Human platelets express endothelial protein C receptor, which can be utilized to enhance localization of factor VIIa activity.
Human platelets express endothelial protein C receptor, which can be utilized to enhance localization of factor VIIa activity.
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DOI：
10.1111/jth.14165
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发表时间：
2018-09
期刊：
影响因子：
--
通讯作者：
Hoffman M
中科院分区：
文献类型：
--
作者：
Fager AM;Machlus KR;Ezban M;Hoffman M
高剂量因子VIIa（FVIIa）通常用作有效的旁路剂，用于治疗具有抑制性抗体的血友病患者，这些抑制性抗体损害因子替代。然而，FVIIa结合活化血小板以促进止血的机制尚未完全了解。FVIIa-DVQ是相对于FVIIa具有增强的组织因子（TF）非依赖性活性和止血功效的FVIIa类似物。我们以前的研究表明，FVIIa-DVQ表现出更大的血小板结合，从而表明除了脂质组成以外的特征有助于血小板-FVIIa相互作用。内皮细胞蛋白C受体（EPCR）也作为内皮细胞上FVIIa的受体起作用。因此，我们假设与EPCR的相互作用可能在血小板-FVIIa结合中发挥作用。在本研究中，我们使用流式细胞术分析显示，在过量蛋白C或抗EPCR抗体存在下，FVIIa和FVIIa-DVQ的血小板结合被部分抑制。这种降低的结合导致因子Xa和凝血酶生成测定中两种分子的活性相应降低。与EPCR的结合增强足以解释与野生型FVIIa相比FVIIa-DVQ的血小板结合增加。由于EPCR蛋白表达以前没有在血小板中显示，我们证实了EPCR在血小板中使用免疫荧光，流式细胞术，免疫沉淀和质谱的存在。这项工作代表了人类血小板表达EPCR的首次证明，并表明EPCR结合的调节可用于增强合理设计的FVIIa类似物的止血功效。
High-dose factor VIIa (FVIIa) is routinely used as an effective bypassing agent to treat hemophilia patients with inhibitory antibodies that compromise factor replacement. However, the mechanism by which FVIIa binds activated platelets to promote hemostasis is not fully understood. FVIIa-DVQ is an analog of FVIIa with enhanced tissue factor (TF)-independent activity and hemostatic efficacy relative to FVIIa. Our previous studies have shown that FVIIa-DVQ exhibits greater platelet binding, thereby suggesting that features in addition to lipid composition contribute to platelet-FVIIa interactions. Endothelial cell protein C receptor (EPCR) also functions as a receptor for FVIIa on endothelial cells. We therefore hypothesized that an interaction with EPCR might play a role in platelet-FVIIa binding. In the present study, we used flow cytometric analyses to show that platelet binding of both FVIIa and FVIIa-DVQ is partially inhibited in the presence of excess Protein C or an anti-EPCR antibody. This decreased binding results in a corresponding decrease in the activity of both molecules in factor Xa and thrombin generation assays. Enhanced binding to EPCR was sufficient to account for the increased platelet binding of FVIIa-DVQ compared to wild type FVIIa. As EPCR protein expression has not previously been shown in platelets, we confirmed the presence of EPCR in platelets using immunofluorescence, flow cytometry, immunoprecipitation, and mass spectrometry. This work represents the first demonstration that human platelets express EPCR, and suggests that modulation of EPCR binding could be utilized to enhance the hemostatic efficacy of rationally designed FVIIa analogs.
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DOI：
10.1007/978-1-61779-307-3_12
发表时间：
2012-01-01
期刊：
PLATELETS AND MEGAKARYOCYTES, VOL 3: ADDITIONAL PORTOCOLS AND PERSPECTIVES
影响因子：
--
作者：
Amisten, Stefan
通讯作者：
Amisten, Stefan
影响因子：
9
作者：
Esmon, Charles T.
通讯作者：
Esmon, Charles T.
影响因子：
7.5
作者：
Keshava, Shiva;Sundaram, Jagan;Rao, L. Vijaya Mohan
通讯作者：
Rao, L. Vijaya Mohan
影响因子：
20.3
作者：
Feng, Dengmin;Whinna, Herbert;Stafford, Darrel W.
通讯作者：
Stafford, Darrel W.
影响因子：
10.4
作者：
Hoffman, M.;Volovyk, Z.;Monroe, D. M.
通讯作者：
Monroe, D. M.