1
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Paul A, Shukla D. Oligomerization of Monoamine Transporters. Subcell Biochem 2024; 104:119-137. [PMID: 38963486 DOI: 10.1007/978-3-031-58843-3_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/05/2024]
Abstract
Transporters of the monoamine transporter (MAT) family regulate the uptake of important neurotransmitters like dopamine, serotonin, and norepinephrine. The MAT family functions using the electrochemical gradient of ions across the membrane and comprises three transporters, dopamine transporter (DAT), serotonin transporter (SERT), and norepinephrine transporter (NET). MAT transporters have been observed to exist in monomeric states to higher-order oligomeric states. Structural features, allosteric modulation, and lipid environment regulate the oligomerization of MAT transporters. NET and SERT oligomerization are regulated by levels of PIP2 present in the membrane. The kink present in TM12 in the MAT family is crucial for dimer interface formation. Allosteric modulation in the dimer interface hinders dimer formation. Oligomerization also influences the transporters' function, trafficking, and regulation. This chapter will focus on recent studies on monoamine transporters and discuss the factors affecting their oligomerization and its impact on their function.
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Affiliation(s)
- Arnav Paul
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, IL, USA
| | - Diwakar Shukla
- Department of Chemical and Biomolecular Engineering, Department of Bioengineering, Center for Biophysics and Quantitative Biology, Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
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2
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Yang D, Zhao Z, Tajkhorshid E, Gouaux E. Structures and membrane interactions of native serotonin transporter in complexes with psychostimulants. Proc Natl Acad Sci U S A 2023; 120:e2304602120. [PMID: 37436958 PMCID: PMC10629533 DOI: 10.1073/pnas.2304602120] [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: 03/20/2023] [Accepted: 05/03/2023] [Indexed: 07/14/2023] Open
Abstract
The serotonin transporter (SERT) is a member of the SLC6 neurotransmitter transporter family that mediates serotonin reuptake at presynaptic nerve terminals. SERT is the target of both therapeutic antidepressant drugs and psychostimulant substances such as cocaine and methamphetamines, which are small molecules that perturb normal serotonergic transmission by interfering with serotonin transport. Despite decades of studies, important functional aspects of SERT such as the oligomerization state of native SERT and its interactions with potential proteins remain unresolved. Here, we develop methods to isolate SERT from porcine brain (pSERT) using a mild, nonionic detergent, utilize fluorescence-detection size-exclusion chromatography to investigate its oligomerization state and interactions with other proteins, and employ single-particle cryo-electron microscopy to elucidate the structures of pSERT in complexes with methamphetamine or cocaine, providing structural insights into psychostimulant recognition and accompanying pSERT conformations. Methamphetamine and cocaine both bind to the central site, stabilizing the transporter in an outward open conformation. We also identify densities attributable to multiple cholesterol or cholesteryl hemisuccinate (CHS) molecules, as well as to a detergent molecule bound to the pSERT allosteric site. Under our conditions of isolation, we find that pSERT is best described as a monomeric entity, isolated without interacting proteins, and is ensconced by multiple cholesterol or CHS molecules.
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Affiliation(s)
- Dongxue Yang
- Vollum Institute, Oregon Health and Science University, Portland, OR97239
| | - Zhiyu Zhao
- Department of Biochemistry, NIH Center for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL61801
| | - Emad Tajkhorshid
- Department of Biochemistry, NIH Center for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL61801
| | - Eric Gouaux
- Vollum Institute, Oregon Health and Science University, Portland, OR97239
- HHMI, Oregon Health and Science University, Portland, OR97239
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3
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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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4
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Cross-Linking and Functional Analyses for Dimerization of a Cysteine Mutant of Glycine Transporter 1. Int J Mol Sci 2022; 23:ijms232416157. [PMID: 36555800 PMCID: PMC9781295 DOI: 10.3390/ijms232416157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Revised: 12/10/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
Glycine transporter 1 (GlyT1) is responsible for the reuptake of glycine, which regulates glutamate signaling as a co-agonist with N-methyl-D-aspartic acid (NMDA) receptors in the excitatory synapse and has been proposed to be a potential target in the development of therapies for a broad range of disorders of the central nervous system. Despite significant progress in characterizing structure and transport mechanism of the transporter, the regulation of transport function through oligomerization remains to be understood. In the present work, association of two forms of GlyT1 into dimers and higher order oligomers was detected by coimmunoprecipitation. To investigate functional properties of dimers of a GlyT1 cysteine mutant L288C, we performed oxidative cross-linking of the positioned cysteine residues in extracellular loop 3 (EL3) near the extracellular end of TM6. By analyzing the effect of copper phenanthroline (CuP)-induced dimerization on transport function, cross-linking of L288C was found to inhibit transport activity. In addition, an intramolecular ion pair Lys286-Glu289 was revealed to be critical for stabilizing EL3 in a conformation that modulates CuP-induced dimerization and transport function of the GlyT1 L288C mutant. Furthermore, the influence of transporter conformation on GlyT1 L288C dimerization was investigated. The substrate glycine, in the presence of both Na+ and Cl-, significantly reduced oxidative cross-linking, suggesting a large-scale rotation of the bundle domain during substrate transport impairs interfacial interactions between L288C protomers. The present study provides new insights into structural and functional elements regulating GlyT1 transport activity through its dimerization or oligomerization.
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5
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Miller DR, Bu AM, Gopinath A, Martinez LR, Khoshbouei H. Methamphetamine dysregulation of the central nervous system and peripheral immunity. J Pharmacol Exp Ther 2021; 379:372-385. [PMID: 34535563 DOI: 10.1124/jpet.121.000767] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 09/16/2021] [Indexed: 11/22/2022] Open
Abstract
Methamphetamine (METH) is a potent psychostimulant that increases extracellular monoamines such as dopamine and norepinephrine and affects multiple tissue and cell types. The reinforcing properties of METH underlie its significant abuse potential and dysregulation of peripheral immunity and central nervous system functions. Together, the constellation of METH's effects on cellular targets and regulatory processes have shown to lead to immune suppression and neurodegeneration in METH addicts and animal models of METH exposure. Here we extensively review many of the cell types and mechanisms of METH-induced dysregulation of the central nervous system and peripheral immune system. Significance Statement Emerging research has begun to show that methamphetamine not only regulates dopaminergic neuronal activity, it also affects non-neuronal brain cells, such as microglia and astrocytes as well immunological cells of the periphery. The bi-directional communication between dopaminergic neurons in the CNS and peripheral immune cells becomes dysregulated by a constellation of dysfunctional neuronal and cell types revealing multiple targets that must be considered at the interface between basic and clinical neuroscience.
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Affiliation(s)
| | | | - Adithya Gopinath
- Department of Neuroscience, University of Florida, United States
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6
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Aguilar JI, Cheng MH, Font J, Schwartz AC, Ledwitch K, Duran A, Mabry SJ, Belovich AN, Zhu Y, Carter AM, Shi L, Kurian MA, Fenollar-Ferrer C, Meiler J, Ryan RM, Mchaourab HS, Bahar I, Matthies HJ, Galli A. Psychomotor impairments and therapeutic implications revealed by a mutation associated with infantile Parkinsonism-Dystonia. eLife 2021; 10:68039. [PMID: 34002696 PMCID: PMC8131106 DOI: 10.7554/elife.68039] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 05/02/2021] [Indexed: 12/30/2022] Open
Abstract
Parkinson disease (PD) is a progressive, neurodegenerative disorder affecting over 6.1 million people worldwide. Although the cause of PD remains unclear, studies of highly penetrant mutations identified in early-onset familial parkinsonism have contributed to our understanding of the molecular mechanisms underlying disease pathology. Dopamine (DA) transporter (DAT) deficiency syndrome (DTDS) is a distinct type of infantile parkinsonism-dystonia that shares key clinical features with PD, including motor deficits (progressive bradykinesia, tremor, hypomimia) and altered DA neurotransmission. Here, we define structural, functional, and behavioral consequences of a Cys substitution at R445 in human DAT (hDAT R445C), identified in a patient with DTDS. We found that this R445 substitution disrupts a phylogenetically conserved intracellular (IC) network of interactions that compromise the hDAT IC gate. This is demonstrated by both Rosetta molecular modeling and fine-grained simulations using hDAT R445C, as well as EPR analysis and X-ray crystallography of the bacterial homolog leucine transporter. Notably, the disruption of this IC network of interactions supported a channel-like intermediate of hDAT and compromised hDAT function. We demonstrate that Drosophila melanogaster expressing hDAT R445C show impaired hDAT activity, which is associated with DA dysfunction in isolated brains and with abnormal behaviors monitored at high-speed time resolution. We show that hDAT R445C Drosophila exhibit motor deficits, lack of motor coordination (i.e. flight coordination) and phenotypic heterogeneity in these behaviors that is typically associated with DTDS and PD. These behaviors are linked with altered dopaminergic signaling stemming from loss of DA neurons and decreased DA availability. We rescued flight coordination with chloroquine, a lysosomal inhibitor that enhanced DAT expression in a heterologous expression system. Together, these studies shed some light on how a DTDS-linked DAT mutation underlies DA dysfunction and, possibly, clinical phenotypes shared by DTDS and PD.
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Affiliation(s)
- Jenny I Aguilar
- Department of Pharmacology, Vanderbilt University, Nashville, United States.,Department of Surgery, University of Alabama at Birmingham, Birmingham, United States
| | - Mary Hongying Cheng
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, United States
| | - Josep Font
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Alexandra C Schwartz
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, United States
| | - Kaitlyn Ledwitch
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Chemistry, Vanderbilt University, Nashville, United States
| | - Amanda Duran
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Chemistry, Vanderbilt University, Nashville, United States
| | - Samuel J Mabry
- Department of Surgery, University of Alabama at Birmingham, Birmingham, United States
| | - Andrea N Belovich
- Department of Biomedical Sciences, Idaho College of Osteopathic Medicine, Meridian, United States
| | - Yanqi Zhu
- Department of Surgery, University of Alabama at Birmingham, Birmingham, United States
| | - Angela M Carter
- Department of Surgery, University of Alabama at Birmingham, Birmingham, United States
| | - Lei Shi
- Computational Chemistry and Molecular Biophysics Section, NIDA, NIH, Baltimore, United States
| | - Manju A Kurian
- Molecular Neurosciences, Developmental Neurosciences, University College London (UCL), London, United Kingdom
| | | | - Jens Meiler
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Chemistry, Vanderbilt University, Nashville, United States.,Institute for Drug Discovery, Leipzig University Medical School, Leipzig, Germany
| | - Renae Monique Ryan
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Hassane S Mchaourab
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, United States
| | - Ivet Bahar
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, United States
| | - Heinrich Jg Matthies
- Department of Surgery, University of Alabama at Birmingham, Birmingham, United States
| | - Aurelio Galli
- Department of Surgery, University of Alabama at Birmingham, Birmingham, United States.,Center for Inter-systemic Networks and Enteric Medical Advances, University of Alabama at Birmingham, Birmingham, United States
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7
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Dynamic control of the dopamine transporter in neurotransmission and homeostasis. NPJ Parkinsons Dis 2021; 7:22. [PMID: 33674612 PMCID: PMC7935902 DOI: 10.1038/s41531-021-00161-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 01/08/2021] [Indexed: 01/31/2023] Open
Abstract
The dopamine transporter (DAT) transports extracellular dopamine into the intracellular space contributing to the regulation of dopamine neurotransmission. A reduction of DAT density is implicated in Parkinson's disease (PD) by neuroimaging; dopamine turnover is dopamine turnover is elevated in early symptomatic PD and in presymptomatic individuals with monogenic mutations causal for parkinsonism. As an integral plasma membrane protein, DAT surface expression is dynamically regulated through endocytic trafficking, enabling flexible control of dopamine signaling in time and space, which in turn critically modulates movement, motivation and learning behavior. Yet the cellular machinery and functional implications of DAT trafficking remain enigmatic. In this review we summarize mechanisms governing DAT trafficking under normal physiological conditions and discuss how PD-linked mutations may disturb DAT homeostasis. We highlight the complexity of DAT trafficking and reveal DAT dysregulation as a common theme in genetic models of parkinsonism.
