Decoding cytosolic Ca2+ oscillations

Osteogenic differentiation of mesenchymal stem cells in cell-laden culture of self-assembling peptide hydrogels

Mesenchymal stem cell (MSC) osteogenic differentiation requires scaffolds to support multiple stages of growth and differentiation signals. Fluorenyl-9-methoxycarbonyl diphenylalanine (Fmoc-FF) peptides self-assemble to create 3D nanofibers. Here, we cultured MSC in 2D and 3D Fmoc-FF layers to support their osteogenic differentiation. The stiffness of the hydrogels was tunable between 100 and 10,000 Pa which allows precise modulation of the cellular microenvironment. Scaffold stiffness impacted cell viability which softer scaffolds (100 Pa) favored higher viability. MSC formed spheroids in 3D hydrogel and showed spread morphology in 2D overlayers. Our results demonstrate that the Fmoc-FF 3D cultures significantly enhanced osteogenic differentiation, as evidenced by increased calcium deposition, elevated phosphatase activity, and the secretion of osteocalcin. We propose that the peptides provide integrin-binding sites that activate a cytoplasmic feedback loop essential for differentiation. These findings suggest that self-assembled Fmoc-FF peptide hydrogels, is a promising platform for bone tissue engineering applications.

Heterogeneity of intracellular calcium signaling of glioblastoma cells depends on intratumoral location and migration state

Background

Glioblastoma (GB), is an incurable brain tumor characterized by extreme malignancy and invasiveness, and the cellular mechanisms underlying such a severe phenotype are not completely understood. Although calcium (Ca2+) plays an important part in tumor proliferation and infiltration, it remains unclear whether Ca2+ signaling in GB cells is related to its location within the tumor and on the infiltrative potential of the cells.

Methods

In this study, we developed a stably transfected GL261 cell line that coexpresses a red fluorescent protein for actin cytoskeleton staining and the intracellular Ca2+ sensor, GCaMP6s. By means of intravital 2-photon imaging, we have characterized the morphological and functional properties of cells at different locations within the tumor.

Results

Our results showed that cells located at the tumor core are densely packed and rounded in shape, contrasting sharply with the polarized morphology observed in the peripheral cells. This anatomical heterogeneity corresponded to notable variations of the physiological phenotype: cells at the tumor core displayed low Ca2+ activity and very limited motility, while peripheral cells displayed intense Ca2+ activity and increased migration rates. Moreover, peripheral cells formed a cellular ensemble characterized by synchronized Ca2+ activity accompanied by a directionally biased collective motility.

Conclusions

These findings suggest that GB cells manifest activity patterns depending upon their spatial location within the tumor and that these correlate with their migration.

Roles for TRPV4 in disease: A discussion of possible mechanisms

The transient receptor potential vanilloid 4 (TRPV4) ion channel is a ubiquitously expressed Ca2+-permeable ion channel that controls intracellular calcium ([Ca2+]i) homeostasis in various types of cells. The physiological roles for TRPV4 are tissue specific and the mechanisms behind this specificity remain mostly unclarified. It is noteworthy that mutations in the TRPV4 channel have been associated to a broad spectrum of congenital diseases, with most of these mutations mainly resulting in gain-of-function. Mutations have been identified in human patients showing a variety of phenotypes and symptoms, mostly related to skeletal and neuromuscular disorders. Since TRPV4 is so widely expressed throughout the body, it comes as no surprise that the literature is growing in evidence linking this protein to malfunction in systems other than the skeletal and neuromuscular. In this review, we summarize the expression patterns of TRPV4 in several tissues and highlight findings of recent studies that address critical structural and functional features of this channel, particularly focusing on its interactions and signaling pathways related to Ca2+ entry. Moreover, we discuss the roles of TRPV4 mutations in some diseases and pinpoint some of the mechanisms underlying pathological states where TRPV4's malfunction is prominent.

The potential of TRP channels as new prognostic and therapeutic targets against prostate cancer progression

Prostate cancer (PCa) is the second deadliest cancer among men worldwide. Particularly critical is its development towards metastatic androgen-independent forms for which the current therapies are ineffective. Indeed, the 5-year relative survival for PCa drops dramatically to 34 % in the presence of metastases. The superfamily of Transient Receptor Potential (TRP) channels could answer the urgent request to identify new prognostic and therapeutic tools against metastatic PCa. Indeed, this class of ion channels revealed an appealing de-regulation during PCa development and its progression towards aggressive forms. Altered expression and/or functionality of several TRPs have been associated with the PCa metastatic cascade by significantly impacting tumor growth, invasiveness, and angiogenesis. In this review, we will dissect the contribution of TRP channels in such hallmarks of PCa and then discuss their applicability as new prognostic and therapeutic agents in the fight against metastatic PCa. In particular, the great potential of TRPM8, TRPV6, and TRPA1 in opening the way to new treatment perspectives will be highlighted.

Spatiotemporal orchestration of calcium-cAMP oscillations on AKAP/AC nanodomains is governed by an incoherent feedforward loop

The nanoscale organization of enzymes associated with the dynamics of second messengers is critical for ensuring compartmentation and localization of signaling molecules in cells. Specifically, the spatiotemporal orchestration of cAMP and Ca2+ oscillations is critical for many cellular functions. Previous experimental studies have shown that the formation of nanodomains of A-kinase anchoring protein 79/150 (AKAP150) and adenylyl cyclase 8 (AC8) on the surface of pancreatic MIN6 β cells modulates the phase of Ca2+-cAMP oscillations from out-of-phase to in-phase. In this work, we develop computational models of the Ca2+/cAMP pathway and AKAP/AC nanodomain formation that give rise to the two important predictions: instead of an arbitrary phase difference, the out-of-phase Ca2+/cAMP oscillation reaches Ca2+ trough and cAMP peak simultaneously, which is defined as inversely out-of-phase; the in-phase and inversely out-of-phase oscillations associated with Ca2+-cAMP dynamics on and away from the nanodomains can be explained by an incoherent feedforward loop. Factors such as cellular surface-to-volume ratio, compartment size, and distance between nanodomains do not affect the existence of in-phase or inversely out-of-phase Ca2+/cAMP oscillation, but cellular surface-to-volume ratio and compartment size can affect the time delay for the inversely out-of-phase Ca2+/cAMP oscillation while the distance between two nanodomains does not. Finally, we predict that both the Turing pattern-generated nanodomains and experimentally measured nanodomains demonstrate the existence of in-phase and inversely out-of-phase Ca2+/cAMP oscillation when the AC8 is at a low level, consistent with the behavior of an incoherent feedforward loop. These findings unveil the key circuit motif that governs cAMP and Ca2+ oscillations and advance our understanding of how nanodomains can lead to spatial compartmentation of second messengers.

Spatiotemporal Insights into Glioma Oncostream Dynamics: Unraveling Formation, Stability, and Disassembly Pathways

Glioblastoma (GBM) remains a challenge in Neuro-oncology, with a poor prognosis showing only a 5% survival rate beyond two years. This is primarily due to its aggressiveness and intra-tumoral heterogeneity, which limits complete surgical resection and reduces the efficacy of existing treatments. The existence of oncostreams-neuropathological structures comprising aligned spindle-like cells from both tumor and non-tumor origins- is discovered earlier. Oncostreams are closely linked to glioma aggressiveness and facilitate the spread into adjacent healthy brain tissue. A unique molecular signature intrinsic to oncostreams, with overexpression of key genes (i.e., COL1A1, ACTA2) that drive the tumor's mesenchymal transition and malignancy is also identified. Pre-clinical studies on genetically engineered mouse models demonstrated that COL1A1 inhibition disrupts oncostreams, modifies TME, reduces mesenchymal gene expression, and extends survival. An in vitro model using GFP+ NPA cells to investigate how various treatments affect oncostream dynamics is developed. Analysis showed that factors such as cell density, morphology, neurotransmitter agonists, calcium chelators, and cytoskeleton-targeting drugs influence oncostream formation. This data illuminate the patterns of glioma migration and suggest anti-invasion strategies that can improve GBM patient outcomes when combined with traditional therapies. This work highlights the potential of targeting oncostreams to control glioma invasion and enhance treatment efficacy.

