title: Plasminogen activation initiated by single-chain urokinase-type plasminogen activator. Potentiation by U937 monocytes.
abstract: The binding of urokinase-type plasminogen activators (u-PA) to receptors on various cell types has been proposed to be an important feature of many cellular processes requiring extracellular proteolysis. We have investigated the effect of single-chain u-PA binding to the monocyte-like cell line U937 on plasminogen activation. A 16-fold acceleration of the activation of plasminogen was observed at optimal concentrations of single-chain u-PA. This potentiation was abolished by the addition of either 6-aminohexanoic acid or the amino-terminal fragment of u-PA, thus demonstrating the requirement for specific binding of both single-chain u-PA and plasminogen to the cells. The mechanism of the enhancement of plasmin generation appears to be due primarily to an increase in the rate of feedback activation of single-chain u-PA to the more active two-chain u-PA by cell-bound plasmin, initially generated by single-chain u-PA. This increased activity of the plasminogen activation system in the presence of U937 cells provides a mechanism whereby u-PAs may exert their influence in a variety of cell-associated proteolytic events.
authors.affiliation: Thrombosis Research Unit, King's College School of Medicine and Dentistry, London, United Kingdom.
authors.forename: V
authors.initials: V
authors.lastname: Ellis
authors.forename: M F
authors.initials: MF
authors.lastname: Scully
authors.forename: V V
authors.initials: VV
authors.lastname: Kakkar
mesh_terms: D002460:Cell Line; D005341:Fibrinolysin / Q000378:metabolism; D005342:Fibrinolysis; D006801:Humans; D007700:Kinetics; D009000:Monocytes / Q000378:metabolism; D010958:Plasminogen / Q000378:metabolism*; D010960:Plasminogen Activators / Q000378:metabolism*; D011485:Protein Binding; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
chemical_list: D010958:Plasminogen; D010960:Plasminogen Activators; D005341:Fibrinolysin; D014568:Urokinase-Type Plasminogen Activator