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Wayne Clarence Hodgson - One of the best experts on this subject based on the ideXlab platform.
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inhibition of presynaptic neurotoxins in taipan venom by suramin
Neurotoxicity Research, 2014Co-Authors: Sanjaya Kuruppu, Janeyuth Chaisakul, Ian A Smith, Wayne Clarence HodgsonAbstract:Taipans are amongst the most venomous snakes in the world, and neurotoxicity is a major life-threatening symptom of envenoming by these snakes. Three species of taipans exist, and the venom from each species contains a presynaptic neurotoxin which accounts for much of the neurotoxicity observed following human envenoming. The high cost of antivenom used to treat neurotoxicity has resulted in the need to develop alternative but effective therapies. Therefore, in this study, we examined the ability of the P2Y receptor antagonist suramin to prevent the in vitro neurotoxic effects of the three presynaptic neurotoxins in taipan venoms: Taipoxin, paradoxin and cannitoxin. Toxins were purchased from commercial sources or purified in house, using multiple steps of gel filtration chromatography. All three toxins (11 nM) inhibited nerve-mediated twitches in the chick biventer cervicis nerve–muscle preparation within 300 min. The presence of suramin (0.3 mM) completely blocked the Taipoxin and cannitoxin-mediated inhibition of nerve-mediated twitches within the course of the experiment (P < 0.0001). However, paradoxin induced a 32 % decrease in twitch height even in the presence of suramin within 360 min. This was significantly different compared to toxin alone (P < 0.0001). We also examined the effect of suramin on the neurotoxic effects of textilotoxin and the products of phospholipase A2 action. Each toxin alone or in the presence of suramin failed to inhibit the responses to exogenous agonists ACh, CCh or KCl. Our results warrant clinical studies aimed determining the efficacy of suramin in preventing the onset of neurotoxicity following taipan envenoming.
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differential myotoxic and cytotoxic activities of pre synaptic neurotoxins from papuan taipan oxyuranus scutellatus and irian jayan death adder acanthophis rugosus venoms
Basic & Clinical Pharmacology & Toxicology, 2013Co-Authors: Janeyuth Chaisakul, Geoffrey K Isbister, Helena C Parkington, Nicki Konstantakopoulos, Wayne Clarence HodgsonAbstract:Pre-synaptic PLA(2) neurotoxins are important components of many Australasian elapid snake venoms. These toxins disrupt neurotransmitter release. Taipoxin, a pre-synaptic neurotoxin isolated from the venom of the coastal taipan (Oxyuranus scutellatus), causes necrosis and muscle degeneration. The present study examined the myotoxic and cytotoxic activities of venoms from Papuan taipan (O. scutellatus) and Irian Jayan death adder (Acanthophis rugosus), and also tested their pre-synaptic neurotoxins; cannitoxin and P-EPTX-Ar1a. Based on size-exclusion chromatography analysis, cannitoxin represents 16% of O. scutellatus venom, while P-EPTX-Ar1a represents 6% of A. rugosus venom. In the chick biventer cervicis nerve-muscle preparation, A. rugosus venom displayed significantly higher myotoxic activity than O. scutellatus venom as indicated by inhibition of direct twitches, and an increase in baseline tension. Both cannitoxin and P-EPTX-Ar1a, displayed marked myotoxic activity. A. rugosus venom (50-300 μg/ml) produced concentration-dependent inhibition of cell proliferation in rat skeletal muscle cell lines (L6), while 300 μg/ml of O. scutellatus venom was required to inhibit cell proliferation, following 24-hr incubation. P-EPTX-Ar1a had greater cytotoxicity than cannitoxin, inhibiting cell proliferation after 24-hr incubation in L6 cells. Lactate dehydrogenase levels were increased after 1-hr incubation with A. rugosus venom (100-250 μg/ml), O. scutellatus venom (200-250 μg/ml) and P-EPTX-Ar1a (1-2 μM), but not cannitoxin (1-2 μM), suggesting venoms/toxin generated cell necrosis. Thus, A. rugosus and O. scutellatus venoms possess different myotoxic and cytotoxic activities. The proportion of pre-synaptic neurotoxin in the venoms and PLA(2) activity of the whole venoms are unlikely to be responsible for these activities. Language: en
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isolation and pharmacological characterization of cannitoxin a presynaptic neurotoxin from the venom of the papuan taipan oxyuranus scutellatus canni
Journal of Pharmacology and Experimental Therapeutics, 2005Co-Authors: Sanjaya Kuruppu, Ian A Smith, Shane Reeve, Yajnavalka Banerjee, Manjunatha R Kini, Wayne Clarence HodgsonAbstract:The Papuan taipan ( Oxyuranus scutellatus canni ) is widely distributed throughout much of Papua New Guinea. Although neurotoxicity is a major symptom of envenomation, no neurotoxins have been isolated from this venom. Using a series of size exclusion chromatography steps, we report the isolation of cannitoxin, a presynaptic neurotoxin (44,848 Da) that represents approximately 16% of the whole venom. The toxin displayed high phospholipase A2 (PLA2) activity (330 ± 5 μmol/min/mg) and caused concentration-dependent (11–66 nM) inhibition of indirect (0.2 ms; 0.1 Hz; supramaximal V) twitches of the chick biventer cervicis nerve-muscle preparation without effecting nicotinic receptor agonists. Prior addition of CSL Taipan antivenom (5 U/ml) or inhibition of phospholipase A2 activity by incubation with 4-bromophenacyl bromide prevented the inhibition of twitches. Cannitoxin is composed of three different subunits, α, β, and γ, with the possibility of two β isomers. However, only the α subunit displayed in vitro neurotoxic activity of its own. Thus, cannitoxin is similar in structure and pharmacology to Taipoxin, which has been isolated from the closely related Australian species O. scutellatus scutellatus (coastal taipan).
Ornella Rossetto - One of the best experts on this subject based on the ideXlab platform.
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calcium overload in nerve terminals of cultured neurons intoxicated by alpha latrotoxin and snake pla2 neurotoxins
Toxicon, 2009Co-Authors: Erik Tedesco, Michela Rigoni, Paola Caccin, Eugene V Grishin, Ornella Rossetto, Cesare MontecuccoAbstract:Snake presynaptic neurotoxins with phospholipase A2 (PLA2) activity cause degeneration of the neuromuscular junction. They induce depletion of synaptic vesicles and increase the membrane permeability to Ca(2+) which fluxes from the outside into the nerve terminal. Moreover, several toxins were shown to enter the nerve terminals of cultured neurons, where they may display their PLA2 activity on internal membranes. The relative contribution of these different actions in nerve terminal degeneration remains to be established. To gather information on this point, we have compared the effects of beta-bungarotoxin, Taipoxin, notexin and textilotoxin with those of alpha-latrotoxin on the basis of the notion that this latter toxin is well known to cause massive Ca(2+) influx and exocytosis of synaptic vesicles. All the parameters analysed here, including calcium imaging, are very similar for the two classes of neurotoxins. This indicates that Ca(2+) overloading plays a major role in the degeneration of nerve terminals induced by the snake presynaptic neurotoxins.
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Taipoxin induces synaptic vesicle exocytosis and disrupts the interaction of synaptophysin i with vamp2
Molecular Pharmacology, 2005Co-Authors: Dario Bonanomi, Michela Rigoni, Ornella Rossetto, Maria Pennuto, Flavia ValtortaAbstract:The application of the snake neurotoxin Taipoxin to hippocampal neurons in culture induced Ca2+-dependent synaptic vesicle (SV) exocytosis, with swelling of nerve terminals and redistribution of SV proteins to the axolemma. Using digital imaging videomicroscopy to measure fluorescence resonance energy transfer in live neurons, we also found that Taipoxin modulates the machinery for neurosecretion by causing dissociation of the SV proteins synaptobrevin 2 and synaptophysin I at a stage preceding Taipoxin-induced facilitation of SV fusion. These early effects of the toxin are followed by severe impairment of SV exo-endocytosis, which might underlie the prevention of neurotransmitter release reported after intoxication by Taipoxin.
