The Experts below are selected from a list of 1122 Experts worldwide ranked by ideXlab platform

Marta N. Cordeiro - One of the best experts on this subject based on the ideXlab platform.

  • Immunodetection of toxins in historesin-embedded sections of Phoneutria nigriventer venom glands using laser confocal scanning microscopy.
    Toxicon, 2019
    Co-Authors: Luciana Maria Silva, Paulo Filemon Paolucci Pimenta, Rafael Nacif-pimenta, Marta N. Cordeiro, Carlos Chávez-olórtegui, Paula Ladeira Ortolani, Layla Mosqueira Moura, Consuelo Latorre Fortes-dias
    Abstract:

    In the last decades, main advances were achieved in the identification, structural and pharmacological characterization of Phoneutria nigriventer toxins. However, studies on the venom-producing apparatus are rare. Presently, we applied immunolabeling to historesin-embedded cross-sections of P. nigriventer venom glands. Toxins and toxin-secreting cells were successfully located in situ, using laser confocal scanning microscopy. The methodological strategy was successful and may be applied in future studies on venom glands and other secreting tissues, in general.

  • Phoneutria nigriventer spider toxin pntx2 1 δ ctenitoxin pn1a is a modulator of sodium channel gating
    Toxins, 2018
    Co-Authors: Steve Peigneur, Ana Luiza Bittencourt Paiva, Marta N. Cordeiro, Maria Elena De Lima, Marcia Helena Borges, Marcelo Ribeiro Vasconcelos Diniz, Jan Tytgat
    Abstract:

    : Spider venoms are complex mixtures of biologically active components with potentially interesting applications for drug discovery or for agricultural purposes. The spider Phoneutria nigriventer is responsible for a number of envenomations with sometimes severe clinical manifestations in humans. A more efficient treatment requires a comprehensive knowledge of the venom composition and of the action mechanism of the constituting components. PnTx2-1 (also called δ-ctenitoxin-Pn1a) is a 53-amino-acid-residue peptide isolated from the venom fraction PhTx2. Although PnTx2-1 is classified as a neurotoxin, its molecular target has remained unknown. This study describes the electrophysiological characterization of PnTx2-1 as a modulator of voltage-gated sodium channels. PnTx2-1 is investigated for its activity on seven mammalian NaV-channel isoforms, one insect NaV channel and one arachnid NaV channel. Furthermore, comparison of the activity of both PnTx2-1 and PnTx2-6 on NaV1.5 channels reveals that this family of Phoneutria toxins modulates the cardiac NaV channel in a bifunctional manner, resulting in an alteration of the inactivation process and a reduction of the sodium peak current.

  • Phoneutria nigriventer Spider Toxin PnTx2-1 (δ-Ctenitoxin-Pn1a) Is a Modulator of Sodium Channel Gating
    MDPI AG, 2018
    Co-Authors: Steve Peigneur, Marcelo R.v. Diniz, Marta N. Cordeiro, Maria Elena De Lima, Marcia Helena Borges, Ana Luiza B. Paiva, Jan Tytgat
    Abstract:

    Spider venoms are complex mixtures of biologically active components with potentially interesting applications for drug discovery or for agricultural purposes. The spider Phoneutria nigriventer is responsible for a number of envenomations with sometimes severe clinical manifestations in humans. A more efficient treatment requires a comprehensive knowledge of the venom composition and of the action mechanism of the constituting components. PnTx2-1 (also called δ-ctenitoxin-Pn1a) is a 53-amino-acid-residue peptide isolated from the venom fraction PhTx2. Although PnTx2-1 is classified as a neurotoxin, its molecular target has remained unknown. This study describes the electrophysiological characterization of PnTx2-1 as a modulator of voltage-gated sodium channels. PnTx2-1 is investigated for its activity on seven mammalian NaV-channel isoforms, one insect NaV channel and one arachnid NaV channel. Furthermore, comparison of the activity of both PnTx2-1 and PnTx2-6 on NaV1.5 channels reveals that this family of Phoneutria toxins modulates the cardiac NaV channel in a bifunctional manner, resulting in an alteration of the inactivation process and a reduction of the sodium peak current

  • β δ prit1 a highly insecticidal toxin from the venom of the brazilian spider Phoneutria reidyi f o pickard cambridge 1897
    Toxicon, 2015
    Co-Authors: Leida Calegário Oliveira, Marta N. Cordeiro, Michael K. Richardson, Suely G. Figueiredo, Paulo S.l. Beirão, A M C Pimenta, Fabiana V. Campos, Beatriz R. Adaime, Mariefrance Martineauclaire, Maria Elena De Lima
    Abstract:

    A potent insecticidal toxin, β/δ-PrIT1, molecular mass of 5598.86 [M+H](+), was characterized from Phoneutria reidyi spider venom. Its partial amino acid sequence showed high similarity with insecticidal spider toxins from the genus Phoneutria. β/δ-PrIT1 was very toxic (LD50 = 4 nmol/g) to flies (Musca domestica), but not to mice (Mus musculus). Kinetic studies showed that (125)I-β/δ-PrIT1 binds to two distinct sites in insect sodium channels, with close affinity (Kd1 = 34.7 pM and Kd2 = 35.1 pM). Its association is rather fast (t1/2(1) = 1.4 min, t1/2(2) = 8.5 min) and its dissociation is a slower process (t1/2(1) = 5.4 min, t1/2(2) = 32.8 min). On rat brain synaptosomes β/δ-PrIT1 partially competed (∼30%) with the beta-toxin (125)I-CssIV, but did not compete with the alpha-toxin of reference (125)I-AaII, nor with the beta-toxin (125)I-TsVII. On cockroach nerve cord synaptosomes, β/δ-PrIT1 did not compete with the anti-insect toxin (125)I-LqqIT1, but it competed (IC50 = 80 pM) with the "alpha-like" toxin (125)I-BomIV. In cockroach neurons, β/δ-PrIT1 inhibited the inactivation of Nav-channels and it shifted the sodium channel activation to hyperpolarizing potentials. These results indicate two different binding sites for β/δ-PrIT1, leading to two different pharmacological responses. β/δ-PrIT1 is one of the most toxic spider toxins to insects without apparent toxicity to mammals, and provide new model for the development of insecticides.

  • β/δ-PrIT1, a highly insecticidal toxin from the venom of the Brazilian spider Phoneutria reidyi (F.O. Pickard-Cambridge, 1897).
    Toxicon, 2015
    Co-Authors: Leida Calegário Oliveira, Marta N. Cordeiro, Michael K. Richardson, Suely G. Figueiredo, Paulo S.l. Beirão, A M C Pimenta, Fabiana V. Campos, Beatriz R. Adaime, Marie-france Martin-eauclaire, Maria Elena De Lima
    Abstract:

    A potent insecticidal toxin, β/δ-PrIT1, molecular mass of 5598.86 [M+H](+), was characterized from Phoneutria reidyi spider venom. Its partial amino acid sequence showed high similarity with insecticidal spider toxins from the genus Phoneutria. β/δ-PrIT1 was very toxic (LD50 = 4 nmol/g) to flies (Musca domestica), but not to mice (Mus musculus). Kinetic studies showed that (125)I-β/δ-PrIT1 binds to two distinct sites in insect sodium channels, with close affinity (Kd1 = 34.7 pM and Kd2 = 35.1 pM). Its association is rather fast (t1/2(1) = 1.4 min, t1/2(2) = 8.5 min) and its dissociation is a slower process (t1/2(1) = 5.4 min, t1/2(2) = 32.8 min). On rat brain synaptosomes β/δ-PrIT1 partially competed (∼30%) with the beta-toxin (125)I-CssIV, but did not compete with the alpha-toxin of reference (125)I-AaII, nor with the beta-toxin (125)I-TsVII. On cockroach nerve cord synaptosomes, β/δ-PrIT1 did not compete with the anti-insect toxin (125)I-LqqIT1, but it competed (IC50 = 80 pM) with the "alpha-like" toxin (125)I-BomIV. In cockroach neurons, β/δ-PrIT1 inhibited the inactivation of Nav-channels and it shifted the sodium channel activation to hyperpolarizing potentials. These results indicate two different binding sites for β/δ-PrIT1, leading to two different pharmacological responses. β/δ-PrIT1 is one of the most toxic spider toxins to insects without apparent toxicity to mammals, and provide new model for the development of insecticides.

Maria Elena De Lima - One of the best experts on this subject based on the ideXlab platform.

  • Phoneutria nigriventer spider toxin pntx2 1 δ ctenitoxin pn1a is a modulator of sodium channel gating
    Toxins, 2018
    Co-Authors: Steve Peigneur, Ana Luiza Bittencourt Paiva, Marta N. Cordeiro, Maria Elena De Lima, Marcia Helena Borges, Marcelo Ribeiro Vasconcelos Diniz, Jan Tytgat
    Abstract:

    : Spider venoms are complex mixtures of biologically active components with potentially interesting applications for drug discovery or for agricultural purposes. The spider Phoneutria nigriventer is responsible for a number of envenomations with sometimes severe clinical manifestations in humans. A more efficient treatment requires a comprehensive knowledge of the venom composition and of the action mechanism of the constituting components. PnTx2-1 (also called δ-ctenitoxin-Pn1a) is a 53-amino-acid-residue peptide isolated from the venom fraction PhTx2. Although PnTx2-1 is classified as a neurotoxin, its molecular target has remained unknown. This study describes the electrophysiological characterization of PnTx2-1 as a modulator of voltage-gated sodium channels. PnTx2-1 is investigated for its activity on seven mammalian NaV-channel isoforms, one insect NaV channel and one arachnid NaV channel. Furthermore, comparison of the activity of both PnTx2-1 and PnTx2-6 on NaV1.5 channels reveals that this family of Phoneutria toxins modulates the cardiac NaV channel in a bifunctional manner, resulting in an alteration of the inactivation process and a reduction of the sodium peak current.

  • Phoneutria nigriventer venom: A pharmacological treasure.
    Toxicon, 2018
    Co-Authors: Steve Peigneur, Maria Elena De Lima, Jan Tytgat
    Abstract:

    In millions of years, spiders have optimized their venoms in order to assure successful prey capture and defence against predators. Spider venoms have become unique cocktails of biological active components enabling potentially interesting application for drug discovery or for agricultural purposes. The venom of Phoneutria nigriventer has been studied for over 60 years. This spider is responsible for a high number of envenomations with severe clinical manifestations in humans, which necessitates a comprehensive knowledge of its venom composition. With over 40 different neurotoxic peptides characterized so far and still many more awaiting identification, this venom is undoubtedly a pharmacological treasure. This review provides an overview of the Phoneutria nigriventer toxins known today and describes their mechanism of action at a molecular level. We critically discuss the potential of the Phoneutria nigriventer venom peptides as pharmaceutical tools or lead compounds for drug development.

  • Phoneutria nigriventer Spider Toxin PnTx2-1 (δ-Ctenitoxin-Pn1a) Is a Modulator of Sodium Channel Gating
    MDPI AG, 2018
    Co-Authors: Steve Peigneur, Marcelo R.v. Diniz, Marta N. Cordeiro, Maria Elena De Lima, Marcia Helena Borges, Ana Luiza B. Paiva, Jan Tytgat
    Abstract:

    Spider venoms are complex mixtures of biologically active components with potentially interesting applications for drug discovery or for agricultural purposes. The spider Phoneutria nigriventer is responsible for a number of envenomations with sometimes severe clinical manifestations in humans. A more efficient treatment requires a comprehensive knowledge of the venom composition and of the action mechanism of the constituting components. PnTx2-1 (also called δ-ctenitoxin-Pn1a) is a 53-amino-acid-residue peptide isolated from the venom fraction PhTx2. Although PnTx2-1 is classified as a neurotoxin, its molecular target has remained unknown. This study describes the electrophysiological characterization of PnTx2-1 as a modulator of voltage-gated sodium channels. PnTx2-1 is investigated for its activity on seven mammalian NaV-channel isoforms, one insect NaV channel and one arachnid NaV channel. Furthermore, comparison of the activity of both PnTx2-1 and PnTx2-6 on NaV1.5 channels reveals that this family of Phoneutria toxins modulates the cardiac NaV channel in a bifunctional manner, resulting in an alteration of the inactivation process and a reduction of the sodium peak current

  • β δ prit1 a highly insecticidal toxin from the venom of the brazilian spider Phoneutria reidyi f o pickard cambridge 1897
    Toxicon, 2015
    Co-Authors: Leida Calegário Oliveira, Marta N. Cordeiro, Michael K. Richardson, Suely G. Figueiredo, Paulo S.l. Beirão, A M C Pimenta, Fabiana V. Campos, Beatriz R. Adaime, Mariefrance Martineauclaire, Maria Elena De Lima
    Abstract:

    A potent insecticidal toxin, β/δ-PrIT1, molecular mass of 5598.86 [M+H](+), was characterized from Phoneutria reidyi spider venom. Its partial amino acid sequence showed high similarity with insecticidal spider toxins from the genus Phoneutria. β/δ-PrIT1 was very toxic (LD50 = 4 nmol/g) to flies (Musca domestica), but not to mice (Mus musculus). Kinetic studies showed that (125)I-β/δ-PrIT1 binds to two distinct sites in insect sodium channels, with close affinity (Kd1 = 34.7 pM and Kd2 = 35.1 pM). Its association is rather fast (t1/2(1) = 1.4 min, t1/2(2) = 8.5 min) and its dissociation is a slower process (t1/2(1) = 5.4 min, t1/2(2) = 32.8 min). On rat brain synaptosomes β/δ-PrIT1 partially competed (∼30%) with the beta-toxin (125)I-CssIV, but did not compete with the alpha-toxin of reference (125)I-AaII, nor with the beta-toxin (125)I-TsVII. On cockroach nerve cord synaptosomes, β/δ-PrIT1 did not compete with the anti-insect toxin (125)I-LqqIT1, but it competed (IC50 = 80 pM) with the "alpha-like" toxin (125)I-BomIV. In cockroach neurons, β/δ-PrIT1 inhibited the inactivation of Nav-channels and it shifted the sodium channel activation to hyperpolarizing potentials. These results indicate two different binding sites for β/δ-PrIT1, leading to two different pharmacological responses. β/δ-PrIT1 is one of the most toxic spider toxins to insects without apparent toxicity to mammals, and provide new model for the development of insecticides.

  • β/δ-PrIT1, a highly insecticidal toxin from the venom of the Brazilian spider Phoneutria reidyi (F.O. Pickard-Cambridge, 1897).
    Toxicon, 2015
    Co-Authors: Leida Calegário Oliveira, Marta N. Cordeiro, Michael K. Richardson, Suely G. Figueiredo, Paulo S.l. Beirão, A M C Pimenta, Fabiana V. Campos, Beatriz R. Adaime, Marie-france Martin-eauclaire, Maria Elena De Lima
    Abstract:

