Synergism between protein-kinase C and cAMP-dependent pathways in the expression of the interleukin-1 beta gene is mediated via the activator-protein-1 (AP-1) enhancer activity.
In many different cell types treatment with phorbol esters (e.g. 4 beta-phorbol 12-myristate 13-acetate, PMA) leads to the activation of protein-kinase C (PKC) and subsequently to the activation of the activator-protein-1(AP-1)-responsive gene expression. We have previously reported that a structural analog of cAMP (dibutyryl cAMP, Bt2cAMP) or agents elevating the endogenous cAMP levels strongly enhanced the PMA-induced interleukin-1 beta(IL-1 beta)-gene expression in human myeloid leukemia cells (THP-1, HL-60). We have now examined the role of AP-1 in the regulation of the IL-1 beta gene expression by PKC and cAMP in THP-1 cells. AP-1 is a complex composed of products of the jun and fos gene families. Our studies show that Bt2cAMP enhances the PMA-induced c-fos and jun-B expression, but inhibits c-jun expression. Electrophoretic mobility-shift assay revealed that Bt2cAMP also increased the PMA-induced AP-1 DNA-binding activity. The functional role of the increased AP-1 DNA-binding activity was studied by transfecting THP-1 cells with reporter constructs containing AP-1 sites [Col-TREx5/TK-CAT and IL-1 beta-X-CAT, which contains the putative 12-O-tetradecanoyl-phorbol-13-acetate(TPA)-responsive element of the IL-1 beta gene]. Transient transfection assay demonstrated that Bt2cAMP similarly increased the PMA-induced transcription from both of these reporter constructs. Taken together, these results suggest that cAMP increases the PMA-induced AP-1 activity which then leads to increased IL-1 beta expression.
Department of Bacteriology and Immunology, University of Helsinki, Finland.
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D000242:Cyclic AMP / Q000378:metabolism* / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D006801:Humans; D007375:Interleukin-1 / Q000235:genetics*; D011493:Protein Kinase C / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D007375:Interleukin-1; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D004247:DNA; D000242:Cyclic AMP; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate