1
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Pathak D, Sriram K. Neuron-astrocyte omnidirectional signaling in neurological health and disease. Front Mol Neurosci 2023; 16:1169320. [PMID: 37363320 PMCID: PMC10286832 DOI: 10.3389/fnmol.2023.1169320] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Accepted: 05/09/2023] [Indexed: 06/28/2023] Open
Abstract
Astrocytes are an abundantly distributed population of glial cells in the central nervous system (CNS) that perform myriad functions in the normal and injured/diseased brain. Astrocytes exhibit heterogeneous phenotypes in response to various insults, a process known as astrocyte reactivity. The accuracy and precision of brain signaling are primarily based on interactions involving neurons, astrocytes, oligodendrocytes, microglia, pericytes, and dendritic cells within the CNS. Astrocytes have emerged as a critical entity within the brain because of their unique role in recycling neurotransmitters, actively modulating the ionic environment, regulating cholesterol and sphingolipid metabolism, and influencing cellular crosstalk in diverse neural injury conditions and neurodegenerative disorders. However, little is known about how an astrocyte functions in synapse formation, axon specification, neuroplasticity, neural homeostasis, neural network activity following dynamic surveillance, and CNS structure in neurological diseases. Interestingly, the tripartite synapse hypothesis came to light to fill some knowledge gaps that constitute an interaction of a subpopulation of astrocytes, neurons, and synapses. This review highlights astrocytes' role in health and neurological/neurodegenerative diseases arising from the omnidirectional signaling between astrocytes and neurons at the tripartite synapse. The review also recapitulates the disruption of the tripartite synapse with a focus on perturbations of the homeostatic astrocytic function as a key driver to modulate the molecular and physiological processes toward neurodegenerative diseases.
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2
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Brewton HW, Robinson SL, Thiele TE. Astrocyte expression in the extended amygdala of C57BL/6J mice is sex-dependently affected by chronic intermittent and binge-like ethanol exposure. Alcohol 2023; 108:55-64. [PMID: 36539069 PMCID: PMC10033386 DOI: 10.1016/j.alcohol.2022.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 12/12/2022] [Accepted: 12/12/2022] [Indexed: 12/23/2022]
Abstract
Excessive ethanol drinking is a major problem within the United States, causing alterations in brain plasticity and neurocognitive function. Astrocytes are glial cells that regulate neurosynaptic plasticity, modulate neurochemicals, and monitor other homeostatic roles. Astrocytes have been found to play a part in modulating excessive ethanol consumption. The basolateral amygdala (BLA), central amygdala (CeA), and bed nucleus of the stria terminalis (BNST) are brain regions that process stress, anxiety, and reward; they are also implicated in modulating ethanol intake. Little is understood, however, about how astrocyte expression in each region is modulated by chronic and binge-like ethanol drinking patterns. In the present report, we utilized two separate animal models of excessive drinking: chronic intermittent ethanol (CIE) and "Drinking-in-the-dark" (DID). Following these paradigms, animal brains were processed through immunohistochemistry (IHC) and stained for glial fibrillary acidic protein (GFAP). Collected data illustrated a sex-dependent relationship between ethanol intake and GFAP immunoreactivity (IR) in the BLA and BNST, but not in the CeA. Specifically, CIE and DID ethanol drinking resulted in blunted GFAP-IR (specifically via GFAP-positive cell count) in the BLA and BNST, particularly in males. These findings may implicate sex-dependent ethanol-induced changes in BLA and BNST astrocytes, providing a potential therapeutic target for anxiety and stress disorders.
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Affiliation(s)
- Honoreé W Brewton
- Department of Psychology & Neuroscience, University of North Carolina at Chapel Hill, North Carolina, 27599-3270, United States
| | - Stacey L Robinson
- Department of Psychology & Neuroscience, University of North Carolina at Chapel Hill, North Carolina, 27599-3270, United States; The Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, North Carolina 27599-3270, United States
| | - Todd E Thiele
- Department of Psychology & Neuroscience, University of North Carolina at Chapel Hill, North Carolina, 27599-3270, United States; The Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, North Carolina 27599-3270, United States.
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3
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Liu Y, Shen X, Zhang Y, Zheng X, Cepeda C, Wang Y, Duan S, Tong X. Interactions of glial cells with neuronal synapses, from astrocytes to microglia and oligodendrocyte lineage cells. Glia 2023; 71:1383-1401. [PMID: 36799296 DOI: 10.1002/glia.24343] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 01/06/2023] [Accepted: 01/08/2023] [Indexed: 02/18/2023]
Abstract
The mammalian brain is a complex organ comprising neurons, glia, and more than 1 × 1014 synapses. Neurons are a heterogeneous group of electrically active cells, which form the framework of the complex circuitry of the brain. However, glial cells, which are primarily divided into astrocytes, microglia, oligodendrocytes (OLs), and oligodendrocyte precursor cells (OPCs), constitute approximately half of all neural cells in the mammalian central nervous system (CNS) and mainly provide nutrition and tropic support to neurons in the brain. In the last two decades, the concept of "tripartite synapses" has drawn great attention, which emphasizes that astrocytes are an integral part of the synapse and regulate neuronal activity in a feedback manner after receiving neuronal signals. Since then, synaptic modulation by glial cells has been extensively studied and substantially revised. In this review, we summarize the latest significant findings on how glial cells, in particular, microglia and OL lineage cells, impact and remodel the structure and function of synapses in the brain. Our review highlights the cellular and molecular aspects of neuron-glia crosstalk and provides additional information on how aberrant synaptic communication between neurons and glia may contribute to neural pathologies.
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Affiliation(s)
- Yao Liu
- Songjiang Institute and Songjiang Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xi Shen
- Songjiang Institute and Songjiang Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yuhan Zhang
- College of Basic Medical Science, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xiaoli Zheng
- Songjiang Institute and Songjiang Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Carlos Cepeda
- Intellectual and Developmental Disabilities Research Center, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Yao Wang
- Department of Assisted Reproduction, The Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shumin Duan
- Songjiang Institute and Songjiang Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Liangzhu Laboratory, MOE Frontier Science Center for Brain Science and Brain-Machine Integration, State Key Laboratory of Brain-Machine Intelligence, Zhejiang University, Hangzhou, China
| | - Xiaoping Tong
- Songjiang Institute and Songjiang Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Research Center for Brain Science and Brain-Inspired Intelligence, Shanghai, China
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4
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Schwarz K, Schmitz F. Synapse Dysfunctions in Multiple Sclerosis. Int J Mol Sci 2023; 24:ijms24021639. [PMID: 36675155 PMCID: PMC9862173 DOI: 10.3390/ijms24021639] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 01/11/2023] [Accepted: 01/12/2023] [Indexed: 01/18/2023] Open
Abstract
Multiple sclerosis (MS) is a chronic neuroinflammatory disease of the central nervous system (CNS) affecting nearly three million humans worldwide. In MS, cells of an auto-reactive immune system invade the brain and cause neuroinflammation. Neuroinflammation triggers a complex, multi-faceted harmful process not only in the white matter but also in the grey matter of the brain. In the grey matter, neuroinflammation causes synapse dysfunctions. Synapse dysfunctions in MS occur early and independent from white matter demyelination and are likely correlates of cognitive and mental symptoms in MS. Disturbed synapse/glia interactions and elevated neuroinflammatory signals play a central role. Glutamatergic excitotoxic synapse damage emerges as a major mechanism. We review synapse/glia communication under normal conditions and summarize how this communication becomes malfunctional during neuroinflammation in MS. We discuss mechanisms of how disturbed glia/synapse communication can lead to synapse dysfunctions, signaling dysbalance, and neurodegeneration in MS.
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5
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Zheng Y, Pan L, Wang F, Yan J, Wang T, Xia Y, Yao L, Deng K, Zheng Y, Xia X, Su Z, Chen H, Lin J, Ding Z, Zhang K, Zhang M, Chen Y. Neural function of Bmal1: an overview. Cell Biosci 2023; 13:1. [PMID: 36593479 PMCID: PMC9806909 DOI: 10.1186/s13578-022-00947-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 12/19/2022] [Indexed: 01/04/2023] Open
Abstract
Bmal1 (Brain and muscle arnt-like, or Arntl) is a bHLH/PAS domain transcription factor central to the transcription/translation feedback loop of the biologic clock. Although Bmal1 is well-established as a major regulator of circadian rhythm, a growing number of studies in recent years have shown that dysfunction of Bmal1 underlies a variety of psychiatric, neurodegenerative-like, and endocrine metabolism-related disorders, as well as potential oncogenic roles. In this review, we systematically summarized Bmal1 expression in different brain regions, its neurological functions related or not to circadian rhythm and biological clock, and pathological phenotypes arising from Bmal1 knockout. This review also discusses oscillation and rhythmicity, especially in the suprachiasmatic nucleus, and provides perspective on future progress in Bmal1 research.
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Affiliation(s)
- Yuanjia Zheng
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China ,grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Lingyun Pan
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Feixue Wang
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Jinglan Yan
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Taiyi Wang
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Yucen Xia
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Lin Yao
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Kelin Deng
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Yuqi Zheng
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Xiaoye Xia
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Zhikai Su
- grid.411866.c0000 0000 8848 7685The Second Clinical College, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong China
| | - Hongjie Chen
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Jie Lin
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Zhenwei Ding
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Kaitong Zhang
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Meng Zhang
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Yongjun Chen
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China ,grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China ,Center for Brain Science and Brain-Inspired Intelligence, Guangdong-Hong Kong-Macao Greater Bay Area, Guangzhou, China
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6
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Eraso‐Pichot A, Pouvreau S, Olivera‐Pinto A, Gomez‐Sotres P, Skupio U, Marsicano G. Endocannabinoid signaling in astrocytes. Glia 2023; 71:44-59. [PMID: 35822691 PMCID: PMC9796923 DOI: 10.1002/glia.24246] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 06/28/2022] [Accepted: 07/04/2022] [Indexed: 01/07/2023]
Abstract
The study of the astrocytic contribution to brain functions has been growing in popularity in the neuroscience field. In the last years, and especially since the demonstration of the involvement of astrocytes in synaptic functions, the astrocyte field has revealed multiple functions of these cells that seemed inconceivable not long ago. In parallel, cannabinoid investigation has also identified different ways by which cannabinoids are able to interact with these cells, modify their functions, alter their communication with neurons and impact behavior. In this review, we will describe the expression of different endocannabinoid system members in astrocytes. Moreover, we will relate the latest findings regarding cannabinoid modulation of some of the most relevant astroglial functions, namely calcium (Ca2+ ) dynamics, gliotransmission, metabolism, and inflammation.
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Affiliation(s)
- Abel Eraso‐Pichot
- U1215 Neurocentre MagendieInstitut national de la santé et de la recherche médicale (INSERM)BordeauxFrance,University of BordeauxBordeauxFrance
| | - Sandrine Pouvreau
- U1215 Neurocentre MagendieInstitut national de la santé et de la recherche médicale (INSERM)BordeauxFrance,University of BordeauxBordeauxFrance
| | - Alexandre Olivera‐Pinto
- U1215 Neurocentre MagendieInstitut national de la santé et de la recherche médicale (INSERM)BordeauxFrance,University of BordeauxBordeauxFrance
| | - Paula Gomez‐Sotres
- U1215 Neurocentre MagendieInstitut national de la santé et de la recherche médicale (INSERM)BordeauxFrance,University of BordeauxBordeauxFrance
| | - Urszula Skupio
- U1215 Neurocentre MagendieInstitut national de la santé et de la recherche médicale (INSERM)BordeauxFrance,University of BordeauxBordeauxFrance
| | - Giovanni Marsicano
- U1215 Neurocentre MagendieInstitut national de la santé et de la recherche médicale (INSERM)BordeauxFrance,University of BordeauxBordeauxFrance
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7
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Fekete CD, Nishiyama A. Presentation and integration of multiple signals that modulate oligodendrocyte lineage progression and myelination. Front Cell Neurosci 2022; 16:1041853. [PMID: 36451655 PMCID: PMC9701731 DOI: 10.3389/fncel.2022.1041853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Accepted: 10/17/2022] [Indexed: 11/15/2022] Open
Abstract
Myelination is critical for fast saltatory conduction of action potentials. Recent studies have revealed that myelin is not a static structure as previously considered but continues to be made and remodeled throughout adulthood in tune with the network requirement. Synthesis of new myelin requires turning on the switch in oligodendrocytes (OL) to initiate the myelination program that includes synthesis and transport of macromolecules needed for myelin production as well as the metabolic and other cellular functions needed to support this process. A significant amount of information is available regarding the individual intrinsic and extrinsic signals that promote OL commitment, expansion, terminal differentiation, and myelination. However, it is less clear how these signals are made available to OL lineage cells when needed, and how multiple signals are integrated to generate the correct amount of myelin that is needed in a given neural network state. Here we review the pleiotropic effects of some of the extracellular signals that affect myelination and discuss the cellular processes used by the source cells that contribute to the variation in the temporal and spatial availability of the signals, and how the recipient OL lineage cells might integrate the multiple signals presented to them in a manner dialed to the strength of the input.
