title: Disabled-2 is required for efficient hemostasis and platelet activation by thrombin in mice.
abstract: OBJECTIVE
  The essential role of platelet activation in hemostasis and thrombotic diseases focuses attention on unveiling the underlying intracellular signals of platelet activation. Disabled-2 (Dab2) has been implicated in platelet aggregation and in the control of clotting responses. However, there is not yet any in vivo study to provide direct evidence for the role of Dab2 in hemostasis and platelet activation.
  
  
  RESULTS
  Megakaryocyte lineage-restricted Dab2 knockout (Dab2(-/-)) mice were generated to delineate in vivo functions of Dab2 in platelets. Dab2(-/-) mice appeared normal in size with prolonged bleeding time and impaired thrombus formation. Although normal in platelet production and granule biogenesis, Dab2(-/-) platelets elicited a selective defect in platelet aggregation and spreading on fibrinogen in response to low concentrations of thrombin, but not other soluble agonists. Investigation of the role of Dab2 in thrombin signaling revealed that Dab2 has no effect on the expression of thrombin receptors and the outside-in signaling. Dab2(-/-) platelets stimulated by low concentrations of thrombin were normal in Gαq-mediated calcium mobilization and protein kinase C activation, but were defective in Gα₁₂/₁₃-mediated RhoA-ROCKII activation. The attenuated Gα₁₂/₁₃ signaling led to impaired ADP release, Akt-mammalian target of rapamycin and integrin αIIbβ3 activation, fibrinogen binding, and clot retraction. The defective responses of Dab2(-/-) platelets to low concentrations of thrombin stimulation may contribute to the impaired hemostasis and thrombosis of Dab2(-/-) mice.
  
  
  CONCLUSIONS
  This study sheds new insight in platelet biology and represents the first report demonstrating that Dab2 is a key regulator of hemostasis and thrombosis by functional interplay with Gα₁₂/₁₃-mediated thrombin signaling.
authors.affiliation: From the Graduate Institute of Biomedical Sciences (H.-J.T., Y.-W.C., C.-P.T.), and Department of Medical Biotechnology and Laboratory Science (C.-L.H., D.-Y.H., C.-C.L., C.-P.T.), College of Medicine, Chang Gung University, Taoyuan, Taiwan; Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA (J.A.C.); Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung, Taiwan (J.-C.C.); Molecular Medicine Research Center, Chang Gung University (C.-P.T.) and Department of Family Medicine (C.-P.T.), Chang Gung Memorial Hospital, Taoyuan, Taiwan.
authors.forename: Hui-Ju
authors.initials: HJ
authors.lastname: Tsai
authors.affiliation: From the Graduate Institute of Biomedical Sciences (H.-J.T., Y.-W.C., C.-P.T.), and Department of Medical Biotechnology and Laboratory Science (C.-L.H., D.-Y.H., C.-C.L., C.-P.T.), College of Medicine, Chang Gung University, Taoyuan, Taiwan; Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA (J.A.C.); Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung, Taiwan (J.-C.C.); Molecular Medicine Research Center, Chang Gung University (C.-P.T.) and Department of Family Medicine (C.-P.T.), Chang Gung Memorial Hospital, Taoyuan, Taiwan.
authors.forename: Chien-Ling
authors.initials: CL
authors.lastname: Huang
authors.affiliation: From the Graduate Institute of Biomedical Sciences (H.-J.T., Y.-W.C., C.-P.T.), and Department of Medical Biotechnology and Laboratory Science (C.-L.H., D.-Y.H., C.-C.L., C.-P.T.), College of Medicine, Chang Gung University, Taoyuan, Taiwan; Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA (J.A.C.); Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung, Taiwan (J.-C.C.); Molecular Medicine Research Center, Chang Gung University (C.-P.T.) and Department of Family Medicine (C.-P.T.), Chang Gung Memorial Hospital, Taoyuan, Taiwan.
