糖蛋白VI是PF4/抗PF4 IgG复合物的受体，在肝素诱导的血小板减少症（HIT）中有助于血小板激活。

Glycoprotein VI is a receptor for the PF4/anti-PF4 IgG complex and contributes to platelet activation in heparin-induced thrombocytopenia (HIT).

作者信息

Francischetti Ivo M B, Dane Kathryn E, Galgo Ed L, Streiff Michael B, Andersen John F

机构信息

Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.

Department of Pharmacy, The Johns Hopkins Hospital, Baltimore, Maryland, USA.

出版信息

J Thromb Haemost. 2025 Jul 22. doi: 10.1016/j.jtha.2025.07.016.

DOI:10.1016/j.jtha.2025.07.016

PMID:40706961

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC12396540/

Abstract

BACKGROUND

Platelet factor 4 (PF4) plays a central role in heparin-induced thrombocytopenia (HIT). PF4 is a positively charged tetramer that forms immune complexes with anti-PF4 immunoglobulin G, activating platelets via FcγRIIA. Despite extensive study, a platelet receptor for PF4 within these complexes has not been clearly defined.

OBJECTIVE

We hypothesized that glycoprotein VI (GPVI), a collagen receptor known to interact with multiple ligands, binds PF4 and contributes to platelet activation in HIT.

METHODS

We used platelet aggregation assays, surface plasmon resonance, and AlphaFold 3 modeling to investigate interactions between PF4, the HIT-mimicking monoclonal antibody KKO, and GPVI.

RESULTS

Platelet aggregation triggered by PF4/KKO or HIT patient sera was reduced by anti-GPVI antibodies or the anti-GPVI Fab fragment ACT017. Surface plasmon resonance showed that PF4 binds GPVI with a dissociation constant of Kd approximately equal to 1 μM, but PF4/KKO complexes exhibited enhanced binding, with a 5 to 17-fold reduction in dissociation rate and Kd approximately equal to 30 to 100 nM. This interaction was blocked by heparin. In contrast, the nonpathogenic anti-PF4 antibody RTO had no effect. AlphaFold 3 modeling predicted electrostatic interactions between anionic GPVI surfaces and the PF4/KKO complex, with PF4 tetramers contacting both the GPVI D2 domain and KKO Fab.

CONCLUSION

GPVI functions as a receptor for PF4/HIT antibody complex, engaging FcγRIIA and contributing to platelet activation in HIT.

摘要

背景

血小板因子4（PF4）在肝素诱导的血小板减少症（HIT）中起核心作用。PF4是一种带正电荷的四聚体，可与抗PF4免疫球蛋白G形成免疫复合物，通过FcγRIIA激活血小板。尽管进行了广泛研究，但这些复合物中PF4的血小板受体尚未明确界定。

目的

我们假设糖蛋白VI（GPVI），一种已知可与多种配体相互作用的胶原受体，可结合PF4并在HIT中促进血小板激活。

方法

我们使用血小板聚集试验、表面等离子体共振和AlphaFold 3建模来研究PF4、模拟HIT的单克隆抗体KKO和GPVI之间的相互作用。

结果

抗GPVI抗体或抗GPVI Fab片段ACT017可降低PF4/KKO或HIT患者血清引发的血小板聚集。表面等离子体共振显示，PF4与GPVI结合，解离常数Kd约为1 μM，但PF4/KKO复合物表现出增强的结合，解离速率降低5至17倍，Kd约为30至100 nM。这种相互作用被肝素阻断。相比之下，非致病性抗PF4抗体RTO没有效果。AlphaFold 3建模预测了阴离子GPVI表面与PF4/KKO复合物之间的静电相互作用，PF4四聚体与GPVI D2结构域和KKO Fab均接触。