title: A Human Platelet Receptor Protein Microarray Identifies the High Affinity Immunoglobulin E Receptor Subunit α (FcεR1α) as an Activating Platelet Endothelium Aggregation Receptor 1 (PEAR1) Ligand.
abstract: Genome-wide association studies to identify loci responsible for platelet function and cardiovascular disease susceptibility have repeatedly identified polymorphisms linked to a gene encoding platelet endothelium aggregation receptor 1 (PEAR1), an "orphan" cell surface receptor that is activated to stabilize platelet aggregates. To investigate how PEAR1 signaling is initiated, we sought to identify its extracellular ligand by creating a protein microarray representing the secretome and receptor repertoire of the human platelet. Using an avid soluble recombinant PEAR1 protein and a systematic screening assay designed to detect extracellular interactions, we identified the high affinity immunoglobulin E (IgE) receptor subunit α (FcεR1α) as a PEAR1 ligand. FcεR1α and PEAR1 directly interacted through their membrane-proximal Ig-like and 13th epidermal growth factor domains with a relatively strong affinity (KD ∼ 30 nm). Precomplexing FcεR1α with IgE potently inhibited the FcεR1α-PEAR1 interaction, and this was relieved by the anti-IgE therapeutic omalizumab. Oligomerized FcεR1α potentiated platelet aggregation and led to PEAR1 phosphorylation, an effect that was also inhibited by IgE. These findings demonstrate how a protein microarray resource can be used to gain important insight into the function of platelet receptors and provide a mechanistic basis for the initiation of PEAR1 signaling in platelet aggregation.
authors.affiliation: From the ‡Cell Surface Signalling Laboratory, Wellcome Trust Sanger Institute, Cambridge, CB10 1SA, United Kingdom and.
authors.forename: Yi
authors.initials: Y
authors.lastname: Sun
authors.affiliation: §Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, University of Leuven, Leuven 3000, Belgium.
authors.forename: Christophe
authors.initials: C
authors.lastname: Vandenbriele
authors.affiliation: §Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, University of Leuven, Leuven 3000, Belgium.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Kauskot
authors.affiliation: §Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, University of Leuven, Leuven 3000, Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: Verhamme
authors.affiliation: §Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, University of Leuven, Leuven 3000, Belgium.
authors.forename: Marc F
authors.initials: MF
authors.lastname: Hoylaerts
authors.affiliation: From the ‡Cell Surface Signalling Laboratory, Wellcome Trust Sanger Institute, Cambridge, CB10 1SA, United Kingdom and gw2@sanger.ac.uk.
authors.forename: Gavin J
authors.initials: GJ
authors.lastname: Wright
mesh_terms: D001665:Binding Sites; D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015870:Gene Expression; D057809:HEK293 Cells; D006801:Humans; D007073:Immunoglobulin E / Q000737:chemistry* / Q000235:genetics; D007700:Kinetics; D008024:Ligands; D000069444:Omalizumab / Q000737:chemistry; D010766:Phosphorylation; D010974:Platelet Aggregation / Q000187:drug effects*; D040081:Protein Array Analysis; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000235:genetics; D017455:Receptors, IgE / Q000737:chemistry* / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology
chemical_list: C543355:FcepsilonRI alpha-chain, human; D008024:Ligands; C502809:PEAR1 protein, human; D011956:Receptors, Cell Surface; D017455:Receptors, IgE; D011994:Recombinant Proteins; D000069444:Omalizumab; D007073:Immunoglobulin E