Suehiro K, Gailit J, Plow E F
Joseph J. Jacobs Center for Thrombosis and Vascular Biology, Department of Molecular Cardiology, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
J Biol Chem. 1997 Feb 21;272(8):5360-6. doi: 10.1074/jbc.272.8.5360.
Previous studies have shown that fibrinogen can associate with endothelial cells via an Arg-Gly-Asp (RGD) recognition specificity. In the present study, we have characterized the specificity of fibrinogen binding to endothelial cells under different cation conditions. Fibrinogen binding to suspended endothelial cells was selectively supported by Mn2+ and was suppressed by Ca2+. The Mn2+-supported interaction was completely inhibited by RGD peptides but not by alphavbeta3 blocking monoclonal antibodies. In contrast, the interaction was completely blocked by two alpha5beta1 monoclonal antibodies. This interaction was not mediated by fibronectin bound to the integrin; could be demonstrated with purified alpha5beta1; and also was observed with a second alpha5beta1-bearing cell type, platelets. The binding of fibrinogen to alpha5beta1 on endothelial cells in the presence of Mn2+ was time-dependent, specific, saturable, and of high affinity (Kd = 65 nM). By employing anti-peptide monoclonal antibodies, the carboxyl-terminal RGD sequence at Aalpha 572-574 was implicated in fibrinogen recognition by alpha5beta1. Two circumstances were identified in which alpha5beta1 interacted with fibrinogen in the presence of Ca2+: when the receptor was activated with monoclonal antibody (8A2) or when the fibrinogen was presented as an immobilized substratum. These results identify fibrinogen as a ligand for alpha5beta1 on endothelial and other cells, an interaction which may have broad biological implications.
先前的研究表明，纤维蛋白原可通过精氨酸 - 甘氨酸 - 天冬氨酸（RGD）识别特异性与内皮细胞结合。在本研究中，我们已对不同阳离子条件下纤维蛋白原与内皮细胞结合的特异性进行了表征。纤维蛋白原与悬浮内皮细胞的结合受到Mn2 +的选择性支持，并受到Ca2 +的抑制。Mn2 +支持的相互作用被RGD肽完全抑制，但不被αvβ3阻断单克隆抗体抑制。相反，该相互作用被两种α5β1单克隆抗体完全阻断。这种相互作用不是由与整合素结合的纤连蛋白介导的；可以用纯化的α5β1证明；并且在第二种带有α5β1的细胞类型血小板中也观察到了这种相互作用。在Mn2 +存在下，纤维蛋白原与内皮细胞上的α5β1的结合是时间依赖性的、特异性的、可饱和的且具有高亲和力（Kd = 65 nM）。通过使用抗肽单克隆抗体，Aα572 - 574处的羧基末端RGD序列与α5β1对纤维蛋白原的识别有关。确定了两种情况，其中在Ca2 +存在下α5β1与纤维蛋白原相互作用：当受体用单克隆抗体（8A2）激活时，或当纤维蛋白原作为固定化底物呈现时。这些结果确定纤维蛋白原为内皮细胞和其他细胞上α5β1的配体，这种相互作用可能具有广泛的生物学意义。
