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Hovde MJ, Larson GH, Vaughan RA, Foster JD. Model systems for analysis of dopamine transporter function and regulation. Neurochem Int 2018; 123:13-21. [PMID: 30179648 DOI: 10.1016/j.neuint.2018.08.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Revised: 08/23/2018] [Accepted: 08/31/2018] [Indexed: 02/07/2023]
Abstract
The dopamine transporter (DAT) plays a critical role in dopamine (DA) homeostasis by clearing transmitter from the extraneuronal space after vesicular release. DAT serves as a site of action for a variety of addictive and therapeutic reuptake inhibitors, and transport dysfunction is associated with transmitter imbalances in disorders such as schizophrenia, attention deficit hyperactive disorder, bipolar disorder, and Parkinson disease. In this review, we describe some of the model systems that have been used for in vitro analyses of DAT structure, function and regulation, and discuss a potential relationship between transporter kinetic values and membrane cholesterol.
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Affiliation(s)
- Moriah J Hovde
- Department of Biomedical Sciences, University of North Dakota, School of Medicine and Health Sciences, Grand Forks, ND, 58202, USA
| | - Garret H Larson
- Department of Biomedical Sciences, University of North Dakota, School of Medicine and Health Sciences, Grand Forks, ND, 58202, USA
| | - Roxanne A Vaughan
- Department of Biomedical Sciences, University of North Dakota, School of Medicine and Health Sciences, Grand Forks, ND, 58202, USA
| | - James D Foster
- Department of Biomedical Sciences, University of North Dakota, School of Medicine and Health Sciences, Grand Forks, ND, 58202, USA.
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2
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Pittman JT, Dodd CA, Klein BG. Immunohistochemical Changes in the Mouse Striatum Induced by the Pyrethroid Insecticide Permethrin. Int J Toxicol 2016; 22:359-70. [PMID: 14555407 DOI: 10.1177/109158180302200504] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Epidemiological studies have linked insecticide exposure and Parkinson's disease. In addition, some insecticides produce damage or physiological disruption within the dopaminergic nigrostriatal pathway of non-humans. This study employed immunohistochemical analysis in striatum of the C57BL/6 mouse to clarify tissue changes suggested by previous pharmacological studies of the pyrethroid insecticide permethrin. Dopamine transporter, tyrosine hydroxylase, and glial fibrillary acidic protein immunoreactivities were examined in caudate-putamen to distinguish changes in amount of dopamine transporter immunoreactive protein from degeneration or other damage to dopaminergic neuropil. Weight-matched pairs of pesticide-treated and vehicle-control mice were dosed and sacrificed on the same days. Permethrin at 0.8, 1.5 and 3.0 mg/kg were the low doses and at 200 mg/kg the high dose. Brains from matched pairs of mice were processed on the same slides using the avidin-biotin technique. Four fields were morphometrically located in each of the serial sections of caudateputamen, digitally photographed, and immunopositive image pixels were counted and compared between members of matched pairs of permethrin-treated and vehicle-control mice. For low doses, only 3.0 mg/kg produced a significant decrease in dopamine transporter immunostaining. The high dose of permethrin did not produce a significant change in dopamine transporter or tyrosine hydroxylase immunostaining, but resulted in a significant increase in glial fibrillary acidic protein immunostaining. These data suggest that a low dose of permethrin can reduce the amount of dopamine transporter immunoreactive protein in the caudate-putamen. They also suggest that previously reported reductions in dopamine uptake of striatal synaptosomes of high-dose mice may be due to nondegenerative tissue damage within this region as opposed to reductions of dopamine transporter protein or death of nigrostriatal terminals. These data provide further evidence that insecticides can affect the primary neurodegenerative substrate of Parkinson's disease.
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Affiliation(s)
- Julian T Pittman
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia 24061, USA
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3
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Abstract
Biogenic amine transporters mediate two important steps in the reuptake and recycling of monoamines released by neurons in the central nervous system. First, high-affinity transporters found in the plasma membrane of neurons and glial cells mediate the removal of neurotransmitter from the extracellular space, thus terminating the action of the monoamines serotonin, norepinephrine, and dopamine. Within the cell, vesicular transporters repackage monoamines into vesicles for additional cycles of release. Two gene families are involved in the transport of the biogenic amines—the Na+/Cl--dependent plasma membrane carriers and the H+-dependent vesicular amine carriers. These transporters are known to regulate neurotransmitter con centrations in monoaminergic pathways and are the primary targets for a wide variety of clinically important antidepressants, antihypertensives, stimulants, and stimulant drugs of abuse. The Neuroscientist 1:259-267, 1995
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Affiliation(s)
- Susan G. Amara
- The Vollum Institute and Howard Hughes Medical Institute
Oregon Health Sciences University Portland, Oregon
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4
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Min C, Zheng M, Zhang X, Guo S, Kwon KJ, Shin CY, Kim HS, Cheon SH, Kim KM. N-linked Glycosylation on the N-terminus of the dopamine D2 and D3 receptors determines receptor association with specific microdomains in the plasma membrane. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1853:41-51. [PMID: 25289757 DOI: 10.1016/j.bbamcr.2014.09.024] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 08/30/2014] [Accepted: 09/29/2014] [Indexed: 10/24/2022]
Abstract
Numerous G protein-coupled receptors (GPCRs) are glycosylated at extracellular regions. The regulatory roles of glycosylation on receptor function vary across receptor types. In this study, we used the dopamine D₂and D₃receptors as an experimental model to understand the underlying principles governing the functional roles of glycosylation. We used the pharmacological inhibitor, tunicamycin, to inhibit glycosylation, generated chimeric D₂and D₃receptors by swapping their respective N-termini, and produced the glycosylation site mutant D₂and D₃receptors to study the roles of glycosylation on receptor functions, including cell surface expression, signaling, and internalization through specific microdomains. Our results demonstrate that glycosylation on the N-terminus of the D₃ receptor is involved in the development of desensitization and proper cell surface expression. In addition, glycosylation on the N-terminus mediates the internalization of D₂and D₃receptors within the caveolae and clathrin-coated pit microdomains of the plasma membrane, respectively, by regulating receptor interactions with caveolin-1 and clathrin. In conclusion, this study shows for the first time that glycosylation on the N-terminus of GPCRs is involved in endocytic pathway selection through specific microdomains. These data suggest that changes in the cellular environment that influence posttranslational modification could be an important determinant of intracellular GPCR trafficking.
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Affiliation(s)
- Chengchun Min
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju, Republic of Korea
| | - Mei Zheng
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju, Republic of Korea
| | - Xiaohan Zhang
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju, Republic of Korea
| | - Shuohan Guo
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju, Republic of Korea
| | - Kyoung-Ja Kwon
- Department of Pharmacology, College of Medicine, Konkuk University, Seoul, Republic of Korea
| | - Chan Young Shin
- Department of Pharmacology, College of Medicine, Konkuk University, Seoul, Republic of Korea
| | - Hyeong-Suk Kim
- Department of Forensic Medicine, College of Medicine, Chonnam National University, Gwang-Ju, Republic of Korea
| | - Seung Hoon Cheon
- Department of Medicinal Chemistry, College of Pharmacy, Chonnam National University, Gwang-Ju, Republic of Korea
| | - Kyeong-Man Kim
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju, Republic of Korea.
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5
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Covey DP, Juliano SA, Garris PA. Amphetamine elicits opposing actions on readily releasable and reserve pools for dopamine. PLoS One 2013; 8:e60763. [PMID: 23671560 PMCID: PMC3643976 DOI: 10.1371/journal.pone.0060763] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 03/02/2013] [Indexed: 11/18/2022] Open
Abstract
Amphetamine, a highly addictive drug with therapeutic efficacy, exerts paradoxical effects on the fundamental communication modes employed by dopamine neurons in modulating behavior. While amphetamine elevates tonic dopamine signaling by depleting vesicular stores and driving non-exocytotic release through reverse transport, this psychostimulant also activates phasic dopamine signaling by up-regulating vesicular dopamine release. We hypothesized that these seemingly incongruent effects arise from amphetamine depleting the reserve pool and enhancing the readily releasable pool. This novel hypothesis was tested using in vivo voltammetry and stimulus trains of varying duration to access different vesicular stores. We show that amphetamine actions are stimulus dependent in the dorsal striatum. Specifically, amphetamine up-regulated vesicular dopamine release elicited by a short-duration train, which interrogates the readily releasable pool, but depleted release elicited by a long-duration train, which interrogates the reserve pool. These opposing actions of vesicular dopamine release were associated with concurrent increases in tonic and phasic dopamine responses. A link between vesicular depletion and tonic signaling was supported by results obtained for amphetamine in the ventral striatum and cocaine in both striatal sub-regions, which demonstrated augmented vesicular release and phasic signals only. We submit that amphetamine differentially targeting dopamine stores reconciles the paradoxical activation of tonic and phasic dopamine signaling. Overall, these results further highlight the unique and region-distinct cellular mechanisms of amphetamine and may have important implications for its addictive and therapeutic properties.
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Affiliation(s)
- Dan P. Covey
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
| | - Steven A. Juliano
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
| | - Paul A. Garris
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
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6
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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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7
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Ramsson ES, Covey DP, Daberkow DP, Litherland MT, Juliano SA, Garris PA. Amphetamine augments action potential-dependent dopaminergic signaling in the striatum in vivo. J Neurochem 2011; 117:937-48. [PMID: 21443523 DOI: 10.1111/j.1471-4159.2011.07258.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Amphetamine (AMPH) is thought to disrupt normal patterns of action potential-dependent dopaminergic signaling by depleting dopamine (DA) vesicular stores and promoting non-exocytotic DA efflux. Voltammetry in brain slices concurrently demonstrates these key drug effects, along with competitive inhibition of neuronal DA uptake. Here, we perform comparable kinetic and voltammetric analyses in vivo to determine whether AMPH acts qualitatively and quantitatively similar in the intact brain. Fast-scan cyclic voltammetry measured extracellular DA in dorsal and ventral striata of urethane-anesthetized rats. Electrically evoked recordings were analyzed to determine K(m) and V(max) for DA uptake and vesicular DA release, while background voltammetric current indexed basal DA concentration. AMPH (0.5, 3, and 10 mg/kg i.p.) robustly increased evoked DA responses in both striatal subregions. The predominant contributor to these elevated levels was competitive uptake inhibition, as exocytotic release was unchanged in the ventral striatum and only modestly decreased in the dorsal striatum. Increases in basal DA levels were not detected. These results are consistent with AMPH augmenting action potential-dependent dopaminergic signaling in vivo across a wide, behaviorally relevant dose range. Future work should be directed at possible causes for the distinct in vitro and in vivo pharmacology of AMPH.
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Affiliation(s)
- Eric S Ramsson
- School of Biological Sciences, Illinois State University, Normal, Illinois 61790-4120, USA
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8
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Cruz-Muros I, Afonso-Oramas D, Abreu P, Pérez-Delgado MM, Rodríguez M, González-Hernández T. Aging effects on the dopamine transporter expression and compensatory mechanisms. Neurobiol Aging 2009; 30:973-86. [DOI: 10.1016/j.neurobiolaging.2007.09.009] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2007] [Revised: 08/31/2007] [Accepted: 09/19/2007] [Indexed: 10/22/2022]
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Richards TL, Zahniser NR. Rapid substrate-induced down-regulation in function and surface localization of dopamine transporters: rat dorsal striatum versus nucleus accumbens. J Neurochem 2009; 108:1575-84. [PMID: 19183252 DOI: 10.1111/j.1471-4159.2009.05910.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The dopamine transporter (DAT) substrates dopamine, d-amphetamine (AMPH), and methamphetamine are known to rapidly and transiently reduce DAT activity and/or surface expression in dorsal striatum and heterologous expression systems. We sought to determine if similar substrate-induced regulation of DATs occurs in rat nucleus accumbens. In dorsal striatum synaptosomes, brief (15-min) in vitro substrate pre-exposure markedly decreased maximal [(3)H]dopamine uptake velocity whereas identical substrate pre-exposure in nucleus accumbens synaptosomes produced a smaller, non-significant reduction. However, 45 min after systemic AMPH administration, maximal ex vivo [(3)H]dopamine uptake velocity was significantly reduced in both brain regions. Protein kinase C inhibition blocked AMPH's down-regulation of DAT activity. DAT synaptosomal surface expression was not modified following either the brief in vitro or in vivo AMPH pre-exposure but was reduced after a longer (1-h) in vitro pre-exposure in both brain regions. Together, our findings suggest that relatively brief substrate exposure results in greater down-regulation of DAT activity in dorsal striatum than in nucleus accumbens. Moreover, exposure to AMPH appears to regulate striatal DATs in a biphasic manner, with an initial protein kinase C-dependent decrease in DAT-mediated uptake velocity and then, with longer exposure, a reduction in DAT surface expression.
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Affiliation(s)
- Toni L Richards
- School of Medicine, Department of Pharmacology, University of Colorado Denver, Aurora, Colorado, USA.
