006, PR China; Department of Pharmacy, Yan'an Hospital Affiliated to Kunming Medical University, Kunming 650051, PR China
| | - Zeping Yang
- School of Pharmaceutical Sciences, Sun Yat-sen University, University Town, Guangzhou 510006, PR China
| | - Zhi Li
- School of Pharmaceutical Sciences, Sun Yat-sen University, University Town, Guangzhou 510006, PR China
| | - Huihui Deng
- School of Pharmaceutical Sciences, Sun Yat-sen University, University Town, Guangzhou 510006, PR China
| | - Long Li
- School of Pharmaceutical Sciences, Sun Yat-sen University, University Town, Guangzhou 510006, PR China
| | - Xiao Peng
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, PR China
| | - Min Feng
- School of Pharmaceutical Sciences, Sun Yat-sen University, University Town, Guangzhou 510006, PR China.
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22
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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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23
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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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24
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Scalise M, Pochini L, Galluccio M, Console L, Indiveri C. Glutamine Transport and Mitochondrial Metabolism in Cancer Cell Growth. Front Oncol 2017; 7:306. [PMID: 29376023 PMCID: PMC5770653 DOI: 10.3389/fonc.2017.00306] [Citation(s) in RCA: 129] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 11/28/2017] [Indexed: 12/20/2022] Open
Abstract
The concept that cancer is a metabolic disease is now well acknowledged: many cancer cell types rely mostly on glucose and some amino acids, especially glutamine for energy supply. These findings were corroborated by overexpression of plasma membrane nutrient transporters, such as the glucose transporters (GLUTs) and some amino acid transporters such as ASCT2, LAT1, and ATB0,+, which became promising targets for pharmacological intervention. On the basis of their sodium-dependent transport modes, ASCT2 and ATB0+ have the capacity to sustain glutamine need of cancer cells; while LAT1, which is sodium independent will have the role of providing cancer cells with some amino acids with plausible signaling roles. According to the metabolic reprogramming of many types of cancer cells, glucose is mainly catabolized by aerobic glycolysis in tumors, while the fate of Glutamine is completed at mitochondrial level where the enzyme Glutaminase converts Glutamine to Glutamate. Glutamine rewiring in cancer cells is heterogeneous. For example, Glutamate is converted to α-Ketoglutarate giving rise to a truncated form of Krebs cycle. This reprogrammed pathway leads to the production of ATP mainly at substrate level and regeneration of reducing equivalents needed for cells growth, redox balance, and metabolic energy. Few studies on hypothetical mitochondrial transporter for Glutamine are reported and indirect evidences suggested its presence. Pharmacological compounds able to inhibit Glutamine metabolism may represent novel drugs for cancer treatments. Interestingly, well acknowledged targets for drugs are the Glutamine transporters of plasma membrane and the key enzyme Glutaminase.
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Affiliation(s)
- Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia, Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Lorena Pochini
- Department DiBEST (Biologia, Ecologia, Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Michele Galluccio
- Department DiBEST (Biologia, Ecologia, Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Lara Console
- Department DiBEST (Biologia, Ecologia, Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia, Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy.,CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnology, Bari, Italy
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25
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Potent inhibitors of human LAT1 (SLC7A5) transporter based on dithiazole and dithiazine compounds for development of anticancer drugs. Biochem Pharmacol 2017; 143:39-52. [DOI: 10.1016/j.bcp.2017.07.006] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 07/07/2017] [Indexed: 12/11/2022]
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26
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Phenylglycine analogs are inhibitors of the neutral amino acid transporters ASCT1 and ASCT2 and enhance NMDA receptor-mediated LTP in rat visual cortex slices. Neuropharmacology 2017; 126:70-83. [PMID: 28807674 DOI: 10.1016/j.neuropharm.2017.08.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 07/31/2017] [Accepted: 08/09/2017] [Indexed: 01/18/2023]
Abstract
The N-methyl-d-aspartate receptor (NMDA) co-agonist d-serine is a substrate for the neutral amino acid transporters ASCT1 (SLC1A4) and ASCT2 (SLC1A5). We identified l-phenylglycine (PG) and its analogs as inhibitors of ASCT1 and ASCT2. PG analogs were shown to be non-substrate inhibitors of ASCT1 and ASCT2 with a range of activities relative to other amino acid transport systems, including sodium-dependent glutamate transporters, the sodium-independent d-serine transporter asc-1 and system L. L-4-chloroPG was the most potent and selective ASCT1/2 inhibitor identified. The PG analogs facilitated theta-burst induced long-term potentiation in rat visual cortex slices in a manner that was dependent on extracellular d-serine. For structurally-related PG analogs, there was an excellent correlation between ASCT1/2 transport inhibition and enhancement of LTP which was not the case for inhibition of asc-1 or system L. The ability of PG analogs to enhance LTP is likely due to inhibition of d-serine transport by ASCT1/2, leading to elevated extracellular levels of d-serine and increased NMDA receptor activity. These results suggest that ASCT1/2 may play an important role in regulating extracellular d-serine and NMDA receptor-mediated physiological effects and that ASCT1/2 inhibitors have the potential for therapeutic benefit.
