Slo2.1 Potassium Channel Knockout Mice have an Altered Metabolic Phenotype in Cardiac Mitochondria

Abstract

Mitochondrial K+ channels are important mediators of cell protection against stress. Although the existence of mitochondrial K+ channels can be demonstrated phenomenologically, intense debate surrounds their molecular identity, their role in patho-physiology, and their regulation by endogenous signals. The mammalian Slo family of K+ channels consists of Slo1, Slo2.1, Slo2.2 and Slo3. While Slo3 expression is restricted to the germline, Slo1, Slo2.1 and Slo2.2 are widely expressed. Examination of these channels has been limited to pharmacologic profiling which is hampered by overlapping sensitivities to activators and inhibitors, and off-target effects of small molecules. Work from our lab using genetic knockout mice has demonstrated that Slo1 in intrinsic cardiac neurons is required for protection against ischemia/reperfusion injury elicited by ischemic preconditioning, while Slo2.1 in cardiomyocytes is required for protection via anesthetic preconditioning. Slo2.1 is expressed in the heart and has been detected in the cell membranes of cardiomyocytes. We predict that Slo2.1 may also be a mitochondrial potassium channel. Herein we use pharmacologic activators and inhibitors of Slo2 channels in wildtype and Slo2.1-/- mice to demonstrate the presence of Slo2.1 in cardiac mitochondria. This was also confirmed directly by electophysiology (patch clamp) of isolated mitochondrial inner membranes (mitoplasts). Additional analysis of hearts, cardiomyocytes, and cardiac mitochondria from these knockout mice has revealed a metabolic phenotype, indicating a functional relationship between mitochondrial potassium channels and regulation of mitochondrial oxidative phosphorylation. These data demonstrate a role for Slo2.1 in the regulation of cardiac mitochondrial function.