title: Integrin alpha IIb beta 3-mediated pp125FAK phosphorylation and platelet spreading on fibrinogen are regulated by PI 3-kinase.
abstract: Activation of the focal adhesion kinase pp125FAK correlates with its phosphorylation on tyrosine residues and is mediated by multiple receptor-ligand pairs. In platelets, pp125FAK phosphorylation is triggered by alpha IIb beta 3 integrin or Fc gamma RII receptor interaction with immobilized fibrinogen and IgG, respectively. In this study we used platelets as a model system to explore the role of PI 3-kinase relative to pp125FAK phosphorylation. Treatment of the platelets with two PI 3-kinase inhibitors, wortmannin and LY294002, inhibited in a dose-dependent manner alpha IIb beta 3-mediated platelet spreading on fibrinogen having no effect on platelet spreading on IgG. Both inhibitors also completely abolished alpha IIb beta 3-mediated pp125FAK phosphorylation but not pp72syk phosphorylation. Furthermore, Fc gamma RII- and thrombin-induced pp125FAK phosphorylation were not affected by wortmannin and LY294002. Finally, the PI 3-kinase inhibitors' effect on alpha IIb beta 3-mediated spreading and pp125FAK phosphorylation was reversed by phorbol ester treatment. These results establish that the role of PI 3-kinase relative to pp125FAK phosphorylation in platelets is receptor type-specific yet essential for alpha IIb beta 3-mediated cell spreading and pp125FAK phosphorylation.
authors.affiliation: Department of Surgery, Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA.
authors.forename: P
authors.initials: P
authors.lastname: Ji
authors.forename: B
authors.initials: B
authors.lastname: Haimovich
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000097:blood*; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005340:Fibrinogen / Q000494:pharmacology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D007074:Immunoglobulin G / Q000494:pharmacology; D066298:In Vitro Techniques; D009025:Morpholines / Q000494:pharmacology; D010703:Phorbol Esters / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000097:blood*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D010973:Platelet Adhesiveness / Q000187:drug effects / Q000502:physiology*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000097:blood*; D000077191:Wortmannin