G. Courtois et al., CHARACTERIZATION OF A MUTANT-CELL LINE THAT DOES NOT ACTIVATE NF-KAPPA-B IN RESPONSE TO MULTIPLE STIMULI, Molecular and cellular biology, 17(3), 1997, pp. 1441-1449
Numerous genes required during the immune or inflammation response as
well as the adhesion process are regulated by nuclear factor kappa B (
NF-kappa B). Associated with its inhibitor, I kappa B, NF-kappa B resi
des as an inactive form in the cytoplasm. Upon stimulation by various
agents, I kappa B is proteolyzed and NF-kappa B translocates to the nu
cleus, where it activates its target genes. The transduction pathways
that lead to I kappa B inactivation remain poorly understood. In this
study, we have characterized a cellular mutant, the 70/Z3-derived 1.3E
2 murine pre-B cell line, that does not activate NF-kappa B in respons
e to several stimuli. We demonstrate that upon stimulation by lipopoly
saccharide, Taxol, phorbol myristate acetate, interleukin-l, or double
-stranded RNA, I kappa B alpha is not degraded, as a result of an abse
nce of induced phosphorylation on serines 32 and 36. Neither a mutatio
n in I kappa B alpha nor a mutation in p50 or relA, the two major subu
nits of NF-kappa B in this cell line, accounts for this phosphorylatio
n defect. As well as culminating in the inducible phosphorylation of I
kappa B alpha on serines 32 and 36, all the stimuli that are inactive
on 1.3E2 cells exhibit a sensitivity to the antioxidant pyrrolidine d
ithiocarbamate (PDTC). In contrast, stimuli such as hyperosmotic shock
or phosphatase inhibitors, which use PDTC-insensitive pathways, induc
e I kappa B alpha degradation in 1.3E2. Analysis of the redox status o
f 1.3E2 does not reveal any difference from wild-type 70Z/3. We also r
eport that the human T-cell leukemia virus type 1 (HTLV-1)-derived Tax
trans-activator induces NF-kappa B activity in 1.3E2, suggesting that
this viral protein does not operate via the defective pathway. Finall
y, we show that two other I kappa B molecules, I kappa B beta and the
recently identified I kappa B epsilon, are not degraded in the 1.3E2 c
ell line following stimulation. Our results demonstrate that 1.3E2 is
a cellular transduction mutant exhibiting a defect in a step that is r
equired by several different stimuli to activate NF-KB. In addition, t
his analysis suggests a common step in the signaling pathways that tri
gger I kappa B alpha, I kappa B beta, and I kappa B epsilon degradatio
n.