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Ge YX, Shang B, Chen WZ, Lu Y, Wang J. Adult-onset of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome with hypothyroidism and psychiatric disorders. eNeurologicalSci 2017; 6:16-20. [PMID: 29260009 PMCID: PMC5721577 DOI: 10.1016/j.ensci.2016.11.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 11/02/2016] [Indexed: 01/11/2023] Open
Abstract
Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) is a clinical syndrome associated with mitochondrial disorders (MIDs). This report illustrates a case of MELAS syndrome with hypothyroidism and psychiatric disorders, which is different from the common clinical manifestations of MELAS syndrome, such as exercise intolerance, migraine-like headaches, hearing loss and seizures etc. There are considerable interests in the possibility that mitochondrial dysfunction may play a role in the pathogenesis of endocrine dysfunctions and psychiatric disorders in MELAS syndrome.
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Key Words
- ADC, apparent diffusion coefficient
- ATP, adenosine triphosphate
- BAEP, Brainstem auditory evoked potential
- CSF, Cerebral spinal fluid
- CT, Computed tomography
- Cr, creatine
- DNA, deoxyribonucleic acid
- DWI, diffusion-weighted image
- Endocrine dysfunction
- FLAIR, fluid-attenuated inversion recovery
- MELAS
- MELAS, mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes
- MIDs, Mitochondrial disorders
- MRC, mitochondrial respiratory chain
- MRI, magnetic resonance imaging
- Mitochondrial disorders
- NAA, N-acetyl aspartic acid
- OB, oligoclonal bands
- Psychiatric disorders
- RFLP, restriction fragment length polymorphism
- ROI, region of interest
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Affiliation(s)
- Yu-Xing Ge
- Department of Neurology, Tongji University Affiliated Tenth People's Hospital, 200072 Shanghai, PR China
| | - Bo Shang
- Department of Neurology, Tongji University Affiliated Tenth People's Hospital, 200072 Shanghai, PR China
| | - Wen-Zhen Chen
- Department of Neurology, Tongji University Affiliated Tenth People's Hospital, 200072 Shanghai, PR China
| | - You Lu
- Department of Neurology, Tongji University Affiliated Tenth People's Hospital, 200072 Shanghai, PR China
| | - Jue Wang
- Department of Neurology, Tongji University Affiliated Tenth People's Hospital, 200072 Shanghai, PR China
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Lecca D, Fumagalli M, Ceruti S, Abbracchio MP. Intertwining extracellular nucleotides and their receptors with Ca2+ in determining adult neural stem cell survival, proliferation and final fate. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0433. [PMID: 27377726 DOI: 10.1098/rstb.2015.0433] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/31/2016] [Indexed: 02/07/2023] Open
Abstract
In the central nervous system (CNS), during both brain and spinal cord development, purinergic and pyrimidinergic signalling molecules (ATP, UTP and adenosine) act synergistically with peptidic growth factors in regulating the synchronized proliferation and final specification of multipotent neural stem cells (NSCs) to neurons, astrocytes or oligodendrocytes, the myelin-forming cells. Some NSCs still persist throughout adulthood in both specific 'neurogenic' areas and in brain and spinal cord parenchyma, retaining the potentiality to generate all the three main types of adult CNS cells. Once CNS anatomical structures are defined, purinergic molecules participate in calcium-dependent neuron-to-glia communication and also control the behaviour of adult NSCs. After development, some purinergic mechanisms are silenced, but can be resumed after injury, suggesting a role for purinergic signalling in regeneration and self-repair also via the reactivation of adult NSCs. In this respect, at least three different types of adult NSCs participate in the response of the adult brain and spinal cord to insults: stem-like cells residing in classical neurogenic niches, in particular, in the ventricular-subventricular zone (V-SVZ), parenchymal oligodendrocyte precursor cells (OPCs, also known as NG2-glia) and parenchymal injury-activated astrocytes (reactive astrocytes). Here, we shall review and discuss the purinergic regulation of these three main adult NSCs, with particular focus on how and to what extent modulation of intracellular calcium levels by purinoceptors is mandatory to determine their survival, proliferation and final fate.This article is part of the themed issue 'Evolution brings Ca(2+) and ATP together to control life and death'.
