The Experts below are selected from a list of 768 Experts worldwide ranked by ideXlab platform
Kenneth J. Clemetson - One of the best experts on this subject based on the ideXlab platform.
-
alboluxin a snake c type lectin from trimeresurus albolabris venom is a potent platelet agonist acting via gpib and gpvi
Thrombosis and Haemostasis, 2002Co-Authors: Xiaoyan Du, Edith Magnenat, Timothy N C Wells, Kenneth J. ClemetsonAbstract:Alboluxin, a potent platelet activator, was purified from Trimere-surus albolabris venom with a mass of 120 kDa non-reduced and, after reduction, subunits of 17 and 24 kDa. Alboluxin induced a tyro-sine phosphorylation profile in platelets that resembles those produced by collagen and Convulxin, involving the time dependent tyrosine phos-phorylation of Fc receptor chain (Fc), phospholipase C2 (PLCγ2), LAT and p72 SYK . Antibodies against both GPIb and GPVI inhibited platelet aggregation induced by alboluxin, whereas antibodies against α2 Β1 had no effect. Inhibition of αIIbβ3 reduced the aggregation respon-se to alboluxin, as well as tyrosine phosphorylation of platelet proteins, showing that activation of αIIbβ3 and binding of fibrinogen are involv-ed in alboluxin-induced platelet aggregation and it is not simply ag-glutination. N-terminal sequence data from the -subunit of alboluxin indicates that it belongs to the snake C-type lectin family. The C-type lectin subunits are larger than usual possibly due to post-translational modifications such as glycosylation. Alboluxin is a hexameric (αβ) 3 snake C-type lectin which activates platelets via both GPIb and GPVI.
-
alboluxin a snake c type lectin from trimeresurus albolabris venom is a potent platelet agonist acting via gpib and gpvi
Thrombosis and Haemostasis, 2002Co-Authors: Edith Magnenat, Timothy N C Wells, Kenneth J. ClemetsonAbstract:Alboluxin, a potent platelet activator, was purified from Trimeresurus albolabris venom with a mass of 120 kDa non-reduced and, after reduction, subunits of 17 and 24 kDa. Alboluxin induced a tyrosine phosphorylation profile in platelets that resembles those produced by collagen and Convulxin, involving the time dependent tyrosine phosphorylation of Fc receptor gamma chain (Fc gamma), phospholipase Cgamma2 (PLCgamma2), LAT and p72SYK. Antibodies against both GPIb and GPVI inhibited platelet aggregation induced by alboluxin, whereas antibodies against alpha2beta1 had no effect. Inhibition of alphaIIb beta3 reduced the aggregation response to alboluxin, as well as tyrosine phosphorylation of platelet proteins, showing that activation of alphaIIb beta3 and binding of fibrinogen are involved in alboluxin-induced platelet aggregation and it is not simply agglutination. N-terminal sequence data from the beta-subunit of alboluxin indicates that it belongs to the snake C-type lectin family. The C-type lectin subunits are larger than usual possibly due to post-translational modifications such as glycosylation. Alboluxin is a hexameric (alphabeta)3 snake C-type lectin which activates platelets via both GPIb and GPVI.
-
surface expression and functional characterization of alpha granule factor v in human platelets effects of ionophore a23187 thrombin collagen and Convulxin
Blood, 2000Co-Authors: Lorenzo Alberio, Kenneth J. Clemetson, O Safa, Charles T Esmon, George L DaleAbstract:Factor V (FV) present in platelet alpha-granules has a significant but incompletely understood role in hemostasis. This report demonstrates that a fraction of platelets express very high levels of surface-bound, alpha-granule FV on simultaneous activation with 2 agonists, thrombin and Convulxin, an activator of the collagen receptor glycoprotein VI. This subpopulation of activated platelets represents 30.7% +/- 4.7% of the total population and is referred to as Convulxin and thrombin-induced-FV (COAT-FV) platelets. COAT-FV platelets are also observed on activation with thrombin plus collagen types I, V, or VI, but not with type III. No single agonist examined was able to produce COAT-FV platelets, although ionophore A23187 in conjunction with either thrombin or Convulxin did generate this population. COAT-FV platelets bound annexin-V, indicating exposure of aminophospholipids and were enriched in young platelets as identified by the binding of thiazole orange. The functional significance of COAT-FV platelets was investigated by demonstrating that factor Xa preferentially bound to COAT-FV platelets, that COAT-FV platelets had more FV activity than either thrombin or A23187-activated platelets, and that COAT-FV platelets were capable of generating more prothrombinase activity than any other physiologic agonist examined. Microparticle production by dual stimulation with thrombin and Convulxin was less than that observed with A23187, indicating that microparticles were not responsible for all the activities observed. These data demonstrate a new procoagulant component produced from dual stimulation of platelets with thrombin and collagen. COAT-FV platelets may explain the unique role of alpha-granule FV and the hemostatic effectiveness of young platelets. (Blood. 2000;95:1694-1702)
-
platelet activation and signal transduction by Convulxin a c type lectin from crotalus durissus terrificus tropical rattlesnake venom via the p62 gpvi collagen receptor
Journal of Biological Chemistry, 1997Co-Authors: Janos Polgar, Edith Magnenat, Timothy N C Wells, Jeannine M Clemetson, Beate E Kehrel, Markus Wiedemann, Kenneth J. ClemetsonAbstract:Convulxin, a powerful platelet activator, was isolated from Crotalus durissus terrificus venom, and 20 amino acid N-terminal sequences of both subunits were determined. These indicated that Convulxin belongs to the heterodimeric C-type lectin family. Neither antibodies against GPIb nor echicetin had any effect on Convulxin-induced platelet aggregation showing that, in contrast to other venom C-type lectins acting on platelets, GPIb is not involved in Convulxin-induced platelet activation. In addition, partially reduced/denatured Convulxin only affects collagen-induced platelet aggregation. The mechanism of Convulxin-induced platelet activation was examined by platelet aggregation, detection of time-dependent tyrosine phosphorylation of platelet proteins, and binding studies with 125I-Convulxin. Convulxin induces signal transduction in part like collagen, involving the time-dependent tyrosine phosphorylation of Fc receptor gamma chain, phospholipase Cgamma2, p72(SYK), c-Cbl, and p36-38. However, unlike collagen, pp125(FAK) and some other bands are not tyrosine-phosphorylated. Convulxin binds to a glycosylated 62-kDa membrane component in platelet lysate and to p62/GPVI immunoprecipitated by human anti-p62/GPVI antibodies. Convulxin subunits inhibit both aggregation and tyrosine phosphorylation in response to collagen. Piceatannol, a tyrosine kinase inhibitor with some specificity for p72(SYK), showed differential effects on collagen and Convulxin-stimulated signaling. These results suggest that Convulxin uses the p62/GPVI but not the alpha2beta1 part of the collagen signaling pathways to activate platelets. Occupation and clustering of p62/GPVI may activate Src family kinases phosphorylating Fc receptor gamma chain and, by a mechanism previously described in T- and B-cells, activate p72(SYK) that is critical for downstream activation of platelets.
-
platelet activation and signal transduction by Convulxin a c type lectin from crotalus durissus terrificus tropical rattlesnake venom via the p62 gpvi collagen receptor
Journal of Biological Chemistry, 1997Co-Authors: Janos Polgar, Edith Magnenat, Timothy N C Wells, Jeannine M Clemetson, Beate E Kehrel, Markus Wiedemann, Kenneth J. ClemetsonAbstract:Abstract Convulxin, a powerful platelet activator, was isolated from Crotalus durissus terrificus venom, and 20 amino acid N-terminal sequences of both subunits were determined. These indicated that Convulxin belongs to the heterodimeric C-type lectin family. Neither antibodies against GPIb nor echicetin had any effect on Convulxin-induced platelet aggregation showing that, in contrast to other venom C-type lectins acting on platelets, GPIb is not involved in Convulxin-induced platelet activation. In addition, partially reduced/denatured Convulxin only affects collagen-induced platelet aggregation. The mechanism of Convulxin-induced platelet activation was examined by platelet aggregation, detection of time-dependent tyrosine phosphorylation of platelet proteins, and binding studies with 125I-Convulxin. Convulxin induces signal transduction in part like collagen, involving the time-dependent tyrosine phosphorylation of Fc receptor γ chain, phospholipase Cγ2, p72SYK, c-Cbl, and p36–38. However, unlike collagen, pp125FAK and some other bands are not tyrosine-phosphorylated. Convulxin binds to a glycosylated 62-kDa membrane component in platelet lysate and to p62/GPVI immunoprecipitated by human anti-p62/GPVI antibodies. Convulxin subunits inhibit both aggregation and tyrosine phosphorylation in response to collagen. Piceatannol, a tyrosine kinase inhibitor with some specificity for p72SYK, showed differential effects on collagen and Convulxin-stimulated signaling. These results suggest that Convulxin uses the p62/GPVI but not the α2β1 part of the collagen signaling pathways to activate platelets. Occupation and clustering of p62/GPVI may activate Src family kinases phosphorylating Fc receptor γ chain and, by a mechanism previously described in T- and B-cells, activate p72SYK that is critical for downstream activation of platelets.