Ca2+ oscillation in vascular smooth muscle cells control myogenic spontaneous vasomotion and counteract post-ischemic no-reflow

Ischemic stroke produces the highest adult disability. Despite successful recanalization, no-reflow, or the futile restoration of the cerebral perfusion after ischemia, is a major cause of brain lesion expansion. However, the vascular mechanism underlying this hypoperfusion is largely unknown, and no approach is available to actively promote optimal reperfusion to treat no-reflow. Here, by combining two-photon laser scanning microscopy (2PLSM) and a mouse middle cerebral arteriolar occlusion (MCAO) model, we find myogenic vasomotion deficits correlated with post-ischemic cerebral circulation interruptions and no-reflow. Transient occlusion-induced transient loss of mitochondrial membrane potential (ΔΨm) permanently impairs mitochondria-endoplasmic reticulum (ER) contacts and abolish Ca2+ oscillation in smooth muscle cells (SMCs), the driving force of myogenic spontaneous vasomotion. Furthermore, tethering mitochondria and ER by specific overexpression of ME-Linker in SMCs restores cytosolic Ca2+ homeostasis, remotivates myogenic spontaneous vasomotion, achieves optimal reperfusion, and ameliorates neurological injury. Collectively, the maintaining of arteriolar myogenic vasomotion and mitochondria-ER contacts in SMCs, are of critical importance in preventing post-ischemic no-reflow.

The Multifaceted Functions of TRPV4 and Calcium Oscillations in Tissue Repair

The transient receptor potential vanilloid 4 (TRPV4) specifically functions as a mechanosensitive ion channel and is responsible for conveying changes in physical stimuli such as mechanical stress, osmotic pressure, and temperature. TRPV4 enables the entry of cation ions, particularly calcium ions, into the cell. Activation of TRPV4 channels initiates calcium oscillations, which trigger intracellular signaling pathways involved in a plethora of cellular processes, including tissue repair. Widely expressed throughout the body, TRPV4 can be activated by a wide array of physicochemical stimuli, thus contributing to sensory and physiological functions in multiple organs. This review focuses on how TRPV4 senses environmental cues and thereby initiates and maintains calcium oscillations, critical for responses to organ injury, tissue repair, and fibrosis. We provide a summary of TRPV4-induced calcium oscillations in distinct organ systems, along with the upstream and downstream signaling pathways involved. In addition, we delineate current animal and disease models supporting TRPV4 research and shed light on potential therapeutic targets for modulating TRPV4-induced calcium oscillation to promote tissue repair while reducing tissue fibrosis.

Store-Operated Ca2+ Entry as a Putative Target of Flecainide for the Treatment of Arrhythmogenic Cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is a genetic disorder that may lead patients to sudden cell death through the occurrence of ventricular arrhythmias. ACM is characterised by the progressive substitution of cardiomyocytes with fibrofatty scar tissue that predisposes the heart to life-threatening arrhythmic events. Cardiac mesenchymal stromal cells (C-MSCs) contribute to the ACM by differentiating into fibroblasts and adipocytes, thereby supporting aberrant remodelling of the cardiac structure. Flecainide is an Ic antiarrhythmic drug that can be administered in combination with β-adrenergic blockers to treat ACM due to its ability to target both Nav1.5 and type 2 ryanodine receptors (RyR2). However, a recent study showed that flecainide may also prevent fibro-adipogenic differentiation by inhibiting store-operated Ca2+ entry (SOCE) and thereby suppressing spontaneous Ca2+ oscillations in C-MSCs isolated from human ACM patients (ACM C-hMSCs). Herein, we briefly survey ACM pathogenesis and therapies and then recapitulate the main molecular mechanisms targeted by flecainide to mitigate arrhythmic events, including Nav1.5 and RyR2. Subsequently, we describe the role of spontaneous Ca2+ oscillations in determining MSC fate. Next, we discuss recent work showing that spontaneous Ca2+ oscillations in ACM C-hMSCs are accelerated to stimulate their fibro-adipogenic differentiation. Finally, we describe the evidence that flecainide suppresses spontaneous Ca2+ oscillations and fibro-adipogenic differentiation in ACM C-hMSCs by inhibiting constitutive SOCE.

Astrocyte store-operated calcium entry is required for centrally mediated neuropathic pain

Central sensitization is a critical step in chronic neuropathic pain formation following acute nerve injury. Central sensitization is defined by nociceptive and somatosensory circuitry changes in the spinal cord leading to dysfunction of antinociceptive gamma-aminobutyric acid (GABA)ergic cells (Li et al., 2019), amplification of ascending nociceptive signals, and hypersensitivity (Woolf, 2011). Astrocytes are key mediators of the neurocircuitry changes that underlie central sensitization and neuropathic pain, and astrocytes respond to and regulate neuronal function through complex Ca2+ signaling mechanisms. Clear definition of the astrocyte Ca2+ signaling mechanisms involved in central sensitization may lead to new therapeutic targets for treatment of chronic neuropathic pain, as well as enhance our understanding of the complex central nervous system (CNS) adaptions that occur following nerve injury. Ca2+ release from astrocyte endoplasmic reticulum (ER) Ca2+ stores via the inositol 1,4,5-trisphosphate receptor (IP3R) is required for centrally mediated neuropathic pain (Kim et al, 2016); however recent evidence suggests the involvement of additional astrocyte Ca2+ signaling mechanisms. We therefore investigated the role of astrocyte store-operated Ca2+ entry (SOCE), which mediates Ca2+ influx in response to ER Ca2+ store depletion. Using an adult Drosophila melanogaster model of central sensitization based on thermal allodynia in response to leg amputation nerve injury (Khuong et al., 2019), we show that astrocytes exhibit SOCE-dependent Ca2+ signaling events three to four days following nerve injury. Astrocyte-specific suppression of Stim and Orai, the key mediators of SOCE Ca2+ influx, completely inhibited the development of thermal allodynia seven days following injury, and also inhibited the loss of ventral nerve cord (VNC) GABAergic neurons that is required for central sensitization in flies. We lastly show that constitutive SOCE in astrocytes results in thermal allodynia even in the absence of nerve injury. Our results collectively demonstrate that astrocyte SOCE is necessary and sufficient for central sensitization and development of hypersensitivity in Drosophila, adding key new understanding to the astrocyte Ca2+ signaling mechanisms involved in chronic pain.

Calcium Homeostasis in the Development of Resistant Breast Tumors

Cancer is one of the main health problems worldwide. Only in 2020, this disease caused more than 19 million new cases and almost 10 million deaths, with breast cancer being the most diagnosed worldwide. Today, despite recent advances in breast cancer treatment, a significant percentage of patients will either not respond to therapy or will eventually experience lethal progressive disease. Recent studies highlighted the involvement of calcium in the proliferation or evasion of apoptosis in breast carcinoma cells. In this review, we provide an overview of intracellular calcium signaling and breast cancer biology. We also discuss the existing knowledge on how altered calcium homeostasis is implicated in breast cancer development, highlighting the potential utility of Ca2+ as a predictive and prognostic biomarker, as well as its potential for the development of new pharmacological treatments to treat the disease.

