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Huot P, Fox SH, Brotchie JM. Monoamine reuptake inhibitors in Parkinson's disease. PARKINSON'S DISEASE 2015; 2015:609428. [PMID: 25810948 PMCID: PMC4355567 DOI: 10.1155/2015/609428] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 12/26/2014] [Indexed: 12/13/2022]
Abstract
The motor manifestations of Parkinson's disease (PD) are secondary to a dopamine deficiency in the striatum. However, the degenerative process in PD is not limited to the dopaminergic system and also affects serotonergic and noradrenergic neurons. Because they can increase monoamine levels throughout the brain, monoamine reuptake inhibitors (MAUIs) represent potential therapeutic agents in PD. However, they are seldom used in clinical practice other than as antidepressants and wake-promoting agents. This review article summarises all of the available literature on use of 50 MAUIs in PD. The compounds are divided according to their relative potency for each of the monoamine transporters. Despite wide discrepancy in the methodology of the studies reviewed, the following conclusions can be drawn: (1) selective serotonin transporter (SERT), selective noradrenaline transporter (NET), and dual SERT/NET inhibitors are effective against PD depression; (2) selective dopamine transporter (DAT) and dual DAT/NET inhibitors exert an anti-Parkinsonian effect when administered as monotherapy but do not enhance the anti-Parkinsonian actions of L-3,4-dihydroxyphenylalanine (L-DOPA); (3) dual DAT/SERT inhibitors might enhance the anti-Parkinsonian actions of L-DOPA without worsening dyskinesia; (4) triple DAT/NET/SERT inhibitors might exert an anti-Parkinsonian action as monotherapy and might enhance the anti-Parkinsonian effects of L-DOPA, though at the expense of worsening dyskinesia.
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Affiliation(s)
- Philippe Huot
- Toronto Western Research Institute, Toronto Western Hospital, University Health Network, 399 Bathurst Street, Toronto, ON, Canada M5T 2S8
- Division of Neurology, Movement Disorder Clinic, Toronto Western Hospital, University Health Network, University of Toronto, 399 Bathurst Street, Toronto, ON, Canada M5T 2S8
- Department of Pharmacology and Division of Neurology, Faculty of Medicine, Université de Montréal and Centre Hospitalier de l'Université de Montréal, Montréal, QC, Canada
| | - Susan H. Fox
- Toronto Western Research Institute, Toronto Western Hospital, University Health Network, 399 Bathurst Street, Toronto, ON, Canada M5T 2S8
- Division of Neurology, Movement Disorder Clinic, Toronto Western Hospital, University Health Network, University of Toronto, 399 Bathurst Street, Toronto, ON, Canada M5T 2S8
| | - Jonathan M. Brotchie
- Toronto Western Research Institute, Toronto Western Hospital, University Health Network, 399 Bathurst Street, Toronto, ON, Canada M5T 2S8
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The Role of Cysteines and Histidins of the Norepinephrine Transporter. Neurochem Res 2013; 38:1303-14. [DOI: 10.1007/s11064-013-1022-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Revised: 03/11/2013] [Accepted: 03/14/2013] [Indexed: 12/17/2022]
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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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Sogawa C, Mitsuhata C, Kumagai-Morioka K, Sogawa N, Ohyama K, Morita K, Kozai K, Dohi T, Kitayama S. Expression and function of variants of human catecholamine transporters lacking the fifth transmembrane region encoded by exon 6. PLoS One 2010; 5:e11945. [PMID: 20700532 PMCID: PMC2916826 DOI: 10.1371/journal.pone.0011945] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Accepted: 07/11/2010] [Indexed: 11/30/2022] Open
Abstract
