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Bagalkot T, Sorkin A. Amphetamine Induces Sex-Dependent Loss of the Striatal Dopamine Transporter in Sensitized Mice. eNeuro 2024; 11:ENEURO.0491-23.2023. [PMID: 38164591 PMCID: PMC10849026 DOI: 10.1523/eneuro.0491-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 12/10/2023] [Accepted: 12/12/2023] [Indexed: 01/03/2024] Open
Abstract
Dopamine transporter (DAT) controls dopamine signaling in the brain through the reuptake of synaptically released dopamine. DAT is a target of abused psychostimulants such as amphetamine (Amph). Acute Amph administration induces transient DAT endocytosis, which, among other Amph effects on dopaminergic neurons, elevates extracellular dopamine. However, the effects of repeated Amph abuse, leading to behavioral sensitization and drug addiction, on DAT are unknown. Hence, we developed a 14 d Amph-sensitization protocol in knock-in mice expressing HA-epitope-tagged DAT (HA-DAT) and investigated the effects of Amph challenge on sensitized HA-DAT animals. The Amph challenge resulted in the highest locomotor activity on Day 14 in both sexes, which was sustained for 1 h in male but not female mice. Strikingly, significant (by 30-60%) loss of the HA-DAT protein in the striatum was caused by the Amph challenge of sensitized males but not females. Amph also reduced V max of dopamine transport in the striatal synaptosomes of males without changing K m values. Consistently, immunofluorescence microscopy revealed a significant increase of HA-DAT colocalization with the endosomal protein VPS35 only in Amph-challenged males. Amph-induced loss of striatal HA-DAT in sensitized mice was blocked by chloroquine, vacuolin-1, and inhibitor of Rho-associated kinases ROCK1/2, indicative of the involvement of endocytic trafficking in the DAT protein loss. Interestingly, an apparent degradation of HA-DAT protein was observed in the nucleus accumbens and not in the dorsal striatum. We propose that Amph challenge in sensitized mice triggers Rho-mediated endocytosis and post-endocytic trafficking of DAT in a brain-region-specific and sex-dependent manner.
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Affiliation(s)
- Tarique Bagalkot
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh 15261, Pennsylvania
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh 15261, Pennsylvania
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2
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Nikolaus S, Chao OY, Beu M, Henke J, Antke C, Wang AL, Fazari B, Mamlins E, Huston JP, Giesel FL. The 5-HT 1A receptor agonist 8-OH-DPAT modulates motor/exploratory activity, recognition memory and dopamine transporter binding in the dorsal and ventral striatum. Neurobiol Learn Mem 2023; 205:107848. [PMID: 37865262 DOI: 10.1016/j.nlm.2023.107848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 10/09/2023] [Accepted: 10/18/2023] [Indexed: 10/23/2023]
Abstract
In the present studies, we assessed the effect of the 5-HT1A receptor (R) agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) on motor and exploratory behaviors, object and place recognition and dopamine transporter (DAT) and serotonin transporter (SERT) binding in the rat brain. In Experiment I, motor/exploratory behaviors were assessed in an open field after injection of either 8-OH-DPAT (0.1 and 3 mg/kg) or vehicle for 30 min without previous habituation to the open field. In Experiment II, rats underwent a 5-min exploration trial in an open field with two identical objects. After injection of either 8-OH-DPAT (0.1 and 3 mg/kg) or vehicle, rats underwent a 5-min test trial with one of the objects replaced by a novel one and the other object transferred to a novel place. Subsequently, N-o-fluoropropyl-2b-carbomethoxy-3b-(4-[123I]iodophenyl)-nortropane ([123I]FP-CIT; 11 ± 4 MBq) was injected into the tail vein. Regional radioactivity accumulations were determined post mortem with a well counter. In both experiments, 8-OH-DPAT dose-dependently increased ambulation and exploratory head-shoulder motility, whereas rearing was dose-dependently decreased. In the test rial of Experiment II, there were no effects of 8-OH-DPAT on overall activity, sitting and grooming. 8-OH-DPAT dose-dependently impaired recognition of object and place. 8-OH-DPAT (3 mg/kg) increased DAT binding in the dorsal striatum relative to both vehicle and 0.1 mg/kg 8-OH-DPAT. Furthermore, in the ventral striatum, DAT binding was decreased after 3 mg/kg 8-OH-DPAT relative to vehicle. Findings indicate that motor/exploratory behaviors, memory for object and place and regional dopamine function may be modulated by the 5-HT1AR. Since, after 8-OH-DPAT, rats exhibited more horizontal and less (exploratory) vertical motor activity, while overall activity was not different between groups, it may be inferred, that the observed impairment of object recognition was not related to a decrease of motor activity as such, but to a decrease of intrinsic motivation, attention and/or awareness, which are relevant accessories of learning. Furthermore, the present findings on 8-OH-DPAT action indicate associations not only between motor/exploratory behavior and the recognition of object and place but also between the respective parameters and the levels of available DA in dorsal and ventral striatum.
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Affiliation(s)
- Susanne Nikolaus
- Department of Nuclear Medicine, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany.
| | - Owen Y Chao
- Department of Biomedical Sciences, University of Minnesota Medical School, Duluth, MN 55812, USA
| | - Markus Beu
- Department of Nuclear Medicine, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Jan Henke
- Department of Nuclear Medicine, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Christina Antke
- Department of Nuclear Medicine, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - An-Li Wang
- Department of Pharmacology and Toxicology, Jacob School of Medicine and Biomedical Sciences, University at Buffalo, 1021 Main Street, Buffalo, NY 14203, USA
| | - Benedetta Fazari
- Institute of Anatomy II, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Universitätsstr. 1, D-40225 Düsseldorf, Germany
| | - Eduards Mamlins
- Department of Nuclear Medicine, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Joseph P Huston
- Center for Behavioural Neuroscience, Institute of Experimental Psychology, Heinrich-Heine University, Universitätsstr. 1, D-40225 Düsseldorf, Germany
| | - Frederik L Giesel
- Department of Nuclear Medicine, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
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3
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Bagalkot T, Sorkin A. Endocytic down-regulation of the striatal dopamine transporter by amphetamine in sensitized mice in sex-dependent manner. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.17.541165. [PMID: 37293021 PMCID: PMC10245703 DOI: 10.1101/2023.05.17.541165] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Dopamine transporter (DAT) controls dopamine signaling in the brain through the reuptake of synaptically released dopamine. DAT is a target of abused psychostimulants such as amphetamine (Amph). Acute Amph is proposed to cause transient DAT endocytosis which among other Amph effects on dopaminergic neurons elevates extracellular dopamine. However, the effects of repeated Amph abuse, leading to behavioral sensitization and drug addiction, on DAT traffic are unknown. Hence, we developed a 14-day Amph-sensitization protocol in knock-in mice expressing HA-epitope tagged DAT (HA-DAT) and investigated effects of Amph challenge on HA-DAT in sensitized animals. Amph challenge resulted in the highest locomotor activity on day 14 in both sexes, which was however sustained for 1 hour in male but not female mice. Strikingly, significant (by 30-60%) reduction in the amount of the HA-DAT protein in striatum was observed in response to Amph challenge of sensitized males but not females. Amph reduced Vmax of dopamine transport in striatal synaptosomes of males without changing Km values. Consistently, immunofluorescence microscopy revealed a significant increase of HA-DAT co-localization with the endosomal protein VPS35 only in males. Amph-induced HA-DAT down-regulation in the striatum of sensitized mice was blocked by chloroquine, vacuolin-1 (inhibitor of PIKfive kinase), and inhibitor of Rho-associated kinases (ROCK1/2), indicative of the involvement of endocytic trafficking in DAT down-regulation. Interestingly, HA-DAT protein down-regulation was observed in nucleus accumbens and not in dorsal striatum. We propose that Amph challenge in sensitized mice leads to ROCK-dependent endocytosis and post-endocytic traffic of DAT in a brain-region-specific and sex-dependent manner.
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Dutta CN, Christov-Moore L, Ombao H, Douglas PK. Neuroprotection in late life attention-deficit/hyperactivity disorder: A review of pharmacotherapy and phenotype across the lifespan. Front Hum Neurosci 2022; 16:938501. [PMID: 36226261 PMCID: PMC9548548 DOI: 10.3389/fnhum.2022.938501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Accepted: 08/16/2022] [Indexed: 11/13/2022] Open
Abstract
For decades, psychostimulants have been the gold standard pharmaceutical treatment for attention-deficit/hyperactivity disorder (ADHD). In the United States, an astounding 9% of all boys and 4% of girls will be prescribed stimulant drugs at some point during their childhood. Recent meta-analyses have revealed that individuals with ADHD have reduced brain volume loss later in life (>60 y.o.) compared to the normal aging brain, which suggests that either ADHD or its treatment may be neuroprotective. Crucially, these neuroprotective effects were significant in brain regions (e.g., hippocampus, amygdala) where severe volume loss is linked to cognitive impairment and Alzheimer's disease. Historically, the ADHD diagnosis and its pharmacotherapy came about nearly simultaneously, making it difficult to evaluate their effects in isolation. Certain evidence suggests that psychostimulants may normalize structural brain changes typically observed in the ADHD brain. If ADHD itself is neuroprotective, perhaps exercising the brain, then psychostimulants may not be recommended across the lifespan. Alternatively, if stimulant drugs are neuroprotective, then this class of medications may warrant further investigation for their therapeutic effects. Here, we take a bottom-up holistic approach to review the psychopharmacology of ADHD in the context of recent models of attention. We suggest that future studies are greatly needed to better appreciate the interactions amongst an ADHD diagnosis, stimulant treatment across the lifespan, and structure-function alterations in the aging brain.
