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Abstract
Endocytosis is a vesicle-based mechanism by which eukaryotic cells internalize extracellular material. There are several types of this universal mechanism linked to different types of endocytosed cargo, including pathogens; therefore, several approaches can be applied. Here, we describe techniques that are applicable to study the internalization of flaviviruses; dextrans; transporters, such as, glutamate transporter vGlut1; and peptidergic signaling molecules, including atrial natriuretic peptide into astrocytes, the most heterogeneous neuroglial cells, which play a key homeostatic role in the central nervous system.
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Affiliation(s)
- Maja Potokar
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
- Celica BIOMEDICAL, Ljubljana, Slovenia
| | - Jernej Jorgačevski
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
- Celica BIOMEDICAL, Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
- Celica BIOMEDICAL, Ljubljana, Slovenia.
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2
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Zorec R, Parpura V, Verkhratsky A. Astroglial vesicular network: evolutionary trends, physiology and pathophysiology. Acta Physiol (Oxf) 2018; 222. [PMID: 28665546 DOI: 10.1111/apha.12915] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 05/17/2017] [Accepted: 06/24/2017] [Indexed: 12/13/2022]
Abstract
Intracellular organelles, including secretory vesicles, emerged when eukaryotic cells evolved some 3 billion years ago. The primordial organelles that evolved in Archaea were similar to endolysosomes, which developed, arguably, for specific metabolic tasks, including uptake, metabolic processing, storage and disposal of molecules. In comparison with prokaryotes, cell volume of eukaryotes increased by several orders of magnitude and vesicle traffic emerged to allow for communication between distant intracellular locations. Lysosomes, first described in 1955, a prominent intermediate of endo- and exocytotic pathways, operate virtually in all eukaryotic cells including astroglia, the most heterogeneous type of homeostatic glia in the central nervous system. Astrocytes support neuronal network activity in particular through elaborated secretion, based on a complex intracellular vesicle network dynamics. Deranged homeostasis underlies disease and astroglial vesicle traffic contributes to the pathophysiology of neurodegenerative (Alzheimer's disease, Huntington's disease), neurodevelopmental diseases (intellectual deficiency, Rett's disease) and neuroinfectious (Zika virus) disorders. This review addresses astroglial cell-autonomous vesicular traffic network, as well as its into primary and secondary vesicular network defects in diseases, and considers this network as a target for developing new therapies for neurological conditions.
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Affiliation(s)
- R. Zorec
- Laboratory of Neuroendocrinology and Molecular Cell Physiology; Institute of Pathophysiology; University of Ljubljana; Ljubljana Slovenia
- Celica; BIOMEDICAL; Ljubljana Slovenia
| | - V. Parpura
- Department of Neurobiology; Civitan International Research Center and Center for Glial Biology in Medicine; Evelyn F. McKnight Brain Institute; Atomic Force Microscopy and Nanotechnology Laboratories; University of Alabama; Birmingham AL USA
| | - A. Verkhratsky
- Laboratory of Neuroendocrinology and Molecular Cell Physiology; Institute of Pathophysiology; University of Ljubljana; Ljubljana Slovenia
- Celica; BIOMEDICAL; Ljubljana Slovenia
- Faculty of Biology; Medicine and Health; The University of Manchester; Manchester UK
- Achucarro Center for Neuroscience; IKERBASQUE; Basque Foundation for Science; Bilbao Spain
- Department of Neurosciences; University of the Basque Country UPV/EHU and CIBERNED; Leioa Spain
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3
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Jorgačevski J, Potokar M, Kreft M, Guček A, Mothet JP, Zorec R. Astrocytic Vesicle-based Exocytosis in Cultures and Acutely Isolated Hippocampal Rodent Slices. J Neurosci Res 2017; 95:2152-2158. [PMID: 28370180 DOI: 10.1002/jnr.24051] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 02/02/2017] [Accepted: 02/22/2017] [Indexed: 01/05/2023]
Abstract
