Ryanodine receptor calcium release channels

Chlorantraniliprole Combined with Wilforine, an Environmentally Friendly and Efficient Chemical Control Strategy for Spodoptera frugiperda by Regulating Calcium Homeostasis

Spodoptera frugiperda poses a significant threat to global food security, having developed resistance to numerous chemical insecticides. Chlorantraniliprole is among the emergency control agents for managing S. frugiperda. Wilforine, a plant-derived pesticide, has emerged as a promising candidate for novel pesticide development. In this study, we employed a combination of advanced methodologies to elucidate the mechanism underlying the action of these compounds. We demonstrated that chlorantraniliprole disrupts calcium homeostasis by regulating SfRyR, ultimately inducing apoptosis. Additionally, we identified SfSERCA as the target of wilforine, revealing its role in regulating Ca2+-ATPase activity in S. frugiperda. Through the dual interference of dsSfRyR and dsSfSERCA, we analyzed the synergistic effects of chlorantraniliprole and wilforine against S. frugiperda. This approach identified a highly efficient and low-toxicity combination of the two compounds. It proposes an environmentally friendly chemical control strategy by leveraging the synergistic mechanism to regulate the calcium homeostasis in the pest cells.

Ryanodine Receptors in Islet Cell Function: Calcium Signaling, Hormone Secretion, and Diabetes

Ryanodine receptors (RyRs) are large intracellular Ca2+ release channels primarily found in muscle and nerve cells and also present at low levels in pancreatic islet endocrine cells. This review examines the role of RyRs in islet cell function, focusing on calcium signaling and hormone secretion, while addressing the ongoing debate regarding their significance due to their limited expression. We explore conflicting experimental results and their potential causes, synthesizing current knowledge on RyR isoforms in islet cells, particularly in beta and delta cells. The review discusses how RyR-mediated calcium-induced calcium release enhances, rather than drives, glucose-stimulated insulin secretion. We examine the phosphorylation-dependent regulation of beta-cell RyRs, the concept of "leaky ryanodine receptors", and the roles of RyRs in endoplasmic reticulum stress, apoptosis, store-operated calcium entry, and beta-cell electrical activity. The relationship between RyR dysfunction and the development of impaired insulin secretion in diabetes is assessed, noting their limited role in human diabetes pathogenesis given the disease's polygenic nature. We highlight the established role of RyR-mediated CICR in the mechanism of action of common type 2 diabetes treatments, such as glucagon-like peptide-1, which enhances insulin secretion. By integrating findings from electrophysiological, molecular, and clinical studies, this review provides a balanced perspective on RyRs in islet cell physiology and pathology, emphasizing their significance in both normal insulin secretion and current diabetes therapies.

NOX4-driven mitochondrial oxidative stress in aging promotes myocardial remodeling and increases susceptibility to ventricular tachyarrhythmia

Aging-associated mitochondrial oxidative stress has been implicated in ventricular tachyarrhythmias (VT), but the specific proarrhythmic mechanisms of mitochondrial pro-oxidative systems remain unclear. NADPH oxidase 4 (NOX4) expression in the heart increases with age, leading to mitochondrial oxidative stress, dysfunction, and adverse myocardial remodeling. This study investigated the susceptibility to aging-associated ventricular arrhythmia and the associated triggers and substrates using transgenic mice with mitochondria-targeted Nox4 overexpression (Nox4TG mice). Nox4TG mice showed a significantly higher incidence of pacing-induced VT, associated with shorter action potential duration (APD) due to increased transient outward potassium currents. Fractional sarcoplasmic reticulum (SR) Ca2+ release and Ca2+ leak remained intact despite these changes. However, the frequency of Ca2+ sparks was reduced, and ryanodine receptor 2 (RyR2) oxidation was observed. Compensatory upregulation of SERCA expression in response to RyR2 inhibition accelerated SR Ca2+ reuptake and improved cardiomyocyte mechanical relaxation. Nox4TG mice exhibited extensive ventricular fibrosis and marked pro-inflammatory macrophage infiltration, with elevated TNF, TGF-β, and MKI67 expression. Treatment with Setanaxib, a NOX1/NOX4 inhibitor, or co-expression of mitochondrial catalase in Nox4TG (Nox4TG + mCAT) mice, mitigated fibrosis, reduced inflammation, and protected against VT. These findings suggest that mitochondrial NOX4 overexpression promotes VT through electrical remodeling and pro-arrhythmogenic structural changes despite RyR2 oxidation and dysfunction. In conclusion, aging-related NOX4-driven mitochondrial oxidative stress increases the risk of VT by promoting changes in the electrical and structural properties of the myocardium, highlighting potential therapeutic strategies that target NOX4 in cardiac pathologies associated with aging.

Mitochondria-organelle crosstalk in establishing compartmentalized metabolic homeostasis

Mitochondria serve as central hubs in cellular metabolism by sensing, integrating, and responding to metabolic demands. This integrative function is achieved through inter-organellar communication, involving the exchange of metabolites, lipids, and signaling molecules. The functional diversity of metabolite exchange and pathway interactions is enabled by compartmentalization within organelle membranes. Membrane contact sites (MCSs) are critical for facilitating mitochondria-organelle communication, creating specialized microdomains that enhance the efficiency of metabolite and lipid exchange. MCS dynamics, regulated by tethering proteins, adapt to changing cellular conditions. Dysregulation of mitochondrial-organelle interactions at MCSs is increasingly recognized as a contributing factor in the pathogenesis of multiple diseases. Emerging technologies, such as advanced microscopy, biosensors, chemical-biology tools, and functional genomics, are revolutionizing our understanding of inter-organellar communication. These approaches provide novel insights into the role of these interactions in both normal cellular physiology and disease states. This review will highlight the roles of metabolite transporters, lipid-transfer proteins, and mitochondria-organelle interfaces in the coordination of metabolism and transport.

The Role of RyR2 Mutations in Congenital Heart Diseases: Insights Into Cardiac Electrophysiological Mechanisms

Ryanodine receptor 2 (RyR2) protein, a calcium ion release channel in the sarcoplasmic reticulum (SR) of myocardial cells, plays a crucial role in regulating cardiac systolic and diastolic functions. Mutations in RyR2 and its dysfunction are implicated in various congenital heart diseases (CHDs). Studies have shown that mutations in the RYR2 gene, which encodes the RyR2 protein, are linked to several cardiac arrhythmias, including catecholaminergic polymorphic ventricular tachycardia (CPVT), long QT syndrome (LQTS), calcium release deficiency syndrome (CRDS), and atrial fibrillation (AF). Additionally, RyR2 mutations have been associated with multiple genetic cardiomyopathies, such as left ventricular non-compaction cardiomyopathy (LVNC), arrhythmogenic right ventricular cardiomyopathy (ARVC), hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). Through various cell and animal models, researchers have developed mutant RyR2 models demonstrated that these mutations often lead to calcium dysregulation, typically resulting in either a gain or loss of function. This comprehensive review delves into the current understanding of RyR2 mutations and their impact on cardiac electrophysiology, focusing on the molecular mechanisms linking these mutations to arrhythmias and cardiomyopathies-an essential step in advancing diagnostic and therapeutic strategies.

Oral administration of cyantraniliprole to wistar rats during pregnancy and lactation alters maternal behavior and harms the female reproductive system of pubertal and adult offspring

Over the past years, global pesticide use has increased by 20%. New insecticidal molecules, like cyantraniliprole, aim to reduce side effects due to the high toxicity of pesticides and their harmful effects on health and the environment. Its mechanism involves binding to ryanodine receptors, causing rapid calcium ion release. As a new molecule, studies on its effects on mammals are scarce. This work evaluates oral cyantraniliprole's impacts during pregnancy and lactation on maternal behavior and the reproductive system of female offspring. Approved by CEUA-UEL (OF. CIRC. CEUA n. 20/2020), Wistar rats were mated, and after pregnancy diagnosis, divided into control groups, C1, C10, and C150, receiving water and cyantraniliprole at 1, 10, and 150 mg/kg/day, respectively, by gavage. Maternal behavior, offspring physical development, uterine and ovarian histology, and oxidative stress levels were analyzed. Maternal exposure to 150 mg/kg/day was toxic to pregnancy, causing loss of the experimental group. Analysis showed significant changes in maternal behavior in C1 and C10, with increased pup contact, longer breastfeeding, and less cleaning time. No changes in offspring development were observed in C1 and C10. Histology and oxidative stress analysis of the ovaries showed no changes, while uterine analysis indicated thickening and increased oxidative stress.

