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Tega Y, Kubo Y, Miura H, Ri K, Tomise A, Akanuma SI, Hosoya KI. Carrier-Mediated Process of Putrescine Elimination at the Rat Blood-Retinal Barrier. Int J Mol Sci 2023; 24:ijms24109003. [PMID: 37240348 DOI: 10.3390/ijms24109003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 05/15/2023] [Accepted: 05/16/2023] [Indexed: 05/28/2023] Open
Abstract
Putrescine is a bioactive polyamine. Its retinal concentration is strictly controlled to maintain a healthy sense of vision. The present study investigated putrescine transport at the blood-retinal barrier (BRB) to gain a better understanding of the mechanisms of putrescine regulation in the retina. Our microdialysis study showed that the elimination rate constant during the terminal phase was significantly greater (1.90-fold) than that of [14C]D-mannitol, which is a bulk flow marker. The difference in the apparent elimination rate constants of [3H]putrescine and [14C]D-mannitol was significantly decreased by unlabeled putrescine and spermine, suggesting active putrescine transport from the retina to the blood across the BRB. Our study using model cell lines of the inner and outer BRB showed that [3H]putrescine transport was time-, temperature-, and concentration-dependent, suggesting the involvement of carrier-mediated processes in putrescine transport at the inner and outer BRB. [3H]Putrescine transport was significantly reduced under Na+-free, Cl--free, and K+-replacement conditions, and attenuated by polyamines or organic cations such as choline, a choline transporter-like protein (CTL) substrate. Rat CTL1 cRNA-injected oocytes exhibited marked alterations in [3H]putrescine uptake, and CTL1 knockdown significantly reduced [3H]putrescine uptake in model cell lines, suggesting the possible participation of CTL1 in putrescine transport at the BRB.
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Affiliation(s)
- Yuma Tega
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
| | - Yoshiyuki Kubo
- Laboratory of Drug Disposition and Pharmacokinetics, Faculty of Pharma-Sciences, Teikyo University, Kaga 2-11-1, Tokyo 173-8605, Japan
| | - Hiroaki Miura
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
| | - Kairi Ri
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
| | - Ayaka Tomise
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
| | - Shin-Ichi Akanuma
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
| | - Ken-Ichi Hosoya
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
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Koehl B, Vrignaud C, Mikdar M, Nair TS, Yang L, Landry S, Laiguillon G, Giroux‐Lathuile C, Anselme‐Martin S, El Kenz H, Hermine O, Mohandas N, Cartron JP, Colin Y, Detante O, Marlu R, Le Van Kim C, Carey TE, Azouzi S, Peyrard T. Lack of the human choline transporter-like protein SLC44A2 causes hearing impairment and a rare red blood phenotype. EMBO Mol Med 2023; 15:e16320. [PMID: 36695047 PMCID: PMC9994479 DOI: 10.15252/emmm.202216320] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 01/06/2023] [Accepted: 01/10/2023] [Indexed: 01/26/2023] Open
Abstract
Blood phenotypes are defined by the presence or absence of specific blood group antigens at the red blood cell (RBC) surface, due to genetic polymorphisms among individuals. The recent development of genomic and proteomic approaches enabled the characterization of several enigmatic antigens. The choline transporter-like protein CTL2 encoded by the SLC44A2 gene plays an important role in platelet aggregation and neutrophil activation. By investigating alloantibodies to a high-prevalence antigen of unknown specificity, found in patients with a rare blood type, we showed that SLC44A2 is also expressed in RBCs and carries a new blood group system. Furthermore, we identified three siblings homozygous for a large deletion in SLC44A2, resulting in complete SLC44A2 deficiency. Interestingly, the first-ever reported SLC44A2-deficient individuals suffer from progressive hearing impairment, recurrent arterial aneurysms, and epilepsy. Furthermore, SLC44A2null individuals showed no significant platelet aggregation changes and do not suffer from any apparent hematological disorders. Overall, our findings confirm the function of SLC44A2 in hearing preservation and provide new insights into the possible role of this protein in maintaining cerebrovascular homeostasis.
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Affiliation(s)
- Bérengère Koehl
- Université Paris Cité and Université des Antilles, INSERM, BIGRParisFrance
- Department of Child HematologyReference Center for Sickle‐Cell Disease Robert Debré University Hospital, Assistance Publique‐Hôpitaux de ParisParisFrance
| | - Cédric Vrignaud
- Université Paris Cité and Université des Antilles, INSERM, BIGRParisFrance
| | - Mahmoud Mikdar
- Université Paris Cité and Université des Antilles, INSERM, BIGRParisFrance
| | - Thankam S Nair
- Kresge Hearing Research Institute, Department of Otolaryngology/Head and Neck SurgeryUniversity of MichiganAnn ArborMIUSA
| | - Lucy Yang
- Kresge Hearing Research Institute, Department of Otolaryngology/Head and Neck SurgeryUniversity of MichiganAnn ArborMIUSA
| | - Seyve Landry
- Hemostasis LaboratoryGrenoble Alpes University Hospital GrenobleGrenobleFrance
| | - Guy Laiguillon
- Établissement Français de Sang (EFS) Ile‐de‐France, Centre National de Référence pour les Groupes SanguinsParisFrance
| | | | - Sophie Anselme‐Martin
- Etablissement Français du Sang Auvergne Rhône Alpes, Immunohematology LaboratoryGrenobleFrance
| | - Hanane El Kenz
- Department of Transfusion, Blood Bank, CHU‐Brugmann and Hôpital Universitaire des Enfants Reine FabiolaUniversité Libre de BruxellesBrusselsBelgium
| | - Olivier Hermine
- Université de Paris, Imagine Institute, INSERM UMR 1163ParisFrance
| | - Narla Mohandas
- Red Cell Physiology Laboratory, New York Blood CenterNew YorkNYUSA
| | | | - Yves Colin
- Université Paris Cité and Université des Antilles, INSERM, BIGRParisFrance
| | - Olivier Detante
- Stroke Unit, Neurology Department, Grenoble Hospital, Grenoble Institute of Neurosciences, Inserm U1216University of Grenoble AlpesGrenobleFrance
| | - Raphaël Marlu
- Hemostasis LaboratoryGrenoble Alpes University Hospital GrenobleGrenobleFrance
- University Grenoble Alpes, CNRS UMR5525, TIMCGrenobleFrance
| | | | - Thomas E Carey
- Kresge Hearing Research Institute, Department of Otolaryngology/Head and Neck SurgeryUniversity of MichiganAnn ArborMIUSA
| | - Slim Azouzi
- Université Paris Cité and Université des Antilles, INSERM, BIGRParisFrance
- Établissement Français de Sang (EFS) Ile‐de‐France, Centre National de Référence pour les Groupes SanguinsParisFrance
| | - Thierry Peyrard
- Université Paris Cité and Université des Antilles, INSERM, BIGRParisFrance
- Établissement Français de Sang (EFS) Ile‐de‐France, Centre National de Référence pour les Groupes SanguinsParisFrance
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3
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Gyimesi G, Hediger MA. Transporter-Mediated Drug Delivery. Molecules 2023; 28:molecules28031151. [PMID: 36770817 PMCID: PMC9919865 DOI: 10.3390/molecules28031151] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 01/12/2023] [Accepted: 01/18/2023] [Indexed: 01/27/2023] Open
Abstract
Transmembrane transport of small organic and inorganic molecules is one of the cornerstones of cellular metabolism. Among transmembrane transporters, solute carrier (SLC) proteins form the largest, albeit very diverse, superfamily with over 400 members. It was recognized early on that xenobiotics can directly interact with SLCs and that this interaction can fundamentally determine their efficacy, including bioavailability and intertissue distribution. Apart from the well-established prodrug strategy, the chemical ligation of transporter substrates to nanoparticles of various chemical compositions has recently been used as a means to enhance their targeting and absorption. In this review, we summarize efforts in drug design exploiting interactions with specific SLC transporters to optimize their therapeutic effects. Furthermore, we describe current and future challenges as well as new directions for the advanced development of therapeutics that target SLC transporters.
