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Iyer KA, Alix K, Eltit JM, Solis E, Pan X, Argade MD, Khatri S, De Felice LJ, Sweet DH, Schulte MK, Dukat M. Multi-modal antidepressant-like action of 6- and 7-chloro-2-aminodihydroquinazolines in the mouse tail suspension test. Psychopharmacology (Berl) 2019; 236:2093-2104. [PMID: 30805668 DOI: 10.1007/s00213-019-05203-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 02/14/2019] [Indexed: 01/08/2023]
Abstract
RATIONALE 2-Amino-6-chloro-3,4-dihydroquinazoline (e.g., A6CDQ) represents a novel putative antidepressant originally thought to act through a 5-HT3 serotonin receptor antagonist mechanism. Here, we investigated this further by examining a positional isomer of A6CDQ (i.e., A7CDQ). MATERIALS AND METHODS 5-HT3 receptor and transporter activity (uptake-1 and uptake-2) were investigated using a variety of in vitro assays and the in vivo mouse tail suspension test (TST). RESULTS Although A7CDQ binds at 5-HT3 receptors with low affinity (Ki = 1975 nM) compared to A6CDQ (Ki = 80 nM), it retained 5-HT3 receptor antagonist action (IC50 = 5.77 and 0.26 μM, respectively). In the mouse TST A7CDQ produced antidepressant-like actions (ED50 = 0.09 mg/kg) comparable to that of A6CDQ. In addition, A6CDQ was found to be a 5-HT releasing agent (Km = 2.8 μM) at hSERT and a reuptake inhibitor (IC50 = 1.8 μM) at hNET, whereas A7CDQ was a weak reuptake inhibitor (Km = 43.6 μM) at SERT but a releasing agent (EC50 = 3.3 μM) at hNET. Moreover, A6CDQ and A7CDQ were potent inhibitors of uptake-2 (e.g.; OCT3 IC50 = 3.9 and 5.9 μM, respectively). CONCLUSIONS A simple shift of a substituent in a common quinazoline scaffold from one position to another (i.e., a chloro group from the 6- to the 7-position) resulted in a common action in the TST but via a somewhat different mechanism. A6CDQ and A7CDQ might represent the first members of a new class of potential antidepressants with a unique multi-modal mechanism of action.
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Affiliation(s)
- Kavita A Iyer
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, PO Box 980540, Richmond, VA, 23298-540, USA
| | - Katie Alix
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, PO Box 980540, Richmond, VA, 23298-540, USA
| | - Jose M Eltit
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Ernesto Solis
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Xiaolei Pan
- Department of Pharmaceutics, School of Pharmacy, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Malaika D Argade
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, PO Box 980540, Richmond, VA, 23298-540, USA
| | - Shailesh Khatri
- Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of Sciences, Philadelphia, PA, 19104, USA
| | - Louis J De Felice
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Douglas H Sweet
- Department of Pharmaceutics, School of Pharmacy, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Marvin K Schulte
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, Kasiska Division of Health Sciences, Idaho State University, Pocatello, ID, 83209, USA
| | - Małgorzata Dukat
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, PO Box 980540, Richmond, VA, 23298-540, USA.
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Abstract
It is well established that glutamate and GABA signal through both ionotropic and metabotropic receptors. Conversely, it is thought that, with one exception, monoamines (dopamine, serotonin, and norepinephrine) signal via metabotropic receptors. Given their capacity to generate fast-acting currents, I suggest that the monoamine transporters should be considered as ionotropic receptors.
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Affiliation(s)
- Louis J De Felice
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA 23284, USA
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3
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Ruchala I, Harris A, De Felice LJ, Eltit JM. Voltage-Gated Calcium Channels as Detecting Tools of Psychoactive Drugs. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.1822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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4
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Abstract
Serotonin transporters (SERTs) are largely recognized for one aspect of their function—to transport serotonin back into the presynaptic terminal after its release. Another aspect of their function, however, may be to generate currents large enough to have physiological consequences. The standard model for electrogenic transport is the alternating access model, in which serotonin is transported with a fixed ratio of co-transported ions resulting in net charge per cycle. The alternating access model, however, cannot account for all the observed currents through SERT or other monoamine transporters. Furthermore, SERT agonists like ecstasy or antagonists like fluoxetine generate or suppress currents that the standard model cannot support. Here we survey evidence for a channel mode of transport in which transmitters and ions move through a pore. Available structures for dopamine and serotonin transporters, however, provide no evidence for a pore conformation, raising questions of whether the proposed channel mode actually exists or whether the structural data are perhaps missing a transient open state.
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Affiliation(s)
- Louis J De Felice
- Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA
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5
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De Felice LJ, Cameron KN. Comments on 'A quantitative model of amphetamine action on the serotonin transporter', by Sandtner et al., Br J Pharmacol 171: 1007-1018. Br J Pharmacol 2015; 172:4772-4. [PMID: 24824549 DOI: 10.1111/bph.12767] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 02/26/2014] [Indexed: 01/03/2023] Open
Affiliation(s)
- Louis J De Felice
- Department Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, USA
| | - Krasnodara N Cameron
- Department Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, USA
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Tang QY, Kolanos R, De Felice LJ, Glennon RA. Structural analysis of dopamine- and amphetamine-induced depolarization currents in the human dopamine transporter. ACS Chem Neurosci 2015; 6:551-8. [PMID: 25594379 DOI: 10.1021/cn500282f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Amphetamine (AMPH) induces depolarizing currents through the human dopamine transporter (hDAT). Recently we discovered that the S(+) enantiomer of AMPH induces a current through hDAT that persists long after its removal from the external milieu. The persistent current is less prominent for R(-)AMPH and essentially absent for dopamine (DA)-induced currents. Related agents such as methamphetamine also exhibit persistent currents, which are present in both frog oocyte and mammalian HEK expression systems. Here, we study hDAT-expressing Xenopus laevis oocytes voltage-clamped and exposed from outside to DA, S(+)AMPH, R(-)AMPH, and related synthesized compounds, including stereoisomers. The goal of the study was to determine how structural transitioning from dopamine to amphetamine influences hDAT potency and action. At saturating concentrations, S(+)AMPH or R(-)AMPH induce a sharply rising depolarizing current from -60 mV that is comparable in amplitude to DA-induced currents. The magnitude and duration of the currents and the presence or absence of persistent currents depend on the concentration, duration of exposure, and chemical structure and enantiomeric versions of the agents.
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Affiliation(s)
- Qiong-Yao Tang
- Department
of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298, United States
- Jiangsu
Province Key Laboratory of Anesthesiology, Xuzhou Medical College, Xuzhou 221004, People’s Republic of China
| | - Renata Kolanos
- Department
of Medicinal Chemistry, Virginia Commonwealth University School of Pharmacy, Richmond, Virginia 23298, United States
| | - Louis J De Felice
- Department
of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298, United States
| | - Richard A Glennon
- Department
of Medicinal Chemistry, Virginia Commonwealth University School of Pharmacy, Richmond, Virginia 23298, United States
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7
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Cameron KN, Solis E, Ruchala I, De Felice LJ, Eltit JM. Monoamine Transporters Produce Calcium Signals through L-Type Calcium Channel Activation. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.2523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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Solis E, Zdravkovic I, Kolanos R, Sakloth F, Noskov SY, Glennon RA, De Felice LJ. Characterization of a Secondary Site of Drug Action on the Human Dopamine Transporter. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.2521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Steele T, De Felice LJ. Computational and Experimental Investigation of the Human and D. Melanogaster Dopamine Transporters. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.2519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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10
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De Felice LJ, Noskov SY, Schnetkamp PP. Transporters inChannels. Channels (Austin) 2014. [DOI: 10.4161/chan.2.5.7482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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11
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Ruchala I, Cabra V, Solis E, Glennon RA, De Felice LJ, Eltit JM. Electrical coupling between the human serotonin transporter and voltage-gated Ca(2+) channels. Cell Calcium 2014; 56:25-33. [PMID: 24854234 DOI: 10.1016/j.ceca.2014.04.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 04/18/2014] [Accepted: 04/19/2014] [Indexed: 10/25/2022]
Abstract
Monoamine transporters have been implicated in dopamine or serotonin release in response to abused drugs such as methamphetamine or ecstasy (MDMA). In addition, monoamine transporters show substrate-induced inward currents that may modulate excitability and Ca(2+) mobilization, which could also contribute to neurotransmitter release. How monoamine transporters modulate Ca(2+) permeability is currently unknown. We investigate the functional interaction between the human serotonin transporter (hSERT) and voltage-gated Ca(2+) channels (CaV). We introduce an excitable expression system consisting of cultured muscle cells genetically engineered to express hSERT. Both 5HT and S(+)MDMA depolarize these cells and activate the excitation-contraction (EC)-coupling mechanism. However, hSERT substrates fail to activate EC-coupling in CaV1.1-null muscle cells, thus implicating Ca(2+) channels. CaV1.3 and CaV2.2 channels are natively expressed in neurons. When these channels are co-expressed with hSERT in HEK293T cells, only cells expressing the lower-threshold L-type CaV1.3 channel show Ca(2+) transients evoked by 5HT or S(+)MDMA. In addition, the electrical coupling between hSERT and CaV1.3 takes place at physiological 5HT concentrations. The electrical coupling between monoamine neurotransmitter transporters and Ca(2+) channels such as CaV1.3 is a novel mechanism by which endogenous substrates (neurotransmitters) or exogenous substrates (like ecstasy) could modulate Ca(2+)-driven signals in excitable cells.
