Key result
Murine Kcnk3 channels function as potassium-selective leak conductances that open across physiological voltages but are inhibited by physiological proton levels in a potassium-sensitive manner.
The study characterizes the biophysical properties of the murine cardiac leak channel Kcnk3, demonstrating that its proton block and voltage gating are potassium-dependent.
May modulate cardiac excitability in acidosis; leaves open translation of murine Kcnk3 properties to human channels.
Potassium leak conductances were recently revealed to exist as independent molecular entities. Here, the genomic structure, cardiac localization, and biophysical properties of a murine example are considered. Kcnk3 subunits have two pore-forming P domains and unique functional attributes. At steady state, Kcnk3 channels behave like open, potassium-selective, transmembrane holes that are inhibited by physiological levels of proton. With voltage steps, Kcnk3 channels open and close in two phases, one appears to be immediate and one is time-dependent (tau = approximately 5 ms). Both proton block and gating are potassium-sensitive; this produces an anomalous increase in outward flux as external potassium levels rise because of decreased proton block. Single Kcnk3 channels open across the physiological voltage range; hence they are "leak" conductances; however, they open only briefly and rarely even after exposure to agents that activate other potassium channels.
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Lopes et al. (2000) studied Murine cardiac leak channel Kcnk3. Murine Kcnk3 channels function as potassium-selective leak conductances that open across physiological voltages but are inhibited by physiological proton levels in a potassium-sensitive manner.
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