Search Results (242)

Background/Objectives: Malignant hyperthermia (MH) is a life-threatening pharmacogenetic disorder of skeletal muscle primarily associated with pathogenic variants in RYR1; however, a substantial proportion of MH-susceptible individuals lack identifiable variants in known genes. This study aimed to identify novel genetic contributors in Ca²⁺-induced Ca²⁺ release (CICR)-positive patients without RYR1 variants and to evaluate their functional relevance. Methods: Among 29 CICR-positive individuals without pathogenic variants identified by gene panel testing, five patients underwent whole-exome sequencing (WES). In one family, heterozygous variants in ANO5 (p.Arg547Gln) and ORAI3 (p.Arg287Cys) were identified. To evaluate their functional significance, intracellular Ca²⁺ dynamics were analyzed in primary myotubes derived from Case 165, an affected individual carrying both variants, and compared with those from CICR-negative controls and CICR-positive patients harboring RYR1 variants. Results: Myotubes derived from Case 165 demonstrated enhanced sensitivity to caffeine and 4-chloro-m-cresol, elevated resting intracellular Ca²⁺ levels, and greater Ca²⁺ reduction under Ca²⁺-free conditions compared with CICR-negative controls, resembling the phenotype observed in the RYR1 variant group. In contrast, dantrolene-induced Ca²⁺ reduction was significantly greater only in the RYR1 variant group. Conclusions: These findings suggest that ANO5 and ORAI3 variants may contribute to abnormal Ca²⁺ regulation in MH-susceptible individuals without RYR1 mutations and highlight the importance of combining genomic analysis with functional validation to identify novel genetic contributors to MH susceptibility. Full article

Ryanodine receptor-like (RyR-like) is a key endoplasmic reticulum (ER) Ca²⁺ release channel governing intracellular Ca²⁺ homeostasis and cellular stress responses in invertebrates. However, its function in bivalves under high-temperature stress remains unclear. In the present study, one RyR-like was identified from Yesso scallop Patinopecten yessoensis (PyRyR-like). Its function in regulating intracellular Ca²⁺, IRE1α-mediated unfolded protein response (UPR) and apoptosis in the mantle after high-temperature (25 °C) treatment was investigated using molecular cloning, qRT-PCR, Western blot, pull-down assay, cellular calcium imaging, TUNEL and histology assays; High temperature treatment significantly increased intracellular Ca²⁺ content at 1 and 6 h (p < 0.05), but decreased it at 3, 12 and 24 h (p < 0.05); meanwhile, the cAMP level, PyPKA activity, mRNA expression level of PyRyR-like, and protein expression levels of PyFKBP12 and PyGRP78 were significantly increased at different times. However, high temperature did not affect the expression level of PyNVL and PyXBP1(S). The SPRY and RYR domains of PyRyR-like separately interacted with PyFKBP12 and PyPKA. Moreover, RyR antagonist Dantrolene reversed high-temperature-induced alterations in Ca concentration, PKA activity, and core UPR- and apoptosis-related molecules, and suppressed Caspase-3 activity. These findings suggest that PyRyR-like plays an important role in the high-temperature response of scallops by regulating intracellular Ca²⁺ homeostasis and mediating UPR activation and apoptosis, providing new insight into the molecular mechanism underlying scallop adaptation to high temperature. Full article

