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Liang Y, Pan C, Yin T, Wang L, Gao X, Wang E, Quang H, Huang D, Tan L, Xiang K, Wang Y, Alexander PB, Li Q, Yao T, Zhang Z, Wang X. Branched-Chain Amino Acid Accumulation Fuels the Senescence-Associated Secretory Phenotype. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2303489. [PMID: 37964763 PMCID: PMC10787106 DOI: 10.1002/advs.202303489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Revised: 10/07/2023] [Indexed: 11/16/2023]
Abstract
The essential branched-chain amino acids (BCAAs) leucine, isoleucine, and valine play critical roles in protein synthesis and energy metabolism. Despite their widespread use as nutritional supplements, BCAAs' full effects on mammalian physiology remain uncertain due to the complexities of BCAA metabolic regulation. Here a novel mechanism linking intrinsic alterations in BCAA metabolism is identified to cellular senescence and the senescence-associated secretory phenotype (SASP), both of which contribute to organismal aging and inflammation-related diseases. Altered BCAA metabolism driving the SASP is mediated by robust activation of the BCAA transporters Solute Carrier Family 6 Members 14 and 15 as well as downregulation of the catabolic enzyme BCAA transaminase 1 during onset of cellular senescence, leading to highly elevated intracellular BCAA levels in senescent cells. This, in turn, activates the mammalian target of rapamycin complex 1 (mTORC1) to establish the full SASP program. Transgenic Drosophila models further indicate that orthologous BCAA regulators are involved in the induction of cellular senescence and age-related phenotypes in flies, suggesting evolutionary conservation of this metabolic pathway during aging. Finally, experimentally blocking BCAA accumulation attenuates the inflammatory response in a mouse senescence model, highlighting the therapeutic potential of modulating BCAA metabolism for the treatment of age-related and inflammatory diseases.
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Affiliation(s)
- Yaosi Liang
- Department of Pharmacology and Cancer BiologyDuke University Medical CenterDurhamNC27710USA
| | - Christopher Pan
- Department of Pharmacology and Cancer BiologyDuke University Medical CenterDurhamNC27710USA
| | - Tao Yin
- Department of Pharmacology and Cancer BiologyDuke University Medical CenterDurhamNC27710USA
| | - Lu Wang
- Department of Pharmacology and Cancer BiologyDuke University Medical CenterDurhamNC27710USA
- State Key Laboratory of Molecular BiologyShanghai Institute of Biochemistry and Cell BiologyCenter for Excellence in Molecular Cell ScienceChinese Academy of SciencesShanghai200031China
| | - Xia Gao
- Department of Pharmacology and Cancer BiologyDuke University Medical CenterDurhamNC27710USA
- Children's Nutrition Research CenterDepartment of PediatricsBaylor College of MedicineHoustonTX77030USA
| | - Ergang Wang
- Department of Pharmacology and Cancer BiologyDuke University Medical CenterDurhamNC27710USA
| | - Holly Quang
- Children's Nutrition Research CenterDepartment of PediatricsBaylor College of MedicineHoustonTX77030USA
| | - De Huang
- Department of Pharmacology and Cancer BiologyDuke University Medical CenterDurhamNC27710USA
- School of Basic Medical SciencesDivision of Life Sciences and MedicineUniversity of Science and Technology of ChinaHefei230026China
| | - Lianmei Tan
- Department of Pharmacology and Cancer BiologyDuke University Medical CenterDurhamNC27710USA
| | - Kun Xiang
- Department of Pharmacology and Cancer BiologyDuke University Medical CenterDurhamNC27710USA
| | - Yu Wang
- Center for Regenerative MedicineMassachusetts General HospitalHarvard Medical SchoolBostonMA02114USA
| | - Peter B. Alexander
- Department of Pharmacology and Cancer BiologyDuke University Medical CenterDurhamNC27710USA
| | - Qi‐Jing Li
- Department of ImmunologyDuke University Medical CenterDurhamNC27710USA
- Institute of Molecular and Cell BiologyAgency for ScienceTechnology and Research (A*STAR)Singapore138673Singapore
- Singapore Immunology NetworkAgency for ScienceTechnology and Research (A*STAR)Singapore138673Singapore
| | - Tso‐Pang Yao
- Department of Pharmacology and Cancer BiologyDuke University Medical CenterDurhamNC27710USA
| | - Zhao Zhang
- Department of Pharmacology and Cancer BiologyDuke University Medical CenterDurhamNC27710USA
| | - Xiao‐Fan Wang
- Department of Pharmacology and Cancer BiologyDuke University Medical CenterDurhamNC27710USA
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2
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Flux coupling, not specificity, shapes the transport and phylogeny of SLC6 glycine transporters. Proc Natl Acad Sci U S A 2022; 119:e2205874119. [PMID: 36191186 PMCID: PMC9564218 DOI: 10.1073/pnas.2205874119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
ATB[Formula: see text] (SLC6A14) is a member of the amino acid transporter branch of the SLC6 family along with GlyT1 (SLC6A9) and GlyT2 (SLC6A5), two glycine-specific transporters coupled to 2:1 and 3:1 Na[Formula: see text]:Cl[Formula: see text], respectively. In contrast, ATB[Formula: see text] exhibits broad substrate specificity for all neutral and cationic amino acids, and its ionic coupling remains unsettled. Using the reversal potential slope method, we demonstrate a 3:1:1 Na[Formula: see text]:Cl[Formula: see text]:Gly stoichiometry for ATB[Formula: see text] that is consistent with its 2.1 e/Gly charge coupling. Like GlyT2, ATB[Formula: see text] behaves as a unidirectional transporter with virtually no glycine efflux at negative potentials after uptake, except by heteroexchange as remarkably shown by leucine activation of NMDARs in Xenopus oocytes coexpressing both membrane proteins. Analysis and computational modeling of the charge movement of ATB[Formula: see text] reveal a higher affinity for sodium in the absence of substrate than GlyT2 and a gating mechanism that locks Na[Formula: see text] into the apo-transporter at depolarized potentials. A 3:1 Na[Formula: see text]:Cl[Formula: see text] stoichiometry justifies the concentrative transport properties of ATB[Formula: see text] and explains its trophic role in tumor growth, while rationalizing its phylogenetic proximity to GlyT2 despite their extreme divergence in specificity.
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3
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Anderson CMH, Edwards N, Watson AK, Althaus M, Thwaites DT. Reshaping the Binding Pocket of the Neurotransmitter:Solute Symporter (NSS) Family Transporter SLC6A14 (ATB 0,+) Selectively Reduces Access for Cationic Amino Acids and Derivatives. Biomolecules 2022; 12:biom12101404. [PMID: 36291613 PMCID: PMC9599917 DOI: 10.3390/biom12101404] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Revised: 09/25/2022] [Accepted: 09/29/2022] [Indexed: 11/16/2022] Open
Abstract
SLC6A14 (ATB0,+) is unique among SLC proteins in its ability to transport 18 of the 20 proteinogenic (dipolar and cationic) amino acids and naturally occurring and synthetic analogues (including anti-viral prodrugs and nitric oxide synthase (NOS) inhibitors). SLC6A14 mediates amino acid uptake in multiple cell types where increased expression is associated with pathophysiological conditions including some cancers. Here, we investigated how a key position within the core LeuT-fold structure of SLC6A14 influences substrate specificity. Homology modelling and sequence analysis identified the transmembrane domain 3 residue V128 as equivalent to a position known to influence substrate specificity in distantly related SLC36 and SLC38 amino acid transporters. SLC6A14, with and without V128 mutations, was heterologously expressed and function determined by radiotracer solute uptake and electrophysiological measurement of transporter-associated current. Substituting the amino acid residue occupying the SLC6A14 128 position modified the binding pocket environment and selectively disrupted transport of cationic (but not dipolar) amino acids and related NOS inhibitors. By understanding the molecular basis of amino acid transporter substrate specificity we can improve knowledge of how this multi-functional transporter can be targeted and how the LeuT-fold facilitates such diversity in function among the SLC6 family and other SLC amino acid transporters.
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Affiliation(s)
- Catriona M. H. Anderson
- School of Natural & Environmental Sciences, Faculty of Science, Engineering & Agriculture, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
- Correspondence: (C.M.H.A.); (D.T.T.)
| | - Noel Edwards
- Biosciences Institute, Faculty of Medical Sciences, Framlington Place, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Andrew K. Watson
- Biosciences Institute, Faculty of Medical Sciences, Framlington Place, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Mike Althaus
- School of Natural & Environmental Sciences, Faculty of Science, Engineering & Agriculture, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
- Department of Natural Sciences & Institute for Functional Gene Analytics, Bonn-Rhein-Sieg University of Applied Sciences, 53359 Rheinbach, Germany
| | - David T. Thwaites
- Biosciences Institute, Faculty of Medical Sciences, Framlington Place, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
- Correspondence: (C.M.H.A.); (D.T.T.)
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4
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Sivaprakasam S, Sikder MOF, Ramalingam L, Kaur G, Dufour JM, Moustaid-Moussa N, Wachtel MS, Ganapathy V. SLC6A14 deficiency is linked to obesity, fatty liver, and metabolic syndrome but only under conditions of a high-fat diet. Biochim Biophys Acta Mol Basis Dis 2021; 1867:166087. [PMID: 33513428 DOI: 10.1016/j.bbadis.2021.166087] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 01/19/2021] [Accepted: 01/21/2021] [Indexed: 02/06/2023]
Abstract
SLC6A14 is a Na+/Cl--coupled transporter for neutral/cationic amino acids, expressed in ileum and colon. A single-nucleotide polymorphism (SNP), rs2011162 (-22,510C > G), in SLC6A14 coding for the 3'-untranslated region (3'-UTR) is associated with obesity in humans. But the impact of this polymorphism on the transporter expression and its connection to obesity are not known. Our objective was to address these issues. The impact of rs2011162 (-22,510C > G) on SLC6A14 expression was monitored using a luciferase reporter. The link between Slc6a14 and obesity was investigated in wild type and Slc6a14-/- mice when fed a normal diet or a high-fat diet. The obesity-associated 3'-UTR polymorphism reduced SLC6A14 expression. With a high-fat diet, Slc6a14-/- mice gained more weight than wild type mice. With normal diet, there was no difference between the two genotypes. The gain in body weight with the high-fat diet in Slc6a14-/- mice was accompanied with metabolic syndrome. With the high-fat diet, Slc6a14-/- mice showed increased food intake, developed fatty liver, and altered plasma amino acid profile. The high-fat diet-associated hepatic steatosis in Slc6a14-/- mice showed male preponderance. We conclude that the 3'-UTR SNP in SLC6A14 associated with obesity decreases the expression of SLC6A14 and that the deficiency of SLC6A14 is linked to obesity. This is supported by the findings that Slc6a14-/- mice develop obesity, fatty liver, and metabolic syndrome. This connection is evident only with a high-fat diet. Therefore, dietary/pharmacologic interventions that induce SLC6A14 expression in the intestinal tract might have potential for obesity prevention.1.
