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Yamashita M, Hori T. A Novel Method to Monitor GABA Loading into Synaptic Vesicles by Combining Patch Pipette Perfusion and Intracellular, Caged-GABA Photolysis in Brain Slice Preparations. Methods Mol Biol 2022; 2417:113-120. [PMID: 35099795 DOI: 10.1007/978-1-0716-1916-2_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
A given concentration of GABA can be introduced into a presynaptic terminal by patch clamping the soma of a presynaptic neuron, if the neuron has a relatively short axon. By combining patch pipette perfusion or intracellular, caged-GABA photolysis, it is possible to measure various parameters related to synaptic vesicle filling with GABA.
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Affiliation(s)
- Manami Yamashita
- Department of Physiology, Faculty of Medicine, Osaka Medical and Pharmaceutical University, Osaka, Japan.
| | - Tetsuya Hori
- Cellular and Molecular Synaptic Function Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan.
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2
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Birinci Y, Preobraschenski J, Ganzella M, Jahn R, Park Y. Isolation of large dense-core vesicles from bovine adrenal medulla for functional studies. Sci Rep 2020; 10:7540. [PMID: 32371955 PMCID: PMC7200684 DOI: 10.1038/s41598-020-64486-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 04/17/2020] [Indexed: 01/17/2023] Open
Abstract
Large dense-core vesicles (LDCVs) contain a variety of neurotransmitters, proteins, and hormones such as biogenic amines and peptides, together with microRNAs (miRNAs). Isolation of LDCVs is essential for functional studies including vesicle fusion, vesicle acidification, monoamine transport, and the miRNAs stored in LDCVs. Although several methods were reported for purifying LDCVs, the final fractions are significantly contaminated by other organelles, compromising biochemical characterization. Here we isolated LDCVs (chromaffin granules) with high yield and purity from bovine adrenal medulla. The fractionation protocol combines differential and continuous sucrose gradient centrifugation, allowing for reducing major contaminants such as mitochondria. Purified LDCVs show robust acidification by the endogenous V-ATPase and undergo SNARE-mediated fusion with artificial membranes. Interestingly, LDCVs contain specific miRNAs such as miR-375 and miR-375 is stabilized by protein complex against RNase A. This protocol can be useful in research on the biological functions of LDCVs.
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Affiliation(s)
- Yelda Birinci
- Department of Molecular Biology and Genetics, Koç University, Istanbul, 34450, Turkey
| | - Julia Preobraschenski
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Am Faßberg 11, 37077, Göttingen, Germany
| | - Marcelo Ganzella
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Am Faßberg 11, 37077, Göttingen, Germany
| | - Reinhard Jahn
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Am Faßberg 11, 37077, Göttingen, Germany.
| | - Yongsoo Park
- Department of Molecular Biology and Genetics, Koç University, Istanbul, 34450, Turkey. .,Neurological Disorders Research Center, Qatar Biomedical Research Institute (QBRI), Hamad Bin Khalifa University (HBKU), Qatar Foundation, PO Box 34110, Doha, Qatar.
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3
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Eriksen J, Li F, Edwards RH. The mechanism and regulation of vesicular glutamate transport: Coordination with the synaptic vesicle cycle. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183259. [PMID: 32147354 DOI: 10.1016/j.bbamem.2020.183259] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 03/02/2020] [Accepted: 03/02/2020] [Indexed: 01/30/2023]
Abstract
The transport of classical neurotransmitters into synaptic vesicles generally relies on a H+ electrochemical gradient (∆μH+). Synaptic vesicle uptake of glutamate depends primarily on the electrical component ∆ψ as the driving force, rather than the chemical component ∆pH. However, the vesicular glutamate transporters (VGLUTs) belong to the solute carrier 17 (SLC17) family, which includes closely related members that function as H+ cotransporters. Recent work has also shown that the VGLUTs undergo allosteric regulation by H+ and Cl-, and exhibit an associated Cl- conductance. These properties appear to coordinate VGLUT activity with the large ionic shifts that accompany the rapid recycling of synaptic vesicles driven by neural activity. Recent structural information also suggests common mechanisms that underlie the apparently divergent function of SLC17 family members, and that confer allosteric regulation.
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Affiliation(s)
- Jacob Eriksen
- Department of Physiology, UCSF School of Medicine, United States of America; Department of Neurology, UCSF School of Medicine, United States of America
| | - Fei Li
- Department of Physiology, UCSF School of Medicine, United States of America; Department of Neurology, UCSF School of Medicine, United States of America
| | - Robert H Edwards
- Department of Physiology, UCSF School of Medicine, United States of America; Department of Neurology, UCSF School of Medicine, United States of America.
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4
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Yamashita M, Kawaguchi SY, Hori T, Takahashi T. Vesicular GABA Uptake Can Be Rate Limiting for Recovery of IPSCs from Synaptic Depression. Cell Rep 2019; 22:3134-3141. [PMID: 29562170 DOI: 10.1016/j.celrep.2018.02.080] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Revised: 01/05/2018] [Accepted: 02/21/2018] [Indexed: 11/16/2022] Open
Abstract
Synaptic efficacy plays crucial roles in neuronal circuit operation and synaptic plasticity. Presynaptic determinants of synaptic efficacy are neurotransmitter content in synaptic vesicles and the number of vesicles undergoing exocytosis at a time. Bursts of presynaptic firings depress synaptic efficacy, mainly due to depletion of releasable vesicles, whereas recovery from strong depression is initiated by endocytic vesicle retrieval followed by refilling of vesicles with neurotransmitter. We washed out presynaptic cytosolic GABA to induce a rundown of IPSCs at cerebellar inhibitory cell pairs in slices from rats and then allowed fast recovery by elevating GABA concentration using photo-uncaging. The time course of this recovery coincided with that of IPSCs from activity-dependent depression induced by a train of high-frequency stimulation. We conclude that vesicular GABA uptake can be a limiting step for the recovery of inhibitory neurotransmission from synaptic depression.
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Affiliation(s)
- Manami Yamashita
- Laboratory of Molecular Synaptic Function, Graduate School of Brain Science, Doshisha University, Kyoto 610-0394, Japan; Department of Physiology, Faculty of Medicine, Osaka Medical College, Osaka 569-8686, Japan
| | - Shin-Ya Kawaguchi
- Society-Academia Collaboration for Innovation, Kyoto University, Kyoto 606-8501, Japan
| | - Tetsuya Hori
- Department of Neurophysiology, Graduate School of Life and Medical Sciences, Doshisha University, Kyoto 610-0394, Japan.
| | - Tomoyuki Takahashi
- Cellular and Molecular Synaptic Function Unit, Okinawa Institute of Science and Technology (OIST) Graduate University, Okinawa 904-0495, Japan.
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5
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Dubouskaya TG, Hrynevich SV, Fedorovich SV. The Combined Effect of Glucose and β-Hydroxybutyrate on the Membrane Potential of Synaptosomal Mitochondria. Biophysics (Nagoya-shi) 2019. [DOI: 10.1134/s0006350919030060] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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6
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Mulvihill KG. Presynaptic regulation of dopamine release: Role of the DAT and VMAT2 transporters. Neurochem Int 2018; 122:94-105. [PMID: 30465801 DOI: 10.1016/j.neuint.2018.11.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 10/28/2018] [Accepted: 11/08/2018] [Indexed: 01/23/2023]
Abstract
The signaling dynamics of the neurotransmitter dopamine has been established to have an important role in a variety of behavioural processes including motor control, cognition, and emotional processing. Key regulators of transmitter release and the signaling dynamics of dopamine are the plasma membrane reuptake transporter (DAT) and the vesicular monoamine transporter (VMAT2). These proteins serve to remove dopamine molecules from the extracellular and cytosolic space, respectively and both determine the amount of transmitter released from synaptic vesicles. This review provides an overview of how these transporter proteins are involved in molecular regulation and function together to govern the dynamics of vesicular release with opposing effects on the quantal size and extracellular concentration of dopamine. These transporter proteins are both focal points of convergence for a variety of regulatory molecular cascades as well as targets for many pharmacological agents. The ratio between these transporters is argued to be useful as a molecular marker for delineating dopamine functional subsystems that may differ in transmitter release patterns.
