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Cervetto C, Amaroli A, Amato S, Gatta E, Diaspro A, Maura G, Signore A, Benedicenti S, Marcoli M. Photons Induce Vesicular Exocytotic Release of Glutamate in a Power-Dependent Way. Int J Mol Sci 2023; 24:10977. [PMID: 37446155 DOI: 10.3390/ijms241310977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Revised: 06/20/2023] [Accepted: 06/27/2023] [Indexed: 07/15/2023] Open
Abstract
Increasing evidence indicates that photobiomodulation, based on tissue irradiation with photons in the red to near-infrared spectrum, may be an effective therapeutic approach to central nervous system disorders. Although nervous system functionality has been shown to be affected by photons in animal models, as well as in preliminary evidence in healthy subjects or in patients with neuropsychiatric disorders, the mechanisms involved in the photobiomodulation effects have not yet been clarified. We previously observed that photobiomodulation could stimulate glutamate release. Here, we investigate mechanisms potentially involved in the glutamate-releasing effect of photons from adult mouse cerebrocortical nerve terminals. We report evidence of photon ability to induce an exocytotic vesicular release of glutamate from the terminals of glutamatergic neurons in a power-dependent way. It can be hypothesized that photobiomodulation, depending on the potency, can release glutamate in a potentially neurotoxic or physiological range.
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Affiliation(s)
- Chiara Cervetto
- Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Viale Cembrano 4, 16148 Genova, Italy
- Interuniversity Center for the Promotion of the 3Rs Principles in Teaching and Research (Centro 3R), 56122 Pisa, Italy
| | - Andrea Amaroli
- Department of Earth, Environment and Life Sciences, University of Genova, Viale Benedetto XV 5, 16132 Genova, Italy
| | - Sarah Amato
- Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Viale Cembrano 4, 16148 Genova, Italy
| | - Elena Gatta
- DIFILAB, Department of Physics, University of Genova, Via Dodecaneso 33, 16146 Genova, Italy
| | - Alberto Diaspro
- DIFILAB, Department of Physics, University of Genova, Via Dodecaneso 33, 16146 Genova, Italy
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia-IIT, Via Morego 30, 16133 Genova, Italy
- Biophysics Institute, National Research Council-CNR, Via de Marini, 6, 16149 Genova, Italy
| | - Guido Maura
- Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Viale Cembrano 4, 16148 Genova, Italy
| | - Antonio Signore
- Therapeutic Dentistry Department, Institute of Dentistry, Sechenov First Moscow State Medical University, Trubetskaya Str. 8, b. 2, 119992 Moskow, Russia
| | - Stefano Benedicenti
- Department of Surgical Sciences and Integrated Diagnostics, University of Genova, Viale Benedetto XV 6, 16132 Genova, Italy
| | - Manuela Marcoli
- Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Viale Cembrano 4, 16148 Genova, Italy
- Interuniversity Center for the Promotion of the 3Rs Principles in Teaching and Research (Centro 3R), 56122 Pisa, Italy
- Center of Excellence for Biomedical Research, University of Genova, 16132 Genova, Italy
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2
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Bustos E, Manríquez J, Colín-González AL, Rangel-López E, Santamaría A. Electrochemical Detection of Neurotransmitters in the Brain and Other Molecules with Biological Activity in the Nervous System: Dopamine Analysis. CURR ORG CHEM 2020. [DOI: 10.2174/1385272824666200204121746] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Monitoring the appropriate functions of the brain is a priority when the diagnosis
of neurological diseases is carried out. In this regard, there are different analytical
techniques to detect neurotransmitters and other molecules with biological activity in
the nervous system. Among several analytical procedures, electrochemical techniques are
very important since they can be applied in situ, without loss of sensibility and/or minimal
handling of samples. In addition, it is also possible to combine them with specific detectors
designed on the basis of chemically-modified electrodes in order to improve detection
limits by promoting molecular recognition capabilities at their surfaces, thus favoring the
development of electrochemical detection in vivo by microelectrodes. In this mini-review,
we will describe the major characteristics of this analytical method and its advantages for
the detection of neurotransmitters (mostly dopamine) in vivo.
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Affiliation(s)
- Erika Bustos
- Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S.C., CIDETEQ, Parque Tecnologico Queretaro, Sanfandila, Pedro Escobedo, 76703, Queretaro, Mexico
| | - Juan Manríquez
- Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S.C., CIDETEQ, Parque Tecnologico Queretaro, Sanfandila, Pedro Escobedo, 76703, Queretaro, Mexico
| | - Ana Laura Colín-González
- Insttuto Nacional de Neurologia y Neurocirugia, INNN, Insurgentes Sur No. 3877, Mexico, D.F., C.P. 14269, Mexico
| | - Edgar Rangel-López
- Insttuto Nacional de Neurologia y Neurocirugia, INNN, Insurgentes Sur No. 3877, Mexico, D.F., C.P. 14269, Mexico
| | - Abel Santamaría
- Insttuto Nacional de Neurologia y Neurocirugia, INNN, Insurgentes Sur No. 3877, Mexico, D.F., C.P. 14269, Mexico
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3
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Moriyama Y, Hatano R, Moriyama S, Uehara S. Vesicular polyamine transporter as a novel player in amine-mediated chemical transmission. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183208. [PMID: 32004521 DOI: 10.1016/j.bbamem.2020.183208] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 01/23/2020] [Accepted: 01/26/2020] [Indexed: 02/06/2023]
Abstract
The solute carrier 18B1 (SLC18B1) is the most recently identified gene of the vesicular amine transporter family and is conserved in the animal kingdom from insects to humans. Proteoliposomes containing the purified human SLC18B1 protein transport not only monoamines, but also polyamines, such as spermidine (Spd) and spermine (Spm), using an electrochemical gradient of H+ established by vacuolar H+-ATPase (V-ATPase) as the driving force. SLC18B1 gene knockdown abolished the exocytosis of polyamines from mast cells, which affected the secretion of histamine. SLC18B1 gene knockout decreased polyamine levels by ~20% in the brain, and impaired short- and long-term memory. Thus, the SLC18B1 protein is responsible for the vesicular storage and release of polyamines, and functions as a vesicular polyamine transporter (VPAT). VPAT may define when, where, and how polyamine-mediated chemical transmission occurs, providing insights into the more versatile and complex features of amine-mediated chemical transmission than currently considered.
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Affiliation(s)
- Yoshinori Moriyama
- Department of Biochemistry, Matsumoto Dental University, Shiojiri 399-0781, Japan; Division of Endocrinology and Metabolism, Department of Internal Medicine, Kurume University School of Medicine, Kurume 830-0011, Japan; CYRIC Tohoku University, Sendai 980-8578, Japan.
| | - Ryo Hatano
- Department of Medicinal Physiology, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan
| | - Satomi Moriyama
- Laboratory of Bio-Molecular Dynamics, Department of Collaborative Research, Nara Medical University, Kashihara 634-8521, Japan
| | - Shunsuke Uehara
- Department of Biochemistry, Matsumoto Dental University, Shiojiri 399-0781, Japan
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4
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Menchini RJ, Chaudhry FA. Multifaceted regulation of the system A transporter Slc38a2 suggests nanoscale regulation of amino acid metabolism and cellular signaling. Neuropharmacology 2019; 161:107789. [PMID: 31574264 DOI: 10.1016/j.neuropharm.2019.107789] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 09/16/2019] [Accepted: 09/20/2019] [Indexed: 02/07/2023]
Abstract
Amino acids are essential for cellular protein synthesis, growth, metabolism, signaling and in stress responses. Cell plasma membranes harbor specialized transporters accumulating amino acids to support a variety of cellular biochemical pathways. Several transporters for neutral amino acids have been characterized. However, Slc38a2 (also known as SA1, SAT2, ATA2, SNAT2) representing the classical transport system A activity stands in a unique position: Being a secondarily active transporter energized by the electrochemical gradient of Na+, it creates steep concentration gradients for amino acids such as glutamine: this may subsequently drive the accumulation of additional neutral amino acids through exchange via transport systems ASC and L. Slc38a2 is ubiquitously expressed, yet in a cell-specific manner. In this review, we show that Slc38a2 is regulated at the transcriptional and translational levels as well as by ions and proteins through direct interactions. We describe how Slc38a2 senses amino acid availability and passes this onto intracellular signaling pathways and how it regulates protein synthesis, cellular proliferation and apoptosis through the mechanistic (mammalian) target of rapamycin (mTOR) and general control nonderepressible 2 (GCN2) pathways. Furthermore, we review how this extensively regulated transporter contributes to cellular osmoadaptation and how it is regulated by endoplasmic reticulum stress and various hormonal stimuli to promote cellular metabolism, cellular signaling and cell survival. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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Affiliation(s)
| | - Farrukh Abbas Chaudhry
- Department of Molecular Medicine, University of Oslo, Oslo, Norway; Department of Plastic and Reconstructive Surgery, Oslo University Hospital, Oslo, Norway
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5
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Majumder P, Khare S, Athreya A, Hussain N, Gulati A, Penmatsa A. Dissection of Protonation Sites for Antibacterial Recognition and Transport in QacA, a Multi-Drug Efflux Transporter. J Mol Biol 2019; 431:2163-2179. [PMID: 30910733 DOI: 10.1016/j.jmb.2019.03.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 03/14/2019] [Accepted: 03/19/2019] [Indexed: 01/05/2023]
Abstract
QacA is a drug:H+ antiporter with 14 transmembrane helices that confers antibacterial resistance to methicillin-resistant Staphylococcus aureus strains, with homologs in other pathogenic organisms. It is a highly promiscuous antiporter, capable of H+-driven efflux of a wide array of cationic antibacterial compounds and dyes. Our study, using a homology model of QacA, reveals a group of six protonatable residues in its vestibule. Systematic mutagenesis resulted in the identification of D34 (TM1), and a cluster of acidic residues in TM13 including E407 and D411 and D323 in TM10, as being crucial for substrate recognition and transport of monovalent and divalent cationic antibacterial compounds. The transport and binding properties of QacA and its mutants were explored using whole cells, inside-out vesicles, substrate-induced H+ release and microscale thermophoresis-based assays. The activity of purified QacA was also observed using proteoliposome-based substrate-induced H+ transport assay. Our results identify two sites, D34 and D411 as vital players in substrate recognition, while E407 facilitates substrate efflux as a protonation site. We also observe that E407 plays an additional role as a substrate recognition site for the transport of dequalinium, a divalent quaternary ammonium compound. These observations rationalize the promiscuity of QacA for diverse substrates. The study unravels the role of acidic residues in QacA with implications for substrate recognition, promiscuity and processive transport in multidrug efflux transporters, related to QacA.
