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Seizure Apr 2024
Topics: Humans; Ryanodine Receptor Calcium Release Channel; Tachycardia, Ventricular; Epilepsy, Generalized; Male; Female; Mutation
PubMed: 38583245
DOI: 10.1016/j.seizure.2024.04.003 -
Stem Cell Research Jun 2024RYR1 variants are a common cause of congenital myopathies, including multi-minicore disease (MmD) and central core disease (CCD). Here, we generated iPSC lines from two...
RYR1 variants are a common cause of congenital myopathies, including multi-minicore disease (MmD) and central core disease (CCD). Here, we generated iPSC lines from two CCD patients with dominant RYR1 missense variants that affect the transmembrane (pore) and SPRY3 protein domains (p.His4813Tyr and p.Asn1346Lys, respectively). Both lines had typical iPSC morphology, expressed canonical pluripotency markers, exhibited trilineage differentiation potential, and had normal karyotypes. Together with existing RYR1 iPSC lines, these represent important tools to study and develop treatments for RYR1-related myopathies.
Topics: Humans; Ryanodine Receptor Calcium Release Channel; Induced Pluripotent Stem Cells; Mutation, Missense; Myopathy, Central Core; Adult; Cell Line; Male; Cell Differentiation; Female
PubMed: 38582058
DOI: 10.1016/j.scr.2024.103411 -
MedRxiv : the Preprint Server For... Mar 2024Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare inherited arrhythmia caused by mutations in the ryanodine receptor type 2 (RyR2). Diagnosis of...
Location of ryanodine receptor type 2 mutation predicts age of onset of sudden death in catecholaminergic polymorphic ventricular tachycardia - A systematic review and meta-analysis of case-based literature.
BACKGROUND
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare inherited arrhythmia caused by mutations in the ryanodine receptor type 2 (RyR2). Diagnosis of CPVT often occurs after a major cardiac event, thus posing a severe threat to the patient's health.
METHODS
Publication databases, including PubMed, Scopus, and Embase, were searched for articles on patients with RyR2-CPVT mutations and their associated clinical presentation. Articles were reviewed by two independent reviewers and mutations were analyzed for demographic information, mutation distribution, and therapeutics. The human RyR2 cryo-EM structure was used to model CPVT mutations and predict the diagnosis and outcomes of CPVT patients.
FINDINGS
We present a database of 1008 CPVT patients from 227 papers. Data analyses revealed that patients most often experienced exercise-induced syncope in their early teenage years but the diagnosis of CPVT took a decade. Mutations located near key regulatory sites in the channel were associated with earlier onset of CPVT symptoms including sudden cardiac death.
INTERPRETATION
The present study provides a road map for predicting clinical outcomes based on the location of RyR2 mutations in CPVT patients. The study was partially limited by the inconsistency in the depth of information provided in each article, but nevertheless is an important contribution to the understanding of the clinical and molecular basis of CPVT and suggests the need for early diagnosis and creative approaches to disease management.
FUNDING
The work was supported by grant NIH R01HL145473, P01 HL164319 R25HL156002, T32 HL120826.
PubMed: 38559077
DOI: 10.1101/2024.03.15.24304349 -
International Journal of Molecular... Mar 2024Malignant hyperthermia (MH) is a pharmacogenetic condition of skeletal muscle that manifests in hypermetabolic responses upon exposure to volatile anaesthetics. This...
