Naimushin Ya A, Mazurov A V
Institute of Experimental Cardiology, Russian Cardiology Research and Production Complex, Russian Ministry of Health, Moscow, 121552, Russia.
Biochemistry (Mosc). 2005 Jul;70(7):782-9. doi: 10.1007/s10541-005-0184-2.
The ability of different ligands of glycoprotein (GP) IIb-IIIa (alphaIIb/beta3-integrin) to support platelet aggregation stimulated by activating anti-GP IIb-IIIa monoclonal antibody (monoAB) CRC54 has been investigated. Antibody CRC54 stimulated aggregation of washed platelets not only in the presence of fibrinogen, the main GP IIb-IIIa ligand, but also in the presence of von Willebrand factor (vWF). Unlike these ligands, fibronectin failed to support CRC54-induced aggregation. Fibrinogen and vWF dependent platelet aggregation was completely suppressed by GP IIb-IIIa antagonists--preparations Monafram (F(ab')2 fragments of monoAB that blocked GP IIb-IIIa receptor activity) and aggrastat (RGD-like peptidomimetic). However, aggregation stimulated in the presence of vWF was also completely inhibited by monoAB AK2 directed against GP Ib and capable of blocking its binding with vWF. CRC54-induced aggregation of platelets from patient with GP Ib deficiency in the presence of vWF was significantly lower than aggregation of platelets from normal donors and was not inhibited by anti-GP Ib antibody but still blocked by GP IIb-IIIa antagonist Monafram. Monafram also suppressed CRC54-stimulated platelet adhesion to plastic-adsorbed fibrinogen, vWF, and fibronectin. Unlike CRC54-induced platelet aggregation supported by fluid phase vWF, CRC54-induced adhesion to adsorbed vWF was not affected by anti-GP Ib antibody. Aggregation induced by CRC54 in the presence of fibrinogen and vWF was only partially suppressed by prostaglandin E1, an inhibitor of platelet activation, and was associated with serotonin release from platelet granules only when Ca2+ concentration was decreased from 1 mM (physiological level) to 0.1 mM. The data indicate that vWF supports CRC54-induced platelet aggregation via interaction with two receptors--GP IIb-IIIa and GP Ib. Aggregation induced by CRC54 in the presence of vWF or fibrinogen is only partially dependent on platelet activation and is accompanied with granule secretion only at low Ca2+ concentrations.
研究了糖蛋白（GP）IIb-IIIa（αIIb/β3整合素）的不同配体支持激活的抗GP IIb-IIIa单克隆抗体（单克隆抗体）CRC54刺激的血小板聚集的能力。抗体CRC54不仅在主要的GP IIb-IIIa配体纤维蛋白原存在下，而且在血管性血友病因子（vWF）存在下，均可刺激洗涤血小板的聚集。与这些配体不同，纤连蛋白不能支持CRC54诱导的聚集。GP IIb-IIIa拮抗剂——制剂Monafram（阻断GP IIb-IIIa受体活性的单克隆抗体的F(ab')2片段）和阿昔单抗（RGD样拟肽）可完全抑制纤维蛋白原和vWF依赖性血小板聚集。然而，针对GP Ib且能够阻断其与vWF结合的单克隆抗体AK2也可完全抑制在vWF存在下刺激的聚集。在vWF存在下，CRC54诱导的GP Ib缺乏患者血小板聚集显著低于正常供体血小板聚集，且不受抗GP Ib抗体抑制，但仍可被GP IIb-IIIa拮抗剂Monafram阻断。Monafram还可抑制CRC54刺激的血小板对塑料吸附的纤维蛋白原、vWF和纤连蛋白的黏附。与液相vWF支持的CRC54诱导的血小板聚集不同，CRC54诱导的对吸附vWF的黏附不受抗GP Ib抗体影响。在纤维蛋白原和vWF存在下，CRC54诱导的聚集仅被血小板激活抑制剂前列腺素E1部分抑制，且仅当Ca2+浓度从1 mM（生理水平）降至0.1 mM时，才与血小板颗粒释放5-羟色胺有关。数据表明，vWF通过与两种受体——GP IIb-IIIa和GP Ib相互作用支持CRC54诱导的血小板聚集。在vWF或纤维蛋白原存在下，CRC54诱导的聚集仅部分依赖于血小板激活，且仅在低Ca2+浓度下伴有颗粒分泌。