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Affiliation(s)
- Puja Majumder
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
| | - Shashank Khare
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
| | - Arunabh Athreya
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
| | - Nazia Hussain
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
| | - Ashutosh Gulati
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
| | - Aravind Penmatsa
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
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6
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Mukherjee AB, Appu AP, Sadhukhan T, Casey S, Mondal A, Zhang Z, Bagh MB. Emerging new roles of the lysosome and neuronal ceroid lipofuscinoses. Mol Neurodegener 2019; 14:4. [PMID: 30651094 PMCID: PMC6335712 DOI: 10.1186/s13024-018-0300-6] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 12/04/2018] [Indexed: 12/04/2022] Open
Abstract
Neuronal Ceroid Lipofuscinoses (NCLs), commonly known as Batten disease, constitute a group of the most prevalent neurodegenerative lysosomal storage disorders (LSDs). Mutations in at least 13 different genes (called CLNs) cause various forms of NCLs. Clinically, the NCLs manifest early impairment of vision, progressive decline in cognitive and motor functions, seizures and a shortened lifespan. At the cellular level, all NCLs show intracellular accumulation of autofluorescent material (called ceroid) and progressive neuron loss. Despite intense studies the normal physiological functions of each of the CLN genes remain poorly understood. Consequently, the development of mechanism-based therapeutic strategies remains challenging. Endolysosomal dysfunction contributes to pathogenesis of virtually all LSDs. Studies within the past decade have drastically changed the notion that the lysosomes are merely the terminal degradative organelles. The emerging new roles of the lysosome include its central role in nutrient-dependent signal transduction regulating metabolism and cellular proliferation or quiescence. In this review, we first provide a brief overview of the endolysosomal and autophagic pathways, lysosomal acidification and endosome-lysosome and autophagosome-lysosome fusions. We emphasize the importance of these processes as their dysregulation leads to pathogenesis of many LSDs including the NCLs. We also describe what is currently known about each of the 13 CLN genes and their products and how understanding the emerging new roles of the lysosome may clarify the underlying pathogenic mechanisms of the NCLs. Finally, we discuss the current and emerging therapeutic strategies for various NCLs.
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Affiliation(s)
- Anil B. Mukherjee
- Section on Developmental Genetics, Program on Endocrinology and Molecular Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, Maryland 20892-1830 USA
| | - Abhilash P. Appu
- Section on Developmental Genetics, Program on Endocrinology and Molecular Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, Maryland 20892-1830 USA
| | - Tamal Sadhukhan
- Section on Developmental Genetics, Program on Endocrinology and Molecular Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, Maryland 20892-1830 USA
| | - Sydney Casey
- Section on Developmental Genetics, Program on Endocrinology and Molecular Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, Maryland 20892-1830 USA
| | - Avisek Mondal
- Section on Developmental Genetics, Program on Endocrinology and Molecular Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, Maryland 20892-1830 USA
| | - Zhongjian Zhang
- Section on Developmental Genetics, Program on Endocrinology and Molecular Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, Maryland 20892-1830 USA
- Present address: Institute of Psychiatry and Neuroscience, Xinxiang Medical University, Xinxiang, 453003 Henan China
| | - Maria B. Bagh
- Section on Developmental Genetics, Program on Endocrinology and Molecular Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, Maryland 20892-1830 USA
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7
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Kandasamy P, Gyimesi G, Kanai Y, Hediger MA. Amino acid transporters revisited: New views in health and disease. Trends Biochem Sci 2018; 43:752-789. [PMID: 30177408 DOI: 10.1016/j.tibs.2018.05.003] [Citation(s) in RCA: 252] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 05/23/2018] [Accepted: 05/25/2018] [Indexed: 02/09/2023]
Abstract
Amino acid transporters (AATs) are membrane-bound transport proteins that mediate transfer of amino acids into and out of cells or cellular organelles. AATs have diverse functional roles ranging from neurotransmission to acid-base balance, intracellular energy metabolism, and anabolic and catabolic reactions. In cancer cells and diabetes, dysregulation of AATs leads to metabolic reprogramming, which changes intracellular amino acid levels, contributing to the pathogenesis of cancer, obesity and diabetes. Indeed, the neutral amino acid transporters (NATs) SLC7A5/LAT1 and SLC1A5/ASCT2 are likely involved in several human malignancies. However, a clinical therapy that directly targets AATs has not yet been developed. The purpose of this review is to highlight the structural and functional diversity of AATs, their diverse physiological roles in different tissues and organs, their wide-ranging implications in human diseases and the emerging strategies and tools that will be necessary to target AATs therapeutically.
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Affiliation(s)
- Palanivel Kandasamy
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland
| | - Gergely Gyimesi
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland
| | - Yoshikatsu Kanai
- Division of Bio-system Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan.
| | - Matthias A Hediger
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland.
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8
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Chang R, Eriksen J, Edwards RH. The dual role of chloride in synaptic vesicle glutamate transport. eLife 2018; 7:e34896. [PMID: 30040066 PMCID: PMC6057745 DOI: 10.7554/elife.34896] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 06/07/2018] [Indexed: 01/23/2023] Open
Abstract
The transport of glutamate into synaptic vesicles exhibits an unusual form of regulation by Cl- as well as an associated Cl- conductance. To distinguish direct effects of Cl- on the transporter from indirect effects via the driving force Δψ, we used whole endosome recording and report the first currents due to glutamate flux by the vesicular glutamate transporters (VGLUTs). Chloride allosterically activates the VGLUTs from both sides of the membrane, and we find that neutralization of an arginine in transmembrane domain four suffices for the lumenal activation. The dose dependence suggests that Cl- permeates through a channel and glutamate through a transporter. Competition between the anions nonetheless indicates that they use a similar permeation pathway. By controlling both ionic gradients and Δψ, endosome recording isolates different steps in the process of synaptic vesicle filling, suggesting distinct roles for Cl- in both allosteric activation and permeation.
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Affiliation(s)
- Roger Chang
- Department of PhysiologyUCSF School of MedicineSan FranciscoUnited States
- Department of NeurologyUCSF School of MedicineSan FranciscoUnited States
- Graduate Program in Biomedical SciencesUCSF School of MedicineSan FranciscoUnited States
| | - Jacob Eriksen
- Department of PhysiologyUCSF School of MedicineSan FranciscoUnited States
- Department of NeurologyUCSF School of MedicineSan FranciscoUnited States
| | - Robert H Edwards
- Department of PhysiologyUCSF School of MedicineSan FranciscoUnited States
- Department of NeurologyUCSF School of MedicineSan FranciscoUnited States
- Graduate Program in Biomedical SciencesUCSF School of MedicineSan FranciscoUnited States
- Kavli Institute for Fundamental NeuroscienceUCSF School of MedicineSan FranciscoUnited States
- Weill Institute for NeurosciencesUCSF School of MedicineSan FranciscoUnited States
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9
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Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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10
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Verkhratsky A, Nedergaard M. Physiology of Astroglia. Physiol Rev 2018; 98:239-389. [PMID: 29351512 PMCID: PMC6050349 DOI: 10.1152/physrev.00042.2016] [Citation(s) in RCA: 899] [Impact Index Per Article: 149.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/22/2017] [Accepted: 04/27/2017] [Indexed: 02/07/2023] Open
Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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11
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Lovrić J, Dunevall J, Larsson A, Ren L, Andersson S, Meibom A, Malmberg P, Kurczy ME, Ewing AG. Nano Secondary Ion Mass Spectrometry Imaging of Dopamine Distribution Across Nanometer Vesicles. ACS NANO 2017; 11:3446-3455. [PMID: 27997789 DOI: 10.1021/acsnano.6b07233] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We report an approach to spatially resolve the content across nanometer neuroendocrine vesicles in nerve-like cells by correlating super high-resolution mass spectrometry imaging, NanoSIMS, with transmission electron microscopy (TEM). Furthermore, intracellular electrochemical cytometry at nanotip electrodes is used to count the number of molecules in individual vesicles to compare to imaged amounts in vesicles. Correlation between the NanoSIMS and TEM provides nanometer resolution of the inner structure of these organelles. Moreover, correlation with electrochemical methods provides a means to quantify and relate vesicle neurotransmitter content and release, which is used to explain the slow transfer of dopamine between vesicular compartments. These nanoanalytical tools reveal that dopamine loading/unloading between vesicular compartments, dense core and halo solution, is a kinetically limited process. The combination of NanoSIMS and TEM has been used to show the distribution profile of newly synthesized dopamine across individual vesicles. Our findings suggest that the vesicle inner morphology might regulate the neurotransmitter release event during open and closed exocytosis from dense core vesicles with hours of equilibrium needed to move significant amounts of catecholamine from the protein dense core despite its nanometer size.
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Affiliation(s)
- Jelena Lovrić
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology , Gothenburg SE-412 96, Sweden
- National Centre for Imaging Mass Spectrometry, Chalmers University of Technology and University of Gothenburg , Gothenburg SE-412 96, Sweden
| | - Johan Dunevall
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology , Gothenburg SE-412 96, Sweden
| | - Anna Larsson
- Department of Chemistry and Molecular Biology, University of Gothenburg , Gothenburg SE-412 96, Sweden
| | - Lin Ren
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology , Gothenburg SE-412 96, Sweden
| | - Shalini Andersson
- Cardiovascular and Metabolic Diseases, Innovative Medicines and Early Development Biotech Unit, AstraZeneca , Mölndal SE-431 50, Sweden
| | - Anders Meibom
- Laboratory for Biological Geochemistry, École Polytechnique Fédérale de Lausanne and Center for Advanced Surface Analysis, Institute of Earth Sciences, University of Lausanne , Lausanne CH-1015, Switzerland
| | - Per Malmberg
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology , Gothenburg SE-412 96, Sweden
- National Centre for Imaging Mass Spectrometry, Chalmers University of Technology and University of Gothenburg , Gothenburg SE-412 96, Sweden
| | - Michael E Kurczy
- Cardiovascular and Metabolic Diseases, Innovative Medicines and Early Development Biotech Unit, AstraZeneca , Mölndal SE-431 50, Sweden
| | - Andrew G Ewing
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology , Gothenburg SE-412 96, Sweden
- National Centre for Imaging Mass Spectrometry, Chalmers University of Technology and University of Gothenburg , Gothenburg SE-412 96, Sweden
- Department of Chemistry and Molecular Biology, University of Gothenburg , Gothenburg SE-412 96, Sweden
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12
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Lohr KM, Masoud ST, Salahpour A, Miller GW. Membrane transporters as mediators of synaptic dopamine dynamics: implications for disease. Eur J Neurosci 2017; 45:20-33. [PMID: 27520881 PMCID: PMC5209277 DOI: 10.1111/ejn.13357] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Revised: 07/12/2016] [Accepted: 08/02/2016] [Indexed: 12/14/2022]
Abstract
Dopamine was first identified as a neurotransmitter localized to the midbrain over 50 years ago. The dopamine transporter (DAT; SLC6A3) and the vesicular monoamine transporter 2 (VMAT2; SLC18A2) are regulators of dopamine homeostasis in the presynaptic neuron. DAT transports dopamine from the extracellular space into the cytosol of the presynaptic terminal. VMAT2 then packages this cytosolic dopamine into vesicular compartments for subsequent release upon neurotransmission. Thus, DAT and VMAT2 act in concert to move the transmitter efficiently throughout the neuron. Accumulation of dopamine in the neuronal cytosol can trigger oxidative stress and neurotoxicity, suggesting that the proper compartmentalization of dopamine is critical for neuron function and risk of disease. For decades, studies have examined the effects of reduced transporter function in mice (e.g. DAT-KO, VMAT2-KO, VMAT2-deficient). However, we have only recently been able to assess the effects of elevated transporter expression using BAC transgenic methods (DAT-tg, VMAT2-HI mice). Complemented with in vitro work and neurochemical techniques to assess dopamine compartmentalization, a new focus on the importance of transporter proteins as both models of human disease and potential drug targets has emerged. Here, we review the importance of DAT and VMAT2 function in the delicate balance of neuronal dopamine.
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Affiliation(s)
- Kelly M Lohr
- Department of Environmental Health, Rollins School of Public Health, Emory University, 1518 Clifton Road, Atlanta, GA, 30322, USA
| | - Shababa T Masoud
- Department of Pharmacology and Toxicology, University of Toronto, ON, Canada
| | - Ali Salahpour
- Department of Pharmacology and Toxicology, University of Toronto, ON, Canada
| | - Gary W Miller
- Department of Environmental Health, Rollins School of Public Health, Emory University, 1518 Clifton Road, Atlanta, GA, 30322, USA
- Center for Neurodegenerative Diseases, Emory University, Atlanta, GA, USA
- Department of Pharmacology, Emory University, Atlanta, GA, USA
- Department of Neurology, Emory University, Atlanta, GA, USA
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13
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Moen MN, Fjær R, Hamdani EH, Laerdahl JK, Menchini RJ, Vigeland MD, Sheng Y, Undlien DE, Hassel B, Salih MA, El Khashab HY, Selmer KK, Chaudhry FA. Pathogenic variants in KCTD7 perturb neuronal K+ fluxes and glutamine transport. Brain 2016; 139:3109-3120. [PMID: 27742667 DOI: 10.1093/brain/aww244] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 06/11/2016] [Accepted: 08/17/2016] [Indexed: 12/11/2022] Open
Abstract
Progressive myoclonus epilepsy is a heterogeneous group of disorders characterized by myoclonic and tonic-clonic seizures, ataxia and cognitive decline. We here present two affected brothers. At 9 months of age the elder brother developed ataxia and myoclonic jerks. In his second year he lost the ability to walk and talk, and he developed drug-resistant progressive myoclonus epilepsy. The cerebrospinal fluid level of glutamate was decreased while glutamine was increased. His younger brother manifested similar symptoms from 6 months of age. By exome sequencing of the proband we identified a novel homozygous frameshift variant in the potassium channel tetramerization domain 7 (KCTD7) gene (NM_153033.1:c.696delT: p.F232fs), which results in a truncated protein. The identified F232fs variant is inherited in an autosomal recessive manner, and the healthy consanguineous parents carry the variant in a heterozygous state. Bioinformatic analyses and structure modelling showed that KCTD7 is a highly conserved protein, structurally similar to KCTD5 and several voltage-gated potassium channels, and that it may form homo- or heteromultimers. By heterologous expression in Xenopus laevis oocytes, we demonstrate that wild-type KCTD7 hyperpolarizes cells in a K+ dependent manner and regulates activity of the neuronal glutamine transporter SAT2 (Slc38a2), while the F232fs variant impairs K+ fluxes and obliterates SAT2-dependent glutamine transport. Characterization of four additional disease-causing variants (R94W, R184C, N273I, Y276C) bolster these results and reveal the molecular mechanisms involved in the pathophysiology of KCTD7-related progressive myoclonus epilepsy. Thus, our data demonstrate that KCTD7 has an impact on K+ fluxes, neurotransmitter synthesis and neuronal function, and that malfunction of the encoded protein may lead to progressive myoclonus epilepsy.
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Affiliation(s)
- Marivi Nabong Moen
- 1 The Institute of Basic Medical Sciences, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Roar Fjær
- 2 Department of Medical Genetics, Oslo University Hospital and University of Oslo, Norway
| | - El Hassan Hamdani
- 1 The Institute of Basic Medical Sciences, Department of Molecular Medicine, University of Oslo, Oslo, Norway.,3 Department of Medical Biochemistry, Oslo University Hospital, Oslo, Norway
| | - Jon K Laerdahl
- 4 Department of Microbiology, Oslo University Hospital, Oslo, Norway.,5 Bioinformatics Core Facility, Department of Informatics, University of Oslo, Oslo, Norway
| | - Robin Johansen Menchini
- 1 The Institute of Basic Medical Sciences, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Magnus Dehli Vigeland
- 2 Department of Medical Genetics, Oslo University Hospital and University of Oslo, Norway
| | - Ying Sheng
- 2 Department of Medical Genetics, Oslo University Hospital and University of Oslo, Norway
| | - Dag Erik Undlien
- 2 Department of Medical Genetics, Oslo University Hospital and University of Oslo, Norway
| | - Bjørnar Hassel
- 6 Department of Complex Neurology and Neurohabilitation, Oslo University Hospital, Oslo, Norway
| | - Mustafa A Salih
- 7 Division of Paediatric Neurology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Heba Y El Khashab
- 7 Division of Paediatric Neurology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.,8 Department of Paediatrics, Ain Shams University, Cairo, Egypt
| | - Kaja Kristine Selmer
- 2 Department of Medical Genetics, Oslo University Hospital and University of Oslo, Norway.,9 National Centre for Rare Epilepsy-related Disorders, Oslo University Hospital, Oslo, Norway
| | - Farrukh Abbas Chaudhry
- 1 The Institute of Basic Medical Sciences, Department of Molecular Medicine, University of Oslo, Oslo, Norway .,3 Department of Medical Biochemistry, Oslo University Hospital, Oslo, Norway
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14
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Lohr KM, Chen M, Hoffman CA, McDaniel MJ, Stout KA, Dunn AR, Wang M, Bernstein AI, Miller GW. Vesicular Monoamine Transporter 2 (VMAT2) Level Regulates MPTP Vulnerability and Clearance of Excess Dopamine in Mouse Striatal Terminals. Toxicol Sci 2016; 153:79-88. [PMID: 27287315 DOI: 10.1093/toxsci/kfw106] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The vesicular monoamine transporter 2 (VMAT2) packages neurotransmitters for release during neurotransmission and sequesters toxicants into vesicles to prevent neuronal damage. In mice, low VMAT2 levels causes catecholaminergic cell loss and behaviors resembling Parkinson's disease, while high levels of VMAT2 increase dopamine release and protect against dopaminergic toxicants. However, comparisons across these VMAT2 mouse genotypes were impossible due to the differing genetic background strains of the animals. Following back-crossing to a C57BL/6 line, we confirmed that mice with approximately 95% lower VMAT2 levels compared with wild-type (VMAT2-LO) display significantly reduced vesicular uptake, progressive dopaminergic terminal loss with aging, and exacerbated 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity. Conversely, VMAT2-overexpressing mice (VMAT2-HI) are protected from the loss of striatal terminals following MPTP treatment. We also provide evidence that enhanced vesicular filling in the VMAT2-HI mice modifies the handling of newly synthesized dopamine, indicated by changes in indirect measures of extracellular dopamine clearance. These results confirm the role of VMAT2 in the protection of vulnerable nigrostriatal dopamine neurons and may also provide new insight into the side effects of L-DOPA treatments in Parkinson's disease.
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Affiliation(s)
- Kelly M Lohr
- *Department of Environmental Health, Rollins School of Public Health
| | - Merry Chen
- *Department of Environmental Health, Rollins School of Public Health
| | - Carlie A Hoffman
- *Department of Environmental Health, Rollins School of Public Health
| | | | - Kristen A Stout
- *Department of Environmental Health, Rollins School of Public Health
| | - Amy R Dunn
- *Department of Environmental Health, Rollins School of Public Health
| | - Minzheng Wang
- *Department of Environmental Health, Rollins School of Public Health
| | | | - Gary W Miller
- *Department of Environmental Health, Rollins School of Public Health Center for Neurodegenerative Diseases Department of Pharmacology Department of Neurology, Emory University, Atlanta, Georgia, 30322
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15
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Münster-Wandowski A, Zander JF, Richter K, Ahnert-Hilger G. Co-existence of Functionally Different Vesicular Neurotransmitter Transporters. Front Synaptic Neurosci 2016; 8:4. [PMID: 26909036 PMCID: PMC4754932 DOI: 10.3389/fnsyn.2016.00004] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Accepted: 02/01/2016] [Indexed: 01/25/2023] Open
Abstract
The vesicular transmitter transporters VGLUT, VGAT, VMAT2 and VAChT, define phenotype and physiological properties of neuronal subtypes. VGLUTs concentrate the excitatory amino acid glutamate, VGAT the inhibitory amino acid GABA, VMAT2 monoamines, and VAChT acetylcholine (ACh) into synaptic vesicle (SV). Following membrane depolarization SV release their content into the synaptic cleft. A strict segregation of vesicular transporters is mandatory for the precise functioning of synaptic communication and of neuronal circuits. In the last years, evidence accumulates that subsets of neurons express more than one of these transporters leading to synaptic co-release of different and functionally opposing transmitters and modulation of synaptic plasticity. Synaptic co-existence of transporters may change during pathological scenarios in order to ameliorate misbalances in neuronal activity. In addition, evidence increases that transporters also co-exist on the same vesicle providing another layer of regulation. Generally, vesicular transmitter loading relies on an electrochemical gradient ΔμH+ driven by the proton ATPase rendering the lumen of the vesicle with respect to the cytosol positive (Δψ) and acidic (ΔpH). While the activity of VGLUT mainly depends on the Δψ component, VMAT, VGAT and VAChT work best at a high ΔpH. Thus, a vesicular synergy of transporters depending on the combination may increase or decrease the filling of SV with the principal transmitter. We provide an overview on synaptic co-existence of vesicular transmitter transporters including changes in the excitatory/inhibitory balance under pathological conditions. Additionally, we discuss functional aspects of vesicular synergy of transmitter transporters.
