Rybak M E
Thromb Haemost. 1986 Apr 30;55(2):240-5.
Platelet membrane glycoproteins IIb and IIIa and platelet thrombospondin were incorporated onto phosphatidylcholine liposomes, by freeze thawing and sonication. Protein orientation on the liposomes was confirmed by susceptibility to neuraminidase cleavage and binding to lentil lectin-Sepharose (GPIIb-IIIa liposomes) and to heparin-Sepharose (thrombospondin liposomes). Glycoproteins IIb-IIIa bound 125I-fibrinogen with Kd of 7.5 X 10(-7)M. Binding was reversible and calcium-dependent. IIb-IIIa liposomes underwent fibrinogen-dependent aggregation in the presence of 10 mM CaCl2. Maximal aggregate formation was observed with a combination of IIb-IIIa liposomes and thrombospondin liposomes. This aggregation was partially inhibited by preincubation with monoclonal antibodies to the IIb-IIIa complex. Addition of EDTA caused complete reversal of aggregates. Thrombospondin liposomes also underwent fibrinogen and calcium dependent aggregation, however, this aggregation was less than that observed with the GPIIb-IIIa liposomes. Maximal aggregate formation was observed with a mixture of IIb-IIIa liposomes and thrombospondin liposomes. These studies demonstrate that GPIIb-IIIa and thrombospondin can be incorporated into phospholipid vesicles with preservation of function. Direct evidence is provided to demonstrate that glycoprotein IIb and IIIa and fibrinogen are sufficient for platelet aggregation and to demonstrate that thrombospondin may also contribute to platelet aggregation.
通过冻融和超声处理，将血小板膜糖蛋白IIb和IIIa以及血小板凝血酶敏感蛋白整合到磷脂酰胆碱脂质体上。通过对神经氨酸酶切割的敏感性以及与扁豆凝集素-琼脂糖（GPIIb-IIIa脂质体）和肝素-琼脂糖（凝血酶敏感蛋白脂质体）的结合，证实了脂质体上蛋白质的取向。糖蛋白IIb-IIIa以7.5×10⁻⁷M的解离常数结合¹²⁵I-纤维蛋白原。结合是可逆的且依赖于钙。在10 mM氯化钙存在下，IIb-IIIa脂质体发生纤维蛋白原依赖性聚集。在IIb-IIIa脂质体和凝血酶敏感蛋白脂质体组合时观察到最大聚集体形成。这种聚集被与IIb-IIIa复合物的单克隆抗体预孵育部分抑制。加入乙二胺四乙酸导致聚集体完全逆转。凝血酶敏感蛋白脂质体也发生纤维蛋白原和钙依赖性聚集，然而，这种聚集小于在GPIIb-IIIa脂质体中观察到的聚集。在IIb-IIIa脂质体和凝血酶敏感蛋白脂质体混合物中观察到最大聚集体形成。这些研究表明，GPIIb-IIIa和凝血酶敏感蛋白可以整合到磷脂囊泡中并保留功能。提供了直接证据来证明糖蛋白IIb和IIIa以及纤维蛋白原足以引起血小板聚集，并证明凝血酶敏感蛋白也可能有助于血小板聚集。