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Affiliation(s)
- Cintya Nirvana Dutta
- Biostatistics Group, Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
- School of Modeling, Simulation, and Training, and Computer Science, University of Central Florida, Orlando, FL, United States
| | - Leonardo Christov-Moore
- Brain and Creativity Institute, University of Southern California, Los Angeles, CA, United States
| | - Hernando Ombao
- Biostatistics Group, Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
| | - Pamela K. Douglas
- School of Modeling, Simulation, and Training, and Computer Science, University of Central Florida, Orlando, FL, United States
- Department of Psychiatry and Biobehavioral Medicine, University of California, Los Angeles, Los Angeles, CA, United States
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Román V, Kedves R, Kelemen K, Némethy Z, Sperlágh B, Lendvai B, Vizi ES. Contribution of analog signaling to neurotransmitter interactions and behavior: Role of transporter-mediated nonquantal dopamine release. Physiol Rep 2021; 9:e15088. [PMID: 34762352 PMCID: PMC8582292 DOI: 10.14814/phy2.15088] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 09/28/2021] [Accepted: 10/08/2021] [Indexed: 11/28/2022] Open
Abstract
Neuronal networks cause changes in behaviorally important information processing through the vesicular release of neurotransmitters governed by the rate and timing of action potentials (APs). Herein, we provide evidence that dopamine (DA), nonquantally released from the cytoplasm, may exert similar effects in vivo. In mouse slice preparations, (+/-)-3,4-methylenedioxy-methamphetamine (MDMA, or ecstasy) and β-phenylethylamine (β-PEA)-induced DA release in the striatum and nucleus accumbens (NAc), two regions of the brain involved in reward-driven and social behavior and inhibited the axonal stimulation-induced release of tritiated acetylcholine ([3 H]ACh) in the striatum. The DA transporter (DAT) inhibitor (GBR-12909) prevented MDMA and β-PEA from causing DA release. GBR-12909 could also restore some of the stimulated acetylcholine release reduced by MDMA or β-PEA in the striatum confirming the fundamental role of DAT. In addition, hypothermia could prevent the β-PEA-induced release in the striatum and in the NAc. Sulpiride, a D2 receptor antagonist, also prevented the inhibitory effects of MDMA or β-PEA on stimulated ACh release, suggesting they act indirectly via binding of DA. Reflecting the neurochemical interactions in brain slices at higher system level, MDMA altered the social behavior of rats by preferentially enhancing passive social behavior. Similar to the in vitro effects, GBR-12909 treatment reversed specific elements of the MDMA-induced changes in behavior, such as passive social behavior, while left others including social play unchanged. The changes in behavior by the high level of extracellular DA-- a significant amount originating from cytoplasmic release--suggest that in addition to digital computation through synapses, the brain also uses analog communication, such as DA signaling, to mediate some elements of complex behaviors, but in a much longer time scale.
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Affiliation(s)
- Viktor Román
- Pharmacology and Drug Safety ResearchGedeon Richter Plc.BudapestHungary
| | - Rita Kedves
- Pharmacology and Drug Safety ResearchGedeon Richter Plc.BudapestHungary
| | - Kristóf Kelemen
- Pharmacology and Drug Safety ResearchGedeon Richter Plc.BudapestHungary
| | - Zsolt Némethy
- Pharmacology and Drug Safety ResearchGedeon Richter Plc.BudapestHungary
| | | | - Balázs Lendvai
- Pharmacology and Drug Safety ResearchGedeon Richter Plc.BudapestHungary
| | - E. Sylvester Vizi
- Institute of Experimental MedicineBudapestHungary
- Department of Pharmacology and PharmacotherapySemmelweis UniversityBudapestHungary
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Fernández G, Krapacher F, Ferreras S, Quassollo G, Mari MM, Pisano MV, Montemerlo A, Rubianes MD, Bregonzio C, Arias C, Paglini MG. Lack of Cdk5 activity is involved on Dopamine Transporter expression and function: Evidences from an animal model of Attention-Deficit Hyperactivity Disorder. Exp Neurol 2021; 346:113866. [PMID: 34537209 DOI: 10.1016/j.expneurol.2021.113866] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 09/08/2021] [Accepted: 09/14/2021] [Indexed: 11/29/2022]
Abstract
Attention deficit/Hyperactivity disorder (ADHD) is one of the most diagnosed psychiatric disorders nowadays. The core symptoms of the condition include hyperactivity, impulsiveness and inattention. The main pharmacological treatment consists of psychostimulant drugs affecting Dopamine Transporter (DAT) function. We have previously shown that genetically modified mice lacking p35 protein (p35KO), which have reduced Cdk5 activity, present key hallmarks resembling those described in animal models useful for studying ADHD. The p35KO mouse displays spontaneous hyperactivity and shows a calming effect of methylphenidate or amphetamine treatment. Interestingly, dopaminergic neurotransmission is altered in these mice as they have an increased Dopamine (DA) content together with a low DA turnover. This led us to hypothesize that the lack of Cdk5 activity affects DAT expression and/or function in this animal model. In this study, we performed biochemical assays, cell-based approaches, quantitative fluorescence analysis and functional studies that allowed us to demonstrate that p35KO mice exhibit decreased DA uptake and reduced cell surface DAT expression levels in the striatum (STR). These findings are supported by in vitro observations in which the inhibition of Cdk5 activity in N2a cells induced a significant increase in constitutive DAT endocytosis with a concomitant increase in DAT localization to recycling endosomes. Taken together, these data provide evidences regarding the role of Cdk5/p35 in DAT expression and function, thus contributing to the knowledge of DA neurotransmission physiology and also providing therapeutic options for the treatment of DA pathologies such as ADHD.
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Affiliation(s)
- Guillermo Fernández
- Laboratory of Neurophysiology, Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Favio Krapacher
- Laboratory of Neurophysiology, Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Soledad Ferreras
- Laboratory of Neurophysiology, Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Gonzalo Quassollo
- Laboratory of Neurophysiology, Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Macarena Mariel Mari
- Laboratory of Neurophysiology, Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - María Victoria Pisano
- Laboratory of Neurophysiology, Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Antonella Montemerlo
- Instituto de Investigaciones en Fisicoquímica de Córdoba, INFIQC-CONICET, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - María Dolores Rubianes
- Instituto de Investigaciones en Fisicoquímica de Córdoba, INFIQC-CONICET, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Claudia Bregonzio
- Instituto de Farmacología Experimental Córdoba, IFEC-CONICET, Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Carlos Arias
- Laboratory of Neurophysiology, Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina; Instituto de Investigaciones Psicológicas, IIPSI-CONICET, Facultad de Psicología, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - María Gabriela Paglini
- Laboratory of Neurophysiology, Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina; Instituto de Virología "Dr. J. M. Vanella", Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Córdoba, Argentina.
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Ryan RM, Ingram SL, Scimemi A. Regulation of Glutamate, GABA and Dopamine Transporter Uptake, Surface Mobility and Expression. Front Cell Neurosci 2021; 15:670346. [PMID: 33927596 PMCID: PMC8076567 DOI: 10.3389/fncel.2021.670346] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Accepted: 03/15/2021] [Indexed: 01/31/2023] Open
Abstract
Neurotransmitter transporters limit spillover between synapses and maintain the extracellular neurotransmitter concentration at low yet physiologically meaningful levels. They also exert a key role in providing precursors for neurotransmitter biosynthesis. In many cases, neurons and astrocytes contain a large intracellular pool of transporters that can be redistributed and stabilized in the plasma membrane following activation of different signaling pathways. This means that the uptake capacity of the brain neuropil for different neurotransmitters can be dynamically regulated over the course of minutes, as an indirect consequence of changes in neuronal activity, blood flow, cell-to-cell interactions, etc. Here we discuss recent advances in the mechanisms that control the cell membrane trafficking and biophysical properties of transporters for the excitatory, inhibitory and modulatory neurotransmitters glutamate, GABA, and dopamine.
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Affiliation(s)
- Renae M. Ryan
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
| | - Susan L. Ingram
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, United States
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Ingram SM, Rana T, Manson AM, Yayah FM, Jackson EGB, Anderson C, Davids BO, Goodwin JS. Optogenetically-induced multimerization of the dopamine transporter increases uptake and trafficking to the plasma membrane. J Biol Chem 2021; 296:100787. [PMID: 34015332 PMCID: PMC8203837 DOI: 10.1016/j.jbc.2021.100787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 05/07/2021] [Accepted: 05/13/2021] [Indexed: 11/19/2022] Open
Abstract
The dopamine transporter (DAT) is essential for the reuptake of the released neurotransmitter dopamine (DA) in the brain. Psychostimulants, methamphetamine and cocaine, have been reported to induce the formation of DAT multimeric complexes in vivo and in vitro. The interpretation of DAT multimer function has been primarily in the context of compounds that induce structural and functional modifications of the DAT, complicating the understanding of the significance of DAT multimers. To examine multimerization in the absence of DAT ligands as well as in their presence, we developed a novel, optogenetic fusion chimera of cryptochrome 2 and DAT with an mCherry fluorescent reporter (Cry2-DAT). Using blue light to induce Cry2-DAT multimeric protein complex formation, we were able to simultaneously test the functional contributions of DAT multimerization in the absence or presence of substrates or inhibitors with high spatiotemporal precision. We found that blue light-stimulated Cry2-DAT multimers significantly increased IDT307 uptake and MFZ 9-18 binding in the absence of ligands as well as after methamphetamine and nomifensine treatment. Blue light-induced Cry2-DAT multimerization increased colocalization with recycling endosomal marker Rab11 and had decreased presence in Rab5-positive early endosomes and Rab7-positive late endosomes. Our data suggest that the increased uptake and binding results from induced and rapid trafficking of DAT multimers to the plasma membrane. Our data suggest that DAT multimers may function to help maintain DA homeostasis.
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Affiliation(s)
- Shalonda M Ingram
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Tanu Rana
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Ashley M Manson
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Faisal M Yayah
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Evan G B Jackson
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Christopher Anderson
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Benem-Orom Davids
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - J Shawn Goodwin
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA.
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Ojiakor O, Rylett R. Modulation of sodium-coupled choline transporter CHT function in health and disease. Neurochem Int 2020; 140:104810. [DOI: 10.1016/j.neuint.2020.104810] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 06/16/2020] [Accepted: 07/09/2020] [Indexed: 12/27/2022]
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10
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Bartolomé-Martín D, Ibáñez I, Piniella D, Martínez-Blanco E, Pelaz SG, Zafra F. Identification of potassium channel proteins Kv7.2/7.3 as common partners of the dopamine and glutamate transporters DAT and GLT-1. Neuropharmacology 2019; 161:107568. [PMID: 30885609 DOI: 10.1016/j.neuropharm.2019.03.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2018] [Revised: 02/19/2019] [Accepted: 03/06/2019] [Indexed: 12/12/2022]
Abstract
Dopamine and glutamate transporters (DAT and GLT-1, respectively) share some biophysical characteristics, as both are secondary active carriers coupled to electrochemical ion gradients. In order to identify common or specific components of their respective proteomes, we performed a proximity labelling assay (BioID) in the hippocampal cell line HT22. While most of the identified proteins were specific for each transporter (and will be analyzed elsewhere), we detected two membrane proteins in the shared interactome of GLT-1 and DAT: the transmembrane protein 263 (Tmem263) and the potassium channel protein Kv7.3. However, only Kv7.3 formed immunoprecipitable complexes with GLT-1 and DAT in lysates of transfected HEK293 cells. Moreover, either DAT or GLT-1 co-clustered with Kv7.2/7.3 along the axonal tracts in co-transfected primary neurons, indicating a close spatial proximity between these proteins. Kv7.3, forming heterotetramers with the closely related subunit Kv7.2, underlies the M-currents that control the resting membrane potential and spiking activity in neurons. To investigate whether the presence of the potassium channel affected DAT or GLT-1 function, we performed uptake determinations using radioactive substrate and electrophysiological measurements. Uptake through both transporters was mildly stimulated by the presence of the channel, an effect that was reversed by the potassium channel blocker XE-991. Electrophysiological recording (in transfected HT22 and differentiated SH-SY5Y cells) indicated that the depolarizing effect induced by the presence of the neurotransmitter was reverted by the activity of the potassium channel. Altogether, these data suggest a tight spatial and functional relationship between the DAT/GLT-1 transporters and the Kv7.2/7.3 potassium channel that immediately readjusts the membrane potential of the neuron, probably to limit the neurotransmitter-mediated neuronal depolarization. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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Affiliation(s)
- David Bartolomé-Martín
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain; IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Ignacio Ibáñez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain; IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Dolores Piniella
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain; IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Elena Martínez-Blanco
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain; IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Sara G Pelaz
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain
| | - Francisco Zafra
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain; IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain.
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11
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Liu JJ, Hezghia A, Shaikh SR, Cenido JF, Stark RE, Mann JJ, Sublette ME. Regulation of monoamine transporters and receptors by lipid microdomains: implications for depression. Neuropsychopharmacology 2018; 43:2165-2179. [PMID: 30022062 PMCID: PMC6135777 DOI: 10.1038/s41386-018-0133-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 05/24/2018] [Accepted: 06/18/2018] [Indexed: 12/16/2022]
Abstract
Lipid microdomains ("rafts") are dynamic, nanoscale regions of the plasma membrane enriched in cholesterol and glycosphingolipids, that possess distinctive physicochemical properties including higher order than the surrounding membrane. Lipid microdomain integrity is thought to affect neurotransmitter signaling by regulating membrane-bound protein signaling. Among the proteins potentially affected are monoaminergic receptors and transporters. As dysfunction of monoaminergic neurotransmission is implicated in major depressive disorder and other neuropsychiatric conditions, interactions with lipid microdomains may be of clinical importance. This systematic review evaluates what is known about the molecular relationships of monoamine transporter and receptor regulation to lipid microdomains. The PubMed/MeSH database was searched for original studies published in English through August 2017 concerning relationships between lipid microdomains and serotonin, dopamine and norepinephrine transporters and receptors. Fifty-seven publications were identified and assessed. Strong evidence implicates lipid microdomains in the regulation of serotonin and norepinephrine transporters; serotonin 1A, 2A, 3A, and 7A receptors; and dopamine D1 and β2 adrenergic receptors. Results were conflicting or more complex regarding lipid microdomain associations with the dopamine transporter, D2, D3, and D5 receptors; and negative with respect to β1 adrenergic receptors. Indirect evidence suggests that antidepressants, lipid-lowering drugs, and polyunsaturated fatty acids may exert effects on depression and suicide by altering the lipid milieu, thereby affecting monoaminergic transporter and receptor signaling. The lipid composition of membrane subdomains is involved in localization and trafficking of specific monoaminergic receptors and transporters. Elucidating precise mechanisms whereby lipid microdomains modulate monoamine neurotransmission in clinical contexts can have critical implications for pharmacotherapeutic targeting.
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Affiliation(s)
- Joanne J Liu
- Department of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, New York, NY, USA
- Chestnut Hill Hospital, Philadelphia, PA, USA
| | - Adrienne Hezghia
- Department of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, New York, NY, USA
- Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, The State University of New York, Buffalo, NY, USA
| | - Saame Raza Shaikh
- Department of Nutrition, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Joshua F Cenido
- Department of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, New York, NY, USA
- Department of Psychiatry, Charles R. Drew University of Medicine and Science, Los Angeles, CA, USA
| | - Ruth E Stark
- Department of Chemistry and Biochemistry and CUNY Institute for Macromolecular Assemblies, The City College of New York, New York, NY, USA
- Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY, USA
| | - J John Mann
- Department of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, New York, NY, USA
- Department of Psychiatry, Columbia University, New York, NY, USA
- Department of Radiology, Columbia University, New York, NY, USA
| | - M Elizabeth Sublette
- Department of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, New York, NY, USA.
- Department of Psychiatry, Columbia University, New York, NY, USA.
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12
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Won JH, Kim SK, Shin IC, Ha HC, Jang JM, Back MJ, Kim DK. Dopamine transporter trafficking is regulated by neutral sphingomyelinase 2/ceramide kinase. Cell Signal 2018; 44:171-187. [DOI: 10.1016/j.cellsig.2018.01.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 12/18/2017] [Accepted: 01/07/2018] [Indexed: 12/13/2022]
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13
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Zhen J, Reith MEA. Functional properties of dopamine transporter oligomers after copper linking. J Neurochem 2017; 144:162-171. [PMID: 29168892 DOI: 10.1111/jnc.14259] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2017] [Revised: 10/29/2017] [Accepted: 11/02/2017] [Indexed: 12/13/2022]
Abstract
Although it is universally accepted that dopamine transporters (DATs) exist in monomers, dimers and tetramers (i.e. dimers of dimers), it is not known whether the oligomeric organization of DAT is a prerequisite for its ability to take up dopamine (DA), or whether each DAT protomer, the subunit of quaternary structure, functions independently in terms of DA translocation. In this study, copper phenanthroline (CuP) was used to selectively target surface DAT: increasing concentrations of CuP gradually cross-linked natural DAT dimers in LLC-PK1 cells stably expressing hDAT and thereby reduced DA uptake functionality until all surface DATs were inactivated. DATs that were not cross-linked by CuP showed normal DA uptake with DA Km at ~ 0.5 μM and DA efflux with basal and amphetamine-induced DA efflux as much as control values. The cocaine analog 2β-carbomethoxy-3β-[4-fluorophenyl]-tropane (CFT) was capable to bind to copper-cross-linked DATs, albeit with an affinity more than fivefold decreased (Kd of CFT = 109 nM after cross-linking vs 19 nM before). A kinetic analysis is offered describing the changing amounts of dimers and monomers with increasing [CuP], allowing the estimation of dimer functional activity compared with a DAT monomer. Consonant with previous conclusions for serotonin transporter and NET that only one protomer of an oligomer is active at the time, the present data indicated a functional activity of the DAT dimer of 0.74 relative to a monomer.
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Affiliation(s)
- Juan Zhen
- Department of Psychiatry, New York University School of Medicine, New York City, New York, USA
| | - Maarten E A Reith
- Department of Psychiatry, New York University School of Medicine, New York City, New York, USA.,Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York City, New York, USA
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14
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Perdikaris P, Tsarouchi M, Fanarioti E, Natsaridis E, Mitsacos A, Giompres P. Long lasting effects of chronic WIN55,212-2 treatment on mesostriatal dopaminergic and cannabinoid systems in the rat brain. Neuropharmacology 2017; 129:1-15. [PMID: 29113897 DOI: 10.1016/j.neuropharm.2017.11.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 10/16/2017] [Accepted: 11/03/2017] [Indexed: 01/14/2023]
Abstract
Cannabinoid administration modulates dopamine transmission via an indirect, multisynaptic mechanism that includes the activation of cannabinoid type-1 receptor (CB1R). The present study evaluated in rodents, the effects of acute and chronic (20 days) WIN55,212-2 administration, a non-selective CB1R agonist, on dopamine uptake and synthesis in the mesolimbic and nigrostriatal dopaminergic pathways and associate them to its effects on the endocannabinoid system. The effect of spontaneous withdrawal, after different abstinence periods (7 days, 20 days), was also assessed. Acute and chronic administration of WIN55,212-2 decreased dopamine transporter (DAT) binding and mRNA levels, as well as tyrosine hydroxylase (TH) mRNA expression in the substantia nigra (SN) and ventral tegmental area (VTA). In the striatum, chronic WIN55,212-2 administration led to decreased protein expression of DAT and TH, whereas no alterations were observed after acute administration, suggesting a diminished dopamine uptake and synthesis after chronic agonist treatment. Furthermore, after chronic agonist treatment, we observed reduced CB1R binding and mRNA levels in SN and striatum, providing evidence for a possible regulatory role of the endocannabinoid system on dopaminergic function. Seven days after WIN55,212-2 cessation, we observed a rebound increase in mRNA, binding and total protein levels of DAT and TH in VTA, SN and striatum proposing the existence of a biphasic expression pattern, which was also observed in CB1R binding levels. Within the 20-day period of abstinence, TH mRNA and protein levels and CB1R binding levels remain increased. The above results indicate that chronic CB1R agonist treatment induces long-lasting control of the mesostriatal dopaminergic activity.
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Affiliation(s)
- Panagiotis Perdikaris
- Laboratory of Human and Animal Physiology, Department of Biology, University of Patras, Patras, Greece
| | - Martha Tsarouchi
- Laboratory of Human and Animal Physiology, Department of Biology, University of Patras, Patras, Greece
| | - Eleni Fanarioti
- Laboratory of Human and Animal Physiology, Department of Biology, University of Patras, Patras, Greece
| | - Evangelos Natsaridis
- Laboratory of Human and Animal Physiology, Department of Biology, University of Patras, Patras, Greece
| | - Ada Mitsacos
- Laboratory of Physiology, Department of Medicine, University of Patras, Patras, Greece
| | - Panagiotis Giompres
- Laboratory of Human and Animal Physiology, Department of Biology, University of Patras, Patras, Greece.
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15
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Brodnik ZD, Ferris MJ, Jones SR, España RA. Reinforcing Doses of Intravenous Cocaine Produce Only Modest Dopamine Uptake Inhibition. ACS Chem Neurosci 2017; 8:281-289. [PMID: 27936579 DOI: 10.1021/acschemneuro.6b00304] [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] [Indexed: 01/14/2023] Open
Abstract
The reinforcing efficacy of cocaine is thought to stem from inhibition of the dopamine transporter (DAT) and subsequent increases in extracellular dopamine concentrations in the brain. In humans, this hypothesis has generally been supported by positron emission tomography imaging studies where the percent of DATs occupied by cocaine is used as a measure of cocaine activity in the brain. Interpretation of these studies, however, often relies on the assumption that measures of DAT occupancy directly correspond with functional DAT blockade. In the current studies, we used in vivo and in vitro fast scan cyclic voltammetry in mice to measure dopamine uptake inhibition following varying doses of cocaine as well as two high affinity DAT inhibitors. We then compared dopamine clearance rates following these drug treatments to dopamine clearance obtained from DAT knockout mice as a proxy for complete DAT blockade. We found that administration of abused doses of cocaine resulted in approximately 2% of maximal DAT blockade. Overall, our data indicate that abused doses of cocaine produce a relatively modest degree of DA uptake inhibition, and suggest that the relationship between DAT occupancy and functional blockade of the DAT is more complex than originally posited.
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Affiliation(s)
- Zachary D. Brodnik
- Department
of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129, United States
| | - Mark J. Ferris
- Department
of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27501, United States
| | - Sara R. Jones
- Department
of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27501, United States
| | - Rodrigo A. España
- Department
of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129, United States
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16
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Sulzer D, Cragg SJ, Rice ME. Striatal dopamine neurotransmission: regulation of release and uptake. ACTA ACUST UNITED AC 2016; 6:123-148. [PMID: 27141430 DOI: 10.1016/j.baga.2016.02.001] [Citation(s) in RCA: 236] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Dopamine (DA) transmission is governed by processes that regulate release from axonal boutons in the forebrain and the somatodendritic compartment in midbrain, and by clearance by the DA transporter, diffusion, and extracellular metabolism. We review how axonal DA release is regulated by neuronal activity and by autoreceptors and heteroreceptors, and address how quantal release events are regulated in size and frequency. In brain regions densely innervated by DA axons, DA clearance is due predominantly to uptake by the DA transporter, whereas in cortex, midbrain, and other regions with relatively sparse DA inputs, the norepinephrine transporter and diffusion are involved. We discuss the role of DA uptake in restricting the sphere of influence of DA and in temporal accumulation of extracellular DA levels upon successive action potentials. The tonic discharge activity of DA neurons may be translated into a tonic extracellular DA level, whereas their bursting activity can generate discrete extracellular DA transients.
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Affiliation(s)
- David Sulzer
- Depts of Psychiatry, Neurology, & Pharmacology, NY State Psychiatric Institute, Columbia University, New York, NY, USA
| | - Stephanie J Cragg
- Dept Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Margaret E Rice
- Depts of Neurosurgery & Neuroscience and Physiology, New York University School of Medicine, New York, NY, USA
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17
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Membrane potential shapes regulation of dopamine transporter trafficking at the plasma membrane. Nat Commun 2016; 7:10423. [PMID: 26804245 PMCID: PMC4737753 DOI: 10.1038/ncomms10423] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 12/09/2015] [Indexed: 12/17/2022] Open
Abstract
The dopaminergic system is essential for cognitive processes, including reward, attention and motor control. In addition to DA release and availability of synaptic DA receptors, timing and magnitude of DA neurotransmission depend on extracellular DA-level regulation by the dopamine transporter (DAT), the membrane expression and trafficking of which are highly dynamic. Data presented here from real-time TIRF (TIRFM) and confocal microscopy coupled with surface biotinylation and electrophysiology suggest that changes in the membrane potential alone, a universal yet dynamic cellular property, rapidly alter trafficking of DAT to and from the surface membrane. Broadly, these findings suggest that cell-surface DAT levels are sensitive to membrane potential changes, which can rapidly drive DAT internalization from and insertion into the cell membrane, thus having an impact on the capacity for DAT to regulate extracellular DA levels. The dopaminergic system has important roles in a number of cognitive process. Here, the authors use detailed analysis of dopamine transporter trafficking to show its levels at the cell surface are sensitive to changes in membrane potential.
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18
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Nikolaus S, Antke C, Hautzel H, Mueller HW. Pharmacological treatment with L-DOPA may reduce striatal dopamine transporter binding in in vivo imaging studies. Nuklearmedizin 2015; 55:21-8. [PMID: 26642370 DOI: 10.3413/nukmed-0764-15-08] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 11/20/2015] [Indexed: 11/20/2022]
Abstract
Numerous neurologic and psychiatric conditions are treated with pharmacological compounds, which lead to an increase of synaptic dopamine (DA) levels. One example is the DA precursor L-3,4-dihydroxyphenylalanine (L-DOPA), which is converted to DA in the presynaptic terminal. If the increase of DA concentrations in the synaptic cleft leads to competition with exogenous radioligands for presynaptic binding sites, this may have implications for DA transporter (DAT) imaging studies in patients under DAergic medication. This paper gives an overview on those findings, which, so far, have been obtained on DAT binding in human Parkinson's disease after treatment with L-DOPA. Findings, moreover, are related to results obtained on rats, mice or non-human primates. Results indicate that DAT imaging may be reduced in the striata of healthy animals, in the unlesioned striata of animal models of unilateral Parkinson's disease and in less severly impaired striata of Parkinsonian patients, if animal or human subjects are under acute or subchronic treatment with L-DOPA. If also striatal DAT binding is susceptible to alterations of synaptic DA levels, this may allow to quantify DA reuptake in analogy to DA release by assessing the competition between endogenous DA and the administered exogenous DAT radioligand.
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Affiliation(s)
- S Nikolaus
- Susanne Nikolaus, Clinic of Nuclear Medicine, University Hospital, Moorenstr. 5, 40225 Düsseldorf, Germany, Tel. +49/(0)211/811 70-48, Fax -41,
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19
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Insights in how amphetamine ROCKs (Rho-associated containing kinase) membrane protein trafficking. Proc Natl Acad Sci U S A 2015; 112:15538-9. [PMID: 26607447 DOI: 10.1073/pnas.1520960112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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20
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Diallinas G. Understanding transporter specificity and the discrete appearance of channel-like gating domains in transporters. Front Pharmacol 2014; 5:207. [PMID: 25309439 PMCID: PMC4162363 DOI: 10.3389/fphar.2014.00207] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 08/22/2014] [Indexed: 12/12/2022] Open
Abstract
Transporters are ubiquitous proteins mediating the translocation of solutes across cell membranes, a biological process involved in nutrition, signaling, neurotransmission, cell communication and drug uptake or efflux. Similarly to enzymes, most transporters have a single substrate binding-site and thus their activity follows Michaelis-Menten kinetics. Substrate binding elicits a series of structural changes, which produce a transporter conformer open toward the side opposite to the one from where the substrate was originally bound. This mechanism, involving alternate outward- and inward-facing transporter conformers, has gained significant support from structural, genetic, biochemical and biophysical approaches. Most transporters are specific for a given substrate or a group of substrates with similar chemical structure, but substrate specificity and/or affinity can vary dramatically, even among members of a transporter family that show high overall amino acid sequence and structural similarity. The current view is that transporter substrate affinity or specificity is determined by a small number of interactions a given solute can make within a specific binding site. However, genetic, biochemical and in silico modeling studies with the purine transporter UapA of the filamentous ascomycete Aspergillus nidulans have challenged this dogma. This review highlights results leading to a novel concept, stating that substrate specificity, but also transport kinetics and transporter turnover, are determined by subtle intramolecular interactions between a major substrate binding site and independent outward- or cytoplasmically-facing gating domains, analogous to those present in channels. This concept is supported by recent structural evidence from several, phylogenetically and functionally distinct transporter families. The significance of this concept is discussed in relationship to the role and potential exploitation of transporters in drug action.
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21
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Protein phosphatases but not reactive oxygen species play functional role in acute amphetamine-mediated dopamine release. Cell Biochem Biophys 2014; 66:831-41. [PMID: 23625176 DOI: 10.1007/s12013-013-9608-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Drug abuse-induced neurodegeneration can be triggered by elevated production of reactive oxygen species (ROS). Involvement of oxidative stress in acute amphetamine (AMPH)-mediated dopamine (DA) release, however, has not been completely understood yet. In order to elucidate the dopaminergic response of PC12 cells to a single dose of 10 μM AMPH, ROS production was measured as related to the extracellular DA level. Due to the spontaneous oxidation of peroxide-sensitive fluorophore 2',7'-dichlorofluorescin diacetate (DCFH-DA) to 2',7'-dichlorofluorescein (DCF), the increase in fluorescence could not be unambiguously attributed to AMPH-triggered ROS production. Based on Amplex Red fluorescence, no ROS production was detected after acute AMPH application. Our data strongly suggest that ROS development was not the main triggering factor for immediate DA release after acute AMPH treatment. On the other hand, AMPH-induced elevation of DA levels in rat brain striatal slices was quenched by the water soluble antioxidant, N-acetylcysteine (NAC) at 10 mM. In this study, we also investigated the contribution of protein phosphatases to the AMPH-induced rat brain striatal dopaminergic response. The experimental protocol, double AMPH challenge was applied for screening the effect of NAC and cantharidin on AMPH-mediated DA release. Here we show that AMPH-mediated DA release increased nearly twofold in striatal rat brain slices pretreated for 30 min with 1000 μM cantharidin, a selective PP1 and PP2A inhibitor. These findings prove the lack of ROS inhibitory action on protein phosphatase activity in acute AMPH-mediated DA efflux.
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22
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Jørgensen TN, Christensen PM, Gether U. Serotonin-induced down-regulation of cell surface serotonin transporter. Neurochem Int 2014; 73:107-12. [PMID: 24462583 DOI: 10.1016/j.neuint.2014.01.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 01/06/2014] [Accepted: 01/09/2014] [Indexed: 01/15/2023]
Abstract
The serotonin transporter (SERT) terminates serotonergic signaling and enables refilling of synaptic vesicles by mediating reuptake of serotonin (5-HT) released into the synaptic cleft. The molecular and cellular mechanisms controlling SERT activity and surface expression are not fully understood. Here we demonstrate that the substrate 5-HT itself causes acute down-regulation of SERT cell surface expression. To assess surface SERT expression by ELISA, we used a SERT variant (TacSERT) where the N-terminus of SERT was fused to the intracellular tail of the extracellularly FLAG-tagged single-membrane spanning protein Tac. In stably transfected HEK293 cells, 5-HT caused a dose-dependent reduction in TacSERT surface signal with an EC50 value equivalent to the Km value observed for 5-HT uptake. The 5-HT-induced reduction in surface signal reached maximum within 40-60min and was blocked by the selective SERT inhibitor S-citalopram. 5-HT-induced reduction in SERT expression was further supported by surface biotinylation experiments showing 5-HT-induced reduction in wild type SERT plasma membrane levels. Moreover, preincubation with 5-HT lowered the Vmax for 5-HT uptake in cultured raphe serotonergic neurons, indicting that endogenous cell-surface resident SERT likewise is down-regulated in the presence of substrate.
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Affiliation(s)
- Trine Nygaard Jørgensen
- Molecular Neuropharmacology Laboratory, Department of Neuroscience and Pharmacology, The Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Peter Møller Christensen
- Molecular Neuropharmacology Laboratory, Department of Neuroscience and Pharmacology, The Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Ulrik Gether
- Molecular Neuropharmacology Laboratory, Department of Neuroscience and Pharmacology, The Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark.
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23
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Kivell BM, Ewald AWM, Prisinzano TE. Salvinorin A analogs and other κ-opioid receptor compounds as treatments for cocaine abuse. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2014; 69:481-511. [PMID: 24484985 DOI: 10.1016/b978-0-12-420118-7.00012-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Acute activation of kappa-opioid receptors produces anti-addictive effects by regulating dopamine levels in the brain. Unfortunately, classic kappa-opioid agonists have undesired side effects such as sedation, aversion, and depression, which restrict their clinical use. Salvinorin A (Sal A), a novel kappa-opioid receptor agonist extracted from the plant Salvia divinorum, has been identified as a potential therapy for drug abuse and addiction. Here, we review the preclinical effects of Sal A in comparison with traditional kappa-opioid agonists and several new analogs. Sal A retains the anti-addictive properties of traditional kappa-opioid receptor agonists with several improvements including reduced side effects. However, the rapid metabolism of Sal A makes it undesirable for clinical development. In an effort to improve the pharmacokinetics and tolerability of this compound, kappa-opioid receptor agonists based on the structure of Sal A have been synthesized. While work in this field is still in progress, several analogs with improved pharmacokinetic profiles have been shown to have anti-addictive effects. While in its infancy, it is clear that these compounds hold promise for the future development of anti-addictive therapeutics.