Cassian Bon - One of the best experts on this subject based on the ideXlab platform.
-
Convulxin binding to platelet receptor gpvi competition with collagen related peptides
Biochemical and Biophysical Research Communications, 2000Co-Authors: F Niedergang, Cassian Bon, Ivo M B Francischetti, A Alcover, C G Knight, Richard W Farndale, M J Barnes, Mireille LeducAbstract:Abstract Convulxin (CVX), a potent platelet aggregating protein from the venom of the snake Crotalus durissus terrificus, is known to bind to the platelet collagen receptor, glycoprotein VI (GPVI). CVX binding to human platelets was investigated by flow cytometry, using fluorescein labeled Convulxin (FITC-CVX). Scatchard analysis indicated high and low affinity binding sites with Kd values of 0.6 and 4 nM and Bmax values of 1200 and 2000 binding sites per platelet. FITC-CVX binding was inhibited by collagen related peptides (CRPs) comprising a repeated GPO sequence, namely GCO(GPO)10GCOGNH2 and GKO(GPO)10GKOGNH2, which also bind to receptor GPVI. These peptides (monomeric or cross-linked forms) gave a high affinity inhibition of 10–20% for concentrations between 10 ng/ml and 5 μg/ml, followed by a second phase of inhibition at concentrations greater than 5 μg/ml. It was shown also that the inhibition of FITC-CVX binding by CRPs was independent on the time of preincubation of platelets with CRPs, and the same percentage of inhibition was seen with various concentrations of Convulxin. Confocal microscopy of the distribution of FITC-CVX binding sites on platelets showed an homogeneous distribution of FITC-CVX bound to GPVI, although some limited clustering may exist.
-
adhesion and activation of human platelets induced by Convulxin involve glycoprotein vi and integrin α21
Journal of Biological Chemistry, 1997Co-Authors: Martine Jandrotperrus, Minoru Okuma, Annehelene Lagrue, Cassian BonAbstract:We analyzed the interaction of Convulxin (Cvx), a 72-kDa protein isolated from the venom of Crotalus durissus terrificus, with human platelets. Cvx is a potent platelet agonist that induces an increase in the intracellular Ca2+concentration ([Ca2+] i), granule exocytosis and aggregation. 125I-Labeled Cvx binds specifically and rapidly to platelets at binding sites of high and moderate affinity. Platelets adhere to immobilized Cvx in a time-dependent but cation-independent manner. Platelet exocytosis and aggregation induced by Cvx were inhibited by an anti-integrin α21 monoclonal antibody (6F1) and by the Fab fragments of a polyclonal anti-glycoprotein VI (GPVI) antibody. Both the adhesion of platelets to Cvx and the Cvx-induced increase in [Ca2+] i were inhibited by anti-GPVI Fab fragments but not by 6F1. Ligand blotting assay showed that 125I-Cvx binds to a 57-kDa platelet protein with an electrophoretic mobility identical to that of GPVI. In addition, we observed the following: (i)125I-Cvx binds to GPVI immunoprecipitated by the anti-GPVI antibody from a platelet lysate, and (ii) Cvx inhibits the binding of anti-GPVI IgG to GPVI. Taken together, these results demonstrate that GPVI behaves as a Cvx receptor and that the α21 integrin appears to be involved in the later stages of Cvx-induced platelet activation,i.e. exocytosis and aggregation.
