Caveolin-3 negatively regulates recombinant cardiac KATP channels

We have recently shown that ATP-sensitive potassium (KATP) channels in the heart are localized in the caveolae of cardiac myocytes and regulated by caveolae-related signaling. However, little is known about the role of caveolins, signature proteins of caveolae, in cardiac KATP channel function. The present study was designed to explore the potential functional interaction between caveolin-3 and KATP channels. The cardiac KATP channel subunits Kir6.2 and SUR2A were transiently transfected in HEK293T cells with or without co-transfection of caveolin-3 or caveolin-1. Our data demonstrated that the recombinant KATP channel activity in HEK293T cells was inhibited by expression of caveolin-3, but not caveolin-1. The application of caveolin-3 scaffolding domain peptide, corresponding to amino acid residues 55-74 of caveolin-3, blocked the inhibitory effect of caveolin-3 on KATP channels. However, the same peptide did not have any significant effect on KATP channels in HEK293T cells without caveolin-3 expression. We further confirmed that KATP channels co-immunoprecipitated with caveolin-3 but not caveolin-1. The association of KATP channels with caveolin-3 was largely prevented by caveolin-3 scaffolding domain peptide. Our results indicate that caveolin-3 negatively regulates Kir6.2/SUR2A channel function.