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Affiliation(s)
| | | | - Karin Richter
- Institute of Integrative Neuroanatomy, Charité-Universitätsmedizin Berlin Berlin, Germany
| | - Gudrun Ahnert-Hilger
- Institute of Integrative Neuroanatomy, Charité-Universitätsmedizin Berlin Berlin, Germany
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16
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Verkhratsky A, Matteoli M, Parpura V, Mothet JP, Zorec R. Astrocytes as secretory cells of the central nervous system: idiosyncrasies of vesicular secretion. EMBO J 2016; 35:239-57. [PMID: 26758544 DOI: 10.15252/embj.201592705] [Citation(s) in RCA: 282] [Impact Index Per Article: 35.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 12/01/2015] [Indexed: 11/09/2022] Open
Abstract
Astrocytes are housekeepers of the central nervous system (CNS) and are important for CNS development, homeostasis and defence. They communicate with neurones and other glial cells through the release of signalling molecules. Astrocytes secrete a wide array of classic neurotransmitters, neuromodulators and hormones, as well as metabolic, trophic and plastic factors, all of which contribute to the gliocrine system. The release of neuroactive substances from astrocytes occurs through several distinct pathways that include diffusion through plasmalemmal channels, translocation by multiple transporters and regulated exocytosis. As in other eukaryotic cells, exocytotic secretion from astrocytes involves divergent secretory organelles (synaptic-like microvesicles, dense-core vesicles, lysosomes, exosomes and ectosomes), which differ in size, origin, cargo, membrane composition, dynamics and functions. In this review, we summarize the features and functions of secretory organelles in astrocytes. We focus on the biogenesis and trafficking of secretory organelles and on the regulation of the exocytotic secretory system in the context of healthy and diseased astrocytes.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Life Sciences, The University of Manchester, Manchester, UK Achucarro Center for Neuroscience, IKERBASQUE Basque Foundation for Science, Bilbao, Spain Department of Neurosciences, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain University of Nizhny Novgorod, Nizhny Novgorod, Russia Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology University of Ljubljana, Ljubljana, Slovenia Celica BIOMEDICAL, Ljubljana, Slovenia
| | - Michela Matteoli
- CNR Institute of Neuroscience, Milano, Italy Humanitas Research Hospital, Rozzano, Italy
| | - Vladimir Parpura
- Department of Neurobiology, Civitan International Research Center and Center for Glial Biology in Medicine, Evelyn F. McKnight Brain Institute, Atomic Force Microscopy & Nanotechnology Laboratories University of Alabama at Birmingham, Birmingham, AL, USA
| | - Jean-Pierre Mothet
- Team Gliotransmission & Synaptopathies, Aix-Marseille University CNRS, CRN2M UMR7286, Marseille, France
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology University of Ljubljana, Ljubljana, Slovenia Celica BIOMEDICAL, Ljubljana, Slovenia
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17
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Malet M, Brumovsky PR. VGLUTs and Glutamate Synthesis-Focus on DRG Neurons and Pain. Biomolecules 2015; 5:3416-37. [PMID: 26633536 PMCID: PMC4693284 DOI: 10.3390/biom5043416] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Revised: 11/13/2015] [Accepted: 11/17/2015] [Indexed: 12/14/2022] Open
Abstract
The amino acid glutamate is the principal excitatory transmitter in the nervous system, including in sensory neurons that convey pain sensation from the periphery to the brain. It is now well established that a family of membrane proteins, termed vesicular glutamate transporters (VGLUTs), serve a critical function in these neurons: they incorporate glutamate into synaptic vesicles. VGLUTs have a central role both under normal neurotransmission and pathological conditions, such as neuropathic or inflammatory pain. In the present short review, we will address VGLUTs in the context of primary afferent neurons. We will focus on the role of VGLUTs in pain triggered by noxious stimuli, peripheral nerve injury, and tissue inflammation, as mostly explored in transgenic mice. The possible interplay between glutamate biosynthesis and VGLUT-dependent packaging in synaptic vesicles, and its potential impact in various pain states will be presented.
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Affiliation(s)
- Mariana Malet
- Institute of Research on Translational Medicine, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Austral University, Avenida Juan D. Perón 1500, Pilar, Buenos Aires 1629AHJ, Argentina.
| | - Pablo R Brumovsky
- Institute of Research on Translational Medicine, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Austral University, Avenida Juan D. Perón 1500, Pilar, Buenos Aires 1629AHJ, Argentina.
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18
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Omote H, Miyaji T, Hiasa M, Juge N, Moriyama Y. Structure, Function, and Drug Interactions of Neurotransmitter Transporters in the Postgenomic Era. Annu Rev Pharmacol Toxicol 2015; 56:385-402. [PMID: 26514205 DOI: 10.1146/annurev-pharmtox-010814-124816] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Vesicular neurotransmitter transporters are responsible for the accumulation of neurotransmitters in secretory vesicles and play essential roles in chemical transmission. The SLC17 family contributes to sequestration of anionic neurotransmitters such as glutamate, aspartate, and nucleotides. Identification and subsequent cellular and molecular biological studies of SLC17 transporters unveiled the principles underlying the actions of these transporters. Recent progress in reconstitution methods in combination with postgenomic approaches has advanced studies on neurotransmitter transporters. This review summarizes the molecular properties of SLC17-type transporters and recent findings regarding the novel SLC18 transporter.
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Affiliation(s)
- Hiroshi Omote
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan; ,
| | - Takaaki Miyaji
- Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan
| | - Miki Hiasa
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan; ,
| | - Narinobu Juge
- Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan
| | - Yoshinori Moriyama
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan; , .,Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan
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19
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Larhammar M, Patra K, Blunder M, Emilsson L, Peuckert C, Arvidsson E, Rönnlund D, Preobraschenski J, Birgner C, Limbach C, Widengren J, Blom H, Jahn R, Wallén-Mackenzie Å, Kullander K. SLC10A4 is a vesicular amine-associated transporter modulating dopamine homeostasis. Biol Psychiatry 2015; 77:526-36. [PMID: 25176177 DOI: 10.1016/j.biopsych.2014.07.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 07/14/2014] [Accepted: 07/16/2014] [Indexed: 01/11/2023]
Abstract
BACKGROUND The neuromodulatory transmitters, biogenic amines, have profound effects on multiple neurons and are essential for normal behavior and mental health. Here we report that the orphan transporter SLC10A4, which in the brain is exclusively expressed in presynaptic vesicles of monoaminergic and cholinergic neurons, has a regulatory role in dopamine homeostasis. METHODS We used a combination of molecular and behavioral analyses, pharmacology, and in vivo amperometry to assess the role of SLC10A4 in dopamine-regulated behaviors. RESULTS We show that SLC10A4 is localized on the same synaptic vesicles as either vesicular acetylcholine transporter or vesicular monoamine transporter 2. We did not find evidence for direct transport of dopamine by SLC10A4; however, synaptic vesicle preparations lacking SLC10A4 showed decreased dopamine vesicular uptake efficiency. Furthermore, we observed an increased acidification in synaptic vesicles isolated from mice overexpressing SLC10A4. Loss of SLC10A4 in mice resulted in reduced striatal serotonin, noradrenaline, and dopamine concentrations and a significantly higher dopamine turnover ratio. Absence of SLC10A4 led to slower dopamine clearance rates in vivo, which resulted in accumulation of extracellular dopamine. Finally, whereas SLC10A4 null mutant mice were slightly hypoactive, they displayed hypersensitivity to administration of amphetamine and tranylcypromine. CONCLUSIONS Our results demonstrate that SLC10A4 is a vesicular monoaminergic and cholinergic associated transporter that is important for dopamine homeostasis and neuromodulation in vivo. The discovery of SLC10A4 and its role in dopaminergic signaling reveals a novel mechanism for neuromodulation and represents an unexplored target for the treatment of neurological and mental disorders.
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Affiliation(s)
| | | | - Martina Blunder
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Lina Emilsson
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | | | - Emma Arvidsson
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Daniel Rönnlund
- Department of Biomolecular Physics, Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | - Julia Preobraschenski
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | | | | | - Jerker Widengren
- Department of Biomolecular Physics, Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | - Hans Blom
- Department of Biomolecular Physics, Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | - Reinhard Jahn
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | | | - Klas Kullander
- Department of Neuroscience, Uppsala University, Uppsala, Sweden..
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20
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Omote H, Moriyama Y. Vesicular neurotransmitter transporters: an approach for studying transporters with purified proteins. Physiology (Bethesda) 2014; 28:39-50. [PMID: 23280356 DOI: 10.1152/physiol.00033.2012] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Vesicular storage and subsequent release of neurotransmitters are the key processes of chemical signal transmission. In this process, vesicular neurotransmitter transporters are responsible for loading the signaling molecules. The use of a "clean biochemical" approach with purified, recombinant transporters has helped in the identification of novel vesicular neurotransmitter transporters and in the analysis of the control of signal transmission.
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Affiliation(s)
- Hiroshi Omote
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University, Okayama, Japan
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21
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Lawal HO, Terrell A, Lam HA, Djapri C, Jang J, Hadi R, Roberts L, Shahi V, Chou MT, Biedermann T, Huang B, Lawless GM, Maidment NT, Krantz DE. Drosophila modifier screens to identify novel neuropsychiatric drugs including aminergic agents for the possible treatment of Parkinson's disease and depression. Mol Psychiatry 2014; 19:235-42. [PMID: 23229049 PMCID: PMC3610854 DOI: 10.1038/mp.2012.170] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Revised: 08/21/2012] [Accepted: 09/17/2012] [Indexed: 01/05/2023]
Abstract
Small molecules that increase the presynaptic function of aminergic cells may provide neuroprotection in Parkinson's disease (PD) as well as treatments for attention deficit hyperactivity disorder (ADHD) and depression. Model genetic organisms such as Drosophila melanogaster may enhance the detection of new drugs via modifier or 'enhancer/suppressor' screens, but this technique has not been applied to processes relevant to psychiatry. To identify new aminergic drugs in vivo, we used a mutation in the Drosophila vesicular monoamine transporter (dVMAT) as a sensitized genetic background and performed a suppressor screen. We fed dVMAT mutant larvae ∼ 1000 known drugs and quantitated rescue (suppression) of an amine-dependent locomotor deficit in the larva. To determine which drugs might specifically potentiate neurotransmitter release, we performed an additional secondary screen for drugs that require presynaptic amine storage to rescue larval locomotion. Using additional larval locomotion and adult fertility assays, we validated that at least one compound previously used clinically as an antineoplastic agent potentiates the presynaptic function of aminergic circuits. We suggest that structurally similar agents might be used to development treatments for PD, depression and ADHD, and that modifier screens in Drosophila provide a new strategy to screen for neuropsychiatric drugs. More generally, our findings demonstrate the power of physiologically based screens for identifying bioactive agents for select neurotransmitter systems.