Astrocytes are excitable neural cells that contribute to brain information processing via bidirectional communication with neurons. This involves the release of gliosignaling molecules that affect synapses patterning and activity. Mechanisms mediating the release of these molecules likely consist of non-vesicular and vesicular-based mechanisms. It is the vesicle-based regulated exocytosis that is an evolutionary more complex process. It is well established that the release of gliosignaling molecules has profound effects on information processing in different brain regions (e.g., hippocampal astrocytes contribute to long-term potentiation [LTP]), which has traditionally been considered as one of the cellular mechanisms underlying learning and memory. However, the paradigm of vesicle-based regulated release of gliosignaling molecules from astrocytes is still far from being unanimously accepted. One of the most important questions is to what extent can the conclusions obtained from cultured astrocytes be translated to in vivo conditions. Here, we overview the properties of vesicle mobility and their fusion with the plasma membrane in cultured astrocytes and compare these parameters to those recorded in astrocytes from acute brain hippocampal slices. The results from both experimental models are similar, which validates experiments on isolated astrocytes and further supports arguments in favor of in vivo vesicle-based exocytotic release of gliosignaling molecules. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Jernej Jorgačevski
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia.,Celica Biomedical, Tehnološki Park 24, 1000, Ljubljana, Slovenia
| | - Maja Potokar
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia.,Celica Biomedical, Tehnološki Park 24, 1000, Ljubljana, Slovenia
| | - Marko Kreft
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia.,Celica Biomedical, Tehnološki Park 24, 1000, Ljubljana, Slovenia.,Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000, Ljubljana, Slovenia
| | - Alenka Guček
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia
| | - Jean-Pierre Mothet
- Team Gliotransmission and Synaptopathies, Aix-Marseille Université, CNRS, CRN2M UMR7286, Marseille, France
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia.,Celica Biomedical, Tehnološki Park 24, 1000, Ljubljana, Slovenia
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4
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Zorec R, Parpura V, Vardjan N, Verkhratsky A. Astrocytic face of Alzheimer’s disease. Behav Brain Res 2017; 322:250-257. [DOI: 10.1016/j.bbr.2016.05.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2016] [Revised: 04/16/2016] [Accepted: 05/08/2016] [Indexed: 10/21/2022]
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5
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Astrocytic Pathological Calcium Homeostasis and Impaired Vesicle Trafficking in Neurodegeneration. Int J Mol Sci 2017; 18:ijms18020358. [PMID: 28208745 PMCID: PMC5343893 DOI: 10.3390/ijms18020358] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Revised: 01/30/2017] [Accepted: 01/31/2017] [Indexed: 02/08/2023] Open
Abstract
Although the central nervous system (CNS) consists of highly heterogeneous populations of neurones and glial cells, clustered into diverse anatomical regions with specific functions, there are some conditions, including alertness, awareness and attention that require simultaneous, coordinated and spatially homogeneous activity within a large area of the brain. During such events, the brain, representing only about two percent of body mass, but consuming one fifth of body glucose at rest, needs additional energy to be produced. How simultaneous energy procurement in a relatively extended area of the brain takes place is poorly understood. This mechanism is likely to be impaired in neurodegeneration, for example in Alzheimer’s disease, the hallmark of which is brain hypometabolism. Astrocytes, the main neural cell type producing and storing glycogen, a form of energy in the brain, also hold the key to metabolic and homeostatic support in the central nervous system and are impaired in neurodegeneration, contributing to the slow decline of excitation-energy coupling in the brain. Many mechanisms are affected, including cell-to-cell signalling. An important question is how changes in cellular signalling, a process taking place in a rather short time domain, contribute to the neurodegeneration that develops over decades. In this review we focus initially on the slow dynamics of Alzheimer’s disease, and on the activity of locus coeruleus, a brainstem nucleus involved in arousal. Subsequently, we overview much faster processes of vesicle traffic and cytosolic calcium dynamics, both of which shape the signalling landscape of astrocyte-neurone communication in health and neurodegeneration.
