The Experts below are selected from a list of 1143 Experts worldwide ranked by ideXlab platform
Derek R Laver - One of the best experts on this subject based on the ideXlab platform.
-
Secretoneurin Is an Endogenous Calcium/Calmodulin-Dependent Protein Kinase II Inhibitor That Attenuates Ca2+-Dependent Arrhythmia
Circulation-arrhythmia and Electrophysiology, 2019Co-Authors: Anett Hellebø Ottesen, Derek R Laver, Cathrine R. Carlson, Olav Søvik Eken, Mani Sadredini, Peder L. Myhre, Xin Shen, Bjørn Dalhus, Per Kristian Lunde, Jouni KurolaAbstract:Background: Circulating SN (secretoneurin) concentrations are increased in patients with myocardial dysfunction and predict poor outcome. Because SN inhibits CaMKIIδ (Ca2+/calmodulin-dependent protein kinase IIδ) activity, we hypothesized that upregulation of SN in patients protects against cardiomyocyte mechanisms of arrhythmia. Methods: Circulating levels of SN and other biomarkers were assessed in patients with catecholaminergic polymorphic ventricular tachycardia (CPVT; n=8) and in resuscitated patients after ventricular arrhythmia–induced cardiac arrest (n=155). In vivo effects of SN were investigated in CPVT mice (RyR2 [Ryanodine Receptor 2]-R2474S) using adeno-associated virus-9–induced overexpression. Interactions between SN and CaMKIIδ were mapped using pull-down experiments, mutagenesis, ELISA, and structural homology modeling. Ex vivo actions were tested in Langendorff hearts and effects on Ca2+ homeostasis examined by fluorescence (fluo-4) and patch-clamp recordings in isolated cardiomyocytes....
-
Calmodulin Mutants Linked to Catecholaminergic Polymorphic Ventricular Tachycardia Fail to Inhibit Human RyR2 Channels.
Journal of the American College of Cardiology, 2017Co-Authors: Kafa Walweel, Nieves Gomez-hurtado, Christopher N. Johnson, Walter J. Chazin, Ye Wint Oo, Nicole A. Beard, Cris Dos Remedios, Dirk F. Van Helden, Björn C. Knollmann, Derek R LaverAbstract:Calmodulin (CaM) is a calcium-binding protein that can directly inhibit cardiac Ryanodine Receptor calcium release channels (Ryanodine Receptor 2 [RyR2]) [(1)][1]. CaM mutations can cause an autosomal-dominant form of catecholaminergic polymorphic ventricular tachycardia (CPVT), a syndrome
-
cardiac calcium release channel Ryanodine Receptor 2 regulation by halogenated anesthetics
Anesthesiology, 2017Co-Authors: Derek R Laver, John Attia, Christopher Oldmeadow, Anthony W QuailAbstract:Background:Halogenated anesthetics activate cardiac Ryanodine Receptor 2–mediated sarcoplasmic reticulum Ca2+ release, leading to sarcoplasmic reticulum Ca2+ depletion, reduced cardiac function, and providing cell protection against ischemia-reperfusion injury. Anesthetic activation of Ryanodine rec
-
multiple modes of Ryanodine Receptor 2 inhibition by flecainide
Molecular Pharmacology, 2014Co-Authors: Divya Mehra, Björn C. Knollmann, D F Van Helden, Mohammad S Imtiaz, Derek R LaverAbstract:Catecholaminergic polymorphic ventricular tachycardia (CPVT) causes sudden cardiac death due to mutations in cardiac Ryanodine Receptors (RyR2), calsequestrin, or calmodulin. Flecainide, a class I antiarrhythmic drug, inhibits Na+ and RyR2 channels and prevents CPVT. The purpose of this study is to identify inhibitory mechanisms of flecainide on RyR2. RyR2 were isolated from sheep heart, incorporated into lipid bilayers, and investigated by single-channel recording under various activating conditions, including the presence of cytoplasmic ATP (2 mM) and a range of cytoplasmic [Ca2+], [Mg2+], pH, and [caffeine]. Flecainide applied to either the cytoplasmic or luminal sides of the membrane inhibited RyR2 by two distinct modes: 1) a fast block consisting of brief substate and closed events with a mean duration of ∼1 ms, and 2) a slow block consisting of closed events with a mean duration of ∼1 second. Both inhibition modes were alleviated by increasing cytoplasmic pH from 7.4 to 9.5 but were unaffected by luminal pH. The slow block was potentiated in RyR2 channels that had relatively low open probability, whereas the fast block was unaffected by RyR2 activation. These results show that these two modes are independent mechanisms for RyR2 inhibition, both having a cytoplasmic site of action. The slow mode is a closed-channel block, whereas the fast mode blocks RyR2 in the open state. At diastolic cytoplasmic [Ca2+] (100 nM), flecainide possesses an additional inhibitory mechanism that reduces RyR2 burst duration. Hence, multiple modes of action underlie RyR2 inhibition by flecainide.
