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Duan H, Zhou Y, Shi X, Luo Q, Gao J, Liang L, Liu W, Peng L, Deng D, Hu J. Allosteric and transport modulation of human concentrative nucleoside transporter 3 at the atomic scale. Phys Chem Chem Phys 2021; 23:25401-25413. [PMID: 34751688 DOI: 10.1039/d1cp03756k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Nucleosides are important precursors of nucleotide synthesis in cells, and nucleoside transporters play an important role in many physiological processes by mediating transmembrane transport and absorption. During nucleoside transport, such proteins undergo a significant conformational transition between the outward- and inward-facing states, which leads to alternating access of the substrate-binding site to either side of the membrane. In this work, a variety of molecular simulation methods have been applied to comparatively investigate the motion modes of human concentrative nucleoside transporter 3 (hCNT3) in three states, as well as global and local cavity conformational changes; and finally, a possible elevator-like transport mechanism consistent with experimental data was proposed. The results of the Gaussian network model (GNM) and anisotropic network model (ANM) show that hCNT3 as a whole tends to contract inwards and shift towards a membrane inside, exhibiting an allosteric process that is more energetically favorable than the rigid conversion. To reveal the complete allosteric process of hCNT3 in detail, a series of intermediate conformations were obtained by an adaptive anisotropic network model (aANM). One of the simulated intermediate states is similar to that of a crystal structure, which indicates that the allosteric process is reliable; the state with lower energy is slightly inclined to the inward-facing structure rather than the expected intermediate crystal structure. The final HOLE analysis showed that except for the outward-facing state, the transport channels were gradually enlarged, which was conductive to the directional transport of nucleosides. Our work provides a theoretical basis for the multistep elevator-like transportation mechanism of nucleosides, which helps to further understand the dynamic recognition between nucleoside substrates and hCNT3 as well as the design of nucleoside anticancer drugs.
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Affiliation(s)
- Huaichuan Duan
- School of Pharmacy, Sichuan Industrial Institute of Antibiotics, Chengdu University, Chengdu, China.
| | - Yanxia Zhou
- Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, Department of Obstetrics, West China Second Hospital, Sichuan University, Chengdu, China.
| | - Xiaodong Shi
- School of Pharmacy, Sichuan Industrial Institute of Antibiotics, Chengdu University, Chengdu, China.
| | - Qing Luo
- School of Pharmacy, Sichuan Industrial Institute of Antibiotics, Chengdu University, Chengdu, China.
| | - Jiaxing Gao
- School of Pharmacy, Sichuan Industrial Institute of Antibiotics, Chengdu University, Chengdu, China.
| | - Li Liang
- School of Pharmacy, Sichuan Industrial Institute of Antibiotics, Chengdu University, Chengdu, China.
| | - Wei Liu
- School of Pharmacy, Sichuan Industrial Institute of Antibiotics, Chengdu University, Chengdu, China.
| | - Lianxin Peng
- School of Pharmacy, Sichuan Industrial Institute of Antibiotics, Chengdu University, Chengdu, China.
| | - Dong Deng
- Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, Department of Obstetrics, West China Second Hospital, Sichuan University, Chengdu, China.
| | - Jianping Hu
- School of Pharmacy, Sichuan Industrial Institute of Antibiotics, Chengdu University, Chengdu, China.
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Abstract
Nucleosides play central roles in all facets of life, from metabolism to cellular signaling. Because of their physiochemical properties, nucleosides are lipid bilayer impermeable and thus rely on dedicated transport systems to cross biological membranes. In humans, two unrelated protein families mediate nucleoside membrane transport: the concentrative and equilibrative nucleoside transporter families. The objective of this review is to provide a broad outlook on the current status of nucleoside transport research. We will discuss the role played by nucleoside transporters in human health and disease, with emphasis placed on recent structural advancements that have revealed detailed molecular principles of these important cellular transport systems and exploitable pharmacological features.