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Verkhratsky A, Zorec R, Rodriguez JJ, Parpura V. Neuroglia: Functional Paralysis and Reactivity in Alzheimer’s Disease and Other Neurodegenerative Pathologies. ADVANCES IN NEUROBIOLOGY 2017; 15:427-449. [DOI: 10.1007/978-3-319-57193-5_17] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Zorec R, Parpura V, Verkhratsky A. Astroglial Vesicular Trafficking in Neurodegenerative Diseases. Neurochem Res 2016; 42:905-917. [DOI: 10.1007/s11064-016-2055-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 08/30/2016] [Accepted: 08/31/2016] [Indexed: 12/20/2022]
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8
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Vardjan N, Horvat A, Anderson JE, Yu D, Croom D, Zeng X, Lužnik Z, Kreft M, Teng YD, Kirov SA, Zorec R. Adrenergic activation attenuates astrocyte swelling induced by hypotonicity and neurotrauma. Glia 2016; 64:1034-49. [PMID: 27018061 DOI: 10.1002/glia.22981] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 02/18/2016] [Accepted: 02/18/2016] [Indexed: 12/29/2022]
Abstract
Edema in the central nervous system can rapidly result in life-threatening complications. Vasogenic edema is clinically manageable, but there is no established medical treatment for cytotoxic edema, which affects astrocytes and is a primary trigger of acute post-traumatic neuronal death. To test the hypothesis that adrenergic receptor agonists, including the stress stimulus epinephrine protects neural parenchyma from damage, we characterized its effects on hypotonicity-induced cellular edema in cortical astrocytes by in vivo and in vitro imaging. After epinephrine administration, hypotonicity-induced swelling of astrocytes was markedly reduced and cytosolic 3'-5'-cyclic adenosine monophosphate (cAMP) was increased, as shown by a fluorescence resonance energy transfer nanosensor. Although, the kinetics of epinephrine-induced cAMP signaling was slowed in primary cortical astrocytes exposed to hypotonicity, the swelling reduction by epinephrine was associated with an attenuated hypotonicity-induced cytosolic Ca(2+) excitability, which may be the key to prevent astrocyte swelling. Furthermore, in a rat model of spinal cord injury, epinephrine applied locally markedly reduced neural edema around the contusion epicenter. These findings reveal new targets for the treatment of cellular edema in the central nervous system.
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Affiliation(s)
- Nina Vardjan
- Celica, BIOMEDICAL, Tehnološki park 24, Ljubljana, 1000, Slovenia.,Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, Ljubljana, 1000, Slovenia
| | - Anemari Horvat
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, Ljubljana, 1000, Slovenia
| | - Jamie E Anderson
- Departments of Neurosurgery and Physical Medicine & Rehabilitation, Harvard Medical School, Boston, Massachusetts
| | - Dou Yu
- Departments of Neurosurgery and Physical Medicine & Rehabilitation, Harvard Medical School, Boston, Massachusetts
| | - Deborah Croom
- Brain and Behaviour Discovery Institute, Medical College of Georgia, Augusta, Georgia.,Department of Neurosurgery, Medical College of Georgia, Augusta, Georgia
| | - Xiang Zeng
- Departments of Neurosurgery and Physical Medicine & Rehabilitation, Harvard Medical School, Boston, Massachusetts
| | - Zala Lužnik
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, Ljubljana, 1000, Slovenia
| | - Marko Kreft
- Celica, BIOMEDICAL, Tehnološki park 24, Ljubljana, 1000, Slovenia.,Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, Ljubljana, 1000, Slovenia.,Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, Ljubljana, 1000, Slovenia
| | - Yang D Teng
- Departments of Neurosurgery and Physical Medicine & Rehabilitation, Harvard Medical School, Boston, Massachusetts.,Division of SCI Research, VA Boston Healthcare System, Boston, Massachusetts
| | - Sergei A Kirov
- Brain and Behaviour Discovery Institute, Medical College of Georgia, Augusta, Georgia.,Department of Neurosurgery, Medical College of Georgia, Augusta, Georgia
| | - Robert Zorec
- Celica, BIOMEDICAL, Tehnološki park 24, Ljubljana, 1000, Slovenia.,Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, Ljubljana, 1000, Slovenia
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9
