The urokinase-type plasminogen activator receptor mediates tyrosine phosphorylation of focal adhesion proteins and activation of mitogen-activated protein kinase in cultured endothelial cells.
Urokinase-type plasminogen activator (uPA) binds to cells via a specific glycosylphosphatidylinositol-anchored receptor. Although occupancy of the uPA receptor (uPAR) has been shown to alter cellular function and to induce gene expression, the signaling mechanism has not been characterized. Urokinase induced an increase in the tyrosine phosphorylation of multiple proteins in bovine aortic endothelial cells. In contrast, low molecular weight uPA did not induce this response. Analysis by immunoblotting demonstrated tyrosine phosphorylation of focal adhesion kinase (FAK), the focal adhesion-associated proteins paxillin and p130(cas), and mitogen-activated protein kinase (MAPK) following the occupancy of the uPAR by uPA. Treatment of cells with phosphatidylinositol-specific phospholipase C, which cleaves glycosylphosphatidylinositol-linked proteins from the cell surface, blocked the uPA-induced tyrosine phosphorylation of FAK, indicating the requirement of an intact uPAR on the cell surface. The uPA-induced activation of MAPK was completely inhibited by genistein, but not by 4-amino-5-(4-methylphenyl)-7-(t-butyl)pyrazolo[3, 4-d]pyrimidine, a specific inhibitor of Src family kinases. Thus, this study demonstrates a novel role for the uPAR in endothelial cell signal transduction that involves the activation of FAK and MAPK, which are mediated by the receptor-binding domain of uPA. This may have important implications for the mechanism through which uPA influences cell migration and differentiation.
Tang
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Department of Pharmacology, Vanderbilt University School of Medicine and Nashville Veterans Affairs Medical Center, Nashville, Tennessee 37232, USA.
Kerins
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Hao
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Inagami
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Vaughan
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D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002417:Cattle; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002478:Cells, Cultured; D050719:Crk-Associated Substrate Protein; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004730:Endothelium, Vascular / Q000201:enzymology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004792:Enzyme Precursors / Q000378:metabolism*; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019833:Genistein / Q000494:pharmacology; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D010960:Plasminogen Activators / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D050717:Retinoblastoma-Like Protein p130; D014443:Tyrosine / Q000378:metabolism*; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*; D019061:src-Family Kinases / Q000037:antagonists & inhibitors
C108123:4-amino-5-(4-methylphenyl)-7-(tert-butyl)pyrazolo(3,4-d)pyrimidine; D015815:Cell Adhesion Molecules; D050719:Crk-Associated Substrate Protein; D003598:Cytoskeletal Proteins; D004791:Enzyme Inhibitors; D004792:Enzyme Precursors; D051419:Paxillin; D010750:Phosphoproteins; D011506:Proteins; D011720:Pyrazoles; D011743:Pyrimidines; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D050717:Retinoblastoma-Like Protein p130; D014443:Tyrosine; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019061:src-Family Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator