title: Calpain regulation of cytoskeletal signaling complexes in von Willebrand factor-stimulated platelets. Distinct roles for glycoprotein Ib-V-IX and glycoprotein IIb-IIIa (integrin alphaIIbbeta3) in von Willebrand factor-induced signal transduction.
abstract: The adhesion of platelets to sites of vascular injury is critically dependent on the binding of subendothelial bound von Willebrand factor (vWf) to the platelet surface glycoprotein complexes, GP Ib-V-IX and GP IIb-IIIa (integrin alphaIIbbeta3). There is growing evidence that the binding of vWf to these receptors is not only essential for stable platelet adhesion but is also important for the transduction of activation signals required for changes in platelet morphology, granule secretion, and platelet aggregation. In this study we have investigated signaling events induced by vWf binding to GP Ib-V-IX in both spreading and aggregated platelets. The adhesion of platelets to vWf resulted in dramatic actin filament reorganization, as assessed by immunofluorescence with fluorescein isothiocyanate-conjugated phalloidin, and the cytoskeletal recruitment of various structural proteins (talin and integrin alphaIIbbeta3) and signaling enzymes (pp60c-src, focal adhesion kinase (FAK), phosphatidylinositol 3-kinase (PI 3-kinase), and protein-tyrosine phosphatase (PTP)-1B). Time course experiments in both spreading and aggregated platelets revealed that talin, FAK, and PTP-1B were proteolyzed after translocation to the cytoskeleton. The proteolysis of these proteins was dependent on the presence of extracellular calcium and was specifically inhibited by pretreating platelets with the membrane-permeable calpain inhibitors calpeptin, E64d, and MDL 28,170, but not with the membrane-impermeable inhibitors leupeptin, E64, and calpastatin. The cytoskeletal translocation of signaling enzymes in vWf-stimulated platelets was abolished by pretreating platelets with an anti-GP Ib-V-IX antibody but was unaffected by blocking ligand binding to integrin alphaIIbbeta3. In contrast, calpain activation in vWf-stimulated platelets required ligand binding to both GP Ib-V-IX and integrin alphaIIbbeta3. The activation of calpain in both spreading and aggregated platelets resulted in a substantial decrease in the level of tyrosine phosphorylation of multiple platelet proteins and was associated with a 50-80% reduction in the amount of cytoskeletal associated talin, integrin alphaIIbbeta3, PI 3-kinase, FAK, pp60(c-)src, and PTP-1B. These studies suggest a potentially important role for calpain in regulating the formation and/or stability of cytoskeletal signaling complexes in vWf-stimulated platelets. Furthermore, they demonstrate distinct roles for GP Ib-V-IX and integrin alphaIIbbeta3 in vWf-induced signal transduction.
authors.affiliation: Department of Medicine, Monash Medical School, the Australian Centre for Blood Diseases, Box Hill Hospital, Victoria 3128, Australia.
authors.forename: Y
authors.initials: Y
authors.lastname: Yuan
authors.forename: S M
authors.initials: SM
authors.lastname: Dopheide
authors.forename: C
authors.initials: C
authors.lastname: Ivanidis
authors.forename: H H
authors.initials: HH
authors.lastname: Salem
authors.forename: S P
authors.initials: SP
authors.lastname: Jackson
mesh_terms: D001792:Blood Platelets / Q000166:cytology / Q000502:physiology*; D002154:Calpain / Q000502:physiology*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D003599:Cytoskeleton / Q000502:physiology*; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D066298:In Vitro Techniques; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D010973:Platelet Adhesiveness; D010974:Platelet Aggregation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000502:physiology*; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000502:physiology*; D010980:Platelet Membrane Glycoproteins / Q000502:physiology*; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000502:physiology*; D015398:Signal Transduction; D016608:Talin / Q000378:metabolism; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D015815:Cell Adhesion Molecules; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D019038:Platelet Glycoprotein GPIb-IX Complex; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D016608:Talin; D014841:von Willebrand Factor; C028254:von Willebrand factor receptor; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D016392:Proto-Oncogene Proteins pp60(c-src); D017027:Protein Tyrosine Phosphatases; D002154:Calpain