OC 49.2 - Spatio-temporal control of fibrin formation by platelet glycoprotein V

Monday, July 11, 2022

3:00 PM – 3:15 PM

Location: ExCel Center, ICC Capital Suite Room 1

Presentation Format: In-Person

Presenting Author(s)

Sarah Beck, PhD

Postdoc
Institute of Experimental Biomedicine - Chair I, University Hospital and Rudolf Virchow Center for Integrative and Translational Bioimaging, Würzburg, Germany
Würzburg, Bayern, Germany

Co-Author(s)

Patricia Öftering, MSc

PhD student
University Hospital Würzburg and Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Germany
Würzburg, Bayern, Germany
Renhao Li, PhD

Professor of Pediatrics
Aflac Cancer and Blood Disorders Center, Children’s Healthcare of Atlanta, Department of Pediatrics, Emory University School of Medicine
Atlanta, Georgia, United States
KH

Katherina Hemmen

Postdoc
Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Germany
Würzburg, Bayern, Germany
Magdolna Nagy, PhD

Postdoctoral Researcher
Coagulation Profile, Maastricht, the Netherlands
Maastricht, Limburg, Netherlands
YW

Yingchun Wang

MD, PhD
Aflac Cancer and Blood Disorders Center, Children's Healthcare of Atlanta, Department of Pediatrics, Emory University School of Medicine, Atlanta, USA
Atlanta, Georgia, United States
AZ

Alessandro Zarpellon

Postdoctoral fellow
Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA
La Jolla, California, United States
MS

Michael K. Schuhmann

Group leader
University Hospital Würzburg
Würzburg, Bayern, Germany
GS

Guido Stoll

Professor
University Hospital Würzburg
Würzburg, Bayern, Germany
ZR

Zaverio Ruggeri

Professor
Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA
La Jolla, California, United States
KH

Katrin Heinze

Professor
Rudolf Virchow Center for Integrative and Translational Biomaging University of Würzburg, Germany
Würzburg, Bayern, Germany
JW

Johan W. M. Heemskerk

Emeritus Professor
Synapse research insitute
MAASTRICHT, Limburg, Netherlands
WR

Wolfram Ruf

Scientific Director
University Medicine of the Johannes Gutenberg University Mainz, Center for Thrombosis and Hemostasis (CTH)
Mainz, Rheinland-Pfalz, Germany
David Stegner, PhD

Professor
Institute of Experimental Biomedicine - Chair I, University Hospital and Rudolf Virchow Center for Integrative and Translational Bioimaging, Würzburg, Germany
Würzburg, Bayern, Germany
BN

Bernhard Nieswandt

Professor
Institute of Experimental Biomedicine - Chair I, University Hospital Würzburg and Rudolf Virchow Center for Integrative and Translational Biomaging, University of Würzburg, Germany
Würzburg, Bayern, Germany

Background: Platelet activation and coagulation at sites of vascular injury are crucial for hemostasis but can promote thrombosis in vascular pathologies. During platelet activation, the abundant platelet glycoprotein (GP)V is cleaved by thrombin, however the function of membrane-bound as well as cleaved GPV remains unknown.

Aims: To elucidate the role of platelet GPV cleavage and its functional relevance at sites of vascular injury.

Methods: We used genetic and pharmacological approaches (Gp5-/- and Gp5dThr mice – thrombin-insensitive GPV, new anti-GPV antibodies, recombinant GPV ectodomain) to assess thrombus formation, thrombin generation and fibrin formation in vitro and in vivo.

Results: Platelets of Gp5-/- mice were hyperreactive to low thrombin concentrations under conditions where GPIbα was required for platelet responsiveness to thrombin. In contrast to Gp5-/- platelets, Gp5dThr platelets or blockade of thrombin-mediated GPV cleavage were not hyperreactive, indicating a key regulatory role of membrane-bound GPV for thrombin-dependent platelet activation.
Surprisingly, both Gp5-/- and Gp5dThr mice showed accelerated thrombus formation following vascular injury in vivo, suggesting that cleaved GPV controls thrombus formation by a mechanism unrelated to regulation of platelet activation. We uncovered that soluble (s)GPV regulates thrombin-dependent fibrin formation under flow. Specifically, we demonstrated (I) direct interaction of sGPV with thrombin in a pulldown assay, (II) accumulation of sGPV with fibrin in platelet-free areas of thrombi by super-resolution microscopy, (III) increased availability of free thrombin and fibrin formation in Gp5-/- and Gp5dThr mice and after blockade of GPV cleavage, and (IV) inhibition of thrombus formation by sGPV. Thus, sGPV localized to growing thrombi, limited thrombin-dependent fibrin formation and protected from arterial thrombosis without interfering with initial hemostatic platelet adhesion. Accordingly, genetic or pharmacologic defects in hemostatic platelet function were rescued by blockade of GPV cleavage.

Conclusion(s): GPV spatio-temporally controls fibrin formation and thereby provides a platelet-based mechanism that locally limits excessive fibrin formation and thrombus growth.