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Involvement of nuclear factor‐kappa B in bcl‐xL‐induced interleukin 8 expression in glioblastoma
Author(s) -
Gabellini Chiara,
Castellini Laura,
Trisciuoglio Daniela,
Kracht Michael,
Zupi Gabriella,
Del Bufalo Donatella
Publication year - 2008
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2008.05661.x
Subject(s) - bcl xl , electrophoretic mobility shift assay , interleukin 8 , microbiology and biotechnology , ectopic expression , p50 , phosphorylation , biology , cytoplasm , signal transduction , nfkb1 , gene expression , transcription factor , cell culture , chemistry , apoptosis , gene , cytokine , programmed cell death , biochemistry , immunology , genetics
We recently reported that bcl‐xL regulates interleukin 8 (CXCL8) protein expression and promoter activity in glioblastoma cells. In this paper we demonstrate that CXCL8 induction by bcl‐xL is mediated through a nuclear factor‐kappa B (NF‐kB)‐dependent mechanism. Mutational studies on the CXCL8 promoter showed that NF‐kB binding site was required for bcl‐xL‐induced promoter activity and an enhanced nuclear expression of NF‐kB subunits p65 and p50 was observed after bcl‐xL over‐expression. Electrophoretic mobility shift assay showed an increased DNA‐binding activity of NF‐kB in bcl‐xL over‐expressing cells and the use of specific antibodies confirmed the involvement of p65 and p50 in NF‐kB activity on CXCL8 promoter sequence. NF‐kB activity regulation by bcl‐xL involved IkBα and IKK complex signaling pathway. In fact, bcl‐xL over‐expression induced a decrease of cytoplasmic expression of the IkBα protein, paralleled by an increase in the phosphorylation of the same IkBα and IKKα/β. Moreover, the down‐regulation of the ectopic or endogenous bcl‐xL expression through RNA interference confirmed the ability of bcl‐xL to modulate NF‐kB pathway, and the transient expression of a degradation‐resistant form of the cytoplasmic NF‐kB inhibitor IkBα in bcl‐xL transfectants confirmed the involvement of that inhibitor in bcl‐xL‐induced CXCL8 expression and promoter activity. In conclusion, our results demonstrate the role of NF‐kB as the mediator of bcl‐xL‐induced CXCL8 up‐regulation in glioblastoma cells.