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Venegas FC, Rosas D, Delgado N, Estay-Olmos C, Iturriaga-Vásquez P, Rivera-Meza M, Torres GE, Renard GM, Sotomayor-Zárate R. Early-life exposure to sex hormones promotes voluntary ethanol intake in adulthood. A vulnerability factor to drug addiction. Prog Neuropsychopharmacol Biol Psychiatry 2024; 133:111001. [PMID: 38565388 DOI: 10.1016/j.pnpbp.2024.111001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 03/29/2024] [Accepted: 03/30/2024] [Indexed: 04/04/2024]
Abstract
While there is extensive research on alcohol dependence, the factors that make an individual vulnerable to developing alcoholism haven't been explored much. In this study, we aim to investigate how neonatal exposure to sex hormones affects alcohol intake and the regulation of the mesolimbic pathway in adulthood. The study aimed to investigate the impact of neonatal exposure to a single dose of testosterone propionate (TP) or estradiol valerate (EV) on ethanol consumption in adult rats. The rats were subjected to a two-bottle free-choice paradigm, and the content of dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the nucleus accumbens (NAcc) was measured using HPLC-ED. The expression of critical DA-related proteins in the mesolimbic pathway was evaluated through RT-qPCR and western blot analysis. Supraphysiological neonatal exposure to EV or TP resulted in increased ethanol intake over four weeks in adulthood. In addition, the DA and DOPAC content was reduced and increased in the NAcc of EV and TP-treated rats, and β-endorphin content in the hypothalamus decreased in EV-treated rats. The VTA μ receptor and DA type 2 form short receptor (D2S) expression were significantly reduced in EV and TP male rats. Finally, in an extended 6-week protocol, the increase in ethanol consumption induced by EV was mitigated during the initial two hours post-naloxone injection. Neonatal exposure to sex hormones is a detrimental stimulus for the brain, which can facilitate the development of addictive behaviors, including alcohol use disorder.
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Affiliation(s)
- Francisca C Venegas
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Department of Biomedical Sciences, University of Padua, Italy
| | - Daniela Rosas
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Nicol Delgado
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Camila Estay-Olmos
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Patricio Iturriaga-Vásquez
- Departamento de Ciencias Químicas y Recursos Naturales, Facultad de Ingeniería y Ciencias, Universidad de la Frontera, Temuco, Chile
| | - Mario Rivera-Meza
- Departamento de Química Farmacológica y Toxicológica, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Gonzalo E Torres
- Department of Molecular Pharmacology & Neuroscience, Stritch School of Medicine, Loyola University Chicago, USA
| | - Georgina M Renard
- Centro de Investigación Biomédica y Aplicada (CIBAP), Escuela de Medicina, Facultad de Ciencias Médicas, Universidad de Santiago de Chile (USACH), Santiago, Chile.
| | - Ramón Sotomayor-Zárate
- Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.
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2
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Robles A, Dinamarca-Villarroel L, Torres GE, Fierro A. Collective and Coordinated Conformational Changes Determine Agonism or Antagonism at the Human Trace Amine-Associated Receptor 1. ACS Omega 2023; 8:43051-43059. [PMID: 38024694 PMCID: PMC10652269 DOI: 10.1021/acsomega.3c06315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 10/13/2023] [Accepted: 10/17/2023] [Indexed: 12/01/2023]
Abstract
The human trace amine-associated receptor (hTAAR1), a G protein-coupled receptor, has been postulated as a new target in the treatment of neuropsychiatric conditions. The mechanism associated with activation or inactivation by agonists or antagonists in hTAAR1 and other GPCRs has not yet been fully elucidated. In this study, we combined computational methods including homology modeling, docking, and molecular dynamic simulations to reveal novel conformational changes associated with agonist and antagonist interactions in hTAAR1. Our findings suggest a differential cascade of coordinated movements based on the presence of either an agonist or antagonist and primarily involving the second extracellular loop, transmembrane domain 5, and the third intracellular domains of hTAAR1. Our study provides an opportunity to predict the effects on new ligands with agonistic or antagonistic activity at hTAAR1 based on the reported conformational changes.
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Affiliation(s)
- Agustín
I. Robles
- Departamento
de Química Orgánica, Escuela de Química, Facultad
de Química y de Farmacia, Pontificia
Universidad Católica de Chile, Santiago 7820436, Chile
- Department
of Molecular Pharmacology & Neuroscience, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois 60611-2001, United States
| | - Luis Dinamarca-Villarroel
- Departamento
de Química Orgánica, Escuela de Química, Facultad
de Química y de Farmacia, Pontificia
Universidad Católica de Chile, Santiago 7820436, Chile
- Department
of Molecular Pharmacology & Neuroscience, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois 60611-2001, United States
| | - Gonzalo E. Torres
- Department
of Molecular Pharmacology & Neuroscience, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois 60611-2001, United States
| | - Angélica Fierro
- Departamento
de Química Orgánica, Escuela de Química, Facultad
de Química y de Farmacia, Pontificia
Universidad Católica de Chile, Santiago 7820436, Chile
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3
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Stokes C, Pino JA, Hagan DW, Torres GE, Phelps EA, Horenstein NA, Papke RL. Betel quid: New insights into an ancient addiction. Addict Biol 2022; 27:e13223. [PMID: 36001424 PMCID: PMC9552247 DOI: 10.1111/adb.13223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Accepted: 07/22/2022] [Indexed: 11/27/2022]
Abstract
The use of areca nuts (areca) in the form of betel quids constitutes the fourth most common addiction in the world, associated with high risk for oral disease and cancer. Areca is a complex natural product, making it difficult to identify specific components associated with the addictive and carcinogenic properties. It is commonly believed that the muscarinic agonist arecoline is at the core of the addiction. However, muscarinic receptor activation is not generally believed to support drug-taking behaviour. Subjective accounts of areca use include descriptions of both sedative and stimulatory effects, consistent with the presence of multiple psychoactive agents. We have previously reported partial agonism of α4-containing nicotinic acetylcholine receptors by arecoline and subsequent inhibition of those receptors by whole areca broth. In the present study, we report the inhibition of nicotinic acetylcholine receptors and other types of neurotransmitter receptors with compounds of high molecular weight in areca and the ability of low molecular weight areca extract to activate GABA and glutamate receptors. We confirm the presence of a high concentration of GABA and glutamate in areca. Additionally, data also indicate the presence of a dopamine and serotonin transporter blocking activity in areca that could account for the reported stimulant and antidepressant activity. Our data suggest that toxic elements of high molecular weight may contribute to the oral health liability of betel quid use, while two distinct low molecular weight components may provide elements of reward, and the nicotinic activity of arecoline contributes to the physical dependence of addiction.
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Affiliation(s)
- Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 Gainesville, FL 32610
| | - Jose A. Pino
- Department of Medicine, School of Medicine, University of Atacama, Copiapó, Chile
| | - D. Walker Hagan
- Department of Biomedical Engineering University of Florida, PO Box 100267 Gainesville, FL 32611
| | - Gonzalo E. Torres
- Department of Molecular, Cellular, and Biomedical Sciences, City University of New York School of Medicine at City College, New York, NY 10031
| | - Edward A. Phelps
- Department of Biomedical Engineering University of Florida, PO Box 100267 Gainesville, FL 32611
| | - Nicole A. Horenstein
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611-7200
| | - Roger L. Papke
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 Gainesville, FL 32610
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Pino JA, Awadallah N, Norris AM, Torres GE. A Plate-Based Assay for the Measurement of Endogenous Monoamine Release in Acute Brain Slices. J Vis Exp 2021. [PMID: 34459801 DOI: 10.3791/62127] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Monoamine neurotransmitters are associated with numerous neurologic and psychiatric ailments. Animal models of such conditions have shown alterations in monoamine neurotransmitter release and uptake dynamics. Technically complex methods such as electrophysiology, Fast Scan Cyclic Voltammetry (FSCV), imaging, in vivo microdialysis, optogenetics, or use of radioactivity are required to study monoamine function. The method presented here is an optimized two-step approach for detecting monoamine release in acute brain slices using a 48-well plate containing tissue holders for examining monoamine release, and high-performance liquid chromatography coupled with electrochemical detection (HPLC-ECD) for monoamine release measurement. Briefly, rat brain sections containing regions of interest, including prefrontal cortex, hippocampus, and dorsal striatum were obtained using a tissue slicer or vibratome. These regions of interest were dissected from the whole brain and incubated in an oxygenated physiological buffer. Viability was examined throughout the experimental time course, by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The acutely dissected brain regions were incubated in varying drug conditions that are known to induce monoamine release through the transporter (amphetamine) or through the activation of exocytotic vesicular release (KCl). After incubation, the released products in the supernatant were collected and analyzed through an HPLC-ECD system. Here, basal monoamine release is detected by HPLC from acute brain slices. This data supports previous in vivo and in vitro results showing that AMPH and KCl induce monoamine release. This method is particularly useful for studying mechanisms associated with monoamine transporter-dependent release and provides an opportunity to screen compounds affecting monoamine release in a rapid and low-cost manner.
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Affiliation(s)
- Jose A Pino
- Department of Medicine, School of Medicine, Universidad de Atacama;
| | - Nora Awadallah
- Department of Molecular, Cellular, and Biomedical Sciences, City University of New York School of Medicine at City College
| | - Alessandra M Norris
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine
| | - Gonzalo E Torres
- Department of Molecular, Cellular, and Biomedical Sciences, City University of New York School of Medicine at City College;
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Pino JA, Nuñez-Vivanco G, Hidalgo G, Reyes Parada M, Khoshbouei H, Torres GE. Identification of Critical Residues in the Carboxy Terminus of the Dopamine Transporter Involved in the G Protein βγ-Induced Dopamine Efflux. Front Pharmacol 2021; 12:642881. [PMID: 33841159 PMCID: PMC8025876 DOI: 10.3389/fphar.2021.642881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 02/11/2021] [Indexed: 11/13/2022] Open
Abstract
The dopamine transporter (DAT) plays a crucial role in the regulation of brain dopamine (DA) homeostasis through the re-uptake of DA back into the presynaptic terminal. In addition to re-uptake, DAT is also able to release DA through a process referred to as DAT-mediated DA efflux. This is the mechanism by which potent and highly addictive psychostimulants, such as amphetamine (AMPH) and its analogues, increase extracellular DA levels in motivational and reward areas of the brain. Recently, we discovered that G protein βγ subunits (Gβγ) binds to the DAT, and that activation of Gβγ results in DAT-mediated efflux - a similar mechanism as AMPH. Previously, we have shown that Gβγ binds directly to a stretch of 15 residues within the intracellular carboxy terminus of DAT (residues 582-596). Additionally, a TAT peptide containing residues 582 to 596 of DAT was able to block the Gβγ-induced DA efflux through DAT. Here, we use a combination of computational biology, mutagenesis, biochemical, and functional assays to identify the amino acid residues within the 582-596 sequence of the DAT carboxy terminus involved in the DAT-Gβγ interaction and Gβγ-induced DA efflux. Our in-silico protein-protein docking analysis predicted the importance of F587 and R588 residues in a network of interactions with residues in Gβγ. In addition, we observed that mutating R588 to alanine residue resulted in a mutant DAT which exhibited attenuated DA efflux induced by Gβγ activation. We demonstrate that R588, and to a lesser extent F5837, located within the carboxy terminus of DAT play a critical role in the DAT-Gβγ physical interaction and promotion of DA efflux. These results identify a potential new pharmacological target for the treatment of neuropsychiatric conditions in which DAT functionality is implicated including ADHD and substance use disorder.