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Hu M, Zhao H, Yang B, Yang S, Liu H, Tian H, Shui G, Chen Z, E L, Lai J, Song W. ZmCTLP1 is required for the maintenance of lipid homeostasis and the basal endosperm transfer layer in maize kernels. THE NEW PHYTOLOGIST 2021; 232:2384-2399. [PMID: 34559890 PMCID: PMC9292782 DOI: 10.1111/nph.17754] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 09/15/2021] [Indexed: 05/26/2023]
Abstract
Maize kernel weight is influenced by the unloading of nutrients from the maternal placenta and their passage through the transfer tissue of the basal endosperm transfer layer (BETL) and the basal intermediate zone (BIZ) to the upper part of the endosperm. Here, we show that Small kernel 10 (Smk10) encodes a choline transporter-like protein 1 (ZmCTLP1) that facilitates choline uptake and is located in the trans-Golgi network (TGN). Its loss of function results in reduced choline content, leading to smaller kernels with a lower starch content. Mutation of ZmCTLP1 disrupts membrane lipid homeostasis and the normal development of wall in-growths. Expression levels of Mn1 and ZmSWEET4c, two kernel filling-related genes, are downregulated in the smk10, which is likely to be one of the major causes of incompletely differentiated transfer cells. Mutation of ZmCTLP1 also reduces the number of plasmodesmata (PD) in transfer cells, indicating that the smk10 mutant is impaired in PD formation. Intriguingly, we also observed premature cell death in the BETL and BIZ of the smk10 mutant. Together, our results suggest that ZmCTLP1-mediated choline transport affects kernel development, highlighting its important role in lipid homeostasis, wall in-growth formation and PD development in transfer cells.
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Affiliation(s)
- Mingjian Hu
- State Key Laboratory of Plant Physiology and Biochemistry and National Maize Improvement CenterDepartment of Plant Genetics and BreedingChina Agricultural UniversityBeijing100193China
| | - Haiming Zhao
- State Key Laboratory of Plant Physiology and Biochemistry and National Maize Improvement CenterDepartment of Plant Genetics and BreedingChina Agricultural UniversityBeijing100193China
| | - Bo Yang
- State Key Laboratory of Plant Physiology and Biochemistry and National Maize Improvement CenterDepartment of Plant Genetics and BreedingChina Agricultural UniversityBeijing100193China
| | - Shuang Yang
- State Key Laboratory of Plant Physiology and Biochemistry and National Maize Improvement CenterDepartment of Plant Genetics and BreedingChina Agricultural UniversityBeijing100193China
| | - Haihong Liu
- State Key Laboratory of Plant Physiology and BiochemistryCollege of Biological SciencesChina Agricultural UniversityBeijing100193China
| | - He Tian
- State Key Laboratory of Molecular Developmental BiologyInstitute of Genetics and Developmental BiologyChinese Academy of SciencesBeijing100101China
| | - Guanghou Shui
- State Key Laboratory of Molecular Developmental BiologyInstitute of Genetics and Developmental BiologyChinese Academy of SciencesBeijing100101China
| | - Zongliang Chen
- State Key Laboratory of Plant Physiology and Biochemistry and National Maize Improvement CenterDepartment of Plant Genetics and BreedingChina Agricultural UniversityBeijing100193China
- Waksman Institute of MicrobiologyRutgers UniversityPiscatawayNJ08854‐8020USA
| | - Lizhu E
- State Key Laboratory of Plant Physiology and Biochemistry and National Maize Improvement CenterDepartment of Plant Genetics and BreedingChina Agricultural UniversityBeijing100193China
- Center for Crop Functional Genomics and Molecular BreedingChina Agricultural UniversityBeijing100193China
| | - Jinsheng Lai
- State Key Laboratory of Plant Physiology and Biochemistry and National Maize Improvement CenterDepartment of Plant Genetics and BreedingChina Agricultural UniversityBeijing100193China
- Center for Crop Functional Genomics and Molecular BreedingChina Agricultural UniversityBeijing100193China
| | - Weibin Song
- State Key Laboratory of Plant Physiology and Biochemistry and National Maize Improvement CenterDepartment of Plant Genetics and BreedingChina Agricultural UniversityBeijing100193China
- Center for Crop Functional Genomics and Molecular BreedingChina Agricultural UniversityBeijing100193China
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5
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Inazu M. Functional Expression of Choline Transporters in the Blood-Brain Barrier. Nutrients 2019; 11:nu11102265. [PMID: 31547050 PMCID: PMC6835570 DOI: 10.3390/nu11102265] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 09/12/2019] [Accepted: 09/16/2019] [Indexed: 12/24/2022] Open
Abstract
Cholinergic neurons in the central nervous system play a vital role in higher brain functions, such as learning and memory. Choline is essential for the synthesis of the neurotransmitter acetylcholine by cholinergic neurons. The synthesis and metabolism of acetylcholine are important mechanisms for regulating neuronal activity. Choline is a positively charged quaternary ammonium compound that requires transporters to pass through the plasma membrane. Currently, there are three groups of choline transporters with different characteristics, such as affinity for choline, tissue distribution, and sodium dependence. They include (I) polyspecific organic cation transporters (OCT1-3: SLC22A1-3) with a low affinity for choline, (II) high-affinity choline transporter 1 (CHT1: SLC5A7), and (III) choline transporter-like proteins (CTL1-5: SLC44A1-5). Brain microvascular endothelial cells, which comprise part of the blood-brain barrier, take up extracellular choline via intermediate-affinity choline transporter-like protein 1 (CTL1) and low-affinity CTL2 transporters. CTL2 is responsible for excreting a high concentration of choline taken up by the brain microvascular endothelial cells on the brain side of the blood-brain barrier. CTL2 is also highly expressed in mitochondria and may be involved in the oxidative pathway of choline metabolism. Therefore, CTL1- and CTL2-mediated choline transport to the brain through the blood-brain barrier plays an essential role in various functions of the central nervous system by acting as the rate-limiting step of cholinergic neuronal activity.
