title: VGLUT1 and VGAT are sorted to the same population of synaptic vesicles in subsets of cortical axon terminals.
abstract: Glutamate and GABA mediate most of the excitatory and inhibitory synaptic transmission; they are taken up and accumulated in synaptic vesicles by specific vesicular transporters named VGLUT1-3 and VGAT, respectively. Recent studies show that VGLUT2 and VGLUT3 are co-expressed with VGAT. Because of the relevance this information has for our understanding of synaptic physiology and plasticity, we investigated whether VGLUT1 and VGAT are co-expressed in rat cortical neurons. In cortical cultures and layer V cortical terminals we observed a population of terminals expressing VGLUT1 and VGAT. Post-embedding immunogold studies showed that VGLUT1+/VGAT+ terminals formed both symmetric and asymmetric synapses. Triple-labeling studies revealed GABAergic synapses expressing VGLUT1 and glutamatergic synapses expressing VGAT. Immunoisolation studies showed that anti-VGAT immunoisolated vesicles contained VGLUT1 and anti-VGLUT1 immunoisolated vesicles contained VGAT. Finally, vesicles containing VGAT resident in glutamatergic terminals undergo active recycling. In conclusion, we demonstrate that in neocortex VGLUT1 and VGAT are co-expressed in a subset of axon terminals forming both symmetric and asymmetric synapses, that VGLUT1 and VGAT are sorted to the same vesicles and that vesicles at synapses expressing the vesicular heterotransporter participate in the exo-endocytotic cycle.
authors.affiliation: Department of Neuroscience, Università Politecnica delle Marche, Ancona, Italy.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Fattorini
authors.forename: Claudia
authors.initials: C
authors.lastname: Verderio
authors.forename: Marcello
authors.initials: M
authors.lastname: Melone
authors.forename: Silvia
authors.initials: S
authors.lastname: Giovedì
authors.forename: Fabio
authors.initials: F
authors.lastname: Benfenati
authors.forename: Michela
authors.initials: M
authors.lastname: Matteoli
authors.forename: Fiorenzo
authors.initials: F
authors.lastname: Conti
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000378:metabolism* / Q000648:ultrastructure; D004705:Endocytosis / Q000502:physiology; D005089:Exocytosis / Q000502:physiology; D008297:Male; D017729:Presynaptic Terminals / Q000378:metabolism* / Q000648:ultrastructure; D021382:Protein Sorting Signals / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013572:Synaptic Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D050598:Vesicular Glutamate Transport Protein 1 / Q000096:biosynthesis / Q000378:metabolism* / Q000648:ultrastructure; D050495:Vesicular Inhibitory Amino Acid Transport Proteins / Q000096:biosynthesis / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D021382:Protein Sorting Signals; C118623:Slc32a1 protein, rat; D050598:Vesicular Glutamate Transport Protein 1; D050495:Vesicular Inhibitory Amino Acid Transport Proteins