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Affiliation(s)
- Davide Lecca
- Laboratory of Molecular and Cellular Pharmacology of Purinergic Transmission, Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, 20133 Milan, Italy
| | - Marta Fumagalli
- Laboratory of Molecular and Cellular Pharmacology of Purinergic Transmission, Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, 20133 Milan, Italy
| | - Stefania Ceruti
- Laboratory of Molecular and Cellular Pharmacology of Purinergic Transmission, Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, 20133 Milan, Italy
| | - Maria P Abbracchio
- Laboratory of Molecular and Cellular Pharmacology of Purinergic Transmission, Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, 20133 Milan, Italy
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Marinelli C, Bertalot T, Zusso M, Skaper SD, Giusti P. Systematic Review of Pharmacological Properties of the Oligodendrocyte Lineage. Front Cell Neurosci 2016; 10:27. [PMID: 26903812 PMCID: PMC4751280 DOI: 10.3389/fncel.2016.00027] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 01/25/2016] [Indexed: 12/12/2022] Open
Abstract
Oligodendrogenesis and oligodendrocyte precursor maturation are essential processes during the course of central nervous system development, and lead to the myelination of axons. Cells of the oligodendrocyte lineage are generated in the germinal zone from migratory bipolar oligodendrocyte precursor cells (OPCs), and acquire cell surface markers as they mature and respond specifically to factors which regulate proliferation, migration, differentiation, and survival. Loss of myelin underlies a wide range of neurological disorders, some of an autoimmune nature—multiple sclerosis probably being the most prominent. Current therapies are based on the use of immunomodulatory agents which are likely to promote myelin repair (remyelination) indirectly by subverting the inflammatory response, aspects of which impair the differentiation of OPCs. Cells of the oligodendrocyte lineage express and are capable of responding to a diverse array of ligand-receptor pairs, including neurotransmitters and nuclear receptors such as γ-aminobutyric acid, glutamate, adenosine triphosphate, serotonin, acetylcholine, nitric oxide, opioids, prostaglandins, prolactin, and cannabinoids. The intent of this review is to provide the reader with a synopsis of our present state of knowledge concerning the pharmacological properties of the oligodendrocyte lineage, with particular attention to these receptor-ligand (i.e., neurotransmitters and nuclear receptor) interactions that can influence oligodendrocyte migration, proliferation, differentiation, and myelination, and an appraisal of their therapeutic potential. For example, many promising mediators work through Ca2+ signaling, and the balance between Ca2+ influx and efflux can determine the temporal and spatial properties of oligodendrocytes (OLs). Moreover, Ca2+ signaling in OPCs can influence not only differentiation and myelination, but also process extension and migration, as well as cell death in mature mouse OLs. There is also evidence that oligodendroglia exhibit Ca2+ transients in response to electrical activity of axons for activity-dependent myelination. Cholinergic antagonists, as well as endocannabinoid-related lipid-signaling molecules target OLs. An understanding of such pharmacological pathways may thus lay the foundation to allow its leverage for therapeutic benefit in diseases of demyelination.
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Affiliation(s)
- Carla Marinelli
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua Padua, Italy
| | - Thomas Bertalot
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua Padua, Italy
| | - Morena Zusso
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua Padua, Italy
| | - Stephen D Skaper
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua Padua, Italy
| | - Pietro Giusti
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua Padua, Italy
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Cheli VT, Santiago González DA, Spreuer V, Paez PM. Voltage-gated Ca2+ entry promotes oligodendrocyte progenitor cell maturation and myelination in vitro. Exp Neurol 2014; 265:69-83. [PMID: 25542980 DOI: 10.1016/j.expneurol.2014.12.012] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2014] [Revised: 11/14/2014] [Accepted: 12/12/2014] [Indexed: 11/16/2022]
Abstract
We have previously shown that the expression of voltage-operated Ca(++) channels (VOCCs) is highly regulated in the oligodendroglial lineage and is essential for proper oligodendrocyte progenitor cell (OPC) migration. Here we assessed the role of VOCCs, in particular the L-type, in oligodendrocyte maturation. We used pharmacological treatments to activate or block voltage-gated Ca(++) uptake and siRNAs to specifically knock down the L-type VOCC in primary cultures of mouse OPCs. Activation of VOCCs by plasma membrane depolarization increased OPC morphological differentiation as well as the expression of mature oligodendrocyte markers. On the contrary, inhibition of L-type Ca(++) channels significantly delayed OPC development. OPCs transfected with siRNAs for the Cav1.2 subunit that conducts L-type Ca(++) currents showed reduce Ca(++) influx by ~75% after plasma membrane depolarization, indicating that Cav1.2 is heavily involved in mediating voltage-operated Ca(++) entry in OPCs. Cav1.2 knockdown induced a decrease in the proportion of oligodendrocytes that expressed myelin proteins, and an increase in cells that retained immature oligodendrocyte markers. Moreover, OPC proliferation, but not cell viability, was negatively affected after L-type Ca(++) channel knockdown. Additionally, we have tested the ability of L-type VOCCs to facilitate axon-glial interaction during the first steps of myelin formation using an in vitro co-culture system of OPCs with cortical neurons. Unlike control OPCs, Cav1.2 deficient oligodendrocytes displayed a simple morphology, low levels of myelin proteins expression and appeared to be less capable of establishing contacts with neurites and axons. Together, this set of in vitro experiments characterizes the involvement of L-type VOCCs on OPC maturation as well as the role played by these Ca(++) channels during the early phases of myelination.
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Affiliation(s)
- V T Cheli
- Hunter James Kelly Research Institute, Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, SUNY, University at Buffalo, NYS Center of Excellence, 701 Ellicott St., Buffalo, NY 14203, USA
| | - D A Santiago González
- Hunter James Kelly Research Institute, Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, SUNY, University at Buffalo, NYS Center of Excellence, 701 Ellicott St., Buffalo, NY 14203, USA
| | - V Spreuer
- Hunter James Kelly Research Institute, Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, SUNY, University at Buffalo, NYS Center of Excellence, 701 Ellicott St., Buffalo, NY 14203, USA
| | - P M Paez
- Hunter James Kelly Research Institute, Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, SUNY, University at Buffalo, NYS Center of Excellence, 701 Ellicott St., Buffalo, NY 14203, USA.
