Open Access
CC BY-NC-ND 4.0 · Thromb Haemost 2016; 116(01): 87-95
DOI: 10.1160/TH15-09-0700
Cellular Haemostasis and Platelets
Schattauer GmbH

The functions of the A1A2A3 domains in von Willebrand factor include multimerin 1 binding

D'Andra N. Parker
1   Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
,
Subia Tasneem
1   Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
,
Richard W. Farndale
2   Department of Biochemistry, University of Cambridge, Cambridge, UK
,
Dominique Bihan
2   Department of Biochemistry, University of Cambridge, Cambridge, UK
,
J. Evan Sadler
3   Department of Medicine, Washington University School of Medicine, Saint Louis, Missouri, USA
,
Silvie Sebastian
4   Laboratory of Clinical Chemistry and Haematology, University Medical Centre Utrecht, Utrecht, Netherlands
,
Philip G. De Groot
4   Laboratory of Clinical Chemistry and Haematology, University Medical Centre Utrecht, Utrecht, Netherlands
,
Catherine P. M. Hayward
5   Medicine, Pathology and Molecular Medicine, McMaster University, Hamilton Regional Laboratory Medicine Program, Hamilton, Ontario, Canada
› Author Affiliations

Financial support: This study was supported by the Heart and Stroke Foundation (CPMH), the Canadian Institutes of Health Research (CPMH), the British Heart Foundation (RWF), The Wellcome Trust (RWF), and the National Institutes of Health (JES).
Further Information

Correspondence to:

Catherine P. M. Hayward
McMaster University Medical Centre
HSC 2N29A, 1200 Main St. West
Hamilton, Ontario, Canada L8N 3Z5
Phone: +1 905 521 2100 Ext. 76274   
Fax: +1 905 521 2338   

Publication History

Received: 03 September 2015

Accepted after major revision: 18 March 2016

Publication Date:
27 November 2017 (online)

 

Summary

Multimerin 1 (MMRN1) is a massive, homopolymeric protein that is stored in platelets and endothelial cells for activation-induced release. In vitro, MMRN1 binds to the outer surfaces of activated platelets and endothelial cells, the extracellular matrix (including collagen) and von Willebrand factor (VWF) to support platelet adhesive functions. VWF associates with MMRN1 at high shear, not static conditions, suggesting that shear exposes cryptic sites within VWF that support MMRN1 binding. Modified ELISA and surface plasmon resonance were used to study the structural features of VWF that support MMRN1 binding, and determine the affinities for VWF-MMRN1 binding. High shear microfluidic platelet adhesion assays determined the functional consequences for VWF-MMRN1 binding. VWF binding to MMRN1 was enhanced by shear exposure and ristocetin, and required VWF A1A2A3 region, specifically the A1 and A3 domains. VWF A1A2A3 bound to MMRN1 with a physiologically relevant binding affinity (KD: 2.0 ± 0.4 nM), whereas the individual VWF A1 (KD: 39.3 ± 7.7 nM) and A3 domains (KD: 229 ± 114 nM) bound to MMRN1 with lower affinities. VWF A1A2A3 was also sufficient to support the adhesion of resting platelets to MMRN1 at high shear, by a mechanism dependent on VWF-GPIbD binding. Our study provides new information on the molecular basis of MMRN1 binding to VWF, and its role in supporting platelet adhesion at high shear. We propose that at sites of vessel injury, MMRN1 that is released following activation of platelets and endothelial cells, binds to VWF A1A2A3 region to support platelet adhesion at arterial shear rates.


 


Conflicts of interest

None declared.


Correspondence to:

Catherine P. M. Hayward
McMaster University Medical Centre
HSC 2N29A, 1200 Main St. West
Hamilton, Ontario, Canada L8N 3Z5
Phone: +1 905 521 2100 Ext. 76274   
Fax: +1 905 521 2338