-
divergent regulation of Ryanodine Receptor 2 calcium release channels by arrhythmogenic human calmodulin missense mutants
Circulation Research, 2014Co-Authors: Hyun Seok Hwang, Derek R Laver, Yi Yang, Florentin R Nitu, Christopher N. Johnson, Walter J. Chazin, Kafa Walweel, Laetitia Pereira, Michela Faggioni, Alfred L GeorgeAbstract:Rationale:Calmodulin (CaM) mutations are associated with an autosomal dominant syndrome of ventricular arrhythmia and sudden death that can present with divergent clinical features of catecholaminergic polymorphic ventricular tachycardia (CPVT) or long QT syndrome (LQTS). CaM binds to and inhibits Ryanodine Receptor (RyR2) Ca release channels in the heart, but whether arrhythmogenic CaM mutants alter RyR2 function is not known. Objective:To gain mechanistic insight into how human CaM mutations affect RyR2 Ca channels. Methods and Results:We studied recombinant CaM mutants associated with CPVT (N54I and N98S) or LQTS (D96V, D130G, and F142L). As a group, all LQTS-associated CaM mutants (LQTS-CaMs) exhibited reduced Ca affinity, whereas CPVT-associated CaM mutants (CPVT-CaMs) had either normal or modestly lower Ca affinity. In permeabilized ventricular myocytes, CPVT-CaMs at a physiological intracellular concentration (100 nmol/L) promoted significantly higher spontaneous Ca wave and spark activity, a typic...
Hsiangting Ho - One of the best experts on this subject based on the ideXlab platform.
-
muscarinic stimulation facilitates sarcoplasmic reticulum ca release by modulating Ryanodine Receptor 2 phosphorylation through protein kinase g and ca calmodulin dependent protein kinase ii
Hypertension, 2016Co-Authors: Hsiangting Ho, Andriy E Belevych, Ingrid M Bonilla, Przemyslaw B Radwanski, Igor V Kubasov, Hector H Valdivia, Karsten E Schober, Cynthia A Carnes, Sandor GyorkeAbstract:Although the effects and the underlying mechanism of sympathetic stimulation on cardiac Ca handling are relatively well established both in health and disease, the modes of action and mechanisms of parasympathetic modulation are poorly defined. Here, we demonstrate that parasympathetic stimulation initiates a novel mode of excitation–contraction coupling that enhances the efficiency of cardiac sarcoplasmic reticulum Ca store utilization. This efficient mode of excitation–contraction coupling involves reciprocal changes in the phosphorylation of Ryanodine Receptor 2 at Ser-2808 and Ser-2814. Specifically, Ser-2808 phosphorylation was mediated by muscarinic Receptor subtype 2 and activation of PKG (protein kinase G), whereas dephosphorylation of Ser-2814 involved activation of muscarinic Receptor subtype 3 and decreased reactive oxygen species–dependent activation of CaMKII (Ca/calmodulin-dependent protein kinase II). The overall effect of these changes in phosphorylation of Ryanodine Receptor 2 is an increase in systolic Ca release at the low sarcoplasmic reticulum Ca content and a paradoxical reduction in aberrant Ca leak. Accordingly, cholinergic stimulation of cardiomyocytes isolated from failing hearts improved Ca cycling efficiency by restoring altered Ryanodine Receptor 2 phosphorylation balance.
