Alboluxin, a Snake C-type Lectin from Trimeresurus albolabris Venom is a Potent Platelet Agonist acting via GPIb and GPVI

Summary

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 γ chain (Fcγ), phospholipase Cγ2 (PLCγ2), LAT and p72^SYK. Antibodies against both GPIb and GPVI inhibited platelet aggregation induced by alboluxin, whereas antibodies against α₂β₁ had no effect. Inhibition of α_IIbβ₃ reduced the aggregation response to alboluxin, as well as tyrosine phosphorylation of platelet proteins, showing that activation of α_IIbβ₃ and binding of fibrinogen are involved in alboluxin-induced platelet aggregation and it is not simply agglutination. N-terminal sequence data from the β-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.

Keywords

Alboluxin - platelet aggregation - GPIb - GPVI - tyrosine phosphorylation

• References

• 1 Clemetson KJ. Platelet collagen receptors: A new target for inhibition?. Haemostasis 1999; 29: 16-26.
• 2 Clemetson KJ. Primary haemostasis: Sticky fingers cement the relationship. Current Biology 1999; 09: 110-2.
• 3 Du X, Plow EF, Frelinger III AL, O’Toole TE, Loftus JC, Ginsberg MH. Ligands “activate” integrin α_IIbβ₃ (platelet GPIIb-IIIa). Cell 1991; 65: 409-16.
• 4 Moroi M, Onitsuka I, Imaizumi T, Jung SM. Involvement of activated integrin α₂β₁ in the firm adhesion of platelets onto a surface of immobilized collagen under flow conditions. Thromb Haemost 2000; 83: 769-76.
• 5 Clemetson JM, Polgar J, Magnenat E, Wells TN, Clemetson KJ. The platelet collagen receptor glycoprotein VI is a member of the immunoglobulin superfamily closely related to FcαR and the natural killer receptors. J Biol Chem 1999; 274: 29019-24.
• 6 Clemetson KJ, Polgar J, Clemetson JM. Snake venom C-type lectins as tools in platelet research. Platelets 1998; 09: 165-9.
• 7 Andrews RK, Berndt MC. Snake venom modulators of platelet adhesion receptors and their ligands. Toxicon 2000; 38: 775-91.
• 8 Fujimura Y, Kawasaki T, Titani K. Snake venom proteins modulating the interaction between von Willebrand factor and platelet glycoprotein Ib. Thromb Haemost 1996; 76: 633-9.
• 9 Peng M, Lu W, Kirby PE. Alboaggregin-B: A new platelet agonist that binds to platelet membrane glycoprotein Ib. Biochemistry 1991; 30: 11529-36.
• 10 Andrews RK, Kroll MH, Ward CM, Rose JW, Scarborough RM, Smith AI, Lopez JA, Berndt MC. Binding of a novel 50-kilodalton alboaggregin from Trimeresurus albolabris and related viper venom proteins to the platelet membrane glycoprotein Ib-IX-V complex. Effect on platelet aggregation and glycoprotein Ib-mediated platelet activation. Biochemistry 1996; 35: 12629-39.
• 11 Dormann D, Clemetson JM, Navdaev A, Kehrel BE, Clemetson KJ. Alboaggregin A activates platelets by a mechanism involving glycoprotein VI as well as glycoprotein Ib. Blood 2001; 97: 929-36.
• 12 Wicki AN, Clemetson JM, Steiner B, Schnippering W, Clemetson KJ. Isolation and characterization of glycoprotein Ib. Methods Enzymol 1992; 215: 276-88.
• 13 Polar J, Clemetson JM, Kehrel BE, Wiedemann M, Magnenat EM, Timothy NCW, Clemetson KJ. Platelet activation and signal transduction by convulxin, a C-type lectin from Crotalus durissus terrificus (tropical rattlesnake) venom via the p62/GPVI collagen receptor. J Biol Chem 1997; 272: 13576-83.
• 14 Peng M, Lu W, Beviglia L, Niewiarowski S, Kirby EP. Echicetin: a snake venom protein that inhibits binding of von Willebrand factor and alboaggregins to platelet glycoprotein Ib. Blood 1993; 81: 2321-8.
• 15 Laemmli UK. Cleavage of structural proteins during the assembly of the head of bacteriophage. Nature 1970; 227: 680-5.
• 16 Morrissey JH. Silver stain for proteins in polyacrylamide gels: a modified procedure with enhanced uniform sensitivity. Anal Biochem 1981; 117: 307-10.
• 17 Watson SP, Gibbins J. Collagen receptor signaling in platelets: extending the role of the ITAM. Immunology Today 1998; 19: 260-3.
• 18 Peng M, Lu W, Kirby EP. Characterization of three alboaggregins purified from Trimeresurus albolabris venom. Thromb Haemost 1992; 67: 702-7.
• 19 Usami Y, Fujimura Y, Suzuki M, Ozeki Y, Nishio K, Fukui H, Titani K. Primary structure of two-chain botrocetin, a von Willebrand factor modulator purified from the venom of Bothrops jararaca . Proc Natl Acad Sci USA 1993; 90: 928-32.
• 20 Leduc M, Bon C. Cloning of subunits of convulxin, a collagen-like plateletaggregating protein from Crotalus durissus terrificus venom. Biochem J 1998; 333: 389-93.
• 21 Usami Y, Suzuki M, Yoshida E, Sakurai Y, Hirano K, Kawasaki T, Fujimura Y, Titani K. Primary structure of alboaggregin-B purified from the venom of Trimeresurus albolabris . Biochem Biophys Res Commun 1996; 219: 727-33.