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Affiliation(s)
- Sathish Sivaprakasam
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Mohd O F Sikder
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
| | - Latha Ramalingam
- Department of Nutritional Sciences, Texas Tech University, Lubbock, TX 79409, USA.
| | - Gurvinder Kaur
- Obesity Research Institute, Texas Tech University, Lubbock, TX 79409, USA; Department of Medical Education, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Jannette M Dufour
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA; Obesity Research Institute, Texas Tech University, Lubbock, TX 79409, USA
| | - Naima Moustaid-Moussa
- Department of Nutritional Sciences, Texas Tech University, Lubbock, TX 79409, USA; Obesity Research Institute, Texas Tech University, Lubbock, TX 79409, USA
| | - Mitchell S Wachtel
- Department of Pathology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Vadivel Ganapathy
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
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5
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To VPTH, Masagounder K, Loewen ME. Critical transporters of methionine and methionine hydroxyl analogue supplements across the intestine: What we know so far and what can be learned to advance animal nutrition. Comp Biochem Physiol A Mol Integr Physiol 2021; 255:110908. [PMID: 33482339 DOI: 10.1016/j.cbpa.2021.110908] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 12/15/2020] [Accepted: 01/11/2021] [Indexed: 11/19/2022]
Abstract
DL-methionine (DL-Met) and its analogue DL-2-hydroxy-4-(methylthio) butanoic acid (DL-methionine hydroxyl analogue or DL-MHA) have been used as nutritional supplements in the diets of farmed raised animals. Knowledge of the intestinal transport mechanisms involved in these products is important for developing dietary strategies. This review provides updated information of the expression, function, and transport kinetics in the intestine of known Met-linked transporters along with putative MHA-linked transporters. As a neutral amino acid (AA), the transport of DL-Met is facilitated by multiple apical sodium-dependent/-independent high-/low-affinity transporters such as ASCT2, B0AT1 and rBAT/b0,+AT. The basolateral transport largely relies on the rate-limiting uniporter LAT4, while the presence of the basolateral antiporter y+LAT1 is probably necessary for exchanging intracellular cationic AAs and Met in the blood. In contrast, the intestinal transport kinetics of DL-MHA have been scarcely studied. DL-MHA transport is generally accepted to be mediated simply by the proton-dependent monocarboxylate transporter MCT1. However, in-depth mechanistic studies have indicated that DL-MHA transport is also achieved through apical sodium monocarboxylate transporters (SMCTs). In any case, reliance on either a proton or sodium gradient would thus require energy input for both Met and MHA transport. This expanding knowledge of the specific transporters involved now allows us to assess the effect of dietary ingredients on the expression and function of these transporters. Potentially, the resulting information could be furthered with selective breeding to reduce overall feed costs.
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Affiliation(s)
- Van Pham Thi Ha To
- Veterinary Biomedical Science, University of Saskatchewan, Saskatoon, SK, Canada
| | | | - Matthew E Loewen
- Veterinary Biomedical Science, University of Saskatchewan, Saskatoon, SK, Canada.
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6
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Nałęcz KA. Amino Acid Transporter SLC6A14 (ATB 0,+) - A Target in Combined Anti-cancer Therapy. Front Cell Dev Biol 2020; 8:594464. [PMID: 33195271 PMCID: PMC7609839 DOI: 10.3389/fcell.2020.594464] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 09/30/2020] [Indexed: 12/12/2022] Open
Abstract
Cancer cells are characterized by quick growth and proliferation, demanding constant supply of various nutrients. Several plasma membrane transporters delivering such compounds are upregulated in cancer. Solute carrier family 6 member 14 (SLC6A14), known as amino acid transporter B0,+ (ATB0,+) transports all amino acids with exception of the acidic ones: aspartate and glutamate. Its malfunctioning is correlated with several pathological states and it is upregulated in solid tumors. The high expression of SLC6A14 is prognostic and unfavorable in pancreatic cancer, while in breast cancer it is expressed in estrogen receptor positive cells. As many plasma membrane transporters it resides in endoplasmic reticulum (ER) membrane after translation before further trafficking through Golgi to the cell surface. Transporter exit from ER is strictly controlled. The proper folding of SLC6A14 was shown to be controlled from the cytoplasmic side by heat shock proteins, further exit from ER and formation of coatomer II (COPII) coated vesicles depends on specific interaction with COPII cargo-recognizing subunit SEC24C, phosphorylated by kinase AKT. Inhibition of heat shock proteins, known to be upregulated in cancer, directs SLC6A14 to degradation. Targeting proteins regulating SLC6A14 trafficking is proposed as an additional pharmacological treatment of cancer.
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Affiliation(s)
- Katarzyna A Nałęcz
- Laboratory of Transport Through Biomembranes, Nencki Institute of Experimental Biology, Warsaw, Poland
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7
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Zhang L, Sui C, Yang W, Luo Q. Amino acid transporters: Emerging roles in drug delivery for tumor-targeting therapy. Asian J Pharm Sci 2020; 15:192-206. [PMID: 32373199 PMCID: PMC7193455 DOI: 10.1016/j.ajps.2019.12.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 11/22/2019] [Accepted: 12/22/2019] [Indexed: 12/16/2022] Open
Abstract
Amino acid transporters, which play a vital role in transporting amino acids for the biosynthesis of mammalian cells, are highly expressed in types of tumors. Increasing studies have shown the feasibility of amino acid transporters as a component of tumor-targeting therapy. In this review, we focus on tumor-related amino acid transporters and their potential use in tumor-targeting therapy. Firstly, the expression characteristics of amino acid transporters in cancer and their relationship with tumor growth are reviewed. Secondly, the recognition requirements are discussed, focusing on the "acid-base" properties, conformational isomerism and structural analogues. Finally, recent developments in amino acid transporter-targeting drug delivery strategies are highlighted, including prodrugs and nanocarriers, with special attention to the latest findings of molecular mechanisms and targeting efficiency of transporter-mediated endocytosis. We aim to offer related clues that might lead to valuable tumor-targeting strategies by the utilization of amino acid transporters.
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Affiliation(s)
- Ling Zhang
- Department of Biotherapy, The First Affiliated Hospital of China Medical University, Shenyang 110001, China
| | - Chengguang Sui
- Department of Biotherapy, The First Affiliated Hospital of China Medical University, Shenyang 110001, China
| | - Wenhan Yang
- Department of Pharmacy, The First Affiliated Hospital of China Medical University, Shenyang 110001, China
- Department of Pharmacy, China Medical University, Shenyang 110001, China
| | - Qiuhua Luo
- Department of Pharmacy, The First Affiliated Hospital of China Medical University, Shenyang 110001, China
- Department of Pharmacy, China Medical University, Shenyang 110001, China
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8
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Palazzolo L, Paravicini C, Laurenzi T, Adobati S, Saporiti S, Guerrini U, Gianazza E, Indiveri C, Anderson CMH, Thwaites DT, Eberini I. SLC6A14, a Pivotal Actor on Cancer Stage: When Function Meets Structure. SLAS DISCOVERY 2019; 24:928-938. [DOI: 10.1177/2472555219867317] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
SLC6A14 (ATB0,+) is a sodium- and chloride-dependent neutral and dibasic amino acid transporter that regulates the distribution of amino acids across cell membranes. The transporter is overexpressed in many human cancers characterized by an increased demand for amino acids; as such, it was recently acknowledged as a novel target for cancer therapy. The knowledge on the molecular mechanism of SLC6A14 transport is still limited, but some elegant studies on related transporters report the involvement of the 12 transmembrane α-helices in the transport mechanism, and describe structural rearrangements mediated by electrostatic interactions with some pivotal gating residues.In the present work, we constructed a SLC6A14 model in outward-facing conformation via homology modeling and used molecular dynamics simulations to predict amino acid residues critical for substrate recognition and translocation. We docked the proteinogenic amino acids and other known substrates in the SLC6A14 binding site to study both gating regions and the exposed residues involved in transport. Interestingly, some of these residues correspond to those previously identified in other LeuT-fold transporters; however, we could also identify a novel relevant residue with such function.For the first time, by combined approaches of molecular docking and molecular dynamics simulations, we highlight the potential role of these residues in neutral amino acid transport. This novel information unravels new aspects of the human SLC6A14 structure–function relationship and may have important outcomes for cancer treatment through the design of novel inhibitors of SLC6A14-mediated transport.
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Affiliation(s)
- Luca Palazzolo
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milano, Italy
| | - Chiara Paravicini
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milano, Italy
| | - Tommaso Laurenzi
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milano, Italy
| | - Sara Adobati
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milano, Italy
| | - Simona Saporiti
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milano, Italy
| | - Uliano Guerrini
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milano, Italy
| | - Elisabetta Gianazza
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milano, Italy
| | - Cesare Indiveri
- Dipartimento di Biologia, Ecologia e Scienze della Terra, Università della Calabria, Arcavacata di Rende, Italy
| | - Catriona M. H. Anderson
- Institute for Cell & Molecular Biosciences, Faculty of Medical Sciences, Framlington Place, Newcastle University, Newcastle upon Tyne, UK
| | - David T. Thwaites
- Institute for Cell & Molecular Biosciences, Faculty of Medical Sciences, Framlington Place, Newcastle University, Newcastle upon Tyne, UK
| | - Ivano Eberini
- Dipartimento di Scienze Farmacologiche e Biomolecolari & DSRC, Università degli Studi di Milano, Milano, Italy
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9
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Sikder MOF, Yang S, Ganapathy V, Bhutia YD. The Na+/Cl−-Coupled, Broad-Specific, Amino Acid Transporter SLC6A14 (ATB0,+): Emerging Roles in Multiple Diseases and Therapeutic Potential for Treatment and Diagnosis. AAPS JOURNAL 2017; 20:12. [DOI: 10.1208/s12248-017-0164-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 10/13/2017] [Indexed: 12/21/2022]
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10
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Gorrieri G, Scudieri P, Caci E, Schiavon M, Tomati V, Sirci F, Napolitano F, Carrella D, Gianotti A, Musante I, Favia M, Casavola V, Guerra L, Rea F, Ravazzolo R, Di Bernardo D, Galietta LJV. Goblet Cell Hyperplasia Requires High Bicarbonate Transport To Support Mucin Release. Sci Rep 2016; 6:36016. [PMID: 27786259 PMCID: PMC5081536 DOI: 10.1038/srep36016] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 10/05/2016] [Indexed: 12/15/2022] Open
Abstract
Goblet cell hyperplasia, a feature of asthma and other respiratory diseases, is driven by the Th-2 cytokines IL-4 and IL-13. In human bronchial epithelial cells, we find that IL-4 induces the expression of many genes coding for ion channels and transporters, including TMEM16A, SLC26A4, SLC12A2, and ATP12A. At the functional level, we find that IL-4 enhances calcium- and cAMP-activated chloride/bicarbonate secretion, resulting in high bicarbonate concentration and alkaline pH in the fluid covering the apical surface of epithelia. Importantly, mucin release, elicited by purinergic stimulation, requires the presence of bicarbonate in the basolateral solution and is defective in cells derived from cystic fibrosis patients. In conclusion, our results suggest that Th-2 cytokines induce a profound change in expression and function in multiple ion channels and transporters that results in enhanced bicarbonate transport ability. This change is required as an important mechanism to favor release and clearance of mucus.
