title: Integrin activation state determines selectivity for novel recognition sites in fibrillar collagens.
abstract: Only three recognition motifs, GFOGER, GLOGER, and GASGER, all present in type I collagen, have been identified to date for collagen-binding integrins, such as alpha(2)beta(1). Sequence alignment was used to investigate the occurrence of related motifs in other human fibrillar collagens, and located a conserved array of novel GER motifs within their triple helical domains. We compared the integrin binding properties of synthetic triple helical peptides containing examples of such sequences (GLSGER, GMOGER, GAOGER, and GQRGER) or the previously identified motifs. Recombinant inserted (I) domains of integrin subunits alpha(1), alpha(2) and alpha(11) all bound poorly to all motifs other than GFOGER and GLOGER. Similarly, alpha(2)beta(1) -containing resting platelets adhered well only to GFOGER and GLOGER, while ADP-activated platelets, HT1080 cells and two active alpha(2)I domain mutants (E318W, locked open) bound all motifs well, indicating that affinity modulation determines the sequence selectivity of integrins. GxO/SGER peptides inhibited platelet adhesion to collagen monomers with order of potency F >/= L >/= M > A. These results establish GFOGER as a high affinity sequence, which can interact with the alpha(2)I domain in the absence of activation and suggest that integrin reactivity of collagens may be predicted from their GER content.
authors.affiliation: Department of Biochemistry, University of Cambridge, Downing Site, Cambridge CB2 1QW, United Kingdom. prms2@mole.bio.cam.ac.uk
authors.forename: Pia R-M
authors.initials: PR
authors.lastname: Siljander
authors.forename: Samir
authors.initials: S
authors.lastname: Hamaia
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Peachey
authors.forename: David A
authors.initials: DA
authors.lastname: Slatter
authors.forename: Peter A
authors.initials: PA
authors.lastname: Smethurst
authors.forename: Willem H
authors.initials: WH
authors.lastname: Ouwehand
authors.forename: C Graham
authors.initials: CG
authors.lastname: Knight
authors.forename: Richard W
authors.initials: RW
authors.lastname: Farndale
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D002460:Cell Line; D024042:Collagen Type I / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D039001:Integrin alpha Chains / Q000235:genetics / Q000378:metabolism; D038982:Integrin alpha2beta1 / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010973:Platelet Adhesiveness / Q000502:physiology; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D024042:Collagen Type I; D039001:Integrin alpha Chains; D038982:Integrin alpha2beta1; D010455:Peptides; D011993:Recombinant Fusion Proteins