Fundamentals of Cellular Calcium Signaling: A Primer

Calcium bridges built by mitochondria-associated endoplasmic reticulum membranes: potential targets for neural repair in neurological diseases

The exchange of information and materials between organelles plays a crucial role in regulating cellular physiological functions and metabolic levels. Mitochondria-associated endoplasmic reticulum membranes serve as physical contact channels between the endoplasmic reticulum membrane and the mitochondrial outer membrane, formed by various proteins and protein complexes. This microstructural domain mediates several specialized functions, including calcium (Ca 2+ ) signaling, autophagy, mitochondrial morphology, oxidative stress response, and apoptosis. Notably, the dysregulation of Ca 2+ signaling mediated by mitochondria-associated endoplasmic reticulum membranes is a critical factor in the pathogenesis of neurological diseases. Certain proteins or protein complexes within these membranes directly or indirectly regulate the distance between the endoplasmic reticulum and mitochondria, as well as the transduction of Ca 2+ signaling. Conversely, Ca 2+ signaling mediated by mitochondria-associated endoplasmic reticulum membranes influences other mitochondria-associated endoplasmic reticulum membrane-associated functions. These functions can vary significantly across different neurological diseases-such as ischemic stroke, traumatic brain injury, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease-and their respective stages of progression. Targeted modulation of these disease-related pathways and functional proteins can enhance neurological function and promote the regeneration and repair of damaged neurons. Therefore, mitochondria-associated endoplasmic reticulum membranes-mediated Ca 2+ signaling plays a pivotal role in the pathological progression of neurological diseases and represents a significant potential therapeutic target. This review focuses on the effects of protein complexes in mitochondria-associated endoplasmic reticulum membranes and the distinct roles of mitochondria-associated endoplasmic reticulum membranes-mediated Ca 2+ signaling in neurological diseases, specifically highlighting the early protective effects and neuronal damage that can result from prolonged mitochondrial Ca 2+ overload or deficiency. This article provides a comprehensive analysis of the various mechanisms of Ca 2+ signaling mediated by mitochondria-associated endoplasmic reticulum membranes in neurological diseases, contributing to the exploration of potential therapeutic targets for promoting neuroprotection and nerve repair.

Mechanism of starvation induced autophagy and apoptosis in the midgut of silkworm, Bombyx mori, based on calcium homeostasis

Starvation can induce autophagy and apoptosis in intestinal cells. To elucidate the underlying mechanisms, we investigated autophagy and apoptosis in the midgut of the model insect, silkworm (Bombyx mori), focusing on calcium homeostasis. The results indicated that the body weight of silkworms decreased, along with damage to the morphology of their digestive tracts and midguts after starvation treatment. Additionally, mitochondrial swelling, autophagy and apoptosis were observable. Further investigation revealed that starvation upregulated the transcription of Ca2+ release channel-associated genes (e.g., BmIP3R, BmRyR) but suppressed the expression of Ca2+ efflux genes (BmPMCA), resulting in Ca2+ overload in midgut cells and subsequent upregulation of BmCalpain transcription. In addition, starvation increased the transcription of key autophagy genes (BmATG5, BmATG7, BmATG8) and the expression of the LC3-II protein. Upon prolonged starvation, the NtATG5 protein levels increased, a process that facilitated the transition from autophagy to apoptosis. These results indicate that Ca2+ overload activates the calpain-mediated apoptosis pathway and promotes apoptosis of midgut cells. The present study reveals the significant role that Ca2+ plays in the occurrence and transformation of autophagy and apoptosis induced by starvation treatment, thus providing a new research strategy for investigating the damage caused by starvation in biological organisms.

Exploring the Ca2+ signaling and cytotoxicity induced by the alantolactone in breast cancer cells and its potential implications in treatment using the Ca2+ chelating agent BAPTA-AM

Alantolactone, a bioactive sesquiterpene lactone derived from the roots of Inula helenium (elecampane), has garnered attention in biomedical and pharmacological research for its diverse therapeutic properties, including anticancer, anti-inflammatory, antimicrobial, and antioxidant activities. Despite its well-documented bioactivity, the effects of alantolactone on calcium ion (Ca2+) signaling and the underlying mechanisms in human breast cancer cells remain poorly understood. This study explored how alantolactone influences intracellular Ca2+ levels ([Ca2+]i), cell viability, and the role of Ca2+-dependent pathways in T-47D human breast cancer cells. Specifically, it examined the relationship between Ca2+ signaling and cytotoxicity in cells exposed to alantolactone, with or without the Ca2+ chelator BAPTA-AM. The findings reveal that alantolactone (25-75 μM) increases [Ca2+]i in a concentration-dependent manner, while concentrations of 25-100 μM induce cytotoxicity, an effect that can be reversed by BAPTA-AM pre-treatment. Removing extracellular Ca2+ significantly inhibits Ca2+ influx, and both SKF96365 and 2-APB, modulators of store-operated Ca2+ channels, block the alantolactone-induced Ca2+ entry. Additionally, in a Ca2+-free environment, thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+ pump, suppresses the alantolactone-induced rise in [Ca2+]i, while alantolactone reduces the [Ca2+]i increase triggered by thapsigargin. Moreover, inhibiting phospholipase C (PLC) with U73122 abolishes the alantolactone-induced [Ca2+]i elevation. These results suggest that alantolactone-induced cell death in T-47D cells is Ca2+-dependent, involving Ca2+ entry via store-operated channels and Ca2+ release from the endoplasmic reticulum, with PLC playing a pivotal role. Importantly, the ability of BAPTA-AM to reverse alantolactone's cytotoxic effects highlights its potential therapeutic significance in breast cancer research.

Theoretical evaluation of the biological activity of hydrogen

Hydrogen (H2), the simplest and most ubiquitous molecule in the universe, has garnered significant scientific interest over the past two decades because of its potential as an effective antioxidant and anti-inflammatory agent. Traditionally considered inert, H2 is now being re-evaluated for its unique bioactive properties. H2 selectively neutralizes reactive oxygen and nitrogen species, mitigating oxidative stress without disrupting essential cellular functions. This review therefore aims to provide a theoretical evaluation of the biological activity of H2, focusing on its pharmacokinetics, including absorption, distribution, and retention within biological systems. The pharmacokinetic profile of H2 is crucial for understanding its potential therapeutic applications. The interaction of H2 with protein pockets is of particular interest, as these sites may serve as reservoirs or active sites for H2, influencing its biological activity and retention time. Additionally, the impact of H2 on cellular signaling pathways, including those regulating glucose metabolism and oxidative stress responses, will be explored, offering insights into its potential as a modulator of metabolic and redox homeostasis. Finally, interactions with ferromagnetic molecules within biological environments, as well as effects on cellular signaling mechanisms, add another layer of complexity to the biological role of H2. By synthesizing the current research, this review seeks to elucidate the underlying mechanisms by which H2 may exert therapeutic effects while also identifying critical areas for further investigation. Understanding these aspects is essential for fully characterizing the pharmacodynamic profile of H2 and assessing its clinical potential in the treatment of oxidative stress-related disorders.

Osteogenic Potential of 3D-Printed Porous Poly(lactide-co-trimethylene carbonate) Scaffolds Coated with Mg-Doped Hydroxyapatite

Extrusion-based 3D printing of thermoplastic polymers presents significant potential for bone tissue engineering. However, a key limitation is the frequent absence of filament porosity and the inherent osteoconductive properties. This study addresses these challenges by fabricating poly(lactide-co-trimethylene carbonate) (PLATMC) scaffolds with dual-scale porosity: macroporosity achieved through controlled filament spacing and microporosity introduced via NaCl leaching. The inclusion of NaCl generated rough, porous surfaces that were well-suited for dip-coating with magnesium-carbonate-doped hydroxyapatite (MgCHA), thereby imparting osteoconductive functionality. Thermal analysis revealed that salt incorporation had minimal impact on the polymer's thermal stability. Rheological studies and computational modeling indicated that NaCl reduced the viscosity under shear, leading to enhanced printability and faster extrusion speeds. After leaching, the scaffolds exhibited approximately 34% microporosity, which significantly increased water uptake and swelling capacity, despite the roughened surfaces slightly elevating hydrophobicity. The mechanical properties of PLATMC (with nonporous filaments) and p-PLATMC (with porous filaments) scaffolds showed a modulus of elasticity of 566 ± 118 and 101 ± 20 MPa, respectively, with strain values of 178 ± 54% and 84 ± 28%. Biological evaluations highlighted the compatibility of the p-PLATMC scaffolds. Cell viability and proliferation assays confirmed sustained cellular interaction over a 14 day period. Notably, alkaline phosphatase (ALP) activity was elevated in the porous scaffolds, and the MgCHA coating significantly enhanced mineral deposition by day 28, suggesting improved osteogenic potential. In conclusion, this study presents a robust strategy for fabricating 3D-printed PLATMC scaffolds with integrated filament porosity, offering a viable platform for osteoconductive coatings in bone tissue engineering applications.

