A novel antithrombotic role for high molecular weight kininogen as inhibitor of plasminogen activator inhibitor-1 function.
The adhesive glycoprotein vitronectin (VN) forms a function-stabilizing complex with plasminogen activator inhibitor-1 (PAI-1), the major fibrinolysis inhibitor in both plasma and vessel wall connective tissue. VN also interacts with two-chain high molecular weight kininogen (HKa), particularly its His-Gly-Lys-rich domain 5, and both HKa and PAI-1 are antiadhesive factors that have been shown to compete for binding to VN. In this study the influence of HKa and domain 5 on the antifibrinolytic function of PAI-1 was investigated. In a purified system, HKa and particularly domain 5 inhibited the binding of PAI-1 to VN and promoted PAI-1 displacement from both isolated VN as well as subendothelial extracellular matrix-associated VN. The sequence Gly(486)-Lys(502) of HKa domain 5 was identified as responsible for this inhibition. Although having no direct effect on PAI-1 activity itself, HKa domain 5 or the peptide Gly(486)-Lys(502) markedly destabilized the VN.PAI-1 complex interaction, resulting in a significant reduction of PAI-1 inhibitory function on plasminogen activators, resembling the effect of VN antibodies that prevent stabilization of PAI-1. Furthermore, high affinity fibrin binding of PAI-1 in the presence of VN as well as the VN-dependent fibrin clot stabilization by the inhibitor were abrogated in the presence of the kininogen forms mentioned. Taken together, our data indicate that the peptide Gly(486)-Lys(502) derived from domain 5 of HKa serves to interfere with PAI-1 function. Based on these observations potential low molecular weight PAI-1 inhibitors could be designed for the use in therapeutic interventions against thromboembolic complications.
Chavakis
Triantafyllos
T
Institute for Biochemistry, Third Department of Internal Medicine, Justus Liebig University, Giessen D-35392, Germany. triantafyllos.chavakis@innere.med.uni-giessen.de
Pixley
Robin A
RA
Isordia-Salas
Irma
I
Colman
Robert W
RW
Preissner
Klaus T
KT
D001667:Binding, Competitive; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology; D005109:Extracellular Matrix / Q000378:metabolism; D005337:Fibrin / Q000737:chemistry / Q000378:metabolism; D005341:Fibrinolysin / Q000378:metabolism; D005343:Fibrinolytic Agents / Q000494:pharmacology*; D005998:Glycine / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D007704:Kininogens / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D008239:Lysine / Q000737:chemistry; D017395:Plasminogen Activator Inhibitor 1 / Q000502:physiology*; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D014471:Umbilical Veins / Q000166:cytology; D019096:Vitronectin / Q000378:metabolism
D005343:Fibrinolytic Agents; D007704:Kininogens; D017395:Plasminogen Activator Inhibitor 1; D020033:Protein Isoforms; D019096:Vitronectin; D005337:Fibrin; D005341:Fibrinolysin; D008239:Lysine; D005998:Glycine