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Affiliation(s)
- José A Pino
- Departamento de Medicina, Facultad de Medicina, Universidad de Atacama, Copiapó, Chile
| | - Gabriel Nuñez-Vivanco
- Centro de Bioinformática, Simulación y Modelado, Facultad de Ingeniería, Universidad de Talca, Talca, Chile
| | - Gabriela Hidalgo
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, FL, United States
| | - Miguel Reyes Parada
- Centro de Investigación Biomédica y Aplicada (CIBAP), Escuela de Medicina, Facultad de Ciencias Médicas, Universidad de Santiago de Chile, Santiago, Chile.,Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Talca, Chile
| | - Habibeh Khoshbouei
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, FL, United States
| | - Gonzalo E Torres
- Department of Molecular, Cellular and Biomedical Sciences, CUNY School of Medicine at City College of New York, New York, NY, United States
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Buford TW, Sun Y, Roberts LM, Banerjee A, Peramsetty S, Knighton A, Verma A, Morgan D, Torres GE, Li Q, Carter CS. Angiotensin (1-7) delivered orally via probiotic, but not subcutaneously, benefits the gut-brain axis in older rats. GeroScience 2020; 42:1307-1321. [PMID: 32451847 PMCID: PMC7525634 DOI: 10.1007/s11357-020-00196-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 04/27/2020] [Indexed: 12/21/2022] Open
Abstract
To (1) investigate the efficacy of multiple doses of an orally delivered probiotic bacteria Lactobacillus paracasei (LP) modified to express angiotensin (1-7) (LP-A) in altering physiologic parameters relevant to the gut-brain axis in older rats and to (2) compare this strategy with subcutaneous delivery of synthetic Ang(1-7) peptide on circulating Ang(1-7) concentrations and these gut-brain axis parameters. Male 24-month-old F344BN rats received oral gavage of LP-A, or subcutaneous injection of Ang(1-7) for 0×, 1×, 3×, or 7×/week over 4 weeks. Circulating RAS analytes, inflammatory cytokines, and tryptophan and its downstream metabolites were measured by ELISA, electrochemiluminescence, and LC-MS respectively. Microbiome taxonomic analysis of fecal samples was performed via 16S-based PCR. Inflammatory and tryptophan-related mRNA expression was measured in colon and pre-frontal cortex. All dosing regimens of LP-A induced beneficial changes in fecal microbiome including overall microbiota community structure and α-diversity, while the 3×/week also significantly increased expression of the anti-inflammatory species Akkermansia muciniphila. The 3×/week also increased serum serotonin and the neuroprotective analyte 2-picolinic acid. In the colon, LP-A increased quinolinate phosphoribosyltransferase expression (1×/week) and increased kynurenine aminotransferase II (1× and 3×/week) mRNA expression. LP-A also significantly reduced neuro-inflammatory gene expression in the pre-frontal cortex (3×/week: COX2, IL-1β, and TNFα; 7×/week: COX2 and IL-1β). Subcutaneous delivery of Ang(1-7) increased circulating Ang(1-7) and reduced angiotensin II, but most gut-brain parameters were unchanged in response. Oral-but not subcutaneous-Ang(1-7) altered physiologic parameters related to gut-brain axis, with the most effects observed in 3×/week oral dosing regimen in older rats.
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Affiliation(s)
- Thomas W. Buford
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL USA ,Integrative Center for Aging Research, University of Alabama at Birmingham, Birmingham, AL USA
| | - Yi Sun
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL USA ,Integrative Center for Aging Research, University of Alabama at Birmingham, Birmingham, AL USA
| | - Lisa M. Roberts
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL USA ,Integrative Center for Aging Research, University of Alabama at Birmingham, Birmingham, AL USA
| | - Anisha Banerjee
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL USA ,Integrative Center for Aging Research, University of Alabama at Birmingham, Birmingham, AL USA
| | - Sujitha Peramsetty
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL USA ,Integrative Center for Aging Research, University of Alabama at Birmingham, Birmingham, AL USA
| | - Anthony Knighton
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL USA ,Integrative Center for Aging Research, University of Alabama at Birmingham, Birmingham, AL USA
| | - Amrisha Verma
- Department of Ophthalmology, University of Florida, Gainesville, FL USA
| | - Drake Morgan
- Department of Psychiatry, University of Florida, Gainesville, FL USA
| | - Gonzalo E. Torres
- Department of Molecular, Cellular, and Biomedical Sciences, City College of New York, New York, NY USA
| | - Qiuhong Li
- Department of Ophthalmology, University of Florida, Gainesville, FL USA
| | - Christy S. Carter
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL USA ,Integrative Center for Aging Research, University of Alabama at Birmingham, Birmingham, AL USA
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Koutzoumis DN, Vergara M, Pino J, Buddendorff J, Khoshbouei H, Mandel RJ, Torres GE. Alterations of the gut microbiota with antibiotics protects dopamine neuron loss and improve motor deficits in a pharmacological rodent model of Parkinson's disease. Exp Neurol 2019; 325:113159. [PMID: 31843492 DOI: 10.1016/j.expneurol.2019.113159] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 12/02/2019] [Accepted: 12/12/2019] [Indexed: 12/18/2022]
Abstract
Parkinson's disease (PD) is a debilitating condition resulting in motor and non-motor symptoms affecting approximately 10 million people worldwide. Currently, there are no pharmacological treatments that can cure the condition or effectively halt its progression. The focus of PD research has been primarily on the neurobiological basis and consequences of dopamine (DA) neuron degeneration given that the loss of DA neurons projecting from the substantia nigra to the dorsal striatum results in the development of cardinal PD motor symptoms. Alternatively, gastrointestinal dysfunction is well recognized in PD patients, and often occurs prior to the development of motor symptoms. The gut microbiota, which contains thousands of bacterial species, play important roles in intestinal barrier integrity and function, metabolism, immunity and brain function. Pre-clinical and clinical studies suggest an important link between alterations in the composition of the gut microbiota and psychiatric and neurological conditions, including PD. Several reports have documented gut dysbiosis and alterations in the composition of the gut microbiota in PD patients. Therefore, the goal of this study was to explore the contribution of the gut microbiota to the behavioral and neurochemical alterations in a rodent toxin model of DA depletion that reproduces the motor symptoms associated with PD. We observed that chronic treatment of adult rats with non-absorbable antibiotics ameliorates the neurotoxicity of 6-hydroxydopamine (6-OHDA) in a unilateral lesion model. Specifically, immunohistochemistry against the dopaminergic neuron marker tyrosine hydroxylase (TH) showed an attenuation of the degree of 6-OHDA-induced dopaminergic neuron loss in antibiotic treated animals compared to control animals. In addition, we observed a reduction in the expression of pro-inflammatory markers in the striatum of antibiotic-treated animals. The degree of motor dysfunction after 6-OHDA was also attenuated in antibiotic-treated animals as measured by paw-rearing measurements in the cylinder test, forepaw stepping test, and ipsilateral rotations observed in the amphetamine-induced rotation test. These results implicate the gut microbiota as a potential contributor to pathology in the development of PD. Further studies are necessary to understand the specific mechanisms involved in transducing alterations in the gut microbiota to changes in dopaminergic neuron loss and motor dysfunction.
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Affiliation(s)
- Dimitri N Koutzoumis
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine, 1200 Newell Drive, Gainesville, FL 32610., United States of America
| | - Macarena Vergara
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine, 1200 Newell Drive, Gainesville, FL 32610., United States of America
| | - Jose Pino
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine, 1200 Newell Drive, Gainesville, FL 32610., United States of America; Department of Medicine, School of Medicine, University of Atacama, 1581 Los Carrera Ave, Copiapo, Chile
| | - Julia Buddendorff
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine, 1200 Newell Drive, Gainesville, FL 32610., United States of America
| | - Habibeh Khoshbouei
- Department of Neuroscience, University of Florida College of Medicine, 1149 Newell Drive, Gainesville, FL 32610, United States of America
| | - Ronald J Mandel
- Department of Neuroscience, University of Florida College of Medicine, 1149 Newell Drive, Gainesville, FL 32610, United States of America
| | - Gonzalo E Torres
- Department of Molecular, Cellular, and Biomedical Sciences, City University of New York School of Medicine at City College, 160 Convent Ave, NY, New York 10031, United States of America.
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8
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Velásquez VB, Zamorano GA, Martínez-Pinto J, Bonansco C, Jara P, Torres GE, Renard GM, Sotomayor-Zárate R. Programming of Dopaminergic Neurons by Early Exposure to Sex Hormones: Effects on Morphine-Induced Accumbens Dopamine Release, Reward, and Locomotor Behavior in Male and Female Rats. Front Pharmacol 2019; 10:295. [PMID: 30971928 PMCID: PMC6443923 DOI: 10.3389/fphar.2019.00295] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Accepted: 03/11/2019] [Indexed: 11/13/2022] Open
Abstract
Neonatal programming with sex hormones produces long-term functional changes in various tissues, including the brain. Previously, we demonstrated a higher content of dopamine and an increase in potassium-induced dopamine release in the nucleus accumbens of adult rats exposed to estradiol valerate. On the other hand, sex hormones also affect the opioid system increasing the expression of the μ opioid receptor and β-endorphins. Here, we investigated if neonatal programming with sex hormones alters the response to morphine during adulthood in rats and predispose them to neurochemical, rewarding and behavioral activating effects. We examined the effects of neonatal exposure to a single dose of estradiol valerate or testosterone propionate on morphine-induced (5 mg/kg, i.v.) dopamine release in the nucleus accumbens and morphine-induced (3 mg/kg, s.c.) locomotor activity and conditioned place preference when these rats were adults. Our results showed a significant increase in morphine-induced dopamine release in the nucleus accumbens of rats that were exposed neonatally to estradiol compared with control rats. This effect was correlated with higher place preference and locomotor activity induced by morphine in adult rats neonatally exposed to estradiol valerate. However, the effect of morphine on dopamine release and behaviors was similar in rats treated with testosterone compared to control rats. Additionally, the expression of mu (μ) opioid receptor, dopamine receptor type 1 (D1) and dopamine receptor type 2 (D2) in the nucleus accumbens of adult rats was not different after treatment with sex hormones. Taken together, our results demonstrated an enhancement of pharmacological effects produced by morphine in rats neonatally programmed with estradiol valerate, suggesting that early exposure to sex hormones could represent a vulnerability factor in the development of addiction to opioid drugs such as morphine and heroin in adulthood.