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Affiliation(s)
- Iwona Ruchala
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Vanessa Cabra
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Ernesto Solis
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Richard A Glennon
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Louis J De Felice
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Jose M Eltit
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States.
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Kolanos R, Solis E, Sakloth F, De Felice LJ, Glennon RA. "Deconstruction" of the abused synthetic cathinone methylenedioxypyrovalerone (MDPV) and an examination of effects at the human dopamine transporter. ACS Chem Neurosci 2013; 4:1524-9. [PMID: 24116392 PMCID: PMC3867964 DOI: 10.1021/cn4001236] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 10/09/2013] [Indexed: 11/30/2022] Open
Abstract
Synthetic cathinones, β-keto analogues of amphetamine (or, more correctly, of phenylalkylamines), represent a new and growing class of abused substances. Several such analogues have been demonstrated to act as dopamine (DA) releasing agents. Methylenedioxypyrovalerone (MDPV) was the first synthetic cathinone shown to act as a cocaine-like DA reuptake inhibitor. MDPV and seven deconstructed analogues were examined to determine which of MDPV's structural features account(s) for uptake inhibition. In voltage-clamped (-60 mV) Xenopus oocytes transfected with the human DA transporter (hDAT), all analogues elicited inhibitor-like behavior shown as hDAT-mediated outward currents. Using hDAT-expressing mammalian cells we determined the affinities of MDPV and its analogues to inhibit uptake of [3H]DA by hDAT that varied over a broad range (IC50 values ca. 135 to >25,000 nM). The methylenedioxy group of MDPV made a minimal contribution to affinity, the carbonyl group and a tertiary amine are more important, and the extended α-alkyl group seems most important. Either a tertiary amine, or the extended α-alkyl group (but not both), are required for the potent nature of MDPV as an hDAT inhibitor.
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Affiliation(s)
- Renata Kolanos
- Department
of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - Ernesto Solis
- Department
of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - Farhana Sakloth
- Department
of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - Louis J. De Felice
- Department
of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - Richard A. Glennon
- Department
of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298, United States
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Cameron KN, Kolanos R, Solis E, Glennon RA, De Felice LJ. Bath salts components mephedrone and methylenedioxypyrovalerone (MDPV) act synergistically at the human dopamine transporter. Br J Pharmacol 2013; 168:1750-7. [PMID: 23170765 DOI: 10.1111/bph.12061] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Revised: 10/20/2012] [Accepted: 11/09/2012] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND AND PURPOSE Bath salts is the street name for drug combinations that contain synthetic cathinone analogues, among them possibly mephedrone (MEPH) and certainly methylenedioxypyrovalerone (MDPV). In animal studies, cathinone and certain cathinone analogues release dopamine (DA), similar to the action of amphetamine (AMPH) and methamphetamine (METH). AMPH and METH act on the human DA transporter (hDAT); thus, we investigated MEPH and MDPV acting at hDAT. EXPERIMENTAL APPROACH We recorded electrical currents mediated by hDAT expressed in Xenopus laevis oocytes and exposed to: DA, METH, a known hDAT stimulant and DA releaser, MEPH, MDPV, MEPH + MDPV, or cocaine, a known hDAT inhibitor. KEY RESULTS DA, METH and MEPH induce an inward current (depolarizing) when the oocyte is held near the resting potential (-60 mV), therefore acting as excitatory hDAT substrates. Structurally analogous MDPV induces an outward (hyperpolarizing) current similar to cocaine, therefore acting as an inhibitory non-substrate blocker. CONCLUSIONS AND IMPLICATIONS Two components of bath salts, MEPH and MDPV, produce opposite effects at hDAT that are comparable with METH and cocaine, respectively. In our assay, MEPH is nearly as potent as METH; however, MDPV is much more potent than cocaine and its effect is longer lasting. When applied in combination, MEPH exhibits faster kinetics than MDPV, viz., the MEPH depolarizing current occurs seconds before the slower MDPV hyperpolarizing current. Bath salts containing MEPH (or a similar drug) and MDPV might then be expected initially to release DA and subsequently prevent its reuptake via hDAT. Such combined action possibly underlies some of the reported effects of bath salts abuse.
