Jon Storm-Mathisen

Publications of Jon Storm-Mathisen

• A role for glutamate transporters in the regulation of insulin secretion.

  Authors: Runhild Gammelsaeter, Thierry Coppola, Païkan Marcaggi, Jon Storm-Mathisen, Farrukh A Chaudhry, David Attwell, Romano Regazzi, Vidar Gundersen

  PloS one. 01/2011; 6(8):e22960.

  In the brain, glutamate is an extracellular transmitter that mediates cell-to-cell communication. Prior to synaptic release it is pumped into vesicles by vesicular glutamate transporters (VGLUTs). ToIn the brain, glutamate is an extracellular transmitter that mediates cell-to-cell communication. Prior to synaptic release it is pumped into vesicles by vesicular glutamate transporters (VGLUTs). To inactivate glutamate receptor responses after release, glutamate is taken up into glial cells or neurons by excitatory amino acid transporters (EAATs). In the pancreatic islets of Langerhans, glutamate is proposed to act as an intracellular messenger, regulating insulin secretion from β-cells, but the mechanisms involved are unknown. By immunogold cytochemistry we show that insulin containing secretory granules express VGLUT3. Despite the fact that they have a VGLUT, the levels of glutamate in these granules are low, indicating the presence of a protein that can transport glutamate out of the granules. Surprisingly, in β-cells the glutamate transporter EAAT2 is located, not in the plasma membrane as it is in brain cells, but exclusively in insulin-containing secretory granules, together with VGLUT3. In EAAT2 knock out mice, the content of glutamate in secretory granules is higher than in wild type mice. These data imply a glutamate cycle in which glutamate is carried into the granules by VGLUT3 and carried out by EAAT2. Perturbing this cycle by knocking down EAAT2 expression with a small interfering RNA, or by over-expressing EAAT2 or a VGLUT in insulin granules, significantly reduced the rate of granule exocytosis. Simulations of granule energetics suggest that VGLUT3 and EAAT2 may regulate the pH and membrane potential of the granules and thereby regulate insulin secretion. These data suggest that insulin secretion from β-cells is modulated by the flux of glutamate through the secretory granules.

• The spontaneously hypertensive rat model of ADHD - The importance of selecting the appropriate reference strain.

  Authors: Terje Sagvolden, Espen Borgå Johansen, Grete Wøien, S Ivar Walaas, Jon Storm-Mathisen, Linda Hildegard Bergersen, Oivind Hvalby, Vidar Jensen, Heidi Aase, Vivienne A Russell, Peter R Killeen, Tania Dasbanerjee, Frank A Middleton, Stephen V Faraone

  Neuropharmacology. 09/2009;

  Although several molecular and genetic manipulations may produce hyperactive animals, hyperactivity alone is insufficient for the animal to qualify as a model of ADHD. Based on a wider range ofAlthough several molecular and genetic manipulations may produce hyperactive animals, hyperactivity alone is insufficient for the animal to qualify as a model of ADHD. Based on a wider range of criteria - behavioral, genetic and neurobiological - the spontaneously hypertensive rat (SHR) obtained from Charles River, Germany (SHR/NCrl) at present constitutes the best validated animal model of ADHD combined subtype (ADHD-C), and the Wistar Kyoto substrain obtained from Harlan, UK (WKY/NHsd) is its most appropriate control. Although other rat strains may behave like WKY/NHsd rats, genetic results indicate significant differences when compared to the WKY/NHsd substrain, making them less suitable controls for the SHR/NCrl. The use of WKY/NCrl, outbred Wistar, Sprague Dawley or other rat strains as controls for SHRs may produce spurious neurobiological differences. Consequently, data may be misinterpreted if insufficient care is taken in the selection of the control group. It appears likely that the use of different control strains may underlie some of the discrepancies in results and interpretations in studies involving the SHR and WKY. Finally, we argue that WKY rats obtained from Charles River, Germany (WKY/NCrl) provide a promising model for the predominantly inattentive subtype of ADHD (ADHD-PI); in this case also the WKY/NHsd substrain should be used as control.

• System A Transporter SAT2 Mediates Replenishment of Dendritic Glutamate Pools Controlling Retrograde Signaling by Glutamate.