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Affiliation(s)
| | | | | | - Christian Bonansco
- Laboratorio de Neurofisiología, Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Pablo Jara
- Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile
| | - Gonzalo E Torres
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL, United States
| | - Georgina M Renard
- Centro de Investigación Biomédica y Aplicada (CIBAP), Escuela de Medicina, Facultad de Ciencias Médicas, Universidad de Santiago de Chile, Santiago, Chile
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9
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Lebowitz JJ, Pino JA, Mackie PM, Lin M, Hurst C, Divita K, Collins AT, Koutzoumis DN, Torres GE, Khoshbouei H. Clustered Kv2.1 decreases dopamine transporter activity and internalization. J Biol Chem 2019; 294:6957-6971. [PMID: 30824538 DOI: 10.1074/jbc.ra119.007441] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Revised: 02/26/2019] [Indexed: 01/16/2023] Open
Abstract
The dopamine transporter (DAT) regulates dopamine neurotransmission via reuptake of dopamine released into the extracellular space. Interactions with partner proteins alter DAT function and thereby dynamically shape dopaminergic tone important for normal brain function. However, the extent and nature of these interactions are incompletely understood. Here, we describe a novel physical and functional interaction between DAT and the voltage-gated K+ channel Kv2.1 (potassium voltage-gated channel subfamily B member 1 or KCNB1). To examine the functional consequences of this interaction, we employed a combination of immunohistochemistry, immunofluorescence live-cell microscopy, co-immunoprecipitation, and electrophysiological approaches. Consistent with previous reports, we found Kv2.1 is trafficked to membrane-bound clusters observed both in vivo and in vitro in rodent dopamine neurons. Our data provide evidence that clustered Kv2.1 channels decrease DAT's lateral mobility and inhibit its internalization, while also decreasing canonical transporter activity by altering DAT's conformational equilibrium. These results suggest that Kv2.1 clusters exert a spatially discrete homeostatic braking mechanism on DAT by inducing a relative increase in inward-facing transporters. Given recent reports of Kv2.1 dysregulation in neurological disorders, it is possible that alterations in the functional interaction between DAT and Kv2.1 affect dopamine neuron activity.
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Affiliation(s)
- Joseph J Lebowitz
- From the Departments of Neuroscience and.,T32 in Movement Disorders and Neurorestoration, Fixel Center for Neurological Diseases, UF Health, Gainesville, Florida 32610
| | - Jose A Pino
- Pharmacology and Experimental Therapeutics, College of Medicine, University of Florida, Gainesville, Florida 32610 and
| | | | - Min Lin
- From the Departments of Neuroscience and
| | | | | | | | - Dimitri N Koutzoumis
- Pharmacology and Experimental Therapeutics, College of Medicine, University of Florida, Gainesville, Florida 32610 and
| | - Gonzalo E Torres
- Pharmacology and Experimental Therapeutics, College of Medicine, University of Florida, Gainesville, Florida 32610 and
| | - Habibeh Khoshbouei
- From the Departments of Neuroscience and .,T32 in Movement Disorders and Neurorestoration, Fixel Center for Neurological Diseases, UF Health, Gainesville, Florida 32610
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10
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Dib T, Martínez-Pinto J, Reyes-Parada M, Torres GE, Sotomayor-Zárate R. Neonatal programming with testosterone propionate reduces dopamine transporter expression in nucleus accumbens and methylphenidate-induced locomotor activity in adult female rats. Behav Brain Res 2018; 346:80-85. [DOI: 10.1016/j.bbr.2017.12.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 11/16/2017] [Accepted: 12/01/2017] [Indexed: 12/13/2022]
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11
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Colon-Perez LM, Pino JA, Saha K, Pompilus M, Kaplitz S, Choudhury N, Jagnarine DA, Geste JR, Levin BA, Wilks I, Setlow B, Bruijnzeel AW, Khoshbouei H, Torres GE, Febo M. Functional connectivity, behavioral and dopaminergic alterations 24 hours following acute exposure to synthetic bath salt drug methylenedioxypyrovalerone. Neuropharmacology 2018; 137:178-193. [PMID: 29729891 DOI: 10.1016/j.neuropharm.2018.04.031] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 04/26/2018] [Accepted: 04/29/2018] [Indexed: 12/22/2022]
Abstract
Among cathinone drugs known as bath salts, methylenedioxypyrovalerone (MDPV) exerts its potent actions via the dopamine (DA) system, and at intoxicating doses may produce adverse behavioral effects. Previous work by our group suggests that prolonged alterations in correlated neural activity between cortical and striatal areas could underlie, at least in part, the adverse reactions to this bath salt drug. In the present study, we assessed the effect of acute MDPV administration on brain functional connectivity at 1 and 24 h in rats. Using graph theory metrics to assess in vivo brain functional network organization we observed that 24 h after MDPV administration there was an increased clustering coefficient, rich club index, and average path length. Increases in these metrics suggests that MDPV produces a prolonged pattern of correlated activity characterized by greater interactions between subsets of high degree nodes but a reduced interaction with regions outside this core subset. Further analysis revealed that the core set of nodes include prefrontal cortical, amygdala, hypothalamic, somatosensory and striatal areas. At the molecular level, MDPV downregulated the dopamine transporter (DAT) in striatum and produced a shift in its subcellular distribution, an effect likely to involve rapid internalization at the membrane. These new findings suggest that potent binding of MDPV to DAT may trigger internalization and a prolonged alteration in homeostatic regulation of DA and functional brain network reorganization. We propose that the observed MDPV-induced network reorganization and DAergic changes may contribute to previously reported adverse behavioral responses to MDPV.
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Affiliation(s)
- Luis M Colon-Perez
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL 32610, USA; Center for Addiction Research and Education (CARE), College of Medicine, University of Florida, Gainesville, FL 32610, USA; Advanced Magnetic Resonance Imaging and Spectroscopy (AMRIS) Facility, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Jose A Pino
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Kaustuv Saha
- Department of Neuroscience, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Marjory Pompilus
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Sherman Kaplitz
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Nafisa Choudhury
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Darin A Jagnarine
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Jean R Geste
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Brandon A Levin
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Isaac Wilks
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Barry Setlow
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL 32610, USA; Department of Neuroscience, College of Medicine, University of Florida, Gainesville, FL 32610, USA; The McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL 32610, USA; Center for Addiction Research and Education (CARE), College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Adriaan W Bruijnzeel
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL 32610, USA; Department of Neuroscience, College of Medicine, University of Florida, Gainesville, FL 32610, USA; The McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL 32610, USA; Center for Addiction Research and Education (CARE), College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Habibeh Khoshbouei
- Department of Neuroscience, College of Medicine, University of Florida, Gainesville, FL 32610, USA; The McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL 32610, USA; Center for Addiction Research and Education (CARE), College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Gonzalo E Torres
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL 32610, USA; Center for Addiction Research and Education (CARE), College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Marcelo Febo
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL 32610, USA; Department of Neuroscience, College of Medicine, University of Florida, Gainesville, FL 32610, USA; The McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL 32610, USA; Center for Addiction Research and Education (CARE), College of Medicine, University of Florida, Gainesville, FL 32610, USA; Advanced Magnetic Resonance Imaging and Spectroscopy (AMRIS) Facility, College of Medicine, University of Florida, Gainesville, FL 32610, USA.
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12
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Lebowitz J, Pino Reyes JA, Divita K, Henckel C, Lin M, Torres GE, Khoshbouei H. Dopamine Transporter Activation Reduces Kv2.1 Activation Potential and Cluster Size. FASEB J 2018. [DOI: 10.1096/fasebj.2018.32.1_supplement.553.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Joe Lebowitz
- NeuroscienceUniversity of Florida College of MedicineGainesvilleFL
| | - Jose A. Pino Reyes
- Pharmacology & Experimental TherapeuticsUniversity of Florida College of MedicineGainesvilleFL
| | - Keeley Divita
- NeuroscienceUniversity of Florida College of MedicineGainesvilleFL
| | - Cheyenne Henckel
- NeuroscienceUniversity of Florida College of MedicineGainesvilleFL
| | - Min Lin
- NeuroscienceUniversity of Florida College of MedicineGainesvilleFL
| | - Gonzalo E. Torres
- Pharmacology & Experimental TherapeuticsUniversity of Florida College of MedicineGainesvilleFL
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13
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Parra LA, Baust TB, Smith AD, Jaumotte JD, Zigmond MJ, Torres S, Leak RK, Pino JA, Torres GE. The Molecular Chaperone Hsc70 Interacts with Tyrosine Hydroxylase to Regulate Enzyme Activity and Synaptic Vesicle Localization. J Biol Chem 2016; 291:17510-22. [PMID: 27365397 DOI: 10.1074/jbc.m116.728782] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Indexed: 12/25/2022] Open
Abstract
We previously reported that the vesicular monoamine transporter 2 (VMAT2) is physically and functionally coupled with Hsc70 as well as with the dopamine synthesis enzymes tyrosine hydroxylase (TH) and aromatic amino acid decarboxylase, providing a novel mechanism for dopamine homeostasis regulation. Here we expand those findings to demonstrate that Hsc70 physically and functionally interacts with TH to regulate the enzyme activity and synaptic vesicle targeting. Co-immunoprecipitation assays performed in brain tissue and heterologous cells demonstrated that Hsc70 interacts with TH and aromatic amino acid decarboxylase. Furthermore, in vitro binding assays showed that TH directly binds the substrate binding and carboxyl-terminal domains of Hsc70. Immunocytochemical studies indicated that Hsc70 and TH co-localize in midbrain dopaminergic neurons. The functional significance of the Hsc70-TH interaction was then investigated using TH activity assays. In both dopaminergic MN9D cells and mouse brain synaptic vesicles, purified Hsc70 facilitated an increase in TH activity. Neither the closely related protein Hsp70 nor the unrelated Hsp60 altered TH activity, confirming the specificity of the Hsc70 effect. Overexpression of Hsc70 in dopaminergic MN9D cells consistently resulted in increased TH activity whereas knockdown of Hsc70 by short hairpin RNA resulted in decreased TH activity and dopamine levels. Finally, in cells with reduced levels of Hsc70, the amount of TH associated with synaptic vesicles was decreased. This effect was rescued by addition of purified Hsc70. Together, these data demonstrate a novel interaction between Hsc70 and TH that regulates the activity and localization of the enzyme to synaptic vesicles, suggesting an important role for Hsc70 in dopamine homeostasis.
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Affiliation(s)
| | | | - Amanda D Smith
- Neurology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Juliann D Jaumotte
- Neurology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Michael J Zigmond
- Neurology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Soledad Torres
- the Centro de Investigación y Modelamiento de Fenómenos Aleatorios Valparaíso, Faculty of Engineering, Universidad de Valparaíso, 2362905 Valparaíso, Chile
| | - Rehana K Leak
- the Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282, and
| | - Jose A Pino
- the Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, Florida 32610
| | - Gonzalo E Torres
- the Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, Florida 32610
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14
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Reddy IA, Pino JA, Weikop P, Osses N, Sørensen G, Bering T, Valle C, Bluett RJ, Erreger K, Wortwein G, Reyes JG, Graham D, Stanwood GD, Hackett TA, Patel S, Fink-Jensen A, Torres GE, Galli A. Glucagon-like peptide 1 receptor activation regulates cocaine actions and dopamine homeostasis in the lateral septum by decreasing arachidonic acid levels. Transl Psychiatry 2016; 6:e809. [PMID: 27187231 PMCID: PMC5070047 DOI: 10.1038/tp.2016.86] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 02/19/2016] [Accepted: 03/30/2016] [Indexed: 12/12/2022] Open
Abstract
Agonism of the glucagon-like peptide 1 (GLP-1) receptor (GLP-1R) has been effective at treating aspects of addictive behavior for a number of abused substances, including cocaine. However, the molecular mechanisms and brain circuits underlying the therapeutic effects of GLP-1R signaling on cocaine actions remain elusive. Recent evidence has revealed that endogenous signaling at the GLP-1R within the forebrain lateral septum (LS) acts to reduce cocaine-induced locomotion and cocaine conditioned place preference, both considered dopamine (DA)-associated behaviors. DA terminals project from the ventral tegmental area to the LS and express the DA transporter (DAT). Cocaine acts by altering DA bioavailability by targeting the DAT. Therefore, GLP-1R signaling might exert effects on DAT to account for its regulation of cocaine-induced behaviors. We show that the GLP-1R is highly expressed within the LS. GLP-1, in LS slices, significantly enhances DAT surface expression and DAT function. Exenatide (Ex-4), a long-lasting synthetic analog of GLP-1 abolished cocaine-induced elevation of DA. Interestingly, acute administration of Ex-4 reduces septal expression of the retrograde messenger 2-arachidonylglycerol (2-AG), as well as a product of its presynaptic degradation, arachidonic acid (AA). Notably, AA reduces septal DAT function pointing to AA as a novel regulator of central DA homeostasis. We further show that AA oxidation product γ-ketoaldehyde (γ-KA) forms adducts with the DAT and reduces DAT plasma membrane expression and function. These results support a mechanism in which postsynaptic septal GLP-1R activation regulates 2-AG levels to alter presynaptic DA homeostasis and cocaine actions through AA.
