title: Calcium-permeable AMPA receptors trigger vesicular glutamate release from Bergmann gliosomes.
abstract: The Bergmann glia is equipped with Ca2+-permeable AMPA receptors for glutamate, indispensable for structural and functional relations between the Bergmann glia and parallel/climbing fibers-Purkinje cell synapses. To better understand roles for the Bergmann AMPA receptors, herein we investigate on gliotransmitter release and Ca2+ signals in isolated Bergmann glia processes obtained from adult rat cerebellum. We found that: 1) the rat cerebellar purified astrocyte processes (gliosomes) expressed astrocytic and Bergmann markers and exhibited negligible contamination by nerve terminals, microglia, or oligodendrocytes; 2) activation of Ca2+-permeable AMPA receptors caused Ca2+ signals in the processes, and the release of glutamate from the processes; 3) effectiveness of rose bengal, trypan blue or bafilomycin A1, indicated that activation of the AMPA receptors evoked vesicular glutamate release. Cerebellar purified nerve terminals appeared devoid of glutamate-releasing Ca2+-permeable AMPA receptors, indicating that neuronal contamination may not be the source of the signals detected. Ultrastructural analysis indicated the presence of vesicles in the cytoplasm of the processes; confocal imaging confirmed the presence of vesicular glutamate transporters in Bergmann glia processes. We conclude that: a vesicular mechanism for release of the gliotransmitter glutamate is present in mature Bergmann processes; entry of Ca2+ through the AMPA receptors located on Bergmann processes is coupled with vesicular glutamate release. The findings would add a new role for a well-known Bergmann target for glutamate (the Ca2+-permeable AMPA receptors) and a new actor (the gliotransmitter glutamate) at the cerebellar excitatory synapses onto Purkinje cells.
authors.affiliation: Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Viale Cembrano 4, 16148 Genova, Italy; Centre of Excellence for Biomedical Research CEBR, University of Genova, Viale Benedetto XV, 5, 16132 Genova, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Cervetto
authors.affiliation: Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Viale Cembrano 4, 16148 Genova, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Frattaroli
authors.affiliation: Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Viale Cembrano 4, 16148 Genova, Italy.
authors.forename: Arianna
authors.initials: A
authors.lastname: Venturini
authors.affiliation: Department of Experimental Medicine, Section of Biochemistry, Italian Institute of Biostructures and Biosystems, University of Genova, Via L.B. Alberti 2, 16132 Genova, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Passalacqua
authors.affiliation: CNR, Biophysics Institute, Via de Marinis 6, 16146 Genova, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Nobile
authors.affiliation: CNR, Biophysics Institute, Via de Marinis 6, 16146 Genova, Italy.
authors.forename: Susanna
authors.initials: S
authors.lastname: Alloisio
authors.affiliation: Department of Experimental Medicine, University of Genova, Via L. B. Alberti 2, 16132 Genova, Italy; Experimental Imaging Center, Scientific Institute San Raffaele, Via Olgettina 60, 20132 Milano, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Tacchetti
authors.affiliation: Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Viale Cembrano 4, 16148 Genova, Italy; Centre of Excellence for Biomedical Research CEBR, University of Genova, Viale Benedetto XV, 5, 16132 Genova, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Maura
authors.affiliation: Department of Biomedical, Metabolic Sciences and Neuroscience, University of Modena and Reggio Emilia, Via Campi 287, 41125 Modena, Italy; Department of Neuroscience, Karolinska Institutet, Retzius väg 8, Stockholm, Sweden.
authors.forename: Luigi Francesco
authors.initials: LF
authors.lastname: Agnati
authors.affiliation: Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Viale Cembrano 4, 16148 Genova, Italy; Centre of Excellence for Biomedical Research CEBR, University of Genova, Viale Benedetto XV, 5, 16132 Genova, Italy. Electronic address: marcoli@pharmatox.unige.it.
authors.forename: Manuela
authors.initials: M
authors.lastname: Marcoli
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D002531:Cerebellum / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D022162:Cytoplasmic Vesicles / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D018698:Glutamic Acid / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000378:metabolism*; D056969:Voltage-Sensitive Dye Imaging
chemical_list: D018091:Receptors, AMPA; D018698:Glutamic Acid; D002118:Calcium
keywords: (S)-AMPA (PubChem CID: 158397); (S)-CPW 399 (PubChem CID: 657004); 1-Naphthylacetyl spermine trihydrochloride (PubChem CID: 16219727); Cerebellum; Fura 2am (PubChem CID: 3086531); GYKI 52466 (PubChem CID: 3538); Gliosomes; Gliotransmitter release; GluA2-lacking AMPA receptor; Neuroglia; Rose bengal (PubChem CID: 32343); Trypan blue (PubChem CID 9562061)