• Catherine Meyer-Schwesinger, Tobias N Meyer, Henning Sievert, Elion Hoxha, Marlies Sachs, Eva-Maria Klupp, Silvia Münster, Stefan Balabanov, Lucie Carrier, Udo Helmchen, Friedrich Thaiss, and Rolf A K Stahl.
• Department of Internal Medicine, Nephrology, Nierenregister, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. c.meyer-schwesinger@uke.uni-hamburg.de
• Am. J. Pathol. 2011 May 1; 178 (5): 2044-57.

AbstractUbiquitin C-terminal hydrolase L1 (UCH-L1), a key protease of the ubiquitin-proteasome system (UPS), is associated with neurodegenerative diseases and cancer. Recently, de novo expression of UCH-L1 was described in podocytes in patients with membranous nephropathy (MN), in which UCH-L1 expression correlated with increased ubiquitin content. The objective of the present study was to investigate the role of UCH-L1 in ubiquitin homeostasis and proteasomal degradation in a rat model of MN. After disease induction, UCH-L1 expression increased in podocytes and coincided with decreased glomerular monoubiquitin content. After an initial increase in proteasomal activity, the UPS was impaired. In addition to an increase of ubiquitin in podocytes, aggregates were observed 1 year after disease induction, as in MN in human beings. Inhibition of UCH-L1 hydrolase function in MN reduced UPS impairment and ameliorated proteinuria. In contrast, inhibition of proteasomal activity enhanced UPS impairment, resulting in increased proteinuria. Stable UCH-L1 overexpression in cultured podocytes resulted in accumulation of monoubiquitin and polyubiquitin proteins. In contrast, stable knock-down of UCH-L1 reduced monoubiquitin and polyubiquitin proteins and significantly increased proteasomal activity, indicating that the observed effects in rat MN also occurred in cultured podocytes. These data demonstrate that UCH-L1 activity results in polyubiquitin accumulation, proteasome inhibition, and disease aggravation in experimental models of MN.Copyright © 2011 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

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