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Paez PM, Cheli VT, Ghiani CA, Spreuer V, Handley VW, Campagnoni AT. Golli myelin basic proteins stimulate oligodendrocyte progenitor cell proliferation and differentiation in remyelinating adult mouse brain. Glia 2012; 60:1078-93. [PMID: 22447683 DOI: 10.1002/glia.22336] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 03/09/2012] [Indexed: 02/06/2023]
Abstract
Golli myelin basic proteins are necessary for normal myelination, acting via voltage and store-dependent Ca(2+) entry at multiple steps during oligodendrocyte progenitor cell (OPC) development. To date nothing is known regarding the role of golli proteins in demyelination or remyelination events. Here the effects of golli ablation and overexpression in myelin loss and recovery were examined using the cuprizone (CPZ) model of demyelination/remyelination. We found severe demyelination in the corpus callosum (CC) of golli-overexpressing mice (JOE) during the CPZ treatment, which was accompanied by an increased number of reactive astrocytes and activation of microglia/macrophages. During demyelination of JOE brains, a significant increase in the number of proliferating OPCs was found in the CC as well as in the subventricular zone, and our data indicate that these progenitors matured and fully remyelinated the CC of JOE animals after CPZ withdrawal. In contrast, in the absence of golli (golli-KO mice) delayed myelin loss associated with a smaller immune response, and a lower number of OPCs was found in these mice during the CPZ treatment. Furthermore, incomplete remyelination was observed after CPZ removal in large areas of the CC of golli-KO mice, reflecting irregular recovery of the oligodendrocyte population and subsequent myelin sheath formation. Our findings demonstrate that golli proteins sensitize mature oligodendrocytes to CPZ-induced demyelination, while at the same time stimulate the proliferation/recruitment of OPCs during demyelination, resulting in accelerated remyelination.
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Affiliation(s)
- Pablo M Paez
- Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-7332, USA.
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Stout RF, Parpura V. Voltage-gated calcium channel types in cultured C. elegans CEPsh glial cells. Cell Calcium 2011; 50:98-108. [PMID: 21684004 DOI: 10.1016/j.ceca.2011.05.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2011] [Revised: 05/12/2011] [Accepted: 05/15/2011] [Indexed: 12/20/2022]
Abstract
The four cephalic sensilla sheath (CEPsh) glial cells are important for development of the nervous system of Caenorhabditis elegans. Whether these invertebrate glia can generate intracellular Ca(2+) increases, a hallmark of mammalian glial cell excitability, is not known. To address this issue, we developed a transgenic worm with the specific co-expression of genetically encoded red fluorescent protein and green Ca(2+) sensor in CEPsh glial cells. This allowed us to identify CEPsh cells in culture and monitor their Ca(2+) dynamics. We show that CEPsh glial cells, in response to depolarization, generate various intracellular Ca(2+) increases mediated by voltage-gated Ca(2+) channels (VGCCs). Using a pharmacological approach, we find that the L-type is the preponderant VGCC type mediating Ca(2+) dynamics. Additionally, using a genetic approach we demonstrate that mutations in three known VGCC α(1)-subunit genes, cca-1, egl-19 and unc-2, can affect Ca(2+) dynamics of CEPsh glial cells. We suggest that VGCC-mediated Ca(2+) dynamics in the CEPsh glial cells are complex and display heterogeneity. These findings will aid understanding of how CEPsh glial cells contribute to the operation of the C. elegans nervous system.
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Affiliation(s)
- Randy F Stout
- Department of Neurobiology, Center for Glial Biology in Medicine, Atomic Force Microscopy & Nanotechnology Laboratories, Civitan International Research Center, Evelyn F. McKnight Brain Institute, University of Alabama, Birmingham, AL 35294, USA
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Paez P, Fulton D, Colwell C, Campagnoni A. Voltage-operated Ca2+and Na+channels in the oligodendrocyte lineage. J Neurosci Res 2009; 87:3259-66. [DOI: 10.1002/jnr.21938] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Targeted overexpression of a golli-myelin basic protein isoform to oligodendrocytes results in aberrant oligodendrocyte maturation and myelination. ASN Neuro 2009; 1:AN20090029. [PMID: 19715557 PMCID: PMC2785512 DOI: 10.1042/an20090029] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Recently, several in vitro studies have shown that the golli–myelin basic proteins regulate Ca2+ homoeostasis in OPCs (oligodendrocyte precursor cells) and immature OLs (oligodendrocytes), and that a number of the functions of these cells are affected by cellular levels of the golli proteins. To determine the influence of golli in vivo on OL development and myelination, a transgenic mouse was generated in which the golli isoform J37 was overexpressed specifically within OLs and OPCs. The mouse, called JOE (J37-overexpressing), is severely hypomyelinated between birth and postnatal day 50. During this time, it exhibits severe intention tremors that gradually abate at later ages. After postnatal day 50, ultrastructural studies and Northern and Western blot analyses indicate that myelin accumulates in the brain, but never reaches normal levels. Several factors appear to underlie the extensive hypomyelination. In vitro and in vivo experiments indicate that golli overexpression causes a significant delay in OL maturation, with accumulation of significantly greater numbers of pre-myelinating OLs that fail to myelinate axons during the normal myelinating period. Immunohistochemical studies with cell death and myelin markers indicate that JOE OLs undergo a heightened and extended period of cell death and are unable to effectively myelinate until 2 months after birth. The results indicate that increased levels of golli in OPC/OLs delays myelination, causing significant cell death of OLs particularly in white matter tracts. The results provide in vivo evidence for a significant role of the golli proteins in the regulation of maturation of OLs and normal myelination.
