The Phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P3) Binder Rasa3 Regulates Phosphoinositide 3-kinase (PI3K)-dependent Integrin αIIbβ3 Outside-in Signaling.
The Phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P3) Binder Rasa3 Regulates Phosphoinositide 3-kinase (PI3K)-dependent Integrin αIIbβ3 Outside-in Signaling.
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DOI：
10.1074/jbc.m116.746867
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发表时间：
2017-02-03
期刊：
影响因子：
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通讯作者：
Hers I
中科院分区：
文献类型：
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作者：
Battram AM;Durrant TN;Agbani EO;Heesom KJ;Paul DS;Piatt R;Poole AW;Cullen PJ;Bergmeier W;Moore SF;Hers I
脂质激酶的I类PI 3 K家族在整合素αIIbβ3功能中发挥重要作用，从而支持血栓生长和固结。在这里，我们确定Ras/Rap 1GAP Rasa 3（GAP 1 IP 4 BP）是人血小板中主要的磷脂酰肌醇3，4，5-三磷酸结合蛋白，也是整合素αIIbβ3由外向内信号传导的关键调节因子。我们证明，细胞溶质Rasa 3易位到质膜上的PI 3 K依赖的方式后，激活人血小板。在表达整合素αIIbβ3的CHO细胞中表达野生型Rasa 3可阻断Rap 1活性和整合素αIIbβ3介导的在纤维蛋白原上的扩散。相反，Rap 1GAP缺陷型（P489 V）和Ras/Rap 1GAP缺陷型（R371 Q）Rasa 3没有影响。我们还发现，在不同的血小板减少症小鼠模型中表达的两种Rasa 3突变体（H794 L和G125 V）缺乏Ras和Rap 1GAP活性，并且不影响整合素αIIbβ3介导的CHO细胞在纤维蛋白原上的扩散。来自表达GAP缺陷型Rasa 3（H794 L）的血小板减少小鼠的血小板显示在纤维蛋白原上的扩展增加，这与野生型血小板相反，对PI 3 K抑制剂不敏感。总之，这些结果支持Rasa 3在PI 3 K依赖性整合素αIIbβ3介导的由外向内信号传导和细胞扩散中的重要作用。
The class I PI3K family of lipid kinases plays an important role in integrin αIIbβ3 function, thereby supporting thrombus growth and consolidation. Here, we identify Ras/Rap1GAP Rasa3 (GAP1IP4BP) as a major phosphatidylinositol 3,4,5-trisphosphate-binding protein in human platelets and a key regulator of integrin αIIbβ3 outside-in signaling. We demonstrate that cytosolic Rasa3 translocates to the plasma membrane in a PI3K-dependent manner upon activation of human platelets. Expression of wild-type Rasa3 in integrin αIIbβ3-expressing CHO cells blocked Rap1 activity and integrin αIIbβ3-mediated spreading on fibrinogen. In contrast, Rap1GAP-deficient (P489V) and Ras/Rap1GAP-deficient (R371Q) Rasa3 had no effect. We furthermore show that two Rasa3 mutants (H794L and G125V), which are expressed in different mouse models of thrombocytopenia, lack both Ras and Rap1GAP activity and do not affect integrin αIIbβ3-mediated spreading of CHO cells on fibrinogen. Platelets from thrombocytopenic mice expressing GAP-deficient Rasa3 (H794L) show increased spreading on fibrinogen, which in contrast to wild-type platelets is insensitive to PI3K inhibitors. Together, these results support an important role for Rasa3 in PI3K-dependent integrin αIIbβ3-mediated outside-in signaling and cell spreading.