ATP2B4 is an essential gene for epidermal growth factor-induced macropinocytosis in A431 cells

Macropinocytosis (MPC) is a large-scale endocytosis pathway that involves actin-dependent membrane ruffle formation and subsequent ruffle closure to generate macropinosomes for the uptake of fluid-phase cargos. MPC is categorized into two types: constitutive and stimuli-induced. Constitutive MPC in macrophages relies on extracellular Ca2+ sensing by a calcium-sensing receptor. However, the link between stimuli-induced MPC and Ca2+ remains unclear. Here, we find that both intracellular and extracellular Ca2+ are required for epidermal growth factor (EGF)-induced MPC in A431 human epidermoid carcinoma cells. Through investigation of mammalian homologs of coelomocyte uptake defective (CUP) genes, we identify ATP2B4, encoding for a Ca2+ pump called the plasma membrane calcium ATPase 4 (PMCA4), as a Ca2+-related regulator of EGF-induced MPC. Knockout (KO) of ATP2B4, as well as depletion of extracellular/intracellular Ca2+, inhibited ruffle closure and macropinosome formation, without affecting ruffle formation. We demonstrate the importance of PMCA4 activity itself, independent of interactions with other proteins via its C-terminus known as a PDZ domain-binding motif. Additionally, we show that ATP2B4-KO reduces EGF-stimulated Ca2+ oscillation during MPC. Our findings suggest that EGF-induced MPC requires ATP2B4-dependent Ca2+ dynamics.

The involvement of calcium in the toxic effect of 4-methylethcathinone on SH-SY5Y cells

Neurotoxicity induced by psychoactive substances is often accompanied by an imbalance of intracellular calcium ions. It is unclear whether calcium ions play a role in the toxicity induced by psychoactive substances. In the present study, we aimed to evaluate the occurrence of calcium dysregulation and its contribution to cytotoxicity in human neurotypic SH-SY5Y cells challenged with a recently developed psychoactive substance 4-methylethcathinone (4-MEC). An increase in the intracellular calcium was detected by inductively coupled plasma atomic emission spectrometry and Fluo-3 AM dye in SH-SY5Y cells after being treated with 4-MEC. The increase of intracellular Ca2+ level mediated G0/G1 cell cycle arrest and ROS/endoplasmic reticulum stress-autophagy signaling pathways to achieve the toxicity of 4-MEC. In particular, N-acetyl-L-cysteine, a classical antioxidant, was found to be a potential treatment for 4-MEC-induced toxicity. Taken together, our results demonstrate that an increase in intracellular calcium content is one of the mechanisms of 4-MEC-induced toxicity. This study provides a molecular basis for the toxicity mechanism and therapeutic intervention of psychoactive substances.

Distinct regulation of two flagella by calcium during chemotaxis of male gametes in the brown alga Mutimo cylindricus (Cutleriaceae, Tilopteridales)

Brown algal male gametes show chemotaxis to the sex pheromone that is released from female gametes. The chemotactic behavior of the male gametes is controlled by the changes in the beating of two flagella known as the anterior and posterior flagellum. Our previous study using Mutimo cylindricus showed that the sex pheromone induced an increment in both the deflection angle of the anterior flagellum and sustained unilateral bend of the posterior flagellum, but the mechanisms regulating these two flagellar waveforms were not fully revealed. In this study, we analyzed the changes in swimming path and flagellar waveforms with a high-speed recording system under different calcium conditions. The extracellular Ca2+ concentration at 10-3 M caused an increment in the deflection angle of the anterior flagellum only when ionomycin was absent. No sustained unilateral bend of the posterior flagellum was induced either in the absence or presence of ionomycin in extracellular Ca2+ concentrations below 10-2 M. Real-time Ca2+ imaging revealed that there is a spot near the basal part of anterior flagellum showing higher Ca2+ than in the other parts of the cell. The intensity of the spot slightly decreased when male gametes were treated with the sex pheromone. These results suggest that Ca2+-dependent changes in the anterior and posterior flagellum are regulated by distinct mechanisms and that the increase in the anterior flagellar deflection angle and sustained unilateral bend of the posterior flagellum may not be primarily induced by the Ca2+ concentration.

Experimental Investigation on the Effects of Mineral Water Composition on the Leaching of Cement-Based Materials

The common phenomenon observed for concrete in aggressive water is leaching, which involves the dissolution of cement hydration products. Many studies have focused on leaching in demineralised water or acid attacks, but mineral water still deserves further investigation. In most standards, the aggressiveness of a given water body is determined by its pH and not its composition. The effect of the calcium content of the water on degradation is yet to be determined. In this paper, the leaching of Portland cement-based mortar was induced by two types of drinking water with different calcium contents and buffer capacity in controlled conditions. The Langelier saturation index (LSI) was used to describe water aggressiveness based on the calco-carbonic equilibrium. The studied waters had the same pH but LSIs of +0.5 and -1.0 corresponding to scaling with respect to aggressive water; demineralised water was used as a reference. Microstructural damage was checked by TGA and X-ray microtomography. Macroscopic measurements were used to monitor global degradation. The soft water caused a 53% deeper deterioration of the mortar sample than the hard water. Soft water-induced leaching was found to be similar yet slower to leaching via demineralised water (with a mass loss of -2.01% and -2.16% after 200 days, respectively). In contrast, hard water induced strongly time-dependent leaching, and the damage was located close to the surface. The roughness of leached specimens was 18% higher in hard water than in soft water. The formation of calcite on the sample surface not only affects the leaching rate by creating a protective surface layer, but it could also act as a calcium ion pump.

Effect of Moderate Static Magnetic Fields on Mice Oocyte Vitrification: Calcium-Related Genes Expression

The ability to cryopreserve oocytes without ultrastructural injury has been a concern in the development and use of methods to preserve female reproduction. The stability of the cell membrane must be preserved to reduce the damage caused by ice crystals during vitrification. One approach that has been explored is the use of static magnetic fields (SMFs), which are believed to influence cell membrane stability. In this study, the in vitro effects of SMF that range between 20-80 mT on the vitrification of mice germinal vesicle (GV) oocytes were studied. The viability and mitochondrial (Mt) membrane potential of both vitrified and nonvitrified oocytes were assessed using Trypan blue and JC1 staining. The high in vitro maturation (IVM) rate and high Mt membrane potential in metaphase II (MII) oocytes were taken into account to determine the optimal magnetic field intensity, that is, 20 mT. None of the SMF conditions resulted in intact spindles in MII oocytes. The study also explored the expression of store-operated calcium entry (Stim1, Orai1, and Ip3r) and meiosis resumption (Ccnb, Cdk) genes in GV and MII oocytes of both vitrified and control groups. The results show that the expressions of Orai1 and Ccnb genes in Vit-MII-SMF oocytes were considerably increased. However, no significant difference in Stim1 expression was observed between the groups. The Vit-MII-SMF group exhibited a significantly higher Ccnb expression compared to other groups. In vitro fertilization (IVF) was performed to evaluate the 2 pronuclear (2PN) rates. The findings demonstrated that using 20 mT SMF improved 2PN rates compared to the nonvitrified groups. This study provides a deeper understanding of the effects of moderate SMF and vitrification on the expression of calcium channel genes in GV and MII oocytes. The results suggest that applying a 20 mT SMF can help prevent cryoinjury and enhance the characteristics of vitrified-warmed oocytes.

Human Rad51 Protein Requires Higher Concentrations of Calcium Ions for D-Loop Formation than for Oligonucleotide Strand Exchange

Human Rad51 protein (HsRad51)-promoted DNA strand exchange, a crucial step in homologous recombination, is regulated by proteins and calcium ions. Both the activator protein Swi5/Sfr1 and Ca2+ ions stimulate different reaction steps and induce perpendicular DNA base alignment in the presynaptic complex. To investigate the role of base orientation in the strand exchange reaction, we examined the Ca2+ concentration dependence of strand exchange activities and structural changes in the presynaptic complex. Our results show that optimal D-loop formation (strand exchange with closed circular DNA) required Ca2+ concentrations greater than 5 mM, whereas 1 mM Ca2+ was sufficient for strand exchange between two oligonucleotides. Structural changes indicated by increased fluorescence intensity of poly(dεA) (a poly(dA) analog) reached a plateau at 1 mM Ca2+. Ca2+ > 2 mM was required for saturation of linear dichroism signal intensity at 260 nm, associated with rigid perpendicular DNA base orientation, suggesting a correlation with the stimulation of D-loop formation. Therefore, Ca2+ exerts two different effects. Thermal stability measurements suggest that HsRad51 binds two Ca2+ ions with KD values of 0.2 and 2.5 mM, implying that one step is stimulated by one Ca2+ bond and the other by two Ca2+ bonds. Our results indicate parallels between the Mg2+ activation of RecA and the Ca2+ activation of HsRad51.