  Authors: Monica Jenstad, Abrar Z Quazi, Misha Zilberter, Camilla Haglerød, Paul Berghuis, Navida Saddique, Michel Goiny, Doungjai Buntup, Svend Davanger, Finn-Mogens S Haug, Carol A Barnes, Bruce L McNaughton, Ole Petter Ottersen, Jon Storm-Mathisen, Tibor Harkany, Farrukh A Chaudhry

  Cerebral cortex (New York, N.Y. : 1991). 11/2008;

  Glutamate mediates several modes of neurotransmission in the central nervous system including recently discovered retrograde signaling from neuronal dendrites. We have previously identified theGlutamate mediates several modes of neurotransmission in the central nervous system including recently discovered retrograde signaling from neuronal dendrites. We have previously identified the system N transporter SN1 as being responsible for glutamine efflux from astroglia and proposed a system A transporter (SAT) in subsequent transport of glutamine into neurons for neurotransmitter regeneration. Here, we demonstrate that SAT2 expression is primarily confined to glutamatergic neurons in many brain regions with SAT2 being predominantly targeted to the somatodendritic compartments in these neurons. SAT2 containing dendrites accumulate high levels of glutamine. Upon electrical stimulation in vivo and depolarization in vitro, glutamine is readily converted to glutamate in activated dendritic subsegments, suggesting that glutamine sustains release of the excitatory neurotransmitter via exocytosis from dendrites. The system A inhibitor MeAIB (alpha-methylamino-iso-butyric acid) reduces neuronal uptake of glutamine with concomitant reduction in intracellular glutamate concentrations, indicating that SAT2-mediated glutamine uptake can be a prerequisite for the formation of glutamate. Furthermore, MeAIB inhibited retrograde signaling from pyramidal cells in layer 2/3 of the neocortex by suppressing inhibitory inputs from fast-spiking interneurons. In summary, we demonstrate that SAT2 maintains a key metabolic glutamine/glutamate balance underpinning retrograde signaling by dendritic release of the neurotransmitter glutamate.

• Synapsin- and Actin-Dependent Frequency Enhancement in Mouse Hippocampal Mossy Fiber Synapses.

  Authors: Simen G Owe, Vidar Jensen, Emma Evergren, Arnaud Ruiz, Oleg Shupliakov, Dimitri M Kullmann, Jon Storm-Mathisen, S Ivar Walaas, Oivind Hvalby, Linda H Bergersen

  Cerebral cortex (New York, N.Y. : 1991). 07/2008;

  The synapsin proteins have different roles in excitatory and inhibitory synaptic terminals. We demonstrate a differential role between types of excitatory terminals. Structural and functional aspectsThe synapsin proteins have different roles in excitatory and inhibitory synaptic terminals. We demonstrate a differential role between types of excitatory terminals. Structural and functional aspects of the hippocampal mossy fiber (MF) synapses were studied in wild-type (WT) mice and in synapsin double-knockout mice (DKO). A severe reduction in the number of synaptic vesicles situated more than 100 nm away from the presynaptic membrane active zone was found in the synapsin DKO animals. The ultrastructural level gave concomitant reduction in F-actin immunoreactivity observed at the periactive endocytic zone of the MF terminals. Frequency facilitation was normal in synapsin DKO mice at low firing rates ( approximately 0.1 Hz) but was impaired at firing rates within the physiological range ( approximately 2 Hz). Synapses made by associational/commissural fibers showed comparatively small frequency facilitation at the same frequencies. Synapsin-dependent facilitation in MF synapses of WT mice was attenuated by blocking F-actin polymerization with cytochalasin B in hippocampal slices. Synapsin III, selectively seen in MF synapses, is enriched specifically in the area adjacent to the synaptic cleft. This may underlie the ability of synapsin III to promote synaptic depression, contributing to the reduced frequency facilitation observed in the absence of synapsins I and II.

• Vesicular Glutamate and GABA Transporters Sort to Distinct Sets of Vesicles in a Population of Presynaptic Terminals.

  Authors: Jean-Luc Boulland, Monica Jenstad, Amber J Boekel, Floris G Wouterlood, Robert H Edwards, Jon Storm-Mathisen, Farrukh A Chaudhry

  Cerebral cortex (New York, N.Y. : 1991). 06/2008;

  Vesicular glutamate transporters (VGLUTs) 1 and 2 are expressed by neurons generally accepted to release glutamate as a neurotransmitter, whereas VGLUT3 appears in populations usually associated withVesicular glutamate transporters (VGLUTs) 1 and 2 are expressed by neurons generally accepted to release glutamate as a neurotransmitter, whereas VGLUT3 appears in populations usually associated with a different classical transmitter. We now demonstrate VGLUT2 as well as the vesicular GABA transporter (VGAT) in a subset of presynaptic terminals in the dentate gyrus of the rat hippocampal formation. The terminals are distributed in a characteristic band overlapping with the outer part of the granule cell layer and the inner zone of the molecular layer. Within the terminals, which make asymmetric as well as symmetric synapses onto the somatodendritic compartment of the dentate granule cells, the 2 transporters localize to distinct populations of synaptic vesicles. Moreover, the axons forming these terminals originate in the supramammillary nucleus (SuM). Our data reconcile previous apparently conflicting reports on the physiology of the dentate afferents from SuM and demonstrate that both glutamate and GABA may be released from a single nerve terminal.

