C560Rβ3 caused platelet integrin αIIbβ3 to bind fibrinogen continuously, but resulted in a severe bleeding syndrome and increased murine mortality
C560Rβ3 caused platelet integrin αIIbβ3 to bind fibrinogen continuously, but resulted in a severe bleeding syndrome and increased murine mortality
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DOI：
10.1111/jth.12209
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发表时间：
2013-06-01
影响因子：
10.4
通讯作者：
Wilcox, D. A.
中科院分区：
文献类型：
--
作者：
Fang, J.;Nurden, P.;Wilcox, D. A.
背景和目的通过人慢病毒转导和移植修饰巨核细胞，使其表达足够水平的C560R(3)氨基酸替代，以研究激活的（IIb3）构象如何影响小鼠体内血小板。患者/方法在我们之前报道的Glanzmann血栓缺失患者的R560(3)突变中，R560(3)小鼠血小板自发结合抗体仅识别与其配体纤维蛋白原结合的活化（IIb3）。结果在小鼠模型中，我们发现(IIb)-R560(3)突变介导的纤维蛋白原的持续结合发生在p -选择素表面表达缺失的情况下，这表明整合素处于活跃构象，尽管血小板以静止的方式循环。值得注意的是，只有35%的R560(3)突变型小鼠在移植后存活了6个月，而87%的C560(3)野生型小鼠仍然存活。病理检查显示R560(3)小鼠脾肿大，髓外造血，含铁血黄素增高，提示出血。R560(3)巨核细胞和血小板形态异常，颗粒分布不规则。有趣的是，R560(3)洗涤后的血小板在同时加入纤维蛋白原和生理激动剂时可以聚集，但在体外和体内激活之前，血小板暴露于纤维蛋白原时，聚集失败。结论纤维蛋白原持续占据IIb3破坏血小板结构和功能，导致出血死亡，与Glanzmann血栓减少症一致，而不是血栓形成状态。
Background and objectives(3)-Deficient megakaryocytes were modified by human (3)-lentivirus transduction and transplantation to express sufficient levels of a C560R(3) amino acid substitution, for investigation of how an activated (IIb3) conformation affects platelets invivo in mice.Patient/MethodsAs in our previous report of an R560(3) mutation in a patient with Glanzmann thrombasthenia, R560(3) murine platelets spontaneously bound antibody that only recognizes activated (IIb3) bound to its ligand, fibrinogen.ResultsWith this murine model, we showed that (IIb)-R560(3) mutation-mediated continuous binding of fibrinogen occurred in the absence of P-selectin surface expression, indicating that the integrin was in an active conformation, although the platelets circulated in a quiescent manner. Remarkably, only 35% of R560(3) mutant' mice survived for 6months after transplantation, whereas 87% of C560(3) wild-type' mice remained alive. Pathologic examination revealed that R560(3) mice had enlarged spleens with extramedullary hematopoiesis and increased hemosiderin, indicating hemorrhage. R560(3) megakaryocytes and platelets showed abnormal morphology and irregular granule distribution. Interestingly, R560(3) washed platelets could aggregate upon simultaneous addition of fibrinogen and physiologic agonists, but aggregation failed when platelets were exposed to fibrinogen before activation invitro and invivo.ConclusionsThe results demonstrate that continuous occupancy of IIb3 with fibrinogen disrupts platelet structure and function, leading to hemorrhagic death consistent with Glanzmann thrombasthenia rather than a thrombotic state.