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Kolen B, Borghans B, Kortzak D, Lugo V, Hannack C, Guzman RE, Ullah G, Fahlke C. Vesicular glutamate transporters are H +-anion exchangers that operate at variable stoichiometry. Nat Commun 2023; 14:2723. [PMID: 37169755 PMCID: PMC10175566 DOI: 10.1038/s41467-023-38340-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 04/26/2023] [Indexed: 05/13/2023] Open
Abstract
Vesicular glutamate transporters accumulate glutamate in synaptic vesicles, where they also function as a major Cl- efflux pathway. Here we combine heterologous expression and cellular electrophysiology with mathematical modeling to understand the mechanisms underlying this dual function of rat VGLUT1. When glutamate is the main cytoplasmic anion, VGLUT1 functions as H+-glutamate exchanger, with a transport rate of around 600 s-1 at -160 mV. Transport of other large anions, including aspartate, is not stoichiometrically coupled to H+ transport, and Cl- permeates VGLUT1 through an aqueous anion channel with unitary transport rates of 1.5 × 105 s-1 at -160 mV. Mathematical modeling reveals that H+ coupling is sufficient for selective glutamate accumulation in model vesicles and that VGLUT Cl- channel function increases the transport efficiency by accelerating glutamate accumulation and reducing ATP-driven H+ transport. In summary, we provide evidence that VGLUT1 functions as H+-glutamate exchanger that is partially or fully uncoupled by other anions.
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Affiliation(s)
- Bettina Kolen
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Bart Borghans
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Daniel Kortzak
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Victor Lugo
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Cora Hannack
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Raul E Guzman
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Ghanim Ullah
- Department of Physics, University of South Florida, Tampa, FL, 33620, USA
| | - Christoph Fahlke
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428, Jülich, Germany.
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2
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Moriyama Y, Hasuzawa N, Nomura M. Is the vesicular nucleotide transporter a molecular target of eicosapentaenoic acid? Front Pharmacol 2022; 13:1080189. [PMID: 36569286 PMCID: PMC9768625 DOI: 10.3389/fphar.2022.1080189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 11/21/2022] [Indexed: 12/12/2022] Open
Abstract
Vesicular nucleotide transporter (VNUT), an active transporter for nucleotides in secretory vesicles, is responsible for the vesicular storage of ATP and plays an essential role in purinergic chemical transmission. Inhibition of VNUT decreases the concentration of ATP in the luminal space of secretory vesicles, followed by decreased vesicular ATP release, resulting in the blockade of purinergic chemical transmission. Very recently, Miyaji and colleagues reported that eicosapentaenoic acid (EPA) is a potent VNUT inhibitor and effective in treating neuropathic and inflammatory pain and insulin resistance through inhibition of vesicular storage and release of ATP. However, our validation study indicated that, in bovine adrenal chromaffin granule membrane vesicles, EPA inhibited the formation of an electrochemical gradient of protons across the membrane with the concentration of 50% inhibition (IC50) being 1.0 μM without affecting concanamycin B-sensitive ATPase activity. Essentially, similar results were obtained with proteoliposomes containing purified vacuolar H+-ATPase. Consistent with these observations, EPA inhibited the ATP-dependent uptakes of ATP and dopamine by chromaffin granule membrane vesicles, with ID50 being 1.2 and 1.0 μM, respectively. Furthermore, EPA inhibited ATP-dependent uptake of L-glutamate by mouse brain synaptic vesicles with ID50 being 0.35 μM. These results indicate that EPA at sub-μM acts as a proton conductor and increases proton permeability across the membrane, regardless of the presence or absence of VNUT, thereby inhibiting non-specifically the vesicular storage of neurotransmitters. Thus, EPA may affect a broader range of chemical transmission than proposed.
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Eriksen J, Li F, Stroud RM, Edwards RH. Allosteric Inhibition of a Vesicular Glutamate Transporter by an Isoform-Specific Antibody. Biochemistry 2021; 60:2463-2470. [PMID: 34319067 DOI: 10.1021/acs.biochem.1c00375] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The role of glutamate in excitatory neurotransmission depends on its transport into synaptic vesicles by the vesicular glutamate transporters (VGLUTs). The three VGLUT isoforms exhibit a complementary distribution in the nervous system, and the knockout of each produces severe, pleiotropic neurological effects. However, the available pharmacology lacks sensitivity and specificity, limiting the analysis of both transport mechanism and physiological role. To develop new molecular probes for the VGLUTs, we raised six mouse monoclonal antibodies to VGLUT2. All six bind to a structured region of VGLUT2, five to the luminal face, and one to the cytosolic. Two are specific to VGLUT2, whereas the other four bind to both VGLUT1 and 2; none detect VGLUT3. Antibody 8E11 recognizes an epitope spanning the three extracellular loops in the C-domain that explains the recognition of both VGLUT1 and 2 but not VGLUT3. 8E11 also inhibits both glutamate transport and the VGLUT-associated chloride conductance. Since the antibody binds outside the substrate recognition site, it acts allosterically to inhibit function, presumably by restricting conformational changes. The isoform specificity also shows that allosteric inhibition provides a mechanism to distinguish between closely related transporters.
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Affiliation(s)
- Jacob Eriksen
- Departments of Neurology and Physiology, UCSF School of Medicine, 600 16th Street, San Francisco, California 94143, United States
| | - Fei Li
- Departments of Neurology and Physiology, UCSF School of Medicine, 600 16th Street, San Francisco, California 94143, United States.,Department of Biochemistry and Biophysics, UCSF School of Medicine, 600 16th Street, San Francisco, California 94143, United States
| | - Robert M Stroud
- Department of Biochemistry and Biophysics, UCSF School of Medicine, 600 16th Street, San Francisco, California 94143, United States
| | - Robert H Edwards
- Departments of Neurology and Physiology, UCSF School of Medicine, 600 16th Street, San Francisco, California 94143, United States
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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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Du X, Li J, Li M, Yang X, Qi Z, Xu B, Liu W, Xu Z, Deng Y. Research progress on the role of type I vesicular glutamate transporter (VGLUT1) in nervous system diseases. Cell Biosci 2020; 10:26. [PMID: 32158532 PMCID: PMC7057577 DOI: 10.1186/s13578-020-00393-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 02/24/2020] [Indexed: 12/14/2022] Open
Abstract
Glutamate (Glu) is the predominant excitatory neurotransmitter in the central nervous system (CNS). Glutamatergic transmission is critical for controlling neuronal activity. In presynaptic neurons, Glu is stored in synaptic vesicles and released by stimulation. The homeostasis of glutamatergic system is maintained by a set of transporters in the membrane of synaptic vesicles. The family of vesicular Glu transporters in mammals is comprised of three highly homologous proteins: VGLUT1-3. Among them, VGLUT1 accounts for the largest proportion. However, most of the Glu is transported into the synaptic vesicles via the type 1 vesicle Glu transporter (VGLUT1). So, the expression of particular VGLUT1 is largely complementary with limited overlap and so far it is most specific markers for neurons that use Glu as neurotransmitter. Controlling the activity of VGLUT1 could potentially modulate the efficiency of excitatory neuro-transmission and change the filling level of synaptic vesicles. This review summarizes the recent knowledge concerning molecular and functional characteristic of VGLUT1, their development, contribution to a series of central nervous system and peripheral nervous system diseases such as learning and memory disorders, Alzheimer's disease, Parkinson's disease and sensitized nociception or pain pathology et al.
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Affiliation(s)
- Xianchao Du
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122 Liaoning People’s Republic of China
| | - Jiashuo Li
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122 Liaoning People’s Republic of China
| | - Minghui Li
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122 Liaoning People’s Republic of China
| | - Xinxin Yang
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122 Liaoning People’s Republic of China
| | - Zhipeng Qi
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122 Liaoning People’s Republic of China
| | - Bin Xu
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122 Liaoning People’s Republic of China
| | - Wei Liu
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122 Liaoning People’s Republic of China
| | - Zhaofa Xu
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122 Liaoning People’s Republic of China
| | - Yu Deng
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122 Liaoning People’s Republic of China
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Thompson CM, Chao CK. VGLUT substrates and inhibitors: A computational viewpoint. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183175. [PMID: 31923412 DOI: 10.1016/j.bbamem.2020.183175] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 12/30/2019] [Accepted: 12/31/2019] [Indexed: 02/07/2023]
Abstract
The vesicular glutamate transporters (VGLUTs) bind and move glutamate (Glu) from the cytosol into the lumen of synaptic vesicles using a H+-electrochemical gradient (ΔpH and Δψ) generated by the vesicular H+-ATPase. VGLUTs show very low Glu binding and to date, no three-dimensional structure has been elucidated. Prior studies have attempted to identify the key residues involved in binding VGLUT substrates and inhibitors using homology models and docking experiments. Recently, the inward and outward oriented crystal structures of d-galactonate transporter (DgoT) emerged as possible structure templates for VGLUT. In this review, a new homology model for VGLUT2 based on DgoT has been developed and used to conduct docking experiments to identify and differentiate residues and binding orientations involved in ligand interactions. This review describes small molecule-ligand interactions including docking using a VGLUT2 homology model derived from DgoT.
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Affiliation(s)
- Charles M Thompson
- Center for Structural and Functional Neurosciences, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, United States.
| | - Chih-Kai Chao
- Center for Structural and Functional Neurosciences, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, United States
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7
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Amino acid transporters in the regulation of insulin secretion and signalling. Biochem Soc Trans 2019; 47:571-590. [PMID: 30936244 DOI: 10.1042/bst20180250] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 02/24/2019] [Accepted: 02/25/2019] [Indexed: 01/02/2023]
Abstract
Amino acids are increasingly recognised as modulators of nutrient disposal, including their role in regulating blood glucose through interactions with insulin signalling. More recently, cellular membrane transporters of amino acids have been shown to form a pivotal part of this regulation as they are primarily responsible for controlling cellular and circulating amino acid concentrations. The availability of amino acids regulated by transporters can amplify insulin secretion and modulate insulin signalling in various tissues. In addition, insulin itself can regulate the expression of numerous amino acid transporters. This review focuses on amino acid transporters linked to the regulation of insulin secretion and signalling with a focus on those of the small intestine, pancreatic β-islet cells and insulin-responsive tissues, liver and skeletal muscle. We summarise the role of the amino acid transporter B0AT1 (SLC6A19) and peptide transporter PEPT1 (SLC15A1) in the modulation of global insulin signalling via the liver-secreted hormone fibroblast growth factor 21 (FGF21). The role of vesicular vGLUT (SLC17) and mitochondrial SLC25 transporters in providing glutamate for the potentiation of insulin secretion is covered. We also survey the roles SNAT (SLC38) family and LAT1 (SLC7A5) amino acid transporters play in the regulation of and by insulin in numerous affective tissues. We hypothesise the small intestine amino acid transporter B0AT1 represents a crucial nexus between insulin, FGF21 and incretin hormone signalling pathways. The aim is to give an integrated overview of the important role amino acid transporters have been found to play in insulin-regulated nutrient signalling.
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Vesicular nucleotide transporter (VNUT): appearance of an actress on the stage of purinergic signaling. Purinergic Signal 2017; 13:387-404. [PMID: 28616712 DOI: 10.1007/s11302-017-9568-1] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 05/05/2017] [Indexed: 12/17/2022] Open
Abstract
Vesicular storage of ATP is one of the processes initiating purinergic chemical transmission. Although an active transport mechanism was postulated to be involved in the processes, a transporter(s) responsible for the vesicular storage of ATP remained unidentified for some time. In 2008, SLC17A9, the last identified member of the solute carrier 17 type I inorganic phosphate transporter family, was found to encode the vesicular nucleotide transporter (VNUT) that is responsible for the vesicular storage of ATP. VNUT transports various nucleotides in a membrane potential-dependent fashion and is expressed in the various ATP-secreting cells. Mice with knockout of the VNUT gene lose vesicular storage and release of ATP from neurons and neuroendocrine cells, resulting in blockage of the initiation of purinergic chemical transmission. Thus, VNUT plays an essential role in the vesicular storage and release of ATP. The VNUT knockout mice exhibit resistance for neuropathic pain and a therapeutic effect against diabetes by way of increased insulin sensitivity. Thus, VNUT inhibitors and suppression of VNUT gene expression may be used for therapeutic purposes through suppression of purinergic chemical transmission. This review summarizes the studies to date on VNUT and discusses what we have learned about the relevance of vesicular ATP release as a potential drug target.
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9
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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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Kehrl J, Althaus JC, Showalter HD, Rudzinski DM, Sutton MA, Ueda T. Vesicular Glutamate Transporter Inhibitors: Structurally Modified Brilliant Yellow Analogs. Neurochem Res 2017; 42:1823-1832. [DOI: 10.1007/s11064-017-2198-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Revised: 01/27/2017] [Accepted: 01/30/2017] [Indexed: 12/22/2022]
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Moriyama S, Iharada M, Omote H, Moriyama Y, Hiasa M. Function and expression of a splicing variant of vesicular glutamate transporter 1. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:931-940. [PMID: 28188742 DOI: 10.1016/j.bbamem.2017.02.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 01/30/2017] [Accepted: 02/05/2017] [Indexed: 10/20/2022]
Abstract
Vesicular glutamate transporter (VGLUT) is an active transporter responsible for vesicular storage of glutamate in synaptic vesicles and plays an essential role in glutamatergic neurotransmission. VGLUT consists of three isoforms, VGLUT1, VGLUT2, and VGLUT3. The VGLUT1 variant, VGLUT1v, with an additional 75-base pair sequence derived from a second intron between exons 2 and 3, which corresponds to 25 amino acid residues in the 1st loop of VGLUT1, is the only splicing variant among VGLUTs, although whether VGLUT1v protein is actually translated at the protein level remains unknown. In the present study, VGLUT1v was expressed in insect cells, solubilized, purified to near homogeneity, and its transport activity was examined. Proteoliposomes containing purified VGLUT1v were shown to accumulate glutamate upon imposition of an inside-positive membrane potential (Δψ). The Δψ-driven glutamate uptake activity requires Cl- and its pharmacological profile and kinetics are comparable to those of other VGLUTs. The retinal membrane contained two VGLUT1 moieties with apparent molecular masses of 65 and 57kDa. VGLUT1v-specific antibodies against an inserted 25-amino acid residue sequence identified a 65-kDa immunoreactive polypeptide. Immunohistochemical analysis indicated that VGLUT1v immunoreactivity is present in photoreceptor cells and is associated with synaptic vesicles. VGLUT1v immunoreactivity is also present in pinealocytes, but not in other areas, including the brain. These results indicated that VGLUT1v exists in a functional state in rat photosensitive cells and is involved in glutamatergic chemical transmission.
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Affiliation(s)
- Satomi Moriyama
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan
| | - Masafumi Iharada
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan
| | - Hiroshi Omote
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan
| | - Yoshinori Moriyama
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan.
| | - Miki Hiasa
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan.
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Takeuchi T, Harada Y, Moriyama S, Furuta K, Tanaka S, Miyaji T, Omote H, Moriyama Y, Hiasa M. Vesicular Polyamine Transporter Mediates Vesicular Storage and Release of Polyamine from Mast Cells. J Biol Chem 2017; 292:3909-3918. [PMID: 28082679 DOI: 10.1074/jbc.m116.756197] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Revised: 01/04/2017] [Indexed: 01/12/2023] Open
Abstract
Mast cells are secretory cells that play an important role in host defense by discharging various intragranular contents, such as histamine and serotonin, upon stimulation of Fc receptors. The granules also contain spermine and spermidine, which can act as modulators of mast cell function, although the mechanism underlying vesicular storage remains unknown. Vesicular polyamine transporter (VPAT), the fourth member of the SLC18 transporter family, is an active transporter responsible for vesicular storage of spermine and spermidine in neurons. In the present study, we investigated whether VPAT functions in mast cells. RT-PCR and Western blotting indicated VPAT expression in murine bone marrow-derived mast cells (BMMCs). Immunohistochemical analysis indicated that VPAT is colocalized with VAMP3 but not with histamine, serotonin, cathepsin D, VAMP2, or VAMP7. Membrane vesicles from BMMCs accumulated spermidine upon the addition of ATP in a reserpine- and bafilomycin A1-sensitive manner. BMMCs secreted spermine and spermidine upon the addition of either antigen or A23187 in the presence of Ca2+, and the antigen-mediated release, which was shown to be temperature-dependent and sensitive to bafilomycin A1 and tetanus toxin, was significantly suppressed by VPAT gene RNA interference. Under these conditions, expression of vesicular monoamine transporter 2 was unaffected, but antigen-dependent histamine release was significantly suppressed, which was recovered by the addition of 1 mm spermine. These results strongly suggest that VPAT is expressed and is responsible for vesicular storage of spermine and spermidine in novel secretory granules that differ from histamine- and serotonin-containing granules and is involved in vesicular release of these polyamines from mast cells.
