ORAI-mediated calcium influx in T cell proliferation, apoptosis and tolerance

Klf10 is involved in extracellular matrix calcification of chondrocytes alleviating chondrocyte senescence

Osteoarthritis (OA) is a chronic degenerative disease resulting joint disability and pain. Accumulating evidences suggest that chondrocyte extracellular matrix calcification plays an important role in the development of OA. Here, we showed that Krüppel-like factor 10 (Klf10) was involved in the regulation of chondrocyte extracellular matrix calcification by regulating the expression of Frizzled9. Knockdown of Klf10 attenuated TBHP induced calcification and reduced calcium content in chondrocytes. Restoring extracellular matrix calcification of chondrocytes could aggravate chondrocyte senescence. Destabilization of a medial meniscus (DMM) mouse model of OA, in vivo experiments revealed that knockdown Klf10 improved the calcification of articular cartilage and ameliorated articular cartilage degeneration. These findings suggested that knockdown Klf10 inhibited extracellular matrix calcification-related changes in chondrocytes and alleviated chondrocyte senescence.

Anti-Inflammatory Effects of Alphitolic Acid Isolated from Agrimonia coreana Nakai Extracts Are Mediated via the Inhibition of ICRAC Activity in T Cells

Agrimonia pilosa Ledeb., an important medicinal herb in traditional East Asian medicine, is primarily used to treat abdominal pain, dysentery, and hemostasis. There are ten other reported species of Agrimonia plants, including Agrimonia coreana Nakai-a naturally growing species in South Korea-and Agrimonia eupatoria Linn. Although recent studies have isolated numerous active constituents and investigated their effects, the medicinal utility of this herb is not yet fully explored. Through patch-clamp recording, a previous study reported that Agrimonia plant extracts inhibit the function of Ca2+ release-activated Ca2+ channels (CRACs). Herein, we aimed to identify and isolate the main compounds in A. coreana responsible for CRAC inhibition while assessing the anti-inflammatory effects mediated by this inhibition. We demonstrated for the first time that alphitolic acid isolated from A. coreana has a dose-dependent inhibitory effect on CRAC activity and, thus, an inhibitory effect on intracellular calcium increase. Furthermore, analysis of human CD4+ T cell proliferation via the carboxyfluorescein diacetate succinimidyl ester method revealed that alphitolic acid inhibited T cell proliferation in a concentration-dependent manner. Our findings provide a theoretical basis for the potential therapeutic use of alphitolic acid in the treatment of inflammatory diseases.

2-D-gal Targets Terminal Fucosylation to Inhibit T-cell Response in a Mouse Skin Transplant Model

BACKGROUND

Organ allograft rejection is mainly driven by T-cell response. Studies have shown that fucosylation plays essential roles in the immune cell development and function. Terminal fucosylation inhibitor, 2-deoxy-D-galactose (2-D-gal), has been reported to suppress immunoresponse of macrophages, but its effects on T-cell-mediated immune response and transplant rejection have not been fully explored.

METHODS

The terminal fucosylation level in T cells was detected through ulex europaeus agglutinin-I staining. The consequences of 2-D-gal on murine T-cell proliferation, activation, cytokine secretion, and cell cycle were investigated in vitro. T-cell receptor signaling cascades were examined. Last, mouse skin transplant model was utilized to evaluate the regulatory effects of 2-D-gal on T-cell response in vivo.

RESULTS

The expression of fucosyltransferase1 was upregulated in CD3/CD28-activated T cells along with an elevation of α(1,2)-fucosylation level as seen by ulex europaeus agglutinin-I staining. Furthermore, 2-D-gal suppressed T-cell activation and proliferation, decrease cytokines production, arrest cell cycle, and prevent the activation of T-cell receptor signaling cascades. In vivo experiments showed that 2-D-gal limited T-cell proliferation to prolong skin allograft in mice. This was accompanied by lower level of inflammatory cytokines, and were comparable to those treated with Cyclosporin A.

CONCLUSIONS

Terminal fucosylation appears to play a role in T-cell activation and proliferation, and its inhibitor, 2-D-gal, can suppress T-cell activation and proliferation both in vitro and in vivo. In a therapeutic context, inhibiting terminal fucosylation may be a potential strategy to prevent allogeneic transplant rejection.

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.

The calcium channel modulator 2-APB hydrolyzes in physiological buffers and acts as an effective radical scavenger and inhibitor of the NADPH oxidase 2

2-aminoethoxydiphenyl borate (2-APB) is commonly used as a tool to modulate calcium signaling in physiological studies. 2-APB has a complex pharmacology and acts as activator or inhibitor of a variety of Ca²⁺ channels and transporters. While unspecific, 2-APB is one of the most-used agents to modulate store-operated calcium entry (SOCE) mediated by the STIM-gated Orai channels. Due to its boron core structure, 2-APB tends to readily hydrolyze in aqueous environment, a property that results in a complex physicochemical behavior. Here, we quantified the degree of hydrolysis in physiological conditions and identified the hydrolysis products diphenylborinic acid and 2-aminoethanol by NMR. Notably, we detected a high sensitivity of 2-APB/diphenylborinic acid towards decomposition by hydrogen peroxide to compounds such as phenylboronic acid, phenol, and boric acid, which were, in contrast to 2-APB itself and diphenylborinic acid, insufficient to affect SOCE in physiological experiments. Consequently, the efficacy of 2-APB as a Ca²⁺ signal modulator strongly depends on the reactive oxygen species (ROS) production within the experimental system. The antioxidant behavior of 2-APB towards ROS and its resulting decomposition are inversely correlated to its potency to modulate Ca²⁺ signaling as shown by electron spin resonance spectroscopy (ESR) and Ca²⁺ imaging. Finally, we observed a strong inhibitory effect of 2-APB, i.e., its hydrolysis product diphenylborinic acid, on NADPH oxidase (NOX2) activity in human monocytes. These new 2-APB properties are highly relevant for Ca²⁺ and redox signaling studies and for pharmacological application of 2-APB and related boron compounds.

Cavβ1 regulates T cell expansion and apoptosis independently of voltage-gated Ca2+ channel function

TCR stimulation triggers Ca2+ signals that are critical for T cell function and immunity. Several pore-forming α and auxiliary β subunits of voltage-gated Ca2+ channels (VGCC) were reported in T cells, but their mechanism of activation remains elusive and their contribution to Ca2+ signaling in T cells is controversial. We here identify CaVβ1, encoded by Cacnb1, as a regulator of T cell function. Cacnb1 deletion enhances apoptosis and impairs the clonal expansion of T cells after lymphocytic choriomeningitis virus (LCMV) infection. By contrast, Cacnb1 is dispensable for T cell proliferation, cytokine production and Ca2+ signaling. Using patch clamp electrophysiology and Ca2+ recordings, we are unable to detect voltage-gated Ca2+ currents or Ca2+ influx in human and mouse T cells upon depolarization with or without prior TCR stimulation. mRNAs of several VGCC α1 subunits are detectable in human (CaV3.3, CaV3.2) and mouse (CaV2.1) T cells, but they lack transcription of many 5' exons, likely resulting in N-terminally truncated and non-functional proteins. Our findings demonstrate that although CaVβ1 regulates T cell function, these effects are independent of VGCC channel activity.