Too much of a good thing: The case of SOCE in cellular apoptosis

Intracellular calcium (Ca2+) is an essential second messenger in eukaryotic cells regulating numerous cellular functions such as contraction, secretion, immunity, growth, and metabolism. Ca2+ signaling is also a key signal transducer in the intrinsic apoptosis pathway. The store-operated Ca2+ entry pathway (SOCE) is ubiquitously expressed in eukaryotic cells, and is the primary Ca2+ influx pathway in non-excitable cells. SOCE is mediated by the endoplasmic reticulum Ca2+ sensing STIM proteins, and the plasma membrane Ca2+-selective Orai channels. A growing number of studies have implicated SOCE in regulating cell death primarily via the intrinsic apoptotic pathway in a variety of tissues and in response to physiological stressors such as traumatic brain injury, ischemia reperfusion injury, sepsis, and alcohol toxicity. Notably, the literature points to excessive cytosolic Ca2+ influx through SOCE in vulnerable cells as a key factor tipping the balance towards cellular apoptosis. While the literature primarily addresses the functions of STIM1 and Orai1, STIM2, Orai2 and Orai3 are also emerging as potential regulators of cell death. Here, we review the functions of STIM and Orai proteins in regulating cell death and the implications of this regulation to human pathologies.

Identification of calcium metabolism related score associated with the poor outcome in papillary thyroid carcinoma

Introduction

Papillary thyroid carcinoma is a type of thyroid cancer that exhibits significant variability in prognosis. Extensive research indicates that the impaired signaling of 1,25(OH)2D3-VDR may be a crucial factor in the development and progression of PTC.

Methods

To investigate this further, Integrated analysis mRNA expression information from The Cancer Genome Atlas and GEO, we compared gene expression in cancer and normal tissues and identified differentially expressed genes (DEGs). Through this analysis, we identified DEGs and calculated risk estimates for seven genetic markers.

Results

Subsequently, we constructed predictive models using LASSO-Cox regression to test the predictive value of these markers. Our results revealed that 64 calcium metabolism-related genes showed significant differences between tumor and normal tissues. Ten of the identified DEGs were significantly associated with overall survival, indicating their potential role in disease progression. Using the average risk score for the seven genetic markers, we divided patients into high- and low-risk groups. We found that patients in the low-risk group had significantly better overall survival than those in the high-risk group, highlighting the importance of these genetic markers in predicting prognosis. Further analysis using Cox regression demonstrated that the risk levels had independent predictive power. Additionally, we conducted functional analysis of the identified genetic markers, which showed significant differences in immune status between the two patient groups. We also investigated the effect of these calcium metabolism-related genes on thyroid cancer biological functions, immune microenvironment, and drug resistance.

Discussion

Our findings provide evidence of a novel genetic signature associated with calcium metabolism, which can predict prognosis in patients with PTC. These results may have significant implications for the development of new diagnostic and therapeutic approaches to improve outcomes for PTC patients.

Calcium-dependent modulation of BKCa channel activity induced by plasmonic gold nanoparticles in pulmonary artery smooth muscle cells and hippocampal neurons

AIM

Gold nanoparticles are widely used for biomedical applications, but the precise molecular mechanism of their interaction with cellular structures is still unclear. Assuming that intracellular calcium fluctuations associated with surface plasmon-induced calcium entry could modulate the activity of potassium channels, we studied the effect of 5 nm gold nanoparticles on calcium-dependent potassium channels and associated calcium signaling in freshly isolated rat pulmonary artery smooth muscle cells and cultured hippocampal neurons.

METHODS

Outward potassium currents were recorded using patch-clamp techniques. Changes in intracellular calcium concentration were measured using the high affinity Ca²⁺ fluorescent indicator fluo-3 and laser confocal microscope.

RESULTS

In pulmonary artery smooth muscle cells, plasmonic gold nanoparticles increased the amplitude of currents via large-conductance Ca²⁺ -activated potassium channels, which was potentiated by green laser irradiation near plasmon resonance wavelength (532 nm). Buffering of intracellular free calcium with ethylene glycol-bis-N,N,N',N'-tetraacetic acid (EGTA) abolished these effects. Furthermore, using confocal laser microscopy it was found that application of gold nanoparticles caused oscillations of intracellular calcium concentration that were decreasing in amplitude with time. In cultured hippocampal neurons gold nanoparticles inhibited the effect of EGTA slowing down the decline of the BK_Ca current while partially restoring the amplitude of the slow after hyperpolarizing currents.

CONCLUSION

We conclude that fluctuations in intracellular calcium can modulate plasmonic gold nanoparticles-induced gating of BK_Ca channels in smooth muscle cells and neurons through an indirect mechanism, probably involving the interaction of plasmon resonance with calcium-permeable ion channels, which leads to a change in intracellular calcium level.

Autonomous rhythmic activity in glioma networks drives brain tumour growth

Diffuse gliomas, particularly glioblastomas, are incurable brain tumours¹. They are characterized by networks of interconnected brain tumour cells that communicate via Ca²⁺ transients^2-6. However, the networks' architecture and communication strategy and how these influence tumour biology remain unknown. Here we describe how glioblastoma cell networks include a small, plastic population of highly active glioblastoma cells that display rhythmic Ca²⁺ oscillations and are particularly connected to others. Their autonomous periodic Ca²⁺ transients preceded Ca²⁺ transients of other network-connected cells, activating the frequency-dependent MAPK and NF-κB pathways. Mathematical network analysis revealed that glioblastoma network topology follows scale-free and small-world properties, with periodic tumour cells frequently located in network hubs. This network design enabled resistance against random damage but was vulnerable to losing its key hubs. Targeting of autonomous rhythmic activity by selective physical ablation of periodic tumour cells or by genetic or pharmacological interference with the potassium channel KCa3.1 (also known as IK1, SK4 or KCNN4) strongly compromised global network communication. This led to a marked reduction of tumour cell viability within the entire network, reduced tumour growth in mice and extended animal survival. The dependency of glioblastoma networks on periodic Ca²⁺ activity generates a vulnerability⁷ that can be exploited for the development of novel therapies, such as with KCa3.1-inhibiting drugs.

TRPC3 governs the spatiotemporal organization of cellular Ca2+ signatures by functional coupling to IP3 receptors

Communication between TRPC channels and IP3 receptors (IP3R) is considered pivotal in the generation of spatiotemporal Ca2+signaling patterns. Here we revisited the role of TRPC3-IP3R coupling for local Ca2+ signaling within TRPC3-harbouring micro/nanodomains using R-GECO as a reporter, fused to the channel´s C-terminus. Cytoplasmic Ca2+ changes at TRPC3 originated from both the entry of Ca2+ through the TRPC channel and Ca2+ mobilization via IP3R. Local Ca2+ changes at TRPC3 channels expressed in HEK293 cells were predominantly biphasic with IP3R-dependent initial Ca2+ transients, while exclusively monophasic signals were recorded when all three IP3R isoforms were lacking. Abrogation of Ca2+ entry through TRPC3 by point mutations, which impair Ca2+ permeability (E630Q), cation permeation (E630K), or DAG sensitivity (G652A), promoted microdomain Ca2+ oscillations. Ca2+ signals at E630Q, E630K, and G652A channels featured initial Ca2+ transients along with oscillatory activity. Similarly, when extracellular Ca2+ was omitted, IP3R-mediated Ca2+ transients and Ca2+ oscillations were promoted at the cytoplasmic face of wild-type TRPC3 channels. By contrast, oscillations, as well as initial Ca2+ transients, were virtually lacking, when the TRPC3 channels were sensitized by preexposure to low-level PLC activity. TIRF imaging provided evidence for dynamic colocalization of TRPC3 and IP3R. We suggest that TRPC3-mediated Ca2+ entry controls IP3R activity at ER-PM junctions to determine Ca2+ signaling signatures and enable specificity of downstream signaling.