Structural insights into transmembrane helix S0 facilitated RyR1 channel gating by Ca2+/ATP

The type-1 ryanodine receptor (RyR1) is an intracellular calcium release channel for skeletal muscle excitation-contraction coupling. Previous structural studies showed that the RyR1 activity is modulated by the exogenous regulators including caffeine, ryanodine, PCB-95 and diamide. An additional transmembrane helix, located adjacent to S1 and S4, has been observed in some structures, although its function remains unclear. Here, we report that using a mild purification procedure, this helix is co-purified with RyR1 and is designated as S0. When RyR1 is coupled with S0, it can be activated by Ca2+ to an open state; however when decoupled from S0, it remains in primed state. S0 regulates the channel conformation by directly affecting the TM domain via the pVSD-S0-S4/S5 linker coupling, which facilitates the dilation of S6. Our results demonstrate that S0 is an essential component of RyR1 and plays a key role in the physiological regulation of RyR1 channel gating.

Melatonin lessens the susceptibility to atrial fibrillation in sleep deprivation by ameliorating Ca2+ mishandling in response to mitochondrial oxidative stress

BACKGROUND

The antiarrhythmic effect of melatonin(MLT) has been demonstrated in several studies; however, this hypothesis has recently been contested. Our research seeks to determine if exogenous MLT supplementation can reduce atrial fibrillation (AF) susceptibility due to sleep deprivation (SD) by addressing Ca2+ mishandling and atrial mitochondrial oxidative stress.

METHODS

Adult rats received daily MLT or vehicle injections and were exposed to a modified water tank. We evaluated MLT's impact on AF susceptibility by analyzing atrial electrical and structural changes, calcium handling, and oxidative stress markers. Techniques used included electrophysiological recording, echocardiography, optical mapping, histopathology, and molecular assays to understand MLT's protective effects against sleep deprivation-induced AF.

RESULTS

Our findings indicate that MLT treatment effectively mitigates SD-induced AF, safeguards against atrial structural alterations, diminishes mitochondrial oxidative stress and normalizes calcium dynamics. Notably, MLT corrected calcium transient duration (CaD), action potential duration (APD), and conduction heterogeneity, shortened calcium transient refractoriness, and improved arrhythmogenic atrial alternans and spatially discordant alternans, thereby lowering the arrhythmogenic potential of the atria during sleep deprivation. In terms of mechanisms, MLT prevents SD-induced activation of ROS/CaMKII in atrial cardiomyocytes, reversing calcium transient refractoriness and inhibiting arrhythmogenic alternans.

CONCLUSIONS

MLT significantly decreases the susceptibility to SD-induced AF by ameliorating mitochondrial oxidative stress and Ca2+ mishandling. These findings suggest a potential therapeutic application of MLT as an antiarrhythmic intervention for SD-related AF and underscore the need for further investigation, including clinical studies, to validate these mechanisms.

Calcium-mediated regulation of mitophagy: implications in neurodegenerative diseases

Calcium signaling plays a pivotal role in diverse cellular processes through precise spatiotemporal regulation and interaction with effector proteins across distinct subcellular compartments. Mitochondria, in particular, act as central hubs for calcium buffering, orchestrating energy production, redox balance and apoptotic signaling, among others. While controlled mitochondrial calcium uptake supports ATP synthesis and metabolic regulation, excessive accumulation can trigger oxidative stress, mitochondrial membrane permeabilization, and cell death. Emerging findings underscore the intricate interplay between calcium homeostasis and mitophagy, a selective type of autophagy for mitochondria elimination. Although the literature is still emerging, this review delves into the bidirectional relationship between calcium signaling and mitophagy pathways, providing compelling mechanistic insights. Furthermore, we discuss how disruptions in calcium homeostasis impair mitophagy, contributing to mitochondrial dysfunction and the pathogenesis of common neurodegenerative diseases.

Mechanism of acclimation to chronic intermittent hypoxia in the gills of largemouth bass (Micropterus salmoides)

The acclimation response of fish gills to chronic intermittent hypoxia (CIH) is an important aspect to understand, as anthropogenically induced hypoxia in water bodies has been a stressor for fish for many years and is expected to persist in the future. In order to investigate the acclimation response of fish gills to CIH stress, we conducted a study using largemouth bass (Micropterus salmoides) exposed to intermittent hypoxia (dissolved oxygen level, 2.0 mg·L-1) for either 1 or 3 h per day, over a period of 8 weeks. Our findings indicate that exposure to CIH induced remodeling of the gills and an increase in gill surface area. This remodeling of the gills may be attributed to changes in cell growth and proliferation, which are influenced by the activation of the MAPK signaling pathway. We also observed significant upregulation of genes related to glycolysis (fba, pgam1, pepck, atp-pfk, pfk-2, g6pi, gapd-1, and pk), while genes associated with cholesterol synthesis (3β-hsd, cyp51, dsdr- × 1, dsdr, and dhcr7) were downregulated following CIH exposure. Furthermore, we observed the presence of elongated megamitochondria in mitochondria-rich cells within the gills of fish exposed to hypoxia. Additionally, numerous genes involved in calcium signaling pathways were upregulated in the gills of largemouth bass, suggesting an enhanced sensitivity of gills to environmental cues in hypoxia conditions. However, the expression levels of certain genes related to innate and adaptive immune responses were inhibited following CIH exposure. Moreover, the number of mucous cells decreased after CIH exposure. This may have made the gills more susceptible to infection by pathogens, although it facilitated oxygen uptake. These findings highlight the potential vulnerability of gills to pathogenic organisms in the presence of CIH. Overall, our study contributes to a better understanding of how fish acclimate to CIH.

Flecainide Specifically Targets the Monovalent Countercurrent Through the Cardiac Ryanodine Receptor, While a Dominant Opposing Ca2+/Ba2+ Current Is Present

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a highly arrhythmogenic syndrome triggered by stress, primarily linked to gain-of-function point mutations in the cardiac ryanodine receptor (RyR2). Flecainide, as an effective therapy for CPVT, is a known blocker of the surface-membrane Na+ channel, also affecting the intracellular RyR2 channel. The therapeutic relevance of the flecainide-RyR2 interaction remains controversial, as flecainide blocks only the RyR2 current flowing in the opposite direction to the physiological Ca2+ release from the sarcoplasmic reticulum (SR). However, it has been proposed that charge-compensating countercurrent from the cytosol to SR lumen plays a critical role, and its reduction may indeed suppress excessive diastolic SR Ca2+ release through RyR2 channels in CPVT. Monitoring single-channel properties, we examined whether flecainide can target intracellular pathways for charge-balancing currents carried by RyR2 and SR Cl- channels under cell-like conditions. Particularly, the Tris+ countercurrent flowed through the RyR2 channel simultaneously with a dominant reverse Ca2+/Ba2+ current. We demonstrate that flecainide blocked the RyR2-mediated countercurrent without affecting channel activity. In contrast, the SR Cl- channel was completely resistant to flecainide. Based on these findings, it is reasonable to propose that the primary intracellular target of flecainide in vivo is the RyR2-mediated countercurrent.

Endoplasmic Reticulum Calcium Signaling in Hippocampal Neurons

The endoplasmic reticulum (ER) is a key organelle in cellular homeostasis, regulating calcium levels and coordinating protein synthesis and folding. In neurons, the ER forms interconnected sheets and tubules that facilitate the propagation of calcium-based signals. Calcium plays a central role in the modulation and regulation of numerous functions in excitable cells. It is a versatile signaling molecule that influences neurotransmitter release, muscle contraction, gene expression, and cell survival. This review focuses on the intricate dynamics of calcium signaling in hippocampal neurons, with particular emphasis on the activation of voltage-gated and ionotropic glutamate receptors in the plasma membrane and ryanodine and inositol 1,4,5-trisphosphate receptors in the ER. These channels and receptors are involved in the generation and transmission of electrical signals and the modulation of calcium concentrations within the neuronal network. By analyzing calcium fluctuations in neurons and the associated calcium handling mechanisms at the ER, mitochondria, endo-lysosome and cytosol, we can gain a deeper understanding of the mechanistic pathways underlying neuronal interactions and information transfer.

Genetic Variants Linked to Opioid Addiction: A Genome-Wide Association Study

Opioid use disorder (OUD) affects millions of people worldwide. While it is known that OUD originates from many factors, including social and environmental factors, the role of genetic variants in developing the disease has also been reported. This study aims to investigate the genetic variants associated with the risk of developing OUD upon exposure. Twenty-three subjects who had previously been given opioid-based painkillers to undergo minor surgical treatment were recruited at Prisma Health Upstate clinic and elsewhere. Eleven were considered nonpersistent opioid users (controls), and 12 were persistent opioid users (cases) at the time of sample collection after an initial surgery. The subjects were asked to provide saliva samples, which were subjected to DNA sequencing at Clemson University Center for Human Genetics, and variant calling was performed. The genome-wide association studies (GWASs) for genes known to be associated with OUD resulted in 13 variants (intronic or SNV) with genome-wide significance (raw p-value < 0.01) and two missense variants, rs6265 (p.Val66Met in BNDF isoform a) and rs1799971 (p.Asn40Asp) in OPRM1, previously reported in the literature. Furthermore, extending the GWASs to find all genomic variants and filtering the variants to include only variants found in cases (persistent opioid users) but not in controls (nonpersistent opioid users) resulted in 11 new variants (p-value < 0.005). Considering that OUD is a complex disease and the effect might come from different variants in the same genes, we performed a co-occurrence analysis of variants on the genes. We identified eight additional genes that harbor multiple variants, including four genes: LRFN3, ZMIZ1, RYR3, and OR1L6, with three or more variants in the case subjects but not in the control individuals. The performed PPI network construction, along with functional enrichment, indicated that the variants occur in calcium signaling, circadian entrainment, morphine addiction, alcoholism, and opioid signaling pathways, which are closely related to OUD or addiction in general.

