title: Fibrinogen contains cryptic PAI-1 binding sites that are exposed on binding to solid surfaces or limited proteolysis.
abstract: OBJECTIVE
  In this work, we identified the fibrinogen sequence that on exposure serves as the primary binding site for functionally active PAI-1 and to a lesser extent for its latent form. In contrast, this site only weakly interacts with PAI-1 substrate.
  
  
  RESULTS
  The binding site is located in the N-terminal alpha (20-88) segment of fibrinogen, in the region exposed on (1) adsorption of fibrinogen to solid surfaces; (2) the release of fibrinopeptide A during thrombin conversion of fibrinogen to fibrin; and (3) plasmin degradation of fibrinogen. This region was first identified by the yeast 2-hybrid system, then its binding characteristics were evaluated using the recombinant alpha(16-120) fragment and its shorter version, the alpha(20-88) fragment, in a solid phase binding assay and plasmon surface resonance measurements. Because fibrinogen fragment E does not bind PAI-1, it suggests that sequences of Aalpha chain interacting with PAI-1 are located in the N-terminal part of the alpha(20-88) segment.
  
  
  CONCLUSIONS
  Therefore, PAI-1 directly bound to the alpha(20-88) and thus concentrated in fibrinogen/fibrin, particularly at sites of injury and inflammation, may account for the recent observations that both its active and latent forms stimulate cell migration and wound healing.
authors.affiliation: Center of Medical Biology, Polish Academy of Sciences, Lodz, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Smolarczyk
authors.forename: Joanna
authors.initials: J
authors.lastname: Boncela
authors.forename: Jacek
authors.initials: J
authors.lastname: Szymanski
authors.forename: Ann
authors.initials: A
authors.lastname: Gils
authors.forename: Czeslaw S
authors.initials: CS
authors.lastname: Cierniewski
mesh_terms: D000327:Adsorption; D001665:Binding Sites / Q000502:physiology; D005337:Fibrin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005340:Fibrinogen / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005341:Fibrinolysin / Q000378:metabolism; D015723:Gene Library; D006801:Humans; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D020349:Surface Plasmon Resonance; D013927:Thrombosis / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D019096:Vitronectin / Q000378:metabolism
chemical_list: D010446:Peptide Fragments; D017395:Plasminogen Activator Inhibitor 1; D019096:Vitronectin; C464794:fibrinogen Aalpha; D005337:Fibrin; D005340:Fibrinogen; D005341:Fibrinolysin