• Beta-amyloid 25-35 peptide reduces the expression of glutamine transporter SAT1 in cultured cortical neurons.

  Authors: Doungjai Buntup, Oivind Skare, Tom Tallak Solbu, Farrukh A Chaudhry, Jon Storm-Mathisen, Wipawan Thangnipon

  Neurochemical research. 03/2008; 33(2):248-56.

  Beta-amyloid (Abeta) peptides may cause malfunction and death of neurons in Alzheimer's disease. We investigated the effect of Abeta on key transporters of amino acid neurotransmission in cellsBeta-amyloid (Abeta) peptides may cause malfunction and death of neurons in Alzheimer's disease. We investigated the effect of Abeta on key transporters of amino acid neurotransmission in cells cultured from rat cerebral cortex. The cultures were treated with Abeta(25-35) at 3 and 10 microM for 12 and 24 h followed by quantitative analysis of immunofluorescence intensity. In mixed neuronal-glial cell cultures (from P1 rats), Abeta reduced the concentration of system A glutamine transporter 1 (SAT1), by up to 50% expressed relative to the neuronal marker microtubule-associated protein 2 (MAP2) in the same cell. No significant effects were detected on vesicular glutamate transporters VGLUT1 or VGLUT2 in neurons, or on glial system N glutamine transporter 1 (SN1). In neuronal cell cultures (from E18 rats), Abeta(25-35) did not reduce SAT1 immunoreactivity, suggesting that the observed effect depends on the presence of astroglia. The results indicate that Abeta may impair neuronal function and transmitter synthesis, and perhaps reduce excitotoxicity, through a reduction in neuronal glutamine uptake.

• Immunogold quantification of amino acids and proteins in complex subcellular compartments.

  Authors: Linda H Bergersen, Jon Storm-Mathisen, Vidar Gundersen

  Nature protocols. 02/2008; 3(1):144-52.

  An increasing number of imaging techniques are in use to study the localization of molecules involved in cell-to-cell signaling. Here we describe the use of immunogold procedures to detect andAn increasing number of imaging techniques are in use to study the localization of molecules involved in cell-to-cell signaling. Here we describe the use of immunogold procedures to detect and quantify molecules on electron micrographs. To measure the areas of the subcellular compartments under investigation, the protocol uses an overlay screen with an array of regularly spaced points. On the basis of this, the densities of the gold-labeled molecules can be calculated. Despite the limited lateral resolution of the immunogold method as used by many investigators ( approximately 30 nm), it is possible to measure the content of molecules associated with tiny tissue compartments, e.g., synaptic vesicles and different types of membrane, such as plasma membranes and vesicle membranes. The quantification protocol can be carried out without using computer programs. The entire protocol can be completed in approximately 15 d.

• The components required for amino acid neurotransmitter signaling are present in adipose tissues.

  Authors: Anne Nicolaysen, Runhild Gammelsaeter, Jon Storm-Mathisen, Vidar Gundersen, Per Ole Iversen

  Journal of lipid research. 11/2007; 48(10):2123-32.

  The adipocyte does not only serve as fuel storage but produces and secretes compounds with modulating effects on food intake and energy homeostasis. Although there is firm evidence for a centrallyThe adipocyte does not only serve as fuel storage but produces and secretes compounds with modulating effects on food intake and energy homeostasis. Although there is firm evidence for a centrally mediated regulation of adipocyte function via the autonomous nervous system, little is known about signaling between adipocytes. Amino acid neurotransmitters are candidates for such paracrine signaling. Here, we applied immunohistochemistry to detect components required for amino acid transmitter signaling in rat fat depots. In interscapular brown adipose tissue as well as in interscapular, mesenteric, perirenal, and epididymal white adipose tissues, we demonstrate robust immunosignals for the excitatory neurotransmitter glutamate, the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), and the GABA-synthesizing enzyme glutamate decarboxylase (GAD) isoforms GAD65 and GAD67. Moreover, all adipose tissues stained for the vesicular glutamate transporter VGLUT1 and the vesicular GABA transporter VGAT in addition to the vesicle marker synaptophysin. Electron microscopic immunocytochemistry showed that VGLUT1 and VGAT, but not VGLUT2 or VGLUT3, are localized in vesicular organelles in adipocytes. The receptors for glutamate (subunits GluR2/3 and NR1 but not mGluR2) and for GABA (GABA(A)Ralpha2) were present in the adipocytes. The presence of glutamate, GABA, their vesicular transporters, and their receptors indicates a paracrine signaling role for amino acids in adipose tissues.

