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Estave PM, Albertson SE, Karkhanis AN, Jones SR. Co-targeting the kappa opioid receptor and dopamine transporter reduces motivation to self-administer cocaine and partially reverses dopamine system dysregulation. Sci Rep 2024; 14:6509. [PMID: 38499566 PMCID: PMC10948819 DOI: 10.1038/s41598-024-53463-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Accepted: 01/31/2024] [Indexed: 03/20/2024] Open
Abstract
Cocaine disrupts dopamine (DA) and kappa opioid receptor (KOR) system activity, with long-term exposure reducing inhibiton of DA uptake by cocaine and increasing KOR system function. Single treatment therapies have not been successful for cocaine use disorder; therefore, this study focuses on a combination therapy targeting the dopamine transporter (DAT) and KOR. Sprague Dawley rats self-administered 5 days of cocaine (1.5 mg/kg/inf, max 40 inf/day, FR1), followed by 14 days on a progressive ratio (PR) schedule (0.19 mg/kg/infusion). Behavioral effects of individual and combined administration of phenmetrazine and nBNI were then examined using PR. Additionally, ex vivo fast scan cyclic voltammetry was then used to assess alterations in DA and KOR system activity in the nucleus accumbens before and after treatments. Chronic administration of phenmetrazine as well as the combination of phenmetrazine and nBNI-but not nBNI alone-significantly reduced PR breakpoints. In addition, the combination of phenmetrazine and nBNI partially reversed cocaine-induced neurodysregulations of the KOR and DA systems, indicating therapeutic benefits of targeting the DA and KOR systems in tandem. These data highlight the potential benefits of the DAT and KOR as dual-cellular targets to reduce motivation to administer cocaine and reverse cocaine-induced alterations of the DA system.
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Affiliation(s)
- Paige M Estave
- Department of Physiology and Pharmacology, Wake University Forest School of Medicine, Medical Center Blvd., Winston-Salem, NC, 27157, USA
| | - Steven E Albertson
- Department of Physiology and Pharmacology, Wake University Forest School of Medicine, Medical Center Blvd., Winston-Salem, NC, 27157, USA
| | - Anushree N Karkhanis
- Department of Psychology, Binghamton University - State University of New York, Binghamton, NY, 13902, USA
| | - Sara R Jones
- Department of Physiology and Pharmacology, Wake University Forest School of Medicine, Medical Center Blvd., Winston-Salem, NC, 27157, USA.
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Fu T, Zeng S, Zheng Q, Zhu F. The Important Role of Transporter Structures in Drug Disposition, Efficacy, and Toxicity. Drug Metab Dispos 2023; 51:1316-1323. [PMID: 37295948 DOI: 10.1124/dmd.123.001275] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 05/27/2023] [Accepted: 06/02/2023] [Indexed: 06/12/2023] Open
Abstract
The ATP-binding cassette (ABC) and solute carrier (SLC) transporters are critical determinants of drug disposition, clinical efficacy, and toxicity as they specifically mediate the influx and efflux of various substrates and drugs. ABC transporters can modulate the pharmacokinetics of many drugs via mediating the translocation of drugs across biologic membranes. SLC transporters are important drug targets involved in the uptake of a broad range of compounds across the membrane. However, high-resolution experimental structures have been reported for a very limited number of transporters, which limits the study of their physiologic functions. In this review, we collected structural information on ABC and SLC transporters and described the application of computational methods in structure prediction. Taking P-glycoprotein (ABCB1) and serotonin transporter (SLC6A4) as examples, we assessed the pivotal role of structure in transport mechanisms, details of ligand-receptor interactions, drug selectivity, the molecular mechanisms of drug-drug interactions, and differences caused by genetic polymorphisms. The data collected contributes toward safer and more effective pharmacological treatments. SIGNIFICANCE STATEMENT: The experimental structure of ATP-binding cassette and solute carrier transporters was collected, and the application of computational methods in structure prediction was described. P-glycoprotein and serotonin transporter were used as examples to reveal the pivotal role of structure in transport mechanisms, drug selectivity, the molecular mechanisms of drug-drug interactions, and differences caused by genetic polymorphisms.
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Affiliation(s)
- Tingting Fu
- College of Pharmaceutical Sciences, The Second Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang University, Hangzhou, China (F.Z.); School of Pharmaceutical Sciences, Jilin University, Changchun, China (T.F., Q.Z.); College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China (S.Z., F.Z.); and Innovation Institute for Artificial Intelligence in Medicine of Zhejiang University, Alibaba-Zhejiang University Joint Research Center of Future Digital Healthcare, Hangzhou, China (F.Z.)
| | - Su Zeng
- College of Pharmaceutical Sciences, The Second Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang University, Hangzhou, China (F.Z.); School of Pharmaceutical Sciences, Jilin University, Changchun, China (T.F., Q.Z.); College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China (S.Z., F.Z.); and Innovation Institute for Artificial Intelligence in Medicine of Zhejiang University, Alibaba-Zhejiang University Joint Research Center of Future Digital Healthcare, Hangzhou, China (F.Z.)
| | - Qingchuan Zheng
- College of Pharmaceutical Sciences, The Second Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang University, Hangzhou, China (F.Z.); School of Pharmaceutical Sciences, Jilin University, Changchun, China (T.F., Q.Z.); College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China (S.Z., F.Z.); and Innovation Institute for Artificial Intelligence in Medicine of Zhejiang University, Alibaba-Zhejiang University Joint Research Center of Future Digital Healthcare, Hangzhou, China (F.Z.)
| | - Feng Zhu
- College of Pharmaceutical Sciences, The Second Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang University, Hangzhou, China (F.Z.); School of Pharmaceutical Sciences, Jilin University, Changchun, China (T.F., Q.Z.); College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China (S.Z., F.Z.); and Innovation Institute for Artificial Intelligence in Medicine of Zhejiang University, Alibaba-Zhejiang University Joint Research Center of Future Digital Healthcare, Hangzhou, China (F.Z.)
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Nepal B, Das S, Reith ME, Kortagere S. Overview of the structure and function of the dopamine transporter and its protein interactions. Front Physiol 2023; 14:1150355. [PMID: 36935752 PMCID: PMC10020207 DOI: 10.3389/fphys.2023.1150355] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 02/21/2023] [Indexed: 03/06/2023] Open
Abstract
The dopamine transporter (DAT) plays an integral role in dopamine neurotransmission through the clearance of dopamine from the extracellular space. Dysregulation of DAT is central to the pathophysiology of numerous neuropsychiatric disorders and as such is an attractive therapeutic target. DAT belongs to the solute carrier family 6 (SLC6) class of Na+/Cl- dependent transporters that move various cargo into neurons against their concentration gradient. This review focuses on DAT (SCL6A3 protein) while extending the narrative to the closely related transporters for serotonin and norepinephrine where needed for comparison or functional relevance. Cloning and site-directed mutagenesis experiments provided early structural knowledge of DAT but our contemporary understanding was achieved through a combination of crystallization of the related bacterial transporter LeuT, homology modeling, and subsequently the crystallization of drosophila DAT. These seminal findings enabled a better understanding of the conformational states involved in the transport of substrate, subsequently aiding state-specific drug design. Post-translational modifications to DAT such as phosphorylation, palmitoylation, ubiquitination also influence the plasma membrane localization and kinetics. Substrates and drugs can interact with multiple sites within DAT including the primary S1 and S2 sites involved in dopamine binding and novel allosteric sites. Major research has centered around the question what determines the substrate and inhibitor selectivity of DAT in comparison to serotonin and norepinephrine transporters. DAT has been implicated in many neurological disorders and may play a role in the pathology of HIV and Parkinson's disease via direct physical interaction with HIV-1 Tat and α-synuclein proteins respectively.
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Affiliation(s)
- Binod Nepal
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Sanjay Das
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Maarten E. Reith
- Department of Psychiatry, New York University School of Medicine, New York City, NY, United States
| | - Sandhya Kortagere
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States
- *Correspondence: Sandhya Kortagere,
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A high-affinity cocaine binding site associated with the brain acid soluble protein 1. Proc Natl Acad Sci U S A 2022; 119:e2200545119. [PMID: 35412917 PMCID: PMC9169839 DOI: 10.1073/pnas.2200545119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Cocaine is a monoamine transport inhibitor. Current models attributing pharmacologic actions of cocaine to inhibiting the activity of the amine transporters alone failed to translate to the clinic. Cocaine inhibition of the dopamine, serotonin, and norepinephrine transporters is relatively weak, suggesting that blockade of the amine transporters alone cannot account for the actions of cocaine, especially at low doses. There is evidence for significantly more potent actions of cocaine, suggesting the existence of a high-affinity receptor(s) for the drug. Identifying and characterizing such receptors will deepen our understanding of cocaine pharmacologic actions and pave the way for therapeutic development. Here we identify a high-affinity cocaine binding site associated with BASP1 that is involved in mediating the drug’s psychotropic actions. Cocaine exerts its stimulant effect by inhibiting dopamine (DA) reuptake, leading to increased dopamine signaling. This action is thought to reflect the binding of cocaine to the dopamine transporter (DAT) to inhibit its function. However, cocaine is a relatively weak inhibitor of DAT, and many DAT inhibitors do not share cocaine’s behavioral actions. Further, recent reports show more potent actions of the drug, implying the existence of a high-affinity receptor for cocaine. We now report high-affinity binding of cocaine associated with the brain acid soluble protein 1 (BASP1) with a dissociation constant (Kd) of 7 nM. Knocking down BASP1 in the striatum inhibits [3H]cocaine binding to striatal synaptosomes. Depleting BASP1 in the nucleus accumbens but not the dorsal striatum diminishes locomotor stimulation in mice. Our findings imply that BASP1 is a pharmacologically relevant receptor for cocaine.
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5
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Ragu Varman D, Subler MA, Windle JJ, Jayanthi LD, Ramamoorthy S. Novelty-induced hyperactivity and suppressed cocaine induced locomotor activation in mice lacking threonine 53 phosphorylation of dopamine transporter. Behav Brain Res 2021; 408:113267. [PMID: 33794225 DOI: 10.1016/j.bbr.2021.113267] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Revised: 03/03/2021] [Accepted: 03/24/2021] [Indexed: 12/26/2022]
Abstract
Dopamine (DA) transporter (DAT) is dynamically regulated by several protein kinases and the Thr53 phosphorylation of DAT (pT53-DAT) is documented in heterologous cell models and in rat brain. However, the role of endogenous pT53-DAT in living animals has never been addressed. Here we generated and studied the pT53-lacking DAT mouse model (DAT-Ala53) by CRISPR/Cas9 technology. DAT-Ala53 mice showed normal growth, body weight, body temperature, grip strength, and sucrose preference while pT53-DAT was completely absent. However, DAT-Ala53 mice showed hyperlocomotion, pronounced vertical exploratory behavior, and stereotypy in a novel environment compared to wild-type littermates (WT). DAT-Ala53 mice displayed unaltered levels of monoamines, glutamate, and GABA in the striatum compared to WT. There were also no significant differences between DAT-Ala53 mice and WT in tyrosine hydroxylase (TH) and phospho-TH levels, or in total and surface DAT levels, or in DA-transport kinetic parameters Vmax and Km. Immunohistochemical and colocalization analyses of TH and DAT in caudate-putamen and nucleus accumbens revealed no significant differences between DAT-Ala53 and WT mice. Interestingly, cocaine's potency to inhibit striatal DA transport and cocaine-induced locomotor activation were significantly reduced in the DAT-Ala53 mice. Also, ERK1/2 inhibitors completely failed to inhibit striatal DA uptake in DAT-Ala53 mice. Collectively, our findings reveal that the mice lacking pT53-DAT display novelty-induced hyperactive phenotype despite having normal transporter protein expression, DA-transport kinetics and DA-linked markers. The results also reveal that the lack of endogenous pT53-DAT renders DAT resistant to ERK1/2 inhibition and also less susceptible to cocaine inhibition and cocaine-evoked locomotor stimulation.