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Potokar M, Jorgačevski J, Lacovich V, Kreft M, Vardjan N, Bianchi V, D'Adamo P, Zorec R. Impaired αGDI Function in the X-Linked Intellectual Disability: The Impact on Astroglia Vesicle Dynamics. Mol Neurobiol 2016; 54:2458-2468. [PMID: 26971292 DOI: 10.1007/s12035-016-9834-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 03/04/2016] [Indexed: 11/25/2022]
Abstract
X-linked non-syndromic intellectual disability (XLID) is a common mental disorder recognized by cognitive and behavioral deficits. Mutations in the brain-specific αGDI, shown to alter a subset of RAB GTPases redistribution in cells, are linked to XLID, likely via changes in vesicle traffic in neurons. Here, we show directly that isolated XLID mice astrocytes, devoid of pathologic tissue environment, exhibit vesicle mobility deficits. Contrary to previous studies, we show that astrocytes express two GDI proteins. The siRNA-mediated suppression of expression of αGDI especially affected vesicle dynamics. A similar defect was recorded in astrocytes from the Gdi1 -/Y mouse model of XLID and in astrocytes with recombinant mutated human XLID αGDI. Endolysosomal vesicles studied here are involved in the release of gliosignaling molecules as well as in regulating membrane receptor density; thus, the observed changes in astrocytic vesicle mobility may, over the long time-course, profoundly affect signaling capacity of these cells, which optimize neural activity.
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Affiliation(s)
- Maja Potokar
- Celica Biomedical, Tehnološki park 24, 1000, Ljubljana, Slovenia
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia
| | - Jernej Jorgačevski
- Celica Biomedical, Tehnološki park 24, 1000, Ljubljana, Slovenia
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia
| | | | - Marko Kreft
- Celica Biomedical, Tehnološki park 24, 1000, Ljubljana, Slovenia
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia
- Biotechnical Faculty, University of Ljubljana, 1000, Ljubljana, Slovenia
| | - Nina Vardjan
- Celica Biomedical, Tehnološki park 24, 1000, Ljubljana, Slovenia
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia
| | - Veronica Bianchi
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, 20132, Milan, Italy
| | - Patrizia D'Adamo
- Celica Biomedical, Tehnološki park 24, 1000, Ljubljana, Slovenia
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, 20132, Milan, Italy
| | - Robert Zorec
- Celica Biomedical, Tehnološki park 24, 1000, Ljubljana, Slovenia.
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia.
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10
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Zorec R, Horvat A, Vardjan N, Verkhratsky A. Memory Formation Shaped by Astroglia. Front Integr Neurosci 2015; 9:56. [PMID: 26635551 PMCID: PMC4648070 DOI: 10.3389/fnint.2015.00056] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Accepted: 10/28/2015] [Indexed: 12/13/2022] Open
Abstract
Astrocytes, the most heterogeneous glial cells in the central nervous system (CNS), execute a multitude of homeostatic functions and contribute to memory formation. Consolidation of synaptic and systemic memory is a prolonged process and hours are required to form long-term memory. In the past, neurons or their parts have been considered to be the exclusive cellular sites of these processes, however, it has now become evident that astrocytes provide an important and essential contribution to memory formation. Astrocytes participate in the morphological remodeling associated with synaptic plasticity, an energy-demanding process that requires mobilization of glycogen, which, in the CNS, is almost exclusively stored in astrocytes. Synaptic remodeling also involves bidirectional astroglial-neuronal communication supported by astroglial receptors and release of gliosignaling molecules. Astroglia exhibit cytoplasmic excitability that engages second messengers, such as Ca2+, for phasic, and cyclic adenosine monophosphate (cAMP), for tonic signal coordination with neuronal processes. The detection of signals by astrocytes and the release of gliosignaling molecules, in particular by vesicle-based mechanisms, occurs with a significant delay after stimulation, orders of magnitude longer than that present in stimulus–secretion coupling in neurons. These particular arrangements position astrocytes as integrators ideally tuned to support time-dependent memory formation.