• Changes in vesicular transporters for gamma-aminobutyric acid and glutamate reveal vulnerability and reorganization of hippocampal neurons following pilocarpine-induced seizures.

  Authors: Jean-Luc Boulland, Lotfi Ferhat, Tom Tallak Solbu, Nadine Ferrand, Farrukh Abbas Chaudhry, Jon Storm-Mathisen, Monique Esclapez

  The Journal of comparative neurology. 08/2007; 503(3):466-85.

  The reorganizations of the overall intrinsic glutamatergic and gamma-aminobutyric acid (GABA)-ergic hippocampal networks as well as the time course of these reorganizations during development ofThe reorganizations of the overall intrinsic glutamatergic and gamma-aminobutyric acid (GABA)-ergic hippocampal networks as well as the time course of these reorganizations during development of pilocarpine-induced temporal lobe epilepsy were studied with in situ hybridization and immunohistochemistry experiments for the vesicular glutamate transporter 1 (VGLUT1) and the vesicular GABA transporter (VGAT). These transporters are particularly interesting as specific markers for glutamatergic and GABAergic neurons, respectively, whose expression levels could reflect the demand for synaptic transmission and their average activity. We report that 1) concomitantly with the loss of some subpopulations of VGAT-containing neurons, there was an up-regulation of VGAT synthesis in all remaining GABA neurons as early as 1 week after pilocarpine injection. This enhanced synthesis is characterized by marked increases in the relative amount of VGAT mRNAs in interneurons associated with increased intensity of axon terminal labeling for VGAT in all hippocampal layers. 2) There was a striking loss of mossy cells during the latent period, demonstrated by a long-term decrease of VGLUT1 mRNA-containing hilar neurons and associated loss of VGLUT1-containing terminals in the dentate gyrus inner molecular layer. 3) There were aberrant VGLUT1-containing terminals at the chronic stage resulting from axonal sprouting of granule and pyramidal cells. This is illustrated by a recovery of VGLUT1 immunoreactivity in the inner molecular layer and an increased VGLUT1 immunolabeling in the CA1-CA3 dendritic layers. These data indicate that an increased activity of remaining GABAergic interneurons occurs during the latent period, in parallel with the loss of vulnerable glutamatergic and GABAergic neurons preceding the reorganization of glutamatergic networks.

• Propionate increases neuronal histone acetylation, but is metabolized oxidatively by glia. Relevance for propionic acidemia.

  Authors: Nga H T Nguyen, Cecilie Morland, Susana Villa Gonzalez, Frode Rise, Jon Storm-Mathisen, Vidar Gundersen, Bjørnar Hassel

  Journal of neurochemistry. 06/2007; 101(3):806-14.

  In propionic acidemia, propionate acts as a metabolic toxin in liver cells by accumulating in mitochondria as propionyl-CoA and its derivative, methylcitrate, two tricarboxylic acid cycle inhibitors.In propionic acidemia, propionate acts as a metabolic toxin in liver cells by accumulating in mitochondria as propionyl-CoA and its derivative, methylcitrate, two tricarboxylic acid cycle inhibitors. Little is known about the cerebral metabolism of propionate, although clinical effects of propionic acidemia are largely neurological. We found that propionate was metabolized oxidatively by glia: [3-(14)C]propionate injected into mouse striatum or cortex, gave a specific activity of glutamine that was 5-6 times that of glutamate, indicating metabolism in cells that express glutamine synthetase, i.e., glia. Further, cultured cerebellar astrocytes metabolized [3-(14)C]propionate; cultured neurons did not. However, both cultured cerebellar neurons and astrocytes took up [3H]propionate, and propionate exposure increased histone acetylation in cultured neurons and astrocytes as well as in hippocampal CA3 pyramidal neurons of wake mice. The inability of neurons to metabolize propionate may be due to lack of mitochondrial propionyl-CoA synthetase activity or transport of propionyl residues into mitochondria, as cultured neurons expressed propionyl-CoA carboxylase, a mitochondrial matrix enzyme, and oxidized isoleucine, which becomes converted into propionyl-CoA intramitochondrially. The glial metabolism of propionate suggests astrocytic vulnerability in propionic acidemia when intramitochondrial propionyl-CoA may accumulate. Propionic acidemia may alter both neuronal and glial gene expression by affecting histone acetylation.

