Tao Rencai, Xie Xubin, Wu Jianhua, Fang Ying
School of Bioscience & Bioengineering, South China University of Technology, Guangzhou 510006, P. R. China.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi. 2023 Oct 25;40(5):876-885. doi: 10.7507/1001-5515.202302043.
In resting platelets, the 17 domain of filamin a (FLNa17) constitutively binds to the platelet membrane glycoprotein Ibα (GPIbα) at its cytoplasmic tail (GPIbα-CT) and inhibits the downstream signal activation, while the binding of ligand and blood shear force can activate platelets. To imitate the pull force transmitted from the extracellular ligand of GPIbα and the lateral tension from platelet cytoskeleton deformation, two pulling modes were applied on the GPIbα-CT/FLNa17 complex, and the molecular dynamics simulation method was used to explore the mechanical regulation on the affinity and mechanical stability of the complex. In this study, at first, nine pairs of key hydrogen bonds on the interface between GPIbα-CT and FLNa17 were identified, which was the basis for maintaining the complex structural stability. Secondly, it was found that these hydrogen bonding networks would be broken down and lead to the dissociation of FLNa17 from GPIbα-CT only under the axial pull force; but, under the lateral tension, the secondary structures at both terminals of FLNa17 would unfold to protect the interface of the GPIbα-CT/FLNa17 complex from mechanical damage. In the range of 0~40 pN, the increase of pull force promoted outward-rotation of the nitrogen atom of the 563 phenylalanine (PHE -N) at GPIbα-CT and the dissociation of the complex. This study for the first time revealed that the extracellular ligand-transmitted axial force could more effectively relieve the inhibition of FLNa17 on the downstream signal of GPIbα than pure mechanical tension at the atomic level, and would be useful for further understanding the platelet intracellular force-regulated signal pathway.
在静息血小板中，细丝蛋白A的17结构域（FLNa17）在其细胞质尾部（GPIbα-CT）与血小板膜糖蛋白Ibα（GPIbα）组成性结合，并抑制下游信号激活，而配体结合和血流剪切力可激活血小板。为模拟从GPIbα的细胞外配体传递的拉力以及血小板细胞骨架变形产生的侧向张力，对GPIbα-CT/FLNa17复合物施加了两种拉伸模式，并采用分子动力学模拟方法探究对该复合物亲和力和机械稳定性的力学调控。在本研究中，首先，确定了GPIbα-CT与FLNa17界面上的九对关键氢键，这是维持复合物结构稳定性的基础。其次，发现这些氢键网络仅在轴向拉力作用下会被破坏并导致FLNa17从GPIbα-CT上解离；但是，在侧向张力作用下，FLNa17两端的二级结构会展开以保护GPIbα-CT/FLNa17复合物的界面免受机械损伤。在0~40皮牛范围内，拉力增加促使GPIbα-CT处563位苯丙氨酸的氮原子（PHE-N）向外旋转并导致复合物解离。本研究首次在原子水平揭示，细胞外配体传递的轴向力比纯机械张力能更有效地解除FLNa17对GPIbα下游信号的抑制，这将有助于进一步理解血小板细胞内力调节信号通路。