    A potent insecticidal toxin, β/δ-PrIT1, molecular mass of 5598.86 [M+H](+), was characterized from Phoneutria reidyi spider venom. Its partial amino acid sequence showed high similarity with insecticidal spider toxins from the genus Phoneutria. β/δ-PrIT1 was very toxic (LD50 = 4 nmol/g) to flies (Musca domestica), but not to mice (Mus musculus). Kinetic studies showed that (125)I-β/δ-PrIT1 binds to two distinct sites in insect sodium channels, with close affinity (Kd1 = 34.7 pM and Kd2 = 35.1 pM). Its association is rather fast (t1/2(1) = 1.4 min, t1/2(2) = 8.5 min) and its dissociation is a slower process (t1/2(1) = 5.4 min, t1/2(2) = 32.8 min). On rat brain synaptosomes β/δ-PrIT1 partially competed (∼30%) with the beta-toxin (125)I-CssIV, but did not compete with the alpha-toxin of reference (125)I-AaII, nor with the beta-toxin (125)I-TsVII. On cockroach nerve cord synaptosomes, β/δ-PrIT1 did not compete with the anti-insect toxin (125)I-LqqIT1, but it competed (IC50 = 80 pM) with the "alpha-like" toxin (125)I-BomIV. In cockroach neurons, β/δ-PrIT1 inhibited the inactivation of Nav-channels and it shifted the sodium channel activation to hyperpolarizing potentials. These results indicate two different binding sites for β/δ-PrIT1, leading to two different pharmacological responses. β/δ-PrIT1 is one of the most toxic spider toxins to insects without apparent toxicity to mammals, and provide new model for the development of insecticides.

S G Figueiredo - One of the best experts on this subject based on the ideXlab platform.

  • Leftward Shift in the Voltage-Dependence for Ca^2+ Currents Activation Induced by a New Toxin from Phoneutria reidyi (Aranae, Ctenidae) Venom
    Cellular and Molecular Neurobiology, 2007
    Co-Authors: L B Vieira, M Richardson, M V Gomez, H J Reis, M M Santoro, A. M. C. Pimenta, M. P. Bemquerer, J. S. Cruz, R. Ferreira-de-oliveira, S G Figueiredo
    Abstract:

    Various neurotoxins have been described from the venom of the Brazilian spider Phoneutria nigriventer , but little is known about the venoms of the other species of this genus. In the present work, we describe the purification and some structural and pharmacological features of a new toxin (PRTx3-7) from Phoneutria reidyi that causes flaccid paralysis in mice. The observed molecular mass (4627.26 Da) was in accordance with the calculated mass for the amidated form of the amino acid sequence (4627.08 Da). The presence of an α-amidated C-terminus was confirmed by MS/MS analysis of the C-terminal peptide, isolated after enzymatic digestion of the native protein with Glu-C endoproteinase. The purified protein was injected (intracerebro-ventricular) into mice at dose levels of 5 μg/mouse causing immediate agitation and clockwise gyration, followed by the gradual development of general flaccid paralysis. PRTx3-7 at 1 μM inhibited by 20% the KCl-induced increase on [Ca^2+]_i in rat brain synaptosomes. The HEK cells permanently expressing L, N, P/Q and R HVA Ca^2+ channels were also used to better characterize the pharmacological features of PRTx3-7. To our surprise, PRTx3-7 shifted the voltage-dependence for activation towards hyperpolarized membrane potentials for L (−4 mV), P/Q (−8 mV) and R (−5 mV) type Ca^2+ currents. In addition, the new toxin also affected the steady state of inactivation of L-, N- and P/Q-type Ca^2+ currents.

  • Comparison of the partial proteomes of the venoms of Brazilian spiders of the genus Phoneutria.
    Comparative biochemistry and physiology. Toxicology & pharmacology : CBP, 2005
    Co-Authors: M Richardson, A M C Pimenta, M P Bemquerer, M M Santoro, P S L Beirao, M E Lima, S G Figueiredo, C Bloch, E A R Vasconcelos, F A P Campos
    Abstract:

