title: Combined modulation of the mitochondrial ATP-dependent potassium channel and the permeability transition pore causes prolongation of the biphasic calcium dynamics.
abstract: The permeability transition pore (PTP) and the ATP-dependent potassium (mtK-ATP) channel of mitochondria are known to play key roles in mitochondrially mediated apoptosis. We investigated how modulation of the permeability transition pore (PTP) and the ATP-dependent potassium (mtK-ATP) channel, either as single elements or in combination, affects the proapoptotic intracellular calcium ([Ca(2+)](i)) transients and the mitochondrial membrane potential (psi(m)). For this purpose a model was established exploring the [Ca(2+)](i) transients in N2A cells using continuous application of ATP that causes a biphasic [Ca(2+)](i) response. This response was sensitive to endoplasmatic reticulum (ER) Ca(2+) depletion and a smooth ER Ca(2+)-ATPase (SERCA) antagonist. PTP inhibition by cyclosporine A (CsA) or its non-immunosuppressive derivative NIM811 caused an amplification of the secondary [Ca(2+)](i) peak and induced a hyperpolarization of psi(m). Both the putative mtK-ATP channel inhibitor 5-hydroxydecanoate (5-HD) and the opener diazoxide ameliorated the ATP-induced secondary [Ca(2+)](i) peak. The effect of diazoxide was accompanied by a depolarization of psi(m) whereas 5-HD had no effect on psi(m). When diazoxide and CsA or NIM811 were applied together the secondary [Ca(2+)](i) rise did not return to baseline and a not significant hyperpolarization of psi(m) was observed. So, simultaneous inhibition of PTP and activation of the mtK-ATP channel prevents the increased slope of the secondary [Ca(2+)](i) peak induced by CsA (or NIM811) and also the depolarization after diazoxide application. Hence, we propose that modulation of one of these channels leads to functional changes of the other channel by means of Delta[Ca(2+)](i) and Deltapsi(m).
authors.affiliation: Institute of Medical Neurobiology, Otto-von-Guericke University Magdeburg, Leipzigerstr. 44, D-39120 Magdeburg, Germany. yuliya.dahlem@medizin.uni-magdeburg.de
authors.forename: Yuliya A
authors.initials: YA
authors.lastname: Dahlem
authors.forename: Gerald
authors.initials: G
authors.lastname: Wolf
authors.forename: Detlef
authors.initials: D
authors.lastname: Siemen
authors.forename: Thomas F W
authors.initials: TF
authors.lastname: Horn
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism*; D000083162:Mitochondrial Permeability Transition Pore; D008954:Models, Biological; D009447:Neuroblastoma; D015221:Potassium Channels / Q000378:metabolism*; D012235:Rhodamines / Q000378:metabolism / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
chemical_list: D007473:Ion Channels; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D015221:Potassium Channels; D012235:Rhodamines; C401833:tetramethylrhodamine methyl ester; D000255:Adenosine Triphosphate; D002118:Calcium