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Affiliation(s)
- Nicholas J. Wright
- Department of Biochemistry, Duke University Medical Center, 303 Research Drive, Durham, North Carolina, 27710, USA
| | - Seok-Yong Lee
- Department of Biochemistry, Duke University Medical Center, 303 Research Drive, Durham, North Carolina, 27710, USA
- Correspondence and requests for materials should be addressed to: S.-Y. Lee., , tel: 919-684-1005, fax: 919-684-8885
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3
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Zhou Y, Liao L, Wang C, Li J, Chi P, Xiao Q, Liu Q, Guo L, Sun L, Deng D. Cryo-EM structure of the human concentrative nucleoside transporter CNT3. PLoS Biol 2020; 18:e3000790. [PMID: 32776918 PMCID: PMC7440666 DOI: 10.1371/journal.pbio.3000790] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 08/20/2020] [Accepted: 07/20/2020] [Indexed: 01/17/2023] Open
Abstract
Concentrative nucleoside transporters (CNTs), members of the solute carrier (SLC) 28 transporter family, facilitate the salvage of nucleosides and therapeutic nucleoside derivatives across the plasma membrane. Despite decades of investigation, the structures of human CNTs remain unknown. We determined the cryogenic electron microscopy (cryo-EM) structure of human CNT (hCNT) 3 at an overall resolution of 3.6 Å. As with its bacterial homologs, hCNT3 presents a trimeric architecture with additional N-terminal transmembrane helices to stabilize the conserved central domains. The conserved binding sites for the substrate and sodium ions unravel the selective nucleoside transport and distinct coupling mechanism. Structural comparison of hCNT3 with bacterial homologs indicates that hCNT3 is stabilized in an inward-facing conformation. This study provides the molecular determinants for the transport mechanism of hCNTs and potentially facilitates the design of nucleoside drugs.
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Affiliation(s)
- Yanxia Zhou
- Division of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, China
| | - Lianghuan Liao
- Hefei National Laboratory for Physical Sciences at Microscale, CAS Centre for Excellence in Molecular Cell Science, School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Chen Wang
- Division of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, China
| | - Jialu Li
- Division of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, China
| | - Pengliang Chi
- Division of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, China
| | - Qingjie Xiao
- Division of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, China
| | - Qingting Liu
- Division of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, China
| | - Li Guo
- Division of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, China
| | - Linfeng Sun
- Hefei National Laboratory for Physical Sciences at Microscale, CAS Centre for Excellence in Molecular Cell Science, School of Life Sciences, University of Science and Technology of China, Hefei, China
- * E-mail: (LS); (DD)
| | - Dong Deng
- Division of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, China
- * E-mail: (LS); (DD)
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4
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Cytosolic N- and C-Termini of the Aspergillus nidulans FurE Transporter Contain Distinct Elements that Regulate by Long-Range Effects Function and Specificity. J Mol Biol 2019; 431:3827-3844. [DOI: 10.1016/j.jmb.2019.07.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 07/04/2019] [Accepted: 07/04/2019] [Indexed: 01/05/2023]
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5
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Pastor-Anglada M, Urtasun N, Pérez-Torras S. Intestinal Nucleoside Transporters: Function, Expression, and Regulation. Compr Physiol 2018; 8:1003-1017. [PMID: 29978890 DOI: 10.1002/cphy.c170039] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The gastrointestinal tract is the absorptive organ for nutrients found in foods after digestion. Nucleosides and, to a lesser extent nucleobases, are the late products of nucleoprotein digestion. These metabolites are absorbed by nucleoside (and nucleobase) transporter (NT) proteins. NTs are differentially distributed along the gastrointestinal tract showing also polarized expression in epithelial cells. Concentrative nucleoside transporters (CNTs) are mainly located at the apical side of enterocytes, whereas equilibrative nucleoside transporters (ENTs) facilitate the basolateral efflux of nucleosides and nucleobases to the bloodstream. Moreover, selected nucleotides and the bioactive nucleoside adenosine act directly on intestinal cells modulating purinergic signaling. NT-polarized insertion is tightly regulated. However, not much is known about the modulation of intestinal NT function in humans, probably due to the lack of appropriate cell models retaining CNT functional expression. Thus, the possibility of nutritional regulation of intestinal NTs has been addressed using animal models. Besides the nutrition-related role of NT proteins, orally administered drugs also need to cross the intestinal barrier, this event being a major determinant of drug bioavailability. In this regard, NT proteins might also play a role in pharmacology, thereby allowing the absorption of nucleoside- and nucleobase-derived drugs. The relative broad selectivity of these membrane transporters also suggests clinically relevant drug-drug interactions when using combined therapies. This review focuses on all these physiological and pharmacological aspects of NT protein biology. © 2017 American Physiological Society. Compr Physiol 8:1003-1017, 2018.