Wound Repair of the Cell Membrane: Lessons from Dictyostelium Cells

The cell membrane is frequently subjected to damage, either through physical or chemical means. The swift restoration of the cell membrane's integrity is crucial to prevent the leakage of intracellular materials and the uncontrolled influx of extracellular ions. Consequently, wound repair plays a vital role in cell survival, akin to the importance of DNA repair. The mechanisms involved in wound repair encompass a series of events, including ion influx, membrane patch formation, endocytosis, exocytosis, recruitment of the actin cytoskeleton, and the elimination of damaged membrane sections. Despite the absence of a universally accepted general model, diverse molecular models have been proposed for wound repair in different organisms. Traditional wound methods not only damage the cell membrane but also impact intracellular structures, including the underlying cortical actin networks, microtubules, and organelles. In contrast, the more recent improved laserporation selectively targets the cell membrane. Studies on Dictyostelium cells utilizing this method have introduced a novel perspective on the wound repair mechanism. This review commences by detailing methods for inducing wounds and subsequently reviews recent developments in the field.

In vivo cytosolic H2O2 changes and Ca2+ homeostasis in mouse skeletal muscle

Hydrogen peroxide (H2O2) and calcium ions (Ca2+) are functional regulators of skeletal muscle contraction and metabolism. Although H2O2 is one of the activators of the type-1 ryanodine receptor (RyR1) in the Ca2+ release channel, the interdependence between H2O2 and Ca2+ dynamics remains unclear. This study tested the following hypotheses using an in vivo model of mouse tibialis anterior (TA) skeletal muscle. 1) Under resting conditions, elevated cytosolic H2O2 concentration ([H2O2]cyto) leads to a concentration-dependent increase in cytosolic Ca2+ concentration ([Ca2+]cyto) through its effect on RyR1; and 2) in hypoxia (cardiac arrest) and muscle contractions (electrical stimulation), increased [H2O2]cyto induces Ca2+ accumulation. Cytosolic H2O2 (HyPer7) and Ca2+ (Fura-2) dynamics were resolved by TA bioimaging in young C57BL/6J male mice under four conditions: 1) elevated exogenous H2O2; 2) cardiac arrest; 3) twitch (1 Hz, 60 s) contractions; and 4) tetanic (30 s) contractions. Exogenous H2O2 (0.1-100 mM) induced a concentration-dependent increase in [H2O2]cyto (+55% at 0.1 mM; +280% at 100 mM) and an increase in [Ca2+]cyto (+3% at 1.0 mM; +8% at 10 mM). This increase in [Ca2+]cyto was inhibited by pharmacological inhibition of RyR1 by dantrolene. Cardiac arrest-induced hypoxia increased [H2O2]cyto (+33%) and [Ca2+]cyto (+20%) 50 min postcardiac arrest. Compared with the exogenous 1.0 mM H2O2 condition, [H2O2]cyto after tetanic muscle contractions rose less than one-tenth as much, whereas [Ca2+]cyto was 4.7-fold higher. In conclusion, substantial increases in [H2O2]cyto levels evoke only modest Ca2+ accumulation via their effect on the sarcoplasmic reticulum RyR1. On the other hand, contrary to hypoxia secondary to cardiac arrest, increases in [H2O2]cyto from muscle contractions are small, indicating that H2O2 generation is unlikely to be a primary factor driving the significant Ca2+ accumulation after, especially tetanic, muscle contractions.NEW & NOTEWORTHY We developed an in vivo mouse myocyte H2O2 imaging model during exogenous H2O2 loading, ischemic hypoxia induced by cardiac arrest, and muscle contractions. In this study, the interrelationship between cytosolic H2O2 levels and Ca2+ homeostasis during muscle contraction and hypoxic conditions was revealed. These results contribute to the elucidation of the mechanisms of muscle fatigue and exercise adaptation.

Mechanistic Investigation of WWOX Function in NF-kB-Induced Skin Inflammation in Psoriasis

Psoriasis is a chronic inflammatory skin disease characterized by epidermal hyperproliferation, aberrant differentiation of keratinocytes, and dysregulated immune responses. WW domain-containing oxidoreductase (WWOX) is a non-classical tumor suppressor gene that regulates multiple cellular processes, including proliferation, apoptosis, and migration. This study aimed to explore the possible role of WWOX in the pathogenesis of psoriasis. Immunohistochemical analysis showed that the expression of WWOX was increased in epidermal keratinocytes of both human psoriatic lesions and imiquimod-induced mice psoriatic model. Immortalized human epidermal keratinocytes were transduced with a recombinant adenovirus expressing microRNA specific for WWOX to downregulate its expression. Inflammatory responses were detected using Western blotting, real-time quantitative reverse transcription polymerase chain reaction (PCR), and enzyme-linked immunosorbent assay. In human epidermal keratinocytes, WWOX knockdown reduced nuclear factor-kappa B signaling and levels of proinflammatory cytokines induced by polyinosinic: polycytidylic acid [(poly(I:C)] in vitro. Furthermore, calcium chelator and protein kinase C (PKC) inhibitors significantly reduced poly(I:C)-induced inflammatory reactions. WWOX plays a role in the inflammatory reaction of epidermal keratinocytes by regulating calcium and PKC signaling. Targeting WWOX could be a novel therapeutic approach for psoriasis in the future.

Achilles' Heel-The Significance of Maintaining Microenvironmental Homeostasis in the Nucleus Pulposus for Intervertebral Discs

The dysregulation of intracellular and extracellular environments as well as the aberrant expression of ion channels on the cell membrane are intricately linked to a diverse array of degenerative disorders, including intervertebral disc degeneration. This condition is a significant contributor to low back pain, which poses a substantial burden on both personal quality of life and societal economics. Changes in the number and function of ion channels can disrupt the water and ion balance both inside and outside cells, thereby impacting the physiological functions of tissues and organs. Therefore, maintaining ion homeostasis and stable expression of ion channels within the cellular microenvironment may prove beneficial in the treatment of disc degeneration. Aquaporin (AQP), calcium ion channels, and acid-sensitive ion channels (ASIC) play crucial roles in regulating water, calcium ions, and hydrogen ions levels. These channels have significant effects on physiological and pathological processes such as cellular aging, inflammatory response, stromal decomposition, endoplasmic reticulum stress, and accumulation of cell metabolites. Additionally, Piezo 1, transient receptor potential vanilloid type 4 (TRPV4), tension response enhancer binding protein (TonEBP), potassium ions, zinc ions, and tungsten all play a role in the process of intervertebral disc degeneration. This review endeavors to elucidate alterations in the microenvironment of the nucleus pulposus during intervertebral disc degeneration (IVDD), with a view to offer novel insights and approaches for exploring therapeutic interventions against disc degeneration.

A chitosan-coated lentinan-loaded calcium alginate hydrogel induces broad-spectrum resistance to plant viruses by activating Nicotiana benthamiana calmodulin-like (CML) protein 3

Control of plant virus diseases largely depends on the induced plant defence achieved by the external application of synthetic chemical inducers with the ability to modify defence-signalling pathways. However, most of the molecular mechanisms underlying these chemical inducers remain unknown. Here, we developed a chitosan-coated lentinan-loaded hydrogel and discovered how it protects plants from different virus infections. The hydrogel was synthesized by coating chitosan on the surface of the calcium alginate-lentinan (LNT) hydrogel (SL-gel) to form a CSL-gel. CSL-gels exhibit the capacity to prolong the stable release of lentinan and promote Ca2+ release. Application of CSL-gels on the root of plants induces broad-spectrum resistance against plant viruses (TMV, TRV, PVX and TuMV). RNA-seq analysis identified that Nicotiana benthamiana calmodulin-like protein gene 3 (NbCML3) is upregulated by the sustained release of Ca2+ from the CSL-gel, and silencing and overexpression of NbCML alter the susceptibility and resistance of tobacco to TMV. Our findings provide evidence that this novel and synthetic CSL-gel strongly inhibits the infection of plant viruses by the sustainable release of LNT and Ca2+ . This study uncovers a novel mode of action by which CSL-gels trigger NbCML3 expression through the stable and sustained release of Ca2+ .

Elevated extracellular calcium ions accelerate the proliferation and migration of HepG2 cells and decrease cisplatin sensitivity

Hepatoblastoma is the most frequent liver malignancy in children. HepG2 has been discovered as a hepatoblastoma-derived cell line and tends to form clumps in culture. Intriguingly, we observed that the addition of calcium ions reduced cell clumping and disassociated HepG2 cells. The calcium signal is in connection with a series of processes critical in the tumorigenesis. Here, we demonstrated that extracellular calcium ions induced morphological changes and enhanced the epithelial-mesenchymal transition in HepG2 cells. Mechanistically, calcium ions promoted HepG2 proliferation and migration by up-regulating the phosphorylation levels of focal adhesion kinase (FAK), protein kinase B, and p38 mitogen-activated protein kinase. The inhibitor of FAK or Ca 2+/calmodulin-dependent kinase Ⅱ (CaMKⅡ) reversed the Ca 2+-induced effects on HepG2 cells, including cell proliferation and migration, epithelial-mesenchymal transition protein expression levels, and phosphorylation levels of FAK and protein kinase B. Moreover, calcium ions decreased HepG2 cells' sensitivity to cisplatin. Furthermore, we found that the expression levels of FAK and CaMKⅡ were increased in hepatoblastoma. The group with high expression levels of FAK and CaMKⅡ exhibited significantly lower ImmunoScore as well as CD8 + T and NK cells. The expression of CaMKⅡ was positively correlated with that of PDCD1 and LAG3. Correspondingly, the expression of FAK was negatively correlated with that of TNFSF9, TNFRSF4, and TNFRSF18. Collectively, extracellular calcium accelerates HepG2 cell proliferation and migration via FAK and CaMKⅡ and enhances cisplatin resistance. FAK and CaMKⅡ shape immune cell infiltration and responses in tumor microenvironments, thereby serving as potential targets for hepatoblastoma.

