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Wolin IAV, Heinrich IA, Nascimento APM, Welter PG, Sosa LDV, De Paul AL, Zanotto-Filho A, Nedel CB, Lima LD, Osterne VJS, Pinto-Junior VR, Nascimento KS, Cavada BS, Leal RB. ConBr lectin modulates MAPKs and Akt pathways and triggers autophagic glioma cell death by a mechanism dependent upon caspase-8 activation. Biochimie 2020; 180:186-204. [PMID: 33171216 DOI: 10.1016/j.biochi.2020.11.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 10/26/2020] [Accepted: 11/02/2020] [Indexed: 01/03/2023]
Abstract
Glioblastoma multiforme is the most aggressive type of glioma, with limited treatment and poor prognosis. Despite some advances over the last decade, validation of novel and selective antiglioma agents remains a challenge in clinical pharmacology. Prior studies have shown that leguminous lectins may exert various biological effects, including antitumor properties. Accordingly, this study aimed to evaluate the mechanisms underlying the antiglioma activity of ConBr, a lectin extracted from the Canavalia brasiliensis seeds. ConBr at lower concentrations inhibited C6 glioma cell migration while higher levels promoted cell death dependent upon carbohydrate recognition domain (CRD) structure. ConBr increased p38MAPK and JNK and decreased ERK1/2 and Akt phosphorylation. Moreover, ConBr inhibited mTORC1 phosphorylation associated with accumulation of autophagic markers, such as acidic vacuoles and LC3 cleavage. Inhibition of early steps of autophagy with 3-methyl-adenine (3-MA) partially protected whereas the later autophagy inhibitor Chloroquine (CQ) had no protective effect upon ConBr cytotoxicity. ConBr also augmented caspase-3 activation without affecting mitochondrial function. Noteworthy, the caspase-8 inhibitor IETF-fmk attenuated ConBr induced autophagy and C6 glioma cell death. Finally, ConBr did not show cytotoxicity against primary astrocytes, suggesting a selective antiglioma activity. In summary, our results indicate that ConBr requires functional CRD lectin domain to exert antiglioma activity, and its cytotoxicity is associated with MAPKs and Akt pathways modulation and autophagy- and caspase-8- dependent cell death.
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Affiliation(s)
- Ingrid A V Wolin
- Departamento de Bioquímica e Programa de Pós-graduação Em Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, 88040-900, Florianópolis, Santa Catarina, Brazil
| | - Isabella A Heinrich
- Departamento de Bioquímica e Programa de Pós-graduação Em Neurociências, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, 88040-900, Florianópolis, Santa Catarina, Brazil
| | - Ana Paula M Nascimento
- Departamento de Bioquímica e Programa de Pós-graduação Em Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, 88040-900, Florianópolis, Santa Catarina, Brazil
| | - Priscilla G Welter
- Departamento de Bioquímica e Programa de Pós-graduação Em Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, 88040-900, Florianópolis, Santa Catarina, Brazil
| | - Liliana Del V Sosa
- Centro de Microscopía Electrónica, Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Ciudad Universitaria, 5000, Córdoba, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Investigaciones en Ciencias de La Salud (INICSA), Córdoba, Argentina
| | - Ana Lucia De Paul
- Centro de Microscopía Electrónica, Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Ciudad Universitaria, 5000, Córdoba, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Investigaciones en Ciencias de La Salud (INICSA), Córdoba, Argentina
| | - Alfeu Zanotto-Filho
- Departamento de Farmacologia e Programa de Pós-graduação Em Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, 88040-900, Florianópolis, Santa Catarina, Brazil
| | - Cláudia Beatriz Nedel
- Departamento de Biologia Celular, Embriologia e Genética, Laboratório de Biologia Celular de Gliomas, Programa de Pós-graduação Em Biologia Celular e Do Desenvolvimento, Universidade Federal de Santa Catarina, Campus Universitário, 88040-900, Florianópolis, Santa Catarina, Brazil
| | - Lara Dias Lima
- Departamento de Bioquímica e Biologia Molecular, BioMolLab, Universidade Federal Do Ceará, CEP, 60020-181, Fortaleza, Ceará, Brazil
| | - Vinicius Jose Silva Osterne
- Departamento de Bioquímica e Biologia Molecular, BioMolLab, Universidade Federal Do Ceará, CEP, 60020-181, Fortaleza, Ceará, Brazil
| | | | - Kyria S Nascimento
- Departamento de Bioquímica e Biologia Molecular, BioMolLab, Universidade Federal Do Ceará, CEP, 60020-181, Fortaleza, Ceará, Brazil
| | - Benildo S Cavada
- Departamento de Bioquímica e Biologia Molecular, BioMolLab, Universidade Federal Do Ceará, CEP, 60020-181, Fortaleza, Ceará, Brazil
| | - Rodrigo B Leal
- Departamento de Bioquímica e Programa de Pós-graduação Em Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, 88040-900, Florianópolis, Santa Catarina, Brazil; Departamento de Bioquímica e Programa de Pós-graduação Em Neurociências, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, 88040-900, Florianópolis, Santa Catarina, Brazil.