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Affiliation(s)
- Bronwyn M Kivell
- School of Biological Sciences, Centre for Biodiscovery, Victoria University of Wellington, Wellington, New Zealand
| | - Amy W M Ewald
- School of Biological Sciences, Centre for Biodiscovery, Victoria University of Wellington, Wellington, New Zealand
| | - Thomas E Prisinzano
- Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas, USA.
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24
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Monoamine transporter inhibitors and substrates as treatments for stimulant abuse. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2014; 69:129-76. [PMID: 24484977 DOI: 10.1016/b978-0-12-420118-7.00004-4] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The acute and chronic effects of abused psychostimulants on monoamine transporters and associated neurobiology have encouraged development of candidate medications that target these transporters. Monoamine transporters, in general, and dopamine transporters, in particular, are critical molecular targets that mediate abuse-related effects of psychostimulants such as cocaine and amphetamine. Moreover, chronic administration of psychostimulants can cause enduring changes in neurobiology reflected in dysregulation of monoamine neurochemistry and behavior. The current review will evaluate evidence for the efficacy of monoamine transporter inhibitors and substrates to reduce abuse-related effects of stimulants in preclinical assays of stimulant self-administration, drug discrimination, and reinstatement. In considering deployment of monoamine transport inhibitors and substrates as agonist-type medications to treat stimulant abuse, the safety and abuse liability of the medications are an obvious concern, and this will also be addressed. Future directions in drug discovery should identify novel medications that retain efficacy to decrease stimulant use but possess lower abuse liability and evaluate the degree to which efficacious medications can attenuate or reverse neurobiological effects of chronic stimulant use.
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25
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Rickhag M, Hansen FH, Sørensen G, Strandfelt KN, Andresen B, Gotfryd K, Madsen KL, Vestergaard-Klewe I, Ammendrup-Johnsen I, Eriksen J, Newman AH, Füchtbauer EM, Gomeza J, Woldbye DPD, Wörtwein G, Gether U. A C-terminal PDZ domain-binding sequence is required for striatal distribution of the dopamine transporter. Nat Commun 2013; 4:1580. [PMID: 23481388 PMCID: PMC3646413 DOI: 10.1038/ncomms2568] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 01/31/2013] [Indexed: 01/27/2023] Open
Abstract
The dopamine transporter (DAT) mediates reuptake of dopamine from the synaptic cleft. The cellular mechanisms controlling DAT levels in striatal nerve terminals remain poorly understood. DAT contains a C-terminal PDZ (PSD-95/Discs-large/ZO-1) domain binding sequence believed to bind synaptic scaffolding proteins, but its functional significance is uncertain. Here we demonstrate that two different DAT knock-in mice with disrupted PDZ-binding motifs (DAT-AAA and DAT+Ala) are characterized by dramatic loss of DAT expression in the striatum, causing hyperlocomotion and attenuated response to amphetamine. In cultured dopaminergic neurons and striatal slices from DAT-AAA mice, we find markedly reduced DAT surface levels and evidence for enhanced constitutive internalization. In DAT-AAA neurons, but not in wild type neurons, surface levels are rescued in part by expression of a dominant-negative dynamin mutation (K44A). Our findings suggest that PDZ domain interactions are critical for synaptic distribution of DAT in vivo and thereby for proper maintenance of dopamine homeostasis.
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Affiliation(s)
- Mattias Rickhag
- Molecular Neuropharmacology Laboratory, Lundbeck Foundation Center for Biomembranes in Nanomedicine, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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26
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Hong WC, Amara SG. Differential targeting of the dopamine transporter to recycling or degradative pathways during amphetamine- or PKC-regulated endocytosis in dopamine neurons. FASEB J 2013; 27:2995-3007. [PMID: 23612789 DOI: 10.1096/fj.12-218727] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The dopamine transporter (DAT) clears the extracellular dopamine released during neurotransmission and is a major target for both therapeutic and addictive psychostimulant amphetamines. Amphetamine exposure or activation of protein kinase C (PKC) by the phorbol ester PMA has been shown to down-regulate cell surface DAT. However, in dopamine neurons, the trafficking itinerary and fate of internalized DAT has not been elucidated. By monitoring surface-labeled DAT in transfected dopamine neurons from embryonic rat mesencephalic cultures, we find distinct sorting and fates of internalized DAT after amphetamine or PMA treatment. Although both drugs promote DAT internalization above constitutive endocytosis in dopamine neurons, PMA induces ubiquitination of DAT and leads to accumulation of DAT on LAMP1-positive endosomes. In contrast, after amphetamine exposure DAT is sorted to recycling endosomes positive for Rab11 and the transferrin receptor. Furthermore, quantitative assessment of DAT recycling using an antibody-feeding assay reveals that significantly less DAT returns to the surface of dopamine neurons after internalization by PMA, compared with vehicle or amphetamine treatment. These results demonstrate that, in neurons, the DAT is sorted differentially to recycling and degradative pathways after psychostimulant exposure or PKC activation, which may allow for either the transient or sustained inhibition of DAT during dopamine neurotransmission.
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Affiliation(s)
- Weimin C Hong
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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Keith DJ, Wolfrum K, Eshleman AJ, Janowsky A. Melittin initiates dopamine transporter internalization and recycling in transfected HEK-293 cells. Eur J Pharmacol 2012; 690:13-21. [PMID: 22683840 DOI: 10.1016/j.ejphar.2012.05.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Revised: 05/02/2012] [Accepted: 05/15/2012] [Indexed: 12/26/2022]
Abstract
The dopamine transporter removes the neurotransmitter from the synapse, regulating dopamine availability. The transporter can be internalized and its function is blocked by cocaine and other ligands. Melittin inhibits dopamine transporter function and causes internalization of the recombinant transporter in stably transfected HEK-293 cells, but the specific pathways for internalization and disposition of the transporter are unknown. Here we report that melittin treatment increased both transporter internalization and colocalization with clathrin, effects that were blocked by pretreatment with cocaine. Density gradient centrifugation revealed that melittin treatment caused the dopamine transporter to associate with a density fraction containing the early endosome marker Rab 5A. Confocal microscopy revealed that melittin treatment also increased transporter colocalization with Rab 5A and decreased colocalization with the late endosome marker Rab 7 and the recycling endosome marker Rab 11. Following 60 min of melittin treatment, the transporter was trafficked back to the membrane. By comparison, phorbol ester treatment increased transporter colocalization with early endosome antigen 1 and Rab 7 in a time-dependent manner. Cocaine treatment alone does not affect transporter trafficking in these cells. Results indicate multiple dopamine transporter internalization and recycling pathways that depend on transporter-ligand interactions and post-translational modifications.
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Affiliation(s)
- Dove J Keith
- Graduate Program in Neuroscience, VA Medical Center, Portland, OR 97239, USA
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28
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HIV-1 Tat protein decreases dopamine transporter cell surface expression and vesicular monoamine transporter-2 function in rat striatal synaptosomes. J Neuroimmune Pharmacol 2012; 7:629-39. [PMID: 22570010 DOI: 10.1007/s11481-012-9369-9] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 04/16/2012] [Indexed: 12/13/2022]
Abstract
The dopamine (DA) transporter (DAT) and vesicular monoamine transporter (VMAT2) proteins interact as a biochemical complex to regulate dopaminergic neurotransmission. We have reported that HIV-1Tat(1-86) decreases the specific [(3)H]DA uptake and [(3)H]WIN 35,428 binding sites without a change in total DAT immunoreactivity in rat striatum (Zhu et al., 2009b). The present study determined the effects of Tat on DAT phosphorylation and trafficking, and vesicular [(3)H]DA uptake. Pre-incubation of rat striatal synaptosomes with the protein kinase C (PKC) inhibitor bisindolylmaleimide I (1 μM) completely blocked Tat(1-86)-induced reduction of [(3)H]DA uptake, indicating that Tat regulates DAT function through a PKC-dependent mechanism. After exposure of synaptosomes to Tat(1-86) (1 μM), DAT immunoreactivity was decreased in plasma membrane enriched fractions (P3) and increased in vesicle-enriched fractions (P4) relative to controls without change in total synaptosomal fractions (P2), suggesting that Tat-induced inhibition of DA uptake is attributable to DAT internalization. Although both DAT and VMAT2 proteins are essential for the regulation of DA disposition in synapse and cytosol, Tat inhibited the specific [(3)H]DA uptake into vesicles (P4) and synaptosomes (P2) by 35 % and 26 %, respectively, inferring that the inhibitory effect of Tat was more profound in VMAT2 protein than in DAT protein. Taken together, the current study reveals that Tat inhibits DAT function through a PKC and trafficking-dependent mechanism and that Tat impacts the dopaminergic tone by regulating both DAT and VMAT2 proteins. These findings provide new insight into understanding the pharmacological mechanisms of HIV-1 viral protein-induced dysfunction of DA neurotransmission in HIV-infected patients.
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Kimmel HL, Nye JA, Voll R, Mun J, Stehouwer J, Goodman MM, Votaw JR, Carroll FI, Howell LL. Simultaneous measurement of extracellular dopamine and dopamine transporter occupancy by cocaine analogs in squirrel monkeys. Synapse 2012; 66:501-8. [PMID: 22237864 DOI: 10.1002/syn.21536] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 12/31/2011] [Indexed: 11/09/2022]
Abstract
Several classes of drugs bind to the dopamine transporter (DAT) with high affinity, but some are weaker positive reinforcers than cocaine, suggesting that affinity for and occupancy of the DAT is not the only determinant of a drug's reinforcing effectiveness. Other factors such as the rate of onset have been positively and strongly correlated with the reinforcing effects of DAT inhibitors in nonhuman primates. In the current studies, we examined the effects of acute systemic administration of cocaine and three cocaine analogs (RTI-150, RTI-177, and RTI-366) on binding to DAT in squirrel monkey brain using positron emission tomography (PET) neuroimaging. During the PET scan, we also measured drug effects on dopamine (DA) levels in the caudate using in vivo microdialysis. In general, our results suggest a lack of concordance between drug occupancy at DAT and changes in DA levels. These studies also indicate that acute cocaine administration decreases the availability of plasma membrane DAT for binding, even after cocaine is no longer blocking DA uptake as evidence by a return to basal DA levels.
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Affiliation(s)
- Heather L Kimmel
- Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia 30329, USA.
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30
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Abstract
Cholinergic neurons are endowed with a high-affinity choline uptake system for efficient synthesis of acetylcholine at the presynaptic terminals. The high-affinity choline transporter CHT1 is responsible for choline uptake, the rate-limiting step in acetylcholine synthesis. However, endogenous physiological factors that affect CHT1 expression or function and consequently regulate the acetylcholine synthesis rate are essentially unknown. Here we demonstrate that extracellular substrate decreases the cell-surface expression of CHT1 in rat brain synaptosomes, primary cultures from the basal forebrain, and mammalian cell lines transfected with CHT1. Extracellular choline rapidly decreases cell-surface CHT1 expression by accelerating its internalization, a process that is mediated by a dynamin-dependent endocytosis pathway in HEK293 cells. Specific inhibitor hemicholinium-3 decreases the constitutive internalization rate and thereby increases cell-surface CHT1 expression. We also demonstrate that the constitutive internalization of CHT1 depends on extracellular pH in cultured cells. Our results collectively suggest that the internalization of CHT1 is induced by extracellular substrate, providing a novel feedback mechanism for the regulation of acetylcholine synthesis at the cholinergic presynaptic terminals.