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Affiliation(s)
- I A Reddy
- Neuroscience Program, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - J A Pino
- Instituto de Química, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL, USA
| | - P Weikop
- Laboratory of Neuropsychiatry, Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark
- Psychiatric Centre Copenhagen, University Hospital Copenhagen, Copenhagen, Denmark
| | - N Osses
- Instituto de Química, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - G Sørensen
- Laboratory of Neuropsychiatry, Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark
- Psychiatric Centre Copenhagen, University Hospital Copenhagen, Copenhagen, Denmark
| | - T Bering
- Laboratory of Neuropsychiatry, Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - C Valle
- Departamento de Ciencias Básicas, Universidad de Viña del Mar, Viña del Mar, Chile
| | - R J Bluett
- Neuroscience Program, Vanderbilt University School of Medicine, Nashville, TN, USA
- Department of Psychiatry, Vanderbilt University Medical Center, Nashville, TN, USA
| | - K Erreger
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - G Wortwein
- Laboratory of Neuropsychiatry, Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark
- Department of Public Health, University of Copenhagen, Copenhagen, Denmark
| | - J G Reyes
- Instituto de Química, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - D Graham
- Department of Biomedical Sciences and Center for Brain Repair, Florida State University, Tallahassee, FL, USA
| | - G D Stanwood
- Department of Biomedical Sciences and Center for Brain Repair, Florida State University, Tallahassee, FL, USA
| | - T A Hackett
- Neuroscience Program, Vanderbilt University School of Medicine, Nashville, TN, USA
- Department of Hearing and Speech Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - S Patel
- Department of Psychiatry, Vanderbilt University Medical Center, Nashville, TN, USA
| | - A Fink-Jensen
- Laboratory of Neuropsychiatry, Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark
- Psychiatric Centre Copenhagen, University Hospital Copenhagen, Copenhagen, Denmark
| | - G E Torres
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL, USA
| | - A Galli
- Neuroscience Program, Vanderbilt University School of Medicine, Nashville, TN, USA
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA
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15
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Harun R, Hare KM, Brough EM, Munoz MJ, Grassi CM, Torres GE, Grace AA, Wagner AK. Fast-scan cyclic voltammetry demonstrates that L-DOPA produces dose-dependent, regionally selective bimodal effects on striatal dopamine kinetics in vivo. J Neurochem 2016; 136:1270-1283. [PMID: 26611352 PMCID: PMC4884169 DOI: 10.1111/jnc.13444] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 11/17/2015] [Accepted: 11/18/2015] [Indexed: 11/29/2022]
Abstract
Parkinson's disease (PD) is a debilitating condition that is caused by a relatively specific degeneration of dopaminergic (DAergic) neurons of the substantia nigra pars compacta. L-DOPA was introduced as a viable treatment option for PD over 40 years ago and still remains the most common and effective therapy for PD. Though the effects of L-DOPA to augment striatal DA production are well known, little is actually known about how L-DOPA alters the kinetics of DA neurotransmission that contribute to its beneficial and adverse effects. In this study, we examined the effects of L-DOPA administration (50 mg/kg carbidopa + 0, 100, and 250 mg/kg L-DOPA) on regional electrically stimulated DA response kinetics using fast-scan cyclic voltammetry in anesthetized rats. We demonstrate that L-DOPA enhances DA release in both the dorsal striatum (D-STR) and nucleus accumbens (NAc), but surprisingly causes a delayed inhibition of release in the D-STR. In both regions, L-DOPA progressively attenuated reuptake kinetics, predominantly through a decrease in Vmax . These findings have important implications on understanding the pharmacodynamics of L-DOPA, which may be informative for understanding its therapeutic effects and also common side effects like L-DOPA-induced dyskinesias (LID). L-DOPA is commonly used to treat Parkinsonian symptoms, but little is known about how it affects presynaptic DA neurotransmission. Using in vivo fast-scan cyclic voltammetry, we show L-DOPA inhibits DA reuptake in a region-specific and dose-dependent manner, and L-DOPA has paradoxical effects on release. These findings may be important when considering mechanisms for L-DOPA's therapeutic benefits and adverse side-effects.
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Affiliation(s)
- Rashed Harun
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department of Physical Medicine & Rehabilitation, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania, USA
- Safar Center for Resuscitation Research, Pittsburgh, Pennsylvania, USA
| | - Kristin M Hare
- Department of Physical Medicine & Rehabilitation, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Elizabeth M Brough
- Department of Physical Medicine & Rehabilitation, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania, USA
- Safar Center for Resuscitation Research, Pittsburgh, Pennsylvania, USA
| | - Miranda J Munoz
- Department of Physical Medicine & Rehabilitation, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania, USA
- Department of Biological Sciences, Carnegie Mellon University, Mellon College of Science, Pittsburgh, Pennsylvania, USA
| | - Christine M Grassi
- Department of Physical Medicine & Rehabilitation, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Gonzalo E Torres
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department of Neurobiology, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Anthony A Grace
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Departments of Psychiatry and Psychology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Amy K Wagner
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department of Physical Medicine & Rehabilitation, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania, USA
- Safar Center for Resuscitation Research, Pittsburgh, Pennsylvania, USA
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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16
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Bondi CO, Taha AY, Tock JL, Totah NK, Cheon Y, Torres GE, Rapoport SI, Moghaddam B. Adolescent behavior and dopamine availability are uniquely sensitive to dietary omega-3 fatty acid deficiency. Biol Psychiatry 2014; 75:38-46. [PMID: 23890734 PMCID: PMC3858419 DOI: 10.1016/j.biopsych.2013.06.007] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 06/04/2013] [Accepted: 06/11/2013] [Indexed: 12/11/2022]
Abstract
BACKGROUND Understanding the nature of environmental factors that contribute to behavioral health is critical for successful prevention strategies in individuals at risk for psychiatric disorders. These factors are typically experiential in nature, such as stress and urbanicity, but nutrition--in particular dietary deficiency of omega-3 polyunsaturated fatty acids (n-3 PUFAs)-has increasingly been implicated in the symptomatic onset of schizophrenia and mood disorders, which typically occurs during adolescence to early adulthood. Thus, adolescence might be the critical age range for the negative impact of diet as an environmental insult. METHODS A rat model involving consecutive generations of n-3 PUFA deficiency was developed on the basis of the assumption that dietary trends toward decreased consumption of these fats began 4-5 decades ago when the parents of current adolescents were born. Behavioral performance in a wide range of tasks as well as markers of dopamine-related neurotransmission was compared in adolescents and adults fed n-3 PUFA adequate and deficient diets. RESULTS In adolescents, dietary n-3 PUFA deficiency across consecutive generations produced a modality-selective and task-dependent impairment in cognitive and motivated behavior distinct from the deficits observed in adults. Although this dietary deficiency affected expression of dopamine-related proteins in both age groups in adolescents but not adults, there was an increase in tyrosine hydroxylase expression that was selective to the dorsal striatum. CONCLUSIONS These data support a nutritional contribution to optimal cognitive and affective functioning in adolescents. Furthermore, they suggest that n-3 PUFA deficiency disrupts adolescent behaviors through enhanced dorsal striatal dopamine availability.
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Affiliation(s)
- Corina O. Bondi
- Department of Neuroscience, Univ. of Pittsburgh, Pittsburgh, PA
| | - Ameer Y. Taha
- Brain Physiology and Metabolism Section, Laboratory of Neurosciences, National Institute on Aging, NIH, Bethesda, MD
| | - Jody L. Tock
- Department of Neuroscience, Univ. of Pittsburgh, Pittsburgh, PA
| | - Nelson K. Totah
- Department of Neuroscience, Univ. of Pittsburgh, Pittsburgh, PA
| | - Yewon Cheon
- Brain Physiology and Metabolism Section, Laboratory of Neurosciences, National Institute on Aging, NIH, Bethesda, MD
| | | | - Stanley I. Rapoport
- Brain Physiology and Metabolism Section, Laboratory of Neurosciences, National Institute on Aging, NIH, Bethesda, MD
| | - Bita Moghaddam
- Department of Neuroscience, Univ. of Pittsburgh, Pittsburgh, PA
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17
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Garcia-Olivares J, Torres-Salazar D, Owens WA, Baust T, Siderovski DP, Amara SG, Zhu J, Daws LC, Torres GE. Inhibition of dopamine transporter activity by G protein βγ subunits. PLoS One 2013; 8:e59788. [PMID: 23555781 PMCID: PMC3608556 DOI: 10.1371/journal.pone.0059788] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 02/18/2013] [Indexed: 12/15/2022] Open
Abstract
Uptake through the Dopamine Transporter (DAT) is the primary mechanism of terminating dopamine signaling within the brain, thus playing an essential role in neuronal homeostasis. Deregulation of DAT function has been linked to several neurological and psychiatric disorders including ADHD, schizophrenia, Parkinson’s disease, and drug addiction. Over the last 15 years, several studies have revealed a plethora of mechanisms influencing the activity and cellular distribution of DAT; suggesting that fine-tuning of dopamine homeostasis occurs via an elaborate interplay of multiple pathways. Here, we show for the first time that the βγ subunits of G proteins regulate DAT activity. In heterologous cells and brain tissue, a physical association between Gβγ subunits and DAT was demonstrated by co-immunoprecipitation. Furthermore, in vitro pull-down assays using purified proteins established that this association occurs via a direct interaction between the intracellular carboxy-terminus of DAT and Gβγ. Functional assays performed in the presence of the non-hydrolyzable GTP analog GTP-γ-S, Gβγ subunit overexpression, or the Gβγ activator mSIRK all resulted in rapid inhibition of DAT activity in heterologous systems. Gβγ activation by mSIRK also inhibited dopamine uptake in brain synaptosomes and dopamine clearance from mouse striatum as measured by high-speed chronoamperometry in vivo. Gβγ subunits are intracellular signaling molecules that regulate a multitude of physiological processes through interactions with enzymes and ion channels. Our findings add neurotransmitter transporters to the growing list of molecules regulated by G-proteins and suggest a novel role for Gβγ signaling in the control of dopamine homeostasis.