Background The transporters for dopamine (DAT) and norepinephrine (NET) are members of the Na+- and Cl−-dependent neurotransmitter transporter family SLC6. There is a line of evidence that alternative splicing results in several isoforms of neurotransmitter transporters including NET. However, its relevance to the physiology and pathology of the neurotransmitter reuptake system has not been fully elucidated. Methodology/Principal Findings We found novel isoforms of human DAT and NET produced by alternative splicing in human blood cells (DAT) and placenta (NET), both of which lacked the region encoded by exon 6. RT-PCR analyses showed a difference in expression between the full length (FL) and truncated isoforms in the brain and peripheral tissues, suggesting tissue-specific alternative splicing. Heterologous expression of the FL but not truncated isoforms of DAT and NET in COS-7 cells revealed transport activity. However, immunocytochemistry with confocal microscopy and a cell surface biotinylation assay demonstrated that the truncated as well as FL isoform was expressed at least in part in the plasma membrane at the cell surface, although the truncated DAT was distributed to the cell surface slower than FL DAT. A specific antibody to the C-terminus of DAT labeled the variant but not FL DAT, when cells were not treated with Triton for permeabilization, suggesting the C-terminus of the variant to be located extracellulary. Co-expression of the FL isoform with the truncated isoform in COS-7 cells resulted in a reduced uptake of substrates, indicating a dominant negative effect of the variant. Furthermore, an immunoprecipitation assay revealed physical interaction between the FL and truncated isoforms. Conclusions/Significance The unique expression and function and the proposed membrane topology of the variants suggest the importance of isoforms of catecholamine transporters in monoaminergic signaling in the brain and peripheral tissues.
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Affiliation(s)
- Chiharu Sogawa
- Department of Dental Pharmacology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Chieko Mitsuhata
- Department of Pediatric Dentistry, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan
| | - Kei Kumagai-Morioka
- Department of Dental Pharmacology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan
| | - Norio Sogawa
- Department of Dental Pharmacology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Kazumi Ohyama
- RI Research Center, Okayama University Dental School, Okayama, Japan
| | - Katsuya Morita
- Department of Dental Pharmacology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan
| | - Katsuyuki Kozai
- Department of Pediatric Dentistry, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan
| | - Toshihiro Dohi
- Department of Dental Pharmacology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan
| | - Shigeo Kitayama
- Department of Dental Pharmacology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
- * E-mail:
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Sogawa C, Kumagai K, Sogawa N, Morita K, Dohi T, Kitayama S. C-terminal region regulates the functional expression of human noradrenaline transporter splice variants. Biochem J 2007; 401:185-95. [PMID: 16965261 PMCID: PMC1698689 DOI: 10.1042/bj20060495] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The NET [noradrenaline (norepinephrine) transporter], an Na+/Cl--dependent neurotransmitter transporter, has several isoforms produced by alternative splicing in the C-terminal region, each differing in expression and function. We characterized the two major isoforms of human NET, hNET1, which has seven C-terminal amino acids encoded by exon 15, and hNET2, which has 18 amino acids encoded by exon 16, by site-directed mutagenesis in combination with NE (noradrenaline) uptake assays and cell surface biotinylation. Mutants lacking one third or more of the 24 amino acids encoded by exon 14 exhibited neither cell surface expression nor NE uptake activity, with the exception of the mutant lacking the last eight amino acids of hNET2, whose expression and uptake resembled that of the WT (wild-type). A triple alanine replacement of a candidate motif (ENE) in this region mimicked the influences of the truncation. Deletion of either the last three or another four amino acids of the C-terminus encoded by exon 15 in hNET1 reduced the cell surface expression and NE uptake, whereas deletion of all seven residues reduced the transport activity but did not affect the cell surface expression. Replacement of RRR, an endoplasmic reticulum retention motif, by alanine residues in the C-terminus of hNET2 resulted in a similar expression and function compared with the WT, while partly recovering the effects of the mutation of ENE. These findings suggest that in addition to the function of the C-terminus, the common proximal region encoded by exon 14 regulates the functional expression of splice variants, such as hNET1 and hNET2.