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Affiliation(s)
- Kevin G Mulvihill
- Department of Psychology, Brock University, St. Catharines, ON, L2S 3A1, Canada.
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7
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Preobraschenski J, Cheret C, Ganzella M, Zander JF, Richter K, Schenck S, Jahn R, Ahnert-Hilger G. Dual and Direction-Selective Mechanisms of Phosphate Transport by the Vesicular Glutamate Transporter. Cell Rep 2018; 23:535-545. [DOI: 10.1016/j.celrep.2018.03.055] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 02/13/2018] [Accepted: 03/14/2018] [Indexed: 11/30/2022] Open
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8
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Farsi Z, Jahn R, Woehler A. Proton electrochemical gradient: Driving and regulating neurotransmitter uptake. Bioessays 2017; 39. [PMID: 28383767 DOI: 10.1002/bies.201600240] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Accumulation of neurotransmitters in the lumen of synaptic vesicles (SVs) relies on the activity of the vacuolar-type H+ -ATPase. This pump drives protons into the lumen, generating a proton electrochemical gradient (ΔμH+ ) across the membrane. Recent work has demonstrated that the balance between the chemical (ΔpH) and electrical (ΔΨ) components of ΔμH+ is regulated differently by some distinct vesicle types. As different neurotransmitter transporters use ΔpH and ΔΨ with different relative efficiencies, regulation of this gradient balance has the potential to influence neurotransmitter uptake. Nevertheless, the underlying mechanisms responsible for this regulation remain poorly understood. In this review, we provide an overview of current neurotransmitter uptake models, with a particular emphasis on the distinct roles of the electrical and chemical gradients and current hypotheses for regulatory mechanisms.
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Affiliation(s)
- Zohreh Farsi
- Max-Delbrück Center for Molecular Medicine, Berlin Institute for Medical Systems Biology, Berlin, Germany
| | - Reinhard Jahn
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Andrew Woehler
- Max-Delbrück Center for Molecular Medicine, Berlin Institute for Medical Systems Biology, Berlin, Germany
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9
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Unique pH dynamics in GABAergic synaptic vesicles illuminates the mechanism and kinetics of GABA loading. Proc Natl Acad Sci U S A 2016; 113:10702-7. [PMID: 27601664 DOI: 10.1073/pnas.1604527113] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
GABA acts as the major inhibitory neurotransmitter in the mammalian brain, shaping neuronal and circuit activity. For sustained synaptic transmission, synaptic vesicles (SVs) are required to be recycled and refilled with neurotransmitters using an H(+) electrochemical gradient. However, neither the mechanism underlying vesicular GABA uptake nor the kinetics of GABA loading in living neurons have been fully elucidated. To characterize the process of GABA uptake into SVs in functional synapses, we monitored luminal pH of GABAergic SVs separately from that of excitatory glutamatergic SVs in cultured hippocampal neurons. By using a pH sensor optimal for the SV lumen, we found that GABAergic SVs exhibited an unexpectedly higher resting pH (∼6.4) than glutamatergic SVs (pH ∼5.8). Moreover, unlike glutamatergic SVs, GABAergic SVs displayed unique pH dynamics after endocytosis that involved initial overacidification and subsequent alkalization that restored their resting pH. GABAergic SVs that lacked the vesicular GABA transporter (VGAT) did not show the pH overshoot and acidified further to ∼6.0. Comparison of luminal pH dynamics in the presence or absence of VGAT showed that VGAT operates as a GABA/H(+) exchanger, which is continuously required to offset GABA leakage. Furthermore, the kinetics of GABA transport was slower (τ > 20 s at physiological temperature) than that of glutamate uptake and may exceed the time required for reuse of exocytosed SVs, allowing reuse of incompletely filled vesicles in the presence of high demand for inhibitory transmission.
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10
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Aubrey KR. Presynaptic control of inhibitory neurotransmitter content in VIAAT containing synaptic vesicles. Neurochem Int 2016; 98:94-102. [PMID: 27296116 DOI: 10.1016/j.neuint.2016.06.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 05/21/2016] [Accepted: 06/07/2016] [Indexed: 12/13/2022]
Abstract
In mammals, fast inhibitory neurotransmission is carried out by two amino acid transmitters, γ-aminobutyric acid (GABA) and glycine. The higher brain uses only GABA, but in the spinal cord and brain stem both GABA and glycine act as inhibitory signals. In some cases GABA and glycine are co-released from the same neuron where they are co-packaged into synaptic vesicles by a shared vesicular inhibitory amino acid transporter, VIAAT (also called vGAT). The vesicular content of all other classical neurotransmitters (eg. glutamate, monoamines, acetylcholine) is determined by the presence of a specialized vesicular transporter. Because VIAAT is non-specific, the phenotype of inhibitory synaptic vesicles is instead predicted to be dependent on the relative concentration of GABA and glycine in the cytosol of the presynaptic terminal. This predicts that changes in GABA or glycine supply should be reflected in vesicle transmitter content but as yet, the mechanisms that control GABA versus glycine uptake into synaptic vesicles and their potential for modulation are not clearly understood. This review summarizes the most relevant experimental data that examines the link between GABA and glycine accumulation in the presynaptic cytosol and the inhibitory vesicle phenotype. The accumulated evidence challenges the hypothesis that vesicular phenotype is determined simply by the competition of inhibitory transmitter for VIAAT and instead suggest that the GABA/glycine balance in vesicles is dynamically regulated.
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Affiliation(s)
- Karin R Aubrey
- Pain Management Research Institute, Kolling Institute of Medical Research & Northern Clinical School, University of Sydney at Royal North Shore Hospital, Pacific Hwy, St Leonards, NSW, 2065, Australia.
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11
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Farsi Z, Preobraschenski J, van den Bogaart G, Riedel D, Jahn R, Woehler A. Single-vesicle imaging reveals different transport mechanisms between glutamatergic and GABAergic vesicles. Science 2016; 351:981-4. [DOI: 10.1126/science.aad8142] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 01/14/2016] [Indexed: 12/13/2022]
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12
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Takamori S. Presynaptic Molecular Determinants of Quantal Size. Front Synaptic Neurosci 2016; 8:2. [PMID: 26903855 PMCID: PMC4744840 DOI: 10.3389/fnsyn.2016.00002] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Accepted: 01/25/2016] [Indexed: 01/22/2023] Open
Abstract
The quantal hypothesis for the release of neurotransmitters at the chemical synapse has gained wide acceptance since it was first worked out at the motor endplate in frog skeletal muscle in the 1950’s. Considering the morphological identification of synaptic vesicles (SVs) at the nerve terminals that appeared to be homogeneous in size, the hypothesis proposed that signal transduction at synapses is mediated by the release of neurotransmitters packed in SVs that are individually uniform in size; the amount of transmitter in a synaptic vesicle is called a quantum. Although quantal size—the amplitude of the postsynaptic response elicited by the release of neurotransmitters from a single vesicle—clearly depends on the number and sensitivity of the postsynaptic receptors, accumulating evidence has also indicated that the amount of neurotransmitters stored in SVs can be altered by various presynaptic factors. Here, I provide an overview of the concepts and underlying presynaptic molecular underpinnings that may regulate quantal size.
