title: TNF induced cleavage of HSP90 by cathepsin D potentiates apoptotic cell death.
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).
authors.affiliation: Institute of Immunology, Christian-Albrechts-University of Kiel, Kiel, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Fritsch
authors.affiliation: Institute of Immunology, Christian-Albrechts-University of Kiel, Kiel, Germany.
authors.forename: Ricarda
authors.initials: R
authors.lastname: Fickers
authors.affiliation: Institute of Immunology, Christian-Albrechts-University of Kiel, Kiel, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Klawitter
authors.affiliation: Institute of Immunology, Christian-Albrechts-University of Kiel, Kiel, Germany.
authors.forename: Vinzenz
authors.initials: V
authors.lastname: Särchen
authors.affiliation: Institute of Immunology, Christian-Albrechts-University of Kiel, Kiel, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Zingler
authors.affiliation: Institute of Immunology, Christian-Albrechts-University of Kiel, Kiel, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Adam
authors.affiliation: Institute of Immunology, Christian-Albrechts-University of Kiel, Kiel, Germany.
authors.forename: Ottmar
authors.initials: O
authors.lastname: Janssen
authors.affiliation: Leibniz Institute for Molecular Pharmacology, Berlin, Germany.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Krause
authors.affiliation: Institute of Immunology, Christian-Albrechts-University of Kiel, Kiel, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schütze
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D002402:Cathepsin D / Q000378:metabolism*; D045744:Cell Line, Tumor; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D059748:Proteolysis / Q000187:drug effects; D040901:Proteomics / Q000379:methods; D015398:Signal Transduction / Q000187:drug effects; D013379:Substrate Specificity; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D018841:HSP90 Heat-Shock Proteins; D014409:Tumor Necrosis Factor-alpha; D020169:Caspases; D002402:Cathepsin D
keywords: HSP90; TNF-R1; apoptosis; cathepsin D