Jiang Xiaoyan, Sun Xiaoxi, Lin Jiangguo, Ling Yingchen, Fang Ying, Wu Jianhua
Institute of Biomechanics/School of Biology and Biological Engineering, South China University of Technology, Guangzhou, China.
Research Department of Medical Sciences, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China.
Front Mol Biosci. 2021 Apr 22;8:638396. doi: 10.3389/fmolb.2021.638396. eCollection 2021.
Interaction of leukocyte integrin macrophage-1 antigen (Mac-1) to platelet glycoprotein Ibα (GPIbα) is critical for platelet-leukocyte crosstalk in hemostasis and inflammatory responses to vessel injuries under hemodynamic environments. The mechano-regulation and its molecular basis for binding of Mac-1 to GPIbα remain unclear, mainly coming from the lack of crystal structure of the Mac-1/GPIbα complex. We herein built a Mac-1/GPIbα complex model through a novel computer strategy, which included a flexible molecular docking and system equilibrium followed by a "force-ramp + snapback" molecular dynamics (MD) simulation. With this model, a series of "ramp-clamp" steered molecular dynamics (SMD) simulations were performed to examine the GPIbα-Mac-1 interaction under various loads. The results demonstrated that the complex was mechano-stable for both the high rupture force (>250 pN) at a pulling velocity of 3 Å/ns and the conformational conservation under various constant tensile forces (≤75 pN); a catch-slip bond transition was predicted through the dissociation probability, examined with single molecular AFM measurements, reflected by the interaction energy and the interface H-bond number, and related to the force-induced allostery of the complex; besides the mutation-identified residues D222 and R218, the residues were also dominant in the binding of Mac-1 to GPIbα. This study recommended a valid computer strategy for building a likely wild-type docking model of a complex, provided a novel insight into the mechanical regulation mechanism and its molecular basis for the interaction of Mac-1 with GPIbα, and would be helpful for understanding the platelet-leukocyte interaction in hemostasis and inflammatory responses under mechano-microenvironments.
白细胞整合素巨噬细胞-1抗原（Mac-1）与血小板糖蛋白Ibα（GPIbα）的相互作用对于止血过程中血小板-白细胞的相互作用以及血流动力学环境下对血管损伤的炎症反应至关重要。Mac-1与GPIbα结合的机械调节及其分子基础仍不清楚，主要是由于缺乏Mac-1/GPIbα复合物的晶体结构。我们在此通过一种新颖的计算机策略构建了Mac-1/GPIbα复合物模型，该策略包括灵活的分子对接和系统平衡，随后进行“力斜坡+回拉”分子动力学（MD）模拟。利用该模型，进行了一系列“斜坡-钳位”引导分子动力学（SMD）模拟，以研究不同负载下GPIbα-Mac-1的相互作用。结果表明，该复合物在3 Å/ns的拉伸速度下具有较高的破裂力（>250 pN）时机械稳定，并且在各种恒定拉力（≤75 pN）下构象保守；通过解离概率预测了一种捕捉-滑动键转变，通过单分子原子力显微镜测量进行检测，由相互作用能和界面氢键数反映，并与复合物的力诱导变构有关；除了通过突变鉴定的残基D222和R218外，这些残基在Mac-1与GPIbα的结合中也起主导作用。本研究推荐了一种有效的计算机策略来构建复合物可能的野生型对接模型，为Mac-1与GPIbα相互作用的机械调节机制及其分子基础提供了新的见解，并有助于理解机械微环境下止血和炎症反应中的血小板-白细胞相互作用。