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Affiliation(s)
- Krasnodara N Cameron
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA 23298, USA
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Solis E, Cameron KN, Kolanos R, Glennon RA, De Felice LJ. Methylene‐dioxy‐pyrovalerone (MDPV) is a potent inhibitor of hDAT and hNET. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.885.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Ernesto Solis
- Physiology and BiophysicsVirginia Commonwealth UniversityRichmondVA
| | | | - Renata Kolanos
- Medicinal ChemistryVirginia Commonwealth UniversityRichmondVA
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Cabra V, Leal-Pinto E, Samso M, Glennon RA, De Felice LJ, Eltit JM. S(+)MDMA and 5-HT Evoke Dissimilar Ionic Currents in Human Serotonin Transporter-Expressing Cells. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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16
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Rodriguez-Menchaca AA, Solis E, Cameron K, De Felice LJ. S(+)amphetamine induces a persistent leak in the human dopamine transporter: molecular stent hypothesis. Br J Pharmacol 2012; 165:2749-57. [PMID: 22014068 DOI: 10.1111/j.1476-5381.2011.01728.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Wherever they are located, dopamine transporters (DATs) clear dopamine (DA) from the extracellular milieu to help regulate dopaminergic signalling. Exposure to amphetamine (AMPH) increases extracellular DA in the synaptic cleft, which has been ascribed to DAT reverse transport. Increased extracellular DA prolongs postsynaptic activity and reinforces abuse and hedonic behaviour. EXPERIMENTAL APPROACH Xenopus laevis oocytes expressing human (h) DAT were voltage-clamped and exposed to DA, R(-)AMPH, or S(+)AMPH. KEY RESULTS At -60mV, near neuronal resting potentials, S(+)AMPH induced a depolarizing current through hDAT, which after removing the drug, persisted for more than 30 min. This persistent leak in the absence of S(+)AMPH was in contrast to the currents induced by R(-)AMPH and DA, which returned to baseline immediately after their removal. Our data suggest that S(+)AMPH and Na(+) carry the initial S(+)AMPH-induced current, whereas Na+ and Cl(-) carry the persistent leak current. We propose that the persistent current results from the internal action of S(+)AMPH on hDAT because the temporal effect was consistent with S(+)AMPH influx, and intracellular S(+)AMPH activated the effect. The persistent current was dependent on Na(+) and was blocked by cocaine. Intracellular injection of S(+)AMPH also activated a DA-induced persistent leak current. CONCLUSIONS AND IMPLICATIONS We report a hitherto unknown action of S(+)AMPH on hDAT that potentially affects AMPH-induced DA release. We propose that internal S(+)AMPH acts as a molecular stent that holds the transporter open even after external S(+)AMPH is removed. Amphetamine-induced persistent leak currents are likely to influence dopaminergic signalling, DA release mechanisms, and amphetamine abuse.