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Affiliation(s)
- Chiharu Sogawa
- *Department of Dental Pharmacology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8525, Japan
| | - Kei Kumagai
- †Department of Dental Pharmacology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima 734-8553, Japan
| | - Norio Sogawa
- *Department of Dental Pharmacology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8525, Japan
| | - Katsuya Morita
- †Department of Dental Pharmacology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima 734-8553, Japan
| | - Toshihiro Dohi
- †Department of Dental Pharmacology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima 734-8553, Japan
| | - Shigeo Kitayama
- *Department of Dental Pharmacology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8525, Japan
- To whom correspondence should be addressed (email )
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Abstract
For many years, the norepinephrine transporter (NET) was considered a 'static' protein that contributed to the termination of the action of norepinephrine in the synapse of noradrenergic neurons. The concept that the NET is dynamically regulated, adjusting noradrenergic transmission by changing its function and/or expression, was considered initially in the mid 1980s. Since that time, a plethora of studies demonstrate that the NET is regulated by several intracellular and extracellular signaling molecules, and that phosphorylation of the NET is a major pathway regulating its cell surface expression and thereby its function. The NET is a target of action of a number of drugs that are used long-term therapeutically or abused chronically. This has driven numerous investigations of how the NET and its function are regulated by long-term exposure to drugs. While repeated exposure to many drugs has been shown to affect NET function and expression, the intracellular mechanisms for these effects remains elusive.
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Affiliation(s)
- Prashant Mandela
- Department of Pharmacology & Toxicology, University of Mississippi Medical Center, Jackson, USA
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Abstract
AbstractMolecular-genetic imaging in living organisms has become a new field with the exceptional growth over the past 5 years. Modern imaging is based on three technologies: nuclear, magnetic resonance and optical imaging. Most current molecular-genetic imaging strategies are “indirect,” coupling a “reporter gene” with a complimentary “reporter probe.” The reporter transgene usually encodes for an enzyme, receptor or transporter that selectively interacts with a radiolabeled probe and results in accumulation of radioactivity in the transduced cell. In addition, reporter systems based on the expression of fluorescence or bioluminescence proteins are becoming more widely applied in small animal imaging. This review begins with a description of Positron Emission Tomography (PET)-based imaging genes and their complimentary radiolabeled probes that we think will be the first to enter clinical trials. Then we describe other imaging genes, mostly for optical imaging, which have been developed by investigators working with a variety of disease models in mice. Such optical reporters are unlikely to enter the clinic, at least not in the near-term. Reporter gene constructs can be driven by constitutive promoter elements and used to monitor gene therapy vectors and the efficacy of gene targeting and transduction, as well as to monitor adoptive cell-based therapies. Inducible promoters can be used as “sensors” to monitor endogenous cell processes, including specific intracellular molecular-genetic events and the activity of signaling pathways, by regulating the magnitude of reporter gene expression.
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Schwartz JW, Piston D, DeFelice LJ. Molecular microfluorometry: converting arbitrary fluorescence units into absolute molecular concentrations to study binding kinetics and stoichiometry in transporters. Handb Exp Pharmacol 2006:23-57. [PMID: 16722229 DOI: 10.1007/3-540-29784-7_2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Cotransporters use energy stored in Na+ or H+ gradients to transport neurotransmitters or other substrates against their own gradient. Cotransport is rapid and efficient, and at synapses it helps terminate signaling. Cotransport in norepinephrine (NET), epinephrine (EpiT), dopamine (DAT), and serotonin (SERT) transporters couples downhill Na+ flux to uphill transmitter flux. NETs, for example, attenuate signaling at adrenergic synapses by efficiently clearing NE from the synaptic cleft, thus preparing the synapse for the next signal. Transport inhibition with tricyclic antidepressants prolongs neurotransmitter presence in the synaptic cleft, potentially alleviating symptoms of depression. Transport inhibition with cocaine or amphetamine, which respectively block or replace normal transport, may result in hyperactivity. Little is known about the kinetic interactions of substrates or drugs with transporters, largely because the techniques that have been successful in discovering trans- porter agonists and antagonists do not yield detailed kinetic information. Mechanistic data are for the most part restricted to global parameters, such as Km and Vmax, measured from large populations of transporter molecules averaged over thousands of cells. Three relatively new techniques used in transporter research are electrophysiology, amperometry, and microfluorometry. This review focuses on fluorescence-based methodologies, which--unlike any other technique-permit the simultaneous measurement of binding and transport. Microfluorometry provides unique insights into binding kinetics and transport mechanisms from a quantitative analysis of fluorescence data. Here we demonstrate how to quantify the number of bound substrate molecules, the number of transported substrate molecules, and the kinetics of substrate binding to individual transporters. Although we describe experiments on a specific neurotransmitter transporter, these methods are applicable to other membrane proteins.
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Affiliation(s)
- J W Schwartz
- Imaging Center, Stowers Institute for Medical Research, 1000 E 50th St., Kansas City, MO 64110, USA
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Cleary S, Brouwers FM, Eisenhofer G, Pacak K, Christie DL, Lipski J, McNeil AR, Phillips JK. Expression of the noradrenaline transporter and phenylethanolamine N-methyltransferase in normal human adrenal gland and phaeochromocytoma. Cell Tissue Res 2005; 322:443-53. [PMID: 16047163 DOI: 10.1007/s00441-005-0026-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Accepted: 05/30/2005] [Indexed: 11/30/2022]
Abstract
Expression of the noradrenaline transporter (NAT) was examined in normal human adrenal medulla and phaeochromocytoma by using immunohistochemistry and confocal microscopy. The enzymes tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) were used as catecholamine biosynthetic markers and chromogranin A (CGA) as a marker for secretory granules. Catecholamine content was measured by using high performance liquid chromatography (HPLC). In normal human adrenal medulla (n=5), all chromaffin cells demonstrated strong TH, PNMT and NAT immunoreactivity. NAT was co-localized with PNMT and was located within the cytoplasm with a punctate appearance. Human phaeochromocytomas demonstrated strong TH expression (n=20 samples tested) but variable NAT and PNMT expression (n=24). NAT immunoreactivity ranged from absent (n=3) to weak (n=10) and strong (n=11) and, in some cases, occupied an apparent nuclear location. Unlike the expression seen in normal human adrenal medullary tissue, NAT expression was not consistently co-localized with PNMT. PNMT also showed highly variable expression that was poorly correlated with tumour adrenaline content. Immunoreactivity for CGA was colocalized with NAT within the cytoplasm of normal human chromaffin cells (n=4). This co-localization was not consistent in phaeochromocytoma tumour cells (n=7). The altered pattern of expression for both NAT and PNMT in phaeochromocytoma indicates a significant disruption in the regulation and possibly in the function of these proteins in adrenal medullary tumours.
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Affiliation(s)
- Susannah Cleary
- Division of Health Science, Murdoch University, Perth, Western Australia, 6150, Australia
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10
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Mash DC, Ouyang Q, Qin Y, Pablo J. Norepinephrine transporter immunoblotting and radioligand binding in cocaine abusers. J Neurosci Methods 2005; 143:79-85. [PMID: 15763139 DOI: 10.1016/j.jneumeth.2004.09.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The norepinephrine transporter (NET) is a membrane protein responsible for transporting extracellular norepinephrine. The cocaine and tricyclic antidepressant-sensitive NET belongs to a family of sodium and chloride coupled transporters that include the monoamines dopamine and serotonin and the amino acids GABA and glycine. The regional distribution of the NET has been defined by synaptosomal uptake of norepinephrine and by autoradiographic approaches in rodent and primate brain. However, the NET has not been well characterized in the human brain due to the overall low abundance of protein expressed in axon terminals. Recently, immunolocalization studies have been used to identify the regional distribution of the cytoplasmic NET epitope in rodent brain. We report here on the characteristics of drug interactions with the native NET protein in human postmortem brain. Antisera raised against a 17-amino acid peptide from the N-terminus of the hNET recognized an 80 kDa species in human cerebral cortex. Chronic exposure to cocaine upregulated NET protein expression and [3H]nisoxetine binding sites in the insular cortex from brains of cocaine addicts. These results demonstrate that immunologic and radioligand binding approaches afford specific labeling of the native transport protein in postmortem human brain.
