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Advances in Experimental Medicine and... 2024This chapter will describe basic structural and functional features of the contractile apparatus of muscle cells of the heart, namely, cardiomyocytes and smooth muscle... (Review)
Review
This chapter will describe basic structural and functional features of the contractile apparatus of muscle cells of the heart, namely, cardiomyocytes and smooth muscle cells. Cardiomyocytes form the contractile myocardium of the heart, while smooth muscle cells form the contractile coronary vessels. Both muscle types have distinct properties and will be considered with respect to their cellular appearance (brick-like cross-striated versus spindle-like smooth), arrangement of contractile proteins (sarcomeric versus non-sarcomeric organization), calcium activation mechanisms (thin-filament versus thick-filament regulation), contractile features (fast and phasic versus slow and tonic), energy metabolism (high oxygen versus low oxygen demand), molecular motors (type II myosin isoenzymes with high adenosine diphosphate [ADP]-release rate versus myosin isoenzymes with low ADP-release rates), chemomechanical energy conversion (high adenosine triphosphate [ATP] consumption and short duty ratio versus low ATP consumption and high duty ratio of myosin II cross-bridges [XBs]), and excitation-contraction coupling (calcium-induced calcium release versus pharmacomechanical coupling). Part of the work has been published (Neuroscience - From Molecules to Behavior", Chap. 22, Galizia and Lledo eds 2013, Springer-Verlag; with kind permission from Springer Science + Business Media).
Topics: Humans; Myocardial Contraction; Animals; Myocytes, Cardiac; Calcium; Energy Metabolism; Myocytes, Smooth Muscle; Excitation Contraction Coupling
PubMed: 38884723
DOI: 10.1007/978-3-031-44087-8_21 -
Nature Communications Jun 2024Calmodulin transduces [Ca] information regulating the rhythmic Ca cycling between the sarcoplasmic reticulum and cytoplasm during contraction and relaxation in cardiac...
Calmodulin transduces [Ca] information regulating the rhythmic Ca cycling between the sarcoplasmic reticulum and cytoplasm during contraction and relaxation in cardiac and skeletal muscle. However, the structural dynamics by which calmodulin modulates the sarcoplasmic reticulum Ca release channel, the ryanodine receptor, at physiologically relevant [Ca] is unknown. Using fluorescence lifetime FRET, we resolve different structural states of calmodulin and Ca-driven shifts in the conformation of calmodulin bound to ryanodine receptor. Skeletal and cardiac ryanodine receptor isoforms show different calmodulin-ryanodine receptor conformations, as well as binding and structural kinetics with 0.2-ms resolution, which reflect different functional roles of calmodulin. These FRET methods provide insight into the physiological calmodulin-ryanodine receptor structural states, revealing additional distinct structural states that complement cryo-EM models that are based on less physiological conditions. This technology will drive future studies on pathological calmodulin-ryanodine receptor interactions and dynamics with other important ryanodine receptor bound modulators.
Topics: Ryanodine Receptor Calcium Release Channel; Calmodulin; Calcium; Myocardium; Kinetics; Animals; Muscle, Skeletal; Fluorescence Resonance Energy Transfer; Humans; Protein Conformation; Protein Binding; Sarcoplasmic Reticulum
PubMed: 38879623
DOI: 10.1038/s41467-024-48951-5 -
The Journal of Physical Chemistry. B Jun 2024Defects in the binding of the calcium sensing protein calmodulin (CaM) to the L-type calcium channel (Ca1.2) or to the ryanodine receptor type 2 (RyR2) can lead to...
