Glutamate receptor activation triggers a calcium-dependent and SNARE protein-dependent release of the gliotransmitter D-serine.
The gliotransmitter D-serine is released upon (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate and metabotropic glutamate receptor stimulation, but the mechanisms involved are unknown. Here, by using a highly sensitive bioassay to continuously monitor extracellular D-serine levels, we have investigated the pathways used in its release. We reveal that D-serine release is inhibited by removal of extracellular calcium and augmented by increasing extracellular calcium or after treatment with the Ca(2+) ionophore A23187. Furthermore, release of the amino acid is considerably reduced after depletion of thapsigargin-sensitive intracellular Ca(2+) stores or chelation of intracellular Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetate-acetoxymethyl ester. Interestingly, D-serine release also was markedly reduced by concanamycin A, a vacuolar-type H(+)-ATPase inhibitor, indicating a role for the vesicular proton gradient in the transmitter storage/release. In addition, agonist-evoked D-serine release was sensitive to tetanus neurotoxin. Finally, immunocytochemical and sucrose density gradient analysis revealed that a large fraction of D-serine colocalized with synaptobrevin/VAMP2, suggesting that it is stored in VAMP2-bearing vesicles. In summary, our study reveals the cellular mechanisms subserving D-serine release and highlights the importance of the glial cell exocytotic pathway in influencing CNS levels of extracellular D-serine.
Mothet
Jean-Pierre
JP
Laboratoire de Neurobiologie Cellulaire et Moléculaire, Centre National de la Recherche Scientifique Unité Propre de Recherche 9040, Institut Fédératif de Neurobiologie Alfred Fessard, F-91198 Gif-sur-Yvette, France. mothet@nbcm.cnrs-gif.fr
Pollegioni
Loredano
L
Ouanounou
Gilles
G
Martineau
Magalie
M
Fossier
Philippe
P
Baux
Gérard
G
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002478:Cells, Cultured; D018942:Macrolides / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism; D050683:R-SNARE Proteins; D051381:Rats; D017470:Receptors, Glutamate / Q000378:metabolism*; D018092:Kainic Acid Receptors / Q000378:metabolism; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism; D050600:SNARE Proteins; D012694:Serine / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism*
D002118:Calcium; D018942:Macrolides; D008565:Membrane Proteins; D050683:R-SNARE Proteins; D017470:Receptors, Glutamate; D018092:Kainic Acid Receptors; D018094:Receptors, Metabotropic Glutamate; D050600:SNARE Proteins; D012694:Serine; D033921:Vesicular Transport Proteins; C036978:concanamycin A