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31
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Vargas-Medrano J, Castrejon-Tellez V, Plenge F, Ramirez I, Miranda M. PKCβ-dependent phosphorylation of the glycine transporter 1. Neurochem Int 2011; 59:1123-32. [PMID: 21864610 DOI: 10.1016/j.neuint.2011.08.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 08/01/2011] [Accepted: 08/05/2011] [Indexed: 10/17/2022]
Abstract
The extracellular levels of the neurotransmitter glycine in the brain are tightly regulated by the glycine transporter 1 (GlyT1) and the clearance rate for glycine depends on its rate of transport and the levels of cell surface GlyT1. Over the years, it has been shown that PKC tightly regulates the activity of several neurotransmitter transporters. In the present work, by stably expressing three N-terminus GlyT1 isoforms in porcine aortic endothelial cells and assaying for [(32)P]-orthophosphate metabolic labeling, we demonstrated that the isoforms GlyT1a, GlyT1b, and GlyT1c were constitutively phosphorylated, and that phosphorylation was dramatically enhanced, in a time dependent fashion, after PKC activation by phorbol ester. The phosphorylation was PKC-dependent, since pre-incubation of the cells with bisindolylmaleimide I, a selective PKC inhibitor, abolished the phorbol ester-induced phosphorylation. Blotting with specific anti-phospho-tyrosine antibodies did not yield any signal that could correspond to GlyT1 tyrosine phosphorylation, suggesting that the phosphorylation occurs at serine and/or threonine residues. In addition, a 23-40%-inhibition on V(max) was obtained by incubation with phorbol ester without a significant change on the apparent Km value. Furthermore, pre-incubation of the cells with the selective PKCα/β inhibitor Gö6976 abolished the downregulation effect of phorbol ester on uptake and phosphorylation, whereas the selective PKCβ inhibitors (PKCβ inhibitor or LY333531) prevented the phosphorylation without affecting glycine uptake, defining a specific role of classical PKC on GlyT1 uptake and phosphorylation. Taken together, these data suggest that conventional PKCα/β regulates the uptake of glycine, whereas PKCβ is responsible for GlyT1 phosphorylation.
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Affiliation(s)
- Javier Vargas-Medrano
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX 79968, USA
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32
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Sager JJ, Torres GE. Proteins interacting with monoamine transporters: current state and future challenges. Biochemistry 2011; 50:7295-310. [PMID: 21797260 DOI: 10.1021/bi200405c] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Plasma membrane and vesicular transporters for the biogenic amines, dopamine, norepinephrine, and serotonin, represent a group of proteins that play a crucial role in the regulation of neurotransmission. Clinically, mono amine transporters are the primary targets for the actions of many therapeutic agents used to treat mood disorders, as well as the site of action for highly addictive psychostimulants such as cocaine, amphetamine, methamphetamine, and 3,4-methylenedioxymethamphetamine. Over the past decade, the use of approaches such as yeast two-hybrid and proteomics has identified a multitude of transporter interacting proteins, suggesting that the function and regulation of these transporters are more complex than previously anticipated. With the increasing number of interacting proteins, the rules dictating transporter synthesis, assembly, targeting, trafficking, and function are beginning to be deciphered. Although many of these protein interactions have yet to be fully characterized, current knowledge is beginning to shed light on novel transporter mechanisms involved in monoamine homeostasis, the molecular actions of psychostimulants, and potential disease mechanisms. While future studies resolving the spatial and temporal resolution of these, and yet unknown, interactions will be needed, the realization that monoamine transporters do not work alone opens the path to a plethora of possible pharmacological interventions.
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Affiliation(s)
- Jonathan J Sager
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
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Zhu J, Bardo MT, Green TA, Wedlund PJ, Dwoskin LP. Nicotine increases dopamine clearance in medial prefrontal cortex in rats raised in an enriched environment. J Neurochem 2011; 103:2575-88. [PMID: 17953677 DOI: 10.1111/j.1471-4159.2007.04951.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Environmental enrichment results in differential behavioral and neurochemical responsiveness to nicotine. The present study investigates dopamine clearance (CL(DA) ) in striatum and medial prefrontal cortex (mPFC) using in vivo voltammetry in rats raised in enriched (EC) or impoverished conditions (IC) and administered nicotine (0.4 mg/kg) or saline. Baseline CL(DA) in striatum or mPFC was not different between EC and IC. Across repeated DA application, striatal CL(DA) increased in saline-control EC and IC. CL(DA) increased in mPFC in saline-control IC; CL(DA) did not change in saline-control EC. Thus, enrichment differentially alters dynamic responses of the dopamine transporter (DAT) to repeated DA application in mPFC, but not in striatum. In EC, nicotine increased mPFC CL(DA) compared to saline-control, but had no effect on CL(DA) in IC; nicotine had no effect in striatum in EC or IC. Compared to respective saline-controls, nicotine increased dihydroxyphenylacetic acid content in striatum and mPFC in EC, but not in IC. Nicotine also had no effect on DA content in striatum or mPFC in EC or IC. Results indicate that enrichment eliminated the dynamic response of mPFC DAT to repeated DA application in saline-control and augmented the nicotine-induced increase in DAT function in mPFC, but not in striatum.
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Affiliation(s)
- Jun Zhu
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky, USA
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34
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Kristensen AS, Andersen J, Jørgensen TN, Sørensen L, Eriksen J, Loland CJ, Strømgaard K, Gether U. SLC6 neurotransmitter transporters: structure, function, and regulation. Pharmacol Rev 2011; 63:585-640. [PMID: 21752877 DOI: 10.1124/pr.108.000869] [Citation(s) in RCA: 591] [Impact Index Per Article: 45.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The neurotransmitter transporters (NTTs) belonging to the solute carrier 6 (SLC6) gene family (also referred to as the neurotransmitter-sodium-symporter family or Na(+)/Cl(-)-dependent transporters) comprise a group of nine sodium- and chloride-dependent plasma membrane transporters for the monoamine neurotransmitters serotonin (5-hydroxytryptamine), dopamine, and norepinephrine, and the amino acid neurotransmitters GABA and glycine. The SLC6 NTTs are widely expressed in the mammalian brain and play an essential role in regulating neurotransmitter signaling and homeostasis by mediating uptake of released neurotransmitters from the extracellular space into neurons and glial cells. The transporters are targets for a wide range of therapeutic drugs used in treatment of psychiatric diseases, including major depression, anxiety disorders, attention deficit hyperactivity disorder and epilepsy. Furthermore, psychostimulants such as cocaine and amphetamines have the SLC6 NTTs as primary targets. Beginning with the determination of a high-resolution structure of a prokaryotic homolog of the mammalian SLC6 transporters in 2005, the understanding of the molecular structure, function, and pharmacology of these proteins has advanced rapidly. Furthermore, intensive efforts have been directed toward understanding the molecular and cellular mechanisms involved in regulation of the activity of this important class of transporters, leading to new methodological developments and important insights. This review provides an update of these advances and their implications for the current understanding of the SLC6 NTTs.
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Affiliation(s)
- Anders S Kristensen
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Copenhagen, Denmark.
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35
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Abstract
Spontaneous and/or stimulated neural activity of the nigrostriatal dopamine (DA) pathway makes amines run out from the neurons. This DA dynamic follows a rather complex path, running in or out the terminals, and flushing or diffusing into the extracellular space. The location of this leakage is not limited to the axon terminals; it also occurs from the cell bodies and dendrites. This molecular release mechanism was, for a long time, considered as being produced, in part, by the exocytosis of previously stored vesicles. The DA carrier protein (DAT, DA transporter) embedded in the DA cell membrane is known to clear previously released amines through an inward DA influx. The DAT also appears to be an active vector of amine release. Particular local conditions and the presence of numerous psychostimulant substances are able to trigger an outward efflux of DA through the DAT. This process, delivering slowly large amounts of amine could play a major regulatory role in extracellular DA homeostasis.
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Affiliation(s)
- Vincent Leviel
- INSERM U846, Stem Cell and Brain Research Institute, Bron, France.
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36
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Mannangatti P, Arapulisamy O, Shippenberg TS, Ramamoorthy S, Jayanthi LD. Cocaine up-regulation of the norepinephrine transporter requires threonine 30 phosphorylation by p38 mitogen-activated protein kinase. J Biol Chem 2011; 286:20239-50. [PMID: 21498515 DOI: 10.1074/jbc.m111.226811] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The norepinephrine (NE) transporter (NET) regulates NE signaling by rapidly clearing synaptic NE. Cocaine binds NET and modulates NE transport. These actions contribute to rewarding effects and abuse liability of cocaine. Activation of mitogen-activated protein kinase (MAPK) cascades is implicated in cocaine-induced neuroadaptations. However, the role of MAPK and the mechanisms involved in cocaine modulation of NET are not clear. Acute intra-peritoneal injections of cocaine (20 mg/kg body weight) to rats resulted in increased NE uptake by prefrontal cortex (PFC) synaptosomes with a parallel increase in the surface expression of endogenous NET. Cocaine also enhanced the immunoreactivity of phospho-p38 MAPK in the PFC synaptosomes without affecting the total p38 MAPK. In vitro cocaine (30-50 μM) treatment of rat PFC synaptosomes increased native NET function, surface expression, and phosphorylation in a manner sensitive to p38 MAPK inhibition by PD169316. We next examined cocaine-elicited effects on wild-type human NET (hNET) expressed heterologously in human placental trophoblast cells to gain more insights into the mechanisms involved. Cocaine treatment of hNET expressing human placental trophoblast cells up-regulated the function, surface expression, and phosphorylation of hNET in a PD169316-sensitive manner. In addition, cocaine inhibited constitutive endocytosis of hNET. Mutational analysis of serine and threonine residues revealed that substitution of threonine 30, located at the amino terminus of hNET with alanine (T30A-hNET), abolished cocaine-induced up-regulation of NET function, surface expression, and phosphorylation. Furthermore, cocaine did not alter T30A-hNET endocytosis. These studies identify a novel molecular mechanism that cocaine-activated p38 MAPK-mediated phosphorylation of NET-T30 dictates surface NET availability, and hence, NE transport.
