Fibrinogen contains cryptic PAI-1 binding sites that are exposed on binding to solid surfaces or limited proteolysis.
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.
Smolarczyk
Katarzyna
K
Center of Medical Biology, Polish Academy of Sciences, Lodz, Poland.
Boncela
Joanna
J
Szymanski
Jacek
J
Gils
Ann
A
Cierniewski
Czeslaw S
CS
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
D010446:Peptide Fragments; D017395:Plasminogen Activator Inhibitor 1; D019096:Vitronectin; C464794:fibrinogen Aalpha; D005337:Fibrin; D005340:Fibrinogen; D005341:Fibrinolysin