title: Impaired thrombin-induced platelet activation and thrombus formation in mice lacking the Ca(2+)-dependent tyrosine kinase Pyk2.
abstract: In the present study, we used a knockout murine model to analyze the contribution of the Ca(2+)-dependent focal adhesion kinase Pyk2 in platelet activation and thrombus formation in vivo. We found that Pyk2-knockout mice had a tail bleeding time that was slightly increased compared with their wild-type littermates. Moreover, in an in vivo model of femoral artery thrombosis, the time to arterial occlusion was significantly prolonged in mice lacking Pyk2. Pyk2-deficient mice were also significantly protected from collagen plus epinephrine-induced pulmonary thromboembolism. Ex vivo aggregation of Pyk2-deficient platelets was normal on stimulation of glycoprotein VI, but was significantly reduced in response to PAR4-activating peptide, low doses of thrombin, or U46619. Defective platelet aggregation was accompanied by impaired inside-out activation of integrin α(IIb)β(3) and fibrinogen binding. Granule secretion was only slightly reduced in the absence of Pyk2, whereas a marked inhibition of thrombin-induced thromboxane A(2) production was observed, which was found to be responsible for the defective aggregation. Moreover, we have demonstrated that Pyk2 is implicated in the signaling pathway for cPLA(2) phosphorylation through p38 MAPK. The results of the present study show the importance of the focal adhesion kinase Pyk2 downstream of G-protein-coupled receptors in supporting platelet aggregation and thrombus formation.
authors.affiliation: Department of Biology and Biotechnology, Division of Biochemistry, University of Pavia, Pavia, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Canobbio
authors.forename: Lina
authors.initials: L
authors.lastname: Cipolla
authors.forename: Alessandra
authors.initials: A
authors.lastname: Consonni
authors.forename: Stefania
authors.initials: S
authors.lastname: Momi
authors.forename: Gianni
authors.initials: G
authors.lastname: Guidetti
authors.forename: Barbara
authors.initials: B
authors.lastname: Oliviero
authors.forename: Marco
authors.initials: M
authors.lastname: Falasca
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Okigaki
authors.forename: Cesare
authors.initials: C
authors.lastname: Balduini
authors.forename: Paolo
authors.initials: P
authors.lastname: Gresele
authors.forename: Mauro
authors.initials: M
authors.lastname: Torti
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D051418:Focal Adhesion Kinase 2 / Q000235:genetics*; D054501:Group II Phospholipases A2 / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation; D015539:Platelet Activation / Q000187:drug effects / Q000235:genetics*; D010974:Platelet Aggregation / Q000187:drug effects / Q000235:genetics; D015398:Signal Transduction; D013917:Thrombin / Q000378:metabolism* / Q000494:pharmacology; D013927:Thrombosis / Q000235:genetics* / Q000378:metabolism*; D013928:Thromboxane A2 / Q000096:biosynthesis; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D013928:Thromboxane A2; D051418:Focal Adhesion Kinase 2; D048051:p38 Mitogen-Activated Protein Kinases; D054501:Group II Phospholipases A2; D013917:Thrombin; D002118:Calcium