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Affiliation(s)
- Durairaj Ragu Varman
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Mark A Subler
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Jolene J Windle
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Lankupalle D Jayanthi
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Sammanda Ramamoorthy
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, 23298, USA.
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Association between methylphenidate treatment and risk of seizure: a population-based, self-controlled case-series study. THE LANCET CHILD & ADOLESCENT HEALTH 2020; 4:435-443. [PMID: 32450123 DOI: 10.1016/s2352-4642(20)30100-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 03/25/2020] [Accepted: 03/25/2020] [Indexed: 12/21/2022]
Abstract
BACKGROUND Individuals with attention-deficit hyperactivity disorder (ADHD) are at increased risk of seizures. Stimulant medications such as methylphenidate are the most commonly prescribed treatment for ADHD, but the association between their therapeutic use and the risk of seizures is unclear. We aimed to investigate the association between methylphenidate treatment and the risk of seizure. METHODS For this population-based observational study, we used the electronic medical record database of the Hong Kong Clinical Data Analysis And Reporting System to identify individuals aged 6-25 years who received at least one methylphenidate prescription during the study period. Individuals with records of seizure or epilepsy before the study period were excluded. Individuals treated with methylphenidate who had seizures during the study period were included in the subsequent analyses, and a self-controlled case-series design was used to control for time-invariant individual characteristics. We did additional analyses using skin infection as a negative control outcome. We compared relative incidence of seizure during periods when individuals were exposed to methylphenidate with that during non-exposed periods. FINDINGS Of 29 604 individuals prescribed methylphenidate between Jan 1, 2001, and Dec 31, 2017, 269 (199 males and 70 females) had incident seizures. The mean age at baseline was 6·66 years (SD 2·01) and the median age at the incident seizure was 9·69 years (IQR 7·62-12·99). The overall incidence of seizure during methylphenidate treatment was 4·4 per 10 000 patient-years. We detected an increased risk of seizure during the first 30 days of methylphenidate treatment compared with that during non-exposed periods, with an incidence rate ratio of 4·01 (95% CI 2·09-7·68). No increase in risk was identified during the following 31-180 days of treatment (1·13, 0·56-2·25) or during subsequent treatment (1·38, 0·92-2·07). We did not identify an increased risk in any risk window for the negative control outcome analysis. No individuals died because of a seizure during the study period. INTERPRETATION The incidence of seizures was higher in the period immediately after the start of methylphenidate treatment than in the non-exposed period. No increased risk was observed during continuation of methylphenidate treatment. The association between methylphenidate treatment and seizures immediately after initiation of medication can be seen as a potential safety signal. Monitoring of neurological outcomes in individuals with ADHD is recommended when they first start methylphenidate treatment. FUNDING Hong Kong Research Grants Council.
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7
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Wu CS, Jew CP, Sun H, Ballester Rosado CJ, Lu HC. mGlu5 in GABAergic neurons modulates spontaneous and psychostimulant-induced locomotor activity. Psychopharmacology (Berl) 2020; 237:345-361. [PMID: 31646346 PMCID: PMC7024012 DOI: 10.1007/s00213-019-05367-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 09/22/2019] [Indexed: 12/17/2022]
Abstract
RATIONALE A role of group I metabotropic glutamate receptor 5 (mGlu5) in regulating spontaneous locomotion and psychostimulant-induced hyperactivity has been proposed. OBJECTIVES This study aims to determine if mGlu5 in GABAergic neurons regulates spontaneous or psychostimulant-induced locomotion. METHODS We generated mice specifically lacking mGlu5 in forebrain GABAergic neuron by crossing DLX-Cre mice with mGlu5flox/flox mice to generate DLX-mGlu5 KO mice. The locomotion of adult mice was examined in the open-field assay (OFA) and home cage setting. The effects of the mGlu5 antagonist 6-methyl-2-(phenylethynyl)pyridine (MPEP), cocaine, and methylphenidate on acute motor behaviors in DLX-mGlu5 KO and littermate control mice were assessed in OFA. Striatal synaptic plasticity of these mice was examined with field potential electrophysiological recordings. RESULTS Deleting mGlu5 from forebrain GABAergic neurons results in failure to induce long-term depression (LTD) in the dorsal striatum and absence of habituated locomotion in both novel and familiar settings. In a familiar environment (home cage), DLX-mGlu5 KO mice were hyperactive. In the OFA, DLX-mGlu5 KO mice exhibited initial hypo-activity, and then gradually increased their locomotion with time, resulting in no habituation response. DLX-mGlu5 KO mice exhibited almost no locomotor response to MPEP (40 mg/kg), while the same dose elicited hyperlocomotion in control mice. The DLX-mGlu5 KO mice also showed reduced hyperactivity response to cocaine, while they retained normal hyperactivity response to methylphenidate, albeit with delayed onset. CONCLUSION mGlu5 in forebrain GABAergic neurons is critical to trigger habituation upon the initiation of locomotion as well as to mediate MPEP-induced hyperlocomotion and modulate psychostimulant-induced hyperactivity.
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Affiliation(s)
- Chia-Shan Wu
- The Cain Foundation Laboratories, Baylor College of Medicine, Houston, 77030, TX, USA.
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, 77030, TX, USA.
- Department of Nutrition and Food Science, Texas A&M University, 123 Cater-Mattil, 2253 TAMU, College Station, TX, 77843, USA.
| | - Christopher P Jew
- The Cain Foundation Laboratories, Baylor College of Medicine, Houston, 77030, TX, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, 77030, TX, USA
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Hao Sun
- The Cain Foundation Laboratories, Baylor College of Medicine, Houston, 77030, TX, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, 77030, TX, USA
| | - Carlos J Ballester Rosado
- The Cain Foundation Laboratories, Baylor College of Medicine, Houston, 77030, TX, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, 77030, TX, USA
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Hui-Chen Lu
- The Cain Foundation Laboratories, Baylor College of Medicine, Houston, 77030, TX, USA.
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, 77030, TX, USA.
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, 77030, USA.
- Linda and Jack Gill Center, Department of Psychological and Brain Sciences, Indiana University, 1101 E. 10th Street, Bloomington, IN, 47405, USA.
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Foroughi K, Khaksari M, Shayannia A. Molecular Docking Studies of Methamphetamine and Amphetamine- Related Derivatives as an Inhibitor against Dopamine Receptor. Curr Comput Aided Drug Des 2018; 16:122-133. [PMID: 30514192 DOI: 10.2174/1573409915666181204144411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 11/14/2018] [Accepted: 11/29/2018] [Indexed: 11/22/2022]
Abstract
BACKGROUND The catecholamines such as dopamine, norepinephrine, and epinephrine are neurotransmitters that regulate different physiological functions of the central nervous system. Some evidence suggests that the degeneration of dopamine neurons in the substantia nigra contributes to Parkinson's Disease (PD), which is a neurodegenerative disorder and it is responsible for the major symptoms of PD. It is suggested that replenishment of striatal dopamine through the oral administration of the dopamine precursor, levodopa, can compensate for the lack of endogenously produced dopamine. Some studies have shown competitive inhibition of dopamine receptor such as methamphetamine, and other amphetamine-related derivatives, which block dopamine receptor activity to uptake dopamine. METHODS In this study, 3D structures of amphetamine, methamphetamine, cocaine, methylphenidate, cathinone, MDMA, and mephedrone were obtained from the PubChem database, which has reported some evidence about their inhibitory effect with dopamine receptor. Then, these structures were provided for molecular docking analysis by Autodock Vina software. Eventually, the binding energies between docked dopamine receptor and them were calculated and their interactions were prognosticated. RESULTS Our results indicated that all chemicals can interact with dopamine receptor molecule in the active site of dopamine and the minimum binding energies belong to Cocaine and Methylphenidate with -7.9 Kcal/mol and -7.2 Kcal/mol, respectively. CONCLUSION It might be concluded that amphetamine, methamphetamine, cocaine, methylphenidate, cathinone, MDMA, and mephedrone could act as potential inhibitors of DA receptor for dopamine uptake, which could cause degenerative disorders.
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Affiliation(s)
- Kobra Foroughi
- Department of Medical Biotechnology, School of Medicine, Shahroud University of Medical Sciences, Shahroud, Iran
| | - Mehdi Khaksari
- Addiction Research Center, Shahroud University of Medical Sciences, Shahroud, Iran
| | - Asghar Shayannia
- Department of Medical Biotechnology, School of Medicine, Shahroud University of Medical Sciences, Shahroud, Iran
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Zsilla G, Hegyi DE, Baranyi M, Vizi ES. 3,4-Methylenedioxymethamphetamine, mephedrone, and β-phenylethylamine release dopamine from the cytoplasm by means of transporters and keep the concentration high and constant by blocking reuptake. Eur J Pharmacol 2018; 837:72-80. [DOI: 10.1016/j.ejphar.2018.08.037] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 08/24/2018] [Accepted: 08/29/2018] [Indexed: 02/02/2023]
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Sahai MA, Davidson C, Dutta N, Opacka-Juffry J. Mechanistic Insights into the Stimulant Properties of Novel Psychoactive Substances (NPS) and Their Discrimination by the Dopamine Transporter-In Silico and In Vitro Exploration of Dissociative Diarylethylamines. Brain Sci 2018; 8:brainsci8040063. [PMID: 29642450 PMCID: PMC5924399 DOI: 10.3390/brainsci8040063] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 03/21/2018] [Accepted: 03/22/2018] [Indexed: 12/31/2022] Open
Abstract
Novel psychoactive substances (NPS) may have unsuspected addiction potential through possessing stimulant properties. Stimulants normally act at the dopamine transporter (DAT) and thus increase dopamine (DA) availability in the brain, including nucleus accumbens, within the reward and addiction pathway. This paper aims to assess DAT responses to dissociative diarylethylamine NPS by means of in vitro and in silico approaches. We compared diphenidine (DPH) and 2-methoxydiphenidine (methoxphenidine, 2-MXP/MXP) for their binding to rat DAT, using autoradiography assessment of [125I]RTI-121 displacement in rat striatal sections. The drugs' effects on electrically-evoked DA efflux were measured by means of fast cyclic voltammetry in rat accumbens slices. Computational modeling, molecular dynamics and alchemical free energy simulations were used to analyse the atomistic changes within DAT in response to each of the five dissociatives: DPH, 2-MXP, 3-MXP, 4-MXP and 2-Cl-DPH, and to calculate their relative binding free energy. DPH increased DA efflux as a result of its binding to DAT, whereas MXP had no significant effect on either DAT binding or evoked DA efflux. Our computational findings corroborate the above and explain the conformational responses and atomistic processes within DAT during its interactions with the dissociative NPS. We suggest DPH can have addictive liability, unlike MXP, despite the chemical similarities of these two NPS.
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Affiliation(s)
- Michelle A Sahai
- Department of Life Sciences, University of Roehampton, London SW15 4JD, UK.
| | - Colin Davidson
- St George's, University of London, London SW17 0RE, UK.
- Pharmacy & Biomedical Sciences, University of Central Lancashire, Preston PR1 2HE, UK.