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Affiliation(s)
- Masato Inazu
- Institute of Medical Science, Tokyo Medical University, Tokyo 160-8402, Japan.
- Department of Molecular Preventive Medicine, Tokyo Medical University, Tokyo 160-8402, Japan.
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SLC44A2 single nucleotide polymorphisms, isoforms, and expression: Association with severity of Meniere's disease? Genomics 2016; 108:201-208. [PMID: 27829169 DOI: 10.1016/j.ygeno.2016.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 10/27/2016] [Accepted: 11/05/2016] [Indexed: 11/22/2022]
Abstract
SLC44A2 was discovered as the target of an antibody that causes hearing loss. Knockout mice develop age related hearing loss, loss of sensory cells and spiral ganglion neurons. SLC44A2 has polymorphic sites implicated in human disease. Transfusion related acute lung injury (TRALI) is linked to rs2288904 and genome wide association studies link rs2288904 and rs9797861 to venous thromboembolism (VTE), coronary artery disease and stroke. Here we report linkage disequilibrium of rs2288904 with rs3087969 and the association of these SLC44A2 SNPs with Meniere's disease severity. Tissue-specific isoform expression differences suggest that the N-terminal domain is linked to different functions in different cell types. Heterozygosity at rs2288904 CGA/CAA and rs3087969 GAT/GAC showed a trend for association with intractable Meniere's disease compared to less severe disease and to controls. The association of SLC44A2 SNPs with VTE suggests that thrombi affecting cochlear vessels could be a factor in Meniere's disease.
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Dettmer J, Ursache R, Campilho A, Miyashima S, Belevich I, O'Regan S, Mullendore DL, Yadav SR, Lanz C, Beverina L, Papagni A, Schneeberger K, Weigel D, Stierhof YD, Moritz T, Knoblauch M, Jokitalo E, Helariutta Y. CHOLINE TRANSPORTER-LIKE1 is required for sieve plate development to mediate long-distance cell-to-cell communication. Nat Commun 2014; 5:4276. [PMID: 25008948 DOI: 10.1038/ncomms5276] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2013] [Accepted: 06/02/2014] [Indexed: 11/09/2022] Open
Abstract
Phloem, a plant tissue responsible for long-distance molecular transport, harbours specific junctions, sieve areas, between the conducting cells. To date, little is known about the molecular framework related to the biogenesis of these sieve areas. Here we identify mutations at the CHER1/AtCTL1 locus of Arabidopsis thaliana. The mutations cause several phenotypic abnormalities, including reduced pore density and altered pore structure in the sieve areas associated with impaired phloem function. CHER1 encodes a member of a poorly characterized choline transporter-like protein family in plants and animals. We show that CHER1 facilitates choline transport, localizes to the trans-Golgi network, and during cytokinesis is associated with the phragmoplast. Consistent with its function in the elaboration of the sieve areas, CHER1 has a sustained, polar localization in the forming sieve plates. Our results indicate that the regulation of choline levels is crucial for phloem development and conductivity in plants.
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Affiliation(s)
- Jan Dettmer
- 1] Cell Biology Division, Department of Biology, University of Erlangen-Nuremberg, 91058 Erlangen, Germany [2]
| | - Robertas Ursache
- 1] Institute of Biotechnology, Department of Biological and Environmental Sciences, University of Helsinki, Helsinki FIN-00014, Finland [2]
| | - Ana Campilho
- 1] Institute for Molecular and Cell Biology (IBMC), University of Porto, Porto 4150-180, Portugal [2]
| | - Shunsuke Miyashima
- Institute of Biotechnology, Department of Biological and Environmental Sciences, University of Helsinki, Helsinki FIN-00014, Finland
| | - Ilya Belevich
- Institute of Biotechnology, Department of Biological and Environmental Sciences, University of Helsinki, Helsinki FIN-00014, Finland
| | - Seana O'Regan
- Neurophotonics Laboratory, CNRS/Université Paris Descartes, 45, rue des Saints-Pères, 75270 Paris, France
| | - Daniel Leroy Mullendore
- School of Biological Sciences, Washington State University, Pullman, Washington 99164-4236, USA
| | - Shri Ram Yadav
- Institute of Biotechnology, Department of Biological and Environmental Sciences, University of Helsinki, Helsinki FIN-00014, Finland
| | - Christa Lanz
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tuebingen, Germany
| | - Luca Beverina
- Department of Materials Science, University of Milano-Bicocca, Via R. Cozzi 55, 20125 Milano, Italy
| | - Antonio Papagni
- Department of Materials Science, University of Milano-Bicocca, Via R. Cozzi 55, 20125 Milano, Italy
| | - Korbinian Schneeberger
- Max Planck Institute for Plant Breeding Research, Department for Plant Developmental Biology, 50829 Cologne, Germany
| | - Detlef Weigel
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tuebingen, Germany
| | - York-Dieter Stierhof
- ZMBP, Mikroskopie, Universität Tübingen, Auf der Morgenstelle 5, 72076 Tübingen, Germany
| | - Thomas Moritz
- Department of Forest Genetics and Plant Physiology, Umeå Plant Science Center, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden
| | - Michael Knoblauch
- School of Biological Sciences, Washington State University, Pullman, Washington 99164-4236, USA
| | - Eija Jokitalo
- Institute of Biotechnology, Department of Biological and Environmental Sciences, University of Helsinki, Helsinki FIN-00014, Finland
| | - Ykä Helariutta
- Institute of Biotechnology, Department of Biological and Environmental Sciences, University of Helsinki, Helsinki FIN-00014, Finland
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8
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Inazu M. Choline transporter-like proteins CTLs/SLC44 family as a novel molecular target for cancer therapy. Biopharm Drug Dispos 2014; 35:431-49. [PMID: 24532461 DOI: 10.1002/bdd.1892] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2013] [Revised: 01/31/2014] [Accepted: 02/07/2014] [Indexed: 12/13/2022]
Abstract
Choline is essential for the synthesis of the major membrane phospholipid phosphatidylcholine (PC), the methyl donor betaine and the neurotransmitter acetylcholine (ACh). Elevated levels of choline and up-regulated choline kinase activity have been detected in various cancers. Thus, the intracellular accumulation of choline through choline transporters is the rate-limiting step in phospholipid metabolism and a prerequisite for cancer cell proliferation. Previous studies have demonstrated abnormalities in choline uptake and choline phospholipid metabolism in cancer cells using the imaging of cancer with positron emission tomography (PET) and magnetic resonance spectroscopy (MRS). The aberrant choline metabolism in cancer cells is strongly correlated with their malignant progression. Using quantitative real-time PCR, the mRNA expression of choline transporters was measured, and it was found that choline transporter-like proteins CTLs/SLC44 family are highly expressed in various cancer cell lines. Choline uptake through CTLs is associated with cell viability, and the functional inhibition of CTLs could promote apoptotic cell death. Furthermore, non-neuronal cholinergic systems that include CTLs-mediated choline transport are associated with cell proliferation and their inhibition promotes apoptotic cell death in colon cancer, small cell lung cancer and human leukemic T-cells. The identification of this new CTLs-mediated choline transport system provides a potential new target for cancer therapy.