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Affiliation(s)
- Shigeo Takamori
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University Kyoto, Japan
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13
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14
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Zimmermann J, Herman MA, Rosenmund C. Co-release of glutamate and GABA from single vesicles in GABAergic neurons exogenously expressing VGLUT3. Front Synaptic Neurosci 2015; 7:16. [PMID: 26441632 PMCID: PMC4585203 DOI: 10.3389/fnsyn.2015.00016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 09/04/2015] [Indexed: 12/17/2022] Open
Abstract
The identity of the vesicle neurotransmitter transporter expressed by a neuron largely corresponds with the primary neurotransmitter that cell releases. However, the vesicular glutamate transporter subtype 3 (VGLUT3) is mainly expressed in non-glutamatergic neurons, including cholinergic, serotonergic, or GABAergic neurons. Though a functional role for glutamate release from these non-glutamatergic neurons has been demonstrated, the interplay between VGLUT3 and the neuron’s characteristic neurotransmitter transporter, particularly in the case of GABAergic neurons, at the synaptic and vesicular level is less clear. In this study, we explore how exogenous expression of VGLUT3 in striatal GABAergic neurons affects the packaging and release of glutamate and GABA in synaptic vesicles (SVs). We found that VGLUT3 expression in isolated, autaptic GABAergic neurons leads to action potential evoked release of glutamate. Under these conditions, glutamate and GABA could be packaged together in single vesicles release either spontaneously or asynchronously. However, the presence of glutamate in GABAergic vesicles did not affect uptake of GABA itself, suggesting a lack of synergy in vesicle filling for these transmitters. Finally, we found postsynaptic detection of glutamate released from GABAergic terminals difficult when bona fide glutamatergic synapses were present, suggesting that co-released glutamate cannot induce postsynaptic glutamate receptor clustering.
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Affiliation(s)
- Johannes Zimmermann
- Neurowissenschaftliches Forschungszentrum (NWFZ), NeuroCure Exzellenzcluster, CCO Charité Universitätsmedizin Berlin, Germany
| | - Melissa A Herman
- Neurowissenschaftliches Forschungszentrum (NWFZ), NeuroCure Exzellenzcluster, CCO Charité Universitätsmedizin Berlin, Germany
| | - Christian Rosenmund
- Neurowissenschaftliches Forschungszentrum (NWFZ), NeuroCure Exzellenzcluster, CCO Charité Universitätsmedizin Berlin, Germany
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15
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Hackett JT, Ueda T. Glutamate Release. Neurochem Res 2015; 40:2443-60. [PMID: 26012367 DOI: 10.1007/s11064-015-1622-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2015] [Revised: 05/17/2015] [Accepted: 05/20/2015] [Indexed: 12/18/2022]
Abstract
Our aim was to review the processes of glutamate release from both biochemical and neurophysiological points of view. A large body of evidence now indicates that glutamate is specifically accumulated into synaptic vesicles, which provides strong support for the concept that glutamate is released from synaptic vesicles and is the major excitatory neurotransmitter. Evidence suggests the notion that synaptic vesicles, in order to sustain the neurotransmitter pool of glutamate, are endowed with an efficient mechanism for vesicular filling of glutamate. Glutamate-loaded vesicles undergo removal of Synapsin I by CaM kinase II-mediated phosphorylation, transforming to the release-ready pool. Vesicle docking to and fusion with the presynaptic plasma membrane are thought to be mediated by the SNARE complex. The Ca(2+)-dependent step in exocytosis is proposed to be mediated by synaptotagmin.
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Affiliation(s)
- John T Hackett
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, 22908-0736, USA
| | - Tetsufumi Ueda
- Molecular and Behavioral Neuroscience Institute, The University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109-2200, USA. .,Department of Pharmacology, Medical School, The University of Michigan, Ann Arbor, MI, 48109, USA. .,Department of Psychiatry, Medical School, The University of Michigan, Ann Arbor, MI, 48109, USA.
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16
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Influence of Glucose Deprivation on Membrane Potentials of Plasma Membranes, Mitochondria and Synaptic Vesicles in Rat Brain Synaptosomes. Neurochem Res 2015; 40:1188-96. [DOI: 10.1007/s11064-015-1579-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 04/02/2015] [Accepted: 04/08/2015] [Indexed: 12/26/2022]
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Preobraschenski J, Zander JF, Suzuki T, Ahnert-Hilger G, Jahn R. Vesicular Glutamate Transporters Use Flexible Anion and Cation Binding Sites for Efficient Accumulation of Neurotransmitter. Neuron 2014; 84:1287-301. [DOI: 10.1016/j.neuron.2014.11.008] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/04/2014] [Indexed: 11/16/2022]
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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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19
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Tarasenko A, Krupko O, Himmelreich N. New insights into molecular mechanism(s) underlying the presynaptic action of nitric oxide on GABA release. Biochim Biophys Acta Gen Subj 2014; 1840:1923-32. [PMID: 24480299 DOI: 10.1016/j.bbagen.2014.01.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 01/17/2014] [Accepted: 01/21/2014] [Indexed: 12/31/2022]
Abstract
BACKGROUND Nitric oxide (NO) is an important presynaptic modulator of synaptic transmission. Here, we aimed to correlate the release of the major inhibitory neurotransmitter GABA with intracellular events occurring in rat brain axon terminals during their exposure to NO in the range of nanomolar-low micromolar concentrations. METHODS Using [(3)H]GABA and fluorescent dyes (Fluo 4-AM, acridine orange and rhodamine 6G), the following parameters were evaluated: vesicular and cytosolic GABA pools, intracellular calcium concentration, synaptic vesicle acidification, and mitochondrial membrane potential. Diethylamine NONOate (DEA/NO) and S-nitroso-N-acetylpenicillamine (SNAP) were used as NO donors. RESULTS DEA/NO and SNAP (in the presence of dithiothreitol (DTT)) stimulated external Ca(2+)-independent [(3)H]GABA release, which was not attributed to a rise in intracellular calcium concentration. [(3)H]GABA release coincided with increasing GABA level in cytosol and decreasing the vesicular GABA content available for exocytotic release. There was a strong temporal correlation between NO-induced increase in cytosolic [GABA] and dissipation of both synaptic vesicle proton gradient and mitochondrial membrane potential. Dissipation was reversible, and recovery of both parameters correlated in time with re-accumulation of [(3)H]GABA into synaptic vesicles. The molar ratio of DTT to SNAP determined the rate and duration of the recovery processes. CONCLUSIONS We suggest that NO can stimulate GABA release via GABA transporter reversal resulting from increased GABA levels in cytosol. The latter is reversible and appears to be due to S-nitrosylation of key proteins, which affect the energy status of the pre-synapse. GENERAL SIGNIFICANCE Our findings provide new insight into molecular mechanism(s) underlying the presynaptic action of nitric oxide on inhibitory neurotransmission.
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Affiliation(s)
- Alla Tarasenko
- Department of Neurochemistry, Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Leontovich Str. 9, Kyiv 01601, Ukraine.
| | - Olga Krupko
- Department of Neurochemistry, Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Leontovich Str. 9, Kyiv 01601, Ukraine.
| | - Nina Himmelreich
- Department of Neurochemistry, Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Leontovich Str. 9, Kyiv 01601, Ukraine.
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Abstract
NAAG (N-acetylaspartylglutamate) is an abundant neuropeptide in the vertebrate nervous system. It is released from synaptic terminals in a calcium-dependent manner and has been shown to act as an agonist at the type II metabotropic glutamate receptor mGluR3. It has been proposed that NAAG may also be released from axons. So far, however, it has remained unclear how NAAG is transported into synaptic or other vesicles before it is secreted. In the present study, we demonstrate that uptake of NAAG and the related peptide NAAG2 (N-acetylaspartylglutamylglutamate) into vesicles depends on the sialic acid transporter sialin (SLC17A5). This was demonstrated using cell lines expressing a cell surface variant of sialin and by functional reconstitution of sialin in liposomes. NAAG uptake into sialin-containing proteoliposomes was detectable in the presence of an active H+-ATPase or valinomycin, indicating that transport is driven by membrane potential rather than H+ gradient. We also show that sialin is most probably the major and possibly only vesicular transporter for NAAG and NAAG2, because ATP-dependent transport of both peptides was not detectable in vesicles isolated from sialin-deficient mice.
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21
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Burette AC, Weinberg RJ, Sassani P, Abuladze N, Kao L, Kurtz I. The sodium-driven chloride/bicarbonate exchanger in presynaptic terminals. J Comp Neurol 2012; 520:1481-92. [PMID: 22102085 DOI: 10.1002/cne.22806] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The sodium-driven chloride/bicarbonate exchanger (NDCBE), a member of the SLC4 family of bicarbonate transporters, was recently found to modulate excitatory neurotransmission in hippocampus. By using light and electron microscopic immunohistochemistry, we demonstrate here that NDCBE is expressed throughout the adult rat brain, and selectively concentrates in presynaptic terminals, where it is closely associated with synaptic vesicles. NDCBE is in most glutamatergic axon terminals, and is also present in the terminals of parvalbumin-positive γ-aminobutyric acid (GABA)ergic cells. These findings suggest that NDCBE can regulate glutamatergic transmission throughout the brain, and point to a role for NDCBE as a possible regulator of GABAergic neurotransmission.