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Affiliation(s)
- Aldo A Rodriguez-Menchaca
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA
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Solis E, Zdravkovic I, Tomlinson ID, Noskov SY, Rosenthal SJ, De Felice LJ. 4-(4-(dimethylamino)phenyl)-1-methylpyridinium (APP+) is a fluorescent substrate for the human serotonin transporter. J Biol Chem 2012; 287:8852-63. [PMID: 22291010 DOI: 10.1074/jbc.m111.267757] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Monoamine transporters terminate synaptic neurotransmission and are molecular targets for antidepressants and psychostimulants. Fluorescent reporters can monitor real-time transport and are amenable for high-throughput screening. However, until now, their use has mostly been successful to study the catecholamine transporters but not the serotonin (5HT) transporter. Here, we use fluorescence microscopy, electrophysiology, pharmacology, and molecular modeling to compare fluorescent analogs of 1-methyl-4-phenylpyridinium (MPP(+)) as reporters for the human serotonin transporter (hSERT) in single cells. The fluorescent substrate 4-(4-(dimethylamino)phenyl)-1-methylpyridinium (APP(+)) exhibits superior fluorescence uptake in hSERT-expressing HEK293 cells than other MPP(+) analogs tested. APP(+) uptake is Na(+)- and Cl(-)-dependent, displaced by 5HT, and inhibited by fluoxetine, suggesting APP(+) specifically monitors hSERT activity. ASP(+), which was previously used to study catecholamine transporters, is 10 times less potent than APP(+) at inhibiting 5HT uptake and has minimal hSERT-mediated uptake. Furthermore, in hSERT-expressing oocytes voltage-clamped to -60 mV, APP(+) induced fluoxetine-sensitive hSERT-mediated inward currents, indicating APP(+) is a substrate, whereas ASP(+) induced hSERT-mediated outward currents and counteracted 5HT-induced hSERT currents, indicating ASP(+) possesses activity as an inhibitor. Extra-precise ligand receptor docking of APP(+) and ASP(+) in an hSERT homology model showed both ASP(+) and APP(+) docked favorably within the active region; accordingly, comparable concentrations are required to elicit their opposite electrophysiological responses. We conclude APP(+) is better suited than ASP(+) to study hSERT transport fluorometrically.
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Affiliation(s)
- Ernesto Solis
- Graduate Training Program in Neuroscience, Vanderbilt University School of Medicine, Nashville, Tennessee 23235, USA.
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Cameron KN, Kolanos R, Solis E, Vekariya RH, Glennon RA, De Felice LJ. Bath Salts: A Synthetic Cathinone Whose Two Major Components Act Similar to Methamphetamine and Cocaine on the Human Dopamine Transporter. Biophys J 2012. [DOI: 10.1016/j.bpj.2011.11.1178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022] Open
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Goodwin JS, Larson GA, Swant J, Sen N, Javitch JA, Zahniser NR, De Felice LJ, Khoshbouei H. Amphetamine and methamphetamine differentially affect dopamine transporters in vitro and in vivo. J Biol Chem 2008; 284:2978-2989. [PMID: 19047053 DOI: 10.1074/jbc.m805298200] [Citation(s) in RCA: 150] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The psychostimulants d-amphetamine (AMPH) and methamphetamine (METH) release excess dopamine (DA) into the synaptic clefts of dopaminergic neurons. Abnormal DA release is thought to occur by reverse transport through the DA transporter (DAT), and it is believed to underlie the severe behavioral effects of these drugs. Here we compare structurally similar AMPH and METH on DAT function in a heterologous expression system and in an animal model. In the in vitro expression system, DAT-mediated whole-cell currents were greater for METH stimulation than for AMPH. At the same voltage and concentration, METH released five times more DA than AMPH and did so at physiological membrane potentials. At maximally effective concentrations, METH released twice as much [Ca(2+)](i) from internal stores compared with AMPH. [Ca(2+)](i) responses to both drugs were independent of membrane voltage but inhibited by DAT antagonists. Intact phosphorylation sites in the N-terminal domain of DAT were required for the AMPH- and METH-induced increase in [Ca(2+)](i) and for the enhanced effects of METH on [Ca(2+)](i) elevation. Calmodulin-dependent protein kinase II and protein kinase C inhibitors alone or in combination also blocked AMPH- or METH-induced Ca(2+) responses. Finally, in the rat nucleus accumbens, in vivo voltammetry showed that systemic application of METH inhibited DAT-mediated DA clearance more efficiently than AMPH, resulting in excess external DA. Together these data demonstrate that METH has a stronger effect on DAT-mediated cell physiology than AMPH, which may contribute to the euphoric and addictive properties of METH compared with AMPH.
