title: G-protein coupled receptor-evoked glutamate exocytosis from astrocytes: role of prostaglandins.
abstract: Astrocytes are highly secretory cells, participating in rapid brain communication by releasing glutamate. Recent evidences have suggested that this process is largely mediated by Ca(2+)-dependent regulated exocytosis of VGLUT-positive vesicles. Here by taking advantage of VGLUT1-pHluorin and TIRF illumination, we characterized mechanisms of glutamate exocytosis evoked by endogenous transmitters (glutamate and ATP), which are known to stimulate Ca(2+) elevations in astrocytes. At first we characterized the VGLUT1-pHluorin expressing vesicles and found that VGLUT1-positive vesicles were a specific population of small synaptic-like microvesicles containing glutamate but which do not express VGLUT2. Endogenous mediators evoked a burst of exocytosis through activation of G-protein coupled receptors. Subsequent glutamate exocytosis was reduced by about 80% upon pharmacological blockade of the prostaglandin-forming enzyme, cyclooxygenase. On the other hand, receptor stimulation was accompanied by extracellular release of prostaglandin E2 (PGE2). Interestingly, administration of exogenous PGE2 produced per se rapid, store-dependent burst exocytosis of glutamatergic vesicles in astrocytes. Finally, when PGE2-neutralizing antibody was added to cell medium, transmitter-evoked exocytosis was again significantly reduced (by about 50%). Overall these data indicate that cyclooxygenase products are responsible for a major component of glutamate exocytosis in astrocytes and that large part of such component is sustained by autocrine/paracrine action of PGE2.
authors.affiliation: Department of Fundamental Neurosciences, Faculty of Biology and Medicine, University of Lausanne, rue du Bugnon 9, 1005 Lausanne, Switzerland.
authors.forename: Corrado
authors.initials: C
authors.lastname: Cali
authors.affiliation: Department of Fundamental Neurosciences, Faculty of Biology and Medicine, University of Lausanne, rue du Bugnon 9, 1005 Lausanne, Switzerland.
authors.forename: Jan
authors.identifier: 0000-0001-7871-8619
authors.initials: J
authors.lastname: Lopatar
authors.affiliation: Department of Fundamental Neurosciences, Faculty of Biology and Medicine, University of Lausanne, rue du Bugnon 9, 1005 Lausanne, Switzerland.
authors.forename: Francesco
authors.identifier: 0000-0003-0696-7039
authors.initials: F
authors.lastname: Petrelli
authors.affiliation: Department of Fundamental Neurosciences, Faculty of Biology and Medicine, University of Lausanne, rue du Bugnon 9, 1005 Lausanne, Switzerland.
authors.forename: Luca
authors.identifier: 0000-0002-9488-5422
authors.initials: L
authors.lastname: Pucci
authors.affiliation: Department of Fundamental Neurosciences, Faculty of Biology and Medicine, University of Lausanne, rue du Bugnon 9, 1005 Lausanne, Switzerland.
authors.forename: Paola
authors.identifier: 0000-0002-8279-3600
authors.initials: P
authors.lastname: Bezzi
mesh_terms: D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology; D001241:Aspirin / Q000494:pharmacology; D001253:Astrocytes / Q000502:physiology*; D002478:Cells, Cultured; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000037:antagonists & inhibitors / Q000494:pharmacology; D005089:Exocytosis / Q000502:physiology*; D018698:Glutamic Acid / Q000502:physiology*; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D007213:Indomethacin / Q000494:pharmacology; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000502:physiology; D011453:Prostaglandins / Q000502:physiology*; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism
chemical_list: D019138:Antibodies, Blocking; D016861:Cyclooxygenase Inhibitors; D011453:Prostaglandins; D043562:Receptors, G-Protein-Coupled; C493466:Slc17a7 protein, rat; D050598:Vesicular Glutamate Transport Protein 1; D018698:Glutamic Acid; D008734:Methoxyhydroxyphenylglycol; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone; D001241:Aspirin; C010117:3,4-dihydroxyphenylglycol; D007213:Indomethacin