Tissue Factor Regulates Plasminogen Binding and Activation

Abstract

Tissue factor (TF) has been implicated in several important biologic processes, including fibrin formation, atherogenesis, angiogenesis, and tumor cell migration. In that plasminogen activators have been implicated in the same processes, the potential for interactions between TF and the plasminogen activator system was examined. Plasminogen was found to bind directly to the extracellular domain of TF apoprotein (amino acids 1-219) as determined by optical biosensor interaction analysis. A fragment of plasminogen containing kringles 1 through 3 also bound to TF apoprotein, whereas isolated kringle 4 and miniplasminogen did not. Expression of TF on the surface of a stably transfected Chinese hamster ovary (CHO) cell line stimulated plasminogen binding to the cells by 70% more than to control cells. Plasminogen bound to a site on the TF apoprotein that appears to be distinct from the binding site for factors VII and VIIa as judged by a combination of biosensor and cell assays. TF enhanced two-chain urokinase (tcuPA) activation of Glu-plasminogen, but not of miniplasminogen, in a dose-dependent, saturable manner (half maximal stimulation at 59 pmol/L). TF apoprotein induced an effect similar to that of relipidated TF, but a relatively higher concentration of the apoprotein was required (half maximal stimulation at 3.8 nmol/L). The stimulatory effect of TF on plasminogen activation was confirmed when plasmin formation was examined directly on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In accord with this, TF inhibited fibrinolysis by approximately 74% at a concentration of 14 nmol/L and almost totally inhibited the binding of equimolar concentrations of plasminogen to human umbilical vein endothelial cells and human trophoblasts. Further, CHO cells expressing TF inhibited uPA-mediated fibrinolysis relative to a wild-type control. TF apoprotein and plasminogen were found to colocalize in atherosclerotic plaque. These data suggest that plasminogen localization and activation may be modulated at extravascular sites through a high-affinity interaction between kringles 1 through 3 of plasminogen and the extracellular domain of TF.

Plasminogen binding and cancer promises and pitfalls

“…Surface receptors that bind glu-plasminogen in a lysine-dependent manner may be classified into two classes. Class 1 binding proteins possess a pre-existing C- 1 Alpha-enolase (81) Intracellular glycolytic enzyme U937 (81) Rat neuronal cells (99) No 1.9* (95) 1.4* (98) 1.0** (46) Cytokeratin 8 (83) Intermediate filament Hepatocytes and MCF-7 cells (83) No 0.16* TIP4a (84) Nuclear ATPase and DNA helicase activity ND 5 No 0.57* 2 Actin (85) Microfilament Endothelial cells (97) MCF-7 and MDA-MB-231 cells (62) No ND Amphoterin (86) Multiple biological functions associated with nervous system Neuronal cells (86) yes ND Annexin II (87) Ca ++ /phospholipid binding protein Endothelial cells (87) Yes 0.16* (88) Glycoprotein IIIb/IIa (78) integrin Platelets (78) Synovial fibroblasts complexed with alpha2macroglobulin (89) Yes ND GP330 (90) Autoantigen associated with Heymann nephritis glomerular epithelial cells (90) Yes~0.25* Tetranectin (92,93) c-type lectin Colocalised with plasminogen in ECM of colonic tumor (103) , melanoma tissue (57) Yes 0.5* Extracellular domain of tissue factor apoprotein (94) Integral membrane glycoprotein initiates extrinsic pathway of coagulation Colocalised with plasminogen in luminal epithelial and smooth muscle cells within a human atherosclerotic plaque (94) Yes 0.1 and 2**…”

“…A bona-fide receptor must be shown to be at the cell-surface orientated towards the extracellular environment where it can bind plasminogen so as to be efficiently activated. Other than immunocytochemical localization, a definitive study showed that CHO cells engineered to express cell surface tissue factor bound 70% more plasminogen than control CHO cell lines (93). Furthermore, care must be taken to ensure that receptor isolation procedures, especially when using whole cell lysates, do not simply result in the isolation of intracellular proteins that fortuitously bind plasminogen.…”

“…Global analysis of the interaction suggested a two-state conformational change reaction, with an overall K d of 1 µM. Using similar technology, Fan et al (1998) found that the binding process between glu-plasminogen and immobilized purified extracellular domain of tissue factor apoprotein reflects either multiple binding sites with different affinities, co-operativity or more complex models. Therefore, it is possible that the binding mechanisms may have been oversimplified in previous studies using endpoint assays.…”

“…5 Not determined terminal lysine residue and include alpha-enolase (80), cytokeratin 8 (81,82), and TIP49a (83). Class 2 proteins do not have a pre-existing C-terminal lysine residue and include actin (84), amphoterin (85), annexin II (86,87), glycoprotein IIIb/IIa (77,88), GP330 (89,90), tetranectin (91,92), and extracellular domain of tissue factor apoprotein (93). For actin and annexin II partial plasmin digestion reveals a new carboxy-terminal lysine residue resulting in maximal plasminogen binding and activation (86,94).…”

Role of Protein C Inhibitor and Tissue Factor in Fertilization

“…These include tissue factor pathway inhibitor (TFPI), plasminogen, and filamin. 49,[51][52][53] TF procoagulant activity is inhibited by TFPI when it is in complex with FVIIa and FXa. 45 The TF cytoplasmic domain binds filamin, which supports TF-dependent adhesion contacts associated with cytoskeletal reorganization.…”