ASSOCIATION OF A PHOSPHOLIPASE A(2) (14-3-3-PROTEIN) WITH THE PLATELET GLYCOPROTEIN IB-IX COMPLEX

Platelet adhesion to subendothelial von Willebrand factor involves rec eptor recognition by the platelet glycoprotein (GP) Ib-IX and initiate s activation signals that contribute to primary hemostasis. We show he re that GPIb-IX is specifically associated with an intracellular 29-kD a protein. The physicochemical characteristics and amino acid sequence of this protein indicate that it is identical to the human zeta-isofo rm 14-3-3 protein, previously characterized as a platelet phospholipas e A(2) (PLA(2)). As activation of PLA(2) is an early event in GPIb-IX- mediated signaling, this result suggests that ligand occupancy of GPIb -IX may directly activate PLA(2), leading to platelet activation.