Vacuolal and Peroxisomal Calcium Ion Transporters in Yeasts and Fungi: Key Role in the Translocation of Intermediates in the Biosynthesis of Fungal Metabolites

Highlights

The intracellular calcium content plays a key role in the expression of genes involved in the biosynthesis and secretion of fungal metabolites.

The cytosolic calcium concentration in fungi is maintained by influx through the cell membrane and by release from store organelles.

Some MSF transporters, e.g., PenV of Penicillium chrysogenum and CefP of Acremonium chrysogenum belong to the TRP calcium ion channels.

A few of the numerous calcium ion transporters existing in organelles of different filamentous fungi have been characterized at the functional and subcellular localization levels.

The cytosolic calcium signal seems to be transduced by the calcitonin/calcineurin cascade controlling the expression of many fungal genes.

Abstract

The intracellular calcium content in fungal cells is influenced by a large number of environmental and nutritional factors. Sharp changes in the cytosolic calcium level act as signals that are decoded by the cell gene expression machinery, resulting in several physiological responses, including differentiation and secondary metabolites biosynthesis. Expression of the three penicillin biosynthetic genes is regulated by calcium ions, but there is still little information on the role of this ion in the translocation of penicillin intermediates between different subcellular compartments. Using advanced information on the transport of calcium in organelles in yeast as a model, this article reviews the recent progress on the transport of calcium in vacuoles and peroxisomes and its relation to the translocation of biosynthetic intermediates in filamentous fungi. The Penicillium chrysogenum PenV vacuole transporter and the Acremonium chrysogenum CefP peroxisomal transporter belong to the transient receptor potential (TRP) class CSC of calcium ion channels. The PenV transporter plays an important role in providing precursors for the biosynthesis of the tripeptide δ-(-α-aminoadipyl-L-cysteinyl-D-valine), the first intermediate of penicillin biosynthesis in P. chrysogenum. Similarly, CefP exerts a key function in the conversion of isopenicillin N to penicillin N in peroxisomes of A. chrysogenum. These TRP transporters are different from other TRP ion channels of Giberella zeae that belong to the Yvc1 class of yeast TRPs. Recent advances in filamentous fungi indicate that the cytosolic calcium concentration signal is connected to the calcitonin/calcineurin signal transduction cascade that controls the expression of genes involved in the subcellular translocation of intermediates during fungal metabolite biosynthesis. These advances open new possibilities to enhance the expression of important biosynthetic genes in fungi.

Calcium responses to external mechanical stimuli in the multicellular stage of Dictyostelium discoideum

Calcium acts as a second messenger to regulate many cellular functions, including cell motility. In Dictyostelium discoideum, the cytosolic calcium level oscillates synchronously, and calcium waves propagate through the cell population during the early stages of development, including aggregation. In the unicellular phase, the calcium response through Piezo channels also functions in mechanosensing. However, calcium dynamics during multicellular morphogenesis are still unclear. Here, live imaging of cytosolic calcium revealed that calcium wave propagation, depending on cAMP relay, disappeared at the onset of multicellular body (slug) formation. Later, other forms of occasional calcium bursts and their propagation were observed in both anterior and posterior regions of migrating slugs. This calcium signaling also occurred in response to mechanical stimuli. Two pathways—calcium release from the endoplasmic reticulum via IP3 receptor and calcium influx from outside the cell—were involved in calcium signals induced by mechanical stimuli. These data suggest that calcium signaling is involved in mechanosensing in both the unicellular and multicellular phases of Dictyostelium development using different molecular mechanisms.

A Post-GWAS Functional Analysis Confirming Effects of Three BTA13 Genes CACNB2, SLC39A12, and ZEB1 on Dairy Cattle Reproduction

In our previous GWAS of Chinese and Nordic dairy cattle, genes CACNB2, SLC39A12, and ZEB1 locating on BTA 13 were suggested as candidate genes for reproduction. In this study, validation of these associations was performed in an independent population with records of nine reproductive traits. More importantly, functions of these genes in the reproductive process were verified by employing the expression data of ovarian follicles. The potential variants within the three genes were firstly detected in 68 Chinese Holstein bulls, and then screened in 1,588 Chinese Holstein cows using the KASP (Kompetitive allele-specific PCR) method. There were nine variants with polymorphisms in CACNB2, five in SLC39A12, and four in ZEB1, respectively, of which one SNP was in the upstream regulatory region, two in exon region, four in downstream regulatory region, and 11 SNPs in intronic regions. Amongst the 18 variants, g.33267056T/G in CACNB2 explained the largest phenotypic variance for age at first calving (0.011%), interval from first to last insemination (0.004%), and calving ease (0.002%), while g.32751518G/A in SLC39A12 contributed the most to stillbirth in heifers (0.038%). Two haplotype blocks were constructed for CACNB2 while one each for SLC39A12 and ZEB1, which were significantly associated with five reproductive traits, including age at the first service, age at the first calving, calving ease in heifers and cows, and the interval from calving to the first insemination. We then studied the profile of gene expression in granulosa cells isolated from four developmental stages of ovarian follicles from eight dairy cows. All three genes were differentially expressed between ovarian follicles with different sizes (p < 0.05), indicating their potential roles in the reproductive process of dairy cows. This study successfully demonstrated the associations of three BTA 13 genes CACNB2, SLC39A12, and ZEB1 with reproduction and further examined their expression levels in ovarian follicles directly. These findings can be beneficial for the ongoing genomic selection program for reproductive traits which have long been considered as traits that are difficult to achieve genetic improvement due to the lack of efficient genetic markers.

X-ray irradiation triggers immune response in human T-lymphocytes via store-operated Ca2+ entry and NFAT activation

Radiation therapy efficiently eliminates cancer cells and reduces tumor growth. To understand collateral agonistic and antagonistic effects of this treatment on the immune system, we examined the impact of x-ray irradiation on human T cells. We find that, in a major population of leukemic Jurkat T cells and peripheral blood mononuclear cells, clinically relevant radiation doses trigger delayed oscillations of the cytosolic Ca²⁺ concentration. They are generated by store-operated Ca²⁺ entry (SOCE) following x-ray–induced clustering of Orai1 and STIM1 and formation of a Ca²⁺ release–activated Ca²⁺ (CRAC) channel. A consequence of the x-ray–triggered Ca²⁺ signaling cascade is translocation of the transcription factor nuclear factor of activated T cells (NFAT) from the cytosol into the nucleus, where it elicits the expression of genes required for immune activation. The data imply activation of blood immune cells by ionizing irradiation, with consequences for toxicity and therapeutic effects of radiation therapy.

Ca2+ entry through reverse Na+/Ca2+ exchanger in NCI-H716, glucagon-like peptide-1 secreting cells

Glucagon like peptide-1 (GLP-1) released from enteroendocine L-cells in the intestine has incretin effects due to its ability to amplify glucose-dependent insulin secretion. Promotion of an endogenous release of GLP-1 is one of therapeutic targets for type 2 diabetes mellitus. Although the secretion of GLP-1 in response to nutrient or neural stimuli can be triggered by cytosolic Ca²⁺ elevation, the stimulus-secretion pathway is not completely understood yet. Therefore, the aim of this study was to investigate the role of reverse Na⁺/Ca²⁺ exchanger (rNCX) in Ca²⁺ entry induced by muscarinic stimulation in NCI-H716 cells, a human enteroendocrine GLP-1 secreting cell line. Intracellular Ca²⁺ was repetitively oscillated by the perfusion of carbamylcholine (CCh), a muscarinic agonist. The oscillation of cytosolic Ca²⁺ was ceased by substituting extracellular Na⁺ with Li⁺ or NMG⁺. KB-R7943, a specific rNCX blocker, completely diminished CCh-induced cytosolic Ca²⁺ oscillation. Type 1 Na⁺/Ca²⁺ exchanger (NCX₁) proteins were expressed in NCI-H716 cells. These results suggest that rNCX might play a crucial role in Ca²⁺ entry induced by cholinergic stimulation in NCI-H716 cells, a GLP-1 secreting cell line.