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Affiliation(s)
- Deborah C Mash
- Department of Neurology (D4-5), School of Medicine, University of Miami, 1501 N.W. 9th Avenue, Miami, FL 33136, USA.
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Stamm S, Ben-Ari S, Rafalska I, Tang Y, Zhang Z, Toiber D, Thanaraj TA, Soreq H. Function of alternative splicing. Gene 2004; 344:1-20. [PMID: 15656968 DOI: 10.1016/j.gene.2004.10.022] [Citation(s) in RCA: 651] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2004] [Revised: 09/10/2004] [Accepted: 10/21/2004] [Indexed: 02/06/2023]
Abstract
Alternative splicing is one of the most important mechanisms to generate a large number of mRNA and protein isoforms from the surprisingly low number of human genes. Unlike promoter activity, which primarily regulates the amount of transcripts, alternative splicing changes the structure of transcripts and their encoded proteins. Together with nonsense-mediated decay (NMD), at least 25% of all alternative exons are predicted to regulate transcript abundance. Molecular analyses during the last decade demonstrate that alternative splicing determines the binding properties, intracellular localization, enzymatic activity, protein stability and posttranslational modifications of a large number of proteins. The magnitude of the effects range from a complete loss of function or acquisition of a new function to very subtle modulations, which are observed in the majority of cases reported. Alternative splicing factors regulate multiple pre-mRNAs and recent identification of physiological targets shows that a specific splicing factor regulates pre-mRNAs with coherent biological functions. Therefore, evidence is now accumulating that alternative splicing coordinates physiologically meaningful changes in protein isoform expression and is a key mechanism to generate the complex proteome of multicellular organisms.
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Affiliation(s)
- Stefan Stamm
- Institute for Biochemistry, University of Erlangen, Fahrstrasse 17, 91054 Erlangen, Germany.
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Kitayama S, Dohi T. Norepinephrine transporter splice variants and their interaction with substrates and blockers. Eur J Pharmacol 2003; 479:65-70. [PMID: 14612138 DOI: 10.1016/j.ejphar.2003.08.057] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Norepinephrine transporter (NET), a member of the Na+/Cl--dependent neurotransmitter transporter family, displays species-specific isoforms produced by alternative RNA splicing. This occurs at 3'-flanking coding and noncoding regions, resulting in different carboxy-terminals. When these NET splice variants were expressed in cultured cell lines, the characteristics of substrate transport and the sensitivity to uptake inhibitors differed between isoforms. The different functional expression suggests the physiological importance of the action and interaction of NET splice variants in synaptic transmission.
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Affiliation(s)
- Shigeo Kitayama
- Department of Dental Pharmacology, Okayama University, Graduate School of Medicine and Dentistry, Shikata 2-5-1, Okayama 700-8525, Japan.
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Hahn MK, Blakely RD. Monoamine transporter gene structure and polymorphisms in relation to psychiatric and other complex disorders. THE PHARMACOGENOMICS JOURNAL 2003; 2:217-35. [PMID: 12196911 DOI: 10.1038/sj.tpj.6500106] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2002] [Revised: 03/05/2002] [Accepted: 03/05/2002] [Indexed: 01/23/2023]
Abstract
The norepinephrine, dopamine and serotonin transporters (NET, DAT and SERT, respectively), limit cellular signaling by recapturing released neurotransmitter, and serve as targets for antidepressants and drugs of abuse, emphasizing the integral role these molecules play in neurotransmission and pathology. This has compelled researchers to search for polymorphisms in monoamine (MA) transporter genes. Studies support linkage and association of MA transporter genetic variation in psychiatric and other complex disorders. Understanding the contribution of MA transporter polymorphisms to human behavior, disease susceptibility and response to pharmacotherapies will involve further progress in linkage and association that will be aided by both definition of highly selective phenotypes and utilization of a large number of polymorphic markers. The relationship of polymorphisms to alterations in transport capacity, likely a complex interaction, involving genetic background, disease state, and medication, will elucidate the means by which MA transporter genetic variability contributes to our individuality.