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8
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Sorkina T, Cheng MH, Bagalkot TR, Wallace C, Watkins SC, Bahar I, Sorkin A. Direct coupling of oligomerization and oligomerization-driven endocytosis of the dopamine transporter to its conformational mechanics and activity. J Biol Chem 2021; 296:100430. [PMID: 33610553 PMCID: PMC8010718 DOI: 10.1016/j.jbc.2021.100430] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 02/08/2021] [Accepted: 02/16/2021] [Indexed: 12/15/2022] Open
Abstract
Dopamine transporter (DAT) mediates the reuptake of synaptically released dopamine, and thus controls the duration and intensity of dopamine neurotransmission. Mammalian DAT has been observed to form oligomers, although the mechanisms of oligomerization and its role in DAT activity and trafficking remain largely unknown. We discovered a series of small molecule compounds that stabilize trimers and induce high-order oligomers of DAT and concomitantly promote its clathrin-independent endocytosis. Using a combination of chemical cross-linking, fluorescence resonance energy transfer microscopy, antibody-uptake endocytosis assay, live-cell lattice light sheet microscopy, ligand binding and substrate transport kinetics analyses, and molecular modeling and simulations, we investigated molecular basis of DAT oligomerization and endocytosis induced by these compounds. Our study showed that small molecule–induced DAT oligomerization and endocytosis are favored by the inward-facing DAT conformation and involve interactions of four hydrophobic residues at the interface between transmembrane (TM) helices TM4 and TM9. Surprisingly, a corresponding quadruple DAT mutant displays altered dopamine transport kinetics and increased cocaine-analog binding. The latter is shown to originate from an increased preference for outward-facing conformation and inward-to-outward transition. Taken together, our results demonstrate a direct coupling between conformational dynamics of DAT, functional activity of the transporter, and its oligomerization leading to endocytosis. The high specificity of such coupling for DAT makes the TM4-9 hub a new target for pharmacological modulation of DAT activity and subcellular localization.
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Affiliation(s)
- Tatiana Sorkina
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Mary Hongying Cheng
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Tarique R Bagalkot
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Callen Wallace
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Simon C Watkins
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Ivet Bahar
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Alexander Sorkin
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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9
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Zeppelin T, Pedersen KB, Berglund NA, Periole X, Schiøtt B. Effect of palmitoylation on the dimer formation of the human dopamine transporter. Sci Rep 2021; 11:4164. [PMID: 33602981 PMCID: PMC7893171 DOI: 10.1038/s41598-021-83374-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 02/01/2021] [Indexed: 01/01/2023] Open
Abstract
The human dopamine transporter (hDAT) is one in three members of the monoamine transporter family (MAT). hDAT is essential for regulating the dopamine concentration in the synaptic cleft through dopamine reuptake into the presynaptic neuron; thereby controlling hDAT dopamine signaling. Dysfunction of the transporter is linked to several psychiatric disorders. hDAT and the other MATs have been shown to form oligomers in the plasma membrane, but only limited data exists on which dimeric and higher order oligomeric states are accessible and energetically favorable. In this work, we present several probable dimer conformations using computational coarse-grained self-assembly simulations and assess the relative stability of the different dimer conformations using umbrella sampling replica exchange molecular dynamics. Overall, the dimer conformations primarily involve TM9 and/or TM11 and/or TM12 at the interface. Furthermore, we show that a palmitoyl group (palm) attached to hDAT on TM12 modifies the free energy of separation for interfaces involving TM12, suggesting that S-palmitoylation may change the relative abundance of dimers involving TM12 in a biological context. Finally, a comparison of the identified interfaces of hDAT and palmitoylated hDAT to the human serotonin transporter interfaces and the leucine transporter interface, suggests similar dimer conformations across these protein family.
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Affiliation(s)
- Talia Zeppelin
- Department of Chemistry, Aarhus University, Aarhus C, Denmark
| | - Kasper B Pedersen
- Department of Chemistry, Aarhus University, Aarhus C, Denmark.,Interdisciplinary Nanoscience Center, Aarhus University, Aarhus C, Denmark
| | - Nils A Berglund
- Department of Chemistry, Aarhus University, Aarhus C, Denmark
| | - Xavier Periole
- Department of Chemistry, Aarhus University, Aarhus C, Denmark. .,School of Biological Sciences, University of Auckland & Canterbury, Auckland & Christchurch, New Zealand.
| | - Birgit Schiøtt
- Department of Chemistry, Aarhus University, Aarhus C, Denmark. .,Interdisciplinary Nanoscience Center, Aarhus University, Aarhus C, Denmark.
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10
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Ingram SM, Rana T, Manson AM, Yayah FM, Jackson EGB, Anderson C, Davids BO, Goodwin JS. Optogenetically-induced multimerization of the dopamine transporter increases uptake and trafficking to the plasma membrane. J Biol Chem 2021; 296:100787. [PMID: 34015332 PMCID: PMC8203837 DOI: 10.1016/j.jbc.2021.100787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 05/07/2021] [Accepted: 05/13/2021] [Indexed: 11/19/2022] Open
Abstract
The dopamine transporter (DAT) is essential for the reuptake of the released neurotransmitter dopamine (DA) in the brain. Psychostimulants, methamphetamine and cocaine, have been reported to induce the formation of DAT multimeric complexes in vivo and in vitro. The interpretation of DAT multimer function has been primarily in the context of compounds that induce structural and functional modifications of the DAT, complicating the understanding of the significance of DAT multimers. To examine multimerization in the absence of DAT ligands as well as in their presence, we developed a novel, optogenetic fusion chimera of cryptochrome 2 and DAT with an mCherry fluorescent reporter (Cry2-DAT). Using blue light to induce Cry2-DAT multimeric protein complex formation, we were able to simultaneously test the functional contributions of DAT multimerization in the absence or presence of substrates or inhibitors with high spatiotemporal precision. We found that blue light-stimulated Cry2-DAT multimers significantly increased IDT307 uptake and MFZ 9-18 binding in the absence of ligands as well as after methamphetamine and nomifensine treatment. Blue light-induced Cry2-DAT multimerization increased colocalization with recycling endosomal marker Rab11 and had decreased presence in Rab5-positive early endosomes and Rab7-positive late endosomes. Our data suggest that the increased uptake and binding results from induced and rapid trafficking of DAT multimers to the plasma membrane. Our data suggest that DAT multimers may function to help maintain DA homeostasis.
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Affiliation(s)
- Shalonda M Ingram
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Tanu Rana
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Ashley M Manson
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Faisal M Yayah
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Evan G B Jackson
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Christopher Anderson
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - Benem-Orom Davids
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA
| | - J Shawn Goodwin
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, School of Medicine, Meharry Medical College, Nashville, Tennessee, USA.
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11
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Jayaraman K, Das AK, Luethi D, Szöllősi D, Schütz GJ, Reith MEA, Sitte HH, Stockner T. SLC6 transporter oligomerization. J Neurochem 2020; 157:919-929. [PMID: 32767560 PMCID: PMC8247324 DOI: 10.1111/jnc.15145] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 07/31/2020] [Accepted: 07/31/2020] [Indexed: 12/18/2022]
Abstract
Transporters of the solute carrier 6 (SLC6) family mediate the reuptake of neurotransmitters such as dopamine, norepinephrine, serotonin, GABA, and glycine. SLC6 family members are 12 transmembrane helix‐spanning proteins that operate using the transmembrane sodium gradient for transport. These transporters assume various quaternary arrangements ranging from monomers to complex stoichiometries with multiple subunits. Dopamine and serotonin transporter oligomerization has been implicated in trafficking of newly formed proteins from the endoplasmic reticulum to the plasma membrane with a pre‐fixed assembly. Once at the plasma membrane, oligomers are kept fixed in their quaternary assembly by interaction with phosphoinositides. While it remains unclear how oligomer formation precisely affects physiological transporter function, it has been shown that oligomerization supports the activity of release‐type psychostimulants. Most recently, single molecule microscopy experiments unveiled that the stoichiometry differs between individual members of the SLC6 family. The present overview summarizes our understanding of the influence of plasma membrane constituents on transporter oligomerization, describes the known interfaces between protomers and discusses open questions. ![]()
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Affiliation(s)
- Kumaresan Jayaraman
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Anand K Das
- Institute of Applied Physics, Vienna University of Technology, Vienna, Austria
| | - Dino Luethi
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria.,Institute of Applied Physics, Vienna University of Technology, Vienna, Austria
| | - Dániel Szöllősi
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Gerhard J Schütz
- Institute of Applied Physics, Vienna University of Technology, Vienna, Austria
| | - Maarten E A Reith
- Department of Psychiatry, New York University School of Medicine, New York City, NY, USA
| | - Harald H Sitte
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Thomas Stockner
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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12
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Abstract
Cell nutrition, detoxification, signalling, homeostasis and response to drugs, processes related to cell growth, differentiation and survival are all mediated by plasma membrane (PM) proteins called transporters. Despite their distinct fine structures, mechanism of function, energetic requirements, kinetics and substrate specificities, all transporters are characterized by a main hydrophobic body embedded in the PM as a series of tightly packed, often intertwined, α-helices that traverse the lipid bilayer in a zigzag mode, connected with intracellular or extracellular loops and hydrophilic N- and C-termini. Whereas longstanding genetic, biochemical and biophysical evidence suggests that specific transmembrane segments, and also their connecting loops, are responsible for substrate recognition and transport dynamics, emerging evidence also reveals the functional importance of transporter N- and C-termini, in respect to transport catalysis, substrate specificity, subcellular expression, stability and signalling. This review highlights selected prototypic examples of transporters in which their termini play important roles in their functioning.
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Affiliation(s)
- Emmanuel Mikros
- Faculty of Pharmacy, National and Kapodistrian University of Athens, Panepistimioupolis, 15771 Athens, Greece
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, 15781 Athens, Greece
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13
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Yu Y, de Campos RPS, Hong S, Krastev DL, Sadanand S, Leung Y, Wheeler AR. A microfluidic platform for continuous monitoring of dopamine homeostasis in dopaminergic cells. MICROSYSTEMS & NANOENGINEERING 2019; 5:10. [PMID: 31057937 PMCID: PMC6409360 DOI: 10.1038/s41378-019-0049-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 01/08/2019] [Accepted: 01/10/2019] [Indexed: 05/24/2023]
Abstract
Homeostasis of dopamine, a classical neurotransmitter, is a key indicator of neuronal health. Dysfunction in the regulation of dopamine is implicated in a long list of neurological disorders, including addiction, depression, and neurodegeneration. The existing methods used to evaluate dopamine homeostasis in vitro are inconvenient and do not allow for continuous non-destructive measurement. In response to this challenge, we introduce an integrated microfluidic system that combines dopaminergic cell culture and differentiation with electroanalytical measurements of extracellular dopamine in real-time at any point during an assay. We used the system to examine the behavior of differentiated SH-SY5Y cells upon exposure to four dopamine transporter ant/agonists (cocaine, ketamine, epigallocatechin gallate, and amphetamine) and study their pharmacokinetics. The IC50 values of cocaine, ketamine, and epigallocatechin gallate were determined to be (average ± standard deviation) 3.7 ± 1.1 µM, 51.4 ± 17.9 µM, and 2.6 ± 0.8 µM, respectively. Furthermore, we used the new system to study amphetamine-mediated dopamine release to probe the related phenomena of dopamine transporter-mediated reverse-transport and dopamine release from vesicles. We propose that this platform, which is the first platform to simultaneously evaluate uptake and release, could be useful to screen for drugs and other agents that target dopaminergic neurons and the function of the dopamine transporter. More broadly, this platform should be adaptable for any application that could benefit from high-temporal resolution electroanalysis combined with multi-day cell culture using small numbers of cells.