-
Convulxin a potent platelet aggregating protein from crotalus durissus terrificus venom specifically binds to platelets
Toxicon, 1997Co-Authors: Ivo M B Francischetti, B Saliou, Mireille Leduc, Celia R Carlini, Mohamed Hatmi, J Randon, Ahmad Faili, Cassian BonAbstract:Convulxin, a very potent aggregating protein from rattlesnake venom, was purified by a new procedure and its heterodimeric structure α3μ3 was confirmed. The polypeptide N-terminal sequences of Convulxin subunits were determined by Edman degradation. They are very similar and appear homologous to botrocetin from Bothrops jararaca venom and to rattlesnake lectin from Crotalus atrox venom, both being classified among the C-type lectin family. The binding of 125I-labelled Convulxin to blood platelets has also been analysed under equilibrium conditions. These studies indicated that Convulxin binds to platelets with a high affinity (d = 30 pM) on a small number of binding sites (1000 binding sites per cell). The high-affinity binding of Convulxin appears specific to platelets, since it is not observed on other cell types such as neutrophils and erythrocytes. Also, the high-affinity binding of Convulxin to membranes platelet is not inhibited by α-thrombin, fibrinogen, collagen, laminin binding inhibitor, RGDS peptide, adenosine diphosphate, platelet-activating factor-acether, serotonin or epinephrine. This, together with the recent observation that platelet activation by Convulxin is partially mediated by phospholipase C and involves other mechanisms as well, indicates that Convulxin may interact with a specific platelet acceptor (receptor) protein which has yet to be characterized.
-
Convulxin a potent platelet aggregating protein from crotalus durissus terrificus venom specifically binds to platelets
Toxicon, 1997Co-Authors: Ivo M B Francischetti, B Saliou, Mireille Leduc, Celia R Carlini, Mohamed Hatmi, J Randon, Ahmad Faili, Cassian BonAbstract:Convulxin, a very potent aggregating protein from rattlesnake venom, was purified by a new procedure and its heterodimeric structure alpha 3 beta 3 was confirmed. The polypeptide N-terminal sequences of Convulxin subunits were determined by Edman degradation. They are very similar and appear homologous to botrocetin from Bothrops jararaca venom and to rattlesnake lectin from Crotalus atrox venom, both being classified among the C-type lectin family. The binding of 125I-labelled Convulxin to blood platelets has also been analysed under equilibrium conditions. These studies indicated that Convulxin binds to platelets with a high affinity (Kd = 30 pM) on a small number of binding sites (1000 binding sites per cell). The high-affinity binding of Convulxin appears specific to platelets, since it is not observed on other cell types such as neutrophils and erythrocytes. Also, the high-affinity binding of Convulxin to membranes platelet is not inhibited by alpha-thrombin, fibrinogen, collagen, laminin binding inhibitor, RGDS peptide, adenosine diphosphate, platelet-activating factor-acether, serotonin or epinephrine. This, together with the recent observation that platelet activation by Convulxin is partially mediated by phospholipase C and involves other mechanisms as well, indicates that Convulxin may interact with a specific platelet acceptor (receptor) protein which has yet to be characterized.
Ivo M B Francischetti - One of the best experts on this subject based on the ideXlab platform.
-
Convulxin binding to platelet receptor gpvi competition with collagen related peptides
Biochemical and Biophysical Research Communications, 2000Co-Authors: F Niedergang, Cassian Bon, Ivo M B Francischetti, A Alcover, C G Knight, Richard W Farndale, M J Barnes, Mireille LeducAbstract:Abstract Convulxin (CVX), a potent platelet aggregating protein from the venom of the snake Crotalus durissus terrificus, is known to bind to the platelet collagen receptor, glycoprotein VI (GPVI). CVX binding to human platelets was investigated by flow cytometry, using fluorescein labeled Convulxin (FITC-CVX). Scatchard analysis indicated high and low affinity binding sites with Kd values of 0.6 and 4 nM and Bmax values of 1200 and 2000 binding sites per platelet. FITC-CVX binding was inhibited by collagen related peptides (CRPs) comprising a repeated GPO sequence, namely GCO(GPO)10GCOGNH2 and GKO(GPO)10GKOGNH2, which also bind to receptor GPVI. These peptides (monomeric or cross-linked forms) gave a high affinity inhibition of 10–20% for concentrations between 10 ng/ml and 5 μg/ml, followed by a second phase of inhibition at concentrations greater than 5 μg/ml. It was shown also that the inhibition of FITC-CVX binding by CRPs was independent on the time of preincubation of platelets with CRPs, and the same percentage of inhibition was seen with various concentrations of Convulxin. Confocal microscopy of the distribution of FITC-CVX binding sites on platelets showed an homogeneous distribution of FITC-CVX bound to GPVI, although some limited clustering may exist.