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Affiliation(s)
- Alain C Burette
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
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22
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Buddhala C, Suarez M, Modi J, Prentice H, Ma Z, Tao R, Wu JY. Calpain cleavage of brain glutamic acid decarboxylase 65 is pathological and impairs GABA neurotransmission. PLoS One 2012; 7:e33002. [PMID: 22427928 PMCID: PMC3299728 DOI: 10.1371/journal.pone.0033002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 02/02/2012] [Indexed: 11/19/2022] Open
Abstract
Previously, we have shown that the GABA synthesizing enzyme, L-glutamic acid decarboxylase 65 (GAD65) is cleaved to form its truncated form (tGAD65) which is 2-3 times more active than the full length form (fGAD65). The enzyme responsible for cleavage was later identified as calpain. Calpain is known to cleave its substrates either under a transient physiological stimulus or upon a sustained pathological insult. However, the precise role of calpain cleavage of fGAD65 is poorly understood. In this communication, we examined the cleavage of fGAD65 under diverse pathological conditions including rats under ischemia/reperfusion insult as well as rat brain synaptosomes and primary neuronal cultures subjected to excessive stimulation with high concentration of KCl. We have shown that the formation of tGAD65 progressively increases with increasing stimulus concentration both in rat brain synaptosomes and primary rat embryo cultures. More importantly, direct cleavage of synaptic vesicle - associated fGAD65 by calpain was demonstrated and the resulting tGAD65 bearing the active site of the enzyme was detached from the synaptic vesicles. Vesicular GABA transport of the newly synthesized GABA was found to be reduced in calpain treated SVs. Furthermore, we also observed that the levels of tGAD65 in the focal cerebral ischemic rat brain tissue increased corresponding to the elevation of local glutamate as indicated by microdialysis. Moreover, the levels of tGAD65 was also proportional to the degree of cell death when the primary neuronal cultures were exposed to high KCl. Based on these observations, we conclude that calpain-mediated cleavage of fGAD65 is pathological, presumably due to decrease in the activity of synaptic vesicle - associated fGAD65 resulting in a decrease in the GABA synthesis - packaging coupling process leading to reduced GABA neurotransmission.
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Affiliation(s)
- Chandana Buddhala
- Department of Biomedical Science, Charles E Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida, United States of America,
| | - Marjorie Suarez
- Department of Biomedical Science, Charles E Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida, United States of America,
| | - Jigar Modi
- Department of Biomedical Science, Charles E Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida, United States of America,
| | - Howard Prentice
- Department of Biomedical Science, Charles E Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida, United States of America,
| | - Zhiyuan Ma
- Department of Biomedical Science, Charles E Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida, United States of America,
| | - Rui Tao
- Department of Biomedical Science, Charles E Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida, United States of America,
| | - Jang Yen Wu
- Department of Biomedical Science, Charles E Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida, United States of America,
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Abstract
Neurotransmitter identity is a defining feature of all neurons because it constrains the type of information they convey, but many neurons release multiple transmitters. Although the physiological role for corelease has remained poorly understood, the vesicular uptake of one transmitter can regulate filling with the other by influencing expression of the H(+) electrochemical driving force. In addition, the sorting of vesicular neurotransmitter transporters and other synaptic vesicle proteins into different vesicle pools suggests the potential for distinct modes of release. Corelease thus serves multiple roles in synaptic transmission.
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Affiliation(s)
- Thomas S Hnasko
- Departments of Physiology & Neurology, University of California, San Francisco, California 94158-2517, USA.
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24
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Presynaptic CLC-3 determines quantal size of inhibitory transmission in the hippocampus. Nat Neurosci 2011; 14:487-94. [PMID: 21378974 PMCID: PMC3072292 DOI: 10.1038/nn.2775] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Accepted: 02/02/2011] [Indexed: 11/21/2022]
Abstract
The absence of the chloride channel CLC-3 in Clcn3−/− mice results in hippocampal degeneration with a distinct temporal-spatial sequence reminiscent of neuronal loss in temporal lobe epilepsy. We examined how the loss of CLC-3 might impact GABAergic synaptic transmission in the hippocampus. An electrophysiological study of synaptic function in Clcn3+/+ and Clcn3-−/− mice in hippocampal slices before the onset of neurodegeneration, revealed a significant decrease in the amplitude and frequency of mIPSCs. We found that CLC-3 colocalizes with the vesicular GABA transporter VGAT in the CA1 region of the hippocampus. Cl−-induced acidification of inhibitory synaptic vesicles showed a significant dependence on CLC-3 expression. The decrement in inhibitory transmission in the Clcn3−/− animals suggests a decrease in neurotransmitter loading of synaptic vesicles which we attributed to defective vesicular acidification. Our observations extend the role of Cl− in inhibitory transmission from that of a postsynaptic permeant species to a presynaptic regulatory element.
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25
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Behrendorff N, Floetenmeyer M, Schwiening C, Thorn P. Protons released during pancreatic acinar cell secretion acidify the lumen and contribute to pancreatitis in mice. Gastroenterology 2010; 139:1711-20, 1720.e1-5. [PMID: 20691184 DOI: 10.1053/j.gastro.2010.07.051] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2009] [Revised: 06/18/2010] [Accepted: 07/30/2010] [Indexed: 01/13/2023]
Abstract
BACKGROUND & AIMS Secretory granules are acidic; cell secretion will therefore lead to extracellular acidification. We propose that during secretion, protons co-released with proteins from secretory granules of pancreatic acinar cells acidify the restricted extracellular space of the pancreatic lumen to regulate normal physiological and pathophysiological functions in this organ METHODS Extracellular changes in pH were quantified in real time using 2-photon microscopy analysis of pancreatic tissue fragments from mouse models of acute pancreatitis (mice given physiological concentrations [10 -20 pM] of cholecystokinin or high concentrations of [100 nM] cerulein). The effects of extracellular changes in pH on cell behavior and structures were measured. RESULTS With physiological stimulation, secretory granule fusion (exocytosis) caused acidification of the pancreatic lumen. Acidifications specifically affected intracellular calcium responses and accelerated the rate of recovery from agonist-evoked calcium signals. Protons therefore appear to function as negative-feedback, extracellular messengers during coupling of cell stimuli with secretion. At high concentrations of cerulein, large increases in secretory activity were associated with extreme, prolonged acidification of the luminal space. These pathological changes in pH led to disruption of intercellular junctional coupling, measured by movement of occludin and E-cadherin. CONCLUSIONS By measuring changes in extracellular pH in pancreas of mice, we observed that luminal acidification resulted from exocytosis of zymogen granules from acinar cells. This process is part of normal organ function but could contribute to the tissue damage in cases of acute pancreatitis.
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Affiliation(s)
- Natasha Behrendorff
- School of Biomedical Sciences, University of Queensland, Brisbane, Australia
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26
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Juge N, Muroyama A, Hiasa M, Omote H, Moriyama Y. Vesicular inhibitory amino acid transporter is a Cl-/gamma-aminobutyrate Co-transporter. J Biol Chem 2009; 284:35073-8. [PMID: 19843525 DOI: 10.1074/jbc.m109.062414] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The vesicular inhibitory amino acid transporter (VIAAT) is a synaptic vesicle protein responsible for the vesicular storage of gamma-aminobutyrate (GABA) and glycine which plays an essential role in GABAergic and glycinergic neurotransmission. The transport mechanism of VIAAT remains largely unknown. Here, we show that proteoliposomes containing purified VIAAT actively took up GABA upon formation of membrane potential (Deltapsi) (positive inside) but not DeltapH. VIAAT-mediated GABA uptake had an absolute requirement for Cl(-) and actually accompanied Cl(-) movement. Kinetic analysis indicated that one GABA molecule and two Cl(-) equivalents were transported during one transport cycle. VIAAT in which Glu(213) was specifically mutated to alanine completely lost the ability to take up both GABA and Cl(-). Essentially the same results were obtained with glycine, another substrate of VIAAT. These results demonstrated that VIAAT is a vesicular Cl(-) transporter that co-transports Cl(-) with GABA or glycine in a Deltapsi dependent manner. It is concluded that Cl(-) plays an essential role in vesicular storage of GABA and glycine.