authors.forename: Yao-Wen
authors.initials: YW
authors.lastname: Chang
authors.affiliation: From the Graduate Institute of Biomedical Sciences (H.-J.T., Y.-W.C., C.-P.T.), and Department of Medical Biotechnology and Laboratory Science (C.-L.H., D.-Y.H., C.-C.L., C.-P.T.), College of Medicine, Chang Gung University, Taoyuan, Taiwan; Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA (J.A.C.); Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung, Taiwan (J.-C.C.); Molecular Medicine Research Center, Chang Gung University (C.-P.T.) and Department of Family Medicine (C.-P.T.), Chang Gung Memorial Hospital, Taoyuan, Taiwan.
authors.forename: Ding-Yuan
authors.initials: DY
authors.lastname: Huang
authors.affiliation: From the Graduate Institute of Biomedical Sciences (H.-J.T., Y.-W.C., C.-P.T.), and Department of Medical Biotechnology and Laboratory Science (C.-L.H., D.-Y.H., C.-C.L., C.-P.T.), College of Medicine, Chang Gung University, Taoyuan, Taiwan; Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA (J.A.C.); Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung, Taiwan (J.-C.C.); Molecular Medicine Research Center, Chang Gung University (C.-P.T.) and Department of Family Medicine (C.-P.T.), Chang Gung Memorial Hospital, Taoyuan, Taiwan.
authors.forename: Chung-Ching
authors.initials: CC
authors.lastname: Lin
authors.affiliation: From the Graduate Institute of Biomedical Sciences (H.-J.T., Y.-W.C., C.-P.T.), and Department of Medical Biotechnology and Laboratory Science (C.-L.H., D.-Y.H., C.-C.L., C.-P.T.), College of Medicine, Chang Gung University, Taoyuan, Taiwan; Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA (J.A.C.); Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung, Taiwan (J.-C.C.); Molecular Medicine Research Center, Chang Gung University (C.-P.T.) and Department of Family Medicine (C.-P.T.), Chang Gung Memorial Hospital, Taoyuan, Taiwan.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Cooper
authors.affiliation: From the Graduate Institute of Biomedical Sciences (H.-J.T., Y.-W.C., C.-P.T.), and Department of Medical Biotechnology and Laboratory Science (C.-L.H., D.-Y.H., C.-C.L., C.-P.T.), College of Medicine, Chang Gung University, Taoyuan, Taiwan; Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA (J.A.C.); Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung, Taiwan (J.-C.C.); Molecular Medicine Research Center, Chang Gung University (C.-P.T.) and Department of Family Medicine (C.-P.T.), Chang Gung Memorial Hospital, Taoyuan, Taiwan.
authors.forename: Ju-Chien
authors.initials: JC
authors.lastname: Cheng
authors.affiliation: From the Graduate Institute of Biomedical Sciences (H.-J.T., Y.-W.C., C.-P.T.), and Department of Medical Biotechnology and Laboratory Science (C.-L.H., D.-Y.H., C.-C.L., C.-P.T.), College of Medicine, Chang Gung University, Taoyuan, Taiwan; Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA (J.A.C.); Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung, Taiwan (J.-C.C.); Molecular Medicine Research Center, Chang Gung University (C.-P.T.) and Department of Family Medicine (C.-P.T.), Chang Gung Memorial Hospital, Taoyuan, Taiwan. ctseng@mail.cgu.edu.tw.
authors.forename: Ching-Ping
authors.initials: CP
authors.lastname: Tseng
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D000244:Adenosine Diphosphate / Q000502:physiology; D000818:Animals; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D004195:Disease Models, Animal; D006487:Hemostasis / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D015539:Platelet Activation / Q000502:physiology*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000502:physiology; D011493:Protein Kinase C / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D058570:TOR Serine-Threonine Kinases / Q000502:physiology; D013917:Thrombin / Q000502:physiology*; D013927:Thrombosis / Q000503:physiopathology*; D054460:rho-Associated Kinases / Q000502:physiology; D020742:rhoA GTP-Binding Protein / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; C495611:Nostrin protein, mouse; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D000244:Adenosine Diphosphate; C546843:mTOR protein, mouse; D058570:TOR Serine-Threonine Kinases; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D013917:Thrombin; D020742:rhoA GTP-Binding Protein
keywords: Dab2 protein, mouse; platelet activation; thrombin