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Affiliation(s)
- Marçal Pastor-Anglada
- Biochemistry and Molecular Pharmacology Section, Department of Biochemistry and Molecular Biomedicine, Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain.,Oncology Program, National Biomedical Research Institute on Liver and Gastrointestinal Diseases (CIBER EHD), Instituto de Salud Carlos III, Barcelona, Spain.,Genetics, Molecular Biology and Gene Therapy Program, Institut de Recerca Sant Joan de Déu (IR SJD), Esplugues de Llobregat, Barcelona, Spain
| | - Nerea Urtasun
- Biochemistry and Molecular Pharmacology Section, Department of Biochemistry and Molecular Biomedicine, Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain.,Oncology Program, National Biomedical Research Institute on Liver and Gastrointestinal Diseases (CIBER EHD), Instituto de Salud Carlos III, Barcelona, Spain.,Genetics, Molecular Biology and Gene Therapy Program, Institut de Recerca Sant Joan de Déu (IR SJD), Esplugues de Llobregat, Barcelona, Spain
| | - Sandra Pérez-Torras
- Biochemistry and Molecular Pharmacology Section, Department of Biochemistry and Molecular Biomedicine, Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain.,Oncology Program, National Biomedical Research Institute on Liver and Gastrointestinal Diseases (CIBER EHD), Instituto de Salud Carlos III, Barcelona, Spain.,Genetics, Molecular Biology and Gene Therapy Program, Institut de Recerca Sant Joan de Déu (IR SJD), Esplugues de Llobregat, Barcelona, Spain
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6
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Arimany-Nardi C, Claudio-Montero A, Viel-Oliva A, Schmidtke P, Estarellas C, Barril X, Bidon-Chanal A, Pastor-Anglada M. Identification and Characterization of a Secondary Sodium-Binding Site and the Main Selectivity Determinants in the Human Concentrative Nucleoside Transporter 3. Mol Pharm 2017; 14:1980-1987. [DOI: 10.1021/acs.molpharmaceut.7b00085] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- C. Arimany-Nardi
- Departament
de Bioquímica i Biomedicina Molecular, Facultat de Biologia and Institute of Biomedicine (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain
- Oncology
Program, National Biomedical Research Institute on Liver and Gastrointestinal
Diseases (CIBER EHD), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - A. Claudio-Montero
- Departament
de Bioquímica i Biomedicina Molecular, Facultat de Biologia and Institute of Biomedicine (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain
- Oncology
Program, National Biomedical Research Institute on Liver and Gastrointestinal
Diseases (CIBER EHD), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - A. Viel-Oliva
- Departament
de Bioquímica i Biomedicina Molecular, Facultat de Biologia and Institute of Biomedicine (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain
- Oncology
Program, National Biomedical Research Institute on Liver and Gastrointestinal
Diseases (CIBER EHD), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - P. Schmidtke
- Departament
de Farmàcia i Tecnologia Farmacèutica, i Fisicoquímica,
Facultat de Farmàcia i Ciències de l′Alimentació
and Institute of Biomedicine (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - C. Estarellas
- Departament
de Nutrició, Ciències de l′Alimentació
i Gastronomia, Facultat de Farmàcia i Ciències de l′Alimentació
and Institute of Biomedicine (IBUB), Campus de l′Alimentació
de Torribera, Universitat de Barcelona, 08921 Santa Coloma
de Gramenet, Spain
| | - X. Barril
- Departament
de Farmàcia i Tecnologia Farmacèutica, i Fisicoquímica,
Facultat de Farmàcia i Ciències de l′Alimentació
and Institute of Biomedicine (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain
| | - A. Bidon-Chanal
- Departament
de Nutrició, Ciències de l′Alimentació
i Gastronomia, Facultat de Farmàcia i Ciències de l′Alimentació
and Institute of Biomedicine (IBUB), Campus de l′Alimentació
de Torribera, Universitat de Barcelona, 08921 Santa Coloma
de Gramenet, Spain
| | - M. Pastor-Anglada
- Departament
de Bioquímica i Biomedicina Molecular, Facultat de Biologia and Institute of Biomedicine (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain
- Oncology
Program, National Biomedical Research Institute on Liver and Gastrointestinal
Diseases (CIBER EHD), Instituto de Salud Carlos III, 28029 Madrid, Spain
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7
