Zou Siying, Teixeira Alexandra M, Yin Mingzhu, Xiang Yaozu, Xavier-Ferrucio Juliana, Zhang Ping-Xia, Hwa John, Min Wang, Krause Diane S
Diane S. Krause, Yale Stem Cell Center, 10 Amistad Street, Room 214I, New Haven, CT 06509, USA, Tel.: +1 203 785 7089, Fax: +1 203 785 4305, E-mail:
Thromb Haemost. 2016 Aug 30;116(3):506-16. doi: 10.1160/TH15-11-0848. Epub 2016 Jun 23.
Leukemia-Associated RhoGEF (LARG) is highly expressed in platelets, which are essential for maintaining normal haemostasis. We studied the function of LARG in murine and human megakaryocytes and platelets with Larg knockout (KO), shRNA-mediated knockdown and small molecule-mediated inhibition. We found that LARG is important for human, but not murine, megakaryocyte maturation. Larg KO mice exhibit macrothrombocytopenia, internal bleeding in the ovaries and prolonged bleeding times. KO platelets have impaired aggregation, α-granule release and integrin α2bβ3 activation in response to thrombin and thromboxane, but not to ADP. The same agonist-specific reductions in platelet aggregation occur in human platelets treated with a LARG inhibitor. Larg KO platelets have reduced RhoA activation and myosin light chain phosphorylation, suggesting that Larg plays an agonist-specific role in platelet signal transduction. Using two different in vivo assays, Larg KO mice are protected from in vivo thrombus formation. Together, these results establish that LARG regulates human megakaryocyte maturation, and is critical for platelet function in both humans and mice.
白血病相关的Rho鸟嘌呤核苷酸交换因子（LARG）在血小板中高表达，而血小板对于维持正常止血至关重要。我们利用Larg基因敲除（KO）、短发夹RNA（shRNA）介导的敲低以及小分子介导的抑制方法，研究了LARG在小鼠和人类巨核细胞及血小板中的功能。我们发现，LARG对人类巨核细胞成熟很重要，但对小鼠巨核细胞成熟不重要。Larg基因敲除小鼠表现出大血小板减少、卵巢内出血以及出血时间延长。基因敲除的血小板在响应凝血酶和血栓素时，其聚集、α颗粒释放及整合素α2bβ3激活受损，但对二磷酸腺苷（ADP）无此反应。在用LARG抑制剂处理的人类血小板中，也出现了相同的激动剂特异性血小板聚集减少现象。Larg基因敲除的血小板中RhoA激活及肌球蛋白轻链磷酸化减少，这表明Larg在血小板信号转导中发挥激动剂特异性作用。通过两种不同的体内试验，发现Larg基因敲除小鼠可免受体内血栓形成的影响。总之，这些结果表明LARG调节人类巨核细胞成熟，并且对人类和小鼠的血小板功能都至关重要。
