Oncotarget

Research Papers:

TNF induced cleavage of HSP90 by cathepsin D potentiates apoptotic cell death

Jürgen Fritsch _, Ricarda Fickers, Jan Klawitter, Vinzenz Särchen, Philipp Zingler, Dieter Adam, Ottmar Janssen, Eberhard Krause and Stefan Schütze

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Oncotarget. 2016; 7:75774-75789. https://doi.org/10.18632/oncotarget.12411

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Abstract

Jürgen Fritsch1, Ricarda Fickers1, Jan Klawitter1, Vinzenz Särchen1, Philipp Zingler1, Dieter Adam1, Ottmar Janssen1, Eberhard Krause2, Stefan Schütze1

1Institute of Immunology, Christian-Albrechts-University of Kiel, Kiel, Germany

2Leibniz Institute for Molecular Pharmacology, Berlin, Germany

Correspondence to:

Jürgen Fritsch, email: Juergen.Fritsch@uksh.de

Keywords: TNF-R1, apoptosis, HSP90, cathepsin D

Received: August 08, 2016    Accepted: September 20, 2016    Published: October 03, 2016

ABSTRACT

During apoptosis induction by TNF, the extrinsic and intrinsic apoptosis pathways converge at the lysosomal-mitochondrial interface. Earlier studies showed that the lysosomal aspartic protease Cathepsin D (CtsD) cleaves Bid to tBid, resulting in the amplification of the initial apoptotic cascade via mitochondrial outer membrane permeabilization (MOMP).

The goal of this study was to identify further targets for CtsD that might be involved in activation upon death receptor ligation. Using a proteomics screen, we identified the heat shock protein 90 (HSP90) to be cleaved by CtsD after stimulation of U937 or other cell lines with TNF, FasL and TRAIL. HSP90 cleavage corresponded to apoptosis sensitivity of the cell lines to the different stimuli. After mutation of the cleavage site, HSP90 partially prevented apoptosis induction in U937 and Jurkat cells. Overexpression of the cleavage fragments in U937 and Jurkat cells showed no effect on apoptosis, excluding a direct pro-apoptotic function of these fragments. Pharmacological inhibition of HSP90 with 17AAG boosted ligand mediated apoptosis by enhancing Bid cleavage and caspase-9 activation. Together, we demonstrated that HSP90 plays an anti-apoptotic role in death receptor signalling and that CtsD-mediated cleavage of HSP90 sensitizes cells for apoptosis. These findings identify HSP90 as a potential target for cancer therapy in combination with death ligands (e.g. TNF or TRAIL).


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