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 α 2 β 1 had no effect. Inhibition of α IIb β 3 reduced the aggregation response to alboluxin, as well as tyrosine phosphorylation of platelet proteins, showing that activation of α IIb β 3 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.