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Rizzo FR, Federici M, Mercuri NB. 3,4-Methylenedioxymethamphetamine (MDMA) Alters Synaptic Dopamine Release in the Dorsal Striatum Through Nicotinic Receptors and DAT Inhibition. Neuroscience 2018; 377:69-76. [PMID: 29510210 DOI: 10.1016/j.neuroscience.2018.02.037] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 02/14/2018] [Accepted: 02/22/2018] [Indexed: 10/17/2022]
Abstract
An increase of extracellular dopamine (DA) has been implicated in the psychostimulant properties of 3,4-methylenedioxymethamphetamine (MDMA). Although this drug has been reported to affect the DA uptake transporter (DAT), it might activate other mechanisms to regulate the outflow of DA in the brain. Our aim was to examine the overall effects of MDMA on the release of DA in the striatum. We studied the effect of MDMA on stimulus-evoked synaptic DA release in dorsal striatal slices of mice using in vitro amperometric techniques. We also tested the effects of MDMA on the nicotine-induced responses in substantia nigra pars compacta (SNpc) neurons using intracellular electrophysiological recordings. MDMA (1-30 µM) depressed the amplitude and prolonged the decay-time of synaptic DA release in the striatum. Interestingly, in the presence of the broad nicotinic receptor antagonist mecamylamine, and the more selective α4β2 antagonist dihydroβerythroidine (DHβE), MDMA enhanced both peak and duration of DA release. A similar effect was found on cocaine-insensitive (DAT-CI) mice slices. Concentrations of MDMA higher than 100 µM enhanced striatal DA outflow that was in turn, reduced by cocaine. Electrophysiological recordings of dopaminergic neurons in SNpc showed that MDMA depressed the effects of nicotine. Our data are consistent with a prevalent MDMA-induced inhibition of the synaptic release of DA in the dorsal striatum mediated by an interaction with nicotinic receptors. This drug also blocks DAT acting on a different site from cocaine and, at higher concentrations, has amphetamine-like releasing properties.
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Affiliation(s)
| | | | - Nicola Biagio Mercuri
- University of Rome 'Tor Vergata', 00133 Rome, Italy; IRCSS Fondazione Santa Lucia, 00143 Rome, Italy.
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12
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Efimova EV, Gainetdinov RR, Budygin EA, Sotnikova TD. Dopamine transporter mutant animals: a translational perspective. J Neurogenet 2017; 30:5-15. [PMID: 27276191 DOI: 10.3109/01677063.2016.1144751] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The dopamine transporter (DAT) plays an important homeostatic role in the control of both the extracellular and intraneuronal concentrations of dopamine, thereby providing effective control over activity of dopaminergic transmission. Since brain dopamine is known to be involved in numerous neuropsychiatric disorders, investigations using mice with genetically altered DAT function and thus intensity of dopamine-mediated signaling have provided numerous insights into the pathology of these disorders and novel pathological mechanisms that could be targeted to provide new therapeutic approaches for these disorders. In this brief overview, we discuss recent investigations involving animals with genetically altered DAT function, particularly focusing on translational studies providing new insights into pathology and pharmacology of dopamine-related disorders. Perspective applications of these and newly developed models of DAT dysfunction are also discussed.
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Affiliation(s)
- Evgeniya V Efimova
- a Institute of Translational Biomedicine, St. Petersburg State University , St. Petersburg , Russia ;,b Skolkovo Institute of Science and Technology , Skolkovo , Moscow Region , Russia
| | - Raul R Gainetdinov
- a Institute of Translational Biomedicine, St. Petersburg State University , St. Petersburg , Russia ;,b Skolkovo Institute of Science and Technology , Skolkovo , Moscow Region , Russia
| | - Evgeny A Budygin
- a Institute of Translational Biomedicine, St. Petersburg State University , St. Petersburg , Russia ;,c Department of Neurobiology and Anatomy , Wake Forest School of Medicine , Winston-Salem , NC , USA
| | - Tatyana D Sotnikova
- a Institute of Translational Biomedicine, St. Petersburg State University , St. Petersburg , Russia
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Amphetamine Reverses Escalated Cocaine Intake via Restoration of Dopamine Transporter Conformation. J Neurosci 2017; 38:484-497. [PMID: 29175958 DOI: 10.1523/jneurosci.2604-17.2017] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 11/14/2017] [Accepted: 11/17/2017] [Indexed: 12/27/2022] Open
Abstract
Cocaine abuse disrupts dopamine system function, and reduces cocaine inhibition of the dopamine transporter (DAT), which results in tolerance. Although tolerance is a hallmark of cocaine addiction and a DSM-V criterion for substance abuse disorders, the molecular adaptations producing tolerance are unknown, and testing the impact of DAT changes on drug taking behaviors has proven difficult. In regard to treatment, amphetamine has shown efficacy in reducing cocaine intake; however, the mechanisms underlying these effects have not been explored. The goals of this study were twofold; we sought to (1) identify the molecular mechanisms by which cocaine exposure produces tolerance and (2) determine whether amphetamine-induced reductions in cocaine intake are connected to these mechanisms. Using cocaine self-administration and fast-scan cyclic voltammetry in male rats, we show that low-dose, continuous amphetamine treatment, during self-administration or abstinence, completely reversed cocaine tolerance. Amphetamine treatment also reversed escalated cocaine intake and decreased motivation to obtain cocaine as measured in a behavioral economics task, thereby linking tolerance to multiple facets of cocaine use. Finally, using fluorescence resonance energy transfer imaging, we found that cocaine tolerance is associated with the formation of DAT-DAT complexes, and that amphetamine disperses these complexes. In addition to extending our basic understanding of DATs and their role in cocaine reinforcement, we serendipitously identified a novel therapeutic target: DAT oligomer complexes. We show that dispersion of oligomers is concomitant with reduced cocaine intake, and propose that pharmacotherapeutics aimed at these complexes may have potential for cocaine addiction treatment.SIGNIFICANCE STATEMENT Tolerance to cocaine's subjective effects is a cardinal symptom of cocaine addiction and a DSM-V criterion for substance abuse disorders. However, elucidating the molecular adaptions that produce tolerance and determining its behavioral impact have proven difficult. Using cocaine self-administration in rats, we link tolerance to cocaine effects at the dopamine transporter (DAT) with aberrant cocaine-taking behaviors. Further, tolerance was associated with multi-DAT complexes, which formed after cocaine exposure. Treatment with amphetamine deconstructed DAT complexes, reversed tolerance, and decreased cocaine seeking. These data describe the behavioral consequence of cocaine tolerance, provide a putative mechanism for its development, and suggest that compounds that disperse DAT complexes may be efficacious treatments for cocaine addiction.
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14
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Krout D, Pramod AB, Dahal RA, Tomlinson MJ, Sharma B, Foster JD, Zou MF, Boatang C, Newman AH, Lever JR, Vaughan RA, Henry LK. Inhibitor mechanisms in the S1 binding site of the dopamine transporter defined by multi-site molecular tethering of photoactive cocaine analogs. Biochem Pharmacol 2017; 142:204-215. [PMID: 28734777 DOI: 10.1016/j.bcp.2017.07.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 07/17/2017] [Indexed: 10/19/2022]
Abstract
Dopamine transporter (DAT) blockers like cocaine and many other abused and therapeutic drugs bind and stabilize an inactive form of the transporter inhibiting reuptake of extracellular dopamine (DA). The resulting increases in DA lead to the ability of these drugs to induce psychomotor alterations and addiction, but paradoxical findings in animal models indicate that not all DAT antagonists induce cocaine-like behavioral outcomes. How this occurs is not known, but one possibility is that uptake inhibitors may bind at multiple locations or in different poses to stabilize distinct conformational transporter states associated with differential neurochemical endpoints. Understanding the molecular mechanisms governing the pharmacological inhibition of DAT is therefore key for understanding the requisite interactions for behavioral modulation and addiction. Previously, we leveraged complementary computational docking, mutagenesis, peptide mapping, and substituted cysteine accessibility strategies to identify the specific adduction site and binding pose for the crosslinkable, photoactive cocaine analog, RTI 82, which contains a photoactive azide attached at the 2β position of the tropane pharmacophore. Here, we utilize similar methodology with a different cocaine analog N-[4-(4-azido-3-I-iodophenyl)-butyl]-2-carbomethoxy-3-(4-chlorophenyl)tropane, MFZ 2-24, where the photoactive azide is attached to the tropane nitrogen. In contrast to RTI 82, which crosslinked into residue Phe319 of transmembrane domain (TM) 6, our findings show that MFZ 2-24 adducts to Leu80 in TM1 with modeling and biochemical data indicating that MFZ 2-24, like RTI 82, occupies the central S1 binding pocket with the (+)-charged tropane ring nitrogen coordinating with the (-)-charged carboxyl side chain of Asp79. The superimposition of the tropane ring in the three-dimensional binding poses of these two distinct ligands provides strong experimental evidence for cocaine binding to DAT in the S1 site and the importance of the tropane moiety in competitive mechanisms of DA uptake inhibition. These findings set a structure-function baseline for comparison of typical and atypical DAT inhibitors and how their interactions with DAT could lead to the loss of cocaine-like behaviors.
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Affiliation(s)
- Danielle Krout
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, ND 58202, USA
| | - Akula Bala Pramod
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, ND 58202, USA
| | - Rejwi Acharya Dahal
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, ND 58202, USA
| | - Michael J Tomlinson
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, ND 58202, USA
| | - Babita Sharma
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, ND 58202, USA
| | - James D Foster
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, ND 58202, USA
| | - Mu-Fa Zou
- Medicinal Chemistry Section, National Institute on Drug Abuse - Intramural Research Program, Baltimore, MD 21224, USA
| | - Comfort Boatang
- Medicinal Chemistry Section, National Institute on Drug Abuse - Intramural Research Program, Baltimore, MD 21224, USA
| | - Amy Hauck Newman
- Medicinal Chemistry Section, National Institute on Drug Abuse - Intramural Research Program, Baltimore, MD 21224, USA
| | - John R Lever
- Research Service, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO, 65201, USA; Department of Radiology and Radiopharmaceutical Sciences Institute, University of Missouri, Columbia, MO 65211, USA
| | - Roxanne A Vaughan
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, ND 58202, USA.
| | - L Keith Henry
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, ND 58202, USA.
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15
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Abstract
HIV-associated neurocognitive disorder (HAND) remains highly prevalent in HIV infected individuals and represents a special group of neuropathological disorders, which are associated with HIV-1 viral proteins, such as transactivator of transcription (Tat) protein. Cocaine abuse increases the incidence of HAND and exacerbates its severity by enhancing viral replication. Perturbation of dopaminergic transmission has been implicated as a risk factor of HAND. The presynaptic dopamine (DA) transporter (DAT) is essential for DA homeostasis and dopaminergic modulation of the brain function including cognition. Tat and cocaine synergistically elevate synaptic DA levels by acting directly on human DAT (hDAT), ultimately leading to dysregulation of DA transmission. Through integrated computational modeling and experimental validation, key residues have been identified in hDAT that play a critical role in Tat-induced inhibition of DAT and induce transporter conformational transitions. This review presents current information regarding neurological changes in DAT-mediated dopaminergic system associated with HIV infection, DAT-mediated adaptive responses to Tat as well as allosteric modulatory effects of novel compounds on hDAT. Understanding the molecular mechanisms by which Tat induces DAT-mediated dysregulation of DA system is of great clinical interest for identifying new targets for an early therapeutic intervention for HAND.