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27
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Structure activity relationships of benzylproline-derived inhibitors of the glutamine transporter ASCT2. Bioorg Med Chem Lett 2016; 27:398-402. [PMID: 28057420 DOI: 10.1016/j.bmcl.2016.12.063] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 12/23/2016] [Accepted: 12/24/2016] [Indexed: 11/20/2022]
Abstract
The glutamine transporter ASCT2 has been identified as a promising target to inhibit rapid growth of cancer cells. However, ASCT2 pharmacology is not well established. In this report, we performed a systematic structure activity analysis of a series of substituted benzylproline derivatives. Substitutions on the phenyl ring resulted in compounds with characteristics of ASCT2 inhibitors. Apparent binding affinity increased with increasing hydrophobicity of the side chain. In contrast, interaction of the ASCT2 binding site with specific positions on the phenyl ring was not observed. The most potent compound inhibits the ASCT2 anion conductance with a Ki of 3μM, which is in the same range as that of more bulky and higher molecular weight inhibitors recently reported by others. The experimental results are consistent with computational analysis based on docking of the inhibitors against an ASCT2 homology model. The benzylproline scaffold provides a valuable tool for further improving binding potency of future ASCT2 inhibitors.
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Colas C, Ung PMU, Schlessinger A. SLC Transporters: Structure, Function, and Drug Discovery. MEDCHEMCOMM 2016; 7:1069-1081. [PMID: 27672436 PMCID: PMC5034948 DOI: 10.1039/c6md00005c] [Citation(s) in RCA: 124] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The human Solute Carrier (SLC) transporters are important targets for drug development. Structure-based drug discovery for SLC transporters requires the description of their structure, dynamics, and mechanism of interaction with small molecule ligands and ions. The recent determination of atomic structures of human SLC transporters and their homologs, combined with improved computational power and prediction methods have led to an increased applicability of structure-based drug design methods for human SLC members. In this review, we provide an overview of the SLC transporters' structures and transport mechanisms. We then describe computational techniques, such as homology modeling and virtual screening that are emerging as key tools to discover chemical probes for human SLC members. We illustrate the utility of these methods by presenting case studies in which rational integration of computation and experiment was used to characterize SLC members that transport key nutrients and metabolites, including the amino acid transporters LAT-1 and ASCT2, the SLC13 family of citric acid cycle intermediate transporters, and the glucose transporter GLUT1. We conclude with a brief discussion about future directions in structure-based drug discovery for the human SLC superfamily, one of the most structurally and functionally diverse protein families in human.
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Affiliation(s)
- Claire Colas
- Department of Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | - Peter Man-Un Ung
- Department of Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | - Avner Schlessinger
- Department of Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai, New York, NY 10029
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029
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29
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Scalise M, Pochini L, Galluccio M, Indiveri C. Glutamine transport. From energy supply to sensing and beyond. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1147-1157. [PMID: 26951943 DOI: 10.1016/j.bbabio.2016.03.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 03/01/2016] [Accepted: 03/02/2016] [Indexed: 12/16/2022]
Abstract
Glutamine is the most abundant amino acid in plasma and is actively involved in many biosynthetic and regulatory processes. It can be synthesized endogenously but becomes "conditionally essential" in physiological or pathological conditions of high proliferation rate. To accomplish its functions glutamine has to be absorbed and distributed in the whole body. This job is efficiently carried out by a network of membrane transporters that differ in transport mechanisms and energetics, belonging to families SLC1, 6, 7, 38, and possibly, 25. Some of the transporters are involved in glutamine traffic across different membranes for metabolic purposes; others are involved in specific signaling functions through mTOR. Structure/function relationships and regulatory aspects of glutamine transporters are still at infancy. In the while, insights in involvement of these transporters in cell redox control, cancer metabolism and drug interactions are arising, stimulating basic research to uncover molecular mechanisms of transport and regulation. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi.
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Affiliation(s)
- Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via P. Bucci 4C, 87036 Arcavacata di Rende, Italy
| | - Lorena Pochini
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via P. Bucci 4C, 87036 Arcavacata di Rende, Italy
| | - Michele Galluccio
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via P. Bucci 4C, 87036 Arcavacata di Rende, Italy
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via P. Bucci 4C, 87036 Arcavacata di Rende, Italy.
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30
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The Glutamine Transporters and Their Role in the Glutamate/GABA-Glutamine Cycle. ADVANCES IN NEUROBIOLOGY 2016; 13:223-257. [PMID: 27885631 DOI: 10.1007/978-3-319-45096-4_8] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Glutamine is a key amino acid in the CNS, playing an important role in the glutamate/GABA-glutamine cycle (GGC). In the GGC, glutamine is transferred from astrocytes to neurons, where it will replenish the inhibitory and excitatory neurotransmitter pools. Different transporters participate in this neural communication, i.e., the transporters responsible for glutamine efflux from astrocytes and influx into the neurons, such as the members of the SNAT, LAT, y+LAT, and ASC families of transporters. The SNAT family consists of the transporter isoforms SNAT3 and SNAT5 that are related to efflux from the astrocytic compartment, and SNAT1 and SNAT2 that are associated with glutamine uptake into the neuronal compartment. The isoforms SNAT7 and SNAT8 do not have their role completely understood, but they likely also participate in the GGC. The isoforms LAT2 and y+LAT2 facilitate the exchange of neutral amino acids and cationic amino acids (y+LAT2 isoform) and have been associated with glutamine efflux from astrocytes. ASCT2 is a Na+-dependent antiporter, the participation of which in the GGC also remains to be better characterized. All these isoforms are tightly regulated by transcriptional and translational mechanisms, which are induced by several determinants such as amino acid deprivation, hormones, pH, and the activity of different signaling pathways. Dysfunctional glutamine transporter activity has been associated with the pathophysiological mechanisms of certain neurologic diseases, such as Hepatic Encephalopathy and Manganism. However, there might also be other neuropathological conditions associated with an altered GGC, in which glutamine transporters are dysfunctional. Hence, it appears to be of critical importance that the physiological and pathological aspects of glutamine transporters are thoroughly investigated.
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31
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Schulte ML, Khodadadi AB, Cuthbertson ML, Smith JA, Manning HC. 2-Amino-4-bis(aryloxybenzyl)aminobutanoic acids: A novel scaffold for inhibition of ASCT2-mediated glutamine transport. Bioorg Med Chem Lett 2015; 26:1044-1047. [PMID: 26750251 DOI: 10.1016/j.bmcl.2015.12.031] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 12/03/2015] [Accepted: 12/10/2015] [Indexed: 01/24/2023]
Abstract
Herein, we report the discovery of 2-amino-4-bis(aryloxybenzyl)aminobutanoic acids as novel inhibitors of ASCT2(SLC1A5)-mediated glutamine accumulation in mammalian cells. Focused library development led to two novel ASCT2 inhibitors that exhibit significantly improved potency compared with prior art in C6 (rat) and HEK293 (human) cells. The potency of leads reported here represents a 40-fold improvement over our most potent, previously reported inhibitor and represents, to our knowledge, the most potent pharmacological inhibitors of ASCT2-mediated glutamine accumulation in live cells. These and other compounds in this novel series exhibit tractable chemical properties for further development as potential therapeutic leads.
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Affiliation(s)
- Michael L Schulte
- Vanderbilt Center for Molecular Probes, Vanderbilt University Medical Center, Nashville, TN 37232, United States; Vanderbilt University Institute of Imaging Science (VUIIS), Vanderbilt University Medical Center, Nashville, TN 37232, United States; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN 37232, United States
| | - Alexandra B Khodadadi
- Vanderbilt Center for Molecular Probes, Vanderbilt University Medical Center, Nashville, TN 37232, United States; Vanderbilt University Institute of Imaging Science (VUIIS), Vanderbilt University Medical Center, Nashville, TN 37232, United States
| | - Madison L Cuthbertson
- Hume-Fogg Academic High School, Metropolitan Nashville Public Schools, Nashville, TN 37203, United States
| | - Jarrod A Smith
- Vanderbilt Center for Structural Biology, Vanderbilt University, Nashville, TN 37232, United States; Department of Biochemistry, Vanderbilt University, Nashville, TN 37232, United States
| | - H Charles Manning
- Vanderbilt Center for Molecular Probes, Vanderbilt University Medical Center, Nashville, TN 37232, United States; Vanderbilt University Institute of Imaging Science (VUIIS), Vanderbilt University Medical Center, Nashville, TN 37232, United States; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN 37232, United States; Vanderbilt-Ingram Cancer Center (VICC), Vanderbilt University Medical Center, Nashville, TN 37232, United States; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37232, United States; Department of Neurosurgery, Vanderbilt University Medical Center, Nashville, TN 37232, United States; Department of Chemistry, Vanderbilt University, Nashville, TN 37232, United States
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32
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Colas C, Grewer C, Otte NJ, Gameiro A, Albers T, Singh K, Shere H, Bonomi M, Holst J, Schlessinger A. Ligand Discovery for the Alanine-Serine-Cysteine Transporter (ASCT2, SLC1A5) from Homology Modeling and Virtual Screening. PLoS Comput Biol 2015; 11:e1004477. [PMID: 26444490 PMCID: PMC4596572 DOI: 10.1371/journal.pcbi.1004477] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 07/23/2015] [Indexed: 12/20/2022] Open
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.
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Affiliation(s)
- Claire Colas
- Department of Pharmacology and Systems Therapeutics, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Christof Grewer
- Department of Chemistry, Binghamton University, Binghamton, New York, United States of America
| | - Nicholas James Otte
- Origins of Cancer Laboratory Centenary Program, Camperdown, Australia
- Sydney Medical School, University of Sydney, Sydney, Australia
| | - Armanda Gameiro
- Department of Chemistry, Binghamton University, Binghamton, New York, United States of America
| | - Thomas Albers
- Department of Chemistry, Binghamton University, Binghamton, New York, United States of America
| | - Kurnvir Singh
- Department of Chemistry, Binghamton University, Binghamton, New York, United States of America
| | - Helen Shere
- Department of Pharmacology and Systems Therapeutics, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | | | - Jeff Holst
- Origins of Cancer Laboratory Centenary Program, Camperdown, Australia
- Sydney Medical School, University of Sydney, Sydney, Australia
- * E-mail: (JH); (AS)
| | - Avner Schlessinger
- Department of Pharmacology and Systems Therapeutics, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- * E-mail: (JH); (AS)
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33
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Console L, Scalise M, Tarmakova Z, Coe IR, Indiveri C. N-linked glycosylation of human SLC1A5 (ASCT2) transporter is critical for trafficking to membrane. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1636-45. [PMID: 25862406 DOI: 10.1016/j.bbamcr.2015.03.017] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 03/26/2015] [Accepted: 03/31/2015] [Indexed: 12/11/2022]
Abstract
The human amino acid transporter SLC1A5 (ASCT2) contains two N-glycosylation sites (N163 and N212) located in the large extracellular loop. In the homology structural model of ASCT2 these Asn residues are extracellularly exposed. Mutants of the two Asn exhibited altered electrophoretic mobility. N163Q and N212Q displayed multiple bands with apparent molecular masses from 80kDa to 50kDa. N163/212Q displayed a single band of 50kDa corresponding to the unglycosylated protein. The presence in membrane of WT and mutants was evaluated by protein biotinylation assay followed by immunoblotting. The double mutation significantly impaired the presence of the protein in membrane, without impairment in protein synthesis. [(3)H]glutamine transport was measured in cells transiently transfected with the WT or mutants. N163/212Q exhibited a strongly reduced transport activity correlating with reduced surface expression. The same proteins extracted from cells and reconstituted in liposomes showed comparable transport activities demonstrating that the intrinsic transport function of the mutants was not affected. The rate of endocytosis of ASCT2 was assayed by a reversible biotinylation strategy. N212Q and N163/212Q showed strongly increased rates of endocytosis respect to WT. ASCT2 stability was determined using cycloheximide. N163Q or N163/212Q showed a slightly or significantly lower stability with respect to WT. To assess trafficking to the membrane, a brefeldin-based assay, which caused retention of proteins in ER, was performed. One hour after brefeldin removal WT protein was localized to the plasma membrane while the double mutant was localized in the cytosol. The results demonstrate that N-glycosylation is critical for trafficking.
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Affiliation(s)
- Lara Console
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via P. Bucci 4C, 87036 Arcavacata di Rende, Italy; Department of Chemistry and Biology, Ryerson University, 350 Victoria St., Toronto M5B 2K3, Canada
| | - Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via P. Bucci 4C, 87036 Arcavacata di Rende, Italy
| | - Zlatina Tarmakova
- Department of Chemistry and Biology, Ryerson University, 350 Victoria St., Toronto M5B 2K3, Canada
| | - Imogen R Coe
- Department of Chemistry and Biology, Ryerson University, 350 Victoria St., Toronto M5B 2K3, Canada
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via P. Bucci 4C, 87036 Arcavacata di Rende, Italy
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Kaira K, Sunose Y, Arakawa K, Sunaga N, Shimizu K, Tominaga H, Oriuchi N, Nagamori S, Kanai Y, Oyama T, Takeyoshi I. Clinicopathological significance of ASC amino acid transporter-2 expression in pancreatic ductal carcinoma. Histopathology 2014; 66:234-43. [DOI: 10.1111/his.12464] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Accepted: 05/16/2014] [Indexed: 12/16/2022]
Affiliation(s)
- Kyoichi Kaira
- Department of Medicine and Molecular Science; Gunma University Graduate School of Medicine; Gunma Japan
- Department of Diagnostic Pathology; Gunma University Graduate School of Medicine; Gunma Japan
| | - Yutaka Sunose
- Department of Thoracic and Visceral Surgery; Gunma University Graduate School of Medicine; Gunma Japan
| | | | - Noriaki Sunaga
- Department of Medicine and Molecular Science; Gunma University Graduate School of Medicine; Gunma Japan
| | - Kimihiro Shimizu
- Department of Thoracic and Visceral Surgery; Gunma University Graduate School of Medicine; Gunma Japan
| | - Hideyuki Tominaga
- Department of Molecular Imaging; Gunma University Graduate School of Medicine; Gunma Japan
| | - Noboru Oriuchi
- Department of Diagnostic Radiology and Nuclear Medicine; Gunma University Graduate School of Medicine; Maebashi Gunma Japan
| | - Shushi Nagamori
- Division of Bio-system Pharmacology; Graduate School of Medicine; Osaka University; Osaka Japan
| | - Yoshikatsu Kanai
- Division of Bio-system Pharmacology; Graduate School of Medicine; Osaka University; Osaka Japan
| | - Tetsunari Oyama
- Department of Diagnostic Pathology; Gunma University Graduate School of Medicine; Gunma Japan
| | - Izumi Takeyoshi
- Department of Thoracic and Visceral Surgery; Gunma University Graduate School of Medicine; Gunma Japan
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35
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2-Substituted Nγ-glutamylanilides as novel probes of ASCT2 with improved potency. Bioorg Med Chem Lett 2014; 25:113-6. [PMID: 25435145 DOI: 10.1016/j.bmcl.2014.10.098] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 10/28/2014] [Accepted: 10/30/2014] [Indexed: 11/20/2022]
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.
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36
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Pochini L, Scalise M, Galluccio M, Indiveri C. Membrane transporters for the special amino acid glutamine: structure/function relationships and relevance to human health. Front Chem 2014; 2:61. [PMID: 25157349 PMCID: PMC4127817 DOI: 10.3389/fchem.2014.00061] [Citation(s) in RCA: 176] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 07/16/2014] [Indexed: 12/26/2022] Open
Abstract
Glutamine together with glucose is essential for body's homeostasis. It is the most abundant amino acid and is involved in many biosynthetic, regulatory and energy production processes. Several membrane transporters which differ in transport modes, ensure glutamine homeostasis by coordinating its absorption, reabsorption and delivery to tissues. These transporters belong to different protein families, are redundant and ubiquitous. Their classification, originally based on functional properties, has recently been associated with the SLC nomenclature. Function of glutamine transporters is studied in cells over-expressing the transporters or, more recently in proteoliposomes harboring the proteins extracted from animal tissues or over-expressed in microorganisms. The role of the glutamine transporters is linked to their transport modes and coupling with Na+ and H+. Most transporters share specificity for other neutral or cationic amino acids. Na+-dependent co-transporters efficiently accumulate glutamine while antiporters regulate the pools of glutamine and other amino acids. The most acknowledged glutamine transporters belong to the SLC1, 6, 7, and 38 families. The members involved in the homeostasis are the co-transporters B0AT1 and the SNAT members 1, 2, 3, 5, and 7; the antiporters ASCT2, LAT1 and 2. The last two are associated to the ancillary CD98 protein. Some information on regulation of the glutamine transporters exist, which, however, need to be deepened. No information at all is available on structures, besides some homology models obtained using similar bacterial transporters as templates. Some models of rat and human glutamine transporters highlight very similar structures between the orthologs. Moreover the presence of glycosylation and/or phosphorylation sites located at the extracellular or intracellular faces has been predicted. ASCT2 and LAT1 are over-expressed in several cancers, thus representing potential targets for pharmacological intervention.
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Affiliation(s)
- Lorena Pochini
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria Arcavacata di Rende, Italy
| | - Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria Arcavacata di Rende, Italy
| | - Michele Galluccio
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria Arcavacata di Rende, Italy
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria Arcavacata di Rende, Italy
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37
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Transport mechanism and regulatory properties of the human amino acid transporter ASCT2 (SLC1A5). Amino Acids 2014; 46:2463-75. [DOI: 10.1007/s00726-014-1808-x] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 07/06/2014] [Indexed: 02/06/2023]
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38
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Schlessinger A, Khuri N, Giacomini KM, Sali A. Molecular modeling and ligand docking for solute carrier (SLC) transporters. Curr Top Med Chem 2014; 13:843-56. [PMID: 23578028 DOI: 10.2174/1568026611313070007] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Revised: 01/29/2013] [Accepted: 02/01/2013] [Indexed: 12/21/2022]
Abstract
Solute Carrier (SLC) transporters are membrane proteins that transport solutes, such as ions, metabolites, peptides, and drugs, across biological membranes, using diverse energy coupling mechanisms. In human, there are 386 SLC transporters, many of which contribute to the absorption, distribution, metabolism, and excretion of drugs and/or can be targeted directly by therapeutics. Recent atomic structures of SLC transporters determined by X-ray crystallography and NMR spectroscopy have significantly expanded the applicability of structure-based prediction of SLC transporter ligands, by enabling both comparative modeling of additional SLC transporters and virtual screening of small molecules libraries against experimental structures as well as comparative models. In this review, we begin by describing computational tools, including sequence analysis, comparative modeling, and virtual screening, that are used to predict the structures and functions of membrane proteins such as SLC transporters. We then illustrate the applications of these tools to predicting ligand specificities of select SLC transporters, followed by experimental validation using uptake kinetic measurements and other assays. We conclude by discussing future directions in the discovery of the SLC transporter ligands.
