Single-chain urokinase-type plasminogen activator bound to its receptor is relatively resistant to plasminogen activator inhibitor type 1.

Urokinase-type plasminogen activator (uPA) is synthesized as single-chain protein (scuPA) with little intrinsic activity. scuPA is activated when it is converted to two-chain urokinase (tcuPA) by plasmin or when it binds as a single-chain molecule to its cellular receptor (uPAR). Previous data indicate that complexes between scuPA and its receptor have somewhat higher affinity for plasminogen than does tcuPA. The current study indicates that plasminogen activator activity of scuPA bound to recombinant, soluble uPAR (suPAR) is also fivefold less sensitive to inhibition by plasminogen activator type 1 (PAI-1) than is soluble or receptor-bound tcuPA. Binding of PaI-1 to suPAR/scuPA complexes is totally reversible and can be overcome by increasing the concentration of plasminogen, suggesting a competitive mechanism of inhibition (Ki = 18 nmol/L). Binding of scuPA to suPAR also retards its cleavage by plasmin. These results indicates that binding of single-chain urokinase to its receptor promotes its activity, retards its inhibition, and protects it from conversion to a two-chain form of the enzyme, a step that may precede its inactivation and clearance from cell surfaces. These results are consistent with a physiologic role for receptor-bound single-chain urokinase as a cellular plasminogen activator.

[1]  B. Schwartz,et al.  Interaction of Single-chain Urokinase and Plasminogen Activator Inhibitor Type 1 (*) , 1995, The Journal of Biological Chemistry.

[2]  J. Henkin,et al.  Enhancement of the Enzymatic Activity of Single-chain Urokinase Plasminogen Activator by Soluble Urokinase Receptor (*) , 1995, The Journal of Biological Chemistry.

[3]  J. Potempa,et al.  The serpin superfamily of proteinase inhibitors: structure, function, and regulation. , 1994, The Journal of biological chemistry.

[4]  S. Gabbe,et al.  Insulinlike growth factors. Their regulation of glucose and amino acid transport in placental trophoblasts isolated from first-trimester chorionic villi. , 1994, The Journal of reproductive medicine.

[5]  S. Gabbe,et al.  Study of thromboxane and prostacyclin metabolism in an in vitro model of first-trimester human trophoblast. , 1992, American journal of obstetrics and gynecology.

[6]  B. Schwartz,et al.  Single chain urokinase. Augmentation of enzymatic activity upon binding to monocytes. , 1991, The Journal of biological chemistry.

[7]  K. Danø,et al.  Plasminogen activation by receptor-bound urokinase. A kinetic study with both cell-associated and isolated receptor. , 1991, The Journal of biological chemistry.

[8]  K. Danø,et al.  Plasminogen Activation by Receptor-Bound Urokinase , 1991, Seminars in thrombosis and hemostasis.

[9]  S. Gillies,et al.  High level expression of human proteins in murine hybridoma cells: induction by methotrexate in the absence of gene amplification. , 1991, Biochimica et biophysica acta.

[10]  L. Rosenfeld,et al.  Interaction of single-chain urokinase-type plasminogen activator with human endothelial cells. , 1990, The Journal of biological chemistry.

[11]  T. Lindahl,et al.  The mechanism of the reaction between human plasminogen-activator inhibitor 1 and tissue plasminogen activator. , 1990, The Biochemical journal.

[12]  D. Loskutoff,et al.  Bovine plasminogen activator inhibitor 1: specificity determinations and comparison of the active, latent, and guanidine-activated forms. , 1988, Biochemistry.

[13]  D. Loskutoff,et al.  Kinetic analysis of the interactions between plasminogen activator inhibitor 1 and both urokinase and tissue plasminogen activator. , 1988, Archives of biochemistry and biophysics.

[14]  E. Kruithof,et al.  Plasminogen activator inhibitors--a review. , 1988, Enzyme.

[15]  V. Gurewich,et al.  Activation of plasminogen by single-chain urokinase or by two-chain urokinase--a demonstration that single-chain urokinase has a low catalytic activity (pro-urokinase). , 1987, Blood.

[16]  K. Danø,et al.  Plasminogen activator inhibitor from human fibrosarcoma cells binds urokinase-type plasminogen activator, but not its proenzyme. , 1986, The Journal of biological chemistry.

[17]  K. Danø,et al.  Plasminogen activators catalyse conversion of inhibitor from fibrosarcoma cells to an inactive form with a lower apparent molecular mass , 1986, FEBS letters.

[18]  T. Suyama,et al.  Proteolytic cleavage of single-chain pro-urokinase induces conformational change which follows activation of the zymogen and reduction of its high affinity for fibrin. , 1985, The Journal of biological chemistry.

[19]  D. Loskutoff,et al.  Endothelial cells produce a latent inhibitor of plasminogen activators that can be activated by denaturants. , 1985, The Journal of biological chemistry.

[20]  E. Kruithof,et al.  Demonstration of a fast-acting inhibitor of plasminogen activators in human plasma. , 1984, Blood.