Defects in the binding of the calcium sensing protein calmodulin (CaM) to the L-type calcium channel (Ca1.2) or to the ryanodine receptor type 2 (RyR2) can lead to dangerous cardiac arrhythmias with distinct phenotypes, such as long-QT syndrome (LQTS) and catecholaminergic ventricular tachycardia (CPVT). Certain CaM mutations lead to LQTS while other mutations lead to CPVT, but the mechanisms by which a specific mutation can lead to each disease phenotype are not well-understood. In this study, we use long, 2 μs molecular dynamics simulations and a multitrajectory approach to identify the key binding interactions between the IQ domain of Ca1.2 and CaM. Five key interactions are found between Ca1.2 and CaM in the C-lobe, 1 in the central linker, and 2 in the N-lobe. In addition, while 5 key interactions appear between residues 120-149 in the C-lobe of CaM when it interacts with Ca1.2, only 1 key interaction is found within this region of CaM when it interacts with the RyR2. We show that this difference in the distribution of key interactions correlates with the known distribution of CaM mutations that lead to LQTS or CPVT. This correlation suggests that a disruption of key binding interactions is a plausible mechanism that can lead to these two different disease phenotypes.
Topics: Calmodulin; Molecular Dynamics Simulation; Calcium Channels, L-Type; Protein Binding; Humans; Binding Sites; Ryanodine Receptor Calcium Release Channel
PubMed: 38870543
DOI: 10.1021/acs.jpcb.4c02251 -
Journal of the American Heart... Jun 2024Chronic sympathetic stimulation drives desensitization and downregulation of β1 adrenergic receptor (βAR) in heart failure. We aim to explore the differential...
BACKGROUND
Chronic sympathetic stimulation drives desensitization and downregulation of β1 adrenergic receptor (βAR) in heart failure. We aim to explore the differential downregulation subcellular pools of βAR signaling in the heart.
METHODS AND RESULTS
We applied chronic infusion of isoproterenol to induced cardiomyopathy in male C57BL/6J mice. We applied confocal and proximity ligation assay to examine βAR association with L-type calcium channel, ryanodine receptor 2, and SERCA2a ((Sarco)endoplasmic reticulum calcium ATPase 2a) and Förster resonance energy transfer-based biosensors to probe subcellular βAR-PKA (protein kinase A) signaling in ventricular myocytes. Chronic infusion of isoproterenol led to reduced βAR protein levels, receptor association with L-type calcium channel and ryanodine receptor 2 measured by proximity ligation (puncta/cell, 29.65 saline versus 14.17 isoproterenol, <0.05), and receptor-induced PKA signaling at the plasma membrane (Förster resonance energy transfer, 28.9% saline versus 1.9% isoproterenol, <0.05) and ryanodine receptor 2 complex (Förster resonance energy transfer, 30.2% saline versus 10.6% isoproterenol, <0.05). However, the βAR association with SERCA2a was enhanced (puncta/cell, 51.4 saline versus 87.5 isoproterenol, <0.05), and the receptor signal was minimally affected. The isoproterenol-infused hearts displayed decreased PDE4D (phosphodiesterase 4D) and PDE3A and increased PDE2A, PDE4A, and PDE4B protein levels. We observed a reduced role of PDE4 and enhanced roles of PDE2 and PDE3 on the βAR-PKA activity at the ryanodine receptor 2 complexes and myocyte shortening. Despite the enhanced βAR association with SERCA2a, the endogenous norepinephrine-induced signaling was reduced at the SERCA2a complexes. Inhibiting monoamine oxidase A rescued the norepinephrine-induced PKA signaling at the SERCA2a and myocyte shortening.
CONCLUSIONS
This study reveals distinct mechanisms for the downregulation of subcellular βAR signaling in the heart under chronic adrenergic stimulation.
Topics: Animals; Receptors, Adrenergic, beta-1; Male; Down-Regulation; Signal Transduction; Ryanodine Receptor Calcium Release Channel; Mice, Inbred C57BL; Isoproterenol; Cyclic AMP-Dependent Protein Kinases; Myocytes, Cardiac; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Calcium Channels, L-Type; Disease Models, Animal; Mice; Heart Failure; Cardiomyopathies; Fluorescence Resonance Energy Transfer
PubMed: 38860414
DOI: 10.1161/JAHA.123.033733 -
Philosophical Transactions of the Royal... Jul 2024The roles of Ca-induced calcium release in synaptic plasticity and metaplasticity are poorly understood. The present study has addressed the role of intracellular Ca...