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Chun SE, Thakkar N, Oh Y, Park JE, Han S, Ryoo G, Hahn H, Maeng SH, Lim YR, Han BW, Lee W. The N-terminal region of organic anion transporting polypeptide 1B3 (OATP1B3) plays an essential role in regulating its plasma membrane trafficking. Biochem Pharmacol 2017; 131:98-105. [PMID: 28216016 DOI: 10.1016/j.bcp.2017.02.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 02/14/2017] [Indexed: 10/20/2022]
Abstract
Organic anion transporting polypeptide 1B3 (OATP1B3) is a major influx transporter mediating the hepatic uptake of various endogenous substrates as well as clinically important drugs such as statins and anticancer drugs. However, molecular mechanisms controlling the membrane trafficking of OATP1B3 have been largely unknown. Several reports recently indicated the presence of a distinct, cancer-type OATP1B3 variant lacking the N-terminal 28 amino acids compared to OATP1B3 expressed in non-malignant hepatocytes. Interestingly, the cancer-type OATP1B3 variant is located predominantly in the cytoplasm, implicating the involvement of the N-terminal region of OATP1B3 in its membrane trafficking. In the current study, we set out to experimentally validate the importance of the N-terminal region of OATP1B3 and to identify responsible sequence motif(s) in that region. A number of truncation or point mutants of OATP1B3 were transiently expressed in HEK293T, HCT-8 or MDCK II cells and their expression in cytoplasmic and surface membrane fractions were analyzed by immunoblotting. Our results indicated that the N-terminal sequence of OATP1B3, in particular, at the amino acid positions between 12 and 28, may be indispensable in its membrane trafficking. Moreover, our results using a fusion construct indicated that the first 50 amino acids of OATP1B3 are sufficient for its membrane localization. The importance of the N-terminal region in membranous localization was shared among the other OATP1B subfamily members, OATP1B1 and rat Oatp1b2. Our efforts to identify the responsible amino acid(s) or structure motif(s) in the N-terminal region did not pinpoint individual amino acids or motifs with putative secondary structures. Our current findings however demonstrate that the N-terminal region is important for the membrane localization of the OATP1B subfamily members and should facilitate future investigations of the mechanisms involved in the regulation and membrane trafficking of these important transporter proteins.
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Affiliation(s)
- Se-Eun Chun
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-Gu, Seoul, Republic of Korea
| | - Nilay Thakkar
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY, USA
| | - Yunseok Oh
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-Gu, Seoul, Republic of Korea
| | - Ji Eun Park
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-Gu, Seoul, Republic of Korea
| | - Songhee Han
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-Gu, Seoul, Republic of Korea
| | - Gongmi Ryoo
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-Gu, Seoul, Republic of Korea
| | - Hyunggu Hahn
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-Gu, Seoul, Republic of Korea
| | - Sang Hyun Maeng
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-Gu, Seoul, Republic of Korea
| | - Young-Ran Lim
- Department of Biological Sciences, Konkuk University, Seoul, Republic of Korea
| | - Byung Woo Han
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-Gu, Seoul, Republic of Korea
| | - Wooin Lee
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-Gu, Seoul, Republic of Korea.
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Fernández‐Calotti P, Casulleras O, Antolin M, Guarner F, Pastor‐Anglada M. Galectin‐4 interacts with the drug transporter human concentrative nucleoside transporter 3 to regulate its function. FASEB J 2015; 30:544-54. [DOI: 10.1096/fj.15-272773] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 09/21/2015] [Indexed: 12/31/2022]
Affiliation(s)
- Paula Fernández‐Calotti
- Department of Biochemistry and Molecular BiologyUniversity of BarcelonaInstitute of Biomedicine (IBUB)BarcelonaSpain
- Oncology ProgramNational Biomedical Research Institute of Liver and Gastrointestinal Diseases (CIBER EHD)Instituto de Salud Carlos IIIMadridSpain
| | - Olga Casulleras
- Department of Biochemistry and Molecular BiologyUniversity of BarcelonaInstitute of Biomedicine (IBUB)BarcelonaSpain
- Oncology ProgramNational Biomedical Research Institute of Liver and Gastrointestinal Diseases (CIBER EHD)Instituto de Salud Carlos IIIMadridSpain