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16
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Cocaine Potency at the Dopamine Transporter Tracks Discrete Motivational States During Cocaine Self-Administration. Neuropsychopharmacology 2017; 42:1893-1904. [PMID: 28139678 PMCID: PMC5520781 DOI: 10.1038/npp.2017.24] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 12/23/2016] [Accepted: 01/12/2017] [Indexed: 02/07/2023]
Abstract
Although the dopamine transporter (DAT) is the primary site of action for cocaine, and the dopamine system is known to mediate the reinforcing effects of cocaine, the dopaminergic variations underlying individual differences in cocaine self-administration behaviors are not fully understood. Recent advances in the application of economic principles to operant tasks in rodents have allowed for the within-subject, within-session determination of both consummatory and appetitive responding for reinforcers. Here we combined a behavioral economics approach with cocaine self-administration and ex vivo voltammetric recording of dopamine signaling in the core of the nucleus accumbens of rats to determine the relationship between dopamine signaling and discrete aspects of cocaine taking and seeking. We found neither dopamine release or uptake tracked individual differences in cocaine consumption or the reinforcing efficacy of cocaine. Cocaine potency at the DAT was correlated with reinforcing efficacy, but was not related to cocaine consumption. Further, we introduce a novel analysis that determines perseverative responding within the same procedure, and find that cocaine potency at the DAT also tracks differences in perseverative responding. Together, we demonstrate that cocaine effects at the DAT determine the reinforcing efficacy of cocaine, and perseverative responding for sub-threshold doses of cocaine that do not maintain responding when presented in isolation. Surprisingly, we find that variations in cocaine potency do not account for differences in cocaine consumption, suggesting that satiation for cocaine is determined by other targets or mechanisms. Finally, we outline a novel approach for relating drug-target interactions and potency to discrete motivational states during a single self-administration session.
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17
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Krout D, Rodriquez M, Brose SA, Golovko MY, Henry LK, Thompson BJ. Inhibition of the Serotonin Transporter Is Altered by Metabolites of Selective Serotonin and Norepinephrine Reuptake Inhibitors and Represents a Caution to Acute or Chronic Treatment Paradigms. ACS Chem Neurosci 2017; 8:1011-1018. [PMID: 27959497 PMCID: PMC5437659 DOI: 10.1021/acschemneuro.6b00343] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Previous studies of transgenic mice carrying a single isoleucine to methionine substitution (I172M) in the serotonin transporter (SERT) demonstrated a loss of sensitivity to multiple antidepressants (ADs) at SERT. However, the ability of AD metabolites to antagonize SERT was not assessed. Here, we evaluated the selectivity and potency of these metabolites for inhibition of SERT in mouse brain-derived synaptosomes and blood platelets from wild-type (I172 mSERT) and the antidepressant-insensitive mouse M172 mSERT. The metabolites norfluoxetine and desmethylsertraline lost the selectivity demonstrated by the parent compounds for inhibition of wild-type mSERT over M172 mSERT, whereas desvenlafaxine and desmethylcitalopram retained selectivity. Furthermore, we show that the metabolite desmethylcitalopram accumulates in the brain and that the metabolites desmethylcitalopram, norfluoxetine, and desvenlafaxine inhibit serotonin uptake in wild-type mSERT at potencies similar to those of their parent compounds, suggesting that metabolites may play a role in effects observed following AD administration in wild-type and M172 mice.
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Affiliation(s)
- Danielle Krout
- Department
of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, North Dakota 58202, United States
| | - Meghan Rodriquez
- Department
of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, North Dakota 58202, United States
| | - Stephen A. Brose
- Department
of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, North Dakota 58202, United States
| | - Mikhail Y. Golovko
- Department
of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, North Dakota 58202, United States
| | - L. Keith Henry
- Department
of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, North Dakota 58202, United States
| | - Brent J. Thompson
- Department
of Biomedical Sciences, Oakland University William Beaumont School of Medicine, Rochester, Michigan 48309, United States
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18
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Calipari ES, Ferris MJ, Siciliano CA, Jones SR. Differential influence of dopamine transport rate on the potencies of cocaine, amphetamine, and methylphenidate. ACS Chem Neurosci 2015; 6:155-62. [PMID: 25474655 PMCID: PMC4304485 DOI: 10.1021/cn500262x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
![]()
Dopamine
transporter (DAT) levels vary across brain regions and
individuals, and are altered by drug history and disease states; however,
the impact of altered DAT expression on psychostimulant effects in
brain has not been systematically explored. Using fast scan cyclic
voltammetry, we measured the effects of elevated DAT levels on presynaptic
dopamine parameters as well as the uptake inhibition potency of the
blockers cocaine and methylphenidate (MPH) and the releaser amphetamine
(AMPH) in the nucleus accumbens core. Here we found that increases
in DAT levels, resulting from either genetic overexpression or MPH
self-administration, caused markedly increased maximal rates of uptake
(Vmax) that were positively correlated
with the uptake inhibition potency of AMPH and MPH, but not cocaine.
AMPH and MPH were particularly sensitive to DAT changes, with a 100%
increase in Vmax resulting in a 200% increase
in potency. The relationship between Vmax and MPH potency was the same as that for AMPH, but was different
from that for cocaine, indicating that MPH more closely resembles
a releaser with regard to uptake inhibition. Conversely, the effects
of MPH on stimulated dopamine release were similar to those of cocaine,
with inverted U-shaped increases in release over a concentration–response
curve. This was strikingly different from the release profile of AMPH,
which showed only reductions at high concentrations, indicating that
MPH is not a pure releaser. These data indicate that although MPH
is a DAT blocker, its uptake-inhibitory actions are affected by DAT
changes in a similar manner to releasers. Together, these data show
that fluctuations in DAT levels alter the potency of releasers and
MPH but not blockers and suggest an integral role of the DAT in the
addictive potential of AMPH and related compounds.
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Affiliation(s)
- Erin S. Calipari
- Department
of Physiology
and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, United States
| | - Mark J. Ferris
- Department
of Physiology
and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, United States
| | - Cody A. Siciliano
- Department
of Physiology
and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, United States
| | - Sara R. Jones
- Department
of Physiology
and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, United States
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19
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Dahal RA, Pramod AB, Sharma B, Krout D, Foster JD, Cha JH, Cao J, Newman AH, Lever JR, Vaughan RA, Henry LK. Computational and biochemical docking of the irreversible cocaine analog RTI 82 directly demonstrates ligand positioning in the dopamine transporter central substrate-binding site. J Biol Chem 2014; 289:29712-27. [PMID: 25179220 PMCID: PMC4207985 DOI: 10.1074/jbc.m114.571521] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 08/09/2014] [Indexed: 12/20/2022] Open
Abstract
The dopamine transporter (DAT) functions as a key regulator of dopaminergic neurotransmission via re-uptake of synaptic dopamine (DA). Cocaine binding to DAT blocks this activity and elevates extracellular DA, leading to psychomotor stimulation and addiction, but the mechanisms by which cocaine interacts with DAT and inhibits transport remain incompletely understood. Here, we addressed these questions using computational and biochemical methodologies to localize the binding and adduction sites of the photoactivatable irreversible cocaine analog 3β-(p-chlorophenyl)tropane-2β-carboxylic acid, 4'-azido-3'-iodophenylethyl ester ([(125)I]RTI 82). Comparative modeling and small molecule docking indicated that the tropane pharmacophore of RTI 82 was positioned in the central DA active site with an orientation that juxtaposed the aryliodoazide group for cross-linking to rat DAT Phe-319. This prediction was verified by focused methionine substitution of residues flanking this site followed by cyanogen bromide mapping of the [(125)I]RTI 82-labeled mutants and by the substituted cysteine accessibility method protection analyses. These findings provide positive functional evidence linking tropane pharmacophore interaction with the core substrate-binding site and support a competitive mechanism for transport inhibition. This synergistic application of computational and biochemical methodologies overcomes many uncertainties inherent in other approaches and furnishes a schematic framework for elucidating the ligand-protein interactions of other classes of DA transport inhibitors.
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Affiliation(s)
- Rejwi Acharya Dahal
- From the Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203
| | - Akula Bala Pramod
- From the Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203
| | - Babita Sharma
- From the Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203
| | - Danielle Krout
- From the Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203
| | - James D Foster
- From the Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203
| | - Joo Hwan Cha
- the Medicinal Chemistry Section, National Institute on Drug Abuse-Intramural Research Program, Baltimore, Maryland 21224
| | - Jianjing Cao
- the Medicinal Chemistry Section, National Institute on Drug Abuse-Intramural Research Program, Baltimore, Maryland 21224
| | - Amy Hauck Newman
- the Medicinal Chemistry Section, National Institute on Drug Abuse-Intramural Research Program, Baltimore, Maryland 21224
| | - John R Lever
- the Research Service, Harry S. Truman Memorial Veterans Hospital, Columbia, Missouri 65201, and the Department of Radiology, Radiopharmaceutical Sciences Institute, and Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri 65211
| | - Roxanne A Vaughan
- From the Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203,
| | - L Keith Henry
- From the Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203,
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20
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Thirtamara Rajamani K, O'Neill B, Han DD, Frostholm A, Rotter A, Gu HH. Inactivation of the catalytic phosphatase domain of PTPRT/RPTPρ increases social interaction in mice. Autism Res 2014; 8:19-28. [PMID: 24895325 DOI: 10.1002/aur.1390] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 04/21/2014] [Indexed: 01/26/2023]
Abstract
Receptor protein tyrosine phosphatase rho (RPTPρ, gene symbol PTPRT) is a transmembrane protein expressed at high levels in the developing hippocampus, olfactory bulb, cortex, and cerebellum. It has an extracellular domain that interacts with other cell adhesion molecules, and it has two intracellular phosphatase domains, one of which is catalytically active. In a recent genome-wide association study, PTPRT was identified as a potential candidate gene for autism spectrum disorder (ASD) susceptibility. Mutation of a critical aspartate to alanine (D1046A) in the PTPRT catalytic domain inactivates phosphatase function but retains substrate binding. We have generated a knockin mouse line carrying the PTPRT D1046A mutation. The D1046A mutation in homozygous knockin mice did not significantly change locomotor activities or anxiety-related behaviors. In contrast, male homozygous mice had significantly higher social approach scores than wild-type animals. Our results suggest that PTPRT phosphatase function is important in modulating neural pathways involved in mouse social behaviors relevant to the symptoms in human ASD patients.
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Affiliation(s)
- Keerthi Thirtamara Rajamani
- Department of Pharmacology, The Ohio State University, Columbus, Ohio; Neuroscience Graduate Studies Program, The Ohio State University, Columbus, Ohio
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21
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Calipari ES, Ferris MJ, Melchior JR, Bermejo K, Salahpour A, Roberts DCS, Jones SR. Methylphenidate and cocaine self-administration produce distinct dopamine terminal alterations. Addict Biol 2014; 19:145-55. [PMID: 22458761 DOI: 10.1111/j.1369-1600.2012.00456.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Methylphenidate (MPH) is a commonly abused psychostimulant prescribed for the treatment of attention deficit hyperactivity disorder. MPH has a mechanism of action similar to cocaine (COC) and is commonly characterized as a dopamine transporter (DAT) blocker. While there has been extensive work aimed at understanding dopamine (DA) nerve terminal changes following COC self-administration, very little is known about the effects of MPH self-administration on the DA system. We used fast scan cyclic voltammetry in nucleus accumbens core slices from animals with a 5-day self-administration history of 40 injections/day of either MPH (0.56 mg/kg) or COC (1.5 mg/kg) to explore alterations in baseline DA release and uptake kinetics as well as alterations in the interaction of each compound with the DAT. Although MPH and COC have similar behavioral effects, the consequences of self-administration on DA system parameters were found to be divergent. We show that COC self-administration reduced DAT levels and maximal rates of DA uptake, as well as reducing electrically stimulated release, suggesting decreased DA terminal function. In contrast, MPH self-administration increased DAT levels, DA uptake rates and DA release, suggesting enhanced terminal function, which was supported by findings of increased metabolite/DA tissue content ratios. Tyrosine hydroxylase messenger RNA, protein and phosphorylation levels were also assessed in both groups. Additionally, COC self-administration reduced COC-induced DAT inhibition, while MPH self-administration increased MPH-induced DAT inhibition, suggesting opposite pharmacodynamic effects of these two drugs. These findings suggest that the factors governing DA system adaptations are more complicated than simple DA uptake blockade.