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Affiliation(s)
- Yue Yu
- Institute for Biomaterials and Biomedical Engineering, University of Toronto, 164 College St, Toronto, ON M5s 3G9 Canada
- Donnelly Centre for Cellular and Biomolecular Research, 160 College St., Toronto, ON M5S 3E1 Canada
| | - Richard P. S. de Campos
- Donnelly Centre for Cellular and Biomolecular Research, 160 College St., Toronto, ON M5S 3E1 Canada
- Department of Chemistry, University of Toronto, 80 St George St., Toronto, ON M5S 3H6 Canada
| | - Seolim Hong
- Department of Human Biology, University of Toronto, 300 Huron Street, Toronto, ON M5S 3J6 Canada
| | - Dimitar L. Krastev
- Donnelly Centre for Cellular and Biomolecular Research, 160 College St., Toronto, ON M5S 3E1 Canada
- Department of Human Biology, University of Toronto, 300 Huron Street, Toronto, ON M5S 3J6 Canada
| | - Siddharth Sadanand
- Donnelly Centre for Cellular and Biomolecular Research, 160 College St., Toronto, ON M5S 3E1 Canada
| | - Yen Leung
- Donnelly Centre for Cellular and Biomolecular Research, 160 College St., Toronto, ON M5S 3E1 Canada
| | - Aaron R. Wheeler
- Institute for Biomaterials and Biomedical Engineering, University of Toronto, 164 College St, Toronto, ON M5s 3G9 Canada
- Donnelly Centre for Cellular and Biomolecular Research, 160 College St., Toronto, ON M5S 3E1 Canada
- Department of Chemistry, University of Toronto, 80 St George St., Toronto, ON M5S 3H6 Canada
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14
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Das AK, Kudlacek O, Baumgart F, Jaentsch K, Stockner T, Sitte HH, Schütz GJ. Dopamine transporter forms stable dimers in the live cell plasma membrane in a phosphatidylinositol 4,5-bisphosphate-independent manner. J Biol Chem 2019; 294:5632-5642. [PMID: 30705091 PMCID: PMC6462504 DOI: 10.1074/jbc.ra118.006178] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 01/28/2019] [Indexed: 01/01/2023] Open
Abstract
The human dopamine transporter (hDAT) regulates the level of the neurotransmitter dopamine (DA) in the synaptic cleft and recycles DA for storage in the presynaptic vesicular pool. Many neurotransmitter transporters exist as oligomers, but the physiological role of oligomerization remains unclear; for example, it has been speculated to be a prerequisite for amphetamine-induced release and protein trafficking. Previous studies point to an oligomeric quaternary structure of hDAT; however, the exact stoichiometry and the fraction of co-existing oligomeric states are not known. Here, we used single-molecule brightness analysis to quantify the degree of oligomerization of heterologously expressed hDAT fused to monomeric GFP (mGFP–hDAT) in Chinese hamster ovary (CHO) cells. We observed that monomers and dimers of mGFP–hDAT co-exist and that higher-order molecular complexes of mGFP–hDAT are absent at the plasma membrane. The mGFP–hDAT dimers were stable over several minutes, and the fraction of dimers was independent of the mGFP–hDAT surface density. Furthermore, neither oxidation nor depletion of cholesterol had any effect on the fraction of dimers. Unlike for the human serotonin transporter (hSERT), in which direct binding of phosphatidylinositol 4,5-bisphosphate (PIP2) stabilized the oligomers, the stability of mGFP–hDAT dimers was PIP2 independent.
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Affiliation(s)
- Anand Kant Das
- From the Institute of Applied Physics, TU Wien, Getreidemarkt 9, A-1060, Vienna and
| | - Oliver Kudlacek
- the Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University Vienna, Waehringerstrasse 13a, A-1090 Vienna, Austria
| | - Florian Baumgart
- From the Institute of Applied Physics, TU Wien, Getreidemarkt 9, A-1060, Vienna and
| | - Kathrin Jaentsch
- the Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University Vienna, Waehringerstrasse 13a, A-1090 Vienna, Austria
| | - Thomas Stockner
- the Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University Vienna, Waehringerstrasse 13a, A-1090 Vienna, Austria
| | - Harald H Sitte
- the Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University Vienna, Waehringerstrasse 13a, A-1090 Vienna, Austria
| | - Gerhard J Schütz
- From the Institute of Applied Physics, TU Wien, Getreidemarkt 9, A-1060, Vienna and
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15
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Thal LB, Tomlinson ID, Quinlan MA, Kovtun O, Blakely RD, Rosenthal SJ. Single Quantum Dot Imaging Reveals PKCβ-Dependent Alterations in Membrane Diffusion and Clustering of an Attention-Deficit Hyperactivity Disorder/Autism/Bipolar Disorder-Associated Dopamine Transporter Variant. ACS Chem Neurosci 2019; 10:460-471. [PMID: 30153408 PMCID: PMC6411462 DOI: 10.1021/acschemneuro.8b00350] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The dopamine transporter (DAT) is a transmembrane protein that terminates dopamine signaling in the brain by driving rapid dopamine reuptake into presynaptic nerve terminals. Several lines of evidence indicate that DAT dysfunction is linked to neuropsychiatric disorders such as attention-deficit/hyperactivity disorder (ADHD), bipolar disorder (BPD), and autism spectrum disorder (ASD). Indeed, individuals with these disorders have been found to express the rare, functional DAT coding variant Val559, which confers anomalous dopamine efflux (ADE) in vitro and in vivo. To elucidate the impact of the DAT Val559 variant on membrane diffusion dynamics, we implemented our antagonist-conjugated quantum dot (QD) labeling approach to monitor the lateral mobility of single particle-labeled transporters in transfected HEK-293 and SK-N-MC cells. Our results demonstrate significantly higher diffusion coefficients of DAT Val559 compared to those of DAT Ala559, effects likely determined by elevated N-terminal transporter phosphorylation. We also provide pharmacological evidence that PKCβ-mediated signaling supports enhanced DAT Val559 membrane diffusion rates. Additionally, our results are complimented with diffusion rates of phosphomimicked and phosphorylation-occluded DAT variants. Furthermore, we show DAT Val559 has a lower propensity for membrane clustering, which may be caused by a mutation-derived shift out of membrane microdomains leading to faster lateral membrane diffusion rates. These findings further demonstrate a functional impact of DAT Val559 and suggest that changes in transporter localization and lateral mobility may sustain ADE and contribute to alterations in dopamine signaling underlying multiple neuropsychiatric disorders.
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16
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Jayaraman K, Morley AN, Szöllősi D, Wassenaar TA, Sitte HH, Stockner T. Dopamine transporter oligomerization involves the scaffold domain, but spares the bundle domain. PLoS Comput Biol 2018; 14:e1006229. [PMID: 29874235 PMCID: PMC6005636 DOI: 10.1371/journal.pcbi.1006229] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 06/18/2018] [Accepted: 05/24/2018] [Indexed: 12/11/2022] Open
Abstract
The human dopamine transporter (hDAT) is located on presynaptic neurons, where it plays an essential role in limiting dopaminergic signaling by temporarily curtailing high neurotransmitter concentration through rapid re-uptake. Transport by hDAT is energized by transmembrane ionic gradients. Dysfunction of this transporter leads to disease states, such as Parkinson’s disease, bipolar disorder or depression. It has been shown that hDAT and other members of the monoamine transporter family exist in oligomeric forms at the plasma membrane. Several residues are known to be involved in oligomerization, but interaction interfaces, oligomer orientation and the quarternary arrangement in the plasma membrane remain poorly understood. Here we examine oligomeric forms of hDAT using a direct approach, by following dimerization of two randomly-oriented hDAT transporters in 512 independent simulations, each being 2 μs in length. We employed the DAFT (docking assay for transmembrane components) approach, which is an unbiased molecular dynamics simulation method to identify oligomers, their conformations and populations. The overall ensemble of a total of >1 ms simulation time revealed a limited number of symmetric and asymmetric dimers. The identified dimer interfaces include all residues known to be involved in dimerization. Importantly, we find that the surface of the bundle domain is largely excluded from engaging in dimeric interfaces. Such an interaction would typically lead to inhibition by stabilization of one conformation, while substrate transport relies on a large scale rotation between the inward-facing and the outward-facing state. The human dopamine transporter efficiently removes the neurotransmitter dopamine from the synaptic cleft. Alteration of dopamine transporter function is associated with several neurological diseases, including mood disorders or attention-deficit hyperactivity disorder, but is also a major player in addiction and drug abuse. Functional studies have revealed that not only is transporter oligomerization involved in surface expression and endocytosis, but, more importantly, in reverse transport (efflux) of dopamine that is triggered by amphetamine-like drugs of abuse. Structural knowledge of transporter oligomerization is largely missing. We performed a large scale comprehensive computational study on transporter oligomerization to reveal dimer geometries and the residues involved in the interfaces. The dimer conformations we find in our dataset are fully consistent with all available experimental data in the literature, but also show novel interfaces. We further verified all dimer geometries by free energy calculations. Our results identified an unpredicted—but for the mechanism of substrate transport essential—property: the bundle domain, which moves during the transport cycle, is excluded from contributing to dimer interfaces, thereby allowing for unrestrained movements necessary to translocate substrates through the membrane.
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Affiliation(s)
- Kumaresan Jayaraman
- Medical University of Vienna Center for Physiology and Pharmacology, Institute of Pharmacology, Vienna, Austria
| | - Alex N. Morley
- Medical University of Vienna Center for Physiology and Pharmacology, Institute of Pharmacology, Vienna, Austria
| | - Daniel Szöllősi
- Medical University of Vienna Center for Physiology and Pharmacology, Institute of Pharmacology, Vienna, Austria
| | - Tsjerk A. Wassenaar
- Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands
| | - Harald H. Sitte
- Medical University of Vienna Center for Physiology and Pharmacology, Institute of Pharmacology, Vienna, Austria
| | - Thomas Stockner
- Medical University of Vienna Center for Physiology and Pharmacology, Institute of Pharmacology, Vienna, Austria
- * E-mail:
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17
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Sorkina T, Ma S, Larsen MB, Watkins SC, Sorkin A. Small molecule induced oligomerization, clustering and clathrin-independent endocytosis of the dopamine transporter. eLife 2018; 7:32293. [PMID: 29630493 PMCID: PMC5896956 DOI: 10.7554/elife.32293] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 03/22/2018] [Indexed: 12/14/2022] Open
Abstract
Clathrin-independent endocytosis (CIE) mediates internalization of many transmembrane proteins but the mechanisms of cargo recruitment during CIE are poorly understood. We found that the cell-permeable furopyrimidine AIM-100 promotes dramatic oligomerization, clustering and CIE of human and mouse dopamine transporters (DAT), but not of their close homologues, norepinephrine and serotonin transporters. All effects of AIM-100 on DAT and the occupancy of substrate binding sites in the transporter were mutually exclusive, suggesting that AIM-100 may act by binding to DAT. Surprisingly, AIM-100-induced DAT endocytosis was independent of dynamin, cholesterol-rich microdomains and actin cytoskeleton, implying that a novel endocytic mechanism is involved. AIM-100 stimulated trafficking of internalized DAT was also unusual: DAT accumulated in early endosomes without significant recycling or degradation. We propose that AIM-100 augments DAT oligomerization through an allosteric mechanism associated with the DAT conformational state, and that oligomerization-triggered clustering leads to a coat-independent endocytosis and subsequent endosomal retention of DAT.
