1
|
Drew D, Boudker O. Ion and lipid orchestration of secondary active transport. Nature 2024; 626:963-974. [PMID: 38418916 DOI: 10.1038/s41586-024-07062-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 01/12/2024] [Indexed: 03/02/2024]
Abstract
Transporting small molecules across cell membranes is an essential process in cell physiology. Many structurally diverse, secondary active transporters harness transmembrane electrochemical gradients of ions to power the uptake or efflux of nutrients, signalling molecules, drugs and other ions across cell membranes. Transporters reside in lipid bilayers on the interface between two aqueous compartments, where they are energized and regulated by symported, antiported and allosteric ions on both sides of the membrane and the membrane bilayer itself. Here we outline the mechanisms by which transporters couple ion and solute fluxes and discuss how structural and mechanistic variations enable them to meet specific physiological needs and adapt to environmental conditions. We then consider how general bilayer properties and specific lipid binding modulate transporter activity. Together, ion gradients and lipid properties ensure the effective transport, regulation and distribution of small molecules across cell membranes.
Collapse
Affiliation(s)
- David Drew
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
| | - Olga Boudker
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, USA.
- Howard Hughes Medical Institute, Weill Cornell Medicine, New York, NY, USA.
| |
Collapse
|
2
|
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.
Collapse
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.
| |
Collapse
|
3
|
Bhatt M, Gauthier-Manuel L, Lazzarin E, Zerlotti R, Ziegler C, Bazzone A, Stockner T, Bossi E. A comparative review on the well-studied GAT1 and the understudied BGT-1 in the brain. Front Physiol 2023; 14:1145973. [PMID: 37123280 PMCID: PMC10137170 DOI: 10.3389/fphys.2023.1145973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 03/30/2023] [Indexed: 05/02/2023] Open
Abstract
γ-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system (CNS). Its homeostasis is maintained by neuronal and glial GABA transporters (GATs). The four GATs identified in humans are GAT1 (SLC6A1), GAT2 (SLC6A13), GAT3 (SLC6A11), and betaine/GABA transporter-1 BGT-1 (SLC6A12) which are all members of the solute carrier 6 (SLC6) family of sodium-dependent transporters. While GAT1 has been investigated extensively, the other GABA transporters are less studied and their role in CNS is not clearly defined. Altered GABAergic neurotransmission is involved in different diseases, but the importance of the different transporters remained understudied and limits drug targeting. In this review, the well-studied GABA transporter GAT1 is compared with the less-studied BGT-1 with the aim to leverage the knowledge on GAT1 to shed new light on the open questions concerning BGT-1. The most recent knowledge on transporter structure, functions, expression, and localization is discussed along with their specific role as drug targets for neurological and neurodegenerative disorders. We review and discuss data on the binding sites for Na+, Cl-, substrates, and inhibitors by building on the recent cryo-EM structure of GAT1 to highlight specific molecular determinants of transporter functions. The role of the two proteins in GABA homeostasis is investigated by looking at the transport coupling mechanism, as well as structural and kinetic transport models. Furthermore, we review information on selective inhibitors together with the pharmacophore hypothesis of transporter substrates.
Collapse
Affiliation(s)
- Manan Bhatt
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy
- Centre for Neuroscience—University of Insubria, Varese, Italy
| | - Laure Gauthier-Manuel
- Department of Biophysics II/Structural Biology, University of Regensburg, Regensburg, Germany
| | - Erika Lazzarin
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Waehringerstr, Vienna
| | - Rocco Zerlotti
- Department of Biophysics II/Structural Biology, University of Regensburg, Regensburg, Germany
- Nanion Technologies GmbH, Munich, Germany
| | - Christine Ziegler
- Department of Biophysics II/Structural Biology, University of Regensburg, Regensburg, Germany
| | | | - Thomas Stockner
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Waehringerstr, Vienna
- *Correspondence: Thomas Stockner, ; Elena Bossi,
| | - Elena Bossi
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy
- Centre for Neuroscience—University of Insubria, Varese, Italy
- *Correspondence: Thomas Stockner, ; Elena Bossi,
| |
Collapse
|
4
|
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.
Collapse
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,
| |
Collapse
|
5
|
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.