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Affiliation(s)
- Giulia Gorrieri
- U.O.C. Genetica Medica, Istituto Giannina Gaslini, Genova, Italy
| | - Paolo Scudieri
- U.O.C. Genetica Medica, Istituto Giannina Gaslini, Genova, Italy
| | - Emanuela Caci
- U.O.C. Genetica Medica, Istituto Giannina Gaslini, Genova, Italy
| | - Marco Schiavon
- Department of Thoracic Surgery, University of Padova, Italy
| | - Valeria Tomati
- U.O.C. Genetica Medica, Istituto Giannina Gaslini, Genova, Italy
| | - Francesco Sirci
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy
| | | | - Diego Carrella
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy
| | - Ambra Gianotti
- U.O.C. Genetica Medica, Istituto Giannina Gaslini, Genova, Italy
| | - Ilaria Musante
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy
| | - Maria Favia
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Italy
| | - Valeria Casavola
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Italy
| | - Lorenzo Guerra
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Italy
| | - Federico Rea
- Department of Thoracic Surgery, University of Padova, Italy
| | - Roberto Ravazzolo
- U.O.C. Genetica Medica, Istituto Giannina Gaslini, Genova, Italy.,DINOGMI, University of Genova, Italy
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11
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Transcriptomic and Immunohistochemical Profiling of SLC6A14 in Pancreatic Ductal Adenocarcinoma. BIOMED RESEARCH INTERNATIONAL 2015; 2015:593572. [PMID: 26106611 PMCID: PMC4461733 DOI: 10.1155/2015/593572] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 04/24/2015] [Indexed: 12/20/2022]
Abstract
We used a target-centric strategy to identify transporter proteins upregulated in pancreatic ductal adenocarcinoma (PDAC) as potential targets for a functional imaging probe to complement existing anatomical imaging approaches. We performed transcriptomic profiling (microarray and RNASeq) on histologically confirmed primary PDAC tumors and normal pancreas tissue from 33 patients, including five patients whose tumors were not visible on computed tomography. Target expression was confirmed with immunohistochemistry on tissue microarrays from 94
PDAC patients. The best imaging target identified was SLC6A14 (a neutral and basic amino acid transporter). SLC6A14 was overexpressed at the transcriptional level in all patients and expressed at the protein level in 95% of PDAC tumors. Very little is known about the role of SLC6A14 in PDAC and our results demonstrate that this target merits further investigation as a candidate transporter for functional imaging of PDAC.
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12
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Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, Spedding M, Peters JA, Harmar AJ. The Concise Guide to PHARMACOLOGY 2013/14: transporters. Br J Pharmacol 2013; 170:1706-96. [PMID: 24528242 PMCID: PMC3892292 DOI: 10.1111/bph.12450] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. Transporters are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, nuclear hormone receptors and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.
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Affiliation(s)
- Stephen PH Alexander
- School of Life Sciences, University of Nottingham Medical SchoolNottingham, NG7 2UH, UK
| | - Helen E Benson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Elena Faccenda
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Adam J Pawson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Joanna L Sharman
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | | | - John A Peters
- Neuroscience Division, Medical Education Institute, Ninewells Hospital and Medical School, University of DundeeDundee, DD1 9SY, UK
| | - Anthony J Harmar
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
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13
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Abstract
The solute carrier 6 (SLC6) family of the human genome comprises transporters for neurotransmitters, amino acids, osmolytes and energy metabolites. Members of this family play critical roles in neurotransmission, cellular and whole body homeostasis. Malfunction or altered expression of these transporters is associated with a variety of diseases. Pharmacological inhibition of the neurotransmitter transporters in this family is an important strategy in the management of neurological and psychiatric disorders. This review provides an overview of the biochemical and pharmacological properties of the SLC6 family transporters.
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Affiliation(s)
- Stefan Bröer
- Research School of Biology, Australian National University, Canberra, ACT, Australia.
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14
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Kooijmans SAA, Senyschyn D, Mezhiselvam MM, Morizzi J, Charman SA, Weksler B, Romero IA, Couraud PO, Nicolazzo JA. The involvement of a Na⁺- and Cl⁻-dependent transporter in the brain uptake of amantadine and rimantadine. Mol Pharm 2012; 9:883-93. [PMID: 22352408 DOI: 10.1021/mp2004127] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Despite their structural similarity, the two anti-influenza adamantane compounds amantadine (AMA) and rimantadine (RIM) exhibit strikingly different rates of blood-brain barrier (BBB) transport. However, the molecular mechanisms facilitating the higher rate of in situ BBB transport of RIM, relative to AMA, remain unclear. The aim of this study, therefore, was to determine whether differences in the extent of brain uptake between these two adamantanes also occurred in vivo, and elucidate the potential carrier protein facilitating their BBB transport using immortalized human brain endothelial cells (hCMEC/D3). Following oral administration to Swiss Outbred mice, RIM exhibited 2.4-3.0-fold higher brain-to-plasma exposure compared to AMA, which was not attributable to differences in the degree of plasma protein binding. At concentrations representative of those obtained in vivo, the hCMEC/D3 cell uptake of RIM was 4.5-15.7-fold higher than that of AMA, with Michaelis-Menten constants 6.3 and 238.4 μM, respectively. The hCMEC/D3 cellular uptake of both AMA and RIM was inhibited by various cationic transporter inhibitors (cimetidine, choline, quinine, and tetraethylammonium) and was dependent on extracellular pH, membrane depolarization and Na⁺ and Cl⁻ ions. Such findings indicated the involvement of the neutral and cationic amino acid transporter B⁰,⁺ (ATB⁰,⁺) in the uptake of AMA and RIM, which was demonstrated to be expressed (at the protein level) in the hCMEC/D3 cells. Indeed, AMA and RIM appeared to interact with this transporter, as shown by a 53-70% reduction in the hCMEC/D3 uptake of the specific ATB⁰,⁺ substrate ³H-glycine in their presence. These studies suggest the involvement of ATB⁰,⁺ in the disposition of these cationic drugs across the BBB, a transporter with the potential to be exploited for targeted drug delivery to the brain.
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Affiliation(s)
- Sander A A Kooijmans
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
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15
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Karunakaran S, Ramachandran S, Coothankandaswamy V, Elangovan S, Babu E, Periyasamy-Thandavan S, Gurav A, Gnanaprakasam JP, Singh N, Schoenlein PV, Prasad PD, Thangaraju M, Ganapathy V. SLC6A14 (ATB0,+) protein, a highly concentrative and broad specific amino acid transporter, is a novel and effective drug target for treatment of estrogen receptor-positive breast cancer. J Biol Chem 2011; 286:31830-8. [PMID: 21771784 PMCID: PMC3173074 DOI: 10.1074/jbc.m111.229518] [Citation(s) in RCA: 144] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 07/12/2011] [Indexed: 01/11/2023] Open
Abstract
SLC6A14, also known as ATB(0,+), is an amino acid transporter with unique characteristics. It transports 18 of the 20 proteinogenic amino acids. However, this transporter is expressed only at low levels in normal tissues. Here, we show that the transporter is up-regulated specifically in estrogen receptor (ER)-positive breast cancer, demonstrable with primary human breast cancer tissues and human breast cancer cell lines. SLC6A14 is an estrogen/ER target. The transport features of SLC6A14 include concentrative transport of leucine (an activator of mTOR), glutamine (an essential amino acid for nucleotide biosynthesis and substrate for glutaminolysis), and arginine (an essential amino acid for tumor cells), suggesting that ER-positive breast cancer cells up-regulate SLC6A14 to meet their increased demand for these amino acids. Consequently, treatment of ER-positive breast cancer cells in vitro with α-methyl-DL-tryptophan (α-MT), a selective blocker of SLC6A14, induces amino acid deprivation, inhibits mTOR, and activates autophagy. Prolongation of the treatment with α-MT causes apoptosis. Addition of an autophagy inhibitor (3-methyladenine) during α-MT treatment also induces apoptosis. These effects of α-MT are specific to ER-positive breast cancer cells, which express the transporter. The ability of α-MT to cause amino acid deprivation is significantly attenuated in MCF-7 cells, an ER-positive breast cancer cell line, when SLC6A14 is silenced with shRNA. In mouse xenograft studies, α-MT by itself is able to reduce the growth of the ER-positive ZR-75-1 breast cancer cells. These studies identify SLC6A14 as a novel and effective drug target for the treatment of ER-positive breast cancer.
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Affiliation(s)
- Senthil Karunakaran
- From the Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia 30912
| | - Sabarish Ramachandran
- From the Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia 30912
| | - Veena Coothankandaswamy
- From the Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia 30912
| | - Selvakumar Elangovan
- From the Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia 30912
| | - Ellappan Babu
- From the Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia 30912
| | - Sudharsan Periyasamy-Thandavan
- From the Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia 30912
| | - Ashish Gurav
- From the Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia 30912
| | - Jaya P. Gnanaprakasam
- From the Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia 30912
| | - Nagendra Singh
- From the Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia 30912
| | - Patricia V. Schoenlein
- From the Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia 30912
| | - Puttur D. Prasad
- From the Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia 30912
| | - Muthusamy Thangaraju
- From the Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia 30912
| | - Vadivel Ganapathy
- From the Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia 30912
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16
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Nakanishi T, Tamai I. Solute Carrier Transporters as Targets for Drug Delivery and Pharmacological Intervention for Chemotherapy. J Pharm Sci 2011; 100:3731-50. [DOI: 10.1002/jps.22576] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Revised: 03/29/2011] [Accepted: 03/31/2011] [Indexed: 01/11/2023]
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17
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Sikora AG, Gelbard A, Davies MA, Sano D, Ekmekcioglu S, Kwon J, Hailemichael Y, Jayaraman P, Myers JN, Grimm EA, Overwijk WW. Targeted inhibition of inducible nitric oxide synthase inhibits growth of human melanoma in vivo and synergizes with chemotherapy. Clin Cancer Res 2010; 16:1834-44. [PMID: 20215556 PMCID: PMC2858983 DOI: 10.1158/1078-0432.ccr-09-3123] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
PURPOSE Aberrant expression of inflammatory molecules, such as inducible nitric oxide (NO) synthase (iNOS), has been linked to cancer, suggesting that their inhibition is a rational therapeutic approach. Whereas iNOS expression in melanoma and other cancers is associated with poor clinical prognosis, in vitro and in vivo studies suggest that iNOS and NO can have both protumor and antitumor effects. We tested the hypothesis that targeted iNOS inhibition would interfere with human melanoma growth and survival in vivo in a preclinical model. EXPERIMENTAL DESIGN We used an immunodeficient non-obese diabetic/severe combined immunodeficient xenograft model to test the susceptibility of two different human melanoma lines to the orally-given iNOS-selective small molecule antagonist N(6)-(1-iminoethyl)-l-lysine-dihydrochloride (L-nil) with and without cytotoxic cisplatin chemotherapy. RESULTS L-nil significantly inhibited melanoma growth and extended the survival of tumor-bearing mice. L-nil treatment decreased the density of CD31+ microvessels and increased the number of apoptotic cells in tumor xenografts. Proteomic analysis of melanoma xenografts with reverse-phase protein array identified alterations in the expression of multiple cell signaling and survival genes after L-nil treatment. The canonical antiapoptotic protein Bcl-2 was downregulated in vivo and in vitro after L-nil treatment, which was associated with increased susceptibility to cisplatin-mediated tumor death. Consistent with this observation, combination therapy with L-nil plus cisplatin in vivo was more effective than either drug alone, without increased toxicity. CONCLUSIONS These data support the hypothesis that iNOS and iNOS-derived NO support tumor growth in vivo and provide convincing preclinical validation of targeted iNOS inhibition as therapy for solid tumors.