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8
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Kruyer A. Astrocyte Heterogeneity in Regulation of Synaptic Activity. Cells 2022; 11:cells11193135. [PMID: 36231097 PMCID: PMC9562199 DOI: 10.3390/cells11193135] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 10/02/2022] [Accepted: 10/02/2022] [Indexed: 02/07/2023] Open
Abstract
Our awareness of the number of synapse regulatory functions performed by astroglia is rapidly expanding, raising interesting questions regarding astrocyte heterogeneity and specialization across brain regions. Whether all astrocytes are poised to signal in a multitude of ways, or are instead tuned to surrounding synapses and how astroglial signaling is altered in psychiatric and cognitive disorders are fundamental questions for the field. In recent years, molecular and morphological characterization of astroglial types has broadened our ability to design studies to better analyze and manipulate specific functions of astroglia. Recent data emerging from these studies will be discussed in depth in this review. I also highlight remaining questions emerging from new techniques recently applied toward understanding the roles of astrocytes in synapse regulation in the adult brain.
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Affiliation(s)
- Anna Kruyer
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC 29425, USA
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9
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Ballin M, Griep W, Patel M, Karl M, Mentrup T, Rivera‐Monroy J, Foo B, Schwappach B, Schröder B. The intramembrane proteases
SPPL2a
and
SPPL2b
regulate the homeostasis of selected
SNARE
proteins. FEBS J 2022; 290:2320-2337. [PMID: 36047592 DOI: 10.1111/febs.16610] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 06/28/2022] [Accepted: 08/30/2022] [Indexed: 01/15/2023]
Abstract
Signal peptide peptidase (SPP) and SPP-like (SPPL) aspartyl intramembrane proteases are known to contribute to sequential processing of type II-oriented membrane proteins referred to as regulated intramembrane proteolysis. The ER-resident family members SPP and SPPL2c were shown to also cleave tail-anchored proteins, including selected SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins facilitating membrane fusion events. Here, we analysed whether the related SPPL2a and SPPL2b proteases, which localise to the endocytic or late secretory pathway, are also able to process SNARE proteins. Therefore, we screened 18 SNARE proteins for cleavage by SPPL2a and SPPL2b based on cellular co-expression assays, of which the proteins VAMP1, VAMP2, VAMP3 and VAMP4 were processed by SPPL2a/b demonstrating the capability of these two proteases to proteolyse tail-anchored proteins. Cleavage of the four SNARE proteins was scrutinised at the endogenous level upon SPPL2a/b inhibition in different cell lines as well as by analysing VAMP1-4 levels in tissues and primary cells of SPPL2a/b double-deficient (dKO) mice. Loss of SPPL2a/b activity resulted in an accumulation of VAMP1-4 in a cell type- and tissue-dependent manner, identifying these proteins as SPPL2a/b substrates validated in vivo. Therefore, we propose that SPPL2a/b control cellular levels of VAMP1-4 by initiating the degradation of these proteins, which might impact cellular trafficking.
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Affiliation(s)
- Moritz Ballin
- Biochemical Institute Christian Albrechts University Kiel Kiel Germany
- Institute of Physiological Chemistry Technische Universität Dresden Dresden Germany
| | - Wolfram Griep
- Biochemical Institute Christian Albrechts University Kiel Kiel Germany
- Institute of Physiological Chemistry Technische Universität Dresden Dresden Germany
| | - Mehul Patel
- Institute of Physiological Chemistry Technische Universität Dresden Dresden Germany
| | - Martin Karl
- Institute of Physiological Chemistry Technische Universität Dresden Dresden Germany
| | - Torben Mentrup
- Institute of Physiological Chemistry Technische Universität Dresden Dresden Germany
| | - Jhon Rivera‐Monroy
- Department of Molecular Biology University Medical Center Göttingen Göttingen Germany
| | - Brian Foo
- Department of Molecular Biology University Medical Center Göttingen Göttingen Germany
| | - Blanche Schwappach
- Department of Molecular Biology University Medical Center Göttingen Göttingen Germany
| | - Bernd Schröder
- Institute of Physiological Chemistry Technische Universität Dresden Dresden Germany
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10
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Vadisiute A, Meijer E, Szabó F, Hoerder-Suabedissen A, Kawashita E, Hayashi S, Molnár Z. The role of snare proteins in cortical development. Dev Neurobiol 2022; 82:457-475. [PMID: 35724379 PMCID: PMC9539872 DOI: 10.1002/dneu.22892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 05/18/2022] [Accepted: 05/25/2022] [Indexed: 12/01/2022]
Abstract
Neural communication in the adult nervous system is mediated primarily through chemical synapses, where action potentials elicit Ca2+ signals, which trigger vesicular fusion and neurotransmitter release in the presynaptic compartment. At early stages of development, the brain is shaped by communication via trophic factors and other extracellular signaling, and by contact-mediated cell-cell interactions including chemical synapses. The patterns of early neuronal impulses and spontaneous and regulated neurotransmitter release guide the precise topography of axonal projections and contribute to determining cell survival. The study of the role of specific proteins of the synaptic vesicle release machinery in the establishment, plasticity, and maintenance of neuronal connections during development has only recently become possible, with the advent of mouse models where various members of the N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex have been genetically manipulated. We provide an overview of these models, focusing on the role of regulated vesicular release and/or cellular excitability in synaptic assembly, development and maintenance of cortical circuits, cell survival, circuit level excitation-inhibition balance, myelination, refinement, and plasticity of key axonal projections from the cerebral cortex. These models are important for understanding various developmental and psychiatric conditions, and neurodegenerative diseases.
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Affiliation(s)
- Auguste Vadisiute
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, UK
| | - Elise Meijer
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, UK
| | - Florina Szabó
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, UK
| | - Anna Hoerder-Suabedissen
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, UK
| | - Eri Kawashita
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, UK
- Department of Pathological Biochemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto, Japan
| | - Shuichi Hayashi
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, UK
- Department of Anatomy, Kawasaki Medical School, Kurashiki, Okayama, Japan
| | - Zoltán Molnár
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, UK
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11
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Pillai AG, Nadkarni S. Amyloid pathology disrupts gliotransmitter release in astrocytes. PLoS Comput Biol 2022; 18:e1010334. [PMID: 35913987 PMCID: PMC9371304 DOI: 10.1371/journal.pcbi.1010334] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 08/11/2022] [Accepted: 06/28/2022] [Indexed: 01/11/2023] Open
Abstract
Accumulation of amyloid-beta (Aβ) is associated with synaptic dysfunction and destabilization of astrocytic calcium homeostasis. A growing body of evidence support astrocytes as active modulators of synaptic transmission via calcium-mediated gliotransmission. However, the details of mechanisms linking Aβ signaling, astrocytic calcium dynamics, and gliotransmission are not known. We developed a biophysical model that describes calcium signaling and the ensuing gliotransmitter release from a single astrocytic process when stimulated by glutamate release from hippocampal neurons. The model accurately captures the temporal dynamics of microdomain calcium signaling and glutamate release via both kiss-and-run and full-fusion exocytosis. We investigate the roles of two crucial calcium regulating machineries affected by Aβ: plasma-membrane calcium pumps (PMCA) and metabotropic glutamate receptors (mGluRs). When we implemented these Aβ-affected molecular changes in our astrocyte model, it led to an increase in the rate and synchrony of calcium events. Our model also reproduces several previous findings of Aβ associated aberrant calcium activity, such as increased intracellular calcium level and increased spontaneous calcium activity, and synchronous calcium events. The study establishes a causal link between previous observations of hyperactive astrocytes in Alzheimer’s disease (AD) and Aβ-induced modifications in mGluR and PMCA functions. Analogous to neurotransmitter release, gliotransmitter exocytosis closely tracks calcium changes in astrocyte processes, thereby guaranteeing tight control of synaptic signaling by astrocytes. However, the downstream effects of AD-related calcium changes in astrocytes on gliotransmitter release are not known. Our results show that enhanced rate of exocytosis resulting from modified calcium signaling in astrocytes leads to a rapid depletion of docked vesicles that disrupts the crucial temporal correspondence between a calcium event and vesicular release. We propose that the loss of temporal correspondence between calcium events and gliotransmission in astrocytes pathologically alters astrocytic modulation of synaptic transmission in the presence of Aβ accumulation. Signaling by astrocytes is critical to information processing at synapses, and its aberration plays a central role in neurological diseases, especially Alzheimer’s disease (AD). A complete characterization of calcium signaling and the resulting pattern of gliotransmitter release from fine astrocytic processes are not accessible to current experimental tools. We developed a biophysical model that can quantitatively describe signaling by astrocytes in response to a wide range of synaptic activity. We show that AD-related molecular alterations disrupt the concurrence of calcium and gliotransmitter release events, a characterizing feature that enables astrocytes to influence synaptic signaling.
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Affiliation(s)
| | - Suhita Nadkarni
- Indian Institute of Science Education and Research Pune, Pune, India
- * E-mail:
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12
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Georgiou L, Echeverría A, Georgiou A, Kuhn B. Ca + activity maps of astrocytes tagged by axoastrocytic AAV transfer. SCIENCE ADVANCES 2022; 8:eabe5371. [PMID: 35138891 PMCID: PMC8827655 DOI: 10.1126/sciadv.abe5371] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 12/17/2021] [Indexed: 05/27/2023]
Abstract
Astrocytes exhibit localized Ca2+ microdomain (MD) activity thought to be actively involved in information processing in the brain. However, functional organization of Ca2+ MDs in space and time in relationship to behavior and neuronal activity is poorly understood. Here, we first show that adeno-associated virus (AAV) particles transfer anterogradely from axons to astrocytes. Then, we use this axoastrocytic AAV transfer to express genetically encoded Ca2+ indicators at high-contrast circuit specifically. In combination with two-photon microscopy and unbiased, event-based analysis, we investigated cortical astrocytes embedded in the vibrissal thalamocortical circuit. We found a wide range of Ca2+ MD signals, some of which were ultrafast (≤300 ms). Frequency and size of signals were extensively increased by locomotion but only subtly with sensory stimulation. The overlay of these signals resulted in behavior-dependent maps with characteristic Ca2+ activity hotspots, maybe representing memory engrams. These functional subdomains are stable over days, suggesting subcellular specialization.
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13
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Wichmann C, Kuner T. Heterogeneity of glutamatergic synapses: cellular mechanisms and network consequences. Physiol Rev 2022; 102:269-318. [PMID: 34727002 DOI: 10.1152/physrev.00039.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Chemical synapses are commonly known as a structurally and functionally highly diverse class of cell-cell contacts specialized to mediate communication between neurons. They represent the smallest "computational" unit of the brain and are typically divided into excitatory and inhibitory as well as modulatory categories. These categories are subdivided into diverse types, each representing a different structure-function repertoire that in turn are thought to endow neuronal networks with distinct computational properties. The diversity of structure and function found among a given category of synapses is referred to as heterogeneity. The main building blocks for this heterogeneity are synaptic vesicles, the active zone, the synaptic cleft, the postsynaptic density, and glial processes associated with the synapse. Each of these five structural modules entails a distinct repertoire of functions, and their combination specifies the range of functional heterogeneity at mammalian excitatory synapses, which are the focus of this review. We describe synapse heterogeneity that is manifested on different levels of complexity ranging from the cellular morphology of the pre- and postsynaptic cells toward the expression of different protein isoforms at individual release sites. We attempt to define the range of structural building blocks that are used to vary the basic functional repertoire of excitatory synaptic contacts and discuss sources and general mechanisms of synapse heterogeneity. Finally, we explore the possible impact of synapse heterogeneity on neuronal network function.
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Affiliation(s)
- Carolin Wichmann
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, InnerEarLab and Institute for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Thomas Kuner
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, Heidelberg, Germany
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14
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Abstract
Drug addiction remains a key biomedical challenge facing current neuroscience research. In addition to neural mechanisms, the focus of the vast majority of studies to date, astrocytes have been increasingly recognized as an "accomplice." According to the tripartite synapse model, astrocytes critically regulate nearby pre- and postsynaptic neuronal substrates to craft experience-dependent synaptic plasticity, including synapse formation and elimination. Astrocytes within brain regions that are implicated in drug addiction exhibit dynamic changes in activity upon exposure to cocaine and subsequently undergo adaptive changes themselves during chronic drug exposure. Recent results have identified several key astrocytic signaling pathways that are involved in cocaine-induced synaptic and circuit adaptations. In this review, we provide a brief overview of the role of astrocytes in regulating synaptic transmission and neuronal function, and discuss how cocaine influences these astrocyte-mediated mechanisms to induce persistent synaptic and circuit alterations that promote cocaine seeking and relapse. We also consider the therapeutic potential of targeting astrocytic substrates to ameliorate drug-induced neuroplasticity for behavioral benefits. While primarily focusing on cocaine-induced astrocytic responses, we also include brief discussion of other drugs of abuse where data are available.
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15
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Chipman PH, Fung CCA, Pazo Fernandez A, Sawant A, Tedoldi A, Kawai A, Ghimire Gautam S, Kurosawa M, Abe M, Sakimura K, Fukai T, Goda Y. Astrocyte GluN2C NMDA receptors control basal synaptic strengths of hippocampal CA1 pyramidal neurons in the stratum radiatum. eLife 2021; 10:70818. [PMID: 34693906 PMCID: PMC8594917 DOI: 10.7554/elife.70818] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 10/22/2021] [Indexed: 12/12/2022] Open
Abstract
Experience-dependent plasticity is a key feature of brain synapses for which neuronal N-Methyl-D-Aspartate receptors (NMDARs) play a major role, from developmental circuit refinement to learning and memory. Astrocytes also express NMDARs, although their exact function has remained controversial. Here, we identify in mouse hippocampus, a circuit function for GluN2C NMDAR, a subtype highly expressed in astrocytes, in layer-specific tuning of synaptic strengths in CA1 pyramidal neurons. Interfering with astrocyte NMDAR or GluN2C NMDAR activity reduces the range of presynaptic strength distribution specifically in the stratum radiatum inputs without an appreciable change in the mean presynaptic strength. Mathematical modeling shows that narrowing of the width of presynaptic release probability distribution compromises the expression of long-term synaptic plasticity. Our findings suggest a novel feedback signaling system that uses astrocyte GluN2C NMDARs to adjust basal synaptic weight distribution of Schaffer collateral inputs, which in turn impacts computations performed by the CA1 pyramidal neuron.
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Affiliation(s)
| | - Chi Chung Alan Fung
- Neural Coding and Brain Computing Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Japan
| | | | | | - Angelo Tedoldi
- RIKEN Center for Brain Science, Wako-shi, Saitama, Japan
| | - Atsushi Kawai
- RIKEN Center for Brain Science, Wako-shi, Saitama, Japan
| | | | | | - Manabu Abe
- Department of Animal Model Development, Brain Research Institute, Niigata University, Niigata, Japan
| | - Kenji Sakimura
- Department of Animal Model Development, Brain Research Institute, Niigata University, Niigata, Japan
| | - Tomoki Fukai
- Neural Coding and Brain Computing Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Japan
| | - Yukiko Goda
- RIKEN Center for Brain Science, Wako-shi, Saitama, Japan
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16
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Lee KM, Talikoti A, Shelton K, Grotewiel M. Tyramine synthesis, vesicular packaging, and the SNARE complex function coordinately in astrocytes to regulate Drosophila alcohol sedation. Addict Biol 2021; 26:e13019. [PMID: 33538092 PMCID: PMC8225576 DOI: 10.1111/adb.13019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 01/08/2021] [Accepted: 01/19/2021] [Indexed: 12/21/2022]
Abstract
Identifying mechanisms underlying alcohol-related behaviors could provide important insights regarding the etiology of alcohol use disorder. To date, most genetic studies on alcohol-related behavior in model organisms have focused on neurons, leaving the causal roles of glial mechanisms less comprehensively investigated. Here, we report our studies on the role of Tyrosine decarboxylase 2 (Tdc2), which converts tyrosine to the catecholamine tyramine, in glial cells in Drosophila alcohol sedation. Using genetic approaches that drove transgene expression constitutively in all glia, constitutively in astrocytes and conditionally in glia during adulthood, we found that knockdown and overexpression of Tdc2, respectively, increased and decreased the sensitivity to alcohol sedation in flies. Manipulation of the genes tyramine β-hydroxylase and tyrosine hydroxylase, which respectively synthesize octopamine and dopamine from tyramine and tyrosine, had no discernable effect on alcohol sedation, suggesting that Tdc2 affects alcohol sedation by regulating tyramine production. We also found that knockdown of the vesicular monoamine transporter (VMAT) and disruption of the SNARE complex in all glia or selectively in astrocytes increased sensitivity to alcohol sedation and that both VMAT and the SNARE complex functioned downstream of Tdc2. Our studies support a model in which the synthesis of tyramine and vesicle-mediated release of tyramine from adult astrocytes regulates alcohol sedation in Drosophila. Considering that tyramine is functionally orthologous to norepinephrine in mammals, our results raise the possibility that gliotransmitter synthesis release could be a conserved mechanism influencing behavioral responses to alcohol as well as alcohol use disorder.
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Affiliation(s)
- Kristen M. Lee
- Neuroscience Graduate Program, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Ananya Talikoti
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Keith Shelton
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Mike Grotewiel
- Neuroscience Graduate Program, Virginia Commonwealth University, Richmond, Virginia, USA
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia, USA
- Virginia Commonwealth University Alcohol Research Center, Virginia Commonwealth University, Richmond, Virginia, USA
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17
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Gobbo D, Scheller A, Kirchhoff F. From Physiology to Pathology of Cortico-Thalamo-Cortical Oscillations: Astroglia as a Target for Further Research. Front Neurol 2021; 12:661408. [PMID: 34177766 PMCID: PMC8219957 DOI: 10.3389/fneur.2021.661408] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 05/11/2021] [Indexed: 12/21/2022] Open
Abstract
The electrographic hallmark of childhood absence epilepsy (CAE) and other idiopathic forms of epilepsy are 2.5-4 Hz spike and wave discharges (SWDs) originating from abnormal electrical oscillations of the cortico-thalamo-cortical network. SWDs are generally associated with sudden and brief non-convulsive epileptic events mostly generating impairment of consciousness and correlating with attention and learning as well as cognitive deficits. To date, SWDs are known to arise from locally restricted imbalances of excitation and inhibition in the deep layers of the primary somatosensory cortex. SWDs propagate to the mostly GABAergic nucleus reticularis thalami (NRT) and the somatosensory thalamic nuclei that project back to the cortex, leading to the typical generalized spike and wave oscillations. Given their shared anatomical basis, SWDs have been originally considered the pathological transition of 11-16 Hz bursts of neural oscillatory activity (the so-called sleep spindles) occurring during Non-Rapid Eye Movement (NREM) sleep, but more recent research revealed fundamental functional differences between sleep spindles and SWDs, suggesting the latter could be more closely related to the slow (<1 Hz) oscillations alternating active (Up) and silent (Down) cortical activity and concomitantly occurring during NREM. Indeed, several lines of evidence support the fact that SWDs impair sleep architecture as well as sleep/wake cycles and sleep pressure, which, in turn, affect seizure circadian frequency and distribution. Given the accumulating evidence on the role of astroglia in the field of epilepsy in the modulation of excitation and inhibition in the brain as well as on the development of aberrant synchronous network activity, we aim at pointing at putative contributions of astrocytes to the physiology of slow-wave sleep and to the pathology of SWDs. Particularly, we will address the astroglial functions known to be involved in the control of network excitability and synchronicity and so far mainly addressed in the context of convulsive seizures, namely (i) interstitial fluid homeostasis, (ii) K+ clearance and neurotransmitter uptake from the extracellular space and the synaptic cleft, (iii) gap junction mechanical and functional coupling as well as hemichannel function, (iv) gliotransmission, (v) astroglial Ca2+ signaling and downstream effectors, (vi) reactive astrogliosis and cytokine release.
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Affiliation(s)
- Davide Gobbo
- Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
| | - Anja Scheller
- Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
| | - Frank Kirchhoff
- Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
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18
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Broadhead MJ, Miles GB. A common role for astrocytes in rhythmic behaviours? Prog Neurobiol 2021; 202:102052. [PMID: 33894330 DOI: 10.1016/j.pneurobio.2021.102052] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 03/03/2021] [Accepted: 04/13/2021] [Indexed: 01/16/2023]
Abstract
Astrocytes are a functionally diverse form of glial cell involved in various aspects of nervous system infrastructure, from the metabolic and structural support of neurons to direct neuromodulation of synaptic activity. Investigating how astrocytes behave in functionally related circuits may help us understand whether there is any conserved logic to the role of astrocytes within neuronal networks. Astrocytes are implicated as key neuromodulatory cells within neural circuits that control a number of rhythmic behaviours such as breathing, locomotion and circadian sleep-wake cycles. In this review, we examine the evidence that astrocytes are directly involved in the regulation of the neural circuits underlying six different rhythmic behaviours: locomotion, breathing, chewing, gastrointestinal motility, circadian sleep-wake cycles and oscillatory feeding behaviour. We discuss how astrocytes are integrated into the neuronal networks that regulate these behaviours, and identify the potential gliotransmission signalling mechanisms involved. From reviewing the evidence of astrocytic involvement in a range of rhythmic behaviours, we reveal a heterogenous array of gliotransmission mechanisms, which help to regulate neuronal networks. However, we also observe an intriguing thread of commonality, in the form of purinergic gliotransmission, which is frequently utilised to facilitate feedback inhibition within rhythmic networks to constrain a given behaviour within its operational range.
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Affiliation(s)
- Matthew J Broadhead
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, UK.
| | - Gareth B Miles
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, UK
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19
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Nwachukwu KN, Evans WA, Sides TR, Trevisani CP, Davis A, Marshall SA. Chemogenetic manipulation of astrocytic signaling in the basolateral amygdala reduces binge-like alcohol consumption in male mice. J Neurosci Res 2021; 99:1957-1972. [PMID: 33844860 DOI: 10.1002/jnr.24841] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 03/21/2021] [Indexed: 12/18/2022]
Abstract
Binge drinking is a common occurrence in the United States, but a high concentration of alcohol in the blood has been shown to have reinforcing and reciprocal effects on the neuroimmune system in both dependent and non-dependent scenarios. The first part of this study examined alcohol's effects on the astrocytic response in the central amygdala and basolateral amygdala (BLA) in a non-dependent model. C57BL/6J mice were given access to either ethanol, water, or sucrose during a "drinking in the dark" paradigm, and astrocyte number and astrogliosis were measured using immunohistochemistry. Results indicate that non-dependent consumption increased glial fibrillary acidic protein (GFAP) density but not the number of GFAP+ cells, suggesting that non-dependent ethanol is sufficient to elicit astrocyte activation. The second part of this study examined how astrocytes impacted behaviors and the neurochemistry related to alcohol using the chemogenetic tool, DREADDs (designer receptors exclusively activated by designer drugs). Transgenic GFAP-hM3Dq mice were administered clozapine N-oxide both peripherally, affecting the entire central nervous system (CNS), or directly into the BLA. In both instances, GFAP-Gq-signaling activation significantly reduced ethanol consumption and correlating blood ethanol concentrations. However, GFAP-Gq-DREADD activation throughout the CNS had more broad effects resulting in decreased locomotor activity and sucrose consumption. More targeted GFAP-Gq-signaling activation in the BLA only impacted ethanol consumption. Finally, a glutamate assay revealed that after GFAP-Gq-signaling activation glutamate concentrations in the amygdala were partially normalized to control levels. Altogether, these studies support the theory that astrocytes represent a viable target for alcohol use disorder therapies.
