Calcium Release Channels: Structure and Function of IP3 Receptors and Ryanodine Receptors

Intracellular calcium channels: Potential targets for type 2 diabetes mellitus?

Type 2 diabetes mellitus (T2DM) is a prevalent metabolic disorder. Despite the availability of numerous pharmacotherapies, a range of adverse reactions, including hypoglycemia, gastrointestinal discomfort, and lactic acidosis, limits their patient applicability and long-term application. Therefore, it is necessary to screen novel therapeutic drugs for T2DM treatment that have high efficacy but few adverse effects. AMP-activated protein kinase (AMPK) stands out as one of the most powerful targets for T2DM treatment. It can be activated through energy-sensing or calcium signaling. Medications that activate AMPK through the energy-sensing mechanism exhibit remarkable potency, but they are accompanied by lactic acidosis, carrying an alarmingly high mortality rate. Interestingly, medications that activate AMPK through calcium signaling, such as gliclazide, seldom induce lactic acidosis. However, the efficacy of gliclazide is much lower than metformin. Therefore, it is necessary to explore targets that activate AMPK via calcium signaling to avoid lactic acidosis while maintaining high potency. Ion channels are the main controller of intracellular calcium flow. Specific agonists and inhibitors targeting ion channels have been reported to activate AMPK. In this review, we will summarize the structure and function of calcium-permeable ion channels and discuss the potential of targeting these calcium channels for T2DM treatment.

Skeletal and dental tissue mineralization: The potential role of the endoplasmic reticulum/Golgi complex and the endolysosomal and autophagic transport systems

This paper presents a review of the potential role of the endoplasmic reticulum/Golgi complex and intracellular vesicles in mediating events leading to or associated with vertebrate tissue mineralization. The possible importance of these organelles in this process is suggested by observations that calcium ions accumulate in the tubules and lacunae of the endoplasmic reticulum and Golgi. Similar levels of calcium ions (approaching millimolar) are present in vesicles derived from endosomes, lysosomes and autophagosomes. The cellular level of phosphate ions in these organelles is also high (millimolar). While the source of these ions for mineral formation has not been identified, there are sound reasons for considering that they may be liberated from mitochondria during the utilization of ATP for anabolic purposes, perhaps linked to matrix synthesis. Published studies indicate that calcium and phosphate ions or their clusters contained as cargo within the intracellular organelles noted above lead to formation of extracellular mineral. The mineral sequestered in mitochondria has been documented as an amorphous calcium phosphate. The ion-, ion cluster- or mineral-containing vesicles exit the cell in plasma membrane blebs, secretory lysosomes or possibly intraluminal vesicles. Such a cell-regulated process provides a means for the rapid transport of ions or mineral particles to the mineralization front of skeletal and dental tissues. Within the extracellular matrix, the ions or mineral may associate to form larger aggregates and potential mineral nuclei, and they may bind to collagen and other proteins. How cells of hard tissues perform their housekeeping and other biosynthetic functions while transporting the very large volumes of ions required for mineralization of the extracellular matrix is far from clear. Addressing this and related questions raised in this review suggests guidelines for further investigations of the intracellular processes promoting the mineralization of the skeletal and dental tissues.

The molecular mechanisms underlying retinal ganglion cell apoptosis and optic nerve regeneration in glaucoma (Review)

Glaucoma is a neurodegenerative disease characterized by progressive and irreversible necrosis and apoptosis of retinal ganglion cells (RGCs). Deformation of the lamina cribrosa (LC) has been identified as a factor leading to damage to the optic nerve and capillaries passing through the LC, ultimately causing visual field defects and glaucoma development. Recent advancements in molecular biology, both domestically and internationally, have enabled a more comprehensive and in‑depth understanding of glaucoma pathogenesis. In the present review, the role of molecular signaling pathways associated with RGCs apoptosis, optic nerve protection and regeneration, and LC damage and remodeling in the development of glaucoma, are summarized and discussed. The insights provided herein may offer new targets and ideas for interventions and treatment strategies for glaucoma.

Involvement of BK Channels and Ryanodine Receptors in Salicylate-induced Tinnitus

Neural hyperexcitability of the central auditory system is a key pathological characteristic of tinnitus, but its underlying molecular mechanisms remain elusive. The large-conductance Ca2+-activated K+ channel (BK) plays a crucial role in down- or upregulating neuronal activity. This study aims to investigate the role of BK channels in mediating tinnitus-associated neural hyperexcitability and elucidate the mechanisms behind it. Immunofluorescent staining revealed extensive expression of the BK channels on neurons within the central auditory system of rats. After long-term systemic administration of salicylate, a stable tinnitus inducer, we observed a significant change in the expression levels of BKα and β4 subunits in the rat central auditory system. In addition, salicylate was found to enhance the outward potassium currents mediated by the BK channel when exogenously expressed in HEK293 cells. Interestingly, this effect could be blocked by ryanodine, a potent inhibitor of ryanodine receptors (RyRs). Molecular docking identified Gln4020 within the central domain of RyR as a key residue in RyR-salicylate interactions. The results indicated that salicylate might directly activate RyRs leading to Ca2+ release from endoplasmic reticulum, and increased BK currents subsequently. Systemic treatment with paxilline, a potent blocker of BK channel, selectively reversed the increased P4/P1 amplitude ratios in the frequency region of tinnitus perception induced by single-dose salicylate administration. These results suggest that BK channels and ryanodine receptors may play a selective role in salicylate-induced tinnitus.

Calcium release via IP3R/RyR channels contributes to the nuclear and mitochondrial Ca2+ signals elicited by neuronal stimulation

The brain constantly adapts to environmental changes by modifying the expression of genes that enable synaptic plasticity, learning and memory. The expression of several of these genes requires nuclear calcium (Ca2+) signals, which in turn requires that Ca2+ signals generated by neuronal activity at the synapses or the soma propagate to the nucleus. Since cytoplasmic Ca2+ diffusion is highly restricted, Ca2+ signal propagation to the nucleus requires the participation of other cellular mechanisms. The inositol trisphosphate receptor (IP3R) and the ryanodine receptor (RyR) channels, both of which reside in the endoplasmic reticulum (ER) membrane, play key roles in cellular Ca2+ signal generation. Yet, their roles in the generation of nuclear and mitochondrial Ca2+ signals induced by neuronal activity require further investigation. Here, the impact of IP3R1 or RyR2 knockdown on gabazine-induced nuclear and mitochondrial Ca2+ signals in neurons was evaluated. To this aim, recombinant adeno-associated viruses (rAAVs) were used to introduce small hairpin RNAs (shRNAs) to knockdown type-1 (IP3R1) and type-2 (RyR2) channel expression in cultured rat hippocampal neurons. Additionally, synaptic contact numbers were assessed through immunocytochemistry. Knockdown of IP3R1 or RyR2 channels significantly reduced their protein contents and the generation of gabazine-induced nuclear and mitochondrial Ca2+ signals, without altering synaptic contact numbers. Our results highlight the contribution of IP3R1 and RyR2 channels to the generation of nuclear and mitochondrial Ca2+ signal induced by neuronal activity, reinforcing the role that these Ca2+ release channels play in hippocampal synaptic plasticity and memory formation.

Septin 3 regulates memory and L-LTP-dependent extension of endoplasmic reticulum into spines

Transient memories are converted to persistent memories at the synapse and circuit/systems levels. The synapse-level consolidation parallels electrophysiological transition from early- to late-phase long-term potentiation of synaptic transmission (E-/L-LTP). While glutamate signaling upregulations coupled with dendritic spine enlargement are common underpinnings of E-LTP and L-LTP, synaptic mechanisms conferring persistence on L-LTP remain unclear. Here, we show that L-LTP induced at the perforant path-hippocampal dentate gyrus (DG) synapses accompanies cytoskeletal remodeling that involves actin and the septin subunit SEPT3. L-LTP in DG neurons causes fast spine enlargement, followed by SEPT3-dependent smooth endoplasmic reticulum (sER) extension into enlarged spines. Spines containing sER show greater Ca2+ responses upon synaptic input and local synaptic activity. Consistently, Sept3 knockout in mice (Sept3-/-) impairs memory consolidation and causes a scarcity of sER-containing spines. These findings indicate a concept that sER extension into active spines serves as a synaptic basis of memory consolidation.

