31 Kang, G. Leech, C. A. Chepurny, O. G. Coetzee, W. A. Holz, G. G. 2008 J Physiol 586 5 1307-19 Mar 1 1469-7793 (Electronic) 18202100 Rats Patch-Clamp Techniques KATP Channels/*metabolism Insulin-Secreting Cells/cytology/*metabolism Humans Guanine Nucleotide Exchange Factors/*metabolism Cyclic AMP-Dependent Protein Kinases/metabolism Cyclic AMP/analogs & derivatives/*metabolism Cells, Cultured Cell Line Animals Adenosine Triphosphate/*physiology Signal Transduction Cells Cultured Protein kinase A (PKA)-independent actions of adenosine 3',5'-cyclic monophosphate (cAMP) are mediated by Epac, a cAMP sensor expressed in pancreatic beta-cells. Evidence that Epac might mediate the cAMP-dependent inhibition of beta-cell ATP-sensitive K(+) channels (K(ATP)) was provided by one prior study of human beta-cells and a rat insulin-secreting cell line (INS-1 cells) in which it was demonstrated that an Epac-selective cAMP analogue (ESCA) inhibited a sulphonylurea-sensitive K(+) current measured under conditions of whole-cell recording. Using excised patches of plasma membrane derived from human beta-cells and rat INS-1 cells, we now report that 2'-O-Me-cAMP, an ESCA that activates Epac but not PKA, sensitizes single K(ATP) channels to the inhibitory effect of ATP, thereby reducing channel activity. In the presence of 2'-O-Me-cAMP (50 microM), the dose-response relationship describing ATP-dependent inhibition of K(ATP) channel activity (NP(o)) is left-shifted such that the concentration of ATP producing 50% inhibition (IC(50)) is reduced from 22 microM to 1 microM for human beta-cells, and from 14 microM to 4 microM for rat INS-1 cells. Conversely, when patches are exposed to a fixed concentration of ATP (10 microM), the administration of 2'-O-Me-cAMP inhibits channel activity in a dose-dependent and reversible manner (IC(50) 12 microM for both cell types). A cyclic nucleotide phosphodiesterase-resistant ESCA (Sp-8-pCPT-2'-O-Me-cAMPS) also inhibits K(ATP) channel activity, thereby demonstrating that the inhibitory actions of ESCAs reported here are unlikely to arise as a consequence of their hydrolysis to bioactive derivatives of adenosine. On the basis of such findings it is concluded that there exists in human beta-cells and rat INS-1 cells a novel form of ion channel modulation in which the ATP sensitivity of K(ATP) channels is regulated by Epac. R01 DK045817/DK/NIDDK NIH HHS/United StatesR01 DK069575/DK/NIDDK NIH HHS/United StatesR01 HL064838/HL/NHLBI NIH HHS/United StatesJournal ArticleResearch Support, N.I.H., ExtramuralResearch Support, Non-U.S. Gov'tEngland http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=18202100