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Taipoxin induces synaptic vesicle exocytosis and disrupts the interaction of synaptophysin I with VAMP2
2005Co-Authors: Dario Bonanomi, Michela Rigoni, Ornella Rossetto, Cesare Montecucco, Maria Pennuto, Flavia ValtortaAbstract:The application of the snake neurotoxin Taipoxin to hippocam-pal neurons in culture induced Ca2-dependent synaptic ves-icle (SV) exocytosis, with swelling of nerve terminals and redis-tribution of SV proteins to the axolemma. Using digital imaging videomicroscopy to measure fluorescence resonance energy transfer in live neurons, we also found that Taipoxin modulates the machinery for neurosecretion by causing dissociation of the SV proteins synaptobrevin 2 and synaptophysin I at a stage preceding Taipoxin-induced facilitation of SV fusion. These early effects of the toxin are followed by severe impairment of SV exo-endocytosis, which might underlie the prevention of neurotransmitter release reported after intoxication by Taipoxin. Transfer of information in the brain occurs mainly through the exocytotic release of neurotransmitters that are con
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snake presynaptic neurotoxins with phospholipase a2 activity induce punctate swellings of neurites and exocytosis of synaptic vesicles
Journal of Cell Science, 2004Co-Authors: Michela Rigoni, Paola Caccin, Ornella Rossetto, Cesare Montecucco, Giampietro Schiavo, Anne E Weston, Federica Allegrini, Maria Pennuto, Flavia ValtortaAbstract:The mechanisms of action of four snake presynaptic phospholipase A2 neurotoxins were investigated in cultured neurons isolated from various parts of the rat brain. Strikingly, physiological concentrations of notexin, β-bungarotoxin, Taipoxin or textilotoxin induced a dose-dependent formation of discrete bulges at various sites of neuronal projections. Neuronal bulging was paralleled by the redistribution of the two synaptic vesicle markers synaptophysin I (SypI) and vesicle-attached membrane protein 2 (VAMP2) to the bulges, and by the exposure of the luminal domain of synaptotagmin on the cell surface. These neurotoxins induced glutamate release from cultured neurons similarly to the known evoked release of acetylcholine from neuromuscular junctions. In addition, partial fragmentation of F-actin and neurofilaments was observed in neurons, but not in astrocytes. These findings indicate that these snake presynaptic neurotoxins act with by same mechanism and that the observed phenotype results from the fusion of synaptic vesicles with the plasma membrane not balanced by an adequate membrane retrieval. These changes closely resemble those occurring at neuromuscular junctions of intoxicated animals and fully qualify these primary neuronal cultures as pertinent models for studying the molecular mode of action of these neurotoxins.
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Taipoxin induces f actin fragmentation and enhances release of catecholamines in bovine chromaffin cells
Journal of Neurochemistry, 2003Co-Authors: Patricia Neco, Ornella Rossetto, Cesare Montecucco, Anabel Gil, Luis M GutierrezAbstract:Adrenomedullary bovine chromaffin cells were used to study the uptake and cellular effects of the phospholipase type A2 (PLA2) neurotoxin Taipoxin in a neuroendocrine model. This toxin entered rapidly inside cultured cells. Within 1 h, Taipoxin accumulated on the plasma membrane, independently of calcium presence, and caused fragmentation of the F-actin cytoskeleton. Toxin-induced cell death occurred after 24 h of incubation with the appearance of toxin containing large vesicles. Secretory experiments performed in cell populations showed an increased exocytosis in Taipoxin-treated cells stimulated by depolarization or by incubation with the calcium-ionophore A23187. Like F-actin fragmentation, this effect is abolished by replacement of Ca2+ with Sr2+ during toxin incubation. The effect of Taipoxin on exocytosis is not enhanced by latrunculin A, a F-actin disassembling drug altering secretion. Secretory studies in single Taipoxin-treated cells using amperometry, showed an increase in the number of released vesicles without modification of the kinetic parameters of individual vesicle fusions. Taken together, these results suggest that Taipoxin causes F-actin fragmentation and enhances secretion by redistribution of vesicles among secretory pools.
David J Williams - One of the best experts on this subject based on the ideXlab platform.
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development of a chicken derived antivenom against the taipan snake oxyuranus scutellatus venom and comparison with an equine antivenom
Toxicon, 2016Co-Authors: Diego Navarro, Maria Herrera, Nils Ramirez, Mauren Villalta, Alvaro Segura, Mariangela Vargas, Aarón Gómez, David J WilliamsAbstract:A chicken-derived antivenom (ChDAv) towards taipan snake (Oxyuranus scutellatus) venom was produced by purifying anti-taipan IgY from egg yolks of hens immunized with taipan venom. The productivity, antivenomic profile, neutralization ability, pharmacokinetic properties and immunogenicity of the ChDAv were compared with those of an antivenom produced in horses (EDAv). We found that 382 eggs are required to produce the mass of anti-taipan antibodies contained in one liter of equine hyperimmune plasma, and that 63 chickens would be needed to generate the amount of anti-taipan antibodies annually produced by one horse. It was estimated that, in Costa Rica, the production of anti-taipan antibodies could be 40% cheaper if chickens were used as immunoglobulin source, instead of horses. During antivenomic assessment, ChDAv showed lower ability to immunocapture the α subunit of Taipoxin, the most important neurotoxin in the venom. ChDAv showed a lower ability to neutralize the coagulant and lethal activities of taipan venom. ChDAv was more immunogenic in rabbits than EDAv, probably due to the fact that chickens are phylogenetically more distant to rabbits than horses. This finding may explain why clearance from rabbit bloodstream was faster for chicken-IgY than for equine-IgG in a pharmacokinetic study. In conclusion, the production of anti-taipan antivenom was less effective when chicken egg yolks were used as source of immunoglobulins instead of horses.
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doi:10.4269/ajtmh.14-0333 Copyright © 2014 by The American Society of Tropical Medicine and Hygiene Antivenomic Characterization of Two Antivenoms Against the Venom of the Taipan,
2016Co-Authors: Owen K. Paiva, Mauren Villalta, Ana Helena Pagotto, Solange M T Serrano, Simon D. Jensen, David J WilliamsAbstract:Abstract. Antivenoms manufactured by bioCSL Limited (Australia) and Instituto Clodomiro Picado (Costa Rica) against the venom of the taipan snakes (Oxyuranus scutellatus) from Australia and Papua New Guinea (PNG), respec-tively, were compared using antivenomics, an analytical approach that combines proteomics with immunoaffinity chro-matography. Both antivenoms recognized all venom proteins present in venom from PNG O. scutellatus, although a pattern of partial recognition was observed for some components. In the case of the Australian O. scutellatus venom, both antivenoms immunorecognized the majority of the components, but the CSL antivenom showed a stronger pattern of immunoreactivity, which was revealed by the percentage of retained proteins in the immunoaffinity column. Antivenoms interacted with Taipoxin in surface plasmon resonance. These observations on antivenomics agree with previous neutralization studies
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antivenomic characterization of two antivenoms against the venom of the taipan oxyuranus scutellatus from papua new guinea and australia