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Affiliation(s)
- Tomoya Takeuchi
- From the Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530
| | - Yuika Harada
- From the Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530
| | - Satomi Moriyama
- From the Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530
| | - Kazuyuki Furuta
- the Department of Immunobiology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama 700-8530, and
| | - Satoshi Tanaka
- the Department of Immunobiology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama 700-8530, and
| | - Takaaki Miyaji
- the Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan
| | - Hiroshi Omote
- From the Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530
| | - Yoshinori Moriyama
- From the Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530,
| | - Miki Hiasa
- From the Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530,
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14
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Omote H, Miyaji T, Hiasa M, Juge N, Moriyama Y. Structure, Function, and Drug Interactions of Neurotransmitter Transporters in the Postgenomic Era. Annu Rev Pharmacol Toxicol 2015; 56:385-402. [PMID: 26514205 DOI: 10.1146/annurev-pharmtox-010814-124816] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Vesicular neurotransmitter transporters are responsible for the accumulation of neurotransmitters in secretory vesicles and play essential roles in chemical transmission. The SLC17 family contributes to sequestration of anionic neurotransmitters such as glutamate, aspartate, and nucleotides. Identification and subsequent cellular and molecular biological studies of SLC17 transporters unveiled the principles underlying the actions of these transporters. Recent progress in reconstitution methods in combination with postgenomic approaches has advanced studies on neurotransmitter transporters. This review summarizes the molecular properties of SLC17-type transporters and recent findings regarding the novel SLC18 transporter.
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Affiliation(s)
- Hiroshi Omote
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan; ,
| | - Takaaki Miyaji
- Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan
| | - Miki Hiasa
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan; ,
| | - Narinobu Juge
- Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan
| | - Yoshinori Moriyama
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan; , .,Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan
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15
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3-aminoglutarate is a “silent” false transmitter for glutamate neurons. Neuropharmacology 2015; 97:436-46. [DOI: 10.1016/j.neuropharm.2015.05.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2015] [Revised: 04/25/2015] [Accepted: 05/08/2015] [Indexed: 11/27/2022]
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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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17
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Accardi A. Unveiling the secret lives of glutamate transporters: VGLUTs engage in multiple transport modes. Neuron 2015; 84:1110-2. [PMID: 25521371 DOI: 10.1016/j.neuron.2014.12.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Accumulation of glutamate in synaptic vesicles is mediated by vesicular glutamate transporters called VGLUTs. In the current issue of Neuron, Preobraschenski et al. (2014) show that the VGLUTs, in addition to transporting glutamate, also provide the conductances necessary to maintain the appropriate voltage and pH inside these vesicles.
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Affiliation(s)
- Alessio Accardi
- Department of Anesthesiology, Department of Physiology and Biophysics, Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA.
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18
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Identification of a mammalian vesicular polyamine transporter. Sci Rep 2014; 4:6836. [PMID: 25355561 PMCID: PMC4213795 DOI: 10.1038/srep06836] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 10/10/2014] [Indexed: 01/11/2023] Open
Abstract
Spermine and spermidine act as neuromodulators upon binding to the extracellular site(s) of various ionotropic receptors, such as N-methyl-d-aspartate receptors. To gain access to the receptors, polyamines synthesized in neurons and astrocytes are stored in secretory vesicles and released upon depolarization. Although vesicular storage is mediated in an ATP-dependent, reserpine-sensitive fashion, the transporter responsible for this process remains unknown. SLC18B1 is the fourth member of the SLC18 transporter family, which includes vesicular monoamine transporters and vesicular acetylcholine transporter. Proteoliposomes containing purified human SLC18B1 protein actively transport spermine and spermidine by exchange of H(+). SLC18B1 protein is predominantly expressed in the hippocampus and is associated with vesicles in astrocytes. SLC18B1 gene knockdown decreased both SLC18B1 protein and spermine/spermidine contents in astrocytes. These results indicated that SLC18B1 encodes a vesicular polyamine transporter (VPAT).
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19
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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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20
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Tamura Y, Ogita K, Ueda T. A new VGLUT-specific potent inhibitor: pharmacophore of Brilliant Yellow. Neurochem Res 2014; 39:117-28. [PMID: 24248859 PMCID: PMC4025951 DOI: 10.1007/s11064-013-1196-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Revised: 11/05/2013] [Accepted: 11/07/2013] [Indexed: 10/26/2022]
Abstract
The increased concentration of glutamate in synaptic vesicles, mediated by the vesicular glutamate transporter (VGLUT), is an initial vital step in glutamate synaptic transmission. Evidence indicates that aberrant overexpression of VGLUT is involved in certain pathophysiologies of the central nervous system. VGLUT is subject to inhibition by various types of agents. The most potent VGLUT-specific inhibitor currently known is Trypan Blue, which is highly charged, hence membrane-impermeable. We have sought a potent, VGLUT-specific agent amenable to easy modification to a membrane-permeable analog. We provide evidence that Brilliant Yellow exhibits potent, VGLUT-specific inhibition, with a Ki value of 12 nM. Based upon structure-activity relationship studies and molecular modeling, we have defined the potent inhibitory pharmacophore of Brilliant Yellow. This study provides new insight into development of a membrane-permeable agent to lead to specific blockade, with high potency, of accumulation of glutamate into synaptic vesicles in neurons.
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Affiliation(s)
- Yutaka Tamura
- Molecular and Behavioral Neuroscience Institute, Medical School, The University of Michigan, 109 Zina Pitcher Place, Ann Arbor, Michigan 48109-2200, USA
| | - Kiyokazu Ogita
- Molecular and Behavioral Neuroscience Institute, Medical School, The University of Michigan, 109 Zina Pitcher Place, Ann Arbor, Michigan 48109-2200, USA
| | - Tetsufumi Ueda
- Molecular and Behavioral Neuroscience Institute, Medical School, The University of Michigan, 109 Zina Pitcher Place, Ann Arbor, Michigan 48109-2200, USA
- Department of Pharmacology, Medical School, The University of Michigan, Ann Arbor, Michigan 48109, USA
- Department of Psychiatry, Medical School, The University of Michigan, Ann Arbor, Michigan 48109, USA
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21
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Karlsen AS, Rath MF, Rohde K, Toft T, Møller M. Developmental and diurnal expression of the synaptosomal-associated protein 25 (Snap25) in the rat pineal gland. Neurochem Res 2012; 38:1219-28. [PMID: 23135794 DOI: 10.1007/s11064-012-0918-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 09/19/2012] [Accepted: 10/25/2012] [Indexed: 11/24/2022]
Abstract
Snap25 (synaptosomal-associated protein) is a 25 kDa protein, belonging to the SNARE-family (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) of proteins, essential for synaptic and secretory vesicle exocytosis. Snap25 has by immunohistochemistry been demonstrated in the rat pineal gland but the biological importance of this is unknown. In this study, we demonstrate a high expression of mRNA encoding Snap25 in all parts of the rat pineal complex, the superficial-, and deep-pineal gland, as well as in the pineal stalk. Snap25 showed a low pineal expression during embryonic stages with a strong increase in expression levels just after birth. The expression showed no day/night variations. Neither removal of the sympathetic input to the pineal gland by superior cervical ganglionectomy nor bilateral decentralization of the superior cervical ganglia significantly affected the expression of Snap25 in the gland. The pineal expression levels of Snap25 were not changed following intraperitoneal injection of isoproterenol. The strong expression of Snap25 in the pineal gland suggests the presence of secretory granules and microvesicles in the rat pinealocyte supporting the concept of a vesicular release. At the transcriptional level, this Snap25-based release mechanism does not exhibit any diurnal rhythmicity and is regulated independently of the sympathetic nervous input to the gland.
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Affiliation(s)
- Anna S Karlsen
- Department of Neuroscience and Pharmacology, Faculty of Health Sciences, Panum Institute, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark.
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22
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Takeda K, Ishida A, Takahashi K, Ueda T. Synaptic vesicles are capable of synthesizing the VGLUT substrate glutamate from α-ketoglutarate for vesicular loading. J Neurochem 2012; 121:184-96. [PMID: 22309504 DOI: 10.1111/j.1471-4159.2012.07684.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Synaptic vesicle loading of glutamate is a pivotal step in glutamate synaptic transmission. The molecular machinery responsible for this step is comprised of v-type proton-pump ATPase and a vesicular glutamate transporter. Recent evidence indicates that synaptic vesicles are endowed with glycolytic ATP-synthesizing enzymes, providing energy for immediate use by vesicle-bound proton-pump ATPase. In this study, we provide evidence that synaptic vesicles are also capable of synthesizing the vesicular glutamate transporter substrate glutamate, from α-ketoglutarate and l-aspartate (as the amino group donor); glutamate thus produced is taken up into vesicles. We also report a finding that α-ketoglutarate-derived glutamate uptake into synaptic vesicles and aspartate aminotransferase are inhibited by 2,3-pyrazinedicarboxylate. Evidence is given that this is a selective inhibitor for aspartate aminotransferase. These observations provide insight into understanding the nerve endings' mechanism for high efficiency in glutamate transmission. Finding this inhibitor may have implications for further experimentation on the role of α-ketoglutarate-derived glutamate in glutamate transmission.
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Affiliation(s)
- Kouji Takeda
- Molecular & Behavioral Neuroscience Institute, Medical School, The University of Michigan, Ann Arbor, Michigan, USA
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23
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Omote H, Miyaji T, Juge N, Moriyama Y. Vesicular Neurotransmitter Transporter: Bioenergetics and Regulation of Glutamate Transport. Biochemistry 2011; 50:5558-65. [DOI: 10.1021/bi200567k] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Hiroshi Omote
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan
| | - Takaaki Miyaji
- Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan
| | - Narinobu Juge
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan
| | - Yoshinori Moriyama
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan
- Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan
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24
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Bustos DM, Bailey MJ, Sugden D, Carter DA, Rath MF, Møller M, Coon SL, Weller JL, Klein DC. Global daily dynamics of the pineal transcriptome. Cell Tissue Res 2011; 344:1-11. [PMID: 21302120 DOI: 10.1007/s00441-010-1094-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Accepted: 11/16/2010] [Indexed: 10/18/2022]
Abstract
Transcriptome profiling of the pineal gland has revealed night/day differences in the expression of a major fraction of the genes active in this tissue, with two-thirds of these being nocturnal increases. A set of over 600 transcripts exhibit two-fold to >100-fold daily differences in abundance. These changes appear to be primarily attributable to adrenergic-cyclic-AMP-dependent mechanisms, which are controlled via a neural pathway that includes the suprachiasmatic nucleus, the master circadian oscillator. In addition to melatonin synthesis, night/day differences in gene expression impact genes associated with several specialized functions, including the immune/inflammation response, photo-transduction, and thyroid hormone/retinoic acid biology. The following nonspecialized cellular features are also affected: adhesion, cell cycle/cell death, cytoskeleton, DNA modification, endothelium, growth, RNA modification, small molecule biology, transcription factors, vesicle biology, signaling involving Ca(2+), cyclic nucleotides, phospholipids, mitogen-activated protein kinases, the Wnt signaling pathway, and protein phosphorylation.
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Affiliation(s)
- Diego M Bustos
- Instituto Tecnológico de Chascomús (Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús), Camino Circunvalación Laguna km 6 cc164, B7130IWA, Chascomús, Argentina
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25
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Juge N, Gray JA, Omote H, Miyaji T, Inoue T, Hara C, Uneyama H, Edwards RH, Nicoll RA, Moriyama Y. Metabolic control of vesicular glutamate transport and release. Neuron 2010; 68:99-112. [PMID: 20920794 DOI: 10.1016/j.neuron.2010.09.002] [Citation(s) in RCA: 288] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/17/2010] [Indexed: 12/16/2022]
Abstract
Fasting has been used to control epilepsy since antiquity, but the mechanism of coupling between metabolic state and excitatory neurotransmission remains unknown. Previous work has shown that the vesicular glutamate transporters (VGLUTs) required for exocytotic release of glutamate undergo an unusual form of regulation by Cl(-). Using functional reconstitution of the purified VGLUTs into proteoliposomes, we now show that Cl(-) acts as an allosteric activator, and the ketone bodies that increase with fasting inhibit glutamate release by competing with Cl(-) at the site of allosteric regulation. Consistent with these observations, acetoacetate reduced quantal size at hippocampal synapses and suppresses glutamate release and seizures evoked with 4-aminopyridine in the brain. The results indicate an unsuspected link between metabolic state and excitatory neurotransmission through anion-dependent regulation of VGLUT activity.
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Affiliation(s)
- Narinobu Juge
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
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26
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Pietrancosta N, Kessler A, Favre-Besse FC, Triballeau N, Quentin T, Giros B, El Mestikawy S, Acher FC. Rose Bengal analogs and vesicular glutamate transporters (VGLUTs). Bioorg Med Chem 2010; 18:6922-33. [PMID: 20708942 DOI: 10.1016/j.bmc.2010.06.069] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Revised: 06/21/2010] [Accepted: 06/21/2010] [Indexed: 10/19/2022]
Abstract
Vesicular glutamate transporters (VGLUTs) allow the loading of presynaptic glutamate vesicles and thus play a critical role in glutamatergic synaptic transmission. Rose Bengal (RB) is the most potent known VGLUT inhibitor (Ki 25 nM); therefore we designed, synthesized and tested in brain preparations, a series of analogs based on this scaffold. We showed that among the two tautomers of RB, the carboxylic and not the lactonic form is active against VGLUTs and generated a pharmacophore model to determine the minimal structure requirements. We also tested RB specificity in other neurotransmitter uptake systems. RB proved to potently inhibit VMAT (Ki 64 nM) but weakly VACHT (Ki>9.7 microM) and may be a useful tool in glutamate/acetylcholine co-transmission studies.
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Affiliation(s)
- Nicolas Pietrancosta
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR8601 CNRS, Université Paris Descartes, 45 rue des Saints-Pères, 75270 Paris 06, France
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27
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Iharada M, Miyaji T, Fujimoto T, Hiasa M, Anzai N, Omote H, Moriyama Y. Type 1 sodium-dependent phosphate transporter (SLC17A1 Protein) is a Cl(-)-dependent urate exporter. J Biol Chem 2010; 285:26107-13. [PMID: 20566650 DOI: 10.1074/jbc.m110.122721] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
SLC17A1 protein (NPT1) is the first identified member of the SLC17 phosphate transporter family and mediates the transmembrane cotransport of Na(+)/P(i) in oocytes. Although this protein is believed to be a renal polyspecific anion exporter, its transport properties are not well characterized. Here, we show that proteoliposomes containing purified SLC17A1 transport various organic anions such as p-aminohippuric acid and acetylsalicylic acid (aspirin) in an inside positive membrane potential (Deltapsi)-dependent manner. We found that NPT1 also transported urate. The uptake characteristics were similar to that of SLC17 members in its Cl(-) dependence and inhibitor sensitivity. When arginine 138, an essential amino acid residue for members of the SLC17 family such as the vesicular glutamate transporter, was specifically mutated to alanine, the resulting mutant protein was inactive in Deltapsi-dependent anion transport. Heterologously expressed and purified human NPT1 carrying the single nucleotide polymorphism mutation that is associated with increased risk of gout in humans exhibited 32% lower urate transport activity compared with the wild type protein. These results strongly suggested that NPT1 is a Cl(-)-dependent polyspecific anion exporter involved in urate excretion under physiological conditions.
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Affiliation(s)
- Masafumi Iharada
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Tokyo, Japan
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28
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Abstract
ATP is a major chemical transmitter in purinergic signal transmission. Before secretion, ATP is stored in secretory vesicles found in purinergic cells. Although the presence of active transport mechanisms for ATP has been postulated for a long time, the proteins responsible for its vesicular accumulation remains unknown. The transporter encoded by the human and mouse SLC17A9 gene, a novel member of an anion transporter family, was predominantly expressed in the brain and adrenal gland. The mouse and bovine counterparts were associated with adrenal chromaffin granules. Proteoliposomes containing purified transporter actively took up ATP, ADP, and GTP by using membrane potential as the driving force. The uptake properties of the reconstituted transporter were similar to that of the ATP uptake by synaptic vesicles and chromaffin granules. Suppression of endogenous SLC17A9 expression in PC12 cells decreased exocytosis of ATP. These findings strongly suggest that SLC17A9 protein is a vesicular nucleotide transporter and should lead to the elucidation of the molecular mechanism of ATP secretion in purinergic signal transmission.
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29
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Chaudhry FA, Edwards RH, Fonnum F. Vesicular neurotransmitter transporters as targets for endogenous and exogenous toxic substances. Annu Rev Pharmacol Toxicol 2008; 48:277-301. [PMID: 17883368 DOI: 10.1146/annurev.pharmtox.46.120604.141146] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Exocytotic release of neurotransmitters requires their accumulation inside preformed secretory vesicles. Distinct vesicular transport activities translocate classical transmitters into synaptic vesicles energized by a H+ electrochemical gradient (Delta(mu(H+))), with subtle but important differences in dependence on the electrical and chemical components. The vesicular transporters also interact with toxic compounds and drugs. They mediate neuroprotection by sequestering toxic compounds as well as neurotransmitters into vesicles, reducing their concentration in the cytosol where they may have detrimental effects. Both therapeutic agents and psychostimulants interfering with vesicular transport have yielded insight into the pathogenesis of psychiatric as well as neurodegenerative diseases. Thus, specific inhibitors have helped to characterize both the physiological role and mechanism of vesicular neurotransmitter transport.
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Affiliation(s)
- Farrukh A Chaudhry
- Centre for Molecular Biology and Neuroscience, The Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway.
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30
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Winter HC, Ueda T. The glutamate uptake system in presynaptic vesicles: further characterization of structural requirements for inhibitors and substrates. Neurochem Res 2007; 33:223-31. [PMID: 17940888 DOI: 10.1007/s11064-007-9493-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2007] [Accepted: 08/28/2007] [Indexed: 12/01/2022]
Abstract
Noncyclic fluorine-substituted and cyclic analogs of glutamic acid were tested for their ability to inhibit glutamate uptake in isolated bovine presynaptic vesicles, in order to assess the specific structural requirements of the glutamate translocation system in the vesicle membrane. Cyclic analogs that permitted close interaction between the positive and negative charges of the glutamate molecule were effective inhibitors; maximum inhibitory potency was observed with L-trans-1-aminocyclopentane-1,3-dicarboxylic acid (L-t-ACPD), while D-t-ACPD was less active. Analogs with a larger or smaller ring (as in trans-1-aminocyclohexane-1,3-dicarboxylic acid or trans-1-aminocyclobutane-1,3-dicarboxylic acid) were also inhibitory, but somewhat less so. trans-ACPD was also taken up by the vesicles with a time course and ATP dependence similar to uptake of glutamate, and this uptake was inhibited by glutamate. The K(m) value for t-ACPD uptake was similar to its K(i) for inhibition of glutamate uptake, while its rate of uptake was lower than that of glutamate. Fluorine-substituted noncyclic analogs with substitutions at the 4-carbon were less effective than glutamic acid itself, although 4,4-difluoroglutamic acid was equal in activity to the unsubstituted compound. Inhibition by these derivatives appeared to be competitive in nature, and they probably were also transported by the vesicle uptake system.
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Affiliation(s)
- Harry C Winter
- Molecular and Behavioral Neuroscience Institute, The University of Michigan Medical School, 109 Zina Pitcher Place, Ann Arbor, MI 48109-2200, USA
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31
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Nogami H, Ogasawara K, Mimura Y, Mogi K, Shutoh F, Hisano S. Developmentally-regulated expression of tissue-specific splice variant of rat vesicular glutamate transporter 1 in retina and pineal gland. J Neurochem 2006; 99:142-53. [PMID: 16987242 DOI: 10.1111/j.1471-4159.2006.04049.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Three distinct subtypes of vesicular glutamate transporters (VGLUTs) have been identified to date that are expressed basically in a cell type-specific manner. We have found a splice variant of VGLUT1 mRNA that is expressed almost exclusively in photosensitive tissues, i.e. the retina and the pineal gland. The variant mRNA, termed VGLUT1v, contains an additional 75 base pair sequence derived from part of a second intron (designated as exon IIa) between exons 2 and 3. The variant accounted for approximately 70% and 25%of VGLUT1 mRNA in the adult retina and pineal gland, respectively. The expression of VGLUT1v was developmentally regulated in both tissues. Organ culture showed that expression of the variant in the retina increased in association with the development of rod cells, suggesting that VGLUT1v is expressed in rod cells. In situ hybridization with variant-specific probes showed expression of VGLUT1v in the inner segment layer of photoreceptor cells. On the other hand, variant expression did not parallel the development of rhodopsin-positive cells in the pineal gland. As rod cells and pinealocytes are known to release glutamate continuously at ribbon synapses, it is possible that the variant has some functional advantage over the wild-type transporter in such a specialized manner of glutamate release.
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Affiliation(s)
- Haruo Nogami
- Laboratory of Neuroendocrinology, Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, Japan.
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32
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Juge N, Yoshida Y, Yatsushiro S, Omote H, Moriyama Y. Vesicular glutamate transporter contains two independent transport machineries. J Biol Chem 2006; 281:39499-506. [PMID: 17046815 DOI: 10.1074/jbc.m607670200] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vesicular glutamate transporters (VGLUTs) are responsible for the vesicular storage of l-glutamate and play an essential role in glutamatergic signal transmission in the central nervous system. The molecular mechanism of the transport remains unknown. Here, we established a novel in vitro assay procedure, which includes purification of wild and mutant VGLUT2 and their reconstitution with purified bacterial F(o)F(1)-ATPase (F-ATPase) into liposomes. Upon the addition of ATP, the proteoliposomes facilitated l-glutamate uptake in a membrane potential (DeltaPsi)-dependent fashion. The ATP-dependent l-glutamate uptake exhibited an absolute requirement for approximately 4 mm Cl(-), was sensitive to Evans blue, but was insensitive to d,l-aspartate. VGLUT2s with mutations in the transmembrane-located residues Arg(184), His(128), and Glu(191) showed a dramatic loss in l-glutamate transport activity, whereas Na(+)-dependent inorganic phosphate (P(i)) uptake remained comparable to that of the wild type. Furthermore, P(i) transport did not require Cl(-) and was not inhibited by Evans blue. Thus, VGLUT2 appears to possess two intrinsic transport machineries that are independent of each other: a DeltaPsi-dependent l-glutamate uptake and a Na(+)-dependent P(i) uptake.
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Affiliation(s)
- Narinobu Juge
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama 700-8530, Japan
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33
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Morimoto R, Uehara S, Yatsushiro S, Juge N, Hua Z, Senoh S, Echigo N, Hayashi M, Mizoguchi T, Ninomiya T, Udagawa N, Omote H, Yamamoto A, Edwards RH, Moriyama Y. Secretion of L-glutamate from osteoclasts through transcytosis. EMBO J 2006; 25:4175-86. [PMID: 16957773 PMCID: PMC1570443 DOI: 10.1038/sj.emboj.7601317] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2005] [Accepted: 08/08/2006] [Indexed: 01/11/2023] Open
Abstract
Osteoclasts are involved in the catabolism of the bone matrix and eliminate the resulting degradation products through transcytosis, but the molecular mechanism and regulation of transcytosis remain poorly understood. Upon differentiation, osteoclasts express vesicular glutamate transporter 1 (VGLUT1), which is essential for vesicular storage and subsequent exocytosis of glutamate in neurons. VGLUT1 is localized in transcytotic vesicles and accumulates L-glutamate. Osteoclasts secrete L-glutamate and the bone degradation products upon stimulation with KCl or ATP in a Ca2+-dependent manner. KCl- and ATP-dependent secretion of L-glutamate was absent in osteoclasts prepared from VGLUT1-/- knockout mice. Osteoclasts express mGluR8, a class III metabotropic glutamate receptor. Its stimulation by a specific agonist inhibits secretion of L-glutamate and bone degradation products, whereas its suppression by a specific antagonist stimulates bone resorption. Finally, it was found that VGLUT1-/- mice develop osteoporosis. Thus, in bone-resorbing osteoclasts, L-glutamate and bone degradation products are secreted through transcytosis and the released L-glutamate is involved in autoregulation of transcytosis. Glutamate signaling may play an important role in the bone homeostasis.
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Affiliation(s)
- Riyo Morimoto
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Shunsuke Uehara
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Shouki Yatsushiro
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Narinobu Juge
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Zhaolin Hua
- Departments of Neurology and Physiology, Graduate Programs in Neuroscience and Cell Biology, University of California San Francisco School of Medicine, CA, USA
| | - Shigenori Senoh
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Noriko Echigo
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Mitsuko Hayashi
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | | | - Tadashi Ninomiya
- Institute for Oral Science, Matsumoto Dental University, Shiojiri, Japan
| | - Nobuyuki Udagawa
- Department of Biochemistry, Matsumoto Dental University, Shiojiri, Japan
| | - Hiroshi Omote
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Akitsugu Yamamoto
- Department of Cell Biology, Nagahama Institute of Bioscience and Technology, Nagahama, Japan
| | - Robert H Edwards
- Departments of Neurology and Physiology, Graduate Programs in Neuroscience and Cell Biology, University of California San Francisco School of Medicine, CA, USA
| | - Yoshinori Moriyama
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
- Department of Membrane Biochemistry, Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan. Tel.: +81 86 251 7933/7934; Fax: +81 86 251 7935; E-mail:
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34
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Abstract
The expression of vesicular glutamate transporters (VGLUTs) 1 and 2 accounts for the ability of most traditionally accepted excitatory neurons to release glutamate by exocytosis. However, several cell populations (serotonin and dopamine neurons) have been demonstrated to release glutamate in vitro and do not obviously express these transporters. Rather, these neurons express a novel, third isoform that in fact appears confined to neurons generally associated with a transmitter other than glutamate. They include serotonin and possibly dopamine neurons, cholinergic interneurons in the striatum, and GABAergic interneurons of the hippocampus and cortex. Although the physiological role of VGLUT3 remains largely conjectural, several observations in vivo suggest that the glutamate release mediated by VGLUT3 has an important role in synaptic transmission, plasticity, and development.
