Metabolism and Bioenergetics
ATP-sensitive Potassium Channel in Mitochondria of the Eukaryotic Microorganism Acanthamoeba castellanii*

https://doi.org/10.1074/jbc.M701496200Get rights and content
Under a Creative Commons license
open access

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 ± 7to166 ± 10 picosiemens, inhibition by 1 mm ATP/Mg2+ 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.

Cited by (0)

*

This work was supported by a grant from the Polish Ministry of Education and Science (PBZ-MIN-012/P04/06) and by the Polish Mitochondrial Network. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.