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10
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Bjorklund NL, Sorg BA, Schenk JO. Neuronal dopamine transporter activity, density and methamphetamine inhibition are differentially altered in the nucleus accumbens and striatum with no changes in glycosylation in rats behaviorally sensitized to methamphetamine. Synapse 2008; 62:736-45. [DOI: 10.1002/syn.20528] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Walker QD, Kuhn CM. Cocaine increases stimulated dopamine release more in periadolescent than adult rats. Neurotoxicol Teratol 2008; 30:412-8. [PMID: 18508233 DOI: 10.1016/j.ntt.2008.04.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Revised: 03/25/2008] [Accepted: 04/15/2008] [Indexed: 11/17/2022]
Abstract
The neural mechanisms responsible for the enhanced adolescent vulnerability for initiating drug abuse are unclear. We investigated whether age differences in dopamine neurotransmission could explain cocaine's enhanced psychomotor effects in the periadolescent rat. Electrical stimulation of the medial forebrain bundle of anesthetized post-natal age 28 days (PN28) and PN65 rats elicited dopamine release in caudate nucleus and nucleus accumbens core before and after 15 mg/kg cocaine i.p. Extracellular dopamine concentrations were greater in PN65 than PN28 caudate following 20 and 60 Hz stimulations and in the PN65 nucleus accumbens following 60 Hz stimulations. Cocaine increased dopamine concentrations elicited by 20 Hz stimulations 3-fold in the adult, but almost 9-fold in periadolescent caudate. Dopamine release rate was lower in the periadolescent caudate although total dopamine clearance was similar to that of adults. The periadolescent caudate achieved adult levels of clearance by compensating for a lower V(max) with higher uptake affinity. Tighter regulation of extracellular dopamine by the higher uptake/release ratio in periadolescents led to greater increases after cocaine. In nucleus accumbens, dopamine release and V(max) were lower in periadolescents than adults, but uptake affinity and cocaine effects were similar. Immaturity of dopamine neurotransmission in dorsal striatum may underlie enhanced acute responses to psychostimulants in adolescent rats and suggests a mechanism for the greater vulnerability of adolescent humans to drug addiction.
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Affiliation(s)
- Q David Walker
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, United States
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12
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Volz TJ, Fleckenstein AE, Hanson GR. Methamphetamine-induced alterations in monoamine transport: implications for neurotoxicity, neuroprotection and treatment. Addiction 2007; 102 Suppl 1:44-8. [PMID: 17493052 DOI: 10.1111/j.1360-0443.2007.01771.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIM To review studies delineating the neurotoxic effects of methamphetamine on monoamine transport in dopaminergic neurons of the striatum and nucleus accumbens. METHOD The scope of this review includes the English language dopamine transporter and vesicular monoamine transporter-2 primary literature to April 2006 identified by Pubmed, Science Citation Index and SciFinder Scholar literature searches. RESULTS Changes in the function of the plasmalemmal dopamine transporter and the vesicular monoamine transporter-2 are key components of methamphetamine-induced persistent dopaminergic deficits. These deficits include persistent reductions in dopamine content, dopamine transporter density and tyrosine hydroxylase activity. The striatum is susceptible to these effects of methamphetamine while the nucleus accumbens is resistant. Differences in dopamine transporter density and activity, extracellular dopamine levels and antioxidant levels in these two brain regions may, in part, account for the resistance of the nucleus accumbens. CONCLUSION These findings concerning the nature of methamphetamine-induced changes in plasmalemmal and vesicular dopamine transport have very important implications for drug targets and for understanding the etiology of dopaminergic neurodegenerative processes, such as those associated with methamphetamine addiction and Parkinson's disease.
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Affiliation(s)
- Trent J Volz
- Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, UT 84112, USA
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Uhl GR, Lin Z. The top 20 dopamine transporter mutants: structure–function relationships and cocaine actions. Eur J Pharmacol 2003; 479:71-82. [PMID: 14612139 DOI: 10.1016/j.ejphar.2003.08.058] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Our laboratory and others elucidated the primary amino acid sequences of the dopamine transporter (DAT) by cloning its cDNA and genomic sequences more than 12 years ago. Motivations for this work included the ideas that cocaine's interactions with DAT accounted for its rewarding properties and that selective inhibitors of DAT/cocaine interactions might thus provide good anticocaine medications. Such ideas supported interest in the detailed structure-function relationships of cocaine/DAT interactions, and in the construction and characterization of extensive series of site-directed DAT mutants. We can now select the most interesting 20 cocaine-analog selective mutations of the more than 100 single- and multiple amino acid substitution mutations that we have characterized. These mutants selectively reduce the affinities of the mutant DATs for cocaine analogs, but (absolutely or relatively) spare their affinities for dopamine. Several themes relevant to cocaine/DAT interactions emerge from these mutants. First, such mutations are found in a number of different DAT domains. Secondly, many but not all of these mutations lie in groups, near each other and near the same faces of presumably helical DAT transmembrane domains. Third, most are also conserved in the serotonin transporter (SERT), a transporter that is now strongly implicated in cocaine reward based on data from knockout mice. We discuss the results from these "top 20" mutants in light of the strengths and limitations of current DAT models and data from other studies. Taken together, these studies appear to indicate direct or indirect participation of several specific portions of DAT in selective recognition of cocaine analogs. These studies provide a strong basis for redirected studies aimed at producing dopamine- and serotonin-sparing cocaine antagonists that would represent combined DAT/SERT disinhibitors.
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Affiliation(s)
- George R Uhl
- Molecular Neurobiology Branch, NIDA-IRP, NIH, 5500 Nathan Shock Drive, PO Box 5180, Baltimore, MD 21224, USA.
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Gulley JM, Zahniser NR. Rapid regulation of dopamine transporter function by substrates, blockers and presynaptic receptor ligands. Eur J Pharmacol 2003; 479:139-52. [PMID: 14612145 DOI: 10.1016/j.ejphar.2003.08.064] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The extracellular actions of dopamine are terminated primarily through its binding to dopamine transporters and translocation back into dopamine neurons. The transporter thereby serves as an optimal target to regulate dopamine neurotransmission. Although acute pharmacological blockade of dopamine transporters is known to reversibly inhibit transporter function by preventing the binding of its endogenous substrate dopamine, it recently has become clear that dopamine transporter substrates, such as amphetamines, and blockers, such as cocaine, also have the ability to rapidly and persistently regulate transporter function after their direct pharmacological effect has subsided. Presynaptic receptor ligands can also regulate dopamine transporter function. This has been investigated most extensively for dopamine D2 receptors, but there is also evidence for regulation by gamma-aminobutyric acid (GABA) GABAB receptors, metabotropic glutamate, nicotinic acetylcholine, serotonin, sigma2- and kappa-opioid receptors. The focus of this review is the rapid, typically reversible, regulation of dopamine transporter velocity by substrates, blockers and presynaptic receptor ligands. The research discussed here suggests that a common mechanism through which these different classes of compounds regulate transporter activity is by altering the cell surface expression of dopamine transporters.
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Affiliation(s)
- Joshua M Gulley
- Department of Pharmacology and Neuroscience Program, University of Colorado Health Sciences Center, Campus Box C-236, 4200 E Ninth Avenue, Denver, CO 80262, USA.
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Schenk JO. The functioning neuronal transporter for dopamine: kinetic mechanisms and effects of amphetamines, cocaine and methylphenidate. PROGRESS IN DRUG RESEARCH. FORTSCHRITTE DER ARZNEIMITTELFORSCHUNG. PROGRES DES RECHERCHES PHARMACEUTIQUES 2003; 59:111-31. [PMID: 12458965 DOI: 10.1007/978-3-0348-8171-5_4] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The dopamine transporter (DAT) is a transmembrane spanning protein that catalyzes the transport of dopamine across the neuronal membrane to concentrate the neurotransmitter inside the cell. Although the uptake of dopamine has been studied since the 1960s, more recent advances in knowledge of the protein itself and in making kinetically resolved measurements of its action have led to more insights into its mechanism and pharmacology. The literature of the kinetics of transporters and kinetic measurements of DAT activity is reviewed to provide an overview of the multisubstrate mechanism of DAT activity, its pharmacology with regard to amphetamine, cocaine and methylphenidate, and correlations of DAT activity with some behavioral outputs.