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Affiliation(s)
- Tatiana Sorkina
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Shiqi Ma
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Mads Breum Larsen
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
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18
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Dimer Interface of the Human Serotonin Transporter and Effect of the Membrane Composition. Sci Rep 2018; 8:5080. [PMID: 29572541 PMCID: PMC5865177 DOI: 10.1038/s41598-018-22912-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 03/02/2018] [Indexed: 12/11/2022] Open
Abstract
The oligomeric state of membrane proteins has recently emerged in many cases as having an effect on their function. However, the intrinsic dynamics of their spatial organization in cells and model systems makes it challenging to characterize. Here we use molecular dynamics (MD) simulations at multiple resolutions to determine the dimer conformation of the human serotonin transporter (hSERT). From self-assembly simulations we predict dimer candidates and subsequently quantify their relative strength. We use umbrella sampling (US) replica exchange MD simulations for which we present extensive analysis of their efficiency and improved sampling compared to regular US MD simulations. The data shows that the most stable hSERT dimer interface is symmetrical and involves transmembrane helix 12 (TM12), similar to the crystal structure of the bacterial homologue LeuT, but with a slightly different orientation. We also describe the supramolecular organization of hSERT from a 250 μs self-assembly simulation. Finally, the effects of the presence of phosphatidylinositol bisphosphate or cholesterol in the membrane model has been quantified for the TM12-TM12 predicted interface. Collectively, the presented data bring new insight to the area of protein and lipid interplay in biological membranes.
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19
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Zhen J, Reith MEA. Functional properties of dopamine transporter oligomers after copper linking. J Neurochem 2017; 144:162-171. [PMID: 29168892 DOI: 10.1111/jnc.14259] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2017] [Revised: 10/29/2017] [Accepted: 11/02/2017] [Indexed: 12/13/2022]
Abstract
Although it is universally accepted that dopamine transporters (DATs) exist in monomers, dimers and tetramers (i.e. dimers of dimers), it is not known whether the oligomeric organization of DAT is a prerequisite for its ability to take up dopamine (DA), or whether each DAT protomer, the subunit of quaternary structure, functions independently in terms of DA translocation. In this study, copper phenanthroline (CuP) was used to selectively target surface DAT: increasing concentrations of CuP gradually cross-linked natural DAT dimers in LLC-PK1 cells stably expressing hDAT and thereby reduced DA uptake functionality until all surface DATs were inactivated. DATs that were not cross-linked by CuP showed normal DA uptake with DA Km at ~ 0.5 μM and DA efflux with basal and amphetamine-induced DA efflux as much as control values. The cocaine analog 2β-carbomethoxy-3β-[4-fluorophenyl]-tropane (CFT) was capable to bind to copper-cross-linked DATs, albeit with an affinity more than fivefold decreased (Kd of CFT = 109 nM after cross-linking vs 19 nM before). A kinetic analysis is offered describing the changing amounts of dimers and monomers with increasing [CuP], allowing the estimation of dimer functional activity compared with a DAT monomer. Consonant with previous conclusions for serotonin transporter and NET that only one protomer of an oligomer is active at the time, the present data indicated a functional activity of the DAT dimer of 0.74 relative to a monomer.
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Affiliation(s)
- Juan Zhen
- Department of Psychiatry, New York University School of Medicine, New York City, New York, USA
| | - Maarten E A Reith
- Department of Psychiatry, New York University School of Medicine, New York City, New York, USA.,Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York City, New York, USA
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20
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Karam CS, Javitch JA. Phosphorylation of the Amino Terminus of the Dopamine Transporter: Regulatory Mechanisms and Implications for Amphetamine Action. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2017; 82:205-234. [PMID: 29413521 DOI: 10.1016/bs.apha.2017.09.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Amphetamines (AMPHs) are potent psychostimulants that are widely used and abused, with profound medical and societal impact. Their actions at dopaminergic neurons are thought to mediate their therapeutic efficacy as well as their liability for abuse and dependence. AMPHs target the dopamine transporter (DAT), the plasmalemmal membrane protein that mediates the inactivation of released dopamine (DA) through its reuptake. AMPHs act as substrates for DAT and are known to cause mobilization of dopamine (DA) to the cell exterior via DAT-mediated reverse transport (efflux). It has become increasingly evident that the mechanisms that regulate AMPH-induced DA efflux are distinct from those that regulate DA uptake. Central to these mechanisms is the phosphorylation of the DAT amino (N)-terminus, which has been repeatedly demonstrated to facilitate DAT-mediated DA efflux, without impacting other aspects of DAT physiology. This review aims to summarize the current status of knowledge regarding DAT N-terminal phosphorylation and its regulation by protein modulators and the membrane microenvironment. A better understanding of these mechanisms may lead to the identification of novel therapeutic approaches that interfere selectively with the pharmacological effects of AMPHs without altering the physiological function of DAT.
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Affiliation(s)
- Caline S Karam
- College of Physicians & Surgeons, Columbia University, New York, NY, United States; Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY, United States
| | - Jonathan A Javitch
- College of Physicians & Surgeons, Columbia University, New York, NY, United States; Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY, United States.
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21
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Asjad HMM, Kasture A, El-Kasaby A, Sackel M, Hummel T, Freissmuth M, Sucic S. Pharmacochaperoning in a Drosophila model system rescues human dopamine transporter variants associated with infantile/juvenile parkinsonism. J Biol Chem 2017; 292:19250-19265. [PMID: 28972153 PMCID: PMC5702666 DOI: 10.1074/jbc.m117.797092] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 09/06/2017] [Indexed: 12/19/2022] Open
Abstract
Point mutations in the gene encoding the human dopamine transporter (hDAT, SLC6A3) cause a syndrome of infantile/juvenile dystonia and parkinsonism. To unravel the molecular mechanism underlying these disorders and investigate possible pharmacological therapies, here we examined 13 disease-causing DAT mutants that were retained in the endoplasmic reticulum when heterologously expressed in HEK293 cells. In three of these mutants, i.e. hDAT-V158F, hDAT-G327R, and hDAT-L368Q, the folding deficit was remedied with the pharmacochaperone noribogaine or the heat shock protein 70 (HSP70) inhibitor pifithrin-μ such that endoplasmic reticulum export of and radioligand binding and substrate uptake by these DAT mutants were restored. In Drosophila melanogaster, DAT deficiency results in reduced sleep. We therefore exploited the power of targeted transgene expression of mutant hDAT in Drosophila to explore whether these hDAT mutants could also be pharmacologically rescued in an intact organism. Noribogaine or pifithrin-μ treatment supported hDAT delivery to the presynaptic terminals of dopaminergic neurons and restored sleep to normal length in DAT-deficient (fumin) Drosophila lines expressing hDAT-V158F or hDAT-G327R. In contrast, expression of hDAT-L368Q in the Drosophila DAT mutant background caused developmental lethality, indicating a toxic action not remedied by pharmacochaperoning. Our observations identified those mutations most likely amenable to pharmacological rescue in the affected children. In addition, our findings also highlight the challenges of translating insights from pharmacochaperoning in cell culture to the clinical situation. Because of the evolutionary conservation in dopaminergic neurotransmission between Drosophila and people, pharmacochaperoning of DAT in D. melanogaster may allow us to bridge that gap.
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Affiliation(s)
- H M Mazhar Asjad
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Ameya Kasture
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Ali El-Kasaby
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Michael Sackel
- the Department of Neurobiology, University of Vienna, A-1090 Vienna, Austria
| | - Thomas Hummel
- the Department of Neurobiology, University of Vienna, A-1090 Vienna, Austria
| | - Michael Freissmuth
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Sonja Sucic
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
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22
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Karam CS, Sen N, Javitch JA. Phospho-specific antibodies targeting the amino terminus of the human dopamine transporter. J Chem Neuroanat 2017; 83-84:91-98. [PMID: 28571709 DOI: 10.1016/j.jchemneu.2017.05.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 05/11/2017] [Indexed: 11/29/2022]
Abstract
The dopamine transporter (DAT), which mediates the inactivation of released dopamine through its reuptake, is the primary molecular target for the actions of psychostimulants. An increasing number of studies support an essential role for phosphorylation of serines (Ser) in the distal amino (N) terminus of DAT in regulating its function. Still, the molecular details of the regulation of phosphorylation and its impact on function are not fully understood. To address this, we have developed and characterized two distinct phospho-antibodies that recognize human DAT when it is phosphorylated at Ser7 or Ser12. Our data show that treatment of cells with phorbol 12-myristate 13-acetate (PMA), amphetamine (AMPH) or okadaic acid (OA) leads to an increase in the phosphorylation of DAT at both residues and that these responses are dependent on the activity of protein kinase C. We also show that AMPH-induced and OA-induced phosphorylation of DAT are dependent on Ca2+/calmodulin-dependent protein kinase α. Our data further suggest that the lipid raft localization of DAT is necessary for efficient N-terminal phosphorylation and for the associated behavioral effects of AMPH, demonstrating the potential of these novel antibodies as powerful tools to study DAT regulation and function in vivo.
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Affiliation(s)
- Caline S Karam
- Department of Psychiatry, College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA; Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Namita Sen
- Department of Psychiatry, College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA; Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Jonathan A Javitch
- Department of Psychiatry, College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA; Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY 10032, USA; Department of Pharmacology, College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA.
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23
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Current understanding of methamphetamine-associated dopaminergic neurodegeneration and psychotoxic behaviors. Arch Pharm Res 2017; 40:403-428. [DOI: 10.1007/s12272-017-0897-y] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 12/02/2016] [Indexed: 12/21/2022]
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24
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Gur M, Cheng MH, Zomot E, Bahar I. Effect of Dimerization on the Dynamics of Neurotransmitter:Sodium Symporters. J Phys Chem B 2017; 121:3657-3666. [PMID: 28118712 PMCID: PMC5402697 DOI: 10.1021/acs.jpcb.6b09876] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
![]()
Dimerization
is a common feature among the members of the neurotransmitter:sodium
symporter (NSS) family of membrane proteins. Yet, the effect of dimerization
on the mechanism of action of NSS members is not fully understood.
In this study, we examined the collective dynamics of two members
of the family, leucine transporter (LeuT) and dopamine transporter
(DAT), to assess the significance of dimerization in modulating the
functional motions of the monomers. We used to this aim the anisotropic
network model (ANM), an efficient and robust method for modeling the
intrinsic motions of proteins and their complexes. Transporters belonging
to the NSS family are known to alternate between outward-facing (OF)
and inward-facing (IF) states, which enables the uptake and release
of their substrate (neurotransmitter) respectively, as the substrate
is transported from the exterior to the interior of the cell. In both
LeuT and DAT, dimerization is found to alter the collective motions
intrinsically accessible to the individual monomers in favor of the
functional transitions (OF ↔ IF), suggesting
that dimerization may play a role in facilitating transport.
