title: Overexpression of Par-4 sensitizes TRAIL-induced apoptosis via inactivation of NF-kappaB and Akt signaling pathways in renal cancer cells.
abstract: The prostate-apoptosis-response-gene-4 (Par-4) is up-regulated in prostate cells undergoing programmed cell death. Furthermore, Par-4 protein has been shown to function as an effector of cell death in response to various apoptotic stimuli that trigger mitochondria and membrane receptor-mediated cell death pathways. In this study, we investigated how Par-4 modulates TRAIL-mediated apoptosis in TRAIL-resistant Caki cells. Par-4 overexpressing cells were strikingly sensitive to apoptosis induced by TRAIL compared with control cells. Par-4 overexpressing Caki cells treated with TRAIL showed an increased activation of the initiator caspase-8 and the effector caspase-3, together with an enforced cleavage of XIAP and c-FLIP. TRAIL-induced reduction of XIAP and c-FLIP protein levels in Par-4 overexpressing cells was prevented by z-VAD pretreatment. In addition, the surface DR5 protein level was increased in TRAIL-treated Par-4 overexpressing cells. Interestingly, even though a deletion of leucine zipper domain in Par-4 recovered Bcl-2 level to basal level induced by wild type Par-4, it partly decreased sensitivity to TRAIL in Caki cells. In addition, exposure of Caki/Par-4 cells to TRAIL led to reduction of phosphorylated Akt levels, but deletion of leucine zipper domain of Par-4 did not affect these phosphorylated Akt levels. In conclusion, we here provide evidence that ectopic expression of Par-4 sensitizes Caki cells to TRAIL via modulation of multiple targets, including DR5, Bcl-2, Akt, and NF-kappaB.
authors.affiliation: Department of Immunology, School of Medicine, Keimyung University, 194 DongSan-Dong Jung-Gu, Taegu 700-712, South Korea.
authors.forename: Tae-Jin
authors.initials: TJ
authors.lastname: Lee
authors.forename: Ji-Hoon
authors.initials: JH
authors.lastname: Jang
authors.forename: Hyo-Jeong
authors.initials: HJ
authors.lastname: Noh
authors.forename: Eun-Jung
authors.initials: EJ
authors.lastname: Park
authors.forename: Kyeong-Sook
authors.initials: KS
authors.lastname: Choi
authors.forename: Taeg-Kyu
authors.initials: TK
authors.lastname: Kwon
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000737:chemistry / Q000378:metabolism*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D045744:Cell Line, Tumor; D003513:Cycloheximide / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007680:Kidney Neoplasms / Q000201:enzymology / Q000473:pathology*; D016350:Leucine Zippers; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017434:Protein Structure, Tertiary; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D053218:Receptors, Death Domain / Q000378:metabolism; D017384:Sequence Deletion; D015398:Signal Transduction / Q000187:drug effects*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; C491901:FAS protein, human; D016328:NF-kappa B; D053218:Receptors, Death Domain; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha; D051636:X-Linked Inhibitor of Apoptosis Protein; D019014:fas Receptor; C101296:prostate apoptosis response-4 protein; D003513:Cycloheximide; D051057:Proto-Oncogene Proteins c-akt; D053181:Caspase 8