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Affiliation(s)
- Padmanabhan Mannangatti
- Department of Neurosciences, Division of Neuroscience Research, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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37
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Is slow-onset long-acting monoamine transport blockade to cocaine as methadone is to heroin? Implication for anti-addiction medications. Neuropsychopharmacology 2010; 35:2564-78. [PMID: 20827272 PMCID: PMC2978747 DOI: 10.1038/npp.2010.133] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The success of methadone in treating opiate addiction has suggested that long-acting agonist therapies may be similarly useful for treating cocaine addiction. Here, we examined this hypothesis, using the slow-onset long-acting monoamine reuptake inhibitor 31,345, a trans-aminotetralin analog, in a variety of addiction-related animal models, and compared it with methadone's effects on heroin's actions in the same animal models. Systemic administration of 31,345 produced long-lasting enhancement of electrical brain-stimulation reward (BSR) and extracellular nucleus accumbens (NAc) dopamine (DA). Pretreatment with 31,345 augmented cocaine-enhanced BSR, prolonged cocaine-enhanced NAc DA, and produced a long-term (24-48 h) reduction in cocaine self-administration rate without obvious extinction pattern, suggesting an additive effect of 31,345 with cocaine. In contrast, methadone pretreatment not only dose-dependently inhibited heroin self-administration with an extinction pattern but also dose-dependently inhibited heroin-enhanced BSR and NAc DA, suggesting functional antagonism by methadone of heroin's actions. In addition, 31,345 appears to possess significant abuse liability, as it produces dose-dependent enhancement of BSR and NAc DA, maintains a low rate of self-administration behavior, and dose-dependently reinstates drug-seeking behavior. In contrast, methadone only partially maintains self-administration with an extinction pattern, and fails to induce reinstatement of drug-seeking behavior. These findings suggest that 31,345 is a cocaine-like slow-onset long-acting monoamine transporter inhibitor that may act as an agonist therapy for cocaine addiction. However, its pattern of action appears to be significantly different from that of methadone. Ideal agonist substitutes for cocaine should fully emulate methadone's actions, that is, functionally antagonizing cocaine's action while blocking monoamine transporters to augment synaptic DA.
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38
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Foster JD, Vaughan RA. Palmitoylation controls dopamine transporter kinetics, degradation, and protein kinase C-dependent regulation. J Biol Chem 2010; 286:5175-86. [PMID: 21118819 DOI: 10.1074/jbc.m110.187872] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Palmitoylation is a lipid modification that confers diverse functions to target proteins and is a contributing factor for many neuronal diseases. In this study, we demonstrate using [(3)H]palmitic acid labeling and acyl-biotinyl exchange that native and expressed dopamine transporters (DATs) are palmitoylated, and using the palmitoyl acyltransferase inhibitor 2-bromopalmitate (2BP), we identify several associated functions. Treatment of rat striatal synaptosomes with 2BP using lower doses or shorter times caused robust inhibition of transport V(max) that occurred with no losses of DAT protein or changes in DAT surface levels, indicating that acute loss of palmitoylation leads to reduction of transport kinetics. Treatment of synaptosomes or cells with 2BP using higher doses or longer times resulted in DAT protein losses and production of transporter fragments, implicating palmitoylation in regulation of transporter degradation. Site-directed mutagenesis indicated that palmitoylation of rat DAT occurs at Cys-580 at the intracellular end of transmembrane domain 12 and at one or more additional unidentified site(s). Cys-580 mutation also led to production of transporter degradation fragments and to increased phorbol ester-induced down-regulation, further supporting palmitoylation in opposing DAT turnover and in opposing protein kinase C-mediated regulation. These results identify S-palmitoylation as a major regulator of DAT properties that could significantly impact acute and long term dopamine transport capacity.
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Affiliation(s)
- James D Foster
- Department of Biochemistry and Molecular Biology, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58202-9037, USA
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39
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Ramamoorthy S, Shippenberg TS, Jayanthi LD. Regulation of monoamine transporters: Role of transporter phosphorylation. Pharmacol Ther 2010; 129:220-38. [PMID: 20951731 DOI: 10.1016/j.pharmthera.2010.09.009] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Accepted: 09/24/2010] [Indexed: 10/18/2022]
Abstract
Presynaptic biogenic amine transporters mediate reuptake of released amines from the synapse, thus regulating serotonin, dopamine and norepinephrine neurotransmission. Medications utilized in the treatment of depression, attention deficit-hyperactivity disorder and other psychiatric disorders possess high affinity for amine transporters. In addition, amine transporters are targets for psychostimulants. Altered expression of biogenic amine transporters has long been implicated in several psychiatric and degenerative disorders. Therefore, appropriate regulation and maintenance of biogenic amine transporter activity is critical for the maintenance of normal amine homoeostasis. Accumulating evidence suggests that cellular protein kinases and phosphatases regulate amine transporter expression, activity, trafficking and degradation. Amine transporters are phosphoproteins that undergo dynamic control under the influence of various kinase and phosphatase activities. This review presents a brief overview of the role of amine transporter phosphorylation in the regulation of amine transport in the normal and diseased brain. Understanding the molecular mechanisms by which phosphorylation events affect amine transporter activity is essential for understanding the contribution of transporter phosphorylation to the regulation of monoamine neurotransmission and for identifying potential new targets for the treatment of various brain diseases.
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Affiliation(s)
- Sammanda Ramamoorthy
- Department of Neurosciences, Division of Neuroscience Research, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
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40
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Differential subcellular distribution of endosomal compartments and the dopamine transporter in dopaminergic neurons. Mol Cell Neurosci 2010; 46:148-58. [PMID: 20816972 DOI: 10.1016/j.mcn.2010.08.016] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Revised: 08/19/2010] [Accepted: 08/26/2010] [Indexed: 12/26/2022] Open
Abstract
Dopamine (DA) transporter (DAT) functions at the surface of dopaminergic neurons to clear extracellular DA. DAT surface levels are regulated by endocytosis. However, the endosome-lysosome system is not well characterized in dopaminergic neurons and the endocytic trafficking of endogenous DAT is poorly studied. Hence we analyzed the distribution of endocytic compartments and DAT localization in cultured rat embryonic and postnatal neurons using fluorescence microscopy. Early Rab5 and EEA.1 containing endosomes were mostly found in somatodendritic regions of neurons, whereas endosomes containing recycling markers were primarily found in axons. In axons, DAT was located mainly in recycling endosomes and plasma membrane whereas in cell bodies and dendrites DAT was detected in early, late and recycling endosomal compartments. Subcellular fractionation of adult rat striatal synaptosomes demonstrated that DAT is enriched in fractions containing plasma membrane and recycling endosomes. This pattern of DAT distribution was not altered upon activation of protein kinase C in postnatal DA neurons. Altogether, our data suggest that axonal DAT mainly shuttles between the plasma membrane and recycling endosomes, whereas in the somatodendritic region of neurons DAT traffics through all conventional endosomal pathways.
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41
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Cervinski MA, Foster JD, Vaughan RA. Syntaxin 1A regulates dopamine transporter activity, phosphorylation and surface expression. Neuroscience 2010; 170:408-16. [PMID: 20643191 DOI: 10.1016/j.neuroscience.2010.07.025] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2009] [Revised: 06/15/2010] [Accepted: 07/13/2010] [Indexed: 10/19/2022]
Abstract
We investigated the functional relationship between the soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) protein syntaxin 1A (syn 1A) and the dopamine transporter (DAT) by treating rat striatal tissue with Botulinum Neurotoxin C (BoNT/C) and co-transfecting syn 1A with DAT in non-neuronal cells, followed by analysis of DAT activity, phosphorylation, and regulation. Treatment of striatal slices with BoNT/C resulted in elevated dopamine (DA) transport Vmax and reduced DAT phosphorylation, while heterologous co-expression of syn 1A led to reduction in DAT surface expression and transport Vmax. Syn 1A was present in DAT immunoprecipitation complexes, supporting a direct or indirect interaction between the proteins. Phorbol ester regulation of DA transport activity was retained in BoNT/C-treated synaptosomes and syn 1A transfected cells, demonstrating that protein kinase C (PKC) and syn 1A effects occur through independent processes. These findings reveal a novel mechanism for regulation of DAT activity and phosphorylation, and suggest the potential for syn 1A to impact DA neurotransmission through effects on reuptake.
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Affiliation(s)
- M A Cervinski
- Department of Biochemistry and Molecular Biology, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58203, USA
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42
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Eriksen J, Bjørn-Yoshimoto WE, Jørgensen TN, Newman AH, Gether U. Postendocytic sorting of constitutively internalized dopamine transporter in cell lines and dopaminergic neurons. J Biol Chem 2010; 285:27289-27301. [PMID: 20551317 DOI: 10.1074/jbc.m110.131003] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The dopamine transporter (DAT) mediates reuptake of released dopamine and is the target for psychostimulants, such as cocaine and amphetamine. DAT undergoes marked constitutive endocytosis, but little is known about the fate and sorting of the endocytosed transporter. To study DAT sorting in cells lines, we fused the one-transmembrane segment protein Tac to DAT, thereby generating a transporter (TacDAT) with an extracellular antibody epitope suited for trafficking studies. TacDAT was functional and endocytosed constitutively in HEK293 cells. According to an ELISA-based assay, TacDAT intracellular accumulation was increased by the lysosomal protease inhibitor leupeptin and by monensin, an inhibitor of lysosomal degradation and recycling. Monensin also reduced TacDAT surface expression consistent with partial recycling. In both HEK293 cells and in the dopaminergic cell line 1Rb3An27, constitutively internalized TacDAT displayed primary co-localization with the late endosomal marker Rab7, less co-localization with the "short loop" recycling marker Rab4, and little co-localization with the marker of "long loop" recycling endosomes, Rab11. Removal by mutation of N-terminal ubiquitination sites did not affect this sorting pattern. The sorting pattern was distinct from a bona fide recycling membrane protein, the beta(2)-adrenergic receptor, that co-localized primarily with Rab11 and Rab4. Constitutively internalized wild type DAT probed with the fluorescently tagged cocaine analogue JHC 1-64, exhibited the same co-localization pattern as TacDAT in 1Rb3An27 cells and in cultured midbrain dopaminergic neurons. We conclude that DAT is constitutively internalized and sorted in a ubiquitination-independent manner to late endosomes/lysosomes and in part to a Rab4 positive short loop recycling pathway.
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Affiliation(s)
- Jacob Eriksen
- Molecular Neuropharmacology Group and Center for Pharmacogenomics, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, Panum Institute, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Walden Emil Bjørn-Yoshimoto
- Molecular Neuropharmacology Group and Center for Pharmacogenomics, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, Panum Institute, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Trine Nygaard Jørgensen
- Molecular Neuropharmacology Group and Center for Pharmacogenomics, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, Panum Institute, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Amy Hauck Newman
- Medicinal Chemistry Section, Intramural Research Program, National Institute on Drug Abuse, Baltimore, Maryland 21224
| | - Ulrik Gether
- Molecular Neuropharmacology Group and Center for Pharmacogenomics, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, Panum Institute, University of Copenhagen, DK-2200 Copenhagen, Denmark.
