A novel mitochondrial potassium channel in embryonic hippocampal mitochondra

Abstract

Since 1991, when in Nature Inoue and co-workers described the first potassium channel in the inner mitochondrial membrane, ATP-regulated (mitoKATP), four other channels were found. ATP-regulated (mitoKATP), large-conductance calcium activated (mitoBKCa), voltage-dependent (mitoKv1.3), intermediate-conductance calcium-activated potassium channel (mitoIKCa), were identified by the electrophysiological techniques. The last, TWIK-related acid-sensitive potassium channel (TASK-3) was identified with the use of immunofluorescence methods.Patch-clamp single channel studies on mitochondria isolated from embryonic rat hippocampus revealed the presence of the potassium channel which has outwardly rectifying activity at the symmetrical conditions (150mM/150mM KCl). The channel displayed a conductance of 61 pS, at positive voltages, and also strong voltage dependence. Patch-clamp studies at the mitoplast-attached mode showed that this channel was not sensitive to the classical activators and inhibitors of the mitochondrial potassium channels, but regulated by the pH and arachidonic acid.In summary, by the single channel recordings, we characterized for the first time an ion channel which was cation selective, permeable to potassium ions and displayed voltage sensitivity. The channel not correspond to the potassium ion channels described earlier in the inner mitochondrial membrane.Grant sponsor: 793/N-DAAD/2010/0 and Nencki Institute of Experimental Biology