The snake venom toxin alboaggregin-A activates glycoprotein VI

The glycoprotein (GP)–Ib-IX-V receptor complex has recently been reported to signal through a pathway similar to that used by the collagen receptor GPVI, with a critical role described for the Fc receptor γ-chain. The evidence for this was based in part on studies with the GPIbα-selective snake venom toxin, alboaggregin-A. In the present study, it is reported that alboaggregin-A has activity at the collagen receptor GPVI in addition to GPIbα, and evidence is provided that this contributes to protein tyrosine phosphorylation, shape change, and GPIIb-IIIa–dependent aggregation. This may explain why responses to alboaggregin-A are distinct from those to von Willebrand factor– ristocetin.