Development and Validation of Ultrasound Hemodynamic-based Prediction Models for Acute Kidney Injury After Renal Transplantation

RATIONALE AND OBJECTIVES

Acute kidney injury (AKI) post-renal transplantation often has a poor prognosis. This study aimed to identify patients with elevated risks of AKI after kidney transplantation.

MATERIALS AND METHODS

A retrospective analysis was conducted on 422 patients who underwent kidney transplants from January 2020 to April 2023. Participants from 2020 to 2022 were randomized to training group (n=261) and validation group 1 (n=113), and those in 2023, as validation group 2 (n=48). Risk factors were determined by employing logistic regression analysis alongside the least absolute shrinkage and selection operator, making use of ultrasound hemodynamic, clinical, and laboratory information. Models for prediction were developed using logistic regression analysis and six machine-learning techniques. The evaluation of the logistic regression model encompassed its discrimination, calibration, and applicability in clinical settings, and a nomogram was created to illustrate the model. SHapley Additive exPlanations were used to explain and visualize the best of the six machine learning models.

RESULTS

The least absolute shrinkage and selection operator combined with logistic regression identified and incorporated five risk factors into the predictive model. The logistic regression model (AUC=0.927 in the validation set 1; AUC=0.968 in the validation set 2) and the random forest model (AUC=0.946 in the validation set 1;AUC=0.996 in the validation set 2) showed good performance post-validation, with no significant difference in their predictive accuracy.

CONCLUSION

These findings can assist clinicians in the early identification of patients at high risk for AKI, allowing for timely interventions and potentially enhancing the prognosis following kidney transplantation.

20 nm nanoparticles trigger calcium influx to endothelial cells via a TRPV4 channel

While increased intracellular calcium (Ca2+) has been identified as a key effect of nanoparticles on endothelial cells, the mechanism has not been fully elucidated or examined under shear stress. Here, we show the effect of several types of 20 nm particles on Ca2+ in the presence of shear stress in human umbilical vein endothelial cells (HUVECs), human coronary artery endothelial cells (HCAECs), and human cardiac microvascular endothelial cells (HMVEC-Cs). Intracellular Ca2+ levels increased by nearly three-fold in these cell types upon exposure to 100 μg mL-1 20 nm Au particles, which was not seen in response to larger or smaller particles. An antagonist to the calcium channel - transient receptor potential vanilloid-type 4 (TRPV4) - drastically reduced the amount of calcium by 9.3-fold in HUVECs exposed to 0.6 Pa shear stress and 100 μg mL-1 20 nm gold particles, a trend upheld in both HCAECs and HMVEC-Cs. Cell alignment in the direction of fluid flow is a well-known phenomenon in endothelial cells, and interestingly, cells in the presence of 20 nm particles with fluid flow had a higher alignment index than cells in the fluid flow alone. When compared with previous works, these results indicated that 20 nm particles may be inducing endothelial permeability by activating the TRPV4 channel in vitro. The potential of nanoparticle delivery technologies hinges on an improved understanding of this effect toward improved delivery with limited toxicity.

Investigation of the morphological, cellular, biochemical, and molecular modifications in the BG01V human embryonic stem cell-derived neuronal cells

Changes in the morphology, metabolic activity, intracellular calcium (Ca2 +) transients, expression of topoisomerase-2β (Topo-2β), and senescence of human embryonic stem cells (hESCs)-derived neuronal cells on basic hESC culture media and neuronal differentiation medium at different time intervals is not clear. Hence, we aimed to investigate the morphological, cellular, biochemical, and molecular alterations in the BG01V hESC-derived neuronal cells on basic hESC culture media and neuronal differentiation media at different time intervals.

MATERIALS AND METHODS

BG01V hESC-derived neuronal cells grown on basic hESC culture media and neuronal differentiation media were evaluated for morphological changes by microscopy, metabolic activity by MTT assay, cell viability by Trypan Blue exclusion assay, cellular activity by estimating the Ca2+ deposits, cellular senescence by senescence-associated beta-galactosidase (SA-β-gal) activity, and level of Topo-2β using Western blotting at different time intervals.

RESULTS

Contrasting to the BG01V hESCs grown on basic hESC culture media, a notable increase in the neuronal cell-like structures, neuritic outgrowth, and expression of nestin protein on neural induction was observed. Higher levels of Ca2+ deposits, metabolic activity, SA-β-gal activity, and Topo-2β expression in BG01V hESC-derived neuronal cells grown on neuronal differentiation media on day 12 compared to hESCs grown on basic hESC culture media including other days were noted.

CONCLUSION

This study suggests the increase of calcium salts reflecting the calcium activity at distinct phases of neuronal differentiation, ranging from neural induction to neurite extension. The metabolic and SA-β-gal activity of BG01V hESC-derived neuronal cells may suggest the ongoing biological aging process. Upregulation and activation of Topo-2β upon differentiation induction at the mid-phase suggest the activation of inducible gene loci and downregulation of Topo-2β at a later stage.

Phytochemical and Structural Portrayal of Barley and Pearl Millet Through FTIR and SEM

In the present study, Pennisetum glaucum variety Shahansha (F1 bajra) and Hordeum vulgare variety Talbina-21 were tested for nutritional profiling, and results exhibited that pearl millet was rich in moisture, fat, carbohydrate, and ash content; whereas, barley had a copious amount of protein and fiber content. Mineral composition analysis showed barley had a plentiful quantity of calcium (43.97 ± 0.06 mg/100 g), phosphorus (350.58 ± 1.39 mg/100 g) and sodium (36.31 ± 0.95 mg/100 g); whereas, pearl millet had higher iron (7.81 ± 0.05 mg/100 g), potassium (306.33 ± 3.2 mg/100 g) and magnesium (135.61 ± 2.19 mg/100 g). Barley also had a high concentration of total phenolic content (204.73 ± 5.5 mg GAE/g) and total flavonoid contents (134.72 ± 4.71 mg QE/g). Antioxidant activity measured through FRAP, ABTS, and DPPH tests indicated distinct antioxidant activity in barley for DPPH (105.72 ± 0.02 mg GAE/g) and ABTS assay (272.08 ± 5.80 μmol TEAC/100 g), while pearl millet showed stronger activity for FRAP assay (5.22 ± 0.04 TE/g). Using Fourier Transform Infrared Spectroscopy (FTIR), functional groups in the flours were identified, and Scanning Electron Microscopy (SEM) revealed that barley had smaller, spherical granules with smooth edges, while pearl millet had a rough, wrinkled surface with hollow cylindrical morphology. The compositional analysis of the flours revealed the presence of various sugars, proteins, ferulic acid, uronic acid, and dietary fiber components (arabinoxylan & β-glucan). Conclusively, millet and barley possess pronounced phenolic composition, high antioxidant potential, and dietary fibers like arabinoxylan & β-glucan offer substantial biological efficacy in human health interventions.

Essential oil extract p‑cresol effect on Ca2+ signaling and its underlying mechanism in DBTRG‑05MG human glioblastoma cells

The effect of para (p)-cresol, an essential oil component, on calcium ion (Ca2+) signaling in human glioblastoma is unknown. The present study aimed to investigate how p-cresol influences intracellular Ca2+ levels ([Ca2+]i) and viability in DBTRG-05MG human glioblastoma cells. Cells were treated with p-cresol to assess its impact on cell viability and [Ca2+]i. Cell viability was evaluated using a WST-1 assay. [Ca2+]i was measured using a fluorescence-based Ca2+ indicator. Cells were loaded with the Ca2+-sensitive dye (fura-2), and fluorescence intensity was recorded before and after p-cresol treatment to determine changes in [Ca2+]i. p-Cresol induced concentration-dependent increases in [Ca2+]i between 50 and 150 µM. At 50-250 µM, p-cresol triggered cell death; this effect was reversed by pretreating the cells with the Ca2+ chelator BAPTA-AM. The removal of extracellular Ca2+ inhibited Ca2+ entry. p-Cresol-induced Ca2+ influx was confirmed by Mn2+-induced quenching of fura-2 fluorescence. Store-operated Ca2+ channel modulators SKF96365 and 2-aminoethoxydiphenyl borate and the protein kinase C inhibitor GF109203X inhibited p-cresol-induced Ca2+ entry, but voltage-gated Ca2+ channel blocker nifedipine did not. Treatment with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin in Ca2+-free medium inhibited p-cresol-induced [Ca2+]i rises; conversely, treatment with p-cresol decreased thapsigargin-induced [Ca2+]i rises. Furthermore, phospholipase C (PLC) inhibition with U73122 abolished p-cresol-induced [Ca2+]i rises. In DBTRG-05MG cells, p-cresol triggered Ca2+-associated cell death. The process involved the entry of Ca2+ through PKC-regulated store-operated Ca2+ channels and release of Ca2+ from the endoplasmic reticulum, which depends on PLC. Additionally, BAPTA-AM, which has Ca2+-chelating properties, may be a promising compound in preventing p-cresol-induced cytotoxicity, a potential breakthrough in neurotoxic research in glioblastoma cell model.