Mfn2 regulates calcium homeostasis and suppresses PASMCs proliferation via interaction with IP3R3 to mitigate pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a chronic disorder characterized by the excessive proliferation of pulmonary arterial smooth muscle cells (PASMCs). Recent studies indicate that Mitochondrial fusion protein 2 (Mfn2) maintains intracellular calcium (Ca2+) homeostasis via the mitochondria-associated endoplasmic reticulum membranes (MAMs) pathway, thereby inhibiting PASMCs proliferation and reducing pulmonary artery pressure. However, the precise mechanisms remain unclear.

METHODS

This study explored the roles of Mfn2 and IP3R3 in PAH progression by assessing their expression in lung tissues of a monocrotaline (MCT)-induced PAH rat model. Immunoprecipitation assays were performed to confirm the interaction between Mfn2 and IP3R3. PASMCs were treated with either silenced or overexpressed Mfn2 and exposed to TNF-ɑ to observe effects on ER stress, IP3R3 expression, mitochondrial Ca2+ transport, and mitochondrial integrity. We also evaluated the effects of 4-phenylbutyric acid (4-PBA) and cistanche phenylethanol glycosides (CPGs) on the Mfn2-IP3R3 interaction in a TNF-α-induced PAH cell model, focusing on Ca2+ transport and mitochondrial structure.

RESULTS

Mfn2 expression was significantly down-regulated in the MCT-induced PAH rat model. Inhibition of ER stress upregulated Mfn2 expression, downregulated IP3R3 expression, increased mitochondrial Ca2+ concentration, and reduced autophagy, improving pulmonary hemodynamics and vascular remodeling. Overexpression of Mfn2 reduced ER stress, decreased IP3R3 expression, decreased mitochondrial Ca2+ transport, and restored mitochondrial integrity. Immunoprecipitation assays confirmed the interaction between Mfn2 and IP3R3. Inhibition of IP3R3 elevated Mfn2 levels, yielding similar beneficial effects as Mfn2 overexpression. 4-PBA and CPGs modulated the Mfn2-IP3R3 signaling axis, effectively inhibiting PAH progression.

CONCLUSIONS

Mfn2 mediates mitochondrial Ca2+ transport via IP3R3, suppressing PASMCs proliferation and pulmonary vascular remodeling, underscoring Mfn2's potential in regulating metabolic processes and vascular remodeling in PAH. These findings provide new insights for developing PAH-targeted therapeutics and establish a theoretical basis for traditional Chinese medicine in PAH prevention and treatment.

Thiophosphate bioisosteres of inositol hexakisphosphate enhance binding affinity and residence time on bacterial virulence factors

Inositol phosphates are essential for mammalian cell signalling with critical roles in cellular processes. The fully phosphorylated inositol phosphate, myo-inositol hexakisphosphate (IP6), modulates numerous eukaryotic proteins and bacterial virulence factors. It has been suggested that the high charge density of IP6 causes restructuring of virulence factors in mammalian cells, activating their enzymatic activity. IP6 is challenging to study due to its phytase instability and propensity to precipitate. Here we suggest that the thiophosphate bioisostere, myo-inositol hexakisthiophosphate (IT6), will mitigate these issues, as thiophosphate substitution has been found to be phytase resistant and improve solubility. Assessment of the chemical properties of IT6 has indeed validated these characteristics. In addition, we performed biophysical characterization of IT6 binding to the virulence factors Salmonella enterica serovar Typhimurium AvrA, Vibrio parahaemolyticus VopA, and Clostridioides difficile TcdB. Our data show that the higher charge density of IT6 increased its binding affinity and residence time on the proteins, which improved stabilization of the bound-state. IT6 is a valuable tool for structural biology research and the described biophysical characteristics of thiophosphate substitution are of value in medicinal chemistry.

Smooth muscle cell Piezo1 depletion results in impaired contractile properties in murine small bowel

Piezo1 is a mechanosensitive cation channel expressed in intestinal muscularis cells (IMCs), including smooth muscle cells (SMCs), interstitial cells of Cajal, and Pdgfrα+ cells, which form the SIP syncytium, crucial for GI contractility. Here, we investigate the effects of SMC-specific Piezo1 deletion on small bowel function. Piezo1 depletion results in weight loss, delayed GI transit, muscularis thinning, and decreased SMCs. Ex vivo analyses demonstrated impaired contractile strength and tone, while in vitro studies using IMC co-cultures show dysrhythmic Ca2+ flux with decreased frequency. Imaging reveal that Piezo1 localizes intracellularly, thereby likely impacting Ca2+ signaling mechanisms modulated by Ca2 + -handling channels located on the sarcoplasmic reticulum and plasma membrane. Our findings suggest that Piezo1 in small bowel SMCs contributes to contractility by maintaining intracellular Ca2+ activity and subsequent signaling within the SIP syncytium. These findings provide new insights into the complex role of Piezo1 in small bowel SMCs and its implications for GI motility.

Unlocking the therapeutic potential of the NFAT pathway in kidney diseases

The nuclear factor of activated T cells (NFAT) is a novel renoprotective transcription factor in an inactive form in the cytoplasm and an active form in the nucleus. NFAT is expressed in T cells, heart, kidney and lymphocytes. NFAT plays an essential role in inducing apoptosis of renal tubular epithelial cells. NFAT levels have been observed to increase significantly during kidney diseases. Further, downregulation or silencing of endogenous NFAT mitigates kidney diseases. NFAT regulation depends upon the intricate interplay between calcium ions and calcineurin (CaN), thus orchestrating the NFAT/calcineurin signalling pathway. When CaN is activated, it induces dephosphorylation of NFAT and localises the active NFAT into the nucleus, which ultimately leads to inflammation, fibrosis and apoptosis of kidney cells. Further, the global incidence (> 800 million) due to kidney disease imposes a significant economic burden on the healthcare system. Therefore, it is crucial to comprehend the pathways involved in the pathophysiology of kidney diseases to develop targeted interventions. Ongoing studies indicate potential therapies, including anandamide, 11R-VIVIT and maxacalcitol to regulate NFAT levels in kidney disease. The present review discusses the role and regulation of NFAT in the pathogenesis of kidney diseases. This is focused on various preclinical studies that have shown NFAT downregulation as a potential therapeutic strategy against kidney disease setting the foundation for future clinical investigations.

Potential therapeutic mechanisms of Draconis Resina in cardiovascular diseases-a narrative review

As a traditional Chinese herbal medicine, Draconis Resina (DR) has garnered significant attention due to its efficacy in treating various clinical diseases. Notably, it demonstrates remarkable therapeutic effects in cardiovascular diseases, such as atherosclerosis, coronary heart disease, and myocardial ischemia-reperfusion injury. A comprehensive understanding of the potential therapeutic mechanisms of DR in cardiovascular diseases can positively influence their prevention and treatment. Therefore, through a thorough literature review, this paper summarizes the primary mechanisms of DR in managing cardiovascular diseases, which include the prevention of thrombosis, inhibition of inflammatory responses, alleviation of oxidative stress, enhancement of endothelial function, and mitigation of myocardial fibrosis. There may remain many untapped therapeutic applications of DR that need further exploration. This review aims to give readers a deeper understanding of the DR and offer new perspectives.

Intranasal Zinc Oxide Nanoparticles Induce Neuronal PANoptosis via Microglial Pathway

Recent data have revealed an increased risk of respiratory exposure during the manufacturing process and application of nanomaterials, resulting in an increased incidence of neurodegenerative diseases in the general population. Zinc oxide nanoparticles (ZNPs) are among the most used nanomaterials in biomedical and manufactured consumer products. In this study, neurological dysfunction after intranasal administration of ZNPs is observed, in which the ZNPs enter the brain via the nose-to-brain pathway and accumulate in microglia but not in astrocytes or neurons. By using a coculture system of microglia and neurons, the ZNPs are found that induce microglia-derived oxidative stress injury and lead to neuronal cell PANoptosis. In this context, ZNPs induced the generation of reactive oxygen species (ROS) originating from microglial NADPH oxidase 2 (NOX2), which further induced neuronal membrane lipid peroxidation and increased Ca2+ influx and mitochondrial DNA release. The leaked mitochondrial DNA subsequently initiates PANoptosis of neurons. Importantly, inhibition of microglial NOX2 activation can significantly alleviate brain oxidative injury and rescue neuronal PANoptosis. This study can advance the understanding of the mode of neuronal cell death while underscoring the importance of the interconnections among glial cells and neurons, which is beneficial for informing effective interventions for respiratory exposure to nanoparticles.

Ashitaba Chalcone 4-Hydroxydericcin Promotes Glucagon-Like Peptide-1 Secretion and Prevents Postprandial Hyperglycemia in Mice

Certain polyphenols improve glucose tolerance by stimulating glucagon-like peptide-1 (GLP-1) secretion from intestinal L-cells. Ashitaba chalcones, 4-hydroxyderricin (4-HD), and xanthoangelol (XAG) have antihyperglycemic effects, but their molecular mechanism, including whether they promote GLP-1 secretion is unknown. This study investigates the 4-HD-induced GLP-1 secretory mechanisms and its anti-hyperglycemic effects. The secretory mechanisms were examined in STC-1 cells and antihyperglycemic effects in male ICR mice. In STC-1 cells, 4-HD, but not XAG, stimulated GLP-1 secretion through membrane depolarization and intracellular Ca2+ increase [Ca2+]i, via the L-type Ca2+ channel (VGCC). Verapamil and nifedipine, blockers of VGCC, and treatment in Ca2+-free buffer abolished 4-HD effects on [Ca2+]i and GLP-1 secretion. Moreover, 4-HD activated CaMKII and ERK1/2. Consistently, oral 4-HD suppressed postprandial hyperglycemia in mice and increased plasma GLP-1 and insulin levels, GLUT4 translocation, and activation of LKB-1 and Akt pathways in skeletal muscle. Furthermore, exendin 9-39, a GLP-1R antagonist, and compound C, an AMPK inhibitor, completely canceled the 4-HD-caused anti-hyperglycemic activities. 4-HD stimulated GLP-1 secretion through membrane depolarization coupled with [Ca2+]i increase via VGCC in L-cells and activated AMPK- and insulin-induced GLUT4 translocation in skeletal muscle. Thus, 4-HD possesses dual mechanisms for the prevention of hyperglycemia.

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.

Next generation sequencing: a possible answer to sudden unexplained deaths in a young South African cohort?

Sudden cardiac death (SCD) is a major public health concern. In sub-Saharan Africa (SSA), including South Africa, there is a lack of reliable statistics on the incidence of SCD, even though there has been a fourfold increase in noncommunicable diseases (NCD), particularly cardiovascular diseases (CVD). Sudden cardiac death contributes to an estimated 50% of all cardiovascular deaths, which highlights South Africa's need for research into better detection, treatment and prevention. This study aimed to identify an inherited cardiac arrhythmogenic disorder, linked to variants in cardiomyopathy- and arrhythmia-related genes, as a potential contributing factor to sudden cardiac deaths. DNA was extracted from blood samples collected at autopsy of 51 sudden unexpected death (SUD) cases, and subjected to next-generation sequencing (NGS) of 49 genes linked to inherited cardiac arrhythmogenic disorders. Variants were annotated and interpretated for clinical significance using the Galaxy bioinformatic platform. In total, 175 different missense variants were identified in the study population (n = 51). Of these, 92.5% (162/175) were known, documented variants, and the remaining 7.4% (13/175) were considered novel. Of the known variants, 78.4% (127/162) were of benign/likely benign significance, 20.4% (33/162) were variants of unknown significance (VUS), and 1.2% (2/162) was pathogenic. The 13 novel variants were analysed using online prediction software, with 92.3% (12/13) predicted to be likely benign and 7.7% (1/13) grouped into the VUS category. Post-mortem genetic testing provided evidence of a genetic arrhythmic/cardiac conduction disorder as the probable pathogenic basis for approximately 4% (2/51) of sudden unexpected death (SUD) cases.

The roles of mitochondria in global and local intracellular calcium signalling

Activation of Ca2+ channels in Ca2+ stores in organelles and the plasma membrane generates cytoplasmic calcium ([Ca2+]c) signals that control almost every aspect of cell function, including metabolism, vesicle fusion and contraction. Mitochondria have a high capacity for Ca2+ uptake and chelation, alongside efficient Ca2+ release mechanisms. Still, mitochondria do not store Ca2+ in a prolonged manner under physiological conditions and lack the capacity to generate global [Ca2+]c signals. However, mitochondria take up Ca2+ at high local [Ca2+]c signals that originate from neighbouring organelles, and also during sustained global elevations of [Ca2+]c. Accumulated Ca2+ in the mitochondria stimulates oxidative metabolism and upon return to the cytoplasm, can produce spatially confined rises in [Ca2+]c to exert control over processes that are sensitive to Ca2+. Thus, the mitochondrial handling of [Ca2+]c is of physiological relevance. Furthermore, dysregulation of mitochondrial Ca2+ handling can contribute to debilitating diseases. We discuss the mechanisms and relevance of mitochondria in local and global calcium signals.

Phospholipase C epsilon 1 as a therapeutic target in cardiovascular diseases

BACKGROUND

Phospholipase C epsilon 1 (PLCε1) can hydrolyze phosphatidylinositol-4,5-bisphosphate and phosphatidylinositol-4-phosphate at the plasma membrane and perinuclear membrane in the cardiovascular system, producing lipid-derived second messengers. These messengers are considered prominent triggers for various signal transduction processes. Notably, diverse cardiac phenotypes have been observed in cardiac-specific and global Plce1 knockout mice under conditions of pathological stress. It is well established that the cardiac-specific Plce1 knockout confers cardioprotective benefits. Therefore, the development of tissue/cell-specific targeting approaches is critical for advancing therapeutic interventions.

AIM OF REVIEW

This review aims to distill the foundational biology and functional significance of PLCε1 in cardiovascular diseases, as well as to explore potential avenues for research and the development of novel therapeutic strategies targeting PLCε1.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Cardiovascular diseases remain the leading cause of morbidity and mortality worldwide, with incidence rates escalating annually. A comprehensive understanding of the multifaceted role of PLCε1 is essential for enhancing the diagnosis, management, and prognostic assessment of patients suffering from cardiovascular diseases.

Bcl-2 and Bcl-xL in Diabetes: Contributions to Endocrine Pancreas Viability and Function

Diabetes is a chronic metabolic disorder whose prevalence increases every year, affecting more than 530 million adults worldwide. Type 1 (T1D) and type 2 diabetes (T2D), the most common forms of diabetes, are characterized by the loss of functional pancreatic β-cells, mostly due to apoptosis. B-cell leukemia/lymphoma 2 (Bcl-2) and B-cell lymphoma-extra large (Bcl-xL), two anti-apoptotic proteins belonging to the Bcl-2 family, are crucial for regulating the intrinsic pathway of apoptosis. However, over the years, they have been implicated in many other cellular processes, including intracellular Ca2+ homeostasis and the regulation of mitochondrial metabolism. Thus, understanding the biological processes in which these proteins are involved may be crucial to designing new therapeutic targets. This review summarizes the roles of Bcl-2 and Bcl-xL in apoptosis and metabolic homeostasis. It focuses on how the dysregulation of Bcl-2 and Bcl-xL affects pancreatic β-cell function and survival, and the consequences for diabetes development.

