Ryanodine receptor patents

Myopathic manifestations across the adult lifespan of patients with malignant hyperthermia susceptibility: a narrative review

Malignant hyperthermia susceptibility (MHS) designates individuals at risk of developing a hypermetabolic reaction triggered by halogenated anaesthetics or the depolarising neuromuscular blocking agent suxamethonium. Over the past few decades, beyond the operating theatre, myopathic manifestations impacting daily life are increasingly recognised as a prevalent phenomenon in MHS patients. At the request of the European Malignant Hyperthermia Group, we reviewed the literature and gathered the opinion of experts to define MHS-related myopathy as a distinct phenotype expressed across the adult lifespan of MHS patients unrelated to anaesthetic exposure; this serves to raise awareness about non-anaesthetic manifestations, potential therapies, and management of MHS-related myopathy. We focused on the clinical presentation, biochemical and histopathological findings, and the impact on patient well-being. The spectrum of symptoms of MHS-related myopathy encompasses muscle cramps, stiffness, myalgias, rhabdomyolysis, and weakness, with a wide age range of onset mainly during adulthood. Histopathological analysis can reveal nonspecific abnormalities suggestive of RYR1 involvement, while metabolic profiling reflects altered energy metabolism in MHS muscle. Myopathic manifestations can significantly impact patient quality of life and lead to functional limitations and socio-economic burden. While currently available therapies can provide symptomatic relief, there is a need for further research into targeted treatments addressing the underlying pathophysiology. Counselling early after establishing the MHS diagnosis, followed by multidisciplinary management involving various medical specialties, is crucial to optimise patient care.

Therapeutic Approaches of Ryanodine Receptor-Associated Heart Diseases

Cardiac diseases are the leading causes of death, with a growing number of cases worldwide, posing a challenge for both healthcare and research. Therefore, the most relevant aim of cardiac research is to unravel the molecular pathomechanisms and identify new therapeutic targets. Cardiac ryanodine receptor (RyR2), the Ca²⁺ release channel of the sarcoplasmic reticulum, is believed to be a good therapeutic target in a group of certain heart diseases, collectively called cardiac ryanopathies. Ryanopathies are associated with the impaired function of the RyR, leading to heart diseases such as congestive heart failure (CHF), catecholaminergic polymorphic ventricular tachycardia (CPVT), arrhythmogenic right ventricular dysplasia type 2 (ARVD2), and calcium release deficiency syndrome (CRDS). The aim of the current review is to provide a short insight into the pathological mechanisms of ryanopathies and discuss the pharmacological approaches targeting RyR2.

Targeting Post-Translational Remodeling of Ryanodine Receptor: A New Track for Alzheimer's Disease Therapy?

Pathologic calcium (Ca2+) signaling linked to Alzheimer's Disease (AD) involves the intracellular Ca2+ release channels/ryanodine receptors (RyRs). RyRs are macromolecular complexes where the protein-protein interactions between RyRs and several regulatory proteins impact the channel function. Pharmacological and genetic approaches link the destabilization of RyRs macromolecular complexes to several human pathologies including brain disorders. In this review, we discuss our recent data, which demonstrated that enhanced neuronal RyR2-mediated Ca2+ leak in AD is associated with posttranslational modifications (hyperphosphorylation, oxidation, and nitrosylation) leading to RyR2 macromolecular complex remodeling, and dissociation of the stabilizing protein Calstabin2 from the channel. We describe RyR macromolecular complex structure and discuss the molecular mechanisms and signaling cascade underlying neuronal RyR2 remodeling in AD. We provide evidence linking RyR2 dysfunction with β-adrenergic signaling cascade that is altered in AD. RyR2 remodeling in AD leads to histopathological lesions, alteration of synaptic plasticity, learning and memory deficits. Targeting RyR macromolecular complex remodeling should be considered as a new therapeutic window to treat/or prevent AD setting and/or progression.

Reversal of Calcium Dysregulation as Potential Approach for Treating Alzheimer's Disease

Despite decades of research and effort, there is still no effective disease-modifying treatment for Alzheimer's Disease (AD). Most of the recent AD clinical trials were targeting amyloid pathway, but all these trials failed. Although amyloid pathology is a hallmark and defining feature of AD, targeting the amyloid pathway has been very challenging due to low efficacy and serious side effects. Alternative approaches or mechanisms for our understanding of the major cause of memory loss in AD need to be considered as potential therapeutic targets. Increasing studies suggest that Ca2+ dysregulation in AD plays an important role in AD pathology and is associated with other AD abnormalities, such as excessive inflammation, increased ROS, impaired autophagy, neurodegeneration, synapse, and cognitive dysfunction. Ca2+ dysregulation in cytosolic space, Endoplasmic Reticulum (ER) and mitochondria have been reported in the context of various AD models. Drugs or strategies, to correct the Ca2+ dysregulation in AD, have been demonstrated to be promising as an approach for the treatment of AD in preclinical models. This review will discuss the mechanisms of Ca2+ dysregulation in AD and associated pathology and discuss potential approaches or strategies to develop novel drugs for the treatment of AD by targeting Ca2+ dysregulation.

Moderate intensity continuous training reverses the detrimental effects of ovariectomy on RyR1 phosphorylation in rat skeletal muscle

High 17β-Estradiol (E2) concentrations in isolated ventricular myocytes as well as a lack of ovarian hormones in cardiac muscle of ovariectomized (OVX) rodents has been shown to lead to arrhythmogenic effects by inducing post-translational modifications, including phosphorylation of the sarcoplasmic reticulum (SR) Ca²⁺ release channel ryanodine receptor-2 (RyR2). The effects of estrogens on the phosphorylation status of the RyR1 in skeletal muscle have not been investigated before. Furthermore, while high intensity exercise has been shown to increase RyR phosphorylation, there is no data on the effects of moderate intensity continuous training (MICT). The aims of the study were to investigate the effects of a 3-day treatment with low (1 nM, moderate (5 nM) and high (10 nM, 100 nM) E2 concentrations on RyR1 mRNA and protein expression and phosphorylation status (pRyRSer²⁸⁴⁴) in cultured C2C12 myotubes and to study the effects of OVX on RyR1 expression and phosphorylation in rat skeletal muscle in combination with 3 weeks of MICT. Treatment with low, physiological E2 concentrations reduced dihydropyridine receptor (DHPR) and RyR1 mRNA content in C2C12 myotubes compared to untreated control cells, whereas RyR1 protein phosphorylation (pRyRSer²⁸⁴⁴) was significantly increased after treatment with high, non-physiological E2 concentrations (p ≤ 0.05). RyR1 protein content (p ≤ 0.05) and pRyRSer²⁸⁴⁴ (p ≤ 0.05) were significantly elevated in skeletal muscle of OVX vs. sham-operated rats. Importantly, pRyRSer²⁸⁴⁴ levels were similar to sham-operated controls in OVX rats after MICT (OVX vs. OVX + MICT, p ≤ 0.05). Our results indicate, that one of the actions of estrogens is to alter skeletal muscle Ca²⁺ homeostasis by modulating the expression and phosphorylation of the RyR1 in skeletal muscle. Notably, regular MICT was able to counteract RyR1 phosphorylation in skeletal muscle of OVX rats.

Ryanodine Receptor 1-Related Myopathies: Diagnostic and Therapeutic Approaches

Ryanodine receptor type 1-related myopathies (RYR1-RM) are the most common class of congenital myopathies. Historically, RYR1-RM classification and diagnosis have been guided by histopathologic findings on muscle biopsy. Main histological subtypes of RYR1-RM include central core disease, multiminicore disease, core-rod myopathy, centronuclear myopathy, and congenital fiber-type disproportion. A range of RYR1-RM clinical phenotypes has also emerged more recently and includes King Denborough syndrome, RYR1 rhabdomyolysis-myalgia syndrome, atypical periodic paralysis, congenital neuromuscular disease with uniform type 1 fibers, and late-onset axial myopathy. This expansion of the RYR1-RM disease spectrum is due, in part, to implementation of next-generation sequencing methods, which include the entire RYR1 coding sequence rather than being restricted to hotspot regions. These methods enhance diagnostic capabilities, especially given historic limitations of histopathologic and clinical overlap across RYR1-RM. Both dominant and recessive modes of inheritance have been documented, with the latter typically associated with a more severe clinical phenotype. As with all congenital myopathies, no FDA-approved treatments exist to date. Here, we review histopathologic, clinical, imaging, and genetic diagnostic features of the main RYR1-RM subtypes. We also discuss the current state of treatments and focus on disease-modulating (nongenetic) therapeutic strategies under development for RYR1-RM. Finally, perspectives for future approaches to treatment development are broached.

Ryanodine receptor dysfunction in human disorders

Regulation of intracellular calcium (Ca²⁺) is critical in all cell types. The ryanodine receptor (RyR), an intracellular Ca²⁺ release channel located on the sarco/endoplasmic reticulum (SR/ER), releases Ca²⁺ from intracellular stores to activate critical functions including muscle contraction and neurotransmitter release. Dysfunctional RyR-mediated Ca²⁺ handling has been implicated in the pathogenesis of inherited and non-inherited conditions including heart failure, cardiac arrhythmias, skeletal myopathies, diabetes, and neurodegenerative diseases. Here we have reviewed the evidence linking human disorders to RyR dysfunction and describe novel approaches to RyR-targeted therapeutics.

Dantrolene requires Mg2+ to arrest malignant hyperthermia

Malignant hyperthermia (MH) is a clinical syndrome of skeletal muscle that presents as a hypermetabolic response to volatile anesthetic gases, where susceptible persons may develop lethally high body temperatures. Genetic predisposition mainly arises from mutations on the skeletal muscle ryanodine receptor (RyR). Dantrolene is administered to alleviate MH symptoms, but its mechanism of action and its influence on the Ca²⁺ transients elicited by MH triggers are unknown. Here, we show that Ca²⁺ release in the absence of Mg²⁺ is unaffected by the presence of dantrolene but that dantrolene becomes increasingly effective as cytoplasmic-free [Mg²⁺] (free [Mg²⁺]_cyto) passes mM levels. Furthermore, we found in human muscle susceptible to MH that dantrolene was ineffective at reducing halothane-induced repetitive Ca²⁺ waves in the presence of resting levels of free [Mg²⁺]_cyto (1 mM). However, an increase of free [Mg²⁺]_cyto to 1.5 mM could increase the period between Ca²⁺ waves. These results reconcile previous contradictory reports in muscle fibers and isolated RyRs, where Mg²⁺ is present or absent, respectively, and define the mechanism of action of dantrolene is to increase the Mg²⁺ affinity of the RyR (or "stabilize" the resting state of the channel) and suggest that the accumulation of the metabolite Mg²⁺ from MgATP hydrolysis is required to make dantrolene administration effective in arresting an MH episode.

FRET-based trilateration of probes bound within functional ryanodine receptors

To locate the biosensor peptide DPc10 bound to ryanodine receptor (RyR) Ca(2+) channels, we developed an approach that combines fluorescence resonance energy transfer (FRET), simulated-annealing, cryo-electron microscopy, and crystallographic data. DPc10 is identical to the 2460-2495 segment within the cardiac muscle RyR isoform (RyR2) central domain. DPc10 binding to RyR2 results in a pathologically elevated Ca(2+) leak by destabilizing key interactions between the RyR2 N-terminal and central domains (unzipping). To localize the DPc10 binding site within RyR2, we measured FRET between five single-cysteine variants of the FK506-binding protein (FKBP) labeled with a donor probe, and DPc10 labeled with an acceptor probe (A-DPc10). Effective donor positions were calculated from simulated-annealing constrained by both the RyR cryo-EM map and the FKBP atomic structure docked to the RyR. FRET to A-DPc10 was measured in permeabilized cardiomyocytes via confocal microscopy, converted to distances, and used to trilaterate the acceptor locus within RyR. Additional FRET measurements between donor-labeled calmodulin and A-DPc10 were used to constrain the trilaterations. Results locate the DPc10 probe within RyR domain 3, ?35 Å from the previously docked N-terminal domain crystal structure. This multiscale approach may be useful in mapping other RyR sites of mechanistic interest within FRET range of FKBP.