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Reid KM, Spaull R, Salian S, Barwick K, Meyer E, Zhen J, Hirata H, Sheipouri D, Benkerroum H, Gorman KM, Papandreou A, Simpson MA, Hirano Y, Farabella I, Topf M, Grozeva D, Carss K, Smith M, Pall H, Lunt P, De Gressi S, Kamsteeg E, Haack TB, Carr L, Guerreiro R, Bras J, Maher ER, Scott RH, Vandenberg RJ, Raymond FL, Chong WK, Sudhakar S, Mankad K, Reith ME, Campeau PM, Harvey RJ, Kurian MA. MED27, SLC6A7, and MPPE1 Variants in a Complex Neurodevelopmental Disorder with Severe Dystonia. Mov Disord 2022; 37:2139-2146. [PMID: 35876425 PMCID: PMC9796674 DOI: 10.1002/mds.29147] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 05/19/2022] [Accepted: 06/13/2022] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Despite advances in next generation sequencing technologies, the identification of variants of uncertain significance (VUS) can often hinder definitive diagnosis in patients with complex neurodevelopmental disorders. OBJECTIVE The objective of this study was to identify and characterize the underlying cause of disease in a family with two children with severe developmental delay associated with generalized dystonia and episodic status dystonicus, chorea, epilepsy, and cataracts. METHODS Candidate genes identified by autozygosity mapping and whole-exome sequencing were characterized using cellular and vertebrate model systems. RESULTS Homozygous variants were found in three candidate genes: MED27, SLC6A7, and MPPE1. Although the patients had features of MED27-related disorder, the SLC6A7 and MPPE1 variants were functionally investigated. SLC6A7 variant in vitro overexpression caused decreased proline transport as a result of reduced cell-surface expression, and zebrafish knockdown of slc6a7 exhibited developmental delay and fragile motor neuron morphology that could not be rescued by L-proline transporter-G396S RNA. Lastly, patient fibroblasts displayed reduced cell-surface expression of glycophosphatidylinositol-anchored proteins linked to MPPE1 dysfunction. CONCLUSIONS We report a family harboring a homozygous MED27 variant with additional loss-of-function SLC6A7 and MPPE1 gene variants, which potentially contribute to a blended phenotype caused by multilocus pathogenic variants. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Kimberley M. Reid
- Molecular Neurosciences, Developmental Neurosciences, Zayed Centre for Research into Rare Disease in ChildrenUCL Great Ormond Street Institute of Child HealthLondonUnited Kingdom
| | - Robert Spaull
- Molecular Neurosciences, Developmental Neurosciences, Zayed Centre for Research into Rare Disease in ChildrenUCL Great Ormond Street Institute of Child HealthLondonUnited Kingdom,Department of NeurologyGreat Ormond Street HospitalLondonUnited Kingdom
| | - Smrithi Salian
- Department of Pediatrics, CHU Sainte‐Justine Research CenterUniversity of MontrealMontrealQuebecCanada
| | - Katy Barwick
- Molecular Neurosciences, Developmental Neurosciences, Zayed Centre for Research into Rare Disease in ChildrenUCL Great Ormond Street Institute of Child HealthLondonUnited Kingdom
| | - Esther Meyer
- Molecular Neurosciences, Developmental Neurosciences, Zayed Centre for Research into Rare Disease in ChildrenUCL Great Ormond Street Institute of Child HealthLondonUnited Kingdom
| | - Juan Zhen
- Cell Therapy and Cell Engineering FacilityMemorial Sloan Kettering Cancer CenterNew YorkNew YorkUSA
| | - Hiromi Hirata
- Department of Chemistry and Biological ScienceCollege of Science and Engineering, Aoyama Gakuin UniversitySagamiharaJapan
| | - Diba Sheipouri
- School of Medical Sciences, University of SydneySydneyNew South WalesAustralia
| | - Hind Benkerroum
- Department of Pediatrics, CHU Sainte‐Justine Research CenterUniversity of MontrealMontrealQuebecCanada
| | - Kathleen M. Gorman
- Department of Neurology and Clinical NeurophysiologyChildren's Health Ireland at Temple StreetDublinIreland,School of Medicine and Medical SciencesUniversity College DublinDublinIreland
| | - Apostolos Papandreou
- Molecular Neurosciences, Developmental Neurosciences, Zayed Centre for Research into Rare Disease in ChildrenUCL Great Ormond Street Institute of Child HealthLondonUnited Kingdom,Department of NeurologyGreat Ormond Street HospitalLondonUnited Kingdom
| | - Michael A. Simpson
- Division of Genetics and Molecular MedicineKing's College London School of MedicineLondonUnited Kingdom
| | - Yoshinobu Hirano
- Department of Chemistry and Biological ScienceCollege of Science and Engineering, Aoyama Gakuin UniversitySagamiharaJapan
| | - Irene Farabella
- Institute of Structural and Molecular Biology, Crystallography/Department of Biological SciencesBirkbeck College, University of LondonLondonUnited Kingdom,CNAG‐CRG, Centre for Genomic Regulation (CRG)The Barcelona Institute of Science and Technology (BIST)BarcelonaSpain
| | - Maya Topf
- Leibniz Institute for Virology (HPI) and Universitätsklinikum Hamburg Eppendorf (UKE)Centre for Structural Systems Biology (CSSB)HamburgGermany,Institute of Structural and Molecular Biology, Crystallography/Department of Biological SciencesBirkbeck College, University of LondonLondonUnited Kingdom
| | - Detelina Grozeva
- Department of Medical GeneticsCambridge Institute for Medical Research, University of CambridgeCambridgeUnited Kingdom,Centre for Trials Research, Neuadd MeirionnyddCardiff UniversityCardiffUnited Kingdom
| | - Keren Carss
- Wellcome Trust Sanger InstituteCambridgeUnited Kingdom
| | - Martin Smith
- Department of NeurologyJohn Radcliffe HospitalOxfordUnited Kingdom
| | - Hardev Pall
- Department of NeurologyQueen Elizabeth HospitalBirminghamUnited Kingdom
| | - Peter Lunt
- Clinical Genetic ServiceGloucester Royal HospitalGloucesterUnited Kingdom
| | - Susanna De Gressi
- Department of PaediatricsCheltenham General HospitalGloucestershireUnited Kingdom
| | - Erik‐Jan Kamsteeg
- Department of Human GeneticsRadboud University Medical CenterNijmegenNetherlands
| | - Tobias B. Haack