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Golli myelin basic proteins regulate oligodendroglial progenitor cell migration through voltage-gated Ca2+ influx. J Neurosci 2009; 29:6663-76. [PMID: 19458236 DOI: 10.1523/jneurosci.5806-08.2009] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Migration of oligodendrocyte progenitor cells (OPCs) from proliferative zones to their final location in the brain is an essential step in nervous system development. Golli proteins, products of the myelin basic protein gene, can modulate voltage-gated Ca(2+) uptake in OPCs during process extension and retraction. Given the importance of process extension/retraction on movement, the consequences of golli expression on OPC migration were examined in vivo and in vitro using time-lapse imaging of isolated OPCs and acute brain slice preparations from golli KO and golli J37 overexpressing mice (JOE). The results indicated that golli stimulated migration, and this enhanced motility was associated with increases in the activity of voltage operated Ca(2+) channels (VOCCs). Activation of VOCCs by high K(+) resulted in a significant increase in the migration speed of JOE OPCs versus control cells and golli-mediated modulation of OPC migration disappeared in the presence of VOCC antagonists. During migration, OPCs generated Ca(2+) oscillations that were dependent on voltage-calcium influx and both the amplitude and frequency of these Ca(2+) transients correlated positively with the rate of cell movement under a variety of pharmacological treatments. The Ca(2+) transient amplitude and the rate of cell movement were significantly lower in KO cells and significantly higher in JOE cells suggesting that the presence of golli promotes OPC migration by increasing the size of voltage-mediated Ca(2+) oscillations. These data define a new molecule that regulates Ca(2+) homeostasis in OPCs, and are the first to demonstrate that voltage-gated Ca(2+) channels can regulate an OPC function, such as migration.
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Regulation of store-operated and voltage-operated Ca2+ channels in the proliferation and death of oligodendrocyte precursor cells by golli proteins. ASN Neuro 2009; 1:AN20090003. [PMID: 19570024 PMCID: PMC2695580 DOI: 10.1042/an20090003] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
OPCs (oligodendrocyte precursor cells) express golli proteins which, through regulation of Ca2+ influx, appear to be important in OPC process extension/retraction and migration. The aim of the present study was to examine further the role of golli in regulating OPC development. The effects of golli ablation and overexpression were examined in primary cultures of OPCs prepared from golli-KO (knockout) and JOE (golli J37-overexpressing) mice. In OPCs lacking golli, or overexpressing golli, differentiation induced by growth factor withdrawal was impaired. Proliferation analysis in the presence of PDGF (platelet-derived growth factor), revealed that golli enhanced the mitogen-stimulated proliferation of OPCs through activation of SOCCs (store-operated Ca2+ channels). PDGF treatment induced a biphasic increase in OPC intracellular Ca2+, and golli specifically increased Ca2+ influx during the second SOCC-dependent phase that followed the initial release of Ca2+ from intracellular stores. This store-operated Ca2+ uptake appeared to be essential for cell division, since specific SOCC antagonists completely blocked the effects of PDGF and golli on OPC proliferation. Additionally, in OPCs overexpressing golli, increased cell death was observed after mitogen withdrawal. This phenomenon could be prevented by exposure to VOCC (voltage-operated Ca2+ channel) blockers, indicating that the effect of golli on cell death involved increased Ca2+ influx through VOCCs. The results showed a clear effect of golli on OPC development and support a role for golli in modulating multiple Ca2+-regulatory events through VOCCs and SOCCs. Our results also suggest that PDGF engagement of its receptor resulting in OPC proliferation proceeds through activation of SOCCs.
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Paez PM, Spreuer V, Handley V, Feng JM, Campagnoni C, Campagnoni AT. Increased expression of golli myelin basic proteins enhances calcium influx into oligodendroglial cells. J Neurosci 2007; 27:12690-9. [PMID: 18003849 PMCID: PMC6673339 DOI: 10.1523/jneurosci.2381-07.2007] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2007] [Revised: 09/28/2007] [Accepted: 10/01/2007] [Indexed: 11/21/2022] Open
Abstract
The myelin basic protein (MBP) gene encodes two families of proteins: the classic MBP constituents of myelin and the golli-MBPs, the function of which is less well understood. Previous work suggests that golli proteins may play a role in Ca2+ homeostasis in oligodendrocytes (OLs) and in T-cells. Overexpression of golli in OL cell lines induces elaboration of sheets and processes. Live imaging of these cells revealed a rapid retraction of the processes and sheets after depolarization with high K+. This phenomenon was associated with a significant increase in [Ca2+]int without changes in cell viability. The results indicated that golli produced its effect through Ca2+ influx, rather than Ca2+ release from intracellular stores. Furthermore, a specific [Ca2+]int chelator (BAPTA) or Cd2+, a specific blocker of voltage-operated Ca2+ channels, abolished the ability of golli to promote process extension in a dose-dependent manner. Analysis of the golli protein identified a myristoylation site at the C terminus of the golli domain, which was essential for the action of golli on Ca2+ influx, suggesting that binding of golli to the plasma membrane is important for modulating Ca2+ homeostasis. High-resolution spatiotemporal analysis along N19 processes revealed higher-amplitude local Ca2+ influx in regions with elevated levels of golli. These findings suggest a key role for golli proteins in regulating voltage-gated Ca2+ channels in OLs during process remodeling. Our observations are consistent with the hypothesis that golli proteins, as a part of a protein complex, modulate Ca2+ influx at the plasma membrane and along OL processes.