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Affiliation(s)
- Robert Zorec
- Laboratory of Neuroendocrinology and Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana Ljubljana, Slovenia ; Celica Biomedical Ljubljana, Slovenia
| | - Anemari Horvat
- Laboratory of Neuroendocrinology and Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana Ljubljana, Slovenia
| | - Nina Vardjan
- Laboratory of Neuroendocrinology and Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana Ljubljana, Slovenia ; Celica Biomedical Ljubljana, Slovenia
| | - Alexei Verkhratsky
- Laboratory of Neuroendocrinology and Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana Ljubljana, Slovenia ; Celica Biomedical Ljubljana, Slovenia ; Faculty of Life Sciences, University of Manchester Manchester, UK ; Achucarro Center for Neuroscience, Ikerbasque, Basque Foundation for Science Bilbao, Spain ; Department of Neurosciences, University of the Basque Country Leioa, Spain ; University of Nizhny Novgorod Nizhny Novgorod, Russia
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11
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Abstract
Neuroglia, the "glue" that fills the space between neurons in the central nervous system, takes active part in nerve cell signaling. Neuroglial cells, astroglia, oligodendroglia, and microglia, are together about as numerous as neurons in the brain as a whole, and in the cerebral cortex grey matter, but the proportion varies widely among brain regions. Glial volume, however, is less than one-fifth of the tissue volume in grey matter. When stimulated by neurons or other cells, neuroglial cells release gliotransmitters by exocytosis, similar to neurotransmitter release from nerve endings, or by carrier-mediated transport or channel flux through the plasma membrane. Gliotransmitters include the common neurotransmitters glutamate and GABA, the nonstandard amino acid d-serine, the high-energy phosphate ATP, and l-lactate. The latter molecule is a "buffer" between glycolytic and oxidative metabolism as well as a signaling substance recently shown to act on specific lactate receptors in the brain. Complementing neurotransmission at a synapse, neuroglial transmission often implies diffusion of the transmitter over a longer distance and concurs with the concept of volume transmission. Transmission from glia modulates synaptic neurotransmission based on energetic and other local conditions in a volume of tissue surrounding the individual synapse. Neuroglial transmission appears to contribute significantly to brain functions such as memory, as well as to prevalent neuropathologies.
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Affiliation(s)
- Vidar Gundersen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Jon Storm-Mathisen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Linda Hildegard Bergersen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
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12
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Chatterjee S, Sikdar SK. Corticosterone treatment results in enhanced release of peptidergic vesicles in astrocytes via cytoskeletal rearrangements. Glia 2013; 61:2050-62. [PMID: 24123181 DOI: 10.1002/glia.22576] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 08/06/2013] [Accepted: 08/26/2013] [Indexed: 12/14/2022]
Abstract
While the effect of stress on neuronal physiology is widely studied, its effect on the functionality of astrocytes is not well understood. We studied the effect of high doses of stress hormone corticosterone, on two physiological properties of astrocytes, i.e., gliotransmission and interastrocytic calcium waves. To study the release of peptidergic vesicles from astrocytes, hippocampal astrocyte cultures were transfected with a plasmid to express pro-atrial natriuretic peptide (ANP) fused with the emerald green fluorescent protein (ANP.emd). The rate of decrease in fluorescence of ANP.emd on application of ionomycin, a calcium ionophore was monitored. Significant increase in the rate of calcium-dependent exocytosis of ANP.emd was observed with the 100 nM and 1 μM corticosterone treatments for 3 h, which depended on the activation of the glucocorticoid receptor. ANP.emd tagged vesicles exhibited increased mobility in astrocyte culture upon corticosterone treatment. Increasing corticosterone concentrations also resulted in concomitant increase in the calcium wave propagation velocity, initiated by focal ATP application. Corticosterone treatment also resulted in increased GFAP expression and F-actin rearrangements. FITC-Phalloidin immunostaining revealed increased formation of cross linked F-actin networks with the 100 nM and 1 μM corticosterone treatment. Alternatively, blockade of actin polymerization and disruption of microtubules prevented the corticosterone-mediated increase in ANP.emd release kinetics. This study reports for the first time the effect of corticosterone on gliotransmission via modulation of cytoskeletal elements. As ANP acts on both neurons and blood vessels, modulation of its release could have functional implications in neurovascular coupling under pathophysiological conditions of stress.
