Effects of urokinase receptor occupancy on plasmin generation and proteolysis of basement membrane by human tumor cells
| Autor: | R L, Cohen, X P, Xi, C W, Crowley, B K, Lucas, A D, Levinson, M A, Shuman |
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| Rok vydání: | 1991 |
| Předmět: |
Binding Sites
Base Sequence Genetic Vectors Molecular Sequence Data Immunology Receptors Cell Surface Cell Biology Hematology Adenocarcinoma Transfection Urokinase-Type Plasminogen Activator Biochemistry Basement Membrane Cell Line Receptors Urokinase Plasminogen Activator Plasminogen Activators Colonic Neoplasms Mutagenesis Site-Directed Humans Fibrinolysin RNA Messenger RNA Neoplasm Oligonucleotide Probes |
| Zdroj: | Blood. 78:479-487 |
| ISSN: | 1528-0020 0006-4971 |
| Popis: | The goal of the present study was to assess the relative importance of receptor-bound and secreted plasminogen activator urokinase (u-PA) in generating cell-surface plasmin and fostering destruction of normal tissue by tumor cells. We first showed that active site-inhibited u-PA could displace endogenous u-PA from the surface of the human colon adenocarcinoma cell line HCT 116. We then prepared expression vectors for u-PA and for a mutant molecule in which the codon for the active site serine residue was changed to encode alanine. Expression of non- functional mutant u-PA decreased the level of cell-bound active u-PA by more than 95% via a mechanism that involved competition for receptor sites. Decreased cell-surface u-PA activity was associated with a decrease in cell-bound plasmin activity to undetectable levels, suggesting that receptor-bound u-PA plays an important role in the generation of plasmin on the cell surface. Transfectants that secreted eightfold to 20-fold elevated levels of active wild-type u-PA showed approximately 50% increases in cell-associated u-PA and only twofold to fourfold increases in cell-associated plasmin, suggesting that the role of secreted u-PA in generating cell-surface plasmin activity was relatively minor. In parent cells and both types of transfectants there was a good correlation between the amount of plasmin bound to the tumor cell surface and the extent to which a basement membrane substrate was degraded. These studies show that receptor-bound u-PA provides an efficient mechanism for plasmin generation on the surface of tumor cells, which, in turn, contributes significantly to their degradative potential. |
| Databáze: | OpenAIRE |
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