Interleukin-1-induced nuclear factor-kappaB-IkappaBalpha autoregulatory feedback loop in hepatocytes. A role for protein kinase calpha in post-transcriptional regulation of ikappabalpha resynthesis.
The IkappaB inhibitors regulate the activity of the potent transcription factor nuclear factor-kappaB (NF-kappaB). Following signal-induced IkappaB proteolysis, NF-kappaB translocates into the nucleus to activate transcription of target genes, including IkappaBalpha itself, initiating the "NF-kappaB-IkappaBalpha autoregulatory feedback loop." Upon IkappaBalpha resynthesis, NF-kappaB is subsequently inactivated and redistributed back into the cytoplasm. We have previously reported a robust NF-kappaB-IkappaBalpha autoregulatory feedback loop in HepG2 hepatocytes. Sixty minutes after tumor necrosis factor (TNF-alpha) stimulation, IkappaBalpha is resynthesized to approximately 2-fold greater level than in control cells and completely inhibits NF-kappaB binding. Here we investigate the mechanism for IkappaBalpha resynthesis comparing the effect of stimulation of TNF-alpha with that of interleukin-1 (IL-1alpha). Although either TNF-alpha or IL-1alpha stimulation of protein kinase C (PKC)-down-regulated cells equivalently induces NF-kappaB translocation, the kinetics of IkappaBalpha resynthesis is slowed. Moreover, pretreatment with selective calcium-dependent PKC inhibitors selectively slowed the kinetics of the IL-1alpha-induced overshoot without affecting that produced by TNF-alpha. Down-regulation of PKCalpha by antisense phosphorothioate oligonucleotides and expression vectors selectively blocked the IL-1alpha-induced IkappaBalpha overshoot. In the absence of PKCalpha, although IL-1alpha induced similar amounts of IkappaBalpha transcription and changes in steady-state mRNA, a greater component of IkappaBalpha mRNA was retained in the nucleus. These data indicate a selective role for PKCalpha in IL-1alpha-induced IkappaBalpha resynthesis, which is mediated, at least in part, by post-transcriptional control of mRNA export.
Han
Y
Y
Department of Internal Medicine, University of Texas Medical Branch, Galveston, Texas 77555-1060, USA.
Meng
T
T
Murray
N R
NR
Fields
A P
AP
Brasier
A R
AR
D001483:Base Sequence; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005246:Feedback; D006801:Humans; D020672:I-kappa B Proteins; D007375:Interleukin-1 / Q000494:pharmacology*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008024:Ligands; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D017931:DNA Primers; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D020672:I-kappa B Proteins; D007375:Interleukin-1; D007527:Isoenzymes; D008024:Ligands; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; C496628:PRKCA protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D013755:Tetradecanoylphorbol Acetate