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Affiliation(s)
- Mert Gur
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States.,Department of Mechanical Engineering, Istanbul Technical University (ITU) , Istanbul 34437, Turkey
| | - Mary Hongying Cheng
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Elia Zomot
- Department of Biomolecular Sciences, Weizmann Institute of Science , Rehovot 7610001, Israel
| | - Ivet Bahar
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
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25
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Membrane potential shapes regulation of dopamine transporter trafficking at the plasma membrane. Nat Commun 2016; 7:10423. [PMID: 26804245 PMCID: PMC4737753 DOI: 10.1038/ncomms10423] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 12/09/2015] [Indexed: 12/17/2022] Open
Abstract
The dopaminergic system is essential for cognitive processes, including reward, attention and motor control. In addition to DA release and availability of synaptic DA receptors, timing and magnitude of DA neurotransmission depend on extracellular DA-level regulation by the dopamine transporter (DAT), the membrane expression and trafficking of which are highly dynamic. Data presented here from real-time TIRF (TIRFM) and confocal microscopy coupled with surface biotinylation and electrophysiology suggest that changes in the membrane potential alone, a universal yet dynamic cellular property, rapidly alter trafficking of DAT to and from the surface membrane. Broadly, these findings suggest that cell-surface DAT levels are sensitive to membrane potential changes, which can rapidly drive DAT internalization from and insertion into the cell membrane, thus having an impact on the capacity for DAT to regulate extracellular DA levels. The dopaminergic system has important roles in a number of cognitive process. Here, the authors use detailed analysis of dopamine transporter trafficking to show its levels at the cell surface are sensitive to changes in membrane potential.
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Verma V. Classic Studies on the Interaction of Cocaine and the Dopamine Transporter. CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE 2015; 13:227-38. [PMID: 26598579 PMCID: PMC4662164 DOI: 10.9758/cpn.2015.13.3.227] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 05/29/2015] [Accepted: 06/05/2015] [Indexed: 11/18/2022]
Abstract
The dopamine transporter is responsible for recycling dopamine after release. Inhibitors of the dopamine transporter, such as cocaine, will stop the reuptake of dopamine and allow it to stay extracellularly, causing prominent changes at the molecular, cellular, and behavioral levels. There is much left to be known about the mechanism and site(s) of binding, as well as the effect that cocaine administration does to dopamine transporter-cocaine binding sites and gene expression which also plays a strong role in cocaine abusers and their behavioral characteristics. Thus, if more light is shed on the dopamine transporter-cocaine interaction, treatments for addiction and even other diseases of the dopaminergic system may not be too far ahead. As today's ongoing research expands on the shoulders of classic research done in the 1990s and 2000s, the foundation of core research done in that time period will be reviewed, which forms the basis of today's work and tomorrow's therapies.
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Affiliation(s)
- Vivek Verma
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA
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27
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Martzoukou O, Karachaliou M, Yalelis V, Leung J, Byrne B, Amillis S, Diallinas G. Oligomerization of the UapA Purine Transporter Is Critical for ER-Exit, Plasma Membrane Localization and Turnover. J Mol Biol 2015; 427:2679-96. [DOI: 10.1016/j.jmb.2015.05.021] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Revised: 05/27/2015] [Accepted: 05/28/2015] [Indexed: 11/29/2022]
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Fischer J, Kleinau G, Müller A, Kühnen P, Zwanziger D, Kinne A, Rehders M, Moeller LC, Führer D, Grüters A, Krude H, Brix K, Biebermann H. Modulation of monocarboxylate transporter 8 oligomerization by specific pathogenic mutations. J Mol Endocrinol 2015; 54:39-50. [PMID: 25527620 DOI: 10.1530/jme-14-0272] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The monocarboxylate transporter 8 (MCT8) is a member of the major facilitator superfamily (MFS). These membrane-spanning proteins facilitate translocation of a variety of substrates, MCT8 specifically transports iodothyronines. Mutations in MCT8 are the underlying cause of severe X-linked psychomotor retardation. At the molecular level, such mutations led to deficiencies in substrate translocation due to reduced cell-surface expression, impaired substrate binding, or decreased substrate translocation capabilities. However, the causal relationships between genotypes, molecular features of mutated MCT8, and patient characteristics have not yet been comprehensively deciphered. We investigated the relationship between pathogenic mutants of MCT8 and their capacity to form dimers (presumably oligomeric structures) as a potential regulatory parameter of the transport function of MCT8. Fourteen pathogenic variants of MCT8 were investigated in vitro with respect to their capacity to form oligomers. Particular mutations close to the substrate translocation channel (S194F, A224T, L434W, and R445C) were found to inhibit dimerization of MCT8. This finding is in contrast to those for other transporters or transmembrane proteins, in which substitutions predominantly at the outer-surface inhibit oligomerization. Moreover, specific mutations of MCT8 located in transmembrane helix 2 (del230F, V235M, and ins236V) increased the capacity of MCT8 variants to dimerize. We analyzed the localization of MCT8 dimers in a cellular context, demonstrating differences in MCT8 dimer formation and distribution. In summary, our results add a new link between the functions (substrate transport) and protein organization (dimerization) of MCT8, and might be of relevance for other members of the MFS. Finally, the findings are discussed in relationship to functional data combined with structural-mechanistical insights into MCT8.
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Affiliation(s)
- Jana Fischer
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Gunnar Kleinau
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Anne Müller
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Peter Kühnen
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Denise Zwanziger
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Anita Kinne
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Maren Rehders
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Lars C Moeller
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Dagmar Führer
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Annette Grüters
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Heiko Krude
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Klaudia Brix
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Heike Biebermann
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
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29
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Zhen J, Antonio T, Cheng SY, Ali S, Jones KT, Reith MEA. Dopamine transporter oligomerization: impact of combining protomers with differential cocaine analog binding affinities. J Neurochem 2015; 133:167-73. [PMID: 25580950 DOI: 10.1111/jnc.13025] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 11/17/2014] [Accepted: 12/16/2014] [Indexed: 11/29/2022]
Abstract
Previous studies point to quaternary assembly of dopamine transporters (DATs) in oligomers. However, it is not clear whether the protomers function independently in the oligomer. Is each protomer an entirely separate unit that takes up dopamine and is inhibited by drugs known to block DAT function? In this work, human embryonic kidney 293 cells were co-transfected with DAT constructs possessing differential binding affinities for the phenyltropane cocaine analog, [³H]WIN35,428. It was assessed whether the binding properties in co-expressing cells capable of forming hetero-oligomers differ from those in preparations obtained from mixed singly transfected cells where such oligomers cannot occur. A method is described that replaces laborious 'mixing' experiments with an in silico method predicting binding parameters from those observed for the singly expressed constructs. Among five pairs of constructs tested, statistically significant interactions were found between protomers of wild-type (WT) and D313N, WT and D345N, and WT and D436N. Compared with predicted Kd values of [³H]WIN35,428 binding to the non-interacting pairs, the observed affinity of the former pair was increased 1.7 fold while the latter two were reduced 2.2 and 4.1 fold, respectively. This is the first report of an influence of protomer composition on the properties of a DAT inhibitor, indicating cooperativity within the oligomer. The dopamine transporter (DAT) can exist as an oligomer but it is unknown whether the protomers function independently. The present results indicate that protomers that are superpotent or deficient in cocaine analog binding can confer enhanced or reduced potency to the oligomer, respectively. In this respect, positive or negative cooperativity is revealed in the DAT oligomer.
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Affiliation(s)
- Juan Zhen
- Department of Psychiatry, New York University School of Medicine, New York, New York, USA
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30
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Braren SH, Drapala D, Tulloch IK, Serrano PA. Methamphetamine-induced short-term increase and long-term decrease in spatial working memory affects protein Kinase M zeta (PKMζ), dopamine, and glutamate receptors. Front Behav Neurosci 2014; 8:438. [PMID: 25566006 PMCID: PMC4270177 DOI: 10.3389/fnbeh.2014.00438] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 12/02/2014] [Indexed: 12/22/2022] Open
Abstract
Methamphetamine (MA) is a toxic, addictive drug shown to modulate learning and memory, yet the neural mechanisms are not fully understood. We investigated the effects of 2 weekly injections of MA (30 mg/kg) on working memory using the radial 8-arm maze (RAM) across 5 weeks in adolescent-age mice. MA-treated mice show a significant improvement in working memory performance 1 week following the first MA injection compared to saline-injected controls. Following 5 weeks of MA abstinence mice were re-trained on a reference and working memory version of the RAM to assess cognitive flexibility. MA-treated mice show significantly more working memory errors without effects on reference memory performance. The hippocampus and dorsal striatum were assessed for expression of glutamate receptors subunits, GluA2 and GluN2B; dopamine markers, dopamine 1 receptor (D1), dopamine transporter (DAT) and tyrosine hydroxylase (TH); and memory markers, protein kinase M zeta (PKMζ) and protein kinase C zeta (PKCζ). Within the hippocampus, PKMζ and GluA2 are both significantly reduced after MA supporting the poor memory performance. Additionally, a significant increase in GluN2B and decrease in D1 identifies dysregulated synaptic function. In the striatum, MA treatment increased cytosolic DAT and TH levels associated with dopamine hyperfunction. MA treatment significantly reduced GluN2B while increasing both PKMζ and PKCζ within the striatum. We discuss the potential role of PKMζ/PKCζ in modulating dopamine and glutamate receptors after MA treatment. These results identify potential underlying mechanisms for working memory deficits induced by MA.
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Affiliation(s)
- Stephen H Braren
- Department of Psychology, Hunter College, City University of New York New York, NY, USA
| | - Damian Drapala
- Department of Psychology, Hunter College, City University of New York New York, NY, USA
| | - Ingrid K Tulloch
- Department of Psychology, Stevenson University Baltimore, MD, USA
| | - Peter A Serrano
- Department of Psychology, Hunter College, City University of New York New York, NY, USA ; Department of Psychology, The Graduate Center, City University of New York New York, NY, USA
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31
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Saha K, Sambo D, Richardson BD, Lin LM, Butler B, Villarroel L, Khoshbouei H. Intracellular methamphetamine prevents the dopamine-induced enhancement of neuronal firing. J Biol Chem 2014; 289:22246-57. [PMID: 24962577 DOI: 10.1074/jbc.m114.563056] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The dysregulation of the dopaminergic system is implicated in multiple neurological and neuropsychiatric disorders such as Parkinson disease and drug addiction. The primary target of psychostimulants such as amphetamine and methamphetamine is the dopamine transporter (DAT), the major regulator of extracellular dopamine levels in the brain. However, the behavioral and neurophysiological correlates of methamphetamine and amphetamine administration are unique from one another, thereby suggesting these two compounds impact dopaminergic neurotransmission differentially. We further examined the unique mechanisms by which amphetamine and methamphetamine regulate DAT function and dopamine neurotransmission; in the present study we examined the impact of extracellular and intracellular amphetamine and methamphetamine on the spontaneous firing of cultured midbrain dopaminergic neurons and isolated DAT-mediated current. In dopaminergic neurons the spontaneous firing rate was enhanced by extracellular application of amphetamine > dopamine > methamphetamine and was DAT-dependent. Amphetamine > methamphetamine similarly enhanced DAT-mediated inward current, which was sensitive to isosmotic substitution of Na(+) or Cl(-) ion. Although isosmotic substitution of extracellular Na(+) ions blocked amphetamine and methamphetamine-induced DAT-mediated inward current similarly, the removal of extracellular Cl(-) ions preferentially blocked amphetamine-induced inward current. The intracellular application of methamphetamine, but not amphetamine, prevented the dopamine-induced increase in the spontaneous firing of dopaminergic neurons and the corresponding DAT-mediated inward current. The results reveal a new mechanism for methamphetamine-induced dysregulation of dopaminergic neurons.