Development of Films from Spent Coffee Grounds' Polysaccharides Crosslinked with Calcium Ions and 1,4-Phenylenediboronic Acid: A Comparative Analysis of Film Properties and Biodegradability

Most polymeric materials are synthetic and derived from petroleum, hence they accumulate in landfills or the ocean, and recent studies have focused on alternatives to replace them with biodegradable materials from renewable sources. Biodegradable wastes from food and agroindustry, such as spent coffee grounds (SCGs), are annually discarded on a large scale and are rich in organic compounds, such as polysaccharides, that could be used as precursors to produce films. Around 6.5 million tons of SCGs are discarded every year, generating an environmental problem around the world. Therefore, it was the aim of this work to develop films from the SCGs polysaccharide fraction, which is comprised of cellulose, galactomannans and arabinogalactans. Two types of crosslinking were performed: the first forming coordination bonds of calcium ions with polysaccharides; and the second through covalent bonds with 1,4-phenylenediboronic acid (PDBA). The films with Ca²⁺ ions exhibited a greater barrier to water vapor with a reduction of 44% of water permeability vapor and 26% greater tensile strength than the control film (without crosslinkers). Films crosslinked with PDBA presented 55-81% higher moisture contents, 85-125% greater permeability to water vapor and 67-150% larger elongations at break than the films with Ca²⁺ ions. Film biodegradability was demonstrated to be affected by the crosslinking density, with the higher the crosslinking density, the longer the time for the film to fully biodegrade. The results are promising and suggest that future research should focus on enhancing the properties of these films to expand the range of possible applications.

Molecular properties of Ca2+ transport through TRPV2 channel: a molecular dynamics simulations study

TRPV channels are a category of nonselective cation channels that are activated by heat and ligands and permeate monovalent and divalent ions. The mechanism of Ca2+ transfer through TRPV2 channel is not well known. Here, we investigated the reaction coordination and energy fluctuation of Ca2+ transition in TRPV2 channel by steered molecular dynamics (SMD) simulations and potential of mean force (PMF) calculation. Results showed that electrostatic interactions between Ca2+ and residues of the first and second gates had main roles in ions transfer through the channel. Also, we recognized important amino acids in this path. Moreover, results indicated that enter and exit of calcium ions need to overcome barrier energies in the first and second gates.Communicated by Ramaswamy H. Sarma.

Recent Advances in Chemotherapeutics for Leishmaniasis: Importance of the Cellular Biochemistry of the Parasite and Its Molecular Interaction with the Host

Leishmaniasis, a category 1 neglected protozoan disease caused by a kinetoplastid pathogen called Leishmania, is transmitted through dipteran insect vectors (phlebotomine, sand flies) in three main clinical forms: fatal visceral leishmaniasis, self-healing cutaneous leishmaniasis, and mucocutaneous leishmaniasis. Generic pentavalent antimonials have long been the drug of choice against leishmaniasis; however, their success is plagued with limitations such as drug resistance and severe side effects, which makes them redundant as frontline therapy for endemic visceral leishmaniasis. Alternative therapeutic regimens based on amphotericin B, miltefosine, and paromomycin have also been approved. Due to the unavailability of human vaccines, first-line chemotherapies such as pentavalent antimonials, pentamidine, and amphotericin B are the only options to treat infected individuals. The higher toxicity, adverse effects, and perceived cost of these pharmaceutics, coupled with the emergence of parasite resistance and disease relapse, makes it urgent to identify new, rationalized drug targets for the improvement in disease management and palliative care for patients. This has become an emergent need and more relevant due to the lack of information on validated molecular resistance markers for the monitoring and surveillance of changes in drug sensitivity and resistance. The present study reviewed the recent advances in chemotherapeutic regimens by targeting novel drugs using several strategies including bioinformatics to gain new insight into leishmaniasis. Leishmania has unique enzymes and biochemical pathways that are distinct from those of its mammalian hosts. In light of the limited number of available antileishmanial drugs, the identification of novel drug targets and studying the molecular and cellular aspects of these drugs in the parasite and its host is critical to design specific inhibitors targeting and controlling the parasite. The biochemical characterization of unique Leishmania-specific enzymes can be used as tools to read through possible drug targets. In this review, we discuss relevant metabolic pathways and novel drugs that are unique, essential, and linked to the survival of the parasite based on bioinformatics and cellular and biochemical analyses.

Unraveling the connection between calreticulin and myeloproliferative neoplasms via calcium signaling

Mutations in the form of insertions and deletions (INDEL) in the calreticulin gene lead to essential thrombocythemia (ET) which is characterized by the formation of thrombosis. However, the connection between calreticulin INDEL and ET remains largely elusive. Through combined molecular dynamics simulation, clustered regularly interspaced short palindromic repeats (CRISPR) and calcium imaging studies on the wild type and mutated isoforms of calreticulin, the mechanism underlying the calreticulin INDEL induced ET was investigated at the molecular level. Our results demonstrate that mutations in exon-9 could lead to significant conformational variations of calreticulin structure and thereby reducing its interaction with calcium ions due to decreased electrostatic contributions. The consequence of mutations on calreticulin's structural integrity was revealed by identifying the key residues and their roles in calcium binding. Furthermore, mutations implemented by CRISPR-Cas9 in exon-9 showed diminished calcium signaling in HEK-293T cells, which agree well with our in-silico findings. The current study might help in understanding the variations of molecular interactions between calreticulin's exon-9 and calcium ions during physiological and pathological conditions. The results might also provide useful information for designing novel therapeutic approaches targeting ET.

Effect of high-pressure homogenization on Ca2+ -induced gel formation of soybean 11 S globulin

BACKGROUND

High-pressure homogenization (HPH) is commonly used as a non-thermal processing technique for soybean and soy protein products, and the preparation of soy protein gel products often requires the synergistic effect of HPH and heat treatment. The dissociative association behavior of 11 S is the key to the protein gel formation state. In this study, therefore, 11 S thermal gels were prepared by high-pressure homogenization and co-induction (90 °C, 30 min) (adding Ca²⁺ to promote gel formation before heat treatment), and the effects of different high-pressure homogenization pressures (0-100 MPa) and co-treatment on the dissociative association behavior of 11 S protein, gel properties, and microstructure of 11 S gels were investigated.

RESULTS

The results showed that HPH at higher pressures led to the breaking of disulfide bonds of aggregates and disrupted non-covalent interactions in protein aggregates, leading to collisions between protein aggregates and the reduction of large protein aggregates. High-pressure homogenization treatment at 60 MPa improved the gel properties of 11 S more. The HPH combined with heating changed the binary and tertiary structure of 11 S soy globulin and enhanced the hydrophobic interaction between 11 S molecules, thus improving the gel properties of 11 S. The change in intermolecular forces reflected the positive effect of HPH treatment on the formation of denser and more homogeneous protein gels.

CONCLUSION

In conclusion, high-pressure homogenization combined with heating can improve the properties of 11 S gels by changing the structure of 11 S protein, providing data and theoretical support for soy protein processing and its further applications. © 2022 Society of Chemical Industry.

Transcriptome and proteome depth analysis indicate ABA, MAPK cascade and Ca2+ signaling co-regulate cold tolerance in Rhododendron chrysanthum Pall

INTRODUCTION

Cold stress is a global common problem that significantly limits plant development and geographical distribution. Plants respond to low temperature stress by evolving interrelated regulatory pathways to respond and adapt to their environment in a timely manner. Rhodoendron chrysanthum Pall. (R. chrysanthum) is a perennial evergreen dwarf shrub used for adornment and medicine that thrives in the Changbai Mountains at high elevations and subfreezing conditions.

METHODS

In this study, a comprehensive investigation of cold tolerance (4°C, 12h) in R. chrysanthum leaves under cold using physiological combined with transcriptomic and proteomic approaches.

RESULTS

There were 12,261 differentially expressed genes (DEGs) and 360 differentially expressed proteins (DEPs) in the low temperature (LT) and normal treatment (Control). Integrated transcriptomic and proteomic analyses showed that MAPK cascade, ABA biosynthesis and signaling, plant-pathogen interaction, linoleic acid metabolism and glycerophospholipid metabolism were significantly enriched in response to cold stress of R. chrysanthum leaves.