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Affiliation(s)
- Jennie Garcia-Olivares
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Delany Torres-Salazar
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - William A. Owens
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America
| | - Tracy Baust
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - David P. Siderovski
- Department of Pharmacology and UNC Neuroscience Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Susan G. Amara
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Jun Zhu
- Department of Pharmaceutical and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina, United States of America
| | - Lynette C. Daws
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America
| | - Gonzalo E. Torres
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- * E-mail:
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18
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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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19
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Lin Z, Canales JJ, Björgvinsson T, Thomsen MM, Qu H, Liu QR, Torres GE, Caine SB. Monoamine transporters: vulnerable and vital doorkeepers. Prog Mol Biol Transl Sci 2011; 98:1-46. [PMID: 21199769 PMCID: PMC3321928 DOI: 10.1016/b978-0-12-385506-0.00001-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Transporters of dopamine, serotonin, and norepinephrine have been empirically used as medication targets for several mental illnesses in the last decades. These protein-targeted medications are effective only for subpopulations of patients with transporter-related brain disorders. Since the cDNA clonings in early 1990s, molecular studies of these transporters have revealed a wealth of information about the transporters' structure-activity relationship (SAR), neuropharmacology, cell biology, biochemistry, pharmacogenetics, and the diseases related to the human genes encoding these transporters among related regulators. Such new information creates a unique opportunity to develop transporter-specific medications based on SAR, mRNA, DNA, and perhaps transporter trafficking regulation for a number of highly relevant diseases including substance abuse, depression, schizophrenia, and Parkinson's disease.
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Affiliation(s)
- Zhicheng Lin
- Department of Psychiatry, Harvard Medical School and Division of Alcohol and Drug Abuse, McLean Hospital, Belmont, MA 02478, USA
| | - Juan J. Canales
- Department of Psychology, Behavioural Neuroscience, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
| | - Thröstur Björgvinsson
- Behavioral Health Partial Hospital and Psychology Internship Programs, McLean Hospital/Harvard Medical School, Belmont, MA 02478, USA
| | - Morgane M. Thomsen
- Department of Psychiatry, Harvard Medical School and Division of Alcohol and Drug Abuse, McLean Hospital, Belmont, MA 02478, USA
| | - Hong Qu
- Center for Bioinformatics, National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Sciences, Peking University. Beijing, 100871 China
| | - Qing-Rong Liu
- Behavioral Neuroscience Branch, Intramural Research Program, National Institute on Drug Abuse, NIH/DHHS, 251 Bayview Boulevard, Baltimore, MD 21224, USA
| | - Gonzalo E. Torres
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - S. Barak Caine
- Department of Psychiatry, Harvard Medical School and Division of Alcohol and Drug Abuse, McLean Hospital, Belmont, MA 02478, USA
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Cartier EA, Parra LA, Baust TB, Quiroz M, Salazar G, Faundez V, Egaña L, Torres GE. A biochemical and functional protein complex involving dopamine synthesis and transport into synaptic vesicles. J Biol Chem 2009; 285:1957-66. [PMID: 19903816 DOI: 10.1074/jbc.m109.054510] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Synaptic transmission depends on neurotransmitter pools stored within vesicles that undergo regulated exocytosis. In the brain, the vesicular monoamine transporter-2 (VMAT(2)) is responsible for the loading of dopamine (DA) and other monoamines into synaptic vesicles. Prior to storage within vesicles, DA synthesis occurs at the synaptic terminal in a two-step enzymatic process. First, the rate-limiting enzyme tyrosine hydroxylase (TH) converts tyrosine to di-OH-phenylalanine. Aromatic amino acid decarboxylase (AADC) then converts di-OH-phenylalanine into DA. Here, we provide evidence that VMAT(2) physically and functionally interacts with the enzymes responsible for DA synthesis. In rat striata, TH and AADC co-immunoprecipitate with VMAT(2), whereas in PC 12 cells, TH co-immunoprecipitates with the closely related VMAT(1) and with overexpressed VMAT(2). GST pull-down assays further identified three cytosolic domains of VMAT(2) involved in the interaction with TH and AADC. Furthermore, in vitro binding assays demonstrated that TH directly interacts with VMAT(2). Additionally, using fractionation and immunoisolation approaches, we demonstrate that TH and AADC associate with VMAT(2)-containing synaptic vesicles from rat brain. These vesicles exhibited specific TH activity. Finally, the coupling between synthesis and transport of DA into vesicles was impaired in the presence of fragments involved in the VMAT(2)/TH/AADC interaction. Taken together, our results indicate that DA synthesis can occur at the synaptic vesicle membrane, where it is physically and functionally coupled to VMAT(2)-mediated transport into vesicles.
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Affiliation(s)
- Etienne A Cartier
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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Requena DF, Parra LA, Baust TB, Quiroz M, Leak RK, Garcia-Olivares J, Torres GE. The molecular chaperone Hsc70 interacts with the vesicular monoamine transporter-2. J Neurochem 2009; 110:581-94. [DOI: 10.1111/j.1471-4159.2009.06135.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Wagner AK, Drewencki LL, Chen X, Santos FR, Khan AS, Harun R, Torres GE, Michael AC, Dixon CE. Chronic methylphenidate treatment enhances striatal dopamine neurotransmission after experimental traumatic brain injury. J Neurochem 2008; 108:986-97. [PMID: 19077052 DOI: 10.1111/j.1471-4159.2008.05840.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Traumatic brain injury (TBI) results in functional deficits that often are effectively treated clinically with the neurostimulant, methylphenidate (MPH). We hypothesized that daily MPH administration would reverse striatal neurotransmission deficits observed in the controlled cortical impact (CCI) model of TBI. CCI or naïve rats received daily injections of MPH (5 mg/kg) or saline for 14 days and were assessed on day 15 using fast scan cyclic voltammetry. Dopamine (DA) transporter (DAT) localization, DA-related proteins, and transcription factor (c-fos) expression were also assessed. CCI resulted in reduced electrically evoked overflow of DA and maximal velocity of DA clearance (V(max)). In contrast, CCI was associated with a decrease in the apparent K(M) of DAT. Daily dose of MPH after CCI resulted in robust increases in evoked DA overflow and V(max) as well as increased apparent K(M). Reductions in total striatal DAT expression occurred after CCI and were not further affected by MPH. In contrast, membrane-bound striatal DAT levels were increased in both CCI groups. MPH post-CCI significantly increased striatal c-fos levels compared with saline. These results support the hypothesis that daily MPH improves striatal DA neurotransmission after CCI. DAT expression and transcriptional changes affecting DA protein function may underlie the injury and MPH-induced alterations in neurotransmission observed.
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Affiliation(s)
- Amy K Wagner
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh School of Medicine, Pennsylvania, USA.
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Parra LA, Baust T, El Mestikawy S, Quiroz M, Hoffman B, Haflett JM, Yao JK, Torres GE. The orphan transporter Rxt1/NTT4 (SLC6A17) functions as a synaptic vesicle amino acid transporter selective for proline, glycine, leucine, and alanine. Mol Pharmacol 2008; 74:1521-32. [PMID: 18768736 DOI: 10.1124/mol.108.050005] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rxt1/NTT4 (SLC6A17) belongs to a gene family of "orphan transporters" whose substrates and consequently functions remain unidentified. Although Rxt1/NTT4 was previously thought to function as a sodium-dependent plasma membrane transporter, recent studies localized the protein to synaptic vesicles of glutamatergic and GABAergic neurons. Here, we provide evidence indicating that Rxt1/NTT4 functions as a vesicular transporter selective for proline, glycine, leucine, and alanine. Using Western blot, immunoprecipitation, immunocytochemistry, and polymerase chain reaction approaches, we demonstrate that PC12 cells express the Rxt1/NTT4 gene and protein. Small interfering RNA (siRNA)-mediated knockdown of Rxt1/NTT4 in PC12 cells resulted in selective reductions in uptake levels for proline, glycine, leucine, and alanine. Likewise, gas chromatography analysis of amino acid content in an enriched synaptic vesicle fraction from wild-type and siRNA-Rxt1/NTT4 PC12 cells revealed that proline, glycine, leucine, and alanine levels were decreased in siRNA-treated cells compared with wild-type cells. Furthermore, Rxt1/NTT4-transfected Chinese hamster ovary (CHO) cells exhibited significant uptake increases of these amino acids compared with mock-transfected CHO cells. Finally, proline uptake in both PC12 cells and Rxt1/NTT4-transfected CHO cells was dependent on the electrochemical gradient maintained by the vacuolar-type H(+)-ATPase. These data indicate that the orphan Rxt1/NTT4 protein functions as a vesicular transporter for proline, glycine, leucine, and alanine, further suggesting its important role in synaptic transmission.
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Affiliation(s)
- Leonardo A Parra
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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Dean ED, Shepherd KR, Li Y, Torres GE, Miller GW. Identification of a novel interaction between α‐synuclein and VMAT2. FASEB J 2008. [DOI: 10.1096/fasebj.22.1_supplement.715.6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- E. Danielle Dean
- Department of Environmental and Occupational HealthEmory UniversityAtlantaGA
- Center for Neurodegenerative Disease
| | - Kennie Raviie Shepherd
- Department of Environmental and Occupational HealthEmory UniversityAtlantaGA
- Center for Neurodegenerative Disease
| | - Yingjie Li
- Department of Environmental and Occupational HealthEmory UniversityAtlantaGA
- Center for Neurodegenerative Disease
| | | | - Gary W. Miller
- Department of Environmental and Occupational HealthEmory UniversityAtlantaGA
- Center for Neurodegenerative Disease
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Abstract
Neurotransmitters are rapidly removed from the extracellular space primarily through the actions of plasma membrane transporters. This uptake process is not only essential in the termination of neurotransmission but also serves to replenish intracellular levels of transmitter for further release. Neurotransmitter transporters couple the inward movement of substrate to the movement of Na(+) down a concentration gradient and, in addition to their transport function, some carriers also display channel-like activities. Five Na(+)/K(+)-dependent glutamate transporter subtypes belong to the solute carrier 1 (SLC1) family and a second family, SLC6, encompasses the Na(+)/Cl(-)-dependent transporters for dopamine, 5-hydroxytryptamine (serotonin), noradrenaline, GABA and glycine. Recent advances, including high-resolution structures from both families, are now providing new insights into the molecular determinants that contribute to substrate translocation and ion channel activities. Other influential studies have explored how cellular regulatory mechanisms modulate transporter function, and how the different functions of the carrier shape the patterns of neurotransmitter signaling. This review focuses on recent studies of glutamate and monoamine transporters as prototypes of the two carrier families.
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Affiliation(s)
- Gonzalo E Torres
- Department of Neurobiology, University of Pittsburgh School of Medicine, 3501 Fifth Avenue, Pittsburgh, PA 15261, USA
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Redman PT, Jefferson BS, Ziegler CB, Mortensen OV, Torres GE, Levitan ES, Aizenman E. A vital role for voltage-dependent potassium channels in dopamine transporter-mediated 6-hydroxydopamine neurotoxicity. Neuroscience 2006; 143:1-6. [PMID: 17027171 PMCID: PMC2673085 DOI: 10.1016/j.neuroscience.2006.08.039] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2006] [Revised: 08/09/2006] [Accepted: 08/18/2006] [Indexed: 11/16/2022]
Abstract
6-Hydroxydopamine (6-OHDA), a neurotoxic substrate of the dopamine transporter (DAT), is widely used in Parkinson's disease models. However, the molecular mechanisms underlying 6-OHDA's selectivity for dopamine neurons and the injurious sequelae that it triggers are not well understood. We tested whether ectopic expression of DAT induces sensitivity to 6-OHDA in non-dopaminergic rat cortical neurons and evaluated the contribution of voltage-dependent potassium channel (Kv)-dependent apoptosis to the toxicity of this compound in rat cortical and midbrain dopamine neurons. Cortical neurons expressing DAT accumulated dopamine and were highly vulnerable to 6-OHDA. Pharmacological inhibition of DAT completely blocked this toxicity. We also observed a p38-dependent Kv current surge in DAT-expressing cortical neurons exposed to 6-OHDA, and p38 antagonists and Kv channel blockers were neuroprotective in this model. Thus, DAT-mediated uptake of 6-OHDA recruited the oxidant-induced Kv channel dependent cell death pathway present in cortical neurons. Finally, we report that 6-OHDA also increased Kv currents in cultured midbrain dopamine neurons and this toxicity was blocked with Kv channel antagonists. We conclude that native DAT expression accounts for the dopamine neuron specific toxicity of 6-OHDA. Following uptake, 6-OHDA triggers the oxidant-associated Kv channel-dependent cell death pathway that is conserved in non-dopaminergic cortical neurons and midbrain dopamine neurons.