-
Convulxin a potent platelet aggregating protein from crotalus durissus terrificus venom specifically binds to platelets
Toxicon, 1997Co-Authors: Ivo M B Francischetti, B Saliou, Mireille Leduc, Celia R Carlini, Mohamed Hatmi, J Randon, Ahmad Faili, Cassian BonAbstract:Convulxin, a very potent aggregating protein from rattlesnake venom, was purified by a new procedure and its heterodimeric structure α3μ3 was confirmed. The polypeptide N-terminal sequences of Convulxin subunits were determined by Edman degradation. They are very similar and appear homologous to botrocetin from Bothrops jararaca venom and to rattlesnake lectin from Crotalus atrox venom, both being classified among the C-type lectin family. The binding of 125I-labelled Convulxin to blood platelets has also been analysed under equilibrium conditions. These studies indicated that Convulxin binds to platelets with a high affinity (d = 30 pM) on a small number of binding sites (1000 binding sites per cell). The high-affinity binding of Convulxin appears specific to platelets, since it is not observed on other cell types such as neutrophils and erythrocytes. Also, the high-affinity binding of Convulxin to membranes platelet is not inhibited by α-thrombin, fibrinogen, collagen, laminin binding inhibitor, RGDS peptide, adenosine diphosphate, platelet-activating factor-acether, serotonin or epinephrine. This, together with the recent observation that platelet activation by Convulxin is partially mediated by phospholipase C and involves other mechanisms as well, indicates that Convulxin may interact with a specific platelet acceptor (receptor) protein which has yet to be characterized.
-
Convulxin a potent platelet aggregating protein from crotalus durissus terrificus venom specifically binds to platelets
Toxicon, 1997Co-Authors: Ivo M B Francischetti, B Saliou, Mireille Leduc, Celia R Carlini, Mohamed Hatmi, J Randon, Ahmad Faili, Cassian BonAbstract:Convulxin, a very potent aggregating protein from rattlesnake venom, was purified by a new procedure and its heterodimeric structure alpha 3 beta 3 was confirmed. The polypeptide N-terminal sequences of Convulxin subunits were determined by Edman degradation. They are very similar and appear homologous to botrocetin from Bothrops jararaca venom and to rattlesnake lectin from Crotalus atrox venom, both being classified among the C-type lectin family. The binding of 125I-labelled Convulxin to blood platelets has also been analysed under equilibrium conditions. These studies indicated that Convulxin binds to platelets with a high affinity (Kd = 30 pM) on a small number of binding sites (1000 binding sites per cell). The high-affinity binding of Convulxin appears specific to platelets, since it is not observed on other cell types such as neutrophils and erythrocytes. Also, the high-affinity binding of Convulxin to membranes platelet is not inhibited by alpha-thrombin, fibrinogen, collagen, laminin binding inhibitor, RGDS peptide, adenosine diphosphate, platelet-activating factor-acether, serotonin or epinephrine. This, together with the recent observation that platelet activation by Convulxin is partially mediated by phospholipase C and involves other mechanisms as well, indicates that Convulxin may interact with a specific platelet acceptor (receptor) protein which has yet to be characterized.
Edith Magnenat - One of the best experts on this subject based on the ideXlab platform.
-
alboluxin a snake c type lectin from trimeresurus albolabris venom is a potent platelet agonist acting via gpib and gpvi
Thrombosis and Haemostasis, 2002Co-Authors: Xiaoyan Du, Edith Magnenat, Timothy N C Wells, Kenneth J. ClemetsonAbstract:Alboluxin, a potent platelet activator, was purified from Trimere-surus albolabris venom with a mass of 120 kDa non-reduced and, after reduction, subunits of 17 and 24 kDa. Alboluxin induced a tyro-sine phosphorylation profile in platelets that resembles those produced by collagen and Convulxin, involving the time dependent tyrosine phos-phorylation of Fc receptor chain (Fc), phospholipase C2 (PLCγ2), LAT and p72 SYK . Antibodies against both GPIb and GPVI inhibited platelet aggregation induced by alboluxin, whereas antibodies against α2 Β1 had no effect. Inhibition of αIIbβ3 reduced the aggregation respon-se to alboluxin, as well as tyrosine phosphorylation of platelet proteins, showing that activation of αIIbβ3 and binding of fibrinogen are involv-ed in alboluxin-induced platelet aggregation and it is not simply ag-glutination. N-terminal sequence data from the -subunit of alboluxin indicates that it belongs to the snake C-type lectin family. The C-type lectin subunits are larger than usual possibly due to post-translational modifications such as glycosylation. Alboluxin is a hexameric (αβ) 3 snake C-type lectin which activates platelets via both GPIb and GPVI.
