title: GTP and GDP activation of K+ channels that can be inhibited by ATP.
abstract: K+ channels that can be inhibited by intracellular ATP have been found in many different cell types. In the insulin-secreting pancreatic islet cells these channels are of crucial importance for stimulus-secretion coupling as glucose stimulation closes the ATP-sensitive channels which leads to depolarization and firing of Ca2+ action potentials. We now demonstrate that nucleotides other than ATP also influence the gating of these K+ channels. In contrast to the action of ATP, GTP (10 microM-1 mM) and GDP (100 microM to 1 mM) evoke dose-dependent channel activation and this effect is immediately reversible. Phosphorylation is not directly involved as non-hydrolysable GTP- and GDP-analogues also evoke channel opening. ATP reversibly inhibits opening of the GTP- or GDP-activated K+ channels.
mesh_terms: D000200:Action Potentials; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D006150:Guanine Nucleotides / Q000494:pharmacology*; D006153:Guanosine Diphosphate / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007515:Islets of Langerhans / Q000378:metabolism*; D010766:Phosphorylation; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D013268:Stimulation, Chemical
chemical_list: D006150:Guanine Nucleotides; D007473:Ion Channels; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D011188:Potassium