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Affiliation(s)
- Andrew G. Sikora
- UT MD Anderson Cancer Center: Dept. of Melanoma Medical Oncology, 1515 Holcombe Blvd, Unit 430, Houston, TX 77030
- UT MD Anderson Cancer Center: Dept. of Head and Neck Surgery, 1515 Holcombe Blvd, Unit 430, Houston, TX 77030
- Departments of Otolaryngology, Immunobiology, Oncological Sciences, and Dermatology, Mount Sinai School of Medicine, One Gustave L. Levy. Place, Box 1189, New York, NY 10029
| | - Alexander Gelbard
- UT MD Anderson Cancer Center: Dept. of Melanoma Medical Oncology, 1515 Holcombe Blvd, Unit 430, Houston, TX 77030
- UT MD Anderson Cancer Center: Dept. of Head and Neck Surgery, 1515 Holcombe Blvd, Unit 430, Houston, TX 77030
- Bobby Alford Department of Otolaryngology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030
| | - Michael A. Davies
- UT MD Anderson Cancer Center: Dept. of Melanoma Medical Oncology, 1515 Holcombe Blvd, Unit 430, Houston, TX 77030
- UT MD Anderson Cancer Center: Dept. Of Systems Biology, 1515 Holcombe Blvd, Unit 430, Houston, TX 77030
| | - Daisuke Sano
- UT MD Anderson Cancer Center: Dept. of Head and Neck Surgery, 1515 Holcombe Blvd, Unit 430, Houston, TX 77030
| | - Suhendan Ekmekcioglu
- UT MD Anderson Cancer Center: Dept. of Experimental Therapeutics, 1515 Holcombe Blvd, Unit 430, Houston, TX 77030
| | - John Kwon
- UT MD Anderson Cancer Center: Dept. of Experimental Therapeutics, 1515 Holcombe Blvd, Unit 430, Houston, TX 77030
| | - Yared Hailemichael
- CORRESPONDING AUTHOR: WWO (; Phone: 713-563-5294; Fax: 713-563-3424).. AGS (; Phone: 212-659-9516; Fax: 212-369-5701)
| | - Padmini Jayaraman
- Departments of Otolaryngology, Immunobiology, Oncological Sciences, and Dermatology, Mount Sinai School of Medicine, One Gustave L. Levy. Place, Box 1189, New York, NY 10029
| | - Jeffrey N. Myers
- UT MD Anderson Cancer Center: Dept. of Head and Neck Surgery, 1515 Holcombe Blvd, Unit 430, Houston, TX 77030
| | - Elizabeth A. Grimm
- UT MD Anderson Cancer Center: Dept. of Experimental Therapeutics, 1515 Holcombe Blvd, Unit 430, Houston, TX 77030
| | - Willem W. Overwijk
- UT MD Anderson Cancer Center: Dept. of Melanoma Medical Oncology, 1515 Holcombe Blvd, Unit 430, Houston, TX 77030
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18
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Nakanishi T, Ross DD, Mitsuoka K. Methods to evaluate transporter activity in cancer. Methods Mol Biol 2010; 637:105-20. [PMID: 20419431 DOI: 10.1007/978-1-60761-700-6_5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Plasma membrane transporter proteins play an important role in taking up nutrients into and effluxing xenobiotics out of cells to sustain cell survival. In the last decade, a number of studies have shown that these physiologically important transporters affect absorption, distribution, and excretion of major anticancer agents in clinical use. More importantly, many transporters have been reported to be differentially upregulated in cancer cells compared to normal tissues, suggesting that the differential expression of transporters in cancer cells may become good targets for enhancing drug delivery as well as diagnostic markers for cancer therapy. Hence, utilizing the knowledge of transporter functions likely provides us with the possibility of delivering a drug to the target tissues, avoiding distribution to other tissues, and improving oral bioavailability. This chapter focuses on methodology to analyze the activity of transporters that are involved in drug transport.
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Affiliation(s)
- Takeo Nakanishi
- Department of Membrane Transport and Biopharmaceutics, School of Pharmaceutical Sciences, Kanazawa University, Kanazawa, Japan
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19
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Okamoto M, Akanuma SI, Tachikawa M, Hosoya KI. Characteristics of glycine transport across the inner blood-retinal barrier. Neurochem Int 2009; 55:789-95. [PMID: 19666071 DOI: 10.1016/j.neuint.2009.08.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Revised: 07/28/2009] [Accepted: 08/01/2009] [Indexed: 10/20/2022]
Abstract
Although glycine plays a pivotal role in neurotransmission and neuromodulation in the retina and is present in high concentration in the retina, the source of retinal glycine is still unclear. The purpose of the present study was to investigate glycine transport across the inner blood-retinal barrier (inner BRB). [(14)C]Glycine transport at the inner BRB was characterized using a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2 cells) as an in vitro model of the inner BRB and in vivo vascular injection techniques. [(14)C]Glycine uptake by TR-iBRB2 cells was Na(+)- and Cl(-)-dependent, and concentration-dependent with Michaelis-Menten constants of 55.4 microM and 8.02 mM, and inhibited by glycine transporter 1 (GlyT1) and system A inhibitors. These uptake studies suggest that GlyT1 and system A are involved in [(14)C]glycine uptake by TR-iBRB2 cells. RT-PCR analysis demonstrated that GlyT1 and system A (encoding ATA 1 and ATA2) mRNA are expressed in TR-iBRB2 cells. An in vivo study suggested that [(14)C]glycine is transported from blood to the retina whereas [(14)C]alpha-methylaminoisobutyric acid, a selective substrate for system A, is not. In conclusion, GlyT1 most likely mediates glycine transport at the inner BRB and is expected to play an important role in regulating the glycine concentration in the neural retina.
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Affiliation(s)
- Masashi Okamoto
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
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20
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Interaction of tryptophan derivatives with SLC6A14 (ATB0,+) reveals the potential of the transporter as a drug target for cancer chemotherapy. Biochem J 2008; 414:343-55. [PMID: 18522536 DOI: 10.1042/bj20080622] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
ATB(0,+) [SLC6A14 (solute carrier family 6 member 14)] is an Na(+)/Cl(-)-coupled amino acid transporter whose expression is upregulated in cancer. 1-Methyltryptophan is an inducer of immune surveillance against tumour cells through its ability to inhibit indoleamine dioxygenase. In the present study, we investigated the role of ATB(0,+) in the uptake of 1-methyltryptophan as a potential mechanism for entry of this putative anticancer drug into tumour cells. These studies show that 1-methyltryptophan is a transportable substrate for ATB(0,+). The transport process is Na(+)/Cl(-)-dependent with an Na(+)/Cl(-)/1-methyltryptophan stoichiometry of 2:1:1. Evaluation of other derivatives of tryptophan has led to identification of alpha-methyltryptophan as a blocker, not a transportable substrate, for ATB(0,+). ATB(0,+) can transport 18 of the 20 proteinogenic amino acids. alpha-Methyltryptophan blocks the transport function of ATB(0,+) with an IC(50) value of approximately 250 muM under conditions simulating normal plasma concentrations of all these 18 amino acids. These results suggest that alpha-methyltryptophan may induce amino acid deprivation in cells which depend on the transporter for their amino acid nutrition. Screening of several mammary epithelial cell lines shows that ATB(0,+) is expressed robustly in some cancer cell lines, but not in all; in contrast, non-malignant cell lines do not express the transporter. Treatment of ATB(0,+)-positive tumour cells with alpha-methyltryptophan leads to suppression of their colony-forming ability, whereas ATB(0,+)-negative cell lines are not affected. The blockade of ATB(0,+) in these cells with alpha-methyltryptophan is associated with cell cycle arrest. These studies reveal the potential of ATB(0,+) as a drug target for cancer chemotherapy.
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21
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Abstract
The beta-alanine carrier was characterized functionally in the 1960s to 1980s at the luminal surface of the ileal mucosal wall and is a Na(+)- and Cl(-)-dependent transporter of a number of essential and non-essential cationic and dipolar amino acids including lysine, arginine and leucine. beta-Alanine carrier-like function has not been demonstrated by any solute carrier transport system identified at the molecular level. A series of experiments were designed to determine whether solute carrier SLC6A14 is the molecular correlate of the intestinal beta-alanine carrier, perhaps the last of the classical intestinal amino acid transport systems to be identified at the molecular level. Following expression of the human SLC6A14 transporter in Xenopus laevis oocytes, the key functional characteristics of the beta-alanine carrier, identified previously in situ in ileum, were demonstrated for the first time. The transport system is both Na(+) and Cl(-) dependent, can transport non-alpha-amino acids such as beta-alanine with low affinity, and has a higher affinity for dipolar and cationic amino acids such as leucine and lysine. N-methylation of its substrates reduces the affinity for transport. These observations confirm the hypothesis that the SLC6A14 gene encodes the transport protein known as the beta-alanine carrier which, due to its broad substrate specificity, is likely to play an important role in absorption of essential nutrients and drugs in the distal regions of the human gastrointestinal tract.
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Affiliation(s)
- Catriona M H Anderson
- Institute for Cell & Molecular Biosciences, Faculty of Medical Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH, UK
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22
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Molecular characterization and expression pattern of taurine transporter in zebrafish during embryogenesis. Life Sci 2008; 82:1004-11. [PMID: 18407297 DOI: 10.1016/j.lfs.2008.02.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 02/09/2008] [Accepted: 02/16/2008] [Indexed: 11/23/2022]
Abstract
Taurine and its transporter (TauT) are expressed in preimplantation embryos, but their role in embryogenesis is not known. To investigate the role of TauT during embryonic development, we cloned and functionally characterized the zebrafish TauT. The zebrafish TauT cDNA codes for a protein of 625 amino acids which is highly homologous to mammalian TauT. When expressed in mammalian cells, zebrafish TauT mediates taurine uptake in a Na(+)/Cl(-)-dependent manner with a Na(+):Cl(-):taurine stoichiometry of 2:1:1. In the zebrafish embryo, taurine and TauT mRNA are present during early cleavage stages, indicating that both the transporter and its substrate are maternally derived. During embryogenesis, zygotic expression of TauT mRNA is evident in the retina, brain, heart, kidney, and blood vessels. Knockdown of TauT by antisense morpholino oligonucleotides leads to cell death in the central nervous system and increased mortality. These findings suggest a specific role for TauT during development in vertebrates.
