title: Mitochondrial large-conductance potassium channel from Dictyostelium discoideum.
abstract: In the present study, we describe the existence of a large-conductance calcium-activated potassium (BKCa) channel in the mitochondria of Dictyostelium discoideum. A single-channel current was recorded in a reconstituted system, using planar lipid bilayers. The large-conductance potassium channel activity of 258±12 pS was recorded in a 50/150 mM KCl gradient solution. The probability of channel opening (the channel activity) was increased by calcium ions and NS1619 (potassium channel opener) and reduced by iberiotoxin (BKCa channel inhibitor). The substances known to modulate BKCa channel activity influenced the bioenergetics of D. discoideum mitochondria. In isolated mitochondria, NS1619 and NS11021 stimulated non-phosphorylating respiration and depolarized membrane potential, indicating the channel activation. These effects were blocked by iberiotoxin and paxilline. Moreover, the activation of the channel resulted in attenuation of superoxide formation, but its inhibition had the opposite effect. Immunological analysis with antibodies raised against mammalian BKCa channel subunits detected a pore-forming α subunit and auxiliary β subunits of the channel in D. discoideum mitochondria. In conclusion, we show for the first time that mitochondria of D. discoideum, a unicellular ameboid protozoon that facultatively forms multicellular structures, contain a large-conductance calcium-activated potassium channel with electrophysiological, biochemical and molecular properties similar to those of the channels previously described in mammalian and plant mitochondria.
authors.affiliation: Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St, 02-093, Warsaw, Poland.
authors.forename: Michal
authors.initials: M
authors.lastname: Laskowski
authors.affiliation: Department of Bioenergetics, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Kicinska
authors.affiliation: Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St, 02-093, Warsaw, Poland.
authors.forename: Adam
authors.initials: A
authors.lastname: Szewczyk
authors.affiliation: Department of Bioenergetics, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland. Electronic address: wiesiaj@amu.edu.pl.
authors.forename: Wieslawa
authors.initials: W
authors.lastname: Jarmuszkiewicz
mesh_terms: D004023:Dictyostelium / Q000378:metabolism*; D004594:Electrophysiology; D004734:Energy Metabolism; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism*
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels
keywords: Bioenergetics; Dictyostelium discoideum; Electrophysiology; Mitochondria; Potassium channel