Collapse
|
6
|
Luethi D, Maier J, Rudin D, Szöllősi D, Angenoorth TJF, Stankovic S, Schittmayer M, Burger I, Yang JW, Jaentsch K, Holy M, Das AK, Brameshuber M, Camacho-Hernandez GA, Casiraghi A, Newman AH, Kudlacek O, Birner-Gruenberger R, Stockner T, Schütz GJ, Sitte HH. Phosphatidylinositol 4,5-bisphosphate (PIP 2) facilitates norepinephrine transporter dimerization and modulates substrate efflux. Commun Biol 2022; 5:1259. [PMID: 36396757 PMCID: PMC9672106 DOI: 10.1038/s42003-022-04210-1] [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: 05/03/2022] [Accepted: 11/01/2022] [Indexed: 11/19/2022] Open
Abstract
The plasmalemmal norepinephrine transporter (NET) regulates cardiovascular sympathetic activity by clearing extracellular norepinephrine in the synaptic cleft. Here, we investigate the subunit stoichiometry and function of NET using single-molecule fluorescence microscopy and flux assays. In particular, we show the effect of phosphatidylinositol 4,5-bisphosphate (PIP2) on NET oligomerization and efflux. NET forms monomers (~60%) and dimers (~40%) at the plasma membrane. PIP2 depletion results in a decrease in the average oligomeric state and decreases NET-mediated substrate efflux while not affecting substrate uptake. Mutation of the putative PIP2 binding residues R121, K334, and R440 to alanines does not affect NET dimerization but results in decreased substrate efflux that is not altered upon PIP2 depletion; this indicates that PIP2 interactions with these residues affect NET-mediated efflux. A dysregulation of norepinephrine and PIP2 signaling have both been implicated in neuropsychiatric and cardiovascular diseases. This study provides evidence that PIP2 directly regulates NET organization and function.
Collapse
Affiliation(s)
- Dino Luethi
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Waehringer Strasse 13A, 1090, Vienna, Austria
- Institute of Applied Physics, TU Wien, Lehargasse 6, 1060, Vienna, Austria
| | - Julian Maier
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Waehringer Strasse 13A, 1090, Vienna, Austria
| | - Deborah Rudin
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Waehringer Strasse 13A, 1090, Vienna, Austria
| | - Dániel Szöllősi
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Waehringer Strasse 13A, 1090, Vienna, Austria
| | - Thomas J F Angenoorth
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Waehringer Strasse 13A, 1090, Vienna, Austria
| | - Stevan Stankovic
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Waehringer Strasse 13A, 1090, Vienna, Austria
| | - Matthias Schittmayer
- Institute of Chemical Technologies and Analytics, TU Wien, Getreidemarkt 9, 1060, Vienna, Austria
| | - Isabella Burger
- Institute of Chemical Technologies and Analytics, TU Wien, Getreidemarkt 9, 1060, Vienna, Austria
| | - Jae-Won Yang
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Waehringer Strasse 13A, 1090, Vienna, Austria
| | - Kathrin Jaentsch
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Waehringer Strasse 13A, 1090, Vienna, Austria
| | - Marion Holy
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Waehringer Strasse 13A, 1090, Vienna, Austria
| | - Anand Kant Das
- Institute of Applied Physics, TU Wien, Lehargasse 6, 1060, Vienna, Austria
- Physics Program, New York University Abu Dhabi, Saadiyat Island, 129188, Abu Dhabi, United Arab Emirates
| | - Mario Brameshuber
- Institute of Applied Physics, TU Wien, Lehargasse 6, 1060, Vienna, Austria
| | - Gisela Andrea Camacho-Hernandez
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse - Intramural Research Program, Baltimore, MD, 21224, USA
| | - Andrea Casiraghi
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse - Intramural Research Program, Baltimore, MD, 21224, USA
- Department of Pharmaceutical Sciences, University of Milan, Via Luigi Mangiagalli 25, 20133, Milan, Italy
| | - Amy Hauck Newman
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse - Intramural Research Program, Baltimore, MD, 21224, USA
| | - Oliver Kudlacek
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Waehringer Strasse 13A, 1090, Vienna, Austria
| | - Ruth Birner-Gruenberger
- Institute of Chemical Technologies and Analytics, TU Wien, Getreidemarkt 9, 1060, Vienna, Austria
- Diagnostic and Research Institute of Pathology, Medical University of Graz, Neue Stiftingtalstrasse 6, 8010, Graz, Austria
| | - Thomas Stockner
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Waehringer Strasse 13A, 1090, Vienna, Austria
| | - Gerhard J Schütz
- Institute of Applied Physics, TU Wien, Lehargasse 6, 1060, Vienna, Austria.
