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Enserink, J. M. et al. A novel Epac-specific cAMP analogue demonstrates independent regulation of Rap1 and ERK. Nature Cell. Biol. 4, 901-906

University of Bergen, Bergen, Hordaland, Norway
Nature Cell Biology (Impact Factor: 20.06). 12/2002; 4(11):901-6. DOI: 10.1038/ncb874
Source: PubMed

ABSTRACT cAMP is involved in a wide variety of cellular processes that were thought to be mediated by protein kinase A (PKA). However, cAMP also directly regulates Epac1 and Epac2, guanine nucleotide-exchange factors (GEFs) for the small GTPases Rap1 and Rap2 (refs 2,3). Unfortunately, there is an absence of tools to discriminate between PKA- and Epac-mediated effects. Therefore, through rational drug design we have developed a novel cAMP analogue, 8-(4-chloro-phenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate (8CPT-2Me-cAMP), which activates Epac, but not PKA, both in vitro and in vivo. Using this analogue, we tested the widespread model that Rap1 mediates cAMP-induced regulation of the extracellular signal-regulated kinase (ERK). However, both in cell lines in which cAMP inhibits growth-factor-induced ERK activation and in which cAMP activates ERK, 8CPT-2Me-cAMP did not affect ERK activity. Moreover, in cell lines in which cAMP activates ERK, inhibition of PKA and Ras, but not Rap1, abolished cAMP-mediated ERK activation. We conclude that cAMP-induced regulation of ERK and activation of Rap1 are independent processes.

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    • "c o m / l o c a t e / m c e higher than that for PKA (Enserink et al., 2002), recent data indicate that Epac and PKA have similar affinity for cAMP, suggesting that physiological relevant cAMP concentrations are able to activate both enzymes (Dao et al., 2006). By using cAMP analogs that selectively activate Epac or PKA (Christensen et al., 2003; Enserink et al., 2002; Holz et al., 2008) it was possible to assess relative roles of PKA and Epac in mediating the effects of cAMP in several cell systems . To date, few data are available on the specific role of Epac in pituitary cells, the only observation suggesting its involvement on a-MSH release and ERK1/2 activation in mouse melanotrophs and AtT20 cell line, respectively (Sedej et al., 2005; Van Kolen et al., 2010). "
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    • "Reagents. 8-(4-Chlorophenylthio)-29-O-methyladenosine-39,59-cy- clic monophosphate, acetoxymethyl ester (007-AM), initially provided by and subsequently purchased from BioLog Life Science Institute (Bremen, Germany), is the highly membrane-permeant and potent acetoxymethyl ester prodrug (Vliem et al., 2008; Chepurny et al., 2009) of 8-(4-chlorophenylthio)-29-O-methyladenosine-39,59-cyclic monophosphate (007), the first selective EPAC agonist that is more than 100-fold less potent for PKA (Enserink et al., 2002; Christensen et al., 2003). After cell penetration of the uncharged prodrug, the active parental compound 007 is released by endogenous esterases and trapped inside the cell due to the negatively charged cyclic phosphate moiety. "
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