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Affiliation(s)
- Erin S Calipari
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston Salem, NC, USA Department of Pharmacology, University of Toronto, Toronto, Canada
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22
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Federici M, Latagliata EC, Ledonne A, Rizzo FR, Feligioni M, Sulzer D, Dunn M, Sames D, Gu H, Nisticò R, Puglisi-Allegra S, Mercuri NB. Paradoxical abatement of striatal dopaminergic transmission by cocaine and methylphenidate. J Biol Chem 2013; 289:264-74. [PMID: 24280216 DOI: 10.1074/jbc.m113.495499] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
We combined in vitro amperometric, optical analysis of fluorescent false neurotransmitters and microdialysis techniques to unveil that cocaine and methylphenidate induced a marked depression of the synaptic release of dopamine (DA) in mouse striatum. In contrast to the classical dopamine transporter (DAT)-dependent enhancement of the dopaminergic signal observed at concentrations of cocaine lower than 3 μM, the inhibitory effect of cocaine was found at concentrations higher than 3 μM. The paradoxical inhibitory effect of cocaine and methylphenidate was associated with a decrease in synapsin phosphorylation. Interestingly, a cocaine-induced depression of DA release was only present in cocaine-insensitive animals (DAT-CI). Similar effects of cocaine were produced by methylphenidate in both wild-type and DAT-CI mice. On the other hand, nomifensine only enhanced the dopaminergic signal either in wild-type or in DAT-CI mice. Overall, these results indicate that cocaine and methylphenidate can increase or decrease DA neurotransmission by blocking reuptake and reducing the exocytotic release, respectively. The biphasic reshaping of DA neurotransmission could contribute to different behavioral effects of psychostimulants, including the calming ones, in attention deficit hyperactivity disorder.
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Affiliation(s)
- Mauro Federici
- From the Laboratorio di Neurologia Sperimentale, Istituto Ricovero e Cura a carattere scientifico (IRCCS) Fondazione Santa Lucia, 00143 Rome, Italy
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23
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Federici M, Latagliata E, Rizzo F, Ledonne A, Gu H, Romigi A, Nisticò R, Puglisi-Allegra S, Mercuri N. Electrophysiological and amperometric evidence that modafinil blocks the dopamine uptake transporter to induce behavioral activation. Neuroscience 2013; 252:118-24. [DOI: 10.1016/j.neuroscience.2013.07.071] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Revised: 07/07/2013] [Accepted: 07/31/2013] [Indexed: 10/26/2022]
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24
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Ferris MJ, Calipari ES, Melchior JR, Roberts DC, España RA, Jones SR. Paradoxical tolerance to cocaine after initial supersensitivity in drug-use-prone animals. Eur J Neurosci 2013; 38:2628-36. [PMID: 23725404 PMCID: PMC3748159 DOI: 10.1111/ejn.12266] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/24/2013] [Accepted: 04/26/2013] [Indexed: 02/05/2023]
Abstract
There is great interest in outlining biological factors and behavioral characteristics that either predispose or predict vulnerability to substance use disorders. Response to an inescapable novel environment has been shown to predict a "drug-use-prone" phenotype that is defined by rapid acquisition of cocaine self-administration. Here, we showed that response to novelty can also predict the neurochemical and behavioral effects of acute and repeated cocaine in rats. We used cocaine self-administration under a fixed-ratio 1 schedule followed by fast-scan cyclic voltammetry in brain slices to measure subsecond dopamine (DA) release and uptake parameters in drug-use-prone and -resistant phenotypes. Despite no significant differences in stimulated release and uptake, animals with high responses to a novel environment had DA transporters that were more sensitive to cocaine-induced uptake inhibition, which corresponded to greater locomotor activating effects of cocaine. These animals also acquired cocaine self-administration more rapidly and, after 5 days of extended access cocaine self-administration, high-responding animals showed robust tolerance to DA uptake inhibition by cocaine. The effects of cocaine remained unchanged in animals with low novelty responses. Similarly, the rate of acquisition was negatively correlated with DA uptake inhibition by cocaine after self-administration. Thus, we showed that tolerance to the cocaine-induced inhibition of DA uptake coexists with a behavioral phenotype that is defined by increased preoccupation with cocaine as measured by rapid acquisition and early high intake.
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Affiliation(s)
- Mark J. Ferris
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
| | - Erin S. Calipari
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
| | - James R. Melchior
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
| | - David C.S. Roberts
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
| | - Rodrigo A. España
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
| | - Sara R. Jones
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
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25
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Rao A, Sorkin A, Zahniser NR. Mice expressing markedly reduced striatal dopamine transporters exhibit increased locomotor activity, dopamine uptake turnover rate, and cocaine responsiveness. Synapse 2013; 67:668-77. [PMID: 23564231 DOI: 10.1002/syn.21671] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 03/23/2013] [Indexed: 02/06/2023]
Abstract
Variations in the expression levels of the dopamine transporter (DAT) can influence responsiveness to psychostimulant drugs like cocaine. To better understand this relationship, we studied a new DAT-low expresser (DAT-LE) mouse model and performed behavioral and biochemical studies with it. Immunoblotting and [(3) H]WIN 35,428 binding analyses revealed that these mice express ∼35% of wildtype (WT) mouse striatal DAT levels. Compared to WT mice, DAT-LE mice were hyperactive in a novel open-field environment. Despite their higher basal locomotor activity, cocaine (10 or 20 mg/kg, i.p.) induced greater locomotor activation in DAT-LE mice than in WT mice. The maximal velocity (Vmax ) of DAT-mediated [(3) H]DA uptake into striatal synaptosomes was reduced by 46% in DAT-LE mice, as compared to WT. Overall, considering the reduced number of DAT binding sites (Bmax ) along with the reduced Vmax in DAT-LE mice, a 2-fold increase in DA uptake turnover rate (Vmax /Bmax ) was found, relative to WT mice. This suggests that neuroadaptive changes have occurred in the DAT-LE mice that would help to compensate for their low DAT numbers. Interestingly, these changes do not include a reduction in tyrosine hydroxylase levels, as was previously reported in DAT knockout homozygous and heterozygous animals. Further, these changes are not sufficient to prevent elevated novelty- and cocaine-induced locomotor activity. Hence, these mice represent a unique model for studying changes of in vivo DAT function and regulation that result from markedly reduced levels of DAT expression.
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Affiliation(s)
- Anjali Rao
- Department of Pharmacology, School of Medicine, University of Colorado, Anschutz Medical Campus, Aurora, Colorado, 80045, USA.
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26
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Calipari ES, Ferris MJ, Salahpour A, Caron MG, Jones SR. Methylphenidate amplifies the potency and reinforcing effects of amphetamines by increasing dopamine transporter expression. Nat Commun 2013; 4:2720. [PMID: 24193139 PMCID: PMC4017736 DOI: 10.1038/ncomms3720] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 10/07/2013] [Indexed: 01/04/2023] Open
Abstract
Methylphenidate (MPH) is commonly diverted for recreational use, but the neurobiological consequences of exposure to MPH at high, abused doses are not well defined. Here we show that MPH self-administration in rats increases dopamine transporter (DAT) levels and enhances the potency of MPH and amphetamine on dopamine responses and drug-seeking behaviours, without altering cocaine effects. Genetic overexpression of the DAT in mice mimics these effects, confirming that MPH self-administration-induced increases in DAT levels are sufficient to induce the changes. Further, this work outlines a basic mechanism by which increases in DAT levels, regardless of how they occur, are capable of increasing the rewarding and reinforcing effects of select psychostimulant drugs, and suggests that individuals with elevated DAT levels, such as ADHD sufferers, may be more susceptible to the addictive effects of amphetamine-like drugs.
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Affiliation(s)
- Erin S. Calipari
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | - Mark J Ferris
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | - Ali Salahpour
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, Canada
| | - Marc G. Caron
- Department of Cell Biology, Medicine and Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Sara R. Jones
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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Kimmel HL, Nye JA, Voll R, Mun J, Stehouwer J, Goodman MM, Votaw JR, Carroll FI, Howell LL. Simultaneous measurement of extracellular dopamine and dopamine transporter occupancy by cocaine analogs in squirrel monkeys. Synapse 2012; 66:501-8. [PMID: 22237864 DOI: 10.1002/syn.21536] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 12/31/2011] [Indexed: 11/09/2022]
Abstract
Several classes of drugs bind to the dopamine transporter (DAT) with high affinity, but some are weaker positive reinforcers than cocaine, suggesting that affinity for and occupancy of the DAT is not the only determinant of a drug's reinforcing effectiveness. Other factors such as the rate of onset have been positively and strongly correlated with the reinforcing effects of DAT inhibitors in nonhuman primates. In the current studies, we examined the effects of acute systemic administration of cocaine and three cocaine analogs (RTI-150, RTI-177, and RTI-366) on binding to DAT in squirrel monkey brain using positron emission tomography (PET) neuroimaging. During the PET scan, we also measured drug effects on dopamine (DA) levels in the caudate using in vivo microdialysis. In general, our results suggest a lack of concordance between drug occupancy at DAT and changes in DA levels. These studies also indicate that acute cocaine administration decreases the availability of plasma membrane DAT for binding, even after cocaine is no longer blocking DA uptake as evidence by a return to basal DA levels.
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Affiliation(s)
- Heather L Kimmel
- Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia 30329, USA.
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Hill ER, Huang X, Zhan CG, Ivy Carroll F, Gu HH. Interaction of tyrosine 151 in norepinephrine transporter with the 2β group of cocaine analog RTI-113. Neuropharmacology 2011; 61:112-20. [PMID: 21420984 DOI: 10.1016/j.neuropharm.2011.03.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 03/10/2011] [Accepted: 03/12/2011] [Indexed: 12/27/2022]
Abstract
Cocaine binds and inhibits dopamine transporter (DAT), norepinephrine transporter (NET) and serotonin transporter. The residues forming cocaine binding sites are unknown. RTI-113, a cocaine analog, is 100× more potent at inhibiting DAT than inhibiting NET. Here we show that removing the hydroxyl group from residue Tyr151 in NET by replacing it with Phe, the corresponding residue in DAT, increased the sensitivity of NET to RTI-113, while the reverse mutation in DAT decreased the sensitivity of DAT to RTI-113. In contrast, RTI-31, another cocaine analog having the same structure as RTI-113 but with the phenyl group at the 2β position replaced by a methyl group, inhibits the transporter mutants equally well whether a hydroxyl group is present at the residue or not. The data suggest that this residue contributes to cocaine binding site and is close to the 2β position of cocaine analogs. These results are consistent with our previously proposed cocaine-DAT binding model where cocaine initially binds to a site that does not overlap with, but is close to, the dopamine-binding site. Computational modeling and molecular docking yielded a binding model that explains the observed changes in RTI-113 inhibition potencies.