Ventricular remodeling occurring in heart failure (HF) involves structural disarray of the sarcolemma T-tubule (TT)–sarcoplasmic reticulum (SR) dyad junctions, thereby disrupting the close apposition of L-type Ca²⁺ channels (Ca_V1.2) with ryanodine receptors (RyR2) that trigger SR Ca²⁺ release and myofilament contraction. In a rat ischemic heart failure model expressing low thyroid hormone (TH) function, we used 3D stochastic optical reconstruction microscopy (STORM) to image RyR2 clusters with Ca_V1.2 channels, and the associated protein junctophilin-2 (Jph2). We tested whether treatment with T3, the biologically active form of TH, throughout progression of the disease would preserve T-tubule structure and dyadic ion channel organization. Confocal microscopy of isolated cardiomyocytes (CMs) stained with ANEPPS membrane dye showed significantly decreased TT density in diseased CMs while T3 treatment attenuated TT disorganization. 3D STORM images of dyadic ion channels labeled with fluorescent-tagged antibodies to RyR-Dylight550, Jph-CF647 and Ca_V1.2/IgG-Dylight488 were captured. A density-based algorithm defined RyR2 clusters, and a 400 nm spherical 3D volume of interest around each RyR2 cluster’s centroid determined the number of Ca_V1.2 and Jph2 localizations associated with each RyR2 cluster. Analysis revealed significant reduction in RyR2 cluster size and number with reduced co-localized Jph2 in failing CMs. T3 treatment increased RyR2 cluster numbers and cluster volumes albeit non-significantly, with increased co-clustering of Jph2. The number of Ca_V1.2 co-localized with RyR2 clusters trended lower in the failing CMs. These results support maintaining TH homeostasis in optimizing the nanoscale organization of Ca²⁺ ion channels in triggering Ca²⁺ release and myofibrillar contraction in patients with heart disease. Full article

Calcium sparks can arise as both voltage-dependent and voltage-independent ligand-activated release events in amphibian skeletal muscle. To assess their gating behavior, calcium sparks were recorded from intact frog skeletal muscle fibers using high-temporal-resolution confocal microscopy (line scans: 15 and 50 µs/line). Sparks were triggered by 1 mmol/L caffeine to open ryanodine receptors (RyRs) or by subthreshold depolarization to a −65 mV membrane potential to activate dihydropyridine receptors (DHPRs). Both treatments increased the frequency of sparks and altered their morphology. The sparks were significantly greater after caffeine treatment than in depolarized cells. The signal mass of sparks (i.e., the amount of calcium released) resembled the amplitude in shape. Additionally, the calcium release flux followed a staggered function during the activation of sparks. The detailed analysis of the sparks’ time profile revealed that the events were activated in a stepwise manner. The average step size (in F/F₀; 0.071 ± 0.003) remained constant regardless of the scanning speed. The number of steps during the activation of sparks followed a linear function based on the spark’s amplitude. Our results suggest that the activation of neighboring release units may occur sequentially, and the amplitude of the sparks depends linearly on the number of activated RyR channels. Full article

How do ryanodine receptors (RyRs) open simultaneously to trigger the contraction of whole myofibrils within a large skeletal muscle cell? One possible answer is the uniformity of mechanosensitive RyRs, which is mechanically forced by the neighboring environment, including proteins. Here, we review papers addressing this proposed “mechanical sarcoplasmic reticulum (SR) paradigm”. Crystals of the molecular complexes comprising RyR and L-type voltage-gated Ca²⁺ channels were observed at the T-tubule/SR junction in situ using cryo-electron tomography. Observations of the SR vesicles isolated from rabbit and scallop cross-striated muscles using negative staining and transmission electron microscope raised a hypothesis of dynamic rearrangement of the Ca²⁺-ATPase (ATPase) molecules in response to cytoplasmic calcium concentration, as follows: (i) At a low calcium concentration where the ratio of operating ATPase molecules to the total molecules is at a submaximal level, the ATPase molecules form, at least in part, their cylindrical crystals in the SR membrane with the help of ATP; this results in the elongation of the SR vesicles. (ii) High concentrations of calcium, at which the ratio of operating ATPase molecules is maximal, reversibly collapse the ATPase crystals to transform the elongated vesicles into round forms comprising tightly attached crystal patches. These data further lead to the idea that the reversible growth of cylindrical ATPase crystals provides a dynamic crystalline network, which acts as an “SR membrane-endoskeletal motor” to manipulate the SR movement. The possibility of interactions between ATPase crystals and neighboring RyR crystals is also discussed. Full article