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Affiliation(s)
- J Shawn Goodwin
- Department of Cancer Biology, Meharry Medical College, Nashville, Tennessee 37208
| | - Gaynor A Larson
- Department of Pharmacology, University of Colorado Denver, Aurora, Colorado 80045
| | - Jarod Swant
- Departments of Neurobiology and Neurotoxicology, Meharry Medical College, Nashville, Tennessee 37208
| | - Namita Sen
- Departments of Psychiatry and Pharmacology, Center for Molecular Recognition, Columbia University, New York, New York 10027-6902
| | - Jonathan A Javitch
- Departments of Psychiatry and Pharmacology, Center for Molecular Recognition, Columbia University, New York, New York 10027-6902
| | - Nancy R Zahniser
- Department of Pharmacology, University of Colorado Denver, Aurora, Colorado 80045
| | - Louis J De Felice
- Center for Molecular Neuroscience, Vanderbilt University, Nashville, Tennessee 37232; Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232
| | - Habibeh Khoshbouei
- Departments of Neurobiology and Neurotoxicology, Meharry Medical College, Nashville, Tennessee 37208
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De Felice LJ, Noskov S, Schnetkamp PPM. Transporters in Channels. Channels (Austin) 2008; 2:305-307. [PMID: 19066449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023] Open
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Tomlinson ID, Chang J, Iwamoto H, De Felice LJ, Blakely RD, Rosenthal SJ. Targeting the human serotonin transporter (hSERT) with quantum dots. Proc SPIE Int Soc Opt Eng 2008; 6866:nihpa155701. [PMID: 19936040 DOI: 10.1117/12.782801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
In this paper we report our work on the development of a human serotonin transporter (hSERT) antagonist that can be conjugated to quantum dots. This approach has been used to target and visualize the human serotonin transporter protein (hSERT). We demonstrate that labeling is blocked by the addition of high affinity hSERT antagonists such as paroxetine. This approach may be useful for the development of fluorescent assays to study the location and temporal dynamics of biogenic amine transporters and also holds promise for the development of plate-based high throughput assays used to identify novel transporter antagonists.
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Affiliation(s)
- I D Tomlinson
- Department of Chemistry,Vanderbilt University, Station B 311822, Nashville, Tennessee, 37235-1822
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Iwamoto H, Blakely RD, De Felice LJ. Na+, Cl-, and pH dependence of the human choline transporter (hCHT) in Xenopus oocytes: the proton inactivation hypothesis of hCHT in synaptic vesicles. J Neurosci 2006; 26:9851-9. [PMID: 17005849 PMCID: PMC6674471 DOI: 10.1523/jneurosci.1862-06.2006] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The recent cloning of the human choline transporter (hCHT) has allowed its expression in Xenopus laevis oocytes and the simultaneous measurement of choline transport and choline-induced current under voltage clamp. hCHT currents and choline transport are evident in cRNA-injected oocytes and significantly enhanced by the hCHT trafficking mutant L530A/V531A. The charge/choline ratio of hCHT varies from 10e/choline at -80 mV to 3e/choline at -20 mV, in contrast with the reported fixed stoichiometry of the Na+-coupled glucose transporter in the same gene family. Ion substitution shows that the choline uptake and choline-induced current are Na+ and Cl- dependent; however, the reversal potential of the induced current suggests a Na+-selective mechanism, consigning Cl- to a regulatory role rather than a coupled, cotransported-ion role. The hCHT-specific inhibitor hemicholinium-3 (HC-3) blocks choline uptake and choline-induced current; in addition, HC-3 alone reveals a constitutive, depolarizing leak current through hCHT. We show that external protons reduce hCHT current, transport, and binding with a similar pKa of 7.4, suggesting proton titration of residue(s) that support choline binding and transport. Given the localization of the choline transporter to synaptic vesicles, we propose that proton inactivation of hCHT prevents acetylcholine and proton leakage from the acidic interior of cholinergic synaptic vesicles. This mechanism would allow cholinergic, activity-triggered delivery of silent choline transporters to the plasma membrane, in which normal pH would reactivate the transporters for choline uptake and subsequent acetylcholine synthesis.
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Affiliation(s)
- Hideki Iwamoto
- Department of Pharmacology and Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville Tennessee 37232-8548
| | - Randy D. Blakely
- Department of Pharmacology and Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville Tennessee 37232-8548
| | - Louis J. De Felice
- Department of Pharmacology and Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville Tennessee 37232-8548
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