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First published online June 8, 2005
doi: 10.1242/10.1242/jcs.02409
Research Article |
1 Hannover Medical School, Carl-Neuberg Straße 1, 30625 Hannover, Germany
2 Department of Immunology, Georg-August-University, Kreuzbergring 57, 37073 Göttingen, Germany
3 Ehime University School of Medicine, Shitsukawa, Shigenobucho, Onsengun, Ehime 791-0295, Japan
4 Medical Faculty of the Charité–Franz Volhard Clinic, HELIOS Klinikum-Berlin and Max Delbrück Center for Molecular Medicine, Wiltbergstrasse 50, 13125 Berlin, Germany
* Author for correspondence (e-mail: dumler.inna{at}mh-hannover.de)
Accepted 30 March 2005
Glomerular mesangial cells (MCs) are central to the pathogenesis of progressive glomeruli-associated renal diseases. However, molecular mechanisms underlying changes in MC functions still remain poorly understood. Here, we show that in MCs, the urokinase-type plasminogen activator (uPA) induces, via its specific receptor (uPAR, CD87), upregulated expression of the complement anaphylatoxin C5a receptor (C5aR, CD88), and modulates C5a-dependent functional responses. This effect is mediated via the interaction of the uPA-specific receptor (uPAR, CD87) and gp130, a signal transducing subunit of the receptor complexes for the IL-6 cytokine family. The Janus kinase Tyk2 and the transcription factor Stat3 serve as downstream components in the signaling cascade resulting in upregulation of C5aR expression. In vivo, expression of C5aR and uPAR was increased in the mesangium of wild-type mice in a lipopolysaccharide (LPS)-induced model of inflammation, whereas in uPAR–/– animals C5aR expression remained unchanged. This is the first demonstration in vitro and in vivo that uPA acts in MCs as a modulator of immune responses via control of immune-competent receptors. The data suggest a novel role for uPA/uPAR in glomeruli-associated renal failure via a signaling cross-talk between the fibrinolytic and immune systems.
Key words: Urokinase, uPA receptor, C5a receptor, Mesangial cells, Inflammation
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