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2
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Naime AA, Lopes MW, Colle D, Dafré AL, Suñol C, da Rocha JBT, Aschner M, Leal RB, Farina M. Glutathione in Chlorpyrifos-and Chlorpyrifos-Oxon-Induced Toxicity: a Comparative Study Focused on Non-cholinergic Toxicity in HT22 Cells. Neurotox Res 2020; 38:603-610. [PMID: 32651842 DOI: 10.1007/s12640-020-00254-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 06/30/2020] [Accepted: 07/03/2020] [Indexed: 12/22/2022]
Abstract
Chlorpyrifos (CPF) is a neurotoxic organophosphorus (OP) insecticide widely used for agricultural purposes. CPF-mediated neurotoxicity is mainly associated with its anticholinesterase activity, which may lead to a cholinergic syndrome. CPF metabolism generates chlorpyrifos-oxon (CPF-O), which possesses higher anticholinesterase activity and, consequently, plays a major role in the cholinergic syndrome observed after CPF poisoning. Recent lines of evidence have also reported non-cholinergic endpoints of CPF- and CPF-O-induced neurotoxicities, but comparisons on the non-cholinergic toxic properties of CPF and CPF-O are lacking. In this study, we compared the non-cholinergic toxicities displayed by CPF and CPF-O in cultured neuronal cells, with a particular emphasis on their pro-oxidant properties. Using immortalized cells derived from mouse hippocampus (HT22 line, which does present detectable acetylcholinesterase activity), we observed that CPF-O was 5-fold more potent in decreasing cell viability compared with CPF. Atropine, a muscarinic acetylcholine receptor antagonist, protected against acetylcholine (ACh)-induced toxicity but failed to prevent the CPF- and CPF-O-induced cytotoxicities in HT22 cells. CPF or CPF-O exposures significantly decreased the levels of the antioxidant glutathione (GSH); this event preceded the significant decrease in cell viability. Pretreatment with N-acetylcysteine (NAC, a GSH precursor) protected against the cytotoxicity induced by both CPF and CPF-O. The present study indicates that GSH depletion is a non-cholinergic event involved in CPF and CPF-O toxicities. The study also shows that in addition of being a more potent AChE inhibitor, CPF-O is also a more potent pro-oxidant molecule when compared with CPF, highlighting the role of CPF metabolism (bioactivation to CPF-O) in the ensuing non-cholinergic toxicity.
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Affiliation(s)
- Aline Aita Naime
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, 88040900, Brazil.
| | - Mark William Lopes
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, 88040900, Brazil
- Area of Biological Sciences, Medical and Health, Centro Universitário para o Desenvolvimento do Alto Vale do Itajaí - UNIDAVI, Rio do Sul, SC, Brazil
| | - Dirleise Colle
- Departamento de Análises Clínicas, Centro de Ciências da Saúde, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
| | - Alcir Luiz Dafré
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, 88040900, Brazil
| | - Cristina Suñol
- Consejo Superior de Investigaciones Científicas (IIBB-CSIC), IDIBAPS, CIBER Epidemiología y Salud Pública (CIBERESP), Institut d'Investigacions Biomèdiques de Barcelona, Barcelona, Spain
| | | | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Rodrigo Bainy Leal
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, 88040900, Brazil
| | - Marcelo Farina
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, 88040900, Brazil.
