Heparin and heparin proteoglycan-mimetics activate platelets via PEAR1 and PI3Kβ

Caroline Kardeby*, Alice Evans, Joana Campos, Afraa M. Al-Wahaibi, Christopher Smith, Alexandre Slater, Eleyna Martin, Sonia Severin, Alexander Brill, Gunnar Pejler, Yi Sun, Steve Watson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Background: Platelet endothelial aggregation receptor 1 (PEAR1) is a single-transmembrane orphan receptor primarily expressed on platelets and endothelial cells. Genetic variants of PEAR1 have repeatedly and independently been identified to be associated with cardiovascular diseases, including coronary artery disease.

Objectives: We have identified sulfated fucoidans and their mimetics as ligands for PEAR1 and proposed that its endogenous ligand is a sulfated proteoglycan. The aim of this study was to test this hypothesis.

Methods: A heparin proteoglycan-mimetic (HPGM) was created by linking unfractionated heparin (UFH) to albumin. The ability of the HPGM, UFH and selectively desulfated heparins to stimulate platelet aggregation and protein phosphorylation was investigated. Nanobodies against the 12th to 13th epidermal growth factor-like repeat of PEAR1 and phosphoinositide 3-kinase (PI3K) isoform-selective inhibitors were tested for the inhibition of platelet activation.

Results: We show that HPGM, heparin conjugated to an albumin protein core, stimulates aggregation and phosphorylation of PEAR1 in washed platelets. Platelet aggregation was abolished by an anti-PEAR1 nanobody, Nb138. UFH stimulated platelet aggregation in washed platelets, but desulfated UFH did not. Furthermore, HPGM, but not UFH, stimulated maximal aggregation in platelet-rich plasma. However, both HPGM and UFH increased integrin αIIbβ3 activation in whole blood. By using PI3K isoform-selective inhibitors, we show that PEAR1 activates PI3Kβ, leading to Akt phosphorylation.

Conclusion: Our findings reveal that PEAR1 is a receptor for heparin and HPGM and that PI3Kβ is a key signaling molecule downstream of PEAR1 in platelets. These findings may have important implications for our understanding of the role of PEAR1 in cardiovascular disease.
Original languageEnglish
Pages (from-to)101-116
Number of pages16
JournalJournal of Thrombosis and Haemostasis
Volume21
Issue number1
Early online date9 Dec 2022
DOIs
Publication statusPublished - 1 Jan 2023

Bibliographical note

Acknowledgments:
C.K. is supported by the European Union’s Horizon 2020 Research and Innovation Program under the Marie Skłodowska-Curie Actions Individual Fellowship grant agreement No 893262, project PAELLA. CK is supported by a British Heart Foundation Accelerator Award (AA/18/2/34218). Research was funded, in whole, or in part, by a Wellcome Trust Investigator Award (204951/B/16/Z). A Creative Commons (CC-BY) license is applied to the Author Accepted Manuscript arising from this submission, in accordance with the grant’s open access conditions. SPW holds a British Heart Foundation Chair (CH03/003). AB is supported by a British Heart Foundation Senior Basic Science Research Fellowship (FS/19/30/34173).

Keywords

  • Fucoidan
  • Glycosaminoglycan
  • Polysaccharide
  • Signal transduction
  • Sulfates

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