Mathematical Analysis of Membrane Transporters Dynamics: A Calcium Fluxes Case Study

A tight control of intracellular [Ca[Formula: see text]] is essential for the survival and normal function of cells. In this study we investigate key mechanistic steps by which calcium is regulated and calcium oscillations could occur using in silico modeling of membrane transporters. To do so we give a deterministic description of intracellular Ca[Formula: see text] dynamics using nonlinear dynamics in order to understand Ca[Formula: see text] signaling. We first present the ordinary differential equations (ODEs) system for cell calcium kinetics and make a preliminary work on Sobol indices. We then describe and analyze complex transporters action. Besides, we analyze the whole system. We finally perform numerical simulations and compare our results to real data.

Spontaneous Calcium Oscillations through Differentiation: A Calcium Imaging Analysis of Rat Cochlear Nucleus Neural Stem Cells

Causal therapies for the auditory-pathway and inner-ear diseases are still not yet available for clinical application. Regenerative medicine approaches are discussed and examined as possible therapy options. Neural stem cells could play a role in the regeneration of the auditory pathway. In recent years, neural stem and progenitor cells have been identified in the cochlear nucleus, the second nucleus of the auditory pathway. The current investigation aimed to analyze cell maturation concerning cellular calcium activity. Cochlear nuclei from PND9 CD rats were microscopically dissected and propagated as neurospheres in free-floating cultures in stem-cell medium (Neurobasal, B27, GlutaMAX, EGF, bFGF). After 30 days, the dissociation and plating of these cells took place under withdrawal of the growth factors and the addition of retinoic acid, which induces neural cell differentiation. Calcium imaging analysis with BAPTA-1/Oregon Green was carried out at different times during the differentiation phase. In addition, the influence of different voltage-dependent calcium channels was analyzed through the targeted application of inhibitors of the L-, N-, R- and T-type calcium channels. For this purpose, comparative examinations were performed on CN NSCs, and primary CN neurons. As the cells differentiated, a significant increase in spontaneous neuronal calcium activity was demonstrated. In the differentiation stage, specific frequencies of the spontaneous calcium oscillations were measured in different regions of the individual cells. Initially, the highest frequency of spontaneous calcium oscillations was ascertainable in the maturing somata. Over time, these were overtaken by calcium oscillations in the axons and dendrites. Additionally, in the area of the growth cones, an increasing activity was determined. By inhibiting voltage-dependent calcium channels, their expression and function in the differentiation process were confirmed. A comparable pattern of maturation of these channels was found in CN NSCs and primary CN neurons. The present results show that neural stem cells of the rat cochlear nucleus differentiated not only morphologically but also functionally. Spontaneous calcium activities are of great relevance in terms of neurogenesis and integration into existing neuronal structures. These functional aspects of neurogenesis within the auditory pathway could serve as future targets for the exogenous control of neuronal regeneration.

Competing Roles of Ca2+ and Nonmuscle Myosin IIA on the Dynamics of the Metastasis-Associated Protein S100A4

The calcium-binding protein S100A4 plays an important role in a wide range of biological processes such as cell motility, invasion, angiogenesis, survival, differentiation, contractility, and tumor metastasis and interacts with a range of partners. To understand the functional roles and interplay of S100A4 binding partners such as Ca²⁺ and nonmuscle myosin IIA (NMIIA), we used molecular dynamics simulations to investigate apo S100A4 and four holo S100A4 structures: S100A4 bound to Ca²⁺, S100A4 bound to NMIIA, S100A4 bound to Ca²⁺ and NMIIA, and a mutated S100A4 bound to Ca²⁺ and NMIIA. Our results show that two competing factors, namely, Ca²⁺-induced activation and NMIIA-induced inhibition, modulate the dynamics of S100A4 in a competitive manner. Moreover, Ca²⁺ binding results in enhanced dynamics, regulating the interactions of S100A4 with NMIIA, while NMIIA induces asymmetric dynamics between the chains of S100A4. The results also show that in the absence of Ca²⁺ the S100A4-NMIIA interaction is weak compared to that of between S100A4 bound to Ca²⁺ and NMIIA, which may offer a quick response to dropping calcium levels. In addition, certain mutations are shown to play a marked role on the dynamics of S100A4. The results described here contribute to understanding the interactions of S100A4 with NMIIA and the functional roles of Ca²⁺, NMIIA, and certain mutations on the dynamics of S100A4. The results of this study could be interesting for the development of inhibitors that exploit the shift of balance between the competing roles of Ca²⁺ and NMIIA.

Ionomycin-induced mouse oocyte activation can disrupt preimplantation embryo development through increased reactive oxygen species reaction and DNA damage

Oocyte activation induced by calcium oscillations is an important process in normal fertilization and subsequent embryogenesis. In the clinical-assisted reproduction, artificial oocyte activation (AOA) is an effective method to improve the clinical outcome of patients with null or low fertilization rate after ICSI. However, little is known about the effect of AOA on preimplantation embryo development in cases with normal fertilization by ICSI. Here, we used ionomycin at different concentrations to activate oocytes after ICSI with normal sperm and evaluated energy metabolism and preimplantation embryo development. We found that a high concentration of ionomycin increased the frequency and amplitude of calcium oscillation patterns, affecting the balance of mitochondrial energy metabolism, leading to increased reactive oxygen species (ROS) and decreased ATP. Eventually, it increases DNA damage and decreases blastocyst formation. In addition, the addition of vitamin C to the culture medium ameliorated the increase in ROS and DNA damage and rescued the abnormal embryo development caused by excessive ionomycin activation. This study provides a perspective that the improper application of AOA may have adverse effects on preimplantation embryo development. Thus, clinical AOA treatment should be cautiously administered.

The human amniotic fluid stem cell secretome triggers intracellular Ca2+ oscillations, NF-κB nuclear translocation and tube formation in human endothelial colony-forming cells

Second trimester foetal human amniotic fluid‐derived stem cells (hAFS) have been shown to possess remarkable cardioprotective paracrine potential in different preclinical models of myocardial injury and drug‐induced cardiotoxicity. The hAFS secretome, namely the total soluble factors released by cells in their conditioned medium (hAFS‐CM), can also strongly sustain in vivo angiogenesis in a murine model of acute myocardial infarction (MI) and stimulates human endothelial colony‐forming cells (ECFCs), the only truly recognized endothelial progenitor, to form capillary‐like structures in vitro. Preliminary work demonstrated that the hypoxic hAFS secretome (hAFS‐CM^Hypo) triggers intracellular Ca²⁺ oscillations in human ECFCs, but the underlying mechanisms and the downstream Ca²⁺‐dependent effectors remain elusive. Herein, we found that the secretome obtained by hAFS undergoing hypoxic preconditioning induced intracellular Ca²⁺ oscillations by promoting extracellular Ca²⁺ entry through Transient Receptor Potential Vanilloid 4 (TRPV4). TRPV4‐mediated Ca²⁺ entry, in turn, promoted the concerted interplay between inositol‐1,4,5‐trisphosphate‐ and nicotinic acid adenine dinucleotide phosphate‐induced endogenous Ca²⁺ release and store‐operated Ca²⁺ entry (SOCE). hAFS‐CM^Hypo‐induced intracellular Ca²⁺ oscillations resulted in the nuclear translocation of the Ca²⁺‐sensitive transcription factor p65 NF‐κB. Finally, inhibition of either intracellular Ca²⁺ oscillations or NF‐κB activity prevented hAFS‐CM^Hypo‐induced ECFC tube formation. These data shed novel light on the molecular mechanisms whereby hAFS‐CM^Hypo induces angiogenesis, thus providing useful insights for future therapeutic strategies against ischaemic‐related myocardial injury.

