Identification of a novel binding site for platelet integrins αIIbβ3 (GPIIbIIIa) and α5β1 in the γC-domain of fibrinogen
Identification of a novel binding site for platelet integrins αIIbβ3 (GPIIbIIIa) and α5β1 in the γC-domain of fibrinogen
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DOI：
10.1074/jbc.m300410200
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发表时间：
2003-08-22
影响因子：
4.8
通讯作者：
Ugarova, TP
中科院分区：
文献类型：
--
作者：
Podolnikova, NP;Yakubenko, VP;Ugarova, TP
血小板与纤维蛋白原的相互作用介导了多种反应，包括黏附、血小板聚集和纤维蛋白凝块回缩。尽管人们认为血小板整合素α(IIb)β(3)与纤维蛋白原GAMMA C区域的AGDV序列和/或AAlpha链上的RGD位点的相互作用参与了凝块回缩和粘连，但最近的数据表明，缺乏这些位点的纤维蛋白原仍然支持凝块回缩。这些发现表明，纤维蛋白原和/或其他整合素中的一个未知部位参与了凝块回缩。在这里，我们已经确定了GammaC中的一个序列，它介导了纤维蛋白原与血小板的结合。在GammaC中复制365-383序列的合成肽，命名为P3，以剂量依赖的方式有效地抑制凝块回缩。此外，P3支持血小板黏附，是血小板与纤维蛋白原片段黏附的有效抑制物。对跨越P3和突变的重组GammaC结构域的重叠多肽的分析表明，P3的活性主要包含在Gamma370-383中。整合素α(IIb)β(3)和β(5)β(1)与P3的识别有关，因为针对这些受体的功能阻断的单抗阻断了血小板与P3的粘附性。直接证据表明，α(IIb)β(3)和α(5)β(1)结合P3是通过使用P3亲和矩阵从血小板裂解物中选择性地捕获这些整合素而获得的。因此，这些数据表明，纤维蛋白原GammaC结构域中的P3序列定义了先前未知的α(IIb)β(3)和α(5)β(1)的识别特异性，并可能作为这些整合素的结合位点。
The interactions of platelets with fibrinogen mediate a variety of responses including adhesion, platelet aggregation, and fibrin clot retraction. Whereas it was assumed that interactions of the platelet integrin alpha(IIb)beta(3) with the AGDV sequence in the gammaC-domain of fibrinogen and/or RGD sites in the Aalpha chains are involved in clot retraction and adhesion, recent data demonstrated that fibrinogen lacking these sites still supported clot retraction. These findings suggested that an unknown site in fibrinogen and/or other integrins participate in clot retraction. Here we have identified a sequence within gammaC that mediates binding of fibrinogen to platelets. Synthetic peptide duplicating the 365 - 383 sequence in gammaC, designated P3, efficiently inhibited clot retraction in a dose-dependent manner. Furthermore, P3 supported platelet adhesion and was an effective inhibitor of platelet adhesion to fibrinogen fragments. Analysis of overlapping peptides spanning P3 and mutant recombinant gammaC-domains demonstrated that the P3 activity is contained primarily within gamma370-383. Integrins alpha(IIb)beta(3) and beta(5)beta(1) were implicated in recognition of P3, since platelet adhesion to the peptide was blocked by function-blocking monoclonal antibodies against these receptors. Direct evidence that alpha(IIb)beta(3) and alpha(5)beta(1) bind P3 was obtained by selective capture of these integrins from platelet lysates using a P3 affinity matrix. Thus, these data suggest that the P3 sequence in the gammaC-domain of fibrinogen defines a previously unknown recognition specificity of alpha(IIb)beta(3) and alpha(5)beta(1) and may function as a binding site for these integrins.