The roles of Ca-induced calcium release in synaptic plasticity and metaplasticity are poorly understood. The present study has addressed the role of intracellular Ca stores in long-term potentiation (LTP) and a form of heterosynaptic metaplasticity known as synaptic tagging and capture (STC) at CA1 synapses in mouse hippocampal slices. The effects of two compounds, ryanodine and cyclopiazonic acid (CPA), were examined on LTP induced by three distinct induction protocols: weak (w), compressed (c) and spaced (s) theta-burst stimulation (TBS). These compounds did not significantly affect LTP induced by the wTBS (one episode of TBS; 25 stimuli) or cTBS (three such episodes with a 10 s inter-episode interval (IEI); 75 stimuli) but substantially inhibited LTP induced by a sTBS (10 min IEI; 75 stimuli). Ryanodine and CPA also prevented a small heterosynaptic potentiation that was observed with the sTBS protocol. Interestingly, these compounds also prevented STC when present during either the sTBS or the subsequent wTBS, applied to an independent input. All of these effects of ryanodine and CPA were similar to that of a calcium-permeable AMPA receptor blocker. In conclusion, Ca stores provide one way in which signals are propagated between synaptic inputs and, by virtue of their role in STC, may be involved in associative long-term memories. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.
Topics: Animals; Long-Term Potentiation; Mice; Synapses; Ryanodine; Calcium; Indoles; Hippocampus; Mice, Inbred C57BL; Neuronal Plasticity; CA1 Region, Hippocampal; Male
PubMed: 38853556
DOI: 10.1098/rstb.2023.0241 -
Journal of Molecular and Cellular... Jun 2024Mutations in ubiquitously expressed presenilin genes (PSENs) lead to early-onset familial Alzheimer's disease (FAD), but patients carrying the mutation also suffer from...
Mutations in ubiquitously expressed presenilin genes (PSENs) lead to early-onset familial Alzheimer's disease (FAD), but patients carrying the mutation also suffer from heart diseases. To elucidate the cardiac myocyte specific effects of PSEN ΔE9, we studied cardiomyocytes derived from induced pluripotent stem cells (iPSC-CMs) from patients carrying AD-causing PSEN1 exon 9 deletion (PSEN1 ΔE9). When compared with their isogenic controls, PSEN1 ΔE9 cardiomyocytes showed increased sarcoplasmic reticulum (SR) Ca leak that was resistant to blockage of ryanodine receptors (RyRs) by tetracaine or inositol-3-reseceptors (IPRs) by 2-ABP. The SR Ca leak did not affect electrophysiological properties of the hiPSC-CMs, but according to experiments and in silico simulations the leak induces a diastolic buildup of [Ca] near the perinuclear SR and reduces the releasable Ca during systole. This demonstrates that PSEN1 ΔE9 induced SR Ca leak has specific effects in iPSC-CMs, reflecting their unique structural and calcium signaling features. The results shed light on the physiological and pathological mechanisms of PSEN1 in cardiac myocytes and explain the intricacies of comorbidity associated with AD-causing mutations in PSEN1.
PubMed: 38851626
DOI: 10.1016/j.yjmcc.2024.06.003 -
Handbook of Experimental Pharmacology Jun 2024β-Adrenoceptors (β-ARs) provide an important therapeutic target for the treatment of cardiovascular disease. Three β-ARs, β-AR, β-AR, β-AR are localized to the...