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Affiliation(s)
- Pablo M. Paez
- Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles Geffen Medical School, Los Angeles, California 90095
| | - Vilma Spreuer
- Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles Geffen Medical School, Los Angeles, California 90095
| | - Vance Handley
- Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles Geffen Medical School, Los Angeles, California 90095
| | - Ji-Ming Feng
- Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles Geffen Medical School, Los Angeles, California 90095
| | - Celia Campagnoni
- Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles Geffen Medical School, Los Angeles, California 90095
| | - Anthony T. Campagnoni
- Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles Geffen Medical School, Los Angeles, California 90095
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Benjamins JA, Nedelkoska L. Cyclic GMP-dependent pathways protect differentiated oligodendrocytes from multiple types of injury. Neurochem Res 2006; 32:321-9. [PMID: 17191140 DOI: 10.1007/s11064-006-9187-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Accepted: 09/27/2006] [Indexed: 12/13/2022]
Abstract
The cyclic GMP analog 8-bromo-cyclic GMP (8-Br-cGMP) protects differentiated murine oligodendrocytes (OLs) from caspase-mediated death initiated by staurosporine, thapsigargin or kainate. Caspase-independent death caused by high levels of NO is also partially prevented by 8-Br-cGMP. Inhibitors of protein kinase G (cGMP-dependent protein kinase, cGK) reversed protection, supporting involvement of cGK. Since NO stimulates soluble guanylate cyclase, increasing cGMP, we treated OLs with low levels of NO and observed partial protection against thapsigargin, staurosporine and kainate. Two inhibitors of mitochondrial pore transition (MPT), cyclosporin A and bongkrekic acid, were poorly protective, indicating that cGMP is not acting primarily by blocking MPT. 8Br-cGMP was more effective than 8Br-cAMP in protecting against staurosporine or release of intracellular Ca(++) by thapsigargin. The cAMP analog exhibited little or no protection against kainate or high levels of NO. Thus cGK signaling is more effective than protein kinase A or phosphodiesterase 3 signaling in preventing OL death.
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Affiliation(s)
- Joyce A Benjamins
- Department of Neurology, Wayne State University School of Medicine, 1228 Elliman Building, 421 E. Canfield Avenue, Detroit, MI 48201, USA.
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Benjamins JA, Nedelkoska L, George EB. Protection of mature oligodendrocytes by inhibitors of caspases and calpains. Neurochem Res 2003; 28:143-52. [PMID: 12587672 DOI: 10.1023/a:1021612615554] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Mature mouse oligodendrocytes (OLs) are susceptible to death in demyelinating diseases such as multiple sclerosis and in brain injury following neurotrauma, ischemia, or stroke. To understand mechanisms leading to death of mature OLs and develop strategies for protection, we utilized cultures of mature mouse OLs to investigate the role of caspases and calpains in OL cell death mediated by different mechanisms. The agents used were (i) staurosporine, which induces apoptotic death via inhibition of protein kinases; (ii) kainate, which activates non-NMDA glutamate receptors; (iii) thapsigargin, which releases intracellular calcium stores; and (iv) SNAP, which releases active NO species and causes necrotic cell death. Inhibitors blocking primary effector caspases (including caspase 3), the FAS (death receptor)-mediated initiator caspases (including caspase 8), and stress-induced caspases (including caspase 9), were tested for their protective effects. Inhibition of caspases 3, 8, and 9 each robustly protected OLs following insult with staurosporine, thapsigargin, or kainate when added at optimal times. The time of addition of the inhibitors for maximal protection varied with the agent, from 1 h of preincubation before addition of staurosporine to 6 h after addition of kainate. Much less protection was seen for the NO generator SNAP under any condition. The role of calcium in OL death in each model was investigated by chelating extracellular Ca++ with EGTA, and by inhibiting the Ca++-activated calpain proteases. Calcium chelation did not protect against staurosporine, but decreased OL death initiated by kainate, thapsigargin, or NO. The calpain inhibitors PD150606 and calpain inhibitor I protected from cell death initiated by staurosporine, kainate, and thapsigargin, but not from cell death initiated by the NO donor SNAP.
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Affiliation(s)
- Joyce A Benjamins
- Department of Neurology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
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James G, Butt AM. P2Y and P2X purinoceptor mediated Ca2+ signalling in glial cell pathology in the central nervous system. Eur J Pharmacol 2002; 447:247-60. [PMID: 12151016 DOI: 10.1016/s0014-2999(02)01756-9] [Citation(s) in RCA: 189] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Activation of purinoceptors by extracellular ATP is an important component of the glial response to injury in the central nervous system (CNS). ATP has been shown to evoke raised cytosolic [Ca(2+)] in astrocytes, oligodendrocytes, and microglia, the three major glial cell types in the CNS. Glial cells express a heterogenous collection of metabotropic P2Y and ionotropic P2X purinoceptors, which respectively mobilise Ca(2+) from intracellular stores and trigger Ca(2+) influx across the plasmalemma. It is likely that different receptors have distinct roles in glial cell physiology and pathology. Our studies on optic nerve glia in situ indicate that P2Y(1) and P2Y(2/4) receptors are activated at low ATP concentrations, suggesting they are the predominant purinoceptors mediating physiological Ca(2+) signalling. Glia also express P2X(1) and P2X(3) purinoceptors, which mediate fast, rapidly desensitising current and may also be important in signalling. At high concentrations, such as occur in CNS injury, ATP induces large and prolonged increases in glial [Ca(2+)](i) with a primary role for P2Y purinoceptors and inositol trisphosphate (IP(3))-dependent release of Ca(2+) from intracellular stores. In addition, we found that high concentrations of ATP activated a significant P2X component that did not desensitise or saturate and was dependent on extracellular Ca(2+). These are characteristic properties of the P2X(7) subtype, and we provide in situ evidence that application of the P2X(7) receptor agonist benzoyl-benzoyl ATP (BzATP) evokes raised [Ca(2+)](i) in optic nerve glia, and that the dye YO-PRO-1, which passes through pore-forming P2X(7) receptors, is taken up by astrocytes, oligodendrocytes and microglia. Glia also express P2X(2) and P2X(4) receptors that are also pore-forming in the presence of sustained high ATP concentrations and which may also be important in the glial injury response. There is evidence that activation of P2 purinoceptors is a key step in triggering reactive changes in glial cells, including expression of immediate early genes, induction of extracellular signal regulated kinase and cyclooxygenase-2, synthesis of phospholipase A(2), release of arachidonic acid, production of prostaglandins and release of interleukins. We show that the ATP-mediated increase in glial [Ca(2+)](i) is potentiated by arachidonic acid and reduced by the inhibition of phospholipase A(2) inhibition. Together, the results implicate ATP as a primary signalling molecule in glial cells and indicate specific roles for P2Y and P2X purinoceptors in glial cell pathology.
