Brown, K.M., Day, J.P., Huston, E., Zimmermann, B., Hampel, K., Christian, F., Romano, D., Terhzaz, S., Lee, L.C., Willis, M.J., Morton, D.B., Beavo, J.A., Shimizu-Albergine, M., Davies, S.A., Kolch, W., Houslay, M.D., Baillie, G.S. (2013). Phosphodiesterase-8A binds to and regulates Raf-1 kinase.  Proc. Natl. Acad. Sci. U.S.A. 110(16): E1533--E1542.

FBrf0221333

Research paper

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.

PMC3631629 (PMC) (EuropePMC)