Antitumor and Antibacterial Efficacy of Gallium Nanoparticles Coated by Ellagic Acid

Cancer is a mortality contributor worldwide, and breast cancer is the most common among women. Despite the numerous breast cancer therapeutic strategies, they either have limitations or sometimes are resisted by cancer, so new approaches are needed to tackle those restrictions. Nanotechnology offers exciting leaps in the diagnosis and treatment of cancer, especially breast cancer. The main objective of this study was to investigate the effect of the newly synthesized gallium nanoparticles coated by Ellagic acid (EA-GaNPs) on the induced mammary gland carcinogenesis in female rats and their antibacterial activities comparison with standard antibiotics (Ketoconazole (100 μg/ml) and Gentamycin (4 μg/ml)) by disc diffusion method using eight different microbial species. The antitumor efficacy of EA-GaNPs was conducted both in vitro and in in vivo. The result of antimicrobial activity of EA-Ga NPs (1 mg/1 mL) revealed moderate toxicity behavior against Gram-positive {Staphylococcus aureus, Bacillus subtilis, Bacillus cereus) and Gram-negative pathogenic bacteria {Escherichia coli, Proteus vulgarfs) also, antifungal activity was detected against {Aspergillus terreus). In vitro study showed that EA-GaNPs inhibited human breast cancer cell line (MCF-7) proliferation with IC50 of 2.86 μg/ml. Although in vivo; the administration of EA-GaNPs to DMBA-treated rats ameliorated the hyperplastic state of mammary gland carcinogenesis induced by DMBA. Additionally, EA-GaNPs administration significantly modulated the activities of ALT and AST, as well as the levels of urea and creatinine in serum. Also, EA-GaNPs administration improved the antioxidant state by increasing Superoxide dismutase activity and GSH content, and decreasing malondialdehyde content in the mammary tissue, besides enhancing the apoptotic activity through elevating the levels of caspase-3 and decreasing the protein intensities of protein kinase B & phosphatidyl inositide 3-kinases. Furthermore, a significant decrease in serum Total iron-binding capacity accompanied by a significant increase in the level of calcium was noted. So, it can be concluded that the newly synthesized nanoparticles EA-GaNPs have an efficient antitumor activity that was manifested by reduction of the viability on the human breast cancer cell line (MCF-7) in vitro. Also, in vivo against the chemically induced mammary gland carcinogenesis in a female rat model. Histopathological findings were in harmony with biochemical and molecular results showing the effectiveness of EA-GaNPs against mammary carcinogenesis. Therefore, EA-GaNPs could be a promising, potent anti-cancer compound.

The effect of IL-2 stimulation and treatment of TRPM3 on channel co-localisation with PIP2 and NK cell function in myalgic encephalomyelitis/chronic fatigue syndrome patients

BACKGROUND

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a serious multifactorial disorder. The origin remains ambiguous, however reduced natural killer (NK) cell cytotoxicity is a consistent immunological feature of ME/CFS. Impaired transient receptor potential melastatin 3 (TRPM3), a phosphatidylinositol dependent channel, and impaired calcium mobilisation have been implicated in ME/CFS pathology. This investigation aimed to examine the localisation of TRPM3 at the NK cell plasma membrane and co-localisation with phosphatidylinositol 4,5-bisphosphate (PIP₂). The effect of IL-2 priming and treatment using pregnenolone sulfate (PregS) and ononetin on TRPM3 co-localisation and NK cell cytotoxicity in ME/CFS patients and healthy controls (HC) was also investigated.

METHODS

NK cells were isolated from 15 ME/CFS patients and 15 age- and sex-matched HC. Immunofluorescent technique was used to determine co-localisation of TRPM3 with the NK cell membrane and with PIP₂ of ME/CFS patients and HC. Flow cytometry was used to determine NK cell cytotoxicity. Following IL-2 stimulation and treatment with PregS and ononetin changes in co-localisation and NK cell cytotoxicity were measured.

RESULTS

Overnight treatment of NK cells with PregS and ononetin resulted in reduced co-localisation of TRPM3 with PIP₂ and actin in HC. Co-localisation of TRPM3 with PIP₂ in NK cells was significantly reduced in ME/CFS patients compared with HC following priming with IL-2. A significant increase in co-localisation of TRPM3 with PIP₂ was reported following overnight treatment with ononetin within ME/CFS patients and between groups. Baseline NK cell cytotoxicity was significantly reduced in ME/CFS patients; however, no changes were observed following overnight incubation with IL-2, PregS and ononetin between HC and ME/CFS patients. IL-2 stimulation significantly enhanced NK cell cytotoxicity in HC and ME/CFS patients.

CONCLUSION

Significant changes in co-localisation suggest PIP₂-dependent TRPM3 function may be impaired in ME/CFS patients. Stimulation of NK cells with IL-2 significantly enhanced cytotoxic function in ME/CFS patients demonstrating normal function compared with HC. A crosstalk exists between IL-2 and TRPM3 intracellular signalling pathways which are dependent on Ca²⁺ influx and PIP₂. While IL-2R responds to IL-2 binding in vitro, Ca²⁺ dysregulation and impaired intracellular signalling pathways impede NK cell function in ME/CFS patients.

Exploiting Ca2+ signaling in T cells to advance cancer immunotherapy

Decades of basic research has established the importance of Ca²⁺ to various T cell functions, such as cytotoxicity, proliferation, differentiation and cytokine secretion. We now have a good understanding of how proximal TCR signaling initiates Ca²⁺ influx and how this influx subsequently changes transcriptional activities in T cells. As chimeric antigen receptor (CAR)-T therapy has achieved great clinical success, is it possible to harness Ca²⁺ signaling to further advance CAR-T research? How is CAR signaling different from TCR signaling? How can functional CARs be identified in a high-throughput way? Quantification of various Ca²⁺ signals downstream of CAR/TCR activation might help answer these questions. Here we first summarized recent studies that used Ca²⁺ dye, genetically-encoded Ca²⁺ indicators (GECI) or transcriptional activity reporters to understand CAR activation in vitro and in vivo. We next reviewed several proof-of-concept reports that manipulate Ca²⁺ signaling by light or ultrasound to achieve precise spatiotemporal control of T cell functions. These efforts, though preliminary, opened up new avenues to solve the on-target/off-tumor problem of therapeutic T cells. Other modalities to regulate Ca²⁺ signaling, such as radio wave and electrical pulse, were also discussed. Thus, monitoring or manipulating Ca²⁺ signaling in T cells provides us many opportunities to advance cancer immunotherapy.

The prospect of serum and glucocorticoid-inducible kinase 1 (SGK1) in cancer therapy: a rising star

Serum and glucocorticoid-inducible kinase 1 (SGK1) is an AGC kinase that has been reported to be involved in a variety of physiological and pathological processes. Recent evidence has accumulated that SGK1 acts as an essential Akt-independent mediator of phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) signaling pathway in cancer. SGK1 is overexpressed in several tumors, including prostate cancer, colorectal carcinoma, glioblastoma, breast cancer, and endometrial cancer. The functions of SGK1 include regulating tumor growth, survival, metastasis, autophagy, immunoregulation, calcium (Ca²⁺) signaling, cancer stem cells, cell cycle, and therapeutic resistance. In this review, we introduce the pleiotropic role of SGK1 in the development and progression of tumors, summarize its downstream targets, and integrate the knowledge provided by preclinical studies that the prospect of SGK1 inhibition as a potential therapeutic approach.

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.

Coelomic Fluid of Lumbricus rubellus Synergistically Enhances Cytotoxic Effect of 5-Fluorouracil through Modulation of Focal Adhesion Kinase and p21 in HT-29 Cancer Cell Line

Coelomic fluid of Lumbricus rubellus (CFL) has attracted interest due to its pharmacological properties, including antitumor effect. Furthermore, it is necessary to evaluate the response to treatment with new cancer therapeutic agents. This study aims to investigate whether the combination of CFL and 5-fluorouracil could reduce FAK protein level and iCa²⁺ and enhance p21 level. Furthermore, it is necessary to evaluate the response to treatment with new cancer therapeutic agents. After 24 hours of treatment, it was necessary to assess the percentage of apoptosis, FAK, and p21 protein expression by flow cytometry. iCa²⁺ concentration was measured using immunofluorescence. The combination therapy of CFL with 5-fluorouracil potently suppressed six treatment groups were included in this study. HT-29 cell lines were cultured and divided into six groups: group 1 was treated with vehicle (negative control), groups 2-5 were treated with 5-fluorouracil, groups 3-5 were treated with either CFL 5, 10, or 20 µg/ml immediately after 5-fluorouracil, and group 6 was treated with CFL 20 µg/ml, the progression of colorectal cancer. Combination of CFL and 5-fluorouracil significantly decreased FAK expression (p<0.05), iCa²⁺ (p<0.05), and increased p21 expression (p<0.05) in HT-29 cells. Our results suggest that CFL has an anticancer potential in colorectal cancer when combined with 5-fluorouracil.

Upregulation of Orai1 and STIM1 expression as well as store-operated Ca2+ entry in ovary carcinoma cells by placental growth factor

Placental growth factor (PlGF) is produced by tumor cells and stimulates tumor growth and metastasis in part by upregulation of hypoxia inducible factor HIF1α. Orchestration of tumor cell proliferation and migration involves oscillations of cytosolic Ca²⁺ activity ([Ca²⁺]_i). The [Ca²⁺]_i oscillations could be accomplished by triggering of intracellular Ca²⁺ release followed by store-operated Ca²⁺-entry (SOCE). Mechanisms accomplishing SOCE include the pore-forming ion channel unit Orai1 and its regulator STIM1. The present study explored whether PlGF influences the expression of Orai1 and STIM1, as well as SOCE and whether this effect impacts on HIF1α expression. To this end, ovary carcinoma cells were cultured for 24 h without and with PlGF (10 ng/ml). Orai1, STIM1 and HIF1α transcript levels were quantified utilizing RT-PCR and Orai1, STIM1 and HIF1α protein levels by Western blotting. [Ca²⁺]_i was estimated from Fura-2-fluorescence and SOCE from increase of [Ca²⁺]_i following Ca²⁺ re-addition after Ca²⁺-store depletion with extracellular Ca²⁺ removal and sarcoendoplasmatic Ca²⁺-ATPase (SERCA) inhibitor thapsigargin (1 μM). As a result, exposure of ovary carcinoma cells to PlGF was followed by a significant increase of Orai1 as well as STIM1 transcript and protein levels. PlGF significantly increased store-operated Ca²⁺-entry following re-addition of extracellular Ca²⁺, an effect virtually abrogated by Orai1 inhibitor MRS1845 (10 μM). PlGF further increased HIF1α transcript and protein levels, an effect again significantly blunted by MRS1845 (10 μM). In conclusion, PlGF upregulates expression of both, Orai1 and STIM1 thus enhancing store-operated Ca²⁺-entry with subsequent upregulation of HIF1α.

To die or not to die SGK1-sensitive ORAI/STIM in cell survival

The pore forming Ca²⁺ release activated Ca²⁺ channel (CRAC) isoforms ORAI1-3 and their regulators STIM1,2 accomplish store operated Ca²⁺ entry (SOCE). Activation of SOCE may lead to cytosolic Ca²⁺ oscillations, which in turn support cell proliferation and cell survival. ORAI/STIM and thus SOCE are upregulated by the serum and glucocorticoid inducible kinase SGK1, a kinase under powerful genomic regulation and activated by phosphorylation via the phosphoinositol-3-phosphate pathway. SGK1 enhances ORAI1 abundance partially by phosphorylation of Nedd4-2, an ubiquitin ligase priming the channel protein for degradation. The SGK1-phosphorylated Nedd4-2 binds to the protein 14-3-3 and is thus unable to ubiquinate ORAI1. SGK1 further increases the ORAI1 and STIM1 protein abundance by activating nuclear factor kappa B (NF-κB), a transcription factor upregulating the expression of STIM1 and ORAI1. SGK1-sensitive upregulation of ORAI/STIM and thus SOCE is triggered by a wide variety of hormones and growth factors, as well as several cell stressors including ischemia, radiation, and cell shrinkage. SGK1 dependent upregulation of ORAI/STIM confers survival of tumor cells and thus impacts on growth and therapy resistance of cancer. On the other hand, SGK1-dependent upregulation of ORAI1 and STIM1 may support survival of neurons and impairment of SGK1-dependent ORAI/STIM activity may foster neurodegeneration. Clearly, further experimental effort is needed to define the mechanisms linking SGK1-dependent upregulation of ORAI1 and STIM1 to cell survival and to define the impact of SGK1-dependent upregulation of ORAI1 and STIM1 on malignancy and neurodegenerative disease.