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Affiliation(s)
- Greg James
- Centre for Neuroscience Research, GKT Guy's Campus, King's College London, Hodgkin Building, SE1 1UL, London, UK
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James G, Butt AM. P2X and P2Y purinoreceptors mediate ATP-evoked calcium signalling in optic nerve glia in situ. Cell Calcium 2001; 30:251-9. [PMID: 11587549 DOI: 10.1054/ceca.2001.0232] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
It is known that ATP acts as an extracellular messenger mediating Ca2+ signalling in glial cells. Here, the mechanisms involved in the ATP-evoked increase in glial [Ca2+]i were studied in situ, in the acutely isolated rat optic nerve. ATP and agonists for P2X (a,b-metATP) and P2Y (2MeSATP) purinoreceptors triggered raised glial [Ca2+]i, and there was no significant difference between cells identified morphologically as astrocytes and oligodendrocytes. Dose-response curves indicated that P2Y receptors were activated at nanomolar concentrations, whereas P2X purinoreceptors were only activated above 10 microM. The rank order of potency for several agonists indicated optic nerve glia expressed heterogeneous purinoreceptors, with P2Y1< or = P2Y2/4< or = P2X. The ATP evoked increase in [Ca2+]i was reversibly blocked by the P2X/Y purinoreceptor antagonist suramin (100 microM) and markedly reduced by thapsigargin (10 microM), which blocks IP3-dependent release of Ca2+ from intracellular stores. Removal of extracellular Ca2+ reduced the ATP evoked increase in [Ca2+]i and completely blocked its recovery, indicating that refilling of intracellular stores was ultimately dependent on Ca2+ influx from the extracellular milieu. The results implicate ATP as an important signal in CNS white matter astrocytes and oligodendrocytes in situ, and indicate that metabotropic P2Y purinoreceptors mobilize intracellular Ca2+ at physiological concentrations of ATP, whereas ionotropic P2X purinoreceptors induce Ca2+ influx across the plasmalemma only at high concentrations of ATP, such as occur following CNS injury.
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Affiliation(s)
- G James
- Neural Damage & Repair Research Group, Centre for Neuroscience Research, King's College London, London, London, UK
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Konat GW, Mouzannar R, Bai H. Higher order chromatin degradation in glial cells: the role of calcium. Neurochem Int 2001; 39:179-86. [PMID: 11434975 DOI: 10.1016/s0197-0186(01)00030-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Higher order chromatin degradation (HOCD), i.e. the scission of nuclear chromatin loops at the matrix attachment regions (MARs), is a hallmark of programmed cell death. We have previously demonstrated that hydrogen peroxide (H(2)O(2)) induces rapid HOCD in cultured oligodendrocytes generating two subpopulations of DNA fragments of >or=400 and 50-200 kb. In the present study, we examined the involvement of calcium in this process. HOCD was induced in primary rat oligodendrocytes by exposure to 1 mM H(2)O(2) and assessed by field inversion gel electrophoresis with and without S1 endonuclease digestion, to detect single and double stranded fragmentation, respectively. Chelating intracellular calcium with BAPTA/AM prior to H(2)O(2) exposure inhibited HOCD in a dose-dependent manner. Complete inhibition of HOCD was attained with 50 muM BAPTA/AM. The pretreatment of cells with desferroxamine mesylate, which may lower intracellular calcium levels, also resulted in a profound inhibition of HOCD, but the initial chromatin digestion into >or=400 kb single stranded DNA fragments was unaffected. Neither removing extracellular calcium nor blocking calcium release from intracellular stores with TMB-8 affected HOCD. Moreover, increasing intracellular calcium with A23187 calcium ionophore did not induce HOCD. Subsequent study in nuclei purified from C6 glioma cells revealed that the endonuclease responsible for HOCD is calcium-independent, but is magnesium-dependent. Magnesium-induced HOCD was not affected by the removal of calcium from nuclei with EGTA, but was practically abrogated in nuclei prepared from BAPTA/AM-pretreated cells. These results indicate that although H(2)O(2)-induced HOCD is not directly mediated by an increase of intracellular calcium concentration, normal resting levels of intracellular calcium are required for the maintenance of MAR-associated endonuclease in an active form.
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Affiliation(s)
- G W Konat
- Department of Neurobiology and Anatomy, West Virginia University School of Medicine, 4052 HSN, P.O. Box 9128, Morgantown, WV 26506-9128, USA.
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Abstract
Intracellular Ca2+ is the key signal that regulates the efficacy of neurotransmitter release and synaptic plasticity in neurons but is also an important second messenger involved in the signal transduction and modulation of gene expression in both excitable and non-excitable cells. Glial cells, including cells of oligodendroglial (OLG) lineage, are capable of responding to extracellular stimuli via changes in the intracellular Ca2+. This review article focuses on the mechanisms of Ca2+ signalling in cells of OLG lineage with the goal of providing the basis for understanding the relevance of receptor- and non-receptor-mediated signalling to oligodendroglial development, myelination, and demyelination. Conclusions to date indicate that cells of OLG lineage exhibit remarkable plasticity with regard to the expression of ion channels and receptors linked to Ca2+ signalling and that perturbation of [Ca2](i) homeostasis contributes to the pathogenesis of demyelinating diseases.