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43
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Schmitt KC, Reith MEA. Regulation of the dopamine transporter: aspects relevant to psychostimulant drugs of abuse. Ann N Y Acad Sci 2010; 1187:316-40. [PMID: 20201860 DOI: 10.1111/j.1749-6632.2009.05148.x] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Dopaminergic signaling in the brain is primarily modulated by dopamine transporters (DATs), which actively translocate extraneuronal dopamine back into dopaminergic neurons. Transporter proteins are highly dynamic, continuously trafficking between plasmalemmal and endosomal membranes. Changes in DAT membrane trafficking kinetics can rapidly regulate dopaminergic tone by altering the number of transporters present at the cell surface. Various psychostimulant DAT ligands-acting either as amphetamine-like substrates or cocaine-like nontranslocated inhibitors-affect transporter trafficking, triggering rapid insertion or removal of plasmalemmal DATs. In this review, we focus on the effects of psychostimulants of addiction (particularly D-methamphetamine and cocaine) on DAT regulation and membrane trafficking, with an emphasis on how these drugs may influence intracellular signaling cascades and transporter-associated scaffolding proteins to affect DAT regulation. In addition, we consider involvement of presynaptic receptors for dopamine and other ligands in DAT regulation. Finally, we discuss possible implications of transporter regulation to the putative toxicity of several substituted amphetamine derivatives commonly used as recreational drugs, as well as to the design of therapeutics for cocaine addiction.
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Affiliation(s)
- Kyle C Schmitt
- Department of Pharmacology, New York University School of Medicine, New York, New York 10016, USA
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Methner DNR, Mayfield RD. Ethanol alters endosomal recycling of human dopamine transporters. J Biol Chem 2010; 285:10310-7. [PMID: 20133946 DOI: 10.1074/jbc.m109.029561] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dynamic membrane trafficking of the monoamine dopamine transporter (DAT) regulates dopaminergic signaling. Various intrinsic and pharmacological modulators can alter this trafficking. Previously we have shown ethanol potentiates in vitro DAT function and increases surface expression. However, the mechanism underlying these changes is unclear. In the present study, we found ethanol directly regulates DAT function by altering endosomal recycling of the transporter. We defined ethanol action on transporter regulation by [(3)H]DA uptake functional analysis combined with biochemical and immunological assays in stably expressing DAT HEK-293 cells. Short-term ethanol exposure potentiated DAT function in a concentration-, but not time-dependent manner. This potentiation was accompanied by a parallel increase in DAT surface expression. Ethanol had no effect on function or surface localization of the ethanol-insensitive mutant (G130T DAT), suggesting a trafficking-dependent mechanism in mediating the ethanol sensitivity of the transporter. The ethanol-induced increase in DAT surface expression occurred without altering the overall size of DAT endosomal recycling pools. We found ethanol increased the DAT membrane insertion rate while having no effect on internalization of the transporter. Ethanol had no effect on the surface expression or trafficking of the endogenously expressing transferrin receptor, suggesting ethanol does not have a nonspecific effect on endosomal recycling. These results define a novel trafficking mechanism by which ethanol regulates DAT function.
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Affiliation(s)
- D Nicole Riherd Methner
- Waggoner Center for Alcohol and Addiction Research, University of Texas, Austin, Texas 78712, USA
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Eriksen J, Jørgensen TN, Gether U. Regulation of dopamine transporter function by protein-protein interactions: new discoveries and methodological challenges. J Neurochem 2010; 113:27-41. [PMID: 20085610 DOI: 10.1111/j.1471-4159.2010.06599.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The dopamine transporter (DAT) plays a key role in regulating dopaminergic signalling in the brain by mediating rapid clearance of dopamine from the synaptic clefts. The psychostimulatory actions of cocaine and amphetamine are primarily the result of a direct interaction of these compounds with DAT leading to attenuated dopamine clearance and for amphetamine even increased dopamine release. In the last decade, intensive efforts have been directed towards understanding the molecular and cellular mechanisms governing the activity and availability of DAT in the plasma membrane of the pre-synaptic neurons. This has led to the identification of a plethora of different kinases, receptors and scaffolding proteins that interact with DAT and hereby either modulate the catalytic activity of the transporter or regulate its trafficking and degradation. Several new tools for studying DAT regulation in live cells have also recently become available such as fluorescently tagged cocaine analogues and fluorescent substrates. Here we review the current knowledge about the role of protein-protein interactions in DAT regulation as well as we describe the most recent methodological developments that have been established to overcome the challenges associated with the study of DAT in endogenous systems.
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Affiliation(s)
- Jacob Eriksen
- Molecular Neuropharmacology Group and Center for Pharmacogenomics, Department of Neuroscience and Pharmacology, The Panum Institute, University of Copenhagen, Copenhagen N, Denmark
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Chen R, Furman CA, Gnegy ME. Dopamine transporter trafficking: rapid response on demand. FUTURE NEUROLOGY 2010; 5:123. [PMID: 20174452 DOI: 10.2217/fnl.09.76] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The dopamine transporter (DAT) is a primary determinant of the concentration of dopamine in the synapse and is involved in a number of psychiatric and neurological diseases. The transporter actively takes up its physiological substrate, dopamine, when it is on the surface of the plasmalemmal membrane, but the concentration of DAT in the membrane is highly regulated by substrate. Substrates initially, and very rapidly, recruit more DAT into the membrane for greater function, but continued presence of substrate downregulates the activity of DAT and even membrane DAT content. This biphasic regulation is orchestrated by numerous signal transduction mechanisms, including a palette of protein kinases. Understanding the mechanisms of rapid regulation of DAT could provide new therapeutic strategies to improve transporter function and modulate responses to its more notorious substrates, amphetamine and methamphetamine.
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Affiliation(s)
- Rong Chen
- Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, MI 48109-5632, USA Tel.: +1 734 763 3083
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Gournas C, Amillis S, Vlanti A, Diallinas G. Transport-dependent endocytosis and turnover of a uric acid-xanthine permease. Mol Microbiol 2010; 75:246-60. [DOI: 10.1111/j.1365-2958.2009.06997.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Mandt BH, Zahniser NR. Low and high cocaine locomotor responding male Sprague-Dawley rats differ in rapid cocaine-induced regulation of striatal dopamine transporter function. Neuropharmacology 2009; 58:605-12. [PMID: 19951714 DOI: 10.1016/j.neuropharm.2009.11.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Revised: 11/24/2009] [Accepted: 11/25/2009] [Indexed: 10/20/2022]
Abstract
Adult outbred Sprague-Dawley rats can be classified as either low or high cocaine responders (LCRs or HCRs, respectively). Importantly, LCRs and HCRs are distinguished by their differential responsiveness to acute cocaine-induced (but not baseline) locomotor activity, inhibition of the dopamine transporter (DAT) and resulting extracellular DA (HCR > LCR), as well as by repeated cocaine-induced locomotor sensitization and measures of cocaine's rewarding and reinforcing effects (LCR > HCR). Curiously, 30 min after acute cocaine HCRs exhibit greater DAT-mediated [(3)H]DA uptake into striatal synaptosomes than LCRs. To investigate this finding further, we measured locomotor activity, striatal [(3)H]DA uptake kinetics and DAT cell surface expression in LCRs and HCRs over an extended period (25-180 min) after a single relatively low-dose of cocaine (10 mg/kg, i.p.). HCRs exhibited the "predicted" locomotor response: a marked initial activation that returned to baseline by 120 min post-injection. While LCRs exhibited a >50% lower maximal locomotor response, this increase was sustained, lasting approximately 33% longer than in HCRs. At 25 min post-cocaine, maximal velocity (V(max)) of [(3)H]DA uptake was significantly higher by 25% in HCRs than LCRs, with no difference in affinity (K(m)). Despite the DAT V(max) difference, however, DAT surface expression did not differ between LCRs and HCRs. There was a similar trend (HCR > LCR) for DAT V(max) at 40 min, but not at 150 or 180 min. These findings suggest that, compared to LCRs, HCRs have an enhanced ability to rapidly up-regulate DAT function in response to acute cocaine, which may contribute to their more "normal" cocaine-induced locomotor activation.
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Affiliation(s)
- Bruce H Mandt
- University of Colorado Denver, Department of Pharmacology, Aurora, CO 80217, USA.
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Sitte HH, Freissmuth M. The reverse operation of Na(+)/Cl(-)-coupled neurotransmitter transporters--why amphetamines take two to tango. J Neurochem 2009; 112:340-55. [PMID: 19891736 DOI: 10.1111/j.1471-4159.2009.06474.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Sodium-chloride coupled neurotransmitter transporters achieve reuptake of their physiological substrate by exploiting the pre-existing sodium-gradient across the cellular membrane. This terminates the action of previously released substrate in the synaptic cleft. However, a change of the transmembrane ionic gradients or specific binding of some psychostimulant drugs to these proteins, like amphetamine and its derivatives, induce reverse operation of neurotransmitter:sodium symporters. This effect eventually leads to an increase in the synaptic concentration of non-exocytotically released neurotransmitters [and - in the case of the norepinephrine transporters, underlies the well-known indirect sympathomimetic activity]. While this action has long been appreciated, the underlying mechanistic details have been surprisingly difficult to understand. Some aspects can be resolved by incorporating insights into the oligomeric nature of transporters, into the nature of the accompanying ion fluxes, and changes in protein kinase activities.
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Affiliation(s)
- Harald H Sitte
- Institute of Pharmacology, Center for Biomolecular Medicine and Pharmacology, Medical University of Vienna, Vienna, Austria
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Visualization of dopamine transporter trafficking in live neurons by use of fluorescent cocaine analogs. J Neurosci 2009; 29:6794-808. [PMID: 19474307 DOI: 10.1523/jneurosci.4177-08.2009] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The dopamine transporter (DAT) mediates reuptake of dopamine from the synaptic cleft and is a target for widely abused psychostimulants such as cocaine and amphetamine. Nonetheless, little is known about the cellular distribution and trafficking of natively expressed DAT. Here we use novel fluorescently tagged cocaine analogs to visualize DAT and DAT trafficking in cultured live midbrain dopaminergic neurons. The fluorescent tags were extended from the tropane N-position of 2beta-carbomethoxy-3beta-(3,4-dichlorophenyl)tropane using an ethylamino-linker. The rhodamine-, OR Green-, or Cy3-labeled ligands had high binding affinity for DAT and enabled specific labeling of DAT in live neurons and visualization by confocal imaging. In the dopaminergic neurons, DAT was uniformly distributed in the plasma membrane of the soma, the neuronal extensions, and varicosities along these extensions. FRAP (fluorescence recovery after photobleaching) experiments demonstrated bidirectional movement of DAT in the extensions and indicated that DAT is highly mobile both in the extensions and in the varicosities (immobile fraction less than approximately 30%). DAT was constitutively internalized into vesicular structures likely representing intracellular transporter pools. The internalization was blocked by lentiviral-mediated expression of dominant-negative dynamin and internalized DAT displayed partial colocalization with the early endosomal marker EGFP-Rab5 and with the transferrin receptor. DAT internalization and function was not affected by activation of protein kinase C (PKC) with phorbol-12-myristate-13-acetate (PMA) or by inhibition with staurosporine or GF109203X. These data are in contrast to findings for DAT in transfected heterologous cells and challenge the paradigm that trafficking and cellular distribution of endogenous DAT is subject to regulation by PKC.
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