title: A distinct set of synaptic-like microvesicles in atroglial cells contain VGLUT3.
abstract: There is increasing evidence for vesicular release of glutamate from astrocytes. We have previously demonstrated existence of VGLUT1 on astrocytic synaptic-like microvesicles (SMLVs) in several brain regions indicating a role in astroglial glutamate release. As VGLUT3 is prominently expressed in non-neuronal cells, this prompted us to investigate whether VGLUT3 is also involved in astroglial release of glutamate. Confocal microscopic investigations revealed that astrocytes in the hippocampus and the frontal cortex, as well as Bergmann glia in the cerebellum were labeled for VGLUT3. Immunogold cytochemistry showed that VGLUT3 gold particles were located over SMLVs in perisynaptic astrocytic and Bergmann glial processes. The specificity of the VGLUT3 immunoreactivity was demonstrated by abolished VGLUT3 labeling in astroglia in VGLUT3 knock-out mice. Double immunogold labeling showed that astrocytic processes contained labeling for VGLUT3 and VGLUT1, but the antibodies labeled separate subpopulations of vesicles in the processes. The ratio of gold particle densities between glial processes and nerve terminals were higher for VGLUT3 than for VGLUT1, suggesting that VGLUT3 is particularly abundant in astrocytic processes. Thus, our data show that VGLUT3 localizes to a distinct set of SMLVs in perisynaptic astroglial processes and suggest that VGLUT3 is important for glutamate release from astrocytes.
authors.affiliation: Department of Anatomy, Institute of Basic Medical Sciences, and Centre for Molecular, Biology and Neuroscience (CMBN), University of Oslo, Norway.
authors.forename: Lasse
authors.initials: L
authors.lastname: Ormel
authors.forename: Mats Julius
authors.initials: MJ
authors.lastname: Stensrud
authors.forename: Farrukh Abbas
authors.initials: FA
authors.lastname: Chaudhry
authors.forename: Vidar
authors.initials: V
authors.lastname: Gundersen
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D006624:Hippocampus / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D051381:Rats; D017208:Rats, Wistar; D013572:Synaptic Vesicles / Q000378:metabolism*; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism; D050496:Vesicular Glutamate Transport Proteins / Q000378:metabolism*
chemical_list: C482103:Slc17a8 protein, rat; D050598:Vesicular Glutamate Transport Protein 1; D050496:Vesicular Glutamate Transport Proteins; D018698:Glutamic Acid; D005974:Glutamate-Ammonia Ligase