Transient nuclear factor κB (NF-κB) activation stimulated by interleukin-1β may be partly dependent on proteasome activity, but not phosphorylation and ubiquitination of the iκBα molecule, in C6 glioma cells

Takashi Uehara, Junko Matsuno, Masayuki Kaneko, Tadashi Nishiya, Masahiro Fujimuro, Hideyoshi Yokosawa, Yasuyuki Nomura

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

We previously reported that several stresses can induce cytokine- induced neutrophil chemoattractant expression in a nuclear factor κB (NF- κB)-dependent manner. In this study, we focused further on the regulation of NF-κB. The activation of NF-κB and the subsequent cytokine-induced neutrophil chemoattractant induction in response to interleukin-1β (IL-1β were inhibited by proteasome inhibitors, MG132 and proteasome inhibitor I. Translocation of NF-κB into nuclei occurs by the phosphorylation, multi- ubiquitination, and degradation of IκBα, a regulatory protein of NF-κB. Nascent IκBα began to degrade 5 min after treatment with IL-1β and disappeared completely after 15 min. However, IκBα returned to basal levels after 45-60 min. Interestingly, resynthesized IκBα was already phosphorylated at Ser32. These results suggest that 1) the upstream signals are still activated, although the translocation of NF-κB peaks at 15 min; and 2) the regulated protein(s) acts downstream of IκBα phosphorylation. Western blotting showed that the resynthesized and phosphorylated IκB molecules were also upward-shifted by multi-ubiquitination in response to IL- 1β treatment. On the other hand, ATP-dependent Leu-Leu-Val-Tyr cleaving activity transiently increased, peaked at 15 min, and then decreased to basal levels at 60 min. Furthermore, the cytosolic fraction that was stimulated by IL-1β for 15 min, but not for 0 and 60 min, could degrade phosphorylated and multi-ubiquitinated IκBα. These results indicate that the transient translocation of NF-κB in response to IL-1β may be partly dependent on transient proteasome activation.

Original languageEnglish
Pages (from-to)15875-15882
Number of pages8
JournalJournal of Biological Chemistry
Volume274
Issue number22
DOIs
Publication statusPublished - May 28 1999
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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