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Affiliation(s)
- Narinobu Juge
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama 700-8530, Japan
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27
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Synaptic vesicle-bound pyruvate kinase can support vesicular glutamate uptake. Neurochem Res 2008; 34:807-18. [PMID: 18751889 DOI: 10.1007/s11064-008-9833-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Accepted: 08/07/2008] [Indexed: 10/21/2022]
Abstract
Glucose metabolism is essential for normal brain function and plays a vital role in synaptic transmission. Recent evidence suggests that ATP synthesized locally by glycolysis, particularly via glyceraldehyde 3-phosphate dehydrogenase/3-phosphoglycerate kinase, is critical for synaptic transmission. We present evidence that ATP generated by synaptic vesicle-associated pyruvate kinase is harnessed to transport glutamate into synaptic vesicles. Isolated synaptic vesicles incorporated [(3)H]glutamate in the presence of phosphoenolpyruvate (PEP) and ADP. Pyruvate kinase activators and inhibitors stimulated and reduced PEP/ADP-dependent glutamate uptake, respectively. Membrane potential was also formed in the presence of pyruvate kinase activators. "ATP-trapping" experiments using hexokinase and glucose suggest that ATP produced by vesicle-associated pyruvate kinase is more readily used than exogenously added ATP. Other neurotransmitters such as GABA, dopamine, and serotonin were also taken up into crude synaptic vesicles in a PEP/ADP-dependent manner. The possibility that ATP locally generated by glycolysis supports vesicular accumulation of neurotransmitters is discussed.
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28
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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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29
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Abstract
Changes in the response to release of a single synaptic vesicle have generally been attributed to postsynaptic modification of receptor sensitivity, but considerable evidence now demonstrates that alterations in vesicle filling also contribute to changes in quantal size. Receptors are not saturated at many synapses, and changes in the amount of transmitter per vesicle contribute to the physiological regulation of release. On the other hand, the presynaptic factors that determine quantal size remain poorly understood. Aside from regulation of the fusion pore, these mechanisms fall into two general categories: those that affect the accumulation of transmitter inside a vesicle and those that affect vesicle size. This review will summarize current understanding of the neurotransmitter cycle and indicate basic, unanswered questions about the presynaptic regulation of quantal size.
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Affiliation(s)
- Robert H Edwards
- Department of Neurology and Physiology, UCSF School of Medicine, San Francisco, CA 94158-2517, USA.
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30
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Tarasenko AS, Storchak LG, Himmelreich NH. alpha-Latrotoxin affects mitochondrial potential and synaptic vesicle proton gradient of nerve terminals. Neurochem Int 2007; 52:392-400. [PMID: 17728017 DOI: 10.1016/j.neuint.2007.07.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2007] [Revised: 07/06/2007] [Accepted: 07/17/2007] [Indexed: 11/29/2022]
Abstract
Ca(2+)-independent [(3)H]GABA release induced by alpha-latrotoxin was found to consist of two sequential processes: a fast initial release realized via exocytosis and more delayed outflow through the plasma membrane GABA transporters [Linetska, M.V., Storchak, L.G., Tarasenko, A.S., Himmelreich, N.H., 2004. Involvement of membrane GABA transporters in alpha-latrotoxin-stimulated [(3)H]GABA release. Neurochem. Int. 44, 303-312]. To characterize the toxin-stimulated events attributable to the transporter-mediated [(3)H]GABA release from rat brain synaptosomes we studied the effect of alpha-latrotoxin on membrane potentials and generation of the synaptic vesicles proton gradient, using fluorescent dyes: potential-sensitive rhodamine 6G and pH-sensitive acridine orange. We revealed that alpha-latrotoxin induced a progressive dose-dependent depolarization of mitochondrial membrane potential and an irreversible run-down of the synaptic vesicle proton gradient. Both processes were insensitive to the presence of cadmium, a potent blocker of toxin-formed transmembrane pores, indicating that alpha-latrotoxin-induced disturbance of the plasma membrane permeability was not responsible to these effects. A gradual dissipation of the synaptic vesicle proton gradient closely coupled with lowering the vesicular GABA transporter activity results in a leakage of the neurotransmitter from synaptic vesicles to cytoplasm. As a consequence, there is an essential increase in GABA concentration in a soluble cytosolic pool that appears to be critical parameter for altering the mode of the plasma membrane GABA transporter operation from inward to outward. Thus, our data allow clarifying what cell processes underlain a recruitment of the plasma membrane transporter-mediated pathway in alpha-LTX-stimulated secretion.
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Affiliation(s)
- A S Tarasenko
- Department of Neurochemistry, Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Leontovich Str. 9, Kiev 01601, Ukraine
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31
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Brunk I, Höltje M, von Jagow B, Winter S, Sternberg J, Blex C, Pahner I, Ahnert-Hilger G. Regulation of vesicular monoamine and glutamate transporters by vesicle-associated trimeric G proteins: new jobs for long-known signal transduction molecules. Handb Exp Pharmacol 2007:305-25. [PMID: 16722242 DOI: 10.1007/3-540-29784-7_15] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Neurotransmitters of neurons and neuroendocrine cells are concentrated first in the cytosol and then in either small synaptic vesicles ofpresynaptic terminals or in secretory vesicles by the activity of specific transporters of the plasma and the vesicular membrane, respectively. In the central nervous system the postsynaptic response depends--amongst other parameters-on the amount of neurotransmitter stored in a given vesicle. Neurotransmitter packets (quanta) vary over a wide range which may be also due to a regulation of vesicular neurotransmitter filling. Vesicular filling is regulated by the availability of transmitter molecules in the cytoplasm, the amount of transporter molecules and an electrochemical proton-mediated gradient over the vesicular membrane. In addition, it is modulated by vesicle-associated heterotrimeric G proteins, Galphao2 and Galphaq. Galphao2 and Galphaq regulate vesicular monoamine transporter (VMAT) activities in brain and platelets, respectively. Galphao2 also regulates vesicular glutamate transporter (VGLUT) activity by changing its chloride dependence. It appears that the vesicular content activates the G protein, suggesting a signal transduction from the luminal site which might be mediated by a vesicular G protein-coupled receptor or as an alternative possibility by the transporter itself. Thus, G proteins control transmitter storage and thereby probablylink the regulation of the vesicular content to intracellular signal cascades.
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Affiliation(s)
- I Brunk
- AG Funktionelle Zellbiologie, Institut für Integrative Neuroanatomie, Centrum für Anatomie, Charité, Universitätsmedizin Berlin, Berlin, Germany
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32
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Agarwal KN. Iron and the brain: neurotransmitter receptors and magnetic resonance spectroscopy. Br J Nutr 2007. [DOI: 10.1079/bjn2000307] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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33
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Lascaratos G, Ji D, Wood JPM, Osborne NN. Visible light affects mitochondrial function and induces neuronal death in retinal cell cultures. Vision Res 2007; 47:1191-201. [PMID: 17306853 DOI: 10.1016/j.visres.2006.12.014] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2006] [Revised: 12/01/2006] [Accepted: 12/08/2006] [Indexed: 12/24/2022]
Abstract
The aim of this study was to provide "proof of principle" for the hypothesis that light would have a detrimental influence on ganglion cells in certain situations, like in glaucoma, by directly impinging on the many mitochondria in their axons within the globe. In this study primary rat retinal cultures and freshly isolated liver mitochondria were exposed to light (400-760 nm; 500-4000 lux) as entering the eye. For culture assessment, 3,(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and 4-[3-(-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetzolio]-1,3-benzene disulfonate (WST-1) reduction assays were used to assess cell and mitochondrial viability, respectively. Furthermore, cultures were stained for reactive oxygen species (ROS), DNA breakdown, numbers of GABA-immunoreactive (IR) cells and caspase-3 content to provide information concerning the effect of light on neuronal survival. Uptake of (3)H-GABA by autoradiography was also used, to assess the effects of light on the energy status of neurons. Light, in an intensity-dependent and trolox-inhibitable manner, reduced cell viability, affected mitochondrial function, increased the number of TUNEL-positive cells, decreased the numbers of GABA-IR neurons and enhanced labelling for ROS. These effects were all exacerbated by the absence of serum. There was also an increased caspase-3 protein content and a reduction of (3)H-GABA uptake in light- compared with dark-treated cultures. These findings support the hypothesis that light can affect mitochondria which could lead to neuronal apoptosis if the energetic status of these neurons is already compromised.
