Activation of NF-kappaB in vivo is regulated by multiple phosphorylations

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Item Type:	Article
Title:	Activation of NF-kappaB in vivo is regulated by multiple phosphorylations
Creators Name:	Naumann, M. and Scheidereit, C.
Abstract:	The activation of nuclear factor kappa B (NF-kappa B) in intact cells is mechanistically not well understood. Therefore we investigated the modifications imposed on NF-kappa B/I kappa B components following stimulation and show that the final step of NF-kappa B induction in vivo involves phosphorylation of several members of the NF-kappa B/I kappa B protein families. In HeLa cells as well as in B cells, TNF-alpha rapidly induced nuclear translocation primarily of p50-p65, but not of c-rel. Both NF-kappa B precursors and I kappa B alpha became strongly phosphorylated with the same kinetics. In addition to the inducible phosphorylation after stimulation, B lymphocytes containing constitutive nuclear NF-kappa B revealed constitutively phosphorylated p65 and I kappa B alpha. Phosphorylation was accompanied by induced processing of the precursors p100 and p105 and by degradation of I kappa B alpha. As an in vitro model we show that phosphorylation of p105 impedes its ability to interact with NF-kappa B, as has been shown before for I kappa B alpha. Surprisingly, even p65, but not c-rel, was phosphorylated after induction in vivo, suggesting that TNF-alpha selectively activates only specific NF-kappa B heteromers and that modifications regulate not only I kappa B molecules but also NF-kappa B molecules. In fact, cellular NF-kappa B activity was phosphorylation-dependent and the DNA binding activity of p65-containing NF-kappa B was enhanced by phosphorylation in vitro. Furthermore, we found that the induction by hydrogen peroxide of NF-kappa B translocation to the nucleus, which is assumed to be triggered by reactive oxygen intermediates, also coincided with incorporation of phosphate into the same subunits that were modified after stimulation by TNF-alpha. Thus, phosphorylation appears to be a general mechanism for activation of NF-kappa B in vivo.
Keywords:	B-Lymphocytes, Cell Line, DNA-Binding Proteins, Hela Cells, I-kappa B Proteins, NF-kappa B, Phosphorylation, Protein Precursors, Post-Translational Protein Processing, Tumor Necrosis Factor-alpha
Source:	EMBO Journal
ISSN:	0261-4189
Publisher:	Oxford University Press
Volume:	13
Number:	19
Page Range:	4597-4607
Date:	3 October 1994
Official Publication:	http://www.ncbi.nlm.nih.gov/pmc/articles/PMC395392/?tool=pubmed
PubMed:	View item in PubMed

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