PMID- 36695374 OWN - NLM STAT- MEDLINE DCOM- 20230126 LR - 20240214 IS - 1538-7836 (Electronic) IS - 1538-7836 (Linking) VI - 21 IP - 1 DP - 2023 Jan TI - Heparin and heparin proteoglycan-mimetics activate platelets via PEAR1 and PI3Kbeta. PG - 101-116 LID - S1538-7836(22)07177-X [pii] LID - 10.1016/j.jtha.2022.10.008 [doi] AB - 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 alphaIIbbeta3 activation in whole blood. By using PI3K isoform-selective inhibitors, we show that PEAR1 activates PI3Kbeta, leading to Akt phosphorylation. CONCLUSION: Our findings reveal that PEAR1 is a receptor for heparin and HPGM and that PI3Kbeta 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. CI - Copyright (c) 2022 The Authors. Published by Elsevier Inc. All rights reserved. FAU - Kardeby, Caroline AU - Kardeby C AD - Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK. Electronic address: c.k.kardeby@bham.ac.uk. FAU - Evans, Alice AU - Evans A AD - Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK. FAU - Campos, Joana AU - Campos J AD - Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK. FAU - Al-Wahaibi, Afraa Moosa AU - Al-Wahaibi AM AD - Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK. FAU - Smith, Christopher W AU - Smith CW AD - Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK. FAU - Slater, Alexandre AU - Slater A AD - Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK. FAU - Martin, Eleyna M AU - Martin EM AD - Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK. FAU - Severin, Sonia AU - Severin S AD - INSERM U1297 and Paul Sabatier University, Institute of Cardiovascular and Metabolic Diseases, Toulouse, France. FAU - Brill, Alexander AU - Brill A AD - Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK. FAU - Pejler, Gunnar AU - Pejler G AD - Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden. FAU - Sun, Yi AU - Sun Y AD - Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK; Centre of Membrane Proteins and Receptors, Universities of Birmingham and Nottingham, Midlands, UK. FAU - Watson, Steve P AU - Watson SP AD - Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK; Centre of Membrane Proteins and Receptors, Universities of Birmingham and Nottingham, Midlands, UK. LA - eng GR - AA/18/2/34218/BHF_/British Heart Foundation/United Kingdom GR - FS/19/30/34173/BHF_/British Heart Foundation/United Kingdom GR - 204951/B/16/Z/WT_/Wellcome Trust/United Kingdom GR - 204951/Z/16/Z/WT_/Wellcome Trust/United Kingdom GR - CH03/003/BHF_/British Heart Foundation/United Kingdom PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20221222 PL - England TA - J Thromb Haemost JT - Journal of thrombosis and haemostasis : JTH JID - 101170508 RN - 0 (heparin proteoglycan) RN - 9005-49-6 (Heparin) RN - EC 2.7.1.- (Phosphatidylinositol 3-Kinases) RN - 0 (Receptors, Cell Surface) RN - 0 (Proteoglycans) RN - 0 (Platelet Glycoprotein GPIIb-IIIa Complex) RN - 0 (Ligands) RN - 0 (Albumins) RN - 0 (PEAR1 protein, human) SB - IM MH - Humans MH - *Heparin/pharmacology/metabolism MH - *Phosphatidylinositol 3-Kinases/metabolism MH - Endothelial Cells/metabolism MH - Receptors, Cell Surface/metabolism MH - Blood Platelets/metabolism MH - Platelet Aggregation MH - Proteoglycans/metabolism MH - Platelet Glycoprotein GPIIb-IIIa Complex/metabolism MH - Ligands MH - Albumins OTO - NOTNLM OT - Fucoidan OT - glycosaminoglycan OT - polysaccharides OT - signal transduction OT - sulfates EDAT- 2023/01/26 06:00 MHDA- 2023/01/27 06:00 CRDT- 2023/01/25 06:42 PHST- 2022/08/04 00:00 [received] PHST- 2022/10/04 00:00 [revised] PHST- 2022/10/25 00:00 [accepted] PHST- 2023/01/25 06:42 [entrez] PHST- 2023/01/26 06:00 [pubmed] PHST- 2023/01/27 06:00 [medline] AID - S1538-7836(22)07177-X [pii] AID - 10.1016/j.jtha.2022.10.008 [doi] PST - ppublish SO - J Thromb Haemost. 2023 Jan;21(1):101-116. doi: 10.1016/j.jtha.2022.10.008. Epub 2022 Dec 22.