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Affiliation(s)
- Masato Inazu
- Institute of Medical Science, Department of Molecular Preventive Medicine, Tokyo Medical University, Shinjuku-ku, Tokyo, Japan
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Abstract
Organic anions and cations (OAs and OCs, respectively) comprise an extraordinarily diverse array of compounds of physiological, pharmacological, and toxicological importance. The kidney, primarily the renal proximal tubule, plays a critical role in regulating the plasma concentrations of these organic electrolytes and in clearing the body of potentially toxic xenobiotics agents, a process that involves active, transepithelial secretion. This transepithelial transport involves separate entry and exit steps at the basolateral and luminal aspects of renal tubular cells. Basolateral and luminal OA and OC transport reflects the concerted activity of a suite of separate proteins arranged in parallel in each pole of proximal tubule cells. The cloning of multiple members of several distinct transport families, the subsequent characterization of their activity, and their subcellular localization within distinct regions of the kidney, now allows the development of models describing the molecular basis of the renal secretion of OAs and OCs. New information on naturally occurring genetic variation of many of these processes provides insight into the basis of observed variability of drug efficacy and unwanted drug-drug interactions in human populations. The present review examines recent work on these issues.
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Affiliation(s)
- Ryan M Pelis
- Novartis Pharmaceuticals Corp., Translational Sciences, East Hanover, New Jersey, USA
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10
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Functional expression of choline transporter-like protein 1 (CTL1) in small cell lung carcinoma cells: A target molecule for lung cancer therapy. Pharmacol Res 2013; 76:119-31. [DOI: 10.1016/j.phrs.2013.07.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 07/22/2013] [Accepted: 07/29/2013] [Indexed: 01/11/2023]
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The choline transporter-like family SLC44: properties and roles in human diseases. Mol Aspects Med 2013; 34:646-54. [PMID: 23506897 DOI: 10.1016/j.mam.2012.10.011] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 03/14/2012] [Indexed: 12/18/2022]
Abstract
The Na(+)-independent, high affinity choline carrier system proposed to supply choline for the synthesis of cell membrane phospholipids was recently associated with SLC44 family members (SLC44A1-5) also called choline-like transporter family. SLC44A1 is widely expressed throughout the nervous system in both neurons and oligodendrocytes, while SLC44A2-4 are mainly detected in peripheral tissues. The subcellular localization of the proteins was mainly addressed for SLC44A1 through the development of specific antibodies. SLC44A1 is detected in both the plasma and mitochondrial membranes where the protein is able to transport choline at high affinity and in a Na(+)-independent manner. The physiological relevance of SLC44A1 as a choline carrier is indicated by its likely involvement in membrane synthesis for cell growth or repair, and also by its role in phospholipid production for the generation of lung surfactant. Moreover, an autoimmune disease has been related to the blockade of SLC44A2 function, which results in the alteration of hair cells in the inner ear and leads to autoimmune hearing loss. In the alloimmune syndrome called transfusion-related acute lung injury, antibodies to SLC44A2 cause a deleterious aggregation of granulocytes. Therefore transporters of the SLC44 family represent attractive and promising targets for therapeutic and diagnostic applications regarding both immune and degenerative diseases.
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12
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Beyer LA, Galano MM, Nair TS, Kommareddi PK, Sha SH, Raphael Y, Carey TE. Age-related changes in expression of CTL2/SLC44A2 and its isoforms in the mouse inner ear. Hear Res 2011; 282:63-8. [PMID: 21986210 DOI: 10.1016/j.heares.2011.09.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Revised: 08/26/2011] [Accepted: 09/19/2011] [Indexed: 11/19/2022]
Abstract
The membrane glycoprotein CTL2/SLC44A2 is expressed by supporting cells in the inner ear and has been identified as a target of antibodies that may induce auto-immune hearing loss. To determine if CTL2/SLC44A2 also has roles in inner ear development and to distinguish between isoform-specific roles, we assessed age-related changes in expression of CTL2/SLC44A2 isoforms and protein in the developing murine inner ear. We determined that both isoform p1 and isoform p2 (named for the upstream p1 and proximal p2 promoters that control alternate exons 1a and 1b) were robustly expressed as early as E14 and persisted during embryonic development, but after birth the p1 isoform fell to barely detectable levels while isoform p2 levels were maintained. This trend continued and became even more apparent later in post-natal development and remained in mature ears until at least 6 weeks of age. In aged (18 mo old) mice, the level of isoform p1 transcripts rose again to levels similar to the p2 isoform like that seen early in development. At the earliest stage examined, CTL2/SLC44A2 protein was expressed in both immature supporting cells and immature sensory cells, but after birth expression in the sensory cells declined in both the utricle and cochlea and by day P1 expression of CTL2/SLC44A2 was restricted to supporting cells. The changes we observed in isoform distribution are indicative of differential developmental roles and age related changes between the two isoforms of CTL2/SLC44A2 in the inner ear.