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Affiliation(s)
- Hakeem O. Lawal
- Department of Psychiatry and Biobehavioral Sciences, Gonda Center for Neuroscience and Genetics Research, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095 USA
| | - Ashley Terrell
- Department of Biological Sciences, University of Minnesota, Minneapolis MN, 55455 USA
| | - Hoa A. Lam
- Department of Psychiatry and Biobehavioral Sciences, Gonda Center for Neuroscience and Genetics Research, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095 USA
| | - Christine Djapri
- Department of Psychiatry and Biobehavioral Sciences, Gonda Center for Neuroscience and Genetics Research, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095 USA
| | - Jennifer Jang
- Department of Psychiatry and Biobehavioral Sciences, Gonda Center for Neuroscience and Genetics Research, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095 USA
| | - Richard Hadi
- Department of Psychiatry and Biobehavioral Sciences, Gonda Center for Neuroscience and Genetics Research, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095 USA
| | - Logan Roberts
- Department of Psychiatry and Biobehavioral Sciences, Gonda Center for Neuroscience and Genetics Research, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095 USA
| | - Varun Shahi
- Department of Psychiatry and Biobehavioral Sciences, Gonda Center for Neuroscience and Genetics Research, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095 USA
| | - Man-Ting Chou
- Department of Psychiatry and Biobehavioral Sciences, Gonda Center for Neuroscience and Genetics Research, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095 USA
| | - Traci Biedermann
- Department of Psychiatry and Biobehavioral Sciences, Gonda Center for Neuroscience and Genetics Research, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095 USA
| | - Brian Huang
- Department of Psychiatry and Biobehavioral Sciences, Gonda Center for Neuroscience and Genetics Research, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095 USA
| | | | - Nigel T. Maidment
- Department of Psychiatry and Biobehavioral Sciences, Gonda Center for Neuroscience and Genetics Research, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095 USA
| | - David E. Krantz
- Department of Psychiatry and Biobehavioral Sciences, Gonda Center for Neuroscience and Genetics Research, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095 USA,Corresponding Author: tel. 1 310 206 8508, fax 1 310 206 9877,
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22
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Jenstad M, Chaudhry FA. The Amino Acid Transporters of the Glutamate/GABA-Glutamine Cycle and Their Impact on Insulin and Glucagon Secretion. Front Endocrinol (Lausanne) 2013; 4:199. [PMID: 24427154 PMCID: PMC3876026 DOI: 10.3389/fendo.2013.00199] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Accepted: 12/16/2013] [Indexed: 12/21/2022] Open
Abstract
Intercellular communication is pivotal in optimizing and synchronizing cellular responses to keep homeostasis and to respond adequately to external stimuli. In the central nervous system (CNS), glutamatergic and GABAergic signals are postulated to be dependent on the glutamate/GABA-glutamine cycle for vesicular loading of neurotransmitters, for inactivating the signal and for the replenishment of the neurotransmitters. Islets of Langerhans release the hormones insulin and glucagon, but share similarities with CNS cells in for example transcriptional control of development and differentiation, and chromatin methylation. Interestingly, CNS proteins involved in secretion of the neurotransmitters and emitting their responses as well as the regulation of these processes, are also found in islet cells. Moreover, high levels of glutamate, GABA, and glutamine and their respective vesicular and plasma membrane transporters have been shown in the islet cells and there is emerging support for these amino acids and their transporters playing important roles in the maturation and secretion of insulin and glucagon. In this review, we will discuss the feasibility of recent data in the field in relation to the biophysical properties of the transporters (Slc1, Slc17, Slc32, and Slc38) and physiology of hormone secretion in islets of Langerhans.
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Affiliation(s)
- Monica Jenstad
- Institute for Medical Informatics, Oslo University Hospital, Oslo, Norway
- Centre for Cancer Biomedicine, University of Oslo, Oslo, Norway
- *Correspondence: Monica Jenstad, Institute for Medical Informatics, Oslo University Hospital, Radiumhospitalet, PO Box 4953 Nydalen, Oslo NO-0424, Norway e-mail:
| | - Farrukh Abbas Chaudhry
- Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
- The Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway
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23
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Punnakkal P, von Schoultz C, Haenraets K, Wildner H, Zeilhofer HU. Morphological, biophysical and synaptic properties of glutamatergic neurons of the mouse spinal dorsal horn. J Physiol 2013; 592:759-76. [PMID: 24324003 PMCID: PMC3934713 DOI: 10.1113/jphysiol.2013.264937] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Interneurons of the spinal dorsal horn are central to somatosensory and nociceptive processing. A mechanistic understanding of their function depends on profound knowledge of their intrinsic properties and their integration into dorsal horn circuits. Here, we have used BAC transgenic mice expressing enhanced green fluorescent protein (eGFP) under the control of the vesicular glutamate transporter (vGluT2) gene (vGluT2::eGFP mice) to perform a detailed electrophysiological and morphological characterisation of excitatory dorsal horn neurons, and to compare their properties to those of GABAergic (Gad67::eGFP tagged) and glycinergic (GlyT2::eGFP tagged) neurons. vGluT2::eGFP was detected in about one-third of all excitatory dorsal horn neurons and, as demonstrated by the co-expression of vGluT2::eGFP with different markers of subtypes of glutamatergic neurons, probably labelled a representative fraction of these neurons. Three types of dendritic tree morphologies (vertical, central, and radial), but no islet cell-type morphology, were identified in vGluT2::eGFP neurons. vGluT2::eGFP neurons had more depolarised action potential thresholds and longer action potential durations than inhibitory neurons, while no significant differences were found for the resting membrane potential, input resistance, cell capacitance and after-hyperpolarisation. Delayed firing and single action potential firing were the single most prevalent firing patterns in vGluT2::eGFP neurons of the superficial and deep dorsal horn, respectively. By contrast, tonic firing prevailed in inhibitory interneurons of the dorsal horn. Capsaicin-induced synaptic inputs were detected in about half of the excitatory and inhibitory neurons, and occurred more frequently in superficial than in deep dorsal horn neurons. Primary afferent-evoked (polysynaptic) inhibitory inputs were found in the majority of glutamatergic and glycinergic neurons, but only in less than half of the GABAergic population. Excitatory dorsal horn neurons thus differ from their inhibitory counterparts in several biophysical properties and possibly also in their integration into the local neuronal circuitry.
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Affiliation(s)
- Pradeep Punnakkal
- Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
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VGLUTs in Peripheral Neurons and the Spinal Cord: Time for a Review. ISRN NEUROLOGY 2013; 2013:829753. [PMID: 24349795 PMCID: PMC3856137 DOI: 10.1155/2013/829753] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Accepted: 08/25/2013] [Indexed: 02/07/2023]
Abstract
Vesicular glutamate transporters (VGLUTs) are key molecules for the incorporation of glutamate in synaptic vesicles across the nervous system, and since their discovery in the early 1990s, research on these transporters has been intense and productive. This review will focus on several aspects of VGLUTs research on neurons in the periphery and the spinal cord. Firstly, it will begin with a historical account on the evolution of the morphological analysis of glutamatergic systems and the pivotal role played by the discovery of VGLUTs. Secondly, and in order to provide an appropriate framework, there will be a synthetic description of the neuroanatomy and neurochemistry of peripheral neurons and the spinal cord. This will be followed by a succinct description of the current knowledge on the expression of VGLUTs in peripheral sensory and autonomic neurons and neurons in the spinal cord. Finally, this review will address the modulation of VGLUTs expression after nerve and tissue insult, their physiological relevance in relation to sensation, pain, and neuroprotection, and their potential pharmacological usefulness.
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Nissen-Meyer LSH, Chaudhry FA. Protein Kinase C Phosphorylates the System N Glutamine Transporter SN1 (Slc38a3) and Regulates Its Membrane Trafficking and Degradation. Front Endocrinol (Lausanne) 2013; 4:138. [PMID: 24106489 PMCID: PMC3788335 DOI: 10.3389/fendo.2013.00138] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 09/16/2013] [Indexed: 01/11/2023] Open
Abstract
The system N transporter SN1 (also known as SNAT3) is enriched on perisynaptic astroglial cell membranes. SN1 mediates electroneutral and bidirectional glutamine transport, and regulates the intracellular as well as the extracellular concentrations of glutamine. We hypothesize that SN1 participates in the glutamate/γ-aminobutyric acid (GABA)-glutamine cycle and regulates the amount of glutamine supplied to the neurons for replenishment of the neurotransmitter pools of glutamate and GABA. We also hypothesize that its activity on the plasma membrane is regulated by protein kinase C (PKC)-mediated phosphorylation and that SN1 activity has an impact on synaptic plasticity. This review discusses reports on the regulation of SN1 by PKC and presents a consolidated model for regulation and degradation of SN1 and the subsequent functional implications. As SN1 function is likely also regulated by PKC-mediated phosphorylation in peripheral organs, the same mechanisms may, thus, have impact on e.g., pH regulation in the kidney, urea formation in the liver, and insulin secretion in the pancreas.
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Affiliation(s)
- Lise Sofie H. Nissen-Meyer
- The Biotechnology Centre, University of Oslo, Oslo, Norway
- The Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
- *Correspondence: Lise Sofie H. Nissen-Meyer and Farrukh Abbas Chaudhry, The Institute of Basic Medical Sciences, University of Oslo, P.O. Box 1110 Blindern, 0317 Oslo, Norway e-mail: ;
| | - Farrukh Abbas Chaudhry
- The Biotechnology Centre, University of Oslo, Oslo, Norway
- The Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
- *Correspondence: Lise Sofie H. Nissen-Meyer and Farrukh Abbas Chaudhry, The Institute of Basic Medical Sciences, University of Oslo, P.O. Box 1110 Blindern, 0317 Oslo, Norway e-mail: ;
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26
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Malet M, Vieytes CA, Lundgren KH, Seal RP, Tomasella E, Seroogy KB, Hökfelt T, Gebhart GF, Brumovsky PR. Transcript expression of vesicular glutamate transporters in lumbar dorsal root ganglia and the spinal cord of mice - effects of peripheral axotomy or hindpaw inflammation. Neuroscience 2013; 248:95-111. [PMID: 23727452 PMCID: PMC3800240 DOI: 10.1016/j.neuroscience.2013.05.044] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Revised: 05/22/2013] [Accepted: 05/22/2013] [Indexed: 11/30/2022]
Abstract
Using specific riboprobes, we characterized the expression of vesicular glutamate transporter (VGLUT)₁-VGLUT₃ transcripts in lumbar 4-5 (L4-5) dorsal root ganglions (DRGs) and the thoracolumbar to lumbosacral spinal cord in male BALB/c mice after a 1- or 3-day hindpaw inflammation, or a 7-day sciatic nerve axotomy. Sham animals were also included. In sham and contralateral L4-5 DRGs of injured mice, VGLUT₁-, VGLUT₂- and VGLUT₃ mRNAs were expressed in ∼45%, ∼69% or ∼17% of neuron profiles (NPs), respectively. VGLUT₁ was expressed in large and medium-sized NPs, VGLUT₂ in NPs of all sizes, and VGLUT₃ in small and medium-sized NPs. In the spinal cord, VGLUT₁ was restricted to a number of NPs at thoracolumbar and lumbar segments, in what appears to be the dorsal nucleus of Clarke, and in mid laminae III-IV. In contrast, VGLUT₂ was present in numerous NPs at all analyzed spinal segments, except the lateral aspects of the ventral horns, especially at the lumbar enlargement, where it was virtually absent. VGLUT₃ was detected in a discrete number of NPs in laminae III-IV of the dorsal horn. Axotomy resulted in a moderate decrease in the number of DRG NPs expressing VGLUT₃, whereas VGLUT₁ and VGLUT₂ were unaffected. Likewise, the percentage of NPs expressing VGLUT transcripts remained unaltered after hindpaw inflammation, both in DRGs and the spinal cord. Altogether, these results confirm previous descriptions on VGLUTs expression in adult mice DRGs, with the exception of VGLUT₁, whose protein expression was detected in a lower percentage of mouse DRG NPs. A detailed account on the location of neurons expressing VGLUTs transcripts in the adult mouse spinal cord is also presented. Finally, the lack of change in the number of neurons expressing VGLUT₁ and VGLUT₂ transcripts after axotomy, as compared to data on protein expression, suggests translational rather than transcriptional regulation of VGLUTs after injury.
