title: Role of the Pyk2-MAP kinase-cPLA2 signaling pathway in shear-dependent platelet aggregation.
abstract: Mechanisms of shear-induced platelet aggregation are not established. Data that ristocetin-induced von Willebrand factor (VWF) binding to glycoprotein (Gp) Ibalpha 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.
authors.affiliation: Michael E. DeBakey VA Medical Center, Baylor College of Medicine and Rice University, Houston, TX 77030, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Sun
authors.forename: Shuju
authors.initials: S
authors.lastname: Feng
authors.forename: Julio C
authors.initials: JC
authors.lastname: Reséndiz
authors.forename: Xin
authors.initials: X
authors.lastname: Lu
authors.forename: William
authors.initials: W
authors.lastname: Durante
authors.forename: Michael H
authors.initials: MH
authors.lastname: Kroll
mesh_terms: D000123:Acetyltransferases / Q000378:metabolism*; D016718:Arachidonic Acid; D001241:Aspirin / Q000494:pharmacology*; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D051418:Focal Adhesion Kinase 2; D006801:Humans; D040542:Mechanotransduction, Cellular / Q000187:drug effects / Q000502:physiology; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D033081:Shear Strength; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013314:Stress, Mechanical; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D014157:Transcription Factors; D016718:Arachidonic Acid; D000123:Acetyltransferases; C111246:HTATIP2 protein, human; D011505:Protein-Tyrosine Kinases; D051418:Focal Adhesion Kinase 2; D048049:Extracellular Signal-Regulated MAP Kinases; D001241:Aspirin