Malignant hyperthermia (MH) is a pharmacogenetic condition of skeletal muscle that manifests in hypermetabolic responses upon exposure to volatile anaesthetics. This condition is caused primarily by pathogenic variants in the calcium-release channel RYR1, which disrupts calcium signalling in skeletal muscle. However, our understanding of MH genetics is incomplete, with no variant identified in a significant number of cases and considerable phenotype diversity. In this study, we applied a transcriptomic approach to investigate the genome-wide gene expression in MH-susceptible cases using muscle biopsies taken for diagnostic testing. Baseline comparisons between muscle from MH-susceptible individuals (MHS, = 8) and non-susceptible controls (MHN, = 4) identified 822 differentially expressed genes (203 upregulated and 619 downregulated) with significant enrichment in genes associated with oxidative phosphorylation (OXPHOS) and fatty acid metabolism. Investigations of 10 OXPHOS target genes in a larger cohort (MHN: = 36; MHS: = 36) validated the reduced expression of and in MHS samples, but the remaining 8 selected were not statistically significant. Further analysis also identified evidence of a sex-linked effect in and expression, and a difference in expression across individuals with MH sub-phenotypes (trigger from in vitro halothane exposure only, MHS ( = 4); trigger to both in vitro halothane and caffeine exposure, MHS ( = 4)). Our data support a link between MH-susceptibility and dysregulated gene expression associated with mitochondrial bioenergetics, which we speculate plays a role in the phenotypic variability observed within MH.
Topics: Humans; Malignant Hyperthermia; Halothane; Oxidative Phosphorylation; Calcium; Muscle, Skeletal; Disease Susceptibility; Biopsy; Gene Expression; Muscle Contraction; Ryanodine Receptor Calcium Release Channel; Carrier Proteins
PubMed: 38542460
DOI: 10.3390/ijms25063489 -
Journal of Clinical Medicine Mar 2024Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a severe hereditary arrhythmia syndrome predominantly affecting children and young adults. It manifests... (Review)
Review
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a severe hereditary arrhythmia syndrome predominantly affecting children and young adults. It manifests through bidirectional or polymorphic ventricular arrhythmia, often culminating in syncope triggered by physical exertion or emotional stress which can lead to sudden cardiac death. Most cases stem from mutations in the gene responsible for encoding the cardiac ryanodine receptor (), or in the Calsequestrin 2 gene (), disrupting the handling of calcium ions within the cardiac myocyte sarcoplasmic reticulum. Diagnosing CPVT typically involves unmasking the arrhythmia through exercise stress testing. This diagnosis emerges in the absence of structural heart disease by cardiac imaging and with a normal baseline electrocardiogram. Traditional first-line treatment primarily involves β-blocker therapy, significantly reducing CPVT-associated mortality. Adjunctive therapies such as moderate exercise training, flecainide, left cardiac sympathetic denervation and implantable cardioverter-defibrillators have been utilized with reasonable success. However, the spectrum of options for managing CPVT has expanded over time, demonstrating decreased rates of arrhythmic events. Furthermore, ongoing research into potential new therapies including gene therapies has the potential to further enhance treatment paradigms. This review aims to succinctly encapsulate the contemporary understanding of the clinical characteristics, diagnostic approach, established therapeutic interventions and the promising future directions in managing CPVT.
PubMed: 38542006
DOI: 10.3390/jcm13061781 -
Biomedicines Feb 2024Glutamate is a major excitatory neurotransmitter that mediates neuronal damage in acute and chronic brain disorders. The effect and mechanism of phillygenin, a natural...
Glutamate is a major excitatory neurotransmitter that mediates neuronal damage in acute and chronic brain disorders. The effect and mechanism of phillygenin, a natural compound with neuroprotective potential, on glutamate release in isolated nerve terminals (synaptosomes) prepared from the rat cerebral cortex were examined. In this study, 4-aminopyridine (4-AP), a potassium channel blocker, was utilized to induce the release of glutamate, which was subsequently quantified via a fluorometric assay. Our findings revealed that phillygenin reduced 4-AP-induced glutamate release, and this inhibitory effect was reversed by removing extracellular Ca or inhibiting vesicular transport with bafilomycin A1. However, exposure to the glutamate transporter inhibitor dl-threo-beta-benzyl-oxyaspartate (dl-TOBA) did not influence the inhibitory effect. Moreover, phillygenin did not change the synaptosomal membrane potential but lowered the 4-AP-triggered increase in intrasynaptosomal Ca concentration ([Ca]). Antagonizing Ca2.2 (N-type) calcium channels blocked the inhibition of glutamate release by phillygenin, whereas pretreatment with the mitochondrial Na/Ca exchanger inhibitor, CGP37157 or the ryanodine receptor inhibitor, dantrolene, both of which block intracellular Ca release, had no effect. The effect of phillygenin on glutamate release triggered by 4-AP was completely abolished when MAPK/ERK inhibitors were applied. Furthermore, phillygenin attenuated the phosphorylation of ERK1/2 and its major presynaptic target, synapsin I, a protein associated with synaptic vesicles. These data collectively suggest that phillygenin mediates the inhibition of evoked glutamate release from synaptosomes primarily by reducing the influx of Ca through Ca2.2 calcium channels, thereby subsequently suppressing the MAPK/ERK/synapsin I signaling cascade.
PubMed: 38540109
DOI: 10.3390/biomedicines12030495 -
Cells Mar 2024The ubiquitous second messenger 3',5'-cyclic adenosine monophosphate (cAMP) regulates cardiac excitation-contraction coupling (ECC) by signaling in discrete subcellular...
The ubiquitous second messenger 3',5'-cyclic adenosine monophosphate (cAMP) regulates cardiac excitation-contraction coupling (ECC) by signaling in discrete subcellular microdomains. Phosphodiesterase subfamilies 4B and 4D are critically involved in the regulation of cAMP signaling in mammalian cardiomyocytes. Alterations of PDE4 activity in human hearts has been shown to result in arrhythmias and heart failure. Here, we sought to systematically investigate specific roles of PDE4B and PDE4D in the regulation of cAMP dynamics in three distinct subcellular microdomains, one of them located at the caveolin-rich plasma membrane which harbors the L-type calcium channels (LTCCs), as well as at two sarco/endoplasmic reticulum (SR) microdomains centered around SR Ca-ATPase (SERCA2a) and cardiac ryanodine receptor type 2 (RyR2). Transgenic mice expressing Förster Resonance Energy Transfer (FRET)-based cAMP-specific biosensors targeted to caveolin-rich plasma membrane, SERCA2a and RyR2 microdomains were crossed to PDE4B-KO and PDE4D-KO mice. Direct analysis of the specific effects of both PDE4 subfamilies on local cAMP dynamics was performed using FRET imaging. Our data demonstrate that all three microdomains are differentially regulated by these PDE4 subfamilies. Whereas both are involved in cAMP regulation at the caveolin-rich plasma membrane, there are clearly two distinct cAMP microdomains at the SR formed around RyR2 and SERCA2a, which are preferentially controlled by PDE4B and PDE4D, respectively. This correlates with local cAMP-dependent protein kinase (PKA) substrate phosphorylation and arrhythmia susceptibility. Immunoprecipitation assays confirmed that PDE4B is associated with RyR2 along with PDE4D. Stimulated Emission Depletion (STED) microscopy of immunostained cardiomyocytes suggested possible co-localization of PDE4B with both sarcolemmal and RyR2 microdomains. In conclusion, our functional approach could show that both PDE4B and PDE4D can differentially regulate cardiac cAMP microdomains associated with calcium homeostasis. PDE4B controls cAMP dynamics in both caveolin-rich plasma membrane and RyR2 vicinity. Interestingly, PDE4B is the major regulator of the RyR2 microdomain, as opposed to SERCA2a vicinity, which is predominantly under PDE4D control, suggesting a more complex regulatory pattern than previously thought, with multiple PDEs acting at the same location.
Topics: Mice; Humans; Animals; Calcium; Ryanodine Receptor Calcium Release Channel; Cyclic AMP; Myocytes, Cardiac; Mice, Transgenic; Caveolins; Mammals
PubMed: 38534320
DOI: 10.3390/cells13060476 -
European Journal of Translational... Mar 2024This presentation reviews images of electron micrographs from various skeletal muscles identifying a consistent association of diydropyridine receptors (DHPR) tetrads...