Type-1 ryanodine receptor (RyR1) is essential for skeletal muscle contraction. This Ca²⁺ release channel is expressed in cardiac myocytes; however, its function remains elusive. Cardiac-specific RyR1 overexpression (OE) mice were generated under the cardiac-specific Myh6 promoter. Cardiac hypertrophy (CH), cardiac functions, and mechanistic changes in RyR1 OE and control (wildtype, WT) mice were assessed using hematoxylin and eosin staining, echocardiography, electrocardiogram, quantitative RT-PCR, Western blotting, [³H]-ryanodine binding assay, confocal microscope, ROS dye Amplex Red and 2′,7′-dichlorofluorescein diacetate. RyR1 OE mice had increased whole heart, left ventricular weight, and left ventricular wall thickness, but decreased cardiac output and stroke volume, thereby presenting CH and heart failure (HF). CH markers like ANF, BNF, and aSKA mRNAs were increased in RyR1 OE heart. RyR1, but not RyR2 or RyR3, expression was increased in the RyR1 OE mouse heart. Similar results were found in mice with TAC-induced CH. RyR1, but not RyR2 mRNA, was increased in cardiac muscle from dogs and humans with CH and/or HF. Maximum [³H]-ryanodine binding was increased, whereas the binding dissociation constant decreased in left ventricular cardiomyocytes from RyR1 OE mice. RyR2-dependent Ca²⁺ sparks were increased, which was blocked by riluzole, a small molecule known to inhibit RyR2. Consistently, ROS was remarkably increased in RyR1 OE cardiac cells. We first generated cardiac-specific RyR1 OE mice; these mice had CH, HF, and increased RyR1 expression with no RyR2 or RyR3 alteration. Similar changes were observed in mice, dogs, and humans with CH and HF. Increased mitochondrial ROS-dependent RyR2 Ca²⁺ release was essential for RyR1-induced CH and HF. Full article

Alzheimer’s disease (AD) is the most common form of dementia, characterized by the progressive accumulation of amyloid β (Aβ) plaques and neurofibrillary tangles of tau protein in and around neurons. However, these markers appear relatively late in the disease, and their direct causality is incompatible with clinical observations. Extensive data suggest that dysregulation of Ca²⁺ signaling is an early event in the pathogenesis of AD. In familial AD (FAD), mutations in presenilin are shown to alter Ca²⁺ homeostasis by affecting the gating properties and/or the expression levels of inositol 1,4,5-trisphosphate (IP₃) receptors (IP₃Rs) and ryanodine receptor (RyRs)—the main channels responsible for Ca²⁺ release from the endoplasmic reticulum (ER). Thus, understanding the mechanism through which these channels disrupt Ca²⁺ homeostasis at different spatiotemporal scales is crucial to determining their role in AD. Here, we use computational modeling to investigate how the gating kinetics of single IP₃R in FAD-affected cells differ from those in wildtype (WT) cells and how these differences translate to impaired Ca²⁺ signaling at subcellular and whole-cell levels. Our detailed analysis reveals a significantly lower threshold for Ca²⁺ oscillations at the whole-cell level in terms of agonist concentration, with higher frequency and amplitudes in FAD-affected cells. These results shed new light on the observed Ca²⁺ hyperactivity in the pre-clinical stage of AD, reporting high-frequency Ca²⁺ oscillations in neurons. Full article

Alkaloids are structurally diverse, nitrogen-containing plant secondary metabolites with well-documented insecticidal activity. This review examines alkaloid-based insecticides, focusing on their chemical diversity, biosynthetic origins, plant distribution, and physicochemical properties relevant to pest control on farms. The principal molecular targets and modes of action are discussed, including interactions with nicotinic acetylcholine receptors, acetylcholinesterase, ryanodine receptors, and GABAergic signaling. Another focus is key metabolic enzymes, together with their activity spectra against major agricultural pests. Recent advances in rational structural modification, supported by crystallographic data, computational modeling, and structure–activity relationship studies, are highlighted as strategies to enhance the potency, selectivity, and stability of these compounds. Toxicological profiles, food residue behavior, analytical challenges, and regulatory considerations are critically assessed, emphasizing that natural origin does not equate to inherent safety. The review further evaluates the role of alkaloid-based insecticides within integrated pest management systems and identifies key research gaps related to environmental safety, non-target effects, and regulatory development and harmonization. It concludes that alkaloids are positioned as potentially valuable tools for sustainable agriculture when deployed within science-based regulatory frameworks and integrated control strategies. Full article

