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Infect. Immun. doi:10.1128/IAI.00545-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Lipopolysaccharide from Salmonella enterica activates NF-B through both classical and alternative pathways in primary B lymphocytes

CNRS, Institut de Biochimie Biophysique Moléculaire et Cellulaire, UMR 8619, Orsay, F-91405; Université Paris-Sud, Laboratoire Activation cellulaire et transduction de signaux, Orsay, F-91405

^* To whom correspondence should be addressed. Email: vongthip.souvannavong{at}u-psud.fr.

	Abstract

Lipopolysaccharides (LPS) are potent polyclonal B lymphocyte activators. Recently, we have shown that LPS inhibits both spontaneous and drug-induced apoptosis in mature B lymphocytes, through cytosolic retention of Bax, a proapoptotic protein of the Bcl-2 family, by preventing its translocation to mitochondria. Research within the last few years has revealed that members of the NF-B transcription factor regulate cell viability by activating genes involved in mitochondria-dependent apoptosis. In this report, we examined the effect of sustained LPS stimulation on cytosolic and nuclear proteins of the IB/NF-B family to determine which NF-B pathway, canonical (classical) or non-canonical (alternative), is activated by this agent in mature B cells. Immunoblotting analyses showed that LPS induced a time-dependent degradation of the NF-B inhibitors IB and IB (preferentially to isoform IB), via IB kinase . In addition, we observed that LPS triggered the processing of NF-B p105 to p50 and that of NF-B p100 to p52, in parallel with nuclear translocation of active p50 and p52, as NF-Bp50/RelA and NF-Bp52/RelB heterodimers, respectively. These results suggest that sustained stimulation with LPS can activate NF-B through both classical and alternative pathways.