Astrocytic vesicles and gliotransmitters: Slowness of vesicular release and synaptobrevin2-laden vesicle nanoarchitecture.
Neurotransmitters released at synapses activate neighboring astrocytes, which in turn, modulate neuronal activity by the release of diverse neuroactive substances that include classical neurotransmitters such as glutamate, GABA or ATP. Neuroactive substances are released from astrocytes through several distinct molecular mechanisms, for example, by diffusion through membrane channels, by translocation via plasmalemmal transporters or by vesicular exocytosis. Vesicular release regulated by a stimulus-mediated increase in cytosolic calcium involves soluble N-ethyl maleimide-sensitive fusion protein attachment protein receptor (SNARE)-dependent merger of the vesicle membrane with the plasmalemma. Up to 25 molecules of synaptobrevin 2 (Sb2), a SNARE complex protein, reside at a single astroglial vesicle; an individual neuronal, i.e. synaptic, vesicle contains ∼70 Sb2 molecules. It is proposed that this paucity of Sb2 molecules in astrocytic vesicles may determine the slow secretion. In the present essay we shall overview multiple aspects of vesicular architecture and types of vesicles based on their cargo and dynamics in astroglial cells.
University of Ljubljana, Institute of Pathophysiology, Laboratory of Neuroendocrinology and Molecular Cell Physiology, Zaloska cesta 4, SI-1000 Ljubljana, Slovenia; Celica, BIOMEDICAL, Technology Park 24, 1000 Ljubljana, Slovenia. Electronic address: robert.zorec@mf.uni-lj.si.
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Zorec
University of Ljubljana, Institute of Pathophysiology, Laboratory of Neuroendocrinology and Molecular Cell Physiology, Zaloska cesta 4, SI-1000 Ljubljana, Slovenia; Celica, BIOMEDICAL, Technology Park 24, 1000 Ljubljana, Slovenia; Faculty of Life Sciences, The University of Manchester, Manchester M13 9PT, UK; Achucarro Center for Neuroscience, IKERBASQUE, 48011 Bilbao, Spain; University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain. Electronic address: Alexej.Verkhratsky@manchester.ac.uk.
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Verkhratsky
Achucarro Center for Neuroscience, IKERBASQUE, 48011 Bilbao, Spain; University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain. Electronic address: j.rodriguez-arellano@ikerbasque.org.
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Rodríguez
Department of Neurobiology, Civitan International Research Center and Center for Glial Biology in Medicine, Evelyn F. McKnight Brain Institute, Atomic Force Microscopy & Nanotechnology Laboratories, 1719 6th Avenue South, CIRC 429, University of Alabama at Birmingham, Birmingham, AL 35294-0021, USA; Department of Biotechnology, University of Rijeka, Radmile Matejčić 2, 51000 Rijeka, Croatia. Electronic address: vlad@uab.edu.
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D000818:Animals; D001253:Astrocytes / Q000378:metabolism* / Q000648:ultrastructure; D005089:Exocytosis / Q000502:physiology; D006801:Humans; D026901:Membrane Transport Proteins / Q000378:metabolism; D013572:Synaptic Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D050988:Vesicle-Associated Membrane Protein 2 / Q000378:metabolism*
D026901:Membrane Transport Proteins; D050988:Vesicle-Associated Membrane Protein 2
ATP; astrocytes; exocytosis; gliotransmission; glutamate; vesicles