Can the Discovery of High-Impact Diagnostics Be Improved by Matching the Sampling Rate of Clinical Diagnostics to the Frequency Domain of Diagnostic Information?

Over the past 30 years, academic and industrial research investigators have developed molecular reporters to visualize cell death in complex biological systems. In parallel, clinical researchers, chemists, biochemists, and molecular biologists have endeavored to translate these molecular tools into clinical imaging agents. Despite these efforts, there are no clinically approved imaging methodologies with which to image cell death consistently and quantitatively. One reason may reside in the intrinsic mismatch between the sampling frequency of translational molecular imaging and the biochemical kinetics that define cell death. Beyond cell death imaging, many active research programs are now attempting to create translational diagnostic pharmaceuticals to image immunological, fibrotic, amyloidotic, and metabolic pathways. Each of these pathways is defined by a unique set of biochemical rate constants, some of which are associated with key predictive pathways. Exhaustively sampling all permutations of pathways and kinetic constants would seem to be an intractable strategy for target identification and validation. Sampling theory, if applied to these pathways, could accelerate the translation of high-impact diagnostics through prioritization of pathways for either AI enhanced diagnostic imaging or AI-enhanced wearable devices. In this perspective, we identify the Nyquist sampling rate as a key criterion for evaluating the optimal application for novel diagnostics. Sampling theory states that to fully characterize a band-limited, stationary, temporal data set, the signal must be sampled at more than twice the rate of the fastest frequency in the signal or, for diagnostics, the discriminatory signal. Through the study of the medical imaging process chain, Nyquist sampling rates of 0.25 day-1 and, more likely, slower than 0.02 day-1 were determined to provide high quality information. By prioritizing low-frequency predictive processes, or "state changes,", imaging researchers may improve the "hit rate" of research programs by appropriately matching the rate of change in diagnostic and predictive information with the limiting sampling rate of medical imaging. Critically, however, high-frequency diagnostic information (and therefore high-frequency biological processes) need not be ignored; these processes are simply better interrogated through continuous monitoring, e.g., by wearable devices combined with machine learning or artificial intelligence.

Organic Bioelectronics in Microphysiological Systems: Bridging the Gap Between Biological Systems and Electronic Technologies

The growing burden of degenerative, cardiovascular, neurodegenerative, and cancerous diseases necessitates innovative approaches to improve our pathophysiological understanding and ability to modulate biological processes. Organic bioelectronics has emerged as a powerful tool in this pursuit, offering a unique ability to interact with biology due to the mixed ionic-electronic conduction and tissue-mimetic mechanical properties of conducting polymers (CPs). These materials enable seamless integration with biological systems across different levels of complexity, from monolayers to complex 3D models, microfluidic chips, and even clinical applications. CPs can be processed into diverse formats, including thin films, hydrogels, 3D scaffolds, and electrospun fibers, allowing the fabrication of advanced bioelectronic devices such as multi-electrode arrays, transistors (EGOFETs, OECTs), ion pumps, and photoactuators. This review examines the integration of CP-based bioelectronics in vivo and in in vitro microphysiological systems, focusing on their ability to monitor key biological events, including electrical activity, metabolic changes, and biomarker concentrations, as well as their potential for electrical, mechanical, and chemical stimulation. We highlight the versatility and biocompatibility of CPs and their role in advancing personalized medicine and regenerative therapies and discuss future directions for organic bioelectronics to bridge the gap between biological systems and electronic technologies.

Subchronic Exposure to Polystyrene Nanoplastics Disrupts Placental Development and Calcium Homeostasis: Insights from In Vivo and In Vitro Models

Nanoplastics have recently emerged as persistent pollutants of global concern that pose substantial risks to human health. However, the long-term adverse effects of nanoplastics on the female reproductive system remain unclear. Polystyrene nanoplastics (PS-NPs; 50 nm diameter) were selected as representative nanosized plastic particles to investigate the potential effects of subchronic prenatal and gestational exposure via drinking water on placental development in ICR (CD-1) mice. Maternal exposure to 10 mg/L PS-NPs induced an increase in fetal resorption rate and significantly increased fetal weight. Further observation of the placental morphology showed that PS-NPs exposure led to an aberrant placental structure and damaged the trophoblast cells. At the cellular level, PS-NPs exposure promoted the proliferation, migration, and invasion of HTR-8/SVneo cells. Mechanistically, transcriptomic and proteomic analyses revealed that PS-NPs triggered placental calcium disturbances and upregulated the Stam2 expression in mice. STAM2 induced by PS-NPs mediates the disruption of trophoblastic calcium homeostasis and regulates cell functions by disturbing the lysosomal degradation of the calcium channel protein IP3R3 and promoting intracellular calcium inflow by increasing the level of TRPV6 in HTR-8/SVneo cells. Therefore, our results indicated that trophoblastic calcium dyshomeostasis is the main mechanism by which subchronic PS-NPs exposure induces abnormal placental development. These findings reveal a link between subchronic PS-NPs exposure and placental damage and elucidate the underlying molecular mechanism, providing evidence for environmental triggers of adverse pregnancy and highlighting the risk of plastic products to pregnant women.

Activation of Endoplasmic Reticulum-Localized Metabotropic Glutamate Receptor 5 (mGlu5) Triggers Calcium Release Distinct from Cell Surface Counterparts in Striatal Neurons

Metabotropic glutamate receptor 5 (mGlu5) plays a fundamental role in synaptic plasticity, potentially serving as a therapeutic target for various neurodevelopmental and psychiatric disorders. Previously, we have shown that mGlu5 can also signal from intracellular membranes in the cortex, hippocampus, and striatum. Using cytoplasmic Ca2+ indicators, we showed that activated cell surface mGlu5 induced a transient Ca2+ increase, whereas the activation of intracellular mGlu5 mediated a sustained Ca2+ elevation in striatal neurons. Here, we used the newly designed ER-targeted Ca2+ sensor, ER-GCaMP6-150, as a robust, specific approach to directly monitor mGlu5-mediated changes in ER Ca2+ itself. Using this sensor, we found that the activation of cell surface mGlu5 led to small declines in ER Ca2+, whereas the activation of ER-localized mGlu5 resulted in rapid, more pronounced changes. The latter could be blocked by the Gq inhibitor FR9000359, the PLC inhibitor U73122, as well as IP3 and ryanodine receptor blockers. These data demonstrate that like cell surface and nuclear mGlu5, ER-localized receptors play a pivotal role in generating and shaping intracellular Ca2+ signals.

Molecular basis for the calcium-dependent activation of the ribonuclease EndoU

Ribonucleases (RNases) are ubiquitous enzymes that process or degrade RNA, essential for cellular functions and immune responses. The EndoU-like superfamily includes endoribonucleases conserved across bacteria, eukaryotes, and certain viruses, with an ancient evolutionary link to the ribonuclease A-like superfamily. Both bacterial EndoU and animal RNase A share a similar fold and function independently of cofactors. In contrast, the eukaryotic EndoU catalytic domain requires divalent metal ions for catalysis, possibly due to an N-terminal extension near the catalytic core. In this study, we use biophysical and computational techniques along with in vitro assays to investigate the calcium-dependent activation of human EndoU. We determine the crystal structure of EndoU bound to calcium and find that calcium binding remote from the catalytic triad triggers water-mediated intramolecular signaling and structural changes, activating the enzyme through allostery. Calcium binding involves residues from both the catalytic core and the N-terminal extension, indicating that the N-terminal extension interacts with the catalytic core to modulate activity in response to calcium. Our findings suggest that similar mechanisms may be present across all eukaryotic EndoUs, highlighting a unique evolutionary adaptation that connects endoribonuclease activity to cellular signaling in eukaryotes.

A deadly taste: linking bitter taste receptors and apoptosis

Humans can perceive five canonical tastes: salty, sour, umami, sweet, and bitter. These tastes are transmitted through the activation of ion channels and receptors. Bitter taste receptors (Taste Family 2 Receptors; T2Rs) are a sub-family of 25 G-protein coupled receptor (GPCR) isoforms that were first identified in type II taste bud cells. T2Rs are activated by a broad array of bitter agonists, which cause an increase in intracellular calcium (Ca2+) and a decrease in cyclic adenosine 3',5'-monophosphate (cAMP). Interestingly, T2Rs are expressed beyond the oral cavity, where they play diverse non-taste roles in cell physiology and disease. Here, we summarize the literature that explores the role of T2Rs in apoptosis. Activation of T2Rs with bitter agonists induces apoptosis in several cancers, the airway epithelia, smooth muscle, and more. In many of these tissues, T2R activation causes mitochondrial Ca2+ overload, a main driver of apoptosis. This response may be a result of T2R cellular localization, nuclear Ca2+ mobilization and/or a remnant of the established immunological roles of T2Rs in other cell types. T2R-induced apoptosis could be pharmacologically leveraged to treat diseases of altered cellular proliferation. Future work must explore additional extra-oral T2R-expressing tissues for apoptotic responses, develop methods for in-vivo studies, and discover high affinity bitter agonists for clinical application.

