Loss of oligophrenin1 leads to uncontrolled Rho activation and increased thrombus formation in mice
Loss of oligophrenin1 leads to uncontrolled Rho activation and increased thrombus formation in mice
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DOI：
10.1111/jth.12834
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发表时间：
2015-04-01
影响因子：
10.4
通讯作者：
Elvers, M.
中科院分区：
文献类型：
--
作者：
Fotinos, A.;Klier, M.;Elvers, M.
背景血小板骨架重组是血小板粘附和血栓形成过程中必不可少的环节，在止血和血栓形成中起着重要作用. Rho GTP酶RhoA、Rac 1和Cdc 42是血小板细胞骨架动力学的主要参与者，并诱导丝状伪足和板状伪足形成以及肌动蛋白聚合，以在活化时强烈增加血小板表面。此外，Rho GTPases在血小板分泌、整合素活化和动脉血栓形成中也起重要作用。目的Rho GTPases受GTPase-activating proteins（GAP）的调节，GAP可刺激GTPases的活性，终止Rho信号通路。血小板中Rho GT3活性的调节尚未明确。最近，我们在血小板中发现了一种RhoGAP-寡聚蛋白1（OPHN 1），它对RhoA、Cdc 42和Rac 1具有很强的GTP酶激活活性。结果本研究首次发现，OPHN 1的缺失导致了Rho的异常激活和血小板细胞骨架重组的增加，包括细胞粘附和纤维蛋白原上片状伪足的形成。此外，来自ophn 1（-/-）小鼠的血小板显示出对血小板活化的增强的敏感性，伴随着肌动蛋白分布和颗粒早期释放的改变。GPVI和PAR 4刺激后血小板活化增强。这转化为升高的血小板血栓形成和促进动脉血栓形成，在低剪切条件下改变止血，如检测到的尾部bleeding time.ConclusionsThe本研究的结果确定OPHN 1作为一个重要的调节血小板细胞骨架重组，并表明，异常调节Rho蛋白导致血小板粘附和血栓形成在低剪切条件下，在体外和体内，这表明小鼠的血栓前表型对于急性血栓性闭塞至关重要。
BackgroundPlatelet cytoskeletal reorganization is essential for platelet adhesion and thrombus formation in hemostasis and thrombosis. The Rho GTPases RhoA, Rac1 and Cdc42 are the main players in cytoskeletal dynamics of platelets and induce filopodia and lamellipodia formation and actin polymerization to strongly increase the platelet surface upon activation. Moreover, they are important for platelet secretion, integrin activation and arterial thrombus formation.ObjectivesRho GTPases are regulated by GTPase-activating proteins (GAPs) that stimulate their GTPase activity to terminate Rho signaling. The regulation of Rho GTPase activity in platelets is not well defined. Recently, we identified oligophrenin1 (OPHN1), a RhoGAP in platelets that exhibits strong GTPase-stimulating activity towards RhoA, Cdc42 and Rac1.ResultsIn the present study we show for the first time, that deficiency of OPHN1 led to abnormal Rho activation and increased platelet cytoskeletal reorganization, including cell adhesion and lamellipodia formation on fibrinogen. Furthermore, platelets from ophn1(-/-) mice showed enhanced susceptibility to platelet activation with alterations in actin distribution and early release of granules. Platelet activation was enhanced following GPVI and PAR4 stimulation. This translated into elevated platelet thrombus formation and promoted arterial thrombosis under low shear conditions with altered hemostasis, as detected by tail bleeding time.ConclusionsThe results of the present study identified OPHN1 as an important regulator of platelet cytoskeletal reorganization and demonstrate that abnormal regulation of Rho proteins leads to increased platelet adhesion and thrombus formation under low shear conditions in vitro and in vivo, suggesting a prothrombotic phenotype of mice critical for acute thrombotic occlusions.