Role of the Pyk2–MAP Kinase–cPLA2 Signaling Pathway in Shear-Dependent Platelet Aggregation


Mechanisms of shear-induced platelet aggregation are not established. Data that ristocetin-induced von Willebrand factor (VWF) binding to glycoprotein (Gp) Ibα activates proline-rich tyrosine kinase 2 (Pyk2) and extracellular-regulated kinase (ERK) has led to speculation that these events are coupled and that a MAP kinase may activate cytosolic phospholipase A2 (cPLA2)-mediated arachidonic acid (AA) release. To test this hypothesis and clarify the role of AA metabolism in shear-induced VWF-dependent platelet aggregation, we examined Pyk2, ERK1/2, and p38 phosphorylation, and arachidonic acid release and metabolism in platelets subjected to pathological shear stress in vitro. We observe tyrosine phosphorylation of Pyk2, p38, and ERK1/2 but no measurable increase in free AA, 12-hydroxyeicosatetraenoic acid, or thromboxane A2. Inhibitors of ERK, p38, or cyclooxygenase activation fail to affect shear-induced platelet aggregation. When washed platelets are aspirin-pretreated, arachidonic acid release becomes measurable and aggregation at 60 and 120 s is attenuated. These data indicate that shear-induced VWF binding to platelet GpIb-IX-V activates Pyk2, ERK1/2, p38, and cPLA2, but that the magnitude of these responses is below the threshold needed to enhance shear-induced VWF-dependent platelet aggregation in the presence of plasma. These results provide a mechanistic basis for the long-standing observation that shear-dependent platelet aggregation is unaffected by the antiplatelet drug aspirin.

DOI: 10.1114/B:ABME.0000039353.97347.28

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@article{Sun2004RoleOT, title={Role of the Pyk2–MAP Kinase–cPLA2 Signaling Pathway in Shear-Dependent Platelet Aggregation}, author={Lei Sun and Shuju Feng and Julio C. Res{\'e}ndiz and Xin Lu and William Durante and Michael Kroll}, journal={Annals of Biomedical Engineering}, year={2004}, volume={32}, pages={1193-1201} }