• [Training and brain health]

  Authors: Linda Hildegard Bergersen, Jon Storm-Mathisen

  Tidsskrift for den Norske lægeforening : tidsskrift for praktisk medicin, ny række. 01/2007; 126(24):3253.

• Distribution of vesicular glutamate transporters 1 and 2 in the rat spinal cord, with a note on the spinocervical tract.

  Authors: Stefan Persson, Jean-Luc Boulland, Marie Aspling, Max Larsson, Robert T Fremeau, Robert H Edwards, Jon Storm-Mathisen, Farrukh A Chaudhry, Jonas Broman

  The Journal of comparative neurology. 09/2006; 497(5):683-701.

  To evaluate whether the organization of glutamatergic fibers systems in the lumbar cord is also evident at other spinal levels, we examined the immunocytochemical distribution of vesicle glutamateTo evaluate whether the organization of glutamatergic fibers systems in the lumbar cord is also evident at other spinal levels, we examined the immunocytochemical distribution of vesicle glutamate transporters 1 and 2 (VGLUT1, VGLUT2) at several different levels of the rat spinal cord. We also examined the expression of VGLUTs in an ascending sensory pathway, the spinocervical tract, and colocalization of VGLUT1 and VGLUT2. Mainly small VGLUT2-immunoreactive varicosities occurred at relatively high densities in most areas, with the highest density in laminae I-II. VGLUT1 immunolabeling, including small and medium-sized to large varicosities, was more differentiated, with the highest density in the deep dorsal horn and in certain nuclei such as the internal basilar nucleus, the central cervical nucleus, and the column of Clarke. Lamina I and IIo displayed a moderate density of small VGLUT1 varicosities at all spinal levels, although in the spinal enlargements a uniform density of such varicosities was evident throughout laminae I-II in the medial half of the dorsal horn. Corticospinal tract axons displayed VGLUT1, indicating that the corticospinal tract is an important source of small VGLUT1 varicosities. VGLUT1 and VGLUT2 were cocontained in small numbers of varicosities in laminae III-IV and IX. Anterogradely labeled spinocervical tract terminals in the lateral cervical nucleus were VGLUT2 immunoreactive. In conclusion, the principal distribution patterns of VGLUT1 and VGLUT2 are essentially similar throughout the rostrocaudal extension of the spinal cord. The mediolateral differences in VGLUT1 distribution in laminae I-II suggest dual origins of VGLUT1-immunoreactive varicosities in this region.

• Induction and targeting of the glutamine transporter SN1 to the basolateral membranes of cortical kidney tubule cells during chronic metabolic acidosis suggest a role in pH regulation.

  Authors: Tom Tallak Solbu, Jean-Luc Boulland, Wasim Zahid, May Kristin Lyamouri Bredahl, Mahmood Amiry-Moghaddam, Jon Storm-Mathisen, Bjørg Ase Roberg, Farrukh A Chaudhry

  Journal of the American Society of Nephrology : JASN. 05/2005; 16(4):869-77.

  During chronic metabolic acidosis (CMA), the plasma levels of glutamine are increased and so is glutamine metabolism in the kidney tubule cells. Degradation of glutamine results in the formation ofDuring chronic metabolic acidosis (CMA), the plasma levels of glutamine are increased and so is glutamine metabolism in the kidney tubule cells. Degradation of glutamine results in the formation of ammonium (NH(4)(+)) and bicarbonate (HCO(3)(-)) ions, which are excreted in the pre-urine and transported to the peritubular blood, respectively. This process contributes to counteract acidosis and to restore normal pH, but the molecular mechanism, the localization of the proteins involved and the regulation of glutamine transport into the renal tubular cells, remains unknown. SN1, a Na(+)- and H(+)-dependent glutamine transporter has previously been identified molecularly, and its mRNA has been detected in tubule cells in the medulla of the kidney. Now shown is the selective targeting of the protein to the basolateral membranes of the renal tubule cells of the S3 segment throughout development of the normal rat kidney. During CMA, SN1 expression increases five- to six-fold and appears also in cortical tubule cells in parallel with the increased expression and activity of phosphate-activated glutaminase, a mitochondrial enzyme involved in ammoniagenesis. However, SN1 remains sorted to the basolateral membranes. The unique ability of SN1 to change transport direction according to physiologic changes in transmembrane gradients of [glutamine] and pH and its sorting to the basolateral membranes and the presence of a putative pH responsive element in the 3' untranslated region (UTR) of the gene (supported here by the demonstration in CMA kidney of a protein that binds SN1 mRNA) are conducive to the function of this transporter in pH regulation.

