OC 41.5 - A novel and unique mechanism of αIIbβ3 regulation in platelets

Monday, July 11, 2022

3:45 PM – 4:00 PM

Location: ExCel Center, S11A

Presentation Format: In-Person

Co-Author(s)

CK

Charly Kusch

PhD student
Institute of Experimental Biomedicine I, University Hospital Würzburg, Germany and Rudolf Virchow Center for Integrative and Translational Biomaging University of Würzburg, Germany
Würzburg, Bayern, 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

Presenting Author(s)

Denise Johnson, MSc

PhD student
Institute of Experimental Biomedicine I, University Hospital Würzburg, Germany and Rudolf Virchow Center for Integrative and Translational Biomaging University of Würzburg, Germany
Würzburg, Bayern, Germany

Co-Author(s)

MM

Mara Meub

PhD student
Department of Biotechnology and Biophysics, Biocenter, University of Würzburg
Würzburg, Bayern, Germany
PN

Paquita Nurden

Professor Emerita
Institut Hospitalo-Universitaire LIRYC, Hôpital Xavier Arnozan, Pessac
Pessac, Aquitaine, France
CG

Carina Gross

Postdoc
Institute of Experimental Biomedicine I, University Hospital Würzburg and Rudolf Virchow Center for Integrative and Translational Biomaging University of Würzburg
Würzburg, Bayern, Germany
DS

Daniela Semeniak

Postdoc
Institute of Experimental Biomedicine I, University Hospital Würzburg and Rudolf Virchow Center for Integrative and Translational Biomaging University of Würzburg
Würzburg, Bayern, Germany
JS

Joachim Schenk

technician
Rudolf Virchow Center for Integrative and Translational Biomaging University of Würzburg
Würzburg, Bayern, Germany
MB

Markus Bender

Principal Investigator
Institute of Experimental Biomedicine, University Hospital Würzburg and Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg
Würzburg, Bayern, Germany
TV

Timo Vögtle

Postdoc
Institute of Experimental Biomedicine I, University Hospital Würzburg
Würzburg, Bayern, Germany
KH

Katrin Heinze

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

Markus Sauer

Professor
Department of Biotechnology and Biophysics, Biocenter, University of Würzburg and Rudolf Virchow Center for Integrative and Translational Biomaging University of Würzburg
Würzburg, Bayern, Germany
AN

Alan T. Nurden

Professor Emeritus
Institut Hospitalo-Universitaire LIRYC, Hôpital Xavier Arnozan, Pessac
Pessac, Aquitaine, France
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: Integrins are heterodimeric adhesion molecules which mediate cell-cell and cell-extracellular matrix interactions. As the dominant platelet integrin, αIIbβ3 plays a central role in in haemostasis, thrombosis, and inflammation.

Aims: In this study, we report a previously unrecognized pathway of αIIbβ3 regulation in platelets that is triggered by monoclonal antibodies (mAbs) against the integrin.

Methods: In vitro and in vivo studies were performed with anti-αIIbβ3 mAbs (MWReg30, JON mAbs). MWReg30 (2 µg/g body weight) was administered intravenously to Fcgr3-/-, Fcgr3-/-:FcgR2b-/- or Fcgr3-/-:Fcgr2bYF/YF mice and the fate of platelets was monitored ex vivo and in vivo.

Results: Binding of anti-αIIbβ3 mAbs almost instantaneously induced clustering and capping of the integrin in platelets and the opsonized platelets were rapidly recruited to the liver in vivo. To avoid their clearance by Fcγ receptor (FcγR)-bearing immune cells, further studies were performed in mice lacking FcγRIII (Fcgr3-/-). Ex vivo analysis of platelets following MWReg30 infusion demonstrated a virtually complete loss of αIIbβ3 and a ~50% reduction in CD9. As a result, the animals displayed a Glanzmann thrombasthenia (GT)-like phenotype. To study this paradoxical loss of αIIbβ3/CD9 in situ, we performed intravital confocal laser-scanning microscopy (IV-LSM) of the liver. Almost immediately after injection of MWReg30, the opsonized platelets attached via the antibody Fc-part to the inhibitory FcγRIIB on liver sinusoidal endothelial cells (LSEC). The targeted integrins clustered at the platelet ‘rear edge’ and finally segregated within a long protrusion or tether. The αIIbβ3-devoid platelet body detached and returned into the circulation (Fig. 1). The flow-dependent release of αIIbβ3/CD9-enriched tethers (termed Platelet-derived Integrin and Tetraspanin-enriched Tethers, PITTs) was reproduced in vitro by employing surface-adsorbed antibodies.

Conclusion(s): This data reveals a novel insight for integrin regulation by mechanosensing in platelets and presumably other cells.

This work was supported by TR240 grant with project number 374031971 and BE5084/5-1.