Cardiac ryanodine receptor phosphorylation: target sites and functional consequences.
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ABSTRACT:
SUBMITTER: Bers DM
PROVIDER: S-EPMC1450001 | biostudies-other | 2006 May
REPOSITORIES: biostudies-other
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Project description:During physical exercise and stress, the sympathetic system stimulates cardiac contractility via β-adrenergic receptor activation, resulting in protein kinase A (PKA)-mediated phosphorylation of the cardiac ryanodine receptor, RyR2, at Ser2808. Hyperphosphorylation of RyR2-S2808 has been proposed as a mechanism contributing to arrhythmogenesis and heart failure. However, the role of RyR2 phosphorylation during β-adrenergic stimulation remains controversial. We examined the contribution of RyR2-S2808 phosphorylation to altered excitation-contraction coupling and Ca(2+) signaling using an experimental approach at the interface of molecular and cellular levels and a transgenic mouse with ablation of the RyR2-S2808 phosphorylation site (RyR2-S2808A). Experimentally challenging the communication between L-type Ca(2+) channels and RyR2 led to a spatiotemporal de-synchronization of RyR2 openings, as visualized using confocal Ca(2+) imaging. β-Adrenergic stimulation re-synchronized RyR2s, but less efficiently in RyR2-S2808A than in control cardiomyocytes, as indicated by comprehensive analysis of RyR2 activation. In addition, spontaneous Ca(2+) waves in RyR2-S2808A myocytes showed significantly slowed propagation and complete absence of acceleration during β-adrenergic stress, unlike wild type cells. Single channel recordings revealed an attenuation of luminal Ca(2+) sensitivity in RyR2-S2808A channels upon addition of PKA. This suggests that phosphorylation of RyR2-S2808 may be involved in RyR2 modulation by luminal (intra-SR) Ca(2+) ([Ca(2+)](SR)). We show here by three independent experimental approaches that PKA-dependent RyR2-S2808 phosphorylation plays significant functional roles at the subcellular level, namely, Ca(2+) release synchronization, Ca(2+) wave propagation and functional adaptation of RyR2 to variable [Ca(2+)](SR). These results indicate a direct mechanistic link between RyR2 phosphorylation and SR luminal Ca(2+) sensing.
| S-EPMC3674825 | biostudies-literature
Project description:The androgen receptor (AR) is a ligand-regulated transcription factor that belongs to the family of nuclear receptors. In addition to regulation by steroid, the AR is also regulated by post-translational modifications generated by signal transduction pathways. Thus, the AR functions not only as a transcription factor but also as a node that integrates multiple extracellular signals. The AR plays an important role in many diseases, including complete androgen insensitivity syndrome, spinal bulbar muscular atrophy, prostate and breast cancer, etc. In the case of prostate cancer, dependence on AR signaling has been exploited for therapeutic intervention for decades. However, the effectiveness of these therapies is limited in advanced disease due to restoration of AR signaling. Greater understanding of the molecular mechanisms involved in AR action will enable the development of improved therapeutics to treat the wide range of AR-dependent diseases. The AR is subject to regulation by a number of kinases through post-translational modifications on serine, threonine, and tyrosine residues. In this paper, we review the AR phosphorylation sites, the kinases responsible for these phosphorylations, as well as the biological context and the functional consequences of these phosphorylations. Finally, what is known about the state of AR phosphorylation in clinical samples is discussed.
| S-EPMC4437516 | biostudies-literature
Project description:BackgroundRyanodine receptor (RyR), a calcium-release channel located in the sarcoplasmic reticulum membrane of muscles, is the target of insecticides used against a wide range of agricultural pests. Mammalian RyRs have been shown to be under the regulatory control of several kinases and phosphatases, but little is known about the regulation of insect RyRs by phosphorylation.ResultsHere we present the crystal structures of wild-type and phospho-mimetic RyR Repeat34 domain containing PKA phosphorylation sites from diamondback moth (DBM), a major lepidopteran pest of cruciferous vegetables. The structure has unique features, not seen in mammalian RyRs, including an additional α-helix near the phosphorylation loop. Using tandem mass spectrometry, we identify several PKA sites clustering in the phosphorylation loop and the newly identified α-helix. Bioinformatics analysis shows that this α-helix is only present in Lepidoptera, suggesting an insect-specific regulation. Interestingly, the specific phosphorylation pattern is temperature-dependent. The thermal stability of the DBM Repeat34 domain is significantly lower than that of the analogous domain in the three mammalian RyR isoforms, indicating a more dynamic domain structure that can be partially unfolded to facilitate the temperature-dependent phosphorylation. Docking the structure into the cryo-electron microscopy model of full-length RyR reveals that the interface between the Repeat34 and neighboring HD1 domain is more conserved than that of the phosphorylation loop region that might be involved in the interaction with SPRY3 domain. We also identify an insect-specific glycerol-binding pocket that could be potentially targeted by novel insecticides to fight the current resistance crisis.ConclusionsThe crystal structures of the DBM Repeat34 domain reveals insect-specific temperature-dependent phosphorylation sites that may regulate insect ryanodine receptor function. It also reveals insect-specific structural features and a potential ligand-binding site that could be targeted in an effort to develop green pesticides with high species-specificity.
| S-EPMC6784350 | biostudies-literature
Project description:Cardiac ryanodine receptor type 2 plays a key role in excitation-contraction coupling. The ryanodine receptor type 2 channel protein is modulated by various post-translational modifications, including phosphorylation by protein kinase A and Ca(2+)/calmodulin protein kinase II. Despite extensive research in this area, the functional effects of ryanodine receptor type 2 phosphorylation remain disputed. In particular, the potential involvement of increased ryanodine receptor type 2 phosphorylation in the pathogenesis of heart failure and arrhythmias remains a controversial area, which is discussed in this review article.
| S-EPMC4008932 | biostudies-literature
Project description:AimsRecent studies suggest that proarrhythmic effects of cardiac glycosides (CGs) on cardiomyocyte Ca(2+) handling involve generation of reactive oxygen species (ROS). However, the specific pathway(s) of ROS production and the subsequent downstream molecular events that mediate CG-dependent arrhythmogenesis remain to be defined.Methods and resultsWe examined the effects of digitoxin (DGT) on Ca(2+) handling and ROS production in cardiomyocytes using a combination of pharmacological approaches and genetic mouse models. Myocytes isolated from mice deficient in NADPH oxidase type 2 (NOX2KO) and mice transgenically overexpressing mitochondrial superoxide dismutase displayed markedly increased tolerance to the proarrhythmic action of DGT as manifested by the inhibition of DGT-dependent ROS and spontaneous Ca(2+) waves (SCW). Additionally, DGT-induced mitochondrial membrane potential depolarization was abolished in NOX2KO cells. DGT-dependent ROS was suppressed by the inhibition of PI3K, PKC, and the mitochondrial KATP channel, suggesting roles for these proteins, respectively, in activation of NOX2 and in mitochondrial ROS generation. Western blot analysis revealed increased levels of oxidized CaMKII in WT but not in NOX2KO hearts treated with DGT. The DGT-induced increase in SCW frequency was abolished in myocytes isolated from mice in which the Ser 2814 CaMKII phosphorylation site on RyR2 is constitutively inactivated.ConclusionThese results suggest that the arrhythmogenic adverse effects of CGs on Ca(2+) handling involve PI3K- and PKC-mediated stimulation of NOX2 and subsequent NOX2-dependent ROS release from the mitochondria; mitochondria-derived ROS then activate CaMKII with consequent phosphorylation of RyR2 at Ser 2814.
| S-EPMC3868350 | biostudies-literature
Project description:During the classic "fight-or-flight" stress response, sympathetic nervous system activation leads to catecholamine release, which increases heart rate and contractility, resulting in enhanced cardiac output. Catecholamines bind to β-adrenergic receptors, causing cAMP generation and activation of PKA, which phosphorylates multiple targets in cardiac muscle, including the cardiac ryanodine receptor/calcium release channel (RyR2) required for muscle contraction. PKA phosphorylation of RyR2 enhances channel activity by sensitizing the channel to cytosolic calcium (Ca²+). Here, we found that mice harboring RyR2 channels that cannot be PKA phosphorylated (referred to herein as RyR2-S2808A+/+ mice) exhibited blunted heart rate and cardiac contractile responses to catecholamines (isoproterenol). The isoproterenol-induced enhancement of ventricular myocyte Ca²+ transients and fractional shortening (contraction) and the spontaneous beating rate of sinoatrial nodal cells were all blunted in RyR2-S2808A+/+ mice. The blunted cardiac response to catecholamines in RyR2-S2808A+/+ mice resulted in impaired exercise capacity. RyR2-S2808A+/+ mice were protected against chronic catecholaminergic-induced cardiac dysfunction. These studies identify what we believe to be new roles for PKA phosphorylation of RyR2 in both the heart rate and contractile responses to acute catecholaminergic stimulation.
| S-EPMC2993575 | biostudies-literature
Project description:Phosphorylation of the voltage-gated Na+ (NaV) channel NaV1.5 regulates cardiac excitability, yet the phosphorylation sites regulating its function and the underlying mechanisms remain largely unknown. Using a systematic, quantitative phosphoproteomic approach, we analyzed NaV1.5 channel complexes purified from nonfailing and failing mouse left ventricles, and we identified 42 phosphorylation sites on NaV1.5. Most sites are clustered, and three of these clusters are highly phosphorylated. Analyses of phosphosilent and phosphomimetic NaV1.5 mutants revealed the roles of three phosphosites in regulating NaV1.5 channel expression and gating. The phosphorylated serines S664 and S667 regulate the voltage dependence of channel activation in a cumulative manner, whereas the nearby S671, the phosphorylation of which is increased in failing hearts, regulates cell surface NaV1.5 expression and peak Na+ current. No additional roles could be assigned to the other clusters of phosphosites. Taken together, our results demonstrate that ventricular NaV1.5 is highly phosphorylated and that the phosphorylation-dependent regulation of NaV1.5 channels is highly complex, site specific, and dynamic.