| | - María Antolin
- Department of GastroenterologyDigestive System Research UnitInstitut de Recerca Vall d'HebronUniversity Hospital Vall d'HebronUniversitat Autònoma de Barcelona, CIBER EHDBarcelonaSpain
| | - Francisco Guarner
- Department of GastroenterologyDigestive System Research UnitInstitut de Recerca Vall d'HebronUniversity Hospital Vall d'HebronUniversitat Autònoma de Barcelona, CIBER EHDBarcelonaSpain
| | - Marçal Pastor‐Anglada
- Department of Biochemistry and Molecular BiologyUniversity of BarcelonaInstitute of Biomedicine (IBUB)BarcelonaSpain
- Oncology ProgramNational Biomedical Research Institute of Liver and Gastrointestinal Diseases (CIBER EHD)Instituto de Salud Carlos IIIMadridSpain
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9
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Arimany-Nardi C, Errasti-Murugarren E, Minuesa G, Martinez-Picado J, Gorboulev V, Koepsell H, Pastor-Anglada M. Nucleoside transporters and human organic cation transporter 1 determine the cellular handling of DNA-methyltransferase inhibitors. Br J Pharmacol 2015; 171:3868-80. [PMID: 24780098 DOI: 10.1111/bph.12748] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 04/02/2014] [Accepted: 04/15/2014] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND AND PURPOSE Inhibitors of DNA methyltransferases (DNMTs), such as azacytidine, decitabine and zebularine, are used for the epigenetic treatment of cancer. Their action may depend upon their translocation across the plasma membrane. The aim of this study was to identify transporter proteins contributing to DNMT inhibitor action. EXPERIMENTAL APPROACH Drug interactions with selected hCNT and hENT proteins were studied in transiently transfected HeLa and MDCK cells. Interaction with human organic cation transporters (hOCTs) was assessed in transiently transfected HeLa cells and Xenopus laevis oocytes. KEY RESULTS Zebularine uptake was mediated by hCNT1, hCNT3 and hENT2. Decitabine interacted with but was not translocated by any nucleoside transporter (NT) type. hCNT expression at the apical domain of MDCK cells promoted net vectorial flux of zebularine. Neither hOCT1 nor hOCT2 transported decitabine, but both were involved in the efflux of zebularine, suggesting these proteins act as efflux transporters. hOCT1 polymorphic variants, known to alter function, decreased zebularine efflux. CONCLUSIONS AND IMPLICATIONS This study highlights the influence of human NTs and hOCTs on the pharmacokinetics and pharmacodynamics of selected DNMT inhibitors. As hOCTs may also behave as efflux transporters, they could contribute either to chemoresistance or to chemosensitivity, depending upon the nature of the drug or combination of drugs being used in cancer therapy.
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Affiliation(s)
- C Arimany-Nardi
- Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina, Universitat de Barcelona (IBUB) & National Biomedical Research Institute on Liver and Gastrointestinal Diseaes (CIBERehd), Barcelona, Spain
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Myeong J, Kwak M, Hong C, Jeon JH, So I. Identification of a membrane-targeting domain of the transient receptor potential canonical (TRPC)4 channel unrelated to its formation of a tetrameric structure. J Biol Chem 2014; 289:34990-5002. [PMID: 25349210 DOI: 10.1074/jbc.m114.584649] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Canonical transient receptor potential (TRPC) channels are Ca(2+)-permeable nonselective cation channels that are activated by a wide variety of stimuli, including G protein-coupled receptors (GPCRs). The TRPC4 channel is expressed in a punctate distribution in the membrane. To identify the regulating region of the channel trafficking to the membrane, we generated deletion mutants of the TRPC4 channel. We determined that when either region that was downstream of the 20 amino acids of the N terminus or the 700-730 amino acids was deleted, the mutants were retained in the endoplasmic reticulum. By coexpression of the wild-type TRPC4 with deletion mutants, we found that the 23-29 amino acids of the N terminus regulate a membrane trafficking. Additionally, by the fluorescence resonance energy transfer (FRET) method, we found that the regions downstream of the 99 amino acid region of the N terminus and upstream of the 730 amino acid region in the C terminus produce assembly of the TRPC4 tetramers. We inferred the candidate proteins that regulate or interact with the 23-29 domain of TRPC4.
