title: ATP-sensitive potassium channel in mitochondria of the eukaryotic microorganism Acanthamoeba castellanii.
abstract: We describe the existence of a potassium ion transport mechanism in the mitochondrial inner membrane of a lower eukaryotic organism, Acanthamoeba castellanii. We found that substances known to modulate potassium channel activity influenced the bioenergetics of A. castellanii mitochondria. In isolated mitochondria, the rate of resting respiration is increased by about 10% in response to potassium channel openers, i.e. diazoxide and BMS-191095, during succinate-, malate-, or NADH-sustained respiration. This effect is strictly dependent on the presence of potassium ions in an incubation medium and is reversed by glibenclamide (a potassium channel blocker). Diazoxide and BMS-191095 also caused a slight but statistically significant depolarization of mitochondrial membrane potential (measured with a TPP(+)-specific electrode), regardless of the respiratory substrate used. The resulting steady state value of membrane potential was restored after treatment with glibenclamide or 1 mM ATP. Additionally, the electrophysiological properties of potassium channels present in the A. castellanii inner mitochondrial membrane are described in the reconstituted system, using black lipid membranes. Conductance from 90 +/- 7 to 166 +/- 10 picosiemens, inhibition by 1 mM ATP/Mg(2+) or glibenclamide, and activation by diazoxide were observed. These results suggest that an ATP-sensitive potassium channel similar to that of mammalian mitochondria is present in A. castellanii mitochondria.
authors: Laboratory of Bioenergetics, Adam Mickiewicz University, 61-614 Poznan, Poland.
authors: Anna
authors: A
authors: Kicinska
authors: Aleksandra
authors: A
authors: Swida
authors: Piotr
authors: P
authors: Bednarczyk
authors: Izabela
authors: I
authors: Koszela-Piotrowska
authors: Katarzyna
authors: K
authors: Choma
authors: Krzysztof
authors: K
authors: Dolowy
authors: Adam
authors: A
authors: Szewczyk
authors: Wieslawa
authors: W
authors: Jarmuszkiewicz
mesh_terms: D048248:Acanthamoeba castellanii / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000378:metabolism; D019069:Cell Respiration / Q000502:physiology; D003981:Diazoxide / Q000378:metabolism; D004594:Electrophysiology; D005905:Glyburide / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism / Q000648:ultrastructure; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: D000889:Anti-Arrhythmia Agents; D015221:Potassium Channels; D000255:Adenosine Triphosphate; D003981:Diazoxide; D011188:Potassium; D005905:Glyburide