-
genetic ablation of Ryanodine Receptor 2 phosphorylation at ser 2808 aggravates ca2 dependent cardiomyopathy by exacerbating diastolic ca2 release
The Journal of Physiology, 2014Co-Authors: Hsiangting Ho, Hector H Valdivia, Carmen R Valdivia, Björn C. Knollmann, Florencia Velezcortes, Sandor GyorkeAbstract:Key points Phosphorylation at Ser-2808 is suggested to result in RyR2 hyperactivity, i.e. ‘leakiness’, thus contributing to the pathology of cardiac diseases. We studied the effect of disabling phosphorylation at Ser-2808 of RyR2 in a genetic model of Ca2+-dependent cardiomyopathy, which was caused by leaky RyR2. RyR2 phosphorylation was high at Ser-2808 in myocytes expressing wild-type (WT) RyR2; protein phosphatase increased RyR2 leakiness in cells expressing WT, but not in mutant RyR2s with disabled Ser-2808 phosphorylation sites. Rather than alleviating cardiac disease, ablation of the Ser-2808 exacerbated the disease phenotype by reducing survival, impairing in vivo cardiac function and enhancing RyR2 Ca2+ leak and mitochondrial damage. These results suggest a novel mode of RyR2 regulation via dephosphorylation at Ser-2808 in normal and diseased hearts. Abstract Phosphorylation of the cardiac Ryanodine Receptor (RyR2) by protein kinase A (PKA) at Ser-2808 is suggested to mediate the physiological ‘fight or flight’ response and contribute to heart failure by rendering the sarcoplasmic reticulum (SR) leaky for Ca2+. In the present study, we examined the potential role of RyR2 phosphorylation at Ser-2808 in the progression of Ca2+-dependent cardiomyopathy (CCM) by using mice genetically modified to feature elevated SR Ca2+ leak while expressing RyR2s that cannot be phosphorylated at this site (S2808A). Surprisingly, rather than alleviating the disease phenotype, constitutive dephosphorylation of Ser-2808 aggravated CCM as manifested by shortened survival, deteriorated in vivo cardiac function, exacerbated SR Ca2+ leak and mitochondrial injury. Notably, the deteriorations of cardiac function, myocyte Ca2+ handling, and mitochondria integrity were consistently worse in mice with heterozygous ablation of Ser-2808 than in mice with complete ablation. Wild-type (WT) and CCM myocytes expressing unmutated RyR2s exhibited a high level of baseline phosphorylation at Ser-2808. Exposure of these CCM cells to protein phosphatase 1 caused a transitory increase in Ca2+ leak attributable to partial dephosphorylation of RyR2 tetramers at Ser-2808 from more fully phosphorylated state. Thus, exacerbated Ca2+ leak through partially dephosphorylated RyR2s accounts for the prevalence of the disease phenotype in the heterozygous S2808A CCM mice. These results do not support the importance of RyR2 hyperphosphorylation in Ca2+-dependent heart disease, and rather suggest roles for the opposite process, the RyR2 dephosphorylation at this residue in physiological and pathophysiological Ca2+ signalling.
-
Genetic ablation of Ryanodine Receptor 2 phosphorylation at Ser‐2808 aggravates Ca2+‐dependent cardiomyopathy by exacerbating diastolic Ca2+ release
The Journal of Physiology, 2014Co-Authors: Hsiangting Ho, Hector H Valdivia, Carmen R Valdivia, Björn C. Knollmann, Florencia Velez-cortes, Sandor GyorkeAbstract:Key points Phosphorylation at Ser-2808 is suggested to result in RyR2 hyperactivity, i.e. ‘leakiness’, thus contributing to the pathology of cardiac diseases. We studied the effect of disabling phosphorylation at Ser-2808 of RyR2 in a genetic model of Ca2+-dependent cardiomyopathy, which was caused by leaky RyR2. RyR2 phosphorylation was high at Ser-2808 in myocytes expressing wild-type (WT) RyR2; protein phosphatase increased RyR2 leakiness in cells expressing WT, but not in mutant RyR2s with disabled Ser-2808 phosphorylation sites. Rather than alleviating cardiac disease, ablation of the Ser-2808 exacerbated the disease phenotype by reducing survival, impairing in vivo cardiac function and enhancing RyR2 Ca2+ leak and mitochondrial damage. These results suggest a novel mode of RyR2 regulation via dephosphorylation at Ser-2808 in normal and diseased hearts. Abstract Phosphorylation of the cardiac Ryanodine Receptor (RyR2) by protein kinase A (PKA) at Ser-2808 is suggested to mediate the physiological ‘fight or flight’ response and contribute to heart failure by rendering the sarcoplasmic reticulum (SR) leaky for Ca2+. In the present study, we examined the potential role of RyR2 phosphorylation at Ser-2808 in the progression of Ca2+-dependent cardiomyopathy (CCM) by using mice genetically modified to feature elevated SR Ca2+ leak while expressing RyR2s that cannot be phosphorylated at this site (S2808A). Surprisingly, rather than alleviating the disease phenotype, constitutive dephosphorylation of Ser-2808 aggravated CCM as manifested by shortened survival, deteriorated in vivo cardiac function, exacerbated SR Ca2+ leak and mitochondrial injury. Notably, the deteriorations of cardiac function, myocyte Ca2+ handling, and mitochondria integrity were consistently worse in mice with heterozygous ablation of Ser-2808 than in mice with complete ablation. Wild-type (WT) and CCM myocytes expressing unmutated RyR2s exhibited a high level of baseline phosphorylation at Ser-2808. Exposure of these CCM cells to protein phosphatase 1 caused a transitory increase in Ca2+ leak attributable to partial dephosphorylation of RyR2 tetramers at Ser-2808 from more fully phosphorylated state. Thus, exacerbated Ca2+ leak through partially dephosphorylated RyR2s accounts for the prevalence of the disease phenotype in the heterozygous S2808A CCM mice. These results do not support the importance of RyR2 hyperphosphorylation in Ca2+-dependent heart disease, and rather suggest roles for the opposite process, the RyR2 dephosphorylation at this residue in physiological and pathophysiological Ca2+ signalling.