DISCUSSION

We analyzed the involvement of ABA biosynthesis and signaling, MAPK cascade, and Ca²⁺ signaling, that may jointly respond to stomatal closure, chlorophyll degradation, and ROS homeostasis under low temperature stress. These results propose an integrated regulatory network of ABA, MAPK cascade and Ca²⁺ signaling comodulating the cold stress in R. chrysanthum, which will provide some insights to elucidate the molecular mechanisms of cold tolerance in plants.

Adsorption and Lubrication of Glutamic Acid-Based Surfactant with Calcium Ions

The adsorption and lubrication of an amino acid-based surfactant at the solid/liquid interface were studied in the presence of calcium ions. The surfactant used here was disodium N-dodecanoylglutamate (C12Glu-2Na). The solid surface used in this study was hydrophobically modified to mimic the hydrophobicity of the skin surface. Quartz crystal microbalance with dissipation monitoring (QCM-D) measurements revealed that the anionic surfactant was adsorbed on the hydrophobically modified solid surface. The replacement of the surfactant solution with CaCl₂ aqueous solution resulted in the desorption of the surfactant to some extent; however, a rigid and elastic adsorption film interacting with calcium ions remained on the solid surface. The adsorption film containing calcium ions lowered the kinetic friction coefficient in aqueous media. The insoluble calcium salt of the surfactant, dispersed in the solution phase, also contributed to lubrication. We expect that the usability of personal care products formulated using amino acid-based surfactants is relevant to such adsorption and lubrication properties.

Activation of Hepatic Branched-Chain α-Ketoacid Dehydrogenase Complex by Vitamin D Deficiency in Rats

Branched-chain α-ketoacid dehydrogenase (BCKDH) complex is a rate-limiting enzyme in branched-chain amino acid catabolism and is subject to inactivation via phosphorylation by BCKDH kinase (BDK). In the present study, we examined the effects of vitamin D-deficiency on hepatic BCKDH and BDK activities in rats. Rats fed a vitamin D-deficient diet long-term showed a slight but significant decrease in plasma Ca concentration, which was associated with an elevation of BCKDH activity and a decrease in BDK activity. These results suggest that vitamin D deficiency promotes BCAA catabolism via BCKDH activation, which resulted from BDK suppression. It is proposed that Ca2+-dependent BDK inhibition by thiamine pyrophosphate may be involved in the BDK suppression.

Induced effect of Ca2+ and Al3+ on chaetominine synthesis by Aspergillus fumigatus CY018 under submerged fermentation

Chaetominine (CHA), an alkaloid with a biological activity obtained from Aspergillus fumigatus CY018, has strong anticancer activity against the human leukemia cells. However, its physiological and biochemical research is limited by CHA yield in the liquid-state fermentation, which is a problem that urgently needs effective biological solution. In this work, Ca²⁺ and Al³⁺ were found to have a strong promoting effect on CHA production after multiple metal ions screening. Then, the addition condition of Ca²⁺ and Al³⁺ was, respectively, optimized CHA production and dry cell weight. The intermediate metabolites were increased with coaddition of Ca²⁺ and Al³⁺ . The activities of key enzymes of DAHPs, AroAs, and TrpCs in the CHA biosynthesis pathway were improved by 3.58-, 3.60-, and 3.34-fold, respectively. Meanwhile, the transcription level of laeA, dahp, cs, and trpC was upregulated by 3.22-, 12.65-, 5.58-, and 6.99-fold, respectively, by coaddition of Ca²⁺ and Al³⁺ . Additionally, the fermentation strategy was successfully scaled up to a 5-L bioreactor, in which CHA production could attain 75.6 mg/L at 336 h. This work demonstrated that Ca²⁺ and Al³⁺ coaddition was an effective strategy for increasing CHA production, and the information obtained might be useful in the fermentation of filamentous fungi with the addition of metal ions.

Calcium Potentiated Carbapenem Effectiveness Against Resistant Enterobacter Species

BACKGROUND

Antimicrobial resistance (AMR) remains a global health challenge, as bacteria display increasing resistance to last-resort antibiotics such as carbapenems. Enterobacter cloacae are evolving and developing high level of resistance to carbapenems. With increasing AMR, availability of antibiotics for treatment dwindles, hence a need to complement antibiotics to enhance activity or reduce the level of resistance. This study explored the use of calcium ions in attenuating bacterial resistance to carbapenems.

METHOD

E. cloacae strains isolated from hospital fomites and air were subjected to antimicrobial susceptibility testing with carbapenem antibiotics (imipenem, meropenem, doripenem and ertapenem) using the disc diffusion (E. coli ATCC 25922 as control). Growth profile, Ca-Adjusted assay and time-kill curve of the strains was determined in the presence and absence of carbapenem antibiotics following a calcium stress assay.

RESULTS

Growth profile showed that all the E. cloacae strains grew markedly well at 37°C relative to ATCC 25922 and all strains displayed 80% to 100% level of resistance to tested antibiotics. The growth rate of the strains in the presence of the antibiotics was comparable to the growth rate in the absence of carbapenems. Conditional growth stress with calcium ions showed a 50% reduction in the level of resistance with doripenem displaying the lowest level of reduction and ertapenem, the highest.

DISCUSSION

The study showed that E. cloacae strains displayed high levels of resistance to carbapenems, increasing the possibility of treatment failure. Challenging strains with calcium prior to antibiotic treatment led to a significant reduction in level of resistance, indicating that calcium ions could affect bacterial strains during antibiotic activity leading to reduction in level of resistance.

CONCLUSION

Calcium supplement could potentiate carbapenem effectiveness and reduce bacterial AMR.

Impacts of Calcium Addition on Humic Acid Fouling and the Related Mechanism in Ultrafiltration Process for Water Treatment

Humic acid (HA) is a major natural organic pollutant widely coexisting with calcium ions (Ca²⁺) in natural water and wastewater bodies, and the coagulation-ultrafiltration process is the most typical solution for surface water treatment. However, little is known about the influences of Ca²⁺ on HA fouling in the ultrafiltration process. This study explored the roles of Ca²⁺ addition in HA fouling and the potential of Ca²⁺ addition for fouling mitigation in the coagulation-ultrafiltration process. It was found that the filtration flux of HA solution rose when Ca²⁺ concentration increased from 0 to 5.0 mM, corresponding to the reduction of the hydraulic filtration resistance. However, the proportion and contribution of each resistance component in the total hydraulic filtration resistance have different variation trends with Ca²⁺ concentration. An increase in Ca²⁺ addition (0 to 5.0 mM) weakened the role of internal blocking resistance (9.02% to 4.81%) and concentration polarization resistance (50.73% to 32.17%) in the total hydraulic resistance but enhanced membrane surface deposit resistance (33.93% to 44.32%). A series of characterizations and thermodynamic analyses consistently suggest that the enlarged particle size caused by the Ca²⁺ bridging effect was the main reason for the decreased filtration resistance of the HA solution. This work revealed the impacts of Ca²⁺ on HA fouling and demonstrated the feasibility to mitigate fouling by adding Ca²⁺ in the ultrafiltration process to treat HA pollutants.

Regulation of PaRBOH1-mediated ROS production in Norway spruce by Ca2+ binding and phosphorylation

Plant respiratory burst oxidase homologs (RBOHs) are plasma membrane-localized NADPH oxidases that generate superoxide anion radicals, which then dismutate to H₂O₂, into the apoplast using cytoplasmic NADPH as an electron donor. PaRBOH1 is the most highly expressed RBOH gene in developing xylem as well as in a lignin-forming cell culture of Norway spruce (Picea abies L. Karst.). Since no previous information about regulation of gymnosperm RBOHs exist, our aim was to resolve how PaRBOH1 is regulated with a focus on phosphorylation. The N-terminal part of PaRBOH1 was found to contain several putative phosphorylation sites and a four-times repeated motif with similarities to the Botrytis-induced kinase 1 target site in Arabidopsis AtRBOHD. Phosphorylation was indicated for six of the sites in in vitro kinase assays using 15 amino-acid-long peptides for each of the predicted phosphotarget site in the presence of protein extracts of developing xylem. Serine and threonine residues showing positive response in the peptide assays were individually mutated to alanine (kinase-inactive) or to aspartate (phosphomimic), and the wild type PaRBOH1 and the mutated constructs transfected to human kidney embryogenic (HEK293T) cells with a low endogenous level of extracellular ROS production. ROS-producing assays with HEK cells showed that Ca²⁺ and phosphorylation synergistically activate the enzyme and identified several serine and threonine residues that are likely to be phosphorylated including a novel phosphorylation site not characterized in other plant species. These were further investigated with a phosphoproteomic study. Results of Norway spruce, the first gymnosperm species studied in relation to RBOH regulation, show that regulation of RBOH activity is conserved among seed plants.