This presentation reviews images of electron micrographs from various skeletal muscles identifying a consistent association of diydropyridine receptors (DHPR) tetrads with alternate ryanodine receptors. Imaging of the junctional gap in triads from various sources provide direct evidence for the association of four diydropyridine receptors (DHPRs), clustered into tetrads, with alternate ryanodine receptors (RyRs). It is not clear whether firing of all four components of a tetrad is necessary to fully activate the opening of the RyR channel.
PubMed: 38516838
DOI: 10.4081/ejtm.2024.12476 -
Biological & Pharmaceutical Bulletin 2024Flopropione (Flo) has been used for gallstone and urolithiasis as a spasmolytic agent almost exclusively in Japan. According to the package insert, its main mechanism is...
Flopropione (Flo) has been used for gallstone and urolithiasis as a spasmolytic agent almost exclusively in Japan. According to the package insert, its main mechanism is catechol-O-methyltransferase (COMT) inhibition and anti-serotonergic effect. This is obviously contrary to pharmacological common sense, but it is described that way in pharmacology textbooks and occurs in questions in the National Examination for Pharmacists in Japan. As this is a serious problem in education, we re-examined the action of Flo. The guinea pig ureter was hardly contracted by serotonin, but noradrenaline (NA) elicited repetitive twitch contraction, which was inhibited by Flo. The sphincter of Oddi (SO) exhibited a spontaneous repetitive twitch contraction, which was inhibited by NA and Flo. The inhibitory effect of NA was reversed by α- and β-blockers, whereas that of Flo was not. Entacapone, a representative COMT inhibitor, did not affect the movement of the ureter and the SO. Nifedipine suppressed carbachol-induced contraction of the taenia coli, spontaneous movement of the SO, and NA-induced contraction of the ureter to almost the same extent, whereas Flo did not inhibit the taenia coli, but inhibited the contraction of the SO and the ureter. The inhibitory pattern of Flo resembled that of the ryanodine receptor agonist 4-chloro-m-cresol and the inositol 1,4,5-trisphosphate (IP) receptor antagonist 2-aminoethoxydiphenyl borate. It is concluded that COMT inhibition or serotonin inhibition is not involved in the spasmolytic action of Flo. Flo might act on ryanodine receptors and/or IP receptors, which are responsible for periodic Ca release from Ca stores, to disrupt coordinated Ca dynamics.
Topics: Animals; Guinea Pigs; Parasympatholytics; Muscle Contraction; Catechol O-Methyltransferase; Serotonin; Catechols; Calcium; Propiophenones
PubMed: 38508741
DOI: 10.1248/bpb.b23-00808 -
Science Advances Mar 2024Excitation-contraction coupling (ECC) is a fundamental mechanism in control of skeletal muscle contraction and occurs at triad junctions, where dihydropyridine receptors...
Excitation-contraction coupling (ECC) is a fundamental mechanism in control of skeletal muscle contraction and occurs at triad junctions, where dihydropyridine receptors (DHPRs) on transverse tubules sense excitation signals and then cause calcium release from the sarcoplasmic reticulum via coupling to type 1 ryanodine receptors (RyR1s), inducing the subsequent contraction of muscle filaments. However, the molecular mechanism remains unclear due to the lack of structural details. Here, we explored the architecture of triad junction by cryo-electron tomography, solved the in situ structure of RyR1 in complex with FKBP12 and calmodulin with the resolution of 16.7 Angstrom, and found the intact RyR1-DHPR supercomplex. RyR1s arrange into two rows on the terminal cisternae membrane by forming right-hand corner-to-corner contacts, and tetrads of DHPRs bind to RyR1s in an alternating manner, forming another two rows on the transverse tubule membrane. This unique arrangement is important for synergistic calcium release and provides direct evidence of physical coupling in ECC.
Topics: Ryanodine Receptor Calcium Release Channel; Calcium; Muscle, Skeletal; Calcium Channels, L-Type; Sarcoplasmic Reticulum; Muscle Contraction
PubMed: 38507485
DOI: 10.1126/sciadv.adl1126