| S-EPMC7797897 | biostudies-literature
Project description:Ryanodine receptor channels at calcium release sites of cardiac myocytes operate on the principle of calcium-induced calcium release. In vitro experiments revealed competition of Ca2+ and Mg2+ in the activation of ryanodine receptors (RyRs) as well as inhibition of RyRs by Mg2+. The impact of RyR modulation by Mg2+ on calcium release is not well understood due to the technical limitations of in situ experiments. We turned instead to an in silico model of a calcium release site (CRS), based on a homotetrameric model of RyR gating with kinetic parameters determined from in vitro measurements. We inspected changes in the activity of the CRS model in response to a random opening of one of 20 realistically distributed RyRs, arising from Ca2+/Mg2+ interactions at RyR channels. Calcium release events (CREs) were simulated at a range of Mg2+-binding parameters at near-physiological Mg2+ and ATP concentrations. Facilitation of Mg2+ binding to the RyR activation site inhibited the formation of sparks and slowed down their activation. Impeding Mg-binding to the RyR activation site enhanced spark formation and speeded up their activation. Varying Mg2+ binding to the RyR inhibition site also dramatically affected calcium release events. Facilitation of Mg2+ binding to the RyR inhibition site reduced the amplitude, relative occurrence, and the time-to-end of sparks, and vice versa. The characteristics of CREs correlated dose-dependently with the effective coupling strength between RyRs, defined as a function of RyR vicinity, single-channel calcium current, and Mg-binding parameters of the RyR channels. These findings postulate the role of Mg2+ in calcium release as a negative modulator of the coupling strength among RyRs in a CRS, translating to damping of the positive feedback of the calcium-induced calcium-release mechanism.
| S-EPMC8821920 | biostudies-literature
Project description:The force frequency relationship (FFR), first described by Bowditch 139 years ago as the observation that myocardial contractility increases proportionally with increasing heart rate, is an important mediator of enhanced cardiac output during exercise. Individuals with heart failure have defective positive FFR that impairs their cardiac function in response to stress, and the degree of positive FFR deficiency correlates with heart failure progression. We have identified a mechanism for FFR involving heart rate dependent phosphorylation of the major cardiac sarcoplasmic reticulum calcium release channel/ryanodine receptor (RyR2), at Ser2814, by calcium/calmodulin-dependent serine/threonine kinase-delta (CaMKIIdelta). Mice engineered with an RyR2-S2814A mutation have RyR2 channels that cannot be phosphorylated by CaMKIIdelta, and exhibit a blunted positive FFR. Ex vivo hearts from RyR2-S2814A mice also have blunted positive FFR, and cardiomyocytes isolated from the RyR2-S2814A mice exhibit impaired rate-dependent enhancement of cytosolic calcium levels and fractional shortening. The cardiac RyR2 macromolecular complexes isolated from murine and human failing hearts have reduced CaMKIIdelta levels. These data indicate that CaMKIIdelta phosphorylation of RyR2 plays an important role in mediating positive FFR in the heart, and that defective regulation of RyR2 by CaMKIIdelta-mediated phosphorylation is associated with the loss of positive FFR in failing hearts.
| S-EPMC2890457 | biostudies-literature
Project description:The ryanodine receptor is the main Ca(2+)-release structure in skeletal and cardiac sarcoplasmic reticulum. In both tissues, phosphorylation of the ryanodine receptor has been proposed to be involved in the regulation of Ca2+ release. In the present study, we have examined the ability of the purified cardiac ryanodine receptor to serve as a substrate for phosphorylation by exogenously added catalytic subunit of the cyclic AMP (cAMP)-dependent protein kinase (PK-A), cyclic GMP (cGMP)-dependent protein kinase (PK-G), or calmodulin-dependent protein kinase (PK-CaM). A large amount of phosphate incorporation was observed for PK-CaM (938 +/- 48 pmol of Pi/mg of purified channel protein), whereas the level of phosphorylation was considerably lower with PK-A or PK-G (345 +/- 139 and 96 +/- 6 pmol/mg respectively). In addition, endogenous PK-CaM activity co-migrates with the ryanodine receptor through several steps of purification, suggesting a strong association of the two proteins. This endogenous PK-CaM activity is abolished by a PK-CaM-specific synthetic peptide inhibitor. Endogenous cAMP- and cGMP-dependent phosphorylation was not observed in the purified ryanodine-receptor preparation. Taken together, these observations imply that PK-CaM is the physiologically relevant protein kinase, capable of phosphorylating the channel protein to a minimum stoichiometry of 2 mol of Pi per mol of tetramer.
| S-EPMC1137694 | biostudies-other