The Platelet Integrin IIb3 Differentially Interacts with Fibrin Versus Fibrinogen
The Platelet Integrin IIb3 Differentially Interacts with Fibrin Versus Fibrinogen
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DOI：
10.1074/jbc.m115.706861
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发表时间：
2016-04-08
影响因子：
4.8
通讯作者：
Bennett, Joel S.
中科院分区：
文献类型：
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作者：
Litvinov, Rustem I.;Farrell, David H.;Bennett, Joel S.
纤维蛋白原与整合素IIb3结合介导血小板在纤维蛋白原包被表面的聚集和扩散。然而，体内IIb3激活和纤维蛋白原转化为纤维蛋白同时发生，尽管纤维蛋白原和纤维蛋白对IIb3介导的血小板功能的相对贡献尚不清楚。在这里，我们比较了IIb3与纤维蛋白和纤维蛋白原的相互作用，以探索它们的不同作用。用激光束捕获被纤维蛋白原或单体纤维蛋白包覆的微球，这些纤维蛋白原是用凝血酶处理固定的纤维蛋白原产生的，并反复与表面附着的纯化IIb3接触。当检测到iib3配体配合物时，测量破裂力并以力直方图显示。单个纤维蛋白与IIb3相互作用的可能性更高，结合强度也更大。iib3 -纤维蛋白相互作用对阿昔单抗和依替巴肽的抑制也不太敏感。纤维蛋白原和纤维蛋白- iib3的相互作用都被RGD肽部分抑制，这表明存在共同的含有RGD的结合基序。这一假设得到了含有突变RGD基序的纤维蛋白变体D97E或D574E的支持。由缺乏C IIb3结合基序的纤维蛋白原/变体制成的纤维蛋白与IIb3的反应性比亲本纤维蛋白原更强。这些结果表明，纤维蛋白比纤维蛋白原更能与IIb3反应。纤维蛋白对IIb3抑制剂也不太敏感，这表明纤维蛋白和纤维蛋白原具有不同的结合要求。特别是，在缺乏c -十二肽和-链RGD序列的情况下，IIb3结合活性的维持表明，纤维蛋白中的IIb3结合位点并不局限于已知的-链和RGD基序。
Fibrinogen binding to the integrin IIb3 mediates platelet aggregation and spreading on fibrinogen-coated surfaces. However, in vivo IIb3 activation and fibrinogen conversion to fibrin occur simultaneously, although the relative contributions of fibrinogen versus fibrin to IIb3-mediated platelet functions are unknown. Here, we compared the interaction of IIb3 with fibrin and fibrinogen to explore their differential effects. A microscopic bead coated with fibrinogen or monomeric fibrin produced by treating the immobilized fibrinogen with thrombin was captured by a laser beam and repeatedly brought into contact with surface-attached purified IIb3. When IIb3-ligand complexes were detected, the rupture forces were measured and displayed as force histograms. Monomeric fibrin displayed a higher probability of interacting with IIb3 and a greater binding strength. IIb3-fibrin interactions were also less sensitive to inhibition by abciximab and eptifibatide. Both fibrinogen- and fibrin-IIb3 interactions were partially inhibited by RGD peptides, suggesting the existence of common RGD-containing binding motifs. This assumption was supported using the fibrin variants D97E or D574E with mutated RGD motifs. Fibrin made from a fibrinogen / variant lacking the C IIb3-binding motif was more reactive with IIb3 than the parent fibrinogen. These results demonstrate that fibrin is more reactive with IIb3 than fibrinogen. Fibrin is also less sensitive to IIb3 inhibitors, suggesting that fibrin and fibrinogen have distinct binding requirements. In particular, the maintenance of IIb3 binding activity in the absence of the C-dodecapeptide and the -chain RGD sequences suggests that the IIb3-binding sites in fibrin are not confined to its known -chain and RGD motifs.