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Affiliation(s)
- Sreejata Chatterjee
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560012, Karnataka, India
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13
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Van Liefferinge J, Massie A, Portelli J, Di Giovanni G, Smolders I. Are vesicular neurotransmitter transporters potential treatment targets for temporal lobe epilepsy? Front Cell Neurosci 2013; 7:139. [PMID: 24009559 PMCID: PMC3757300 DOI: 10.3389/fncel.2013.00139] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 08/11/2013] [Indexed: 12/18/2022] Open
Abstract
The vesicular neurotransmitter transporters (VNTs) are small proteins responsible for packing synaptic vesicles with neurotransmitters thereby determining the amount of neurotransmitter released per vesicle through fusion in both neurons and glial cells. Each transporter subtype was classically seen as a specific neuronal marker of the respective nerve cells containing that particular neurotransmitter or structurally related neurotransmitters. More recently, however, it has become apparent that common neurotransmitters can also act as co-transmitters, adding complexity to neurotransmitter release and suggesting intriguing roles for VNTs therein. We will first describe the current knowledge on vesicular glutamate transporters (VGLUT1/2/3), the vesicular excitatory amino acid transporter (VEAT), the vesicular nucleotide transporter (VNUT), vesicular monoamine transporters (VMAT1/2), the vesicular acetylcholine transporter (VAChT) and the vesicular γ-aminobutyric acid (GABA) transporter (VGAT) in the brain. We will focus on evidence regarding transgenic mice with disruptions in VNTs in different models of seizures and epilepsy. We will also describe the known alterations and reorganizations in the expression levels of these VNTs in rodent models for temporal lobe epilepsy (TLE) and in human tissue resected for epilepsy surgery. Finally, we will discuss perspectives on opportunities and challenges for VNTs as targets for possible future epilepsy therapies.
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14
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Potokar M, Vardjan N, Stenovec M, Gabrijel M, Trkov S, Jorgačevski J, Kreft M, Zorec R. Astrocytic vesicle mobility in health and disease. Int J Mol Sci 2013; 14:11238-58. [PMID: 23712361 PMCID: PMC3709730 DOI: 10.3390/ijms140611238] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 04/26/2013] [Accepted: 05/08/2013] [Indexed: 12/14/2022] Open
Abstract
Astrocytes are no longer considered subservient to neurons, and are, instead, now understood to play an active role in brain signaling. The intercellular communication of astrocytes with neurons and other non-neuronal cells involves the exchange of molecules by exocytotic and endocytotic processes through the trafficking of intracellular vesicles. Recent studies of single vesicle mobility in astrocytes have prompted new views of how astrocytes contribute to information processing in nervous tissue. Here, we review the trafficking of several types of membrane-bound vesicles that are specifically involved in the processes of (i) intercellular communication by gliotransmitters (glutamate, adenosine 5′-triphosphate, atrial natriuretic peptide), (ii) plasma membrane exchange of transporters and receptors (EAAT2, MHC-II), and (iii) the involvement of vesicle mobility carrying aquaporins (AQP4) in water homeostasis. The properties of vesicle traffic in astrocytes are discussed in respect to networking with neighboring cells in physiologic and pathologic conditions, such as amyotrophic lateral sclerosis, multiple sclerosis, and states in which astrocytes contribute to neuroinflammatory conditions.
