title: Extracellular matrix produced by cultured corneal and aortic endothelial cells contains active tissue-type and urokinase-type plasminogen activators.
abstract: Incubation of plasminogen with the subendothelial extracellular matrix (ECM) synthesized by cultured bovine corneal and aortic endothelial cells resulted in generation of fibrinolytic activity, indicated by proteolysis of 125I-fibrin in a time- and dose-dependent manner. Both tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA) were identified in the ECM by fibrin zymography, immunoblotting, and inhibition of plasminogen activation by anti-u-PA and anti-t-PA antibodies. Most of the ECM-resident plasminogen activator (PA) activity did not originate from intracellular PA release occurring when the endothelial cells were lyzed and the ECM exposed, since a comparable amount of PA was associated with the ECM when the cells were lyzed with Triton X-100 or removed intact by treatment with 2 M urea. Active u-PA and t-PA were released from ECM by treatment with heparanase (endo-beta-D-glucuronidase), indicating that some of the ECM-resident PA activity is sequestered by heparan sulfate side chains. These results indicate that both u-PA and t-PA produced by endothelial cells are firmly sequestered in an active form by the subendothelial ECM. It is suggested that ECM-resident plasminogen activators participate in sequential matrix degradation during cell invasion and tumor metastasis. PA activity may also function in release of ECM-bound growth factors (i.e., basic fibroblast growth factor) and activation of proenzymes (i.e., prothrombin), resulting in modulation of the ECM growth-promoting and thrombogenic properties.
authors.affiliation: Department of Radiation and Clinical Oncology, Hadassah University Hospital, Jerusalem, Israel.
authors.forename: G
authors.initials: G
authors.lastname: Korner
authors.forename: T D
authors.initials: TD
authors.lastname: Bjornsson
authors.forename: I
authors.initials: I
authors.lastname: Vlodavsky
mesh_terms: D000042:Absorption; D000818:Animals; D001011:Aorta; D002417:Cattle; D002478:Cells, Cultured; D004728:Endothelium, Corneal / Q000737:chemistry / Q000201:enzymology*; D004730:Endothelium, Vascular / Q000737:chemistry / Q000201:enzymology*; D005109:Extracellular Matrix / Q000737:chemistry / Q000201:enzymology*; D005966:Glucuronidase; D006026:Glycoside Hydrolases / Q000378:metabolism; D008970:Molecular Weight; D017395:Plasminogen Activator Inhibitor 1 / Q000032:analysis; D010959:Tissue Plasminogen Activator / Q000737:chemistry / Q000378:metabolism*; D014568:Urokinase-Type Plasminogen Activator / Q000737:chemistry / Q000378:metabolism*; D000099175:Heparanase
chemical_list: D005966:Glucuronidase; D006026:Glycoside Hydrolases; D017395:Plasminogen Activator Inhibitor 1; D010959:Tissue Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator; D000099175:Heparanase