American Journal of Tropical Medicine and Hygiene, 2014Co-Authors: Maria Herrera, Guillermo León, Mauren Villalta, Alvaro Segura, Mariangela Vargas, Owen Paiva, S Jensen, Ana Helena Pagotto, Solange M T Serrano, David J WilliamsAbstract:Antivenoms manufactured by bioCSL Limited (Australia) and Instituto Clodomiro Picado (Costa Rica) against the venom of the taipan snakes (Oxyuranus scutellatus) from Australia and Papua New Guinea (PNG), respec- tively, were compared using antivenomics, an analytical approach that combines proteomics with immunoaffinity chro- matography. Both antivenoms recognized all venom proteins present in venom from PNG O. scutellatus, although a pattern of partial recognition was observed for some components. In the case of the Australian O. scutellatus venom, both antivenoms immunorecognized the majority of the components, but the CSL antivenom showed a stronger pattern of immunoreactivity, which was revealed by the percentage of retained proteins in the immunoaffinity column. Antivenoms interacted with Taipoxin in surface plasmon resonance. These observations on antivenomics agree with previous neutralization studies. are responsible for the majority of cases: Acanthophis laevis (smooth-scaleddeathadder),Micropechisikaheka(NewGuinea small-eyed snake), and Oxyuranus scutellatus (Papuan taipan). Lower numbers of cases are induced by other Acanthophis species, Pseudechis papuanus (Papuan blacksnake), and Pseudonaja textilis (New Guinea brownsnake). 3 In southern PNG and southern Papua, the vast majority of snakebites are inflicted by O. scutellatus. 3 Envenomings by this large elapid snake are characterized by minor local effects and severe sys- temic manifestations, including irreversible flaccid paralysis, coagulopathy associated with systemic spontaneous bleeding, myotoxicity, acute kidney injury, and cardiac damage. 2-6 The therapy for envenomings by O. scutellatus in PNG is based on the intravenous administration of either CSL Poly- valent Antivenom or CSL Taipan Antivenom (both manufac- tured by bioCSL Limited in Melbourne, Victoria, Australia; CSL). They are F(ab')2 antivenoms generated by pepsin diges- tion and ammonium sulphate precipitation of plasma of hyperimmunized horses. 3 Both of these antivenoms, when administered early, have been shown to be effective in halting coagulopathy and bleeding and reduce the incidence of respi- ratory paralysis. CSL Polyvalent Antivenom is a polyspecific mixture of immunoglobulins (Igs) raised against the venom of Australian elapid species from five genera (Acanthophis, Notechis, Oxyuranus, Pseudechis ,a ndPseudonaja). Although CSL Taipan Antivenom is therapeutically indicated only for treating envenoming by snakes of the genus Oxyuranus ,t his antivenom is also the result of hyperimmunizing horses with venom from the same five genera of Australian elapid snakes used in production of CSL Polyvalent Antivenom. 7 Recently, a
Cesare Montecucco - One of the best experts on this subject based on the ideXlab platform.
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calcium overload in nerve terminals of cultured neurons intoxicated by alpha latrotoxin and snake pla2 neurotoxins
Toxicon, 2009Co-Authors: Erik Tedesco, Michela Rigoni, Paola Caccin, Eugene V Grishin, Ornella Rossetto, Cesare MontecuccoAbstract:Snake presynaptic neurotoxins with phospholipase A2 (PLA2) activity cause degeneration of the neuromuscular junction. They induce depletion of synaptic vesicles and increase the membrane permeability to Ca(2+) which fluxes from the outside into the nerve terminal. Moreover, several toxins were shown to enter the nerve terminals of cultured neurons, where they may display their PLA2 activity on internal membranes. The relative contribution of these different actions in nerve terminal degeneration remains to be established. To gather information on this point, we have compared the effects of beta-bungarotoxin, Taipoxin, notexin and textilotoxin with those of alpha-latrotoxin on the basis of the notion that this latter toxin is well known to cause massive Ca(2+) influx and exocytosis of synaptic vesicles. All the parameters analysed here, including calcium imaging, are very similar for the two classes of neurotoxins. This indicates that Ca(2+) overloading plays a major role in the degeneration of nerve terminals induced by the snake presynaptic neurotoxins.
