SNARE protein-dependent glutamate release from astrocytes

Alfonso Araque, Nianzhen Li, Robert T. Doyle, Philip G. Haydon

Research output: Contribution to journalArticle

339 Scopus citations

Abstract

We investigated the cellular mechanisms underlying the Ca2+-dependent release of glutamate from cultured astrocytes isolated from rat hippocampus. Using Ca2+ imaging and electrophysiological techniques, we analyzed the effects of disrupting astrocytic vesicle proteins on the ability of astrocytes to release glutamate and to cause neuronal electrophysiological responses, i.e., a slow inward current (SIC) and/or an increase in the frequency of miniature synaptic currents. We found that the Ca2+-dependent glutamate release from astrocytes is not caused by the reverse operation of glutamate transporters, because the astrocyte-induced glutamate-mediated responses in neurons were affected neither by inhibitors of glutamate transporters (β-threo-hydroxyaspartate, dihydrokainate, and L-trans- pyrrolidine-2,4-dicarboxylate) nor by replacement of extracellular sodium with lithium. We show that Ca2+-dependent glutamate release from astrocytes requires an electrochemical gradient necessary for glutamate uptake in vesicles, because bafilomycin A1, a vacuolar-type H+-ATPase inhibitor, reduced glutamate release from astrocytes. Injection of astrocytes with the light chain of the neurotoxin Botulinum B that selectively cleaves the vesicle-associated SNARE protein synaptobrevin inhibited the astrocyte- induced glutamate response in neurons. Therefore, the Ca2+-dependent glutamate release from astrocytes is a SNARE protein-dependent process that requires the presence of functional vesicle-associated proteins, suggesting that astrocytes store glutamate in vesicles and that it is released through an exocytotic pathway.

Original languageEnglish (US)
Pages (from-to)666-673
Number of pages8
JournalJournal of Neuroscience
Volume20
Issue number2
DOIs
StatePublished - Jan 15 2000

Keywords

  • Astrocyte calcium waves
  • Astrocyte-neuron signaling
  • Bafilomycin
  • Botulinum neurotoxin
  • Exocytosis
  • SNARE protein
  • Transmitter release
  • V-ATPase

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