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Affiliation(s)
- Kala N Nwachukwu
- Department of Biological & Biomedical Sciences, North Carolina Central University, Durham, NC, USA
| | - William A Evans
- Department of Basic Pharmaceutical Sciences, Fred P. Wilson School of Pharmacy, High Point University, High Point, NC, USA
| | - Tori R Sides
- Department of Biological & Biomedical Sciences, North Carolina Central University, Durham, NC, USA
| | - Christopher P Trevisani
- Department of Basic Pharmaceutical Sciences, Fred P. Wilson School of Pharmacy, High Point University, High Point, NC, USA
| | - Ambryia Davis
- Department of Basic Pharmaceutical Sciences, Fred P. Wilson School of Pharmacy, High Point University, High Point, NC, USA
| | - S Alex Marshall
- Department of Biological & Biomedical Sciences, North Carolina Central University, Durham, NC, USA.,Department of Basic Pharmaceutical Sciences, Fred P. Wilson School of Pharmacy, High Point University, High Point, NC, USA.,Department of Psychology & Neuroscience, University of North Carolina-Chapel Hill, Chapel Hill, NC, USA
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20
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Sensing and Regulating Synaptic Activity by Astrocytes at Tripartite Synapse. Neurochem Res 2021; 46:2580-2585. [PMID: 33837868 PMCID: PMC10159683 DOI: 10.1007/s11064-021-03317-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 03/27/2021] [Accepted: 03/29/2021] [Indexed: 12/11/2022]
Abstract
Astrocytes are recognized as more important cells than historically thought in synaptic function through the reciprocal exchange of signaling with the neuronal synaptic elements. The idea that astrocytes are active elements in synaptic physiology is conceptualized in the Tripartite Synapse concept. This review article presents and discusses recent representative examples that highlight the heterogeneity of signaling in tripartite synapse function and its consequences on neural network function and animal behavior.
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21
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Böhme MA, McCarthy AW, Blaum N, Berezeckaja M, Ponimaskine K, Schwefel D, Walter AM. Glial Synaptobrevin mediates peripheral nerve insulation, neural metabolic supply, and is required for motor function. Glia 2021; 69:1897-1915. [PMID: 33811396 DOI: 10.1002/glia.24000] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 03/12/2021] [Accepted: 03/17/2021] [Indexed: 01/10/2023]
Abstract
Peripheral nerves contain sensory and motor neuron axons coated by glial cells whose interplay ensures function, but molecular details are lacking. SNARE-proteins mediate the exchange and secretion of cargo by fusing vesicles with target organelles, but how glial SNAREs contribute to peripheral nerve function is largely unknown. We, here, identify non-neuronal Synaptobrevin (Syb) as the essential vesicular SNARE in Drosophila peripheral glia to insulate and metabolically supply neurons. We show that tetanus neurotoxin light chain (TeNT-LC), which potently inhibits SNARE-mediated exocytosis from neurons, also impairs peripheral nerve function when selectively expressed in glia, causing nerve disintegration, defective axonal transport, tetanic muscle hyperactivity, impaired locomotion, and lethality. While TeNT-LC disrupts neural function by cleaving neuronal Synaptobrevin (nSyb), it targets non-neuronal Synaptobrevin (Syb) in glia, which it cleaves at low rates: Glial knockdown of Syb (but not nSyb) phenocopied glial TeNT-LC expression whose effects were reverted by a TeNT-LC-insensitive Syb mutant. We link Syb-necessity to two distinct glial subtypes: Impairing Syb function in subperineurial glia disrupted nerve morphology, axonal transport, and locomotion, likely, because nerve-isolating septate junctions (SJs) could not form as essential SJ components (like the cell adhesion protein Neurexin-IV) were mistargeted. Interference with Syb in axon-encircling wrapping glia left nerve morphology and locomotion intact but impaired axonal transport, likely because neural metabolic supply was disrupted due to the mistargeting of metabolite shuffling monocarboxylate transporters. Our study identifies crucial roles of Syb in various glial subtypes to ensure glial-glial and glial-neural interplay needed for proper nerve function, animal motility, and survival.
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Affiliation(s)
- Mathias A Böhme
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), FMP im CharitéCrossOver, Berlin, Germany.,Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Anthony W McCarthy
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), FMP im CharitéCrossOver, Berlin, Germany
| | - Natalie Blaum
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), FMP im CharitéCrossOver, Berlin, Germany
| | - Monika Berezeckaja
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), FMP im CharitéCrossOver, Berlin, Germany
| | - Kristina Ponimaskine
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), FMP im CharitéCrossOver, Berlin, Germany
| | - David Schwefel
- Institute of Medical Physics and Biophysics, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Alexander M Walter
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), FMP im CharitéCrossOver, Berlin, Germany.,Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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22
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Moro N, Ghavim SS, Sutton RL. Massive efflux of adenosine triphosphate into the extracellular space immediately after experimental traumatic brain injury. Exp Ther Med 2021; 21:575. [PMID: 33850547 PMCID: PMC8027727 DOI: 10.3892/etm.2021.10007] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 02/02/2021] [Indexed: 12/14/2022] Open
Abstract
The aim of the current study was to determine effects of mild traumatic brain injury (TBI), with or without blockade of purinergic ATP Y1 (P2Y1) receptors or store-operated calcium channels, on extracellular levels of ATP, glutamate, glucose and lactate. Concentrations of ATP, glutamate, glucose and lactate were measured in cerebral microdialysis samples obtained from the ipsilateral cortex and underlying hippocampus of rats with mild unilateral controlled cortical impact (CCI) or sham injury. Immediately after CCI, a large release of ATP was observed in the cortex (3.53-fold increase of pre-injury value) and hippocampus (2.97-fold increase of pre-injury value), with ATP returning to the baseline levels within 20 min post-injury and remaining stable for during the 3-h sampling period. In agreement with the results of previous studies, there was a significant increase in glutamate 20 min after CCI, which was concomitant with a decrease in extracellular glucose (20 min) and an increase in lactate (40-60 min) in both brain regions after CCI. Addition of a selective P2Y1 receptor blocker (MRS2179 ammonium salt hydrate) to the microdialysis perfusate significantly lowered pre-injury ATP and glutamate levels, and eliminated the post-CCI peaks. Addition of a blocker of store-operated calcium channels [2-aminoethoxy diphenylborinate (2-APB)] to the microdialysis perfusate significantly lowered pre-injury ATP in the hippocampus, and attenuated the post-CCI peak in both the cortex and hippocampus. 2-APB treatment significantly increased baseline glutamate levels, but the values post-injury did not differ from those in the sham group. Pre-injury glucose levels, but not lactate levels, were increased by MRS2179 and decreased by 2-APB. However, none of these treatments substantially altered the CCI-induced reduction in glucose and increase in lactate in the cortex. In conclusion, the results of the present study demonstrated that a short although extensive release of ATP immediately after experimental TBI can be significantly attenuated by blockade of P2Y1 receptors or store-operated calcium channels.
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Affiliation(s)
- Nobuhiro Moro
- Brain Injury Research Center, Department of Neurosurgery, David Geffen School of Medicine, University of California, LA 90095-6901, USA.,Department of Neurological Surgery, Nihon University School of Medicine, Tokyo 173-8610, Japan
| | - Sima S Ghavim
- Brain Injury Research Center, Department of Neurosurgery, David Geffen School of Medicine, University of California, LA 90095-6901, USA
| | - Richard L Sutton
- Brain Injury Research Center, Department of Neurosurgery, David Geffen School of Medicine, University of California, LA 90095-6901, USA
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23
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Ramesh G, Jarzembowski L, Schwarz Y, Poth V, Konrad M, Knapp ML, Schwär G, Lauer AA, Grimm MOW, Alansary D, Bruns D, Niemeyer BA. A short isoform of STIM1 confers frequency-dependent synaptic enhancement. Cell Rep 2021; 34:108844. [PMID: 33730587 DOI: 10.1016/j.celrep.2021.108844] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 12/16/2020] [Accepted: 02/17/2021] [Indexed: 12/25/2022] Open
Abstract
Store-operated Ca2+-entry (SOCE) regulates basal and receptor-triggered Ca2+ signaling with STIM proteins sensing the endoplasmic reticulum (ER) Ca2+ content and triggering Ca2+ entry by gating Orai channels. Although crucial for immune cells, STIM1's role in neuronal Ca2+ homeostasis is controversial. Here, we characterize a splice variant, STIM1B, which shows exclusive neuronal expression and protein content surpassing conventional STIM1 in cerebellum and of significant abundance in other brain regions. STIM1B expression results in a truncated protein with slower kinetics of ER-plasma membrane (PM) cluster formation and ICRAC, as well as reduced inactivation. In primary wild-type neurons, STIM1B is targeted by its spliced-in domain B to presynaptic sites where it converts classic synaptic depression into Ca2+- and Orai-dependent short-term synaptic enhancement (STE) at high-frequency stimulation (HFS). In conjunction with altered STIM1 splicing in human Alzheimer disease, our findings highlight STIM1 splicing as an important regulator of neuronal calcium homeostasis and of synaptic plasticity.
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Affiliation(s)
- Girish Ramesh
- Molecular Biophysics, Saarland University, 66421 Homburg, Germany
| | | | - Yvonne Schwarz
- Molecular Neurophysiology, Saarland University, 66421 Homburg, Germany
| | - Vanessa Poth
- Molecular Biophysics, Saarland University, 66421 Homburg, Germany
| | - Maik Konrad
- Molecular Biophysics, Saarland University, 66421 Homburg, Germany
| | - Mona L Knapp
- Molecular Biophysics, Saarland University, 66421 Homburg, Germany
| | - Gertrud Schwär
- Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), Bld. 48, Saarland University, 66421 Homburg, Germany
| | - Anna A Lauer
- Experimental Neurology, Saarland University, 66421 Homburg, Germany
| | - Marcus O W Grimm
- Experimental Neurology, Saarland University, 66421 Homburg, Germany
| | - Dalia Alansary
- Molecular Biophysics, Saarland University, 66421 Homburg, Germany
| | - Dieter Bruns
- Molecular Neurophysiology, Saarland University, 66421 Homburg, Germany
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24
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Sears SM, Hewett SJ. Influence of glutamate and GABA transport on brain excitatory/inhibitory balance. Exp Biol Med (Maywood) 2021; 246:1069-1083. [PMID: 33554649 DOI: 10.1177/1535370221989263] [Citation(s) in RCA: 64] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
An optimally functional brain requires both excitatory and inhibitory inputs that are regulated and balanced. A perturbation in the excitatory/inhibitory balance-as is the case in some neurological disorders/diseases (e.g. traumatic brain injury Alzheimer's disease, stroke, epilepsy and substance abuse) and disorders of development (e.g. schizophrenia, Rhett syndrome and autism spectrum disorder)-leads to dysfunctional signaling, which can result in impaired cognitive and motor function, if not frank neuronal injury. At the cellular level, transmission of glutamate and GABA, the principle excitatory and inhibitory neurotransmitters in the central nervous system control excitatory/inhibitory balance. Herein, we review the synthesis, release, and signaling of GABA and glutamate followed by a focused discussion on the importance of their transport systems to the maintenance of excitatory/inhibitory balance.
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Affiliation(s)
- Sheila Ms Sears
- Department of Biology, Program in Neuroscience, 2029Syracuse University, Syracuse, NY 13244, USA
| | - Sandra J Hewett
- Department of Biology, Program in Neuroscience, 2029Syracuse University, Syracuse, NY 13244, USA
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25
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Melzer L, Freiman TM, Derouiche A. Rab6A as a Pan-Astrocytic Marker in Mouse and Human Brain, and Comparison with Other Glial Markers (GFAP, GS, Aldh1L1, SOX9). Cells 2021; 10:E72. [PMID: 33466322 PMCID: PMC7824777 DOI: 10.3390/cells10010072] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 12/28/2020] [Accepted: 12/30/2020] [Indexed: 12/18/2022] Open
Abstract
Astrocytes contribute to many higher brain functions. A key mechanism in glia-to-neuron signalling is vesicular exocytosis; however, the identity of exocytosis organelles remains a matter of debate. Since vesicles derived from the trans-Golgi network (TGN) are not considered in this context, we studied the astrocyte TGN by immunocytochemistry applying anti-Rab6A. In mouse brain, Rab6A immunostaining is found to be unexpectedly massive, diffuse in all regions, and is detected preferentially and abundantly in the peripheral astrocyte processes, which is hardly evident without glial fibrillary acid protein (GFAP) co-staining. All cells positive for the astrocytic markers glutamine synthetase (GS), GFAP, aldehyde dehydrogenase 1 family member L1 (Aldh1L1), or SRY (sex determining region Y)-box 9 (SOX9) were Rab6A+. Rab6A is excluded from microglia, oligodendrocytes, and NG2 cells using cell type-specific markers. In human cortex, Rab6A labelling is very similar and associated with GFAP+ astrocytes. The mouse data also confirm the specific astrocytic labelling by Aldh1L1 or SOX9; the astrocyte-specific labelling by GS sometimes debated is replicated again. In mouse and human brain, individual astrocytes display high variability in Rab6A+ structures, suggesting dynamic regulation of the glial TGN. In summary, Rab6A expression is an additional, global descriptor of astrocyte identity. Rab6A might constitute an organelle system with a potential role of Rab6A in neuropathological and physiological processes.
