title: Caspase-8-mediated PAR-4 cleavage is required for TNFα-induced apoptosis.
abstract: The tumor suppressor protein prostate apoptosis response-4 (PAR-4) is silenced in a subset of human cancers and its down-regulation serves as a mechanism for cancer cell survival following chemotherapy. PAR-4 re-expression selectively causes apoptosis in cancer cells but how its pro-apoptotic functions are controlled and executed precisely is currently unknown. We demonstrate here that UV-induced apoptosis results in a rapid caspase-dependent PAR-4 cleavage at EEPD131G, a sequence that was preferentially recognized by caspase-8. To investigate the effect on cell growth for this cleavage event we established stable cell lines that express wild-type-PAR-4 or the caspase cleavage resistant mutant PAR-4 D131G under the control of a doxycycline-inducible promoter. Induction of the wild-type protein but not the mutant interfered with cell proliferation, predominantly through induction of apoptosis. We further demonstrate that TNFα-induced apoptosis leads to caspase-8-dependent PAR-4-cleavage followed by nuclear accumulation of the C-terminal PAR-4 (132-340) fragment, which then induces apoptosis. Taken together, our results indicate that the mechanism by which PAR-4 orchestrates the apoptotic process requires cleavage by caspase-8.
authors.affiliation: Institute of Biochemistry and Molecular Biology, Medical School, RWTH Aachen University, Aachen, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Treude
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Kappes
authors.forename: Dirk
authors.initials: D
authors.lastname: Fahrenkamp
authors.forename: Gerhard
authors.initials: G
authors.lastname: Müller-Newen
authors.forename: Federico
authors.initials: F
authors.lastname: Dajas-Bailador
authors.forename: Oliver H
authors.initials: OH
authors.lastname: Krämer
authors.forename: Bernhard
authors.initials: B
authors.lastname: Lüscher
authors.forename: Jörg
authors.initials: J
authors.lastname: Hartkamp
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D053181:Caspase 8 / Q000378:metabolism*; D045744:Cell Line, Tumor; D005455:Fluorescent Antibody Technique; D006801:Humans; D018613:Microscopy, Confocal; D016297:Mutagenesis, Site-Directed; D009369:Neoplasms / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D014409:Tumor Necrosis Factor-alpha; C101296:prostate apoptosis response-4 protein; C505530:CASP8 protein, human; D053181:Caspase 8