Suppression of KATP currents by gene transfer of a dominant negative Kir6.2 construct

Cardiac ATP-sensitive K+ (KATP) channels (SUR2A plus Kir6.2) couple the metabolic state of the myocyte to its electrical activity via a mechanism that is not well understood. Recent pharmacological evidence suggests that KATP channels may mediate ischemic preconditioning. However, there is no potent pharmaceutical agent that specifically blocks the sarcolemmal KATP channel without significant effects on other cellular proteins. As a molecular tool, the GFG sequence in the H5 loop of the murine Kir6.2 channel was mutated to AFA. This mutated channel subunit (6.2AFA) suppressed wild-type Kir6.2 (6.2WT) channel current in a dominant-negative manner: when co-expressed with SUR2A and 6.2WT, whole-cell KATP current recorded from HEK cells was greatly attenuated. The 6.2AFA subunit also co-assembled with endogenous subunits in both smooth-muscle-derived A10 cells and rat neonatal ventricular myocytes, resulting in a significant reduction of current compared with that recorded from non-transfected or mock-transfected cells (<15% of control for both cell types). This study shows that mutation of GFG-->AFA in the putative pore-forming region of Kir6.2 acts in a dominant-negative manner to suppress current in heterologous systems and in native cells.