β-Adrenergic Signaling Inhibits G _q -Dependent Protein Kinase D Activation by Preventing Protein Kinase D Translocation

Abstract

Rationale Both β-adrenergic (β-AR) and Gq-coupled agonist (GqR) 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 β-AR signaling alone and upon co-activation with GqR agonists. This will test our hypothesis that compartmentalized PKD signaling reconciles disparate findings of protein kinase A (PKA) facilitation and inhibition of PKD activation. Methods and Results We report on the spatial and temporal profiles of PKD activation using GFP-tagged PKD (wildtype or mutant S427E) and targeted FRET based biosensors (DKARs) in adult cardiomyocytes. We find that β-AR/PKA signaling drives local nuclear activation of PKD, without preceding sarcolemmal translocation. We also discover pronounced interference of β-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. Lastly, we show altered S427 phosphorylation in TAC-induced hypertrophy. Conclusions β-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 β-adrenergic and Gq-coupled stimuli.

Modulation of Titin-Based Stiffness in Hypertrophic Cardiomyopathy via Protein Kinase D

“…and an increase in PKD1 expression and activity is seen in failing hearts of rats (Harrison et al, 2006), rabbits and humans (Bossuyt et al, 2008). These findings indicate the importance of PKD1 in regulating cardiac pathophysiology and the potential of the kinase as a therapeutic target in cardiovascular disease (Nichols et al, 2014). As PKD1 showed some beneficial effects on cardiomyocyte function (Haworth et al, 2004;Cuello et al, 2007), we wanted to know if PKD is also involved in the phosphorylation of titin.…”

Emergency Spatiotemporal Shift: The Response of Protein Kinase D to Stress Signals in the Cardiovascular System

“…Some of these conflicting reports likely reflect that global PKD1 measurements do not necessarily capture discrete pools of PKD1 signaling (Qiu and Steinberg, 2016). Indeed, specific examination of PKD microdomain signaling revealed β-AR signaling triggers both local nuclear signaling and inhibits GqR-mediated PKD1 activation by preventing its intracellular translocation (Nichols et al, 2014). Fine-tuning PKD responsiveness to GqR-agonists occurred via PKA-dependent phosphorylation of PKD S427.…”

Protein kinase D activation induces mitochondrial fragmentation and dysfunction in cardiomyocytes

“…; Nichols et al . ), but to date there are no reports confirming the existence and translocation of PKD in cardiac mitochondria and their effect on mitochondrial function in the heart.…”