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Affiliation(s)
- Patrick T. Redman
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Bahiyyah S. Jefferson
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Chandra B. Ziegler
- Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Ole V. Mortensen
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Gonzalo E. Torres
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Edwin S. Levitan
- Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Elias Aizenman
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
- Corresponding author: Dr. Elias Aizenman, Department of Neurobiology, University of Pittsburgh School of Medicine, E1456 BST, Pittsburgh, PA 15261 U.S.A. Tel: (412) 648-9434; fax: (412) 648-1441;
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27
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Abstract
Dopamine (DA) uptake through the neuronal plasma membrane DA transporter (DAT) is essential for the maintenance of normal DA homeostasis in the brain. The DAT-mediated re-uptake system limits not only the intensity but also the duration of DA actions at presynaptic and postsynaptic receptors. This protein is the primary target for cocaine and amphetamine, both highly addictive and major substances of abuse worldwide. DAT is also the molecular target for therapeutic agents used in the treatment of mental disorders, such as attention deficit hyperactivity disorder and depression. Given the role played by the DAT in regulation of DA neurotransmission and its contribution to the abuse potential of psychostimulants, it becomes not only important but also necessary to understand the functional regulation of this protein. To investigate the cellular and molecular mechanisms associated with DAT function and regulation, our laboratory and others have embarked on a systematic search for DAT protein-protein interactions. Recently, a growing number of proteins have been shown to interact with DAT. These novel interactions might be important in the assembly, targeting, trafficking and/or regulation of transporter function. In this review, I summarize the main findings obtained from the characterization of DAT-interacting proteins and discuss the functional implications of these novel interactions. Based on these new data, I propose to use the term DAT proteome to explain how interacting proteins regulate DAT function. These novel interactions might help define new mechanisms associated with the function of the transporter.
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Affiliation(s)
- Gonzalo E Torres
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
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28
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Affiliation(s)
- Gonzalo E Torres
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
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Torres GE, Sweeney AL, Beaulieu JM, Shashidharan P, Caron MG. Effect of torsinA on membrane proteins reveals a loss of function and a dominant-negative phenotype of the dystonia-associated DeltaE-torsinA mutant. Proc Natl Acad Sci U S A 2004; 101:15650-5. [PMID: 15505207 PMCID: PMC524822 DOI: 10.1073/pnas.0308088101] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Most cases of early-onset torsion dystonia (EOTD) are caused by a deletion of one glutamic acid in the carboxyl terminus of a protein named torsinA. The mutation causes the protein to aggregate in perinuclear inclusions as opposed to the endoplasmic reticulum localization of the wild-type protein. Although there is increasing evidence that dysfunction of the dopamine system is implicated in the development of EOTD, the biological function of torsinA and its relation to dopaminergic neurotransmission has remained unexplored. Here, we show that torsinA can regulate the cellular trafficking of the dopamine transporter, as well as other polytopic membrane-bound proteins, including G protein-coupled receptors, transporters, and ion channels. This effect was prevented by mutating the ATP-binding site in torsinA. The dystonia-associated torsinA deletion mutant (DeltaE-torsinA) did not have any effect on the cell surface distribution of polytopic membrane-associated proteins, suggesting that the mutation linked with EOTD results in a loss of function. However, a mutation in the ATP-binding site in DeltaE-torsinA reversed the aggregate phenotype associated with the mutant. Moreover, the deletion mutant acts as a dominant-negative of wild-type torsinA through a mechanism presumably involving association of wild-type and mutant torsinA. Taken together, our results provide evidence for a functional role for torsinA and a loss of function and a dominant-negative phenotype of the DeltaE-torsinA mutation. These properties may contribute to the autosomal dominant nature of the condition.
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Affiliation(s)
- Gonzalo E Torres
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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30
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Quan H, Athirakul K, Wetsel WC, Torres GE, Stevens R, Chen YT, Coffman TM, Caron MG. Hypertension and impaired glycine handling in mice lacking the orphan transporter XT2. Mol Cell Biol 2004; 24:4166-73. [PMID: 15121838 PMCID: PMC400459 DOI: 10.1128/mcb.24.10.4166-4173.2004] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A family of orphan transporters has been discovered that are structurally related to the Na(+)-Cl(-)-dependent neurotransmitter transporters, including the dopamine transporter. One member of this family, the mouse XT2 gene, is predominantly expressed in the kidney and has 95% homology to rat ROSIT (renal osmotic stress-induced Na(+)-Cl(-) organic solute cotransporter). To study the physiological functions of this transporter, we generated XT2-knockout mice by gene targeting. XT2(-/-) mice develop and survive normally with no apparent abnormalities. To attempt to identify potential substrates for XT2, we screened urine from XT2-knockout mice by high-pressure liquid chromatography and mass spectrometry and found significantly elevated concentrations of glycine. To study glycine handling, XT2(+/+) and XT2(-/-) mice were injected with radiolabeled glycine, and urine samples were collected to monitor glycine excretion. After 2 h, XT2(-/-) mice were found to excrete almost twice as much glycine as the XT2(+/+) controls (P = 0.03). To determine whether the absence of the XT2 transporter affected sodium and fluid homeostasis, we measured systolic blood pressure by computerized tail-cuff manometry. Systolic blood pressure was significantly higher in XT2(-/-) mice (127 +/- 3 mmHg) than in wild-type controls (114 +/- 2 mmHg; P < 0.001). This difference in systolic blood pressure was maintained on high and low salt feeding. To examine whether the alteration in blood pressure and the defect in glycine handling were related, we measured systolic blood pressure in the XT2(-/-) mice during dietary glycine supplementation. Glycine loading caused systolic blood pressure to fall in the XT2(-/-) mice from 127 +/- 3 to 115 +/- 3 mmHg (P < 0.001), a level virtually identical to that of the wild-type controls. These data suggest that the XT2 orphan transporter is involved in glycine reabsorption and that the absence of this transporter is sufficient to cause hypertension.
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Affiliation(s)
- Hui Quan
- Department of Cell Biology, Howard Hughes Medical Institute Laboratories, Duke University Medical Center, Durham, North Carolina 27710, USA
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31
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Yao WD, Gainetdinov RR, Arbuckle MI, Sotnikova TD, Cyr M, Beaulieu JM, Torres GE, Grant SGN, Caron MG. Identification of PSD-95 as a Regulator of Dopamine-Mediated Synaptic and Behavioral Plasticity. Neuron 2004; 41:625-38. [PMID: 14980210 DOI: 10.1016/s0896-6273(04)00048-0] [Citation(s) in RCA: 302] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2003] [Revised: 01/13/2004] [Accepted: 01/16/2004] [Indexed: 11/25/2022]
Abstract
To identify the molecular mechanisms underlying psychostimulant-elicited plasticity in the brain reward system, we undertook a phenotype-driven approach using genome-wide microarray profiling of striatal transcripts from three genetic and one pharmacological mouse models of psychostimulant or dopamine supersensitivity. A small set of co-affected genes was identified. One of these genes encoding the synaptic scaffolding protein PSD-95 is downregulated in the striatum of all three mutants and in chronically, but not acutely, cocaine-treated mice. At the synaptic level, enhanced long-term potentiation (LTP) of the frontocortico-accumbal glutamatergic synapses correlates with PSD-95 reduction in every case. Finally, targeted deletion of PSD-95 in an independent line of mice enhances LTP, augments the acute locomotor-stimulating effects of cocaine, but leads to no further behavioral plasticity in response to chronic cocaine. Our findings uncover a previously unappreciated role of PSD-95 in psychostimulant action and identify a molecular and cellular mechanism shared between drug-related plasticity and learning.
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Affiliation(s)
- Wei-Dong Yao
- Howard Hughes Medical Institute Laboratories, Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
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32
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Torres GE, Caron MG. Center stage for the serotonin transporter: a gain-of-function polymorphism in persons with obsessive-compulsive disorder. Mol Pharmacol 2003; 64:196-8. [PMID: 12869622 DOI: 10.1124/mol.64.2.196] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Gonzalo E Torres
- Department of Cell Biology and Howard Hughes Medical Institute, Carl Bldg, Rm. 487, Research Dr., Box 3287, Duke University Medical Center, Durham, North Carolina, USA
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Gainetdinov RR, Bohn LM, Sotnikova TD, Cyr M, Laakso A, Macrae AD, Torres GE, Kim KM, Lefkowitz RJ, Caron MG, Premont RT. Dopaminergic supersensitivity in G protein-coupled receptor kinase 6-deficient mice. Neuron 2003; 38:291-303. [PMID: 12718862 DOI: 10.1016/s0896-6273(03)00192-2] [Citation(s) in RCA: 174] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Brain dopaminergic transmission is a critical component in numerous vital functions, and its dysfunction is involved in several disorders, including addiction and Parkinson's disease. Responses to dopamine are mediated via G protein-coupled dopamine receptors (D1-D5). Desensitization of G protein-coupled receptors is mediated via phosphorylation by members of the family of G protein-coupled receptor kinases (GRK1-GRK7). Here we show that GRK6-deficient mice are supersensitive to the locomotor-stimulating effect of psychostimulants, including cocaine and amphetamine. In addition, these mice demonstrate an enhanced coupling of striatal D2-like dopamine receptors to G proteins and augmented locomotor response to direct dopamine agonists both in intact and in dopamine-depleted animals. The present study indicates that postsynaptic D2-like dopamine receptors are physiological targets for GRK6 and suggests that this regulatory mechanism contributes to central dopaminergic supersensitivity.
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Affiliation(s)
- Raul R Gainetdinov
- Howard Hughes Medical Institute Laboratories, Duke University Medical Center, Durham, NC 27710, USA
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Torres GE, Carneiro A, Seamans K, Fiorentini C, Sweeney A, Yao WD, Caron MG. Oligomerization and trafficking of the human dopamine transporter. Mutational analysis identifies critical domains important for the functional expression of the transporter. J Biol Chem 2003; 278:2731-9. [PMID: 12429746 DOI: 10.1074/jbc.m201926200] [Citation(s) in RCA: 210] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The dopamine transporter (DAT) is a presynaptic plasma membrane protein responsible for the termination of dopaminergic neurotransmission in the central nervous system. While most studies have focused on structure/function analysis, much less information is available regarding the assembly and the trafficking of this protein. To address this problem, we performed a mutational analysis of the DAT protein, combined with biochemical, immunological, and functional approaches. In mammalian cells co-expressing differentially tagged DAT molecules, HA-tagged DAT co-purified with 6His-tagged DAT demonstrating a physical interaction between transporter proteins. Evidence for the functional oligomerization of DAT was obtained using dominant-negative mutants of DAT. Two loss-of-function mutant transporters (Y335A and D79G) that were targeted to the cell surface inhibited wild-type DAT uptake activity without affecting the membrane targeting of the wild-type transporter. Moreover, non-functional amino and carboxyl termini-truncated mutants of DAT inhibited wild-type DAT function by interfering with the normal processing of the wild-type transporter to the cell membrane. Mutations in the leucine repeat of the second transmembrane domain of the transporter could eliminate the dominant-negative effect of all these mutants. In addition, a small fragment comprising the first two transmembrane domains of DAT inhibited wild-type transporter function but not when the leucine repeat motif was mutated. Taken together, our results suggest that the assembly of DAT monomers plays a critical role in the expression and function of the transporter.