TRPV Protein Family-From Mechanosensing to Cancer Invasion

Biophysical cues from the cellular microenvironment are detected by mechanosensitive machineries that translate physical signals into biochemical signaling cascades. At the crossroads of extracellular space and cell interior are located several ion channel families, including TRP family proteins, that are triggered by mechanical stimuli and drive intracellular signaling pathways through spatio-temporally controlled Ca2+-influx. Mechanosensitive Ca2+-channels, therefore, act as critical components in the rapid transmission of physical signals into biologically compatible information to impact crucial processes during development, morphogenesis and regeneration. Given the mechanosensitive nature of many of the TRP family channels, they must also respond to the biophysical changes along the development of several pathophysiological conditions and have also been linked to cancer progression. In this review, we will focus on the TRPV, vanilloid family of TRP proteins, and their connection to cancer progression through their mechanosensitive nature.

TRP Channels Interactome as a Novel Therapeutic Target in Breast Cancer

Breast cancer is one of the most frequent cancer types worldwide and the first cause of cancer-related deaths in women. Although significant therapeutic advances have been achieved with drugs such as tamoxifen and trastuzumab, breast cancer still caused 627,000 deaths in 2018. Since cancer is a multifactorial disease, it has become necessary to develop new molecular therapies that can target several relevant cellular processes at once. Ion channels are versatile regulators of several physiological- and pathophysiological-related mechanisms, including cancer-relevant processes such as tumor progression, apoptosis inhibition, proliferation, migration, invasion, and chemoresistance. Ion channels are the main regulators of cellular functions, conducting ions selectively through a pore-forming structure located in the plasma membrane, protein–protein interactions one of their main regulatory mechanisms. Among the different ion channel families, the Transient Receptor Potential (TRP) family stands out in the context of breast cancer since several members have been proposed as prognostic markers in this pathology. However, only a few approaches exist to block their specific activity during tumoral progress. In this article, we describe several TRP channels that have been involved in breast cancer progress with a particular focus on their binding partners that have also been described as drivers of breast cancer progression. Here, we propose disrupting these interactions as attractive and potential new therapeutic targets for treating this neoplastic disease.

The heterogeneity of cancer endothelium: The relevance of angiogenesis and endothelial progenitor cells in cancer microenvironment

Tumor-associated vessels constitution is the result of angiogenesis, the hallmark of cancer essential for tumor to develop in dimension and to spread throughout the organism. Tumor endothelium is configured as an active functioning organ capable of determine interaction with the immune response and all the other components of the variegate cancer microenvironment, determining reciprocal influence. Angiogenesis is here analyzed in its molecular and cellular mechanisms, multiple mediators and principal players, represented by Endothelial Cells. It is discussed the striking heterogeneity of cancer endothelium, due to morphological and molecular aberrations that it often presents and its multiple origin. Among the cells that participate to the composition of tumor vasculature, Endothelial Progenitor Cells represent an important source for physical sustain and paracrine signaling in the process of angiogenesis. Treatment options are reviewed, with particular focus on novel therapeutic strategies for overcoming tumor resistance to anti-angiogenic agents.

Calcium signaling: breast cancer's approach to manipulation of cellular circuitry

Calcium is a versatile element that participates in cell signaling for a wide range of cell processes such as death, cell cycle, division, migration, invasion, metabolism, differentiation, autophagy, transcription, and others. Specificity of calcium in each of these processes is achieved through modulation of intracellular calcium concentrations by changing the characteristics (amplitude/frequency modulation) or location (spatial modulation) of the signal. Breast cancer utilizes calcium signaling as an advantage for survival and progression. This review integrates evidence showing that increases in expression of calcium channels, GPCRs, pumps, effectors, and enzymes, as well as resulting intracellular calcium signals, lead to high calcium and/or an elevated calcium- mobilizing capacity necessary for malignant functions such as migratory, invasive, proliferative, tumorigenic, or metastatic capacities.

Ca2+ -regulated cell migration revealed by optogenetically engineered Ca2+ oscillations

The ability of a single Ca²⁺ ion to play an important role in cell biology is highlighted by the need for cells to form Ca²⁺ signals in the dimensions of space, time, and amplitude. Thus, spatial and temporal changes in intracellular Ca²⁺ concentration are important for determining cell fate. Optogenetic technology has been developed to provide more precise and targeted stimulation of cells. Here, U2OS cells overexpressing Ca²⁺ translocating channelrhodopsin (CatCh) were used to mediate Ca²⁺ influx through blue light illumination with various parameters, such as intensity, frequency, duty cycle, and duration. We identified that several Ca²⁺‐dependent transcription factors and certain kinases can be activated by specific Ca²⁺ waves. Using a wound‐healing assay, we found that low‐frequency Ca²⁺ oscillations increased cell migration through the activation of NF‐κB. This study explores the regulation of cell migration by Ca²⁺ signals. Thus, we can choose optical parameters to modulate Ca²⁺ waves and achieve activation of specific signaling pathways. This novel methodology can be applied to clarify related cell‐signaling mechanisms in the future.

Messages across time and space

Compartmentalized oscillations of second messengers affect global cellular signaling.

Spatially compartmentalized phase regulation of a Ca2+-cAMP-PKA oscillatory circuit

Signaling networks are spatiotemporally organized to sense diverse inputs, process information, and carry out specific cellular tasks. In β cells, Ca2+, cyclic adenosine monophosphate (cAMP), and Protein Kinase A (PKA) exist in an oscillatory circuit characterized by a high degree of feedback. Here, we describe a mode of regulation within this circuit involving a spatial dependence of the relative phase between cAMP, PKA, and Ca2+. We show that in mouse MIN6 β cells, nanodomain clustering of Ca2+-sensitive adenylyl cyclases (ACs) drives oscillations of local cAMP levels to be precisely in-phase with Ca2+ oscillations, whereas Ca2+-sensitive phosphodiesterases maintain out-of-phase oscillations outside of the nanodomain. Disruption of this precise phase relationship perturbs Ca2+ oscillations, suggesting the relative phase within an oscillatory circuit can encode specific functional information. This work unveils a novel mechanism of cAMP compartmentation utilized for localized tuning of an oscillatory circuit and has broad implications for the spatiotemporal regulation of signaling networks.

Emerging role of transient receptor potential (TRP) channels in cancer progression

Transient receptor potential (TRP) channels comprise a diverse family of ion channels, the majority of which are calcium permeable and show sophisticated regulatory patterns in response to various environmental cues. Early studies led to the recognition of TRP channels as environmental and chemical sensors. Later studies revealed that TRP channels mediated the regulation of intracellular calcium. Mutations in TRP channel genes result in abnormal regulation of TRP channel function or expression, and interfere with normal spatial and temporal patterns of intracellular local Ca2+ distribution. The resulting dysregulation of multiple downstream effectors, depending on Ca2+ homeostasis, is associated with hallmarks of cancer pathophysiology, including enhanced proliferation, survival and invasion of cancer cells. These findings indicate that TRP channels affect multiple events that control cellular fate and play a key role in cancer progression. This review discusses the accumulating evidence supporting the role of TRP channels in tumorigenesis, with emphasis on prostate cancer. [BMB Reports 2020; 53(3): 125-132].