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3
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Anti-glioma properties of DVL, a lectin purified from Dioclea violacea. Int J Biol Macromol 2018; 120:566-577. [DOI: 10.1016/j.ijbiomac.2018.08.106] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 07/17/2018] [Accepted: 08/21/2018] [Indexed: 12/21/2022]
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4
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Salinska E, Sobczuk A, Lazarewicz JW. Dantrolene antagonizes the glycineB site of the NMDA receptor. Neurosci Lett 2008; 432:137-40. [DOI: 10.1016/j.neulet.2007.12.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Revised: 11/05/2007] [Accepted: 12/11/2007] [Indexed: 11/29/2022]
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Zieminska E, Stafiej A, Pitsinos EN, Couladouros EA, Moutsos V, Kozlowska H, Toczylowska B, Lazarewicz JW. Synthetic bastadins modify the activity of ryanodine receptors in cultured cerebellar granule cells. Neurosignals 2007; 15:283-92. [PMID: 17726341 DOI: 10.1159/000107650] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Accepted: 06/15/2007] [Indexed: 12/18/2022] Open
Abstract
Although the interactions of several natural bastadins with the RyR1 isoform of the ryanodine receptor in sarcoplasmic reticulum has been described, their structure-dependent interference with the RyR2 isoform, mainly expressed in cardiac muscle and brain neurons, has not been studied. In this work, we examined calcium transients induced by natural bastadin 10 and several synthetic bastadins in cultured cerebellar granule cells known to contain RyR2. The fluorescent calcium indicator fluo-3 and confocal microscopy were used to evaluate changes in the intracellular Ca(2+) concentration (Ca(i)), and the involvement of ryanodine receptors was assessed using pharmacological tools. Our results demonstrate that apart from the inactive BAST218F6 (a bisdebromo analogue of bastadin 10), synthetic bastadin 5, and synthetic analogues BAST217B, BAST240 and BAST268 (at concentrations >20 microM) increased Ca(i) in a concentration-dependent, ryanodine- and FK-506-sensitive way, with a potency significantly exceeding that of 20 mM caffeine. Moreover, the same active bastadins at a concentration of 5 muM in the presence of ryanodine prevented a thapsigargin-induced increase in Ca(i). These results indicate that bastadins, acting in a structure-dependent manner, modify the activity of RyR2 in primary neuronal culture and provide new information about structure-related pharmacological properties of bastadins.
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Hernández-Fonseca K, Massieu L. Disruption of endoplasmic reticulum calcium stores is involved in neuronal death induced by glycolysis inhibition in cultured hippocampal neurons. J Neurosci Res 2006; 82:196-205. [PMID: 16175570 DOI: 10.1002/jnr.20631] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Disturbances in neuronal calcium homeostasis have been implicated in a variety of neuropathological conditions, including cerebral ischemia, hypoglycemia, and epilepsy, and possibly constitute part of the cell death process associated with chronic neurodegenerative disorders. We investigated if endoplasmic reticulum (ER) calcium stores participate in neuronal death triggered by moderate glycolysis inhibition induced by iodoacetate, an inhibitor of glyceraldehyde-3-phosphate dehydrogenase, in cultured hippocampal neurons. Results show that exposure to iodoacetate leads to a slow partial decrease in cell survival, which is significantly prevented in the absence of Ca(2+) or in the presence of the calcium chelator BAPTA-AM. Treatment with caffeine and a low (1 microM) concentration of ryanodine, which activates the ryanodine receptor (RyR), exacerbates neuronal death, whereas dantrolene and 25 microM ryanodine, which antagonizes RyR, prevents damage. Xestospongin C (XeC), an antagonist of the inositol-3-phosphate (IP(3)) receptor (IP(3)R) also prevents neuronal damage. Inhibitors of the ER calcium ATPase (sarcoendoplasmic reticulum Ca(2+) ATPase; SERCA) have no effect. The decrease in ATP levels induced by iodoacetate is potentiated by caffeine and prevented by dantrolene. Although only a slight increase in glutamate extracellular levels is observed 3.5 hr after iodoacetate exposure, the N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, MK-801, efficiently prevents neuronal damage. Taken together, the data suggest that neuronal death induced during moderate glycolysis inhibition involves calcium influx through NMDA receptors and calcium release from intracellular ER stores. These results might be relevant to the understanding the mechanisms involved in neuronal damage related to aging and chronic neurodegenerative diseases, which have been associated with decreased glucose metabolism.
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7
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Nistratova VL, Pivovarov AS. Inositol triphosphate and ryanodine receptors in the control of the cholinosensitivity of common snail neurons by the Na,K pump during habituation. NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 2005; 35:699-708. [PMID: 16433065 DOI: 10.1007/s11055-005-0113-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The effects of the Na,K pump inhibitor ouabain on habituation of the common snail to tactile stimulation were identical to the ouabain-induced modification of the decrease in the cholinosensitivity of defensive behavior command neurons in the common snail in a cellular model of habituation. Studies addressed the effects of intracellularly delivered ligands of two types of Ca2+ depot receptors--inositol triphosphate (IP3) receptors and ryanodine receptors--on the action of ouabain in the cellular analog of habituation. The IP3 receptor antagonist heparin (0.1 mM), the IP3 receptor agonist inositol triphosphate (0.1 mM), and the ryanodine-dependent Ca2+ mobilization inhibitor dantrolene (0.1 mM) prevented ouabain from modifying the depression of the evoked acetylcholine current. The ryanodine agonist/antagonist ryanodine was used at two concentrations (0.1 and 1 mM) and neither had any effect on the action of ouabain. It is concluded that Ca2+ mobilized from intracellular Ca2+ depots via IP3 receptors is involved in the neuronal mechanism of regulation of the habitation of the common snail to tactile stimulation by the Na,K pump.