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Affiliation(s)
- Kaustuv Saha
- From the Department of Neuroscience and Department of Psychiatry, McKnight Brain Institute, University of Florida College of Medicine, Gainesville, Florida 32611
| | - Danielle Sambo
- From the Department of Neuroscience and Department of Psychiatry, McKnight Brain Institute, University of Florida College of Medicine, Gainesville, Florida 32611
| | - Ben D Richardson
- From the Department of Neuroscience and Department of Psychiatry, McKnight Brain Institute, University of Florida College of Medicine, Gainesville, Florida 32611
| | - Landon M Lin
- From the Department of Neuroscience and Department of Psychiatry, McKnight Brain Institute, University of Florida College of Medicine, Gainesville, Florida 32611
| | - Brittany Butler
- From the Department of Neuroscience and Department of Psychiatry, McKnight Brain Institute, University of Florida College of Medicine, Gainesville, Florida 32611
| | - Laura Villarroel
- From the Department of Neuroscience and Department of Psychiatry, McKnight Brain Institute, University of Florida College of Medicine, Gainesville, Florida 32611
| | - Habibeh Khoshbouei
- From the Department of Neuroscience and Department of Psychiatry, McKnight Brain Institute, University of Florida College of Medicine, Gainesville, Florida 32611
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32
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Vecchio LM, Bermejo MK, Beerepoot P, Ramsey AJ, Salahpour A. N-terminal tagging of the dopamine transporter impairs protein expression and trafficking in vivo. Mol Cell Neurosci 2014; 61:123-32. [PMID: 24886986 DOI: 10.1016/j.mcn.2014.05.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 05/22/2014] [Accepted: 05/29/2014] [Indexed: 01/26/2023] Open
Abstract
The dopamine transporter (DAT) is the primary protein responsible for the uptake of dopamine from the extracellular space back into presynaptic neurons. As such, it plays an important role in the cessation of dopaminergic neurotransmission and in the maintenance of extracellular dopamine homeostasis. Here, we report the development of a new BAC transgenic mouse line that expresses DAT with an N-terminal HA-epitope (HAD-Tg). In this line, two copies of the HA-DAT BAC are incorporated into the genome, increasing DAT mRNA levels by 47%. Despite the increase in mRNA levels, HAD-Tg mice show no significant increase in the level of DAT protein in the striatum, indicating a defect in protein trafficking or stability. By crossing HAD-Tg mice with DAT knockout mice (DAT-KO), we engineered mice that exclusively express HA-tagged DAT in the absence of endogenous DAT (DAT-KO/HAD-Tg). We show that DAT-KO/HAD-Tg mice express only 8.5% of WT DAT levels in the striatum. Importantly, the HA-tagged DAT that is present in DAT-KO/HAD-Tg mice is functional, as it is able to partially rescue the DAT-KO hyperactive phenotype. Finally, we provide evidence that the HA-tagged DAT is retained in the cell body based on a reduction in the striatum:midbrain protein ratio. These results demonstrate that the presence of the N-terminal tag leads to impaired DAT protein expression in vivo due in part to improper trafficking of the tagged transporter, and highlight the importance of the N-terminus in the transport of DAT to striatal terminals.
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Affiliation(s)
- Laura M Vecchio
- Department of Pharmacology, University of Toronto: Medical Sciences Building, Room 4302, 1 King's College Circle, Toronto, ON M5S 1A8, Canada.
| | - M Kristel Bermejo
- Department of Pharmacology, University of Toronto: Medical Sciences Building, Room 4302, 1 King's College Circle, Toronto, ON M5S 1A8, Canada.
| | - Pieter Beerepoot
- Department of Pharmacology, University of Toronto: Medical Sciences Building, Room 4302, 1 King's College Circle, Toronto, ON M5S 1A8, Canada.
| | - Amy J Ramsey
- Department of Pharmacology, University of Toronto: Medical Sciences Building, Room 4302, 1 King's College Circle, Toronto, ON M5S 1A8, Canada.
| | - Ali Salahpour
- Department of Pharmacology, University of Toronto: Medical Sciences Building, Room 4302, 1 King's College Circle, Toronto, ON M5S 1A8, Canada.
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33
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Anderluh A, Klotzsch E, Reismann AWAF, Brameshuber M, Kudlacek O, Newman AH, Sitte HH, Schütz GJ. Single molecule analysis reveals coexistence of stable serotonin transporter monomers and oligomers in the live cell plasma membrane. J Biol Chem 2014; 289:4387-94. [PMID: 24394416 DOI: 10.1074/jbc.m113.531632] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The human serotonin transporter (hSERT) is responsible for the termination of synaptic serotonergic signaling. Although there is solid evidence that SERT forms oligomeric complexes, the exact stoichiometry of the complexes and the fractions of different coexisting oligomeric states still remain enigmatic. Here we used single molecule fluorescence microscopy to obtain the oligomerization state of the SERT via brightness analysis of single diffraction-limited fluorescent spots. Heterologously expressed SERT was labeled either with the fluorescent inhibitor JHC 1-64 or via fusion to monomeric GFP. We found a variety of oligomerization states of membrane-associated transporters, revealing molecular associations larger than dimers and demonstrating the coexistence of different degrees of oligomerization in a single cell; the data are in agreement with a linear aggregation model. Furthermore, oligomerization was found to be independent of SERT surface density, and oligomers remained stable over several minutes in the live cell plasma membrane. Together, the results indicate kinetic trapping of preformed SERT oligomers at the plasma membrane.
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Affiliation(s)
- Andreas Anderluh
- From the Institute of Applied Physics, Vienna University of Technology, Getreidemarkt 9, A-1060 Vienna, Austria
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Gaffaney JD, Shetty M, Felts B, Pramod AB, Foster JD, Henry LK, Vaughan RA. Antagonist-induced conformational changes in dopamine transporter extracellular loop two involve residues in a potential salt bridge. Neurochem Int 2013; 73:16-26. [PMID: 24269640 DOI: 10.1016/j.neuint.2013.11.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 11/04/2013] [Accepted: 11/06/2013] [Indexed: 10/26/2022]
Abstract
Ligand-induced changes in the conformation of extracellular loop (EL) 2 in the rat (r) dopamine transporter (DAT) were examined using limited proteolysis with endoproteinase Asp-N and detection of cleavage products by epitope-specific immunoblotting. The principle N-terminal fragment produced by Asp-N was a 19kDa peptide likely derived by proteolysis of EL2 residue D174, which is present just past the extracellular end of TM3. Production of this fragment was significantly decreased by binding of cocaine and other uptake blockers, but was not affected by substrates or Zn(2+), indicating the presence of a conformational change at D174 that may be related to the mechanism of transport inhibition. DA transport activity and cocaine analog binding were decreased by Asp-N treatment, suggesting a requirement for EL2 integrity in these DAT functions. In a previous study we demonstrated that ligand-induced protease resistance also occurred at R218 on the C-terminal side of rDAT EL2. Here using substituted cysteine accessibility analysis of human (h) DAT we confirm cocaine-induced alterations in reactivity of the homologous R219 and identify conformational sensitivity of V221. Focused molecular modeling of D174 and R218 based on currently available Aquifex aeolicus leucine transporter crystal structures places these residues within 2.9Å of one another, suggesting their proximity as a structural basis for their similar conformational sensitivities and indicating their potential to form a salt bridge. These findings extend our understanding of DAT EL2 and its role in transport and binding functions.
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Affiliation(s)
- Jon D Gaffaney
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202, United States
| | - Madhur Shetty
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202, United States
| | - Bruce Felts
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202, United States
| | - Akula-Bala Pramod
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202, United States
| | - James D Foster
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202, United States
| | - L Keith Henry
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202, United States.
| | - Roxanne A Vaughan
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202, United States.
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35
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Temporal pattern of cocaine intake determines tolerance vs sensitization of cocaine effects at the dopamine transporter. Neuropsychopharmacology 2013; 38:2385-92. [PMID: 23719505 PMCID: PMC3799057 DOI: 10.1038/npp.2013.136] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 05/10/2013] [Accepted: 05/11/2013] [Indexed: 01/07/2023]
Abstract
The dopamine transporter (DAT) is responsible for terminating dopamine (DA) signaling and is the primary site of cocaine's reinforcing actions. Cocaine self-administration has been shown previously to result in changes in cocaine potency at the DAT. To determine whether the DAT changes associated with self-administration are due to differences in intake levels or temporal patterns of cocaine-induced DAT inhibition, we manipulated cocaine access to produce either continuous or intermittent elevations in cocaine brain levels. Long-access (LgA, 6 h) and short-access (ShA, 2 h) continuous self-administration produced similar temporal profiles of cocaine intake that were sustained throughout the session; however, LgA had greater intake. ShA and intermittent-access (IntA, 6 h) produced the same intake, but different temporal profiles, with 'spiking' brain levels in IntA compared with constant levels in ShA. IntA consisted of 5-min access periods alternating with 25-min timeouts, which resulted in bursts of high responding followed by periods of no responding. DA release and uptake, as well as the potency of cocaine for DAT inhibition, were assessed by voltammetry in the nucleus accumbens slices following control, IntA, ShA, and LgA self-administration. Continuous-access protocols (LgA and ShA) did not change DA parameters, but the 'spiking' protocol (IntA) increased both release and uptake of DA. In addition, high continuous intake (LgA) produced tolerance to cocaine, while 'spiking' (IntA) produced sensitization, relative to ShA and naive controls. Thus, intake and pattern can both influence cocaine potency, and tolerance seems to be produced by high intake, while sensitization is produced by intermittent temporal patterns of intake.
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36
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Lima de Souza EC, Groeneweg S, Visser WE, Peeters RP, Visser TJ. Importance of cysteine residues in the thyroid hormone transporter MCT8. Endocrinology 2013; 154:1948-55. [PMID: 23546606 DOI: 10.1210/en.2012-2101] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The thyroid hormone (TH) transporter monocarboxylate transporter 8 (MCT8) is crucial for brain development as demonstrated by the severe psychomotor retardation in patients with MCT8 mutations. MCT8 contains 10 residues of the reactive amino acid cysteine (Cys) whose functional roles were studied using the Cys-specific reagent p-chloromercurybenzenesulfonate (pCMBS) and by site-directed mutagenesis. Pretreatment of JEG3 cells with pCMBS resulted in a dose- and time-dependent decrease of subsequent T3 uptake. Pretreatment with dithiothreitol did not affect TH transport or its inhibition by pCMBS. However, pCMBS inhibition of MCT8 was reversed by dithiothreitol. Inhibition of MCT8 by pCMBS was prevented in the presence of T3. The single and double mutation of C481A and C497A did not affect T3 transport, but the single mutants were less sensitive and the double mutant was completely insensitive to pCMBS. Similar effects on MCT8 were obtained using HgCl2 instead of pCMBS. In conclusion, we have identified Cys481 and Cys497 in MCT8 as the residues modified by pCMBS or HgCl2. These residues are probably located at or near the substrate-recognition site in MCT8. It remains to be investigated whether MCT8 function is regulated by modification of these Cys residues under pathophysiological conditions.