β-Adrenoceptors (β-ARs) provide an important therapeutic target for the treatment of cardiovascular disease. Three β-ARs, β-AR, β-AR, β-AR are localized to the human heart. Activation of β-AR and β-ARs increases heart rate, force of contraction (inotropy) and consequently cardiac output to meet physiological demand. However, in disease, chronic over-activation of β-AR is responsible for the progression of disease (e.g. heart failure) mediated by pathological hypertrophy, adverse remodelling and premature cell death. Furthermore, activation of β-AR is critical in the pathogenesis of cardiac arrhythmias while activation of β-AR directly influences blood pressure haemostasis. There is an increasing awareness of the contribution of β-AR in cardiovascular disease, particularly arrhythmia generation. All β-blockers used therapeutically to treat cardiovascular disease block β-AR with variable blockade of β-AR depending on relative affinity for β-AR vs β-AR. Since the introduction of β-blockers into clinical practice in 1965, β-blockers with different properties have been trialled, used and evaluated, leading to better understanding of their therapeutic effects and tolerability in various cardiovascular conditions. β-Blockers with the property of intrinsic sympathomimetic activity (ISA), i.e. β-blockers that also activate the receptor, were used in the past for post-treatment of myocardial infarction and had limited use in heart failure. The β-blocker carvedilol continues to intrigue due to numerous properties that differentiate it from other β-blockers and is used successfully in the treatment of heart failure. The discovery of β-AR in human heart created interest in the role of β-AR in heart failure but has not resulted in therapeutics at this stage.
PubMed: 38844580
DOI: 10.1007/164_2024_720 -
International Heart Journal 2024Cardiac ryanodine receptor (RyR2) gain-of-function mutations cause catecholaminergic polymorphic ventricular tachycardia (CPVT). Conversely, RyR2 loss-of-function...
Cardiac ryanodine receptor (RyR2) gain-of-function mutations cause catecholaminergic polymorphic ventricular tachycardia (CPVT). Conversely, RyR2 loss-of-function mutations cause a new disease entity, termed calcium release deficiency syndrome (CRDS), which may include RYR2-related long QT syndrome (LQTS). Importantly, unlike CPVT, patients with CRDS do not always exhibit exercise- or epinephrine-induced ventricular arrhythmias, which precludes a diagnosis of CRDS. Here we report a boy and his father, who both experienced exercise-induced cardiac events and harbor the same RYR2 E4107A variant. In the boy, an exercise stress test (EST) and epinephrine provocation test (EPT) did not induce any ventricular arrhythmias. QTc was slightly prolonged (QTc: 474 ms), and an EPT induced QTc prolongation (QTc-baseline: 466 ms, peak: 532 ms, steady-state: 527 ms). In contrast, in his father, QTc was not prolonged (QTc: 417 ms), and neither an EST nor EPT induced QTc prolongation. However, an EST induced multifocal premature ventricular contraction (PVC) bigeminy and bidirectional PVC couplets. Thus, they exhibited distinct clinical phenotypes: the boy exhibited LQTS (or CRDS) phenotype, whereas his father exhibited CPVT phenotype. These findings suggest that, in addition to the altered RyR2 function, other unidentified factors, such as other genetic, epigenetic, and environmental factors, and aging, may be involved in the diverse phenotypic manifestations. Considering that a single RYR2 variant can cause both CPVT and LQTS (or CRDS) phenotypes, in cascade screening of patients with CPVT and CRDS, an EST and EPT are not sufficient and genetic analysis is required to identify individuals who are at increased risk for life-threatening arrhythmias.
Topics: Humans; Ryanodine Receptor Calcium Release Channel; Male; Long QT Syndrome; Phenotype; Tachycardia, Ventricular; Electrocardiography; Pedigree; Adult; Exercise Test; Mutation
PubMed: 38825499
DOI: 10.1536/ihj.23-652 -
Biochemical and Biophysical Research... Sep 2024Excitation-contraction coupling in skeletal muscle myofibers depends upon Ca release from the sarcoplasmic reticulum through the ryanodine receptor/Ca-release channel...