Alfred L George - One of the best experts on this subject based on the ideXlab platform.
-
divergent regulation of Ryanodine Receptor 2 calcium release channels by arrhythmogenic human calmodulin missense mutants
Circulation Research, 2014Co-Authors: Hyun Seok Hwang, Derek R Laver, Yi Yang, Florentin R Nitu, Christopher N. Johnson, Walter J. Chazin, Kafa Walweel, Laetitia Pereira, Michela Faggioni, Alfred L GeorgeAbstract:Rationale:Calmodulin (CaM) mutations are associated with an autosomal dominant syndrome of ventricular arrhythmia and sudden death that can present with divergent clinical features of catecholaminergic polymorphic ventricular tachycardia (CPVT) or long QT syndrome (LQTS). CaM binds to and inhibits Ryanodine Receptor (RyR2) Ca release channels in the heart, but whether arrhythmogenic CaM mutants alter RyR2 function is not known. Objective:To gain mechanistic insight into how human CaM mutations affect RyR2 Ca channels. Methods and Results:We studied recombinant CaM mutants associated with CPVT (N54I and N98S) or LQTS (D96V, D130G, and F142L). As a group, all LQTS-associated CaM mutants (LQTS-CaMs) exhibited reduced Ca affinity, whereas CPVT-associated CaM mutants (CPVT-CaMs) had either normal or modestly lower Ca affinity. In permeabilized ventricular myocytes, CPVT-CaMs at a physiological intracellular concentration (100 nmol/L) promoted significantly higher spontaneous Ca wave and spark activity, a typic...
-
divergent regulation of Ryanodine Receptor 2 calcium release channels by arrhythmogenic human calmodulin missense mutantsnovelty and significance
Circulation Research, 2014Co-Authors: Hyun Seok Hwang, Derek R Laver, Yi Yang, Florentin R Nitu, Christopher N. Johnson, Walter J. Chazin, Kafa Walweel, Laetitia Pereira, Michela Faggioni, Alfred L GeorgeAbstract:Rationale: Calmodulin (CaM) mutations are associated with an autosomal dominant syndrome of ventricular arrhythmia and sudden death that can present with divergent clinical features of catecholaminergic polymorphic ventricular tachycardia (CPVT) or long QT syndrome (LQTS). CaM binds to and inhibits Ryanodine Receptor (RyR2) Ca release channels in the heart, but whether arrhythmogenic CaM mutants alter RyR2 function is not known. Objective: To gain mechanistic insight into how human CaM mutations affect RyR2 Ca channels. Methods and Results: We studied recombinant CaM mutants associated with CPVT (N54I and N98S) or LQTS (D96V, D130G, and F142L). As a group, all LQTS-associated CaM mutants (LQTS-CaMs) exhibited reduced Ca affinity, whereas CPVT-associated CaM mutants (CPVT-CaMs) had either normal or modestly lower Ca affinity. In permeabilized ventricular myocytes, CPVT-CaMs at a physiological intracellular concentration (100 nmol/L) promoted significantly higher spontaneous Ca wave and spark activity, a typical cellular phenotype of CPVT. Compared with wild-type CaM, CPVT-CaMs caused greater RyR2 single-channel open probability and showed enhanced binding affinity to RyR2. Even a 1:8 mixture of CPVT-CaM:wild-type-CaM activated Ca waves, demonstrating functional dominance. In contrast, LQTS-CaMs did not promote Ca waves and exhibited either normal regulation of RyR2 single channels (D96V) or lower RyR2-binding affinity (D130G and F142L). None of the CaM mutants altered Ca/CaM binding to CaM-kinase II. Conclusions: A small proportion of CPVT-CaM is sufficient to evoke arrhythmogenic Ca disturbances, whereas LQTS-CaMs do not. Our findings explain the clinical presentation and autosomal dominant inheritance of CPVT-CaM mutations and suggest that RyR2 interactions are unlikely to explain arrhythmogenicity of LQTS-CaM mutations. # Novelty and Significance {#article-title-50}
Sandor Gyorke - One of the best experts on this subject based on the ideXlab platform.
-
muscarinic stimulation facilitates sarcoplasmic reticulum ca release by modulating Ryanodine Receptor 2 phosphorylation through protein kinase g and ca calmodulin dependent protein kinase ii
Hypertension, 2016Co-Authors: Hsiangting Ho, Andriy E Belevych, Ingrid M Bonilla, Przemyslaw B Radwanski, Igor V Kubasov, Hector H Valdivia, Karsten E Schober, Cynthia A Carnes, Sandor GyorkeAbstract:Although the effects and the underlying mechanism of sympathetic stimulation on cardiac Ca handling are relatively well established both in health and disease, the modes of action and mechanisms of parasympathetic modulation are poorly defined. Here, we demonstrate that parasympathetic stimulation initiates a novel mode of excitation–contraction coupling that enhances the efficiency of cardiac sarcoplasmic reticulum Ca store utilization. This efficient mode of excitation–contraction coupling involves reciprocal changes in the phosphorylation of Ryanodine Receptor 2 at Ser-2808 and Ser-2814. Specifically, Ser-2808 phosphorylation was mediated by muscarinic Receptor subtype 2 and activation of PKG (protein kinase G), whereas dephosphorylation of Ser-2814 involved activation of muscarinic Receptor subtype 3 and decreased reactive oxygen species–dependent activation of CaMKII (Ca/calmodulin-dependent protein kinase II). The overall effect of these changes in phosphorylation of Ryanodine Receptor 2 is an increase in systolic Ca release at the low sarcoplasmic reticulum Ca content and a paradoxical reduction in aberrant Ca leak. Accordingly, cholinergic stimulation of cardiomyocytes isolated from failing hearts improved Ca cycling efficiency by restoring altered Ryanodine Receptor 2 phosphorylation balance.
-
genetic ablation of Ryanodine Receptor 2 phosphorylation at ser 2808 aggravates ca2 dependent cardiomyopathy by exacerbating diastolic ca2 release
The Journal of Physiology, 2014Co-Authors: Hsiangting Ho, Hector H Valdivia, Carmen R Valdivia, Björn C. Knollmann, Florencia Velezcortes, Sandor GyorkeAbstract:Key points Phosphorylation at Ser-2808 is suggested to result in RyR2 hyperactivity, i.e. ‘leakiness’, thus contributing to the pathology of cardiac diseases. We studied the effect of disabling phosphorylation at Ser-2808 of RyR2 in a genetic model of Ca2+-dependent cardiomyopathy, which was caused by leaky RyR2. RyR2 phosphorylation was high at Ser-2808 in myocytes expressing wild-type (WT) RyR2; protein phosphatase increased RyR2 leakiness in cells expressing WT, but not in mutant RyR2s with disabled Ser-2808 phosphorylation sites. Rather than alleviating cardiac disease, ablation of the Ser-2808 exacerbated the disease phenotype by reducing survival, impairing in vivo cardiac function and enhancing RyR2 Ca2+ leak and mitochondrial damage. These results suggest a novel mode of RyR2 regulation via dephosphorylation at Ser-2808 in normal and diseased hearts. Abstract Phosphorylation of the cardiac Ryanodine Receptor (RyR2) by protein kinase A (PKA) at Ser-2808 is suggested to mediate the physiological ‘fight or flight’ response and contribute to heart failure by rendering the sarcoplasmic reticulum (SR) leaky for Ca2+. In the present study, we examined the potential role of RyR2 phosphorylation at Ser-2808 in the progression of Ca2+-dependent cardiomyopathy (CCM) by using mice genetically modified to feature elevated SR Ca2+ leak while expressing RyR2s that cannot be phosphorylated at this site (S2808A). Surprisingly, rather than alleviating the disease phenotype, constitutive dephosphorylation of Ser-2808 aggravated CCM as manifested by shortened survival, deteriorated in vivo cardiac function, exacerbated SR Ca2+ leak and mitochondrial injury. Notably, the deteriorations of cardiac function, myocyte Ca2+ handling, and mitochondria integrity were consistently worse in mice with heterozygous ablation of Ser-2808 than in mice with complete ablation. Wild-type (WT) and CCM myocytes expressing unmutated RyR2s exhibited a high level of baseline phosphorylation at Ser-2808. Exposure of these CCM cells to protein phosphatase 1 caused a transitory increase in Ca2+ leak attributable to partial dephosphorylation of RyR2 tetramers at Ser-2808 from more fully phosphorylated state. Thus, exacerbated Ca2+ leak through partially dephosphorylated RyR2s accounts for the prevalence of the disease phenotype in the heterozygous S2808A CCM mice. These results do not support the importance of RyR2 hyperphosphorylation in Ca2+-dependent heart disease, and rather suggest roles for the opposite process, the RyR2 dephosphorylation at this residue in physiological and pathophysiological Ca2+ signalling.
-
Genetic ablation of Ryanodine Receptor 2 phosphorylation at Ser‐2808 aggravates Ca2+‐dependent cardiomyopathy by exacerbating diastolic Ca2+ release
The Journal of Physiology, 2014Co-Authors: Hsiangting Ho, Hector H Valdivia, Carmen R Valdivia, Björn C. Knollmann, Florencia Velez-cortes, Sandor GyorkeAbstract:Key points Phosphorylation at Ser-2808 is suggested to result in RyR2 hyperactivity, i.e. ‘leakiness’, thus contributing to the pathology of cardiac diseases. We studied the effect of disabling phosphorylation at Ser-2808 of RyR2 in a genetic model of Ca2+-dependent cardiomyopathy, which was caused by leaky RyR2. RyR2 phosphorylation was high at Ser-2808 in myocytes expressing wild-type (WT) RyR2; protein phosphatase increased RyR2 leakiness in cells expressing WT, but not in mutant RyR2s with disabled Ser-2808 phosphorylation sites. Rather than alleviating cardiac disease, ablation of the Ser-2808 exacerbated the disease phenotype by reducing survival, impairing in vivo cardiac function and enhancing RyR2 Ca2+ leak and mitochondrial damage. These results suggest a novel mode of RyR2 regulation via dephosphorylation at Ser-2808 in normal and diseased hearts. Abstract Phosphorylation of the cardiac Ryanodine Receptor (RyR2) by protein kinase A (PKA) at Ser-2808 is suggested to mediate the physiological ‘fight or flight’ response and contribute to heart failure by rendering the sarcoplasmic reticulum (SR) leaky for Ca2+. In the present study, we examined the potential role of RyR2 phosphorylation at Ser-2808 in the progression of Ca2+-dependent cardiomyopathy (CCM) by using mice genetically modified to feature elevated SR Ca2+ leak while expressing RyR2s that cannot be phosphorylated at this site (S2808A). Surprisingly, rather than alleviating the disease phenotype, constitutive dephosphorylation of Ser-2808 aggravated CCM as manifested by shortened survival, deteriorated in vivo cardiac function, exacerbated SR Ca2+ leak and mitochondrial injury. Notably, the deteriorations of cardiac function, myocyte Ca2+ handling, and mitochondria integrity were consistently worse in mice with heterozygous ablation of Ser-2808 than in mice with complete ablation. Wild-type (WT) and CCM myocytes expressing unmutated RyR2s exhibited a high level of baseline phosphorylation at Ser-2808. Exposure of these CCM cells to protein phosphatase 1 caused a transitory increase in Ca2+ leak attributable to partial dephosphorylation of RyR2 tetramers at Ser-2808 from more fully phosphorylated state. Thus, exacerbated Ca2+ leak through partially dephosphorylated RyR2s accounts for the prevalence of the disease phenotype in the heterozygous S2808A CCM mice. These results do not support the importance of RyR2 hyperphosphorylation in Ca2+-dependent heart disease, and rather suggest roles for the opposite process, the RyR2 dephosphorylation at this residue in physiological and pathophysiological Ca2+ signalling.
Hector H Valdivia - One of the best experts on this subject based on the ideXlab platform.