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Affiliation(s)
- R P Seal
- Department of Neurology, UCSF School of Medicine, 600 16th St., GH-N272B, San Francisco CA, 94143-2140, USA
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35
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Uehara S, Jung SK, Morimoto R, Arioka S, Miyaji T, Juge N, Hiasa M, Shimizu K, Ishimura A, Otsuka M, Yamamoto A, Maechler P, Moriyama Y. Vesicular storage and secretion of L-glutamate from glucagon-like peptide 1-secreting clonal intestinal L cells. J Neurochem 2005; 96:550-60. [PMID: 16336630 DOI: 10.1111/j.1471-4159.2005.03575.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Vesicular glutamate transporter (VGLUT) is responsible for the vesicular storage of l-glutamate, and plays an essential role in glutamate-mediated intercellular signal transmission in the CNS and in some neuroendocrine cells. Intestinal L cells are the glucose-responsive neuroendocrine cells responsible for the secretion of glucagon-like peptide 1 (GLP-1). We have shown that intestinal L cells express VGLUT2, a VGLUT isoform, which suggests that L cells secrete L-glutamate. In the present study, we investigated this possibility using GLUTag mouse clonal L cells. RT-PCR and northern blot analyses revealed expression of the VGLUT1 and VGLUT2 genes, but not of the VGLUT3 gene. Western blot analysis revealed immunological counterparts for VGLUT2, whereas an immunological counterpart of VGLUT1 was not detected. Indirect immunofluorescence microscopy revealed a punctate distribution of VGLUT2 immunoreactivity throughout the cells, which co-localized with GLP-1. Double-labeling immunoelectronmicroscopy confirmed the association of VGLUT2 with GLP-1-containing secretory granules. The membrane fraction exhibited ATP-dependent L-glutamate uptake, which was sensitive to bafilomycin A1 (a vacuolar proton ATPase inhibitor) and Evans blue (a VGLUT inhibitor) but insensitive to D,L-aspartate. Upon depolarization with KCl, GLUTag cells secreted appreciable amounts of L-glutamate and GLP-1. D-Glucose and methyl-alpha-D-glucopyranoside, stimulators of exocytosis of GLP-1, also triggered the secretion of L-glutamate. The L-glutamate secretion was partially dependent on Ca2+ and sensitive to bafilomycin A1. These results demonstrated that GLUTag cells stored L-glutamate in secretory granules and secreted it with GLP-1 by exocytosis. As GLUTag cells and intestinal L cells express kainate receptors and plasma membrane glutamate transporters, these results support the concept of L-glutamate-mediated intercellular signaling in the vicinity of intestinal L cells.
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Affiliation(s)
- Shunsuke Uehara
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
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36
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Bole DG, Ueda T. Inhibition of Vesicular Glutamate Uptake by Rose Bengal-Related Compounds: Structure–Activity Relationship. Neurochem Res 2005; 30:363-9. [PMID: 16018580 DOI: 10.1007/s11064-005-2610-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Synaptic vesicular accumulation of glutamate is a vital initial step in glutamate transmission. We have previously shown that Rose Bengal, a polyhalogenated fluorescein analog, is a potent inhibitor of glutamate uptake into synaptic vesicles. Here, we report the structural features of Rose Bengal required for this inhibition. Various Rose Bengal-related compounds, with systematic structural variations, were tested. Results indicate that the four iodo groups and the phenyl group attached to the xanthene moiety are critical for potent inhibitory activity. Replacement of these groups with two iodo groups and an alkyl group, respectively, results in substantial reduction in potency. Of further interest in creating high potency is the critical nature of the oxygen atom which links the two benzene rings of xanthene. Thus, the phenyl group and multiple iodo groups, as well as the bridging oxygen of xanthene, are crucial elements of Rose Bengal required for its potent inhibitory action.
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Affiliation(s)
- David G Bole
- Mental Health Research Institute, University of Michigan Medical School, Ann Arbor, Michigan 48109-0669, USA
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37
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Moriyama Y, Yamamoto A. Glutamatergic Chemical Transmission: Look! Here, There, and Anywhere. J Biochem 2004; 135:155-63. [PMID: 15047716 DOI: 10.1093/jb/mvh018] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Vesicular glutamate transporter (VGLUT) is responsible for the active transport of L-glutamate in synaptic vesicles and thus plays an essential role in the glutamatergic chemical transmission in the central nervous system. VGLUT comprises three isoforms, VGLUT1, 2, and 3, and is a potential marker for the glutamatergic phenotype. Recent studies indicated that VGLUT is also expressed in non-neuronal cells, and localized with various organelles such as synaptic-like microvesicles in the pineal gland, and hormone-containing secretory granules in endocrine cells. L-Glutamate is stored in these organelles, secreted upon various forms of stimulation, and then acts as a paracrine-like modulator. Thus, VGLUTs highlight a novel framework of glutamatergic signaling and reveal its diverse modes of action.
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Affiliation(s)
- Yoshinori Moriyama
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Okayama University, Okayama 700-8530.
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Moriyama Y, Hayashi M. Glutamate-mediated signaling in the islets of Langerhans: a thread entangled. Trends Pharmacol Sci 2004; 24:511-7. [PMID: 14559402 DOI: 10.1016/j.tips.2003.08.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Yoshinori Moriyama
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan.
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Hinoi E, Takarada T, Ueshima T, Tsuchihashi Y, Yoneda Y. Glutamate signaling in peripheral tissues. ACTA ACUST UNITED AC 2004; 271:1-13. [PMID: 14686914 DOI: 10.1046/j.1432-1033.2003.03907.x] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The hypothesis that l-glutamate (Glu) is an excitatory amino acid neurotransmitter in the mammalian central nervous system is now gaining more support after the successful cloning of a number of genes coding for the signaling machinery required for this neurocrine at synapses in the brain. These include Glu receptors (signal detection), Glu transporters (signal termination) and vesicular Glu transporters (signal output through exocytotic release). Relatively little attention has been paid to the functional expression of these molecules required for Glu signaling in peripheral neuronal and non-neuronal tissues; however, recent molecular biological analyses show a novel function for Glu as an extracellular signal mediator in the autocrine and/or paracrine system. Emerging evidence suggests that Glu could play a dual role in mechanisms underlying the maintenance of cellular homeostasis - as an excitatory neurotransmitter in the central neurocrine system and an extracellular signal mediator in peripheral autocrine and/or paracrine tissues. In this review, the possible Glu signaling methods are outlined in specific peripheral tissues including bone, testis, pancreas, and the adrenal, pituitary and pineal glands.
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Affiliation(s)
- Eiichi Hinoi
- Laboratory of Molecular Pharmacology, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa, Japan
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40
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Simonneaux V, Ribelayga C. Generation of the melatonin endocrine message in mammals: a review of the complex regulation of melatonin synthesis by norepinephrine, peptides, and other pineal transmitters. Pharmacol Rev 2003; 55:325-95. [PMID: 12773631 DOI: 10.1124/pr.55.2.2] [Citation(s) in RCA: 443] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Melatonin, the major hormone produced by the pineal gland, displays characteristic daily and seasonal patterns of secretion. These robust and predictable rhythms in circulating melatonin are strong synchronizers for the expression of numerous physiological processes in photoperiodic species. In mammals, the nighttime production of melatonin is mainly driven by the circadian clock, situated in the suprachiasmatic nucleus of the hypothalamus, which controls the release of norepinephrine from the dense pineal sympathetic afferents. The pivotal role of norepinephrine in the nocturnal stimulation of melatonin synthesis has been extensively dissected at the cellular and molecular levels. Besides the noradrenergic input, the presence of numerous other transmitters originating from various sources has been reported in the pineal gland. Many of these are neuropeptides and appear to contribute to the regulation of melatonin synthesis by modulating the effects of norepinephrine on pineal biochemistry. The aim of this review is firstly to update our knowledge of the cellular and molecular events underlying the noradrenergic control of melatonin synthesis; and secondly to gather together early and recent data on the effects of the nonadrenergic transmitters on modulation of melatonin synthesis. This information reveals the variety of inputs that can be integrated by the pineal gland; what elements are crucial to deliver the very precise timing information to the organism. This also clarifies the role of these various inputs in the seasonal variation of melatonin synthesis and their subsequent physiological function.
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Affiliation(s)
- Valerie Simonneaux
- Laboratoire de Neurobiologie Rythmes, UMR 7518 CNRS/ULP, 12, rue de l'Université, 67000 Strasbourg, France.
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Morimoto R, Hayashi M, Yatsushiro S, Otsuka M, Yamamoto A, Moriyama Y. Co-expression of vesicular glutamate transporters (VGLUT1 and VGLUT2) and their association with synaptic-like microvesicles in rat pinealocytes. J Neurochem 2003; 84:382-91. [PMID: 12559000 DOI: 10.1046/j.1471-4159.2003.01532.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A vesicular glutamate transporter (VGLUT) is responsible for the accumulation of l-glutamate in synaptic vesicles in glutamatergic neurons. Two isoforms, VGLUT1 and VGLUT2, have been identified, which are complementarily expressed in these neurons. Mammalian pinealocytes, endocrine cells for melatonin, are also glutamatergic in nature, accumulate l-glutamate in synaptic-like microvesicles (SLMVs), and secrete it through exocytosis. Although the storage of l-glutamate in SLMVs is mediated through a VGLUT, the molecular nature of the transporter is less understood. We recently observed that VGLUT2 is expressed in pinealocytes. In the present study, we show that pinealocytes also express VGLUT1. RT-PCR and northern blot analyses indicated expression of the VGLUT1 gene in pineal gland. Western blotting with specific antibodies against VGLUT1 indicated the presence of VGLUT1 in pineal gland. Indirect immunofluorescence microscopy with a section of pineal gland and cultured cells indicated that VGLUT1 and VGLUT2 are co-localized with process terminal regions of pinealocytes. Furthermore, immunoelectronmicroscopy as well as subcellular fractionation studies revealed that both VGLUT1 and VGLUT2 are specifically associated with SLMVs. These results indicate that both VGLUTs are responsible for storage of l-glutamate in SLMVs in pinealocytes. Pinealocytes are the first exception as to complementary expression of VGLUT1 and VGLUT2.
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Affiliation(s)
- Riyo Morimoto
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Okayama University, Japan.
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42
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Amano T, Matsubayashi H, Ozkan ED, Sasa M, Serikawa T, Ueda T. Aberrant reduction of an inhibitory protein factor in a rat epileptic model. Epilepsy Res 2002; 51:81-91. [PMID: 12350384 DOI: 10.1016/s0920-1211(02)00122-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Certain forms of seizure involve excessive glutamate transmission. We have recently identified a protein, referred to as the inhibitory protein factor (IPF), which potently inhibits glutamate uptake into isolated synaptic vesicles. In an effort to understand the mechanism underlying excessive glutamate transmission associated with seizure, we have analyzed IPF content in various brain regions of the spontaneously epileptic rat, SER (tm/tm, zi/zi), the absence-seizure tremor rat, TM (tm/tm), and the seizure-free control rats zitter ZI (zi/zi) and Wistar tremor control, each at 13 weeks of age. IPF content was found to be markedly reduced in the hippocampus, but not in the other brain regions, of SER, compared to the control and TM rats. TM rats also exhibited reduced IPF content compared to seizure-free controls. These changes appear developmentally regulated; no such alteration was observed in 8-week-old rats, which rarely show seizure. These observations indicate that an aberrant decrease in IPF is associated with certain forms of seizure; this decrease could lead to an abnormal increase in the amount of exocytotically released glutamate through its excessive accumulation in synaptic vesicles.
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Affiliation(s)
- Taku Amano
- Mental Health Research Institute, Medical School, The University of Michigan, Ann Arbor, MI 48109-0669, USA
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43
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Hayashi M, Yamamoto A, Moriyama Y. The internal pH of synaptic-like microvesicles in rat pinealocytes in culture. J Neurochem 2002; 82:698-704. [PMID: 12153493 DOI: 10.1046/j.1471-4159.2002.01025.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Synaptic-like microvesicles (SLMVs) are morphological and functional equivalents of neuronal synaptic vesicles, and are responsible for the storage and secretion of classical neurotransmitters in various endocrine cells. Vacuolar H+-ATPase acidifies the internal space of these organelles and provides a driving force for the uptake of neurotransmitters. Thus, the luminal pH is an important determinant of the function of SLMVs, although its value in living cells is unknown. Here, we determined the luminal pH of SLMVs in living rat pinealocytes by means of an immunoelectronmicroscopic procedure basedon the distribution of an amphipathic amine, 3-(2,4-dinitroanilino)-3'-amino-N-methyldipropylamine (DAMP). Use of double-labeling techniques with antibodies against 2,4-dinitrophenol for DAMP and synaptophysin for SLMVs, and of frozen ultrathin sections enabled us to determine the number of immunogold particles for DAMP per microm2 of SLMVs. Using the density of gold particles, the luminal pH of SLMVs was calculated to be 5.11 +/- 0.01. Treatment with either 1 microm bafilomycin A1, a specific inhibitor of vacuolar H+-ATPase, or 50 mm ammonium chloride, a dissipater of the transmembrane pH gradient, increased the luminal pH to 6.04 +/- 0.07 and 6.05 +/- 0.11, respectively. Simultaneously, the lysosomal pH was found to be 5.14 +/- 0.07, which increased to 5.77 +/- 0.09 and 5.93 +/- 0.13 with bafilomycin A1 and ammonium chloride, respectively. It is concluded that the luminal pH of SLMVs is comparable to that of lysosomes in vivo.
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Affiliation(s)
- Mitsuko Hayashi
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Okayama University, Japan
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44
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Kaneko T, Fujiyama F. Complementary distribution of vesicular glutamate transporters in the central nervous system. Neurosci Res 2002; 42:243-50. [PMID: 11985876 DOI: 10.1016/s0168-0102(02)00009-3] [Citation(s) in RCA: 336] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two vesicular glutamate transporters (VGluTs) have been identified at the molecular level very recently and revealed to possess similar pharmacological characteristics for glutamate uptake. Vesicular glutamate transporter 1 (VGluT1), which was originally named brain-specific Na+-dependent inorganic phosphate cotransporter (BNPI), is mainly expressed in telencephalic regions, whereas vesicular glutamate transporter 2 (VGluT2), formerly referred to as differentiation-associated Na+-dependent inorganic phosphate cotransporter (DNPI), is produced principally in diencephalic and lower brainstem regions. Since no other proteins show as high molecular similarity to VGluT1 or VGluT2 as the two transporters exhibit, it is likely that the mammalian central nervous system use only two gene products for vesicular glutamate uptake. Immunoelectron-microscopic analysis has revealed that the two VGluTs are located on synaptic vesicles in axon terminals making an asymmetric type of synapses, supporting that they serve as vesicular transporters in excitatory terminals. Furthermore, mRNA and immunoreactivity for VGluTs are distributed largely in a complementary fashion to distinct populations of excitatory neurons; for example, in the cerebral cortex, thalamocortical axon terminals use VGluT2, whereas excitatory axon terminals of corticocortical or intracortical fibers seem to apply VGluT1 for glutamate uptake. This complementary distribution might suggest that the two VGluTs have an as yet unknown difference in functions.
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Affiliation(s)
- Takeshi Kaneko
- Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, 606-8501, Kyoto, Japan.
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45
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Identification of the differentiation-associated Na+/PI transporter as a novel vesicular glutamate transporter expressed in a distinct set of glutamatergic synapses. J Neurosci 2002. [PMID: 11756497 DOI: 10.1523/jneurosci.22-01-00142.2002] [Citation(s) in RCA: 329] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Glutamate transport into synaptic vesicles is a prerequisite for its regulated neurosecretion. Here we functionally identify a second isoform of the vesicular glutamate transporter (VGLUT2) that was previously identified as a plasma membrane Na+-dependent inorganic phosphate transporter (differentiation-associated Na+/P(I) transporter). Studies using intracellular vesicles from transiently transfected PC12 cells indicate that uptake by VGLUT2 is highly selective for glutamate, is H+ dependent, and requires Cl- ion. Both the vesicular membrane potential (Deltapsi) and the proton gradient (DeltapH) are important driving forces for vesicular glutamate accumulation under physiological Cl- concentrations. Using an antibody specific for VGLUT2, we also find that this protein is enriched on synaptic vesicles and selective for a distinct class of glutamatergic nerve terminals. The pathway-specific, complementary expression of two different vesicular glutamate transporters suggests functional diversity in the regulation of vesicular release at excitatory synapses. Together, the two isoforms may account for the uptake of glutamate by synaptic vesicles from all central glutamatergic neurons.
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46
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Hayashi M, Otsuka M, Morimoto R, Hirota S, Yatsushiro S, Takeda J, Yamamoto A, Moriyama Y. Differentiation-associated Na+-dependent inorganic phosphate cotransporter (DNPI) is a vesicular glutamate transporter in endocrine glutamatergic systems. J Biol Chem 2001; 276:43400-6. [PMID: 11551935 DOI: 10.1074/jbc.m106244200] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Vesicular glutamate transporter is present in neuronal synaptic vesicles and endocrine synaptic-like microvesicles and is responsible for vesicular storage of L-glutamate. A brain-specific Na(+)-dependent inorganic phosphate transporter (BNPI) functions as a vesicular glutamate transporter in synaptic vesicles, and the expression of this BNPI defines the glutamatergic phenotype in the central nervous system (Bellocchio, E. E., Reimer, R. J., Fremeau, R. T., Jr., and Edwards, R. H. (2000) Science 289, 957-960; Takamori, S., Rhee, J. S., Rosenmund, C., and Jahn, R. (2000) Nature 407, 189-194). However, since not all glutamatergic neurons contain BNPI, an additional transporter(s) responsible for vesicular glutamate uptake has been postulated. Here we report that differentiation-associated Na(+)-dependent inorganic phosphate cotransporter (DNPI), an isoform of BNPI (Aihara, Y., Mashima, H., Onda, H., Hisano, S., Kasuya, H., Hori, T., Yamada, S., Tomura, H., Yamada, Y., Inoue, I., Kojima, I., and Takeda, J. (2000) J. Neurochem. 74, 2622-2625), also transports L-glutamate at the expense of an electrochemical gradient of protons established by the vacuolar proton pump when expressed in COS7 cells. Molecular, biological, and immunohistochemical studies have indicated that besides its presence in neuronal cells DNPI is preferentially expressed in mammalian pinealocytes, alphaTC6 cells, clonal pancreatic alpha cells, and alpha cells of Langerhans islets, these cells being proven to secrete L-glutamate through Ca(2+)-dependent regulated exocytosis followed by its vesicular storage. Pancreatic polypeptide-secreting F cells of Langerhans islets also expressed DNPI. These results constitute evidence that DNPI functions as another vesicular transporter in glutamatergic endocrine cells as well as in neurons.