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Affiliation(s)
- James O Schenk
- Department of Chemistry, School of Molecular Biosciences, and Program in Pharmacology/Toxicology, Washington State University, Pullman, WA 99164-4630, USA.
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Martin-Fardon R, Ben-Shahar O, Weiss F. Non reciprocal cross-sensitization between cocaine and BTCP on locomotor activity in the rat. Pharmacol Biochem Behav 2000; 66:631-5. [PMID: 10899381 DOI: 10.1016/s0091-3057(00)00262-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Measurement of locomotor sensitization was employed to characterize the effect of intermittent treatment with N-[1-(2-benzo[b]thiophenyl)cyclohexyl]piperidine (BTCP) and cocaine in the rat. Like cocaine, BTCP possesses high affinity for the dopamine transporter and inhibits dopamine reuptake. Although both drugs exhibit similar behavioral and neurochemical profiles with acute administration, there is tentative evidence to suggest that following chronic treatment BTCP does not induce neurochemical sensitization, and can attenuate cocaine-induced neurochemical sensitization in the striatum. Male Wistar rats were randomly divided into five groups after determining baseline locomotor activity. Three groups were treated with either saline (saline/saline), cocaine (20 mg/kg; cocaine/cocaine), or BTCP (10 mg/kg; BTCP/BTCP) for 10 days. The remaining two groups were treated with cocaine (20 mg/kg) or BTCP (10 mg/kg) for 3 days, followed by administration of BTCP (10 mg/kg; cocaine/BTCP) or cocaine (20 mg/kg; BTCP/cocaine) for 7 days. Locomotor sensitization was observed in all groups. However, although cross-sensitization on the day of substitution (day 4) was found in the BTCP/cocaine group, cross-sensitization was not observed in the cocaine/BTCP group. These results suggest that although the locomotor-activating effects of BTCP and cocaine are similar, the two drugs do not act identically, and different neural mechanisms may underlie BTCP and cocaineinduced sensitization.
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Affiliation(s)
- R Martin-Fardon
- The Scripps Research Institute, Department of Neuropharmacology, CVN 15, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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17
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Zachor DA, Moore JF, Brezausek C, Theibert A, Percy AK. Cocaine inhibits NGF-induced PC12 cells differentiation through D(1)-type dopamine receptors. Brain Res 2000; 869:85-97. [PMID: 10865062 DOI: 10.1016/s0006-8993(00)02355-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In utero cocaine exposure can adversely affect CNS development. Previous studies showed that cocaine inhibits neuronal differentiation in a dose-dependent fashion in nerve growth factor (NGF)-stimulated PC12 cells. Cocaine binds with high affinity to several neurotransmitter transporters, resulting in elevated neurotransmitter levels in nerve endings. To determine if cocaine inhibits neurite outgrowth through the effects of these neurotransmitters, we applied dopamine, norepinephrine, serotonin, and acetylcholine to NGF-induced PC12 cells. Dopamine was the only neurotransmitter to inhibit neurite outgrowth significantly in a dose-dependent pattern without affecting cell viability. Norepinephrine and acetylcholine did not affect neurite outgrowth, while serotonin enhanced it. Furthermore, GBR 12909, a potent dopamine transporter (DAT) inhibitor, yielded similar effects. We then showed PC12 cells express D(1) and D(2) receptors and DAT proteins. Dopamine uptake measured over time was significantly blocked by cocaine and GBR 12909 which may result in elevated extracellular dopamine. The role of dopamine receptors in PC12 differentiation was further examined by using D(1) and D(2) specific receptor agonists. Only the D(1) agonist, SKF-38393, had a significant dose-dependent inhibitory effect. In addition, a D(1) antagonist produced significant recovery of neurite outgrowth in cocaine-treated cells. These findings suggest that cocaine inhibitory effects on neuronal differentiation are mediated through its binding to the dopamine transporter, resulting in increased dopamine level in the synapses. Subsequently, up regulation of D(1) receptors alters NGF signaling pathways.
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Affiliation(s)
- D A Zachor
- Department of Pediatrics, University of Alabama at Birmingham, 331C, Sparks Building, 1720 Seventh Avenue South, Birmingham, AL 35294-0017, USA.
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18
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Kokoshka JM, Vaughan RA, Hanson GR, Fleckenstein AE. Nature of methamphetamine-induced rapid and reversible changes in dopamine transporters. Eur J Pharmacol 1998; 361:269-75. [PMID: 9865517 DOI: 10.1016/s0014-2999(98)00741-9] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The nature of methamphetamine-induced rapid and transient decreases in dopamine transporter activity was investigated. Regional specificity was demonstrated, since [3H]dopamine uptake was decreased in synaptosomes prepared from the striatum, but not nucleus accumbens, of methamphetamine-treated rats. Differences among effects on dopamine transporter activity and ligand binding were also observed, since a single methamphetamine administration decreased [3H]dopamine uptake without altering [3H]WIN35428 ([3H](-)-2-beta-carbomethoxy-3-beta-(4-fluorophenyl)tropane 1,5-naphthalenedisulfonate) binding in synaptosomes prepared 1 h after injection. Moreover, multiple methamphetamine injections caused a greater decrease in [3H]dopamine uptake than [3H]WIN35428 binding in synaptosomes prepared I h after dosing. Finally, decreases in [3H]dopamine uptake, but not [3H]WIN35428 binding, were partially reversed 24 h after multiple methamphetamine injections. Western blotting indicated that saline- and methamphetamine-affected dopamine transporters co-migrated on sodium dodecyl sulfate (SDS) gels at approximately 80 kDa, and that acute, methamphetamine-induced decreases in [3H]dopamine uptake were not due to loss of dopamine transporter protein. These findings demonstrate heretofore-uncharacterized features of the acute effect of methamphetamine on dopamine transporters.
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Affiliation(s)
- J M Kokoshka
- Department of Pharmacology and Toxicology, University of Utah, Salt Lake City 84112, USA
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19
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Page G, Barrier L, Fauconneau B, Piriou A, Tallineau C, Huguet F. Membrane carbohydrate conjugates desialylation does not alter [3H]-dopamine uptake in rat striatal slices. Neurosci Lett 1998; 255:139-42. [PMID: 9832192 DOI: 10.1016/s0304-3940(98)00675-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Incubation of rat striatal slices induced a large decrease (about 50%) of DA uptake and a slight desialylation of polysialogangliosides (GT1b, GD1b, GD1a) with an increase of monosialogangliosides (GM1). Moreover, a pretreatment of slices by exogenous added neuraminidase of Vibrio cholerae did not modify DA uptake, although the pattern of gangliosides was modified and there was considerable loss (about 45%) of sialic acid in gangliosides and glycoproteins. It was verified that neuraminidase activity occured in synaptic membrane. Thus, DA uptake was apparently not altered by desialylation of plasma membrane carbohydrate conjugates.
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Affiliation(s)
- G Page
- Centre d'Etudes et de Recherche sur les Xénobiotiques, UPRES EA 1223, Faculté de Médecine et de Pharmacie, Poitiers, France
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20
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Palacín M, Estévez R, Bertran J, Zorzano A. Molecular biology of mammalian plasma membrane amino acid transporters. Physiol Rev 1998; 78:969-1054. [PMID: 9790568 DOI: 10.1152/physrev.1998.78.4.969] [Citation(s) in RCA: 584] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Molecular biology entered the field of mammalian amino acid transporters in 1990-1991 with the cloning of the first GABA and cationic amino acid transporters. Since then, cDNA have been isolated for more than 20 mammalian amino acid transporters. All of them belong to four protein families. Here we describe the tissue expression, transport characteristics, structure-function relationship, and the putative physiological roles of these transporters. Wherever possible, the ascription of these transporters to known amino acid transport systems is suggested. Significant contributions have been made to the molecular biology of amino acid transport in mammals in the last 3 years, such as the construction of knockouts for the CAT-1 cationic amino acid transporter and the EAAT2 and EAAT3 glutamate transporters, as well as a growing number of studies aimed to elucidate the structure-function relationship of the amino acid transporter. In addition, the first gene (rBAT) responsible for an inherited disease of amino acid transport (cystinuria) has been identified. Identifying the molecular structure of amino acid transport systems of high physiological relevance (e.g., system A, L, N, and x(c)- and of the genes responsible for other aminoacidurias as well as revealing the key molecular mechanisms of the amino acid transporters are the main challenges of the future in this field.
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Affiliation(s)
- M Palacín
- Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Spain
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21
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Dopamine axon varicosities in the prelimbic division of the rat prefrontal cortex exhibit sparse immunoreactivity for the dopamine transporter. J Neurosci 1998. [PMID: 9502827 DOI: 10.1523/jneurosci.18-07-02697.1998] [Citation(s) in RCA: 378] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The dopamine transporter (DAT) critically regulates the duration of the cellular actions of dopamine and the extent to which dopamine diffuses in the extracellular space. We sought to determine whether the reportedly greater diffusion of dopamine in the rat prefrontal cortex (PFC) as compared with the striatum is associated with a more restricted axonal distribution of the cortical DAT protein. By light microscopy, avidin-biotin-peroxidase immunostaining for DAT was visualized in fibers that were densely distributed within the dorsolateral striatum and the superficial layers of the dorsal anterior cingulate cortex. In contrast, DAT-labeled axons were distributed only sparsely to the deep layers of the prelimbic cortex. By electron microscopy, DAT-immunoreactive profiles in the striatum and cingulate cortex included both varicose and intervaricose segments of axons. However, DAT-labeled processes in the prelimbic cortex were almost exclusively intervaricose axon segments. Immunolabeling for tyrosine hydroxylase in adjacent sections of the prelimbic cortex was localized to both varicosities and intervaricose segments of axons. These qualitative observations were supported by a quantitative assessment in which the diameter of immunoreactive profiles was used as a relative measure of whether varicose or intervaricose axon segments were labeled. These results suggest that considerable extracellular diffusion of dopamine in the prelimbic PFC may result, at least in part, from a paucity of DAT content in mesocortical dopamine axons, as well as a distribution of the DAT protein at a distance from synaptic release sites. The results further suggest that different populations of dopamine neurons selectively target the DAT to different subcellular locations.
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22
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Coulter CL, Happe HK, Murrin LC. Dopamine transporter development in postnatal rat striatum: an autoradiographic study with [3H]WIN 35,428. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1997; 104:55-62. [PMID: 9466707 DOI: 10.1016/s0165-3806(97)00135-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The dopamine transporter mediates the reinforcing effects of cocaine, thus playing a central role in human cocaine addiction, and perhaps providing the mechanism for inducing the effects of prenatal cocaine exposure. This possibility has stimulated growing interest in the normal and abnormal development of this transporter. [3H]WIN 35,428 is a cocaine analog that is useful for studying the distribution and density of the dopamine transporter in striatum and other brain regions. The postnatal development of the dopamine transporter in the rat striatum was measured by quantitative autoradiography with [3H]WIN 35,428. Dopamine transporter levels were low at birth, increased through day 15, followed by much more rapid growth in late postnatal development. The majority of the transporter sites appeared after day 15. Lateral to medial and anterior to posterior gradients in transporter density were established early during development, and there was also an early concentration of transporter in striosomes that became difficult to identify by day 15. Differences between the developmental patterns described here and studies using other ligands for the dopamine transporter suggest there are significant differences in the transporter binding sites for these drugs. These differences in transporter ligand binding characteristics may reflect developmental changes in post-translational modification of the transporter and/or changes in the functional activity rather than simply the presence of the transporter.
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Affiliation(s)
- C L Coulter
- Department of Neurology, Creighton University School of Medicine, Omaha, NE 68131, USA
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23
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Jaber M, Jones S, Giros B, Caron MG. The dopamine transporter: a crucial component regulating dopamine transmission. Mov Disord 1997; 12:629-33. [PMID: 9380041 DOI: 10.1002/mds.870120502] [Citation(s) in RCA: 161] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The dopamine system is implicated in the control of locomotion, cognition, and endocrine function. The relative contribution of the various dopamine-related components is not well established mainly because drugs that target the dopaminergic system often lack selectivity. The in vivo gene inactivation procedure, or knockout, enables the creation of new strains of mice lacking a specific gene. This technique has been applied recently to inactivate the expression of the plasma membrane dopamine transporter. Here we summarize the main findings obtained with these transgenic mice carrying this "genetic defect," leading to a better understanding of the relative contribution of the dopamine transporter regarding locomotor activity, regulation of the expression of peptides under the control of dopaminergic activity, and responses to various drugs targeting the dopamine system. Our results establish not only the central importance of the transporter as the key element controlling dopamine levels in the brain, but also its role as an obligatory target for the behavioral and biochemical action of amphetamine and cocaine. In addition, the genetically altered mice offer a unique model to test the specificity and selectivity of dopamine transporter-acting drugs and may provide important new concepts related to the clinical and social implications of conditions such as Parkinson's disease, schizophrenia, and drug addiction.
