White G C, Fischer T H, Duffy C M
Center for Thrombosis and Hemostasis, Department of Medicine and Pharmacology, University of North Carolina at Chapel Hill, 27599-7035, USA.
Thromb Haemost. 1998 Apr;79(4):832-6.
Platelet membrane glycoproteins (GP) IIb/IIa and rap1b, a 21 kDa GTP binding protein, associate with the triton-insoluble, activation-dependent platelet cytoskeleton with similar rates and divalent cation requirement. To examine the possibility that GPIIb/IIIa was required for rap1b association with the cytoskeleton, experiments were performed to determine if the two proteins were linked under various conditions. Chromatography of lysates from resting platelets on Sephacryl S-300 showed that GPIIb/IIIa and rap1b were well separated and distinct proteins. Immunoprecipitation of GPIIb/IIIa from lysates of resting platelets did not produce rap1b or other low molecular weight GTP binding proteins and immunoprecipitation of rap1b from lysates of resting platelets did not produce GPIIb/IIIa. Finally, rap1b was associated with the activation-dependent cytoskeleton of platelets from a patient with Glanzmann's thrombasthenia who lacks surface expressed glycoproteins IIb and IIIa. Based on these findings, we conclude that no association between GPIIb/IIIa and raplb is found in resting platelets and that rap1b association with the activation-dependent cytoskeleton is at least partly independent of GPIIb/IIIa.
血小板膜糖蛋白（GP）IIb/IIa和rap1b（一种21 kDa的GTP结合蛋白），以相似的速率和二价阳离子需求，与不溶于曲拉通、依赖激活的血小板细胞骨架相关联。为了研究rap1b与细胞骨架的关联是否需要GPIIb/IIIa，进行了实验以确定这两种蛋白在各种条件下是否相互连接。用Sephacryl S - 300对静息血小板裂解物进行色谱分析表明，GPIIb/IIIa和rap1b是分离良好的不同蛋白。从静息血小板裂解物中免疫沉淀GPIIb/IIIa未产生rap1b或其他低分子量GTP结合蛋白，从静息血小板裂解物中免疫沉淀rap1b也未产生GPIIb/IIIa。最后，rap1b与一名缺乏表面表达糖蛋白IIb和IIIa的Glanzmann血小板无力症患者的血小板激活依赖性细胞骨架相关联。基于这些发现，我们得出结论，在静息血小板中未发现GPIIb/IIIa与rap1b之间存在关联，且rap1b与激活依赖性细胞骨架的关联至少部分独立于GPIIb/IIIa。