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Affiliation(s)
- Linda Melzer
- Institute of Anatomy II, Goethe-University, D-60590 Frankfurt am Main, Germany;
| | - Thomas M. Freiman
- Department of Neurosurgery, Rostock University Medical Center, D-18055 Rostock, Germany;
| | - Amin Derouiche
- Institute of Anatomy II, Goethe-University, D-60590 Frankfurt am Main, Germany;
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26
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Caudal LC, Gobbo D, Scheller A, Kirchhoff F. The Paradox of Astroglial Ca 2 + Signals at the Interface of Excitation and Inhibition. Front Cell Neurosci 2020; 14:609947. [PMID: 33324169 PMCID: PMC7726216 DOI: 10.3389/fncel.2020.609947] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 11/03/2020] [Indexed: 12/15/2022] Open
Abstract
Astroglial networks constitute a non-neuronal communication system in the brain and are acknowledged modulators of synaptic plasticity. A sophisticated set of transmitter receptors in combination with distinct secretion mechanisms enables astrocytes to sense and modulate synaptic transmission. This integrative function evolved around intracellular Ca2+ signals, by and large considered as the main indicator of astrocyte activity. Regular brain physiology meticulously relies on the constant reciprocity of excitation and inhibition (E/I). Astrocytes are metabolically, physically, and functionally associated to the E/I convergence. Metabolically, astrocytes provide glutamine, the precursor of both major neurotransmitters governing E/I in the central nervous system (CNS): glutamate and γ-aminobutyric acid (GABA). Perisynaptic astroglial processes are structurally and functionally associated with the respective circuits throughout the CNS. Astonishingly, in astrocytes, glutamatergic as well as GABAergic inputs elicit similar rises in intracellular Ca2+ that in turn can trigger the release of glutamate and GABA as well. Paradoxically, as gliotransmitters, these two molecules can thus strengthen, weaken or even reverse the input signal. Therefore, the net impact on neuronal network function is often convoluted and cannot be simply predicted by the nature of the stimulus itself. In this review, we highlight the ambiguity of astrocytes on discriminating and affecting synaptic activity in physiological and pathological state. Indeed, aberrant astroglial Ca2+ signaling is a key aspect of pathological conditions exhibiting compromised network excitability, such as epilepsy. Here, we gather recent evidence on the complexity of astroglial Ca2+ signals in health and disease, challenging the traditional, neuro-centric concept of segregating E/I, in favor of a non-binary, mutually dependent perspective on glutamatergic and GABAergic transmission.
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Affiliation(s)
- Laura C Caudal
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany
| | - Davide Gobbo
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany
| | - Anja Scheller
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany
| | - Frank Kirchhoff
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany
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27
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Ung K, Tepe B, Pekarek B, Arenkiel BR, Deneen B. Parallel astrocyte calcium signaling modulates olfactory bulb responses. J Neurosci Res 2020; 98:1605-1618. [PMID: 32426930 PMCID: PMC8147697 DOI: 10.1002/jnr.24634] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 03/27/2020] [Accepted: 04/10/2020] [Indexed: 12/17/2022]
Abstract
Astrocytes are the most abundant glial cell in the central nervous system. They modulate synaptic function through a variety of mechanisms, and yet remain relatively understudied with respect to overall neuronal circuit function. Exploiting the tractability of the mouse olfactory system, we manipulated astrocyte activity and examined how astrocytes modulate olfactory bulb responses. Toward this, we genetically targeted both astrocytes and neurons for in vivo widefield imaging of Ca2+ responses to odor stimuli. We found that astrocytes exhibited odor response maps that overlap with excitatory neuronal activity. By manipulating Ca2+ activity in astrocytes using chemical genetics we found that odor-evoked neuronal activity was reciprocally affected, suggesting that astrocyte activation inhibits neuronal odor responses. Subsequently, behavioral experiments revealed that astrocyte manipulations affect both odor detection threshold and discrimination, suggesting that astrocytes play an active role in olfactory sensory processing circuits. Together, these studies show that astrocyte calcium signaling contributes to olfactory behavior through modulation of sensory circuits.
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Affiliation(s)
- Kevin Ung
- Program in Developmental Biology, Houston, TX 77030, USA
| | - Burak Tepe
- Program in Developmental Biology, Houston, TX 77030, USA
| | - Brandon Pekarek
- Department of Molecular and Human Genetics, Houston, TX 77030, USA
| | - Benjamin R. Arenkiel
- Program in Developmental Biology, Houston, TX 77030, USA
- Department of Molecular and Human Genetics, Houston, TX 77030, USA
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX 77030, USA
| | - Benjamin Deneen
- Program in Developmental Biology, Houston, TX 77030, USA
- Center for Cell and Gene Therapy, Houston, TX 77030, USA
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX 77030, USA
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28
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Takata-Tsuji F, Chounlamountri N, Do LD, Philippot C, Novion Ducassou J, Couté Y, Ben Achour S, Honnorat J, Place C, Pascual O. Microglia modulate gliotransmission through the regulation of VAMP2 proteins in astrocytes. Glia 2020; 69:61-72. [PMID: 32633839 DOI: 10.1002/glia.23884] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 06/12/2020] [Accepted: 06/15/2020] [Indexed: 12/31/2022]
Abstract
Vesicular release is one of the release mechanisms of various signaling molecules. In neurons, the molecular machinery involved in vesicular release has been designed through evolution to trigger fast and synchronous release of neurotransmitters. Similar machinery with a slower kinetic and a slightly different molecular assembly allows astrocytes to release various transmitters such as adenosine triphosphate (ATP), glutamate, and D-serine. Astrocytes are important modulators of neurotransmission through gliotransmitter release. We recently demonstrated that microglia, another type of glia, release ATP to modulate synaptic transmission using astrocytes as intermediate. We now report that microglia regulate astrocytic gliotransmission through the regulation of SNARE proteins in astrocytes. Indeed, we found that gliotransmission triggered by P2Y1 agonist is impaired in slices from transgenic mice devoid of microglia. Using total internal reflection fluorescence imaging, we found that the vesicular release of gliotransmitter by astrocytes was different in cultures lacking microglia compared to vesicular release in astrocytes cocultured with microglia. Quantification of the kinetic of vesicular release indicates that the overall release appears to be faster in pure astrocyte cultures with more vesicles close to the membrane when compared to astrocytes cocultured with microglia. Finally, biochemical investigation of SNARE protein expression indicates an upregulation of VAMP2 in absence of microglia. Altogether, these results indicate that microglia seems to be involved in the regulation of an astrocytic phenotype compatible with proper gliotransmission. The mechanisms described in this study could be of importance for central nervous system diseases where microglia are activated.
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Affiliation(s)
- Fuyuko Takata-Tsuji
- INSERM U1217, CNRS UMR5310, Institut NeuroMyoGène, Lyon, France.,Université Claude Bernard Lyon 1 Lyon, Université de Lyon, Lyon, France.,Department of Pharmaceutical Care and Health Sciences, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka, Japan
| | - Naura Chounlamountri
- INSERM U1217, CNRS UMR5310, Institut NeuroMyoGène, Lyon, France.,Université Claude Bernard Lyon 1 Lyon, Université de Lyon, Lyon, France
| | - Le-Duy Do
- INSERM U1217, CNRS UMR5310, Institut NeuroMyoGène, Lyon, France.,Université Claude Bernard Lyon 1 Lyon, Université de Lyon, Lyon, France
| | - Camille Philippot
- INSERM U1217, CNRS UMR5310, Institut NeuroMyoGène, Lyon, France.,Université Claude Bernard Lyon 1 Lyon, Université de Lyon, Lyon, France
| | | | - Yohann Couté
- Université Grenoble Alpes, CEA, INSERM, IRIG, BGE, Grenoble, France
| | - Sarrah Ben Achour
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, Université PSL, CNRS, INSERM, Paris, France
| | - Jérôme Honnorat
- INSERM U1217, CNRS UMR5310, Institut NeuroMyoGène, Lyon, France.,Université Claude Bernard Lyon 1 Lyon, Université de Lyon, Lyon, France.,Centre maladies rares sur les syndromes neurologiques paranéoplasiques, hospices Civils de Lyon, Lyon, France
| | - Christophe Place
- ENS de Lyon, CNRS, Laboratoire de Physique, Université de Lyon, Lyon, France
| | - Olivier Pascual
- INSERM U1217, CNRS UMR5310, Institut NeuroMyoGène, Lyon, France.,Université Claude Bernard Lyon 1 Lyon, Université de Lyon, Lyon, France
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29
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Hoogstraaten RI, van Keimpema L, Toonen RF, Verhage M. Tetanus insensitive VAMP2 differentially restores synaptic and dense core vesicle fusion in tetanus neurotoxin treated neurons. Sci Rep 2020; 10:10913. [PMID: 32616842 PMCID: PMC7331729 DOI: 10.1038/s41598-020-67988-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 06/11/2020] [Indexed: 01/10/2023] Open
Abstract
The SNARE proteins involved in the secretion of neuromodulators from dense core vesicles (DCVs) in mammalian neurons are still poorly characterized. Here we use tetanus neurotoxin (TeNT) light chain, which cleaves VAMP1, 2 and 3, to study DCV fusion in hippocampal neurons and compare the effects on DCV fusion to those on synaptic vesicle (SV) fusion. Both DCV and SV fusion were abolished upon TeNT expression. Expression of tetanus insensitive (TI)-VAMP2 restored SV fusion in the presence of TeNT, but not DCV fusion. Expression of TI-VAMP1 or TI-VAMP3 also failed to restore DCV fusion. Co-transport assays revealed that both TI-VAMP1 and TI-VAMP2 are targeted to DCVs and travel together with DCVs in neurons. Furthermore, expression of the TeNT-cleaved VAMP2 fragment or a protease defective TeNT in wild type neurons did not affect DCV fusion and therefore cannot explain the lack of rescue of DCV fusion by TI-VAMP2. Finally, to test if two different VAMPs might both be required in the DCV secretory pathway, Vamp1 null mutants were tested. However, VAMP1 deficiency did not reduce DCV fusion. In conclusion, TeNT treatment combined with TI-VAMP2 expression differentially affects the two main regulated secretory pathways: while SV fusion is normal, DCV fusion is absent.
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Affiliation(s)
- Rein I Hoogstraaten
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit (VU) Amsterdam and University Medical Center Amsterdam, de Boelelaan 1087, 1018 HV, Amsterdam, The Netherlands
| | - Linda van Keimpema
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit (VU) Amsterdam and University Medical Center Amsterdam, de Boelelaan 1087, 1018 HV, Amsterdam, The Netherlands.,Sylics (Synaptologics BV), PO Box 71033, 1008 BA, Amsterdam, The Netherlands
| | - Ruud F Toonen
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit (VU) Amsterdam and University Medical Center Amsterdam, de Boelelaan 1087, 1018 HV, Amsterdam, The Netherlands.
| | - Matthijs Verhage
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit (VU) Amsterdam and University Medical Center Amsterdam, de Boelelaan 1087, 1018 HV, Amsterdam, The Netherlands. .,Clinical Genetics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit (VU) Amsterdam and University Medical Center Amsterdam, de Boelelaan 1087, 1018 HV, Amsterdam, The Netherlands.
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30
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Iacobas DA, Iacobas S, Stout RF, Spray DC. Cellular Environment Remodels the Genomic Fabrics of Functional Pathways in Astrocytes. Genes (Basel) 2020; 11:genes11050520. [PMID: 32392822 PMCID: PMC7290327 DOI: 10.3390/genes11050520] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 04/27/2020] [Accepted: 05/04/2020] [Indexed: 02/06/2023] Open
Abstract
We profiled the transcriptomes of primary mouse cortical astrocytes cultured alone or co-cultured with immortalized precursor oligodendrocytes (Oli-neu cells). Filters between the cell types prevented formation of hetero-cellular gap junction channels but allowed for free exchange of the two culture media. We previously reported that major functional pathways in the Oli-neu cells are remodeled by the proximity of non-touching astrocytes and that astrocytes and oligodendrocytes form a panglial transcriptomic syncytium in the brain. Here, we present evidence that the astrocyte transcriptome likewise changes significantly in the proximity of non-touching Oli-neu cells. Our results indicate that the cellular environment strongly modulates the transcriptome of each cell type and that integration in a heterocellular tissue changes not only the expression profile but also the expression control and networking of the genes in each cell phenotype. The significant decrease of the overall transcription control suggests that in the co-culture astrocytes are closer to their normal conditions from the brain. The Oli-neu secretome regulates astrocyte genes known to modulate neuronal synaptic transmission and remodels calcium, chemokine, NOD-like receptor, PI3K-Akt, and thyroid hormone signaling, as well as actin-cytoskeleton, autophagy, cell cycle, and circadian rhythm pathways. Moreover, the co-culture significantly changes the gene hierarchy in the astrocytes.
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Affiliation(s)
- Dumitru A Iacobas
- Personalized Genomics Laboratory, Center for Computational Systems Biology, RG Perry College of Engineering, Prairie View A&M University, Prairie View, TX 77446, USA
- DP Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY 10461, USA
- Correspondence: ; Tel.: +1-936-261-9926
| | - Sanda Iacobas
- Department of Pathology, New York Medical College, Valhalla, NY 10595, USA;
| | - Randy F Stout
- Department of Biomedical Sciences, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA;
| | - David C Spray
- DP Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY 10461, USA
- Department of Medicine, Albert Einstein College of Medicine, New York, NY 10461, USA;
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31
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Kofuji P, Araque A. G-Protein-Coupled Receptors in Astrocyte-Neuron Communication. Neuroscience 2020; 456:71-84. [PMID: 32224231 DOI: 10.1016/j.neuroscience.2020.03.025] [Citation(s) in RCA: 119] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 03/13/2020] [Accepted: 03/18/2020] [Indexed: 12/11/2022]
Abstract
Astrocytes, a major type of glial cell, are known to play key supportive roles in brain function, contributing to ion and neurotransmitter homeostasis, maintaining the blood-brain barrier and providing trophic and metabolic support for neurons. Besides these support functions, astrocytes are emerging as important elements in brain physiology through signaling exchange with neurons at tripartite synapses. Astrocytes express a wide variety of neurotransmitter transporters and receptors that allow them to sense and respond to synaptic activity. Principal among them are the G-protein-coupled receptors (GPCRs) in astrocytes because their activation by synaptically released neurotransmitters leads to mobilization of intracellular calcium. In turn, activated astrocytes release neuroactive substances called gliotransmitters, such as glutamate, GABA, and ATP/adenosine that lead to synaptic regulation through activation of neuronal GPCRs. In this review we will present and discuss recent evidence demonstrating the critical roles played by GPCRs in the bidirectional astrocyte-neuron signaling, and their crucial involvement in the astrocyte-mediated regulation of synaptic transmission and plasticity.
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Affiliation(s)
- Paulo Kofuji
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
| | - Alfonso Araque
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
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32
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Belov Kirdajova D, Kriska J, Tureckova J, Anderova M. Ischemia-Triggered Glutamate Excitotoxicity From the Perspective of Glial Cells. Front Cell Neurosci 2020; 14:51. [PMID: 32265656 PMCID: PMC7098326 DOI: 10.3389/fncel.2020.00051] [Citation(s) in RCA: 171] [Impact Index Per Article: 42.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 02/21/2020] [Indexed: 12/21/2022] Open
Abstract
A plethora of neurological disorders shares a final common deadly pathway known as excitotoxicity. Among these disorders, ischemic injury is a prominent cause of death and disability worldwide. Brain ischemia stems from cardiac arrest or stroke, both responsible for insufficient blood supply to the brain parenchyma. Glucose and oxygen deficiency disrupts oxidative phosphorylation, which results in energy depletion and ionic imbalance, followed by cell membrane depolarization, calcium (Ca2+) overload, and extracellular accumulation of excitatory amino acid glutamate. If tight physiological regulation fails to clear the surplus of this neurotransmitter, subsequent prolonged activation of glutamate receptors forms a vicious circle between elevated concentrations of intracellular Ca2+ ions and aberrant glutamate release, aggravating the effect of this ischemic pathway. The activation of downstream Ca2+-dependent enzymes has a catastrophic impact on nervous tissue leading to cell death, accompanied by the formation of free radicals, edema, and inflammation. After decades of “neuron-centric” approaches, recent research has also finally shed some light on the role of glial cells in neurological diseases. It is becoming more and more evident that neurons and glia depend on each other. Neuronal cells, astrocytes, microglia, NG2 glia, and oligodendrocytes all have their roles in what is known as glutamate excitotoxicity. However, who is the main contributor to the ischemic pathway, and who is the unsuspecting victim? In this review article, we summarize the so-far-revealed roles of cells in the central nervous system, with particular attention to glial cells in ischemia-induced glutamate excitotoxicity, its origins, and consequences.
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Affiliation(s)
- Denisa Belov Kirdajova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic (ASCR), Prague, Czechia.,Second Faculty of Medicine, Charles University, Prague, Czechia
| | - Jan Kriska
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic (ASCR), Prague, Czechia.,Second Faculty of Medicine, Charles University, Prague, Czechia
| | - Jana Tureckova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic (ASCR), Prague, Czechia
| | - Miroslava Anderova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic (ASCR), Prague, Czechia.,Second Faculty of Medicine, Charles University, Prague, Czechia
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33
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Lenk K, Satuvuori E, Lallouette J, Ladrón-de-Guevara A, Berry H, Hyttinen JAK. A Computational Model of Interactions Between Neuronal and Astrocytic Networks: The Role of Astrocytes in the Stability of the Neuronal Firing Rate. Front Comput Neurosci 2020; 13:92. [PMID: 32038210 PMCID: PMC6987305 DOI: 10.3389/fncom.2019.00092] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 12/20/2019] [Indexed: 12/12/2022] Open
Abstract
Recent research in neuroscience indicates the importance of tripartite synapses and gliotransmission mediated by astrocytes in neuronal system modulation. Although the astrocyte and neuronal network functions are interrelated, they are fundamentally different in their signaling patterns and, possibly, the time scales at which they operate. However, the exact nature of gliotransmission and the effect of the tripartite synapse function at the network level are currently elusive. In this paper, we propose a computational model of interactions between an astrocyte network and a neuron network, starting from tripartite synapses and spanning to a joint network level. Our model focuses on a two-dimensional setup emulating a mixed in vitro neuron-astrocyte cell culture. The model depicts astrocyte-released gliotransmitters exerting opposing effects on the neurons: increasing the release probability of the presynaptic neuron while hyperpolarizing the post-synaptic one at a longer time scale. We simulated the joint networks with various levels of astrocyte contributions and neuronal activity levels. Our results indicate that astrocytes prolong the burst duration of neurons, while restricting hyperactivity. Thus, in our model, the effect of astrocytes is homeostatic; the firing rate of the network stabilizes to an intermediate level independently of neuronal base activity. Our computational model highlights the plausible roles of astrocytes in interconnected astrocytic and neuronal networks. Our simulations support recent findings in neurons and astrocytes in vivo and in vitro suggesting that astrocytic networks provide a modulatory role in the bursting of the neuronal network.
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Affiliation(s)
- Kerstin Lenk
- BioMediTech, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Eero Satuvuori
- BioMediTech, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland.,Institute for Complex Systems (ISC), National Research Council (CNR), Sesto Fiorentino, Italy.,Department of Physics and Astronomy, University of Florence, Sesto Fiorentino, Italy.,Department of Human Movement Sciences, MOVE Research Institute Amsterdam, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Jules Lallouette
- INRIA, Villeurbanne, France.,LIRIS UMR5205, University of Lyon, Villeurbanne, France
| | | | - Hugues Berry
- INRIA, Villeurbanne, France.,LIRIS UMR5205, University of Lyon, Villeurbanne, France
| | - Jari A K Hyttinen
- BioMediTech, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
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34
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MacDonald AJ, Holmes FE, Beall C, Pickering AE, Ellacott KLJ. Regulation of food intake by astrocytes in the brainstem dorsal vagal complex. Glia 2019; 68:1241-1254. [PMID: 31880353 PMCID: PMC7187409 DOI: 10.1002/glia.23774] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 12/13/2019] [Accepted: 12/17/2019] [Indexed: 02/06/2023]
Abstract
A role for glial cells in brain circuits controlling feeding has begun to be identified with hypothalamic astrocyte signaling implicated in regulating energy homeostasis. The nucleus of the solitary tract (NTS), within the brainstem dorsal vagal complex (DVC), integrates vagal afferent information from the viscera and plays a role in regulating food intake. We hypothesized that astrocytes in this nucleus respond to, and influence, food intake. Mice fed high‐fat chow for 12 hr during the dark phase showed NTS astrocyte activation, reflected in an increase in the number (65%) and morphological complexity of glial‐fibrillary acidic protein (GFAP)‐immunoreactive cells adjacent to the area postrema (AP), compared to control chow fed mice. To measure the impact of astrocyte activation on food intake, we delivered designer receptors exclusively activated by designer drugs (DREADDs) to DVC astrocytes (encompassing NTS, AP, and dorsal motor nucleus of the vagus) using an adeno‐associated viral (AAV) vector (AAV‐GFAP‐hM3Dq_mCherry). Chemogenetic activation with clozapine‐N‐oxide (0.3 mg/kg) produced in greater morphological complexity in astrocytes and reduced dark‐phase feeding by 84% at 4 hr postinjection compared with vehicle treatment. hM3Dq‐activation of DVC astrocytes also reduced refeeding after an overnight fast (71% lower, 4 hr postinjection) when compared to AAV‐GFAP‐mCherry expressing control mice. DREADD‐mediated astrocyte activation did not impact locomotion. hM3Dq activation of DVC astrocytes induced c‐FOS in neighboring neuronal feeding circuits (including in the parabrachial nucleus). This indicates that NTS astrocytes respond to acute nutritional excess, are involved in the integration of peripheral satiety signals, and can reduce food intake when activated.
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Affiliation(s)
- Alastair J MacDonald
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, UK.,School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, UK
| | - Fiona E Holmes
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, UK
| | - Craig Beall
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Anthony E Pickering
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, UK.,Anaesthesia, Pain and Critical Care Sciences, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK
| | - Kate L J Ellacott
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, UK
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35
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The SNAP-25 Protein Family. Neuroscience 2019; 420:50-71. [DOI: 10.1016/j.neuroscience.2018.09.020] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Revised: 08/31/2018] [Accepted: 09/14/2018] [Indexed: 01/04/2023]
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36
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Quinn KE, Mackie DI, Caron KM. Emerging roles of atypical chemokine receptor 3 (ACKR3) in normal development and physiology. Cytokine 2019; 109:17-23. [PMID: 29903572 DOI: 10.1016/j.cyto.2018.02.024] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 02/21/2018] [Accepted: 02/21/2018] [Indexed: 01/16/2023]
Abstract
The discovery that atypical chemokine receptors (ACKRs) can initiate alternative signaling pathways rather than classical G-protein coupled receptor (GPCR) signaling has changed the paradigm of chemokine receptors and their roles in modulating chemotactic responses. The ACKR family has grown over the years, with discovery of new functions and roles in a variety of pathophysiological conditions. However, the extent to which these receptors regulate normal physiology is still continuously expanding. In particular, atypical chemokine receptor 3 (ACKR3) has proven to be an important receptor in mediating normal biological functions, including cardiac development and migration of cortical neurons. In this review, we illustrate the versatile and intriguing role of ACKR3 in physiology.