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Affiliation(s)
- M Jaber
- Howard Hughes Medical Institute Laboratories, Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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24
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Revay R, Vaughan R, Grant S, Kuhar MJ. Dopamine transporter immunohistochemistry in median eminence, amygdala, and other areas of the rat brain. Synapse 1996; 22:93-9. [PMID: 8787132 DOI: 10.1002/(sici)1098-2396(199602)22:2<93::aid-syn1>3.0.co;2-c] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In an extension of our previous work, an antibody directed against a peptide from the N-terminal region of DAT was used to localize specific dopamine transporter immunoreactivity (DAT-IR) in several regions of rat brain. Apparent axons and varicosities were found in the zona incerta, external layer of the median eminence, various nuclei of the amygdala, the cortex-amygdala transition zone, and in periglomerular regions in the olfactory bulb. Apparent stained neuronal perikarya and dendrites were observed in the arcuate nucleus and olfactory bulb. These regions are known to have dopaminergic neurons and innervations, although there was not a perfect correspondence between DAT-IR and the known distribution of dopaminergic neurons. A possible explanation is that different dopamine containing cell groups express different levels of DAT mRNA and protein, as we have previously shown. Also in the tuberoinfundibular neurons, for example, DAT-IR was preferentially localized to distal axons in the median eminence, suggesting intracellular compartmentation.
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Affiliation(s)
- R Revay
- Neuroscience Branch, National Institute on Drug Abuse, Baltimore, Maryland 21224, USA
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25
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Aloyo VJ, Pazdalski PS, Kirifides AL, Harvey JA. Behavioral sensitization, behavioral tolerance, and increased [3H]WIN 35,428 binding in rabbit caudate nucleus after repeated injections of cocaine. Pharmacol Biochem Behav 1995; 52:335-40. [PMID: 8577799 DOI: 10.1016/0091-3057(95)00101-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
This study examined whether changes in the behavioral response to repeated intravenous injections of cocaine hydrochloride (4 mg/kg, twice daily for 22 days) might be related to alterations in the dopamine (DA) transporter as measured by the binding of the potent cocaine analog [3H]WIN 35,428 to membranes derived from fresh caudate tissue. Rabbits demonstrated both tolerance and sensitization. Tolerance occurred for cocaine elicited convulsions, whereas sensitization occurred to the ability of cocaine to elicit motor activity, facial twitches, and head bobbing. Cocaine-exposed animals demonstrated a significant 17% increase in the Bmax of specific [3H]WIN 35,428 binding to caudate membranes with no change in Kd. The increase in Bmax was observed at 42 but not 96 h after the last chronic cocaine administration. There was no change in [3H]WIN 35,428 binding at 42 h after a single injection of cocaine. We suggest that the upregulation of the dopamine transporter in the caudate nucleus reflected the mechanisms involved in tolerance rather than sensitization.
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Affiliation(s)
- V J Aloyo
- Department of Pharmacology, Medical College of Pennsylvania, Philadelphia 19129, USA
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26
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Coulter CL, Happe HK, Bergman DA, Murrin LC. Localization and quantification of the dopamine transporter: comparison of [3H]WIN 35,428 and [125I]RTI-55. Brain Res 1995; 690:217-24. [PMID: 8535839 DOI: 10.1016/0006-8993(95)00614-v] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Transport into the presynaptic terminal by the dopamine transporter is the primary mechanism for removing dopamine from the synaptic cleft. This transporter is a specific marker for dopamine terminals and is a primary site for CNS actions of cocaine. Several radioligands have been developed for analysis of the dopamine transporter. The ligands vary in affinity and specificity, leading to differences in reported transporter density in brain regions. We compared two of the most commonly used ligands, [3H]WIN 35,428 and [125I]RTI-55, analyzing the localization and density of sites in the rat brain using serial sections and quantitative autoradiography. Citalopram at 50 nmol/l was used to block [125I]RTI-55 binding to serotonin transport sites. Transporter density was highest in the striatum and both ligands labeled equivalent numbers of sites, with lateral to medial and anterior to posterior gradients. In most areas the density of sites measured with the two ligands was similar. However, [125I]RTI-55 binding was significantly higher than [3H]WIN 35,428 binding in the substantia nigra zona compacta, ventral tegmental area, subthalamic nucleus and a number of other subcortical nuclear groups while [3H]WIN 35,428 binding was higher in lateral striatum and in olfactory tubercle. These differences could reflect different forms of the transporter, perhaps due to post-translational modifications, and they may provide a basis for differential pharmacological regulation of transporter function in discrete brain regions and disease states.
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Affiliation(s)
- C L Coulter
- Department of Neurology, Creighton University School of Medicine, Omaha, NE 68131, USA
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27
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Carroll FI, Scheffel U, Dannals RF, Boja JW, Kuhar MJ. Development of imaging agents for the dopamine transporter. Med Res Rev 1995; 15:419-44. [PMID: 8531503 DOI: 10.1002/med.2610150503] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- F I Carroll
- Research Triangle Institute, Research Triangle Park, North Carolina 27709, USA
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28
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Garris PA, Wightman RM. Distinct pharmacological regulation of evoked dopamine efflux in the amygdala and striatum of the rat in vivo. Synapse 1995; 20:269-79. [PMID: 7570359 DOI: 10.1002/syn.890200311] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The pharmacological regulation of evoked extracellular dopamine was compared in the basolateral amygdaloid nucleus (BAN) and caudate-putamen (CP) of the urethane-anesthetized rat. The effects of drugs, which alter dopamine uptake, release or degradation, were examined. Dopamine efflux was elicited by electrical stimulation of ascending dopamine fibers and was monitored by fast-scan cyclic voltammetry at Nafion-coated, carbon-fiber microelectrodes. Dopamine uptake inhibitors, nomifensine (25 mg/kg) and cocaine (20 mg/kg), and the dopamine receptor antagonist, haloperidol (0.5 mg/kg), robustly increased evoked extracellular dopamine in the CP. In sharp contrast, these drugs were much less effective in the BAN. The relative potencies of the uptake inhibitors varied between the two regions. Nomifensine was more potent than cocaine in the CP, whereas cocaine was more potent that nomifensine in the BAN. The monoamine oxidase inhibitor, pargyline (75 mg/kg), and the catechol-O-methyltransferase (COMT) inhibitor, Ro 40-7592 (40 mg/kg), had small or negligible effects in either region. No electrochemical evidence was found for the formation of 3-methoxytyramine, the dopamine metabolite formed by the action of COMT on released dopamine, on the time scale of the measurements in control or after pharmacological manipulation of the degradative enzymes for dopamine. The conclusions reached are: (1) potent mechanisms for uptake and autoreceptor inhibition of release, which exist in the CP to tightly control the concentration of extracellular dopamine, are considerably weaker in the BAN; (2) the extracellular clearance of evoked dopamine in the BAN and CP is the result of cellular uptake and not degradation; and (3) these results support the view that the pharmacological regulation of extracellular dopamine is regionally distinct in the brain.