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Affiliation(s)
- Erik R Hill
- Ohio State Biochemistry Program, College of Medicine, The Ohio State University, Columbus, OH 43210, USA
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Ferris MJ, Mateo Y, Roberts DCS, Jones SR. Cocaine-insensitive dopamine transporters with intact substrate transport produced by self-administration. Biol Psychiatry 2011; 69:201-7. [PMID: 20801429 PMCID: PMC3012751 DOI: 10.1016/j.biopsych.2010.06.026] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Revised: 06/15/2010] [Accepted: 06/24/2010] [Indexed: 12/28/2022]
Abstract
BACKGROUND Psychomotor stimulant drugs such as cocaine and amphetamine activate brain dopamine (DA) neurotransmission and support self-administration in humans and laboratory animals. Cocaine amplifies DA signaling by blocking the DA transporter (DAT), and this has been described as the most important mechanism underlying cocaine's reinforcing effects. Amphetamine has the added mechanism of reverse transport of intracellular DA through the DAT. METHODS We used cocaine and amphetamine self-administration under a fixed-ratio 1 schedule followed by microdialysis in freely moving rats to measure extracellular DA levels and fast scan cyclic voltammetry in brain slices to measure subsecond DA release and uptake parameters. RESULTS Following a high dose (1.5 mg/kg intravenous) cocaine self-administration paradigm (40 injections/day × 5 days), the DAT was markedly less sensitive to cocaine, as measured by microdialysis and voltammetry in the nucleus accumbens core. In contrast, the DAT substrate amphetamine retained the same efficacy at the DAT in cocaine self-administering animals, and amphetamine did not mimic cocaine's effect on the DAT when self-administered. A single session of cocaine self-administration caused a significant decrease in the ability of cocaine to inhibit the DAT, a finding that may provide a neurochemical basis for rapid tolerance. The effects of cocaine returned to normal within a few weeks following cessation of self-administration. CONCLUSIONS Here, we, for the first time, demonstrate an in vivo, pharmacologically induced alteration in the sensitivity of the DAT to cocaine that is specific to cocaine, spares DAT and substrate/releaser interactions, and is independent of maximal rate of DA uptake (V(max)).
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Affiliation(s)
- Mark J Ferris
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA
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30
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Larsen MB, Fontana ACK, Magalhães LG, Rodrigues V, Mortensen OV. A catecholamine transporter from the human parasite Schistosoma mansoni with low affinity for psychostimulants. Mol Biochem Parasitol 2011; 177:35-41. [PMID: 21251927 DOI: 10.1016/j.molbiopara.2011.01.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Revised: 12/21/2010] [Accepted: 01/07/2011] [Indexed: 11/25/2022]
Abstract
The trematode Schistosoma mansoni is the primary cause of schistosomiasis, a devastating neglected tropical disease that affects 200 million individuals. Identifying novel therapeutic targets for the treatment of schistosomiasis is therefore of great public interest. The catecholamines norepinephrine (NE) and dopamine (DA) are essential for the survival of the parasite as they cause muscular relaxation and a lengthening in the parasite and thereby control movement. Here we characterize a novel dopamine/norepinephrine transporter (SmDAT) gene transcript, from S. mansoni. The SmDAT is expressed in the adult form and in the sporocyst form (infected snails) of the parasite, and also in the egg and miracidium stage. It is absent in the cercariae stage but curiously a transcript missing the exon encoding transmembrane domain 8 was identified in this stage. Heterologous expression of the cDNA in mammalian cells resulted in saturable, dopamine transport activity with an apparent affinity for dopamine comparable to that of the human dopamine transporter. Efflux experiments reveal notably higher substrate selectivity compared with its mammalian counterparts as amphetamine is a much less potent efflux elicitor against SmDAT compared to the human DAT. Pharmacological characterization of the SmDAT revealed that most human DAT inhibitors including psychostimulants such as cocaine were significantly less potent in inhibiting SmDAT. Like DATs from other simpler organisms the pharmacology for SmDAT was more similar to the human norepinephrine transporter. We were not able to identify other dopamine transporting carriers within the completed parasite genome and we hypothesize that the SmDAT is the only catecholamine transporter in the parasite and could be responsible for not only clearing DA but also NE.
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Affiliation(s)
- Mads B Larsen
- Department of Neurobiology, University of Pittsburgh School of Medicine, PA 15260, USA
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31
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Tammimäki A, Männistö PT. Effect of genetic modifications in the synaptic dopamine clearance systems on addiction-like behaviour in mice. Basic Clin Pharmacol Toxicol 2010; 108:2-8. [PMID: 21118356 DOI: 10.1111/j.1742-7843.2010.00647.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
During the last 15 years, genetically modified mouse lines have proved to be a valuable research tool. This review summarizes research that studied addiction-like behaviour in mice that had a targeted mutation in the genes of the synaptic dopamine removal systems, i.e. in the dopamine transporter (DAT), a vesicular monoamine transporter 2 (VMAT2) or two dopamine-metabolizing enzymes (monoamine oxidase, MAO, mainly MAO-A isoenzyme, and catechol-O-methyltransferase, COMT). Majority of the mice are knockouts but also some knock-in and knock down mouse lines are included. Most studies have explored DAT, and it has been shown to be the critical target in addiction to psychostimulants. Its role in the development of addiction-like behaviour to nicotine, opioids or ethanol is less clear. VMAT2 also seems to be linked to psychostimulant addiction. MAO-A and COMT have a minor role in addiction-like behaviour that is further complicated by a sexual dimorphism.
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Affiliation(s)
- Anne Tammimäki
- Division of Pharmacology and Toxicology, Faculty of Pharmacy, University of Helsinki, Finland.
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Role of aberrant striatal dopamine D1 receptor/cAMP/protein kinase A/DARPP32 signaling in the paradoxical calming effect of amphetamine. J Neurosci 2010; 30:11043-56. [PMID: 20720111 DOI: 10.1523/jneurosci.1682-10.2010] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Attention deficit/hyperactivity disorder (ADHD) is characterized by inattention, impulsivity, and motor hyperactivity. Several lines of research support a crucial role for the dopamine transporter (DAT) gene in this psychiatric disease. Consistently, the most commonly prescribed medications in ADHD treatment are stimulant drugs, known to preferentially act on DAT. Recently, a knock-in mouse [DAT-cocaine insensitive (DAT-CI)] has been generated carrying a cocaine-insensitive DAT that is functional but with reduced dopamine uptake function. DAT-CI mutants display enhanced striatal extracellular dopamine levels and basal motor hyperactivity. Herein, we showed that DAT-CI animals present higher striatal dopamine turnover, altered basal phosphorylation state of dopamine and cAMP-regulated phosphoprotein 32 kDa (DARPP32) at Thr75 residue, but preserved D(2) receptor (D(2)R) function. However, although we demonstrated that striatal D(1) receptor (D(1)R) is physiologically responsive under basal conditions, its stimulus-induced activation strikingly resulted in paradoxical electrophysiological, behavioral, and biochemical responses. Indeed, in DAT-CI animals, (1) striatal LTP was completely disrupted, (2) R-(+)-6-chloro-7,8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrobromide (SKF 81297) treatment induced paradoxical motor calming effects, and (3) SKF 81297 administration failed to increase cAMP/protein kinase A (PKA)/DARPP32 signaling. Such biochemical alteration selectively affected dopamine D(1)Rs since haloperidol, by blocking the tonic inhibition of D(2)R, unmasked a normal activation of striatal adenosine A(2A) receptor-mediated cAMP/PKA/DARPP32 cascade in mutants. Most importantly, our studies highlighted that amphetamine, nomifensine, and bupropion, through increased striatal dopaminergic transmission, are able to revert motor hyperactivity of DAT-CI animals. Overall, our results suggest that the paradoxical motor calming effect induced by these drugs in DAT-CI mutants depends on selective aberrant phasic activation of D(1)R/cAMP/PKA/DARPP32 signaling in response to increased striatal extracellular dopamine levels.
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Furuse T, Wada Y, Hattori K, Yamada I, Kushida T, Shibukawa Y, Masuya H, Kaneda H, Miura I, Seno N, Kanda T, Hirose R, Toki S, Nakanishi K, Kobayashi K, Sezutsu H, Gondo Y, Noda T, Yuasa S, Wakana S. Phenotypic characterization of a newGrin1mutant mouse generated by ENU mutagenesis. Eur J Neurosci 2010; 31:1281-91. [DOI: 10.1111/j.1460-9568.2010.07164.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Huang X, Gu HH, Zhan CG. Mechanism for cocaine blocking the transport of dopamine: insights from molecular modeling and dynamics simulations. J Phys Chem B 2010; 113:15057-66. [PMID: 19831380 DOI: 10.1021/jp900963n] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Molecular modeling and dynamics simulations have been performed to study how cocaine inhibits dopamine transporter (DAT) for the transport of dopamine. The computationally determined DAT-ligand binding mode is totally different from the previously proposed overlap binding mode in which cocaine- and dopamine-binding sites are the same (Beuming, T.; et al. Nat. Neurosci. 2008, 11, 780-789). The new cocaine-binding site does not overlap with, but is close to, the dopamine-binding site. Analysis of all results reveals that when cocaine binds to DAT, the initial binding site is likely the one modeled in this study because this binding site can naturally accommodate cocaine. Then cocaine may move to the dopamine-binding site after DAT makes some necessary conformational change and expands the binding site cavity. It has been demonstrated that cocaine may inhibit the transport of dopamine through both blocking the initial DAT-dopamine binding and reducing the kinetic turnover of the transporter following the DAT-dopamine binding. The relative contributions to the phenomenological inhibition of the transport of dopamine from blocking the initial binding and reducing the kinetic turnover can be different in different types of assays. The obtained general structural and mechanistic insights are consistent with available experimental data and could be valuable for guiding future studies toward understanding cocaine's inhibiting of other transporters.
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Affiliation(s)
- Xiaoqin Huang
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 725 Rose Street, Lexington, Kentucky 40536, USA
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35
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Potencies of cocaine methiodide on major cocaine targets in mice. PLoS One 2009; 4:e7578. [PMID: 19855831 PMCID: PMC2762027 DOI: 10.1371/journal.pone.0007578] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Accepted: 10/05/2009] [Indexed: 11/19/2022] Open
Abstract
Cocaine methiodide (CM), a charged cocaine analog, cannot pass the blood brain barrier. It has been assumed the effects of systemic CM represent cocaine actions in peripheral tissues. However, the IC50 values of CM have not been clearly determined for the major cocaine targets: dopamine, norepinephrine, and serotonin transporters, and sodium channels. Using cells transfected with individual transporters from mice and synaptosomes from mouse striatum tissues, we observed that the inhibition IC50 values for monoamine uptake by CM were 31-fold to 184-fold higher compared to cocaine at each of the transporters. In dorsal root ganglion neurons, cocaine inhibited sodium channels with an apparent IC50 of 75 µM, while CM showed no observable effect at concentrations up to 3 mM. These results indicate that an equal dose of CM will not produce an equivalent peripheral effect of cocaine.
