Chanism remains poorly understood. Here we sought to delineate the intracellular signalling mechanism accountable for NO modulation of sarcolemmal KATP (sarcKATP ) channels in ventricular cardiomyocytes. Cell-attached patch recordings had been performed in transfected human embryonic kidney (HEK) 293 cells and ventricular cardiomyocytes freshly isolated from adult rabbits or genetically modified mice, in combination with pharmacological and biochemical approaches. Bath application from the NO donor NOC-18 enhanced the single-channel activity of Kir6.2/SUR2A (i.e. the principal ventricular-type KATP ) channels in HEK293 cells, whereas the improve was abated by KT5823 [a selective cGMP-dependent protein kinase (PKG) inhibitor], mercaptopropionyl glycine [MPG; a reactive oxygen species (ROS) scavenger], catalase (an H2 O2 -degrading enzyme), myristoylated autocamtide-2 associated inhibitory peptide (mAIP) selective for Ca2+ /calmodulin-dependent protein kinase II (CaMKII) and U0126 [an extracellular signal-regulated protein kinase 1/2 (ERK1/2) inhibitor], respectively. The NO donors NOC-18 and N-(2-deoxy-,-D-glucopyranose-2-)-N2 -acetyl-S-nitroso-D,L-penicillaminamideD.-M. Zhang and Y. Chai contributed equally to this study.C2013 The Authors. The Journal of PhysiologyC2013 The Physiological SocietyDOI: ten.1113/jphysiol.2013.D.-M. Zhang and othersJ Physiol 592.(glycol-SNAP-2) were also capable of stimulating native sarcKATP channels preactivated by the channel opener pinacidil in rabbit ventricular myocytes, by way of reducing the occurrence and the dwelling time of the long PAK medchemexpress closed states while escalating the frequency of channel opening; in contrast, all these alterations had been reversed inside the presence of inhibitors selective for soluble guanylyl cyclase (sGC), PKG, Thymidylate Synthase site calmodulin, CaMKII or ERK1/2. Mimicking the action of NO donors, exogenous H2 O2 potentiated pinacidil-preactivated sarcKATP channel activity in intact cardiomyocytes, however the H2 O2 -induced KATP channel stimulation was obliterated when ERK1/2 or CaMKII activity was suppressed, implying that H2 O2 is positioned upstream of ERK1/2 and CaMKII for KATP channel modulation. Furthermore, genetic ablation (i.e. knockout) of CaMKII, the predominant cardiac CaMKII isoform, diminished ventricular sarcKATP channel stimulation elicited by activation of PKG, unveiling CaMKII as a crucial player. Additionally, proof from kinase activity and Western blot analyses revealed that activation of NO KG signalling augmented CaMKII activity in rabbit ventricular myocytes and, importantly, CaMKII activation by PKG occurred in an ERK1/2-dependent manner, placing ERK1/2 upstream of CaMKII. Taken collectively, these findings recommend that NO modulates ventricular sarcKATP channels by way of a novel sGC GMP KG OS(H2 O2 ) RK1/2 almodulin aMKII ( isoform in unique) signalling cascade, which heightens KATP channel activity by destabilizing the extended closed states although facilitating closed-to-open state transitions. This pathway may perhaps contribute to regulation of cardiac excitability and cytoprotection against ischaemia eperfusion injury, in part, by opening myocardial sarcKATP channels.(Received 6 September 2013; accepted following revision 22 November 2013; initially published online 25 November 2013) Corresponding author Y.-F. Lin: Division of Physiology and Membrane Biology, College of Medicine, University of California Davis, Room 4144, Tupper Hall, 1 Shields Avenue, Davis, CA 95616-8644, USA. E-mail: [email protected].