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Taipoxin induces synaptic vesicle exocytosis and disrupts the interaction of synaptophysin I with VAMP2
2005Co-Authors: Dario Bonanomi, Michela Rigoni, Ornella Rossetto, Cesare Montecucco, Maria Pennuto, Flavia ValtortaAbstract:The application of the snake neurotoxin Taipoxin to hippocam-pal neurons in culture induced Ca2-dependent synaptic ves-icle (SV) exocytosis, with swelling of nerve terminals and redis-tribution of SV proteins to the axolemma. Using digital imaging videomicroscopy to measure fluorescence resonance energy transfer in live neurons, we also found that Taipoxin modulates the machinery for neurosecretion by causing dissociation of the SV proteins synaptobrevin 2 and synaptophysin I at a stage preceding Taipoxin-induced facilitation of SV fusion. These early effects of the toxin are followed by severe impairment of SV exo-endocytosis, which might underlie the prevention of neurotransmitter release reported after intoxication by Taipoxin. Transfer of information in the brain occurs mainly through the exocytotic release of neurotransmitters that are con
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snake presynaptic neurotoxins with phospholipase a2 activity induce punctate swellings of neurites and exocytosis of synaptic vesicles
Journal of Cell Science, 2004Co-Authors: Michela Rigoni, Paola Caccin, Ornella Rossetto, Cesare Montecucco, Giampietro Schiavo, Anne E Weston, Federica Allegrini, Maria Pennuto, Flavia ValtortaAbstract:The mechanisms of action of four snake presynaptic phospholipase A2 neurotoxins were investigated in cultured neurons isolated from various parts of the rat brain. Strikingly, physiological concentrations of notexin, β-bungarotoxin, Taipoxin or textilotoxin induced a dose-dependent formation of discrete bulges at various sites of neuronal projections. Neuronal bulging was paralleled by the redistribution of the two synaptic vesicle markers synaptophysin I (SypI) and vesicle-attached membrane protein 2 (VAMP2) to the bulges, and by the exposure of the luminal domain of synaptotagmin on the cell surface. These neurotoxins induced glutamate release from cultured neurons similarly to the known evoked release of acetylcholine from neuromuscular junctions. In addition, partial fragmentation of F-actin and neurofilaments was observed in neurons, but not in astrocytes. These findings indicate that these snake presynaptic neurotoxins act with by same mechanism and that the observed phenotype results from the fusion of synaptic vesicles with the plasma membrane not balanced by an adequate membrane retrieval. These changes closely resemble those occurring at neuromuscular junctions of intoxicated animals and fully qualify these primary neuronal cultures as pertinent models for studying the molecular mode of action of these neurotoxins.
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Taipoxin induces f actin fragmentation and enhances release of catecholamines in bovine chromaffin cells
Journal of Neurochemistry, 2003Co-Authors: Patricia Neco, Ornella Rossetto, Cesare Montecucco, Anabel Gil, Luis M GutierrezAbstract:Adrenomedullary bovine chromaffin cells were used to study the uptake and cellular effects of the phospholipase type A2 (PLA2) neurotoxin Taipoxin in a neuroendocrine model. This toxin entered rapidly inside cultured cells. Within 1 h, Taipoxin accumulated on the plasma membrane, independently of calcium presence, and caused fragmentation of the F-actin cytoskeleton. Toxin-induced cell death occurred after 24 h of incubation with the appearance of toxin containing large vesicles. Secretory experiments performed in cell populations showed an increased exocytosis in Taipoxin-treated cells stimulated by depolarization or by incubation with the calcium-ionophore A23187. Like F-actin fragmentation, this effect is abolished by replacement of Ca2+ with Sr2+ during toxin incubation. The effect of Taipoxin on exocytosis is not enhanced by latrunculin A, a F-actin disassembling drug altering secretion. Secretory studies in single Taipoxin-treated cells using amperometry, showed an increase in the number of released vesicles without modification of the kinetic parameters of individual vesicle fusions. Taken together, these results suggest that Taipoxin causes F-actin fragmentation and enhances secretion by redistribution of vesicles among secretory pools.
Michela Rigoni - One of the best experts on this subject based on the ideXlab platform.
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calcium overload in nerve terminals of cultured neurons intoxicated by alpha latrotoxin and snake pla2 neurotoxins
Toxicon, 2009Co-Authors: Erik Tedesco, Michela Rigoni, Paola Caccin, Eugene V Grishin, Ornella Rossetto, Cesare MontecuccoAbstract:Snake presynaptic neurotoxins with phospholipase A2 (PLA2) activity cause degeneration of the neuromuscular junction. They induce depletion of synaptic vesicles and increase the membrane permeability to Ca(2+) which fluxes from the outside into the nerve terminal. Moreover, several toxins were shown to enter the nerve terminals of cultured neurons, where they may display their PLA2 activity on internal membranes. The relative contribution of these different actions in nerve terminal degeneration remains to be established. To gather information on this point, we have compared the effects of beta-bungarotoxin, Taipoxin, notexin and textilotoxin with those of alpha-latrotoxin on the basis of the notion that this latter toxin is well known to cause massive Ca(2+) influx and exocytosis of synaptic vesicles. All the parameters analysed here, including calcium imaging, are very similar for the two classes of neurotoxins. This indicates that Ca(2+) overloading plays a major role in the degeneration of nerve terminals induced by the snake presynaptic neurotoxins.