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Affiliation(s)
- Elaine C Lima de Souza
- PhD, Department of Internal Medicine, Erasmus University Medical Center, BO Box 2040, 3000 CA Rotterdam, The Netherlands
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37
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North A, Swant J, Salvatore MF, Gamble-George J, Prins P, Butler B, Mittal MK, Heltsley R, Clark JT, Khoshbouei H. Chronic methamphetamine exposure produces a delayed, long-lasting memory deficit. Synapse 2013; 67:245-57. [PMID: 23280858 DOI: 10.1002/syn.21635] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 12/18/2012] [Indexed: 01/02/2023]
Abstract
Methamphetamine (METH) is a highly addictive and neurotoxic psychostimulant. Its use in humans is often associated with neurocognitive impairment. Whether this is due to long-term deficits in short-term memory and/or hippocampal plasticity remains unclear. Recently, we reported that METH increases baseline synaptic transmission and reduces LTP in an ex vivo preparation of the hippocampal CA1 region from young mice. In the current study, we tested the hypothesis that a repeated neurotoxic regimen of METH exposure in adolescent mice decreases hippocampal synaptic plasticity and produces a deficit in short-term memory. Contrary to our prediction, there was no change in the hippocampal plasticity or short-term memory when measured after 14 days of METH exposure. However, we found that at 7, 14, and 21 days of drug abstinence, METH-exposed mice exhibited a deficit in spatial memory, which was accompanied by a decrease in hippocampal plasticity. Our results support the interpretation that the deleterious cognitive consequences of neurotoxic levels of METH exposure may manifest and persist after drug abstinence. Therefore, therapeutic strategies should consider short-term as well as long-term consequences of methamphetamine exposure.
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Affiliation(s)
- Ashley North
- Department of Physiology, Meharry Medical College, Nashville, TN 37208, USA
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38
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Foroughmand AM, Galehdari H, Dastgerdi BT, Khatami SR, Haidari M. Lack of association between the G-660C polymorphism in the dopamine transporter gene (SLC6A3) and schizophrenia in the Iranian population. INDIAN JOURNAL OF HUMAN GENETICS 2012; 18:222-5. [PMID: 23162299 PMCID: PMC3491297 DOI: 10.4103/0971-6866.100773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND: Dopaminergenic system plays an essential role in the plasticity of the human brain. The dopamine transporter gene (SLC6A3) mediates active reuptake of dopamine from synapsis, terminates dopamine signals, and therefore, is implicated in a number of dopamine-related disorders like psychosis. Variations in the form of single nucleotide polymorphisms in the core promoter of the SLC6A3 gene are reported to be involved in the pathogenesis of schizophrenia. In this study, we also attempted to establish the possible role of the polymorphism G-660C in the SLC6A3 gene promoter in schizophrenia in a case-control study. MATERIALS AND METHODS: The allele and genotype frequency were analyzed in an Iranian cohort of 200 unrelated patients and 200 controls using polymerase chain reaction and restriction fragment length polymorphism. RESULTS: The genotype frequency for case and control groups was GG 100%, GC 0%, CC 0%, and GG 100%, GC 0%, CC 0%, respectively. The C allele was failed in both groups. CONCLUSION: Our data suggest clearly that there is no association between the -660G/C polymorphism and outcome of schizophrenia in the Iranian population.
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Affiliation(s)
- Ali M Foroughmand
- Department of Genetics, Faculty of Sciences, Shahid Chamran University, Ahwaz, Iran
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39
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Sacan A, Ekins S, Kortagere S. Applications and limitations of in silico models in drug discovery. Methods Mol Biol 2012; 910:87-124. [PMID: 22821594 DOI: 10.1007/978-1-61779-965-5_6] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Drug discovery in the late twentieth and early twenty-first century has witnessed a myriad of changes that were adopted to predict whether a compound is likely to be successful, or conversely enable identification of molecules with liabilities as early as possible. These changes include integration of in silico strategies for lead design and optimization that perform complementary roles to that of the traditional in vitro and in vivo approaches. The in silico models are facilitated by the availability of large datasets associated with high-throughput screening, bioinformatics algorithms to mine and annotate the data from a target perspective, and chemoinformatics methods to integrate chemistry methods into lead design process. This chapter highlights the applications of some of these methods and their limitations. We hope this serves as an introduction to in silico drug discovery.
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Affiliation(s)
- Ahmet Sacan
- School of Biomedical Engineering, Drexel University, Philadelphia, PA, USA
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40
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Abstract
AbstractThe development of effective therapeutic interventions for neurodegeneration requires a better understanding of the early events that precede neuronal loss. Recent work in various disease models has begun to emphasize the significance of presynaptic dysfunction as an early event that occurs before manifestation of neurological disorders. Dysregulation of dopamine (DA) homeostasis is implicated in neurodegenerative diseases, drug addiction, and neuropsychiatric disorders. The neuronal plasma membrane dopamine transporter (DAT) is essential for the maintenance of DA homeostasis in the brain. α-synuclein is a 140-amino acid protein that forms a stable complex with DAT and is linked to the pathogenesis of neurodegenerative disease. In this review we will examine the prevailing hypotheses for α-synuclein-regulation of DAT biology.
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Velours J, Stines-Chaumeil C, Habersetzer J, Chaignepain S, Dautant A, Brèthes D. Evidence of the proximity of ATP synthase subunits 6 (a) in the inner mitochondrial membrane and in the supramolecular forms of Saccharomyces cerevisiae ATP synthase. J Biol Chem 2011; 286:35477-35484. [PMID: 21868388 DOI: 10.1074/jbc.m111.275776] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The involvement of subunit 6 (a) in the interface between yeast ATP synthase monomers has been highlighted. Based on the formation of a disulfide bond and using the unique cysteine 23 as target, we show that two subunits 6 are close in the inner mitochondrial membrane and in the solubilized supramolecular forms of the yeast ATP synthase. In a null mutant devoid of supernumerary subunits e and g that are involved in the stabilization of ATP synthase dimers, ATP synthase monomers are close enough in the inner mitochondrial membrane to make a disulfide bridge between their subunits 6, and this proximity is maintained in detergent extract containing this enzyme. The cross-linking of cysteine 23 located in the N-terminal part of the first transmembrane helix of subunit 6 suggests that this membrane-spanning segment is in contact with its counterpart belonging to the ATP synthase monomer that faces it and participates in the monomer-monomer interface.
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Affiliation(s)
- Jean Velours
- CNRS, Institut de Biochimie et Génétique Cellulaires, UMR 5095; Université de Bordeaux, UMR 5095, 1 Rue Camille Saint Saëns, 33077 Bordeaux Cedex.
| | - Claire Stines-Chaumeil
- CNRS, Institut de Biochimie et Génétique Cellulaires, UMR 5095; Université de Bordeaux, UMR 5095, 1 Rue Camille Saint Saëns, 33077 Bordeaux Cedex
| | - Johan Habersetzer
- CNRS, Institut de Biochimie et Génétique Cellulaires, UMR 5095; Université de Bordeaux, UMR 5095, 1 Rue Camille Saint Saëns, 33077 Bordeaux Cedex
| | - Stéphane Chaignepain
- CNRS, Institut de Biochimie et Génétique Cellulaires, UMR 5095; Université de Bordeaux, UMR 5095, 1 Rue Camille Saint Saëns, 33077 Bordeaux Cedex; CNRS, Chimie et Biologie des Membranes et des Nanoobjets, UMR 5248, Allée de Saint Hilaire, Bât B14, 33600 Pessac, France
| | - Alain Dautant
- CNRS, Institut de Biochimie et Génétique Cellulaires, UMR 5095; Université de Bordeaux, UMR 5095, 1 Rue Camille Saint Saëns, 33077 Bordeaux Cedex
| | - Daniel Brèthes
- CNRS, Institut de Biochimie et Génétique Cellulaires, UMR 5095; Université de Bordeaux, UMR 5095, 1 Rue Camille Saint Saëns, 33077 Bordeaux Cedex.
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42
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Sager JJ, Torres GE. Proteins interacting with monoamine transporters: current state and future challenges. Biochemistry 2011; 50:7295-310. [PMID: 21797260 DOI: 10.1021/bi200405c] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Plasma membrane and vesicular transporters for the biogenic amines, dopamine, norepinephrine, and serotonin, represent a group of proteins that play a crucial role in the regulation of neurotransmission. Clinically, mono amine transporters are the primary targets for the actions of many therapeutic agents used to treat mood disorders, as well as the site of action for highly addictive psychostimulants such as cocaine, amphetamine, methamphetamine, and 3,4-methylenedioxymethamphetamine. Over the past decade, the use of approaches such as yeast two-hybrid and proteomics has identified a multitude of transporter interacting proteins, suggesting that the function and regulation of these transporters are more complex than previously anticipated. With the increasing number of interacting proteins, the rules dictating transporter synthesis, assembly, targeting, trafficking, and function are beginning to be deciphered. Although many of these protein interactions have yet to be fully characterized, current knowledge is beginning to shed light on novel transporter mechanisms involved in monoamine homeostasis, the molecular actions of psychostimulants, and potential disease mechanisms. While future studies resolving the spatial and temporal resolution of these, and yet unknown, interactions will be needed, the realization that monoamine transporters do not work alone opens the path to a plethora of possible pharmacological interventions.
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Affiliation(s)
- Jonathan J Sager
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
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43
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Kristensen AS, Andersen J, Jørgensen TN, Sørensen L, Eriksen J, Loland CJ, Strømgaard K, Gether U. SLC6 neurotransmitter transporters: structure, function, and regulation. Pharmacol Rev 2011; 63:585-640. [PMID: 21752877 DOI: 10.1124/pr.108.000869] [Citation(s) in RCA: 591] [Impact Index Per Article: 45.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The neurotransmitter transporters (NTTs) belonging to the solute carrier 6 (SLC6) gene family (also referred to as the neurotransmitter-sodium-symporter family or Na(+)/Cl(-)-dependent transporters) comprise a group of nine sodium- and chloride-dependent plasma membrane transporters for the monoamine neurotransmitters serotonin (5-hydroxytryptamine), dopamine, and norepinephrine, and the amino acid neurotransmitters GABA and glycine. The SLC6 NTTs are widely expressed in the mammalian brain and play an essential role in regulating neurotransmitter signaling and homeostasis by mediating uptake of released neurotransmitters from the extracellular space into neurons and glial cells. The transporters are targets for a wide range of therapeutic drugs used in treatment of psychiatric diseases, including major depression, anxiety disorders, attention deficit hyperactivity disorder and epilepsy. Furthermore, psychostimulants such as cocaine and amphetamines have the SLC6 NTTs as primary targets. Beginning with the determination of a high-resolution structure of a prokaryotic homolog of the mammalian SLC6 transporters in 2005, the understanding of the molecular structure, function, and pharmacology of these proteins has advanced rapidly. Furthermore, intensive efforts have been directed toward understanding the molecular and cellular mechanisms involved in regulation of the activity of this important class of transporters, leading to new methodological developments and important insights. This review provides an update of these advances and their implications for the current understanding of the SLC6 NTTs.
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Affiliation(s)
- Anders S Kristensen
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Copenhagen, Denmark.
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44
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Johnston JM, Aburi M, Provasi D, Bortolato A, Urizar E, Lambert NA, Javitch JA, Filizola M. Making structural sense of dimerization interfaces of delta opioid receptor homodimers. Biochemistry 2011; 50:1682-90. [PMID: 21261298 PMCID: PMC3050604 DOI: 10.1021/bi101474v] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
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Opioid receptors, like other members of the G protein-coupled receptor (GPCR) family, have been shown to associate to form dimers and/or oligomers at the plasma membrane. Whether this association is stable or transient is not known. Recent compelling evidence suggests that at least some GPCRs rapidly associate and dissociate. We have recently calculated binding affinities from free energy estimates to predict transient association between mouse delta opioid receptor (DOR) protomers at a symmetric interface involving the fourth transmembrane (TM4) helix (herein termed “4” dimer). Here we present disulfide cross-linking experiments with DOR constructs with cysteines substituted at the extracellular ends of TM4 or TM5 that confirm the formation of DOR complexes involving these helices. Our results are consistent with the involvement of TM4 and/or TM5 at the DOR homodimer interface, but possibly with differing association propensities. Coarse-grained (CG) well-tempered metadynamics simulations of two different dimeric arrangements of DOR involving TM4 alone or with TM5 (herein termed “4/5” dimer) in an explicit lipid−water environment confirmed the presence of two structurally and energetically similar configurations of the 4 dimer, as previously assessed by umbrella sampling calculations, and revealed a single energetic minimum of the 4/5 dimer. Additional CG umbrella sampling simulations of the 4/5 dimer indicated that the strength of association between DOR protomers varies depending on the protein region at the interface, with the 4 dimer being more stable than the 4/5 dimer.