Profiling calcium signals of in vitro polarized human effector CD4+ T cells

Differentiation of naïve CD4⁺ T cells into effector subtypes with distinct cytokine profiles and physiological roles is a tightly regulated process, the imbalance of which can lead to an inadequate immune response or autoimmune disease. The crucial role of Ca²⁺ signals, mainly mediated by the store operated Ca²⁺ entry (SOCE) in shaping the immune response is well described. However, it is unclear if human effector CD4⁺ T cell subsets show differential Ca²⁺ signatures in response to different stimulation methods. Herein, we provide optimized in vitro culture conditions for polarization of human CD4⁺ effector T cells and characterize their SOCE following both pharmacological store depletion and direct T-cell receptor (TCR) activation. Moreover, we measured whole cell Ca²⁺ release activated Ca²⁺ currents (I_CRAC) and investigated whether the observed differences correlate to the expression of CRAC genes. Our results show that Ca²⁺ profiles of helper CD4⁺ Th1, Th2 and Th17 are distinct and in part shaped by the intensity of stimulation. Regulatory T cells (Treg) are unique being the subtype with the most prominent SOCE response. Analysis of in vivo differentiated Treg unraveled the role of differential expression of ORAI2 in fine-tuning signals in Treg vs. conventional CD4⁺ T cells.

LEFTY2 inhibits endometrial receptivity by downregulating Orai1 expression and store-operated Ca2+ entry

Abstract

Early embryo development and endometrial differentiation are initially independent processes, and synchronization, imposed by a limited window of implantation, is critical for reproductive success. A putative negative regulator of endometrial receptivity is LEFTY2, a member of the transforming growth factor (TGF)-β family. LEFTY2 is highly expressed in decidualizing human endometrial stromal cells (HESCs) during the late luteal phase of the menstrual cycle, coinciding with the closure of the window of implantation. Here, we show that flushing of the uterine lumen in mice with recombinant LEFTY2 inhibits the expression of key receptivity genes, including Cox2, Bmp2, and Wnt4, and blocks embryo implantation. In Ishikawa cells, a human endometrial epithelial cell line, LEFTY2 downregulated the expression of calcium release-activated calcium channel protein 1, encoded by ORAI1, and inhibited store-operated Ca²⁺ entry (SOCE). Furthermore, LEFTY2 and the Orai1 blockers 2-APB, MRS-1845, as well as YM-58483, inhibited, whereas the Ca²⁺ ionophore, ionomycin, strongly upregulated COX2, BMP2 and WNT4 expression in decidualizing HESCs. These findings suggest that LEFTY2 closes the implantation window, at least in part, by downregulating Orai1, which in turn limits SOCE and antagonizes expression of Ca²⁺-sensitive receptivity genes.

Key messages

•Endometrial receptivity is negatively regulated by LEFTY2.

•LEFTY2 inhibits the expression of key murine receptivity genes, including Cox2, Bmp2and Wnt4, and blocks embryo implantation.

•LEFTY2 downregulates the expression of Orai1 and inhibits SOCE.

•LEFTY2 and the Orai1 blockers 2-APB, MRS-1845, and YM-58483 inhibit COX2, BMP2, and WNT4 expression in endometrial cells.

•Targeting LEFTY2 and Orai1 may represent a novel approach for treating unexplained infertility.

Electronic supplementary material

The online version of this article (10.1007/s00109-017-1610-9) contains supplementary material, which is available to authorized users.

Lithium Sensitive ORAI1 Expression, Store Operated Ca2+ Entry and Suicidal Death of Neurons in Chorea-Acanthocytosis

Chorea-Acanthocytosis (ChAc), a neurodegenerative disorder, results from loss-of-function-mutations of chorein-encoding gene VPS13A. In tumour cells chorein up-regulates ORAI1, a Ca²⁺-channel accomplishing store operated Ca²⁺-entry (SOCE) upon stimulation by STIM1. Furthermore SOCE could be up-regulated by lithium. The present study explored whether SOCE impacts on neuron apoptosis. Cortical neurons were differentiated from induced pluripotent stem cells generated from fibroblasts of ChAc patients and healthy volunteers. ORAI1 and STIM1 transcript levels and protein abundance were estimated from qRT-PCR and Western blotting, respectively, cytosolic Ca²⁺-activity ([Ca²⁺]_i) from Fura-2-fluorescence, as well as apoptosis from annexin-V-binding and propidium-iodide uptake determined by flow cytometry. As a result, ORAI1 and STIM1 transcript levels and protein abundance and SOCE were significantly smaller and the percentage apoptotic cells significantly higher in ChAc neurons than in control neurons. Lithium treatment (2 mM, 24 hours) increased significantly ORAI1 and STIM1 transcript levels and protein abundance, an effect reversed by inhibition of Serum & Glucocorticoid inducible Kinase 1. ORAI1 blocker 2-APB (50 µM, 24 hours) significantly decreased SOCE, markedly increased apoptosis and abrogated the anti-apoptotic effect of lithium. In conclusion, enhanced neuronal apoptosis in ChAc at least partially results from decreased ORAI1 expression and SOCE, which could be reversed by lithium treatment.

Role of SOCE architects STIM and Orai proteins in Cell Death

Calcium (Ca²⁺) signaling plays a critical role in regulating plethora of cellular functions including cell survival, proliferation and migration. The perturbations in cellular Ca²⁺ homeostasis can lead to cell death either by activating autophagic pathways or through induction of apoptosis. Endoplasmic reticulum (ER) is the major storehouse of Ca²⁺ within cells and a number of physiological agonists mediate ER Ca²⁺ release by activating IP₃ receptors (IP₃R). This decrease in ER Ca²⁺ levels is sensed by STIM, which physically interacts and activates plasma membrane Ca²⁺ selective Orai channels. Emerging literature implicates a key role for STIM1, STIM2, Orai1 and Orai3 in regulating both cell survival and death pathways. In this review, we will retrospect the work highlighting the role of STIM and Orai homologs in regulating cell death signaling. We will further discuss the rationales that could explain the dual role of STIM and Orai proteins in regulating cell fate decisions.

Intracellular Calcium Mobilization in Response to Ion Channel Regulators via a Calcium-Induced Calcium Release Mechanism

Free intracellular calcium ([Ca²⁺]_i), in addition to being an important second messenger, is a key regulator of many cellular processes including cell membrane potential, proliferation, and apoptosis. In many cases, the mobilization of [Ca²⁺]_i is controlled by intracellular store activation and calcium influx. We have investigated the effect of several ion channel modulators, which have been used to treat a range of human diseases, on [Ca²⁺]_i release, by ratiometric calcium imaging. We show that six such modulators [amiodarone (Ami), dofetilide, furosemide (Fur), minoxidil (Min), loxapine (Lox), and Nicorandil] initiate release of [Ca²⁺]_i in prostate and breast cancer cell lines, PC3 and MCF7, respectively. Whole-cell currents in PC3 cells were inhibited by the compounds tested in patch-clamp experiments in a concentration-dependent manner. In all cases [Ca²⁺]_i was increased by modulator concentrations comparable to those used clinically. The increase in [Ca²⁺]_i in response to Ami, Fur, Lox, and Min was reduced significantly (P < 0.01) when the external calcium was reduced to nM concentration by chelation with EGTA. The data suggest that many ion channel regulators mobilize [Ca²⁺]_i. We suggest a mechanism whereby calcium-induced calcium release is implicated; such a mechanism may be important for understanding the action of these compounds.

