Hantgan R R
Department of Biochemistry, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, NC 27103.
Biochim Biophys Acta. 1988 Jan 18;968(1):36-44. doi: 10.1016/0167-4889(88)90041-9.
The molecular basis of platelet-fibrin interactions has been investigated by using synthetic peptides as potential inhibitors of fibrin protofibril and fibrinogen binding to ADP-stimulated platelets, adhesion of fibrin fibers to the platelet surface, and platelet-mediated clot retraction. Synthetic peptides of sequence RGDS and HHLGGAKQAGDV, corresponding to regions of the fibrinogen alpha- and gamma-chains previously identified as platelet recognition sites, inhibited the binding of radiolabelled soluble fibrin oligomers to ADP-stimulated platelets with IC50 values of 10 and 40 microM, respectively. Synthetic GPRP and GHRP, corresponding to the N-terminal tripeptide sequence of the fibrin alpha-chains and the tetrapeptide sequence of the beta-chains, respectively, were minimally effective in blocking soluble fibrin polymer binding to ADP-stimulated platelets. Platelet functions which are unique to the three-dimensional fibrin network were examined by measurements of the extent of adhesion of fluorophore-labelled fibrin to platelets with a microfluorimetric technique and by light scattering measurements of the time course of clot retraction. Inhibition of fibrin-platelet adhesion by RGDS, HHLGGAKQAGDV and GHRP exhibited a similar, linear dependence reaching 1/2 maximum at about 200 microM, suggesting nonspecific effects. GPRP inhibited fibrin assembly but did not appear to have specific effects on fibrin-platelet adhesion. Only RGDS effected clot retraction, causing a 4-6-fold decrease in rate at 230 microM. These results indicate that fibrinogen and fibrin protofibrils, which are obligatory intermediates on the fibrin assembly pathway, share a set of common platelet recognition sites located at specific regions of the alpha- and gamma-chains of the multinodular fibrin(ogen) molecules. The RGDS site is also involved in mediating interactions between the three-dimensional fibrin network and stimulated platelets.
通过使用合成肽作为纤维蛋白原纤维和纤维蛋白原与ADP刺激的血小板结合、纤维蛋白纤维与血小板表面粘附以及血小板介导的凝块回缩的潜在抑制剂，研究了血小板 - 纤维蛋白相互作用的分子基础。与先前确定为血小板识别位点的纤维蛋白原α链和γ链区域相对应的序列RGDS和HHLGGAKQAGDV合成肽，分别以10和40μM的IC50值抑制放射性标记的可溶性纤维蛋白寡聚体与ADP刺激的血小板的结合。分别对应于纤维蛋白α链的N端三肽序列和β链的四肽序列的合成GPRP和GHRP，在阻断可溶性纤维蛋白聚合物与ADP刺激的血小板结合方面效果甚微。通过用微荧光技术测量荧光团标记的纤维蛋白与血小板的粘附程度以及通过光散射测量凝块回缩的时间进程，研究了三维纤维蛋白网络特有的血小板功能。RGDS、HHLGGAKQAGDV和GHRP对纤维蛋白 - 血小板粘附的抑制表现出相似的线性依赖性，在约200μM时达到最大抑制的1/2，表明存在非特异性作用。GPRP抑制纤维蛋白组装，但似乎对纤维蛋白 - 血小板粘附没有特异性作用。只有RGDS影响凝块回缩，在230μM时导致速率降低4 - 6倍。这些结果表明，作为纤维蛋白组装途径中必不可少的中间体的纤维蛋白原和纤维蛋白原纤维，共享一组位于多结节纤维蛋白（原）分子α链和γ链特定区域的共同血小板识别位点。RGDS位点也参与介导三维纤维蛋白网络与刺激的血小板之间的相互作用。