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Affiliation(s)
- V L Nistratova
- Department of Higher Nervous Activity, M. V. Lomonosov Moscow State University
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8
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Makarewicz D, Ziemińska E, Łazarewicz JW. Dantrolene inhibits NMDA-induced 45Ca uptake in cultured cerebellar granule neurons. Neurochem Int 2003; 43:273-8. [PMID: 12742069 DOI: 10.1016/s0197-0186(03)00012-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Dantrolene is an inhibitor of a skeletal muscle subtype of ryanodine receptors that stabilizes intracellular calcium concentrations and exerts neuroprotective effects in neurons submitted to excitotoxic challenges. The mechanisms of dantrolene-induced neuroprotection are not clear. In this study, using a model of cultured rat cerebellar granule neurons, we demonstrated that dantrolene inhibits NMDA-evoked 45Ca uptake, indicating that this drug may inhibit the activity of NMDA receptor channels. Primary neuronal cultures were incubated for 10 min in Mg(2+)-free ionic medium with NMDA and 45Ca in the presence of different concentrations of dantrolene, then radioactivity in neurons was measured by liquid scintillation spectroscopy. The results demonstrated that dantrolene, applied at micromolar concentrations, inhibits NMDA-evoked 45Ca uptake in neurons in a dose-dependent manner. DMSO, a vehicle to dantrolene, in concentrations used in this study had no effect on NMDA-evoked 45Ca uptake. These results, indicating that dantrolene inhibits activation of the NMDA receptors, might at least partially explain the mechanisms of a dantrolene-evoked protection of neurons against excitotoxicity mediated by agonists of NMDA receptors.
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Affiliation(s)
- Dorota Makarewicz
- Department of Neurochemistry, Medical Research Centre, Polish Academy of Sciences, 5 Pawińskiego Street, 02-106 Warsaw, Poland
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9
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10
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Mundy WR, Shafer TJ, Tilson HA, Kodavanti PR. Extracellular calcium is required for the polychlorinated biphenyl-induced increase of intracellular free calcium levels in cerebellar granule cell culture. Toxicology 1999; 136:27-39. [PMID: 10499848 DOI: 10.1016/s0300-483x(99)00052-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Recent studies from the laboratory indicate that polychlorinated biphenyl (PCB) congeners can alter signal transduction and calcium homeostasis in neuronal preparations. These effects were more pronounced for the ortho-substituted, non-coplanar congeners, although the mechanisms underlying these effects are not clear. In the present study the time-course and concentration-dependent effects of coplanar and non-coplanar PCBs on intracellular free calcium concentration ([Ca2+]i) in cerebellar granule cell cultures were compared using the fluorescent probe fura-2. The ortho-substituted congeners 2,2'-dichlorobiphenyl (DCB) and 2,2',4,6,6'-pentachlorobiphenyl (PeCB) caused a gradual increase of [Ca2+]i while the non-ortho-substituted congeners 4,4'-DCB and 3,3',4,4',5-PeCB had no effect. The increase of [Ca2+]i produced by 2,2'-DCB was time- and concentration-dependent. Further studies examined possible mechanisms for this rise in [Ca2+]i. In contrast to the muscarinic agonist carbachol, the effects of 2,2'-DCB on [Ca2+]i were not blocked by thapsigargin and required the presence of extracellular calcium. The effects of ortho-substituted PCBs may depend on their ability to inhibit calcium sequestration as 2,2'-DCB significantly inhibited 45Ca2+-uptake by microsomes and mitochondria while 3,3',4,4',5-PeCB had no effect. In addition, 2,2'-DCB significantly increased the binding of [3H]inositol 1,4,5-trisphosphate to receptors on cerebellar microsomes, suggesting another possible mechanism by which ortho-substituted PCBs can mobilize [Ca2+]i. These results show that PCBs increase [Ca2+]i in vitro via a mechanism that requires extracelluar calcium, and support previous structure-activity studies indicating that ortho-substituted PCBs are more potent than non-ortho-substituted PCBs.
