Abstract
Controversy surrounds the molecular identity of mitochondrial K+ channels that are important for protection against cardiac ischemia-reperfusion injury. While KNa1.2 (Kcnt2 gene) is necessary for cardioprotection by volatile anesthetics, electrophysiologic evidence for a channel of this type in mitochondria is lacking. The endogenous physiologic role of a potential mito-KNa1.2 channel is also unclear. Herein, single channel patch-clamp of 27 independent cardiac mitochondrial inner membrane (mitoplast) preparations from wild type (WT) mice yielded 6 channels matching the known ion-sensitivity, ion-selectivity, pharmacology and conductance properties of KNa1.2 (slope conductance 138±1 pS). However, similar experiments on 40 preparations from Kcnt2-/- mice yielded zero such channels. The KNa opener bithionol uncoupled respiration in WT but not Kcnt2-/- cardiomyocytes. Furthermore, when oxidizing only fat as substrate, Kcnt2-/- cardiomyocytes and hearts were less responsive to increases in energetic demand. Kcnt2-/- mice also had elevated body fat, but no baseline differences in the cardiac metabolome. These data support the existence of a cardiac mitochondrial KNa1.2 channel, and a role for cardiac KNa1.2 in regulating metabolism under conditions of high energetic demand.
- Non-standard abbreviations
- IR injury
- Ischemia-Reperfusion injury
- IPC
- Ischemic Preconditioning
- APC
- Anesthetic Preconditioning
- KNa
- Sodium activated potassium channel
- KNa1.1
- (channel encoded by Kcnt1 (formerly Slo2.2)), aka Slack, KCa4.1, SLO2.2
- KNa1.2
- (channel encoded by Kcnt2 (formerly Slo2.1)), aka Slick, KCa4.2, SLO2.1
- BT
- Bithionol, aka Bis(2-hydroxy-3,5-dichlorophenyl)Sulfide
- OCR
- Oxygen consumption rate
- ROS
- Reactive oxygen species