| | - Harald H Sitte
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Waehringer Strasse 13A, 1090, Vienna, Austria.
| |
Collapse
|
7
|
Lycas MD, Ejdrup AL, Sørensen AT, Haahr NO, Jørgensen SH, Guthrie DA, Støier JF, Werner C, Newman AH, Sauer M, Herborg F, Gether U. Nanoscopic dopamine transporter distribution and conformation are inversely regulated by excitatory drive and D2 autoreceptor activity. Cell Rep 2022; 40:111431. [PMID: 36170827 PMCID: PMC9617621 DOI: 10.1016/j.celrep.2022.111431] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 07/22/2022] [Accepted: 09/08/2022] [Indexed: 11/30/2022] Open
Abstract
The nanoscopic organization and regulation of individual molecular components in presynaptic varicosities of neurons releasing modulatory volume neurotransmitters like dopamine (DA) remain largely elusive. Here we show, by application of several super-resolution microscopy techniques to cultured neurons and mouse striatal slices, that the DA transporter (DAT), a key protein in varicosities of dopaminergic neurons, exists in the membrane in dynamic equilibrium between an inward-facing nanodomain-localized and outward-facing unclustered configuration. The balance between these configurations is inversely regulated by excitatory drive and DA D2 autoreceptor activation in a manner dependent on Ca2+ influx via N-type voltage-gated Ca2+ channels. The DAT nanodomains contain tens of transporters molecules and overlap with nanodomains of PIP2 (phosphatidylinositol-4,5-bisphosphate) but show little overlap with D2 autoreceptor, syntaxin-1, and clathrin nanodomains. The data reveal a mechanism for rapid alterations of nanoscopic DAT distribution and show a striking link of this to the conformational state of the transporter.
Collapse
Affiliation(s)
- Matthew D Lycas
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark
| | - Aske L Ejdrup
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark
| | - Andreas T Sørensen
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark
| | - Nicolai O Haahr
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark
| | - Søren H Jørgensen
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark
| | - Daryl A Guthrie
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Jonatan F Støier
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark
| | - Christian Werner
- Department of Biotechnology and Biophysics, Biocenter, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Amy Hauck Newman
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Markus Sauer
- Department of Biotechnology and Biophysics, Biocenter, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Freja Herborg
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark
| | - Ulrik Gether
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark.
| |
Collapse
|
8
|
Swain BC, Das AK, Pathak NK, Tripathy U. Z-scan analysis and theoretical studies of dopamine under physiological conditions. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 271:120890. [PMID: 35066443 DOI: 10.1016/j.saa.2022.120890] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Revised: 01/09/2022] [Accepted: 01/10/2022] [Indexed: 06/14/2023]
Abstract
Dopamine (DA) is a widely researched catecholamine best known for its role in motor, motivation, addiction, and reward. Disruption in dopamine homeostasis and signaling within the central nervous system (CNS) can lead to disorders such as attention deficit hyperactivity disorder (ADHD), schizophrenia, Parkinson's disease, and obsessive-compulsive disorder. In the periphery, circulating DA is stored in blood platelets, and its disruption correlates with pathological conditions such as head and neck paragangliomas, Huntington's chorea, and schizophrenia. Various methods to sensitively and selectively detect dopamine have been reported, but sparse attempts have been made to exploit its intrinsic properties. Previously, we have harnessed dopamine's natural mid-ultraviolet auto-fluorescence to carry out its label-free imaging in live brain tissues. Recently, we used the closed-aperture (CA) Z-scan method to provide the first line of evidence on the existence of dopamine nonlinearity. Here, we utilized this simple, sensitive, and straightforward CA Z-scan technique and coupled this with theoretical simulations to further investigate the nonlinear photophysical properties of DA under physiological conditions. Our combined approach revealed that the nonlinear property of dopamine is governed by the thermo-optical effects, and the CA Z-scan profiles can be modulated by parameters such as phase-shift, orders of absorption, and time dependency. Simple and physiologically relevant systems, such as the platelets, are amenable to Z-scan analysis, thereby empowering us to scrutinize in the future if nonlinearity and its alterations, if any, have a direct bearing on DA homeostasis and associated diseases.