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Affiliation(s)
- M K Hahn
- Department of Pharmacology and Center for Molecular Neuroscience, Vanderbilt University, Nashville, TN 37232-6420, USA.
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Torres GE, Gainetdinov RR, Caron MG. Plasma membrane monoamine transporters: structure, regulation and function. Nat Rev Neurosci 2003; 4:13-25. [PMID: 12511858 DOI: 10.1038/nrn1008] [Citation(s) in RCA: 656] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Gonzalo E Torres
- Howard Hughes Medical Institute, Department of Cell Biology, Duke University, Durham, North Carolina 27710, USA
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Dohi T, Kitayama S, Kumagai K, Hashimoto W, Morita K. [Pharmacology of monoamine neurotransmitter transporters]. Nihon Yakurigaku Zasshi 2002; 120:315-26. [PMID: 12491807 DOI: 10.1254/fpj.120.315] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Following exocytotic release, the biogenic amine neurotransmitters, norepinephrine, dopamine, and serotonin are removed from the synaptic cleft by the respective transporter, NET, DAT, and SERT, located on the plasma membrane and then re-stored into synaptic vesicles by vesicular monoamine transporter, VMAT. The molecular cloning of these transporters revealed that NET, DAT, and SERT are members of a sodium-dependent neurotransmitter transporter gene family, while VMATs arise from proton-dependent transporter gene family. Structural features common to NET, DAT, and SERT reveal a putative 12 transmembrane-spanning domain structure with cytosolic N- and C-terminal regions. Recent evidence suggest the regulation of the functional expression of these transporters via phosphorylation, which include direct phosphorylation of transporter proteins and/or of associated proteins that may control transporter function/expression. In addition, the substrates and inhibitors for these transporters appear capable of regulating transporter cell surface expression, thereby suggesting both activity-dependent and pharmacological regulatory mechanisms for transporter expression. Analyses of the genes provide new insight into their relation to neuronal diseases since NET, DAT and SERT are the molecular targets for many antidepressants as well as drugs of abuse such as cocaine and amphetamine. The availability of cDNAs of these and vesicular transporters has permitted detailed pharmacological studies in heterologous expression systems, and thus would promise the development of novel drugs with diverse chemical structures.
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Affiliation(s)
- Toshihiro Dohi
- Department of Dental Pharmacology, Division of Integrated Medical Science, Hiroshima University Graduate School of Biomedical Sciences, Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
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Kitayama S, Kumagai K, Morita K, Dohi T. Identification and functional characterization of the novel isoforms of bovine norepinephrine transporter produced by alternative splicing. Brain Res 2002; 934:152-6. [PMID: 11955478 DOI: 10.1016/s0006-8993(02)02417-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Analyzing variation of bovine norepinephrine transporter (NET) at the 3'-region by RT-PCR in the adrenal glands and the brain revealed four isoforms of NET produced by alternative splicing of four cassettes (C0, C1, C2 and C3) encoded by exons 12-15, designated bNET1a (C0-C1-C2, formerly designated bNET1), bNET1b (C0-C2), bNET2a (C0-C1-C3) and bNET2b (C0-C3, formerly designated bNET2), respectively. Expression of these isoforms in COS-7 cells revealed that the isoforms that contain the C1 cassette encoded by exon 13 (bNET1a and bNET2a) showed a significant increase in [(3)H]norepinephrine uptake and [(3)H]nisoxetine binding, whereas the isoforms which lack the C1 cassette (bNET1b and bNET2b) failed to display those activities despite the selection of either exon 14 or exon 15. These results suggest that the region encoded by exon 13 is indispensable for NET functional expression.
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Affiliation(s)
- Shigeo Kitayama
- Department of Pharmacology, Hiroshima University Faculty of Dentistry, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8553, Japan.
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