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Affiliation(s)
- Gerassimos Lascaratos
- Nuffield Laboratory of Ophthalmology, University of Oxford, Walton Street, Oxford OX2 6AW, UK
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34
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Cavelier P, Attwell D. Neurotransmitter depletion by bafilomycin is promoted by vesicle turnover. Neurosci Lett 2006; 412:95-100. [PMID: 17123716 PMCID: PMC6930131 DOI: 10.1016/j.neulet.2006.10.040] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2006] [Revised: 10/24/2006] [Accepted: 10/25/2006] [Indexed: 11/16/2022]
Abstract
Accumulation of neurotransmitter into synaptic vesicles is powered by the vacuolar proton ATPase. We show here that, in brain slices, application of the H(+)-ATPase inhibitors bafilomycin or concanamycin does not efficiently deplete glutamatergic vesicles of transmitter unless vesicle turnover is increased. Simulations of vesicle energetics suggest either that bafilomycin and concanamycin act on the H(+)-ATPase from inside the vesicle, or that the vesicle membrane potential is maintained after the H(+)-ATPase is inhibited.
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Affiliation(s)
- Pauline Cavelier
- Department of Physiology, University College London, Gower Street, London WC1E 6BT, UK
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35
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Tarasenko AS, Linetska MV, Storchak LG, Himmelreich NH. Effectiveness of extracellular lactate/pyruvate for sustaining synaptic vesicle proton gradient generation and vesicular accumulation of GABA. J Neurochem 2006; 99:787-96. [PMID: 16836653 DOI: 10.1111/j.1471-4159.2006.04109.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effects of extracellular monocarboxylates pyruvate and lactate on membrane potentials, acidification and neurotransmitter filling of synaptic vesicles were investigated in experiments with rat brain synaptosomes using [(3)H]GABA and fluorescent dyes, potential-sensitive rhodamine 6G and pH-sensitive acridine orange. In experiments investigating accumulation of acridine orange in synaptic vesicles within the synaptosomes, monocarboxylates, similarly to glucose, ensured generation of the vesicle proton gradient by available and recycled vesicles, and pyruvate demonstrated the highest efficacy. An increase in the level of proton gradient correlated with enhanced accumulation of [(3)H]GABA in synaptic vesicles and resulted in enlarged exocytosis and attenuated the transporter-mediated [(3)H]GABA release. Pyruvate added to glucose-contained medium caused more active binding of rhodamine 6G by synaptosomes that reflected mitochondrial membrane hyperpolarization, and this intensification of nerve terminal energy metabolism resulted in an increase in total ATP content by approximately 25%. Pyruvate also prolonged the state of metabolic competence of nerve terminal preparations, keeping the mitochondrial potential and synaptic vesicle proton gradient at steady levels over a long period of time. Thus, besides glucose, the extracellular monocarboxylates pyruvate and lactate can provide sufficient support of energy-dependent processes in isolated nerve terminals, allowing effective functioning of neurotransmitter release and reuptake systems.
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Affiliation(s)
- A S Tarasenko
- Department of Neurochemistry, Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kiev, Ukraine
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36
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Frahm C, Siegel G, Grass S, Witte OW. Stable expression of the vesicular GABA transporter following photothrombotic infarct in rat brain. Neuroscience 2006; 140:865-77. [PMID: 16616431 DOI: 10.1016/j.neuroscience.2006.02.045] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Revised: 02/22/2006] [Accepted: 02/22/2006] [Indexed: 11/20/2022]
Abstract
Before exocytotic release of the inhibitory neurotransmitter GABA, this amino acid has to be stored in synaptic vesicles. Accumulation of GABA in vesicles is achieved by a specific membrane-integrated transporter termed vesicular GABA transporter. This vesicular protein is mainly located at presynaptic terminals of GABAergic interneurons. In the present study we investigated the effects of focal ischemia on the expression of the vesicular GABA transporter. Vesicular GABA transporter mRNA and protein expression was examined after photothrombosis in different cortical and hippocampal brain regions of Wistar rats. In situ hybridization and quantitative real-time RT-PCR were performed to analyze vesicular GABA transporter mRNA. Both vesicular GABA transporter mRNA-stained perikarya and mRNA expression levels remained unaffected. Vesicular GABA transporter protein-containing synaptic terminals and somata were visualized by immunohistochemistry. The pattern of vesicular GABA transporter immunoreactivity as well as the protein expression level revealed by semiquantitative image analysis and by Western blot remained stable after stroke. The steady expression of vesicular GABA transporter mRNA and protein after photothrombosis indicates that the exocytotic release mechanism of GABA is not affected by ischemia.
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Affiliation(s)
- C Frahm
- Department of Neurology, Friedrich-Schiller-University, Erlanger Allee 101, 07747 Jena, Germany.
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37
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Ahnert-Hilger G, Höltje M, Pahner I, Winter S, Brunk I. Regulation of vesicular neurotransmitter transporters. Rev Physiol Biochem Pharmacol 2004; 150:140-60. [PMID: 14517724 DOI: 10.1007/s10254-003-0020-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Neurotransmitters are key molecules of neurotransmission. They are concentrated first in the cytosol and then in small synaptic vesicles of presynaptic terminals by the activity of specific neurotransmitter transporters of the plasma and the vesicular membrane, respectively. It has been shown that postsynaptic responses to single neurotransmitter packets vary over a wide range, which may be due to a regulation of vesicular neurotransmitter filling. Vesicular filling depends on the availability of transmitter molecules in the cytoplasm and the active transport into secretory vesicles relying on a proton gradient. In addition, it is modulated by vesicle-associated heterotrimeric G proteins, Galphao2 and Galphaq, which regulate VMAT activities in brain and platelets, respectively, and may also be involved in the regulation of VGLUTs. It appears that the vesicular content activates the G protein, suggesting a signal transduction form the luminal site which might be mediated by a vesicular G-protein coupled receptor or, as an alternative, possibly by the transporter itself. These novel functions of G proteins in the control of transmitter storage may link regulation of the vesicular content to intracellular signal cascades.
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Affiliation(s)
- G Ahnert-Hilger
- Institut für Anatomie und Neurowissenschaftliches Zentrum der Charité, Humboldt-Universität zu Berlin, Philippstr. 12, 10115 Berlin, Germany.
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38
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Weimer RM, Richmond JE. Synaptic vesicle docking: a putative role for the Munc18/Sec1 protein family. Curr Top Dev Biol 2004; 65:83-113. [PMID: 15642380 DOI: 10.1016/s0070-2153(04)65003-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Robby M Weimer
- Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
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39
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Affiliation(s)
- Robby M Weimer
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112-0840, USA
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40
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Jin H, Wu H, Osterhaus G, Wei J, Davis K, Sha D, Floor E, Hsu CC, Kopke RD, Wu JY. Demonstration of functional coupling between gamma -aminobutyric acid (GABA) synthesis and vesicular GABA transport into synaptic vesicles. Proc Natl Acad Sci U S A 2003; 100:4293-8. [PMID: 12634427 PMCID: PMC153086 DOI: 10.1073/pnas.0730698100] [Citation(s) in RCA: 181] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
l-Glutamic acid decarboxylase (GAD) exists as both membrane-associated and soluble forms in the mammalian brain. Here, we propose that there is a functional and structural coupling between the synthesis of gamma-aminobutyric acid (GABA) by membrane-associated GAD and its packaging into synaptic vesicles (SVs) by vesicular GABA transporter (VGAT). This notion is supported by the following observations. First, newly synthesized [(3)H]GABA from [(3)H]l-glutamate by membrane-associated GAD is taken up preferentially over preexisting GABA by using immunoaffinity-purified GABAergic SVs. Second, the activity of SV-associated GAD and VGAT seems to be coupled because inhibition of GAD also decreases VGAT activity. Third, VGAT and SV-associated Ca(2+)calmodulin-dependent kinase II have been found to form a protein complex with GAD. A model is also proposed to link the neuronal stimulation to enhanced synthesis and packaging of GABA into SVs.
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Affiliation(s)
- Hong Jin
- Departments of Molecular Biosciences and Medicinal Chemistry, University of Kansas, Lawrence, KS 66045, USA
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41
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Ikemoto A, Bole DG, Ueda T. Glycolysis and glutamate accumulation into synaptic vesicles. Role of glyceraldehyde phosphate dehydrogenase and 3-phosphoglycerate kinase. J Biol Chem 2003; 278:5929-40. [PMID: 12488440 DOI: 10.1074/jbc.m211617200] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glucose is the major source of brain energy and is essential for maintaining normal brain and neuronal function. Hypoglycemia causes impaired synaptic transmission. This occurs even before significant reduction in global cellular ATP concentration, and relationships among glycolysis, ATP supply, and synaptic transmission are not well understood. We demonstrate that the glycolytic enzymes glyceraldehyde phosphate dehydrogenase (GAPDH) and 3-phosphoglycerate kinase (3-PGK) are enriched in synaptic vesicles, forming a functional complex, and that synaptic vesicles are capable of accumulating the excitatory neurotransmitter glutamate by harnessing ATP produced by vesicle-bound GAPDH/3-PGK at the expense of their substrates. The GAPDH inhibitor iodoacetate suppressed GAPDH/3-PGK-dependent, but not exogenous ATP-dependent, [(3)H]glutamate uptake into isolated synaptic vesicles. It also decreased vesicular [(3)H]glutamate content in the nerve ending preparation synaptosome; this decrease was reflected in reduction of depolarization-induced [(3)H]glutamate release. In contrast, oligomycin, a mitochondrial ATP synthase inhibitor, had minimal effect on any of these parameters. ADP at concentrations above 0.1 mm inhibited vesicular glutamate and dissipated membrane potential. This suggests that the coupled GAPDH/3-PGK system, which converts ADP to ATP, ensures maximal glutamate accumulation into presynaptic vesicles. Together, these observations provide insight into the essential nature of glycolysis in sustaining normal synaptic transmission.
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Affiliation(s)
- Atsushi Ikemoto
- Mental Health Research Institute, University of Michigan Medical School, Ann Arbor, Michigan 48109-0669, USA
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Mittal RD, Pandey A, Mittal B, Agarwal KN. Effect of latent iron deficiency on GABA and glutamate neuroreceptors in rat brain. Indian J Clin Biochem 2003; 18:111-6. [PMID: 23105383 PMCID: PMC3453737 DOI: 10.1007/bf02867677] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Eight weeks of latent iron deficiency in weaned female rats of Sprague Dawley strain maintained on experimental low-iron diet (18-20 mg/kg) did not significantly change the gross body, weight and tissue weights of brain and liver. Packed cell volume (PCV) and hemoglobin concentration remained unaltered. However, non-heme iron content in liver and brain decreased significantly (p<0.001). The activities of glutamate dehydrogenase, glutamic acid decarboxylase, and GABA-transaminase (GABA-T) in brain decreased by 15%, 11.4% and 25.7% respectively. However, this decrease was not statistically significant. Binding of(3)H Muscimol at pH 7.5 and 1 mg protein/assay increased by 143% (p<0.001) in synaptic vesicular membranes from iron-deficient rats as compared to the controls.(3)H glutamate binding to the synaptic vesicles was also carried out under similar condition. However, the L-glutamate binding was reduced by 63% in the vesicular membranes of iron deficient animals. These studies indicate that iron plays important functional role in both excitatory and inhibitory neurotransmitter receptors.
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Affiliation(s)
- Rama Devi Mittal
- Department of Biochemistry, Sanjay Gandhi Post Graduate Institute of Medical Sciences, 226014 Lucknow, India
| | - Amita Pandey
- Department of Biochemistry, Sanjay Gandhi Post Graduate Institute of Medical Sciences, 226014 Lucknow, India
- Department of Genetics, Sanjay Gandhi Post Graduate Institute of Medical Sciences, 226014 Lucknow, India
- Dept. of Urology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, 226014 Lucknow, India
| | - Balraj Mittal
- Department of Genetics, Sanjay Gandhi Post Graduate Institute of Medical Sciences, 226014 Lucknow, India
| | - Kailash Nath Agarwal
- Department of Biochemistry, Sanjay Gandhi Post Graduate Institute of Medical Sciences, 226014 Lucknow, India
- Department of Genetics, Sanjay Gandhi Post Graduate Institute of Medical Sciences, 226014 Lucknow, India
- Dept. of Urology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, 226014 Lucknow, India
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Mittal RD, Pandey A, Mittal B, Agarwal KN. Effect of latent iron deficiency on gaba and glutamate neuroreceptors in rat brain. Indian J Clin Biochem 2002; 17:1-6. [PMID: 23105345 PMCID: PMC3454128 DOI: 10.1007/bf02867966] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Eight weeks of latent iron deficiency in weaned female rats of Sprague Dawley strain maintained on experimental low-iron diet (18-20 mg/Kg) did not significantly change the gross body weight and tissue weights of brain and liver. Packed cell volume (PCV) and hemoglobin concentration remained unaltered. However, non-heme iron content in liver and brain decreased significantly (P<0.001). The activities of glutamate dehydrogenase, glutamic acid decarboxylase, and GABA-transaminase (GABA-T) in brain decreased by 15%, 11.4% and 25.7% respectively. However, this decrease was not statistically significant. Binding of(3)H Muscimol at pH 7.5 and 1 mg protein/assay increased by 143% (P<0.001) in synaptic vesicular membranes from iron-deficient rats as compared to the controls.(3)H glutamate binding to the synaptic vesicles was also carried out under similar condition. However, the L-glutamate binding was reduced by 63% in the vesicular membranes of iron deficient animals. These studies in dicate that iron plays an important functional role in both excitatory and inhibitory neurotransmitter receptors.
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Affiliation(s)
- Rama Devi Mittal
- Department of Biochemistry, Sanjay Gandhi Post Graduate Institute of Medical Sciences, 226014 Lucknow, India
| | - Amita Pandey
- Department of Genetics, Sanjay Gandhi Post Graduate Institute of Medical Sciences, 226014 Lucknow, India
| | - Balraj Mittal
- Department of Genetics, Sanjay Gandhi Post Graduate Institute of Medical Sciences, 226014 Lucknow, India
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Bai L, Xu H, Collins JF, Ghishan FK. Molecular and functional analysis of a novel neuronal vesicular glutamate transporter. J Biol Chem 2001; 276:36764-9. [PMID: 11432869 DOI: 10.1074/jbc.m104578200] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. Packaging and storage of glutamate into glutamatergic neuronal vesicles requires ATP-dependent vesicular glutamate uptake systems, which utilize the electrochemical proton gradient as a driving force. VGLUT1, the first identified vesicular glutamate transporter, is only expressed in a subset of glutamatergic neurons. We report here the molecular cloning and functional characterization of a novel glutamate transporter, VGLUT2, from mouse brain. VGLUT2 has all major functional characteristics of a synaptic vesicle glutamate transporter, including ATP dependence, chloride stimulation, substrate specificity, and substrate affinity. It has 75 and 79% amino acid identity with human and rat VGLUT1, respectively. However, expression patterns of VGLUT2 in brain are different from that of VGLUT1. In addition, VGLUT2 activity is dependent on both membrane potential and pH gradient of the electrochemical proton gradient, whereas VGLUT1 is primarily dependent on only membrane potential. The presence of VGLUT2 in brain regions lacking VGLUT1 suggests that the two isoforms together play an important role in vesicular glutamate transport in glutamatergic neurons.