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Affiliation(s)
- K E Quinn
- Department of Cell Biology and Physiology, 111 MasonFarm Rd., 6312B MBRB CB# 7545, The University of North Carolina, Chapel Hill, NC 27599-7545, USA
| | - D I Mackie
- Department of Cell Biology and Physiology, 111 MasonFarm Rd., 6312B MBRB CB# 7545, The University of North Carolina, Chapel Hill, NC 27599-7545, USA
| | - K M Caron
- Department of Cell Biology and Physiology, 111 MasonFarm Rd., 6312B MBRB CB# 7545, The University of North Carolina, Chapel Hill, NC 27599-7545, USA.
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37
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Schwarz Y, Oleinikov K, Schindeldecker B, Wyatt A, Weißgerber P, Flockerzi V, Boehm U, Freichel M, Bruns D. TRPC channels regulate Ca2+-signaling and short-term plasticity of fast glutamatergic synapses. PLoS Biol 2019; 17:e3000445. [PMID: 31536487 PMCID: PMC6773422 DOI: 10.1371/journal.pbio.3000445] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 10/01/2019] [Accepted: 08/29/2019] [Indexed: 11/18/2022] Open
Abstract
Transient receptor potential (TRP) proteins form Ca2+-permeable, nonselective cation channels, but their role in neuronal Ca2+ homeostasis is elusive. In the present paper, we show that TRPC channels potently regulate synaptic plasticity by changing the presynaptic Ca2+-homeostasis of hippocampal neurons. Specifically, loss of TRPC1/C4/C5 channels decreases basal-evoked secretion, reduces the pool size of readily releasable vesicles, and accelerates synaptic depression during high-frequency stimulation (HFS). In contrast, primary TRPC5 channel-expressing neurons, identified by a novel TRPC5–τ-green fluorescent protein (τGFP) knockin mouse line, show strong short-term enhancement (STE) of synaptic signaling during HFS, indicating a key role of TRPC5 in short-term plasticity. Lentiviral expression of either TRPC1 or TRPC5 turns classic synaptic depression of wild-type neurons into STE, demonstrating that TRPCs are instrumental in regulating synaptic plasticity. Presynaptic Ca2+ imaging shows that TRPC activity strongly boosts synaptic Ca2+ dynamics, showing that TRPC channels provide an additional presynaptic Ca2+ entry pathway, which efficiently regulates synaptic strength and plasticity. Transient receptor potential (TRP) proteins can form non-selective cation channels, but their role in synaptic transmission is poorly understood. This study shows that calcium-permeable TRPC channels provide an additional calcium entry pathway at presynaptic sites and are efficient regulators of synaptic strength and plasticity.
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Affiliation(s)
- Yvonne Schwarz
- Institute for Physiology, Saarland University, CIPMM, Homburg/Saar, Germany
| | | | | | - Amanda Wyatt
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, Homburg/Saar, Germany
| | - Petra Weißgerber
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, Homburg/Saar, Germany
| | - Veit Flockerzi
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, Homburg/Saar, Germany
| | - Ulrich Boehm
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, Homburg/Saar, Germany
| | - Marc Freichel
- Institute of Pharmacology, University of Heidelberg, Heidelberg, Germany
| | - Dieter Bruns
- Institute for Physiology, Saarland University, CIPMM, Homburg/Saar, Germany
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Abstract
The suprachiasmatic nucleus (SCN) of the hypothalamus is remarkable. Despite numbering only about 10,000 neurons on each side of the third ventricle, the SCN is our principal circadian clock, directing the daily cycles of behaviour and physiology that set the tempo of our lives. When this nucleus is isolated in organotypic culture, its autonomous timing mechanism can persist indefinitely, with precision and robustness. The discovery of the cell-autonomous transcriptional and post-translational feedback loops that drive circadian activity in the SCN provided a powerful exemplar of the genetic specification of complex mammalian behaviours. However, the analysis of circadian time-keeping is moving beyond single cells. Technical and conceptual advances, including intersectional genetics, multidimensional imaging and network theory, are beginning to uncover the circuit-level mechanisms and emergent properties that make the SCN a uniquely precise and robust clock. However, much remains unknown about the SCN, not least the intrinsic properties of SCN neurons, its circuit topology and the neuronal computations that these circuits support. Moreover, the convention that the SCN is a neuronal clock has been overturned by the discovery that astrocytes are an integral part of the timepiece. As a test bed for examining the relationships between genes, cells and circuits in sculpting complex behaviours, the SCN continues to offer powerful lessons and opportunities for contemporary neuroscience.
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Astrocytic p38α MAPK drives NMDA receptor-dependent long-term depression and modulates long-term memory. Nat Commun 2019; 10:2968. [PMID: 31273206 PMCID: PMC6609681 DOI: 10.1038/s41467-019-10830-9] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 06/04/2019] [Indexed: 11/08/2022] Open
Abstract
NMDA receptor-dependent long-term depression (LTD) in the hippocampus is a well-known form of synaptic plasticity that has been linked to different cognitive functions. The core mechanism for this form of plasticity is thought to be entirely neuronal. However, we now demonstrate that astrocytic activity drives LTD at CA3-CA1 synapses. We have found that LTD induction enhances astrocyte-to-neuron communication mediated by glutamate, and that Ca2+ signaling and SNARE-dependent vesicular release from the astrocyte are required for LTD expression. In addition, using optogenetic techniques, we show that low-frequency astrocytic activation, in the absence of presynaptic activity, is sufficient to induce postsynaptic AMPA receptor removal and LTD expression. Using cell-type-specific gene deletion, we show that astrocytic p38α MAPK is required for the increased astrocytic glutamate release and astrocyte-to-neuron communication during low-frequency stimulation. Accordingly, removal of astrocytic (but not neuronal) p38α abolishes LTD expression. Finally, this mechanism modulates long-term memory in vivo. How astrocytes influence neuronal plasticity remains unclear, as they are typically considered as modulators of core mechanisms driven by neuronal components. Here, authors show that Long-term depression (LTD) induction in the hippocampus triggers calcium signaling in the astrocyte and enhances SNARE-dependent astrocytic glutamate release, which is then responsible for the activation of postsynaptic NMDA receptors and synaptic depression.
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40
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Souza DG, Almeida RF, Souza DO, Zimmer ER. The astrocyte biochemistry. Semin Cell Dev Biol 2019; 95:142-150. [PMID: 30951895 DOI: 10.1016/j.semcdb.2019.04.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Revised: 03/19/2019] [Accepted: 04/01/2019] [Indexed: 02/06/2023]
Abstract
Astrocytes are a unique and dynamic subtype of glial cells in the central nervous system (CNS). Understanding their biochemical reactions and their influence in the surrounding cells is extremely important in the neuroscience field. They exert important influence in the neurotransmission, ionic homeostasis and also release neuroactive molecules termed gliotransmitters. Additionally, they metabolize, store and release metabolic substrates to meet high brain energy requirements. In this review, we highlight the main biochemical reactions regarding energy metabolism that take place in astrocytes. Special attention is given to synthesis, storage and catabolism of glucose, release of lactate, oxidation of fatty acids, production of ketone bodies, and metabolism of the main neurotransmitters, glutamate and GABA. The recent findings allow proposing these cells as key players controlling the energetic homeostasis in the CNS.
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Affiliation(s)
- Débora G Souza
- Graduate Program in Biological Sciences: Biochemistry, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Roberto F Almeida
- Graduate Program in Biological Sciences: Biochemistry, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil; Exact and Biological Sciences Institute, Biological Sciences Department, Federal University of Ouro Preto, Ouro Preto, Brazil
| | - Diogo O Souza
- Graduate Program in Biological Sciences: Biochemistry, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil; Department of Biochemistry, UFRGS, Porto Alegre, Brazil
| | - Eduardo R Zimmer
- Graduate Program in Biological Sciences: Biochemistry, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil; Department of Pharmacology, UFRGS, Porto Alegre, Brazil; Graduate Program in Biological Sciences: Pharmacology and Therapeutics, UFRGS, Porto Alegre, Brazil; Brain Institute of Rio Grande do Sul (BraIns), Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Brazil.
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41
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Mederos S, Hernández-Vivanco A, Ramírez-Franco J, Martín-Fernández M, Navarrete M, Yang A, Boyden ES, Perea G. Melanopsin for precise optogenetic activation of astrocyte-neuron networks. Glia 2019; 67:915-934. [PMID: 30632636 DOI: 10.1002/glia.23580] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 11/28/2018] [Accepted: 11/30/2018] [Indexed: 12/11/2022]
Abstract
Optogenetics has been widely expanded to enhance or suppress neuronal activity and it has been recently applied to glial cells. Here, we have used a new approach based on selective expression of melanopsin, a G-protein-coupled photopigment, in astrocytes to trigger Ca2+ signaling. Using the genetically encoded Ca2+ indicator GCaMP6f and two-photon imaging, we show that melanopsin is both competent to stimulate robust IP3-dependent Ca2+ signals in astrocyte fine processes, and to evoke an ATP/Adenosine-dependent transient boost of hippocampal excitatory synaptic transmission. Additionally, under low-frequency light stimulation conditions, melanopsin-transfected astrocytes can trigger long-term synaptic changes. In vivo, melanopsin-astrocyte activation enhances episodic-like memory, suggesting melanopsin as an optical tool that could recapitulate the wide range of regulatory actions of astrocytes on neuronal networks in behaving animals. These results describe a novel approach using melanopsin as a precise trigger for astrocytes that mimics their endogenous G-protein signaling pathways, and present melanopsin as a valuable optical tool for neuron-glia studies.
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Affiliation(s)
- Sara Mederos
- Department of Functional and Systems Neurobiology, Instituto Cajal, CSIC, Madrid, Spain
| | | | - Jorge Ramírez-Franco
- Department of Functional and Systems Neurobiology, Instituto Cajal, CSIC, Madrid, Spain
| | | | - Marta Navarrete
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain
| | - Aimei Yang
- Media Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Edward S Boyden
- Media Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts.,McGovern Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Gertrudis Perea
- Department of Functional and Systems Neurobiology, Instituto Cajal, CSIC, Madrid, Spain
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42
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Mederos S, González-Arias C, Perea G. Astrocyte-Neuron Networks: A Multilane Highway of Signaling for Homeostatic Brain Function. Front Synaptic Neurosci 2018; 10:45. [PMID: 30542276 PMCID: PMC6277918 DOI: 10.3389/fnsyn.2018.00045] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2018] [Accepted: 11/12/2018] [Indexed: 12/22/2022] Open
Abstract
Research on glial cells over the past 30 years has confirmed the critical role of astrocytes in pathophysiological brain states. However, most of our knowledge about astrocyte physiology and of the interactions between astrocytes and neurons is based on the premises that astrocytes constitute a homogeneous cell type, without considering the particular properties of the circuits or brain nuclei in which the astrocytes are located. Therefore, we argue that more-sophisticated experiments are required to elucidate the specific features of astrocytes in different brain regions, and even within different layers of a particular circuit. Thus, in addition to considering the diverse mechanisms used by astrocytes to communicate with neurons and synaptic partners, it is necessary to take into account the cellular heterogeneity that likely contributes to the outcomes of astrocyte-neuron signaling. In this review article, we briefly summarize the current data regarding the anatomical, molecular and functional properties of astrocyte-neuron communication, as well as the heterogeneity within this communication.
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Affiliation(s)
- Sara Mederos
- Department of Functional and Systems Neurobiology, Instituto Cajal (IC), CSIC, Madrid, Spain
| | - Candela González-Arias
- Department of Functional and Systems Neurobiology, Instituto Cajal (IC), CSIC, Madrid, Spain
| | - Gertrudis Perea
- Department of Functional and Systems Neurobiology, Instituto Cajal (IC), CSIC, Madrid, Spain
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43
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Durkee CA, Araque A. Diversity and Specificity of Astrocyte-neuron Communication. Neuroscience 2018; 396:73-78. [PMID: 30458223 DOI: 10.1016/j.neuroscience.2018.11.010] [Citation(s) in RCA: 191] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 11/08/2018] [Accepted: 11/09/2018] [Indexed: 01/30/2023]
Abstract
Astrocytes are emerging as important players in synaptic function, and, consequently, on brain function and animal behavior. According to the Tripartite Synapse concept, astrocytes are integral elements involved in synaptic function. They establish bidirectional communication with neurons, whereby they respond to synaptically released neurotransmitters and, in turn, release gliotransmitters that influence neuronal and synaptic activity. Accumulating evidence is revealing that the mechanisms and functional consequences of astrocyte-neuron signaling are more complex than originally thought. Furthermore, astrocyte-neuron signaling is not based on broad, unspecific interaction; rather, it is a synapse-, cell- and circuit-specific phenomenon that presents a high degree of complexity. This diversity and complexity of astrocyte-synapse interactions greatly enhance the degrees of freedom of the neural circuits and the consequent computational power of the neural systems.