-
alboluxin a snake c type lectin from trimeresurus albolabris venom is a potent platelet agonist acting via gpib and gpvi
Thrombosis and Haemostasis, 2002Co-Authors: Edith Magnenat, Timothy N C Wells, Kenneth J. ClemetsonAbstract:Alboluxin, a potent platelet activator, was purified from Trimeresurus albolabris venom with a mass of 120 kDa non-reduced and, after reduction, subunits of 17 and 24 kDa. Alboluxin induced a tyrosine phosphorylation profile in platelets that resembles those produced by collagen and Convulxin, involving the time dependent tyrosine phosphorylation of Fc receptor gamma chain (Fc gamma), phospholipase Cgamma2 (PLCgamma2), LAT and p72SYK. Antibodies against both GPIb and GPVI inhibited platelet aggregation induced by alboluxin, whereas antibodies against alpha2beta1 had no effect. Inhibition of alphaIIb beta3 reduced the aggregation response to alboluxin, as well as tyrosine phosphorylation of platelet proteins, showing that activation of alphaIIb beta3 and binding of fibrinogen are involved in alboluxin-induced platelet aggregation and it is not simply agglutination. N-terminal sequence data from the beta-subunit of alboluxin indicates that it belongs to the snake C-type lectin family. The C-type lectin subunits are larger than usual possibly due to post-translational modifications such as glycosylation. Alboluxin is a hexameric (alphabeta)3 snake C-type lectin which activates platelets via both GPIb and GPVI.
-
platelet activation and signal transduction by Convulxin a c type lectin from crotalus durissus terrificus tropical rattlesnake venom via the p62 gpvi collagen receptor
Journal of Biological Chemistry, 1997Co-Authors: Janos Polgar, Edith Magnenat, Timothy N C Wells, Jeannine M Clemetson, Beate E Kehrel, Markus Wiedemann, Kenneth J. ClemetsonAbstract:Convulxin, a powerful platelet activator, was isolated from Crotalus durissus terrificus venom, and 20 amino acid N-terminal sequences of both subunits were determined. These indicated that Convulxin belongs to the heterodimeric C-type lectin family. Neither antibodies against GPIb nor echicetin had any effect on Convulxin-induced platelet aggregation showing that, in contrast to other venom C-type lectins acting on platelets, GPIb is not involved in Convulxin-induced platelet activation. In addition, partially reduced/denatured Convulxin only affects collagen-induced platelet aggregation. The mechanism of Convulxin-induced platelet activation was examined by platelet aggregation, detection of time-dependent tyrosine phosphorylation of platelet proteins, and binding studies with 125I-Convulxin. Convulxin induces signal transduction in part like collagen, involving the time-dependent tyrosine phosphorylation of Fc receptor gamma chain, phospholipase Cgamma2, p72(SYK), c-Cbl, and p36-38. However, unlike collagen, pp125(FAK) and some other bands are not tyrosine-phosphorylated. Convulxin binds to a glycosylated 62-kDa membrane component in platelet lysate and to p62/GPVI immunoprecipitated by human anti-p62/GPVI antibodies. Convulxin subunits inhibit both aggregation and tyrosine phosphorylation in response to collagen. Piceatannol, a tyrosine kinase inhibitor with some specificity for p72(SYK), showed differential effects on collagen and Convulxin-stimulated signaling. These results suggest that Convulxin uses the p62/GPVI but not the alpha2beta1 part of the collagen signaling pathways to activate platelets. Occupation and clustering of p62/GPVI may activate Src family kinases phosphorylating Fc receptor gamma chain and, by a mechanism previously described in T- and B-cells, activate p72(SYK) that is critical for downstream activation of platelets.