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Affiliation(s)
- B Soliven
- Department of Neurology and Comm. on Neurobiology, The Brain Research Institute, University of Chicago, 5841 S. Maryland, Chicago, IL 60637, USA.
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Althaus HH, Richter-Landsberg C. Glial cells as targets and producers of neurotrophins. INTERNATIONAL REVIEW OF CYTOLOGY 2000; 197:203-77. [PMID: 10761118 DOI: 10.1016/s0074-7696(00)97005-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Glial cells fulfill important tasks within the neural network of the central and peripheral nervous systems. The synthesis and secretion of various polypeptidic factors (cytokines) and a number of receptors, with which glial cells are equipped, allow them to communicate with their environment. Evidence has accumulated during recent years that neurotrophins play an important role not only for neurons but also for glial cells. This brief update of some morphological, immunocytochemical, and biochemical characteristics of glial cell lineages conveys our present knowledge about glial cells as targets and producers of neurotrophins under normal and pathological conditions. The chapter discusses the presence of neurotrophin receptors on glial cells, glial cells as producers of neurotrophins, signaling pathways downstream Trk and p75NTR, and the significance of neurotrophins and their receptors for glial cells during development, in cell death and survival, and in neurological disorders.
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Affiliation(s)
- H H Althaus
- AG Neural Regeneration, Max Planck Institute for Experimental Medicine, Göttingen, Germany
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Althaus HH, Klöppner S, Rohde G, Parvizi N, Schwartz P, Brück W, Holtz W. Myelin basic protein induces cell death of mature pig oligodendrocytes in vitro and produces demyelination in vivo. Neurosci Lett 2000; 283:77-80. [PMID: 10729638 DOI: 10.1016/s0304-3940(00)00920-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two methods prevail at present in producing demyelinated areas in the central nervous system. One uses the detergent-like effect of lysolecithin, the other is based on a cell killing effect of ethidium bromide plus x-irradiation. Unwanted side-effects are inherent in both methods. Based on the fact that myelin basic protein (MBP) kills adult pig oligodendrocytes but almost no astrocytes in vitro, we have used MBP for creating demyelinated areas in the centrum semiovale of the pig brain. These lesions are characterized by a loss of oligodendrocytes and myelin, a preservation of axons and astrocytes, and by the presence of macrophages. Thus, this type of lesion might present an alternative option for studying the fate of transplanted myelinating cells.
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Affiliation(s)
- H H Althaus
- Max-Planck-Institute for Experimental Medicine, AG Neural Regeneration, H. Reinstrasse 3, 37075, Göttingen, Germany.
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Baerwald KD, Corbin JG, Popko B. Major histocompatibility complex heavy chain accumulation in the endoplasmic reticulum of oligodendrocytes results in myelin abnormalities. J Neurosci Res 2000. [DOI: 10.1002/(sici)1097-4547(20000115)59:2<160::aid-jnr2>3.0.co;2-k] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Studzinski DM, Callahan RE, Benjamins JA. Increased intracellular calcium alters myelin gene expression in the N20.1 oligodendroglial cell line. J Neurosci Res 1999. [DOI: 10.1002/(sici)1097-4547(19990901)57:5<633::aid-jnr5>3.0.co;2-i] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
Previous investigations have shown that phorbol esters stimulate process extension in oligodendrocytes (OL), likely by the activation of protein kinase C (PKC). In this report, we demonstrate that treatment of OL with 4beta-phorbol-12, 13-dibutyrate (PDB; 0.1-1 microM) resulted in an increase in intracellular Ca2+ concentration ([Ca2+]i) from 94+/-2 nM (mean+/-S.E.M.) to 244+/-10 nM. This increase was produced by Ca2+ influx through a La3+-insensitive pathway. Changes in [Ca2+]i were also produced by modifying the extracellular Ca2+ concentration ([Ca2+]o) where [Ca2+]i was increased by elevations in [Ca2+]o. In parallel experiments we found that increased [Ca2+]o alone, without concurrent phorbol ester application, resulted in increased OL process extension as determined by the percent of OL with long processes (greater than 3 times the cell body diameter). These results demonstrate that increasing [Ca2+]o stimulates OL process outgrowth. Furthermore, both elevations in [Ca2+]o and PDB exposure increase [Ca2+]i, suggesting that some of the effects of phorbol esters on OL process extension are likely mediated by changes in [Ca2+]i.
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Affiliation(s)
- A S Yoo
- Division of Neurology, Department of Medicine, University of British Columbia, VHHSC, UBC site, 2211 Wesbrook Mall, Vancouver, BC, Canada
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Abstract
In the human demyelinating disorder multiple sclerosis, and its animal model experimental allergic encephalomyelitis, there is a breakdown of the blood-brain barrier and an infiltration of immune cells into the CNS. Infiltrating T lymphocytes and macrophages are believed to be key mediators of the disease process. Considerable circumstantial and experimental evidence has suggested that the pleiotropic cytokine interferon gamma (IFN-gamma), which is exclusively expressed by T cells and natural killer cells, is a deleterious component of the immune response in these disorders. When experimentally introduced into the CNS IFN-gamma promotes many of the pathological changes that occur in immune-mediated demyelinating disorders. In vitro, this cytokine elicits a number of effects on oligodendrocytes, including cell death. The harmful actions of IFN-gamma on CNS myelin are likely mediated through direct effects on the myelinating cells, as well as through the activation of macrophages and microglia. In this review we summarize relevant studies concerning the action of IFN-gamma in demyelinating disorders and discuss possible mechanisms for the observed effects.