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Affiliation(s)
- L Bai
- Department of Pediatrics, Steele Memorial Children's Research Center, University of Arizona Health Sciences Center, Tucson, Arizona 85724, USA.
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Abstract
The amino acid glutamate is the major excitatory neurotransmitter in a range of organisms from Caenorhabditis elegans to mammals, and it mediates the information processing that underlies essentially all behavior. Recent advances in our understanding of glutamate storage and release now illuminate how this ubiquitous amino acid can function as a signalling molecule.
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Affiliation(s)
- R J Reimer
- Departments of Neurology and Physiology, Graduate Programs in Neuroscience, Cell Biology and Biomedical Sciences, University of California, San Francisco, School of Medicine, 513 Parnassus Avenue, 94143-0435, USA
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Finn JP, Merickel A, Edwards RH. Analysis of neurotransmitter transport into secretory vesicles. Methods Enzymol 2001; 296:144-62. [PMID: 9779446 DOI: 10.1016/s0076-6879(98)96012-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Affiliation(s)
- J P Finn
- Department of Microbiology, University of California School of Medicine, Los Angeles 90024, USA
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Gonçalves PP, Meireles SM, Neves P, Vale MG. Distinction between Ca(2+) pump and Ca(2+)/H(+) antiport activities in synaptic vesicles of sheep brain cortex. Neurochem Int 2000; 37:387-96. [PMID: 10825579 DOI: 10.1016/s0197-0186(00)00009-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Synaptic vesicles, isolated from a sheep brain cortex, accumulate Ca(2+) in a manner that depends on the pH and pCa values. In the presence of 100 microM CaCl(2), most of the Ca(2+) taken up by the vesicles was vanadate-inhibited (86%) at pH 7.4, whereas at pH 8.5, part of the Ca(2+) accumulated (36%) was DeltapH-dependent (bafilomycin and CCCP inhibited) and part was insensitive to those drugs (31%). We also observed that both vanadate-sensitive and bafilomycin-sensitive Ca(2+) accumulations were completely released by the Ca(2+) ionophore, ionomycin, and that these processes work with high (K(0.5)=0.6 microM) and low (K(0.5)=217 microM) affinity for Ca(2+), respectively. The DeltapH-dependent Ca(2+) transport appears to be largely operative at Ca(2+) concentrations (>100 microM) which completely inhibited the vanadate-sensitive Ca(2+) uptake. These Ca(2+) effects on the Ca(2+) accumulation were well correlated with those observed on the vanadate-inhibited Ca(2+)-ATPase and bafilomycin-inhibited H(+)-ATPase, respectively. The Ca(2+)-ATPase activity reached a maximum at about 25 microM (pH 7.4) and sharply declined at higher Ca(2+) concentrations. In contrast, Ca(2+) had a significant stimulatory effect on the H(+)-ATPase between 250 and 500 microM Ca(2+) concentration. Furthermore, we found that DeltapH-sensitive Ca(2+) transport was associated with proton release from the vesicles. About 21% of the maximal proton gradient was dissipated by addition of 607.7 microM CaCl(2) to the reaction medium and, if CaCl(2) was present before the proton accumulation, lower pH gradients were reached. Both vanadate-inhibited and bafilomycin-inhibited systems transported Ca(2+) into the same vesicle pool of our preparation, suggesting that they belong to the same cellular compartment. These results indicate that synaptic vesicles of the sheep brain cortex contain two distinct mechanisms of Ca(2+) transport: a high Ca(2+) affinity, proton gradient-independent Ca(2+) pump that has an optimal activity at pH 7.4, and a low Ca(2+) affinity, proton gradient-dependent Ca(2+)/H(+) antiport that works maximally at pH 8.5.
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Affiliation(s)
- P P Gonçalves
- Centro de Biologia Celular, Departamento de Biologia, Universidade de Aveiro, 3810-193 Aveiro, Portugal.
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Takamori S, Rhee JS, Rosenmund C, Jahn R. Identification of a vesicular glutamate transporter that defines a glutamatergic phenotype in neurons. Nature 2000; 407:189-94. [PMID: 11001057 DOI: 10.1038/35025070] [Citation(s) in RCA: 662] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. Synaptic vesicles are loaded with neurotransmitter by means of specific vesicular transporters. Here we show that expression of BNPI, a vesicle-bound transporter associated with sodium-dependent phosphate transport, results in glutamate uptake by intracellular vesicles. Substrate specificity and energy dependence are very similar to glutamate uptake by synaptic vesicles. Stimulation of exocytosis--fusion of the vesicles with the cell membrane and release of their contents--resulted in quantal release of glutamate from BNPI-expressing cells. Furthermore, we expressed BNPI in neurons containing GABA (gamma-aminobutyric acid) and maintained them as cultures of single, isolated neurons that form synapses to themselves. After stimulation of these neurons, a component of the postsynaptic current is mediated by glutamate as it is blocked by a combination of the glutamate receptor antagonists, but is insensitive to a GABA(A) receptor antagonist. We conclude that BNPI functions as vesicular glutamate transporter and that expression of BNPI suffices to define a glutamatergic phenotype in neurons.
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Affiliation(s)
- S Takamori
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
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Bellocchio EE, Reimer RJ, Fremeau RT, Edwards RH. Uptake of glutamate into synaptic vesicles by an inorganic phosphate transporter. Science 2000; 289:957-60. [PMID: 10938000 DOI: 10.1126/science.289.5481.957] [Citation(s) in RCA: 597] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Previous work has identified two families of proteins that transport classical neurotransmitters into synaptic vesicles, but the protein responsible for vesicular transport of the principal excitatory transmitter glutamate has remained unknown. We demonstrate that a protein that is unrelated to any known neurotransmitter transporters and that was previously suggested to mediate the Na(+)-dependent uptake of inorganic phosphate across the plasma membrane transports glutamate into synaptic vesicles. In addition, we show that this vesicular glutamate transporter, VGLUT1, exhibits a conductance for chloride that is blocked by glutamate.
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Affiliation(s)
- E E Bellocchio
- Department of Neurology, University of California at San Francisco School of Medicine, 513 Parnassus Avenue, San Francisco, CA 94143-0435, USA
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50
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Reis M, Farage M, Wolosker H. Chloride-dependent inhibition of vesicular glutamate uptake by alpha-keto acids accumulated in maple syrup urine disease. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1475:114-8. [PMID: 10832024 DOI: 10.1016/s0304-4165(00)00069-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Maple syrup urine disease is a metabolic disorder caused by mutations of the branched chain keto acid dehydrogenase complex, leading to accumulation of alpha-keto acids and their amino acid precursors in the brain. We now report that alpha-ketoisovaleric, alpha-keto-beta-methyl-n-valeric and alpha-ketoisocaproic acids accumulated in the disease inhibit glutamate uptake into rat brain synaptic vesicles. The alpha-keto acids did not affect the electrochemical proton gradient across the membrane, suggesting that they interact directly with the vesicular glutamate carrier. Chloride anions have a biphasic effect on glutamate uptake. Low concentrations activate the uptake (0.2 to 8 mM), while higher concentrations are inhibitory. The alpha-keto acids inhibited glutamate uptake by a new mechanism, involving a change in the chloride dependence for the activation of glutamate uptake. The activation of glutamate uptake by low chloride concentrations was shifted toward higher concentrations of the anion in the presence of alpha-keto acids. Inhibition by alpha-keto acids was abolished at high chloride concentrations (20 to 80 mM), indicating that alpha-keto acids specifically change the stimulatory effect of low chloride concentrations. High glutamate concentrations also reduced the inhibition by alpha-keto acids, an effect observed both in the absence and in the presence of low chloride concentrations. The results suggest that in addition to their possible pathophysiological role in maple syrup urine disease, alpha-keto acids are valuable tools to study the mechanism of vesicular transport of glutamate.
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Affiliation(s)
- M Reis
- Departamento de Bioquímica Médica, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, RJ 21941-590, Cidade Universitária, Brazil
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