Cyantraniliprole, a second-generation diamide insecticide, exhibits broad-spectrum efficacy against numerous insect pests due to its selective activation of insect ryanodine receptors (RyRs). This activation triggers uncontrolled calcium release from the sarcoplasmic reticulum, resulting in sustained muscle contraction, paralysis, and ultimately death. Its unique mode of action, which is different from that of organophosphates, carbamates, pyrethroids, and neonicotinoids, helps minimize cross-resistance, making it a valuable component of integrated pest management (IPM). However, continuous field use has led to the development of resistance, primarily mediated by target-site mutations within the RyR transmembrane domain (e.g., G4946E, I4743M, and I4790K) and by enhanced metabolic detoxification via cytochrome P450 monooxygenases, carboxylesterases, and glutathione S-transferases. These mechanisms often confer cross-resistance to other diamide insecticides, thereby complicating resistance management. Moreover, sublethal exposures can disrupt insect growth, development, and reproduction, potentially accelerating resistance evolution. In addition, cyantraniliprole poses ecological risks due to its toxicity to non-target organisms such as aquatic species, including zebrafish and water fleas, pollinators such as honeybees, and soil fauna, as well as the environmental persistence of its major metabolite, J9Z38. This review comprehensively integrated current knowledge on the molecular mechanisms of action, genetic and metabolic bases of resistance, sublethal effects, and ecotoxicological impacts of cyantraniliprole, along with its environmental fate, plant uptake and translocation, and residue dynamics in agricultural systems. Finally, we discuss potential risk-mitigation strategies, including formulation optimization, application-method improvements, and resistance monitoring. Overall, this review aims to provide a comprehensive scientific foundation for the sustainable use, resistance management, and regulatory assessment of this widely used insecticide. Full article

Cardiac Ca²⁺ handling is critical for excitation–contraction coupling (ECC), with the ryanodine receptor type 2 (RyR2) serving as the key sarcoplasmic reticulum (SR) Ca²⁺ release channel in cardiomyocytes. The dysfunction of RyR2 is linked to fatal cardiac arrhythmias, including heart failure (HF) and catecholaminergic polymorphic ventricular tachycardia (CPVT). This review aims to elucidate the structural basis of RyR2, its core role in cardiac ECC and Ca²⁺ homeostasis, and the regulatory mechanisms of key modulators on its activity. By integrating recent high-resolution cryo-EM structural analyses with molecular and cellular studies on RyR2 regulation, as well as clinical evidence of RyR2 mutations in arrhythmogenic heart diseases, we provide a comprehensive overview of the field. Cryo-EM has unraveled RyR2’s gating mechanisms, ligand-binding sites, and structural features. Functionally, RyR2 mediates calcium-induced calcium release (CICR) and maintains Ca²⁺ homeostasis through coordination with SERCA2a and NCX. Key modulators (CaM, FKBP12.6, and PKA/CaMKII) and disease-linked mutations regulate RyR2 activity through distinct pathways, with defective RyR2 leading to store-overload-induced Ca²⁺ release (SOICR) and arrhythmias. Furthermore, reactive oxygen species (ROS) can induce RyR2 oxidation, establishing a pathological Ca²⁺ leak-ROS cycle in heart disease. In conclusion, RyR2 is a pivotal sensor of myocardial function, with its structural and regulatory mechanisms now well-characterized by recent studies. However, the effects of numerous RyR2 mutations remain unclear, and deeper mechanistic insights will lay a key foundation for developing novel therapies against RyR2-related cardiac diseases. Full article

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that remain widely detectable in the environment and human tissues decades after their ban, raising concerns for brain health. Both dioxin-like (DL) and non-dioxin-like (NDL) congeners interfere with neuronal function through partially distinct pathways, including aryl hydrocarbon receptor activation, disruption of calcium and dopaminergic signaling, oxidative stress, and epigenetic remodeling. Experimental and epidemiological studies indicate that developmental PCB exposure is associated with impaired cognition, attention, motor function, and increased risk of neurodevelopmental disorders. Furthermore, chronic exposure in adulthood has been linked to neurodegenerative diseases. At the cellular level, NDL-PCBs sensitize ryanodine receptors, alter dendritic and axonal growth, promote mitochondrial dysfunction, generate reactive oxygen and nitrogen species, and compromise blood–brain barrier integrity, thereby fostering neuroinflammation, synaptic dysfunction, and neuronal loss. This review synthesizes current evidence on the molecular and cellular mechanismtable s underlying PCB-induced neurotoxicity across the lifespan, highlighting oxidative stress as a central factor, integrating calcium dysregulation, neurotransmitter imbalance, and apoptotic and epigenetic pathways. Finally, potential neuroprotective roles of antioxidant strategies are discussed, emphasizing their relevance for mitigating PCB-related neurodevelopmental and neurodegenerative risk. Full article

Background: Variants in the ryanodine receptor 1 (RYR1) gene have been linked to a range of disorders, from congenital myopathy to adult-onset manifestations, with phenotypes varying from mild to severe. Methods: A retrospective review was conducted on an Israeli cohort of 36 individuals with RYR1 variants, identified through genetic testing as part of a national collaboration among multiple pediatric and adult neuromuscular clinics. Clinical features, molecular data, laboratory results, electromyographic findings, and muscle histology were analyzed. Each variant was classified according to its respective domain within the RYR1 gene. Results: Thirty-six cases were included in the analysis; 31 were from 11 unrelated families, and 5 were sporadic. Nine individuals were asymptomatic with normal CK levels. Most of the 27 affected patients presented with variable degrees of perinatal weakness, often accompanied by respiratory impairment or arthrogryposis. Weakness was predominantly proximal, with clinical courses that included deterioration, improvement, or stabilization. Three cases of King–Denborough syndrome were identified. Additional presentations included malignant hyperthermia and, in isolated cases, periodic paralysis. Muscle biopsies demonstrated considerable histologic heterogeneity, including fiber-size variation, internal nuclei, multiminicores, and fibrosis or dystrophic features. The pathogenic RYR1 variants included five compound-heterozygous genotypes, two homozygous variants, and two heterozygous variants. There was a positive correlation between variants located in the Bsol domain and disease severity. Conclusions: This cohort confirms and expands the clinical and histological diversity associated with RYR1 variants in Israel. Variants in the Bsol domain appear to be indicative of disease severity. Full article

The pressing need for sustainable, plant-based alternatives is highlighted by the growing resistance of agricultural pests to synthetic pesticides. This study examined the pesticidal potential of phytocompounds from C. tora discovered by GC–MS analysis against important tomato insect (T. absoluta) and fungal pathogen (A. solani). The binding stability and interaction dynamics of specific metabolites with fungal virulence (polygalacturonase, MAP kinase HOG1, and effector AsCEP50) and insect neuromuscular (ryanodine receptor and sodium channel protein) targets were assessed using molecular docking and 100 ns molecular dynamics simulations. Among the screened compounds, squalene and 4,7,10,13,16,19-docosahexaenoic acid, methyl ester (DHAME) exhibited the strongest binding affinities and conformational stability, with MM-GBSA binding free energies of −38.09 kcal·mol⁻¹ and −52.81 kcal·mol⁻¹ for squalene complexes in T. absoluta and A. solani, respectively. Persistent hydrophobic and mixed hydrophobic–polar contacts that stabilised active-site residues and limited protein flexibility were found by ProLIF analysis. These lively and dynamic profiles imply that DHAME and squalene may interfere with calcium signalling and stress-response pathways, which are essential for the survival and pathogenicity of pests. Hydrophobic interactions were further confirmed as the primary stabilising force by the preponderance of van der Waals and nonpolar solvation energies. The findings show that C. tora metabolites, especially squalene and DHAME, are promising environmentally friendly biopesticide candidates that have both insecticidal and antifungal properties. Their development as sustainable substitutes in integrated pest management systems are supported by their stability, binding efficacy and predicted biosafety. Full article