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Affiliation(s)
- B Popko
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, 27599, USA.
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Nedelkoska L, Benjamins JA. Binding of cholera toxin B subunit: a surface marker for murine microglia but not oligodendrocytes or astrocytes. J Neurosci Res 1998; 53:605-12. [PMID: 9726431 DOI: 10.1002/(sici)1097-4547(19980901)53:5<605::aid-jnr10>3.0.co;2-#] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
GM1 ganglioside is a receptor for the B subunit of cholera toxin. In lymphocytes, B subunit elicits an influx of extracellular Ca++ (Dixon et al., 1987). To investigate this signaling pathway in glia, we assessed the presence of GM1 ganglioside on the surface of cultured murine central nervous system (CNS) glia by binding of fluorescein-labeled B subunit. B subunit binding was compared to binding of peanut agglutinin, wheat germ agglutinin, and Bandeiraea (Griffonia) simplicifolia lectin (BSL)I, a microglial marker. Antibodies to glial fibrillary acidic protein, A007/O4 antigens, and galactocerebroside were used to identify astrocytes, immature oligodendrocytes (OLs) and mature OLs, respectively. Binding patterns differed based on cell type and developmental stage. Wheat germ and peanut agglutinins bound to the surface of microglia, astrocytes, and immature OLs; neither lectin bound to any significant extent to the surface of membrane sheets of mature OLs, although wheat germ agglutinin was rapidly endocytosed. Cells identified as microglia by BSL I binding and morphology were the only cells to stain brightly on the surface with B subunit. Thus, surface GM1 ganglioside appears to be a highly enriched marker for microglia in these mixed glial cultures. The effects of B subunit on intracellular Ca++ were examined by laser cytometry in glial cultures loaded with Indo-1. No Ca++ responses were observed in microglia. Mature OLs were examined for Ca++ responses to B subunit before and after surface levels of GM1 ganglioside were increased by incubation with exogenous GM1 ganglioside. Again, no Ca++ responses were observed. Thus, cultured microglia and mature OLs do not have the GM1-mediated signal transduction pathway seen in lymphocytes. However, the presence of GM1 ganglioside on microglia may play a role in giving rise to antibodies to this glycolipid in some CNS inflammatory diseases.
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Affiliation(s)
- L Nedelkoska
- Department of Neurology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
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Abstract
Glial cells respond to various electrical, mechanical, and chemical stimuli, including neurotransmitters, neuromodulators, and hormones, with an increase in intracellular Ca2+ concentration ([Ca2+]i). The increases exhibit a variety of temporal and spatial patterns. These [Ca2+]i responses result from the coordinated activity of a number of molecular cascades responsible for Ca2+ movement into or out of the cytoplasm either by way of the extracellular space or intracellular stores. Transplasmalemmal Ca2+ movements may be controlled by several types of voltage- and ligand-gated Ca(2+)-permeable channels as well as Ca2+ pumps and a Na+/Ca2+ exchanger. In addition, glial cells express various metabotropic receptors coupled to intracellular Ca2+ stores through the intracellular messenger inositol 1,4,5-triphosphate. The interplay of different molecular cascades enables the development of agonist-specific patterns of Ca2+ responses. Such agonist specificity may provide a means for intracellular and intercellular information coding. Calcium signals can traverse gap junctions between glial cells without decrement. These waves can serve as a substrate for integration of glial activity. By controlling gap junction conductance, Ca2+ waves may define the limits of functional glial networks. Neuronal activity can trigger [Ca2+]i signals in apposed glial cells, and moreover, there is some evidence that glial [Ca2+]i waves can affect neurons. Glial Ca2+ signaling can be regarded as a form of glial excitability.
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Affiliation(s)
- A Verkhratsky
- Department of Cellular Neurosciences, Max-Delbrück Center for Molecular Medicine, Berlin-Buch, Germany
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Althaus HH, Hempel R, Klöppner S, Engel J, Schmidt-Schultz T, Kruska L, Heumann R. Nerve growth factor signal transduction in mature pig oligodendrocytes. J Neurosci Res 1997; 50:729-42. [PMID: 9418961 DOI: 10.1002/(sici)1097-4547(19971201)50:5<729::aid-jnr10>3.0.co;2-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
It has previously been shown that nerve growth factor (NGF) is of functional significance for mature pig oligodendrocytes (OLs) in culture. The present data give evidence for the expression of TrkA, the so-called high-affinity NGF receptor, and of p75NTR, the so-called low-affinity NGF receptor. TrkA is upregulated during culturing, in contrast to the p75 receptor. Exposure of OLs to NGF induces an autophosphorylation of TrkA via its intrinsic tyrosine kinase. K-252a inhibits the TrkA autophosphorylation, which reduces the OL process formation to control levels. To the tyrosine-phosphorylated sites of TrkA several proteins, such as phospholipase C-gamma1, the adaptor protein SHC, the phosphotyrosine phosphatase SH-PTP2 (SYP) associate via their SH2 phosphotase SH-PTP2 domain. The association of SHC to TrkA is shown by co-immunoprecipitation. Indirect evidence for a possible activation of PLC-gamma1 is given by an NGF-induced increase of oligodendroglial [Ca2+]i. Downstream from TrkA, a mitogen-activated protein kinase cascade, which includes Erk1 and Erk2, is operating. An in-gel myelin basic protein kinase assay revealed that NGF activates predominantly Erk1. Finally, it is shown that NGF stimulates expression of c-fos.
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Affiliation(s)
- H H Althaus
- Max-Planck-Institute for Experimental Medicine, AG Neural Regeneration, Göttingen, Germany.
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