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23
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Uchiyama T, Fujita T, Gukasyan HJ, Kim KJ, Borok Z, Crandall ED, Lee VHL. Functional characterization and cloning of amino acid transporter B(0,+) (ATB(0,+)) in primary cultured rat pneumocytes. J Cell Physiol 2008; 214:645-54. [PMID: 17960566 DOI: 10.1002/jcp.21254] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cationic amino acid transport in primary cultured rat pneumocytes exhibiting characteristics of alveolar epithelial type I-like cells are described. Asymmetry and activator ion dependency of (3)H-L-arginine uptake were characterized from the apical or basolateral fluid of pneumocytes grown on permeable support. Substrate specificity of transport was evaluated as a function of (3)H-L-arginine uptake inhibition in the presence of other amino acids. Transepithelial transport studies estimated (3)H-L-arginine flux in the apical-to-basolateral and basolateral-to-apical directions. Full length cDNA of rat amino acid transporter B(0,+) (rATB(0,+)) was cloned and its relative expression level studied. Results indicate that uptake of (3)H-L-arginine from apical fluid is dependent on Na(+) and Cl(-). Zwitterionic and cationic amino acids (excluding L-proline and anionic amino acids) inhibited uptake of (3)H-L-arginine from apical, but not basolateral incubation fluid. Apical-to-basolateral transepithelial flux of (3)H-L-arginine was 20x higher than basolateral-to-apical transport. Kinetic studies of (3)H-L-arginine uptake from apical fluid revealed maximal velocity (V(max)) and Michaelis-Menten constants (K(t)) of 33.32 +/- 2.12 pmol/mg protein/15 min and 0.50 +/- 0.11 mM, respectively, in a cooperative process having a coupling ratio of 1.18 +/- 0.16 with Na(+) and 1.11 +/- 0.13 with Cl(-). Expression of rATB(0,+) mRNA was identified by RT-PCR and Northern analysis. Corresponding cloned 3.2 kb rATB(0,+) cDNA sequence exhibits pronounced homology in deduced amino acid sequence to mouse (95% identity and 97% similarity) and human (89% identity and 95% similarity) ATB(0,+) homologues. We conclude that rat pneumocytes express ATB(0,+), which may partly contribute towards recovering cationic and neutral amino acids from alveolar luminal fluid.
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Affiliation(s)
- Tomomi Uchiyama
- First Department of Biochemistry, Kyushu University of Health and Welfare, Nobeoka, Miyazaki, Japan
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24
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Park EC, Hayata T, Cho KWY, Han JK. Xenopus cDNA microarray identification of genes with endodermal organ expression. Dev Dyn 2007; 236:1633-49. [PMID: 17474120 DOI: 10.1002/dvdy.21167] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The endoderm is classically defined as the innermost layer of three Metazoan germ layers. During organogenesis, the endoderm gives rise to the digestive and respiratory tracts as well as associated organs such as the liver, pancreas, and lung. At present, however, how the endoderm forms the variety of cell types of digestive and respiratory tracts as well as the budding organs is not well understood. In order to investigate the molecular basis and mechanism of organogenesis and to identify the endodermal organ-related marker genes, we carried out microarray analysis using Xenopus cDNA chips. To achieve this goal, we isolated the Xenopus gut endoderm from three different stages of Xenopus organogenesis, and separated each stage of gut endoderm into anterior and posterior regions. Competitive hybridization of cDNA between the anterior and posterior endoderm regions, to screen genes that specifically expressed in the major organs, revealed 915 candidates. We then selected 104 clones for in situ hybridization analysis. Here, we report the identification and expression patterns of the 104 Xenopus endodermal genes, which would serve as useful markers for studying endodermal organ development.
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Affiliation(s)
- Edmond Changkyun Park
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Kyungbuk, Republic of Korea
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25
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Wu Y, Shen D, Chen Z, Clayton S, Vadgama JV. Taxol induced apoptosis regulates amino acid transport in breast cancer cells. Apoptosis 2006; 12:593-612. [PMID: 17195090 DOI: 10.1007/s10495-006-0007-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2006] [Accepted: 10/13/2006] [Indexed: 12/01/2022]
Abstract
A major outcome from Taxol treatment is induction of tumor cell apoptosis. However, metabolic responses to Taxol-induced apoptosis are poorly understood. In this study, we hypothesize that alterations in specific amino acid transporters may affect the Taxol-induced apoptosis in breast cancer cells. In this case, the activity of the given transporter may serve as a biomarker that could provide a biological assessment of response to drug treatment. We have examined the mechanisms responsible for Taxol-induced neutral amino acid uptake by breast cancer cells, such as MCF-7, BT474, MDAMB231 and T47D. The biochemical and molecular studies include: (1) growth-inhibition (MTT); (2) transport kinetics: (3) substrate-specific inhibition; (4) effect of thiol-modifying agents NEM and NPM; (5) gene expression of amino acid transporters; and (6) apoptotic assays. Our data show that Taxol treatment of MCF-7 cells induced a transient increase in Na(+)-dependent transport of the neutral amino acid transporter B0 at both gene and protein level. This increase was attenuated by blocking the transporter in the presence of high concentrations of the substrate amino acid. Other neutral amino acid transporters such as ATA2 (System A) and ASC were not altered. Amino acid starvation resulted in the expected up-regulation of System A (ATA2) gene, but not for B0 and ASC. B0 was significantly down regulated. Taxol treatment had no significant effect on the uptake of arginine and glutamate as measured by System y(+) and X(-) (GC) respectively. Tunel assays and FACS cell cycle analysis demonstrated that both Taxol- and doxorubicin-induced upregulation of B0 transporter gene with accompanying increase in cell apoptosis, could be reversed partially by blocking the B0 transporter with high concentration of alanine, and/or by inhibiting the caspase pathway. Both Taxol and doxorubicin treatment caused a significant decrease in S-phase of the cell cycle. However, Taxol-induced an increase primarily in the G2 fraction while doxorubicin caused increase in G1/G0 together with a small increase in G2. In summary, our study showed that Taxol induced apoptosis in several breast cancer cells results in activation of amino acid transporter System B0 at both gene and protein level. Similar response was observed with another chemotherapeutic agent Doxorubicin, suggesting that this increase is in response to apoptosis, and not only due to changes in cell cycle related events.
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Affiliation(s)
- Yanyuan Wu
- Division of Cancer Research and Training, Department of Medicine, Charles R. Drew University of Medicine and Science, Los Angeles, CA 90059, USA
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26
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Hatanaka T, Hatanaka Y, Tsuchida JI, Ganapathy V, Setou M. Amino acid transporter ATA2 is stored at the trans-Golgi network and released by insulin stimulus in adipocytes. J Biol Chem 2006; 281:39273-84. [PMID: 17050538 DOI: 10.1074/jbc.m604534200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recently, we cloned the ATA/SNAT transporters responsible for amino acid transport system A. System A is one of the major transport systems for small neutral and glucogenic amino acids represented by alanine and is involved in the metabolism of glucose and fat. Here, we describe the cellular mechanisms that participate in the acute translocation of ATA2 by insulin stimulus in 3T3-L1 adipocytes. We monitored this insulin-stimulated translocation of ATA2 using an expression system of enhanced green fluorescent protein-tagged ATA2. Studies in living cells revealed that ATA2 is stored in a discrete perinuclear site and that the transporter is released in vesicles from this site toward the plasma membrane. In immunofluorescent analysis, the storage site of ATA2 overlapped with the location of syntaxin 6, a marker of the trans-Golgi network (TGN), but not with that of EEA1, a marker of the early endosomes. The ATA2-containing vesicles on or near the plasma membrane were distinct from GLUT4-containing vesicles. Brefeldin A, an inhibitor of vesicular exit from the TGN, caused morphological changes in the ATA2 storage site along with the similar changes in the TGN. In non-transfected adipocytes, brefeldin A inhibited insulin-stimulated uptake of alpha-(methylamino)isobutyric acid more profoundly than insulin-stimulated uptake of 2-deoxy-d-glucose. These data demonstrate that the ATA2 storage site is specifically associated with the TGN and not with the general endosomal recycling system. Thus, the insulin-stimulated translocation pathways for ATA2 and GLUT4 in adipocytes are distinct, involving different storage sites.
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Affiliation(s)
- Takahiro Hatanaka
- Mitsubishi Kagaku Institute of Life Sciences (MITILS), 11 Minamiooya, Machida, Tokyo 194-8511, Japan
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Hatanaka T, Hatanaka Y, Setou M. Regulation of amino acid transporter ATA2 by ubiquitin ligase Nedd4-2. J Biol Chem 2006; 281:35922-30. [PMID: 17003038 DOI: 10.1074/jbc.m606577200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We report here that ubiquitin ligase Nedd4-2 regulates amino acid transporter ATA2 activity on the cell surface. We first found that a proteasome inhibitor MG132 increased the uptake of alpha-(methylamino)isobutyric acid, a model substrate for amino acid transport system A, in 3T3-L1 adipocytes as well as the preadipocytes. Transient expression of Nedd4-2 in Xenopus oocytes and Chinese hamster ovary cells down-regulated the ATA2 transport activity induced by injected cRNA and transfected cDNA, respectively. Neither the Nedd4-2 mutant with defective catalytic domain nor c-Cbl affected the ATA2 activity significantly. RNA-mediated interference of Nedd4-2 increased the ATA2 activity in the cells, and this was associated with decreased polyubiquitination of ATA2 on the cell surface membrane. Immunofluorescent analysis of Nedd4-2 in the adipocytes stably transfected with the enhanced green fluorescent protein (EGFP)-tagged ATA2 showed the co-localization of Nedd4-2 and EGFP-ATA2 in the plasma membrane but not in the perinuclear ATA2 storage site, supporting the idea that the primary site for the ubiquitination of ATA2 is the plasma membrane. These data suggest that ATA2 on the plasma membrane is subject to polyubiquitination by Nedd4-2 with consequent endocytotic sequestration and proteasomal degradation and that this process is an important determinant of the density of ATA2 functioning on the cell surface.
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Affiliation(s)
- Takahiro Hatanaka
- Mitsubishi Kagaku Institute of Life Sciences, 11 Minamiooya, Machida, Tokyo 194-8511, Japan
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Knipp M. How to Control NO Production in Cells: Nω,Nω-Dimethyl-L-Arginine Dimethylaminohydrolase as a Novel Drug Target. Chembiochem 2006; 7:879-89. [PMID: 16680784 DOI: 10.1002/cbic.200500527] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Markus Knipp
- Department of Chemistry, University of Arizona, 1306 East University Boulevard, Tucson, AZ 85721-0041, USA.
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Kwok B, Yamauchi A, Rajesan R, Chan L, Dhillon U, Gao W, Xu H, Wang B, Takahashi S, Semple J, Tamai I, Nezu JI, Tsuji A, Harper P, Ito S. Carnitine/xenobiotics transporters in the human mammary gland epithelia, MCF12A. Am J Physiol Regul Integr Comp Physiol 2006; 290:R793-802. [PMID: 16195500 DOI: 10.1152/ajpregu.00087.2005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The barrier function of the human mammary gland collapses if challenged with cationic drugs, causing their accumulation in milk. However, underlying molecular mechanisms are not well understood. To gain insight into the mechanism, we characterized transport of organic cations in the MCF12A human mammary gland epithelial cells, using carnitine and tetraethylammonium (TEA) as representative nutrient and xenobiotics probes, respectively. Our results show that the mammary gland cells express mRNA and proteins of human (h) novel organic cation transporters (OCTN) 1 and hOCTN2 (a Na+-dependent carnitine carrier with Na+-independent xenobiotics transport function), which belong to the solute carrier superfamily (SLC) of transporters. Other SLC OCTs such as hOCT1 and extraneuronal monoamine transporter (EMT)/hOCT3 are also expressed at mRNA levels, but hOCT2 was undetectable. We further showed mRNA expression of ATB0+ (an amino acid transporter with a Na+/Cl−-dependent carnitine transport activity), and Fly-like putative transporter 2/OCT6 (a splice variant of carnitine transporter 2: a testis-specific Na+-dependent carnitine transporter). TEA uptake was pH dependent. Carnitine uptake was dependent on Na+, and partly on Cl−, compatible with hOCTN2 and ATB0+ function. Modeling analyses predicted multiplicity of the uptake mechanisms with the high-affinity systems characterized by Km of 5.1 μM for carnitine and 1.6 mM for TEA, apparently similar to the reported hOCTN2 parameter for carnitine, and that of EMT/hOCT3 for TEA. Verapamil, cimetidine, carbamazepine, quinidine, and desipramine inhibited the carnitine uptake but required supratherapeutic concentrations, suggesting robustness of the carnitine uptake systems against xenobiotic challenge. Our findings suggest functional roles of a network of multiple SLC organic cation/nutrient transporters in human mammary gland drug transfer.