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MESH Headings
- Animals
- Animals, Newborn
- Calcium/metabolism
- Calcium Channels/metabolism
- Carbachol/pharmacology
- Cells, Cultured
- Cerebellum/cytology
- Cerebellum/drug effects
- Cerebellum/metabolism
- Dose-Response Relationship, Drug
- Environmental Pollutants/toxicity
- Inositol 1,4,5-Trisphosphate Receptors
- L-Lactate Dehydrogenase/metabolism
- Microsomes, Liver/drug effects
- Microsomes, Liver/metabolism
- Mitochondria, Liver/drug effects
- Mitochondria, Liver/metabolism
- Muscarinic Agonists/pharmacology
- Neurons/drug effects
- Neurons/metabolism
- Polychlorinated Biphenyls/toxicity
- Rats
- Rats, Long-Evans
- Receptors, Cytoplasmic and Nuclear/metabolism
- Structure-Activity Relationship
- Thapsigargin/pharmacology
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Affiliation(s)
- W R Mundy
- Neurotoxicology Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
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Meir A, Ginsburg S, Butkevich A, Kachalsky SG, Kaiserman I, Ahdut R, Demirgoren S, Rahamimoff R. Ion channels in presynaptic nerve terminals and control of transmitter release. Physiol Rev 1999; 79:1019-88. [PMID: 10390521 DOI: 10.1152/physrev.1999.79.3.1019] [Citation(s) in RCA: 220] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The primary function of the presynaptic nerve terminal is to release transmitter quanta and thus activate the postsynaptic target cell. In almost every step leading to the release of transmitter quanta, there is a substantial involvement of ion channels. In this review, the multitude of ion channels in the presynaptic terminal are surveyed. There are at least 12 different major categories of ion channels representing several tens of different ion channel types; the number of different ion channel molecules at presynaptic nerve terminals is many hundreds. We describe the different ion channel molecules at the surface membrane and inside the nerve terminal in the context of their possible role in the process of transmitter release. Frequently, a number of different ion channel molecules, with the same basic function, are present at the same nerve terminal. This is especially evident in the cases of calcium channels and potassium channels. This abundance of ion channels allows for a physiological and pharmacological fine tuning of the process of transmitter release and thus of synaptic transmission.
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Affiliation(s)
- A Meir
- Department of Physiology and the Bernard Katz Minerva Centre for Cell Biophysics, Hebrew University Hadassah Medical School, Jerusalem, Israel
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12
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Palnitkar SS, Mickelson JR, Louis CF, Parness J. Pharmacological distinction between dantrolene and ryanodine binding sites: evidence from normal and malignant hyperthermia-susceptible porcine skeletal muscle. Biochem J 1997; 326 ( Pt 3):847-52. [PMID: 9307036 PMCID: PMC1218741 DOI: 10.1042/bj3260847] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Dantrolene inhibits and ryanodine stimulates calcium release from skeletal-muscle sarcoplasmic reticulum (SR), the former by an unknown mechanism, and the latter by activating the ryanodine receptor (RyR), the primary Ca2+-release channel of SR. Dantrolene is used to treat malignant hyperthermia (MH), a genetic predisposition to excessive intracellular Ca2+ release upon exposure to volatile anaesthetics. Porcine MH results from a point mutation in the SR RyR that alters the open probability of the channel, and is reflected in altered [3H]ryanodine binding parameters. Specific binding sites for [3H]dantrolene and [3H]ryanodine co-distribute on SR that has been isolated by discontinuous sucrose gradient centrifugation. If the two drug-binding sites are functionally linked, [3H]dantrolene binding might be affected both by pharmacological and by genetic modulators of the functional state of the RyR. Accordingly, we compared the characteristics of [3H]dantrolene binding to porcine malignant-hyperthermia-susceptible and normal-skeletal-muscle SR, and examined the effects of RyR modulators on [3H]dantrolene binding to these membranes. Additionally, the feasibility of separating the SR binding sites for [3H]dantrolene and [3H]ryanodine was investigated. No significant differences in [3H]dantrolene binding characteristics to SR membranes from the two muscle types were detected, and the Bmax ratio for [3H]dantrolene/[3H]ryanodine was 1.4(+/-0.1):1 in both muscle types. [3H]Dantrolene binding is unaffected by the RyR modulators caffeine, ryanodine, Ruthenium Red and calmodulin, and neither dantrolene nor azumolene have any effect on [3H]ryanodine binding. Additionally, distinct peaks of [3H]dantrolene and [3H]ryanodine binding are detected in SR membranes fractionated by linear sucrose centrifugation, although no differences in protein patterns are detected by SDS/PAGE or Western-blot analysis. We suggest that the binding sites for these two drugs are pharmacologically distinct, and may exist on separate molecules.
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Affiliation(s)
- S S Palnitkar
- Department of Anesthesia, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ 08901, USA
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