FERONIA-like receptor 1-mediated calcium ion homeostasis is involved in the immune response

Calcium (Ca²⁺) is the most abundant divalent cation in plants, and cellular levels of Ca²⁺, which functions as a nutrient and secondary messenger, play a critical role in plant immunity. In the present study, we found that FERONIA-like receptor 1 (FLR1) positively regulates Magnaporthe oryzae resistance and that expression of FLR1 is strongly induced in response to Ca²⁺ deficiency. In addition, the Ca content in the shoots of flr1 was lower than that in wild-type, and the M. oryzae-sensitive phenotype of the flr1 mutant was not rescued by exogenous application of Ca²⁺. Moreover, RNA sequencing revealed 2,697 differentially expressed genes (DEGs) in the flr1 mutant compared with wild-type, and some of these DEGs are involved in cellular metal ion homeostasis and transition metal ion homeostasis. Changes in expression of overlapping genes between the flr1 mutant and in plants under low-Ca²⁺ treatment were consistent in terms of direction, indicating that FLR1 is involved in Ca²⁺ homeostasis. In summary, we detected FLR1-mediated resistance to M. oryzae, a phenomenon associated with Ca²⁺ homeostasis.

Transcriptional Regulatory Role of NELL2 in Preproenkephalin Gene Expression

Preproenkephalin (PPE) is a precursor molecule for multiple endogenous opioid peptides Leu-enkephalin (ENK) and Met-ENK, which are involved in a wide variety of modulatory functions in the nervous system. Despite the functional importance of ENK in the brain, the effect of brain-derived factor(s) on PPE expression is unknown. We report the dual effect of neural epidermal growth factor (EGF)-likelike 2 (NELL2) on PPE gene expression. In cultured NIH3T3 cells, transfection of NELL2 expression vectors induced an inhibition of PPE transcription intracellularly, in parallel with downregulation of protein kinase C signaling pathways and extracellular signal-regulated kinase. Interestingly, these phenomena were reversed when synthetic NELL2 was administered extracellularly. The in vivo disruption of NELL2 synthesis resulted in an increase in PPE mRNA level in the rat brain, suggesting that the inhibitory action of intracellular NELL2 predominates the activation effect of extracellular NELL2 on PPE gene expression in the brain. Biochemical and molecular studies with mutant NELL2 structures further demonstrated the critical role of EGF-like repeat domains in NELL2 for regulation of PPE transcription. These are the first results to reveal the spatio-specific role of NELL2 in the homeostatic regulation of PPE gene expression.

pH-Sensitive Polyacrylic Acid-Gated Mesoporous Silica Nanocarrier Incorporated with Calcium Ions for Controlled Drug Release

In this work, polyacrylic acid-functionalized MCM-41 was synthesized, which was made to interact with calcium ions, in order to realize enhanced pH-responsive nanocarriers for sustained drug release. First, mesoporous silica nanoparticles (MSNs) were prepared by the sol-gel method. Afterward, a (3-trimethoxysilyl)propyl methacrylate (TMSPM) modified surface was prepared by using the post-grafting method, and then the polymerization of the acrylic acid was performed. After adding a calcium chloride solution, polyacrylic acid-functionalized MSNs with calcium-carboxyl ionic bonds in the polymeric layer, which can prevent the cargo from leaking out of the mesopore, were prepared. The structure and morphology of the modified nanoparticles (PAA-MSNs) were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), and N₂ adsorption-desorption analysis, etc. The controlled release of guest molecules was studied by using 5-fluorouracil (5-FU). The drug molecule-incorporated nanoparticles showed different releasing rates under different pH conditions. It is considered that our current materials have the potential as pH-responsive nanocarriers in the field of medical treatment.

Non-clinical studies indicating lack of interactions between iron/calcium ions and linzagolix, an orally available GnRH antagonist

Linzagolix is an orally available gonadotropin-releasing hormone antagonist used to treat sex-hormone-dependent diseases in women. This study aimed to investigate drug-drug interactions between linzagolix and iron/calcium ions in the intended clinical setting by conducting pharmacokinetic studies in vitro and in rats.Insoluble precipitate formation with metal ions was evaluated by measuring linzagolix concentrations in four types of bio-relevant dissolution media (fasted/fed state simulated gastric fluid and fasted/fed state simulated gastric fluid version 2), and chelate complex formation with metal ions was evaluated by release of linzagolix from a cellulose membrane sac. In these in vitro studies, linzagolix showed no potential for insoluble precipitate formation under fasted/fed conditions and no chelate complex formation in the presence of metal ions.In rats, the plasma concentration-time profiles of linzagolix and iron ion were similar regardless of whether they were administered with or without ferrous sulfate and linzagolix choline at clinically relevant doses. Thus, linzagolix and iron ion had no effect on each other's absorption in vivo.In conclusion, linzagolix is unlikely to cause clinically relevant drug-drug interactions by chelating metal ions according to the results of in vitro and in vivo studies.

Study of the Ca2+-dependent gene expression of EuPrt, an extracellular metalloprotease produced by the psychro-tolerant bacterium Exiguobacterium undae Su-1

The effect of a Ca2+ ion on the gene expression of an on-demand type of metalloprotease from psychrotrophic Exiguobacterium undae Su-1 (EuPrt) was studied. We first established a modified mM9 medium for strain Su-1 to examine its effect in more detail. Then, when the strain was cultured in mM9 medium and 1.0 mM CaCl2 was added, we detected the mature EuPrt and its precursor proteins via Western blotting analysis and found the relative protease activity and its transcription increased by 50-fold and 7-fold, respectively, at the peak. Furthermore, the intracellular concentration of Ca2+ ions was analyzed using inductively coupled plasma atomic emission spectroscopy (ICP-AES) with other metal ions along the growth of strain Su-1. The intracellular concentration of Ca2+ ion was found to increase as much as 3-fold in response to the addition of an extracellular Ca2+ ions, indicating that euPrt gene expression is regulated by sensing its intracellular concentration.

Evaluation of pH and calcium ion release at the simulated external root resorption cavities of teeth obturated with bioceramic sealer

Objective

The purpose of this study was to evaluate pH and calcium ion release at the outer dentin surface of simulated external root resorption cavities after root canals obturated with bioceramic root canal sealer compared with those medicated with calcium hydroxide.

Materials and Methods

Sixty extracted human single‐rooted teeth were selected and instrumented. External root resorption cavities were prepared at the lingual surface of the root. The teeth were randomly divided into three groups: (1) Bioceramic sealer group, canals were obturated with gutta‐percha and BioRoot sealer; (2) Calcium hydroxide group, canals were medicated with UltraCal XS; (3) Control group, canals were left empty. Thirty specimens were used for evaluation of pH at 7, 14, and 28 days (n = 10 per group) and the other 30 specimens were used for evaluation of calcium ion diffusion at 28 days (n = 10 per group).

Results

Calcium hydroxide group showed the highest median pH value at all time points (7, 14, and 28 days). Both calcium hydroxide and bioceramic sealer groups showed significantly higher median pH values compared with control (p < .001). Comparing within groups, both bioceramic sealer group and calcium hydroxide group showed significantly decreased median pH over time, while the median pH of the control did not show any significant difference among Days 7, 14, and 28. Both calcium hydroxide and bioceramic sealer groups had significantly higher calcium ion release than control. Notably, bioceramic sealer group showed significantly higher calcium ion release than the calcium hydroxide group (p < .01).

Conclusions

Root canals obturated with gutta‐percha and bioceramic sealer showed high calcium ion levels at the simulated external root resorption cavities but did not show an extended period of alkaline pH.

Endocytosis Involved d-Oligopeptide of Tryptophan and Arginine Displays Ordered Nanostructures and Cancer Cell Stereoselective Toxicity by Autophagy

Owing to their self-aggregation propensity and selective interaction with the anionic membranes, the peptides rich in tryptophan (Trp) and arginine (Arg) are considered for the development of novel anticancer therapeutics. However, the structural insights from the perspective of backbone chirality and spatial orientation of side chains into the selective toxicity of peptides are limited. Here, we investigated the selectivity and cellular uptake of HHC36, a Trp/Arg-rich nonapeptide, and its d-enantiomer (^allDHHC36) and a retroinverso analogue in the lung A549 and breast MDA-MB-231 cancer cells. We realized that the d-peptides can specifically induce autophagy at nontoxic concentrations only in the A549 cells supported from the LC 3-II immunostaining expression in the vicinity of the nucleus and the ultrastructural analysis revealing the autophagosome formation. The autophagic flux was also remarkable in the cells exposed to d-peptides at a far lower concentration in synergism with doxorubicin (DOX). In marked contrast, nonselective cell death was observed only if a high amount of HHC36 was applied. HHC36 tended to irregular collagen-like fibrils relative to ^allDHHC36 that distinctly formed higher-order coiled nanostructures. Interestingly, the short d-peptide fragments were generated in a harsh oxidative condition. Compared with the direct membrane transduction of HHC36, the entry of d-peptides into the lung cancer cells was controlled by endocytosis through the contribution of heparan sulfate proteoglycans (HSPGs) and cholesterol (CHO). However, both l- and d-peptides feasibly crossed the membrane and localized inside the S-phase-arrested cell nucleus. This suggested the likelihood of peptide intercalation with DNA that might differently appear in selective and/or nonselective deaths. These results unraveled the d-handedness-selective toxicity of a self-assembling Trp/Arg-rich sequence that is dependent on the cell type from the aspects of the density of anionic charges and CHO in the outer leaflet of the plasma membrane, as well as the intracellular redox imbalance that may drive the formation of toxic peptide nanostructure fragments.