Cardiomyocyte-specific long noncoding RNA Trdn-as induces mitochondrial calcium overload by promoting the m6A modification of calsequestrin 2 in diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is a medical condition characterized by cardiac remodeling and dysfunction in individuals with diabetes mellitus. Sarcoplasmic reticulum (SR) and mitochondrial Ca2+ overload in cardiomyocytes have been recognized as biological hallmarks in DCM; however, the specific factors underlying these abnormalities remain largely unknown. In this study, we aimed to investigate the role of a cardiac-specific long noncoding RNA, D830005E20Rik (Trdn-as), in DCM. Our results revealed the remarkably upregulation of Trdn-as in the hearts of the DCM mice and cardiomyocytes treated with high glucose (HG). Knocking down Trdn-as in cardiac tissues significantly improved cardiac dysfunction and remodeling in the DCM mice. Conversely, Trdn-as overexpression resulted in cardiac damage resembling that observed in the DCM mice. At the cellular level, Trdn-as induced Ca2+ overload in the SR and mitochondria, leading to mitochondrial dysfunction. RNA-seq and bioinformatics analyses identified calsequestrin 2 (Casq2), a primary calcium-binding protein in the junctional SR, as a potential target of Trdn-as. Further investigations revealed that Trdn-as facilitated the recruitment of METTL14 to the Casq2 mRNA, thereby enhancing the m6A modification of Casq2. This modification increased the stability of Casq2 mRNA and subsequently led to increased protein expression. When Casq2 was knocked down, the promoting effects of Trdn-as on Ca2+ overload and mitochondrial damage were mitigated. These findings provide valuable insights into the pathogenesis of DCM and suggest Trdn-as as a potential therapeutic target for this condition.

Fine-tuned calcium homeostasis is crucial for murine erythropoiesis

Intracellular calcium (Ca2+) is a crucial signaling molecule involved in multiple cellular processes. However, the functional role of Ca2+ in terminal erythropoiesis remains unclear. Here, we uncovered the dynamics of intracellular Ca2+ levels during mouse erythroid development. By using the calcium ionophore ionomycin, we found that low Ca2+ levels are required for the expansion of erythroid progenitors, whereas higher Ca2+ levels led to the differentiation and proliferation of early-stage erythroblasts. Intracellular Ca2+ levels were then gradually reduced, which is required for the nuclear condensation and polarisation at the late stage of erythroid differentiation. However, elevated Ca2+ levels in late-stage erythroblasts, achieved by using ionomycin, promoted erythroid enucleation via calmodulin (CaM)/calcium/calmodulin-dependent protein kinase kinase 1 (CaMKK1)/AMPK signaling. These data suggest that the reduction of intracellular Ca2+ plays a double-edged role at the late stage of erythroid differentiation, which is beneficial for nuclear condensation but compromises terminal enucleation. Our study highlighted the importance of the fine-tuned regulation of intracellular Ca2+ during terminal erythropoiesis, providing cues for the efficient generation of mature and enucleated erythrocytes in vitro.

Biological physics to uncover cell signaling

In this report, I describe some of the subjects and problems that we have addressed over the last 25 years in the area of cell signaling using the tools of biological physics. The report covers part of our work on intracellular Ca2 + signals, pattern formation, transport of messengers in the interior of cells, quantification of biophysical parameters from experiments, and information transmission. The description includes both our modeling and experimental work highlighting how the tools of physics can give useful insights into the workings of biological systems.

Predictive value of serum calcium ion level in patients with colorectal cancer: A retrospective cohort study

BACKGROUND

Serum calcium ion (Ca2+) is an economical and readily available indicator as a routine screening test for hospitalized patients. There are no studies related to serum Ca2+ level and digestive tract malignancy.

AIM

To evaluate the effectiveness of serum Ca2+ level in predicting the prognosis of patients with colorectal cancer (CRC).

METHODS

We retrospectively collected the data of 280 patients diagnosed with CRC who underwent radical surgery at the Affiliated Cancer Hospital of Xinjiang Medical University. By analyzing the clinicopathological features, differences between serum Ca2+ concentrations on the first day after surgery were determined. We used the receiver operating characteristic curve to assess the predictive ability of serum Ca2+ for survival. Survival analyses were performed using the Kaplan-Meier method, and multivariate Cox proportional risk regression was used to determine association between calibration serum Ca2+ levels and CRC survival outcomes.

RESULTS

By receiver operating characteristic curve analysis, the ideal threshold value for Ca2+ the first postoperative day and delta serum calcium (δCa2+) value were 1.975 and 0.245, respectively. Overall survival (OS) and progression-free survival (PFS) were better in both the high Ca2+ group and high δCa2+ group on the first postoperative day. The variables identified through univariate analysis were incorporated into multivariate analysis and showed that tumor differentiation (P = 0.047), T stage (P = 0.019), N stage (P < 0.001), nerve vascular invasion (P = 0.037), carcinoembryonic antigen (P = 0.039), baseline serum Ca2+ level (P = 0.011), and serum Ca2+ level on the first day (P = 0.006) were independent predictors of prognosis for patients undergoing feasible radical CRC surgery. Using the findings from the multifactorial analysis, we developed a nomogram and the calibration showed a good predictive ability.

CONCLUSION

Low serum Ca2+ level on the first postoperative day is an independent risk factor for OS and PFS in CRC.

Editorial on Special Issue: Computational Insights into Calcium Signaling

Calcium is a ubiquitous second messenger and plays a major role in a variety of cellular functions, both within the same cell and between different cells [...].

Jaw1 accelerates the reaction speed of the Ca2+ signals via ITPRs upon GPCR stimulation

Jaw1/LRMP/IRAG2 enhances Ca2+ release via interaction with inositol 1,4,5-trisphosphate receptors (ITPRs), Ca2+ channels on the endoplasmic reticulum, upon G protein-coupled receptor stimulation. While our previous works demonstrated the increases in the maximum amplitude and retention time of the Ca2+ curve with heterogeneous effects on each ITPR subtype: ITPR1, ITPR2, and ITPR3, the effects on the reaction speed remain unclear. In this study, we unveiled the additional roles of Jaw1 in accelerating the signal onset time and rise time to the first peak top, especially in the cells expressing ITPR1. These findings shed more light on the relationship between the expression pattern of Jaw1 and ITPRs, and the heterogeneous pattern of the Ca2+ dynamics, offering insights into their physiological implications.

Ca2+ Signaling in Cardiac Fibroblasts: An Emerging Signaling Pathway Driving Fibrotic Remodeling in Cardiac Disorders

Cardiac fibrosis is a scarring event that occurs in the myocardium in response to multiple cardiovascular disorders, such as acute myocardial infarction (AMI), ischemic cardiomyopathy, dilated cardiomyopathy, hypertensive heart disease, inflammatory heart disease, diabetic cardiomyopathy, and aortic stenosis. Fibrotic remodeling is mainly sustained by the differentiation of fibroblasts into myofibroblasts, which synthesize and secrete most of the extracellular matrix (ECM) proteins. An increase in the intracellular Ca2+ concentration ([Ca2+]i) in cardiac fibroblasts is emerging as a critical mediator of the fibrogenic signaling cascade. Herein, we review the mechanisms that may shape intracellular Ca2+ signals involved in fibroblast transdifferentiation into myofibroblasts. We focus our attention on the functional interplay between inositol-1,4,5-trisphosphate (InsP3) receptors (InsP3Rs) and store-operated Ca2+ entry (SOCE). In accordance with this, InsP3Rs and SOCE drive the Ca2+ response elicited by Gq-protein coupled receptors (GqPCRs) that promote fibrotic remodeling. Then, we describe the additional mechanisms that sustain extracellular Ca2+ entry, including receptor-operated Ca2+ entry (ROCE), P2X receptors, Transient Receptor Potential (TRP) channels, and Piezo1 channels. In parallel, we discuss the pharmacological manipulation of the Ca2+ handling machinery as a promising approach to mitigate or reverse fibrotic remodeling in cardiac disorders.

Cellular and subcellular distribution of the K+-dependent Na+/Ca2+-exchanger subtype 4, NCKX4, in mouse brain

SLC24A4, the gene encoding the K+-dependent Na+/Ca2+-exchanger, NCKX4, is widely expressed in the brain and involved in many neuronal functions. Here we use immunofluorescent staining and electron microscopy to map the expression of the NCKX4 protein across the mouse brain. Our data show that NCKX4 expression is higher in forebrain with particularly intense staining in specific brain regions, including olfactory bulb, ventral pallidum, globus pallidus, hippocampal mossy fibers, substantia nigra, inferior olive and choroid plexus. These areas are closely associated with crucial functions such as learning and memory, reward processing, motor activity, and cerebrospinal fluid production. Co-immunostaining of NCKX4 with marker proteins and immuno-electron microscopy demonstrate that neuronal NCKX4 is not expressed in cell bodies but is confined to distal neuronal processes with preferential expression on the cell surface. In contrast, NCKX4 expression in epithelial cells of the choroid plexus is found exclusively at intracellular sites. We also compared NCKX4 to two other Na+/Ca2+-exchangers, NCKX2 and NCX1. NCKX4 is the only exchanger expressed in choroid plexus and hippocampal mossy fibers. In the substantia nigra, NCKX4 and NCKX2 show striking overlap while NCX1 is absent. In many other brain regions all three exchangers are present. These data suggest both distinct and redundant roles for these exchangers in different brain regions. This novel information provides valuable insight into the mechanisms underlying the contribution of NCKX4 to various physiological processes associated with different brain regions and suggests the existence of undiscovered roles for NCKX4 in the brain.

Functional investigation of a putative calcium-binding site involved in the inhibition of inositol 1,4,5-trisphosphate receptor activity

The regulation of inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) activity is thought to define the spatiotemporal patterns of Ca2+ signals necessary for the appropriate activation of downstream effectors. The binding of both IP3 and Ca2+ is obligatory for IP3R channel opening. Ca2+ however regulates IP3R activity in a biphasic manner. Ca2+ binding to a high-affinity pocket formed by the third armadillo repeat domain and linker domain promotes IP3R channel opening without altering the Ca2+ dependency for channel inactivation. These data suggest that a distinct low-affinity Ca2+-binding site is responsible for the reduction in IP3R activity at higher [Ca2+]. We mutated a cluster of acidic residues in the second armadillo repeat domain and central linker domain of IP3R type 1, reported to coordinate Ca2+ in the cryo-EM structures of the IP3R type 3. This "CD Ca2+-binding site" is well conserved in all IP3R subtypes. CD site Ca2+-binding mutants where the negatively charged glutamic acid residues were mutated to alanine exhibited enhanced sensitivity to IP3-generating agonists. Ca2+-binding mutants displayed spontaneous elemental Ca2+ puffs, and the number of IP3-induced Ca2+ puffs was augmented in cells stably expressing Ca2+-binding site mutants. The inhibitory effect of high [Ca2+] on single-channel open probability (Po) was reduced in mutant channels, and this effect was dependent on [ATP]. This indicates that Ca2+ binding to the putative CD Ca2+ inhibitory site facilitates the reduction in IP3R channel activation at subsaturating, likely physiological cytosolic [ATP], and suggest that at higher [ATP], additional Ca2+-binding motifs may contribute to the biphasic regulation of IP3-induced Ca2+ release.

Pumping the Breaks on Acantholytic Skin Disorders: Targeting Calcium Pumps, Desmosomes, and Downstream Signaling in Darier, Hailey-Hailey, and Grover Disease

Acantholytic skin disorders, by definition, compromise intercellular adhesion between epidermal keratinocytes. The root cause of blistering in these diseases traces back to direct disruption of adhesive cell-cell junctions, exemplified by autoantibody-mediated attack on desmosomes in pemphigus. However, genetic acantholytic disorders originate from more indirect mechanisms. Darier disease and Hailey-Hailey disease arise from mutations in the endoplasmic reticulum calcium pump, SERCA2, and the Golgi calcium/manganese pump, SPCA1, respectively. Though the disease-causing mutations have been known for nearly 25 years, the mechanistic linkage between dysregulation of intracellular ion stores and weakening of cell-cell junctions at the plasma membrane remains puzzling. The molecular underpinnings of a related idiopathic disorder, Grover disease, are even less understood. Due to an incomplete understanding of acantholytic pathology at the molecular level, these disorders lack proven, targeted treatment options, leaving patients with the significant physical and psychological burdens of chronic skin blistering, infections, and pain. This article aims to review what is known at the molecular, cellular, and clinical levels regarding these under-studied disorders and to highlight knowledge gaps and promising ongoing research. Armed with this knowledge, our goal is to aid investigators in defining essential questions about disease pathogenesis and to accelerate progress toward novel therapeutic strategies.

Mercury-Mediated Cardiovascular Toxicity: Mechanisms and Remedies

Mercury is a significant environmental pollutant and public health threat, primarily recognized for its neurotoxic effects. Increasing evidence also highlights its harmful impact on the cardiovascular system, particularly in adults. Exposure to mercury through contaminated soil, air, or water initiates a cascade of pathological events that lead to organ damage, including platelet activation, oxidative stress, enhanced inflammation, and direct injury to critical cells such as cardiomyocytes and endothelial cells. Endothelial activation triggers the upregulation of adhesion molecules, promoting the recruitment of leukocytes and platelets to vascular sites. These interactions activate both platelets and immune cells, creating a pro-inflammatory, prothrombotic environment. A key outcome is the formation of platelet-leukocyte aggregates (PLAs), which exacerbate thromboinflammation and endothelial dysfunction. These processes significantly elevate cardiovascular risks, including thrombosis and vascular inflammation. This study offers a comprehensive analysis of the mechanisms underlying mercury-induced cardiotoxicity, focusing on oxidative stress, inflammation, and cellular dysfunction.

Specific Calcium Signal Responses in Human Keloid-Derived Fibroblasts During Cyclical Stretching: Basic Research

Background

Keloids most commonly develop in the regions where the skin is constantly stretched. Although some keloid-derived fibroblasts exhibit higher single calcium spikes than normal dermal fibroblasts during short-time cyclical stretching, the calcium signal responses to long-time stretching remain unclear.

Methods

This study compared the intracellular Ca2+ dynamics induced by cyclical stretching stimuli between the control group (normal dermal fibroblasts) and the keloid group (keloid-derived fibroblasts). Each group was cyclically exposed to a two-dimensional stretch (10% strain). A confocal laser microscope was used to examine intracellular Ca2+ for 30 min fluorescently. The fluorescence intensity ratio (Fluo-8H/calcein red-orange) was used to evaluate intracellular Ca2+ concentration every 0.5 s. A calcium spike was a transient ratio increase of ≥ 20%. Receiver operating characteristic analysis was performed to determine the cutoff value of a normal calcium spike.

Results

No significant difference was observed between the keloid and control groups in the calcium signal response-positive rates (26.9% vs. 25.0%; p = 0.9). However, the calcium spike amplitudes were significantly higher in the keloid group than in the control group (1.66 vs. 1.41; p = 0.02). The cutoff value was 2.12, and 9.6% of keloid-derived fibroblasts exhibited multiple hypercalcium spikes.

Discussion

We are conducting further research based on the hypothesis that this keloid-specific subpopulation triggers the pathogenesis of keloid formation, that is, collagen overproduction, accelerated angiogenesis, and chronic inflammation.

The emerging roles of the endoplasmic reticulum in mechanosensing and mechanotransduction

Cells are continuously subjected to physical and chemical cues from the extracellular environment, and sense and respond to mechanical cues via mechanosensation and mechanotransduction. Although the role of the cytoskeleton in these processes is well known, the contribution of intracellular membranes has been long neglected. Recently, it has become evident that various organelles play active roles in both mechanosensing and mechanotransduction. In this Review, we focus on mechanosensitive roles of the endoplasmic reticulum (ER), the functions of which are crucial for maintaining cell homeostasis. We discuss the effects of mechanical stimuli on interactions between the ER, the cytoskeleton and other organelles; the role of the ER in intracellular Ca2+ signalling via mechanosensitive channels; and how the unfolded protein response and lipid homeostasis contribute to mechanosensing. The expansive structure of the ER positions it as a key intracellular communication hub, and we additionally explore how this may be leveraged to transduce mechanical signals around the cell. By synthesising current knowledge, we aim to shed light on the emerging roles of the ER in cellular mechanosensing and mechanotransduction.

Engineered Strategies to Interfere with Macrophage Fate in Myocardial Infarction

Myocardial infarction (MI), a severe cardiovascular condition, is typically triggered by coronary artery disease, resulting in ischemic damage and the subsequent necrosis of the myocardium. Macrophages, known for their remarkable plasticity, are capable of exhibiting a range of phenotypes and functions as they react to diverse stimuli within their local microenvironment. In recent years, there has been an increasing number of studies on the regulation of macrophage behavior based on tissue engineering strategies, and its regulatory mechanisms deserve further investigation. This review first summarizes the effects of key regulatory factors of engineered biomaterials (including bioactive molecules, conductivity, and some microenvironmental factors) on macrophage behavior, then explores specific methods for inducing macrophage behavior through tissue engineering materials to promote myocardial repair, and summarizes the role of macrophage-host cell crosstalk in regulating inflammation, vascularization, and tissue remodeling. Finally, we propose some future challenges in regulating macrophage-material interactions and tailoring personalized biomaterials to guide macrophage phenotypes.

Exercise-induced cytosolic calcium oscillations: mechanisms and modulation of T-cell function

This study investigated time-dependent changes in intracellular Ca2⁺ levels in T cells, regulatory mechanisms, and functional effects after acute exercise. Male C57BL/6 mice were assigned to control and exercise groups, with the latter sacrificed at different intervals post-exercise. Murine splenic lymphocytes were isolated, and cytosolic Ca2⁺ levels were measured using Fluo-3/AM. T-cell proliferation was assessed by flow cytometry and CFSE labeling, apoptosis by Annexin V/PI staining, and cytokine levels by CBA. RNA sequencing results were validated by qRT-PCR. The findings revealed that exercise significantly altered intracellular calcium oscillations in CD3+ cells, leading to reduced mitogen-stimulated proliferation, increased IL-6, IL-5, and IL-13 production, and decreased IL-2 secretion. Additionally, there was an increase in the apoptotic fraction of CD3+ cells, with upregulated expression of Cav1.1, Cav3.2, Cav3.3, SERCA2B, PKCθ, Bcl-xL, and FADD, and downregulated Ryr3 (p < 0.05). Transcriptomic analysis identified 607 differentially expressed genes involved in calcium ion binding and related pathways, including calcium signaling and cytokine-cytokine receptor interactions. Thus, acute exercise induces specific calcium oscillation patterns in T cells, mediated by PKCθ, affecting proliferation, apoptosis, and cytokine production. These changes are attributed to increased calcium influx through Cav1.1, Cav3.2, and Cav3.3 channels, decreased calcium reuptake via SERCA2B, and reduced calcium release through Ryr3. This research provides novel insights into how exercise modulates immune cell function by altering calcium levels, potential implications for enhancing immune responses or reducing inflammation.

Ca2+/calmodulin-dependent protein kinase II β decodes ER Ca2+ transients to trigger autophagosome formation

In multicellular organisms, very little is known about how Ca2+ transients on the ER outer surface elicited by autophagy stimuli are sustained and decoded to trigger autophagosome formation. Here, we show that Ca2+/calmodulin-dependent protein kinase II β (CaMKIIβ) integrates ER Ca2+ transients to trigger liquid-liquid phase separation (LLPS) of the autophagosome-initiating FIP200 complex. In response to ER Ca2+ transients, CaMKIIβ is recruited from actin filaments and forms condensates, which serve as sites for the emergence of or interaction with FIP200 puncta. CaMKIIβ phosphorylates FIP200 at Thr269, Thr1127, and Ser1484 to modulate LLPS and properties of the FIP200 complex, thereby controlling its function in autophagosome formation. CaMKIIβ also controls the amplitude, duration, and propagation of ER Ca2+ transients during autophagy induction. CaMKIIβ mutations identified in the neurodevelopmental disorder MRD54 affect the function of CaMKIIβ in autophagy. Our study reveals that CaMKIIβ is essential for sustaining and decoding ER Ca2+ transients to specify autophagosome formation in mammalian cells.

The Roles of Transient Receptor Potential (TRP) Channels Underlying Aberrant Calcium Signaling in Blood-Retinal Barrier Dysfunction

The inner blood-retinal barrier (iBRB) protects the retinal vasculature from the peripheral circulation. Endothelial cells (ECs) are the core component of the iBRB; their close apposition and linkage via tight junctions limit the passage of fluids, proteins, and cells from the bloodstream to the parenchyma. Dysfunction of the iBRB is a hallmark of many retinal disorders. Vascular endothelial growth factor (VEGF) has been identified as the primary driver leading to a dysfunctional iBRB, thereby becoming the main target for therapy. However, a complete understanding of the molecular mechanisms underlying iBRB dysfunction is elusive and alternative therapeutic targets remain unexplored. Calcium (Ca2+) is a universal intracellular messenger whose homeostasis and dynamics are dysregulated in many pathological disorders. Among the extensive components of the cellular Ca2+-signaling toolkit, cation-selective transient receptor potential (TRP) channels are broadly involved in cell physiology and disease and, therefore, are widely studied as possible targets for therapy. Albeit that TRP channels have been discovered in the photoreceptors of Drosophila and have been studied in the neuroretina, their presence and function in the iBRB have only recently emerged. Within this article, we discuss the structure and functions of the iBRB with a particular focus on Ca2+ signaling in retinal ECs and highlight the potential of TRP channels as new targets for retinal diseases.

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.

CaXML: Chemistry-informed machine learning explains mutual changes between protein conformations and calcium ions in calcium-binding proteins using structural and topological features

Proteins' flexibility is a feature in communicating changes in cell signaling instigated by binding with secondary messengers, such as calcium ions, associated with the coordination of muscle contraction, neurotransmitter release, and gene expression. When binding with the disordered parts of a protein, calcium ions must balance their charge states with the shape of calcium-binding proteins and their versatile pool of partners depending on the circumstances they transmit. Accurately determining the ionic charges of those ions is essential for understanding their role in such processes. However, it is unclear whether the limited experimental data available can be effectively used to train models to accurately predict the charges of calcium-binding protein variants. Here, we developed a chemistry-informed, machine-learning algorithm that implements a game theoretic approach to explain the output of a machine-learning model without the prerequisite of an excessively large database for high-performance prediction of atomic charges. We used the ab initio electronic structure data representing calcium ions and the structures of the disordered segments of calcium-binding peptides with surrounding water molecules to train several explainable models. Network theory was used to extract the topological features of atomic interactions in the structurally complex data dictated by the coordination chemistry of a calcium ion, a potent indicator of its charge state in protein. Our design created a computational tool of CaXML, which provided a framework of explainable machine learning model to annotate ionic charges of calcium ions in calcium-binding proteins in response to the chemical changes in an environment. Our framework will provide new insights into protein design for engineering functionality based on the limited size of scientific data in a genome space.

Investigating the interaction between calcium signaling and ferroptosis for novel cancer treatment

BACKGROUND

Drug resistance in cancer is steadily rising, making the development of new therapeutic targets increasingly critical for improving treatment outcomes.

PURPOSE

The mutual regulation of ions is essential for cell growth. Based on this concept, ion interference strategies offer a highly effective approach for cancer treatment. Calcium ions (Ca2+), as major second messengers, are closely associated with ion exchange and homeostasis. Disruptions in this balance can lead to cell death. However, while iron ions are also crucial, the connection between Ca2+and iron-induced cell death (ferroptosis) has not been well established. Therefore, this study suggests that Ca2+ may play a role in the induction of ferroptosis, presenting a novel and efficient target for cancer therapy.

STUDY DESIGN

PubMed, Google Scholar, and Web of Science databases were systematically searched for articles published in the past 15 years on the mechanisms of calcium ion-induced ferroptosis in cancer and related drugs.

RESULTS

The analysis highlights how Ca2+regulate ferroptosis. The mechanisms by which Ca2+influence ferroptosis are summarized based on existing literature, and relevant drugs that act on Ca2+/ferroptosis axis are outlined.

CONCLUSION

Ca2+ regulate ferroptosis primarily through the modulation of reactive oxygen species (ROS) and glutathione (GSH) levels, a mechanism that applies to a wide range of cancer cells as well as paracancerous and normal cells in cancer treatment. Furthermore, plant-derived active compounds exhibit potent anticancer properties and often act on the Ca2+/ferroptosis axis. These natural compounds could play a significant role in the development of new cancer treatment strategies.

Dynamic spectral fluorescence microscopy via event-based & CMOS image-sensor fusion

We present a widefield fluorescence microscope that integrates an event-based image sensor (EBIS) with a CMOS image sensor (CIS) for ultra-fast microscopy with spectral distinction capabilities. The EBIS achieves a temporal resolution of ∼10μs (∼ 100,000 frames/s), while the CIS provides diffraction-limited spatial resolution. A diffractive optical element encodes spectral information into a diffractogram, which is recorded by the CIS. The diffractogram is processed using a deep neural network to resolve the fluorescence of two beads, whose emission peaks are separated by only 7 nm and exhibit an 88% spectral overlap. We validate our microscope by imaging the capillary flow of fluorescent beads, demonstrating a significant advancement in ultra-fast spectral microscopy. This technique holds broad potential for elucidating foundational dynamic biological processes.