-
platelet activation and signal transduction by Convulxin a c type lectin from crotalus durissus terrificus tropical rattlesnake venom via the p62 gpvi collagen receptor
Journal of Biological Chemistry, 1997Co-Authors: Janos Polgar, Edith Magnenat, Timothy N C Wells, Jeannine M Clemetson, Beate E Kehrel, Markus Wiedemann, Kenneth J. ClemetsonAbstract:Abstract Convulxin, a powerful platelet activator, was isolated from Crotalus durissus terrificus venom, and 20 amino acid N-terminal sequences of both subunits were determined. These indicated that Convulxin belongs to the heterodimeric C-type lectin family. Neither antibodies against GPIb nor echicetin had any effect on Convulxin-induced platelet aggregation showing that, in contrast to other venom C-type lectins acting on platelets, GPIb is not involved in Convulxin-induced platelet activation. In addition, partially reduced/denatured Convulxin only affects collagen-induced platelet aggregation. The mechanism of Convulxin-induced platelet activation was examined by platelet aggregation, detection of time-dependent tyrosine phosphorylation of platelet proteins, and binding studies with 125I-Convulxin. Convulxin induces signal transduction in part like collagen, involving the time-dependent tyrosine phosphorylation of Fc receptor γ chain, phospholipase Cγ2, p72SYK, c-Cbl, and p36–38. However, unlike collagen, pp125FAK and some other bands are not tyrosine-phosphorylated. Convulxin binds to a glycosylated 62-kDa membrane component in platelet lysate and to p62/GPVI immunoprecipitated by human anti-p62/GPVI antibodies. Convulxin subunits inhibit both aggregation and tyrosine phosphorylation in response to collagen. Piceatannol, a tyrosine kinase inhibitor with some specificity for p72SYK, showed differential effects on collagen and Convulxin-stimulated signaling. These results suggest that Convulxin uses the p62/GPVI but not the α2β1 part of the collagen signaling pathways to activate platelets. Occupation and clustering of p62/GPVI may activate Src family kinases phosphorylating Fc receptor γ chain and, by a mechanism previously described in T- and B-cells, activate p72SYK that is critical for downstream activation of platelets.
Timothy N C Wells - One of the best experts on this subject based on the ideXlab platform.
-
alboluxin a snake c type lectin from trimeresurus albolabris venom is a potent platelet agonist acting via gpib and gpvi
Thrombosis and Haemostasis, 2002Co-Authors: Xiaoyan Du, Edith Magnenat, Timothy N C Wells, Kenneth J. ClemetsonAbstract:Alboluxin, a potent platelet activator, was purified from Trimere-surus albolabris venom with a mass of 120 kDa non-reduced and, after reduction, subunits of 17 and 24 kDa. Alboluxin induced a tyro-sine phosphorylation profile in platelets that resembles those produced by collagen and Convulxin, involving the time dependent tyrosine phos-phorylation of Fc receptor chain (Fc), phospholipase C2 (PLCγ2), LAT and p72 SYK . Antibodies against both GPIb and GPVI inhibited platelet aggregation induced by alboluxin, whereas antibodies against α2 Β1 had no effect. Inhibition of αIIbβ3 reduced the aggregation respon-se to alboluxin, as well as tyrosine phosphorylation of platelet proteins, showing that activation of αIIbβ3 and binding of fibrinogen are involv-ed in alboluxin-induced platelet aggregation and it is not simply ag-glutination. N-terminal sequence data from the -subunit of alboluxin indicates that it belongs to the snake C-type lectin family. The C-type lectin subunits are larger than usual possibly due to post-translational modifications such as glycosylation. Alboluxin is a hexameric (αβ) 3 snake C-type lectin which activates platelets via both GPIb and GPVI.
-
alboluxin a snake c type lectin from trimeresurus albolabris venom is a potent platelet agonist acting via gpib and gpvi
Thrombosis and Haemostasis, 2002Co-Authors: Edith Magnenat, Timothy N C Wells, Kenneth J. ClemetsonAbstract:Alboluxin, a potent platelet activator, was purified from Trimeresurus albolabris venom with a mass of 120 kDa non-reduced and, after reduction, subunits of 17 and 24 kDa. Alboluxin induced a tyrosine phosphorylation profile in platelets that resembles those produced by collagen and Convulxin, involving the time dependent tyrosine phosphorylation of Fc receptor gamma chain (Fc gamma), phospholipase Cgamma2 (PLCgamma2), LAT and p72SYK. Antibodies against both GPIb and GPVI inhibited platelet aggregation induced by alboluxin, whereas antibodies against alpha2beta1 had no effect. Inhibition of alphaIIb beta3 reduced the aggregation response to alboluxin, as well as tyrosine phosphorylation of platelet proteins, showing that activation of alphaIIb beta3 and binding of fibrinogen are involved in alboluxin-induced platelet aggregation and it is not simply agglutination. N-terminal sequence data from the beta-subunit of alboluxin indicates that it belongs to the snake C-type lectin family. The C-type lectin subunits are larger than usual possibly due to post-translational modifications such as glycosylation. Alboluxin is a hexameric (alphabeta)3 snake C-type lectin which activates platelets via both GPIb and GPVI.
-
platelet activation and signal transduction by Convulxin a c type lectin from crotalus durissus terrificus tropical rattlesnake venom via the p62 gpvi collagen receptor
Journal of Biological Chemistry, 1997Co-Authors: Janos Polgar, Edith Magnenat, Timothy N C Wells, Jeannine M Clemetson, Beate E Kehrel, Markus Wiedemann, Kenneth J. ClemetsonAbstract:Convulxin, a powerful platelet activator, was isolated from Crotalus durissus terrificus venom, and 20 amino acid N-terminal sequences of both subunits were determined. These indicated that Convulxin belongs to the heterodimeric C-type lectin family. Neither antibodies against GPIb nor echicetin had any effect on Convulxin-induced platelet aggregation showing that, in contrast to other venom C-type lectins acting on platelets, GPIb is not involved in Convulxin-induced platelet activation. In addition, partially reduced/denatured Convulxin only affects collagen-induced platelet aggregation. The mechanism of Convulxin-induced platelet activation was examined by platelet aggregation, detection of time-dependent tyrosine phosphorylation of platelet proteins, and binding studies with 125I-Convulxin. Convulxin induces signal transduction in part like collagen, involving the time-dependent tyrosine phosphorylation of Fc receptor gamma chain, phospholipase Cgamma2, p72(SYK), c-Cbl, and p36-38. However, unlike collagen, pp125(FAK) and some other bands are not tyrosine-phosphorylated. Convulxin binds to a glycosylated 62-kDa membrane component in platelet lysate and to p62/GPVI immunoprecipitated by human anti-p62/GPVI antibodies. Convulxin subunits inhibit both aggregation and tyrosine phosphorylation in response to collagen. Piceatannol, a tyrosine kinase inhibitor with some specificity for p72(SYK), showed differential effects on collagen and Convulxin-stimulated signaling. These results suggest that Convulxin uses the p62/GPVI but not the alpha2beta1 part of the collagen signaling pathways to activate platelets. Occupation and clustering of p62/GPVI may activate Src family kinases phosphorylating Fc receptor gamma chain and, by a mechanism previously described in T- and B-cells, activate p72(SYK) that is critical for downstream activation of platelets.
-
platelet activation and signal transduction by Convulxin a c type lectin from crotalus durissus terrificus tropical rattlesnake venom via the p62 gpvi collagen receptor
Journal of Biological Chemistry, 1997Co-Authors: Janos Polgar, Edith Magnenat, Timothy N C Wells, Jeannine M Clemetson, Beate E Kehrel, Markus Wiedemann, Kenneth J. ClemetsonAbstract:Abstract Convulxin, a powerful platelet activator, was isolated from Crotalus durissus terrificus venom, and 20 amino acid N-terminal sequences of both subunits were determined. These indicated that Convulxin belongs to the heterodimeric C-type lectin family. Neither antibodies against GPIb nor echicetin had any effect on Convulxin-induced platelet aggregation showing that, in contrast to other venom C-type lectins acting on platelets, GPIb is not involved in Convulxin-induced platelet activation. In addition, partially reduced/denatured Convulxin only affects collagen-induced platelet aggregation. The mechanism of Convulxin-induced platelet activation was examined by platelet aggregation, detection of time-dependent tyrosine phosphorylation of platelet proteins, and binding studies with 125I-Convulxin. Convulxin induces signal transduction in part like collagen, involving the time-dependent tyrosine phosphorylation of Fc receptor γ chain, phospholipase Cγ2, p72SYK, c-Cbl, and p36–38. However, unlike collagen, pp125FAK and some other bands are not tyrosine-phosphorylated. Convulxin binds to a glycosylated 62-kDa membrane component in platelet lysate and to p62/GPVI immunoprecipitated by human anti-p62/GPVI antibodies. Convulxin subunits inhibit both aggregation and tyrosine phosphorylation in response to collagen. Piceatannol, a tyrosine kinase inhibitor with some specificity for p72SYK, showed differential effects on collagen and Convulxin-stimulated signaling. These results suggest that Convulxin uses the p62/GPVI but not the α2β1 part of the collagen signaling pathways to activate platelets. Occupation and clustering of p62/GPVI may activate Src family kinases phosphorylating Fc receptor γ chain and, by a mechanism previously described in T- and B-cells, activate p72SYK that is critical for downstream activation of platelets.