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Taipoxin induces synaptic vesicle exocytosis and disrupts the interaction of synaptophysin i with vamp2
Molecular Pharmacology, 2005Co-Authors: Dario Bonanomi, Michela Rigoni, Ornella Rossetto, Maria Pennuto, Flavia ValtortaAbstract:The application of the snake neurotoxin Taipoxin to hippocampal neurons in culture induced Ca2+-dependent synaptic vesicle (SV) exocytosis, with swelling of nerve terminals and redistribution of SV proteins to the axolemma. Using digital imaging videomicroscopy to measure fluorescence resonance energy transfer in live neurons, we also found that Taipoxin modulates the machinery for neurosecretion by causing dissociation of the SV proteins synaptobrevin 2 and synaptophysin I at a stage preceding Taipoxin-induced facilitation of SV fusion. These early effects of the toxin are followed by severe impairment of SV exo-endocytosis, which might underlie the prevention of neurotransmitter release reported after intoxication by Taipoxin.
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Taipoxin induces synaptic vesicle exocytosis and disrupts the interaction of synaptophysin I with VAMP2
2005Co-Authors: Dario Bonanomi, Michela Rigoni, Ornella Rossetto, Cesare Montecucco, Maria Pennuto, Flavia ValtortaAbstract:The application of the snake neurotoxin Taipoxin to hippocam-pal neurons in culture induced Ca2-dependent synaptic ves-icle (SV) exocytosis, with swelling of nerve terminals and redis-tribution of SV proteins to the axolemma. Using digital imaging videomicroscopy to measure fluorescence resonance energy transfer in live neurons, we also found that Taipoxin modulates the machinery for neurosecretion by causing dissociation of the SV proteins synaptobrevin 2 and synaptophysin I at a stage preceding Taipoxin-induced facilitation of SV fusion. These early effects of the toxin are followed by severe impairment of SV exo-endocytosis, which might underlie the prevention of neurotransmitter release reported after intoxication by Taipoxin. Transfer of information in the brain occurs mainly through the exocytotic release of neurotransmitters that are con
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snake presynaptic neurotoxins with phospholipase a2 activity induce punctate swellings of neurites and exocytosis of synaptic vesicles
Journal of Cell Science, 2004Co-Authors: Michela Rigoni, Paola Caccin, Ornella Rossetto, Cesare Montecucco, Giampietro Schiavo, Anne E Weston, Federica Allegrini, Maria Pennuto, Flavia ValtortaAbstract:The mechanisms of action of four snake presynaptic phospholipase A2 neurotoxins were investigated in cultured neurons isolated from various parts of the rat brain. Strikingly, physiological concentrations of notexin, β-bungarotoxin, Taipoxin or textilotoxin induced a dose-dependent formation of discrete bulges at various sites of neuronal projections. Neuronal bulging was paralleled by the redistribution of the two synaptic vesicle markers synaptophysin I (SypI) and vesicle-attached membrane protein 2 (VAMP2) to the bulges, and by the exposure of the luminal domain of synaptotagmin on the cell surface. These neurotoxins induced glutamate release from cultured neurons similarly to the known evoked release of acetylcholine from neuromuscular junctions. In addition, partial fragmentation of F-actin and neurofilaments was observed in neurons, but not in astrocytes. These findings indicate that these snake presynaptic neurotoxins act with by same mechanism and that the observed phenotype results from the fusion of synaptic vesicles with the plasma membrane not balanced by an adequate membrane retrieval. These changes closely resemble those occurring at neuromuscular junctions of intoxicated animals and fully qualify these primary neuronal cultures as pertinent models for studying the molecular mode of action of these neurotoxins.