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Affiliation(s)
- Jongyun Myeong
- From the Department of Physiology, Seoul National University College of Medicine
| | - Misun Kwak
- From the Department of Physiology, Seoul National University College of Medicine
| | - Chansik Hong
- From the Department of Physiology, Seoul National University College of Medicine
| | - Ju-Hong Jeon
- From the Department of Physiology, Seoul National University College of Medicine
| | - Insuk So
- From the Department of Physiology, Seoul National University College of Medicine
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11
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12
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Thakkar N, Kim K, Jang ER, Han S, Kim K, Kim D, Merchant N, Lockhart AC, Lee W. A cancer-specific variant of the SLCO1B3 gene encodes a novel human organic anion transporting polypeptide 1B3 (OATP1B3) localized mainly in the cytoplasm of colon and pancreatic cancer cells. Mol Pharm 2012; 10:406-16. [PMID: 23215050 DOI: 10.1021/mp3005353] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OATP1B3 is a member of the OATP (organic anion transporting polypeptides) superfamily, responsible for mediating the transport of numerous endogenous and xenobiotic substances. Although initially reported to be exclusively expressed in the liver, several studies reported that OATP1B3 is frequently expressed in multiple types of cancers and may be associated with differing clinical outcomes. However, a detailed investigation on the expression and function of OATP1B3 protein in cancer has been lacking. In this study, we confirmed that colon and pancreatic cancer cells express variant forms of OATP1B3, different from OATP1B3 wild-type (WT) expressed in the normal liver. OATP1B3 variant 1 (V1), the most prevalent form among the variants, contains alternative exonic sequences (exon 2a) instead of exons 1 and 2 present in OATP1B3 WT. The translated product of OATP1B3 V1 is almost identical to OATP1B3 WT, with exception to the first 28 amino acids at the N-terminus. Exogenous expression of OATP1B3 V1 revealed that OATP1B3 V1 undergoes post-translational modifications and proteasomal degradation to a differing extent compared to OATP1B3 WT. OATP1B3 V1 showed only modest transport activity toward cholecystokin-8 (CCK-8, a prototype OATP1B3 substrate) in contrast to OATP1B3 WT showing a markedly efficient uptake of CCK-8. Consistent with these results, OATP1B3 V1 was localized mainly in the cytoplasm with a much lower extent of trafficking to the surface membrane compared to OATP1B3 WT. In summary, our results demonstrate that colon and pancreatic cancer cells express variant forms of OATP1B3 with only limited transport activity and different subcellular localization compared to OATP1B3 WT. These observed differences at the molecular and functional levels will be important considerations for further investigations of the biological and clinical significance of OATP1B3 expression in cancer.
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Affiliation(s)
- Nilay Thakkar
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky 40536, United States
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13
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Errasti-Murugarren E, Fernández-Calotti P, Veyhl-Wichmann M, Diepold M, Pinilla-Macua I, Pérez-Torras S, Kipp H, Koepsell H, Pastor-Anglada M. Role of the Transporter Regulator Protein (RS1) in the Modulation of Concentrative Nucleoside Transporters (CNTs) in Epithelia. Mol Pharmacol 2012; 82:59-67. [DOI: 10.1124/mol.111.076992] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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14
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Structural determinants for rCNT2 sorting to the plasma membrane of polarized and non-polarized cells. Biochem J 2012; 442:517-25. [DOI: 10.1042/bj20110605] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
rCNT2 (rat concentrative nucleoside transporter 2) (Slc28a2) is a purine-preferring concentrative nucleoside transporter. It is expressed in both non-polarized and polarized cells, where it is localized in the brush border membrane. Since no information about the domains implicated in the plasma membrane sorting of rCNT2 is available, the present study aimed to identify structural and functional requirements for rCNT2 trafficking. The comprehensive topological mapping of the intracellular N-terminal tail revealed two main features: (i) a glutamate-enriched region (NPGLELME) between residues 21 and 28 that seems to be implicated in the stabilization of rCNT2 in the cell surface, since mutagenesis of these conserved glutamates resulted in enhanced endocytosis; and (ii) mutation of a potential protein kinase CK2 domain that led to a loss of brush border-specific sorting. Although the shortest proteins assayed (rCNT2-74AA, -48AA and -37AA) accumulated intracellularly and lost their brush border membrane preference, they were still functional. A deeper analysis of CK2 implication in CNT2 trafficking, using a CK2-specific inhibitor [DMAT (2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole)] and other complementary mutations mimicking the negative charge provided by phosphorylation (S46D and S46E), demonstrated an effect of this kinase on rCNT2 activity. In summary, the N-terminal tail of rCNT2 contains dual sorting signals. An acidic region is responsible for its proper stabilization at the plasma membrane, whereas the putative CK2 domain (Ser46) is implicated in the apical sorting of the transporter.
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