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36
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Thomsen M, Han DD, Gu HH, Caine SB. Lack of cocaine self-administration in mice expressing a cocaine-insensitive dopamine transporter. J Pharmacol Exp Ther 2009; 331:204-11. [PMID: 19602552 DOI: 10.1124/jpet.109.156265] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cocaine addiction is a worldwide public health problem for which there are no established treatments. The dopamine transporter (DAT) is suspected as the primary target mediating cocaine's abuse-related effects based on numerous pharmacological studies. However, in a previous study, DAT knockout mice were reported to self-administer cocaine, generating much debate regarding the importance of the DAT in cocaine's abuse-related effects. Here, we show that mice expressing a "knockin" of a cocaine-insensitive but functional DAT did not self-administer cocaine intravenously despite normal food-maintained responding and normal intravenous self-administration of amphetamine and a direct dopamine agonist. Our results have three implications. First, they imply a crucial role for high-affinity DAT binding of cocaine in mediating its reinforcing effects, reconciling mouse genetic engineering approaches with data from classic pharmacological studies. Second, they demonstrate the usefulness of knockin strategies that modify specific amino acid sequences within a protein. Third, they show that it is possible to alter the DAT protein sequence in such a way as to selectively target its interaction with cocaine, while sparing other behaviors dependent on DAT function. Thus, molecular engineering technology could advance the development of highly specialized compounds such as a dopamine-sparing "cocaine antagonist."
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Affiliation(s)
- Morgane Thomsen
- Alcohol and Drug Abuse Research Center, McLean Hospital/Harvard Medical School, Belmont, MA 02478, USA.
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Wei H, Hill ER, Gu HH. Functional mutations in mouse norepinephrine transporter reduce sensitivity to cocaine inhibition. Neuropharmacology 2008; 56:399-404. [PMID: 18824182 DOI: 10.1016/j.neuropharm.2008.09.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Revised: 08/25/2008] [Accepted: 09/11/2008] [Indexed: 11/19/2022]
Abstract
The transporters of dopamine, norepinephrine and serotonin are molecular targets of cocaine, amphetamine, and therapeutic antidepressants. The residues involved in binding these drugs are unknown. We have performed several rounds of random and site-directed mutagenesis in the mouse norepinephrine transporter and screened for mutants with altered sensitivity to cocaine inhibition of substrate uptake. We have identified a triple mutation that retains close to wild-type transport function but displays a 37-fold decrease in cocaine sensitivity and 24-fold decrease in desipramine sensitivity. In contrast, the mutant's sensitivities to amphetamine, methamphetamine, and methylphenidate are only slightly changed. Our data reveal critical residues contributing to the potent uptake inhibitions by these important drugs. Furthermore, this drug-resistant triple mutant can be used to generate a unique knock-in mouse line to study the role of norepinephrine transporter in the addictive effects of cocaine and the therapeutic effects of desipramine.
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Affiliation(s)
- Hua Wei
- Department of Pharmacology, The Ohio State University, 333 West 10th Avenue, 5072 Graves Hall, Columbus, OH 43210, United States
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38
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Tilley MR, Gu HH. The effects of methylphenidate on knockin mice with a methylphenidate-resistant dopamine transporter. J Pharmacol Exp Ther 2008; 327:554-60. [PMID: 18698001 DOI: 10.1124/jpet.108.141713] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Methylphenidate (Ritalin) is one of the most commonly abused prescription drugs. It is a psychostimulant that inhibits the dopamine and norepinephrine transporters with high affinity. In mice, methylphenidate stimulates locomotor activity, is self-administered, and produces conditioned place preference, typical properties of an addictive drug. We have generated a knockin mouse line bearing a mutant dopamine transporter that is approximately 80-fold less sensitive to cocaine inhibition than wild type. It is interesting to note that this mutant is also almost 50-fold less sensitive to methylphenidate inhibition, suggesting similarities in the binding site for cocaine and methylphenidate. Because methylphenidate is not effective at inhibiting the mutant dopamine transporter, we hypothesized that it would not stimulate locomotor activity or produce reward in the knockin mice. In these knockin mice, doses up to 40 mg/kg methylphenidate either inhibit or fail to stimulate locomotor activity and do not produce conditioned place preference. Doses up to 40 mg/kg methylphenidate also fail to produce stereotypy in the knockin mice. Nisoxetine and desipramine, selective norepinephrine transporter inhibitors, also reduce locomotor activity in wild-type and knockin mice. These results indicate that enhanced dopaminergic neurotransmission is required for methylphenidate's stimulating and rewarding effects. In addition, we observed that drugs enhancing noradrenergic neurotransmission inhibit locomotor activity in mice, which is consistent with the notion that methylphenidate's ability to inhibit the norepinephrine transporter may contribute to its efficacy in treating attention deficit hyperactivity disorder.
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Affiliation(s)
- Michael R Tilley
- Department of Pharmacology, Ohio State University, Columbus, Ohio 43210, USA
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39
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The binding sites for cocaine and dopamine in the dopamine transporter overlap. Nat Neurosci 2008; 11:780-9. [PMID: 18568020 DOI: 10.1038/nn.2146] [Citation(s) in RCA: 265] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Accepted: 05/23/2008] [Indexed: 11/08/2022]
Abstract
Cocaine is a widely abused substance with psychostimulant effects that are attributed to inhibition of the dopamine transporter (DAT). We present molecular models for DAT binding of cocaine and cocaine analogs constructed from the high-resolution structure of the bacterial transporter homolog LeuT. Our models suggest that the binding site for cocaine and cocaine analogs is deeply buried between transmembrane segments 1, 3, 6 and 8, and overlaps with the binding sites for the substrates dopamine and amphetamine, as well as for benztropine-like DAT inhibitors. We validated our models by detailed mutagenesis and by trapping the radiolabeled cocaine analog [3H]CFT in the transporter, either by cross-linking engineered cysteines or with an engineered Zn2+-binding site that was situated extracellularly to the predicted common binding pocket. Our data demonstrate the molecular basis for the competitive inhibition of dopamine transport by cocaine.
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40
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Yeh CB, Lee CS, Ma KH, Lee MS, Chang CJ, Huang WS. Phasic dysfunction of dopamine transmission in Tourette's syndrome evaluated with 99mTc TRODAT-1 imaging. Psychiatry Res 2007; 156:75-82. [PMID: 17716877 DOI: 10.1016/j.pscychresns.2007.01.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2006] [Revised: 12/29/2006] [Accepted: 01/14/2007] [Indexed: 11/18/2022]
Abstract
This study investigated the complex dysregulation of the dopaminergic neurotransmitter system in Tourette's syndrome (TS) patients challenged with methylphenidate (MPH). Eight drug-naïve male patients (aged 21-25 years) who met DSM-IV criteria for TS and had a mean disease severity of 25 on the Yale Global Tic Severity Scale were recruited. Brain (99m)TC TRODAT-1 dopamine transporter (DAT) single photon emission computed tomography (SPECT) was performed 5 days before, and 2 h after 10 mg of orally administered MPH. Eight age-matched healthy males served as controls. Repeated measures analysis of variance was used to measure differences in DAT-binding ratios before and after MPH challenge between the TS patients and controls. The DAT-binding ratios decreased significantly after MPH treatment in both groups. However, a significant interaction between group and MPH effects was found only in the right caudate, which was mainly due to a smaller decline of the DAT-binding ratio after MPH in the TS group than in the controls. Such a distinction was not found in the other striatal sub-regions in the two groups. No correlation, however, was observed between the tic severity score and DAT-binding ratio measured from the whole striatum or its sub-regions. The observed change in the DAT-binding ratio might indicate a functional abnormality of the dopaminergic system in the right caudate nucleus of TS patients. Future studies exploring dopamine transmission are thus needed to understand the pathophysiology of TS.
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Affiliation(s)
- Chin-Bin Yeh
- Department of Psychiatry, Tri-Service General Hospital, National Defense Medical School, Taipei, Taiwan, ROC
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41
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Huang X, Zhan CG. How dopamine transporter interacts with dopamine: insights from molecular modeling and simulation. Biophys J 2007; 93:3627-39. [PMID: 17704152 PMCID: PMC2072054 DOI: 10.1529/biophysj.107.110924] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
By performing homology modeling, molecular docking, and molecular dynamics simulations, we have developed three-dimensional (3D) structural models of both dopamine transporter and dopamine transporter-dopamine complex in the environment of lipid bilayer and solvent water. According to the simulated structure of dopamine transporter-dopamine complex, dopamine was orientated in a hydrophobic pocket at the midpoint of the membrane. The modeled 3D structures provide some detailed structural and mechanistic insights concerning how dopamine transporter (DAT) interacts with dopamine at atomic level, extending our mechanistic understanding of the dopamine reuptake with the help of Na(+) ions. The general features of the modeled 3D structures are consistent with available experimental data. Based on the modeled structures, our calculated binding free energy (DeltaG(bind) = -6.4 kcal/mol) for dopamine binding with DAT is also reasonably close to the experimentally derived DeltaG(bind) value of -7.4 kcal/mol. Finally, a possible dopamine-entry pathway, which involves formation and breaking of the salt bridge between side chains of Arg(85) and Asp(476), is proposed based on the results obtained from the modeling and molecular dynamics simulation. The new structural and mechanistic insights obtained from this computational study are expected to stimulate future, further biochemical and pharmacological studies on the detailed structures and mechanisms of DAT and other homologous transporters.
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Affiliation(s)
- Xiaoqin Huang
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky, USA
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42
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Affiliation(s)
- Gary Rudnick
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8066, USA.
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Chen R, Wei H, Hill ER, Chen L, Jiang L, Han DD, Gu HH. Direct evidence that two cysteines in the dopamine transporter form a disulfide bond. Mol Cell Biochem 2006; 298:41-8. [PMID: 17131045 DOI: 10.1007/s11010-006-9348-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2006] [Accepted: 10/12/2006] [Indexed: 10/23/2022]
Abstract
We have generated a fully functional dopamine transporter (DAT) mutant (dmDATx7) with all cysteines removed except the two cysteines in extracellular loop 2 (EL2). Random mutagenesis at either or both EL2 cysteines did not produce any functional transporter mutants, suggesting that the two cysteines cannot be replaced by any other amino acids. The cysteine-specific reagent MTSEA-biotin labeled dmDATx7 only after a DTT treatment which reduces disulfide bond. Since there are no other cysteines in dmDATx7, the MTSEA-biotin labeling must be on the EL2 cysteines made available by the DTT treatment. This result provides the first direct evidence that the EL2 cysteines form a disulfide bond. Interestingly, the DTT treatment had little effect on transport activity suggesting that the disulfide bond is not necessary for the uptake function of DAT. Our results and previous results are consistent with the notion that the disulfide bond between EL2 cysteines is required for DAT biosynthesis and/or its delivery to the cell surface.
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Affiliation(s)
- Rong Chen
- Department of Pharmacology, The Ohio State University College of Medicine, 333 West 10th Avenue, Columbus, OH 43210, USA
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Chen R, Tilley MR, Wei H, Zhou F, Zhou FM, Ching S, Quan N, Stephens RL, Hill ER, Nottoli T, Han DD, Gu HH. Abolished cocaine reward in mice with a cocaine-insensitive dopamine transporter. Proc Natl Acad Sci U S A 2006; 103:9333-8. [PMID: 16754872 PMCID: PMC1482610 DOI: 10.1073/pnas.0600905103] [Citation(s) in RCA: 213] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
There are three known high-affinity targets for cocaine: the dopamine transporter (DAT), the serotonin transporter (SERT), and the norepinephrine transporter (NET). Decades of studies support the dopamine (DA) hypothesis that the blockade of DAT and the subsequent increase in extracellular DA primarily mediate cocaine reward and reinforcement. Contrary to expectations, DAT knockout (DAT-KO) mice and SERT or NET knockout mice still self-administer cocaine and/or display conditioned place preference (CPP) to cocaine, which led to the reevaluation of the DA hypothesis and the proposal of redundant reward pathways. To study the role of DAT in cocaine reward, we have generated a knockin mouse line carrying a functional DAT that is insensitive to cocaine. In these mice, cocaine suppressed locomotor activity, did not elevate extracellular DA in the nucleus accumbens, and did not produce reward as measured by CPP. This result suggests that blockade of DAT is necessary for cocaine reward in mice with a functional DAT. This mouse model is unique in that it is specifically designed to differentiate the role of DAT from the roles of NET and SERT in cocaine-induced biochemical and behavioral effects.
