Interleukin-1-induced nuclear factor-κB-IκB α autoregulatory feedback loop in hepatocytes. A role for protein kinase Cα in post-transcriptional regulation of IκBα resynthesis

Youqi Han, Tao Meng, Nicole R. Murray, Alan P. Fields, Allan R. Brasier

Research output: Contribution to journalArticle

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Abstract

The IκB inhibitors regulate the activity of the potent transcription factor nuclear factor-κB (NF-κB). Following signal-induced IκB proteolysis, NF-κB translocates into the nucleus to activate transcription of target genes, including IκBα itself, initiating the 'NF-κB-IκBα autoregulatory feedback loop.' Upon IκBα resynthesis, NF-κB is subsequently inactivated and redistributed back into the cytoplasm. We have previously reported a robust NF-κB-IκBα autoregulatory feedback loop in HepG2 hepatocytes. Sixty minutes after tumor necrosis factor (TNF-α) stimulation, IκBα is resynthesized to ~2-fold greater level than in control cells and completely inhibits NF-κB binding. Here we investigate the mechanism for IκBα resynthesis comparing the effect of stimulation of TNF- α with that of interleukin-1 (IL-1α). Although either TNF-α or IL-1α stimulation of protein kinase C (PKC)-down-regulated cells equivalently induces NF-κB translocation, the kinetics of IκBα resynthesis is slowed. Moreover, pretreatment with selective calcium-dependent PKC inhibitors selectively slowed the kinetics of the IL-1α-induced overshoot without affecting that produced by TNF-α. Down-regulation of PKCα by antisense phosphorothioate oligonucleotides and expression vectors selectively blocked the IL-1α-induced IκBα overshoot. In the absence of PKCα, although IL- 1α induced similar amounts of IκBα transcription and changes in steady- state mRNA, a greater component of IκBα mRNA was retained in the nucleus. These data indicate a selective role for PKCα in IL-1α-induced IκBα resynthesis, which is mediated, at least in part, by post-transcriptional control of mRNA export.

Original languageEnglish (US)
Pages (from-to)939-947
Number of pages9
JournalJournal of Biological Chemistry
Volume274
Issue number2
DOIs
StatePublished - Jan 8 1999

Fingerprint

Interleukin-1
Protein Kinase C
Hepatocytes
Feedback
Tumor Necrosis Factor-alpha
Transcription
Messenger RNA
Phosphorothioate Oligonucleotides
Proteolysis
Kinetics
Protein C Inhibitor
Antisense Oligonucleotides
Protein Kinase Inhibitors
Cytoplasm
Transcription Factors
Down-Regulation
Genes

ASJC Scopus subject areas

  • Biochemistry

Cite this

Interleukin-1-induced nuclear factor-κB-IκB α autoregulatory feedback loop in hepatocytes. A role for protein kinase Cα in post-transcriptional regulation of IκBα resynthesis. / Han, Youqi; Meng, Tao; Murray, Nicole R.; Fields, Alan P.; Brasier, Allan R.

In: Journal of Biological Chemistry, Vol. 274, No. 2, 08.01.1999, p. 939-947.

Research output: Contribution to journalArticle

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abstract = "The IκB inhibitors regulate the activity of the potent transcription factor nuclear factor-κB (NF-κB). Following signal-induced IκB proteolysis, NF-κB translocates into the nucleus to activate transcription of target genes, including IκBα itself, initiating the 'NF-κB-IκBα autoregulatory feedback loop.' Upon IκBα resynthesis, NF-κB is subsequently inactivated and redistributed back into the cytoplasm. We have previously reported a robust NF-κB-IκBα autoregulatory feedback loop in HepG2 hepatocytes. Sixty minutes after tumor necrosis factor (TNF-α) stimulation, IκBα is resynthesized to ~2-fold greater level than in control cells and completely inhibits NF-κB binding. Here we investigate the mechanism for IκBα resynthesis comparing the effect of stimulation of TNF- α with that of interleukin-1 (IL-1α). Although either TNF-α or IL-1α stimulation of protein kinase C (PKC)-down-regulated cells equivalently induces NF-κB translocation, the kinetics of IκBα resynthesis is slowed. Moreover, pretreatment with selective calcium-dependent PKC inhibitors selectively slowed the kinetics of the IL-1α-induced overshoot without affecting that produced by TNF-α. Down-regulation of PKCα by antisense phosphorothioate oligonucleotides and expression vectors selectively blocked the IL-1α-induced IκBα overshoot. In the absence of PKCα, although IL- 1α induced similar amounts of IκBα transcription and changes in steady- state mRNA, a greater component of IκBα mRNA was retained in the nucleus. These data indicate a selective role for PKCα in IL-1α-induced IκBα resynthesis, which is mediated, at least in part, by post-transcriptional control of mRNA export.",
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