The snake venom toxin alboaggregin-A activates glycoprotein VI

The glycoprotein (GP)-lb-1X-V receptor complex has recently been reported t o signal through a pathway similar to that used by the collagen receptor GP VI, with a critical role described for the Pc receptor gamma -chain, The ev idence for this was based in part on studies with the GPlb alpha- selective snake venom toxin, alboaggregin-A. In the present study, it is reported th at alboaggregin-A has activity at the collagen receptor GPVI in addition to GPlb alpha, and evidence is provided that this contributes to protein tyro sine phosphorylation, shape change, and GPllb-llla-dependent aggregation. T his may explain why responses to alboaggregin-A are distinct from those to von Willebrand factor-ristocetin.