-
phosphorylation of the Ryanodine Receptor 2 at serine 2030 is required for a complete β adrenergic response
The Journal of General Physiology, 2019Co-Authors: Duilio Michele Potenza, Hector H Valdivia, Radoslav Janicek, Miguel Fernandeztenorio, Emmanuel Camors, Roberto Ramosmondragon, Ernst NiggliAbstract:During physical exercise or stress, the sympathetic system stimulates cardiac contractility via β-adrenergic Receptor (β-AR) activation, resulting in protein kinase A (PKA)–mediated phosphorylation of the cardiac Ryanodine Receptor RyR2. PKA-dependent “hyperphosphorylation” of the RyR2 channel has been proposed as a major impairment that contributes to progression of heart failure. However, the sites of PKA phosphorylation and their phosphorylation status in cardiac diseases are not well defined. Among the known RyR2 phosphorylation sites, serine 2030 (S2030) remains highly controversial as a site of functional impact. We examined the contribution of RyR2-S2030 to Ca2+ signaling and excitation–contraction coupling (ECC) in a transgenic mouse with an ablated RyR2-S2030 phosphorylation site (RyR2-S2030A+/+). We assessed ECC gain by using whole-cell patch–clamp recordings and confocal Ca2+ imaging during β-ARs stimulation with isoproterenol (Iso) and consistent SR Ca2+ loading and L-type Ca2+ current (ICa) triggering. Under these conditions, ECC gain is diminished in mutant compared with WT cardiomyocytes. Resting Ca2+ spark frequency (CaSpF) with Iso is also reduced by mutation of S2030. In permeabilized cells, when SR Ca2+ pump activity is kept constant (using 2D12 antibody against phospholamban), cAMP does not change CaSpF in S2030A+/+ myocytes. Using Ca2+ spark recovery analysis, we found that mutant RyR Ca2+ sensitivity is not enhanced by Iso application, contrary to WT RyRs. Furthermore, ablation of RyR2-S2030 prevents acceleration of Ca2+ waves and increases latency to the first spontaneous Ca2+ release after a train of stimulations during Iso treatment. Together, these results suggest that phosphorylation at S2030 may represent an important step in the modulation of RyR2 activity during β-adrenergic stimulation and a potential target for the development of new antiarrhythmic drugs.
-
muscarinic stimulation facilitates sarcoplasmic reticulum ca release by modulating Ryanodine Receptor 2 phosphorylation through protein kinase g and ca calmodulin dependent protein kinase ii
Hypertension, 2016Co-Authors: Hsiangting Ho, Andriy E Belevych, Ingrid M Bonilla, Przemyslaw B Radwanski, Igor V Kubasov, Hector H Valdivia, Karsten E Schober, Cynthia A Carnes, Sandor GyorkeAbstract:Although the effects and the underlying mechanism of sympathetic stimulation on cardiac Ca handling are relatively well established both in health and disease, the modes of action and mechanisms of parasympathetic modulation are poorly defined. Here, we demonstrate that parasympathetic stimulation initiates a novel mode of excitation–contraction coupling that enhances the efficiency of cardiac sarcoplasmic reticulum Ca store utilization. This efficient mode of excitation–contraction coupling involves reciprocal changes in the phosphorylation of Ryanodine Receptor 2 at Ser-2808 and Ser-2814. Specifically, Ser-2808 phosphorylation was mediated by muscarinic Receptor subtype 2 and activation of PKG (protein kinase G), whereas dephosphorylation of Ser-2814 involved activation of muscarinic Receptor subtype 3 and decreased reactive oxygen species–dependent activation of CaMKII (Ca/calmodulin-dependent protein kinase II). The overall effect of these changes in phosphorylation of Ryanodine Receptor 2 is an increase in systolic Ca release at the low sarcoplasmic reticulum Ca content and a paradoxical reduction in aberrant Ca leak. Accordingly, cholinergic stimulation of cardiomyocytes isolated from failing hearts improved Ca cycling efficiency by restoring altered Ryanodine Receptor 2 phosphorylation balance.
-
genetic ablation of Ryanodine Receptor 2 phosphorylation at ser 2808 aggravates ca2 dependent cardiomyopathy by exacerbating diastolic ca2 release
The Journal of Physiology, 2014Co-Authors: Hsiangting Ho, Hector H Valdivia, Carmen R Valdivia, Björn C. Knollmann, Florencia Velezcortes, Sandor GyorkeAbstract:Key points Phosphorylation at Ser-2808 is suggested to result in RyR2 hyperactivity, i.e. ‘leakiness’, thus contributing to the pathology of cardiac diseases. We studied the effect of disabling phosphorylation at Ser-2808 of RyR2 in a genetic model of Ca2+-dependent cardiomyopathy, which was caused by leaky RyR2. RyR2 phosphorylation was high at Ser-2808 in myocytes expressing wild-type (WT) RyR2; protein phosphatase increased RyR2 leakiness in cells expressing WT, but not in mutant RyR2s with disabled Ser-2808 phosphorylation sites. Rather than alleviating cardiac disease, ablation of the Ser-2808 exacerbated the disease phenotype by reducing