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Affiliation(s)
- Maja Potokar
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
| | - Nina Vardjan
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
| | - Matjaž Stenovec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
| | - Mateja Gabrijel
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
| | - Saša Trkov
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
| | - Jernej Jorgačevski
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
| | - Marko Kreft
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
- Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000 Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +386-1543-7020; Fax: +386-1543-7036
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Falchi AM, Sogos V, Saba F, Piras M, Congiu T, Piludu M. Astrocytes shed large membrane vesicles that contain mitochondria, lipid droplets and ATP. Histochem Cell Biol 2012; 139:221-31. [PMID: 23108569 DOI: 10.1007/s00418-012-1045-x] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/17/2012] [Indexed: 12/24/2022]
Abstract
Various cells types, including stem and progenitor cells, can exchange complex information via plasma membrane-derived vesicles, which can carry signals both in their limiting membrane and lumen. Astrocytes, traditionally regarded as mere supportive cells, play previously unrecognized functions in neuronal modulation and are capable of releasing signalling molecules of different functional significance. In the present study, we provide direct evidence that human fetal astrocytes in culture, expressing the same feature as immature and reactive astrocytes, release membrane vesicles larger than the microvesicles described up to now. We found that these large vesicles, ranging from 1-5 to 8 μm in diameter and expressing on their surface β1-integrin proteins, contain mitochondria and lipid droplets together with ATP. We documented vesicle content with fluorescent-specific dyes and with the immunocytochemistry technique we confirmed that mitochondria and lipid droplets were co-localized in the same vesicle. Scanning electron microscopy and transmission electron microscopy confirmed that astrocytes shed from surface membrane vesicles of the same size as the ones detected by fluorescence microscopy. Our results report for the first time that cultured astrocytes, activated by repetitive stimulation of ATP released from neighboring cells, shed from their surface large membrane vesicles containing mitochondria and lipid droplets.
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Affiliation(s)
- Angela Maria Falchi
- Department of Biomedical Sciences, University of Cagliari, Cittadella Universitaria Monserrato, 09042 Monserrato, CA, Italy.
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16
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Ormel L, Stensrud MJ, Chaudhry FA, Gundersen V. A distinct set of synaptic-like microvesicles in atroglial cells contain VGLUT3. Glia 2012; 60:1289-300. [DOI: 10.1002/glia.22348] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 04/13/2012] [Indexed: 11/09/2022]
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17
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Potokar M, Lacovich V, Chowdhury HH, Kreft M, Zorec R. Rab4 and Rab5 GTPase are required for directional mobility of endocytic vesicles in astrocytes. Glia 2012; 60:594-604. [PMID: 22279005 DOI: 10.1002/glia.22293] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 12/16/2011] [Indexed: 11/07/2022]
Abstract
Rab4 and Rab5 GTPases are key players in the regulation of endocytosis. Although their role has been studied intensively in the past, it is still unclear how they regulate vesicle mobility. In particular, in astrocytes, the most abundant glial cells in the brain, vesicles have been shown to exhibit nondirectional and directional mobility, which can be intermittent, but the underlying switching mechanisms are not known. By using quantitative imaging, we studied the dynamics of single vesicle movements in astrocytes in real time, by transfecting them with different GDP- and GTP-locked mutants of Rab4 and Rab5. Along with the localization of Rab4 and Rab5 on early and late endocytic compartments, we measured the apparent vesicle size by monitoring the area of fluorescent puncta and determined the patterns of vesicle mobility in the presence of wild-type and Rab mutants. Dominant-negative and dominant-positive mutants, Rab4 S22N, Rab5 S34N and Rab4 Q67L, Rab5 Q79L, induced an increase in the apparent vesicle size, especially Rab5 mutants. These mutants also significantly reduced vesicle mobility in terms of vesicle track length, maximal displacement, and speed. In addition, significant reductions in the fraction of vesicles exhibiting directional mobility were observed in cells expressing Rab4 S22N, Rab4 Q67L, Rab5 S34N, and Rab5 Q79L. Our data indicate that changes in the GDP-GTP switch apparently not only affect fusion events in endocytosis and recycling, as already proposed, but also affect the molecular interactions determining directional vesicle mobility, likely involving motor proteins and the cytoskeleton.
