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Platelet collagen receptor Glycoprotein VI‐dimer recognizes fibrinogen and fibrin through their D‐domains, contributing to platelet adhesion and activation during thrombus formation
Author(s) -
Induruwa I.,
Moroi M.,
Bonna A.,
Malcor J.D.,
Howes J.M.,
Warburton E. A.,
Farndale R. W.,
Jung S. M.
Publication year - 2018
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/jth.13919
Subject(s) - gpvi , fibrinogen , platelet membrane glycoprotein , chemistry , fibrin , platelet , platelet activation , biophysics , biochemistry , glycoprotein , immunology , biology
Essentials Glycoprotein VI (GPVI) binds collagen, starting thrombogenesis, and fibrin, stabilizing thrombi. GPVI‐dimers, not monomers, recognize immobilized fibrinogen and fibrin through their D‐domains. Collagen, D‐fragment and D‐dimer may share a common or proximate binding site(s) on GPVI‐dimer. GPVI‐dimer–fibrin interaction supports spreading, activation and adhesion involving αIIbβ3.Summary Background Platelet collagen receptor Glycoprotein VI (GPVI) binds collagen, initiating thrombogenesis, and stabilizes thrombi by binding fibrin. Objectives To determine if GPVI ‐dimer, GPVI‐monomer, or both bind to fibrinogen substrates, and which region common to these substrates contains the interaction site. Methods Recombinant GPVI monomeric extracellular domain ( GPVI ex ) or dimeric Fc‐fusion protein ( GPVI ‐Fc 2 ) binding to immobilized fibrinogen derivatives was measured by ELISA , including competition assays involving collagenous substrates and fibrinogen derivatives. Flow adhesion was performed with normal or Glanzmann thrombasthenic ( GT ) platelets over immobilized fibrinogen, with or without anti‐ GPVI ‐dimer or anti‐α II bβ3. Results Under static conditions, GPVI ex did not bind to any fibrinogen substrate. GPVI ‐Fc 2 exhibited specific, saturable binding to both D‐fragment and D‐dimer, which was inhibited by mF ab‐F (anti‐ GPVI ‐dimer), but showed low binding to fibrinogen and fibrin under our conditions. GPVI ‐Fc 2 binding to D‐fragment or D‐dimer was abrogated by collagen type III , Horm collagen or CRP‐XL (crosslinked collagen‐related peptide), suggesting proximity between the D‐domain and collagen binding sites on GPVI ‐dimer. Under low shear, adhesion of normal platelets to D‐fragment, D‐dimer, fibrinogen and fibrin was inhibited by mF ab‐F (inhibitor of GPVI‐dimer) and abolished by Eptifibatide (inhibitor of α II bβ3), suggesting that both receptors contribute to thrombus formation on these substrates, but α II bβ3 makes a greater contribution. Notably, thrombasthenic platelets showed limited adhesion to fibrinogen substrates under flow, which was further reduced by mF ab‐F, supporting some independent GPVI ‐dimer involvement in this interaction. Conclusion Only dimeric GPVI interacts with fibrinogen D‐domain, at a site proximate to its collagen binding site, to support platelet adhesion/activation/aggregate formation on immobilized fibrinogen and polymerized fibrin.