- Institute of Medical Genetics and Applied GenomicsUniversity of TuebingenTuebingenGermany
| | - Lucinda Carr
- Department of NeurologyGreat Ormond Street HospitalLondonUnited Kingdom
| | - Rita Guerreiro
- Department of Neurodegenerative ScienceVan Andel InstituteGrand RapidsMichiganUSA
| | - Jose Bras
- Department of Neurodegenerative ScienceVan Andel InstituteGrand RapidsMichiganUSA
| | - Eamonn R. Maher
- Department of Medical GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| | - Richard H. Scott
- Department of Clinical GeneticsGreat Ormond Street HospitalLondonUnited Kingdom
| | | | - F. Lucy Raymond
- Centre for Trials Research, Neuadd MeirionnyddCardiff UniversityCardiffUnited Kingdom
| | - Wui K. Chong
- Department of RadiologyGreat Ormond Street HospitalLondonUnited Kingdom,Developmental Neurosciences DepartmentUCL Great Ormond Street Institute of Child HealthLondonUnited Kingdom
| | - Sniya Sudhakar
- Department of RadiologyGreat Ormond Street HospitalLondonUnited Kingdom,Developmental Neurosciences DepartmentUCL Great Ormond Street Institute of Child HealthLondonUnited Kingdom
| | - Kshitij Mankad
- Department of RadiologyGreat Ormond Street HospitalLondonUnited Kingdom,Developmental Neurosciences DepartmentUCL Great Ormond Street Institute of Child HealthLondonUnited Kingdom
| | - Maarten E. Reith
- Department of PsychiatryNew York University School of MedicineNew YorkNew YorkUSA
| | - Philippe M. Campeau
- Department of Pediatrics, CHU Sainte‐Justine Research CenterUniversity of MontrealMontrealQuebecCanada
| | - Robert J. Harvey
- School of Health and Behavioural SciencesUniversity of the Sunshine CoastSippy DownsQueenslandAustralia,Sunshine Coast Health InstituteBirtinyaQueenslandAustralia
| | - Manju A. Kurian
- Molecular Neurosciences, Developmental Neurosciences, Zayed Centre for Research into Rare Disease in ChildrenUCL Great Ormond Street Institute of Child HealthLondonUnited Kingdom,Department of NeurologyGreat Ormond Street HospitalLondonUnited Kingdom
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2
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Synaptotagmin 2 is ectopically overexpressed in excitatory presynapses of a widely used CaMKΙΙα-Cre mouse line. iScience 2022; 25:104692. [PMID: 35856033 PMCID: PMC9287804 DOI: 10.1016/j.isci.2022.104692] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 04/29/2022] [Accepted: 06/27/2022] [Indexed: 12/13/2022] Open
Abstract
The CaMKΙΙα-Cre mouse lines, possibly the most used Cre lines in neuroscience, have resulted in over 800 articles to date. Here, we demonstrate that the second most widely used CaMKΙΙα-Cre line, Tg(Camk2a-cre)2Gsc (or CamiCre), shows ectopic overexpression of synaptotagmin 2, the most efficient Ca2+ sensor for fast synchronous neurotransmitter release, in excitatory presynapses of Cre+ brains. Moreover, the upregulation of immediate-early genes and genes incorporated in bacterial artificial chromosome (BAC) transgenes, such as L-proline transporter Slc6a7, was found in Cre+ hippocampus. The copy number and integration site of the transgene are suggested to have caused the aberrant gene expression in Cre+ brains. Most importantly, CamiCre+ mice showed functional phenotypes, such as hyperactivity and enhanced associative learning, suggesting that neural activities are affected. These unexpected results suggest difficulties in interpreting results from studies using the CamiCre line and raise a warning of potential pitfalls in using Cre driver lines in general. CamiCre+ mice show the ectopic overexpression of SYT2 in excitatory presynapses CamiCre+ mice show the ectopic overexpression of SLC6A7 in hippocampal mossy fibers CamiCre+ mice show hyperactivity and enhanced associative learning Multiple copies of bacterial artificial chromosome (BAC) transgenes are integrated into the Syt2 locus
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3
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P5C as an Interface of Proline Interconvertible Amino Acids and Its Role in Regulation of Cell Survival and Apoptosis. Int J Mol Sci 2021; 22:ijms222111763. [PMID: 34769188 PMCID: PMC8584052 DOI: 10.3390/ijms222111763] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 10/26/2021] [Accepted: 10/28/2021] [Indexed: 12/15/2022] Open
Abstract
Studies of cancer metabolism have focused on the production of energy and the interconversion of carbons between cell cycles. More recently, amino acid metabolism, especially non-essential amino acids (NEAAs), has been investigated, underlining their regulatory role. One of the important mediators in energy production and interconversion of carbons in the cell is Δ1-pyrroline-5-carboxylate (P5C)—the physiological intracellular intermediate of the interconversion of proline, ornithine, and glutamate. As a central component of these conversions, it links the tricarboxylic acid cycle (TCA), urea cycle (UC), and proline cycle (PC). P5C has a cyclic structure containing a tertiary nitrogen atom (N) and is in tautomeric equilibrium with the open-chain form of L-glutamate-γ-semialdehyde (GSAL). P5C is produced by P5C synthase (P5CS) from glutamate, and ornithine via ornithine δ-amino acid transferase (δOAT). It can also be converted to glutamate by P5C dehydrogenase (P5CDH). P5C is both a direct precursor of proline and a product of its degradation. The conversion of P5C to proline is catalyzed by P5C reductase (PYCR), while proline to P5C by proline dehydrogenase/oxidase (PRODH/POX). P5C-proline-P5C interconversion forms a functional redox couple. Their transformations are accompanied by the transfer of a reducing-oxidizing potential, that affect the NADP+/NADPH ratio and a wide variety of processes, e.g., the synthesis of phosphoribosyl pyrophosphate (PRPP), and purine ribonucleotides, which are crucial for DNA synthesis. This review focuses on the metabolism of P5C in the cell as an interconversion mediator of proline, glutamate, and ornithine and its role in the regulation of survival and death with particular emphasis on the metabolic context.
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4
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Qian C, Wu Z, Sun R, Yu H, Zeng J, Rao Y, Li Y. Localization, proteomics, and metabolite profiling reveal a putative vesicular transporter for UDP-glucose. eLife 2021; 10:65417. [PMID: 34269178 PMCID: PMC8373376 DOI: 10.7554/elife.65417] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 07/15/2021] [Indexed: 11/27/2022] Open
Abstract
Vesicular neurotransmitter transporters (VNTs) mediate the selective uptake and enrichment of small-molecule neurotransmitters into synaptic vesicles (SVs) and are therefore a major determinant of the synaptic output of specific neurons. To identify novel VNTs expressed on SVs (thus identifying new neurotransmitters and/or neuromodulators), we conducted localization profiling of 361 solute carrier (SLC) transporters tagging with a fluorescent protein in neurons, which revealed 40 possible candidates through comparison with a known SV marker. We parallelly performed proteomics analysis of immunoisolated SVs and identified seven transporters in overlap. Ultrastructural analysis further supported that one of the transporters, SLC35D3, localized to SVs. Finally, by combining metabolite profiling with a radiolabeled substrate transport assay, we identified UDP-glucose as the principal substrate for SLC35D3. These results provide new insights into the functional role of SLC transporters in neurotransmission and improve our understanding of the molecular diversity of chemical transmitters.
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Affiliation(s)
- Cheng Qian
- School of Life Sciences, Tsinghua University, Beijing, China
| | - Zhaofa Wu
- State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing, China.,PKU-IDG/McGovern Institute for Brain Research, Beijing, China
| | - Rongbo Sun
- State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing, China.,PKU-IDG/McGovern Institute for Brain Research, Beijing, China
| | - Huasheng Yu
- State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing, China.,PKU-IDG/McGovern Institute for Brain Research, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Beijing, China
| | - Jianzhi Zeng
- State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing, China.,PKU-IDG/McGovern Institute for Brain Research, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Beijing, China
| | - Yi Rao
- State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing, China.,PKU-IDG/McGovern Institute for Brain Research, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Beijing, China.,Chinese Institute for Brain Research, Beijing, China
| | - Yulong Li
- State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing, China.,PKU-IDG/McGovern Institute for Brain Research, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Beijing, China.,Chinese Institute for Brain Research, Beijing, China
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5
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Pizzagalli MD, Bensimon A, Superti‐Furga G. A guide to plasma membrane solute carrier proteins. FEBS J 2021; 288:2784-2835. [PMID: 32810346 PMCID: PMC8246967 DOI: 10.1111/febs.15531] [Citation(s) in RCA: 176] [Impact Index Per Article: 58.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 08/07/2020] [Accepted: 08/17/2020] [Indexed: 12/13/2022]
Abstract
This review aims to serve as an introduction to the solute carrier proteins (SLC) superfamily of transporter proteins and their roles in human cells. The SLC superfamily currently includes 458 transport proteins in 65 families that carry a wide variety of substances across cellular membranes. While members of this superfamily are found throughout cellular organelles, this review focuses on transporters expressed at the plasma membrane. At the cell surface, SLC proteins may be viewed as gatekeepers of the cellular milieu, dynamically responding to different metabolic states. With altered metabolism being one of the hallmarks of cancer, we also briefly review the roles that surface SLC proteins play in the development and progression of cancer through their influence on regulating metabolism and environmental conditions.
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Affiliation(s)
- Mattia D. Pizzagalli
- CeMM, Research Center for Molecular Medicine of the Austrian Academy of SciencesViennaAustria
| | - Ariel Bensimon
- CeMM, Research Center for Molecular Medicine of the Austrian Academy of SciencesViennaAustria
| | - Giulio Superti‐Furga
- CeMM, Research Center for Molecular Medicine of the Austrian Academy of SciencesViennaAustria
- Center for Physiology and PharmacologyMedical University of ViennaAustria
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6
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Dalangin R, Kim A, Campbell RE. The Role of Amino Acids in Neurotransmission and Fluorescent Tools for Their Detection. Int J Mol Sci 2020; 21:E6197. [PMID: 32867295 PMCID: PMC7503967 DOI: 10.3390/ijms21176197] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 08/17/2020] [Accepted: 08/24/2020] [Indexed: 12/20/2022] Open
Abstract
Neurotransmission between neurons, which can occur over the span of a few milliseconds, relies on the controlled release of small molecule neurotransmitters, many of which are amino acids. Fluorescence imaging provides the necessary speed to follow these events and has emerged as a powerful technique for investigating neurotransmission. In this review, we highlight some of the roles of the 20 canonical amino acids, GABA and β-alanine in neurotransmission. We also discuss available fluorescence-based probes for amino acids that have been shown to be compatible for live cell imaging, namely those based on synthetic dyes, nanostructures (quantum dots and nanotubes), and genetically encoded components. We aim to provide tool developers with information that may guide future engineering efforts and tool users with information regarding existing indicators to facilitate studies of amino acid dynamics.