Collapse
Affiliation(s)
- Bikash Chandra Swain
- Department of Physics, Indian Institute of Technology (Indian School of Mines), Dhanbad, Jharkhand 826004, India
| | - Anand Kant Das
- Physics Division, New York University Abu Dhabi, Saadiyat Island, 129188 Abu Dhabi, United Arab Emirates
| | - Nitesh Kumar Pathak
- Department of Physics, Indian Institute of Technology (Indian School of Mines), Dhanbad, Jharkhand 826004, India
| | - Umakanta Tripathy
- Department of Physics, Indian Institute of Technology (Indian School of Mines), Dhanbad, Jharkhand 826004, India.
| |
Collapse
|
9
|
Insights into the Role of Membrane Lipids in the Structure, Function and Regulation of Integral Membrane Proteins. Int J Mol Sci 2021; 22:ijms22169026. [PMID: 34445730 PMCID: PMC8396450 DOI: 10.3390/ijms22169026] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 08/15/2021] [Accepted: 08/17/2021] [Indexed: 02/07/2023] Open
Abstract
Membrane proteins exist within the highly hydrophobic membranes surrounding cells and organelles, playing key roles in cellular function. It is becoming increasingly clear that the membrane does not just act as an appropriate environment for these proteins, but that the lipids that make up these membranes are essential for membrane protein structure and function. Recent technological advances in cryogenic electron microscopy and in advanced mass spectrometry methods, as well as the development of alternative membrane mimetic systems, have allowed experimental study of membrane protein–lipid complexes. These have been complemented by computational approaches, exploiting the ability of Molecular Dynamics simulations to allow exploration of membrane protein conformational changes in membranes with a defined lipid content. These studies have revealed the importance of lipids in stabilising the oligomeric forms of membrane proteins, mediating protein–protein interactions, maintaining a specific conformational state of a membrane protein and activity. Here we review some of the key recent advances in the field of membrane protein–lipid studies, with major emphasis on respiratory complexes, transporters, channels and G-protein coupled receptors.
Collapse
|
10
|
Gether U, Sitte HH. It takes two-or more-to tango: Revisiting the role of dopamine transporter oligomerization. J Biol Chem 2021; 296:100629. [PMID: 34237901 PMCID: PMC8100069 DOI: 10.1016/j.jbc.2021.100629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The dopamine transporter utilizes the transmembrane sodium gradient to mediate reuptake of dopamine from the extracellular space. The dopamine transporter can form dimers and possibly also higher order structures in the plasma membrane, and this oligomerization has been implicated in both trafficking and transport. However, we still do not fully understand its biological importance. A study by Sorkina et al. now describes a series of small molecules that link transporter conformation to oligomerization and endocytosis, providing an interesting step forward in an intricate dance.
Collapse
Affiliation(s)
- Ulrik Gether
- Department of Neuroscience, Faculty of Health and Medical Sciences, Maersk Tower 7.5, University of Copenhagen, Copenhagen, Denmark.
| | - Harald H Sitte
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University Vienna, Vienna, Austria
| |
Collapse
|
11
|
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: 59] [Impact Index Per Article: 19.7] [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.
Collapse
|
12
|
Fairweather SJ, Shah N, Brӧer S. Heteromeric Solute Carriers: Function, Structure, Pathology and Pharmacology. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 21:13-127. [PMID: 33052588 DOI: 10.1007/5584_2020_584] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Solute carriers form one of three major superfamilies of membrane transporters in humans, and include uniporters, exchangers and symporters. Following several decades of molecular characterisation, multiple solute carriers that form obligatory heteromers with unrelated subunits are emerging as a distinctive principle of membrane transporter assembly. Here we comprehensively review experimentally established heteromeric solute carriers: SLC3-SLC7 amino acid exchangers, SLC16 monocarboxylate/H+ symporters and basigin/embigin, SLC4A1 (AE1) and glycophorin A exchanger, SLC51 heteromer Ost α-Ost β uniporter, and SLC6 heteromeric symporters. The review covers the history of the heteromer discovery, transporter physiology, structure, disease associations and pharmacology - all with a focus on the heteromeric assembly. The cellular locations, requirements for complex formation, and the functional role of dimerization are extensively detailed, including analysis of the first complete heteromer structures, the SLC7-SLC3 family transporters LAT1-4F2hc, b0,+AT-rBAT and the SLC6 family heteromer B0AT1-ACE2. We present a systematic analysis of the structural and functional aspects of heteromeric solute carriers and conclude with common principles of their functional roles and structural architecture.