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Affiliation(s)
- Maja Potokar
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
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18
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Abstract
Astroglial cells, due to their passive electrical properties, were long considered subservient to neurons and to merely provide the framework and metabolic support of the brain. Although astrocytes do play such structural and housekeeping roles in the brain, these glial cells also contribute to the brain's computational power and behavioural output. These more active functions are endowed by the Ca2+-based excitability displayed by astrocytes. An increase in cytosolic Ca2+ levels in astrocytes can lead to the release of signalling molecules, a process termed gliotransmission, via the process of regulated exocytosis. Dynamic components of astrocytic exocytosis include the vesicular-plasma membrane secretory machinery, as well as the vesicular traffic, which is governed not only by general cytoskeletal elements but also by astrocyte-specific IFs (intermediate filaments). Gliotransmitters released into the ECS (extracellular space) can exert their actions on neighbouring neurons, to modulate synaptic transmission and plasticity, and to affect behaviour by modulating the sleep homoeostat. Besides these novel physiological roles, astrocytic Ca2+ dynamics, Ca2+-dependent gliotransmission and astrocyte–neuron signalling have been also implicated in brain disorders, such as epilepsy. The aim of this review is to highlight the newer findings concerning Ca2+ signalling in astrocytes and exocytotic gliotransmission. For this we report on Ca2+ sources and sinks that are necessary and sufficient for regulating the exocytotic release of gliotransmitters and discuss secretory machinery, secretory vesicles and vesicle mobility regulation. Finally, we consider the exocytotic gliotransmission in the modulation of synaptic transmission and plasticity, as well as the astrocytic contribution to sleep behaviour and epilepsy.
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Ormel L, Stensrud MJ, Bergersen LH, Gundersen V. VGLUT1 is localized in astrocytic processes in several brain regions. Glia 2011; 60:229-38. [DOI: 10.1002/glia.21258] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Accepted: 09/26/2011] [Indexed: 01/26/2023]
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20
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Figueiredo M, Lane S, Tang F, Liu BH, Hewinson J, Marina N, Kasymov V, Souslova EA, Chudakov DM, Gourine AV, Teschemacher AG, Kasparov S. Optogenetic experimentation on astrocytes. Exp Physiol 2010; 96:40-50. [PMID: 21041318 DOI: 10.1113/expphysiol.2010.052597] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- M Figueiredo
- School of Physiology and Pharmacology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
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21
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Domingues AMDJ, Taylor M, Fern R. Glia as transmitter sources and sensors in health and disease. Neurochem Int 2010; 57:359-66. [PMID: 20380859 DOI: 10.1016/j.neuint.2010.03.024] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Revised: 03/19/2010] [Accepted: 03/31/2010] [Indexed: 10/19/2022]
Abstract
Glial cells express a bewildering array of neurotransmitter receptors. To illustrate the complexity of expression, we have assayed non-glutamatergic neurotransmitter receptor mRNA in isolated rat optic nerve, a preparation devoid of neurons and neuronal synapses and from which relatively pure "glial" RNA can be isolated. Of the 44 receptor subunits examined which span the GABA-A, nicotinic, adreno- and glycine receptor families, over three quarters were robustly expressed in this mixed population of white matter glial cells, with several expressed at higher levels than found in control whole brain RNA. In addition to the complexity of glial receptor expression, numerous neurotransmitter release mechanisms have been identified. We have focused on glutamate release from astrocytes, which can occur via at least seven distinct pathways and which is implicated in excitotoxic injury and are neurons and glia. Recent findings suggest that non-glutamatergic receptors can also mediate acute glial injury are also discussed.
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22
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Regulated exocytosis in astrocytic signal integration. Neurochem Int 2010; 57:451-9. [PMID: 20156504 DOI: 10.1016/j.neuint.2010.02.007] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2009] [Revised: 02/07/2010] [Accepted: 02/08/2010] [Indexed: 12/11/2022]
Abstract
Astrocytes can be considered as signal integrators in central nervous system activity. These glial cells can respond to signals from the heterocellular milieu of the brain and subsequently release various molecules to signal to themselves and/or other neighboring neural cells. An important functional module that enables signal integration in astrocytes is exocytosis, a Ca(2+)-dependent process consisting of vesicular fusion to the plasma membrane. Astrocytes utilize regulated exocytosis to release various signaling molecules stored in the vesicular lumen. Here we review the properties of exocytotic release of three classes of gliotransmitters: (i) amino acids, (ii) nucleotides and (iii) peptides. Vesicles may carry not only lumenal cargo, but also membrane-associated molecules. Therefore, we also discuss exocytosis as a delivery mechanism for transporters and receptors to the plasma membrane, where these proteins are involved in astrocytic intercellular signaling.
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