title: Collagen-mimetic peptides mediate flow-dependent thrombus formation by high- or low-affinity binding of integrin alpha2beta1 and glycoprotein VI.
abstract: BACKGROUND
  Collagen acts as a potent surface for platelet adhesion and thrombus formation under conditions of blood flow. Studies using collagen-derived triple-helical peptides have identified the GXX'GER motif as an adhesive ligand for platelet integrin alpha2beta1, and (GPO)(n) as a binding sequence for the signaling collagen receptor, glycoprotein VI (GPVI).
  
  
  OBJECTIVE
  The potency was investigated of triple-helical peptides, consisting of GXX'GER sequences within (GPO)(n) or (GPP)(n) motifs, to support flow-dependent thrombus formation.
  
  
  RESULTS
  At a high-shear rate, immobilized peptides containing both the high-affinity alpha2beta1-binding motif GFOGER and the (GPO)(n) motif supported platelet aggregation and procoagulant activity, even in the absence of von Willebrand factor (VWF). With peptides containing only one of these motifs, co-immobilized VWF was needed for thrombus formation. The (GPO)(n) but not the (GPP)(n) sequence induced GPVI-dependent platelet aggregation and procoagulant activity. Peptides with intermediate affinity (GLSGER, GMOGER) or low-affinity (GASGER, GAOGER) alpha2beta1-binding motifs formed procoagulant thrombi only if both (GPO)(n) and VWF were present. At a low-shear rate, immobilized peptides with high- or low-affinity alpha2beta1-binding motifs mediated formation of thrombi with procoagulant platelets only in combination with (GPO)(n).
  
  
  CONCLUSIONS
  Triple-helical peptides with specific receptor-binding motifs mimic the properties of native collagen I in thrombus formation by binding to both platelet collagen receptors. At a high-shear rate, either GPIb or high-affinity (but not low-affinity) GXX'GER mediates GPVI-dependent formation of procoagulant thrombi. By extension, high-affinity binding for alpha2beta1 can control the overall platelet-adhesive activity of native collagens.
authors.affiliation: Department of Biochemistry, CARIM, University of Maastricht, Maastricht, The Netherlands.
authors.forename: I C A
authors.initials: IC
authors.lastname: Munnix
authors.forename: K
authors.initials: K
authors.lastname: Gilio
authors.forename: P R M
authors.initials: PR
authors.lastname: Siljander
authors.forename: N
authors.initials: N
authors.lastname: Raynal
authors.forename: M A H
authors.initials: MA
authors.lastname: Feijge
authors.forename: T M
authors.initials: TM
authors.lastname: Hackeng
authors.forename: H
authors.initials: H
authors.lastname: Deckmyn
authors.forename: P A
authors.initials: PA
authors.lastname: Smethurst
authors.forename: R W
authors.initials: RW
authors.lastname: Farndale
authors.forename: J W M
authors.initials: JW
authors.lastname: Heemskerk
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002478:Cells, Cultured; D003094:Collagen / Q000737:chemistry*; D006801:Humans; D038982:Integrin alpha2beta1 / Q000378:metabolism*; D018716:Molecular Mimicry; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000378:metabolism*; D010973:Platelet Adhesiveness; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D011485:Protein Binding; D013927:Thrombosis / Q000209:etiology*; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: D038982:Integrin alpha2beta1; D010446:Peptide Fragments; D010980:Platelet Membrane Glycoproteins; C098341:platelet membrane glycoprotein VI; D014841:von Willebrand Factor; D003094:Collagen