Tsai Hui-Ju, Huang Chien-Ling, Chang Yao-Wen, Huang Ding-Yuan, Lin Chung-Ching, Cooper Jonathan A, Cheng Ju-Chien, Tseng Ching-Ping
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.
Arterioscler Thromb Vasc Biol. 2014 Nov;34(11):2404-12. doi: 10.1161/ATVBAHA.114.302602. Epub 2014 Sep 11.
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.
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.
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.
血小板活化在止血和血栓形成疾病中起着至关重要的作用，这使得人们将注意力集中在揭示血小板活化背后的细胞内信号上。Disabled-2（Dab2）已被证明与血小板聚集和凝血反应的控制有关。然而，目前尚无体内研究能直接证明Dab2在止血和血小板活化中的作用。
构建了巨核细胞系特异性Dab2基因敲除（Dab2(-/-)）小鼠，以阐明Dab2在血小板中的体内功能。Dab2(-/-)小鼠体型正常，但出血时间延长，血栓形成受损。尽管Dab2(-/-)小鼠的血小板生成和颗粒生物合成正常，但在低浓度凝血酶刺激下，其血小板在纤维蛋白原上的聚集和铺展出现选择性缺陷，而对其他可溶性激动剂无此反应。对Dab2在凝血酶信号传导中的作用进行研究发现，Dab2对凝血酶受体的表达和外向内信号传导没有影响。低浓度凝血酶刺激的Dab2(-/-)血小板在Gαq介导的钙动员和蛋白激酶C激活方面正常，但在Gα₁₂/₁₃介导的RhoA-ROCKII激活方面存在缺陷。Gα₁₂/₁₃信号减弱导致ADP释放、Akt-雷帕霉素哺乳动物靶标和整合素αIIbβ3激活受损，纤维蛋白原结合和血块回缩也受到影响。Dab2(-/-)血小板对低浓度凝血酶刺激的缺陷反应可能导致Dab2(-/-)小鼠止血和血栓形成受损。
本研究为血小板生物学提供了新的见解，首次报道表明Dab2通过与Gα₁₂/₁₃介导的凝血酶信号功能相互作用，是止血和血栓形成的关键调节因子。