• Commissural propriospinal connections between the lateral aspects of laminae III-IV in the lumbar spinal cord of rats.

  Authors: Mihály Petkó, Gábor Veress, György Vereb, Jon Storm-Mathisen, Miklós Antal

  The Journal of comparative neurology. 01/2005; 480(4):364-77.

  It has been established that there is a strong functional link between sensory neural circuits on the two sides of the spinal cord. In one of our recent studies we provided a morphologicalIt has been established that there is a strong functional link between sensory neural circuits on the two sides of the spinal cord. In one of our recent studies we provided a morphological confirmation of this functional phenomenon, presenting evidence for the presence of a direct commissural connection between the lateral aspects of the dorsal horn on the two sides of the lumbar spinal cord. By using a combination of neural tracing and immunocytochemical detection of neural markers like vesicular glutamate transporters, glutamic acid decarboxylase, glycine transporter, and met-enkephalin (which are characteristic of various subsets of excitatory and inhibitory neurons), we investigated here the distribution, synaptic relations, and neurochemical characteristics of the commissural axon terminals. We found that the cells of origin of commissural fibers in the lateral aspect of the dorsal horn were confined to laminae III-IV and projected to the corresponding area of the contralateral gray matter. Most of the commissural axon terminals established synaptic contacts with dendrites. Axospinous or axosomatic synaptic contacts were found in limited numbers. We demonstrated that interactions among commissural neurons also exist. More than three-fourths of the labeled axon terminals were immunostained for glutamic acid decarboxylase and/or glycine transporter, but none of them showed positive immunoreaction for met-enkephalin and vesicular glutamate transporters. The results indicate that there is a substantial reciprocal commissural synaptic interaction between the lateral aspects of laminae III-IV on the two sides of the lumbar spinal cord and that this pathway may transmit both inhibitory and excitatory signals to their postsynaptic targets.

• Expression of the vesicular glutamate transporters during development indicates the widespread corelease of multiple neurotransmitters.

  Authors: Jean-Luc Boulland, Tayyaba Qureshi, Rebecca P Seal, Amina Rafiki, Vidar Gundersen, Linda H Bergersen, Robert T Fremeau, Robert H Edwards, Jon Storm-Mathisen, Farrukh A Chaudhry

  The Journal of comparative neurology. 01/2005; 480(3):264-80.

  Three closely related proteins transport glutamate into synaptic vesicles for release by exocytosis. Complementary patterns of expression in glutamatergic terminals have been reported for VGLUT1 andThree closely related proteins transport glutamate into synaptic vesicles for release by exocytosis. Complementary patterns of expression in glutamatergic terminals have been reported for VGLUT1 and VGLUT2. VGLUT3 shows expression by many cells not considered to be glutamatergic. Here we describe the changes in VGLUT expression that occur during development. VGLUT1 expression increases gradually after birth and eventually predominates over the other isoforms in telencephalic regions. Expressed at high levels shortly after birth, VGLUT2 declines with age in multiple regions, in the cerebellum by 14-fold. In contrast, Coexpression of the two isoforms occurs transiently during development as well as permanently in a restricted subset of glutamatergic terminals in the adult. VGLUT3 is transiently expressed at high levels by select neuronal populations, including terminals in the cerebellar nuclei, scattered neurons in the cortex, and progenitor-like cells, implicating exocytotic glutamate release in morphogenesis and development. VGLUT3 also colocalizes extensively during development with the neuronal vesicular monoamine transporter VMAT2, with the vesicular acetylcholine transporter VAChT, and with the vesicular gamma-aminobutyric acid transporter VGAT. Such coexpression occurs particularly at some specific developmental stages and is restricted to certain sets of cells. In skeletal muscle, VGLUT3 localizes to granular organelles in the axon terminal as well as in the muscle sarcoplasm. The results suggest novel mechanisms and roles for regulated transmitter release.

• Glycine, GABA and their transporters in pancreatic islets of Langerhans: evidence for a paracrine transmitter interplay.

  Authors: Runhild Gammelsaeter, Marianne Frøyland, Carmen Aragón, Niels Christian Danbolt, Doris Fortin, Jon Storm-Mathisen, Svend Davanger, Vidar Gundersen

  Journal of cell science. 09/2004; 117(Pt 17):3749-58.