Collapse
Affiliation(s)
- Stephen J Fairweather
- Research School of Biology, Australian National University, Canberra, ACT, Australia. .,Resarch School of Chemistry, Australian National University, Canberra, ACT, Australia.
| | - Nishank Shah
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Stefan Brӧer
- Research School of Biology, Australian National University, Canberra, ACT, Australia.
| |
Collapse
|
13
|
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.
Collapse
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.
| |
Collapse
|
14
|
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.
Collapse
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.
| |
Collapse
|
15
|
Guthrie DA, Klein Herenbrink C, Lycas MD, Ku T, Bonifazi A, DeVree BT, Mathiasen S, Javitch JA, Grimm JB, Lavis L, Gether U, Newman AH. Novel Fluorescent Ligands Enable Single-Molecule Localization Microscopy of the Dopamine Transporter. ACS Chem Neurosci 2020; 11:3288-3300. [PMID: 32926777 DOI: 10.1021/acschemneuro.0c00397] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The dopamine transporter (DAT) is critical for spatiotemporal control of dopaminergic neurotransmission and is the target for therapeutic agents, including ADHD medications, and abused substances, such as cocaine. Here, we develop new fluorescently labeled ligands that bind DAT with high affinity and enable single-molecule detection of the transporter. The cocaine analogue MFZ2-12 (1) was conjugated to novel rhodamine-based Janelia Fluorophores (JF549 and JF646). High affinity binding of the resulting ligands to DAT was demonstrated by potent inhibition of [3H]dopamine uptake in DAT transfected CAD cells and by competition radioligand binding experiments on rat striatal membranes. Visualization of binding was substantiated by confocal or TIRF microscopy revealing selective binding of the analogues to DAT transfected CAD cells. Single particle tracking experiments were performed with JF549-conjugated DG3-80 (3) and JF646-conjugated DG4-91 (4) on DAT transfected CAD cells enabling quantification and categorization of the dynamic behavior of DAT into four distinct motion classes (immobile, confined, Brownian, and directed). Finally, we show that the ligands can be used in direct stochastic optical reconstruction microscopy (dSTORM) experiments permitting further analyses of DAT distribution on the nanoscale. In summary, these novel fluorescent ligands are promising new tools for studying DAT localization and regulation with single-molecule resolution.
Collapse
Affiliation(s)
- Daryl A. Guthrie
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health, 333 Cassell Drive, Baltimore, Maryland 21224, United States,
| | - Carmen Klein Herenbrink
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Matthew Domenic Lycas
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Therese Ku
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health, 333 Cassell Drive, Baltimore, Maryland 21224, United States,
| | - Alessandro Bonifazi
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health, 333 Cassell Drive, Baltimore, Maryland 21224, United States,
| | - Brian T. DeVree
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Signe Mathiasen
- Department of Psychiatry, Columbia University Vagelos College of Physicians & Surgeon and Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, United States
| | - Jonathan A. Javitch
- Department of Psychiatry, Columbia University Vagelos College of Physicians & Surgeon and Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, United States
| | - Jonathan B. Grimm
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, Virginia 20147, United States
| | - Luke Lavis
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, Virginia 20147, United States
| | - Ulrik Gether
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Amy Hauck Newman
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health, 333 Cassell Drive, Baltimore, Maryland 21224, United States,
| |
Collapse
|
16
|
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. ![]()
Collapse
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
| |
Collapse
|
17
|
Joseph D, Pidathala S, Mallela AK, Penmatsa A. Structure and Gating Dynamics of Na +/Cl - Coupled Neurotransmitter Transporters. Front Mol Biosci 2019; 6:80. [PMID: 31555663 PMCID: PMC6742698 DOI: 10.3389/fmolb.2019.00080] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Accepted: 08/21/2019] [Indexed: 12/24/2022] Open
Abstract
Neurotransmitters released at the neural synapse through vesicle exocytosis are spatiotemporally controlled by the action of neurotransmitter transporters. Integral membrane proteins of the solute carrier 6 (SLC6) family are involved in the sodium and chloride coupled uptake of biogenic amine neurotransmitters including dopamine, serotonin, noradrenaline and inhibitory neurotransmitters including glycine and γ-amino butyric acid. This ion-coupled symport works through a well-orchestrated gating of substrate through alternating-access, which is mediated through movements of helices that resemble a rocking-bundle. A large array of commercially prescribed drugs and psychostimulants selectively target neurotransmitter transporters thereby modulating their levels in the synaptic space. Drug-induced changes in the synaptic neurotransmitter levels can be used to treat depression or neuropathic pain whereas in some instances prolonged usage can lead to habituation. Earlier structural studies of bacterial neurotransmitter transporter homolog LeuT and recent structure elucidation of the Drosophila dopamine transporter (dDAT) and human serotonin transporter (hSERT) have yielded a wealth of information in understanding the transport and inhibition mechanism of neurotransmitter transporters. Computational studies based on the structures of dDAT and hSERT have shed light on the dynamics of varied components of these molecular gates in affecting the uphill transport of neurotransmitters. This review seeks to address structural dynamics of neurotransmitter transporters at the extracellular and intracellular gates and the effect of inhibitors on the ligand-binding pocket. We also delve into the effect of additional factors including lipids and cytosolic domains that influence the translocation of neurotransmitters across the membrane.
