title: Vesicular glutamate transporter-dependent glutamate release from astrocytes.
abstract: Astrocytes exhibit excitability based on variations of their intracellular Ca2+ concentrations, which leads to glutamate release, that in turn can signal to adjacent neurons. This glutamate-mediated astrocyte-neuron signaling occurs at physiological intracellular Ca2+ levels in astrocytes and includes modulation of synaptic transmission. The mechanism underlying Ca2+-dependent glutamate release from astrocytes is most likely exocytosis, because astrocytes express the protein components of the soluble N-ethyl maleimide-sensitive fusion protein attachment protein receptors complex, including synaptobrevin 2, syntaxin, and synaptosome-associated protein of 23 kDa. Although these proteins mediate Ca2+-dependent glutamate release from astrocytes, it is not well understood whether astrocytes express functional vesicular glutamate transporters (VGLUTs) that are critical for vesicle refilling. Here, we find in cultured and freshly isolated astrocytes the presence of brain-specific Na+-dependent inorganic phosphate cotransporter and differentiation-associated Na+-dependent inorganic phosphate cotransporter that have recently been identified as VGLUTs 1 and 2. Indirect immunocytochemistry showed a punctate pattern of VGLUT immunoreactivity throughout the entire cell body and processes, whereas pharmacological inhibition of VGLUTs abolished mechanically and agonist-evoked Ca2+-dependent glutamate release from astrocytes. Taken together, these data indicate that VGLUTs play a functional role in exocytotic glutamate release from astrocytes.
authors.affiliation: Department of Cell Biology and Neuroscience and Center for Nanoscale Science and Engineering, University of California, Riverside, California 92521, USA.
authors.forename: Vedrana
authors.initials: V
authors.lastname: Montana
authors.forename: Yingchun
authors.initials: Y
authors.lastname: Ni
authors.forename: Vice
authors.initials: V
authors.lastname: Sunjara
authors.forename: Xue
authors.initials: X
authors.lastname: Hua
authors.forename: Vladimir
authors.initials: V
authors.lastname: Parpura
mesh_terms: D026922:Amino Acid Transport Systems, Acidic / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis / Q000187:drug effects / Q000378:metabolism*; D002469:Cell Separation; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes; D018698:Glutamic Acid / Q000378:metabolism*; D008565:Membrane Proteins / Q000096:biosynthesis; D026901:Membrane Transport Proteins; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D050683:R-SNARE Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D012395:Rose Bengal / Q000494:pharmacology; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D050496:Vesicular Glutamate Transport Proteins; D033921:Vesicular Transport Proteins; D014793:Visual Cortex / Q000166:cytology
chemical_list: D026922:Amino Acid Transport Systems, Acidic; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D050683:R-SNARE Proteins; D011993:Recombinant Fusion Proteins; C100493:SNAP23 protein, human; C493475:Slc17a6 protein, rat; C493466:Slc17a7 protein, rat; C482103:Slc17a8 protein, rat; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D050496:Vesicular Glutamate Transport Proteins; D033921:Vesicular Transport Proteins; D012395:Rose Bengal; D018698:Glutamic Acid; D025262:Vacuolar Proton-Translocating ATPases; D002118:Calcium