Two-chain urokinase, receptor, and type 1 inhibitor in cultured human mesangial cells.
Urokinase-type plasminogen activator (u-PA), its receptor (u-PAR), and type 1 inhibitor (PAI-1) in cultured human mesangial cells were investigated. Treatment with phospholipase C (PLC) released plasminogen activators [with relative mol wt (M(r)) of 55,000 and 100,000] and u-PAR into the culture medium. By Western blot, both u-PA and PAI-1 were present in the M(r) 100,000 band. Since PAI-1 binds only active, two-chain u-PA (tcu-PA), formation of the M(r) 100,000 band reflects conversion of the single-chain, proenzyme form of u-PA (scu-PA) to tcu-PA. Immunofluorescence staining of whole cells demonstrated the presence of PAI-1, u-PA, and u-PAR. Immunofluorescence staining and Western blot analysis showed enrichment of PAI-1, u-PA, and u-PAR in a preparation of substratum-attached extracellular matrix and membrane proteins termed adhesion plaques. Using a chromogenic assay, we found that PAI-1 expression in adhesion plaques exceeded that of u-PA. We conclude that cultured human mesangial cells produce receptor-bound u-PA/PAI-1 complexes localized to adhesion plaques.
Audie L. Murphy Memorial Veterans Hospital, Department of Pathology, University of Texas Health Science Center, San Antonio 78284.
W F
WF
Glass
J I
JI
Kreisberg
D A
DA
Troyer
D015153:Blotting, Western; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D005920:Glomerular Mesangium / Q000378:metabolism*; D006801:Humans; D008970:Molecular Weight; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism / Q000494:pharmacology; D017395:Plasminogen Activator Inhibitor 1 / Q000032:analysis / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000032:analysis / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator / Q000032:analysis / Q000378:metabolism*
C524898:PLAUR protein, human; D017395:Plasminogen Activator Inhibitor 1; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D010727:Phosphoric Diester Hydrolases; D014568:Urokinase-Type Plasminogen Activator; D043265:Phosphatidylinositol Diacylglycerol-Lyase