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Affiliation(s)
- Gonzalo E Torres
- Howard Hughes Medical Institute, Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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35
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Affiliation(s)
- Gonzalo E Torres
- Howard Hughes Medical Institute, Department of Cell Biology, Duke University, Durham, North Carolina 27710, USA
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36
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Barbosa J, Ferreira LT, Martins-Silva C, Santos MS, Torres GE, Caron MG, Gomez MV, Ferguson SSG, Prado MAM, Prado VF. Trafficking of the vesicular acetylcholine transporter in SN56 cells: a dynamin-sensitive step and interaction with the AP-2 adaptor complex. J Neurochem 2002; 82:1221-8. [PMID: 12358769 DOI: 10.1046/j.1471-4159.2002.01068.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The pathways by which synaptic vesicle proteins reach their destination are not completely defined. Here we investigated the traffic of a green fluorescent protein (GFP)-tagged version of the vesicular acetylcholine transporter (VAChT) in cholinergic SN56 cells, a model system for neuronal processing of this cargo. GFP-VAChT accumulates in small vesicular compartments in varicosities, but perturbation of endocytosis with a dominant negative mutant of dynamin I-K44A impaired GFP-VAChT trafficking to these processes. The protein in this condition accumulated in the cell body plasma membrane and in large vesicular patches therein. A VAChT endocytic mutant (L485A/L486A) was also located at the plasma membrane, however, the protein was not sorted to dynamin I-K44A generated vesicles. A fusion protein containing the VAChT C-terminal tail precipitated the AP-2 adaptor protein complex from rat brain, suggesting that VAChT directly interacts with the endocytic complex. In addition, yeast two hybrid experiments indicated that the C-terminal tail of VAChT interacts with the micro subunit of AP-2 in a di-leucine (L485A/L486A) dependent fashion. These observations suggest that the di-leucine motif regulates sorting of VAChT from the soma plasma membrane through a clathrin dependent mechanism prior to the targeting of the transporter to varicosities.
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Affiliation(s)
- José Barbosa
- Laboratório de Neurofarmacologia, Departamento de Farmacologia, ICB, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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37
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Haines WR, Voigt MM, Migita K, Torres GE, Egan TM. On the contribution of the first transmembrane domain to whole-cell current through an ATP-gated ionotropic P2X receptor. J Neurosci 2001; 21:5885-92. [PMID: 11487611 PMCID: PMC6763184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023] Open
Abstract
Scanning cysteine mutagenesis was used to identify potential pore-forming residues in and around the first transmembrane domains of ionotropic P2X(2) receptor subunits. Twenty-eight unique cysteine-substituted mutants (R28C-Y55C) were individually expressed in HEK293 cells by lipofection. Twenty-three of these were functional as assayed by application of ATP to transfected voltage-clamped cells. Individual mutants varied in their sensitivity to ATP; otherwise, currents through functional mutant receptors resembled those of the homomeric wild-type (WT) receptor. In five (H33C, R34C, I50C, K53C, and S54C) of 23 functional mutants, coapplication of 30 microm ATP and 500 nm Ag(+) irreversibly inhibited inward current evoked by subsequent applications of ATP alone. These inhibitions did not result in a lateral shift in the agonist concentration-response curve and are unlikely to involve a modification of the agonist binding site. Two (K53C and S54C) of the five residues modified by Ag(+) applied in the presence of ATP when the channels were gating were also modified by 1 mm (2-aminoethyl)methanethiosulfonate applied in the absence of ATP when the channels were closed. These data suggest that domains near either end of the first transmembrane domain influence ion conduction through the pore of the P2X(2) receptor.
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Affiliation(s)
- W R Haines
- Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, St. Louis, Missouri 63104, USA
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38
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Torres GE, Yao WD, Mohn AR, Quan H, Kim KM, Levey AI, Staudinger J, Caron MG. Functional interaction between monoamine plasma membrane transporters and the synaptic PDZ domain-containing protein PICK1. Neuron 2001; 30:121-34. [PMID: 11343649 DOI: 10.1016/s0896-6273(01)00267-7] [Citation(s) in RCA: 242] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PDZ domain-containing proteins play an important role in the targeting and localization of synaptic membrane proteins. Here, we report an interaction between the PDZ domain-containing protein PICK1 and monoamine neurotransmitter transporters in vitro and in vivo. In dopaminergic neurons, PICK1 colocalizes with the dopamine transporter (DAT) and forms a stable protein complex. Coexpression of PICK1 with DAT in mammalian cells and neurons in culture results in colocalization of the two proteins in a cluster pattern and an enhancement of DAT uptake activity through an increase in the number of plasma membrane DAT. Deletion of the PDZ binding site at the carboxyl terminus of DAT abolishes its association with PICK1 and impairs the localization of the transporter in neurons. These findings indicate a role for PDZ-mediated protein interactions in the localization, expression, and function of monoamine transporters.
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Affiliation(s)
- G E Torres
- Howard Hughes Medical Institute, Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
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39
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Haines WR, Torres GE, Voigt MM, Egan TM. Properties of the novel ATP-gated ionotropic receptor composed of the P2X(1) and P2X(5) isoforms. Mol Pharmacol 1999; 56:720-7. [PMID: 10496954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023] Open
Abstract
We recently reported that a novel hetero-oligomeric P2X receptor is formed from the P2X(1) and P2X(5) isoforms when coexpressed in human embryonic kidney 293 cells (). A more complete description of the pharmacology of this novel receptor is presented here. A brief application of ATP to a voltage-clamped cell transiently expressing P2X(1/5) receptors resulted in a biphasic current that rapidly reached a peak and then decayed to a sustained plateau. Washout of ATP was accompanied by generation and fade of a pronounced tail of inward current. EC(50) values were determined from concentration-response curves for a range of agonists. The rank order of agonist potency was ATP >/= 2 methylthio ATP > adenosine 5'-O-(3-thiotriphosphate) > alpha,beta-methylene ATP > ADP > CTP. alpha,beta-methylene ADP, UTP, GTP, and AMP were ineffective. Only ATP and 2 methylthio ATP were full agonists. IC(50) values were determined from concentration-response curves for three commonly used purinergic antagonists. Suramin and pyridoxal phosphate-6-azophenyl-2', 4'-disulfonic acid were equipotent at P2X(1) and P2X(1/5) receptors; however, the P2X(1/5) receptor was much less sensitive to TNP-ATP than was the P2X(1) receptor. The amplitude of peak ATP-gated current was relatively insensitive to changes in [Ca(2+)](O) (1-30 mM). Finally, plateau currents were potentiated by low concentrations of pyridoxal phosphate-6-azophenyl-2', 4'-disulfonic acid and by raising [Ca(2+)](O). These results provide additional information on the pharmacological profile of the recombinant P2X(1/5) receptor channel and provide a basis to further evaluate ATP-induced currents in native tissues.
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Affiliation(s)
- W R Haines
- Department of Pharmacological and Physiological Sciences, St. Louis University School of Medicine, St. Louis, Missouri 63104, USA.
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Abstract
P2X receptors are ATP-gated ion channels found in a variety of tissues and cell types. Seven different subunits (P2X(1)-P2X(7)) have been molecularly cloned and are known to form homomeric, and in some cases heteromeric, channel complexes. However, the molecular determinants leading to the assembly of subunits into P2X receptors are unknown. To address this question we utilized a co-immunoprecipitation assay in which epitope-tagged deletion mutants and chimeric constructs were examined for their ability to co-associate with full-length P2X subunits. Deletion mutants of the P2X(2) receptor subunit were expressed individually and together with P2X(2) or P2X(3) receptor subunits in HEK 293 cells. Deletion of the amino terminus up to the first transmembrane domain (amino acid 28) and beyond (to amino acid 51) did not prevent subunit assembly. Analysis of the carboxyl terminus demonstrated that mutants missing the portion of the protein downstream of the second transmembrane domain could also still co-assemble. However, a mutant terminating 25 amino acids before the second transmembrane domain could not assemble with other subunits or itself, implicating the missing region of the protein in assembly. This finding was supported and extended by data utilizing a chimera strategy that indicated TMD2 is a critical determinant of P2X subunit assembly.
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Affiliation(s)
- G E Torres
- Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA
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41
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Abstract
P2X receptors are a distinct family of ligand-gated ion channels activated by extracellular ATP. Each of the seven identified subunit proteins (P2X1 through P2X7) has been reported to form functional homo-oligomeric channels when expressed in heterologous systems. Functional studies of native receptors, together with patterns of subunit gene expression, suggest that hetero-oligomeric assembly among members of this family may also occur. This prediction is supported by reports describing hetero-oligomeric assembly for three different recombinant subunit combinations. In this report, we systematically examined the ability of all members of the P2X receptor family to interact using a co-immunoprecipitation assay. The seven P2X receptor subunits were differentially epitope-tagged and expressed in various combinations in human embryonic kidney 293 cells. It was found that six of the seven subunits formed homo-oligomeric complexes, the exception being P2X6. When co-assembly between pairs of subunits was examined, all were able to form hetero-oligomeric assemblies with the exception of P2X7. Whereas P2X1, P2X2, P2X5, and P2X6 were able to assemble with most subunits, P2X3 and P2X4 presented a more restricted pattern of co-association. These results suggest that hetero-oligomeric assembly might underlie functional discrepancies observed between P2X responses seen in the native and recombinant settings, while providing for an increased diversity of signaling by ATP.
