title: Growth factor receptor-bound protein 2 contributes to (hem)immunoreceptor tyrosine-based activation motif-mediated signaling in platelets.
abstract: BACKGROUND
  Platelets are anuclear cell fragments derived from bone marrow megakaryocytes (MKs) that safeguard vascular integrity but may also cause pathological vessel occlusion. One major pathway of platelet activation is triggered by 2 receptors that signal through an (hem)immunoreceptor tyrosine-based activation motif (ITAM), the activating collagen receptor glycoprotein (GP) VI and the C-type lectin-like receptor 2 (CLEC-2). Growth factor receptor-bound protein 2 (Grb2) is a ubiquitously expressed adapter molecule involved in signaling processes of numerous receptors in different cell types, but its function in platelets and MKs is unknown.
  
  
  OBJECTIVE
  We tested the hypothesis that Grb2 is a crucial adapter protein in (hem)immunoreceptor tyrosine-based activation motif signaling in platelets.
  
  
  RESULTS
  Here, we show that genetic ablation of Grb2 in MKs and platelets did not interfere with MK differentiation or platelet production. However, Grb2-deficiency severely impaired glycoprotein VI-mediated platelet activation because of defective stabilization of the linker of activated T-cell (LAT) signalosome and activation of downstream signaling proteins that resulted in reduced adhesion, aggregation, and coagulant activity on collagen in vitro. Similarly, CLEC-2-mediated signaling was impaired in Grb2-deficient platelets, whereas the cells responded normally to stimulation of G protein-coupled receptors. In vivo, this selective (hem)immunoreceptor tyrosine-based activation motif signaling defect resulted in prolonged bleeding times but affected arterial thrombus formation only after concomitant treatment with acetylsalicylic acid, indicating that defective glycoprotein VI signaling in the absence of Grb2 can be compensated through thromboxane A2-induced G protein-coupled receptor signaling pathways.
  
  
  CONCLUSIONS
  These results reveal an important contribution of Grb2 in (hem)immunoreceptor tyrosine-based activation motif signaling in platelets in hemostasis and thrombosis by stabilizing the LAT signalosome.
authors.affiliation: Department of Experimental Biomedicine, University Hospital Würzburg (S.D., T.V., M.M., S.S., B.N.) and Rudolf Virchow Center for Experimental Biomedicine (S.D., T.V., C.M.S., H.M.H., B.N.), University of Würzburg, Würzburg, Germany; Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom (S.K.W., C.E.H., S.P.W.); and Department of Biology, Division of Genetics, University of Erlangen, Erlangen, Germany (J.A.A., D.R., L.N.).
authors.forename: Sebastian
authors.initials: S
authors.lastname: Dütting
authors.affiliation: Department of Experimental Biomedicine, University Hospital Würzburg (S.D., T.V., M.M., S.S., B.N.) and Rudolf Virchow Center for Experimental Biomedicine (S.D., T.V., C.M.S., H.M.H., B.N.), University of Würzburg, Würzburg, Germany; Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom (S.K.W., C.E.H., S.P.W.); and Department of Biology, Division of Genetics, University of Erlangen, Erlangen, Germany (J.A.A., D.R., L.N.).
authors.forename: Timo
authors.initials: T
authors.lastname: Vögtle
authors.affiliation: Department of Experimental Biomedicine, University Hospital Würzburg (S.D., T.V., M.M., S.S., B.N.) and Rudolf Virchow Center for Experimental Biomedicine (S.D., T.V., C.M.S., H.M.H., B.N.), University of Würzburg, Würzburg, Germany; Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom (S.K.W., C.E.H., S.P.W.); and Department of Biology, Division of Genetics, University of Erlangen, Erlangen, Germany (J.A.A., D.R., L.N.).
authors.forename: Martina
authors.initials: M
authors.lastname: Morowski
authors.affiliation: Department of Experimental Biomedicine, University Hospital Würzburg (S.D., T.V., M.M., S.S., B.N.) and Rudolf Virchow Center for Experimental Biomedicine (S.D., T.V., C.M.S., H.M.H., B.N.), University of Würzburg, Würzburg, Germany; Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom (S.K.W., C.E.H., S.P.W.); and Department of Biology, Division of Genetics, University of Erlangen, Erlangen, Germany (J.A.A., D.R., L.N.).
authors.forename: Sarah
authors.initials: S
authors.lastname: Schiessl
authors.affiliation: Department of Experimental Biomedicine, University Hospital Würzburg (S.D., T.V., M.M., S.S., B.N.) and Rudolf Virchow Center for Experimental Biomedicine (S.D., T.V., C.M.S., H.M.H., B.N.), University of Würzburg, Würzburg, Germany; Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom (S.K.W., C.E.H., S.P.W.); and Department of Biology, Division of Genetics, University of Erlangen, Erlangen, Germany (J.A.A., D.R., L.N.).
authors.forename: Carmen M
authors.initials: CM
authors.lastname: Schäfer
authors.affiliation: Department of Experimental Biomedicine, University Hospital Würzburg (S.D., T.V., M.M., S.S., B.N.) and Rudolf Virchow Center for Experimental Biomedicine (S.D., T.V., C.M.S., H.M.H., B.N.), University of Würzburg, Würzburg, Germany; Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom (S.K.W., C.E.H., S.P.W.); and Department of Biology, Division of Genetics, University of Erlangen, Erlangen, Germany (J.A.A., D.R., L.N.).
authors.forename: Stephanie K
authors.initials: SK
authors.lastname: Watson
authors.affiliation: Department of Experimental Biomedicine, University Hospital Würzburg (S.D., T.V., M.M., S.S., B.N.) and Rudolf Virchow Center for Experimental Biomedicine (S.D., T.V., C.M.S., H.M.H., B.N.), University of Würzburg, Würzburg, Germany; Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom (S.K.W., C.E.H., S.P.W.); and Department of Biology, Division of Genetics, University of Erlangen, Erlangen, Germany (J.A.A., D.R., L.N.).
authors.forename: Craig E
authors.initials: CE
authors.lastname: Hughes
authors.affiliation: Department of Experimental Biomedicine, University Hospital Würzburg (S.D., T.V., M.M., S.S., B.N.) and Rudolf Virchow Center for Experimental Biomedicine (S.D., T.V., C.M.S., H.M.H., B.N.), University of Würzburg, Würzburg, Germany; Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom (S.K.W., C.E.H., S.P.W.); and Department of Biology, Division of Genetics, University of Erlangen, Erlangen, Germany (J.A.A., D.R., L.N.).
authors.forename: Jochen A
authors.initials: JA
authors.lastname: Ackermann
authors.affiliation: Department of Experimental Biomedicine, University Hospital Würzburg (S.D., T.V., M.M., S.S., B.N.) and Rudolf Virchow Center for Experimental Biomedicine (S.D., T.V., C.M.S., H.M.H., B.N.), University of Würzburg, Würzburg, Germany; Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom (S.K.W., C.E.H., S.P.W.); and Department of Biology, Division of Genetics, University of Erlangen, Erlangen, Germany (J.A.A., D.R., L.N.).
authors.forename: Daniel
authors.initials: D
authors.lastname: Radtke
authors.affiliation: Department of Experimental Biomedicine, University Hospital Würzburg (S.D., T.V., M.M., S.S., B.N.) and Rudolf Virchow Center for Experimental Biomedicine (S.D., T.V., C.M.S., H.M.H., B.N.), University of Würzburg, Würzburg, Germany; Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom (S.K.W., C.E.H., S.P.W.); and Department of Biology, Division of Genetics, University of Erlangen, Erlangen, Germany (J.A.A., D.R., L.N.).
authors.forename: Heike M
authors.initials: HM
authors.lastname: Hermanns
authors.affiliation: Department of Experimental Biomedicine, University Hospital Würzburg (S.D., T.V., M.M., S.S., B.N.) and Rudolf Virchow Center for Experimental Biomedicine (S.D., T.V., C.M.S., H.M.H., B.N.), University of Würzburg, Würzburg, Germany; Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom (S.K.W., C.E.H., S.P.W.); and Department of Biology, Division of Genetics, University of Erlangen, Erlangen, Germany (J.A.A., D.R., L.N.).
authors.forename: Steve P
authors.initials: SP
authors.lastname: Watson
authors.affiliation: Department of Experimental Biomedicine, University Hospital Würzburg (S.D., T.V., M.M., S.S., B.N.) and Rudolf Virchow Center for Experimental Biomedicine (S.D., T.V., C.M.S., H.M.H., B.N.), University of Würzburg, Würzburg, Germany; Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom (S.K.W., C.E.H., S.P.W.); and Department of Biology, Division of Genetics, University of Erlangen, Erlangen, Germany (J.A.A., D.R., L.N.).
authors.forename: Lars
authors.initials: L
authors.lastname: Nitschke
authors.affiliation: Department of Experimental Biomedicine, University Hospital Würzburg (S.D., T.V., M.M., S.S., B.N.) and Rudolf Virchow Center for Experimental Biomedicine (S.D., T.V., C.M.S., H.M.H., B.N.), University of Würzburg, Würzburg, Germany; Centre for Cardiovascular Sciences, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom (S.K.W., C.E.H., S.P.W.); and Department of Biology, Division of Genetics, University of Erlangen, Erlangen, Germany (J.A.A., D.R., L.N.).
authors.forename: Bernhard
authors.initials: B
authors.lastname: Nieswandt
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D002478:Cells, Cultured; D051380:GRB2 Adaptor Protein / Q000235:genetics / Q000502:physiology*; D006487:Hemostasis / Q000235:genetics; D061625:Immunoreceptor Tyrosine-Based Activation Motif / Q000235:genetics*; D061626:Immunoreceptor Tyrosine-Based Inhibition Motif / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D015539:Platelet Activation / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics*; D013927:Thrombosis / Q000235:genetics
chemical_list: D051380:GRB2 Adaptor Protein; C495949:Grb2 protein, mouse
keywords: blood platelets; hemostasis; mice; signal transduction; thrombosis