1. Identification of CCAAT/enhancer-binding proteins as exchange protein activated by cAMP-activated transcription factors that mediate the induction of the SOCS-3 gene
- Author
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Stephen J. Yarwood, Timothy M. Palmer, William A. Sands, and Gillian Borland
- Subjects
Gene isoform ,Umbilical Veins ,Suppressor of Cytokine Signaling Proteins ,Biology ,Biochemistry ,Models, Biological ,Mice ,Cyclic AMP ,Animals ,Protein Isoforms ,Protein kinase A ,Molecular Biology ,Transcription factor ,Regulation of gene expression ,Ccaat-enhancer-binding proteins ,Interleukin-6 ,Cell Biology ,Fibroblasts ,Molecular biology ,Cyclic AMP-Dependent Protein Kinases ,Gene Expression Regulation ,Suppressor of Cytokine Signaling 3 Protein ,Second messenger system ,biology.protein ,CCAAT-Enhancer-Binding Proteins ,Endothelium, Vascular ,Signal transduction ,CREB1 ,Signal Transduction - Abstract
The prototypical second messenger cAMP is a key regulator of immune and inflammatory responses. Its ability to inhibit interleukin (IL)-6 responses is due to induction of suppressor of cytokine signaling-3 (SOCS-3), a negative regulator of IL-6 receptor signaling. We have determined previously that SOCS-3 induction by cAMP occurs independently of cAMP-dependent protein kinase, instead requiring the recently identified cAMP sensor exchange protein activated by cAMP 1 (EPAC1). Here we present evidence to suggest that the C/EBP family of transcription factors link EPAC1 activation to SOCS-3 induction. Firstly, selective activation of EPAC in human umbilical vein endothelial cells increased C/EBP DNA binding activity and recruitment of C/EBPbeta to the SOCS-3 promoter. Secondly, knockdown of C/EBPbeta and -delta isoforms abolished both SOCS-3 induction and inhibition of IL-6 signaling in response to cAMP. Thirdly, overexpression of C/EBPalpha, -beta, or -delta potentiated EPAC-mediated accumulation of SOCS-3. Finally, these effects were not restricted to human umbilical vein endothelial cells, because similar phenomena were observed in murine embryonic fibroblasts in which C/EBPbeta or delta had been deleted. In summary, our findings constitute the first description of an EPAC-C/EBP pathway that can control cAMP-mediated changes in gene expression independently of protein kinase A.
- Published
- 2008