Activating mechanisms of platelet GPIIb-IIIa complex by the interaction of intracellular proteins

为了确定血小板GPIIb-IIIa复合物的激活机制，分析了几种相关蛋白的作用。β3-内切蛋白激活的GPIIb-IIIa复合物。然而，由于它是一种核蛋白，它不能有效地定位在质膜附近。血小板和细胞粘附过程中CD 98激活GPIIb-IIIa复合物。IAP强烈激活GPIIb-IIIa复合物，并诱导可溶性配体结合时，只有当它与血小板反应蛋白的C-末端结构域。包括talin和filamin在内的几种细胞骨架蛋白影响GPIIb-IIIa复合物的功能。为了了解这些下游通路，通过酵母双杂交筛选鉴定了与film结合的蛋白。其中一个克隆是新的cDNA，编码375个氨基酸和45 kDa的蛋白质。推导的氨基酸序列表明，它含有一个富含脯氨酸的结构域在其N-末端的一半和两个LIM结构域在C-末端。因此，我们将其命名为FBLP-1（Filamin Binding LIM Protein-1）。亚细胞定位分析显示FBLP-1与应力纤维共定位，应力纤维从含有GPIIb-IIIa复合物的局灶性粘连延伸。过表达FBLP-1的细胞比不表达FBLP-1的细胞更有效地扩散，表明FBLP-1在血小板粘附中起重要作用。对这些相关蛋白的进一步研究将有助于阐明血小板GPIIb-IIIa复合物的活化机制。

In order to determine the activating mechanisms of platelet GPIIb-IIIa complex, the role of several associated proteins was analyzed. β3-endonexin activated GPIIb-IIIa complex. However it did not effectively localize near the plasma membrane since it was a nuclear protein. CD98 activated GPIIb-IIIa complex during platelet and cell adhesion. IAP strongly activated GPIIb-IIIa complex and induced soluble ligand bindings only when it interacted with C-terminal domain of thrombospondin. Several cytoskeletal proteins including talin and filamin influenced the function of GPIIb-IIIa complex. To know these downstream pathways, proteins that bind to filamins were identified by yeast two hybrid screening. One clone was a novel cDNA, which encoded 375 amino acids and 45kDa protein. Deduced amino acid sequence showed that it contained a proline-rich domain at its N-terminal half and two LIM domains at C-terminus. We therefore, named it as FBLP-1 (Filamin Binding LIM Protein-1). Subcellular localization analysis showed that FBLP-1 co-localized with stress fibers, which stretched from focal adhesions containing GPIIb-IIIa complex. The cells, which over expressed FBLP-1, spread more effectively than the cells which did not express FBLP-1, suggesting that FBLP-1 plays a significant role on platelet adhesion. Further investigation of these associated proteins would clarify the activating mechanisms of platelet GPIIb-IIIa complex.