    The proteomes of the venoms of the Brazilian wandering "armed" spiders Phoneutria nigriventer, Phoneutria reidyi, and Phoneutria keyserlingi, were compared using two-dimensional gel electrophoresis. The venom components were also fractionated using a combination of preparative reverse phase HPLC on Vydac C4, analytical RP-HPLC on Vydac C8 and C18 and cation exchange FPLC on Resource S at pH 6.1 and 4.7, or anion exchange HPLC on Synchropak AX-300 at pH 8.6. The amino acid sequences of the native and S-pyridyl-ethylated proteins and peptides derived from them by enzymatic digestion and chemical cleavages were determined using a Shimadzu PPSQ-21(A) automated protein sequencer, and by MS/MS collision induced dissociations. To date nearly 400 peptides and proteins (1.2-27 kDa) have been isolated in a pure state and, of these, more than 100 have had their complete or partial amino acid sequences determined. These sequences demonstrate, as might be expected, that the venoms of P. reidyi and P. keyserlingi (Family: Ctenidae) both contain a similar range of isoforms of the neurotoxins as those previously isolated from P. nigriventer which are active on neuronal ion (Ca(2+), Na(+) and K(+)) channels and NMDA-type glutamate receptors. In addition two new families of small (3-4 kDa) toxins, some larger protein (>10 kDa) components, and two serine proteinases of the venom of P. nigriventer are described. These enzymes may be responsible for some of the post-translational modification observed in some of the venom components.

  • The toxin Tx4(6-1) from the spider Phoneutria nigriventer slows down Na(+) current inactivation in insect CNS via binding to receptor site 3.
    Journal of Insect Physiology, 2002
    Co-Authors: M E Lima, Maria Stankiewicz, S G Figueiredo, Carlos R. Diniz, Marie-france Martin-eauclaire, Alain Hamon, Milton Cordeiro, Marcel Pelhate
    Abstract:

    Abstract Tx4(6-1) a neurotoxic peptide from the venom of the aggressive South American ‘armed’ spider Phoneutria nigriventer, has been previously isolated and sequenced. It shows no detectable activity in mice but affects the peripheral nervous system of insects by stimulating glutamate release at the neuromuscular junction. Here we investigate possible interactions of the toxin with voltage-activated sodium channels (Nav). We confirm that it is ineffective on mammalian Nav channels, and establish that it competes with the α-like toxin 125 I -Bom IV, for binding on the site 3 of insect Nav channel (IC50 value around 25 nM). The physiological consequences of this binding to the insect Nav channel are shown by electrophysiology: Tx4(6-1) prolongs evoked axonal action potentials (APs) (

  • the toxin tx4 6 1 from the spider Phoneutria nigriventer slows down na current inactivation in insect cns via binding to receptor site 3
    Journal of Insect Physiology, 2002
    Co-Authors: M E Lima, M N Cordeiro, S G Figueiredo, Mariefrance Martineauclaire, C R Diniz, Alain Hamon, M Stankiewicz, Marcel Pelhate
    Abstract:

    Abstract Tx4(6-1) a neurotoxic peptide from the venom of the aggressive South American ‘armed’ spider Phoneutria nigriventer, has been previously isolated and sequenced. It shows no detectable activity in mice but affects the peripheral nervous system of insects by stimulating glutamate release at the neuromuscular junction. Here we investigate possible interactions of the toxin with voltage-activated sodium channels (Nav). We confirm that it is ineffective on mammalian Nav channels, and establish that it competes with the α-like toxin 125 I -Bom IV, for binding on the site 3 of insect Nav channel (IC50 value around 25 nM). The physiological consequences of this binding to the insect Nav channel are shown by electrophysiology: Tx4(6-1) prolongs evoked axonal action potentials (APs) (

Carlos R. Diniz - One of the best experts on this subject based on the ideXlab platform.

  • Properties of the Venom from the South American ‘‘Armed'’ Spider Phoneutria Nigriventer (Keyserling, 1891)
    Journal of Toxicology-toxin Reviews, 2008
    Co-Authors: Marta N. Cordeiro, Suely G. Figueiredo, Paulo S.l. Beirão, John Gilroy, Michael Richardson, Carlos R. Diniz
    Abstract:

    AbstractThe venomous glands of the South American spider Phoneutria nigriventer produce a complex mixture of basic neurotoxic polypeptides ranging in size from 2–16 KDa. Using semiquantitative bioassays combined with a sequence of FPLC and HPLC chromatographic steps we were able to purify more than 25 neurotoxic protein components from this venom, distinct in their chemical and pharmacological properties. The primary sequences of nine of these proteins have been solved. Alignment at the cysteine residues of P. nigriventer neurotoxins with published sequences of neurotoxic proteins from different spider species and other living organisms shows structural similarities, particularly evident in the distribution and location of these residues.

