Regulation of p100 (NFKB2) expression in human monocytes in response to inflammatory mediators and lymphokines.
The transcription factor NF-kappaB plays an important role in the regulated expression of cytokines in human monocytes. A p100 subunit of NF-kappaB has IkappaB-like properties by sequestering the p65 transactivating subunit in the cytosol of cells. In transient transfection assays we demonstrated that p100 has an inhibitory effect on the NF-kappaB-dependent IL-6 promoter activity. In view of this finding, we studied the regulation of the p100 subunit in human monocytes in response to LPS, the inflammatory cytokines IL-1beta and TNF-alpha and lymphokines. The results demonstrate that LPS, IL-1beta, and TNF-alpha induce p100 expression at mRNA and protein level while IFN-gamma, IL-3 and IL-4/IL-10 have no effect. The induction of p100 expression was shown to be mediated by a two-fold increase in the p100 transcription rate and a two-fold increase in p100 mRNA stability. Furthermore the p100 mediated upregulation was dependent on a tyrosine kinase dependent pathway rather than the protein kinase C pathway. NF-kappaB is a complex of either p50 homodimers or a p50/p65 heterodimer. The latter is known to strongly autoregulate p100 transcription. We therefore examined the composition of NF-kappaB induced by LPS vs the different lymphokines. LPS-induced NF-kappaB showed a distinct p65 supershift whereas the composition of NF-kappaB induced by different lymphokines did not show a change in p65. We conclude that the p100 subunit of the transcription factor NF-kappaB is induced by different inflammatory mediators while lymphokines fail to induce p100 expression which may be caused by the induction of NF-kappaB predominantly consisting of p50 homodimers.
de Wit
H
H
Department of Internal Medicine, University of Groningen, The Netherlands.
Dokter
W H
WH
Koopmans
S B
SB
Lummen
C
C
van der Leij
M
M
Smit
J W
JW
Vellenga
E
E
D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007249:Inflammation; D007371:Interferon-gamma / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology*; D016753:Interleukin-10 / Q000494:pharmacology; D007377:Interleukin-3 / Q000494:pharmacology; D015847:Interleukin-4 / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008222:Lymphokines / Q000494:pharmacology*; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D016328:NF-kappa B / Q000096:biosynthesis*; D052003:NF-kappa B p52 Subunit; D014176:Protein Biosynthesis / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis; D011550:Pseudomonas aeruginosa; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D007375:Interleukin-1; D007377:Interleukin-3; D008070:Lipopolysaccharides; D008222:Lymphokines; D016328:NF-kappa B; D052003:NF-kappa B p52 Subunit; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D015847:Interleukin-4; D007371:Interferon-gamma