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Affiliation(s)
- Avner Schlessinger
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, 1700 4th Street, San Francisco, CA 94158, USA.
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Zander CB, Albers T, Grewer C. Voltage-dependent processes in the electroneutral amino acid exchanger ASCT2. ACTA ACUST UNITED AC 2013; 141:659-72. [PMID: 23669717 PMCID: PMC3664696 DOI: 10.1085/jgp.201210948] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Neutral amino acid exchange by the alanine serine cysteine transporter (ASCT)2 was reported to be electroneutral and coupled to the cotransport of one Na+ ion. The cotransported sodium ion carries positive charge. Therefore, it is possible that amino acid exchange is voltage dependent. However, little information is available on the electrical properties of the ASCT2 amino acid transport process. Here, we have used a combination of experimental and computational approaches to determine the details of the amino acid exchange mechanism of ASCT2. The [Na+] dependence of ASCT2-associated currents indicates that the Na+/amino acid stoichiometry is at least 2:1, with at least one sodium ion binding to the amino acid–free apo form of the transporter. When the substrate and two Na+ ions are bound, the valence of the transport domain is +0.81. Consistently, voltage steps applied to ASCT2 in the fully loaded configuration elicit transient currents that decay on a millisecond time scale. Alanine concentration jumps at the extracellular side of the membrane are followed by inwardly directed transient currents, indicative of translocation of net positive charge during exchange. Molecular dynamics simulations are consistent with these results and point to a sequential binding process in which one or two modulatory Na+ ions bind with high affinity to the empty transporter, followed by binding of the amino acid substrate and the subsequent binding of a final Na+ ion. Overall, our results are consistent with voltage-dependent amino acid exchange occurring on a millisecond time scale, the kinetics of which we predict with simulations. Despite some differences, transport mechanism and interaction with Na+ appear to be highly conserved between ASCT2 and the other members of the solute carrier 1 family, which transport acidic amino acids.
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Affiliation(s)
- Catherine B Zander
- Department of Chemistry, Binghamton University, Binghamton, NY 13902, USA
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Inactivation of the glutamine/amino acid transporter ASCT2 by 1,2,3-dithiazoles: proteoliposomes as a tool to gain insights in the molecular mechanism of action and of antitumor activity. Toxicol Appl Pharmacol 2012; 265:93-102. [PMID: 23010140 DOI: 10.1016/j.taap.2012.09.011] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Revised: 09/12/2012] [Accepted: 09/14/2012] [Indexed: 11/21/2022]
Abstract
The ASCT2 transport system catalyses a sodium-dependent antiport of glutamine and other neutral amino acids which is involved in amino acid metabolism. A library of 1,2,3-dithiazoles was designed, synthesized and evaluated as inhibitors of the glutamine/amino acid ASCT2 transporter in the model system of proteoliposomes reconstituted with the rat liver transporter. Fifteen of the tested compounds at concentration of 20μM or below, inhibited more than 50% the glutamine/glutamine antiport catalysed by the reconstituted transporter. These good inhibitors bear a phenyl ring with electron withdrawing substituents. The inhibition was reversed by 1,4-dithioerythritol indicating that the effect was likely owed to the formation of mixed sulfides with the protein's Cys residue(s). A dose-response analysis of the most active compounds gave IC(50) values in the range of 3-30μM. Kinetic inhibition studies indicated a non-competitive inhibition, presumably because of a potential covalent interaction of the dithiazoles with cysteine thiol groups that are not located at the substrate binding site. Indeed, computational studies using a homology structural model of ASCT2 transporter, suggested as possible binding targets, Cys-207 or Cys-210, that belong to the CXXC motif of the protein.
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