title: Ligand-mediated activation of the cAMP-responsive guanine nucleotide exchange factor Epac.
abstract: Epac is a cAMP-dependent exchange factor for the small GTP-binding protein Rap. The activity of Epac is inhibited by a direct interaction between the C-terminal helical part of the cAMP-binding domain, called the lid, and the catalytic region, which is released after binding of cAMP. Herein, we show that the activation properties are very sensitive to modifications of the cyclic nucleotide. Some analogues are inhibitory and others are stimulatory; some are characterized by a much higher activation potential than normal cAMP. Mutational analysis of Epac allows insights into a network of interactions between the cyclic nucleotides and Epac. Mutations in the lid region are able to amplify or to attenuate selectively the activation potency of cAMP analogues. The properties of cAMP analogues previously used for the activation of the cAMP responsive protein kinase A and of 8-(4-chlorophenylthio)-2'-O-methyladenosine-3',5'-cyclicmonophosphate, an analogue highly selective for activation of Epac were investigated in detail.
authors.affiliation: Department of Physiological Chemistry and Centre of Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands.
authors.forename: Holger
authors.initials: H
authors.lastname: Rehmann
authors.forename: Frank
authors.initials: F
authors.lastname: Schwede
authors.forename: Stein O
authors.initials: SO
authors.lastname: Døskeland
authors.forename: Alfred
authors.initials: A
authors.lastname: Wittinghofer
authors.forename: Johannes L
authors.initials: JL
authors.lastname: Bos
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D002151:Calorimetry; D002384:Catalysis; D000242:Cyclic AMP / Q000737:chemistry / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry; D004252:DNA Mutational Analysis; D004305:Dose-Response Relationship, Drug; D005982:Glutathione Transferase / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D008956:Models, Chemical; D016296:Mutagenesis; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013053:Spectrophotometry; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D008024:Ligands; C116122:RAPGEF3 protein, human; D011993:Recombinant Fusion Proteins; D000242:Cyclic AMP; D005982:Glutathione Transferase; D017868:Cyclic AMP-Dependent Protein Kinases; D020827:rap1 GTP-Binding Proteins