Trimeric intracellular cation channel A (TRIC-A) provides counter-ion support for sarcoplasmic reticulum (SR) Ca²⁺ release, yet its physiological role in the intact heart under stress remains poorly defined. Here, we demonstrate that TRIC-A is essential for maintaining balanced SR Ca²⁺ release, mitochondrial integrity, and cardiac resilience during β-adrenergic stimulation. Tric-a^−/− cardiomyocytes exhibited Ca²⁺ transients evoked by electrical stimuli and exaggerated isoproterenol (ISO)-evoked Ca²⁺ release, consistent with SR Ca²⁺ overload. These defects were accompanied by selective upregulation of protein kinase A (PKA)-dependent phosphorylation of ryanodine receptor 2 (RyR2) (S2808) and phospholamban (PLB) (S16). Acute ISO challenge induced mitochondrial swelling, cristae disruption, and Evans Blue Dye uptake, and elevated circulating troponin T in Tric-a^−/− hearts, hallmarks of necrosis-like cell death. Mitochondrial Ca²⁺ uptake inhibition with Ru360 markedly reduced membrane injury, establishing mitochondrial Ca²⁺ overload as the proximal trigger of cardiac cell death. With sustained β-adrenergic stimulation by ISO, Tric-a^−/− hearts developed extensive interstitial and perivascular fibrosis without exaggerated hypertrophy. Cardiac fibroblasts lacked TRIC-A expression and displayed normal Ca²⁺ signaling and activation, indicating that fibrosis arises secondarily from cardiomyocyte injury rather than fibroblast-intrinsic abnormalities. These findings identify TRIC-A as a critical regulator of SR-mitochondrial Ca²⁺ coupling and a key molecular safeguard that protects the heart from catecholamine-induced injury and maladaptive remodeling. Full article

Calcium (Ca²⁺)signaling dysfunction is a central contributor to neuronal hyperexcitability and seizure propagation in epilepsy, yet the intracellular mechanisms underlying the actions of valproic acid (VPA) remain incompletely understood. In this study, we investigated whether VPA modulates Ca²⁺ homeostasis at the level of the endoplasmic reticulum (ER) and how this action influences cytosolic Ca²⁺ dynamics associated with epileptiform activity. ER Ca²⁺ levels were directly measured using ER-targeted aequorin in HeLa and PC12 cells, while cytosolic Ca²⁺ signals were monitored by fura-2 fluorescence imaging in bovine chromaffin cells exposed to veratridine, a model of sustained sodium channel activation and Ca²⁺ oscillations. VPA induced a concentration-dependent release of Ca²⁺ from the ER, with an IC₅₀ of approximately 17 µM. This effect was preserved in permeabilized cells and exhibited activation kinetics comparable to those elicited by inositol 1,4,5-trisphosphate (InsP₃). Pharmacological inhibition of InsP₃ receptors (InsP₃Rs), but not ryanodine receptors or SERCA, abolished VPA-induced ER Ca²⁺ release, supporting a selective InsP₃R-mediated mechanism. Functionally, VPA suppressed the repetitive cytosolic Ca²⁺ oscillations induced by veratridine, while simultaneously producing a sustained elevation of cytosolic Ca²⁺ originating from ER stores and facilitating depolarization-evoked catecholamine secretion. Together, these results support the conclusion that VPA induces InsP₃R-mediated Ca²⁺ mobilization from the endoplasmic reticulum and identify ER Ca²⁺ release as a previously unrecognized intracellular mechanism contributing to its modulatory effects on Ca²⁺ signaling and excitability in epilepsy. Full article