Excitation-contraction coupling in skeletal muscle myofibers depends upon Ca release from the sarcoplasmic reticulum through the ryanodine receptor/Ca-release channel RyR1. The RyR1 contains ∼100 Cys thiols of which ∼30 comprise an allosteric network subject to posttranslational modification by S-nitrosylation, S-palmitoylation and S-oxidation. However, the role and function of these modifications is not understood. Although aberrant S-nitrosylation of multiple unidentified sites has been associated with dystrophic diseases, malignant hyperthermia and other myopathic syndromes, S-nitrosylation in physiological situations is reportedly specific to a single (1 of ∼100) Cys in RyR1, Cys in a manner gated by pO. Using mice expressing a form of RyR1 with a Cys→Ala point mutation to prevent S-nitrosylation at this site, we showed that Cys was the principal target of endogenous S-nitrosylation during normal muscle function. The absence of Cys S-nitrosylation suppressed stimulus-evoked Ca release at physiological pO (at least in part by altering the regulation of RyR1 by Ca/calmodulin), eliminated pO coupling, and diminished skeletal myocyte contractility in vitro and measures of muscle strength in vivo. Furthermore, we found that abrogation of Cys S-nitrosylation resulted in a developmental defect reflected in diminished myofiber diameter, altered fiber subtypes, and altered expression of genes implicated in muscle development and atrophy. Thus, our findings establish a physiological role for pO-coupled S-nitrosylation of RyR1 in skeletal muscle contractility and development and provide foundation for future studies of RyR1 modifications in physiology and disease.
Topics: Ryanodine Receptor Calcium Release Channel; Animals; Muscle, Skeletal; Mice; Calcium; Cysteine; Protein Processing, Post-Translational; Muscle Development; Mice, Transgenic; Calcium Signaling
PubMed: 38820626
DOI: 10.1016/j.bbrc.2024.150163 -
American Journal of Physiology. Heart... May 2024The EF-hand calcium (Ca) sensor protein S100A1 combines inotropic with antiarrhythmic potency in cardiomyocytes (CM). Oxidative posttranslational modification (ox-PTM)...
The EF-hand calcium (Ca) sensor protein S100A1 combines inotropic with antiarrhythmic potency in cardiomyocytes (CM). Oxidative posttranslational modification (ox-PTM) of S100A1's conserved, single cysteine residue (C85) via reactive nitrogen species (i.e. S-nitrosylation or glutathionylation) has been proposed to modulate conformational flexibility of intrinsically disordered sequence fragments and to increase the molecule's affinity towards Ca. In light of the unknown biological functional consequence, we aimed to determine the impact of the C85 moiety of S100A1 as a potential redox-switch. We first uncovered that S100A1 is endogenously glutathionylated in the adult heart in vivo. To prevent glutathionylation of S100A1, we generated S100A1 variants that were unresponsive to ox-PTMs. Overexpression of wildtype (WT) and C85-deficient S100A1 protein variants in isolated CM demonstrated equal inotropic potency, as shown by equally augmented Ca transient amplitudes under basal conditions and β-adrenergic receptor (βAR) stimulation. However, in contrast ox-PTM defective S100A1 variants failed to protect against arrhythmogenic diastolic sarcoplasmic reticulum (SR) Ca waves and ryanodine receptor (RyR2) hypernitrosylation during β-AR stimulation. Despite diastolic performance failure, C85-deficient S100A1 protein variants exerted similar Ca-dependent interaction with the RyR2 than WT-S100A1. Dissecting S100A1's molecular structure-function relationship, our data indicate for the first time that the conserved C85 residue potentially acts as a redox-switch that is indispensable for S100A1's antiarrhythmic but not its inotropic potency in CM. We therefore propose a model where C85's ox-PTM determines S100A1's ability to beneficially control diastolic but not systolic RyR2 activity.
PubMed: 38819384
DOI: 10.1152/ajpheart.00634.2023