  To elucidate the possible roles of the CNS neurotransmitters glycine and GABA in neuroendocrine paracrine signalling, we investigated their localizations, and those of their transport proteins, byTo elucidate the possible roles of the CNS neurotransmitters glycine and GABA in neuroendocrine paracrine signalling, we investigated their localizations, and those of their transport proteins, by confocal immunofluorescence and quantitative post-embedding immuno-electron microscopy in the pancreatic islets of Langerhans. We show that A-cells contain glycine in synaptic-like microvesicles as well as in secretory granules. A-cells express the macromolecules necessary to: (1) concentrate glycine within both organelle types before release (the vesicular GABA/glycine transporter VGAT=VIAAT); and to (2) take up the transmitter from the extracellular space (the plasma membrane glycine transporter GLYT2). Also B-cells have glycine in their microvesicles and granules, but the microvesicle/cytosol ratio is lower than in A-cells, consistent with the presence of GABA (which competes with glycine for vesicular uptake) in the cytosol at a much higher concentration in B-cells than in A-cells. Both A- and B-cells contain GABA in their microvesicles and secretory granules, and the membranes of the two organelle types contain VGAT in both cell types. A-cells as well as B-cells express a plasma membrane transporter GAT3 that mediates uptake of GABA. The localization of VGAT in the cores of A-cell secretory granules, and in the secretory granule membranes in both cell types, indicates novel aspects of the mechanisms for release of glycine and GABA. The discovery that both A- and B-cells possess the molecular machinery for the evoked release of both glycine and GABA from synaptic-like microvesicles suggests that both of the principal inhibitory transmitters in the brain participate in paracrine signalling in the pancreas.

• Vesicular glutamate transporters 1 and 2 target to functionally distinct synaptic release sites.

  Authors: Robert T Fremeau, Kaiwen Kam, Tayyaba Qureshi, Juliette Johnson, David R Copenhagen, Jon Storm-Mathisen, Farrukh A Chaudhry, Roger A Nicoll, Robert H Edwards

  Science (New York, N.Y.). 07/2004; 304(5678):1815-9.

  Vesicular glutamate transporters (VGLUTs) 1 and 2 show a mutually exclusive distribution in the adult brain that suggests specialization for synapses with different properties of release. ConsistentVesicular glutamate transporters (VGLUTs) 1 and 2 show a mutually exclusive distribution in the adult brain that suggests specialization for synapses with different properties of release. Consistent with this distribution, inactivation of the VGLUT1 gene silenced a subset of excitatory neurons in the adult. However, the same cell populations exhibited VGLUT1-independent transmission early in life. Developing hippocampal neurons transiently coexpressed VGLUT2 and VGLUT1 at distinct synaptic sites with different short-term plasticity. The loss of VGLUT1 also reduced the reserve pool of synaptic vesicles. Thus, VGLUT1 plays an unanticipated role in membrane trafficking at the nerve terminal.

• Endocannabinoid-independent retrograde signaling at inhibitory synapses in layer 2/3 of neocortex: involvement of vesicular glutamate transporter 3.

  Authors: Tibor Harkany, Carl Holmgren, Wolfgang Härtig, Tayyaba Qureshi, Farrukh A Chaudhry, Jon Storm-Mathisen, Marton B Dobszay, Paul Berghuis, Gunnar Schulte, Kyle M Sousa, Robert T Fremeau, Robert H Edwards, Ken Mackie, Patrik Ernfors, Yuri Zilberter

  The Journal of neuroscience : the official journal of the Society for Neuroscience. 06/2004; 24(21):4978-88.