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Affiliation(s)
- Rochelin Dalangin
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada; (R.D.); (A.K.)
| | - Anna Kim
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada; (R.D.); (A.K.)
| | - Robert E. Campbell
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada; (R.D.); (A.K.)
- Department of Chemistry, Graduate School of Science, The University of Tokyo, Bunkyo City, Tokyo 113-0033, Japan
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7
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Say B, Dindar Badem N, Ergun U. Serum levels of ischemic modified albumin (IMA) and prolidase in migraine subjects. JOURNAL OF HEALTH SCIENCES AND MEDICINE 2020. [DOI: 10.32322/jhsm.638466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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8
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Ceylan MF, Tural Hesapcioglu S, Kasak M, Senat A, Erel O. Increased prolidase activity and high blood monocyte counts in pediatric bipolar disorder. Psychiatry Res 2019; 271:360-364. [PMID: 30529319 DOI: 10.1016/j.psychres.2018.11.066] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Revised: 11/28/2018] [Accepted: 11/29/2018] [Indexed: 01/05/2023]
Abstract
Various psychological, genetic, and biochemical factors are thought to be involved in the aetiology of pediatric bipolar disorder (PBD). However, few studies have evaluated the biochemical basis of PBD. The level of peripheral blood mononuclear cells and serum prolidase activity were determined in PBD and matched healthy comparison subjects. Blood from 38 (age range: 14-17) PBD-type I and 37 age- and gender-matched healthy comparison subjects was analyzed for numbers of neutrophils, lymphocytes, monocytes, lymphocyte-to-monocyte ratio (LMR), neutrophil-to-lymphocyte ratio (NLR) and serum prolidase activity. The prolidase activity and monocyte count were significantly higher in PBD than the control group. There were no significant differences in numbers of neutrophils, lymphocytes, LMR and NLR between the patient and control groups. These results suggest that the immune system and prolidase activity may be activated in PBD. There is a clinical benefit from the early detection of PBD using serum prolidase activity levels and monocyte counts. Especially, prolidase activity may be a trait marker for diagnosing PBD. However, further studies are needed to verify these findings.
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Affiliation(s)
- Mehmet Fatih Ceylan
- Child and Adolescent Psychiatry Department, Ankara Yildirim Beyazit University Faculty of Medicine, Ankara, Turkey.
| | - Selma Tural Hesapcioglu
- Child and Adolescent Psychiatry Department, Ankara Yildirim Beyazit University Faculty of Medicine, Ankara, Turkey
| | - Meryem Kasak
- Child and Adolescent Psychiatry Department, Ankara Yildirim Beyazit University Faculty of Medicine, Ankara, Turkey
| | - Almila Senat
- Clinical Biochemistry Department, Ankara Yildirim Beyazit University Faculty of Medicine, Ankara, Turkey
| | - Ozcan Erel
- Clinical Biochemistry Department, Ankara Yildirim Beyazit University Faculty of Medicine, Ankara, Turkey
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9
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Schulz D, Morschel J, Schuster S, Eulenburg V, Gomeza J. Inactivation of the Mouse L-Proline Transporter PROT Alters Glutamatergic Synapse Biochemistry and Perturbs Behaviors Required to Respond to Environmental Changes. Front Mol Neurosci 2018; 11:279. [PMID: 30177871 PMCID: PMC6110171 DOI: 10.3389/fnmol.2018.00279] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 07/23/2018] [Indexed: 12/12/2022] Open
Abstract
The endogenous neutral amino acid L-proline exhibits a variety of physiological and behavioral actions in the nervous system, highlighting the importance of accurately regulating its extracellular abundance. The L-proline transporter PROT (Slc6A7) is believed to control the spatial and temporal distribution of L-proline at glutamatergic synapses by rapid uptake of this amino acid into presynaptic terminals. Despite the importance of members of the Slc6 transporter family regulating neurotransmitter signaling and homeostasis in brain, evidence that PROT dysfunction supports risk for mental illness is lacking. Here we report the disruption of the PROT gene by homologous recombination. Mice defective in PROT displayed altered expression of glutamate transmission-related synaptic proteins in cortex and thalamus. PROT deficiency perturbed mouse behavior, such as reduced locomotor activity, decreased approach motivation and impaired memory extinction. Thus, our study demonstrates that PROT regulates behaviors that are needed to respond to environmental changes in vivo and suggests that PROT dysfunctions might contribute to mental disorders showing altered response choice following task contingency changes.
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Affiliation(s)
- Daniel Schulz
- Institute for Pharmaceutical Biology, University of Bonn Bonn, Germany
| | - Julia Morschel
- Institute for Pharmaceutical Biology, University of Bonn Bonn, Germany
| | - Stefanie Schuster
- Institute of Biochemistry, University of Erlangen-Nuremberg Erlangen, Germany
| | - Volker Eulenburg
- Institute of Biochemistry, University of Erlangen-Nuremberg Erlangen, Germany.,Department of Anesthesiology and Intensive Care Medicine, University of Leipzig Leipzig, Germany
| | - Jesús Gomeza
- Institute for Pharmaceutical Biology, University of Bonn Bonn, Germany
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10
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Sommer IE, Bearden CE, van Dellen E, Breetvelt EJ, Duijff SN, Maijer K, van Amelsvoort T, de Haan L, Gur RE, Arango C, Díaz-Caneja CM, Vinkers CH, Vorstman JA. Early interventions in risk groups for schizophrenia: what are we waiting for? NPJ SCHIZOPHRENIA 2016; 2:16003. [PMID: 27336054 PMCID: PMC4849435 DOI: 10.1038/npjschz.2016.3] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 01/29/2016] [Indexed: 12/16/2022]
Abstract
Intervention strategies in adolescents at ultra high-risk (UHR) for psychosis are promising for reducing conversion to overt illness, but have only limited impact on functional outcome. Recent studies suggest that cognition does not further decline during the UHR stage. As social and cognitive impairments typically develop before the first psychotic episode and even years before the UHR stage, prevention should also start much earlier in the groups at risk for schizophrenia and other psychiatric disorders. Early intervention strategies could aim to improve stress resilience, optimize brain maturation, and prevent or alleviate adverse environmental circumstances. These strategies should urgently be tested for efficacy: the prevalence of ~1% implies that yearly ~22 in every 100,000 people develop overt symptoms of this illness, despite the fact that for many of them—e.g., children with an affected first-degree family member or carriers of specific genetic variants—increased risk was already identifiable early in life. Our current ability to recognize several risk groups at an early age not only provides an opportunity, but also implies a clinical imperative to act. Time is pressing to investigate preventive interventions in high-risk children to mitigate or prevent the development of schizophrenia and related psychiatric disorders.
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Affiliation(s)
- Iris E Sommer
- Department of Psychiatry, Brain Center Rudolf Magnus, University Medical Center Utrecht , Utrecht, the Netherlands
| | - Carrie E Bearden
- Semel Institute for Neuroscience and Human Behavior, Departments of Psychiatry and Biobehavioral Sciences and Psychology, University of California , Los Angeles, CA, USA
| | - Edwin van Dellen
- Department of Psychiatry, Brain Center Rudolf Magnus, University Medical Center Utrecht , Utrecht, the Netherlands
| | - Elemi J Breetvelt
- Department of Psychiatry, Brain Center Rudolf Magnus, University Medical Center Utrecht , Utrecht, the Netherlands
| | - Sasja N Duijff
- Department of Psychiatry, Brain Center Rudolf Magnus, University Medical Center Utrecht , Utrecht, the Netherlands
| | - Kim Maijer
- Department of Psychiatry, Brain Center Rudolf Magnus, University Medical Center Utrecht , Utrecht, the Netherlands
| | - Therese van Amelsvoort
- Department of Psychiatry and Psychology, Maastricht University , Maastricht, The Netherlands
| | - Lieuwe de Haan
- Department of Psychiatry, Academic Psychiatric Centre, AMC , Amsterdam, The Netherlands
| | - Raquel E Gur
- Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania , Philadelphia, PA, USA
| | - Celso Arango
- Child and Adolescent Psychiatry Department, Hospital General Universitario Gregorio Marañón, Instituto de Investigación Sanitaria Gregorio Marañón, IiSGM, Centro de Investigación Biomédica en Red de Salud Mental, CIBERSAM, School of Medicine, Universidad Complutense , Madrid, Spain
| | - Covadonga M Díaz-Caneja
- Child and Adolescent Psychiatry Department, Hospital General Universitario Gregorio Marañón, Instituto de Investigación Sanitaria Gregorio Marañón, IiSGM, Centro de Investigación Biomédica en Red de Salud Mental, CIBERSAM, School of Medicine, Universidad Complutense , Madrid, Spain
| | - Christiaan H Vinkers
- Department of Psychiatry, Brain Center Rudolf Magnus, University Medical Center Utrecht , Utrecht, the Netherlands
| | - Jacob As Vorstman
- Department of Psychiatry, Brain Center Rudolf Magnus, University Medical Center Utrecht , Utrecht, the Netherlands
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11
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Güneş M, Bulut M, Demir S, İbiloğlu AO, Kaya MC, Atlı A, Kaplan İ, Camkurt MA, Sir A. Diagnostic performance of increased prolidase activity in schizophrenia. Neurosci Lett 2016; 613:36-40. [DOI: 10.1016/j.neulet.2015.12.036] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 11/22/2015] [Accepted: 12/17/2015] [Indexed: 12/22/2022]
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12
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Zipp GG, Barbosa J, Green MA, Terranova KM, Fink C, Yu XC, Nouraldeen A, Wilson A, Savelieva K, Lanthorn TH, David Kimball S. Novel inhibitors of the high-affinity l-proline transporter as potential therapeutic agents for the treatment of cognitive disorders. Bioorg Med Chem Lett 2014; 24:3886-90. [DOI: 10.1016/j.bmcl.2014.06.049] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 06/17/2014] [Accepted: 06/18/2014] [Indexed: 10/25/2022]
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13
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Blakely RD, Edwards RH. Vesicular and plasma membrane transporters for neurotransmitters. Cold Spring Harb Perspect Biol 2012; 4:a005595. [PMID: 22199021 PMCID: PMC3281572 DOI: 10.1101/cshperspect.a005595] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The regulated exocytosis that mediates chemical signaling at synapses requires mechanisms to coordinate the immediate response to stimulation with the recycling needed to sustain release. Two general classes of transporter contribute to release, one located on synaptic vesicles that loads them with transmitter, and a second at the plasma membrane that both terminates signaling and serves to recycle transmitter for subsequent rounds of release. Originally identified as the target of psychoactive drugs, these transport systems have important roles in transmitter release, but we are only beginning to understand their contribution to synaptic transmission, plasticity, behavior, and disease. Recent work has started to provide a structural basis for their activity, to characterize their trafficking and potential for regulation. The results indicate that far from the passive target of psychoactive drugs, neurotransmitter transporters undergo regulation that contributes to synaptic plasticity.