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Affiliation(s)
| | | | - Hua Wei
- Departments of *Pharmacology
| | - Fuwen Zhou
- Department of Pharmacology, University of Tennessee College of Medicine, Memphis, TN 38163; and
| | - Fu-Ming Zhou
- Department of Pharmacology, University of Tennessee College of Medicine, Memphis, TN 38163; and
| | | | | | - Robert L. Stephens
- Physiology, Ohio State University, 5184b Graves Hall, 333 West 10th Avenue, Columbus, OH 43210
| | | | - Timothy Nottoli
- Section of Comparative Medicine, Yale University, 375 Congress Avenue, New Haven, CT 06520
| | | | - Howard H. Gu
- Departments of *Pharmacology
- Psychiatry
- **To whom correspondence should be addressed. E-mail:
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Gu HH, Wu X, Han DD. Conserved serine residues in serotonin transporter contribute to high-affinity cocaine binding. Biochem Biophys Res Commun 2006; 343:1179-85. [PMID: 16580636 DOI: 10.1016/j.bbrc.2006.03.096] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2006] [Accepted: 03/16/2006] [Indexed: 10/24/2022]
Abstract
Serotonin transporter (SERT) is one of the key protein targets of cocaine. Despite intensive studies, it is not clear where cocaine binds to its targets and what residues are involved in cocaine binding. We have cloned the serotonin transporter from silkworm (Bombyx mori, bmSERT). When expressed in cultured cells, bmSERT is over 20-fold less sensitive to cocaine than Drosophila melanogaster SERT (dmSERT). We performed species-scanning mutagenesis using bmSERT and dmSERT. There are two adjacent threonine residues in transmembrane domain 12 of bmSERT where the corresponding residues are two serines in dmSERT and in all known mammalian monoamine transporters. Replacing the serine residues with threonines in dmSERT reduces cocaine sensitivity; while switching the two threonine residues in bmSERT to serines increased cocaine sensitivity. Mutations at the corresponding residues in dopamine transporter also changed cocaine affinity. Our results suggest that the conserved serine residues in SERT contribute to high-affinity cocaine binding.
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Affiliation(s)
- Howard H Gu
- Department of Pharmacology, The Ohio State University College of Medicine, 333 West 10th Avenue, Columbus, OH 43210, USA.
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Rutter JL. Symbiotic relationship of pharmacogenetics and drugs of abuse. AAPS J 2006; 8:E174-84. [PMID: 16584126 PMCID: PMC2751437 DOI: 10.1208/aapsj080121] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2005] [Accepted: 01/18/2006] [Indexed: 02/03/2023] Open
Abstract
Pharmacogenetics/pharmacogenomics is the study of how genetic variation affects pharmacology, the use of drugs to treat disease. When drug responses are predicted in advance, it is easier to tailor medications to different diseases and individuals. Pharmacogenetics provides the tools required to identify genetic predictors of probable drug response, drug efficacy, and drug-induced adverse events-identifications that would ideally precede treatment decisions. Drug abuse and addiction genetic data have advanced the field of pharmacogenetics in general. Although major findings have emerged, pharmacotherapy remains hindered by issues such as adverse events, time lag to drug efficacy, and heterogeneity of the disorders being treated. The sequencing of the human genome and high-throughput technologies are enabling pharmacogenetics to have greater influence on treatment approaches. This review highlights key studies and identifies important genes in drug abuse pharmacogenetics that provide a basis for better diagnosis and treatment of drug abuse disorders.
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Affiliation(s)
- Joni L Rutter
- National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, 6001 Executive Boulevard, Bethesda, MD 20892, USA.
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Han DD, Gu HH. Comparison of the monoamine transporters from human and mouse in their sensitivities to psychostimulant drugs. BMC Pharmacol 2006; 6:6. [PMID: 16515684 PMCID: PMC1448202 DOI: 10.1186/1471-2210-6-6] [Citation(s) in RCA: 312] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Accepted: 03/03/2006] [Indexed: 12/25/2022] Open
Abstract
Background The plasma membrane neurotransmitter transporters terminate neurotransmissions by the reuptake of the released neurotransmitters. The transporters for the monoamines dopamine, norepinephrine, and serotonin (DAT, NET, and SERT) are targets for several popular psychostimulant drugs of abuse. The potencies of the psychostimulant on the monoamine transporters have been studied by several laboratories. However, there are significant discrepancies in the reported data with differences up to 60-fold. In addition, the drug potencies of the 3 monoamine transporters from mouse have not been compared in the same experiments or along side the human transporters. Further studies and systematic comparisons are needed. Results In this study, we compared the potencies of five psychostimulant drugs to inhibit human and mouse DAT, SERT and NET in the same cellular background. The KI values of cocaine to inhibit the 3 transporters are within a narrow range of 0.2 to 0.7 μM. In comparison, methylphenidate inhibited DAT and NET at around 0.1 μM, while it inhibited SERT at around 100 μM. The order of amphetamine potencies was NET (KI = 0.07–0.1 μM), DAT (KI ≈ 0.6 μM), and SERT (KI between 20 to 40 μM). The results for methamphetamine were similar to those for amphetamine. In contrast, another amphetamine derivative, MDMA (3–4 methylenedioxymethamphetamine), exhibited higher potency at SERT than at DAT. The human and mouse transporters were similar in their sensitivities to each of the tested drugs (KI values are within 4-fold). Conclusion The current and previous studies support the following conclusions: 1) cocaine blocks all 3 monoamine transporters at similar concentrations; 2) methylphenidate inhibits DAT and NET well but a 1000-fold higher concentration of the drug is required to inhibit SERT; 3) Amphetamine and methamphetamine are most potent at NET, while being 5- to 9-fold less potent at DAT, and 200- to 500-fold less potent at SERT; 4) MDMA has moderately higher apparent affinity for SERT and NET than for DAT. The relative potencies of a drug to inhibit DAT, NET and SERT suggest which neurotransmitter systems are disrupted the most by each of these stimulants and thus the likely primary mechanism of drug action.
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Affiliation(s)
- Dawn D Han
- Department of Pharmacology, The Ohio State University College of Medicine, USA
| | - Howard H Gu
- Department of Pharmacology, The Ohio State University College of Medicine, USA
- Department of Psychiatry, The Ohio State University College of Medicine, 333 West 10th Avenue, Columbus, Ohio 43210, USA
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Rudnick G. Structure/function relationships in serotonin transporter: new insights from the structure of a bacterial transporter. Handb Exp Pharmacol 2006:59-73. [PMID: 16722230 DOI: 10.1007/3-540-29784-7_3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Serotonin transporter (SERT) serves the important function of taking up serotonin (5-HT) released during serotonergic neurotransmission. It is the target for important therapeutic drugs and psychostimulants. SERT catalyzes the influx of 5-HT together with Na+ and Cl- in a 1:1:1 stoichiometry. In the same catalytic cycle, there is coupled efflux of one K+ ion. SERT is one member of a large family of amino acid and amine transporters that is believed to utilize similar mechanisms of transport. A bacterial member of this family was recently crystallized, revealing the structural basis of these transporters. In light of the new structure, previous results with SERT have been re-interpreted, providing new insight into the substrate binding site, the permeation pathway, and the conformational changes that occur during the transport cycle.
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Affiliation(s)
- G Rudnick
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520-8066, USA.
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Chen R, Wu X, Wei H, Han DD, Gu HH. Molecular cloning and functional characterization of the dopamine transporter from Eloria noyesi, a caterpillar pest of cocaine-rich coca plants. Gene 2005; 366:152-60. [PMID: 16310975 DOI: 10.1016/j.gene.2005.09.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2005] [Revised: 08/22/2005] [Accepted: 09/07/2005] [Indexed: 11/19/2022]
Abstract
Cocaine is produced by coca plants as a chemical defense to deter feeding by insects. It has been shown that cocaine sprayed on tomato leaves reduces insect feeding, causes abnormal behaviors at low doses and kills feeding insects at doses equivalent to that in coca leaves [Nathanson, J.A., Hunnicutt, E.J., Kantham, L., Scavone, C., 1993. Cocaine as a naturally occurring insecticide. Proc. Natl. Acad. Sci. U. S. A. 90, 9645-9648.]. Most insects avoid coca leaves except the larvae of Eloria noyesi, a caterpillar pest of coca plants, which feeds preferentially on coca leaves. In the current study, we cloned and characterized the dopamine transporters (DATs) from caterpillars of E. noyesi (enDAT) and the silkworm, Bombyx mori (B. mori, bmDAT). The two insect DATs shared 88% amino acid sequence homology and functional similarity. Although enDAT and bmDAT showed the highest affinity for dopamine among endogenous amines, they were more sensitive to mammalian NET-selective inhibitors than to mammalian DAT-selective inhibitors. Despite a high cocaine content in the food source for E. noyesi, cocaine sensitivity of enDAT was similar to that of bmDAT, suggesting that mechanisms other than DAT insensitivity to cocaine, such as cocaine sequestration, might be responsible for cocaine resistance in this species. Given the significant differences in pharmacological profile from mammalian DATs, invertebrate DATs provide excellent tools for identifying regions and residues in the transporters that contribute to high-affinity binding of psychostimulants and antidepressants.
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Affiliation(s)
- Rong Chen
- Department of Pharmacology, College of Medicine and Public Health, The Ohio State University, Columbus, OH 43210, United States
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50
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Surratt CK, Ukairo OT, Ramanujapuram S. Recognition of psychostimulants, antidepressants, and other inhibitors of synaptic neurotransmitter uptake by the plasma membrane monoamine transporters. AAPS JOURNAL 2005; 7:E739-51. [PMID: 16353950 PMCID: PMC2751276 DOI: 10.1208/aapsj070374] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The plasma membrane monoamine transporters terminate neurotransmission by removing dopamine, norepinephrine, or serotonin from the synaptic cleft between neurons. Specific inhibitors for these transporters, including the abused psychostimulants cocaine and amphetamine and the tricyclic and SSRI classes of antidepressants, exert their physiological effects by interfering with synaptic uptake and thus prolonging the actions of the monoamine. Pharmacological, biochemical, and immunological characterization of the many site-directed, chimeric, and deletion mutants generated for the plasma membrane monoamine transporters have revealed much about the commonalities and dissimilarities between transporter substrate, ion, and inhibitor binding sites. Mutations that alter the binding affinity or substrate uptake inhibition potency of inhibitors by at least 3-fold are the focus of this review. These findings are clarifying the picture regarding substrate uptake inhibitor/transporter protein interactions at the level of the drug pharmacophore and the amino acid residue, information necessary for rational design of novel medications for substance abuse and a variety of psychiatric disorders.
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Affiliation(s)
- Christopher K Surratt
- Division of Pharmaceutical Sciences, Mylan School of Pharmacy, Duquesne University, Pittsburgh, PA 15282, USA.
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