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Affiliation(s)
- Lisa A Beyer
- Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI 48109, USA
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13
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Kommareddi PK, Nair TS, Thang LV, Galano MM, Babu E, Ganapathy V, Kanazawa T, McHugh JB, Carey TE. Isoforms, expression, glycosylation, and tissue distribution of CTL2/SLC44A2. Protein J 2010; 29:417-26. [PMID: 20665236 DOI: 10.1007/s10930-010-9268-y] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Antibodies to the solute carrier protein, CTL2/SLC44A2, cause hearing loss in animals, are frequently found in autoimmune hearing loss patients, and are implicated in transfusion-related acute lung injury. We cloned a novel CTL2/SLC44A2 isoform (CTL2 P1) from inner ear and identified an alternate upstream promoter and exon 1a encoding a protein of 704 amino acids which differs in the first 10-12 amino acids from the known exon 1b isoform (CTL2 P2; 706 amino acids). The expression of these CTL2/SLC44A2 isoforms, their posttranslational modifications in tissues and their localization in HEK293 cells expressing rHuCTL2/SLC44A2 were assessed. P1 and P2 isoforms with differing glycosylation are variably expressed in cochlea, tongue, heart, colon, lung, kidney, liver and spleen suggesting tissue specific differences that may influence function in each tissue. Because antibodies to CTL2/SLC44A2 have serious pathologic consequences, it is important to understand its distribution and modifications. Heterologous expression in X. laevis oocytes shows that while human CTL2-P1 does not transport choline, human CTL2-P2 exhibits detectable choline transport activity.
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Affiliation(s)
- P K Kommareddi
- Kresge Hearing Research Institute, Department of Otolaryngology/Head and Neck Surgery, The University of Michigan, 1150 West Medical Center Drive, Room 5311 Medical Science I, Ann Arbor, MI 48109-5516, USA
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14
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Machová E, O'Regan S, Newcombe J, Meunier FM, Prentice J, Dove R, Lisá V, Dolezal V. Detection of choline transporter-like 1 protein CTL1 in neuroblastoma x glioma cells and in the CNS, and its role in choline uptake. J Neurochem 2009; 110:1297-309. [PMID: 19519661 DOI: 10.1111/j.1471-4159.2009.06218.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Choline is an essential nutrient necessary for synthesis of membrane phospholipids, cell signalling molecules and acetylcholine. The aim of this study was to detect and characterize the choline transporter-like 1 (CTL1/SLC44A1) protein in CNS tissues and the hybrid neuroblastoma x glioma cell line NG108-15, which synthesizes acetylcholine and has high affinity choline transport but does not express the cholinergic high affinity choline transporter 1. The presence of CTL1 protein in NG108-15 cells was confirmed using our antibody G103 which recognizes the C-terminal domain of human CTL1. Three different cognate small interfering RNAs were used to decrease CTL1 mRNA in NG108-15 cells, causing lowered CTL1 protein expression, choline uptake and cell growth. None of the small interfering RNAs influenced carnitine transport, demonstrating the absence of major non-specific effects. In parental C6 cells knockdown of CTL1 also reduced high affinity choline transport. Our results support the concept that CTL1 protein is necessary for the high affinity choline transport which supplies choline for cell growth. The presence of CTL1 protein in rat and human CNS regions, where it is found in neuronal, glial and endothelial cells, suggests that malfunction of this transporter could have important implications in nervous system development and repair following injury, and in neurodegenerative diseases.
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Affiliation(s)
- Eva Machová
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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15
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Ishiguro N, Oyabu M, Sato T, Maeda T, Minami H, Tamai I. Decreased biosynthesis of lung surfactant constituent phosphatidylcholine due to inhibition of choline transporter by gefitinib in lung alveolar cells. Pharm Res 2007; 25:417-27. [PMID: 17624579 DOI: 10.1007/s11095-007-9362-9] [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] [Received: 02/07/2007] [Accepted: 05/29/2007] [Indexed: 10/23/2022]
Abstract
PURPOSE We investigated whether gefitinib, an anticancer agent, inhibits phosphatidylcholine (PC) biosynthesis and choline uptake by alveolar epithelial type II cells. MATERIALS AND METHODS Uptake of choline and PC biosynthesis were examined in vitro, using human alveolar epithelia-derived cell line A549 and rat alveolar type (AT) II cells as models. RESULTS Gefitinib reduced the incorporation of [3H]choline into PC in A549 and rat ATII cells. The uptake of [3H]choline by A549 and rat ATII cells was concentration-dependent, and the Km values were 15.0 and 10-100 microM, respectively. The uptake of [3H]choline by A549 and rat ATII cells was weakly Na+-dependent, and inhibited by hemicholinium-3. RT-PCR revealed expression of choline transporter-like protein (CTL)1 and organic cation transporter (OCT)3 mRNAs in both cells. The choline uptake by A549 and rat ATII cells was strongly inhibited by gefitinib with the IC50 value of 6.77 microM and 10.5 microM, respectively. CONCLUSIONS Our results demonstrate that gefitinib reduces PC biosynthesis via inhibition of cellular choline uptake by A549 and rat ATII cells, which is mainly mediated by CTL1, resulting in abnormality of lung surfactant that can be one of mechanisms of the interstitial lung disease associated with gefitinib.
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Affiliation(s)
- Naoki Ishiguro
- Department of Membrane Transport and Pharmacokinetics, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641, Yamasaki, Noda, Chiba, 278-8510, Japan
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16
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Tomi M, Arai K, Tachikawa M, Hosoya KI. Na(+)-independent choline transport in rat retinal capillary endothelial cells. Neurochem Res 2007; 32:1833-42. [PMID: 17520363 DOI: 10.1007/s11064-007-9367-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2007] [Accepted: 04/26/2007] [Indexed: 11/27/2022]
Abstract
The purpose of this study was to clarify the mechanism of the inner blood-retinal barrier (inner BRB) transport of choline and examine the choline uptake ability of rat choline transporter-like protein (CTL) 1. The transcript level of CTL1 in a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2) is more than 100-fold greater than that of CTL3 and CTL4, and no expression of organic cation transporter (OCT) mRNA was detected. The apparent influx permeability clearance of [(3)H]choline in the rat retina was found to be 271 microl/(min x g retina). The [(3)H]choline uptake by TR-iBRB2 cells was Na(+)-independent, potential-dependent, and concentration-dependent with Michaelis-Menten constants of 6.44 microM and 99.7 microM, and inhibited by several organic cations but not tetraethylammonium. The inhibition of CTL1 mRNA by small interfering RNA had little effect on the [(3)H]choline uptake by TR-iBRB2 cells. Rat CTL1-expressing Xenopus laevis oocytes exhibited an increase in the [(3)H]choline uptake by 45% compared with a control. In conclusion, our findings are consistent with Na(+)-independent choline transport being the mechanism for blood-to-retina transport of choline at the inner BRB. Although rat CTL1 expression is associated with the choline uptake, CTL1 does not play a major role in the choline uptake at the inner BRB.
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Affiliation(s)
- Masatoshi Tomi
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
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17
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Michel V, Yuan Z, Ramsubir S, Bakovic M. Choline transport for phospholipid synthesis. Exp Biol Med (Maywood) 2006; 231:490-504. [PMID: 16636297 DOI: 10.1177/153537020623100503] [Citation(s) in RCA: 230] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Choline is an essential nutrient for all cells because it plays a role in the synthesis of the membrane phospholipid components of the cell membranes, as a methyl-group donor in methionine metabolism as well as in the synthesis of the neurotransmitter acetylcholine. Choline deficiency affects the expression of genes involved in cell proliferation, differentiation, and apoptosis, and it has been associated with liver dysfunction and cancer. Abnormal choline transport and metabolism have been implicated in a number of neurodegenerative disorders such as Alzheimer's and Parkinson's disease. Therefore, the study of choline transport and the characteristics of choline transporters are of central importance to understanding the mechanisms that underlie membrane integrity and cell signaling in such disorders. Kinetic studies with radiolabeled choline and inhibitors distinguish three systems for choline transport: (i) low-affinity facilitated diffusion, (ii) high-affinity, Na+-dependent transport, and (iii) intermediate-affinity, Na+-independent transport. It is only recently, however, that the proteins having transport characteristics of at least one of these systems have been identified. They include (i) polyspecific organic cation transporters (OCTs) with low affinity for choline, (ii) high-affinity choline transporters (CHT1s), and (iii) intermediate-affinity choline transporter-like (CTL1) proteins. CHT1 and CTL1 but not OCT transporters are selectively inhibited with hemicholinium-3 and essentially display characteristics of specialized transporters for targeted choline metabolism. CHT1 is abundant in neurons and almost exclusively supplies choline for acetyl-choline synthesis. The focus here is more on newly-discovered CTL1 choline transporters. They are expressed in different organisms and cell types, apparently not for the biosynthesis of acetylcholine but for the production of the most abundant metabolite of choline, the membrane lipid phosphatidylcholine.
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Affiliation(s)
- Vera Michel
- Department of Human Health and Nutritional Sciences, Animal Science and Nutrition Building, Rm. 346, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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18
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Yuan Z, Tie A, Tarnopolsky M, Bakovic M. Genomic organization, promoter activity, and expression of the human choline transporter-like protein 1. Physiol Genomics 2006; 26:76-90. [PMID: 16609143 DOI: 10.1152/physiolgenomics.00107.2005] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Choline transporter-like (CTL) proteins of the CTL1 family are novel transmembrane proteins implicated in choline transport for phospholipid synthesis. In this study, we characterized the 5'-flanking region of the human (h)CTL1 gene and examined some of the possible mechanisms of its regulation, including promoter activity, splicing, and expression. The transcription start site of the hCTL1 gene was mapped by 5'-rapid amplification of cDNA ends (RACE), and the presence of two splice variants, hCTL1a and hCTL1b, was investigated using isoform-specific PCR and 3'-RACE. The hCTL1 promoter region of approximately 900 bp was isolated from MCF-7 human breast cancer cells. The promoter was TATA-less and driven by a long stretch of GC-rich sequence in accordance with widespread expression of hCTL1 at both mRNA and protein levels. Deletion analyses demonstrated that a very strong promoter is contained within 500 bp of the transcription start site, and more upstream regions did not increase its activity. The core promoter that conferred the minimal transcription is within the -188/+27-bp region, and its activity varied in human breast cancer and mouse skeletal muscle cells. Multiple motifs within the promoter regulatory region bound nuclear factors from both cultured cells and normal human skeletal muscle. The motifs within the three regions [S1 (-92/-61 bp), S2 (-174/-145 bp), and S3 (-289/-260 bp)] contained overlapping binding sites for hematopoietic transcription factors and ubiquitous transcription factors, in line with the expected gene function. Genomic analyses demonstrated a high conservation of hCTL1 and mouse CTL1 proximal promoters. Accordingly, mRNA profiles demonstrated that human splice variants were expressed ubiquitously, as demonstrated for the mouse transcripts; however, they differed from the profiles of rat CTL1 transcripts, which were more restricted to neurons and intestinal tissues. The shorter hCTL1b variant contained the cytosolic COOH-terminal motif L651KKR654 for endoplasmic reticulum retrieval/retention. This retention signal was conserved in hCTL1b and rat and mouse CTL1b and is typical for transmembrane proteins of type 1 topology.
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Affiliation(s)
- Zongfei Yuan
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
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19
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Fullerton MD, Wagner L, Yuan Z, Bakovic M. Impaired trafficking of choline transporter-like protein-1 at plasma membrane and inhibition of choline transport in THP-1 monocyte-derived macrophages. Am J Physiol Cell Physiol 2006; 290:C1230-8. [PMID: 16319125 DOI: 10.1152/ajpcell.00255.2005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study investigates choline transport processes and regulation of choline transporter-like protein-1 (CTL1) in human THP-1 monocytic cells and phorbol myristate 13-acetate (PMA)-differentiated macrophages. Choline uptake is saturable and therefore protein-mediated in both cell types, but its transport characteristics change soon after treatments with PMA. The maximal rate of choline uptake intrinsic to monocytic cells is greatly diminished in differentiated macrophages as demonstrated by alterations in Vmax values from 1,973 ± 118 to 380 ± 18 nmol·mg−1·min−1, when the binding affinity did not change significantly ( Km values 56 ± 8 and 53 ± 6 μM, respectively). Treatments with hemicholinim-3 effectively inhibit most of the choline uptake, establishing that a choline-specific transport protein rather than a general transporter is responsible for the observed kinetic parameters. mRNA screening for the expression of various transporters reveals that CTL1 is the most plausible candidate that possesses the described kinetic and inhibitory properties. Fluorescence-activated cell sorting analyses at various times after PMA treatments further demonstrate that the disappearance of CTL1 protein from the cell surface follows the same trend as the reduction in choline uptake. Importantly, the loss of functional CTL1 from the cell surface occurs without significant changes in total CTL1 protein or its mRNA level indicating that an impaired CTL1 trafficking is the key contributing factor to the reduced choline uptake, subsequent to the PMA-induced THP-1 differentiation to macrophages.
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Affiliation(s)
- Morgan D Fullerton
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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20
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Fujita T, Shimada A, Okada N, Yamamoto A. Functional characterization of Na+-independent choline transport in primary cultures of neurons from mouse cerebral cortex. Neurosci Lett 2006; 393:216-21. [PMID: 16239069 DOI: 10.1016/j.neulet.2005.09.069] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2005] [Revised: 09/09/2005] [Accepted: 09/27/2005] [Indexed: 11/23/2022]
Abstract
We report here the functional characteristics of Na+-independent choline transport system in primary cultures of neurons from mouse cerebral cortex. Na+-independent choline transport was saturable with a Michaelis constant (Kt) of 26.7+/-1.2 microM and a maximal velocity (Vmax) of 1.04+/-0.02 nmol/mg protein/10 min. Choline uptake was significantly influenced by extracellular pH and by membrane depolarization. This uptake system was inhibited by various organic cations including unlabeled choline, guanidine, diphenhydramine and the choline analog hemicholinium-3. However, the prototypical organic cation tetraethylammonium and cimetidine showed very little affinity for the Na+-independent choline uptake system in neurons. These results indicate that mouse cerebrocortical neurons express a Na+-independent, high-affinity choline transport system. RT-PCR revealed that choline transporter-like protein 1 (CTL1) and its spliced variant CTL1a, which have been reported to be novel Na+-independent choline transporter, are expressed in mouse cerebrocortical neurons. The Na+-independent transport properties of choline in mouse neurons is similar or identical to that of CTL1 and/or CTL1a. This choline transport system seems to have relevance not only for neuronal physiology but also for the uptake of pharmacologically important organic cation drugs.
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Affiliation(s)
- Takuya Fujita
- Department of Biochemical Pharmacology, Kyoto Pharmaceutical University, Misasagi, Kyoto 607-8414, Japan.
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21
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Nováková J, Mikasová L, Machová E, Lisá V, Dolezal V. Chronic treatment with amyloid β1–42 inhibits non-cholinergic high-affinity choline transport in NG108-15 cells through protein kinase C signaling. Brain Res 2005; 1062:101-10. [PMID: 16256077 DOI: 10.1016/j.brainres.2005.09.021] [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] [Received: 04/30/2005] [Revised: 09/17/2005] [Accepted: 09/25/2005] [Indexed: 01/31/2023]
Abstract
We investigated the influence of the amyloid-beta-peptide(1-42) on hemicholinum-3-sensitive high-affinity choline uptake in NG108-15 cells. RT-PCR analysis revealed the presence of mRNA for a choline transporter-like protein but not for cholinergic high-affinity choline transporter. Differentiation of cells increased both hemicholinum-3-sensitive choline uptake and high-affinity hemicholinium-3 binding. This transport was not influenced by tenfold excess of carnitine. Continuous presence of submicromolar concentrations of amyloid-beta-peptide(1-42) during differentiation resulted in a decrease of both choline uptake and hemicholinium-3 binding. These effects were not present when amyloid-beta-peptide(1-42) was added 5 min prior to measurements. Neither differentiation nor amyloid-beta-peptide(1-42) treatment changed levels of choline transporter-like protein mRNA. Protein kinase C inhibition by staurosporine or its inactivation by continuous presence of tetradecanoyl phorbol acetate prevented the inhibitory effect of amyloid-beta-peptide(1-42) treatment on choline uptake. Activation of protein kinase C by tetradecanoyl phorbol acetate during measurement had inhibitory effect on choline uptake in control but not amyloid-beta-peptide(1-42)-treated cells. The concentration of amyloid-beta-peptide(1-42) maximally effective on hemicholinium-3-sensitive choline uptake had no effect on cell growth, oxidative activity, membrane integrity, number of surface muscarinic receptors, caspase-3 and -8 activities, or uptake of deoxyglucose. Results demonstrate that long-term treatment with non-toxic concentrations of amyloid-beta-peptide(1-42) downregulates choline uptake presumably mediated by a choline transporter-like protein through activation of protein kinase C signaling. The decrease of choline uptake may have relevance to the pathogenesis of Alzheimer's disease.
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Affiliation(s)
- Jana Nováková
- Institute of Physiology, Czech Academy of Sciences, Department of Neurochemistry, Vídenská 1083, 14220 Prague 4, Czech Republic
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22
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Inazu M, Takeda H, Matsumiya T. Molecular and functional characterization of an Na+-independent choline transporter in rat astrocytes. J Neurochem 2005; 94:1427-37. [PMID: 16000150 DOI: 10.1111/j.1471-4159.2005.03299.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this study, we examined the molecular and functional characterization of choline uptake into cultured rat cortical astrocytes. Choline uptake into astrocytes showed little dependence on extracellular Na+. Na+-independent choline uptake was saturable and mediated by a single transport system, with an apparent Michaelis-Menten constant (Km) of 35.7 +/- 4.1 microm and a maximal velocity (Vmax) of 49.1 +/- 2.0 pmol/mg protein/min. Choline uptake was significantly decreased by acidification of the extracellular medium and by membrane depolarization. Na+-independent choline uptake was inhibited by unlabeled choline, acetylcholine and the choline analogue hemicholinium-3. The prototypical organic cation tetrahexylammonium (TEA), and other n-tetraalkylammonium compounds such as tetrabutylammonium (TBA) and tetrahexylammonium (THA), inhibited Na+-independent choline uptake, and their inhibitory potencies were in the order THA > TBA > TEA. Various organic cations, such as 1-methyl-4-tetrahydropyridinium (MPP+), clonidine, quinine, quinidine, guanidine, N-methylnicotinamide, cimetidine, desipramine, diphenhydramine and verapamil, also interacted with the Na+-independent choline transport system. Corticosterone and 17beta-estradiol, known inhibitors of organic cation transporter 3 (OCT3), did not cause any significant inhibition. However, decynium22, which inhibits OCTs, markedly inhibited Na+-independent choline uptake. RT-PCR demonstrated that astrocytes expressed low levels of OCT1, OCT2 and OCT3 mRNA, but the functional characteristics of choline uptake are very different from the known properties of these OCTs. The high-affinity Na+-dependent choline transporter, CHT1, is not expressed in astrocytes as evidenced by RT-PCR. Furthermore, mRNA for choline transporter-like protein 1 (CTL1), and its splice variants CTL1a and CTL1b, was expressed in rat astrocytes, and the inhibition of CTL1 expression by RNA interference completely inhibited Na+-independent choline uptake. We conclude that rat astrocytes express an intermediate-affinity Na+-independent choline transport system. This system seems to occur through a CTL1 and is responsible for the uptake of choline and organic cations in these cells.
