Heparan sulfates are critical regulators of the inhibitory megakaryocyte-platelet receptor G6b-B
- University of Birmingham, United Kingdom
- Wellcome Sanger Institute, United Kingdom
- University Hospital Würzburg, Germany
- Université de Strasbourg, France
- Sygnature Discovery Limited, United Kingdom
- University of Helsinki, Finland
- Helsinki University Hospital Research Institute, Finland
- University of Westminster, United Kingdom
- Peak Proteins Limited, United Kingdom
- Wellcome Trust Sanger Institute, United Kingdom
Abstract
The immunoreceptor tyrosine-based inhibition motif (ITIM)-containing receptor G6b-B is critical for platelet production and activation. Loss of G6b-B results in severe macrothrombocytopenia, myelofibrosis and aberrant platelet function in mice and humans. Using a combination of immunohistochemistry, affinity chromatography and proteomics, we identified the extracellular matrix heparan sulfate (HS) proteoglycan perlecan as a G6b-B binding partner. Subsequent in vitro biochemical studies and a cell-based genetic screen demonstrated that the interaction is specifically mediated by the HS chains of perlecan. Biophysical analysis revealed that heparin forms a high-affinity complex with G6b-B and mediates dimerization. Using platelets from humans and genetically-modified mice, we demonstrate that binding of G6b-B to HS and multivalent heparin inhibits platelet and megakaryocyte function by inducing downstream signaling via the tyrosine phosphatases Shp1 and Shp2. Our findings provide novel insights into how G6b-B is regulated and contribute to our understanding of the interaction of megakaryocytes and platelets with glycans.
Data availability
Diffraction data have been deposited in PDB under the accession code 6R0X
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Crystal structure of platelet factor 4 complexed with fondaparinuxProtein Data Bank, 4R9W.
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Drosophila Robo IG1-2 (monoclinic form)Protein Data Bank, 2VRA.
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CRYSTAL STRUCTURE OF A TERNARY FGF1-FGFR2-HEPARIN COMPLEXProtein Data Bank, 1E0O.
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CRYSTAL STRUCTURE OF A TERNARY FGF2-FGFR1-HEPARIN COMPLEXProtein Data Bank, 1FQ9.
Article and author information
Author details
Funding
British Heart Foundation (RG/15/13/31673)
- Jun Mori
- Alexandra Mazharian
- Yotis A Senis
British Heart Foundation (FS/13/1/29894)
- Yotis A Senis
Deutsche Forschungsgemeinschaft (VO 2134-1/1)
- Timo Vögtle
Medical Research Council (Confidence in Concept 2018)
- Timo Vögtle
- Yotis A Senis
Wellcome (206194)
- Gavin J Wright
British Heart Foundation (FS/15/58/31784)
- Alexandra Mazharian
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: All animal procedures were undertaken with the U.K. Home Office approval (project license No P46252127) in accordance with the Animals (Scientific Procedures) Act of 1986.
Human subjects: Blood was collected from healthy drug-free volunteers. Donors gave full informed consent according to the Helsinki declaration. Ethical approval for collecting blood was granted by Birmingham University Internal Ethical Review (ERN_11-0175 and ERN_15-0973).
Copyright
© 2019, Vögtle et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Heparan sulfates are critical regulators of the inhibitory megakaryocyte-platelet receptor G6b-B
eLife 8:e46840.
https://doi.org/10.7554/eLife.46840
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