Tepary Bean (Phaseolus acutifolius) Lectins as Modulators of Intracellular Calcium Mobilization in Breast Cancer and Normal Breast Cells

Lectins are proteins that specifically recognize carbohydrates on cell membranes, triggering several cellular events such as apoptosis of cancer-transformed cells; however, the mechanisms of action remain incompletely understood. Our research group has reported that a concentrated fraction of Tepary bean lectins (Phaseolus acutifolius; TBLF) exhibits the concentration-dependent induction of apoptosis in colon cancer cells by caspase activation. It is well established that an increase in cytoplasmic calcium ([Ca2+]i) initiates intracellular signals involved in processes such as exocytosis, gene transcription, apoptosis, cell cycle regulation, and muscle contraction, among others. Furthermore, dysregulated calcium signaling has been implicated in various diseases, including certain neurological disorders and cancer. In this study, we aim to demonstrate the effects of native TBLF lectins and a recombinant lectin (rTBL-1) on calcium mobility in breast cancer cells (MCF-7) and non-cancerous cells (MCF-12F). Both TBLF and rTBL-1 increased intracellular calcium concentrations and mobilized calcium from intracellular stores in a concentration-dependent manner; however, the two cell lines exhibited differential responses. While MCF-12F cells restored cytoplasmic calcium concentration, MCF-7 cells maintained a high intracellular calcium concentration. This strongly suggests that lectins can elicit differential cellular responses in cancer and non-cancer cells due to variations in their intrinsic mechanisms of calcium homeostasis. Finally, we demonstrated that TBLF and rTBL-1 can differentially alter Metabolic Cellular Activity (MCA) as a direct measure of cell viability (CVi) in both cell lines. These findings strengthen the evidence of the therapeutic potential of Tepary bean lectins. Undoubtedly, further studies will be necessary to elucidate the mechanisms underlying their applications.

Differentially Expressed Genes in Cardiomyocytes of the First Camelized Mouse Model, Nrapc.255ins78 Mouse

Background/Objectives: The first camelized mouse model (Nrapc.255ins78) was developed to investigate the mechanisms underlying camels' adaptation to extreme environments. Previous studies demonstrated that these mice exhibit a cold-resistant phenotype, characterized by increased expression of inflammatory cytokine-related genes in the heart under cold stress. Nebulin-related anchoring protein (NRAP) plays a critical role in organizing myofibrils during cardiomyocyte development. This study builds on prior research by analyzing the heart transcriptomes of Nrapc.255ins78 mice under non-stress conditions to explore the origins of inflammatory cytokine responses during cold exposure. Methods: RNA sequencing was performed on the hearts of 12-week-old male and female Nrapc.255ins78 and wild-type control mice. Results: Differential expression analysis identified 25 genes, including 12 associated with cell cycle and division, all consistently downregulated in Nrapc.255ins78. Notably, the calcium and integrin-binding protein gene (Cib3) was significantly upregulated (FDR < 0.05; p < 0.001). Conclusions: These differentially expressed genes suggest altered calcium dynamics in cardiomyocytes and mechanisms for maintaining homeostasis, supporting the hypothesis that inflammatory cytokines during cold exposure may represent an adaptive response. These findings provide valuable insights into the genetic mechanisms of temperature adaptation in camels and highlight potential pathways for enhancing stress resistance in other mammals.

Metal Ion Signaling in Biomedicine

Complex multicellular organisms are composed of distinct tissues involving specialized cells that can perform specific functions, making such life forms possible. Species are defined by their genomes, and differences between individuals within a given species directly result from variations in their genetic codes. While genetic alterations can give rise to disease-causing acquisitions of distinct cell identities, it is now well-established that biochemical imbalances within a cell can also lead to cellular dysfunction and diseases. Specifically, nongenetic chemical events orchestrate cell metabolism and transcriptional programs that govern functional cell identity. Thus, imbalances in cell signaling, which broadly defines the conversion of extracellular signals into intracellular biochemical changes, can also contribute to the acquisition of diseased cell states. Metal ions exhibit unique chemical properties that can be exploited by the cell. For instance, metal ions maintain the ionic balance within the cell, coordinate amino acid residues or nucleobases altering folding and function of biomolecules, or directly catalyze specific chemical reactions. Thus, metals are essential cell signaling effectors in normal physiology and disease. Deciphering metal ion signaling is a challenging endeavor that can illuminate pathways to be targeted for therapeutic intervention. Here, we review key cellular processes where metal ions play essential roles and describe how targeting metal ion signaling pathways has been instrumental to dissecting the biochemistry of the cell and how this has led to the development of effective therapeutic strategies.

Structure-Function Diversity of Calcium-Binding Proteins (CaBPs): Key Roles in Cell Signalling and Disease

Calcium (Ca2+) signalling is a fundamental cellular process, essential for a wide range of physiological functions. It is regulated by various mechanisms, including a diverse family of Ca2+-binding proteins (CaBPs), which are structurally and functionally similar to calmodulin (CaM). The CaBP family consists of six members (CaBP1, CaBP2, CaBP4, CaBP5, CaBP7, and CaBP8), each exhibiting unique localisation, structural features, and functional roles. In this review, we provide a structure-function analysis of the CaBP family, highlighting the key similarities and differences both within the family and in comparison to CaM. It has been shown that CaBP1-5 share similar structural and interaction characteristics, while CaBP7 and CaBP8 form a distinct subfamily with unique properties. This review of current CaBP knowledge highlights the critical gaps in our understanding, as some CaBP members are less well characterised than others. We also examine pathogenic mutations within CaBPs and their functional impact, showing the need for further research to improve treatment options for associated disorders.

The Molecular Biology of Placental Transport of Calcium to the Human Foetus

From fertilisation to delivery, calcium must be transported into and within the foetoplacental unit for intracellular signalling. This requires very rapid, precisely located Ca2+ transfers. In addition, from around the eighth week of gestation, increasing amounts of calcium must be routed directly from maternal blood to the foetus for bone mineralisation through a flow-through system, which does not impact the intracellular Ca2+ concentration. These different processes are mediated by numerous membrane-sited Ca2+ channels, transporters, and exchangers. Understanding the mechanisms is essential to direct interventions to optimise foetal development and postnatal bone health and to protect the mother and foetus from pre-eclampsia. Ethical issues limit the availability of human foetal tissue for study. Our insight into the processes of placental Ca2+ handling is advancing rapidly, enabled by developing genetic, analytical, and computer technology. Because of their diverse sources, the reports of new findings are scattered. This review aims to pull the data together and to highlight areas of uncertainty. Areas needing clarification include trafficking, membrane expression, and recycling of channels and transporters in the placental microvilli; placental metabolism of vitamin D in gestational diabetes and pre-eclampsia; and the vascular effects of increased endothelial Orai expression by pregnancy-specific beta-1-glycoproteins PSG1 and PSG9.

Mitochondrial dysfunction in trigeminal ganglion contributes to nociceptive behavior in a nitroglycerin-induced migraine mouse model

Migraine is a chronic episodic neurological disorder. However, its diagnosis and management remain unclear. The pathogenesis of migraine is intricately linked to the dysfunction of mitochondria and aberrant trigeminal neuronal activity. Here, we established a murine migraine model via intraperitoneal administration of nitroglycerin (NTG) to examine alterations in mitochondria-associated proteins and calcium signaling patterns within trigeminal neurons, while also investigating the underlying mechanisms. NTG-treated mice exhibited marked periorbital allodynia, decreased crossing of the central area, and decreased time spent in the central area in the open field test compared to Veh treated animals. Furthermore, increased calcium signaling in response to adenosine triphosphate (ATP) stimulation was observed in the trigeminal ganglion (TG) of mice with migraine. Meanwhile, mRNA levels of genes including nuclear respiratory factor-1 (Nrf1), nuclear respiratory factor-2 (Nrf2) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (Pgc-1) were decreased in the TG. Pharmacological regulation of the mitochondrial function affected NTG-induced migraine chronic pain symptoms. TG mitochondria dysfunctions is implicated in the regulation of mechanical hyperalgesia through the modulation of calcium signaling in an NTG-induced migraine animal model.

IP3 receptor depletion in a spontaneous canine model of Charcot-Marie-Tooth disease 1J with amelogenesis imperfecta

Inositol 1,4,5-trisphosphate receptors (IP3R) mediate Ca2+ release from intracellular stores, contributing to complex regulation of numerous physiological responses. The involvement of the three IP3R genes (ITPR1, ITPR2 and ITPR3) in inherited human diseases has started to shed light on the essential roles of each receptor in different human tissues and cell types. Variants in the ITPR3 gene, which encodes IP3R3, have recently been found to cause demyelinating sensorimotor Charcot-Marie-Tooth neuropathy type 1J (CMT1J). In addition to peripheral neuropathy, immunodeficiency and tooth abnormalities are occasionally present. Here, we report the identification of a homozygous nonsense variant in the ITPR3 gene in Lancashire Heeler dogs, presenting with a severe developmental enamel defect and reduced nerve conduction velocity. We studied the primary skin fibroblasts of the affected dogs and observed that the nonsense variant in ITPR3 led to a complete absence of full-length IP3R3 protein. Unexpectedly, the protein levels of IP3R1 and IP3R2 were also markedly decreased, suggesting co-regulation. Functional Ca2+ measurements revealed reduced IP3R-mediated Ca2+ flux upon stimulation of G-protein-coupled-receptors in the affected dog fibroblasts. These findings highlight the first spontaneous mammalian phenotype caused by a nonsense variant in ITPR3, leading to the loss of IP3R3. The human and canine IP3R3 proteins are highly similar, and our study suggests that the tissue involvement resulting from the receptor's dysfunction is also conserved. In summary, IP3R3 is critical for enamel formation and peripheral nerve maintenance.