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Affiliation(s)
- Caitlin A Durkee
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Alfonso Araque
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
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44
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Shaib AH, Staudt A, Harb A, Klose M, Shaaban A, Schirra C, Mohrmann R, Rettig J, Becherer U. Paralogs of the Calcium-Dependent Activator Protein for Secretion Differentially Regulate Synaptic Transmission and Peptide Secretion in Sensory Neurons. Front Cell Neurosci 2018; 12:304. [PMID: 30254567 PMCID: PMC6141663 DOI: 10.3389/fncel.2018.00304] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 08/21/2018] [Indexed: 12/29/2022] Open
Abstract
The two paralogs of the calcium-dependent activator protein for secretion (CAPS) are priming factors for synaptic vesicles (SVs) and neuropeptide containing large dense-core vesicles (LDCVs). Yet, it is unclear whether CAPS1 and CAPS2 regulate exocytosis of these two vesicle types differentially in dorsal root ganglion (DRG) neurons, wherein synaptic transmission and neuropeptide release are of equal importance. These sensory neurons transfer information from the periphery to the spinal cord (SC), releasing glutamate as the primary neurotransmitter, with co-transmission via neuropeptides in a subset of so called peptidergic neurons. Neuropeptides are key components of the information-processing machinery of pain perception and neuropathic pain generation. Here, we compared the ability of CAPS1 and CAPS2 to support priming of both vesicle types in single and double knock-out mouse (DRG) neurons using a variety of high-resolution live cell imaging methods. While CAPS1 was localized to synapses of all DRG neurons and promoted synaptic transmission, CAPS2 was found exclusively in peptidergic neurons and mediated LDCV exocytosis. Intriguingly, ectopic expression of CAPS2 empowered non-peptidergic neurons to drive LDCV fusion, thereby identifying CAPS2 as an essential molecular determinant for peptidergic signaling. Our results reveal that these distinct functions of both CAPS paralogs are based on their differential subcellular localization in DRG neurons. Our data suggest a major role for CAPS2 in neuropathic pain via control of neuropeptide release.
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Affiliation(s)
- Ali H. Shaib
- Department of Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Angelina Staudt
- Department of Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Ali Harb
- Department of Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
- ZHMB Junior Group, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Margarete Klose
- Department of Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Ahmed Shaaban
- ZHMB Junior Group, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Claudia Schirra
- Department of Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Ralf Mohrmann
- ZHMB Junior Group, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Jens Rettig
- Department of Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Ute Becherer
- Department of Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
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45
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Gómez-Gonzalo M, Zehnder T, Requie LM, Bezzi P, Carmignoto G. Insights into the release mechanism of astrocytic glutamate evoking in neurons NMDA receptor-mediated slow depolarizing inward currents. Glia 2018; 66:2188-2199. [DOI: 10.1002/glia.23473] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 04/27/2018] [Accepted: 05/25/2018] [Indexed: 12/19/2022]
Affiliation(s)
- Marta Gómez-Gonzalo
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences; University of Padova; Padova Italy
| | - Tamara Zehnder
- Department of Fundamental Neurosciences; University of Lausanne; Lausanne Switzerland
| | - Linda Maria Requie
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences; University of Padova; Padova Italy
| | - Paola Bezzi
- Department of Fundamental Neurosciences; University of Lausanne; Lausanne Switzerland
| | - Giorgio Carmignoto
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences; University of Padova; Padova Italy
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46
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Flanagan B, McDaid L, Wade J, Wong-Lin K, Harkin J. A computational study of astrocytic glutamate influence on post-synaptic neuronal excitability. PLoS Comput Biol 2018; 14:e1006040. [PMID: 29659572 PMCID: PMC5919689 DOI: 10.1371/journal.pcbi.1006040] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 04/26/2018] [Accepted: 02/15/2018] [Indexed: 11/18/2022] Open
Abstract
The ability of astrocytes to rapidly clear synaptic glutamate and purposefully release the excitatory transmitter is critical in the functioning of synapses and neuronal circuits. Dysfunctions of these homeostatic functions have been implicated in the pathology of brain disorders such as mesial temporal lobe epilepsy. However, the reasons for these dysfunctions are not clear from experimental data and computational models have been developed to provide further understanding of the implications of glutamate clearance from the extracellular space, as a result of EAAT2 downregulation: although they only partially account for the glutamate clearance process. In this work, we develop an explicit model of the astrocytic glutamate transporters, providing a more complete description of the glutamate chemical potential across the astrocytic membrane and its contribution to glutamate transporter driving force based on thermodynamic principles and experimental data. Analysis of our model demonstrates that increased astrocytic glutamate content due to glutamine synthetase downregulation also results in increased postsynaptic quantal size due to gliotransmission. Moreover, the proposed model demonstrates that increased astrocytic glutamate could prolong the time course of glutamate in the synaptic cleft and enhances astrocyte-induced slow inward currents, causing a disruption to the clarity of synaptic signalling and the occurrence of intervals of higher frequency postsynaptic firing. Overall, our work distilled the necessity of a low astrocytic glutamate concentration for reliable synaptic transmission of information and the possible implications of enhanced glutamate levels as in epilepsy. The role of astrocytes in the excitability and hyperexcitability of neurons is a subject which has gained a lot of attention, particularly in the pathology of neurological disorders including epilepsy. Although not completely understood, the control of glutamate homeostasis is believed to play a role in paroxysmal neuronal hyperexcitability known to precede seizure activity. We have developed a computational model which explores two of the astrocytic homeostatic mechanisms, namely glutamate clearance and gliotransmission, and connect them with a common controlling factor, astrocytic cytoplasmic glutamate concentration. In our model simulations we demonstrate both a slower clearance rate of synaptic glutamate and enhanced astrocytic glutamate release where cytoplasmic glutamate is elevated, both of which contribute to high frequency neuronal firing and conditions for seizure generation. We also describe a viable role for astrocytes as a “high pass” filter, where astrocytic activation in the form of intracellular calcium oscillations is possible for only a certain range of presynaptic neuronal firing rates, the lower bound of the range being reduced where astrocytic glutamate is elevated. In physiological terms this perhaps indicates not only neuronal but also astrocytic glutamate-mediated excitation in the neural-astrocytic network.
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Affiliation(s)
- Bronac Flanagan
- Intelligent Systems Research Centre, University of Ulster, Magee Campus, Derry~Londonderry, Northern Ireland, United Kingdom
- * E-mail:
| | - Liam McDaid
- Intelligent Systems Research Centre, University of Ulster, Magee Campus, Derry~Londonderry, Northern Ireland, United Kingdom
| | - John Wade
- Intelligent Systems Research Centre, University of Ulster, Magee Campus, Derry~Londonderry, Northern Ireland, United Kingdom
| | - KongFatt Wong-Lin
- Intelligent Systems Research Centre, University of Ulster, Magee Campus, Derry~Londonderry, Northern Ireland, United Kingdom
| | - Jim Harkin
- Intelligent Systems Research Centre, University of Ulster, Magee Campus, Derry~Londonderry, Northern Ireland, United Kingdom
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47
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Mayorquin LC, Rodriguez AV, Sutachan JJ, Albarracín SL. Connexin-Mediated Functional and Metabolic Coupling Between Astrocytes and Neurons. Front Mol Neurosci 2018; 11:118. [PMID: 29695954 PMCID: PMC5905222 DOI: 10.3389/fnmol.2018.00118] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 03/27/2018] [Indexed: 01/24/2023] Open
Abstract
The central nervous system (CNS) requires sophisticated regulation of neuronal activity. This modulation is partly accomplished by non-neuronal cells, characterized by the presence of transmembrane gap junctions (GJs) and hemichannels (HCs). This allows small molecule diffusion to guarantee neuronal synaptic activity and plasticity. Astrocytes are metabolically and functionally coupled to neurons by the uptake, binding and recycling of neurotransmitters. In addition, astrocytes release metabolites, such as glutamate, glutamine, D-serine, adenosine triphosphate (ATP) and lactate, regulating synaptic activity and plasticity by pre- and postsynaptic mechanisms. Uncoupling neuroglial communication leads to alterations in synaptic transmission that can be detrimental to neuronal circuit function and behavior. Therefore, understanding the pathways and mechanisms involved in this intercellular communication is fundamental for the search of new targets that can be used for several neurological disease treatments. This review will focus on molecular mechanisms mediating physiological and pathological coupling between astrocytes and neurons through GJs and HCs.
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Affiliation(s)
- Lady C Mayorquin
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia
| | - Andrea V Rodriguez
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia
| | - Jhon-Jairo Sutachan
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia
| | - Sonia L Albarracín
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia
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48
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Critical role for Annexin A7 in secondary brain injury mediated by its phosphorylation after experimental intracerebral hemorrhage in rats. Neurobiol Dis 2018; 110:82-92. [DOI: 10.1016/j.nbd.2017.11.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 10/14/2017] [Accepted: 11/27/2017] [Indexed: 01/27/2023] Open
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49
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Jha MK, Kim JH, Song GJ, Lee WH, Lee IK, Lee HW, An SSA, Kim S, Suk K. Functional dissection of astrocyte-secreted proteins: Implications in brain health and diseases. Prog Neurobiol 2017; 162:37-69. [PMID: 29247683 DOI: 10.1016/j.pneurobio.2017.12.003] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Revised: 10/23/2017] [Accepted: 12/08/2017] [Indexed: 02/07/2023]
Abstract
Astrocytes, which are homeostatic cells of the central nervous system (CNS), display remarkable heterogeneity in their morphology and function. Besides their physical and metabolic support to neurons, astrocytes modulate the blood-brain barrier, regulate CNS synaptogenesis, guide axon pathfinding, maintain brain homeostasis, affect neuronal development and plasticity, and contribute to diverse neuropathologies via secreted proteins. The identification of astrocytic proteome and secretome profiles has provided new insights into the maintenance of neuronal health and survival, the pathogenesis of brain injury, and neurodegeneration. Recent advances in proteomics research have provided an excellent catalog of astrocyte-secreted proteins. This review categorizes astrocyte-secreted proteins and discusses evidence that astrocytes play a crucial role in neuronal activity and brain function. An in-depth understanding of astrocyte-secreted proteins and their pathways is pivotal for the development of novel strategies for restoring brain homeostasis, limiting brain injury/inflammation, counteracting neurodegeneration, and obtaining functional recovery.
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Affiliation(s)
- Mithilesh Kumar Jha
- Department of Pharmacology, Brain Science and Engineering Institute, BK21 Plus KNU Biomedical Convergence Program, Kyungpook National University School of Medicine, Daegu, Republic of Korea; Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Jong-Heon Kim
- Department of Pharmacology, Brain Science and Engineering Institute, BK21 Plus KNU Biomedical Convergence Program, Kyungpook National University School of Medicine, Daegu, Republic of Korea
| | - Gyun Jee Song
- Department of Pharmacology, Brain Science and Engineering Institute, BK21 Plus KNU Biomedical Convergence Program, Kyungpook National University School of Medicine, Daegu, Republic of Korea
| | - Won-Ha Lee
- School of Life Sciences, BK21 Plus KNU Creative BioResearch Group, Kyungpook National University, Daegu, Republic of Korea
| | - In-Kyu Lee
- Department of Internal Medicine, Division of Endocrinology and Metabolism, Kyungpook National University School of Medicine, Daegu, Republic of Korea
| | - Ho-Won Lee
- Department of Neurology, Brain Science and Engineering Institute, Kyungpook National University School of Medicine, Daegu, Republic of Korea
| | - Seong Soo A An
- Department of BioNano Technology, Gachon University, Gyeonggi-do, Republic of Korea
| | - SangYun Kim
- Department of Neurology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Gyeonggi-do, Republic of Korea
| | - Kyoungho Suk
- Department of Pharmacology, Brain Science and Engineering Institute, BK21 Plus KNU Biomedical Convergence Program, Kyungpook National University School of Medicine, Daegu, Republic of Korea.
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50
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Glia: Pulling in opposite directions. Nat Rev Neurosci 2017; 18:643. [PMID: 29042686 DOI: 10.1038/nrn.2017.133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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