Background: Cyclic GMP (cGMP)-dependent protein kinase (PKG) is recognized as an important signaling component in diverse cell types. PKG may influence the function of cardiac ATP-sensitive potassium (K ATP ) channels, an ion channel critical for stress adaptation in the heart; however, the underlying mechanism remains largely unknown. The present study was designed to address this issue. Methods and Findings: Single-channel recordings of cardiac K ATP channels were performed in both cell-attached and inside-out patch configurations using transfected human embryonic kidney (HEK)293 cells and rabbit ventricular cardiomyocytes. We found that Kir6.2/SUR2A (the cardiac-type K ATP ) channels were activated by cGMP-selective phosphodiesterase inhibitor zaprinast in a concentration-dependent manner in cell-attached patches obtained from HEK293 cells, an effect mimicked by the membrane-permeable cGMP analog 8-bromo-cGMP whereas abolished by selective PKG inhibitors. Intriguingly, direct application of PKG moderately reduced rather than augmented Kir6.2/SUR2A single-channel currents in excised, inside-out patches. Moreover, PKG stimulation of Kir6.2/SUR2A channels in intact cells was abrogated by ROS/H 2 O 2 scavenging, antagonism of calmodulin, and blockade of calcium/calmodulin-dependent protein kinase II (CaMKII), respectively. Exogenous H 2 O 2 also concentration-dependently stimulated Kir6.2/SUR2A channels in intact cells, and its effect was prevented by inhibition of calmodulin or CaMKII. PKG stimulation of K ATP channels was confirmed in intact ventricular cardiomyocytes, which was ROS- and CaMKII-dependent. Kinetically, PKG appeared to stimulate these channels by destabilizing the longest closed state while stabilizing the long open state and facilitating opening transitions. Conclusion: The present study provides novel evidence that PKG exerts dual regulation of cardiac K ATP channels, including marked stimulation resulting from intracellular signaling mediated by ROS (H 2 O 2 in particular), calmodulin and CaMKII, alongside of moderate channel suppression likely mediated by direct PKG phosphorylation of the channel or some closely associated proteins. The novel cGMP/PKG/ROS/calmodulin/CaMKII signaling pathway may regulate cardiomyocyte excitability by opening K ATP channels and contribute to cardiac protection against ischemia-reperfusion injury. © 2011 Chai et al.
Chai, Y., Zhang, D. M., & Lin, Y. F. (2011). Activation of cGMP-dependent protein kinase stimulates cardiac ATP-sensitive potassium channels via a ROS/calmodulin/CaMKII signaling cascade. PLoS ONE, 6(3). https://doi.org/10.1371/journal.pone.0018191