  • Functional expression and purification of recombinant Tx1, a sodium channel blocker neurotoxin from the venom of the Brazilian "armed" spider, Phoneutria nigriventer.
    Protein Expression and Purification, 2006
    Co-Authors: Marcelo R.v. Diniz, Marta N. Cordeiro, Maria Elena De Lima, A M C Pimenta, Julian M. Crampton, R. David G. Theakston, Carlos R. Diniz
    Abstract:

    Tx1 from the venom of the Brazilian spider, Phoneutria nigriventer, is a lethal neurotoxic polypeptide of Mr 8600 Da with 14 cysteine residues. It is a novel sodium channel blocker which reversibly inhibits sodium currents in CHO cells expressing recombinant sodium (Nav1.2) channels. We cloned and expressed the Tx1 toxin as a thioredoxin fusion product in the cytoplasm of Escherichia coli. After semipurification by immobilized Ni–ion affinity chromatography, the recombinant Tx1 was purified by reverse phase chromatography and characterized. It displayed similar biochemical and pharmacological properties to the native toxin, and it should be useful for further investigation of structure-function relationship of Na channels.

  • Expression of a functional recombinant Phoneutria nigriventer toxin active on K+ channels.
    Toxicon, 2003
    Co-Authors: Ana Carneiro, Marcus V. Gomez, Evanguedes Kalapothakis, Marta N. Cordeiro, Christopher Kushmerick, Janaina Koenen, M.h.l. Arndt, Carlos Chávez-olórtegui, Carlos R. Diniz, Marco A. M. Prado
    Abstract:

    PnTx3-1 is a peptide isolated from the venom of the spider Phoneutria nigriventer that specifically inhibits A-type K+ currents (IA) in GH3 cells. Here we used a bacterial expression system to produce an NH2-extended mutant of PnTx3-1 (ISEF-PnTx3-1) and tested whether the toxin is functional. The recombinant toxin was purified from bacterial extracts by a combination of affinity and ion-exchange chromatography. The recombinant toxin blocked A-type K+ currents in GH3 cells in a fashion similar to that observed with the wild-type toxin purified from the spider venom. These results suggest that recombinant cDNA methods provide a novel source for the production of functional Phoneutria toxins. The recombinant ISEF-PnTx3-1 should be useful for further understanding of the role of A-type K+ currents in biological processes.

  • Isolation of neurotoxic peptides from the venom of the 'armed' spider Phoneutria nigriventer.
    Toxicon, 2002
    Co-Authors: Leonides Rezende, Marta N. Cordeiro, Eduardo B. Oliveira, Carlos R. Diniz
    Abstract:

    Three neurotoxic fractions, lethal to mice, were isolated from the venom of the spider Phoneutria nigriventer, by gel filtration and reverse phase chromatography (Phoneutria toxins 1, 2 and 3). These toxins have mol. wts in the range 6000-9000, and have different amino acid compositions and N-terminal amino acid sequences. The toxins also differ in the lethality and signs they cause in mice after intracerebro-ventricular injection. The median LD50 being respectively for the whole venom, toxins 1, 2 and 3, 47 +/- 5 micrograms, 45 +/- 4 micrograms, 1.7 +/- 0.7 micrograms and 137 +/- 10 micrograms/kg mouse. Toxins 1 and 2 induce excitatory symptoms in mice and toxin 3 a flaccid paralysis with an ED50 of 40 +/- 5 micrograms/kg mouse as measured also by intracerebro-ventricular injection. The presence in the venom of a non-neurotoxic, smooth muscle active peptide is also described.