Changing expression of vertebrate immunity genes in an anthropogenic environment: a controlled experiment

Background

The effect of anthropogenic environments on the function of the vertebrate immune system is a problem of general importance. For example, it relates to the increasing rates of immunologically-based disease in modern human populations and to the desirability of identifying optimal immune function in domesticated animals. Despite this importance, our present understanding is compromised by a deficit of experimental studies that make adequately matched comparisons between wild and captive vertebrates.

Results

We transferred post-larval fishes (three-spined sticklebacks), collected in the wild, to an anthropogenic (captive) environment. We then monitored, over 11 months, how the systemic expression of immunity genes changed in comparison to cohort-matched wild individuals in the originator population (total n = 299). We found that a range of innate (lyz, defbl2, il1r-like, tbk1) and adaptive (cd8a, igmh) immunity genes were up-regulated in captivity, accompanied by an increase in expression of the antioxidant enzyme, gpx4a. For some genes previously known to show seasonality in the wild, this appeared to be reduced in captive fishes. Captive fishes tended to express immunity genes, including igzh, foxp3b, lyz, defbl2, and il1r-like, more variably. Furthermore, although gene co-expression patterns (analyzed through gene-by-gene correlations and mutual information theory based networks) shared common structure in wild and captive fishes, there was also significant divergence. For one gene in particular, defbl2, high expression was associated with adverse health outcomes in captive fishes.

Conclusion

Taken together, these results demonstrate widespread regulatory changes in the immune system in captive populations, and that the expression of immunity genes is more constrained in the wild. An increase in constitutive systemic immune activity, such as we observed here, may alter the risk of immunopathology and contribute to variance in health in vertebrate populations exposed to anthropogenic environments.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-016-0751-8) contains supplementary material, which is available to authorized users.

The role of Orai-STIM calcium channels in melanocytes and melanoma

Calcium signalling within normal and cancer cells regulates many important cellular functions such as migration, proliferation, differentiation and cytokine secretion. Store operated Ca(2+) entry (SOCE) via the Ca(2+) release activated Ca(2+) (CRAC) channels, which are composed of the plasma membrane based Orai channels and the endoplasmic reticulum stromal interaction molecules (STIMs), is a major Ca(2+) entry route in many cell types. Orai and STIM have been implicated in the growth and metastasis of multiple cancers; however, while their involvement in cancer is presently indisputable, how Orai-STIM-controlled Ca(2+) signals affect malignant transformation, tumour growth and invasion is not fully understood. Here, we review recent studies linking Orai-STIM Ca(2+) channels with cancer, with a particular focus on melanoma. We highlight and examine key molecular players and the signalling pathways regulated by Orai and STIM in normal and malignant cells, we expose discrepancies, and we reflect on the potential of Orai-STIMs as anticancer drug targets. Finally, we discuss the functional implications of future discoveries in the field of Ca(2+) signalling.

Inhibition of Orai1 Store-Operated Calcium Channel Prevents Foam Cell Formation and Atherosclerosis

OBJECTIVE

To determine the role of orai1 store-operated Ca(2+) entry in foam cell formation and atherogenesis.

APPROACH AND RESULTS

Acute administration of oxidized low-density lipoprotein (oxLDL) activates an orai1-dependent Ca(2+) entry in macrophages. Chelation of intracellular Ca(2+), inhibition of orai1 store-operated Ca(2+) entry, or knockdown of orai1 dramatically inhibited oxLDL-induced upregulation of scavenger receptor A, uptake of modified LDL, and foam cell formation. Orai1-dependent Ca(2+) entry induces scavenger receptor A expression and foam cell formation through activation of calcineurin but not calmodulin kinase II. Activation of nuclear factor of activated T cells is not involved in calcineurin signaling to foam cell formation. However, oxLDL dephosohorylates and activates apoptosis signal-regulating kinase 1 in macrophages. Orai1 knockdown prevents oxLDL-induced apoptosis signal-regulating kinase 1 activation. Knockdown of apoptosis signal-regulating kinase 1, or inhibition of its downstream effectors, JNK and p38 mitogen-activated protein kinase, reduces scavenger receptor A expression and foam cell formation. Notably, orai1 expression is increased in atherosclerotic plaques of apolipoprotein E(-/-) mice fed with high-cholesterol diet. Knockdown of orai1 with adenovirus harboring orai1 siRNA or inhibition of orai1 Ca(2+) entry with SKF96365 for 4 weeks dramatically inhibits atherosclerotic plaque development in high-cholesterol diet feeding apolipoprotein E(-/-) mice. In addition, inhibition of orai1 Ca(2+) entry prevents macrophage apoptosis in atherosclerotic plaque. Moreover, the expression of inflammatory genes in atherosclerotic lesions and the infiltration of myeloid cells into the aortic sinus plaques are decreased after blocking orai1 signaling.

CONCLUSIONS

Orai1-dependent Ca(2+) entry promotes atherogenesis possibly by promoting foam cell formation and vascular inflammation, rendering orai1 Ca(2+) channel a potential therapeutic target against atherosclerosis.

Scrophularia orientalis extract induces calcium signaling and apoptosis in neuroblastoma cells

Effective neuroblastoma (NB) treatments are still limited despite treatment options available today. Therefore, this study attempted to identify novel plant extracts that have anticancer effects. Cytotoxicity and increased intracellular calcium levels were determined using the Sulforhodamine B (SRB) assay and Fluo4-AM (acetoxymethyl) staining and fluorescence microscopy in NB cells in order to screen a library of plant extracts. The current study examined the anticancer effects of a dichloromethane extract from Scrophularia orientalis L. (Scrophulariaceae), a plant that has been used in Traditional Chinese Medicine. This extract contained highly potent agents that significantly reduced cell survival and increased calcium levels in NB cells. Further analysis revealed that cell death induced by this extract was associated with intracellular calcium release, opening of the MPTP, caspase 3- and PARP-cleavage suggesting that this extract induced aberrant calcium signaling that resulted in apoptosis via the mitochondrial pathway. Therefore, agents from Scrophularia orientalis may have the potential to lead to new chemo therapeutic anticancer drugs. Furthermore, targeting intracellular calcium signaling may be a novel strategy to develop more effective treatments for NB.

Analysis of Intracellular Calcium Signaling in Human Embryonic Stem Cells

Measurement of changes in intracellular calcium concentration is one of the most common and useful tools for studying signal transduction pathways or cellular responses in basic research and drug screening purposes as well. Increasing number of such applications using human pluripotent stem cells and their derivatives requires development of calcium signal measurements for this special cell type. Here we describe a modified protocol for analysis of calcium signaling events in human embryonic stem cells, which can be used for other pluripotent cell types (such as iPSC) or their differentiated offspring as well.

