Acute phase protein alpha 1-acid glycoprotein interacts with plasminogen activator inhibitor type 1 and stabilizes its inhibitory activity.
alpha(1)-Acid glycoprotein, one of the major acute phase proteins, was found to interact with plasminogen activator inhibitor type 1 (PAI-1) and to stabilize its inhibitory activity toward plasminogen activators. This conclusion is based on the following observations: (a) alpha(1)-acid glycoprotein was identified to bind PAI-1 by a yeast two-hybrid system. Three of 10 positive clones identified by this method to interact with PAI-1 contained almost the entire sequence of alpha(1)-acid glycoprotein; (b) this protein formed complexes with PAI-1 that could be immunoprecipitated from both the incubation mixtures and blood plasma by specific antibodies to either PAI-1 or alpha(1)-acid glycoprotein. Such complexes could be also detected by a solid phase binding assay; and (c) the real-time bimolecular interactions monitored by surface plasmon resonance indicated that the complex of alpha(1)-acid glycoprotein with PAI-1 is less stable than that formed by vitronectin with PAI-1, but in both cases, the apparent K(D) values were in the range of strong interactions (4.51 + 1.33 and 0.58 + 0.07 nm, respectively). The on rate for binding of PAI-1 to alpha(1)-glycoprotein or vitronectin differed by 2-fold, indicating much faster complex formation by vitronectin than by alpha(1)-acid glycoprotein. On the other hand, dissociation of PAI-1 bound to vitronectin was much slower than that from the alpha(1)-acid glycoprotein, as indicated by 4-fold lower k(off) values. Furthermore, the PAI-1 activity toward urokinase-type plasminogen activator and tissue-type plasminogen activator was significantly prolonged in the presence of alpha(1)-acid glycoprotein. These observations suggest that the complex of PAI-1 with alpha(1)-acid glycoprotein can play a role as an alternative reservoir of the physiologically active form of the inhibitor, particularly during inflammation or other acute phase reactions.
Boncela
J
J
Center for Microbiology and Virology, Polish Academy of Sciences 93-232 Lodz, Poland.
Papiewska
I
I
Fijalkowska
I
I
Walkowiak
B
B
Cierniewski
C S
CS
D006801:Humans; D009961:Orosomucoid / Q000378:metabolism*; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D020349:Surface Plasmon Resonance; D010959:Tissue Plasminogen Activator / Q000037:antagonists & inhibitors; D020798:Two-Hybrid System Techniques; D014568:Urokinase-Type Plasminogen Activator / Q000037:antagonists & inhibitors; D019096:Vitronectin / Q000378:metabolism
D009961:Orosomucoid; D017395:Plasminogen Activator Inhibitor 1; D019096:Vitronectin; D010959:Tissue Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator