Lymphotoxin and lipopolysaccharide induce NF-kappaB-p52 generation by a co-translational mechanism

Authors:
Mordmüller B, Krappmann D, Esen M, Wegener E and Scheidereit C
In:
EMBO Rep (2003) 4(1): 82-87
Research Area:
Immunotherapy / Hematology
Cells used in publication:
Dendritic cell (NHDC), human
Species: human
Tissue Origin: blood
Experiment
The classical NF-kappaB activation pathway is mediated by IKKbeta with a subsequent phosphorylation of IkB. An alternative pathway involves IKKa and leads to the phosphorylation and processing of p100, generating p52 DNA-binding complexes. However, it is unknown which physiological stimuli induce p100 processing and the generation of p52 DNA-binding complexes. The authors demonstrate that lmphotoxin b receptor antagonist or lipopolysaccharide (LPS) induces the generation of p52 DNA binding complexes by activating the processing of the p100 precursor. To further reveal the role of Ikappa?, immature dendritic cells were mock-nucleofected or nucleofected with an I?alpha-deltaN expression plasmid. After treatment with LPS upregulation of p100 expression and induced p52 generation was lost.
Abstract
The 'classical' NF-kappaB activation pathway proceeds via IkappaB kinase (IKK)-beta/gamma-mediated phosphorylation, induced ubiquitination and the degradation of small IkappaBs. An alternative, NF-kappaB-inducing kinase and IKK-alpha-dependent pathway, which stimulates the processing of NF-kappaB2/p100, has recently been suggested. However, no physiological stimulus has been shown to trigger the activation of this pathway. Here we demonstrate that persistent stimulation with lymphotoxin beta (LT-beta) receptor agonists or lipopolysaccharide (LPS), but not with interleukin-1beta, tumour necrosis factor-alpha or 12-O-tetradecanoylphorbol-13-acetate, induces the generation of p52 DNA-binding complexes by activating the processing of the p100 precursor. Induction of p52 DNA-binding activity is delayed in comparison with p50/p65 complexes and depends on de novo protein synthesis. p100 is constitutively and inducibly polyubiquitinated, and both ubiquitination and p52 generation are coupled to continuing p100 translation. Thus, both LT-beta receptor agonists and LPS induce NF-kappaB/p100 processing to p52 at the level of the ribosome.