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Affiliation(s)
- Bruce Kwok
- Division of Clinical Pharmacology and Toxicology, Department of Pediatrics, Research Institute, Hospital for Sick Children, 555 Univ. Ave., Toronto, Ontario, Canada M5G 1X8
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30
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Jain-Vakkalagadda B, Pal D, Gunda S, Nashed Y, Ganapathy V, Mitra AK. Identification of a Na+-dependent cationic and neutral amino acid transporter, B(0,+), in human and rabbit cornea. Mol Pharm 2005; 1:338-46. [PMID: 16026003 DOI: 10.1021/mp0499499] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The purpose of this study was to identify and functionally characterize an active transport system for L-arginine on rabbit corneal epithelium and human cornea and study its interaction with the amino acid ester prodrugs of acyclovir (Anand, B. S.; Mitra, A. K. Pharm. Res. 2002, 19, 1194-1202). Transport characteristics of [3H]-L-arginine across freshly excised rabbit corneas were determined at various concentrations, in the absence of sodium and chloride ions. Inhibition studies were conducted in the presence of other amino acids, ouabain, and amino acid ester prodrugs of acyclovir (glycine-ACV, phenylalanine-ACV and gamma-glutamate-ACV). Reverse transcription-polymerase chain reaction (RT-PCR) for amino acid transporter B(0,+) was carried out on total RNA isolated from rabbit cornea, rabbit corneal epithelium, and human cornea. Transport of L-Arg across rabbit cornea was saturable (Km = 306 +/- 72 microM and Vmax = 0.12 +/- 0.01 nmol min(-1) cm(-2)) and was Na+, Cl-, and energy dependent. Transport was inhibited by neutral and cationic amino acids and a B(0,+) system specific inhibitor, BCH (Sloan, J. L.; Mager, S. J. Biol. Chem. 1999, 274, 23740-23745), but not by anionic amino acids. Amino acid prodrugs of ACV (Glu-ACV and Phe-ACV) also inhibited transport of [3H]-L-Arg across rabbit cornea. Amino acid transporter B(0,+) was identified by RT-PCR and its identity confirmed by subcloning and sequencing in rabbit cornea, rabbit corneal epithelium, and human cornea. A Na+-, Cl(-)-, and energy-dependent carrier for L-Arg, B(0,+), was identified on rabbit corneal epithelium and human cornea. Glu-ACV and Phe-ACV appear to be substrates for this transporter. The presence of such transporters on the corneal epithelium may provide new opportunities for transporter-targeted prodrug design for enhanced corneal absorption.
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Affiliation(s)
- Blisse Jain-Vakkalagadda
- Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri-Kansas City, 5005 Rockhill Road, Kansas City, Missouri 64110-2499, USA
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31
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Gupta N, Prasad PD, Ghamande S, Moore-Martin P, Herdman AV, Martindale RG, Podolsky R, Mager S, Ganapathy ME, Ganapathy V. Up-regulation of the amino acid transporter ATB(0,+) (SLC6A14) in carcinoma of the cervix. Gynecol Oncol 2005; 100:8-13. [PMID: 16168467 DOI: 10.1016/j.ygyno.2005.08.016] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2005] [Revised: 08/05/2005] [Accepted: 08/17/2005] [Indexed: 11/20/2022]
Abstract
OBJECTIVE ATB(0,+) is an energy-coupled transporter for arginine and amino acid-based prodrugs. The objective of the study was to examine the expression of this transporter in cervical cancer. METHODS Specimens of normal ectocervical mucosa and cervical squamous cell carcinoma were used for determination of ATB(0,+) mRNA levels by RT-PCR. A commercial dot blot of paired normal cervix and cervical cancer cDNA was also used to quantify ATB(0,+) mRNA. ATB(0,+) mRNA and protein in tissue sections were analyzed by in situ hybridization and immunohistochemistry/immunofluorescence. RESULTS ATB(0,+) mRNA increased 5.6-fold (P < 0.0004) in cervical cancer compared to normal cervix. This was associated with a parallel increase in ATB(0,+) protein. CONCLUSIONS Expression of ATB(0,+) is minimal in normal cervix and is up-regulated in cervical cancer. The up-regulation of this highly concentrative transporter for arginine and prodrugs in cervical cancer has significant clinical and therapeutic relevance.
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Affiliation(s)
- Naren Gupta
- Department of Surgery, Medical College of Georgia, Augusta, GA 30912, USA
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32
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Wieland H, Ullrich S, Lang F, Neumeister B. Intracellular multiplication of Legionella pneumophila depends on host cell amino acid transporter SLC1A5. Mol Microbiol 2005; 55:1528-37. [PMID: 15720558 DOI: 10.1111/j.1365-2958.2005.04490.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The infectious agent of Legionnaires' disease, Legionella (L) pneumophila, multiplies intracellularly in eukaryotic cells. This study has been performed to explore the nutrient requirements of L. pneumophila during intracellular replication. In human monocytes, bacterial replication rate was reduced by 76% in defined medium lacking L-cysteine, L-glutamine or L-serine. SLC1A5 (hATB(0,+)), a neutral amino acid transporter, was upregulated in the host cells after infection with L. pneumophila. Inhibition of SLC1A5 by BCH, a competitive inhibitor of amino acid uptake as well as siRNA silencing of the slc1a5 gene blocked intracellular multiplication of L. pneumophila without compromising viability of host cells. These observations suggest that replication of L. pneumophila depends on the function of host cell SLC1A5.
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Affiliation(s)
- Hagen Wieland
- Institute of Physiology, University of Tuebingen, 72076 Tuebingen, Germany
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33
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Gupta N, Miyauchi S, Martindale RG, Herdman AV, Podolsky R, Miyake K, Mager S, Prasad PD, Ganapathy ME, Ganapathy V. Upregulation of the amino acid transporter ATB0,+ (SLC6A14) in colorectal cancer and metastasis in humans. Biochim Biophys Acta Mol Basis Dis 2005; 1741:215-23. [PMID: 15905073 DOI: 10.1016/j.bbadis.2005.04.002] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2005] [Revised: 04/06/2005] [Accepted: 04/13/2005] [Indexed: 11/26/2022]
Abstract
ATB(0,+) (SLC6A14) is a Na(+)/Cl(-)-coupled arginine transporter expressed at low levels in normal colon. Arginine is an essential amino acid for tumor cells. Arginine is also the substrate for nitric oxide synthases (NOSs). Since arginine and arginine-derived nitric oxide (NO) play a critical role in cancer, we examined the expression of ATB(0,+) in colorectal cancer. Paired normal and cancer tissues from colectomy specimens of 10 patients with colorectal cancer and from the liver tissue of one patient with hepatic metastasis from a colonic primary were used for the analysis of the levels of ATB(0,+) mRNA, inducible NOS (iNOS) mRNA and the corresponding proteins. Tissues samples from the colon, liver, and lymph nodes of an additional patient with metastatic colon cancer were analyzed for ATB(0,+) protein alone. We also examined the levels of nitrotyrosylated proteins. The ATB(0,+) mRNA increased 22.9+/-3.0-fold in colorectal cancer compared to normal tissue and the increase was evident in each of the 10 cases examined. iNOS mRNA increased 5.2+/-1.1-fold in cancer specimens. The changes in mRNA levels were associated with an increase in ATB(0,+), iNOS, and nitrotyrosylated proteins. The increased expression of ATB(0,+) and iNOS was also demonstrated in liver and lymph node specimens with metastases from colonic primaries. This study strongly suggests that the upregulation of ATB(0,+) may have a pathogenic role in colorectal cancer. Since ATB(0,+) is a versatile transporter not only for arginine but also for several drugs including NOS inhibitors, these findings have significant clinical and therapeutic relevance.
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Affiliation(s)
- Naren Gupta
- Department of Surgery, Medical College of Georgia, Augusta, GA 30912-2100, USA
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34
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Rotoli BM, Bussolati O, Sala R, Gazzola GC, Dall'Asta V. The transport of cationic amino acids in human airway cells: expression of system y+L activity and transepithelial delivery of NOS inhibitors. FASEB J 2005; 19:810-2. [PMID: 15746185 DOI: 10.1096/fj.04-2924fje] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The transport of arginine has been characterized in human airway Calu-3 cells. As assessed with RT-PCR, Calu-3 cells express the genes for several transporters, such as the system y+-related SLC7A1, SLC7A2, and SLC7A4; the system y+L-related SLC7A6, SLC7A7, and SLC3A2; and the system B0,+-related SLC6A14. In polarized Calu-3 cell monolayers, apical arginine influx has a leucine-sensitive, sodium-dependent component and a leucine- and lysine-resistant sodium-independent fraction. At the basolateral membrane, arginine transport was fully sodium-independent and partially inhibited by leucine provided that sodium was present in the extracellular medium. Moreover, extracellular leucine trans-stimulated arginine efflux from the basolateral membrane in the presence, but not in the absence, of sodium. The transepithelial, apical to basolateral, arginine transport strictly depended on the presence of sodium and was markedly inhibited by apical leucine, but significantly trans-stimulated by the neutral amino acid added at the basolateral side. When added at the apical side, the NOS-inhibitors NMMA and NIL, CAA analogs with a free carboxyl group, markedly inhibited the apical arginine influx and the transepithelial flux of the cationic amino acid. The same compounds trans-stimulated basolateral arginine efflux. None of these effects were observed in the presence of the methyl ester analog NAME. The basolateral medium of Calu-3 cell monolayers, obtained after incubation in the presence of the three inhibitors at the apical side, inhibited the production of NO by activated murine macrophages. The inhibitory effect of the Calu-3 cell conditioned medium was time-dependent and markedly higher with NMMA and NIL than with NAME. Moreover, the NOS-inhibitory effect of the medium was significantly enhanced if NMMA and NIL, at the apical side, and basolateral leucine were simultaneously present during the conditioning procedure. These results indicate that 1) human airway epithelial cells express a functional system y+L at the basolateral membrane; 2) in this model, transepithelial arginine transport involves apical influx through system B0,+ and basolateral efflux through system y+L, and 3) the same transporters also perform an efficient transepithelial transport of amino acid-like NOS inhibitors.
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Affiliation(s)
- Bianca Maria Rotoli
- Sezione di Patologia Generale e Clinica, Dipartimento di Medicina Sperimentale, Università degli Studi di Parma, Parma, Italy
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35
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Verri T, Dimitri C, Treglia S, Storelli F, De Micheli S, Ulianich L, Vito P, Marsigliante S, Storelli C, Di Jeso B. Multiple pathways for cationic amino acid transport in rat thyroid epithelial cell line PC Cl3. Am J Physiol Cell Physiol 2005; 288:C290-303. [PMID: 15483229 DOI: 10.1152/ajpcell.00053.2004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Information regarding cationic amino acid transport systems in thyroid is limited to Northern blot detection of y+LAT1 mRNA in the mouse. This study investigated cationic amino acid transport in PC cell line clone 3 (PC Cl3 cells), a thyroid follicular cell line derived from a normal Fisher rat retaining many features of normal differentiated follicular thyroid cells. We provide evidence that in PC Cl3 cells plasmalemmal transport of cationic amino acids is Na+independent and occurs, besides diffusion, with the contribution of high-affinity, carrier-mediated processes. Carrier-mediated transport is via y+, y+L, and b0,+systems, as assessed by l-arginine uptake and kinetics, inhibition of l-arginine transport by N-ethylmaleimide and neutral amino acids, and l-cystine transport studies. y+L and y+systems account for the highest transport rate (with y+L > y+) and b0,+for a residual fraction of the transport. Uptake data correlate to expression of the genes encoding for CAT-1, CAT-2B, 4F2hc, y+LAT1, y+LAT2, rBAT, and b0,+AT, an expression profile that is also shown by the rat thyroid gland. In PC Cl3 cells cationic amino acid uptake is under TSH and/or cAMP control (with transport increasing with increasing TSH concentration), and upregulation of CAT-1, CAT-2B, 4F2hc/y+LAT1, and rBAT/b0,+AT occurs at the mRNA level under TSH stimulation. Our results provide the first description of an expression pattern of cationic amino acid transport systems in thyroid cells. Furthermore, we provide evidence that extracellular l-arginine is a crucial requirement for normal PC Cl3 cell growth and that long-term l-arginine deprivation negatively influences CAT-2B expression, as it correlates to reduction of CAT-2B mRNA levels.
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Affiliation(s)
- Tiziano Verri
- Laboratory of General Physiology, Department of Biological and Environmental Sciences and Technologies, University of Lecce, Lecce, Italy.
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Sai Y, Tsuji A. Transporter-mediated drug delivery: recent progress and experimental approaches. Drug Discov Today 2005; 9:712-20. [PMID: 15341785 DOI: 10.1016/s1359-6446(04)03198-8] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
A comprehensive list of drug transporters has recently become available as a result of extensive genome analysis, as well as membrane physiology and molecular biology studies. This review covers recent progress in identification and characterization of drug transporters, illustrative cases of successful drug delivery to, or exclusion from, target organs via transporters, and novel experimental approaches to therapeutics using heterologously transduced transporters in tissues. We aim to provide clues that could lead to efficient strategies for the use of transporters to deliver drugs and/or to optimize lead compounds.
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Affiliation(s)
- Yoshimichi Sai
- Department of Pharmaceutics, Kyoritsu University of Pharmacy, Tokyo 105-8512, Japan
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Inoue K, Fei YJ, Zhuang L, Gopal E, Miyauchi S, Ganapathy V. Functional features and genomic organization of mouse NaCT, a sodium-coupled transporter for tricarboxylic acid cycle intermediates. Biochem J 2004; 378:949-57. [PMID: 14656221 PMCID: PMC1224018 DOI: 10.1042/bj20031261] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2003] [Revised: 12/01/2003] [Accepted: 12/04/2003] [Indexed: 11/17/2022]
Abstract
In the present study, we report on the molecular cloning and functional characterization of mouse NaCT (Na+-coupled citrate transporter), the mouse orthologue of Drosophila Indy. Mouse NaCT consists of 572 amino acids and is highly similar to rat and human NaCTs in primary sequence. The mouse nact gene coding for the transporter is approx. 23 kb long and consists of 12 exons. When expressed in mammalian cells, the cloned transporter mediates the Na+-coupled transport of citrate and succinate. Competition experiments reveal that mouse NaCT also recognizes other tricarboxylic acid cycle intermediates such as malate, fumarate and 2-oxo-glutarate as excellent substrates. The Michaelis-Menten constant for the transport process is 38+/-5 mM for citrate and 37+/-6 mM for succinate at pH 7.5. The transport process is electrogenic and exhibits an obligatory requirement for Na+. Na+-activation kinetics indicates that multiple Na+ ions are involved in the activation process. Extracellular pH has a differential effect on the transport function of mouse NaCT depending on whether the transported substrate is citrate or succinate. The Michaelis-Menten constants for these substrates are also influenced markedly by pH. When examined in the Xenopus laevis oocyte expression system with the two-microelectrode voltage-clamp technique, the transport process mediated by mouse NaCT is electrogenic. The charge-to-substrate ratio is 1 for citrate and 2 for succinate. The most probable transport mechanism predicted by these studies involves the transport of citrate as a tervalent anion and succinate as a bivalent anion with a fixed Na+/substrate stoichiometry of 4:1. The present study provides the first unequivocal evidence for the electrogenic nature of mammalian NaCT.
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Affiliation(s)
- Katsuhisa Inoue
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA
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Naggar H, Fei YJ, Ganapathy V, Smith SB. Regulation of reduced-folate transporter-1 (RFT-1) by homocysteine and identity of transport systems for homocysteine uptake in retinal pigment epithelial (RPE) cells. Exp Eye Res 2003; 77:687-97. [PMID: 14609557 DOI: 10.1016/j.exer.2003.08.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reduced-folate transporter-1 (RFT-1) transports reduced-folates, such as N5-methyltetrahydrofolate (MTF), the predominant circulating form of folate. In RPE, RFT-1 is localized to the apical membrane and is thought to transport folate from RPE to photoreceptor cells. Folate is required for DNA, RNA, protein synthesis and the conversion of homocysteine (Hcy) to methionine. Decreased folate levels are associated with increased Hcy levels. In the present study, we asked whether RFT-1 activity in RPE is altered under high Hcy conditions and examined the transport mechanism for Hcy in RPE. Treatment of ARPE-19 cells, a human RPE cell line, with Hcy at concentrations higher than 50 microM led to a significant decrease in RFT-1 activity. This effect increased as the treatment time increased. The inhibitory effect of Hcy on RFT-1 activity was not non-specific, as the activities of several other nutrient transporters were not affected under identical conditions. The effect of Hcy on RFT-1 was associated primarily with a decrease in the maximal velocity with no detectable change in substrate affinity. The decrease in RFT-1 activity was accompanied by parallel changes in RFT-1 mRNA and protein. Uptake of Hcy in ARPE-19 cells occurred via several transport systems, including Na+-independent systems L and b(0,+) and the Na+-dependent systems B0, ATB(0,+) and A. Studies of the interaction of Hcy with one of the cloned transporters (ATB(0,+)) provided direct evidence for the translocation of Hcy across the membrane via the transporter. We conclude that several transport systems operate in ARPE-19 cells for the entry of Hcy and that high levels of Hcy have deleterious effects on the expression and activity of RFT-1 in these cells.
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Affiliation(s)
- Hany Naggar
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA 30912-2000, USA
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39
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Hatanaka T, Haramura M, Fei YJ, Miyauchi S, Bridges CC, Ganapathy PS, Smith SB, Ganapathy V, Ganapathy ME. Transport of amino acid-based prodrugs by the Na+- and Cl(-) -coupled amino acid transporter ATB0,+ and expression of the transporter in tissues amenable for drug delivery. J Pharmacol Exp Ther 2003; 308:1138-47. [PMID: 14617696 DOI: 10.1124/jpet.103.057109] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We evaluated the potential of the Na(+)- and Cl(-)-coupled amino acid transporter ATB(0,+) as a delivery system for amino acid-based prodrugs. Immunofluorescence analysis indicated that ATB(0,+) is expressed abundantly on the luminal surface of cells lining the lumen of the large intestine and the airways of the lung and in various ocular tissues, including the conjunctival epithelium, the tissues easily amenable for drug delivery. We screened a variety of beta-carboxyl derivatives of aspartate and gamma-carboxyl derivatives of glutamate as potential substrates for this transporter using heterologous expression systems. In mammalian cells expressing the cloned ATB(0,+), several of the aspartate and glutamate derivatives inhibited glycine transport via ATB(0,+). Direct evidence for ATB(0,+)-mediated transport of these derivatives was obtained in Xenopus laevis oocytes using electrophysiological methods. Exposure of oocytes, which express ATB(0,+) heterologously, to aspartate beta-benzyl ester as a model derivative induced inward currents in a Na(+)- and Cl(-)-dependent manner with a Na(+)/Cl(-)/aspartate beta-benzyl ester stoichiometry of 2:1:1. ATB(0,+) transported not only the beta-carboxyl derivatives of aspartate and the gamma-carboxyl derivatives of glutamate but also valacyclovir, which is an alpha-carboxyl ester of acyclovir with valine. The transport of valacyclovir via ATB(0,+) was demonstrable in both heterologous expression systems. This process was dependent on Na(+) and Cl(-). The ability of ATB(0,+) to transport valacyclovir was comparable with that of the peptide transporter PEPT1. These findings suggest that ATB(0,+) has significant potential as a delivery system for amino acid-based drugs and prodrugs.
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Affiliation(s)
- Takahiro Hatanaka
- Department of Medicine, Medical College of Georgia, Augusta, GA 30912, USA
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Ray EC, Avissar NE, Vukcevic D, Toia L, Ryan CK, Berlanga-Acosta J, Sax HC. Growth hormone and epidermal growth factor together enhance amino acid transport systems B0,+ and A in remnant small intestine after massive enterectomy. J Surg Res 2003; 115:164-70. [PMID: 14572788 DOI: 10.1016/s0022-4804(03)00225-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
BACKGROUND Sodium-dependent brush-border nutrient transport is decreased 2 weeks after massive enterectomy. This down-regulation is ameliorated by a 1-week infusion of parenteral growth hormone (GH) and epidermal growth factor (EGF) started 1 week after resection. We hypothesize that glutamine (GLN) transport will be enhanced by earlier and longer growth factor infusion, with differential effects on the Na(+)-dependent GLN transport systems A, B(0,+), and B(0)/ASCT2. MATERIALS AND METHODS New Zealand White rabbits underwent 70% small bowel resection then immediately received parenteral EGF, GH, both EGF and GH, or neither for 2 weeks. Na(+)-dependent 3H-GLN uptake by jejunal and ileal brush-border membrane vesicles was measured and the contribution of systems A, B(0,+), and B(0) was then determined by competitive inhibition. Data were analyzed using one-way analysis of variance. RESULTS In nonresected animals, the relative contribution of the systems was similar in jejunum (A 9%, B(0,+) 20%, and B(0) 71%) and ileum (A 13%, B(0,+) 27%, and B(0) 60%). Na(+)-dependent GLN uptake was reduced by one half in resected untreated controls, primarily because of decreased B(0) activity. EGF or GH alone did not affect Na(+)-dependent GLN transport, but, as a combination, there was increased uptake in the residual ileum and jejunum by 144% and 150%, respectively, over resected controls (P < 0.05). This was twice that achieved by delayed and shorter-duration combination treatment. This augmentation was a result of a 6.1-8.2-fold increase in system A as well as a 3.8-3.9-fold enhancement of system B(0,+) activity in remnant ileum and jejunum (P < 0.01). CONCLUSIONS Parenteral EGF and GH, given in combination for 2 weeks immediately after massive enterectomy, synergistically enhance GLN uptake by systems A and B(0,+).
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Affiliation(s)
- Edward C Ray
- Department of Surgery, University of Rochester Medical Center, Rochester, New York, USA
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Ray EC, Avissar NE, Vukcevic D, Toia L, Ryan CK, Berlanga-Acosta J, Sax HC. Growth hormone and epidermal growth factor together enhance amino acid transport systems B(0,+) and A in remnant small intestine after massive enterectomy. J Surg Res 2003; 113:257-63. [PMID: 12957138 DOI: 10.1016/s0022-4804(03)00185-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND Sodium-dependent brush border nutrient transport is decreased 2 weeks after massive enterectomy. This downregulation is ameliorated by a 1-week infusion of parenteral growth hormone (GH) and epidermal growth factor (EGF) started 1 week after resection. We hypothesized that glutamine (GLN) transport would be enhanced by earlier and longer growth factor infusion, with differential effects on the Na(+)-dependent GLN transport systems A, B(0,+), and B0/ASCT2. MATERIALS AND METHODS New Zealand White rabbits underwent 70% small bowel resection then immediately received parenteral EGF, GH, both, or neither for 2 weeks. Na(+)-dependent 3H-GLN uptake by jejunal and ileal brush-border membrane vesicles was measured and the contribution of systems A, B(0,+), and B0 then determined by competitive inhibition. Data were analyzed using one-way analysis of variance. RESULTS In nonresected animals, the relative contribution of the systems was similar in jejunum (A, 9%, B(0,+), 20%; and B0, 71%) and ileum (A, 13%; B(0,+), 27%; and B0, 60%). Na(+)-dependent GLN uptake was reduced by half in resected, untreated controls, primarily because of decreased B(0) activity. EGF or GH alone did not affect Na(+)-dependent GLN transport, but as a combination, increased uptake in the residual ileum and jejunum by 144% and 150%, respectively, over resected controls (P<0.05). This was twice that achieved by delayed and shorter-duration combination treatment. This augmentation was due to a 6.1- to 8.2-fold increase in system A as well as a 3.8- to 3.9-fold enhancement of system B(0,+) activity in remnant ileum and jejunum (P<0.01). CONCLUSIONS Parenteral EGF and GH, given in combination for 2 weeks immediately after massive enterectomy, synergistically enhance GLN uptake by systems A and B(0,+).
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Affiliation(s)
- Edward C Ray
- Department of Surgery, University of Rochester Medical Center, Rochester, New York 14642, USA
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Sloan JL, Grubb BR, Mager S. Expression of the amino acid transporter ATB 0+ in lung: possible role in luminal protein removal. Am J Physiol Lung Cell Mol Physiol 2003; 284:L39-49. [PMID: 12388375 DOI: 10.1152/ajplung.00164.2002] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Normal lung function requires transepithelial clearance of luminal proteins; however, little is known about the molecular mechanisms of protein transport. Protein degradation followed by transport of peptides and amino acids may play an important role in this process. We previously cloned and functionally characterized the neutral and cationic amino acid transporter ATB(0+) and showed expression in the lung by mRNA analysis. In this study, the tissue distribution, subcellular localization, and function of the transporter in native tissue were investigated. Western blots showed expression of the ATB(0+) protein in mouse lung, stomach, colon, testis, blastocysts, and human lung. Immunohistochemistry revealed that ATB(0+) is predominantly expressed on the apical membrane of ciliated epithelial cells throughout mouse airways from trachea to bronchioles and in alveolar type I cells. Electrical measurements from mouse trachea preparations showed Na(+)- and Cl(-)-dependent, amino acid-induced short-circuit current consistent with the properties of ATB(0+). We hypothesize that, by removing amino acids from the airway lumen, the transporter contributes to protein clearance and, by maintaining a low nutrient environment, plays a role in lung defense.
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Affiliation(s)
- Jennifer L Sloan
- Department of Cell and Molecular Physiology and the Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, NC 27599, USA
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Mann GE, Yudilevich DL, Sobrevia L. Regulation of amino acid and glucose transporters in endothelial and smooth muscle cells. Physiol Rev 2003; 83:183-252. [PMID: 12506130 DOI: 10.1152/physrev.00022.2002] [Citation(s) in RCA: 319] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
While transport processes for amino acids and glucose have long been known to be expressed in the luminal and abluminal membranes of the endothelium comprising the blood-brain and blood-retinal barriers, it is only within the last decades that endothelial and smooth muscle cells derived from peripheral vascular beds have been recognized to rapidly transport and metabolize these nutrients. This review focuses principally on the mechanisms regulating amino acid and glucose transporters in vascular endothelial cells, although we also summarize recent advances in the understanding of the mechanisms controlling membrane transport activity and expression in vascular smooth muscle cells. We compare the specificity, ionic dependence, and kinetic properties of amino acid and glucose transport systems identified in endothelial cells derived from cerebral, retinal, and peripheral vascular beds and review the regulation of transport by vasoactive agonists, nitric oxide (NO), substrate deprivation, hypoxia, hyperglycemia, diabetes, insulin, steroid hormones, and development. In view of the importance of NO as a modulator of vascular tone under basal conditions and in disease and chronic inflammation, we critically review the evidence that transport of L-arginine and glucose in endothelial and smooth muscle cells is modulated by bacterial endotoxin, proinflammatory cytokines, and atherogenic lipids. The recent colocalization of the cationic amino acid transporter CAT-1 (system y(+)), nitric oxide synthase (eNOS), and caveolin-1 in endothelial plasmalemmal caveolae provides a novel mechanism for the regulation of NO production by L-arginine delivery and circulating hormones such insulin and 17beta-estradiol.
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Affiliation(s)
- Giovanni E Mann
- Centre for Cardiovascular Biology and Medicine, Guy's, King's, and St. Thomas' School of Biomedical Sciences, King's College London, London, United Kingdom.
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Nicholson B, Manner CK, MacLeod CL. Cat2 L-arginine transporter-deficient fibroblasts can sustain nitric oxide production. Nitric Oxide 2002; 7:236-43. [PMID: 12446172 DOI: 10.1016/s1089-8603(02)00116-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
High-output nitric oxide (NO) production by nitric oxide synthase 2 (NOS2) contributes to normal cellular processes and pathophysiological conditions. The transport of L-arginine, the substrate for NOS2, is required for sustained NO production by NOS2. L-Arginine can be transported by several kinetically defined transport systems, although the majority of arginine uptake is mediated by transport system y(+), encoded by the Cat1-3 gene family. Using macrophages from Cat2-deficient mice, we previously determined that arginine uptake via CAT2 is absolutely required for sustained NO production. Because NO production by fibroblasts is important in wound healing, we sought to determine whether CAT2 is required for NO production in cytokine-stimulated Cat2-deficient and wild-type embryonic fibroblasts. Although macrophages and fibroblasts both required extracellular L-arginine for NO production, NO synthesis by activated Cat2(-/-) fibroblasts was reduced only 19%, whereas Cat2(-/-) macrophages were virtually unable to produce NO. As expected, activated Cat2(-/-) fibroblasts had reduced system y(+)-mediated arginine uptake. However, their reduced NO output was not the result of a significant difference in intracellular L-arginine levels following cytokine stimulation. Uptake experiments revealed that the L-arginine transport system y(+)L was the major cationic amino acid carrier in fibroblasts of both genotypes. We conclude that NO production in embryonic fibroblasts is only partially dependent on CAT2 and that other compensating transporters provide arginine for NOS2-mediated NO synthesis. The data demonstrate that fibroblasts and macrophages have differential dependence on CAT2-mediated L-arginine transport for NO synthesis. The important physiological implication of this finding is discussed.
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Affiliation(s)
- Benjamin Nicholson
- San Diego Cancer Center, University of California, 9500 Gilman Drive, La Jolla, CA 92093-0064 USA
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Shasby DM. System N in eNdothelium. Am J Physiol Lung Cell Mol Physiol 2002; 282:L1190-1. [PMID: 12003773 DOI: 10.1152/ajplung.00046.2002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Hatanaka T, Huang W, Nakanishi T, Bridges CC, Smith SB, Prasad PD, Ganapathy ME, Ganapathy V. Transport of D-serine via the amino acid transporter ATB(0,+) expressed in the colon. Biochem Biophys Res Commun 2002; 291:291-5. [PMID: 11846403 PMCID: PMC4638383 DOI: 10.1006/bbrc.2002.6441] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
D-Serine, synthesized endogenously in the brain, is an important modulator of glutamatergic neurotransmission. Since colonic bacteria produce D-serine, we asked the question whether there are transport mechanisms in the colon that might make this exogenously produced D-serine available to the host. Here we identify for the first time an amino acid transporter in the intestine for high-affinity active transport of D-serine. This transporter, called ATB(0,+), is a Na(+)- and Cl(-)-coupled transporter for L-enantiomers of neutral and cationic amino acids. Here we demonstrate that ATB(0,+) is also capable of mediating the Na(+)- and Cl(-)-coupled transport of D-serine. The affinity of ATB(0,+) for L-serine and D-serine is similar, the K(t) value for the two enantiomers being approximately 150 microM. In addition to D-serine, ATB(0,+) transports D-alanine, D-methionine, D-leucine, and D-tryptophan. However, several other neutral and cationic amino acids that are transportable substrates for ATB(0,+) as L-enantiomers are not transported when presented as D-enantiomers. ATB(0,+) is expressed in the intestinal tract, interestingly not in the proximal intestine but in the distal intestine. Expression is most predominant in the colon where the transporter is localized to the luminal membrane of colonocytes, making this transporter uniquely suitable for absorption of bacteria-derived D-serine.
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Affiliation(s)
- Takahiro Hatanaka
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia 30912
| | - Wei Huang
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia 30912
| | - Takeo Nakanishi
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia 30912
| | - Christy C. Bridges
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia 30912
| | - Sylvia B. Smith
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, Georgia 30912
| | - Puttur D. Prasad
- Department of Obstetrics and Gynecology, Medical College of Georgia, Augusta, Georgia 30912
| | | | - Vadivel Ganapathy
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia 30912
- Department of Obstetrics and Gynecology, Medical College of Georgia, Augusta, Georgia 30912
- To whom correspondence and reprint requests should be addressed at Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912. Fax: 706-721-6608.,
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Closs EI. Expression, regulation and function of carrier proteins for cationic amino acids. Curr Opin Nephrol Hypertens 2002; 11:99-107. [PMID: 11753094 DOI: 10.1097/00041552-200201000-00015] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Different carrier proteins exhibiting distinct transport properties participate in cationic amino acid transport. There are sodium-independent systems, such as b+, y+, y+L and b0,+, and a sodium-dependent system B0,+, most of which have now been identified at the molecular level. In most non-epithelial cells, members of the cationic amino acid transporter (CAT) family mediating system y+ activity seem to be the major entry pathway for cationic amino acids. CAT proteins underlie complex regulation at the transcriptional, post-transcriptional and activity levels. Recent evidence indicates that individual CAT isoforms are necessary for providing the substrate for nitric oxide synthesis, for example CAT-1 for Ca2+-independent nitric oxide production in endothelial cells and CAT-2B for sustained nitric oxide production in macrophages.
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Affiliation(s)
- Ellen I Closs
- Department of Pharmacology, Johannes Gutenberg University, Mainz, Germany.
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