Kanglaite alleviates lung squamous cell carcinoma through ferroptosis

Kanglaite, a compound predominantly composed of polyunsaturated fatty acids (PUFAs), has been employed in the clinical treatment of adenocarcinoma non-small cell lung cancer (NSCLC) in China for decades. However, its therapeutic efficacy and specific mechanism in the treatment of squamous NSCLC remains unexplored. In this study, we demonstrate that the co-treatment with ferric ion significantly enhances the cytotoxic effects of kanglaite by inducing ferroptosis in NCL-H1703, a cell line of human lung squamous cell carcinoma. Mechanistic investigations reveal that kanglaite induces mitochondrial dysfunction resulting in reactive oxygen species (ROS) excessive production, which is critical for the induction of ferroptosis. Further analysis shows that kanglaite suppresses the PI3K/AKT signaling pathway, leading to increased IP3 generation. IP3 subsequently binds to and activates IP3R, an endoplasmic reticulum (ER) calcium channel, exacerbating the excessive calcium transfer from the ER to mitochondria. The overloaded mitochondrial calcium contributes to its dysfunction and elevates ROS production. To optimize the synergistic effects of ferric ion and kanglaite, we develop a mesoporous silica-based nanodrug delivery system co-loaded with Kanglaite and Fe3O4, which offers several notable advantages, including reduced drug dosage and a faster therapeutic onset. Finally, in an NCL-H1703 xenograft model, the DMSN/Fe3O4-Kanglaite nanodrug significantly inhibited tumor growth. In conclusion, we identified the function and mechanism of kanglaite in treatment of squamous NSCLC and have developed a DMSN/Fe3O4-Kanglaite nanodrug, providing a superior therapeutic approach for the treatment of squamous NSCLC.

Regulation of calcium homeostasis in endoplasmic reticulum-mitochondria crosstalk: implications for skeletal muscle atrophy

This review comprehensively explores the critical role of calcium as an essential small-molecule biomessenger in skeletal muscle function. Calcium is vital for both regulating muscle excitation-contraction coupling and for the development, maintenance, and regeneration of muscle cells. The orchestrated release of calcium from the endoplasmic reticulum (ER) is mediated by receptors such as the ryanodine receptor (RYR) and inositol 1,4,5-trisphosphate receptor (IP3R), which is crucial for skeletal muscle contraction. The sarcoendoplasmic reticulum calcium ATPase (SERCA) pump plays a key role in recapturing calcium, enabling the muscle to return to a relaxed state. A pivotal aspect of calcium homeostasis involves the dynamic interaction between mitochondria and the ER. This interaction includes local calcium signaling facilitated by RYRs and a "quasi-synaptic" mechanism formed by the IP3R-Grp75-VDAC/MCU axis, allowing rapid calcium uptake by mitochondria with minimal interference at the cytoplasmic level. Disruption of calcium transport can lead to mitochondrial calcium overload, triggering the opening of the mitochondrial permeability transition pore and subsequent release of reactive oxygen species and cytochrome C, ultimately resulting in muscle damage and atrophy. This review explores the complex relationship between the ER and mitochondria and how these organelles regulate calcium levels in skeletal muscle, aiming to provide valuable perspectives for future research on the pathogenesis of muscle diseases and the development of prevention strategies.

Exploring genetic associations in systemic lupus erythematosus through Mendelian randomization: implications for novel biomarkers and therapeutic targets

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by a significant health burden. There is an essential need for novel biomarkers and therapeutic targets to improve diagnosis and management. Mendelian randomization (MR) was applied to explore causal links between SLE and various biomarkers like immune cells, metabolites, and inflammatory cytokines using multiple databases. Initially, biomarkers significantly associated with SLE were identified. Bidirectional MR helped clarify these relationships, and a two-step mediation MR examined their effects on SLE risk. Intersection analysis was used to identify biomarkers with consistent effects across datasets. Four biomarkers were identified as having significant associations with SLE risk: 1-palmitoyl-2-arachidonoyl-GPI levels [odds ratio (OR), 1.379; 95% confidence interval (CI), 1.180 to 1.613; FDR, 0.046], IL-17A levels (OR, 2.197; 95% CI, 1.412 to 3.418; FDR, 0.044), N-acetyl-aspartyl-glutamate (NAAG) levels (OR, 0.882; 95% CI, 0.831 to 0.936; FDR, 0.030), and ribitol levels (OR, 0.743; 95% CI, 0.644 to 0.857; FDR, 0.012). Bidirectional MR showed an inverse effect of NAAG on IL-17A levels (OR, 0.978; 95% CI, 0.962 to 0.994; p = 0.006). Mediation analysis indicated that NAAG influenced SLE risk both directly (beta =  - 0.108) and indirectly through IL-17A (beta =  - 0.018), highlighting the potential mediating role of IL-17A. After expanding the significance criteria to p < 0.05, intersection analysis across multiple datasets revealed 29 biomarkers with consistent beta directions, including 19 potential risk factors (beta > 0) and 10 protective factors (beta < 0) for SLE. This research has revealed significant genetic associations with SLE and demonstrated that IL-17A mediates the relationship between NAAG levels and SLE risk, highlighting potential new targets for personalized therapeutic interventions. Key Points • This study employs MR to identify significant genetic associations between various biomarkers and SLE, providing novel insights into potential biomarkers and therapeutic targets. • Four key biomarkers were identified as significantly associated with SLE risk: 1-palmitoyl-2-arachidonoyl-GPI, IL-17A, N-acetyl-aspartyl-glutamate (NAAG), and ribitol. • The findings suggest that NAAG levels have a protective effect against SLE, partly mediated through IL-17A, indicating a complex interplay between these biomarkers in the pathogenesis of SLE. • Intersectional analysis across multiple datasets revealed 29 biomarkers with consistent effects on SLE risk, highlighting new directions for future research and potential personalized therapeutic strategies.

Endoplasmic reticulum's role in multiple sclerosis, exploring potential biomarkers, and pioneering therapeutic strategies: a comprehensive review of literature

BACKGROUND

Multiple Sclerosis (MS) is a complex and chronic autoimmune disease that affects the central nervous system. Inflammation and demyelination characterize it, which results in a range of neurological impairments. The increasing worldwide occurrence of MS, affecting an estimated 2.8 million individuals in 2020, highlights the urgent requirement for further research to tackle the significant impact it has on individuals and healthcare systems globally.

OBJECTIVE

In this study, we wanted to explore the complex function of the endoplasmic reticulum (ER) in the origin, development, and resolution of MS, emphasizing its importance in neuroinflammatory illnesses. The ER has become a central focus in comprehending the pathogenesis of MS. Upon reviewing the literature, we observed a lack of thorough analysis that explores the involvement of endoplasmic reticulum stress in multiple sclerosis. Thus, we aimed through this research to examine the correlations between ER stress and its influence on immunological dysregulation, demyelination, and neurodegeneration in MS.

FINDINGS

Based on the latest clinical trials, we suggested theories that explore possible biomarkers linked to ER stress and the unfolded protein response. Identifying molecules that are suggestive of early stages of illness and can serve as prognostic tools for improving our understanding of the heterogeneity of MS and offering novel approaches for managing the disease. Finally, through our comprehensive search, we wanted to offer a plan for future research, suggesting new and creative methods for managing MS and encouraging the creation of specific treatments that aim to reduce the impact of MS on individuals worldwide.

Sorcin: mechanisms of action in cancer hallmarks, drug resistance and opportunities in therapeutics

Soluble resistant related calcium binding protein (Sorcin) plays an important role in tumor progression, angiogenesis, metastasis, and multidrug resistance. Differential expression of Sorcin across different cancers significantly correlates with key clinicopathological characteristics and survival outcomes, underscoring its potential as a prognostic marker. Its involvement in drug-resistant cancers further advert Sorcin as a promising therapeutic target. This review summarizes the mechanistic role of Sorcin in cancer, its contribution to drug resistance, clinical relevance, and the current and emerging therapeutic approaches aimed at translating Sorcin-targeted therapies into clinical practice.