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Affiliation(s)
- G E Torres
- Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA
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Nowak FV, Torres GE, Hu SB. Differential gene expression response to gonadal hormones by preoptic regulatory factors-1 and -2 in the female rat brain. Neuroendocrinology 1999; 69:191-201. [PMID: 10087451 DOI: 10.1159/000054418] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Steroids and neuropeptides interact in the central nervous system (CNS) to regulate reproductive function and behavior. The preoptic regulatory factors, PORF-1 and PORF-2, are unique neuropeptides for which roles in gender-related brain development and function have been proposed. PORF-1 and PORF-2 expression in rat brain are age, region and gender dependent, and castration or hypophysectomy alter the metabolism of the PORF-1 and PORF-2 mRNAs in male rat brain and testes. If these two peptides have a role in gender-dependent brain function, then gonadal steroids might well affect their expression. The present study was designed to investigate the response of the PORF-1 and PORF-2 mRNAs to sex steroids in the female rat brain and to compare this response to that of two peptides whose roles in the neuroendocrinology of reproduction are well established, gonadotropin-releasing hormone (GnRH) and neuropeptide Y (NPY). Rats were ovariectomized and treated with placebo, estradiol (E2), progesterone (P4) or a combination of the two (E2/P4) and NPY, PORF-2, GnRH and PORF-1 mRNAs were quantified by nuclease protection assays. PORF-1, PORF-2 and GnRH mRNAs were also measured in intact rats during estrus and proestrus. Responses were compared in the preoptic anterior hypothalamus (POA), medial basal hypothalamus (MBH), cerebral cortex (CC) and hippocampus (HIPP). Expression of PORF-1 and PORF-2 was also confirmed in the female rat hypothalamus by in situ hybridization analysis. PORF-1 and PORF-2 mRNAs were detected in the adult female rat brain by both in situ hybridization and ribonuclease protection analyses. In situ hybridization analysis demonstrated that PORF-1 and PORF-2 mRNAs are expressed in hypothalamic neurons. RNase protection analysis showed that PORF-1, PORF-2 and NPY mRNAs were present in all four brain regions examined while GnRH expression was detected only in the MBH and POA. Estradiol alone upregulated expression of the PORF-1 and PORF-2 mRNAs in the ovariectomized rat in the POA and HIPP, and of NPY mRNA in the MBH and HIPP. Progesterone alone had a stimulatory effect on NPY mRNA in the MBH and HIPP. Treatment with a combination of E2/P4 downregulated PORF-2 mRNA in the POA as well as PORF-1, PORF-2 and NPY mRNAs in the CC. In contrast, E2/P4 upregulated the PORF-2 and NPY mRNAs in the HIPP and NPY mRNA in the MBH. In the cycling rat, PORF-1 mRNA levels were higher during proestrus than estrus in both the MBH and POA, while PORF-2 mRNA levels did not change. In contrast GnRH mRNA was lower in the POA and higher in the MBH during proestrus compared with estrus. Thus, intrinsic factors, most likely both ovarian and neuroendocrine, regulate PORF-1 and GnRH expression in the intact cycling rat CNS in a region-dependent manner. In the ovariectomized rat, PORF-1, PORF-2, NPY and GnRH mRNAs all respond in a region-specific manner to sex steroid treatment. These data support the role of PORF-1 and PORF-2 in gender-dependent brain function in the adult female rat.
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Affiliation(s)
- F V Nowak
- Department of Pharmacological Science, St. Louis University Health Sciences Center, St. Louis, Mo., USA.
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Abstract
P2X receptors are a family of ion channels gated by extracellular ATP. Each member of the family can form functional homomeric channels, but only P2X2 and P2X3 have been shown to combine to form a unique heteromeric channel. Data from in situ hybridization studies suggest that P2X1 and P2X5 may also co-assemble. In this study, we tested this hypothesis by expressing recombinant P2X1 and P2X5 receptor subunits either individually or together in human embryonic kidney 293 cells. In cells expressing the homomeric P2X1 receptor, 30 microM alpha,beta-methylene ATP (alpha,beta-me-ATP) evoked robust currents that completely desensitized in less than 1 sec, whereas alpha,beta-me-ATP failed to evoke current in cells expressing the homomeric P2X5 receptor. By contrast, alpha, beta-me-ATP evoked biphasic currents with a pronounced nondesensitizing plateau phase in cells that co-expressed both subunits. Further, the EC50 for alpha,beta-me-ATP was greater in cells expressing both P2X1 and P2X5 than in cells expressing P2X1 alone (5 and 1.6 microM, respectively). Heteromeric assembly was confirmed using a co-immunoprecipitation assay of epitope-tagged P2X1 and P2X5 subunits. In summary, this study provides biochemical and functional evidence of a novel channel formed by P2X subunit heteropolymerization. This finding suggests that heteromeric subunit assembly constitutes an important mechanism for generating functional diversity of ATP-mediated responses.
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Affiliation(s)
- G E Torres
- Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA
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44
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Abstract
P2X receptors are integral membrane proteins that belong to the growing family of transmitter-gated ion channels. The extracellular domain of these receptors contains several consensus sequences for N-linked glycosylation that may contribute to the functional expression of the channel. We have previously reported the extracellular orientation of asparagine residues 182, 239, and 298 of the P2X2 receptor subunit by showing that the protein is glycosylated at each site [Torres, G. E., et al. (1998) FEBS Lett. 425, 19-23 (1)]. In this study, we focused on the consequences of removing N-linked glycosylation from the P2X2 receptor by using two different approaches, tunicamycin treatment or site-directed mutagenesis. HEK-293 cells stably transfected with the P2X2 receptor subunit showed little or no response to ATP after tunicamycin treatment. In addition, loss of function was observed with the elimination of all three N-linked glycosylation sites from P2X2. Cell surface labeling with biotin or indirect immunofluorescence revealed that the expression of the nonglycosylated receptors produced by either tunicamycin or site-directed mutagenesis is greatly reduced at the cell surface, indicating that the nonglycosylated P2X2 receptors are retained inside the cell. These data provide the first direct evidence for a critical role of N-linked glycosylation in the cell surface expression of a P2X receptor subunit.
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Affiliation(s)
- G E Torres
- Department of Pharmacological and Physiological Sciences, St. Louis University Health Sciences Center, Missouri 63104, USA
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Torres GE, Egan TM, Voigt MM. Erratum to: Topological analysis of the ATP-gated ionotropic P2X 2
receptor subunit (FEBS 19946). FEBS Lett 1998. [DOI: 10.1016/s0014-5793(98)00332-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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46
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Abstract
We investigated the transmembrane topology of the P2X2 receptor subunit expressed in HEK 293 cells. Initial studies using two P2X subunits expressed in tandem indicated that the amino- and carboxy-termini are on the same side of the membrane. Immunofluorescence studies showed the cytoplasmic orientation of the amino- and carboxy-termini. Finally, N-glycosylation scanning mutagenesis revealed that reporter sites inserted into the central loop, but not those in the amino- or carboxy-terminal regions, were glycosylated, thus suggesting an extracellular placement for that domain. Our results support a two-transmembrane arrangement for P2X receptors with intracellular amino- and carboxy-termini.
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Affiliation(s)
- G E Torres
- Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, MO 63104, USA
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Torres GE, Arfken CL, Andrade R. 5-Hydroxytryptamine4 receptors reduce afterhyperpolarization in hippocampus by inhibiting calcium-induced calcium release. Mol Pharmacol 1996; 50:1316-22. [PMID: 8913363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Serotonin acting on 5-hydroxytryptamine4 receptors increases membrane excitability in CA1 hippocampal pyramidal cells by reducing the slow calcium-activated afterhyperpolarization. This effect is mediated through an increase in cAMP and activation of protein kinase A, although subsequent steps have not been elucidated. We now report that a significant portion of the calcium responsible for the generation of the afterhyperpolarization originates from the release of intracellular calcium through a calcium-induced calcium-release mechanism. Thus, the afterhyperpolarization is enhanced by caffeine, whereas it is inhibited by dantrolene and ruthenium red, two blockers of calcium-induced calcium release. The afterhyperpolarization is also inhibited by thapsigargin, which depletes intracellular calcium stores. These observations raised the possibility that serotonin might reduce the afterhyperpolarization by regulating calcium-induced calcium release. Consistent with this possibility, administration of calcium-induced calcium-release blockers, as well as of thapsigargin, occluded the ability of serotonin to inhibit the afterhyperpolarization. Similarly, administration of caffeine, which enhances the contribution of calcium-induced calcium release to the afterhyperpolarization, enhanced the effect of serotonin. These results indicate that serotonin inhibits the afterhyperpolarization in the CA1 region of hippocampus by reducing the ability of extracellular calcium to trigger calcium release from intracellular stores. As such, they identify a physiological role for the calcium-induced calcium release in hippocampus and provide evidence for its regulation by G protein-coupled receptors and, more specifically, 5-hydroxytryptamine4 receptors.
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Affiliation(s)
- G E Torres
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
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Torres GE, Chaput Y, Andrade R. Cyclic AMP and protein kinase A mediate 5-hydroxytryptamine type 4 receptor regulation of calcium-activated potassium current in adult hippocampal neurons. Mol Pharmacol 1995; 47:191-7. [PMID: 7838128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
In the CA1 region of the hippocampus, activation of serotonin receptors of the 5-hydroxytryptamine (5-HT)4 subtype increases membrane excitability by reducing the calcium-activated potassium current responsible for the slow afterhyperpolarization observed in these cells. In the present study, the signaling mechanism by which 5-HT4 receptors reduce the afterhyperpolarization in the CA1 region was examined using intracellular recording in brain slices. Administration of the membrane-permeable cAMP analog 8-bromo-cAMP mimicked the effect of serotonin on the afterhyperpolarization, whereas administration of the protein kinase inhibitor staurosporine inhibited the effects of serotonin. These observations suggested a role for protein kinase A in this response. This was confirmed by intracellular injection of the selective protein kinase A inhibitor Rp-adenosine 3',5'-cyclic monophosphothioate ((Rp)-cAMPS), which noncompetitively inhibited the ability of serotonin to reduce the after-hyperpolarization. Additional evidence for the involvement of cAMP in the signaling by 5-HT4 receptors was obtained using the general phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. When this compound was bath administered at concentrations sufficient to enhance a known cAMP-mediated response, a significant enhancement of the ability of 5-HT4 receptors to reduce the afterhyperpolarization was observed. Together, these results indicate that serotonin reduces the afterhyperpolarization in the CA1 region by acting on 5-HT4 receptors that increase intracellular cAMP levels and activate protein kinase A.
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Affiliation(s)
- G E Torres
- Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, Missouri 63104
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Torres GE, Holt IL, Andrade R. Antagonists of 5-HT4 receptor-mediated responses in adult hippocampal neurons. J Pharmacol Exp Ther 1994; 271:255-61. [PMID: 7965722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The study of serotonin-4 (5-HT4) receptors in the central nervous system has been hindered by the lack of effective, selective antagonists. However, recently, several novel compounds have been synthesized and shown to act as antagonists at 5-HT4 receptors in smooth muscle and embryonic neurons in culture. In the present study, intracellular electrophysiological recordings were used to test the effects of three of these compounds: endo-8-methyl-8-azabicyclo[3.2.1]oct-3-yl-2,3-dihydro-6-methoxy- 2-oxo-1H-benzimidazole-1-carboxylate (DAU 6285), [1-[2-(methylsulfonylamino)ethyl]-4-piperidinyl]methyl 1-methyl-1H-indole-3-carboxylate (GR 113808) and 2-diethylaminoethyl-(2-methoxy-4-amino-5-chloro) benzoate (SDZ 205-557) on the 5-HT4 reduction of the afterhyperpolarization seen in adult CA1 hippocampal neurons in brain slices. GR 113808, SDZ 205-557 and DAU 6285 all functioned as competitive antagonists at these 5-HT4 receptors. Although all three compounds tested acted as effective antagonists, they differed considerably in potency. When the potency of these antagonists at the 5-HT4 receptor that mediates the reduction of the afterhyperpolarization was compared with that observed for 5-HT4 receptors in biochemical and binding assays, an excellent correlation was observed. Among the antagonists tested, GR 113808 was the most potent (pA2 = GR 113808 > SDZ 205-507 > DAU 6285). It exhibited an apparent affinity for the 5-HT4 receptors in the low nanomolar range but did not antagonize 5-HT1A, beta-adrenergic or muscarinic receptor-mediated responses when applied at concentrations two orders of magnitude higher.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- G E Torres
- Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, Missouri
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Torres GE, González A, Garnica B, Mireles M. [Types and mechanisms producing respiratory insufficiency. Incidence in Mexico City]. Arch Inst Cardiol Mex 1966; 36:200-24. [PMID: 5935720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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