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Affiliation(s)
- Jennifer M Johnston
- Department of Structural and Chemical Biology, Mount Sinai School of Medicine, New York, New York 10029, United States
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45
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Lin Z, Canales JJ, Björgvinsson T, Thomsen MM, Qu H, Liu QR, Torres GE, Caine SB. Monoamine transporters: vulnerable and vital doorkeepers. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2011; 98:1-46. [PMID: 21199769 PMCID: PMC3321928 DOI: 10.1016/b978-0-12-385506-0.00001-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Transporters of dopamine, serotonin, and norepinephrine have been empirically used as medication targets for several mental illnesses in the last decades. These protein-targeted medications are effective only for subpopulations of patients with transporter-related brain disorders. Since the cDNA clonings in early 1990s, molecular studies of these transporters have revealed a wealth of information about the transporters' structure-activity relationship (SAR), neuropharmacology, cell biology, biochemistry, pharmacogenetics, and the diseases related to the human genes encoding these transporters among related regulators. Such new information creates a unique opportunity to develop transporter-specific medications based on SAR, mRNA, DNA, and perhaps transporter trafficking regulation for a number of highly relevant diseases including substance abuse, depression, schizophrenia, and Parkinson's disease.
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Affiliation(s)
- Zhicheng Lin
- Department of Psychiatry, Harvard Medical School and Division of Alcohol and Drug Abuse, McLean Hospital, Belmont, MA 02478, USA
| | - Juan J. Canales
- Department of Psychology, Behavioural Neuroscience, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
| | - Thröstur Björgvinsson
- Behavioral Health Partial Hospital and Psychology Internship Programs, McLean Hospital/Harvard Medical School, Belmont, MA 02478, USA
| | - Morgane M. Thomsen
- Department of Psychiatry, Harvard Medical School and Division of Alcohol and Drug Abuse, McLean Hospital, Belmont, MA 02478, USA
| | - Hong Qu
- Center for Bioinformatics, National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Sciences, Peking University. Beijing, 100871 China
| | - Qing-Rong Liu
- Behavioral Neuroscience Branch, Intramural Research Program, National Institute on Drug Abuse, NIH/DHHS, 251 Bayview Boulevard, Baltimore, MD 21224, USA
| | - Gonzalo E. Torres
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - S. Barak Caine
- Department of Psychiatry, Harvard Medical School and Division of Alcohol and Drug Abuse, McLean Hospital, Belmont, MA 02478, USA
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46
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Takayama H, Sugio S. Functional expression of milligram quantities of the synthetic human serotonin transporter gene in a tetracycline-inducible HEK293 cell line. Protein Expr Purif 2010; 76:211-20. [PMID: 21129485 DOI: 10.1016/j.pep.2010.11.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Revised: 11/17/2010] [Accepted: 11/23/2010] [Indexed: 11/27/2022]
Abstract
The serotonin transporter (SERT), a member of the solute carrier 6 family, is responsible for reuptake of the monoamine neurotransmitter serotonin (5-hydroxytryptamine) from the synaptic cleft on the neural cells, and a vital target for several antidepressants. To investigate biophysical studies of this pharmacologically relevant transporter, we developed a mammalian expression system with tetracycline-inducible HEK293 cells using synthetic human SERT genes produced by PCR-based self-assembly method. Codon-optimization of this de novo constructed genes and construction of stable cell lines improved expression 3.5-fold and single-step immunoaffinity purification with FLAG-epitope tag yielded around one milligram functional SERT per liter culture medium assessed by [(3)H] imipramine ligand binding. Some characterizations including electrospray ionization MS/MS analysis, subcellular localization and cellular-uptake assay demonstrated that expressed human SERT was properly expressed, folded and fully functional. The long cytosolic N-terminal of SERT was predicted as containing 'intrinsically disordered region (IDR)' (∼85 residues) by DISOPRED2 program. We engineered this salient region by step-wise truncation and ligand binding assay determined that dissociation constant for a series of de novo designed truncation constructs was close to the one for full-length wild type SERT. Our expression platform using synthetic codon-optimized gene and mammalian stable cell lines is feasible to produce milligram-scale functional membrane transporter for further biophysical and biochemical studies.
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Affiliation(s)
- Hidehito Takayama
- R&D Strategy Department, Corporate Strategy Division, Mitsubishi Chemical Corporation, Yokohama, Japan
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47
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Li Y, Cheng SY, Chen N, Reith MEA. Interrelation of dopamine transporter oligomerization and surface presence as studied with mutant transporter proteins and amphetamine. J Neurochem 2010; 114:873-85. [PMID: 20492355 DOI: 10.1111/j.1471-4159.2010.06818.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Our previous work suggested a role for oligomerization in regulating dopamine transporter (DAT) internalization, with d-amphetamine dissociating DAT oligomers and monomers being endocytosed. This model was put to detailed testing in the present work with the use of DAT constructs differentially tagged with Myc or Flag, reversal of tags in co-immunoprecipitation and cross-linking assays, and application of antibodies against different tags in biotinylation experiments. Upon pairing wild-type (WT) DAT with W84L mutant, effects of d-amphetamine on oligomerization (decrease) but not surface DAT are observed. Internalization of W84L monomers appears to be slow as inferred from the inability of d-amphetamine to reduce surface Myc upon co-expressing Flag-WT with Myc-W84L but not Myc-WT with Flag-W84L, and from the sluggish Myc-W84L endocytosis rate (both with or without d-amphetamine). Results obtained for D313N, D345N, or D436N mutants can all be accommodated by a model in which D-amphetamine is unable to dissociate mutant protomers from oligomers (tetramers or higher-order assemblies) that contain them; this interpretation is confirmed in experiments with both tag reversal in co-expression and antibody reversal in western blotting. Upon co-transfecting Myc- and Flag-tagged constructs, resulting tetramers can be calculated to be composed of different species (MycMycMycMyc, MycMycMycFlag, MycMycFlagFlag, MycFlagFlagFlag, and FlagFlagFlagFlag), but it is shown that outcomes predicted by models based on MycMycFlagFlag oligomers are not changed in a major way by the occurrence of the additional species.
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Affiliation(s)
- Yan Li
- Department of Psychiatry, New York University School of Medicine, New York, New York 10016, USA
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48
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Insertion of tetracysteine motifs into dopamine transporter extracellular domains. PLoS One 2010; 5:e9113. [PMID: 20161733 PMCID: PMC2817725 DOI: 10.1371/journal.pone.0009113] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Accepted: 01/18/2010] [Indexed: 01/01/2023] Open
Abstract
The neuronal dopamine transporter (DAT) is a major determinant of extracellular dopamine (DA) levels and is the primary target for a variety of addictive and therapeutic psychoactive drugs. DAT is acutely regulated by protein kinase C (PKC) activation and amphetamine exposure, both of which modulate DAT surface expression by endocytic trafficking. In order to use live imaging approaches to study DAT endocytosis, methods are needed to exclusively label the DAT surface pool. The use of membrane impermeant, sulfonated biarsenic dyes holds potential as one such approach, and requires introduction of an extracellular tetracysteine motif (tetraCys; CCPGCC) to facilitate dye binding. In the current study, we took advantage of intrinsic proline-glycine (Pro-Gly) dipeptides encoded in predicted DAT extracellular domains to introduce tetraCys motifs into DAT extracellular loops 2, 3, and 4. [3H]DA uptake studies, surface biotinylation and fluorescence microscopy in PC12 cells indicate that tetraCys insertion into the DAT second extracellular loop results in a functional transporter that maintains PKC-mediated downregulation. Introduction of tetraCys into extracellular loops 3 and 4 yielded DATs with severely compromised function that failed to mature and traffic to the cell surface. This is the first demonstration of successful introduction of a tetracysteine motif into a DAT extracellular domain, and may hold promise for use of biarsenic dyes in live DAT imaging studies.
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49
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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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50
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Moss FJ, Imoukhuede P, Scott K, Hu J, Jankowsky JL, Quick MW, Lester HA. GABA transporter function, oligomerization state, and anchoring: correlates with subcellularly resolved FRET. J Gen Physiol 2009; 134:489-521. [PMID: 19948998 PMCID: PMC2806419 DOI: 10.1085/jgp.200910314] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Accepted: 11/02/2009] [Indexed: 11/20/2022] Open
Abstract
The mouse gamma-aminobutyric acid (GABA) transporter mGAT1 was expressed in neuroblastoma 2a cells. 19 mGAT1 designs incorporating fluorescent proteins were functionally characterized by [(3)H]GABA uptake in assays that responded to several experimental variables, including the mutations and pharmacological manipulation of the cytoskeleton. Oligomerization and subsequent trafficking of mGAT1 were studied in several subcellular regions of live cells using localized fluorescence, acceptor photobleach Förster resonance energy transfer (FRET), and pixel-by-pixel analysis of normalized FRET (NFRET) images. Nine constructs were functionally indistinguishable from wild-type mGAT1 and provided information about normal mGAT1 assembly and trafficking. The remainder had compromised [(3)H]GABA uptake due to observable oligomerization and/or trafficking deficits; the data help to determine regions of mGAT1 sequence involved in these processes. Acceptor photobleach FRET detected mGAT1 oligomerization, but richer information was obtained from analyzing the distribution of all-pixel NFRET amplitudes. We also analyzed such distributions restricted to cellular subregions. Distributions were fit to either two or three Gaussian components. Two of the components, present for all mGAT1 constructs that oligomerized, may represent dimers and high-order oligomers (probably tetramers), respectively. Only wild-type functioning constructs displayed three components; the additional component apparently had the highest mean NFRET amplitude. Near the cell periphery, wild-type functioning constructs displayed the highest NFRET. In this subregion, the highest NFRET component represented approximately 30% of all pixels, similar to the percentage of mGAT1 from the acutely recycling pool resident in the plasma membrane in the basal state. Blocking the mGAT1 C terminus postsynaptic density 95/discs large/zona occludens 1 (PDZ)-interacting domain abolished the highest amplitude component from the NFRET distributions. Disrupting the actin cytoskeleton in cells expressing wild-type functioning transporters moved the highest amplitude component from the cell periphery to perinuclear regions. Thus, pixel-by-pixel NFRET analysis resolved three distinct forms of GAT1: dimers, high-order oligomers, and transporters associated via PDZ-mediated interactions with the actin cytoskeleton and/or with the exocyst.
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Affiliation(s)
- Fraser J. Moss
- Division of Biology and Program in Bioengineering, California Institute of Technology, Pasadena, CA 91125
| | - P.I. Imoukhuede
- Division of Biology and Program in Bioengineering, California Institute of Technology, Pasadena, CA 91125
| | - Kimberly Scott
- Division of Biology and Program in Bioengineering, California Institute of Technology, Pasadena, CA 91125
| | - Jia Hu
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089
| | - Joanna L. Jankowsky
- Division of Biology and Program in Bioengineering, California Institute of Technology, Pasadena, CA 91125
| | - Michael W. Quick
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089
| | - Henry A. Lester
- Division of Biology and Program in Bioengineering, California Institute of Technology, Pasadena, CA 91125
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