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Affiliation(s)
- P A Garris
- Department of Chemistry, University of North Carolina, Chapel Hill 27599-2390, USA
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29
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Velaz-Faircloth M, Guadaño-Ferraz A, Henzi VA, Fremeau RT. Mammalian brain-specific L-proline transporter. Neuronal localization of mRNA and enrichment of transporter protein in synaptic plasma membranes. J Biol Chem 1995; 270:15755-61. [PMID: 7797577 DOI: 10.1074/jbc.270.26.15755] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The expression of a high affinity Na(+)- (and Cl-) dependent L-proline transporter (PROT) in subpopulations of putative glutamatergic pathways in rat brain raises the possibility of a specific physiological role(s) for this carrier in excitatory neurotransmission (Fremeau, R. T., Jr., Caron, M. G., and Blakely, R. D. (1992) Neuron 8, 915-926). However, the biochemical properties and regional, cellular, and subcellular distribution of the PROT protein have yet to be elucidated. Here, we document the brain-specific expression and neuronal localization of rat PROT mRNA. We also report the first identification and partial biochemical characterization of the mammalian brain PROT protein. An affinity-purified antipeptide antibody was produced that specifically recognized a single 68-kDa PROT protein on immunoblots of rat and human brain tissues. Deglycosylation of rat hippocampal membranes with peptide-N-glycosidase F reduced the apparent molecular mass of the native PROT protein from 68 to 53 kDa, the size of the primary PROT translation product determined by in vitro translation of the rat PROT cDNA in the absence of microsomes. Subcellular fractionation studies demonstrated that the PROT protein was enriched in synaptic plasma membranes but absent from postsynaptic densities. A differential distribution of PROT mRNA and protein was observed in rat striatum, suggesting that the transporter protein is synthesized in neuronal cell bodies in the cortex and exported to axon terminals in the caudate putamen. These findings warrant the consideration of a novel presynaptic regulatory role for this transporter in excitatory synaptic transmission.
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Affiliation(s)
- M Velaz-Faircloth
- Department of Pharmacology, Duke University Medical Center, Durham, North Carolina 27710, USA
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30
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Brüss M, Hammermann R, Brimijoin S, Bönisch H. Antipeptide antibodies confirm the topology of the human norepinephrine transporter. J Biol Chem 1995; 270:9197-201. [PMID: 7721836 DOI: 10.1074/jbc.270.16.9197] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We have raised polyclonal antibodies (N6-28, L211-226, L371-384, and C590-607) against peptides corresponding to hydrophilic sequences of the human norepinephrine transporter (hNET). The antisera immunoprecipitated the [35S]Met-labeled hNET. Antiserum L211-226, directed against a sequence of the putative second (large) extracellular loop of hNET, also immunoprecipitated the human dopamine transporter. Antisera N6-28 and C590-607, raised against a hNET peptide region of the N and the C termini, respectively, recognized a 58-kDa protein from transfected COS-7 cells expressing the hNET. This 58-kDa species represents a functional, glycosylated form of the hNET and not a degradation product. Tunicamycin treatment of transfected COS-7 cells as well as peptide-N-glycosidase F digestion of the transporter converted the 58-kDa species to a 50-kDa form, indicating that the latter represents the hNET core protein. In indirect immunofluorescence studies, our antisera confirmed the originally proposed topology of hNET. Antisera N6-28 and C590-607 detected hNET only in permeabilized cells. In contrast, antisera L211-226 and L371-384 directed against peptide sequences of the second and fourth putative extracellular loop displayed fluorescence signals with the intact cells.
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Affiliation(s)
- M Brüss
- Institut für Pharmakologie und Toxikologie, Universität Bonn, Federal Republic of Germany
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31
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Olivares L, Aragón C, Giménez C, Zafra F. The role of N-glycosylation in the targeting and activity of the GLYT1 glycine transporter. J Biol Chem 1995; 270:9437-42. [PMID: 7721869 DOI: 10.1074/jbc.270.16.9437] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
To elucidate the role of N-glycosylation in the function of the high affinity glycine transporter GLYT1, we have investigated the effect of the glycosylation inhibitor tunicamycin as well as the effect of the disruption of the putative glycosylation sites by site-directed mutagenesis. SDS-polyacrylamide gel electrophoresis of proteins from GLYT1-transfected COS cells reveals a major band of 80-100 kDa and a minor one of 57 kDa. Treatment with tunicamycin produces a 40% inhibition in transport activity and a decrease in the intensity of the 80-100-kDa band, whereas the 57-kDa band decreases in size to yield a 47-kDa protein corresponding to the unglycosylated form of the transporter. Simultaneous mutation of Asn-169, Asn-172, Asn-182, and Asn-188 to Gln also produces the 47-kDa form of the protein, indicating that there are no additional sites for N-glycosylation. Progressive mutation of the potential glycosylation sites produces a progressive decrease in transport activity and in size of the protein, indicating that the four putative glycosylation sites are actually glycosylated. N-Glycosylation of the GLYT1 is not indispensable for the transport activity itself, as demonstrated by enzymatic deglycosylation of the transporter. Analysis of surface proteins by biotinylation and by immunofluorescence demonstrates that a significant portion of the unglycosylated GLYT1 mutant remains in the intracellular compartment. This suggests that the carbohydrate moiety of glycine transporter GLYT1 is necessary for the proper trafficking of the protein to the plasma membrane.
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Affiliation(s)
- L Olivares
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Universidad Autónoma de Madrid, Spain
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32
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Patel AP, Cerruti C, Vaughan RA, Kuhar MJ. Developmentally regulated glycosylation of dopamine transporter. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1994; 83:53-8. [PMID: 7697870 DOI: 10.1016/0165-3806(94)90178-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The dopamine transporter (DAT) in rat striatum was examined during postnatal development and aging after photolabeling with [125I]DEEP. The DAT-[125I]DEEP protein complex from adult rats (2 months) appeared as a broad diffuse band in SDS-PAGE gels with average apparent molecular mass of about 80,000 Da as previously found. However, the molecular mass was lower at birth (day 0) and at postnatal ages 4 and 14 days. In aged rats (104 weeks), the molecular mass was slightly higher than that found in young adults (60 days). In binding experiments with [3H]BTCP, there were age-related differences in Kd and Bmax with decreases in both Kd and Bmax found in aged rats. Treatment of photolabeled membranes with neuraminidase caused a reduction in DAT molecular mass, but age-related differences were maintained. Treatment with N-glycanase greatly reduced or eliminated the age-related differences. Several DAT peptide-specific polyclonal antibodies immunoprecipitated DAT-[125I]DEEP protein complex at different developmental ages. Taken together, these results suggest differential glycosylation of rat DAT occurs during postnatal development and aging; the increase is due to increases in the N-linked sugars rather than changes in either sialic acid content or the polypeptide.