Biotoxicity of paraquat to lung cells mediated by endoplasmic reticulum-mitochondria interaction

The high lethality caused by paraquat (PQ) poisoning has attracted much attention in public and human health due to its high toxicity and lethality. However, the understanding of the mechanism of PQ-induced apoptosis from the perspective of organelles, especially inter-organelle interactions, is still scarce. Exploring the linkage of multiple organelles during PQ poisoning and the molecular mechanisms of PQ poisoning under its mediation will help to gain insight into the mode of PQ poisoning at the organelle level. In this study, we observed that a certain dose of PQ gavage induced oxidative stress, mitochondrial dysfunction and endoplasmic reticulum stress in rat lung tissue cells. PQ toxicity led to the occurrence of Ca2+ overload in the endoplasmic reticulum, and the activated BIP and CHOP pathways directly/indirectly led to the expression of apoptogenic factors Caspase family factors. In addition, PQ promoted Ca2+ release from the endoplasmic reticulum and Ca2+ uptake by mitochondria, which induced the disruption of Bax/Bcl-2 channel proteins in response to the IP3R/RyR/VDAC1&2/MCU Ca2+ axis thereby leading to the release of CytoC, which ultimately induced endoplasmic reticulum stress and apoptotic cell death. In addition, 10 differential proteins were screened and validated by proteomics that may act as upstream and downstream active factors of mitochondria-endoplasmic reticulum interaction-mediated biotoxicity. Our findings provide new perspectives for researchers to explore the toxicity mechanisms of PQ to reduce their adverse effects.

Advances in Understanding Drought Stress Responses in Rice: Molecular Mechanisms of ABA Signaling and Breeding Prospects

Drought stress is a pivotal environmental factor impacting rice production and presents a significant challenge to sustainable agriculture worldwide. This review synthesizes the latest research advancements in the regulatory mechanisms and signaling pathways that rice employs in response to drought stress. It elaborates on the adaptive changes and molecular regulatory mechanisms that occur in rice under drought conditions. The review highlights the perception and initial transmission of drought signals, key downstream signaling networks such as the MAPK and Ca2+ pathways, and their roles in modulating drought responses. Furthermore, the discussion extends to hormonal signaling, especially the crucial role of abscisic acid (ABA) in drought responses, alongside the identification of drought-resistant genes and the application of gene-editing technologies in enhancing rice drought resilience. Through an in-depth analysis of these drought stress regulatory signaling pathways, this review aims to offer valuable insights and guidance for future rice drought resistance breeding and agricultural production initiatives.

Structural biology and molecular pharmacology of voltage-gated ion channels

Voltage-gated ion channels (VGICs), including those for Na+, Ca2+ and K+, selectively permeate ions across the cell membrane in response to changes in membrane potential, thus participating in physiological processes involving electrical signalling, such as neurotransmission, muscle contraction and hormone secretion. Aberrant function or dysregulation of VGICs is associated with a diversity of neurological, psychiatric, cardiovascular and muscular disorders, and approximately 10% of FDA-approved drugs directly target VGICs. Understanding the structure-function relationship of VGICs is crucial for our comprehension of their working mechanisms and role in diseases. In this Review, we discuss how advances in single-particle cryo-electron microscopy have afforded unprecedented structural insights into VGICs, especially on their interactions with clinical and investigational drugs. We present a comprehensive overview of the recent advances in the structural biology of VGICs, with a focus on how prototypical drugs and toxins modulate VGIC activities. We explore how these structures elucidate the molecular basis for drug actions, reveal novel pharmacological sites, and provide critical clues to future drug discovery.

Propofol binds and inhibits skeletal muscle ryanodine receptor 1

BACKGROUND

As the primary Ca2+ release channel in skeletal muscle sarcoplasmic reticulum (SR), mutations in type 1 ryanodine receptor (RyR1) or its binding partners underlie a constellation of muscle disorders, including malignant hyperthermia (MH). In patients with MH mutations, triggering agents including halogenated volatile anaesthetics bias RyR1 to an open state resulting in uncontrolled Ca2+ release, increased sarcomere tension, and heat production. Propofol does not trigger MH and is commonly used for patients at risk of MH. The atomic-level interactions of any anaesthetic with RyR1 are unknown.

METHODS

RyR1 opening was measured by [3H]ryanodine binding in heavy SR vesicles (wild type) and single-channel recordings of MH mutant R615C RyR1 in planar lipid bilayers, each exposed to propofol or the photoaffinity ligand analogue m-azipropofol (AziPm). Activator-mediated wild-type RyR1 opening as a function of propofol concentration was measured by Fura-2 Ca2+ imaging of human skeletal myotubes. AziPm binding sites, reflecting propofol binding, were identified on RyR1 using photoaffinity labelling. Propofol binding affinity to a photoadducted site was predicted using molecular dynamics (MD) simulation.

RESULTS

Both propofol and AziPm decreased RyR1 opening in planar lipid bilayers (P<0.01) and heavy SR vesicles, and inhibited activator-induced Ca2+ release from human skeletal myotube SR. Several putative propofol binding sites on RyR1 were photoadducted by AziPm. MD simulation predicted propofol KD values of 55.8 μM and 1.4 μM in the V4828 pocket in open and closed RyR1, respectively.

CONCLUSIONS

Propofol demonstrated direct binding and inhibition of RyR1 at clinically plausible concentrations, consistent with the hypothesis that propofol partially mitigates malignant hyperthermia by inhibition of induced Ca2+ flux through RyR1.

Unveiling the intricate role of S100A1 in regulating RyR1 activity: A commentary on "Structural insights into the regulation of RyR1 by S100A1"

S100A1, a calcium-binding protein, plays a crucial role in regulating Ca2+ signaling pathways in skeletal and cardiac myocytes via interactions with the ryanodine receptor (RyR) to affect Ca2+ release and contractile performance. Biophysical studies strongly suggest that S100A1 interacts with RyRs but have been inconclusive about both the nature of this interaction and its competition with another important calcium-binding protein, calmodulin (CaM). Thus, high-resolution cryo-EM studies of RyRs in the presence of S100A1, with or without additional CaM, were needed. The elegant work by Weninger et al. demonstrates the interaction between S100A1 and RyR1 through various experiments and confirms that S100A1 activates RyR1 at sub-micromolar Ca2+ concentrations, increasing the open probability of RyR1 channels.

Potential Roles of IP3 Receptors and Calcium in Programmed Cell Death and Implications in Cardiovascular Diseases

Inositol 1,4,5-trisphosphate receptors (IP3Rs) play a crucial role in maintaining intracellular/cytosolic calcium ion (Ca2+i) homeostasis. The release of Ca2+ from IP3Rs serves as a second messenger and a modulatory factor influencing various intracellular and interorganelle communications during both physiological and pathological processes. Accumulating evidence from in vitro, in vivo, and clinical studies supports the notion that the overactivation of IP3Rs is linked to the pathogenesis of various cardiac conditions. The overactivation of IP3Rs results in the dysregulation of Ca2+ concentration ([Ca2+]) within cytosolic, mitochondrial, and nucleoplasmic cellular compartments. In cardiovascular pathologies, two isoforms of IP3Rs, i.e., IP3R1 and IP3R2, have been identified. Notably, IP3R1 plays a pivotal role in cardiac ischemia and diabetes-induced arrhythmias, while IP3R2 is implicated in sepsis-induced cardiomyopathy and cardiac hypertrophy. Furthermore, IP3Rs have been reported to be involved in various programmed cell death (PCD) pathways, such as apoptosis, pyroptosis, and ferroptosis underscoring their multifaceted roles in cardiac pathophysiology. Based on these findings, it is evident that exploring potential therapeutic avenues becomes crucial. Both genetic ablation and pharmacological intervention using IP3R antagonists have emerged as promising strategies against IP3R-related pathologies suggesting their potential therapeutic potency. This review summarizes the roles of IP3Rs in cardiac physiology and pathology and establishes a foundational understanding with a particular focus on their involvement in the various PCD pathways within the context of cardiovascular diseases.

Cryo-EM structures of ryanodine receptors and diamide insecticides reveal the mechanisms of selectivity and resistance

The resistance of pests to common insecticides is a global issue that threatens food production worldwide. Diamide insecticides target insect ryanodine receptors (RyRs), causing uncontrolled calcium release from the sarcoplasmic and endoplasmic reticulum. Despite their high potency and species selectivity, several resistance mutations have emerged. Using a chimeric RyR (chiRyR) approach and cryo-electron microscopy (cryo-EM), we investigate how insect RyRs engage two different diamide insecticides from separate families: flubendiamide, a phthalic acid derivative, and tetraniliprole, an anthranilic compound. Both compounds target the same site in the transmembrane region of the RyR, albeit with different poses, and promote channel opening through coupling with the pore-forming domain. To explore the resistance mechanisms, we also solve two cryo-EM structures of chiRyR carrying the two most common resistance mutations, I4790M and G4946E, both alone and in complex with the diamide insecticide chlorantraniliprole. The resistance mutations perturb the local structure, directly reducing the binding affinity and altering the binding pose. Our findings elucidate the mode of action of different diamide insecticides, reveal the molecular mechanism of resistance mutations, and provide important clues for the development of novel pesticides that can bypass the resistance mutations.

Cryo-EM investigation of ryanodine receptor type 3

Ryanodine Receptor isoform 3 (RyR3) is a large ion channel found in the endoplasmic reticulum membrane of many different cell types. Within the hippocampal region of the brain, it is found in dendritic spines and regulates synaptic plasticity. It controls myogenic tone in arteries and is upregulated in skeletal muscle in early development. RyR3 has a unique functional profile with a very high sensitivity to activating ligands, enabling high gain in Ca2+-induced Ca2+ release. Here we solve high-resolution cryo-EM structures of RyR3 in non-activating and activating conditions, revealing structural transitions that occur during channel opening. Addition of activating ligands yields only open channels, indicating an intrinsically high open probability under these conditions. RyR3 has reduced binding affinity to the auxiliary protein FKBP12.6 due to several sequence variations in the binding interface. We map disease-associated sequence variants and binding sites for known pharmacological agents. The N-terminal region contains ligand binding sites for a putative chloride anion and ATP, both of which are targeted by sequence variants linked to epileptic encephalopathy.

Modulatory Impact of Oxidative Stress on Action Potentials in Pathophysiological States: A Comprehensive Review

Oxidative stress, characterized by an imbalance between the production of reactive oxygen species (ROS) and the body's antioxidant defenses, significantly affects cellular function and viability. It plays a pivotal role in modulating membrane potentials, particularly action potentials (APs), essential for properly functioning excitable cells such as neurons, smooth muscles, pancreatic beta cells, and myocytes. The interaction between oxidative stress and AP dynamics is crucial for understanding the pathophysiology of various conditions, including neurodegenerative diseases, cardiac arrhythmias, and ischemia-reperfusion injuries. This review explores how oxidative stress influences APs, focusing on alterations in ion channel biophysics, gap junction, calcium dynamics, mitochondria, and Interstitial Cells of Cajal functions. By integrating current research, we aim to elucidate how oxidative stress contributes to disease progression and discuss potential therapeutic interventions targeting this interaction.

The p53 target DRAM1 modulates calcium homeostasis and ER stress by promoting contact between lysosomes and the ER through STIM1

It is well established that DNA Damage Regulated Autophagy Modulator 1 (DRAM1), a lysosomal protein and a target of p53, participates in autophagy. The cellular functions of DRAM1 beyond autophagy remain elusive. Here, we show p53-dependent upregulation of DRAM1 in mitochondrial damage-induced Parkinson's disease (PD) models and exacerbation of disease phenotypes by DRAM1. We find that the lysosomal location of DRAM1 relies on its intact structure including the cytosol-facing C-terminal domain. Excess DRAM1 disrupts endoplasmic reticulum (ER) structure, triggers ER stress, and induces protective ER-phagy. Mechanistically, DRAM1 interacts with stromal interacting molecule 1 (STIM1) to tether lysosomes to the ER and perturb STIM1 function in maintaining intracellular calcium homeostasis. STIM1 overexpression promotes cellular health by restoring calcium homeostasis, ER stress response, ER-phagy, and AMP-activated protein kinase (AMPK)-Unc-51 like autophagy activating kinase 1 (ULK1) signaling in cells with excess DRAM1. Thus, by promoting organelle contact between lysosomes and the ER, DRAM1 modulates ER structure and function and cell survival under stress. Our results suggest that DRAM1 as a lysosomal protein performs diverse roles in cellular homeostasis and stress response. These findings may have significant implications for our understanding of the role of the p53/DRAM1 axis in human diseases, from cancer to neurodegenerative diseases.

Dual role of the S5 segment in type 1 ryanodine receptor channel gating

The type 1 ryanodine receptor (RyR1) is a Ca2+ release channel in the sarcoplasmic reticulum that is essential for skeletal muscle contraction. RyR1 forms a channel with six transmembrane segments, in which S5 is the fifth segment and is thought to contribute to pore formation. However, its role in channel gating remains unclear. Here, we performed a functional analysis of several disease-associated mutations in S5 and interpreted the results with respect to the published RyR1 structures to identify potential interactions associated with the mutant phenotypes. We demonstrate that S5 plays a dual role in channel gating: the cytoplasmic side interacts with S6 to reduce the channel activity, whereas the luminal side forms a rigid structural base necessary for S6 displacement in channel opening. These results deepen our understanding of the molecular mechanisms of RyR1 channel gating and provide insight into the divergent disease phenotypes caused by mutations in S5.

Congenital myopathies: pathophysiological mechanisms and promising therapies

Congenital myopathies (CMs) are a kind of non-progressive or slow-progressive muscle diseases caused by genetic mutations, which are currently defined and categorized mainly according to their clinicopathological features. CMs exhibit pleiotropy and genetic heterogeneity. Currently, supportive treatment and pharmacological remission are the mainstay of treatment, with no cure available. Some adeno-associated viruses show promising prospects in the treatment of MTM1 and BIN1-associated myopathies; however, such gene-level therapeutic interventions target only specific mutation types and are not generalizable. Thus, it is particularly crucial to identify the specific causative genes. Here, we outline the pathogenic mechanisms based on the classification of causative genes: excitation-contraction coupling and triadic assembly (RYR1, MTM1, DNM2, BIN1), actin-myosin interaction and production of myofibril forces (NEB, ACTA1, TNNT1, TPM2, TPM3), as well as other biological processes. Furthermore, we provide a comprehensive overview of recent therapeutic advancements and potential treatment modalities of CMs. Despite ongoing research endeavors, targeted strategies and collaboration are imperative to address diagnostic uncertainties and explore potential treatments.

Possible role of high calcium concentrations in rat neocortical neurons in inducing hyper excitatory behavior during emergence from sevoflurane: a proposed pathophysiology

Sevoflurane has been shown to increase the incidence of emergence delirium in children; however, the mechanism remains unclear. Sevoflurane increases cytoplasmic calcium concentration which in turn may play a role in emergence delirium. This study aimed to investigate the level of intracellular calcium in rats experiencing hyperexcitatory behavior after exposure to sevoflurane, as well as the role of magnesium in preventing this phenomenon. After ethical approval, 2-5-week-old Sprague-Dawley rats (n = 34) were insufflated with sevoflurane in a modified anesthesia chamber. One group received magnesium sulphate intraperitoneally. After termination of sevoflurane exposure, the occurrence of hyperexcitation was observed. Brain tissue samples from the rats were studied for intracellular calcium levels under a two-channel laser scanning confocal microscope and were quantitatively calculated using ratiometric calculation. The presence of inflammation or oxidative stress reaction was assessed using nuclear factor κB and malondialdehyde. The incidence of hyperexcitatory behavior post sevoflurane exposure was 9 in 16 rats in the observation group and none in the magnesium group. Tests for inflammation and oxidative stress were within normal limits in both groups. The rats showing hyperexcitation had a higher level of cytosol calcium concentration compared to the other groups. To conclude, the calcium concentration of neocortical neurons in Sprague-Dawley rats with hyperexcitatory behavior is increased after exposure to sevoflurane. Administration of magnesium sulphate can prevent the occurrence of hyperexcitation in experimental animals.

Neurochemical changes in the progression of Huntington's disease: A meta-analysis of in vivo1H-MRS studies

Proton magnetic resonance spectroscopy (1H-MRS) allows measuring specific brain metabolic alterations in Huntington's disease (HD), and these metabolite profiles may serve as non-invasive biomarkers associated with disease progression. Despite this potential, previous findings are inconsistent. Accordingly, we performed a meta-analysis on available in vivo1H-MRS studies in premanifest (Pre-HD) and symptomatic HD stages (Symp-HD), and quantified neurometabolic changes relative to controls in 9 Pre-HD studies (227 controls and 188 mutation carriers) and 14 Symp-HD studies (326 controls and 306 patients). Our results indicated decreased N-acetylaspartate and creatine in the basal ganglia in both Pre-HD and Symp-HD. The overall level of myo-inositol was decreased in Pre-HD while increased in Symp-HD. Besides, Symp-HD patients showed more severe metabolism disruption than Pre-HD patients. Taken together, 1H-MRS is important for elucidating progressive metabolite changes from Pre-HD to clinical conversion; N-acetylaspartate and creatine in the basal ganglia are already sensitive at the preclinical stage and are promising biomarkers for tracking disease progression; overall myo-inositol is a possible characteristic metabolite for distinguishing HD stages.

TROP2 promotes the proliferation of triple-negative breast cancer cells via calcium ion-dependent ER stress signaling pathway

OBJECTIVE

To explore the molecular mechanisms of tumor-associated calcium signal transduction factor 2 (TROP2) affecting the occurrence and development of triple-negative breast cancer (TNBC).

METHODS

The TCGA database, immunohistochemical staining, and qRT-PCR were used to analyze the expression of TROP2 in TNBC tissues and cells. The protein expressions of TROP2 and inositol 1,4,5-trisphosphate receptor (IP3R) after TROP2 knockdown were detected by western blot (WB). Cell proliferation was detected by CCK8 and colony formation assay, Annexin V-APC/PI flow cytometry was used to detect apoptosis, and intracellular calcium ion (Ca2+) was detected by flow cytometry with Fura 2-AM fluorescent probe. Finally, the morphological changes of the endoplasmic reticulum (ER) were observed by transmission electron microscopy, and the expression of ER stress (ERS)-related proteins was detected by WB and immunofluorescence staining.

RESULTS

TROP2 was up-regulated in TNBC tumor tissues and cells. Silencing TROP2 decreased the proliferation rate and clone formation number, and increased the apoptosis rate and the Ca2+ level in TNBC cells. These phenomena were reversed after the addition of 2-APB. In addition, after TROP2 knockdown, the expressions of IP3R and ERS-related proteins were up-regulated, the ER was cystic dilated, and ERS was activated. And the addition of 2-APB significantly inhibited the activation of ERS induced by TROP2 knockdown.

CONCLUSION

TROP2 regulated the proliferation and apoptosis of TNBC cells through a Ca2+-dependent ERS signaling pathway.

JAK activity regulates mesoderm cell fate by controlling MESP1 expression

Cardiac development requires precise gene expression programs at each developmental stage guided by multiple signaling pathways and transcription factors (TFs). MESP1 is transiently expressed in mesoderm, and is essential for subsequent cardiac development, while the precise mechanism regulating its own transcription and mesoderm cell fate is not fully understood. Therefore, we developed a high content screen assay to identify regulators of MESP1 expression in mesodermal cells differentiated from human pluripotent stem cells (hPSCs). The screen identified CYT387, a JAK1/JAK2 kinase inhibitor, as a potent activator of MESP1 expression, which was also found to promote cardiomyocyte differentiation in vitro. Mechanistic studies found that JAK inhibition promotes MESP1 expression by reducing cytoplasmic calcium concentration and subsequently activating canonical WNT signaling. Our study identified a role of JAK signaling in early mesodermal cells, and sheds light on the connection between the JAK-STAT pathway and transcriptional regulation of MESP1, which expands our understanding of mesoderm and cardiac development.

Carvedilol suppresses ryanodine receptor-dependent Ca2+ bursts in human neurons bearing PSEN1 variants found in early onset Alzheimer's disease

Seizures are increasingly being recognized as the hallmark of Alzheimer's disease (AD). Neuronal hyperactivity can be a consequence of neuronal damage caused by abnormal amyloid β (Aß) depositions. However, it can also be a cell-autonomous phenomenon causing AD by Aß-independent mechanisms. Various studies using animal models have shown that Ca2+ is released from the endoplasmic reticulum (ER) via type 1 inositol triphosphate receptors (InsP3R1s) and ryanodine receptors (RyRs). To investigate which is the main pathophysiological mechanism in human neurons, we measured Ca2+ signaling in neural cells derived from three early-onset AD patients harboring Presenilin-1 variants (PSEN1 p.A246E, p.L286V, and p.M146L). Of these, it has been reported that PSEN1 p.A246E and p.L286V did not produce a significant amount of abnormal Aß. We found all PSEN1-mutant neurons, but not wild-type, caused abnormal Ca2+-bursts in a manner dependent on the calcium channel, Ryanodine Receptor 2 (RyR2). Indeed, carvedilol, an RyR2 inhibitor, and VK-II-86, an analog of carvedilol without the β-blocking effects, sufficiently eliminated the abnormal Ca2+ bursts. In contrast, Dantrolene, an inhibitor of RyR1 and RyR3, and Xestospongin c, an IP3R inhibitor, did not attenuate the Ca2+-bursts. The Western blotting showed that RyR2 expression was not affected by PSEN1 p.A246E, suggesting that the variant may activate the RyR2. The RNA-Seq data revealed that ER-stress responsive genes were increased, and mitochondrial Ca2+-transporter genes were decreased in PSEN1A246E cells compared to the WT neurons. Thus, we propose that aberrant Ca2+ signaling is a key link between human pathogenic PSEN1 variants and cell-intrinsic hyperactivity prior to deposition of abnormal Aß, offering prospects for the development of targeted prevention strategies for at-risk individuals.

Bimetallic Nanoplatforms for Prostate Cancer Treatment by Interfering Cellular Communication

Cellular communication mediated by messenger molecules plays an important role in the progression of cancer. Herein, pH-sensitive zeolitic imidazolate framework-8 (ZIF-8) loaded with PtCl2(OH)2(NH3)2 [i.e., Pt(IV)] bimetallic nanoplatforms were developed for prostate cancer therapy by interfering inositol-1, 4, 5-trisphosphate (IP3)-mediated cellular communication. As an important messenger in cells, the function of IP3 was found to be efficiently interfered with by the Pt(IV)-binding inositol unit. This finding effect of Pt(IV) is totally different from its traditional function as a prodrug of cis-platinum for chemotherapy. The decreased IP3 signal further downregulated the cytoplasmic Ca2+ concentration and downstream signal transduction to inhibit proliferation and invasion of tumor cells. Meanwhile, Zn2+ released from ZIF-8 under an acidic tumor microenvironment decreased adenosine triphosphate biosynthesis, which could further limit the cellular communication. Such a proposed strategy of interfering cellular communication has demonstrated its feasibility in this study, which may provide new perspectives for cancer therapy.

From stress fiber to focal adhesion: a role of actin crosslinkers in force transmission

The contractile apparatus, stress fiber (SF), is connected to the cell adhesion machinery, focal adhesion (FA), at the termini of SF. The SF-FA complex is essential for various mechanical activities of cells, including cell adhesion to the extracellular matrix (ECM), ECM rigidity sensing, and cell migration. This mini-review highlights the importance of SF mechanics in these cellular activities. Actin-crosslinking proteins solidify SFs by attenuating myosin-driven flows of actin and myosin filaments within the SF. In the solidified SFs, viscous slippage between actin filaments in SFs and between the filaments and the surrounding cytosol is reduced, leading to efficient transmission of myosin-generated contractile force along the SFs. Hence, SF solidification via actin crosslinking ensures exertion of a large force to FAs, enabling FA maturation, ECM rigidity sensing and cell migration. We further discuss intracellular mechanisms for tuning crosslinker-modulated SF mechanics and the potential relationship between the aberrance of SF mechanics and pathology including cancer.

Calcium signalling and transport in the kidney

The kidney plays a pivotal role in regulating calcium levels within the body. Approximately 98% of the filtered calcium is reabsorbed in the nephron, and this process is tightly controlled to maintain calcium homeostasis, which is required to facilitate optimal bone mineralization, preserve serum calcium levels within a narrow range, and support intracellular signalling mechanisms. The maintenance of these functions is attributed to a delicate balance achieved by various calcium channels, transporters, and calcium-binding proteins in renal cells. Perturbation of this balance due to deficiency or dysfunction of calcium channels and calcium-binding proteins can lead to severe complications. For example, polycystic kidney disease is linked to aberrant calcium transport and signalling. Furthermore, dysregulation of calcium levels can promote the formation of kidney stones. This Review provides an updated description of the key aspects of calcium handling in the kidney, focusing on the function of various calcium channels and the physiological stimuli that control these channels or are communicated through them. A discussion of the role of calcium as an intracellular second messenger and the pathophysiology of renal calcium dysregulation, as well as a summary of gaps in knowledge and future prospects, are also included.

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.

A Dual-Channel Ca2+ Nanomodulator Induces Intracellular Ca2+ Disorders via Endogenous Ca2+ Redistribution for Tumor Radiosensitization

Tumor cells harness Ca2+ to maintain cellular homeostasis and withstand external stresses from various treatments. Here, a dual-channel Ca2+ nanomodulator (CAP-P-NO) is constructed that can induce irreversible intracellular Ca2+ disorders via the redistribution of tumor-inherent Ca2+ for disrupting cellular homeostasis and thus improving tumor radiosensitivity. Stimulated by tumor-overexpressed acid and glutathione, capsaicin and nitric oxide are successively escaped from CAP-P-NO to activate the transient receptor potential cation channel subfamily V member 1 and the ryanodine receptor for the influx of extracellular Ca2+ and the release of Ca2+ in the endoplasmic reticulum, respectively. The overwhelming level of Ca2+ in tumor cells not only impairs the function of organelles but also induces widespread changes in the gene transcriptome, including the downregulation of a set of radioresistance-associated genes. Combining CAP-P-NO treatment with radiotherapy achieves a significant suppression against both pancreatic and patient-derived hepatic tumors with negligible side effects. Together, the study provides a feasible approach for inducing tumor-specific intracellular Ca2+ overload via endogenous Ca2+ redistribution and demonstrates the great potential of Ca2+ disorder therapy in enhancing the sensitivity for tumor radiotherapy.

Newsights of endoplasmic reticulum in hypoxia

The endoplasmic reticulum (ER) is important to cells because of its essential functions, including synthesizing three major nutrients and ion transport. When cellular homeostasis is disrupted, ER quality control (ERQC) system is activated effectively to remove misfolded and unfolded proteins through ER-phagy, ER-related degradation (ERAD), and molecular chaperones. When unfolded protein response (UPR) and ER stress are activated, the cell may be suffering a huge blow, and the most probable consequence is apoptosis. The membrane contact points between the ER and sub-organelles contribute to communication between the organelles. The decrease in oxygen concentration affects the morphology and structure of the ER, thereby affecting its function and further disrupting the stable state of cells, leading to the occurrence of disease. In this study, we describe the functions of ER-, ERQC-, and ER-related membrane contact points and their changes under hypoxia, which will help us further understand ER and treat ER-related diseases.

General anesthetic agents induce neurotoxicity through astrocytes

ABSTRACT

Neuroscientists have recognized the importance of astrocytes in regulating neurological function and their influence on the release of glial transmitters. Few studies, however, have focused on the effects of general anesthetic agents on neuroglia or astrocytes. Astrocytes can also be an important target of general anesthetic agents as they exert not only sedative, analgesic, and amnesic effects but also mediate general anesthetic-induced neurotoxicity and postoperative cognitive dysfunction. Here, we analyzed recent advances in understanding the mechanism of general anesthetic agents on astrocytes, and found that exposure to general anesthetic agents will destroy the morphology and proliferation of astrocytes, in addition to acting on the receptors on their surface, which not only affect Ca2+ signaling, inhibit the release of brain-derived neurotrophic factor and lactate from astrocytes, but are even involved in the regulation of the pro- and anti-inflammatory processes of astrocytes. These would obviously affect the communication between astrocytes as well as between astrocytes and neighboring neurons, other neuroglia, and vascular cells. In this review, we summarize how general anesthetic agents act on neurons via astrocytes, and explore potential mechanisms of action of general anesthetic agents on the nervous system. We hope that this review will provide a new direction for mitigating the neurotoxicity of general anesthetic agents.

A structure-based computational model of IP3R1 incorporating Ca and IP3 regulation

The inositol 1,4,5-triphosphate receptor (IP3R) mediates Ca release in many cell types and is pivotal to a wide range of cellular processes. High-resolution cryoelectron microscopy studies have provided new structural details of IP3R type 1 (IP3R1), showing that channel function is determined by the movement of various domains within and between each of its four subunits. Channel properties are regulated by ligands, such as Ca and IP3, which bind at specific sites and control the interactions between these domains. However, it is not known how the various ligand-binding sites on IP3R1 interact to control the opening of the channel. In this study, we present a coarse-grained model of IP3R1 that accounts for the channel architecture and the location of specific Ca- and IP3-binding sites. This computational model accounts for the domain-domain interactions within and between the four subunits that form IP3R1, and it also describes how ligand binding regulates these interactions. Using a kinetic model, we explore how two Ca-binding sites on the cytosolic side of the channel interact with the IP3-binding site to regulate the channel open probability. Our primary finding is that the bell-shaped open probability of IP3R1 provides constraints on the relative strength of these regulatory binding sites. In particular, we argue that a specific Ca-binding site, whose function has not yet been established, is very likely a channel antagonist. Additionally, we apply our model to show that domain-domain interactions between neighboring subunits exert control over channel cooperativity and dictate the nonlinear response of the channel to Ca concentration. This suggests that specific domain-domain interactions play a pivotal role in maintaining the channel's stability, and a disruption of these interactions may underlie disease states associated with Ca dysregulation.

Potential targets for the treatment of MI: GRP75-mediated Ca2+ transfer in MAM

After myocardial infarction (MI), there is a notable disruption in cellular calcium ion homeostasis and mitochondrial function, which is believed to be intricately linked to endoplasmic reticulum (ER) stress. This research endeavors to elucidate the involvement of glucose regulated protein 75 (GRP75) in post-MI calcium ion homeostasis and mitochondrial function. In MI rats, symptoms of myocardial injury were accompanied by an increase in the activation of ER stress. Moreover, in oxygen-glucose deprivation (OGD)-induced cardiomyocytes, it was confirmed that inhibiting ER stress exacerbated intracellular Ca2+ disruption and cell apoptosis. Concurrently, the co-localization of GRP75 with IP3R and VDAC1 increased under ER stress in cardiomyocytes. In OGD-induced cardiomyocytes, knockdown of GRP75 not only reduced the Ca2+ levels in both the ER and mitochondria and improved the ultrastructure of cardiomyocytes, but it also increased the number of contact points between the ER and mitochondria, reducing mitochondria associated endoplasmic reticulum membrane (MAM) formation, and decreased cell apoptosis. Significantly, knockdown of GRP75 did not affect the protein expression of PERK and hypoxia-inducible factor 1α (HIF-1α). Transcriptome analysis of cardiomyocytes revealed that knockdown of GRP75 mainly influenced the molecular functions of sialyltransferase and IP3R, as well as the biosynthesis of glycosphingolipids and lactate metabolism. The complex interaction between the ER and mitochondria, driven by the GRP75 and its associated IP3R1-GRP75-VDAC1 complex, is crucial for calcium homeostasis and cardiomyocyte's adaptive response to ER stress. Modulating GRP75 could offer a strategy to regulate calcium dynamics, diminish glycolysis, and thereby mitigate cardiomyocyte apoptosis.