Coupling of the Electron Transport Chain with the Mitochondrial BKCa Channel in Rat Astrocytes

Abstract

Potassium channels have been found in the inner mitochondrial membranes of various cells. These channels are regulating the mitochondrial membrane potential, the matrix volume and respiration. In our study, the single-channel activity of a large-conductance Ca2+-regulated potassium (mitoBKCa) channel was measured by a patch-clamping of mitoplasts isolated from rat astrocytes. A potassium-selective current was recorded with a mean conductance of 290 pS. The channel was inhibited by paxilline and iberiotoxin, inhibitors of BKCa channels. Western blot analysis and immunofluorescence demonstrated the presence of the BKCa channel β4 subunit in the inner mitochondrial membranes of the astrocytes. We have shown that substrates of the respiratory chain, such as NADH, succinate, and glutamate/malate are decreasing the activity of the channel at positive voltage. The effect was abolished by rotenone, antimycin and cyanide, inhibitors of the respiratory chain. The interaction of the β4 subunit of mitoBKCa with cytochrome c oxidase was demonstrated by using of Blue Native electrophoresis. Our findings indicate structural and functional coupling of an electron transport chain with the mitoBKCa channel in rat astrocytes.