Inositol Improves Cold Tolerance Through Inhibiting CBL1 and Increasing Ca2+ Influx in Rapeseed (Brassica napus L.)

Rapeseed (Brassica napus L.) is an important oilseed crop worldwide. However, its productivity is significantly affected by various abiotic stresses, including cold stress. Among various stresses, cold stress is an important abiotic factor affecting plant growth, yield, and quality. The calcium channels are regarded as key pathways affecting cold tolerance in plants. Thus, improvement in cold tolerance is of great significance for crop improvement. The current study was designed to examine the beneficial role of exogenous inositol in improving cold stress tolerance in rapeseed. From the RNA-seq results, we identified 35 differently expressed genes encoding different inositol enzymes. The results show that inositol (a cyclic polyol) positively regulated cold tolerance by increasing calcium ion (Ca²⁺) influx in rapeseed. Furthermore, we found that the expression of calcineurin B-like (CBL1) gene was inhibited by inositol. On the other hand, overexpressed plant mediated the Ca²⁺ flux under cold stress suggesting the key role of inositol-Ca²⁺ pathway in cold tolerance. Moreover, the overexpression of BnCBL1-2 in Arabidopsis represented that transgenic plants mediated the Ca²⁺ flux highlighting the vital role of the inositol-Ca²⁺ pathway in conferring cold stress. Our study provides new insights into rapeseed cold tolerance mechanism and introduces a feasible method to improve the cold tolerance of rapeseed quickly.

Binding Energy and Free Energy of Calcium Ion to Calmodulin EF-Hands with the Drude Polarizable Force Field

Calcium ions are important messenger molecules in cells, which bind calcium-binding proteins to trigger many biochemical processes. We constructed four model systems, each containing one EF-hand loop of calmodulin with one calcium ion bound, and investigated the binding energy and free energy of Ca²⁺ by the quantum mechanics symmetry-adapted perturbation theory (SAPT) method and the molecular mechanics with the additive CHARMM36m (C36m) and the polarizable Drude force fields (FFs). Our results show that the explicit introduction of polarizability in the Drude not only yields considerably improved agreement with the binding energy calculated from the SAPT method but is also able to capture each component of the binding energies including electrostatic, induction, exchange, and dispersion terms. However, binding free energies computed with the Drude and the C36m FFs both deviated significantly from the experimental measurements. Detailed analysis indicated that one of main reasons might be that the strong interactions between Ca²⁺ and the side chain nitrogen of Asn/Gln in the Drude FF caused the distorted coordination geometries of calcium. Our work illustrated the importance of polarization in modeling ion-protein interactions and the difficulty in generating accurate and balanced FF models to represent the polarization effects.

Plant Dehydrins: Expression, Regulatory Networks, and Protective Roles in Plants Challenged by Abiotic Stress

Dehydrins, also known as Group II late embryogenesis abundant (LEA) proteins, are classic intrinsically disordered proteins, which have high hydrophilicity. A wide range of hostile environmental conditions including low temperature, drought, and high salinity stimulate dehydrin expression. Numerous studies have furnished evidence for the protective role played by dehydrins in plants exposed to abiotic stress. Furthermore, dehydrins play important roles in seed maturation and plant stress tolerance. Hence, dehydrins might also protect plasma membranes and proteins and stabilize DNA conformations. In the present review, we discuss the regulatory networks of dehydrin gene expression including the abscisic acid (ABA), mitogen-activated protein (MAP) kinase cascade, and Ca²⁺ signaling pathways. Crosstalk among these molecules and pathways may form a complex, diverse regulatory network, which may be implicated in regulating the same dehydrin.

Molecular Evolution of Calcium Signaling and Transport in Plant Adaptation to Abiotic Stress

Adaptation to unfavorable abiotic stresses is one of the key processes in the evolution of plants. Calcium (Ca2+) signaling is characterized by the spatiotemporal pattern of Ca2+ distribution and the activities of multi-domain proteins in integrating environmental stimuli and cellular responses, which are crucial early events in abiotic stress responses in plants. However, a comprehensive summary and explanation for evolutionary and functional synergies in Ca2+ signaling remains elusive in green plants. We review mechanisms of Ca2+ membrane transporters and intracellular Ca2+ sensors with evolutionary imprinting and structural clues. These may provide molecular and bioinformatics insights for the functional analysis of some non-model species in the evolutionarily important green plant lineages. We summarize the chronological order, spatial location, and characteristics of Ca2+ functional proteins. Furthermore, we highlight the integral functions of calcium-signaling components in various nodes of the Ca2+ signaling pathway through conserved or variant evolutionary processes. These ultimately bridge the Ca2+ cascade reactions into regulatory networks, particularly in the hormonal signaling pathways. In summary, this review provides new perspectives towards a better understanding of the evolution, interaction and integration of Ca2+ signaling components in green plants, which is likely to benefit future research in agriculture, evolutionary biology, ecology and the environment.

Aureoverticillactam, a Potent Antifungal Macrocyclic Lactam from Streptomyces aureoverticillatus HN6, Generates Calcium Dyshomeostasis-Induced Cell Apoptosis via the Phospholipase C Pathway in Fusarium oxysporum f. sp. cubense Race 4

Extensive efforts have been made to discover new biofungicides of high efficiency for control of Fusarium oxysporum f. sp. cubense race 4, a catastrophic soilborne phytopathogen causing banana Fusarium wilt worldwide. We confirmed for the first time that aureoverticillactam (YY3) has potent antifungal activity against F. oxysporum f. sp. cubense race 4, with effective dose for 50% inhibition (EC₅₀) of 20.80 μg/ml against hyphal growth and 12.62 μg/ml against spore germination. To investigate its mechanism of action, we observed the cellular ultrastructures of F. oxysporum f. sp. cubense race 4 with YY3 treatment and found that YY3 led to cell wall thinning, mitochondrial deformities, apoptotic degradation of the subcellular fractions, and entocyte leakage. Consistent with these variations, increased permeability of cell membrane and mitochondrial membrane also occurred after YY3 treatment. On the enzymatic level, the activity of mitochondrial complex III, as well as the ATP synthase, was significantly suppressed by YY3 at a concentration >12.50 μg/ml. Moreover, YY3 elevated the cytosolic Ca²⁺ level to promote mitochondrial reactive oxygen species (ROS) production. Cell apoptosis also occurred as expected. On the transcriptome level, key genes involved in the phosphatidylinositol signaling pathway were significantly affected, with the expression level of Plc1 increased approximately fourfold. The expression levels of two apoptotic genes, casA1 and casA2, were also significantly increased by YY3. Of note, phospholipase C activation was observed with YY3 treatment in F. oxysporum f. sp. cubense race 4. These findings indicate that YY3 exerts its antifungal activity by activating the phospholipase C calcium-dependent ROS signaling pathway, which makes it a promising biofungicide.

Ion Channels in Epithelial Dynamics and Morphogenesis

Mechanosensitive ion channels mediate the neuronal sensation of mechanical signals such as sound, touch, and pain. Recent studies point to a function of these channel proteins in cell types and tissues in addition to the nervous system, such as epithelia, where they have been little studied, and their role has remained elusive. Dynamic epithelia are intrinsically exposed to mechanical forces. A response to pull and push is assumed to constitute an essential part of morphogenetic movements of epithelial tissues, for example. Mechano-gated channels may participate in sensing and responding to such forces. In this review, focusing on Drosophila, we highlight recent results that will guide further investigations concerned with the mechanistic role of these ion channels in epithelial cells.

Effective Removal of Calcium and Magnesium Ions from Water by a Novel Alginate-Citrate Composite Aerogel

In this work, a novel alginate/citrate composite aerogel (CA-SC) was synthesized by chemical grafting technology combined with vacuum freeze-drying method, and CA-SC was used for removing calcium (Ca2+) and magnesium (Mg2+) ions from water. The experimental results indicate that the as-prepared CA-SC has a high affinity for Ca2+ and Mg2+ and can remove 96.5% of Ca2+ (or 96.8% of Mg2+) from the corresponding solution. The maximum adsorption capacities of CA-SC for Ca2+ and Mg2+ are 62.38 and 36.23 mg/g, respectively. These values are higher than those of the most reported Ca2+-sorbents and Mg2+-sorbents. The CA-SC adsorbent can be regenerated through a simple pickling step, and its adsorption performance keeps stable after repeated use. Analysis of the adsorption mechanism shows that the CA-SC combines Ca2+ and Mg2+ in water mainly through coordination effect.

Lysosomal TPCN (two pore segment channel) inhibition ameliorates beta-amyloid pathology and mitigates memory impairment in Alzheimer disease

ABBREVIATIONS

Aβ: β-amyloid; AD: Alzheimer disease; AIF1/IBA1: allograft inflammatory factor 1; ALP: autophagy-lysosomal pathway; APP: amyloid beta precursor protein; ATP6V1B1/V-ATPase V1b1: ATPase H+ transporting V1 subunit B1; AVs: autophagy vacuoles; BAF: bafilomycin A₁; CFC: contextual/cued fear conditioning assay; CHX: Ca²⁺/H⁺ exchanger; CTF-β: carboxy-terminal fragment derived from β-secretase; CTSD: cathepsin D; fAD: familial Alzheimer disease; GFAP: glial fibrillary acidic protein; LAMP1: lysosomal associated membrane protein 1; LTP: long-term potentiation; MCOLN1/TRPML1: mucolipin 1; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAPT: microtubule associated protein tau; MWM: Morris water maze; NFT: neurofibrillary tangles; PFC: prefrontal cortex; PSEN1: presenilin 1; SQSTM1/p62: sequestosome 1; TBS: theta burst stimulation; TEM: transmission electronic microscopy; TPCN2/TPC2: two pore segment channel 2; WT: wild-type; V-ATPase: vacuolar type H⁺-ATPase.

Calcium signaling in cancer progression and therapy

The old Greek aphorism 'Panta Rhei' ('everything flows') is true for all living things in general. As a dynamic process, calcium signaling plays fundamental roles in cellular activities under both normal and pathological conditions, with recent researches uncovering its involvement in cell proliferation, migration, survival, gene expression, and more. The major question we address here is how calcium signaling affects cancer progression and whether it could be targeted to combine with classic chemotherapeutics or emerging immunotherapies to improve their efficacy.

Suspension of Amorphous Calcium Phosphate Nanoparticles Impact Commitment of Human Adipose-Derived Stem Cells In Vitro

Amorphous calcium phosphate (aCaP) nanoparticles may trigger the osteogenic commitment of adipose-derived stem cells (ASCs) in vitro. The ASCs of three human donors are investigated using basal culture medium DMEM to either 5 or 50 µg/mL aCaP nanoparticles suspension (control: no nanoparticles). After 7 or 14 days, stem cell marker genes, as well as endothelial, osteogenic, chondrogenic, and adipogenic genes, are analyzed by qPCR. Free calcium and phosphate ion concentrations are assessed in the cell culture supernatant. After one week and 5 µg/mL aCaP, downregulation of osteogenic markers ALP and Runx2 is found, and averaged across the three donors. Our results show that after two weeks, ALP is further downregulated, but Runx2 is upregulated. Endothelial cell marker genes, such as CD31 and CD34, are upregulated with 50 µg/mL aCaP and a 2-week exposure. Inter-donor variability is high: Two out of three donors show a significant upregulation of ALP and Runx2 at day 14 with 50 µg/mL aCaP compared to 5 µg/mL aCaP. Notably, all changes in stem cell commitment are obtained in the absence of an osteogenic medium. While the chemical composition of the culture medium and the saturation status towards calcium phosphate phases remain approximately the same for all conditions, gene expression of ASCs changes considerably. Hence, aCaP nanoparticles show the potential to trigger osteogenic and endothelial commitment in ASCs.

Effect of parathyroid hormone-related protein on intracellular calcium ion and cyclic adenosine monophosphate concentrations in cardiac fibroblasts

Objective

This study aimed to determine the effect of parathyroid hormone-related protein (PTHrP) on proliferation of cardiac fibroblasts (CFs) in primary cultures of neonatal Wistar rats.

Methods

Different PTHrP concentrations were added to CFs of neonatal Wistar rats and the cells were grouped according to the concentrations added. A verapamil (VPL) group and a calcitriol (CAL) group were also established. Changes in cell proliferation and in cyclic adenosine monophosphate and calcium ion levels were identified and recorded.

Results

We found that as the concentration of PTHrP increased, 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT, a tetrazolium salt) colorimetric absorbance values (A values) decreased. These values in the PTHrP groups were significantly lower than those in the control group. MTT colorimetric A values and ³H-thymidine deoxyribose intake were lower in the VPL group, low-dose CAL group, and the PTHrP 10⁻⁷ mol/L group compared with the control group. However, MTT colorimetric A values and ³H-thymidine deoxyribose intake were higher in the high-dose CAL group than in the PTHrP 10⁻⁷ mol/L group. As PTHrP concentrations increased, intracellular cyclic adenosine monophosphate concentrations also increased.

Conclusion

PTHrp, VPL, and low-dose CAL inhibit proliferation of CFs, while high-dose CAL promotes proliferation of CFs.

A mini-review on ion fluxes that regulate NLRP3 inflammasome activation

The activation of NLR family pyrin domain containing 3 (NLRP3) inflammasome can be induced by a wide spectrum of activators. This is unlikely achieved by the binding of different activators directly to the NLRP3 protein itself, as the activators found so far show different forms of chemical structures. Previous studies have shown that these activators can induce potassium ion (K+) and chloride ion (Cl-) efflux, calcium (Ca2+) and other ion mobilization, mitochondrial dysfunction, and lysosomal disruption, all of which are believed to cause NLRP3 inflammasome activation; how these events are induced by the activators and how they coordinate with each other in inducing the NLRP3 inflammasome activation are not fully understood. Increasing evidence suggests that the coordinated change of intracellular ion concentrations may be a common mechanism for the NLRP3 activation by different activators. In this mini-review, we present a brief summary of the current knowledge about how different ionic flows (including K+, sodium ion, Ca2+, magnesium ion, manganese ion, zinc ion, iron ion, and Cl-) are involved in regulating the NLRP3 inflammasome activation in macrophages.

Cyclic Nucleotide-Gated Ion Channel 6 Mediates Thermotolerance in Arabidopsis Seedlings by Regulating Hydrogen Peroxide Production via Cytosolic Calcium Ions

We previously reported the involvement of cyclic nucleotide-gated ion channel 6 (CNGC6) and hydrogen peroxide (H₂O₂) in plant responses to heat shock (HS). To demonstrate their relationship with plant thermotolerance, we assessed the effect of HS on several groups of Arabidopsis (Arabidopsis thaliana) seedlings: wild-type, cngc6 mutant, and its complementation line. Under exposure to HS, the level of H₂O₂ was lower in the cngc6 mutant seedlings than in the wild-type (WT) seedlings but obviously increased in the complementation line. The treatment of Arabidopsis seeds with calcium ions (Ca²⁺) increased the H₂O₂ levels in the seedlings under HS treatment, whereas treatment with a Ca²⁺ chelator (EGTA) inhibited it, indicating that CNGC6 may stimulate the accumulation of H₂O₂ in a manner dependent on an increase in cytosolic Ca²⁺ ([Ca²⁺]_cyt). This point was verified by phenotypic observations and thermotolerance testing with transgenic plants overexpressing AtRbohB and AtRbohD (two genes involved in HS-responsive H₂O₂ production), respectively, in a cngc6 background. Real-time reverse transcription-polymerase chain reactions and Western blotting suggested that CNGC6 enhanced the gene transcription of HS factors (HSFs) and the accumulation of HS proteins (HSPs) via H₂O₂. These upon results indicate that H₂O₂ acts downstream of CNGC6 in the HS signaling pathway, increasing our understanding of the initiation of plants responses to high temperatures.

Exploring the 'cold/hot' properties of traditional Chinese medicine by cell temperature measurement

Context: It is common sense that chewing a mint leaf can cause a cooling feeling, while chewing ginger root will produce a burning feeling. In Traditional Chinese Medicine (TCM), this phenomenon is referred to as 'cold/hot' properties of herbs. Herein, it is reported that TCM with different "cold/hot" properties have different effects on the variation of cells.Objective: To explore the intrinsic 'cold/hot' properties of TCM from the perspective of cellular and molecular biology.Materials and methods: A375 cells were selected using Cancer Cell Line Encyclopaedia (CCLE) analysis and western blots. Hypaconitine and baicalin were selected by structural similarity analysis from 56 and 140 compounds, respectively. A wireless thermometry system was used to measure cellular temperature change induced by different compounds. Alteration of intracellular calcium influx was investigated by means of calcium imaging.Results: The IC₅₀ values of GSK1016790A, HC067047, hypaconitine, and baicalin for A375 cells are 8.363 nM, 816.4 μM, 286.4 μM and 29.84 μM, respectively. And, 8 μM hypaconitine induced obvious calcium influx while 8 μM baicalin inhibited calcium influx induced by TRPV4 activation. Cellular temperature elevated significantly when treated with GSK1016790A or hypaconitine, while the results were reversed when cells were treated with HC067047 or baicalin.Discussion and conclusions: The changes in cellular temperature are speculated to be caused by the alteration of intracellular calcium influx mediated by TRPV4. In addition, the 'cold/hot' properties of compounds in TCM can be classified by using cellular temperature detection.

Revisiting the mechanism of hypoxic pulmonary vasoconstriction using isolated perfused/ventilated mouse lung

Hypoxic Pulmonary Vasoconstriction (HPV) is an important physiological mechanism of the lungs that matches perfusion to ventilation thus maximizing O₂ saturation of the venous blood within the lungs. This study emphasizes on principal pathways in the initiation and modulation of hypoxic pulmonary vasoconstriction with a primary focus on the role of Ca²⁺ signaling and Ca²⁺ influx pathways in hypoxic pulmonary vasoconstriction. We used an ex vivo model, isolated perfused/ventilated mouse lung to evaluate hypoxic pulmonary vasoconstriction. Alveolar hypoxia (utilizing a mini ventilator) rapidly and reversibly increased pulmonary arterial pressure due to hypoxic pulmonary vasoconstriction in the isolated perfused/ventilated lung. By applying specific inhibitors for different membrane receptors and ion channels through intrapulmonary perfusion solution in isolated lung, we were able to define the targeted receptors and channels that regulate hypoxic pulmonary vasoconstriction. We show that extracellular Ca²⁺ or Ca²⁺ influx through various Ca²⁺-permeable channels in the plasma membrane is required for hypoxic pulmonary vasoconstriction. Removal of extracellular Ca²⁺ abolished hypoxic pulmonary vasoconstriction, while blockade of L-type voltage-dependent Ca²⁺ channels (with nifedipine), non-selective cation channels (with 30 µM SKF-96365), and TRPC6/TRPV1 channels (with 1 µM SAR-7334 and 30 µM capsazepine, respectively) significantly and reversibly inhibited hypoxic pulmonary vasoconstriction. Furthermore, blockers of Ca²⁺-sensing receptors (by 30 µM NPS2143, an allosteric Ca²⁺-sensing receptors inhibitor) and Notch (by 30 µM DAPT, a γ-secretase inhibitor) also attenuated hypoxic pulmonary vasoconstriction. These data indicate that Ca²⁺ influx in pulmonary arterial smooth muscle cells through voltage-dependent, receptor-operated, and store-operated Ca²⁺ entry pathways all contribute to initiation of hypoxic pulmonary vasoconstriction. The extracellular Ca²⁺-mediated activation of Ca²⁺-sensing receptors and the cell–cell interaction via Notch ligands and receptors contribute to the regulation of hypoxic pulmonary vasoconstriction.

The Influence of Calcium toward Order/Disorder Conformation of Repeat-in-Toxin (RTX) Structure of Family I.3 Lipase from Pseudomonas fluorescens AMS8

Calcium-binding plays a decisive role in the folding and stabilization of many RTX proteins, especially for the RTX domain. Although many studies have been conducted to prove the contribution of Ca²⁺ ion toward the folding and stabilization of RTX proteins, its functional dynamics and conformational structural changes remain elusive. Here, molecular docking and molecular dynamics (MD) simulations were performed to analyze the contribution of Ca²⁺ ion toward the folding and stabilization of the RTX lipase (AMS8 lipase) structure. AMS8 lipase contains six Ca²⁺ ions (Ca1–Ca6). Three Ca²⁺ ions (Ca3, Ca4, and Ca5) were bound to the RTX parallel β-roll motif repeat structure (RTX domain). The metal ion (Ca²⁺) docking analysis gives a high binding energy, especially for Ca4 and Ca5 which are tightly bound to the RTX domain. The function of each Ca²⁺ ion is further analyzed using the MD simulation. The removal of Ca3, Ca4, and Ca5 caused the AMS8 lipase structure to become unstable and unfolded. The results suggested that Ca3, Ca4, and Ca5 stabilized the RTX domain. In conclusion, Ca3, Ca4, and Ca5 play a crucial role in the folding and stabilization of the RTX domain, which sustain the integrity of the overall AMS8 lipase structure.

Mineral trioxide aggregate suppresses pro-inflammatory cytokine expression via the calcineurin/nuclear factor of activated T cells/early growth response 2 pathway in lipopolysaccharide-stimulated macrophages

AIM

To elucidate mechanisms by which mineral trioxide aggregate (MTA) suppresses pro-inflammatory cytokine mRNA expression in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages.

METHODOLOGY

Mineral trioxide aggregate extracts were prepared by immersing set ProRoot MTA in culture medium. RAW264.7 cells were cultured in the presence of LPS and MTA extracts. mRNA expression levels of interleukin (IL)-1α, IL-6, early growth response 2 (Egr2), suppressor of cytokine signalling 3 (Socs3) and IL-10 were quantified with reverse transcription-quantitative polymerase chain reaction. Phosphorylation of nuclear factor-kappa B (NF-κB) p65 in RAW264.7 cells was analysed by Western blotting. Intracellular calcium imaging was performed with Fluo-4 AM. The activity of nuclear factor of activated T cells (NFAT) was determined by luciferase assays. Enforced expression and silencing of Egr2 in RAW264.7 cells were carried out using an expression vector and specific RNAi, respectively. In vivo kinetics of Egr2⁺ cells in MTA-treated rat molar pulp tissues were examined using immunohistochemistry. Data were analysed by one-way analysis of variance, followed by the Tukey-Kramer test (P < 0.05).

RESULTS

Exposure to MTA extracts resulted in reduced mRNA expression levels of IL-1α and IL-6, as well as reduced expression of phosphorylated NF-κB, in LPS-stimulated RAW264.7 cells. Exposure to MTA extracts induced Ca²⁺ influx, which was blocked by NPS2143, an antagonist of calcium-sensing receptor (CaSR); Ca²⁺ influx then triggered activation of calcineurin/NFAT signalling and enhanced mRNA expression of Egr2. Enforced expression of Egr2 in RAW264.7 cells promoted the expression of both IL-10 and Socs3. In vivo application of MTA onto rat molar pulp tissue resulted in the appearance of Egr2-expressing cells that coexpressed CD163, a typical M2 macrophage marker.

CONCLUSIONS

Mineral trioxide aggregate extracts induced downregulation of IL-1α and IL-6 in LPS-stimulated RAW264.7 cells via CaSR-induced activation of calcineurin/NFAT/Egr2 signalling and subsequent upregulation of IL-10 and Socs3.

Ursolic acid protects against cisplatin‑induced ototoxicity by inhibiting oxidative stress and TRPV1‑mediated Ca2+‑signaling

Cisplatin (CDDP) is widely used in clinical settings for the treatment of various cancers. However, ototoxicity is a major side effect of CDDP, and there is an associated risk of irreversible hearing loss. We previously demonstrated that CDDP could induce ototoxicity via activation of the transient receptor potential vanilloid receptor 1 (TRPV1) pathway and subsequent induction of oxidative stress. The present study investigated whether ursolic acid (UA) treatment could protect against CDDP‑induced ototoxicity. UA is a triterpenoid with strong antioxidant activity widely used in China for the treatment of liver diseases. This traditional Chinese medicine is mainly isolated from bearberry, a Chinese herb. The present results showed that CDDP increased auditory brainstem response threshold shifts in frequencies associated with observed damage to the outer hair cells. Moreover, CDDP increased the expression of TRPV1, calpain 2 and caspase‑3 in the cochlea, and the levels of Ca2+ and 4‑hydroxynonenal. UA co‑treatment significantly attenuated CDDP‑induced hearing loss and inhibited TRPV1 pathway activation. In addition, UA enhanced CDDP‑induced growth inhibition in the human ovarian cancer cell line SKOV3, suggesting that UA synergizes with CDDP in vitro. Collectively, the present data suggested that UA could effectively attenuate CDDP‑induced hearing loss by inhibiting the TRPV1/Ca²+/calpain‑oxidative stress pathway without impairing the antitumor effects of CDDP.

Bright and High-Performance Genetically Encoded Ca2+ Indicator Based on mNeonGreen Fluorescent Protein

Genetically encodable calcium ion (Ca²⁺) indicators (GECIs) based on green fluorescent proteins (GFP) are powerful tools for imaging of cell signaling and neural activity in model organisms. Following almost 2 decades of steady improvements in the Aequorea victoria GFP-based GCaMP series of GECIs, the performance of the most recent generation (i.e., jGCaMP7) may have reached its practical limit due to the inherent properties of GFP. In an effort to sustain the steady progression toward ever-improved GECIs, we undertook the development of a new GECI based on the bright monomeric GFP, mNeonGreen (mNG). The resulting indicator, mNG-GECO1, is 60% brighter than GCaMP6s in vitro and provides comparable performance as demonstrated by imaging Ca²⁺ dynamics in cultured cells, primary neurons, and in vivo in larval zebrafish. These results suggest that mNG-GECO1 is a promising next-generation GECI that could inherit the mantle of GCaMP and allow the steady improvement of GECIs to continue for generations to come.