title: A role for p38 MAP kinase in platelet activation by von Willebrand factor.
abstract: Platelet activation induced by von Willebrand factor (VWF) binding to the membrane GPIb-IX-V receptor involves multiple signal transduction pathways. Among these, recruitment and activation of the FCgammaRIIA and stimulation of phospholipase A2 represent independent events equally essential to support a complete platelet response. Phospholipase A2 is activated by calcium and by phosphorylation through MAP kinases. In this work, we found that VWF stimulated the rapid and sustained phosphorylation of p38 MAP kinase (p38MAPK). In vitro kinase assay revealed that VWF-stimulated phosphorylation of p38MAPK was associated with increased kinase activity. Binding of VWF to GPIb-IX-V, but not to integrin alphaIibbeta3, was required to support phosphorylation of p38MAPK. Neither the blockade of the membrane FCgammaRIIA by a specific monoclonal antibody or the prevention of thromboxane A(2) synthesis by cyclooxygenase inhibitors affected VWF-induced p38MAPK activation. How-ever, phosphorylation of p38MAPK was prevented by the tyro-sine kinase Syk inhibitor piceatannol. Treatment of platelets with the p38MAPK inhibitor SB203580 totally prevented VWF-stimulated platelet aggregation. Moreover, release of arachidonic acid induced by VWF was strongly impaired by inhibition of p38MAPK. We also found that VWF induced phosphorylation of cytosolic phospholipase A(2), and that this process was prevented by the p38MAPK inhibitor SB203580. These results demon-strate that p38MAPK is a key element in the FCgammaRIIA-independent pathway for VWF-induced platelet activation, and is involved in the stimulation of phospholipase A(2) and arachidonic acid release.
authors.affiliation: Center of Excellence on Applied Biology, Department of Biochemistry, University of Pavia, via Bassi 21 27100 Pavia, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Canobbio
authors.forename: Stefania
authors.initials: S
authors.lastname: Reineri
authors.forename: Fabiola
authors.initials: F
authors.lastname: Sinigaglia
authors.forename: Cesare
authors.initials: C
authors.lastname: Balduini
authors.forename: Mauro
authors.initials: M
authors.lastname: Torti
mesh_terms: D000911:Antibodies, Monoclonal / Q000378:metabolism; D015703:Antigens, CD / Q000378:metabolism; D016718:Arachidonic Acid / Q000378:metabolism; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D010766:Phosphorylation; D015539:Platelet Activation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000378:metabolism; D010980:Platelet Membrane Glycoproteins; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D017452:Receptors, IgG / Q000378:metabolism; D012310:Ristocetin / Q000494:pharmacology; D015398:Signal Transduction; D000072377:Syk Kinase; D013928:Thromboxane A2 / Q000378:metabolism; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D016861:Cyclooxygenase Inhibitors; D004792:Enzyme Precursors; C080568:Fc gamma receptor IIA; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D019038:Platelet Glycoprotein GPIb-IX Complex; D010980:Platelet Membrane Glycoproteins; D011725:Pyridines; D017452:Receptors, IgG; C032193:glycoprotein receptor GPIb-IX; D014841:von Willebrand Factor; D012310:Ristocetin; D016718:Arachidonic Acid; D013928:Thromboxane A2; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010741:Phospholipases A; D054467:Phospholipases A2; C093642:SB 203580