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Affiliation(s)
- M Malet
- Faculty of Biomedical Sciences, Austral University, Buenos Aires, Argentina; CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas), Buenos Aires, Argentina
| | - C A Vieytes
- Faculty of Biomedical Sciences, Austral University, Buenos Aires, Argentina
| | - K H Lundgren
- Department of Neurology, University of Cincinnati, Cincinnati, OH, USA
| | - R P Seal
- Pittsburgh Center for Pain Research, Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA, USA
| | - E Tomasella
- Faculty of Biomedical Sciences, Austral University, Buenos Aires, Argentina; CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas), Buenos Aires, Argentina
| | - K B Seroogy
- Department of Neurology, University of Cincinnati, Cincinnati, OH, USA
| | - T Hökfelt
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - G F Gebhart
- Pittsburgh Center for Pain Research, Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA, USA
| | - P R Brumovsky
- Faculty of Biomedical Sciences, Austral University, Buenos Aires, Argentina; CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas), Buenos Aires, Argentina; Pittsburgh Center for Pain Research, Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA, USA.
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SLC18: Vesicular neurotransmitter transporters for monoamines and acetylcholine. Mol Aspects Med 2013; 34:360-72. [PMID: 23506877 DOI: 10.1016/j.mam.2012.07.005] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Accepted: 05/29/2012] [Indexed: 01/06/2023]
Abstract
The exocytotic release of neurotransmitters requires active transport into synaptic vesicles and other types of secretory vesicles. Members of the SLC18 family perform this function for acetylcholine (SLC18A3, the vesicular acetylcholine transporter or VAChT) and monoamines such as dopamine and serotonin (SLC18A1 and 2, the vesicular monoamine transporters VMAT1 and 2, respectively). To date, no specific diseases have been attributed to a mutation in an SLC18 family member; however, polymorphisms in SLC18A1 and SLC18A2 may confer risk for some neuropsychiatric disorders. Additional members of this family include SLC18A4, expressed in insects, and SLC18B1, the function of which is not known. SLC18 is part of the Drug:H(+) Antiporter-1 Family (DHA1, TCID 2.A.1.2) within the Major Facilitator Superfamily (MFS, TCID 2.A.1).
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Van Liefferinge J, Massie A, Portelli J, Di Giovanni G, Smolders I. Are vesicular neurotransmitter transporters potential treatment targets for temporal lobe epilepsy? Front Cell Neurosci 2013; 7:139. [PMID: 24009559 PMCID: PMC3757300 DOI: 10.3389/fncel.2013.00139] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 08/11/2013] [Indexed: 12/18/2022] Open
Abstract
The vesicular neurotransmitter transporters (VNTs) are small proteins responsible for packing synaptic vesicles with neurotransmitters thereby determining the amount of neurotransmitter released per vesicle through fusion in both neurons and glial cells. Each transporter subtype was classically seen as a specific neuronal marker of the respective nerve cells containing that particular neurotransmitter or structurally related neurotransmitters. More recently, however, it has become apparent that common neurotransmitters can also act as co-transmitters, adding complexity to neurotransmitter release and suggesting intriguing roles for VNTs therein. We will first describe the current knowledge on vesicular glutamate transporters (VGLUT1/2/3), the vesicular excitatory amino acid transporter (VEAT), the vesicular nucleotide transporter (VNUT), vesicular monoamine transporters (VMAT1/2), the vesicular acetylcholine transporter (VAChT) and the vesicular γ-aminobutyric acid (GABA) transporter (VGAT) in the brain. We will focus on evidence regarding transgenic mice with disruptions in VNTs in different models of seizures and epilepsy. We will also describe the known alterations and reorganizations in the expression levels of these VNTs in rodent models for temporal lobe epilepsy (TLE) and in human tissue resected for epilepsy surgery. Finally, we will discuss perspectives on opportunities and challenges for VNTs as targets for possible future epilepsy therapies.
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Stensrud M, Chaudhry F, Leergaard T, Bjaalie J, Gundersen V. Vesicular glutamate transporter-3 in the rodent brain: Vesicular colocalization with vesicular γ-aminobutyric acid transporter. J Comp Neurol 2013; 521:3042-56. [DOI: 10.1002/cne.23331] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 03/08/2013] [Accepted: 03/13/2013] [Indexed: 01/12/2023]
Affiliation(s)
- M.J. Stensrud
- Department of Anatomy; Institute of Basic Medical Sciences, and Centre for Molecular Biology and Neuroscience (CMBN), University of Oslo; 0317 Oslo; Norway
| | - F.A. Chaudhry
- The Biotechnology Centre of Oslo and The Centre for Molecular Biology and Neuroscience (CMBN); University of Oslo; 0317 Oslo; Norway
| | - T.B. Leergaard
- Department of Anatomy; Institute of Basic Medical Sciences, and Centre for Molecular Biology and Neuroscience (CMBN), University of Oslo; 0317 Oslo; Norway
| | - J.G. Bjaalie
- Department of Anatomy; Institute of Basic Medical Sciences, and Centre for Molecular Biology and Neuroscience (CMBN), University of Oslo; 0317 Oslo; Norway
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30
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Stornetta RL, Macon CJ, Nguyen TM, Coates MB, Guyenet PG. Cholinergic neurons in the mouse rostral ventrolateral medulla target sensory afferent areas. Brain Struct Funct 2013; 218:455-75. [PMID: 22460939 PMCID: PMC3459297 DOI: 10.1007/s00429-012-0408-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 03/14/2012] [Indexed: 02/07/2023]
Abstract
The rostral ventrolateral medulla (RVLM) primarily regulates respiration and the autonomic nervous system. Its medial portion (mRVLM) contains many choline acetyltransferase (ChAT)-immunoreactive (ir) neurons of unknown function. We sought to clarify the role of these cholinergic cells by tracing their axonal projections. We first established that these neurons are neither parasympathetic preganglionic neurons nor motor neurons because they did not accumulate intraperitoneally administered Fluorogold. We traced their axonal projections by injecting a Cre-dependent vector (floxed-AAV2) expressing either GFP or mCherrry into the mRVLM of ChAT-Cre mice. Transduced neurons expressing GFP or mCherry were confined to the injection site and were exclusively ChAT-ir. Their axonal projections included the dorsal column nuclei, medullary trigeminal complex, cochlear nuclei, superior olivary complex and spinal cord lamina III. For control experiments, the floxed-AAV2 (mCherry) was injected into the RVLM of dopamine beta-hydroxylase-Cre mice. In these mice, mCherry was exclusively expressed by RVLM catecholaminergic neurons. Consistent with data from rats, these catecholaminergic neurons targeted brain regions involved in autonomic and endocrine regulation. These regions were almost totally different from those innervated by the intermingled mRVLM-ChAT neurons. This study emphasizes the advantages of using Cre-driver mouse strains in combination with floxed-AAV2 to trace the axonal projections of chemically defined neuronal groups. Using this technique, we revealed previously unknown projections of mRVLM-ChAT neurons and showed that despite their close proximity to the cardiorespiratory region of the RVLM, these cholinergic neurons regulate sensory afferent information selectively and presumably have little to do with respiration or circulatory control.
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Affiliation(s)
- Ruth L Stornetta
- Department of Pharmacology, University of Virginia Health System, P.O. Box 800735, 1300 Jefferson Park Avenue, Charlottesville, VA 22908-0735, USA.
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31
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Inner hair cells of mice express the glutamine transporter SAT1. Hear Res 2012; 292:59-63. [DOI: 10.1016/j.heares.2012.07.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Revised: 07/11/2012] [Accepted: 07/14/2012] [Indexed: 11/18/2022]
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Häberle J, Shahbeck N, Ibrahim K, Schmitt B, Scheer I, O'Gorman R, Chaudhry FA, Ben-Omran T. Glutamine supplementation in a child with inherited GS deficiency improves the clinical status and partially corrects the peripheral and central amino acid imbalance. Orphanet J Rare Dis 2012; 7:48. [PMID: 22830360 PMCID: PMC3495849 DOI: 10.1186/1750-1172-7-48] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 07/06/2012] [Indexed: 11/10/2022] Open
Abstract
Glutamine synthetase (GS) is ubiquitously expressed in mammalian organisms and is a key enzyme in nitrogen metabolism. It is the only known enzyme capable of synthesising glutamine, an amino acid with many critical roles in the human organism. A defect in GLUL, encoding for GS, leads to congenital systemic glutamine deficiency and has been described in three patients with epileptic encephalopathy. There is no established treatment for this condition.Here, we describe a therapeutic trial consisting of enteral and parenteral glutamine supplementation in a four year old patient with GS deficiency. The patient received increasing doses of glutamine up to 1020 mg/kg/day. The effect of this glutamine supplementation was monitored clinically, biochemically, and by studies of the electroencephalogram (EEG) as well as by brain magnetic resonance imaging and spectroscopy.Treatment was well tolerated and clinical monitoring showed improved alertness. Concentrations of plasma glutamine normalized while levels in cerebrospinal fluid increased but remained below the lower reference range. The EEG showed clear improvement and spectroscopy revealed increasing concentrations of glutamine and glutamate in brain tissue. Concomitantly, there was no worsening of pre-existing chronic hyperammonemia.In conclusion, supplementation of glutamine is a safe therapeutic option for inherited GS deficiency since it corrects the peripheral biochemical phenotype and partially also improves the central biochemical phenotype. There was some clinical improvement but the patient had a long standing severe encephalopathy. Earlier supplementation with glutamine might have prevented some of the neuronal damage.
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Affiliation(s)
- Johannes Häberle
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland.
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33
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Hamdani EH, Gudbrandsen M, Bjørkmo M, Chaudhry FA. The system N transporter SN2 doubles as a transmitter precursor furnisher and a potential regulator of NMDA receptors. Glia 2012; 60:1671-83. [PMID: 22821889 DOI: 10.1002/glia.22386] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Revised: 06/14/2012] [Accepted: 06/15/2012] [Indexed: 12/28/2022]
Abstract
Activation of NMDA receptor requires two co-agonists, glutamate and glycine. Despite its intrinsic role in brain functions molecular mechanisms involved in glutamate replenishment and identification of the origin of glycine have eluded characterization. We have performed direct measurements of glycine flux by SN2 (Slc38a5; also known as SNAT5), executed extensive electrophysiological characterization as well as implemented ratiometric analyses to show that SN2 transport resembles SN1 in mechanism but differ in functional implications. We report that rat SN2 mediates electroneutral and bidirectional transport of glutamine and glycine at perisynaptic astroglial membranes. Sophisticated coupled and uncoupled movements of H(+) differentially associate with glutamine and glycine transport by SN2 and regulate pH(i) and the release mode of the transporter. Consequently, SN2 doubles as a transmitter precursor furnisher and a potential regulator of NMDA receptors.
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Affiliation(s)
- El Hassan Hamdani
- The Biotechnology Center and Center for Molecular Biology and Neuroscience, University of Oslo, Blindern, Oslo, Norway
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34
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Boulland JL, Chaudhry FA. Ontogenetic changes in the distribution of the vesicular GABA transporter VGAT correlate with the excitation/inhibition shift of GABA action. Neurochem Int 2012; 61:506-16. [PMID: 22490609 DOI: 10.1016/j.neuint.2012.03.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 03/19/2012] [Accepted: 03/20/2012] [Indexed: 10/28/2022]
Abstract
GABA is the major inhibitory neurotransmitter in the adult CNS and is among others involved in the synchronization of large neuronal networks. During development, GABA acts as a morphogenetic factor and has transient excitatory actions in many brain regions. One distinct protein, the vesicular GABA transporter (VGAT), has been identified accumulating GABA into presynaptic vesicles prior to its exocytotic release. The function of VGAT and its distribution is well defined in the adult, but its contribution to the transient excitatory action at putative GABAergic nerve terminals in the immature brain and its potential roles in putative glutamatergic nerve terminals remain elusive. We have studied VGAT expression in the brain from late embryonic stages through several postnatal stages until adulthood. Quantitative immunoblotting and immunolabeling of tissue sections at the light microscope and the electron microscope levels show an abrupt augmentation in VGAT staining in the cerebral cortex during the first three postnatal weeks, resembling the increase in other proteins involved in GABA synthesis and recycling in the same time frame - such as GAD65, GAD67, GAT1 (Slc6a1) and SN1 (Slc38a3) - and coincides with the synaptogenetic spurt. Dynamic changes in the expression of VGAT are seen in many cellular populations and in several layers in different brain regions. However, mossy fiber terminals (MFT) elude staining for VGAT. We also demonstrate that VGAT(+) nerve terminals undergo a developmental reorganization so that from targeting primarily the dendrites of the principal neurons in several brain regions in the immature brain, they target the soma of the same cells in the adult. This shift in the targeted subcellular compartment coincides with the conversion of the chloride gradient across neuronal membranes and suggests that it may be important for the shift of GABA action from excitation to inhibition and for the establishment of the potent synchronization of neuronal networks.
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35
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Jacoby J, Kreitzer MA, Alford S, Qian H, Tchernookova BK, Naylor ER, Malchow RP. Extracellular pH dynamics of retinal horizontal cells examined using electrochemical and fluorometric methods. J Neurophysiol 2011; 107:868-79. [PMID: 22090459 DOI: 10.1152/jn.00878.2011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Extracellular H(+) has been hypothesized to mediate feedback inhibition from horizontal cells onto vertebrate photoreceptors. According to this hypothesis, depolarization of horizontal cells should induce extracellular acidification adjacent to the cell membrane. Experiments testing this hypothesis have produced conflicting results. Studies examining carp and goldfish horizontal cells loaded with the pH-sensitive dye 5-hexadecanoylaminofluorescein (HAF) reported an extracellular acidification on depolarization by glutamate or potassium. However, investigations using H(+)-selective microelectrodes report an extracellular alkalinization on depolarization of skate and catfish horizontal cells. These studies differed in the species and extracellular pH buffer used and the presence or absence of cobalt. We used both techniques to examine H(+) changes from isolated catfish horizontal cells under identical experimental conditions (1 mM HEPES, no cobalt). HAF fluorescence indicated an acidification response to high extracellular potassium or glutamate. However, a clear extracellular alkalinization was found using H(+)-selective microelectrodes under the same conditions. Confocal microscopy revealed that HAF was not localized exclusively to the extracellular surface, but rather was detected throughout the intracellular compartment. A high degree of colocalization between HAF and the mitochondrion-specific dye MitoTracker was observed. When HAF fluorescence was monitored from optical sections from the center of a cell, glutamate produced an intracellular acidification. These results are consistent with a model in which depolarization allows calcium influx, followed by activation of a Ca(2+)/H(+) plasma membrane ATPase. Our results suggest that HAF is reporting intracellular pH changes and that depolarization of horizontal cells induces an extracellular alkalinization, which may relieve H(+)-mediated inhibition of photoreceptor synaptic transmission.
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Affiliation(s)
- Jason Jacoby
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, USA
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36
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Presynaptic regulation of quantal size: K+/H+ exchange stimulates vesicular glutamate transport. Nat Neurosci 2011; 14:1285-92. [PMID: 21874016 PMCID: PMC3183113 DOI: 10.1038/nn.2898] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Accepted: 07/11/2011] [Indexed: 11/29/2022]
Abstract
The amount of neurotransmitter stored in a single synaptic vesicle can determine the size of the postsynaptic response, but the factors that regulate vesicle filling remain poorly understood. A proton electrochemical gradient (ΔμH+) generated by the vacuolar H+-ATPase drives the accumulation of classical transmitters into synaptic vesicles. The chemical component of ΔμH+ (ΔpH) has received particular attention for its role in the vesicular transport of cationic transmitters as well as protein sorting and degradation. Thus, considerable work has addressed the factors that promote ΔpH. However, synaptic vesicle uptake of the principal excitatory transmitter glutamate depends on the electrical component of ΔμH+ (Δψ). We now find that rat brain synaptic vesicles express monovalent cation/H+ exchange activity that converts ΔpH into Δψ, and this promotes synaptic vesicle filling with glutamate. Manipulating presynaptic K+ at a glutamatergic synapse influences quantal size, demonstrating that synaptic vesicle K+/H+ exchange regulates glutamate release and synaptic transmission.
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37
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Abstract
Ion-coupled solute transporters are responsible for transporting nutrients, ions, and signaling molecules across a variety of biological membranes. Recent high-resolution crystal structures of several transporters from protein families that were previously thought to be unrelated show common structural features indicating a large structural family representing transporters from all kingdoms of life. This review describes studies that led to an understanding of the conformational changes required for solute transport in this family. The first structure in this family showed the bacterial amino acid transporter LeuT, which is homologous to neurotransmitter transporters, in an extracellularly oriented conformation with a molecule of leucine occluded at the substrate site. Studies with the mammalian serotonin transporter identified positions, buried in the LeuT structure, that defined a potential pathway leading from the cytoplasm to the substrate binding site. Modeling studies utilized an inverted structural repeat within the LeuT crystal structure to predict the conformation of LeuT in which the cytoplasmic permeation pathway, consisting of positions identified in SERT, was open for diffusion of the substrate to the cytoplasm. From the difference between the model and the crystal structures, a simple "rocking bundle" mechanism was proposed, in which a four-helix bundle changed its orientation with respect to the rest of the protein to close the extracellular pathway and open the cytoplasmic one. Subsequent crystal structures from structurally related proteins provide evidence supporting this model for transport.
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Affiliation(s)
- Gary Rudnick
- Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520-8066, United States.
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38
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Protein kinase C-mediated phosphorylation of a single serine residue on the rat glial glutamine transporter SN1 governs its membrane trafficking. J Neurosci 2011; 31:6565-75. [PMID: 21525297 DOI: 10.1523/jneurosci.3694-10.2011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Molecular mechanisms involved in the replenishment of the fast neurotransmitters glutamate and GABA are poorly understood. Glutamine sustains their generation. However, glutamine formation from the recycled transmitters is confined to glial processes and requires facilitators for its translocation across the glial and neuronal membranes. Indeed, glial processes are enriched with the system N transporter SN1 (Slc38a3), which, by bidirectional transport, maintains steady extracellular glutamine levels and thereby furnishes neurons with the primary precursor for fast neurotransmitters. We now demonstrate that SN1 is phosphorylated by protein kinase Cα (PKCα) and PKCγ. Electrophysiological characterization shows that phosphorylation reduces V(max) dramatically, whereas no significant effects are seen on the K(m). Phosphorylation occurs specifically at a single serine residue (S52) in the N-terminal rat (Rattus norvegicus) SN1 and results in sequestration of the protein into intracellular reservoirs. Prolonged activation of PKC results in partial degradation of SN1. These results provide the first demonstration of phosphorylation of SN1 and regulation of its activity at the plasma membrane. Interestingly, membrane trafficking of SN1 resembles that of the glutamate transporter GLT and the glutamate-aspartate transporter GLAST: it involves the same PKC isoforms and occurs in the same glial processes. This suggests that the glutamate/GABA-glutamine cycle may be modified at two key points by similar signaling events and unmasks a prominent role for PKC-dependent phosphorylation. Our data suggest that extracellular glutamine levels may be fine-tuned by dynamic regulation of glial SN1 activity, which may impact on transmitter generation, contribute to defining quantal size, and have profound effects on synaptic plasticity.
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Omote H, Miyaji T, Juge N, Moriyama Y. Vesicular Neurotransmitter Transporter: Bioenergetics and Regulation of Glutamate Transport. Biochemistry 2011; 50:5558-65. [DOI: 10.1021/bi200567k] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Hiroshi Omote
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan
| | - Takaaki Miyaji
- Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan
| | - Narinobu Juge
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan
| | - Yoshinori Moriyama
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan
- Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan
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40
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The Drosophila vesicular monoamine transporter reduces pesticide-induced loss of dopaminergic neurons. Neurobiol Dis 2010; 40:102-12. [PMID: 20472063 DOI: 10.1016/j.nbd.2010.05.008] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 05/04/2010] [Accepted: 05/06/2010] [Indexed: 12/21/2022] Open
Abstract
Dopamine is cytotoxic and may play a role in the development of Parkinson's disease. However, its interaction with environmental risk factors such as pesticides remains poorly understood. The vesicular monoamine transporter (VMAT) regulates intracellular dopamine content, and we have tested the neuroprotective effects of VMAT in vivo using the model organism Drosophila melanogaster. We find that Drosophila VMAT (dVMAT) mutants contain fewer dopaminergic neurons than wild type, consistent with a developmental effect, and that dopaminergic cell loss in the mutant is exacerbated by the pesticides rotenone and paraquat. Overexpression of DVMAT protein does not increase the survival of animals exposed to rotenone, but blocks the loss of dopaminergic neurons caused by this pesticide. These results are the first to demonstrate an interaction between a VMAT and pesticides in vivo, and provide an important model to investigate the mechanisms by which pesticides and cellular DA may interact to kill dopaminergic cells.
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Sitte HH, Freissmuth M. The reverse operation of Na(+)/Cl(-)-coupled neurotransmitter transporters--why amphetamines take two to tango. J Neurochem 2009; 112:340-55. [PMID: 19891736 DOI: 10.1111/j.1471-4159.2009.06474.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Sodium-chloride coupled neurotransmitter transporters achieve reuptake of their physiological substrate by exploiting the pre-existing sodium-gradient across the cellular membrane. This terminates the action of previously released substrate in the synaptic cleft. However, a change of the transmembrane ionic gradients or specific binding of some psychostimulant drugs to these proteins, like amphetamine and its derivatives, induce reverse operation of neurotransmitter:sodium symporters. This effect eventually leads to an increase in the synaptic concentration of non-exocytotically released neurotransmitters [and - in the case of the norepinephrine transporters, underlies the well-known indirect sympathomimetic activity]. While this action has long been appreciated, the underlying mechanistic details have been surprisingly difficult to understand. Some aspects can be resolved by incorporating insights into the oligomeric nature of transporters, into the nature of the accompanying ion fluxes, and changes in protein kinase activities.
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Affiliation(s)
- Harald H Sitte
- Institute of Pharmacology, Center for Biomolecular Medicine and Pharmacology, Medical University of Vienna, Vienna, Austria
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42
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Guillot TS, Miller GW. Protective actions of the vesicular monoamine transporter 2 (VMAT2) in monoaminergic neurons. Mol Neurobiol 2009; 39:149-70. [PMID: 19259829 DOI: 10.1007/s12035-009-8059-y] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2008] [Accepted: 02/18/2009] [Indexed: 12/13/2022]
Abstract
Vesicular monoamine transporters (VMATs) are responsible for the packaging of neurotransmitters such as dopamine, serotonin, norepinephrine, and epinephrine into synaptic vesicles. These proteins evolved from precursors in the major facilitator superfamily of transporters and are among the members of the toxin extruding antiporter family. While the primary function of VMATs is to sequester neurotransmitters within vesicles, they can also translocate toxicants away from cytosolic sites of action. In the case of dopamine, this dual role of VMAT2 is combined-dopamine is more readily oxidized in the cytosol where it can cause oxidative stress so packaging into vesicles serves two purposes: neurotransmission and neuroprotection. Furthermore, the deleterious effects of exogenous toxicants on dopamine neurons, such as MPTP, can be attenuated by VMAT2 activity. The active metabolite of MPTP can be kept within vesicles and prevented from disrupting mitochondrial function thereby sparing the dopamine neuron. The highly addictive drug methamphetamine is also neurotoxic to dopamine neurons by using dopamine itself to destroy the axon terminals. Methamphetamine interferes with vesicular sequestration and increases the production of dopamine, escalating the amount in the cytosol and leading to oxidative damage of terminal components. Vesicular transport seems to resist this process by sequestering much of the excess dopamine, which is illustrated by the enhanced methamphetamine neurotoxicity in VMAT2-deficient mice. It is increasingly evident that VMAT2 provides neuroprotection from both endogenous and exogenous toxicants and that while VMAT2 has been adapted by eukaryotes for synaptic transmission, it is derived from phylogenetically ancient proteins that originally evolved for the purpose of cellular protection.
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Affiliation(s)
- Thomas S Guillot
- Center for Neurodegenerative Disease, Emory University, Atlanta, GA, USA
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43
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Gammelsaeter R, Jenstad M, Bredahl MKL, Gundersen V, Chaudhry FA. Complementary expression of SN1 and SAT2 in the islets of Langerhans suggests concerted action of glutamine transport in the regulation of insulin secretion. Biochem Biophys Res Commun 2009; 381:378-82. [PMID: 19233140 DOI: 10.1016/j.bbrc.2009.02.062] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Accepted: 02/11/2009] [Indexed: 11/29/2022]
Abstract
Insulin and glucagon secretion from the islets of Langerhans is highly regulated. Although an increased plasma glucose level is the major stimulus for insulin exocytosis, roles for glutamine and glutamate have been suggested. Interestingly, the islet cells display elements associated with synaptic transmission. In the central nervous system (CNS), glutamine transport by SN1 and SAT2 sustain the generation of neurotransmitter glutamate. We hypothesized that the same transporters are essential for glutamine transport into the islet cells and for subsequent formation of glutamate acting as an intracellular signaling molecule. We demonstrate that islet cells express several transporters which can mediate glutamine transport. In particular, we show pronounced expression of SN1 and SAT2 in B-cells and A-cells, respectively. The cell-specific expression of these transporters together with their functional characteristics suggest an important role for glutamine in the regulation of insulin secretion.
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Affiliation(s)
- R Gammelsaeter
- The Centre for Molecular Biology and Neuroscience, University of Oslo, N-0317 Oslo, Norway
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44
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Unique luminal localization of VGAT-C terminus allows for selective labeling of active cortical GABAergic synapses. J Neurosci 2009; 28:13125-31. [PMID: 19052203 DOI: 10.1523/jneurosci.3887-08.2008] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neurotransmitter uptake into synaptic vesicles is mediated by vesicular neurotransmitter transporters. Although these transporters belong to different families, they all are thought to share a common overall topology with an even number of transmembrane domains. Using epitope-specific antibodies and mass spectrometry we show that the vesicular GABA transporter (VGAT) possesses an uneven number of transmembrane domains, with the N terminus facing the cytoplasm and the C terminus residing in the synaptic vesicle lumen. Antibodies recognizing the C terminus of VGAT (anti-VGAT-C) selectively label GABAergic nerve terminals of live cultured hippocampal and striatal neurons as confirmed by immunocytochemistry and patch-clamp electrophysiology. Injection of fluorochromated anti-VGAT-C into the hippocampus of mice results in specific labeling of GABAergic synapses in vivo. Overall, our data open the possibility of studying novel GABA release sites, characterizing inhibitory vesicle trafficking, and establishing their contribution to inhibitory neurotransmission at identified GABAergic synapses.
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45
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Parra LA, Baust T, El Mestikawy S, Quiroz M, Hoffman B, Haflett JM, Yao JK, Torres GE. The orphan transporter Rxt1/NTT4 (SLC6A17) functions as a synaptic vesicle amino acid transporter selective for proline, glycine, leucine, and alanine. Mol Pharmacol 2008; 74:1521-32. [PMID: 18768736 DOI: 10.1124/mol.108.050005] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rxt1/NTT4 (SLC6A17) belongs to a gene family of "orphan transporters" whose substrates and consequently functions remain unidentified. Although Rxt1/NTT4 was previously thought to function as a sodium-dependent plasma membrane transporter, recent studies localized the protein to synaptic vesicles of glutamatergic and GABAergic neurons. Here, we provide evidence indicating that Rxt1/NTT4 functions as a vesicular transporter selective for proline, glycine, leucine, and alanine. Using Western blot, immunoprecipitation, immunocytochemistry, and polymerase chain reaction approaches, we demonstrate that PC12 cells express the Rxt1/NTT4 gene and protein. Small interfering RNA (siRNA)-mediated knockdown of Rxt1/NTT4 in PC12 cells resulted in selective reductions in uptake levels for proline, glycine, leucine, and alanine. Likewise, gas chromatography analysis of amino acid content in an enriched synaptic vesicle fraction from wild-type and siRNA-Rxt1/NTT4 PC12 cells revealed that proline, glycine, leucine, and alanine levels were decreased in siRNA-treated cells compared with wild-type cells. Furthermore, Rxt1/NTT4-transfected Chinese hamster ovary (CHO) cells exhibited significant uptake increases of these amino acids compared with mock-transfected CHO cells. Finally, proline uptake in both PC12 cells and Rxt1/NTT4-transfected CHO cells was dependent on the electrochemical gradient maintained by the vacuolar-type H(+)-ATPase. These data indicate that the orphan Rxt1/NTT4 protein functions as a vesicular transporter for proline, glycine, leucine, and alanine, further suggesting its important role in synaptic transmission.
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Affiliation(s)
- Leonardo A Parra
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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46
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Fei H, Grygoruk A, Brooks ES, Chen A, Krantz DE. Trafficking of vesicular neurotransmitter transporters. Traffic 2008; 9:1425-36. [PMID: 18507811 DOI: 10.1111/j.1600-0854.2008.00771.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Vesicular neurotransmitter transporters are required for the storage of all classical and amino acid neurotransmitters in secretory vesicles. Transporter expression can influence neurotransmitter storage and release, and trafficking targets the transporters to different types of secretory vesicles. Vesicular transporters traffic to synaptic vesicles (SVs) as well as large dense core vesicles and are recycled to SVs at the nerve terminal. Some of the intrinsic signals for these trafficking events have been defined and include a dileucine motif present in multiple transporter subtypes, an acidic cluster in the neural isoform of the vesicular monoamine transporter (VMAT) 2 and a polyproline motif in the vesicular glutamate transporter (VGLUT) 1. The sorting of VMAT2 and the vesicular acetylcholine transporter to secretory vesicles is regulated by phosphorylation. In addition, VGLUT1 uses alternative endocytic pathways for recycling back to SVs following exocytosis. Regulation of these sorting events has the potential to influence synaptic transmission and behavior.
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Affiliation(s)
- Hao Fei
- Departments of Psychiatry and Neurobiology, Gonda Goldschmied Neuroscience and Genetics Research Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1761, USA
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47
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Boulland JL, Jenstad M, Boekel AJ, Wouterlood FG, Edwards RH, Storm-Mathisen J, Chaudhry FA. Vesicular glutamate and GABA transporters sort to distinct sets of vesicles in a population of presynaptic terminals. ACTA ACUST UNITED AC 2008; 19:241-8. [PMID: 18502731 DOI: 10.1093/cercor/bhn077] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Vesicular glutamate transporters (VGLUTs) 1 and 2 are expressed by neurons generally accepted to release glutamate as a neurotransmitter, whereas VGLUT3 appears in populations usually associated with a different classical transmitter. We now demonstrate VGLUT2 as well as the vesicular GABA transporter (VGAT) in a subset of presynaptic terminals in the dentate gyrus of the rat hippocampal formation. The terminals are distributed in a characteristic band overlapping with the outer part of the granule cell layer and the inner zone of the molecular layer. Within the terminals, which make asymmetric as well as symmetric synapses onto the somatodendritic compartment of the dentate granule cells, the 2 transporters localize to distinct populations of synaptic vesicles. Moreover, the axons forming these terminals originate in the supramammillary nucleus (SuM). Our data reconcile previous apparently conflicting reports on the physiology of the dentate afferents from SuM and demonstrate that both glutamate and GABA may be released from a single nerve terminal.
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