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Affiliation(s)
- A P Patel
- National Institutes of Health, National Institute on Drug Abuse, Addiction Research Center, Baltimore, MD 21224
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33
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Affiliation(s)
- S Pögün
- Ege University School of Medicine, Department of Physiology, Bornova, Izmir, Turkey
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34
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Varastet M, Riche D, Maziere M, Hantraye P. Chronic MPTP treatment reproduces in baboons the differential vulnerability of mesencephalic dopaminergic neurons observed in Parkinson's disease. Neuroscience 1994; 63:47-56. [PMID: 7898660 DOI: 10.1016/0306-4522(94)90006-x] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Chronic administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to baboons was shown previously to result in a motor syndrome and a pattern of striatal dopaminergic fibre loss similar to those observed in idiopathic Parkinson's disease. In the present study, tyrosine hydroxylase-immunoreactive neurons were quantified in the mesencephalon of control (n = 4) and chronically MPTP-treated (n = 3) baboons. MPTP induced a significant reduction in neuronal cell density in the substantia nigra (63.8% reduction) and the ventral tegmental area (53.1%). Within the substantia nigra, obvious mediolateral and dorsoventral gradients of neuronal cell loss were observed. First, the pars lateralis was more affected than the lateral divisions of the pars compacta (89.6% vs 73.8% cell loss), which in turn were more depleted than the medial divisions (60.1% reduction). Second, the ventral regions of the pars compacta were more degenerated than the dorsal parts (82.4 vs 51.5% decrease). This regional pattern is strikingly similar to that observed in Parkinson's disease and indicates that two subpopulations of dopaminergic neurons are distinguishable on the basis of their differential vulnerability to MPTP. Finally, the present study confirms that chronic mitochondrial complex I inhibition using MPTP in primates is sufficient to reproduce the typical dopaminergic cell loss and striatal fibre depletion observed in Parkinson's disease.
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Affiliation(s)
- M Varastet
- CNRS URA 1285, Service Hospitalier Frédéric Joliot, DRIPP, Orsay, France
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35
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Garris PA, Wightman RM. In vivo voltammetric measurement of evoked extracellular dopamine in the rat basolateral amygdaloid nucleus. J Physiol 1994; 478 ( Pt 2):239-49. [PMID: 7965845 PMCID: PMC1155682 DOI: 10.1113/jphysiol.1994.sp020246] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
1. The in vivo measurement of evoked extracellular dopamine was established in the basolateral amygdaloid nucleus (BAN) using fast-scan cyclic voltammetry at carbon-fibre microelectrodes. 2. The identification of evoked extracellular dopamine in the BAN was based on anatomical, electrochemical and pharmacological criteria. Electrochemical and pharmacological evidence indicated that the species was a catecholamine. Mesencephalic sites eliciting overflow and amygdaloid sites supporting overflow correlated well with the mesoamygdaloid dopamine innervation. 3. Marked differences in the dynamics and magnitude of evoked dopamine overflow were observed in the BAN, caudate-putamen and amygdalo-striatal transition area. The results underscore the importance of making spatially resolved measurements of extracellular dopamine in the amygdala. 4. Mesoamygdaloid dopamine neurons have similar release characteristics as mesostriatal dopamine neurons but share with mesoprefrontal cortical dopamine neurons the ability to use a greater percentage of intraneuronal dopamine stores for release.
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Affiliation(s)
- P A Garris
- Department of Chemistry, University of North Carolina at Chapel Hill 27599-3290
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36
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Melikian H, McDonald J, Gu H, Rudnick G, Moore K, Blakely R. Human norepinephrine transporter. Biosynthetic studies using a site-directed polyclonal antibody. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)32714-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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37
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Abstract
Sodium nitroprusside (SNP), a generator of nitric oxide (NO), decreased [3H]dopamine uptake into rat striatal synaptosomal preparations in a dose-, time- and temperature-dependent fashion. Reduced hemoglobin, a substance that binds NO, prevented the SNP-induced decrease in uptake. Potassium ferri- and ferrocyanide, compounds similar to SNP that do not produce NO, were without effect on uptake. SNP inhibited [3H]dopamine uptake in synaptosomes from nucleus accumbens and olfactory tubercle as well but with a lower potency. SNP inhibited [3H]serotonin and [3H]glutamate uptake but had no effect on [3H]norepinephrine uptake. S-Nitroso-N-acetylpenicillamine (SNAP), another generator of NO, had effects similar to those of SNP. The SNP-induced decrease in [3H]dopamine uptake was due to a Vmax decrease at 100 microM SNP and to both a Vmax and Km change at 300 microM SNP. Depletion of calcium by omission of calcium from buffers and addition of EGTA increased the potency of SNP in inhibiting uptake. There was no change in [3H]WIN 35428 binding to the dopamine transporter with doses of SNP that inhibited uptake. These data indicate that NO can decrease [3H]dopamine transporter function.
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Affiliation(s)
- S Pogun
- Neuroscience Branch, National Institutes of Health, National Institute on Drug Abuse, Addiction Research Center, Baltimore, MD 21224
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38
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Cerruti C, Pilotte NS, Uhl G, Kuhar MJ. Reduction in dopamine transporter mRNA after cessation of repeated cocaine administration. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1994; 22:132-8. [PMID: 8015373 DOI: 10.1016/0169-328x(94)90040-x] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Male, Lewis rats were treated intravenously for 2 weeks with saline or cocaine using a dose and injection schedule that is similar to the doses and patterns of cocaine intake in self-administration studies. Ten days after cessation of treatment, dopamine transporter binding levels were decreased in the nucleus accumbens but not in the striatum. In situ hybridization studies revealed decreases in dopamine transporter mRNA that were restricted to cells of the interfascicular and caudal linear nuclei; these dopaminergic cell groups, found in the ventral tegmentum, project to the nucleus accumbens and other limbic areas. Other dopaminergic cell groups in midbrain which project mainly to other areas did not show a decrease in mRNA. These results indicate that gene expression can be altered many days after withdrawal from cocaine, and provide an example of transporter regulation by a change in gene expression.
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Affiliation(s)
- C Cerruti
- NIH, National Institute on Drug Abuse, Addiction Research Center, Baltimore, MD 21224
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39
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Patel A, Uhl G, Kuhar MJ. Species differences in dopamine transporters: postmortem changes and glycosylation differences. J Neurochem 1993; 61:496-500. [PMID: 8336137 DOI: 10.1111/j.1471-4159.1993.tb02151.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The apparent molecular masses of photoaffinity-labeled dopamine transporters (DATs) from rat, human, dog, and primate kidney COS cells expressing the rat DAT1 cDNA differ. Sequences predicted from cDNA cloning reveal only one amino acid difference between the length of the rat and human DAT but one less site for potential N-linked glycosylation in the human DAT. Possible posttranslational and postmortem bases for species differences in DAT molecular mass were explored. Rat DAT proteins from striata subjected to approximately 5 h of postmortem delay modeled after the human postmortem delay process revealed small but consistent losses in apparent molecular mass and in cocaine analogue binding; the DAT molecular mass displayed no further losses for up to 30 h of model postmortem treatment. Degradative postmortem changes could thus contribute to molecular mass differences between rat and human DATs. Neuraminidase treatment reduced the apparent molecular mass of native rat DAT but not that of the rat DAT expressed in COS cells, suggesting that the sugars added to the DAT expressed in COS cells were different than those added to the rat brain striatal transporter. These differences could account for the somewhat higher Km values for expressed DAT cDNA in COS cells when compared with the wild-type striatal transporter. These results are in accord with the differences in number of predicted N-linked glycosylation sites between rat and human DATs and with cell-type specificity in transporter posttranslational processing.
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Affiliation(s)
- A Patel
- Molecular Pharmacology Section, NIDA Addiction Research Center, Baltimore, Maryland 21224
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