  • Purification and amino acid sequences of six TX3 type neurotoxins from the venom of the Brazilian 'armed' spider Phoneutria nigriventer (keys.)
    Toxicon, 2002
    Co-Authors: Marta N. Cordeiro, Suely G. Figueiredo, Carlos R. Diniz, Ana Do Carmo Valentim, Vera Regina D. Von Eickstedt, John Gilroy, Michael Richardson
    Abstract:

    Abstract Six neurotoxic peptides (Tx3-1 to Tx3-6) were purified from the venom of the spider Phoneutria nigriventer by a combination of gel filtration, reverse phase FPLC on PEP-RPC and PRO-RPC columns, reverse phase HPLC on Vydac C18, and ion exchange HPLC on cationic and anionic columns. These toxins caused different neurological symptoms in mice after intracerebro-ventricular injection. At dose levels of 5 μg/mouse, Tx3-3 and Tx3-4 caused rapid general flaccid paralysis followed by death in 10–30 min; Tx3-2 induced immediate clockwise gyration and flaccid paralysis after 6 hr; Tx3-1, Tx3-5 and Tx3-6 produced paralysis only in the posterior limbs and gradual decreases in movement and aggression during 24 hr. The mol. wt of these cystine-rich peptides were found to be in the range of 3500–8500 by mass spectroscopy and SDS-PAGE. The complete amino acid sequences of the neurotoxins Tx3-1 (40 residues), Tx3-2 (34 residues) and Tx3-6 (55 residues), and the N-terminal sequences of Tx3-3 (34 res.), Tx3-4 (40 res.) and Tx3-5 (36 res.) were established by direct automated Edman degradation, and manual DABITC/PITC microsequence analyses of peptides obtained from digests with various proteases. The structures of these Tx3 neurotoxins from Phoneutria nigriventer exhibited sequence similarities to one another and to the neurotoxins from the venoms of the spiders Hololena curta and Agelenopsis aperta, which were most evident in the location of the Cys residues.

Marcel Pelhate - One of the best experts on this subject based on the ideXlab platform.

  • The toxin Tx4(6-1) from the spider Phoneutria nigriventer slows down Na(+) current inactivation in insect CNS via binding to receptor site 3.
    Journal of Insect Physiology, 2002
    Co-Authors: M E Lima, Maria Stankiewicz, S G Figueiredo, Carlos R. Diniz, Marie-france Martin-eauclaire, Alain Hamon, Milton Cordeiro, Marcel Pelhate
    Abstract:

    Abstract Tx4(6-1) a neurotoxic peptide from the venom of the aggressive South American ‘armed’ spider Phoneutria nigriventer, has been previously isolated and sequenced. It shows no detectable activity in mice but affects the peripheral nervous system of insects by stimulating glutamate release at the neuromuscular junction. Here we investigate possible interactions of the toxin with voltage-activated sodium channels (Nav). We confirm that it is ineffective on mammalian Nav channels, and establish that it competes with the α-like toxin 125 I -Bom IV, for binding on the site 3 of insect Nav channel (IC50 value around 25 nM). The physiological consequences of this binding to the insect Nav channel are shown by electrophysiology: Tx4(6-1) prolongs evoked axonal action potentials (APs) (

  • the toxin tx4 6 1 from the spider Phoneutria nigriventer slows down na current inactivation in insect cns via binding to receptor site 3
    Journal of Insect Physiology, 2002
    Co-Authors: M E Lima, M N Cordeiro, S G Figueiredo, Mariefrance Martineauclaire, C R Diniz, Alain Hamon, M Stankiewicz, Marcel Pelhate
    Abstract:

    Abstract Tx4(6-1) a neurotoxic peptide from the venom of the aggressive South American ‘armed’ spider Phoneutria nigriventer, has been previously isolated and sequenced. It shows no detectable activity in mice but affects the peripheral nervous system of insects by stimulating glutamate release at the neuromuscular junction. Here we investigate possible interactions of the toxin with voltage-activated sodium channels (Nav). We confirm that it is ineffective on mammalian Nav channels, and establish that it competes with the α-like toxin 125 I -Bom IV, for binding on the site 3 of insect Nav channel (IC50 value around 25 nM). The physiological consequences of this binding to the insect Nav channel are shown by electrophysiology: Tx4(6-1) prolongs evoked axonal action potentials (APs) (