The Oscillation Amplitude, Not the Frequency of Cytosolic Calcium, Regulates Apoptosis Induction

Although a rising concentration of cytosolic Ca²⁺ has long been recognized as an essential signal for apoptosis, the dynamical mechanisms by which Ca²⁺ regulates apoptosis are not clear yet. To address this, we constructed a computational model that integrates known biochemical reactions and can reproduce the dynamical behaviors of Ca²⁺-induced apoptosis as observed in experiments. Model analysis shows that oscillating Ca²⁺ signals first convert into gradual signals and eventually transform into a switch-like apoptotic response. Via the two processes, the apoptotic signaling pathway filters the frequency of Ca²⁺ oscillations effectively but instead responds acutely to their amplitude. Collectively, our results suggest that Ca²⁺ regulates apoptosis mainly via oscillation amplitude, rather than frequency, modulation. This study not only provides a comprehensive understanding of how oscillatory Ca²⁺ dynamically regulates the complex apoptotic signaling network but also presents a typical example of how Ca²⁺ controls cellular responses through amplitude modulation.

Integrating Bioelectrical Currents and Ca2+ Signaling with Biochemical Signaling in Development and Pathogenesis

Roles of bioelectrical signals are increasingly recognized in excitable and nonexcitable non-neural tissues. Diverse ion-selective channels, pumps, and gap junctions participate in bioelectrical signaling, including those transporting calcium ions (Ca2+). Ca2+ is the most versatile transported ion, because it serves as an electrical charge carrier and a biochemical regulator for multiple molecular binding, enzyme, and transcription activities. We aspire to learn how bioelectrical signals crosstalk to biochemical/biomechanical signals. In this study, we review four recent studies showing how bioelectrical currents and Ca2+ signaling affect collective dermal cell migration during feather bud elongation, affect chondrogenic differentiation in limb development, couple with mechanical tension in aligning gut smooth muscle, and affect mitochondrial function and skeletal muscle atrophy. We observe bioelectrical signals involved in several developmental and pathological conditions in chickens and mice at multiple spatial scales: cellular, cellular collective, and subcellular. These examples inspire novel concept and approaches for future basic and translational studies.

Intercellular communication controls agonist-induced calcium oscillations independently of gap junctions in smooth muscle cells

In this study, we report the existence of a communication system among human smooth muscle cells that uses mechanical forces to frequency modulate long-range calcium waves. An important consequence of this mechanical signaling is that changes in stiffness of the underlying extracellular matrix can interfere with the frequency modulation of Ca²⁺ waves, causing smooth muscle cells from healthy human donors to falsely perceive a much higher agonist dose than they actually received. This aberrant sensing of contractile agonist dose on stiffer matrices is completely absent in isolated smooth muscle cells, although the isolated cells can sense matrix rigidity. We show that the intercellular communication that enables this collective Ca²⁺ response in smooth muscle cells does not involve transport across gap junctions or extracellular diffusion of signaling molecules. Instead, our data support a collective model in which mechanical signaling among smooth muscle cells regulates their response to contractile agonists.

Signaling through Ca2+ Microdomains from Store-Operated CRAC Channels

Calcium (Ca²⁺) ion microdomains are subcellular regions of high Ca²⁺ concentration that develop rapidly near open Ca²⁺ channels in the plasma membrane or internal stores and generate local regions of high Ca²⁺ concentration. These microdomains are remarkably versatile in that they activate a range of responses that differ enormously in both their temporal and spatial profile. In this review, we describe how Ca²⁺ microdomains generated by store-operated calcium channels, a widespread and conserved Ca²⁺ entry pathway, stimulate different signaling pathways, and how the spatial extent of a Ca²⁺ microdomain can be influenced by Ca²⁺ ATPase pumps.

Basic concepts and physical-chemical phenomena, that have conceptual meaning for the formation of systemic clinical thinking and formalization of the knowledge of systemic structural-functional organization of the human’s organism

From the point of view of perception and generalization processes there are complex, logic and conceptual forms of thinking. Its conceptual form is the highest result of interaction between thinking and speech. While realizing it, human uses the concept, which are logically formed thoughts, that are the meaning of representation in thinking of unity of meaningful features, relations of subjects or phenomena of objective reality. Special concepts, that are used in the science and technique are called terms. They perform a function of corresponding, special, precise marking of subjects and phenomena, their features and interactions. Scientific knowledge are in that way an objective representation of material duality in our consciousness. Certain complex of terms forms a terminological system, that lies in the basis of corresponding sphere of scientific knowledge and conditions a corresponding form and way of thinking. Clinical thinking is a conceptual form, that manifests and represents by the specialized internal speech with gnostic motivation lying in its basis. Its structural elements are corresponding definitions, terms and concepts. Cardinal features of clinical systems are consistency, criticality, justification and substantiation. Principles of perception and main concepts are represented in the article along with short descriptions of physical and chemical phenomena, that have conceptual meaning for the formation of systematic clinical thinking and formalization of systemic structural-functional organization of the human’s organism

A multi-omics analysis reveals the unfolded protein response regulon and stress-induced resistance to folate-based antimetabolites

Stress response pathways are critical for cellular homeostasis, promoting survival through adaptive changes in gene expression and metabolism. They play key roles in numerous diseases and are implicated in cancer progression and chemoresistance. However, the underlying mechanisms are only poorly understood. We have employed a multi-omics approach to monitor changes to gene expression after induction of a stress response pathway, the unfolded protein response (UPR), probing in parallel the transcriptome, the proteome, and changes to translation. Stringent filtering reveals the induction of 267 genes, many of which have not previously been implicated in stress response pathways. We experimentally demonstrate that UPR‐mediated translational control induces the expression of enzymes involved in a pathway that diverts intermediate metabolites from glycolysis to fuel mitochondrial one‐carbon metabolism. Concomitantly, the cells become resistant to the folate-based antimetabolites Methotrexate and Pemetrexed, establishing a direct link between UPR‐driven changes to gene expression and resistance to pharmacological treatment.

The unfolded protein response (UPR) is a stress response pathway implicated in numerous diseases and chemotherapy resistance. Here, the authors define the UPR regulon with a multi-omics strategy, uncovering changes to mitochondrial one-carbon metabolism and concomitant resistance to folate-based therapeutics.

The native ORAI channel trio underlies the diversity of Ca2+ signaling events

The essential role of ORAI1 channels in receptor-evoked Ca2+ signaling is well understood, yet little is known about the physiological activation of the ORAI channel trio natively expressed in all cells. The roles of ORAI2 and ORAI3 have remained obscure. We show that ORAI2 and ORAI3 channels play a critical role in mediating the regenerative Ca2+ oscillations induced by physiological receptor activation, yet ORAI1 is dispensable in generation of oscillations. We reveal that ORAI2 and ORAI3 channels multimerize with ORAI1 to expand the range of sensitivity of receptor-activated Ca2+ signals, reflecting their enhanced basal STIM1-binding and heightened Ca2+-dependent inactivation. This broadened bandwidth of Ca2+ influx is translated by cells into differential activation of NFAT1 and NFAT4 isoforms. Our results uncover a long-sought role for ORAI2 and ORAI3, revealing an intricate control mechanism whereby heteromerization of ORAI channels mediates graded Ca2+ signals that extend the agonist-sensitivity to fine-tune transcriptional control.

IP3 mediated global Ca2+ signals arise through two temporally and spatially distinct modes of Ca2+ release

The 'building-block' model of inositol trisphosphate (IP3)-mediated Ca2+ liberation posits that cell-wide cytosolic Ca2+ signals arise through coordinated activation of localized Ca2+ puffs generated by stationary clusters of IP3 receptors (IP3Rs). Here, we revise this hypothesis, applying fluctuation analysis to resolve Ca2+ signals otherwise obscured during large Ca2+ elevations. We find the rising phase of global Ca2+ signals is punctuated by a flurry of puffs, which terminate before the peak by a mechanism involving partial ER Ca2+ depletion. The continuing rise in Ca2+, and persistence of global signals even when puffs are absent, reveal a second mode of spatiotemporally diffuse Ca2+ signaling. Puffs make only small, transient contributions to global Ca2+ signals, which are sustained by diffuse release of Ca2+ through a functionally distinct process. These two modes of IP3-mediated Ca2+ liberation have important implications for downstream signaling, imparting spatial and kinetic specificity to Ca2+-dependent effector functions and Ca2+ transport.