Electrophysical cardiac remodeling at the molecular level: Insights into ryanodine receptor activation and calcium-induced calcium release from a stochastic explicit-particle model

We present the first-ever, fully discrete, stochastic model of triggered cardiac Ca2+ dynamics. Using anatomically accurate subcellular cardiac myocyte geometries, we simulate the molecular players involved in Ca2+ handling using high-resolution stochastic and explicit-particle methods at the level of an individual cardiac dyadic junction. Integrating data from multiple experimental sources, the model not only replicates the findings of traditional in silico studies and complements in vitro experimental data but also reveals new insights into the molecular mechanisms driving cardiac dysfunction under stress and disease conditions. We improve upon older, nondiscrete models using the same realistic geometry by incorporating molecular mechanisms for spontaneous, as well as triggered calcium-induced calcium release (CICR). Action potentials are used to activate L-type calcium channels (LTCC), triggering CICR through ryanodine receptors (RyRs) on the surface of the sarcoplasmic reticulum. These improvements allow for the specific focus on the couplon: the structure-function relationship between LTCC and RyR. We investigate the electrophysical effects of normal and diseased action potentials on CICR and interrogate the effects of dyadic junction deformation through detubulation and orphaning of RyR. Our work demonstrates the importance of the electrophysical integrity of the calcium release unit on CICR fidelity, giving insights into the molecular basis of heart disease. Finally, we provide a unique, detailed, molecular view of the CICR process using advanced rendering techniques. This easy-to-use model comes complete with tutorials and the necessary software for use and analysis to maximize usability and reproducibility. Our work focuses on quantifying, qualifying, and visualizing the behavior of the molecular species that underlie the function and dysfunction of subcellular cardiomyocyte systems.

Quantitative Single-Molecule Analysis of Ryanodine Receptor 2 Subunit Assembly in Cardiac and Neuronal Tissues

We developed a method for ex vivo receptor encapsulation and single-molecule imaging techniques from neuronal and cardiac tissues, illustrating the method's broad applicability for measuring membrane receptor assembly. Ryanodine receptor 2 (RyR2) is a tetrameric Ca2+ channel governing intracellular Ca2+ dynamics, which is critical for muscle contraction. Employing GFP-RyR2 knock-in mice, we isolated individual receptor proteins in tissue-specific nanovesicles and performed subunit counting analyses to yield quantitative assessment of stoichiometric distributions across different organs. With this method, we explored the potential heterogeneity of brain-derived RyR2, which has been reported to form heteromeric assemblies with other ryanodine receptor isoforms.

Organellular imaging in vivo reveals a depletion of endoplasmic reticular calcium during post-ictal cortical spreading depolarization

During cortical spreading depolarization (CSD), neurons exhibit a dramatic increase in cytosolic calcium, which may be integral to CSD-mediated seizure termination. This calcium increase greatly exceeds that during seizures, suggesting the calcium source may not be solely extracellular. Thus, we sought to determine if the endoplasmic reticulum (ER), the largest intracellular calcium store, is involved. We developed a two-photon calcium imaging paradigm to simultaneously record the cytosol and ER during seizures in awake mice. Paired with direct current recording, we reveal that CSD can manifest as a slow post-ictal cytosolic calcium wave with a concomitant depletion of ER calcium that is spatiotemporally consistent with a calcium-induced calcium release. Importantly, we observed both naturally occurring and electrically induced CSD suppressed post-ictal epileptiform activity. Collectively, this work links ER dynamics to CSD, which serves as an innate process for seizure suppression and a potential mechanism underlying therapeutic electrical stimulation for epilepsy.

Endoplasmic reticulum-resident selenoproteins and their roles in glucose and lipid metabolic disorders

Glucose and lipid metabolic disorders (GLMDs), such as diabetes, dyslipidemia, metabolic syndrome, nonalcoholic fatty liver disease, and obesity, are significant public health issues that negatively impact human health. The endoplasmic reticulum (ER) plays a crucial role at the cellular level for lipid and sterol biosynthesis, intracellular calcium storage, and protein post-translational modifications. Imbalance and dysfunction of the ER can affect glucose and lipid metabolism. As an essential trace element, selenium contributes to various human physiological functions mainly through 25 types of selenoproteins (SELENOs). At least 10 SELENOs, with experimental and/or computational evidence, are predominantly found on the ER membrane or within its lumen. Two iodothyronine deiodinases (DIOs), DIO1 and DIO2, regulate the thyroid hormone deiodination in the thyroid and some external thyroid tissues, influencing glucose and lipid metabolism. Most of the other eight members maintain redox homeostasis in the ER. Especially, SELENOF, SELENOM, and SELENOS are involved in unfolded protein responses; SELENOI catalyzes phosphatidylethanolamine synthesis; SELENOK, SELENON, and SELENOT participate in calcium homeostasis regulation; and the biological significance of thioredoxin reductase 3 in the ER remains unexplored despite its established function in the thioredoxin system. This review examines recent research advances regarding ER SELENOs in GLMDs and aims to provide insights on ER-related pathology through SELENOs regulation.

The Development of Persistent Gastrointestinal Symptoms in Patients With Melanoma Who Have Had an Immune Checkpoint Inhibitor-Related Gastrointestinal Toxicity

INTRODUCTION

Immune-related adverse events (irAE) secondary to immune checkpoint inhibitors (ICI) have gastrointestinal (GI) manifestations, including gastritis, enteritis, and/or colitis. The long-term sequelae of ICI-associated GI toxicities (GI-irAE), particularly the development of disorders of gut-brain interaction, are not well known. We characterized the incidence of persistent GI symptoms after GI-irAE.

METHODS

This is a retrospective study of adults with melanoma treated with ICI and diagnosed with GI-irAE at our institution from 2013 to 2021. All patients had endoscopic and histologic evidence of GI-irAE. The primary outcome was incidence of persistent GI symptoms (diarrhea, abdominal pain, bloating, constipation, fecal incontinence, nausea, vomiting) after resolution of GI-irAE. Hazard ratios evaluated the association between parameters and time to persistent GI symptoms.

RESULTS

One hundred four patients with melanoma (90% stage IV disease) and GI-irAE met inclusion criteria. Thirty-four percent received anti-cytotoxic T lymphocyte-associated protein-4 therapy, 33% anti-programmed death-1, and 34% dual therapy. Patients were treated for GI-irAE for an average of 9 ± 6 weeks. Twenty-eight (27%) patients developed persistent GI symptoms 1.6 ± 0.8 years after GI-irAE. The most common symptom was constipation (17%), followed by bloating (8%) and diarrhea (5%). Over 453 person-years, the incident rate was 6.2% per 100 person-years. Use of cytotoxic T lymphocyte-associated protein-4 single or dual therapy was associated with a 3.51× risk of persistent GI symptoms (95% confidence interval 1.20-10.23).

DISCUSSION

In this cohort of melanoma patients who experienced GI-irAE, 26% developed persistent GI symptoms, most frequently constipation. Future studies should characterize the GI sequelae after GI-irAE, which may shed light on disorders of gut-brain interaction pathogenesis and improve the lives of cancer survivors.

The ion channels of endomembranes

The endomembrane system consists of organellar membranes in the biosynthetic pathway [endoplasmic reticulum (ER), Golgi apparatus, and secretory vesicles] as well as those in the degradative pathway (early endosomes, macropinosomes, phagosomes, autophagosomes, late endosomes, and lysosomes). These endomembrane organelles/vesicles work together to synthesize, modify, package, transport, and degrade proteins, carbohydrates, and lipids, regulating the balance between cellular anabolism and catabolism. Large ion concentration gradients exist across endomembranes: Ca2+ gradients for most endomembrane organelles and H+ gradients for the acidic compartments. Ion (Na+, K+, H+, Ca2+, and Cl-) channels on the organellar membranes control ion flux in response to cellular cues, allowing rapid informational exchange between the cytosol and organelle lumen. Recent advances in organelle proteomics, organellar electrophysiology, and luminal and juxtaorganellar ion imaging have led to molecular identification and functional characterization of about two dozen endomembrane ion channels. For example, whereas IP3R1-3 channels mediate Ca2+ release from the ER in response to neurotransmitter and hormone stimulation, TRPML1-3 and TMEM175 channels mediate lysosomal Ca2+ and H+ release, respectively, in response to nutritional and trafficking cues. This review aims to summarize the current understanding of these endomembrane channels, with a focus on their subcellular localizations, ion permeation properties, gating mechanisms, cell biological functions, and disease relevance.

Isolated Cardiac Ryanodine Receptor Function Varies Between Mammals

Concerted robust opening of cardiac ryanodine receptors' (RyR2) Ca2+ release 1oplasmic reticulum (SR) is fundamental for normal systolic cardiac function. During diastole, infrequent spontaneous RyR2 openings mediate the SR Ca2+ leak that normally constrains SR Ca2+ load. Abnormal large diastolic RyR2-mediated Ca2+ leak events can cause delayed after depolarizations (DADs) and arrhythmias. The RyR2-associated mechanisms underlying these processes are being extensively studied at multiple levels utilizing various model animals. Since there are well-described species-specific differences in cardiac intracellular Ca2+ handing in situ, we tested whether or not single RyR2 function in vitro retains this species specificity. We isolated RyR2-rich heavy SR microsomes from mouse, rat, rabbit, and human ventricular muscle and quantified RyR2 function using identical solutions and methods. The single RyR2 cytosolic Ca2+ sensitivity was similar across these species. However, there were significant species differences in single RyR2 mean open times in both systole and diastole-like solutions. In diastole-like solutions, single rat/mouse RyR2 open probability and frequency of long openings (> 6 ms) were similar, but these values were significantly greater than those of either single rabbit or human RyR2s. We propose these in vitro single RyR2 functional differences across species stem from the species-specific RyR2 regulatory environment present in the source tissue. Our results show the single rabbit RyR2 functional attributes, particularly in diastole-like conditions, replicate those of single human RyR2 best among the species tested.

A potent and selective cis-amide inhibitor of ryanodine receptor 2 as a candidate for cardiac arrhythmia treatment

Ryanodine receptor 2 (RyR2) is a Ca2+ release channel mainly located on the sarcoplasmic reticulum (SR) membrane of heart muscle cells and regulates the concentration of Ca2+ in the cytosol. RyR2 overactivation causes potentially lethal cardiac arrhythmias, but no specific inhibitor is yet available. Herein we developed the first highly potent and selective RyR2 inhibitor, TMDJ-035, containing 3,5-difluoro substituents on the A ring and a 4-fluoro substituent on the B ring, based on a comprehensive structure-activity relationship (SAR) study of tetrazole compound 1. The SAR study also showed that the amide conformation is critical for inhibitory potency. Single-crystal X-ray diffraction analysis and variable-temperature 1H NMR revealed that TMDJ-035 strongly favors cis-amide configuration, while the inactive analogue TMDJ-011 with a secondary amide takes trans-amide configuration. Examination of the selectivity among RyRs indicated that TMDJ-035 displayed high selectivity for RyR2. TMDJ-035 suppressed abnormal Ca2+ waves and transients in isolated cardiomyocytes from RyR2-mutated mice. It appears to be a promising candidate drug for treating cardiac arrhythmias due to RyR2 overactivation, as well as a tool for studying the mechanism and dynamics of RyR2 channel gating.

Gilman reagent toward the synthesis of natural products

With the ever-increasing scope of organocuprates, a well-established Gilman reagent has been considered as an unprecedented synthetic tool in modern organic chemistry. The broad research profile of the Gilman reagent (R2CuLi in THF or Et2O) is owing to its propensity to carry out three kinds of reactions, i.e., epoxide ring opening reactions, 1,4-conjugate addition reactions, and SN2 reactions in a regioselective manner. This review examines the applications of Gilman reagent in the total synthesis of both abundant and scarce natural products of remarkable synthetic pharmaceutical profile reported since 2011. The presented insights will be of a vital roadmap to general organic synthesis and it will contribute to the development of new natural products and their analogues in future drug discovery.

Astrocyte-specific Ca2+ activity: Mechanisms of action, experimental tools, and roles in ethanol-induced dysfunction

Astrocytes are a subtype of non-neuronal glial cells that reside in the central nervous system. Astrocytes have extensive peripheral astrocytic processes that ensheathe synapses to form the tripartite synapse. Through a multitude of pathways, astrocytes can influence synaptic development and structural maturation, respond to neuronal signals, and modulate synaptic transmission. Over the last decade, strong evidence has emerged demonstrating that astrocytes can influence behavioral outcomes in various animal models of cognition. However, the full extent of how astrocytes influence brain function is still being revealed. Astrocyte calcium (Ca2+) signaling has emerged as an important driver of astrocyte-neuronal communication allowing intricate crosstalk through mechanisms that are still not fully understood. Here, we will review the field's current understanding of astrocyte Ca2+ signaling and discuss the sophisticated state-of-the-art tools and approaches used to continue unraveling astrocytes' interesting role in brain function. Using the field of pre-clinical ethanol (EtOH) studies in the context of alcohol use disorder, we focus on how these novel approaches have helped to reveal an important role for astrocyte Ca2+ function in regulating EtOH consumption and how astrocyte Ca2+ dysfunction contributes to the cognitive deficits that emerge after EtOH exposure in a rodent model.

Insights into the mediation of Ca2+ signaling in the promoting effects of LETX-VI on the synthesis and release of dopamine

Latroeggtoxin-VI (LETX-VI) is an active protein and was previously demonstrated to have effects on the synthesis and release of dopamine. Hererin, the involvement of Ca2+ signaling in the effects of LETX-VI on dopamine was systematically investigated, using PC12 cells as a neuron model. LETX-VI was shown to promote dopamine release from PC12 cells both in the presence and absence of extracellular Ca2+; however the presence of extracellular Ca2+ was favorable for enhancing the promoting effects of LETX-VI on dopamine, because LETX-VI facilitated the influx of extracellular Ca2+ through the L-type calcium channels in plasma membrane (PM) to increase cytosolic Ca2+ concentration. LETX-VI was able to penetrate the PM of PC12 cells to act on the Ca2+ channel proteins IP3Rs and RyRs in the endoplasm reticulum (ER) membrane, opening the Ca2+ channels and promoting the release of ER Ca2+ to elevate cytosolic Ca2+ level. With the help of intracellular Ca2+ chelator BAPTA, the elevated cytosolic Ca2+ level was proven to play crucial role for the enhanced promoting effects of LETX-VI on dopamine. Taken together, LETX-VI is able to open the Ca2+ channels in both PM and ER membrane simultaneously to facilitate extracellular Ca2+ influx and ER Ca2+ release, and thus increases the cytosolic Ca2+ concentration to enhance the promoting effects on the synthesis and release of dopamine.

Function of a mutant ryanodine receptor (T4709M) linked to congenital myopathy

Physiological muscle contraction requires an intact ligand gating mechanism of the ryanodine receptor 1 (RyR1), the Ca2+-release channel of the sarcoplasmic reticulum. Some mutations impair the gating and thus cause muscle disease. The RyR1 mutation T4706M is linked to a myopathy characterized by muscle weakness. Although, low expression of the T4706M RyR1 protein can explain in part the symptoms, little is known about the function RyR1 channels with this mutation. In order to learn whether this mutation alters channel function in a manner that can account for the observed symptoms, we examined RyR1 channels isolated from mice homozygous for the T4709M (TM) mutation at the single channel level. Ligands, including Ca2+, ATP, Mg2+ and the RyR inhibitor dantrolene were tested. The full conductance of the TM channel was the same as that of wild type (wt) channels and a population of partial open (subconductive) states were not observed. However, two unique sub-populations of TM RyRs were identified. One half of the TM channels exhibited high open probability at low (100 nM) and high (50 μM) cytoplasmic [Ca2+], resulting in Ca2+-insensitive, constitutively high Po channels. The rest of the TM channels exhibited significantly lower activity within the physiologically relevant range of cytoplasmic [Ca2+], compared to wt. TM channels retained normal Mg2+ block, modulation by ATP, and inhibition by dantrolene. Together, these results suggest that the TM mutation results in a combination of primary and secondary RyR1 dysfunctions that contribute to disease pathogenesis.

