Borland, G., Bird, R. J., Palmer, T. M. and Yarwood, S. J. (2009) Activation of protein kinase Cα by EPAC1 is required for the ERK- and CCAAT/enhancer-binding protein β-dependent induction of the SOCS-3 gene by cyclic AMP in COS1 cells. Journal of Biological Chemistry, 284(26), pp. 17391-17403. (doi: 10.1074/jbc.M109.015370) (PMID:19423709) (PMCID:PMC2719379)
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Publisher's URL: http://dx.doi.org/10.1074/jbc.M109.015370
Abstract
We recently found that induction of the anti-inflammatory SOCS-3 gene by cyclic AMP occurs through novel cyclic AMP-dependent protein kinase-independent mechanisms involving activation of CCAAT/enhancer-binding protein (C/EBP) transcription factors, notably C/EBPβ, by the cyclic AMP GEF EPAC1 and the Rap1 GTPase. In this study we show that down-regulation of phospholipase (PL) Cϵ with small interfering RNA or blockade of PLC activity with chemical inhibitors ablates exchange protein directly activated by cyclic AMP (EPAC)-dependent induction of SOCS-3 in COS1 cells. Consistent with this, stimulation of cells with 1-oleoyl-2-acetyl-sn-glycerol and phorbol 12-myristate 13-acetate, both cell-permeable analogues of the PLC product diacylglycerol, are sufficient to induce SOCS-3 expression in a Ca2+-dependent manner. Moreover, the diacylglycerol- and Ca2+-dependent protein kinase C (PKC) isoform PKCα becomes activated following cyclic AMP elevation or EPAC stimulation. Conversely, down-regulation of PKC activity with chemical inhibitors or small interfering RNA-mediated depletion of PKCα or -δ blocks EPAC-dependent SOCS-3 induction. Using the MEK inhibitor U0126, we found that activation of ERK MAPKs is essential for SOCS-3 induction by either cyclic AMP or PKC. C/EBPβ is known to be phosphorylated and activated by ERK. Accordingly, we found ERK activation to be essential for cyclic AMP-dependent C/EBP activation and C/EBPβ-dependent SOCS-3 induction by cyclic AMP and PKC. Moreover, overexpression of a mutant form of C/EBPβ (T235A), which lacks the ERK phosphorylation site, blocks SOCS-3 induction by cyclic AMP and PKC in a dominant-negative manner. Together, these results indicate that EPAC mediates novel regulatory cross-talk between the cyclic AMP and PKC signaling pathways leading to ERK- and C/EBPβ-dependent induction of the SOCS-3 gene.
| Item Type: | Articles |
|---|---|
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Yarwood, Dr Stephen and Palmer, Dr Timothy and Borland, Dr Gillian |
| Authors: | Borland, G., Bird, R. J., Palmer, T. M., and Yarwood, S. J. |
| College/School: | College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health College of Medical Veterinary and Life Sciences > School of Infection & Immunity College of Medical Veterinary and Life Sciences > School of Molecular Biosciences |
| Journal Name: | Journal of Biological Chemistry |
| Journal Abbr.: | J Biol Chem. |
| Publisher: | American Society for Biochemistry and Molecular Biology, Inc. |
| ISSN: | 0021-9258 |
| ISSN (Online): | 1083-351X |
| Published Online: | 07 May 2009 |
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