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Affiliation(s)
- M Hayashi
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan
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47
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Fleck MW, Barrionuevo G, Palmer AM. Synaptosomal and vesicular accumulation of L-glutamate, L-aspartate and D-aspartate. Neurochem Int 2001; 39:217-25. [PMID: 11434980 DOI: 10.1016/s0197-0186(01)00018-3] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We examined the vesicular accumulation of the excitatory amino-acid (EAA) neurotransmitters, L-glutamate and L-aspartate, together with the non-metabolisable EAA analogue D-aspartate. Synaptosomes derived from whole brain were incubated in various concentrations of [3H]-amino acids under conditions to facilitate vesicular turnover. Synaptosomes were then lysed in hypotonic medium and vesicles immunoprecipitated with monoclonal anti-synaptophysin antibodies coupled to sepharose beads. Using this method, saturable vesicular accumulation was observed for [3H]-L-glutamate, [3H]-L-aspartate, and [3H]-D-aspartate but not for the excitatory amino acid receptor ligands [3H]-AMPA or [3H]-kainate. Vesicular accumulation (t(1/2)=7.45 min) was markedly slower than synaptosomal accumulation (t(1/2)=1.03 min) and was substantially reduced at 4 degrees C. Maximal accumulation of [3H]-L-glutamate, [3H]-L-aspartate, and [3H]-D-aspartate was estimated to be 98, 68, and 112 pmol/mg of synaptosomal protein, respectively, and uptake affinities 1.6, 3.4, and 2.1 mM, respectively. Maximal accumulation of [3H]-L-glutamate was non-competitively inhibited by both 100 microM unlabeled L-aspartate and 100 microM D-aspartate, suggesting that all are accumulated into a common vesicular pool by different transporters.
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Affiliation(s)
- M W Fleck
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
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48
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Nakatsuka S, Hayashi M, Muroyama A, Otsuka M, Kozaki S, Yamada H, Moriyama Y. D-Aspartate is stored in secretory granules and released through a Ca(2+)-dependent pathway in a subset of rat pheochromocytoma PC12 cells. J Biol Chem 2001; 276:26589-96. [PMID: 11333256 DOI: 10.1074/jbc.m011754200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
D-Aspartate in mammalian neuronal and neuroendocrine cells is suggested to play a regulatory role(s) in the neuroendocrine function. Although D-aspartate is known to be released from neuroendocrine cells, the mechanism underlying the release is less understood. Rat pheochromocytoma PC12 cells contain an appreciable amount of D-aspartate (257 +/- 31 pmol/10(7) cells). Indirect immunofluorescence microscopy with specific antibodies against d-aspartate indicated that the amino acid is present within a particulate structure, which is co-localized with dopamine and chromogranin A, markers for secretory granules, but not with synaptophysin, a marker for synaptic-like microvesicles. After sucrose density gradient centrifugation of the postnuclear particulate fraction, about 80% of the d-aspartate was recovered in the secretory granule fraction. Upon the addition of KCl, an appreciable amount of D-aspartate (about 40 pmol/10(7) cells at 10 min) was released from cultured cells on incubation in the presence of Ca(2+) in the medium. The addition of also triggered d-aspartate release. Botulinum neurotoxin type E inhibited about 40% of KCl- and Ca(2+)-dependent d-aspartate release followed by specific cleavage of 25-kDa synaptosomal-associated protein. alpha-Latrotoxin increased the intracellular [Ca(2+)] and caused the Ca(2+)-dependent d-aspartate release. Bafilomycin A1 dissipated the intracellular acidic regions and inhibited 40% of the Ca(2+)-dependent D-aspartate release. These properties are similar to those of the exocytosis of dopamine. Furthermore, digitonin-permeabilized cells took up radiolabeled d-aspartate depending on MgATP, which is sensitive to bafilomycin A1 or 3,5-di-tert-butyl-4-hydroxybenzylidene-malononitrile. Taken together, these results strongly suggest that d-aspartate is stored in secretory granules and then secreted through a Ca(2+)-dependent exocytotic mechanism. Exocytosis of D-aspartate further supports the role(s) of D-aspartate as a chemical transmitter in neuroendocrine cells.
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Affiliation(s)
- S Nakatsuka
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan
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Yamada H, Otsuka M, Hayashi M, Nakatsuka S, Hamaguchi K, Yamamoto A, Moriyama Y. Ca2+-dependent exocytosis of L-glutamate by alphaTC6, clonal mouse pancreatic alpha-cells. Diabetes 2001; 50:1012-20. [PMID: 11334403 DOI: 10.2337/diabetes.50.5.1012] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Pancreatic islet cells express receptors and transporters for L-glutamate and are thus believed to use L-glutamate as an intercellular signaling molecule. However, the mechanism by which L-glutamate appears in the islets is unknown. In the present study, we investigated whether L-glutamate is secreted through exocytosis by alphaTC6 cells (clonal mouse pancreatic alpha-cells). An appreciable amount of L-glutamate was released from cultured cells after the addition of KCl or A23187 in the presence of Ca2+ and 10 mmol/l glucose in the medium. The KCl-induced glutamate release was significantly reduced when assayed in the absence of Ca2+ or when the cells were pretreated with EGTA-AM. The KCl-induced Ca2+-dependent glutamate release was inhibited approximately 40% by voltage-gated Ca2+ channel blockers, such as nifedipine at 20 micromol/l. The degree of KCl-induced Ca2+-dependent glutamate release was correlated with an increase in intracellular [Ca2+], as monitored by fura-2 fluorescence. Botulinum neurotoxin type E inhibited 55% of the KCl-induced Ca2+-dependent glutamate release, followed by specific cleavage of 25 kDa synaptosomal-associated protein. Furthermore, bafilomycin A1, a specific inhibitor of vacuolar H+-ATPase, inhibited 40% of the KCl-induced Ca2+-dependent glutamate release. Immunoelectronmicroscopy with antibodies against synaptophysin, a marker for neuronal synaptic vesicles and endocrine synaptic-like microvesicles, revealed a large number of synaptophysin-positive clear vesicles in cells. Digitonin-permeabilized cells took up L-glutamate only in the presence of MgATP, which is sensitive to bafilomycin A1 or 3,5-di-tert-butyl-4-hydroxybenzylidene-malononitrile (a proton conductor) but insensitive to either oligomycin or vanadate. From these results, it was concluded that alphaTC6 cells accumulate L-glutamate in the synaptophysin-containing vesicles in an ATP-dependent manner and secrete it through a Ca2+-dependent exocytic mechanism. The Ca2+-dependent glutamate release was also triggered when cells were transferred in the medium containing 1 mmol/l glucose, suggesting that low glucose treatment stimulates the release of glutamate. Our results are consistent with the idea that L-glutamate is secreted by alpha-cells through Ca2+-dependent regulated exocytosis.
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Affiliation(s)
- H Yamada
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Okayama University, Japan
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Tamura Y, Ozkan ED, Bole DG, Ueda T. IPF, a vesicular uptake inhibitory protein factor, can reduce the Ca(2+)-dependent, evoked release of glutamate, GABA and serotonin. J Neurochem 2001; 76:1153-64. [PMID: 11181835 DOI: 10.1046/j.1471-4159.2001.00120.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Synaptic vesicles in the nerve terminal play a pivotal role in neurotransmission. Neurotransmitter accumulation into synaptic vesicles is catalyzed by distinct vesicular transporters, harnessing an electrochemical proton gradient generated by V-type proton-pump ATPase. However, little is known about regulation of the transmitter pool size, particularly in regard to amino acid neurotransmitters. We previously provided evidence for the existence of a potent endogenous inhibitory protein factor (IPF), which causes reduction of glutamate and GABA accumulation into isolated, purified synaptic vesicles. In this study we demonstrate that IPF is concentrated most in the synaptosomal cytosol fraction and that, when introduced into the synaptosome, it leads to a decrease in calcium-dependent exocytotic (but not calcium-independent) release of glutamate in a concentration-dependent manner. In contrast, alpha-fodrin (non-erythroid spectrin), which is structurally related to IPF and thought to serve as the precursor for IPF, is devoid of such inhibitory activity. Intrasynaptosomal IPF also caused reduction in exocytotic release of GABA and the monoamine neurotransmitter serotonin. Whether IPF affects vesicular storage of multiple neurotransmitters in vivo would depend upon the localization of IPF. These results raise the possibility that IPF may modulate synaptic transmission by acting as a quantal size regulator of one or more neurotransmitters.
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Affiliation(s)
- Y Tamura
- Mental Health Research Institute, The University of Michigan, Ann Arbor, Michigan, USA
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