S-Nitrosylation Induces Both Autonomous Activation and Inhibition of Calcium/Calmodulin-dependent Protein Kinase II δ.

NO is known to modulate calcium handling and cellular signaling in the myocardium, but key targets for NO in the heart remain unidentified. Recent reports have implied that NO can activate calcium/calmodulin (Ca(2+)/CaM)-dependent protein kinase II (CaMKII) in neurons and the heart. Here we use our novel sensor of CaMKII activation, Camui, to monitor changes in the conformation and activation of cardiac CaMKII (CaMKIIδ) activity after treatment with the NO donor S-nitrosoglutathione (GSNO). We demonstrate that exposure to NO after Ca(2+)/CaM binding to CaMKIIδ results in autonomous kinase activation, which is abolished by mutation of the Cys-290 site. However, exposure of CaMKIIδ to GSNO prior to Ca(2+)/CaM exposure strongly suppresses kinase activation and conformational change by Ca(2+)/CaM. This NO-induced inhibition was ablated by mutation of the Cys-273 site. We found parallel effects of GSNO on CaM/CaMKIIδ binding and CaMKIIδ-dependent ryanodine receptor activation in adult cardiac myocytes. We conclude that NO can play a dual role in regulating cardiac CaMKIIδ activity.

ß-adrenergic signaling inhibits Gq-dependent protein kinase D activation by preventing protein kinase D translocation.

RATIONALE: Both ß-adrenergic receptor (ß-AR) and Gq-coupled receptor (GqR) agonist-driven signaling play key roles in the events, leading up to and during cardiac dysfunction. How these stimuli interact at the level of protein kinase D (PKD), a nodal point in cardiac hypertrophic signaling, remains unclear. OBJECTIVE: To assess the spatiotemporal dynamics of PKD activation in response to ß-AR signaling alone and on coactivation with GqR-agonists. This will test our hypothesis that compartmentalized PKD signaling reconciles disparate findings of PKA facilitation and inhibition of PKD activation. METHODS AND RESULTS: We report on the spatial and temporal profiles of PKD activation using green fluorescent protein-tagged PKD (wildtype or mutant S427E) and targeted fluorescence resonance energy transfer-based biosensors (D-kinase activity reporters) in adult cardiomyocytes. We find that ß-AR/PKA signaling drives local nuclear activation of PKD, without preceding sarcolemmal translocation. We also discover pronounced interference of ß-AR/cAMP/PKA signaling on GqR-induced translocation and activation of PKD throughout the cardiomyocyte. We attribute these effects to direct, PKA-dependent phosphorylation of PKD-S427. We also show that phosphomimetic substitution of S427 likewise impedes GqR-induced PKD translocation and activation. In neonatal myocytes, S427E inhibits GqR-evoked cell growth and expression of hypertrophic markers. Finally, we show altered S427 phosphorylation in transverse aortic constriction-induced hypertrophy. CONCLUSIONS: ß-AR signaling triggers local nuclear signaling and inhibits GqR-mediated PKD activation by preventing its intracellular translocation. PKA-dependent phosphorylation of PKD-S427 fine-tunes the PKD responsiveness to GqR-agonists, serving as a key integration point for ß-adrenergic and Gq-coupled stimuli.