Ivo M B Francischetti, Kathryn E Dane, Ed L Galgo, Michael B Streiff, John F Andersen
{"title":"糖蛋白VI是PF4/抗PF4 IgG复合物的受体,有助于HIT的血小板活化。","authors":"Ivo M B Francischetti, Kathryn E Dane, Ed L Galgo, Michael B Streiff, John F Andersen","doi":"10.1016/j.jtha.2025.07.016","DOIUrl":null,"url":null,"abstract":"<p><strong>Background: </strong>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 IgG, activating platelets via FcγRIIA. Despite extensive study, a platelet receptor for PF4 within these complexes has not been clearly defined.</p><p><strong>Objective: </strong>We hypothesized that glycoprotein VI (GPVI), a collagen receptor known to interact with multiple ligands, binds PF4 and contributes to platelet activation in HIT.</p><p><strong>Methods: </strong>We used platelet aggregation assays, surface plasmon resonance (SPR), and AlphaFold 3 modeling to investigate interactions between PF4, the HIT-mimicking monoclonal antibody KKO, and GPVI.</p><p><strong>Results: </strong>Platelet aggregation triggered by PF4/KKO or HIT patient sera was reduced by anti-GPVI antibodies or the anti-GPVI Fab fragment ACT017. SPR showed that PF4 binds GPVI with a dissociation constant of Kd ≈ 1 μM, but PF4/KKO complexes exhibited enhanced binding, with a 5-17-fold reduction in dissociation rate and Kd ≈ 30-100 nM. This interaction was blocked by heparin. In contrast, the non-pathogenic anti-PF4 antibody RTO had no effect. AlphaFold modeling suggested electrostatic interactions between anionic GPVI surfaces and the PF4/KKO complex, with PF4 tetramers contacting both the GPVI D2 domain and KKO Fab.</p><p><strong>Conclusion: </strong>GPVI functions as a receptor for PF4/anti-PF4 IgG immune complexes, engaging FcγRIIA and contributing to platelet activation in HIT.</p>","PeriodicalId":17326,"journal":{"name":"Journal of Thrombosis and Haemostasis","volume":" ","pages":""},"PeriodicalIF":5.0000,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Glycoprotein VI is a receptor for the PF4/anti-PF4 IgG complex and contributes to platelet activation in HIT.\",\"authors\":\"Ivo M B Francischetti, Kathryn E Dane, Ed L Galgo, Michael B Streiff, John F Andersen\",\"doi\":\"10.1016/j.jtha.2025.07.016\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p><strong>Background: </strong>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 IgG, activating platelets via FcγRIIA. Despite extensive study, a platelet receptor for PF4 within these complexes has not been clearly defined.</p><p><strong>Objective: </strong>We hypothesized that glycoprotein VI (GPVI), a collagen receptor known to interact with multiple ligands, binds PF4 and contributes to platelet activation in HIT.</p><p><strong>Methods: </strong>We used platelet aggregation assays, surface plasmon resonance (SPR), and AlphaFold 3 modeling to investigate interactions between PF4, the HIT-mimicking monoclonal antibody KKO, and GPVI.</p><p><strong>Results: </strong>Platelet aggregation triggered by PF4/KKO or HIT patient sera was reduced by anti-GPVI antibodies or the anti-GPVI Fab fragment ACT017. SPR showed that PF4 binds GPVI with a dissociation constant of Kd ≈ 1 μM, but PF4/KKO complexes exhibited enhanced binding, with a 5-17-fold reduction in dissociation rate and Kd ≈ 30-100 nM. This interaction was blocked by heparin. In contrast, the non-pathogenic anti-PF4 antibody RTO had no effect. AlphaFold modeling suggested electrostatic interactions between anionic GPVI surfaces and the PF4/KKO complex, with PF4 tetramers contacting both the GPVI D2 domain and KKO Fab.</p><p><strong>Conclusion: </strong>GPVI functions as a receptor for PF4/anti-PF4 IgG immune complexes, engaging FcγRIIA and contributing to platelet activation in HIT.</p>\",\"PeriodicalId\":17326,\"journal\":{\"name\":\"Journal of Thrombosis and Haemostasis\",\"volume\":\" \",\"pages\":\"\"},\"PeriodicalIF\":5.0000,\"publicationDate\":\"2025-07-22\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Thrombosis and Haemostasis\",\"FirstCategoryId\":\"3\",\"ListUrlMain\":\"https://doi.org/10.1016/j.jtha.2025.07.016\",\"RegionNum\":2,\"RegionCategory\":\"医学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"HEMATOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Thrombosis and Haemostasis","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1016/j.jtha.2025.07.016","RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"HEMATOLOGY","Score":null,"Total":0}
Glycoprotein VI is a receptor for the PF4/anti-PF4 IgG complex and contributes to platelet activation in HIT.
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 IgG, 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 (SPR), 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. SPR showed that PF4 binds GPVI with a dissociation constant of Kd ≈ 1 μM, but PF4/KKO complexes exhibited enhanced binding, with a 5-17-fold reduction in dissociation rate and Kd ≈ 30-100 nM. This interaction was blocked by heparin. In contrast, the non-pathogenic anti-PF4 antibody RTO had no effect. AlphaFold modeling suggested 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/anti-PF4 IgG immune complexes, engaging FcγRIIA and contributing to platelet activation in HIT.
期刊介绍:
The Journal of Thrombosis and Haemostasis (JTH) serves as the official journal of the International Society on Thrombosis and Haemostasis. It is dedicated to advancing science related to thrombosis, bleeding disorders, and vascular biology through the dissemination and exchange of information and ideas within the global research community.
Types of Publications:
The journal publishes a variety of content, including:
Original research reports
State-of-the-art reviews
Brief reports
Case reports
Invited commentaries on publications in the Journal
Forum articles
Correspondence
Announcements
Scope of Contributions:
Editors invite contributions from both fundamental and clinical domains. These include:
Basic manuscripts on blood coagulation and fibrinolysis
Studies on proteins and reactions related to thrombosis and haemostasis
Research on blood platelets and their interactions with other biological systems, such as the vessel wall, blood cells, and invading organisms
Clinical manuscripts covering various topics including venous thrombosis, arterial disease, hemophilia, bleeding disorders, and platelet diseases
Clinical manuscripts may encompass etiology, diagnostics, prognosis, prevention, and treatment strategies.