IMMUNOGOLD-SURFACE REPLICA STUDY OF ADP-INDUCED LIGAND-BINDING AND FIBRINOGEN RECEPTOR CLUSTERING IN HUMAN-PLATELETS
IMMUNOGOLD-SURFACE REPLICA STUDY OF ADP-INDUCED LIGAND-BINDING AND FIBRINOGEN RECEPTOR CLUSTERING IN HUMAN-PLATELETS
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DOI：
10.1002/aja.1001850207
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发表时间：
1989-06-01
影响因子：
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通讯作者：
BAINTON, DF
中科院分区：
文献类型：
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作者：
ISENBERG, WM;MCEVER, RP;BAINTON, DF
血小板凝聚需要纤维蛋白原与其受体结合，受体是一种由质膜糖蛋白 GPIIb 和 GPIIIa 组成的异二聚体。尽管 GPIIb-IIIa 复合物存在于未刺激的血小板表面，但仅在血小板活化后才与纤维原结合。我们使用免疫金表面复制技术来研究 GPIIb-IIIa 和结合纤维原在未刺激和 ADP 激活的人血小板表面膜上的分布。我们发现金探针单分散在未刺激的血小板表面，尽管细胞表面缺乏免疫反应性纤维蛋白原。为了确定受体是否在配体结合之前聚集或作为其结果，我们研究了ADP刺激后GPIIb-IIIa的表面分布，这导致GPIIb-IIIa的纤维蛋白原受体功能激活而不诱导纤维蛋白原的分泌。在没有添加纤维蛋白原的情况下，ADP 刺激的血小板上未占据但具有结合能力的受体是单分散的。添加纤维蛋白原导致 GPIIb-IIIa 分子聚集在细胞表面。还通过添加纤维蛋白原的GPIIb-IIIa结合结构域——即α-链上的四肽Arg-Gly-Asp-Ser或γ-链十肽γ402-411来诱导聚集。这些结果表明受体占据导致活化血小板中 GPIIb-IIIa 聚集。
Platelet cohesion requires the binding of fibrinogen to its receptor, a heterodimer consisting of the plasma-membrane glycoproteins GPIIb and GPIIIa. Although the GPIIb-IIIa complex is present on the surface of unstimulated platelets, it binds fibrogen only after platelet activation. We have used an immunogold-surface replica technique to study the distribution of GPIIb-IIIa and bound fibrogen over broad expanses of surface membranes in unstimulated and ADP-activated human platelets. We found that the gold probe was monodispersed over the surface of unstimulated platelets, although the cell surface lacked immunoreactive fibrinogen. To ascertain whether the receptors clustered prior to ligand binding or as a consequence thereof, we studied the surface distribution of GPIIb-IIIa after stimulation with ADP, which causes activation of the fibrinogen receptor function of GPIIb-IIIa without inducing the secretion of fibrinogen. In the absence of added fibrinogen, the unoccupied, yet binding-competent receptors on ADP-stimulated platelets were monodispersed. The addition of fibrinogen caused the GPIIb-IIIa molecules to cluster on the cell surface. Clustering was also induced by the addition of the GPIIb-IIIa binding domains of fibrinogen-namely, the tetrapeptide Arg-Gly-Asp-Ser on the .alpha.-chain or the .gamma.-chain decapeptide .gamma.402-411. These results show that receptor occupancy causes clustering of GPIIb-IIIa in activated platelets.