Collapse
Affiliation(s)
- Deepthi Joseph
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | | | | | - Aravind Penmatsa
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| |
Collapse
|
18
|
Monoamine transporters: structure, intrinsic dynamics and allosteric regulation. Nat Struct Mol Biol 2019; 26:545-556. [PMID: 31270469 DOI: 10.1038/s41594-019-0253-7] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 05/14/2019] [Indexed: 12/31/2022]
Abstract
Monoamine transporters (MATs) regulate neurotransmission via the reuptake of dopamine, serotonin and norepinephrine from extra-neuronal regions and thus maintain neurotransmitter homeostasis. As targets of a wide range of compounds, including antidepressants, substances of abuse and drugs for neuropsychiatric and neurodegenerative disorders, their mechanism of action and their modulation by small molecules have long been of broad interest. Recent advances in the structural characterization of dopamine and serotonin transporters have opened the way for structure-based modeling and simulations, which, together with experimental data, now provide mechanistic understanding of their transport function and interactions. Here we review recent progress in the elucidation of the structural dynamics of MATs and their conformational landscape and transitions, as well as allosteric regulation mechanisms.
Collapse
|
19
|
Cheng MH, Ponzoni L, Sorkina T, Lee JY, Zhang S, Sorkin A, Bahar I. Trimerization of dopamine transporter triggered by AIM-100 binding: Molecular mechanism and effect of mutations. Neuropharmacology 2019; 161:107676. [PMID: 31228486 DOI: 10.1016/j.neuropharm.2019.107676] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 06/17/2019] [Accepted: 06/18/2019] [Indexed: 10/26/2022]
Abstract
Recent work demonstrated the propensity of dopamine transporters (DATs) to form trimers or higher oligomers, enhanced upon binding a furopyrimidine, AIM-100. AIM-100 binding promotes DAT endocytosis and thereby moderates dopaminergic transmission. Despite the neurobiological significance of these events, the molecular mechanisms that underlie the stabilization of DAT trimer and the key interactions that modulate the trimerization of DAT, and not serotonin transporter SERT, remain unclear. In the present study, we determined three structural models, termed trimer-W238, -C306 and -Y303, for possible trimerization of DATs . To this aim, we used structural data resolved for DAT and its structural homologs that share the LeuT fold, advanced computational modeling and simulations, site-directed mutagenesis experiments and live-cell imaging assays. The models are in accord with the versatility of LeuT fold to stabilize dimeric or higher order constructs. Selected residues show a high propensity to occupy interfacial regions. Among them, D231-W238 in the extracellular loop EL2, including the intersubunit salt-bridge forming pair D231/D232-R237 (not present in SERT) (in trimer-W238), the loop EL3 (trimers-C306 and -Y303), and W497 on the intracellularly exposed IL5 loop (trimer-C306) and its spatial neighbors (e.g. K525) near the C-terminus are computationally predicted and experimentally confirmed to play important roles in enabling the correct folding and/or oligomerization of DATs in the presence of AIM-100. The study suggests the possibility of controlling the effective transport of dopamine by altering the oligomerization state of DAT upon small molecule binding, as a possible intervention strategy to modulate dopaminergic signaling. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
Collapse
Affiliation(s)
- Mary Hongying Cheng
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Luca Ponzoni
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Tatiana Sorkina
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ji Young Lee
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - She Zhang
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Alexander Sorkin
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ivet Bahar
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
| |
Collapse
|