survival, impairing in vivo cardiac function and enhancing RyR2 Ca2+ leak and mitochondrial damage. These results suggest a novel mode of RyR2 regulation via dephosphorylation at Ser-2808 in normal and diseased hearts. Abstract Phosphorylation of the cardiac Ryanodine Receptor (RyR2) by protein kinase A (PKA) at Ser-2808 is suggested to mediate the physiological ‘fight or flight’ response and contribute to heart failure by rendering the sarcoplasmic reticulum (SR) leaky for Ca2+. In the present study, we examined the potential role of RyR2 phosphorylation at Ser-2808 in the progression of Ca2+-dependent cardiomyopathy (CCM) by using mice genetically modified to feature elevated SR Ca2+ leak while expressing RyR2s that cannot be phosphorylated at this site (S2808A). Surprisingly, rather than alleviating the disease phenotype, constitutive dephosphorylation of Ser-2808 aggravated CCM as manifested by shortened survival, deteriorated in vivo cardiac function, exacerbated SR Ca2+ leak and mitochondrial injury. Notably, the deteriorations of cardiac function, myocyte Ca2+ handling, and mitochondria integrity were consistently worse in mice with heterozygous ablation of Ser-2808 than in mice with complete ablation. Wild-type (WT) and CCM myocytes expressing unmutated RyR2s exhibited a high level of baseline phosphorylation at Ser-2808. Exposure of these CCM cells to protein phosphatase 1 caused a transitory increase in Ca2+ leak attributable to partial dephosphorylation of RyR2 tetramers at Ser-2808 from more fully phosphorylated state. Thus, exacerbated Ca2+ leak through partially dephosphorylated RyR2s accounts for the prevalence of the disease phenotype in the heterozygous S2808A CCM mice. These results do not support the importance of RyR2 hyperphosphorylation in Ca2+-dependent heart disease, and rather suggest roles for the opposite process, the RyR2 dephosphorylation at this residue in physiological and pathophysiological Ca2+ signalling.
-
Genetic ablation of Ryanodine Receptor 2 phosphorylation at Ser‐2808 aggravates Ca2+‐dependent cardiomyopathy by exacerbating diastolic Ca2+ release
The Journal of Physiology, 2014Co-Authors: Hsiangting Ho, Hector H Valdivia, Carmen R Valdivia, Björn C. Knollmann, Florencia Velez-cortes, Sandor GyorkeAbstract:Key points Phosphorylation at Ser-2808 is suggested to result in RyR2 hyperactivity, i.e. ‘leakiness’, thus contributing to the pathology of cardiac diseases. We studied the effect of disabling phosphorylation at Ser-2808 of RyR2 in a genetic model of Ca2+-dependent cardiomyopathy, which was caused by leaky RyR2. RyR2 phosphorylation was high at Ser-2808 in myocytes expressing wild-type (WT) RyR2; protein phosphatase increased RyR2 leakiness in cells expressing WT, but not in mutant RyR2s with disabled Ser-2808 phosphorylation sites. Rather than alleviating cardiac disease, ablation of the Ser-2808 exacerbated the disease phenotype by reducing survival, impairing in vivo cardiac function and enhancing RyR2 Ca2+ leak and mitochondrial damage. These results suggest a novel mode of RyR2 regulation via dephosphorylation at Ser-2808 in normal and diseased hearts. Abstract Phosphorylation of the cardiac Ryanodine Receptor (RyR2) by protein kinase A (PKA) at Ser-2808 is suggested to mediate the physiological ‘fight or flight’ response and contribute to heart failure by rendering the sarcoplasmic reticulum (SR) leaky for Ca2+. In the present study, we examined the potential role of RyR2 phosphorylation at Ser-2808 in the progression of Ca2+-dependent cardiomyopathy (CCM) by using mice genetically modified to feature elevated SR Ca2+ leak while expressing RyR2s that cannot be phosphorylated at this site (S2808A). Surprisingly, rather than alleviating the disease phenotype, constitutive dephosphorylation of Ser-2808 aggravated CCM as manifested by shortened survival, deteriorated in vivo cardiac function, exacerbated SR Ca2+ leak and mitochondrial injury. Notably, the deteriorations of cardiac function, myocyte Ca2+ handling, and mitochondria integrity were consistently worse in mice with heterozygous ablation of Ser-2808 than in mice with complete ablation. Wild-type (WT) and CCM myocytes expressing unmutated RyR2s exhibited a high level of baseline phosphorylation at Ser-2808. Exposure of these CCM cells to protein phosphatase 1 caused a transitory increase in Ca2+ leak attributable to partial dephosphorylation of RyR2 tetramers at Ser-2808 from more fully phosphorylated state. Thus, exacerbated Ca2+ leak through partially dephosphorylated RyR2s accounts for the prevalence of the disease phenotype in the heterozygous S2808A CCM mice. These results do not support the importance of RyR2 hyperphosphorylation in Ca2+-dependent heart disease, and rather suggest roles for the opposite process, the RyR2 dephosphorylation at this residue in physiological and pathophysiological Ca2+ signalling.