  Recent studies implicate dendritic endocannabinoid release from subsynaptic dendrites and subsequent inhibition of neurotransmitter release from nerve terminals as a means of retrograde signaling inRecent studies implicate dendritic endocannabinoid release from subsynaptic dendrites and subsequent inhibition of neurotransmitter release from nerve terminals as a means of retrograde signaling in multiple brain regions. Here we show that type 1 cannabinoid receptor-mediated endocannabinoid signaling is not involved in the retrograde control of synaptic efficacy at inhibitory synapses between fast-spiking interneurons and pyramidal cells in layer 2/3 of the neocortex. Vesicular neurotransmitter transporters, such as vesicular glutamate transporters (VGLUTs) 1 and 2, are localized to presynaptic terminals and accumulate neurotransmitters into synaptic vesicles. A third subtype of VGLUTs (VGLUT3) was recently identified and found localized to dendrites of various cell types. We demonstrate, using multiple immunofluorescence labeling and confocal laser-scanning microscopy, that VGLUT3-like immunoreactivity is present in dendrites of layer 2/3 pyramidal neurons in the rat neocortex. Electron microscopy analysis confirmed that VGLUT3-like labeling is localized to vesicular structures, which show a tendency to accumulate in close proximity to postsynaptic specializations in dendritic shafts of pyramidal cells. Dual whole-cell recordings revealed that retrograde signaling between fast-spiking interneurons and pyramidal cells was enhanced under conditions of maximal efficacy of VGLUT3-mediated glutamate uptake, whereas it was reduced when glutamate uptake was inhibited by incrementing concentrations of the nonselective VGLUT inhibitor Evans blue (0.5-5.0 microm) or intracellular Cl- concentrations (4-145 mm). Our results present further evidence that dendritic vesicular glutamate release, controlled by novel VGLUT isoforms, provides fast negative feedback at inhibitory neocortical synapses, and demonstrate that glutamate can act as a retrograde messenger in the CNS.

• GABAergic synapses in hippocampus exocytose aspartate on to NMDA receptors: quantitative immunogold evidence for co-transmission.

  Authors: Vidar Gundersen, Alexander Talgøy Holten, Jon Storm-Mathisen

  Molecular and cellular neurosciences. 06/2004; 26(1):156-65.

  We previously found evidence for the exocytosis of aspartate from excitatory nerve terminals in hippocampus [J. Neurosci. 18, (1998) 6059]. Here we show, by immunogold electron microscopy inWe previously found evidence for the exocytosis of aspartate from excitatory nerve terminals in hippocampus [J. Neurosci. 18, (1998) 6059]. Here we show, by immunogold electron microscopy in hippocampal slices that aspartate is co-localized and co-exocytosed with GABA from synaptic vesicles in nerve endings assumed to be inhibitory on dentate granule cells and CA1 pyramidal cells. By immunogold double labeling cytochemistry in perfusion fixed hippocampus, we further find that GABA-positive terminals forming symmetric synaptic specializations on perikarya of granule and pyramidal cells express NMDA receptors. In addition, NMDA receptors are present at synapses on granule cell bodies that have asymmetric synaptic specializations and contain high levels of GABA. Glutamate levels are low in the described types of GABA-positive nerve terminals, but high in terminals making asymmetric synapses on dendritic spines, whereas aspartate is localized with high levels in all of these types of terminal. We propose that aspartate is exocytotically released not only from glutamatergic terminals, but also from GABAergic terminals to act on NMDA receptors and may have a role in the regulation of synaptic transmission. Under pathological conditions, release of an excitatory transmitter at an inhibitory synapse could contribute to the development of, for example, epilepsy.

• Highly differential expression of SN1, a bidirectional glutamine transporter, in astroglia and endothelium in the developing rat brain.

  Authors: Jean-Luc Boulland, Amina Rafiki, Line M Levy, Jon Storm-Mathisen, Farrukh A Chaudhry

  Glia. 03/2003; 41(3):260-75.

  The transmitters glutamate and GABA also subserve trophic action and are required for normal development of the brain. They are formed from glutamine, which may be synthesized in glia or extractedThe transmitters glutamate and GABA also subserve trophic action and are required for normal development of the brain. They are formed from glutamine, which may be synthesized in glia or extracted from the blood. In the adult, the glutamine transporter SN1 is expressed in the astroglia. SN1 works in both directions, depending on the concentration gradients of its substrates and cotransported ions, and is thought to regulate extracellular glutamine and to supply the neurons with the transmitter precursor. In this article, we have quantified the expression and studied the localization of SN1 at different developmental stages. SN1 is expressed in astroglia throughout the CNS from embryonic stages through adulthood. No indication of SN1 staining in neuronal elements has been obtained at any stage. Quantitative immunoblotting of whole brain extracts demonstrates increasing expression of SN1 from P0, reaching a peak at P14, twice the adult level. A moderate and slower rise and fall of the expression levels of SN1 occurs in the cerebellum. Strong transient SN1-like staining is also found in Bergmann glia and vascular endothelium in the first postnatal weeks. Strong intracellular staining in the same time period suggests a high rate of SN1 synthesis in the early postnatal period. This coincides with the increasing levels of glutamate and GABA in the CNS and with the time course of synaptogenesis. This study suggests that the expression of SN1 is highly regulated, correlating with the demand for glutamine during the critical period of development.