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Affiliation(s)
- Masato Inazu
- Department of Pharmacology, Tokyo Medical University, Shinjuku-ku, Tokyo, Japan
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23
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Traiffort E, Ruat M, O'Regan S, Meunier FM. Molecular characterization of the family of choline transporter-like proteins and their splice variants. J Neurochem 2005; 92:1116-25. [PMID: 15715662 DOI: 10.1111/j.1471-4159.2004.02962.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We show here that the choline transporter-like (CTL) family is more extensive than initially described with five genes in humans and complex alternative splicing. In adult rat tissues, CTL2-4 mRNAs are mainly detected in peripheral tissues, while CTL1 is widely expressed throughout the nervous system. During rat post-natal development, CTL1 is expressed in several subpopulations of neurones and in the white matter, where its spatio-temporal distribution profile recalls that of myelin basic protein, an oligodendrocyte marker. We identified two major rat splice variants of CTL1 (CTL1a and CTL1b) differing in their carboxy-terminal tails with both able to increase choline transport after transfection in neuroblastoma cells. In the developing brain, CTL1a is expressed in both neurones and oligodendroglial cells, whereas CTL1b is restricted to oligodendroglial cells. These findings suggest specific roles for CTL1 splice variants in both neuronal and oligodendrocyte physiology.
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Affiliation(s)
- E Traiffort
- Institut de Neurobiologie Alfred Fessard IFR 2118 CNRS, Laboratoire de Neurobiologie Cellulaire et Moléculaire, UPR 9040, Gif-sur-Yvette, France.
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Lecomte MJ, De Gois S, Guerci A, Ravassard P, Faucon Biguet N, Mallet J, Berrard S. Differential expression and regulation of the high-affinity choline transporter CHT1 and choline acetyltransferase in neurons of superior cervical ganglia. Mol Cell Neurosci 2005; 28:303-13. [PMID: 15691711 DOI: 10.1016/j.mcn.2004.09.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2004] [Revised: 09/17/2004] [Accepted: 09/22/2004] [Indexed: 11/21/2022] Open
Abstract
Previous studies revealed that leukemia inhibitory factor (LIF) and retinoic acid (RA) induce a noradrenergic to cholinergic switch in cultured sympathetic neurons of superior cervical ganglia (SCG) by up-regulating the coordinate expression of choline acetyltransferase (ChAT) and the vesicular acetylcholine transporter. Here, we examined the effect of both factors on high-affinity choline uptake (HACU) and on expression of the high-affinity choline transporter CHT1. We found that HACU and CHT1-mRNA levels are up-regulated by LIF and down-regulated by RA in these neurons. Thus, in contrast to LIF, RA differentially regulates the expression of the presynaptic cholinergic proteins. Moreover, we showed that untreated SCG neurons express HACU and CHT1-mRNAs at much higher levels than ChAT activity and transcripts. In intact SCG, CHT1-mRNAs are abundant and synthesized by the noradrenergic neurons themselves. This study provides the first example of CHT1 expression in neurons which do not use acetylcholine as neurotransmitter.
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Affiliation(s)
- Marie-José Lecomte
- Laboratoire de la Neurotransmission et des Processus Neurodégénératifs, CNRS, UMR 7091, Bâtiment CERVI, Hôpital de la Pitié-Salpêtrière, 83 boulevard de l'Hôpital, 75013 Paris, France
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25
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Yuan Z, Wagner L, Poloumienko A, Bakovic M. Identification and expression of a mouse muscle-specific CTL1 gene. Gene 2004; 341:305-12. [PMID: 15474312 DOI: 10.1016/j.gene.2004.07.042] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2004] [Revised: 07/01/2004] [Accepted: 07/19/2004] [Indexed: 10/26/2022]
Abstract
In this study, a mouse gene and cDNA encoding for a novel skeletal muscle-specific choline transporter-like protein 1 (mCTL1) were identified and mCTL1 mRNA and protein expression characterized. The mCTL1 cDNA is 2888-bp long; consisting of a 653-amino-acid open-reading frame, 8-11 putative transmembrane domains, three N-glycosylation sites and seven protein kinase C phosphorylation sites. The mCTL1 gene is localized to chromosome 4B2, at 182 kb in length, and encoded by 17 exons. Although the mCTL1 mRNA was expressed in several mouse tissues such as muscle, brain, heart and testis, the protein analyses of multiple tissues and membrane vesicles reveal that mCTL1 is exclusively expressed in skeletal muscle. Expression of His-tagged mCTL1 in Cos-7 cells produces an increase in saturable choline uptake that is sensitive to a Na(+)-ion gradient, ethanolamine and the Ca(2+)-channel blocker verapamil, and insensitive to low concentrations of hemicholinium-3.
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Affiliation(s)
- Zongfei Yuan
- Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
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26
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Hediger MA, Romero MF, Peng JB, Rolfs A, Takanaga H, Bruford EA. The ABCs of solute carriers: physiological, pathological and therapeutic implications of human membrane transport proteinsIntroduction. Pflugers Arch 2003; 447:465-8. [PMID: 14624363 DOI: 10.1007/s00424-003-1192-y] [Citation(s) in RCA: 636] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2003] [Accepted: 10/01/2003] [Indexed: 12/26/2022]
Abstract
The Human Genome Organisation (HUGO) Nomenclature Committee Database provides a list of transporter families of the solute carrier (SLC) gene series (see http://www.gene.ucl.ac.uk/nomenclature/). Currently, it includes 43 families and 298 transporter genes. This special issue features mini-reviews on each of these SLC families written by the experts in each field. A WEB site has been established (http://www.pharmaconference.org/slctable.asp) that gives the latest updates for the SLC families and their members as well as relevant links to gene databases and reviews in the literature. A list of all currently known SLC families, a discussion of additional SLC families and family members as well as a brief summary of non-SLC transporter genes is included in this introduction.
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Affiliation(s)
- Matthias A Hediger
- Membrane Biology Program and Renal Division, Brigham and Women's Hospital, Harvard Institutes of Medicine, 77 Avenue Louis Pasteur, Boston, MA 02115, USA.
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