Eu3+ detects two functionally distinct luminal Ca2+ binding sites in ryanodine receptors

Ryanodine receptors (RyRs) are Ca2+ release channels, gated by Ca2+ in the cytosol and the sarcoplasmic reticulum lumen. Their regulation is impaired in certain cardiac and muscle diseases. Although a lot of data is available on the luminal Ca2+ regulation of RyR, its interpretation is complicated by the possibility that the divalent ions used to probe the luminal binding sites may contaminate the cytoplasmic sites by crossing the channel pore. In this study, we used Eu3+, an impermeable agonist of Ca2+ binding sites, as a probe to avoid this complication and to gain more specific information about the function of the luminal Ca2+ sensor. Single-channel currents were measured from skeletal muscle and cardiac RyRs (RyR1 and RyR2) using the lipid bilayer technique. We show that RyR2 is activated by the luminal addition of Ca2+, whereas RyR1 is inhibited. These results were qualitatively reproducible using Eu3+. The luminal regulation of RyR1 carrying a mutation associated with malignant hyperthermia was not different from that of the wild-type. RyR1 inhibition by Eu3+ was extremely voltage dependent, whereas RyR2 activation did not depend on the membrane potential. These results suggest that the RyR1 inhibition site is in the membrane's electric field (channel pore), whereas the RyR2 activation site is outside. Using in silico analysis and previous results, we predicted putative Ca2+ binding site sequences. We propose that RyR2 bears an activation site, which is missing in RyR1, but both isoforms share the same inhibitory Ca2+ binding site near the channel gate.

Detoxification enzyme is involved in the temperature effect on the toxicity of tetrachlorantraniliprole to Plutella xylostella

The efficacy of insecticides is usually influenced by temperature. Insecticides can be divided into "positive", "negative" and "non-effect" temperature coefficient insecticides (TCI). To assess the temperature-dependent effect of tetrachlorantraniliprole (TET) on Plutella xylostella Linnaeus and to elucidate the mechanism of temperature affects TET toxicity, we determined the toxicity of TET against P. xylostella from 15 °C to 35 °C by leaf dipping method. Moreover, we compared the transcriptome data of the third-instar larvae treated by TET, chlorfenapyr (CHL, non-effect TCI), and the control group at 15, 25, 35 °C, respectively. The results showed that the toxicity of TET against P. xylostella increased with increasing temperature from 15 °C to 35 °C. A total of 21 differential expressed genes (DEGs) of detoxification enzymes were screened by RNA-seq, in which 10 up-regulated genes (3 UGTs, 2 GSTs, 5 P450s) may involve the positive temperature effect of TET, and their expression patterns were consistent with qPCR results. Furthermore, the enzyme activities of GSTs and UGTs significantly increased after TET was treated at 15 °C. Especially, the temperature coefficient (TC) of TET was significantly reduced mixed with UGTs enzyme inhibitor 5-NI. Overall, TET showed higher insecticidal activity with increasing temperature, in which detoxifying enzymes associated with regulation of the positive temperature effect of TET on P. xylostella, such as UGTs, GSTs and P450s, are strongly involved. The transcriptome data provide in-depth information to understand the TET mechanism against diamondback moth. Most importantly, we identified detoxification enzymes that might be involved in regulating TET's positive temperature effect process, and contributed to efficient pest management.

Disruption of ER ion homeostasis maintained by an ER anion channel CLCC1 contributes to ALS-like pathologies

Although anion channel activities have been demonstrated in sarcoplasmic reticulum/endoplasmic reticulum (SR/ER), their molecular identities and functions remain unclear. Here, we link rare variants of Chloride Channel CLIC Like 1 (CLCC1) to amyotrophic lateral sclerosis (ALS)-like pathologies. We demonstrate that CLCC1 is a pore-forming component of an ER anion channel and that ALS-associated mutations impair channel conductance. CLCC1 forms homomultimers and its channel activity is inhibited by luminal Ca2+ but facilitated by phosphatidylinositol 4,5-bisphosphate (PIP2). We identified conserved residues D25 and D181 in CLCC1 N-terminus responsible for Ca2+ binding and luminal Ca2+-mediated inhibition on channel open probability and K298 in CLCC1 intraluminal loop as the critical PIP2-sensing residue. CLCC1 maintains steady-state [Cl-]ER and [K+]ER and ER morphology and regulates ER Ca2+ homeostasis, including internal Ca2+ release and steady-state [Ca2+]ER. ALS-associated mutant forms of CLCC1 increase steady-state [Cl-]ER and impair ER Ca2+ homeostasis, and animals with the ALS-associated mutations are sensitized to stress challenge-induced protein misfolding. Phenotypic comparisons of multiple Clcc1 loss-of-function alleles, including ALS-associated mutations, reveal a CLCC1 dosage dependence in the severity of disease phenotypes in vivo. Similar to CLCC1 rare variations dominant in ALS, 10% of K298A heterozygous mice developed ALS-like symptoms, pointing to a mechanism of channelopathy dominant-negatively induced by a loss-of-function mutation. Conditional knockout of Clcc1 cell-autonomously causes motor neuron loss and ER stress, misfolded protein accumulation, and characteristic ALS pathologies in the spinal cord. Thus, our findings support that disruption of ER ion homeostasis maintained by CLCC1 contributes to ALS-like pathologies.

Strain-dependent effects on neurobehavioral and seizure phenotypes in Scn2aK1422E mice

Pathogenic variants in SCN2A are associated with a range of neurodevelopmental disorders (NDD). Despite being largely monogenic, SCN2A-related NDD show considerable phenotypic variation and complex genotype-phenotype correlations. Genetic modifiers can contribute to variability in disease phenotypes associated with rare driver mutations. Accordingly, different genetic backgrounds across inbred rodent strains have been shown to influence disease-related phenotypes, including those associated with SCN2A-related NDD. Recently, we developed a mouse model of the variant SCN2A-p.K1422E that was maintained as an isogenic line on the C57BL/6J (B6) strain. Our initial characterization of NDD phenotypes in heterozygous Scn2aK1422E mice revealed alterations in anxiety-related behavior and seizure susceptibility. To determine if background strain affects phenotype severity in the Scn2aK1422E mouse model, phenotypes of mice on B6 and [DBA/2J×B6]F1 hybrid (F1D2) strains were compared. Convergent evidence from neurobehavioral assays demonstrated lower anxiety-like behavior in Scn2aK1422E mice compared to wild-type and further suggested that this effect is more pronounced on the B6 background compared to the F1D2 background. Although there were no strain-dependent differences in occurrence of rare spontaneous seizures, response to the chemoconvulsant kainic acid revealed differences in seizure generalization and lethality risk, with variation based on strain and sex. Continued examination of strain-dependent effects in the Scn2aK1422E mouse model could reveal genetic backgrounds with unique susceptibility profiles that would be relevant for future studies on specific traits and enable the identification of highly penetrant phenotypes and modifier genes that could provide clues about the primary pathogenic mechanism of the K1422E variant.

Calcium Handling Remodeling Underlies Impaired Sympathetic Stress Response in Ventricular Myocardium from Cacna1c Haploinsufficient Rats

CACNA1C encodes the pore-forming α1C subunit of the L-type Ca²⁺ channel, Cav1.2. Mutations and polymorphisms of the gene are associated with neuropsychiatric and cardiac disease. Haploinsufficient Cacna1c^+/- rats represent a recently developed model with a behavioral phenotype, but its cardiac phenotype is unknown. Here, we unraveled the cardiac phenotype of Cacna1c^+/- rats with a main focus on cellular Ca²⁺ handling mechanisms. Under basal conditions, isolated ventricular Cacna1c^+/- myocytes exhibited unaltered L-type Ca²⁺ current, Ca²⁺ transients (CaTs), sarcoplasmic reticulum (SR) Ca²⁺ load, fractional release, and sarcomere shortenings. However, immunoblotting of left ventricular (LV) tissue revealed reduced expression of Cav1.2, increased expression of SERCA2a and NCX, and augmented phosphorylation of RyR2 (at S2808) in Cacna1c^+/- rats. The β-adrenergic agonist isoprenaline increased amplitude and accelerated decay of CaTs and sarcomere shortenings in both Cacna1c^+/- and WT myocytes. However, the isoprenaline effect on CaT amplitude and fractional shortening (but not CaT decay) was impaired in Cacna1c^+/- myocytes exhibiting both reduced potency and efficacy. Moreover, sarcolemmal Ca²⁺ influx and fractional SR Ca²⁺ release after treatment with isoprenaline were smaller in Cacna1c^+/- than in WT myocytes. In Langendorff-perfused hearts, the isoprenaline-induced increase in RyR2 phosphorylation at S2808 and S2814 was attenuated in Cacna1c^+/- compared to WT hearts. Despite unaltered CaTs and sarcomere shortenings, Cacna1c^+/- myocytes display remodeling of Ca²⁺ handling proteins under basal conditions. Mimicking sympathetic stress with isoprenaline unmasks an impaired ability to stimulate Ca²⁺ influx, SR Ca²⁺ release, and CaTs caused, in part, by reduced phosphorylation reserve of RyR2 in Cacna1c^+/- cardiomyocytes.

Targeting calcium signaling by inositol trisphosphate receptors: A novel mechanism for the anti-asthmatic effects of Houttuynia cordata

Asthma is a chronic inflammatory disease characterized by airway hypersensitivity and remodeling. The current treatments provide only short-term benefits and may have undesirable side effects; thus, alternative or supplementary therapy is needed. Because intracellular calcium (Ca²⁺) signaling plays an essential role in regulating the contractility and remodeling of airway smooth muscle cells, the targeting of Ca²⁺ signaling is a potential therapeutic strategy for asthma. Houttuynia cordata is a traditional Chinese herb that is used to treat asthma due to its anti-allergic and anti-inflammatory properties. We hypothesized that H. cordata might modulate intracellular Ca²⁺ signaling and could help relieve asthmatic airway remodeling. We found that the mRNA and protein levels of inositol trisphosphate receptors (IP₃Rs) were elevated in interleukin-stimulated primary human bronchial smooth muscle cells and a house dust mite-sensitized model of asthma. The upregulation of IP₃R expression enhanced intracellular Ca²⁺ release upon stimulation and contributed to airway remodeling in asthma. Intriguingly, pretreatment with H. cordata essential oil rectified the disruption of Ca²⁺ signaling, mitigated asthma development, and prevented airway narrowing. Furthermore, our analysis suggested that houttuynin/2-undecanone could be the bioactive component in H. cordata essential oil because we found similar IP₃R suppression in response to the commercially available derivative sodium houttuyfonate. An in silico analysis showed that houttuynin, which downregulates IP₃R expression, binds to the IP₃ binding domain of IP₃R and may mediate a direct inhibitory effect. In summary, our findings suggest that H. cordata is a potential alternative treatment choice that may reduce asthma severity by targeting the dysregulation of Ca²⁺ signaling.

To the Mechanism of the Antiarrhythmic Action of Compound ALM-802: the Role of Ryanodine Receptors

The effect of the compound N¹-(2,3,4-trimethoxy)-N²-{2-[(2,3,4-trimethoxybenzyl)amino]ethyl}-1,2-ethane-diamine (code ALM-802) on the amplitude of the Ca²⁺ response in the cell was studied in in vitro experiments. The concentration of intracellular calcium was assessed using a Fura-2 two-wave probe. The experiments were performed on a culture of isolated rat hippocampal neurons. The effect of compound ALM-802 on the activity of ryanodine receptors (RyR2) was studied on an isolated strip of rat myocardium. The compound ALM-802 (69.8 μM) in hippocampal neurons causes a significant decrease in the amplitude of the Ca²⁺ response induced by addition of KCl to the medium. Experiments performed on an isolated myocardial strip showed that compound ALM-802 (10^-5 M) almost completely blocked the positive inotropic reaction of the strip to the RyR2 agonist caffeine (5×10^-5 M). The data obtained indicate that the decrease in the concentration of Ca²⁺ ions in the cell caused by ALM-802 is due to its ability to block RyR2 located on the membrane of the sarcoplasmic reticulum, which can be associated with the antiarrhythmic activity of the compound.

Design, synthesis, and evaluation of hydrazones as dual inhibitors of ryanodine receptors and acetylcholinesterases for Alzheimer's disease

Alzheimer's disease (AD) implicates neuronal loss, plaque and neurofibrillary tangle formation, and disturbed neuronal Ca²⁺ homeostasis, which leads to severe dementia, memory loss, as well as thinking and behavioral perturbations that could ultimately lead to death. Calcium dysregulation and low acetylcholine levels are two main mechanisms implicated in Alzheimer's disease progression. Simultaneous inhibition of calcium oscillations (store overload-induced Ca²⁺ release [SOICR]) and acetylcholinesterase (AChE) by a single molecule may bring a new breath of hope for AD treatment. Here, we described some dantrolene derivatives as dual inhibitors of the ryanodine receptor and AChE. Two series of acylhydrazone/sulfonylhydrazone derivatives with aromaticgroup were designed and synthesized. In this study, the target compounds were evaluated for their ability to inhibit SOICR and AChE in vitro, using dantrolene and donepezil as positive controls. Compound 22a exhibited excellent and balanced inhibitory potency against SOICR (inhibition (%) = 90.1, IC₅₀ = 0.162 μM) and AChE (inhibition (%) = 93.5, IC₅₀ = 0.372 μM). Docking simulations showed that several preferred compounds could bind to the active sites of both the proteins, further validating the rationality of the design strategy. Potential therapeutic effects in AD were evaluated using the Barnes maze and Morris water maze tests, which demonstrated that compound 22a significantly improved memory and cognitive behavior in AD model mice. Moreover, it was also found that compound 22a could enhance synaptic strength by measuring hippocampal long-term potentiation (LTP) in brain slices. These results suggested that the introduction of a sulfonyl-hydrazone scaffold and aromatic substitution to dantrolene derivatives provided a useful template for the development of potential chemical entities against AD.

A change of heart: understanding the mechanisms regulating cardiac proliferation and metabolism before and after birth

Mammalian cardiomyocytes undergo major maturational changes in preparation for birth and postnatal life. Immature cardiomyocytes contribute to cardiac growth via proliferation and thus the heart has the capacity to regenerate. To prepare for postnatal life, structural and metabolic changes associated with increased cardiac output and function must occur. This includes exit from the cell cycle, hypertrophic growth, mitochondrial maturation and sarcomeric protein isoform switching. However, these changes come at a price: the loss of cardiac regenerative capacity such that damage to the heart in postnatal life is permanent. This is a significant barrier to the development of new treatments for cardiac repair and contributes to heart failure. The transitional period of cardiomyocyte growth is a complex and multifaceted event. In this review, we focus on studies that have investigated this critical transition period as well as novel factors that may regulate and drive this process. We also discuss the potential use of new biomarkers for the detection of myocardial infarction and, in the broader sense, cardiovascular disease.

Gene-Edited Human-Induced Pluripotent Stem Cell Lines to Elucidate DAND5 Function throughout Cardiac Differentiation

(1) Background: The contribution of gene-specific variants for congenital heart disease, one of the most common congenital disabilities, is still far from our complete understanding. Here, we applied a disease model using human-induced pluripotent stem cells (hiPSCs) to evaluate the function of DAND5 on human cardiomyocyte (CM) differentiation and proliferation. (2) Methods: Taking advantage of our DAND5 patient-derived iPSC line, we used CRISPR-Cas9 gene-editing to generate a set of isogenic hiPSCs (DAND5-corrected and DAND5 full-mutant). The hiPSCs were differentiated into CMs, and RT-qPCR and immunofluorescence profiled the expression of cardiac markers. Cardiomyocyte proliferation was analysed by flow cytometry. Furthermore, we used a multi-electrode array (MEA) to study the functional electrophysiology of DAND5 hiPSC-CMs. (3) Results: The results indicated that hiPSC-CM proliferation is affected by DAND5 levels. Cardiomyocytes derived from a DAND5 full-mutant hiPSC line are more proliferative when compared with gene-corrected hiPSC-CMs. Moreover, parallel cardiac differentiations showed a differential cardiac gene expression profile, with upregulated cardiac progenitor markers in DAND5-KO hiPSC-CMs. Microelectrode array (MEA) measurements demonstrated that DAND5-KO hiPSC-CMs showed prolonged field potential duration and increased spontaneous beating rates. In addition, conduction velocity is reduced in the monolayers of hiPSC-CMs with full-mutant genotype. (4) Conclusions: The absence of DAND5 sustains the proliferation of hiPSC-CMs, which alters their electrophysiological maturation properties. These results using DAND5 hiPSC-CMs consolidate the findings of the in vitro and in vivo mouse models, now in a translational perspective. Altogether, the data will help elucidate the molecular mechanism underlying this human heart disease and potentiates new therapies for treating adult CHD.

Genetic and epigenetic effects on couple adjustment in context of romantic relationship: A scoping systematic review

Introduction: Couples' relationships defined by a complex interaction between the two partners and their intrapersonal traits. Romantic; relationships and love are associated with marital satisfaction and stability, as well as couples' happiness and health. Personality traits influence romantic relationships and, personality influenced by genetical and non-genetically factors. The roles of non-genetically factors such as socioeconomic position and external appearance have revealed in determining the quality of romantic relationships. Methods: We; performed a scoping systematic review to assess the association between genetics and epigenetic factors and romantic relationship. Relevant articles were identified by PubMed, EMBASE, Web of Science, Scopus, and the APA PsycInfo searching between inception and 4 June 2022. Results: Different studies evaluated the associated polymorphisms in 15 different genes or chromosomal regions. In the first step; we classified them into four groups: (1) Oxytocin-related signaling pathway (OXTR, CD38, and AVPR1A); (2) Serotonin-related signaling pathway (SLC6A4, HTR1A, and HTR2A); (3) Dopamine and catecholamine-related signaling pathway (DRD1, DRD2, DRD4, ANKK1, and COMT); and (4) other genes (HLA, GABRA2, OPRM1, and Y-DNA haplogroup D-M55). Then, we evaluated and extracted significant polymorphisms that affect couple adjustment and romantic relationships. Discussion: Overall, the findings suggest that genetic and epigenetics variants play a key role in marital adjustment and romantic relationships over time.

RyR2 Serine-2030 PKA Site Governs Ca2+ Release Termination and Ca2+ Alternans

BACKGROUND

PKA (protein kinase A)-mediated phosphorylation of cardiac RyR2 (ryanodine receptor 2) has been extensively studied for decades, but the physiological significance of PKA phosphorylation of RyR2 remains poorly understood. Recent determination of high-resolution 3-dimensional structure of RyR2 in complex with CaM (calmodulin) reveals that the major PKA phosphorylation site in RyR2, serine-2030 (S2030), is located within a structural pathway of CaM-dependent inactivation of RyR2. This novel structural insight points to a possible role of PKA phosphorylation of RyR2 in CaM-dependent inactivation of RyR2, which underlies the termination of Ca²⁺ release and induction of cardiac Ca²⁺ alternans.

METHODS

We performed single-cell endoplasmic reticulum Ca²⁺ imaging to assess the impact of S2030 mutations on Ca²⁺ release termination in human embryonic kidney 293 cells. Here we determined the role of the PKA site RyR2-S2030 in a physiological setting, we generated a novel mouse model harboring the S2030L mutation and carried out confocal Ca²⁺ imaging.

RESULTS

We found that mutations, S2030D, S2030G, S2030L, S2030V, and S2030W reduced the endoplasmic reticulum luminal Ca²⁺ level at which Ca²⁺ release terminates (the termination threshold), whereas S2030P and S2030R increased the termination threshold. S2030A and S2030T had no significant impact on release termination. Furthermore, CaM-wild-type increased, whereas Ca²⁺ binding deficient CaM mutant (CaM-M [a loss-of-function CaM mutation with all 4 EF-hand motifs mutated]), PKA, and Ca²⁺/CaMKII (CaM-dependent protein kinase II) reduced the termination threshold. The S2030L mutation abolished the actions of CaM-wild-type, CaM-M, and PKA, but not CaMKII, in Ca²⁺ release termination. Moreover, we showed that isoproterenol and CaM-M suppressed pacing-induced Ca²⁺ alternans and accelerated Ca²⁺ transient recovery in intact working hearts, whereas CaM-wild-type exerted an opposite effect. The impact of isoproterenol was partially and fully reversed by the PKA inhibitor N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinoline-sulfonamide and the CaMKII inhibitor N-[2-[N-(4-chlorocinnamyl)-N-methylaminomethyl]phenyl]-N-(2-hydroxyethyl)-4-methoxybenzenesulfonamide individually and together, respectively. S2030L abolished the impact of CaM-wild-type, CaM-M, and N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinoline-sulfonamide-sensitive component, but not the N-[2-[N-(4-chlorocinnamyl)-N-methylaminomethyl]phenyl]-N-(2-hydroxyethyl)-4-methoxybenzenesulfonamide-sensitive component, of isoproterenol.

RyR2 regulates store-operated Ca2+ entry, phospholipase C activity, and electrical excitability in the insulinoma cell line INS-1

The ER Ca2+ channel ryanodine receptor 2 (RyR2) is required for maintenance of insulin content and glucose-stimulated insulin secretion, in part, via regulation of the protein IRBIT in the insulinoma cell line INS-1. Here, we examined store-operated and depolarization-dependent Ca2+entry using INS-1 cells in which either RyR2 or IRBIT were deleted. Store-operated Ca2+ entry (SOCE) stimulated with thapsigargin was reduced in RyR2KO cells compared to controls, but was unchanged in IRBITKO cells. STIM1 protein levels were not different between the three cell lines. Basal and stimulated (500 μM carbachol) phospholipase C (PLC) activity was also reduced specifically in RyR2KO cells. Insulin secretion stimulated by tolbutamide was reduced in RyR2KO and IRBITKO cells compared to controls, but was potentiated by an EPAC-selective cAMP analog in all three cell lines. Cellular PIP2 levels were increased and cortical f-actin levels were reduced in RyR2KO cells compared to controls. Whole-cell Cav channel current density was increased in RyR2KO cells compared to controls, and barium current was reduced by acute activation of the lipid phosphatase pseudojanin preferentially in RyR2KO cells over control INS-1 cells. Action potentials stimulated by 18 mM glucose were more frequent in RyR2KO cells compared to controls, and insensitive to the SK channel inhibitor apamin. Taken together, these results suggest that RyR2 plays a critical role in regulating PLC activity and PIP2 levels via regulation of SOCE. RyR2 also regulates β-cell electrical activity by controlling Cav current density and SK channel activation.

Serum bone remodeling parameters and transcriptome profiling reveal abnormal bone metabolism associated with keel bone fractures in laying hens

Keel bone fractures affect welfare, health, and production performance in laying hens. A total of one hundred and twenty 35-wk-old Hy-line Brown laying hens with normal keel (NK) bone were housed in furnished cages and studied for ten weeks to investigate the underlying mechanism of keel bone fractures. At 45 wk of age, the keel bone state of birds was assessed by palpation and X-ray, and laying hens were recognized as NK and fractured keel (FK) birds according to the presence or absence of fractures in keel bone. The serum samples of 10 NK and 10 FK birds were collected to determine bone metabolism-related indexes and slaughtered to collect keel bones for RNA-sequencing (RNA-seq), Micro-CT, and histopathological staining analyses. The results showed that the concentrations of Ca, phosphorus, calcitonin, 25-hydroxyvitamin D₃, and osteocalcin and activities of alkaline phosphatase and tartrate-resistant acid phosphatase (TRAP) in serum samples of FK birds were lower than those of NK birds (P < 0.05), but the concentrations of parathyroid hormone, osteoprotegerin, and corticosterone in serum samples of FK birds were higher than those of NK birds (P < 0.05). TRAP staining displayed that FK bone increased the number of osteoclasts (P < 0.05). Micro-CT analysis indicated that FK bone decreased bone mineral density (P < 0.05). Transcriptome sequencing analysis of NK and FK bones identified 214 differentially expressed genes (DEGs) (|log2FoldChange| > 1, P < 0.05), among which 88 were upregulated and 126 downregulated. Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) analysis indicated that 14 DEGs related to skeletal muscle movement and bone Ca transport (COL6A1, COL6A2, COL6A3, PDGFA, MYLK2, EGF, CAV3, ADRA1D, BDKRB1, CACNA1S, TNN, TNNC1, TNNC2, and RYR3) were enriched in focal adhesion and Ca signaling pathway, regulating bone quality. This study suggests that abnormal bone metabolism related to keel bone fractures is possibly responded to fracture healing in laying hens.

The spatio-temporal properties of calcium transients in hippocampal pyramidal neurons in vitro

The spatio-temporal properties of calcium signals were studied in cultured pyramidal neurons of the hippocampus using two-dimensional fluorescence microscopy and ratiometric dye Fura-2. Depolarization-induced Ca²⁺ transients revealed an asynchronous delayed increase in free Ca²⁺ concentration. We found that the level of free resting calcium in the cell nucleus is significantly lower compared to the soma, sub-membrane, and dendritic tree regions. Calcium release from the endoplasmic reticulum under the action of several stimuli (field stimulation, high K⁺ levels, and caffeine) occurs in all areas studied. Under depolarization, calcium signals developed faster in the dendrites than in other areas, while their amplitude was significantly lower since larger and slower responses inside the soma. The peak value of the calcium response to the application of 10 mM caffeine, ryanodine receptors (RyRs) agonist, does not differ in the sub-membrane zone, central region, and nucleus but significantly decreases in the dendrites. In the presence of caffeine, the delay of Ca²⁺ signals between various areas under depolarization significantly declined. Thirty percentage of the peak amplitude of Ca²⁺ transients at prolonged electric field stimulation corresponded to calcium release from the ER store by RyRs, while short-term stimulation did not depend on them. 20 μM dantrolene, RyRs inhibitor, significantly reduces Ca²⁺ transient under high K⁺ levels depolarization of the neuron. RyRs-mediated enhancement of the Ca²⁺ signal is more pronounced in the central part and nucleus compared to the sub-membrane or dendrites regions of the neuron. In summary, using the ratiometric imaging allowed us to obtain additional information about the involvement of RyRs in the intracellular dynamics of Ca²⁺ signals induced by depolarization or electrical stimulation train, with an underlying change in Ca²⁺ concentration in various regions of interest in hippocampal pyramidal neurons.

Endoplasmic Reticulum Stress Signaling and Neuronal Cell Death

Besides protein processing, the endoplasmic reticulum (ER) has several other functions such as lipid synthesis, the transfer of molecules to other cellular compartments, and the regulation of Ca²⁺ homeostasis. Before leaving the organelle, proteins must be folded and post-translationally modified. Protein folding and revision require molecular chaperones and a favorable ER environment. When in stressful situations, ER luminal conditions or chaperone capacity are altered, and the cell activates signaling cascades to restore a favorable folding environment triggering the so-called unfolded protein response (UPR) that can lead to autophagy to preserve cell integrity. However, when the UPR is disrupted or insufficient, cell death occurs. This review examines the links between UPR signaling, cell-protective responses, and death following ER stress with a particular focus on those mechanisms that operate in neurons.

Ventricular arrhythmias in acute myocardial ischaemia-Focus on the ageing and sex

Annually, approximately 17 million people die from cardiovascular diseases worldwide, half of them suddenly. The most common direct cause of sudden cardiac death is ventricular arrhythmia triggered by an acute coronary syndrome (ACS). The study summarizes the knowledge of the mechanisms of arrhythmia onset during ACS in humans and in animal models and factors that may influence the susceptibility to life-threatening arrhythmias during ACS with particular focus on the age and sex. The real impact of age and sex on the arrhythmic susceptibility within the setting of acute ischaemia is masked by the fact that ACSs result from coronary artery disease appearing with age much earlier among men than among women. However, results of researches show that in ageing process changes with potential pro-arrhythmic significance, such as increased fibrosis, cardiomyocyte hypertrophy, decrease number of gap junction channels, disturbances of the intracellular Ca²⁺ signalling or changes in electrophysiological parameters, occur independently of the development of cardiovascular diseases and are more severe in male individuals. A review of the literature also indicates a marked paucity of research in this area in female and elderly individuals. Greater awareness of sex differences in the aging process could help in the development of personalized prevention methods targeting potential pro-arrhythmic factors in patients of both sexes to reduce mortality during the acute phase of myocardial infarction. This is especially important in an era of aging populations in which women will predominate due to their longer lifespan.

A perinuclear calcium compartment regulates cardiac myocyte hypertrophy

The pleiotropic Ca2+/calmodulin-dependent phosphatase calcineurin is a key regulator of pathological cardiac myocyte hypertrophy. The selective activation of hypertrophic calcineurin signaling under stress conditions has been attributed to compartmentation of Ca2+ signaling in cardiac myocytes. Here, perinuclear signalosomes organized by the scaffold protein muscle A-Kinase Anchoring Protein β (mAKAPβ/AKAP6β) are shown to orchestrate local Ca2+ transients, inducing calcineurin-dependent NFATc nuclear localization and myocyte hypertrophy in response to β-adrenergic receptor activation. Fluorescent biosensors for Ca2+ and calcineurin and protein kinase A (PKA) activity, both diffusely expressed and localized by nesprin-1α to the nuclear envelope, are used to define an autonomous mAKAPβ signaling compartment in adult and neonatal rat ventricular myocytes. Notably, β-adrenergic-stimulated perinuclear Ca2+ and PKA and CaN activity transients depended upon mAKAPβ expression, while Ca2+ elevation and PKA and CaN activity in the cytosol were mAKAPβ independent. Buffering perinuclear cAMP and Ca2+ prevented calcineurin-dependent NFATc nuclear translocation and myocyte hypertrophy, without affecting cardiac myocyte contractility. Additional findings suggest that the perinuclear Ca2+ transients were mediated by signalosome-associated ryanodine receptors regulated by local PKA phosphorylation. These results demonstrate the existence of a functionally independent Ca2+ signaling compartment in the cardiac myocyte regulating hypertrophy and provide a premise for targeting mAKAPβ signalosomes to prevent selectively cardiac hypertrophy in disease.

The crosstalk effect between ferrous and other ions metabolism in ferroptosis for therapy of cancer

Ferroptosis is an iron-dependent cell death process characterized by excessive accumulation of reactive oxygen species and lipid peroxidation. The elucidation of ferroptosis pathways may lead to novel cancer therapies. Current evidence suggests that the mechanism of ferroptosis can be summarized as oxidative stress and antioxidant defense mechanisms. During this process, ferrous ions play a crucial role in cellular oxidation, plasma membrane damage, reactive oxygen species removal imbalance and lipid peroxidation. Although, disregulation of intracellular cations (Fe²⁺, Ca²⁺, Zn²⁺, etc.) and anions (Cl^-, etc.) have been widely reported to be involved in ferroptosis, their specific regulatory mechanisms have not been established. To further understand the crosstalk effect between ferrous and other ions in ferroptosis, we reviewed the ferroptosis process from the perspective of ions metabolism. In addition, the role of ferrous and other ions in tumor therapy is briefly summarized.

Centronuclear Myopathy Caused by Defective Membrane Remodelling of Dynamin 2 and BIN1 Variants

Centronuclear myopathy (CNM) is a congenital myopathy characterised by centralised nuclei in skeletal myofibers. T-tubules, sarcolemmal invaginations required for excitation-contraction coupling, are disorganised in the skeletal muscles of CNM patients. Previous studies showed that various endocytic proteins are involved in T-tubule biogenesis and their dysfunction is tightly associated with CNM pathogenesis. DNM2 and BIN1 are two causative genes for CNM that encode essential membrane remodelling proteins in endocytosis, dynamin 2 and BIN1, respectively. In this review, we overview the functions of dynamin 2 and BIN1 in T-tubule biogenesis and discuss how their dysfunction in membrane remodelling leads to CNM pathogenesis.

Modeling calcium dynamics in neurons with endoplasmic reticulum: existence, uniqueness and an implicit-explicit finite element scheme

Like many other biological processes, calcium dynamics in neurons containing an endoplasmic reticulum is governed by diffusion-reaction equations on interface-separated domains. Interface conditions are typically described by systems of ordinary differential equations that provide fluxes across the interfaces. Using the calcium model as an example of this class of ODE-flux boundary interface problems, we prove the existence, uniqueness and boundedness of the solution by applying comparison theorem, fundamental solution of the parabolic operator and a strategy used in Picard's existence theorem. Then we propose and analyze an efficient implicit-explicit finite element scheme which is implicit for the parabolic operator and explicit for the nonlinear terms. We show that the stability does not depend on the spatial mesh size. Also the optimal convergence rate in H ¹ norm is obtained. Numerical experiments illustrate the theoretical results.

Building Biological Relevance Into Integrative Modelling of Macromolecular Assemblies

Recent advances in structural biophysics and integrative modelling methods now allow us to decipher the structures of large macromolecular assemblies. Understanding the dynamics and mechanisms involved in their biological function requires rigorous integration of all available data. We have developed a complete modelling pipeline that includes analyses to extract biologically significant information by consistently combining automated and interactive human-guided steps. We illustrate this idea with two examples. First, we describe the ryanodine receptor, an ion channel that controls ion flux across the cell membrane through transitions between open and closed states. The conformational changes associated with the transitions are small compared to the considerable system size of the receptor; it is challenging to consistently track these states with the available cryo-EM structures. The second example involves homologous recombination, in which long filaments of a recombinase protein and DNA catalyse the exchange of homologous DNA strands to reliably repair DNA double-strand breaks. The nucleoprotein filament reaction intermediates in this process are short-lived and heterogeneous, making their structures particularly elusive. The pipeline we describe, which incorporates experimental and theoretical knowledge combined with state-of-the-art interactive and immersive modelling tools, can help overcome these challenges. In both examples, we point to new insights into biological processes that arise from such interdisciplinary approaches.

miR-731 modulates the zebrafish heart morphogenesis via targeting Calcineurin/Nfatc3a pathway

BACKGROUND

Zebrafish miR-731 is orthologous of human miR-425, which has been demonstrated to have cardio-protective roles by a variety of mechanisms. The miR-731 morphants show pericardium enlargement, and many DEGs (differentially expressed genes) are enriched in 'Cardiac muscle contraction' and 'Calcium signaling pathway', implying that miR-731 plays a potential role in heart function and development. However，the in vivo physiological role of miR-731 in the heart needs to be fully defined.

METHODS

Zebrafish miR-731 morphants were generated by morpholino knockdown, and miR-731 knockout zebrafish was generated by CRISRP/Cas9. We observed cardiac morphogenesis based on whole-mount in situ hybridization. Furthermore, RNA-seq and qRT-PCR were used to elucidate the molecular mechanism and analyze the gene expression. Double luciferase verification and Western blot were used to verify the target gene.

RESULTS

The depletion of miR-731 in zebrafish embryos caused the deficiency of cardiac development and function, which was associated with reduced heart rate, ventricular enlargement and heart looping disorder. In addition, mechanistic study demonstrated that Calcineurin/Nfatc3a signaling involved in miR-731 depletion induced abnormal cardiac function and developmental defects.

CONCLUSION

MiR-731 regulates cardiac function and morphogenesis through Calcineurin/Nfatc3a signaling.

GENERAL SIGNIFICANCE

Our studies highlight the potential importance of miR-731 in cardiac development.