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

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.