Caveolin-3 negatively regulates endocytic recycling of cardiac K ATP channels.

Sarcolemmal ATP-sensitive potassium (K) channels play a vital role in cardioprotection. Cardiac K channels are enriched in caveolae and physically interact with the caveolae structural protein caveolin-3 (Cav3). Disrupting caveolae impairs the regulation of K channels through several signaling pathways. However, the direct functional effect of Cav3 on K channels is still poorly understood. Here we used the cardiac K channel subtype, Kir6.2/SUR2A, and showed that Cav3 greatly reduced K channel surface density and current amplitude in a caveolae-independent manner. A screen of Cav3 functional domains revealed that a 25 amino acid region in the membrane attachment domain of Cav3 is the minimal effective segment (MAD1). The peptide corresponding to the MAD1 segment decreased K channel current in a concentration-dependent manner with an IC50 of ~5 μM. The MAD1 segment prevented K channel recycling, thus decreased K channel surface density and abolished the cardioprotective effect of ischemic preconditioning. Our research identified the Cav3 MAD1 segment as a novel negative regulator of K channel recycling, providing pharmacological potentials in the treatment of diseases with K channel trafficking defects.