Urokinase synthesis and binding by glomerular epithelial cells in culture.
Fibrin deposits are frequently observed in the course of proliferative extracapillary glomerulonephritis and could be related to a defective local fibrinolysis. We studied human glomerular epithelial cells in culture which were found to release mainly a urokinase-type plasminogen activator (u-PA) identified on zymography by its molecular weight (53 kD), its plasminogen activator activity, and its neutralization by specific polyclonal anti-u-PA IgG. Trace amounts of tissue-type plasminogen activator (t-PA) complexed to a plasminogen activator inhibitor type 1 (PAI-1) were identified with specific antibodies. Specific binding sites were found at the surface of glomerular epithelial cells (kD: 2.10(-9) M), partially occupied by secreted u-PA. The spontaneous u-PA activity of the culture medium conditioned by glomerular epithelial cells was very low, suggesting that u-PA was released in its inactive single chain proenzyme form (SC-u-PA). After activation of SC-u-PA by plasmin, u-PA activity of the culture medium was found to increase in a time- and dose-dependent manner when cells were incubated with phorbol myristic acetate (PMA). This effect was inhibited by H7, a protein kinase C inhibitor. Stimulation of u-PA synthesis by PMA was also observed in two different epithelial tubular cell lines. LLC-PK1 and MDCK cells. However, 8 bromo cyclic AMP which increased u-PA release by LLC-PK1 cells was found to inhibit u-PA release by PMA-stimulated glomerular epithelial cells and MDCK cells. By Northern blot analysis we found that PMA induced an increase of u-PA mRNA level in glomerular epithelial cells and that cyclic AMP had an opposite effect.(ABSTRACT TRUNCATED AT 250 WORDS)
Rondeau
E
E
INSERM, Unité 64, Hôpital Tenon, Paris, France.
Ochi
S
S
Lacave
R
R
He
C J
CJ
Medcalf
R
R
Delarue
F
F
Sraer
J D
JD
D015152:Blotting, Northern; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology; D004792:Enzyme Precursors / Q000096:biosynthesis* / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007678:Kidney Glomerulus / Q000378:metabolism*; D010960:Plasminogen Activators / Q000096:biosynthesis* / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014568:Urokinase-Type Plasminogen Activator / Q000096:biosynthesis* / Q000378:metabolism
D004792:Enzyme Precursors; C524898:PLAUR protein, human; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D000242:Cyclic AMP; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator; D013755:Tetradecanoylphorbol Acetate