I. Rivera-walsh et al., The NF-kappa B signaling pathway is not required for Fas ligand gene induction but mediates protection from activation-induced cell death, J BIOL CHEM, 275(33), 2000, pp. 25222-25230
Stimulation of T cells by antigens or mitogens triggers multiple signaling
pathways leading to activation of genes encoding interleukin-2 and other gr
owth-regulatory cytokines. The same stimuli also activate the gene encoding
an apoptosis-inducing molecule, Fas ligand (FasL), which contributes to ac
tivation-induced cell death. It has been proposed that the signaling pathwa
ys involved in cytokine gene induction also contribute to activation-induce
d Fast expression; however, genetic evidence for this proposal is lacking.
In the present study, the role of the NF-kappa B signaling pathway in Fast
gene expression was examined using a mutant T cell line deficient in an ess
ential NF-kappa B signaling component, I kappa B kinase gamma, These mutant
cells have a blockade in signal-induced activation of NF-kappa B but remai
ned normal in the activation of NF-AT and AP-1 transcription factors. Inter
estingly, the NF-kappa B signaling defect has no effect on mitogen-stimulat
ed Fast gene expression, although it completely blocks the interleukin-2 ge
ne induction. We further demonstrate that NF-kappa B activation is required
for protecting T cells from apoptosis induction by mitogens and an agonist
ic anti-Fas antibody. These genetic results suggest that the NF-kappa B sig
naling pathway is not required for activation-induced Fast expression but r
ather mediates cell growth and protection from activation-induced cell deat
h.