A conformation-dependent epitope of human platelet glycoprotein IIIa.
A conformation-dependent epitope of human platelet glycoprotein IIIa.
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发表时间：
1990-11
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通讯作者：
W. Kouns;C. Wall;M. White;C. Fox;L. Jennings
中科院分区：
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作者：
W. Kouns;C. Wall;M. White;C. Fox;L. Jennings
本研究探讨了人血小板膜糖蛋白IIIa(GP IIIa)的构象状态和纤维蛋白原受体暴露的可能机制。D3GP3是一种针对纯化的GP IIIa产生的IgG1kappa单抗，经免疫沉淀和Western印迹分析证实是针对GP IIIa的。D3GP3与静息血小板的结合引起纤维蛋白原结合(大约5000个分子/血小板)和血小板聚集，但不能分泌。血小板表面膜上表达40,000-50,000个GP IIb-IIIa分子。然而，静息状态下的血小板仅与大约5000个D3GP3分子/血小板结合。用5 mM EDTA解离GP IIb-IIIa复合体或用RGDS多肽或纤维蛋白原占据纤维蛋白原受体，可使D3GP3与血小板的结合增加2-3倍。在没有纤维蛋白原的情况下，用ADP刺激血小板不会导致D3GP3结合量高于对照水平。这些结果表明：1)血小板膜GP IIb-IIIa可以以多种构象存在，2)D3GP3与GP IIIa结合可暴露纤维蛋白原受体，3)RGDS多肽或纤维蛋白原结合导致D3GP3表位暴露，4)在缺乏配体的情况下激活血小板不会引起与RGDS多肽或纤维蛋白原受体相同的构象变化。
This study explores conformational states of human platelet glycoprotein IIIa (GP IIIa) and possible mechanisms of fibrinogen receptor exposure. D3GP3 is an IgG1, kappa monoclonal antibody generated against purified GP IIIa and found to be specific for GP IIIa by immunoprecipitation and Western blot analysis. The binding of D3GP3 to resting platelets caused fibrinogen binding (approximately 5,000 molecules/platelet) and platelet aggregation but not secretion. Platelets express 40,000-50,000 GP IIb-IIIa molecules in their surface membranes. However, resting platelets only bound approximately 5,000 D3GP3 molecules/platelet. D3GP3 binding to platelets could be increased 2-3-fold by dissociation of the GP IIb-IIIa complex with 5 mM EDTA or by occupying the fibrinogen receptor with either RGDS peptides or fibrinogen. Platelet stimulation with ADP in the absence of fibrinogen did not cause increased D3GP3 binding above control levels. These data suggest that 1) GP IIb-IIIa can exist in multiple conformations in the platelet membrane, 2) D3GP3 binding to GP IIIa can expose the fibrinogen receptor, 3) the binding of either RGDS peptides or fibrinogen causes exposure of the D3GP3 epitope, and 4) platelet activation in the absence of ligand does not induce the same conformational changes in GP IIb-IIIa as does receptor occupancy by RGDS peptides or fibrinogen.