Increased GABBR2 Expression on Cell Membranes Causes Increased Ca2 + Inward Flow, Associated with Cognitive Impairment in Early Alzheimer's Disease

Alzheimer's disease (AD) and mild cognitive impairment (MCI) are a serious global public health problem. The aim of this study was to analyze the key molecular pathological mechanisms that occur in early AD progression as well as MCI. Expression profiling data from brain homogenates of 8 normal volunteers, and 6 patients with prodromal AD who had developed MCI were analyzed, and the data were obtained from GSE12685. Further, overexpression of GABBR2 was achieved in human neuroblastoma cell lines SH-SY5Y and BE(2)-M17 using expression plasmid transfection. GABBR2 was significantly overexpressed in brain tissues of patients with prodromal AD who had developed MCI, as compared to normal brains. Moreover, GABBR2 overexpressing cells showed a significant increase in intracellular Ca2+ concentration, a large amount of reactive oxygen species production, a large opening of the mitochondrial permeability transition pore and a significant increase in apoptosis compared with control cells. GABBR2 overexpression was significantly involved in early AD progression and MCI by causing cellular events such as intracellular Ca2+ imbalance, oxidative stress, and mitochondrial dysfunction.

Metal ion formulations for diabetic wound healing: Mechanisms and therapeutic potential

Metals are vital in human physiology, which not only act as enzyme catalysts in the processes of superoxide dismutase and glucose phosphorylation, but also affect the redox process, osmotic adjustment, metabolism and neural signals. However, metal imbalances can lead to diseases such as diabetes, which is marked by chronic hyperglycemia and affects wound healing. The hyperglycemic milieu of diabetes impairs wound healing, posing significant challenges to patient quality of life. Wound healing encompasses a complex cascade of hemostasis, inflammation, proliferation, and remodeling phases, which are susceptible to disruption in hyperglycemic conditions. In recent decades, metals have emerged as critical facilitators of wound repair by enhancing antimicrobial properties (e.g., iron and silver), providing angiogenic stimulation (copper), promoting antioxidant activity and growth factor synthesis (zinc), and supporting wound closure (calcium and magnesium). Consequently, research has pivoted towards the development of metal ion-based therapeutics, including innovative formulations such as nano-hydrogels, nano-microneedle dressings, and microneedle patches. Prepared by combining macromolecular materials such as chitosan, hyaluronic acid and sodium alginate with metals, aiming at improving the management of diabetic wounds. This review delineates the roles of key metals in human physiology and evaluates the application of metal ions in diabetic wound management strategies.

Calcium transfer from the ER to other organelles for optimal signaling in Toxoplasma gondii

Ca2+ signaling in cells begins with the opening of Ca2+ channels in either the plasma membrane (PM) or the endoplasmic reticulum (ER) and results in a dramatic increase in the physiologically low (<100 nM) cytosolic Ca2+ level. The temporal and spatial Ca2+ levels are well regulated to enable precise and specific activation of critical biological processes. Ca2+ signaling regulates pathogenic features of apicomplexan parasites like Toxoplasma gondii which infects approximately one-third of the world's population. T. gondii relies on Ca2+ signals to stimulate traits of its infection cycle and several Ca2+ signaling elements play essential roles in its parasitic cycle. Active egress, an essential step for the infection cycle of T. gondii is preceded by a large increase in cytosolic Ca2+ most likely by release from intracellular stores. Intracellular parasites take up Ca2+ from the host cell during host Ca2+ signaling events to replenish intracellular stores. In this work, we investigated the mechanism by which intracellular stores are replenished with Ca2+ and demonstrated a central role for the SERCA-Ca2+-ATPase in keeping not only the ER filled with Ca2+ but also other stores. We show mitochondrial Ca2+ uptake, by transfer of Ca2+ from the ER likely through membrane contact sites. We propose a central role for the ER in sequestering and redistributing calcium to other intracellular organelles following influx at the PM.

Data-Driven Insights into the Association Between Oxidative Stress and Calcium-Regulating Proteins in Cardiovascular Disease

A growing body of biomedical literature suggests a bidirectional regulatory relationship between cardiac calcium (Ca2+)-regulating proteins and reactive oxygen species (ROS) that is integral to the pathogenesis of various cardiac disorders via oxidative stress (OS) signaling. To address the challenge of finding hidden connections within the growing volume of biomedical research, we developed a data science pipeline for efficient data extraction, transformation, and loading. Employing the CaseOLAP (Context-Aware Semantic Analytic Processing) algorithm, our pipeline quantifies interactions between 128 human cardiomyocyte Ca2+-regulating proteins and eight cardiovascular disease (CVD) categories. Our machine-learning analysis of CaseOLAP scores reveals that the molecular interfaces of Ca2+-regulating proteins uniquely associate with cardiac arrhythmias and diseases of the cardiac conduction system, distinguishing them from other CVDs. Additionally, a knowledge graph analysis identified 59 of the 128 Ca2+-regulating proteins as involved in OS-related cardiac diseases, with cardiomyopathy emerging as the predominant category. By leveraging a link prediction algorithm, our research illuminates the interactions between Ca2+-regulating proteins, OS, and CVDs. The insights gained from our study provide a deeper understanding of the molecular interplay between cardiac ROS and Ca2+-regulating proteins in the context of CVDs. Such an understanding is essential for the innovation and development of targeted therapeutic strategies.

n-Butylidenephthalide recovered calcium homeostasis to ameliorate neurodegeneration of motor neurons derived from amyotrophic lateral sclerosis iPSCs

Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disease that causes muscle atrophy and primarily targets motor neurons (MNs). Approximately 20% of familial ALS cases are caused by gain-of-function mutations in superoxide dismutase 1 (SOD1), leading to MN degeneration and ion channel dysfunction. Previous studies have shown that n-Butylidenephthalide (BP) delays disease progression and prolongs survival in animal models of ALS. However, no studies have been conducted on models from human sources. Herein, we examined the protective efficacy of BP on MNs derived from induced pluripotent stem cells (iPSCs) of an ALS patient harboring the SOD1G85R mutation as well as on those derived from genetically corrected iPSCs (SOD1G85G). Our results demonstrated that the motor neurons differentiated from iPSC with SOD1G85R mutation exhibited characteristics of neuron degeneration (as indicated by the reduction of neurofilament expression) and ion channel dysfunction (in response to potassium chloride (KCl) and L-glutamate stimulation), in contrast to those derived from the gene corrected iPSC (SOD1G85G). Meanwhile, BP treatment effectively restored calcium ion channel function by reducing the expression of glutamate receptors including glutamate ionotropic receptor AMPA type subunit 3 (GluR3) and glutamate ionotropic receptor NMDA type subunit 1 (NMDAR1). Additionally, BP treatment activated autophagic pathway to attenuate neuron degeneration. Overall, this study supports the therapeutic effects of BP on ALS patient-derived neuron cells, and suggests that BP may be a promising candidate for future drug development.

Ca2+ Signaling in Cardiovascular Fibroblasts

Fibrogenesis is a physiological process required for wound healing and tissue repair. It is induced by activation of quiescent fibroblasts, which first proliferate and then change their phenotype into migratory, contractile myofibroblasts. Myofibroblasts secrete extracellular matrix proteins, such as collagen, to form a scar. Once the healing process is terminated, most myofibroblasts undergo apoptosis. However, in some tissues, such as the heart, myofibroblasts remain active and sensitive to neurohumoral factors and inflammatory mediators, which lead eventually to excessive organ fibrosis. Many cellular processes involved in fibroblast activation, including cell proliferation, protein secretion and cell contraction, are highly regulated by intracellular Ca2+ signals. This review summarizes current research on Ca2+ signaling pathways underlying fibroblast activation. We present receptor- and ion channel-mediated Ca2+ signaling pathways, discuss how localized Ca2+ signals of the cell nucleus may be involved in fibroblast activation and present Ca2+-sensitive transcription pathways relevant for fibroblast biology. When investigated, we highlight how the function of Ca2+-handling proteins changes during cardiac and pulmonary fibrosis. Many aspects of Ca2+ signaling remain unexplored in different types of cardiovascular fibroblasts in relation to pathologies, and a better understanding of Ca2+ signaling in fibroblasts will help to design targeted therapies against fibrosis.