title: Prostate apoptosis response 4 (Par-4), a novel substrate of caspase-3 during apoptosis activation.
abstract: Prostate apoptosis response 4 (Par-4) is a ubiquitously expressed proapoptotic tumor suppressor protein. Here, we show for the first time, that Par-4 is a novel substrate of caspase-3 during apoptosis. We found that Par-4 is cleaved during cisplatin-induced apoptosis in human normal and cancer cell lines. Par-4 cleavage generates a C-terminal fragment of ~25 kDa, and the cleavage of Par-4 is completely inhibited by a caspase-3 inhibitor, suggesting that caspase-3 is directly involved in the cleavage of Par-4. Caspase-3-deficient MCF-7 cells do not show Par-4 cleavage in response to cisplatin treatment, and restoration of caspase-3 in MCF-7 cells produces a decrease in Par-4 levels, with the appearance of a cleaved fragment. Additionally, knockdown of Par-4 reduces caspase-3 activation and apoptosis induction. Site-directed mutagenesis reveals that Par-4 cleavage by caspase-3 occurs at an unconventional site, EEPD(131)↓G. Interestingly, overexpression of wild-type Par-4 but not the Par-4 D131A mutant sensitizes cells to cisplatin-induced apoptosis. Upon caspase-3 cleavage, the cleaved fragment of Par-4 accumulates in the nucleus and displays increased apoptotic activity. Overexpression of the cleaved fragment of Par-4 inhibits IκBα phosphorylation and blocks NF-κB nuclear translocation. We have identified a novel specific caspase-3 cleavage site in Par-4, and the cleaved fragment of Par-4 retains proapoptotic activity.
authors.affiliation: Research Group in Molecular Oncology and Endocrinology, Department of Chemistry-Biology, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada.
authors.forename: Parvesh
authors.initials: P
authors.lastname: Chaudhry
authors.forename: Mohan
authors.initials: M
authors.lastname: Singh
authors.forename: Sophie
authors.initials: S
authors.lastname: Parent
authors.forename: Eric
authors.initials: E
authors.lastname: Asselin
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D053148:Caspase 3 / Q000378:metabolism*; D002460:Cell Line; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology; D017931:DNA Primers / Q000235:genetics; D005260:Female; D055785:Gene Knockdown Techniques; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D051017:Apoptosis Regulatory Proteins; D017931:DNA Primers; D010446:Peptide Fragments; D012333:RNA, Messenger; D011994:Recombinant Proteins; C101296:prostate apoptosis response-4 protein; C505407:CASP3 protein, human; D053148:Caspase 3; D002945:Cisplatin