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Affiliation(s)
- Randy D Blakely
- Department of Pharmacology and Psychiatry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-8548, USA
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14
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Vorstman JAS, Turetsky BI, Sijmens-Morcus MEJ, de Sain MG, Dorland B, Sprong M, Rappaport EF, Beemer FA, Emanuel BS, Kahn RS, van Engeland H, Kemner C. Proline affects brain function in 22q11DS children with the low activity COMT 158 allele. Neuropsychopharmacology 2009; 34:739-46. [PMID: 18769474 PMCID: PMC2817942 DOI: 10.1038/npp.2008.132] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The association between the 22q11.2 deletion syndrome (22q11DS) and psychiatric disorders, particularly psychosis, suggests a causal relationship between 22q11DS genes and abnormal brain function. The genes catechol-O-methyl-transferase (COMT) and proline dehydrogenase both reside within the commonly deleted region of 22q11.2. COMT activity and proline levels may therefore be altered in 22q11DS individuals. Associations of both COMT(158) genotype and elevated serum proline levels with abnormal brain function have been reported. Fifty-six 22q11DS children and 75 healthy controls were assessed on physiological measures of brain function, including prepulse inhibition (PPI) of startle, P50 auditory sensory gating and smooth pursuit eye movements (SPEM). COMT(158) genotype and plasma proline levels were determined in the 22q11DS children. We hypothesized an interaction between the COMT(158) genotype and proline, predicting the strongest negative effect of high proline on brain function to occur in 22q11DS children who are carriers of the COMT(met) allele. Of the three physiological measures, only SPEM and PPI were abnormal in the patient sample. With regard to the SPEM performance, there was a significant interaction between the COMT(158) genotype and proline level with significantly decreased SPEM performance in children with high plasma proline levels and the low activity COMT(met) allele. A similar interaction effect was not observed with regard to PPI. These findings are consistent with a model in which elevated proline negatively affects brain function by an increase in dopamine in the prefrontal cortex. 22q11DS patients with low dopamine catabolic capacity are therefore especially vulnerable to this functional disruption.
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Affiliation(s)
- Jacob AS Vorstman
- Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands, Division of Human Genetics, the Children’s Hospital of Philadelphia, Abramson Research Center, Philadelphia, PA, USA,Correspondence: Dr JAS Vorstman, Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht 3584 CX, The Netherlands, Tel: + 31 88 755 7129, Fax: + 31 88 755 5406,
| | - Bruce I Turetsky
- Department of Psychiatry, University of Pennsylvania, Philadelphia, PA, USA
| | - Monique EJ Sijmens-Morcus
- Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Monique G de Sain
- Department of Metabolic Diseases, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Bert Dorland
- Department of Metabolic Diseases, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Mirjam Sprong
- Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Eric F Rappaport
- Department of Biostatistics and Data Management Core, the Children’s Hospital of Philadelphia, Abramson Research Center, Philadelphia, PA, USA
| | - Frits A Beemer
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Beverly S Emanuel
- Division of Human Genetics, the Children’s Hospital of Philadelphia, Abramson Research Center, Philadelphia, PA, USA, Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - René S Kahn
- Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Herman van Engeland
- Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Chantal Kemner
- Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands
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15
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Yu XC, Zhang W, Oldham A, Buxton E, Patel S, Nghi N, Tran D, Lanthorn TH, Bomont C, Shi ZC, Liu Q. Discovery and characterization of potent small molecule inhibitors of the high affinity proline transporter. Neurosci Lett 2009; 451:212-6. [DOI: 10.1016/j.neulet.2009.01.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Revised: 01/05/2009] [Accepted: 01/06/2009] [Indexed: 11/25/2022]
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16
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Chaudhry FA, Boulland JL, Jenstad M, Bredahl MKL, Edwards RH. Pharmacology of neurotransmitter transport into secretory vesicles. Handb Exp Pharmacol 2008:77-106. [PMID: 18064412 DOI: 10.1007/978-3-540-74805-2_4] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Many neuropsychiatric disorders appear to involve a disturbance of chemical neurotransmission, and the mechanism of available therapeutic agents supports this impression. Postsynaptic receptors have received considerable attention as drug targets, but some of the most successful agents influence presynaptic processes, in particular neurotransmitter reuptake. The pharmacological potential of many other presynaptic elements, and in particular the machinery responsible for loading transmitter into vesicles, has received only limited attention. The similarity of vesicular transporters to bacterial drug resistance proteins and the increasing evidence for regulation of vesicle filling and recycling suggest that the pharmacological potential of vesicular transporters has been underestimated. In this review, we discuss the pharmacological effects of psychostimulants and therapeutic agents on transmitter release.
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Affiliation(s)
- Farrukh A Chaudhry
- The Biotechnology Centre of Oslo, University of Oslo, 1125, Blindern, Oslo, 0317, Norway.
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17
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Drgonova J, Liu QR, Hall FS, Krieger RM, Uhl GR. Deletion of v7-3 (SLC6A15) transporter allows assessment of its roles in synaptosomal proline uptake, leucine uptake and behaviors. Brain Res 2007; 1183:10-20. [PMID: 17931606 PMCID: PMC2211565 DOI: 10.1016/j.brainres.2007.09.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Revised: 08/23/2007] [Accepted: 09/04/2007] [Indexed: 10/22/2022]
Abstract
V7-3 (SLC6A15) is the prototype for a gene subfamily whose members have sequence homologies to classical Na+- and Cl(-)-dependent neurotransmitter transporters but display unusual features that include characteristic large fourth extracellular loops. Interest in v7-3 has been increased by the elucidation of its expression in neurons located in cerebral cortex, hippocampus, cerebellum, midbrain and olfactory bulb. To help clarify the role of v7-3 in brain functions, we have created and characterized v7-3 knockout mice. These mice lack functional v7-3 protein but are viable and fertile. While our studies were in progress, v7-3 expression was reported to confer transport of proline and branched-chain amino acids in in vitro expression systems [Takanaga, H., Mackenzie, B., Peng, J.B., Hediger, M.A., 2005b. Characterization of a branched-chain amino-acid transporter SBAT1 (SLC6A15) that is expressed in human brain. Biochem. Biophys. Res. Commun. 337, 892-900; Broer, A., Tietze, N., Kowalczuk, S., Chubb, S., Munzinger, M., Bak, L.K., Broer, S., 2006. The orphan transporter v7-3 (slc6a15) is a Na+-dependent neutral amino acid transporter (B0AT2). Biochem. J. 393, 421-430]. Assessment of amino acid uptake into cortical synaptosomes of v7-3 knockouts identified 15% and 40% reductions in sodium-dependent proline and leucine transport, respectively, compared to wild type controls. Despite these biochemical changes, v7-3 knockout mice demonstrate only modest alterations in rotarod performance with aging and lack reproducible alterations in other motor, memory, anxiety or olfactory tests. Compensation for the lack of v7-3 via other amino acid carriers is likely to leave v7-3 knockouts without gross behavioral manifestations. The current results place v7-3 in the context of other brain transporters that accumulate proline and branched-chain amino acids.
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Affiliation(s)
- Jana Drgonova
- Molecular Neurobiology Branch, NIDA, NIH, 333 Cassell Drive, Baltimore, MD 21224, USA
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18
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Langen KJ, Hamacher K, Pauleit D, Floeth FW, Stoffels G, Bauer D, Reifenberger G, Zilles K, Coenen HH. Evaluation of new 18F-labeled amino acids for brain PET. ACTA ACUST UNITED AC 2006; 210:455-61. [PMID: 16177907 DOI: 10.1007/s00429-005-0033-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- K J Langen
- Brain Imaging Centre West, Jülich, Germany.
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Langen KJ, Hamacher K, Bauer D, Bröer S, Pauleit D, Herzog H, Floeth F, Zilles K, Coenen HH. Preferred stereoselective transport of the D-isomer of cis-4-[18F]fluoro-proline at the blood-brain barrier. J Cereb Blood Flow Metab 2005; 25:607-16. [PMID: 15744252 DOI: 10.1038/sj.jcbfm.9600065] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Generally, L-amino acids are preferably transported into mammalian cells compared with their D-isomers, and only L-amino acids are incorporated into proteins. Former studies, however, indicated that D-[H]proline is accumulated in the brain of mice after injection, while L-[3H]proline is not. We investigated the differential cerebral uptake of the D- and L-isomers of the PET tracer cis-4-[18F]fluoroproline (D-/L-cis-FPro) and of D-/L-[3H]proline (D-/L-Pro) in rats by dual tracer autoradiography and the uptake of D-cis-FPro in two human subjects by PET. The standardized uptake value (SUV) of D-cis-FPro in the cerebral cortex of rats 2 h p.i. was 3.05+/-1.18 (n=9) versus 0.06+/-0.01 (n=4) for L-cis-FPro (P<0.001) and 1.29+/-0.27 (n=4) for D-Pro versus 0.30+/-0.14 (n=9) for L-Pro (P<0.001). Analysis of the rat brain tissue after injection of D-cis-FPro (n=3) revealed no radioactivity in the proteins but a relevant part in the form of L-trans-FPro. The PET studies yielded a four- to five-fold higher SUV and influx rate constant in the human cortex for D-cis-FPro than for L-cis-FPro. We conclude that D-cis-FPro and D-Pro are preferably transported at the blood-brain barrier compared with their L-isomers and isomerized to the L-form within the brain. Thus, D-Pro in the plasma might be a source of intracerebral L-proline, which has been shown to act as a modulator of excitatory neurotransmission.
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Mueller NK, Di S, Paden CM, Herman JP. Activity-dependent modulation of neurotransmitter innervation to vasopressin neurons of the supraoptic nucleus. Endocrinology 2005; 146:348-54. [PMID: 15388644 DOI: 10.1210/en.2004-0539] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Confocal microscopy was used to assess activity-dependent neuroplasticity in neurotransmitter innervation of vasopressin immunoreactive magnocellular neurons in the supraoptic nucleus (SON). Vesicular glutamate transporter 2, glutamic acid decarboxylase, and dopamine beta-hydroxylase (DBH) synaptic boutons were visualized in apposition to vasopressin neurons in the SON. A decrease in DBH synaptic boutons per cell was seen upon salt loading, indicating diminished noradrenergic/adrenergic innervation. Loss of DBH appositions to vasopressin neurons was associated with a general loss of DBH immunoreactivity in the SON. In contrast, the number of vesicular glutamate transporter 2 synaptic boutons per neuron increased with salt loading, consistent with increased glutamatergic drive of magnocellular SON neurons. Salt loading also caused an increase in the total number of glutamic acid decarboxylase synaptic boutons on vasopressinergic neurons, suggesting enhanced inhibitory innervation as well. These studies indicate that synaptic plasticity compensates for increased secretory demand and may indeed underlie increased secretion, perhaps via neurotransmitter-specific, activity-related changes in synaptic contacts on vasopressinergic magnocellular neurons in the SON.
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Affiliation(s)
- Nancy K Mueller
- Department of Psychiatry, University of Cincinnati Medical Center, Cincinnati, Ohio 45237-0506, USA
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21
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Agulhon C, Rostaing P, Ravassard P, Sagné C, Triller A, Giros B. Lysosomal amino acid transporter LYAAT-1 in the rat central nervous system: an in situ hybridization and immunohistochemical study. J Comp Neurol 2003; 462:71-89. [PMID: 12761825 DOI: 10.1002/cne.10712] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A first mammalian lysosomal transporter (LYAAT-1) was recently identified and functionally characterized. Preliminary immunocytochemical data revealed that LYAAT-1 localizes to lysosomes in some neurons. In order to determine whether it is expressed in specific neuron populations and other cell types, and to confirm whether it is localized at the membrane of lysosomes, we used in situ hybridization and immunohistochemistry methods in adult rat central nervous system (CNS). We found that LYAAT-1 is expressed in most areas of the CNS, specifically in neurons, but also in choroid plexus and ependymal epithelium cells. LYAAT-1-IR (immunoreactivity) levels varied among different neuroanatomical structures but were present in neurons independently of the neurotransmitter used (glutamate, GABA, acetylcholine, noradrenaline, serotonin, or glycine). Light and confocal microscopy demonstrated that LYAAT-1 and the lysosomal marker cathepsin D colocalized throughout the brain and electron microscopy showed that LYAAT-1-IR was associated with lysosomal membranes. In addition, LYAAT-1-IR was also found associated with other membranes belonging to the Golgi apparatus and lateral saccules and less frequently with multivesicular bodies, endoplasmic reticulum, and occasionally with the plasma membrane. The localization of LYAAT-1 at the lysosomal membrane is consistent with the view that it mediates amino acid efflux from lysosomes. Furthermore, its cell expression pattern suggests that it may contribute to specialized cellular function in the rat CNS such as neuronal metabolism, neurotransmission, and control of brain amino acid homeostasis.
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Affiliation(s)
- Cendra Agulhon
- Institut National de la Santé et de la Recherche Médicale (INSERM) U513, CHU Henri Mondor, 94000 Créteil, France.
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22
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Craig AM, Boudin H. Molecular heterogeneity of central synapses: afferent and target regulation. Nat Neurosci 2001; 4:569-78. [PMID: 11369937 DOI: 10.1038/88388] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Electrophysiological recordings show a functional spectrum even within a single class of synapse, with individual synapses ranging widely in fundamental properties, including release probability, unitary response and effects of previous stimulation on subsequent response. Molecular and cellular biological approaches have shown a corresponding diversity in the complement of ion channels, receptors, scaffolds and signal transducing proteins that make up individual synapses. Indeed, we believe that each individual synapse is unique, a function of presynaptic cell type, postsynaptic cell type, environment, developmental stage and history of activity. We review here the molecular diversity of glutamatergic and GABAergic synapses in the mammalian brain in the context of potential cell biological mechanisms that may explain how individual cells develop and maintain such a mosaic of synaptic connections.
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Affiliation(s)
- A M Craig
- Department of Anatomy and Neurobiology, Washington University School of Medicine, 660 S. Euclid, Campus Box 8108, 958 McDonnell Sciences Building, St. Louis, Missouri 63110, USA.
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Abstract
This review provides an overview of the distributions, properties and roles of amino acid transport systems in normal and pathological retinal tissues and discusses the roles of specific identified transporters in the mammalian retina. The retina is used in this context as a vehicle for describing neuronal and glial properties, which are in some, but not all cases comparable to those found elsewhere an the brain. Where significant departures are noted, these are discussed in the context of functional specialisations of the retina and its relationship to adjacent supporting tissues such as the retinal pigment epithelium. Specific examples are given where immunocytochemical labelling for amino acid transporters may yield inaccurate results, possibly because of activity-dependent conformation changes of epitopes in these proteins which render the epitopes more or less accessible to antibodies.
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Affiliation(s)
- D V Pow
- Department of Physiology and Pharmacology, School of Biomedical Sciences, University of Queensland, Brisbane 4072, Australia.
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Abstract
To determine whether presynaptic input is necessary for postsynaptic differentiation, we isolated hippocampal neurons in microisland culture and thus deprived pyramidal cells of GABA input and GABAergic neurons of glutamate input. We find that glutamate input is necessary for clustering the AMPA-type glutamate receptor but not for clustering the NMDA receptor or the associated PSD-95 family scaffold in GABAergic cells; GABA input is not necessary for clustering the GABA(A) receptor or gephyrin in pyramidal cells. Isolated neurons showed a surprising mismatch of presynaptic and postsynaptic components. For example, in isolated pyramidal neurons, although GABA(A) receptor clusters covered <4% of the dendritic surface and presynaptic boutons covered <12%, a full two-thirds of the GABA(A) receptor clusters were localized inappropriately opposite the non-GABAergic, presumed glutamatergic, terminals. Furthermore, inhibitory and excitatory postsynaptic components were segregated into separate clusters in isolated cells and apposed to separate boutons of a single axon. Thus, GABA(A) receptors were clustered opposite some terminals, whereas NMDA receptors were clustered opposite other terminals of a single axon. These results suggest the involvement of a synaptogenic signal common to glutamate and GABA synapses that permits experimentally induced mismatching of presynaptic and postsynaptic components in isolated neurons, as well as a second specificity-conferring signal that mediates appropriate matching in mixed cultures.
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L-proline and L-pipecolate induce enkephalin-sensitive currents in human embryonic kidney 293 cells transfected with the high-affinity mammalian brain L-proline transporter. J Neurosci 1999. [PMID: 10414958 DOI: 10.1523/jneurosci.19-15-06290.1999] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The high-affinity mammalian brain L-proline transporter (PROT) belongs to the GAT1 gene family, which includes Na- and Cl-dependent plasma membrane carriers for neurotransmitters, osmolites, and metabolites. These transporters couple substrate flux to transmembrane electrochemical gradients, particularly the Na gradient. In the nervous system, transporters clear synapses and help to replenish transmitters in nerve terminals. The localization of PROT to specific excitatory terminals in rat forebrain suggests a role for this carrier in excitatory transmission (). We investigated the voltage regulation and electrogenicity of this novel transporter, using human embryonic kidney (HEK) 293 cells stably transfected with rat PROT cDNA. In physiological solutions between -140 and -40 mV, L-proline (PRO) and its six-member ring congener L-pipecolate (PIP) induced inward current. The current-voltage relationship and the variance of current fluctuations were similar for PRO- and PIP-induced current, and the ratio of induced variance to the mean current ranged from 20 to 60 fA. Des-Tyr-Leu-enkephalin (GGFL), a competitive peptide inhibitor of PROT, reduced the rat PROT-associated current to control levels. GGFL alone did not elicit currents, and the GGFL-sensitive substrate-induced current was absent in nontransfected cells. Finally, GGFL inhibited PROT-mediated transport only when applied to the extracellular face of PROT. These data suggest that (1) PROT uptake is electrogenic, (2) individual transporter currents are voltage-independent, and (3) GGFL is a nonsubstrate inhibitor that interacts either with an extracellular domain of PROT or in an externally accessible pore.
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