title: NF-κB regulates caspase-4 expression and sensitizes neuroblastoma cells to Fas-induced apoptosis.
abstract: Found in neurons and neuroblastoma cells, Fas-induced apoptosis and accompanied activation of NF-κB signaling were thought to be associated with neurodegenerative diseases. However, the detailed functions of NF-κB activation in Fas killing and the effect of NF-κB activation on its downstream events remain unclear. Here, we demonstrated that agonistic Fas antibody induces cell death in a dose-dependent way and NF-κB signaling is activated as well, in neuroblastoma cells SH-EP1. Unexpectedly, NF-κB activation was shown to be pro-apoptotic, as suggested by the reduction of Fas-induced cell death with either a dominant negative form of IκBα (DN-IκBα) or an IκB kinase-specific inhibitor. To our interest, when analyzing downstream events of NF-κB signaling, we found that DN-IκBα only suppressed the expression of caspase-4, but not other caspases. Vice versa, enhancement of NF-κB activity by p65 (RelA) overexpression increased the expression of caspase-4 at both mRNA and protein levels. More directly, results from dual luciferase reporter assay demonstrated the regulation of caspase-4 promoter activity by NF-κB. When caspase-4 activity was blocked by its dominant negative (DN) form, Fas-induced cell death was substantially reduced. Consistently, the cleavage of PARP and caspase-3 induced by Fas was also reduced. In contrast, the cleavage of caspase-8 remained unaffected in caspase-4 DN cells, although caspase-8 inhibitor could rescue Fas-induced cell death. Collectively, these data suggest that caspase-4 activity is required for Fas-induced cell apoptosis and caspase-4 may act upstream of PARP and caspase-3 and downstream of caspase-8. Overall, we demonstrate that NF-κB can mediate Fas-induced apoptosis through caspase-4 protease, indicating that caspase-4 is a new mediator of NF-κB pro-apoptotic pathway in neuroblastoma cells.
authors.affiliation: College of Life Science and Technology, Xinxiang Medical University, Xinxiang, China.
authors.forename: Hai-Jie
authors.initials: HJ
authors.lastname: Yang
authors.affiliation: College of Life Science and Technology, Xinxiang Medical University, Xinxiang, China.
authors.forename: Mian
authors.initials: M
authors.lastname: Wang
authors.affiliation: College of Life Science and Technology, Xinxiang Medical University, Xinxiang, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.affiliation: College of Life Science and Technology, Xinxiang Medical University, Xinxiang, China.
authors.forename: Bin-Feng
authors.initials: BF
authors.lastname: Cheng
authors.affiliation: College of Life Science and Technology, Xinxiang Medical University, Xinxiang, China.
authors.forename: Xiao-Yu
authors.initials: XY
authors.lastname: Lin
authors.affiliation: College of Life Science and Technology, Xinxiang Medical University, Xinxiang, China.
authors.forename: Zhi-Wei
authors.initials: ZW
authors.lastname: Feng
mesh_terms: D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D053471:Caspases, Initiator / Q000235:genetics*; D045744:Cell Line, Tumor; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D009447:Neuroblastoma / Q000473:pathology*; D015398:Signal Transduction; D015854:Up-Regulation; D019014:fas Receptor / Q000378:metabolism*
chemical_list: D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D019014:fas Receptor; D000072000:NF-KappaB Inhibitor alpha; C093516:CASP4 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053471:Caspases, Initiator