Calcium signaling in interdental cells during the critical developmental period of the mouse cochlea

The tectorial membrane (TM), a complex acellular structure that covers part of the organ of Corti and excites outer hair cells, is required for normal hearing. It consists of collagen fibrils and various glycoproteins, which are synthesized in embryonic and postnatal development by different cochlear cell types including the interdental cells (IDCs). At its modiolar side, the TM is fixed to the apical surfaces of IDCs, which form the covering epithelium of the spiral limbus. We performed confocal membrane imaging and Ca²⁺ imaging in IDCs of the developing mouse cochlea from birth to postnatal day 18 (P18). Using the fluorescent membrane markers FM 4-64 and CellMask™ Deep Red on explanted whole-mount cochlear epithelium, we identified the morphology of IDCs at different z-levels of the spiral limbus. Ca²⁺ imaging of Fluo-8 AM-loaded cochlear epithelia revealed spontaneous intracellular Ca²⁺ transients in IDCs at P0/1, P4/5, and P18. Their relative frequency was lowest on P0/1, increased by a factor of 12.5 on P4/5 and decreased to twice the initial value on P18. At all three ages, stimulation of IDCs with the trinucleotides ATP and UTP at 1 and 10 μM elicited Ca²⁺ transients of varying amplitude and shape. Before the onset of hearing, IDCs responded with robust Ca²⁺ oscillations. At P18, after the onset of hearing, ATP stimulation either caused Ca²⁺ oscillations or an initial Ca²⁺ peak followed by a plateau while the UTP response was unchanged from that at pre-hearing stage. Parameters of spontaneous and nucleotide-evoked Ca²⁺ transients such as amplitude, decay time and duration were markedly reduced during cochlear development, whereas the kinetics of the Ca²⁺ rise did not show relevant changes. Whether low-frequency spontaneous Ca²⁺ transients are necessary for the formation and maintenance of the tectorial membrane e.g. by regulating gene transcription needs to be elucidated in further studies.

Orai, STIM, and PMCA contribute to reduced calcium signal generation in CD8+ T cells of elderly mice

Ca²⁺ is a crucial second messenger for proper T cell function. Considering the relevance of Ca²⁺ signals for T cell functionality it is surprising that no mechanistic insights into T cell Ca²⁺ signals from elderly individuals are reported. The main Ca²⁺ entry mechanism in T cells are STIM-activated Orai channels. Their role during lymphocyte aging is completely unknown. Here, we report not only reduced Ca²⁺ signals in untouched and stimulated, but also in central and effector memory CD8⁺ T cells from elderly (18-24 months) compared to adult (3-6 months) mice. Two mechanisms contribute to the overall reduction in Ca²⁺ signals of CD8⁺ T cells of elderly mice: 1) Reduced Ca²⁺ currents through Orai channels due to decreased expressions of STIMs and Orais. 2) A faster extrusion of Ca²⁺ owing to an increased expression of PMCA4. The reduced Ca²⁺ signals correlated with a resistance of the cytotoxic efficiency of CD8⁺ T cells to varying free [Ca²⁺]_ext with age. In summary, reduced STIM/Orai expression and increased Ca²⁺ clearing rates following enhanced PMCA4 expression contribute to reduced Ca²⁺ signals in CD8⁺ T cells of elderly mice. These changes are apparently relevant to immune function as they reduce the Ca²⁺ dependency of CTL cytotoxicity.

The Endoplasmic Reticulum-Plasma Membrane Junction: A Hub for Agonist Regulation of Ca2+ Entry

Stimulation of cell-surface receptors induces cytosolic Ca²⁺ ([Ca²⁺]_i) increases that are detected and transduced by effector proteins for regulation of cell function. Intracellular Ca²⁺ release, via endoplasmic reticulum (ER) proteins inositol 1,4,5-trisphosphate receptors (IP₃R) and ryanodine receptors (RyR), and Ca²⁺ influx, via store-operated Ca²⁺ entry (SOCE), contribute to the increase in [Ca²⁺]_i The amplitude, frequency, and spatial characteristics of the [Ca²⁺]_i increases are controlled by the compartmentalization of proteins into signaling complexes such as receptor-signaling complexes and SOCE complexes. Both complexes include protein and lipid components, located in the plasma membrane (PM) and ER. Receptor signaling initiates in the PM via phospholipase C (PLC)-mediated hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP₂), and culminates with the activation of IP₃R in the ER. Conversely, SOCE is initiated in the ER by Ca²⁺-sensing stromal interaction molecule (STIM) proteins, which then interact with PM channels Orai1 and TRPC1 to activate Ca²⁺ entry. This review will address how ER-PM junctions serve a central role in agonist regulation of SOCE.

Serum- and Glucocorticoid-inducible Kinase 1 is Essential for Osteoclastogenesis and Promotes Breast Cancer Bone Metastasis

Bone metastasis is a severe complication associated with various carcinomas. It causes debilitating pain and pathologic fractures and dramatically impairs patients' quality of life. Drugs aimed at osteoclast formation significantly reduce the incidence of skeletal complications and are currently the standard treatment for patients with bone metastases. Here, we reported that serum- and glucocorticoid-inducible kinase 1 (SGK1) plays a pivotal role in the formation and function of osteoclasts by regulating the Ca2+ release-activated Ca2+ channel Orai1. We showed that SGK1 inhibition represses osteoclastogenesis in vitro and prevents bone loss in vivo Furthermore, we validated the effect of SGK1 on bone metastasis by using an intracardiac injection model in mice. Inhibition of SGK1 resulted in a significant reduction in bone metastasis. Subsequently, the Oncomine and the OncoLnc database were employed to verify the differential expression and the association with clinical outcome of SGK1 gene in patients with breast cancer. Our data mechanistically demonstrated the regulation of the SGK1 in the process of osteoclastogenesis and revealed SGK1 as a valuable target for curing bone metastasis diseases.

Ca2+ waves coordinate purinergic receptor-evoked integrin activation and polarization

Cells sense extracellular nucleotides through the P2Y class of purinergic G protein-coupled receptors (GPCRs), which stimulate integrin activation through signaling events, including intracellular Ca²⁺ mobilization. We investigated the relationship between P2Y-stimulated repetitive Ca²⁺ waves and fibrinogen binding to the platelet integrin α_IIbβ₃ (GPIIb/IIIa) through confocal fluorescence imaging of primary rat megakaryocytes. Costimulation of the receptors P2Y₁ and P2Y₁₂ generated a series of Ca²⁺ transients that each induced a rapid, discrete increase in fibrinogen binding. The peak and net increase of individual fibrinogen binding events correlated with the Ca²⁺ transient amplitude and frequency, respectively. Using BAPTA loading and selective receptor antagonists, we found that Ca²⁺ mobilization downstream of P2Y₁ was essential for ADP-evoked fibrinogen binding, whereas P2Y₁₂ and the kinase PI3K were also required for α_IIbβ₃ activation and enhanced the number of Ca²⁺ transients. ADP-evoked fibrinogen binding was initially uniform over the cell periphery but subsequently redistributed with a polarity that correlated with the direction of the Ca²⁺ waves. Polarization of α_IIbβ₃ may be mediated by the actin cytoskeleton, because surface-bound fibrinogen is highly immobile, and its motility was enhanced by cytoskeletal disruption. In conclusion, spatial and temporal patterns of Ca²⁺ increase enable fine control of α_IIbβ₃ activation after cellular stimulation. P2Y₁-stimulated Ca²⁺ transients coupled to α_IIbβ₃ activation only in the context of P2Y₁₂ coactivation, thereby providing an additional temporal mechanism of synergy between these Gq- and Gi-coupled GPCRs.