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Proc Natl Acad Sci U S A. 2013 Apr 16;110(16):E1533-42. doi: 10.1073/pnas.1303004110. Epub 2013 Mar 18.

Phosphodiesterase-8A binds to and regulates Raf-1 kinase.

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1
Institute of Cardiovascular and Medical Science, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom.

Abstract

V-raf-1 murine leukemia viral oncogene homolog 1 (Raf-1) is a key activator of the ERK pathway and is a target for cross-regulation of this pathway by the cAMP signaling system. The cAMP-activated protein kinase, PKA, inhibits Raf-1 by phosphorylation on S259. Here, we show that the cAMP-degrading phosphodiesterase-8A (PDE8A) associates with Raf-1 to protect it from inhibitory phosphorylation by PKA, thereby enhancing Raf-1's ability to stimulate ERK signaling. PDE8A binds to Raf-1 with high (picomolar) affinity. Mapping of the interaction domain on PDE8A using peptide array technology identified amino acids 454-465 as the main binding site, which could be disrupted by mutation. A cell-permeable peptide corresponding to this region disrupted the PDE8A/Raf-1 interaction in cells, thereby reducing ERK activation and the cellular response to EGF. Overexpression of a catalytically inactive PDE8A in cells displayed a dominant negative phenotype on ERK activation. These effects were recapitulated at the organism level in genetically modified (PDE8A(-/-)) mice. Similarly, PDE8 deletion in Drosophila melanogaster reduced basal ERK activation and sensitized flies to stress-induced death. We propose that PDE8A is a physiological regulator of Raf-1 signaling in some cells.

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PMID:
23509299
PMCID:
PMC3631629
DOI:
10.1073/pnas.1303004110
[Indexed for MEDLINE]
Free PMC Article
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