Up-regulation of Orai1 expression and store operated Ca(2+) entry following activation of membrane androgen receptors in MCF-7 breast tumor cells

Background

Membrane androgen receptors (mAR) are functionally expressed in a variety of tumor-cells including the breast tumor-cell line MCF-7. They are specifically activated by testosterone albumin conjugates (TAC). The mAR sensitive signaling includes activation of Ras-related C3 botulinum toxin substrate 1 (Rac1) and reorganization of the actin filament network. Signaling of tumor-cells may further involve up-regulation of pore forming Ca²⁺ channel protein Orai1, which accomplishes store operated Ca²⁺ entry (SOCE). This study explored the regulation of Orai1 abundance and SOCE by mAR.

Methods

Actin filaments were visualized utilizing confocal microscopy, Rac1 activity using GST-GBD assay, Orai1 transcript levels by RT-PCR and total protein abundance by western blotting, Orai1 abundance at the cell surface by confocal microscopy and FACS-analysis, cytosolic Ca²⁺ activity ([Ca²⁺]_i) utilizing Fura-2-fluorescence, and SOCE from increase of [Ca²⁺]_i following readdition of Ca²⁺ after store depletion with thapsigargin (1 μM).

Results

TAC treatment of MCF-7 cells was followed by Rac1 activation, actin polymerization, transient increase of Orai1transcript levels and protein abundance, and transient increase of SOCE. The transient increase of Orai1 protein abundance was abrogated by Rac1 inhibitor NSC23766 (50 μM) and by prevention of actin reorganization with cytochalasin B (1 μM).

Conclusions

mAR sensitive Rac1 activation and actin reorganization contribute to the regulation of Orai1 protein abundance and SOCE.

CRAC channels, calcium, and cancer in light of the driver and passenger concept

Advances in next-generation sequencing allow very comprehensive analyses of large numbers of cancer genomes leading to an increasingly better characterization and classification of cancers. Comparing genomic data predicts candidate genes driving development, growth, or metastasis of cancer. Cancer driver genes are defined as genes whose mutations are causally implicated in oncogenesis whereas passenger mutations are defined as not being oncogenic. Currently, a list of several hundred cancer driver mutations is discussed including prominent members like TP53, BRAF, NRAS, or NF1. According to the vast literature on Ca(2+) and cancer, Ca(2+) signals and the underlying Ca(2+) channels and transporters certainly influence the development, growth, and metastasis of many cancers. In this review, I focus on the calcium release-activated calcium (CRAC) channel genes STIM and Orai and their role for cancer development, growth, and metastasis. STIM and Orai genes are being discussed in the context of current cancer concepts with a focus on the driver-passenger hypothesis. One result of this discussion is the hypothesis that a driver analysis of Ca(2+) homeostasis-related genes should not be carried out by looking at isolated genes. Rather a pool of “Ca(2+) genes” might be considered to act as one potential cancer driver. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen.

Temporal protein expression pattern in intracellular signalling cascade during T-cell activation: a computational study

Various T-cell co-receptor molecules and calcium channel CRAC play a pivotal role in the maintenance of cell's functional responses by regulating the production of effector molecules (mostly cytokines) that aids in immune clearance and also maintaining the cell in a functionally active state. Any defect in these co-receptor signalling pathways may lead to an altered expression pattern of the effector molecules. To study the propagation of such defects with time and their effect on the intracellular protein expression patterns, a comprehensive and largest pathway map of T-cell activation network is reconstructed manually. The entire pathway reactions are then translated using logical equations and simulated using the published time series microarray expression data as inputs. After validating the model, the effect of in silico knock down of co-receptor molecules on the expression patterns of their downstream proteins is studied and simultaneously the changes in the phenotypic behaviours of the T-cell population are predicted, which shows significant variations among the proteins expression and the signalling routes through which the response is propagated in the cytoplasm. This integrative computational approach serves as a valuable technique to study the changes in protein expression patterns and helps to predict variations in the cellular behaviour.

Morphological change of CD4(+) T cell during contact with DC modulates T-cell activation by accumulation of F-actin in the immunology synapse

BACKGROUND

The changes in T-cell morphology during immunological synapse (IS) formation are essential for T-cell activation. Previous researches have shown that T cell changed from spherical to elongated and/or flattened during in contact with B cell. As most powerful antigen presenting cell, dendritic cell (DC) has a strong ability to activate T cells. However, the morphological change of T cell which contacts DC and the relationship between morphological change and T-cell activation are not very clear. Thus, we studied the morphological change of CD4(+) T cell during contact with DC.

RESULTS

Using live-cell imaging, we discovered diversity in the T-cell morphological changes during contact with DCs. The elongation-flattening of CD4(+) T cells correlated with a low-level Ca(2+) response and a loss of T-cell receptor (TCR) signalling molecules in the IS, including zeta-chain associated protein kinase 70 (ZAP-70), phospholipase C-γ (PLC-γ) and protein kinase C-θ (PKC-θ), whereas rounding-flattening correlated with sufficient CD4(+) T-cell activation. Different morphological changes were correlated with the different amount of accumulated filamentous actin (F-actin) in the IS. Disruption of F-actin by cytochalasin D impaired the morphological change and the localisation of calcium microdomains in the IS and decreased the calcium response in CD4(+) T cells.

CONCLUSION

Our study discovered the diversity in morphological change of T cells during contacted with DCs. During this process, the different morphological changes of T cells modulate T-cell activation by the different amount of F-actin accumulation in the IS, which controls the distribution of calcium microdomains to affect T-cell activation.

Enhanced Orai1 and STIM1 expression as well as store operated Ca2+ entry in therapy resistant ovary carcinoma cells

Mechanisms underlying therapy resistance of tumor cells include protein kinase Akt. Putative Akt targets include store-operated Ca²⁺-entry (SOCE) accomplished by pore forming ion channel unit Orai1 and its regulator STIM1. We explored whether therapy resistant (A2780cis) differ from therapy sensitive (A2780) ovary carcinoma cells in Akt, Orai1, and STIM1 expression, Ca²⁺-signaling and cell survival following cisplatin (100μM) treatment. Transcript levels were quantified with RT-PCR, protein abundance with Western blotting, cytosolic Ca²⁺-activity ([Ca²⁺]i) with Fura-2-fluorescence, SOCE from increase of [Ca²⁺]i following Ca²⁺-readdition after Ca²⁺-store depletion, and apoptosis utilizing flow cytometry. Transcript levels of Orai1 and STIM1, protein expression of Orai1, STIM1, and phosphorylated Akt, as well as SOCE were significantly higher in A2780cis than A2780 cells. SOCE was decreased by Akt inhibitor III (SH-6, 10μM) in A2780cis but not A2780 cells and decreased in both cell lines by Orai1 inhibitor 2-aminoethoxydiphenyl borate (2-ABP, 50μM). Phosphatidylserine exposure and late apoptosis following cisplatin treatment were significantly lower in A2780cis than A2780 cells, a difference virtually abolished by SH-6 or 2-ABP. In conclusion, Orai1/STIM1 expression and function are increased in therapy resistant ovary carcinoma cells, a property at least in part due to enhanced Akt activity and contributing to therapy resistance in those cells.

The bullseye synapse formed between CD4+ T-cell and staphylococcal enterotoxin B-pulsed dendritic cell is a suppressive synapse in T-cell response

The immunological synapse (IS) is a supermolecular activation cluster formed between T cells and antigen-presenting cells. Although diverse IS structures have been reported, the function of the IS in T-cell activation remains unclear. Here, we found that the bullseye IS, one of IS types at the interface of CD4(+) T cells and staphylococcal enterotoxin B-pulsed dendritic cells, suppressed CD4(+) T-cell activation, whereas multifocal IS, another synapse type, stimulated CD4(+) T-cell activation. Consistent with these results, bullseye IS formation was accompanied by a low-level calcium response in T cells and a loss of T-cell receptor signalling molecules from the synapse, whereas multifocal IS exhibited the opposite. Furthermore, we found that CD4(+)CD25(+) regulatory T cells (T(regs)) more efficiently formed bullseye IS and promoted bullseye IS formation in CD4(+) CD25(-) T cells. Cytotoxic T-lymphocyte antigen-4 (CTLA-4), an inhibitory molecule expressed continuously on T(regs), was localised in bullseye IS. Moreover, blocking CTLA-4 reduced the percentage of bullseye IS formation and promoted T-cell activation. Our data thus indicate that bullseye IS formation is mediated by CTLA-4, and may negatively control T-cell activation as a suppressive synapse.

Patch-clamp measurement of ICRAC and ORAI channel activity

Depletion of internal Ca(2+) stores activates store-operated Ca(2+) channels. The most prominent members of this class of channels are Ca(2+) release-activated Ca(2+) (CRAC) channels, which are present in a variety of cell types including immune cells. CRAC channels are composed of ORAI proteins, which are activated by endoplasmic reticulum-bound STIM proteins on Ca(2+) store depletion. The underlying Ca(2+) current is called ICRAC, which is required for many cellular functions including T-cell activation, mast cell activation, Ca(2+)-dependent gene expression, and refilling of internal Ca(2+) stores. To analyze ICRAC or the Ca(2+) current through heterologously expressed ORAI channels, whole-cell patch clamp is the technique of choice. It allows the direct analysis of ion currents through CRAC/ORAI channels. The patch-clamp technique has been used to determine selectivity, permeability, rectification, inactivation, and several other biophysical and pharmacological properties of the channels, and is the most direct and reliable technique to analyze ICRAC.

Activation of protease-activated receptor 2 reduces glioblastoma cell apoptosis

Background

The pathogenesis of glioma is unclear. The disturbance of the apoptosis process plays a critical role in glioma growth. Factors regulating the apoptosis process are to be further understood. This study aims to investigate the role of protease activated receptor-2 (PAR2) in regulation the apoptosis process in glioma cells.

Results

The results showed that U87 cells and human glioma tissue expressed PAR2. Exposure to tryptase, or the PAR2 active peptide, increased STAT3 phosphorylation in the radiated U87 cells, reduced U87 cell apoptosis, suppressed the expression of p53 in U87 cells.

Conclusions

Activation of PAR2 can reduce the radiated U87 cell apoptosis via modulating the expression of p53. The results implicate that PAR2 may be a novel therapeutic target in the treatment of glioma.

Inverse regulation of melanoma growth and migration by Orai1/STIM2-dependent calcium entry

Spontaneous melanoma phenotype switching is controlled by unknown environmental factors and may determine melanoma outcome and responsiveness to anticancer therapy. We show that Orai1 and STIM2 are highly expressed and control store-operated Ca(2+) entry in human melanoma. Lower extracellular Ca(2+) or silencing of Orai1/STIM2 caused a decrease in intracellular Ca(2+) , which correlated with enhanced proliferation and increased expression of microphthalmia-associated transcription factor, a marker for proliferative melanoma phenotype. In contrast, the invasive and migratory potential of melanoma cells was reduced upon silencing of Orai1 and/or STIM2. Accordingly, markers for a non-proliferative, tumor-maintaining phenotype such as JARID1B and Brn2 decreased. Immunohistochemical staining of primary melanomas and lymph node metastases revealed a heterogeneous distribution of Orai1 and STIM2 with elevated expression in the invasive rim of the tumor. In summary, our results support a dynamic model in which Orai1 and STIM2 inversely control melanoma growth and invasion. Pharmacological tuning of Orai1 and particularly STIM2 might thus prevent metastatic spread and render melanomas more susceptible to conventional therapy.

The neglected CRAC proteins: Orai2, Orai3, and STIM2

Plasma-membrane-localized Orai1 ion channel subunits interacting with ER-localized STIM1 molecules comprise the major subunit composition responsible for calcium release-activated calcium channels. STIM1 "translates" the Ca(2+) store content into Orai1 activity, making it a store-operated channel. Surprisingly, in addition to being the physical activator, STIM1 also modulates Orai1 properties, including its inactivation and permeation (see Chapter 1). STIM1 is thus more than a pure Orai1 activator. Within the past 7 years following the discovery of STIM and Orai proteins, the molecular mechanisms of STIM1/Orai1 activity and their functional importance have been studied in great detail. Much less is currently known about the other isoforms STIM2, Orai2, and Orai3. In this chapter, we summarize the current knowledge about STIM2, Orai2, and Orai3 properties and function. Are these homologues mainly modulators of predominantly STIM1/Orai1-mediated complexes or do store-dependent or -independent functions such as regulation of basal Ca(2+) concentration and activation of Orai3-containing complexes by arachidonic acid or by estrogen receptors point toward their "true" physiological function? Is Orai2 the Orai1 of neurons? A major focus of the review is on the functional relevance of STIM2, Orai2, and Orai3, some of which still remains speculative.

Protein kinase C-dependent activation of CaV1.2 channels selectively controls human TH2-lymphocyte functions

BACKGROUND

In addition to calcium release-activated calcium channel/ORAI calcium channels, the role of voltage-gated calcium (Cav1) channels in T-cell calcium signaling is emerging. Cav1 channels are formed by α1 (CaV1.1 to CaV1.4) and auxiliary subunits. We previously demonstrated that mouse TH2 cells selectively overexpressed CaV1.2 and CaV1.3 channels. Knocking down these channels with Cav1 antisense (AS) oligonucleotides inhibited TH2 functions and experimental asthma.

OBJECTIVE

We investigated the expression profile and role of Cav1 channels in human T-cell subsets, with a focus on TH2 cells.

METHODS

We compared the profile of CaV1 channel subunit expression in T-cell subsets isolated ex vivo from the blood of healthy donors, as well as in vitro-polarized T-cell subsets, and tested the effect of the Cav1 inhibitors nicardipine and Cav1.2AS on their functions.

RESULTS

CaV1.4 expression was detectable in CD4(+) T cells, ex vivo TH1 cells, and TH17 cells, whereas Cav1.2 channels predominated in TH2 cells only. T-cell activation resulted in Cav1.4 downregulation, whereas Cav1.2 expression was selectively maintained in polarized TH2 cells and absent in TH1 or TH9 cells. Nicardipine and CaV1.2AS decreased Ca(2+) and cytokine responses in TH2, but not TH1, cells. Protein kinase C (PKC) α/β inhibition decreased Ca(2+) and cytokine responses, whereas both calcium and cytokine responses induced by PKC activation were inhibited by nicardipine or Cav1.2AS in TH2 cells.

CONCLUSION

This study highlights the selective expression of Cav1.2 channels in human TH2 cells and the role of PKC-dependent Cav1.2 channel activation in TH2 cell function. Blocking PKC or Cav1.2 channel activation in TH2 cells might represent new strategies to treat allergic diseases in human subjects.

CRAC channel inhibition produces greater anti-inflammatory effects than glucocorticoids in CD8 cells from COPD patients

There are increased numbers of pulmonary CD8 lymphocytes in COPD (chronic obstructive pulmonary disease). CRAC (calcium release-activation calcium) channels play a central role in lymphocyte activation though the regulation of the transcription factor NFAT (nuclear factor of activated T-cells). We studied the expression of NFAT in lungs from COPD patients compared with controls, and evaluated the effects of CRAC channel inhibition compared with corticosteroids on NFAT activation and cytokine production in CD8 cells from COPD patients. The effects of the corticosteroid dexamethasone, the calcineurin inhibitor cyclosporin and the CRAC channel inhibitor Synta 66 were studied on cytokine production and NFAT activation using peripheral blood and isolated pulmonary CD8 cells. NFAT1 and CD8 co-expression in the lungs was compared in COPD patients and controls using combined immunohistochemistry and immunofluorescence. NFAT inhibition with either cyclosporin or Synta 66 resulted in significantly greater maximal inhibition of cytokines than dexamethasone in both peripheral blood and pulmonary CD8 cells [e.g. >95% inhibition of IFNγ (interferon γ) production from pulmonary CD8 cells using cyclosporin and Synta 66 compared with <50% using dexamethasone]. The absolute number of pulmonary CD8 cells co-expressing NFAT1 was significantly raised in lungs from COPD patients compared with controls, but the percentage of CD8 cells co-expressing NFAT1 was similar between COPD patients and controls (80.7% compared with 78.5% respectively, P=0.3). Inhibition of NFAT using the CRAC channel Synta 66 produces greater anti-inflammatory effects on CD8 cells from COPD patients than corticosteroids. NFAT is expressed at a high level in pulmonary CD8 cells in COPD.

How ORAI and TRP channels interfere with each other: interaction models and examples from the immune system and the skin

Four types of Ca(2+) selective ion channels are known, ten voltage gated Ca(2+) (CaV) channels, four CatSper channels, three store operated CRAC channels (ORAI channels) and at least two members of the TRPV subfamily (TRPV5, TRPV6). Some of the other TRP channels also show some Ca(2+) selectivity like certain splice variants of TRPM3. In addition to Ca(2+) selective channels, various cation channels play an important role for Ca(2+) entry and furthermore, they may also regulate Ca(2+) entry through other channels by modulating the membrane potential or other means as outlined in this review. Of the different types of cation channels, TRP channels form one of the most prominent families of non-selective cation channels with functional relevance in electrically non-excitable and electrically excitable cell types. Among these, the seven channels of the TRPC subfamily are rather non-selective with very modest Ca(2+) selectivity, whereas in the other subfamilies, cation selectivity ranges from monovalent selectivity (i.e. TRPM4, TRPM5) to divalent selectivity (i.e. TRPM6, TRPM7) or Ca(2+) selectivity (i.e. TRPV5, TRPV6). Rather than discussing the heavily reviewed individual functions of ORAI or TRP channels, we summarize data and present models how TRP and ORAI may functionally interact to guide cellular functions. We focus on T lymphocytes representing a more ORAI-dominated tissue and skin as model system in which both ORAI and TRP channel have been reported to control relevant functions. We present several interaction models how ORAI and TRP may interfere with each other's function.

Barcoding T cell calcium response diversity with methods for automated and accurate analysis of cell signals (MAAACS)

We introduce a series of experimental procedures enabling sensitive calcium monitoring in T cell populations by confocal video-microscopy. Tracking and post-acquisition analysis was performed using Methods for Automated and Accurate Analysis of Cell Signals (MAAACS), a fully customized program that associates a high throughput tracking algorithm, an intuitive reconnection routine and a statistical platform to provide, at a glance, the calcium barcode of a population of individual T-cells. Combined with a sensitive calcium probe, this method allowed us to unravel the heterogeneity in shape and intensity of the calcium response in T cell populations and especially in naive T cells, which display intracellular calcium oscillations upon stimulation by antigen presenting cells.

The adaptive immune response to pathogen invasion requires the stimulation of lymphocytes by antigen-presenting cells. We hypothesized that investigating the dynamics of the T lymphocyte activation by monitoring intracellular calcium fluctuations might help explain the high specificity and selectivity of this phenomenon. However, the quantitative and exhaustive analysis of calcium fluctuations by video microscopy in the context of cell-to-cell contact is a tough challenge. To tackle this, we developed a complete solution named MAAACS (Methods for Automated and Accurate Analysis of Cell Signals), in order to automate the detection, cell tracking, raw data ordering and analysis of calcium signals. Our algorithm revealed that, when in contact with antigen-presenting cells, T lymphocytes generate oscillating calcium signals and not a massive and sustained calcium response as was originally thought. We anticipate our approach providing many more new insights into the molecular mechanisms triggering adaptive immunity.

TGFβ1 and SGK1-sensitive store-operated Ca2+ entry and Orai1 expression in endometrial Ishikawa cells

The serum-and-glucocorticoid-inducible-kinase-1 (SGK1) is ubiquitously expressed and under genomic control by cell stress, hormones and further mediators. A most powerful stimulator of SGK1 expression is transforming growth factor TGFβ1. SGK1 is activated by insulin and growth factors via phosphatidylinositol-3-kinase and the 3-phosphoinositide-dependent kinase PDK1. As shown recently, SGK1 increases the store-operated Ca(2+) entry (SOCE), which is accomplished by the pore-forming ion channel unit Orai. Most recent observations further revealed that SGK1 plays a critical role in the regulation of fertility. SGK1 is up-regulated in the luminal epithelium of women with unexplained infertility but down-regulated in decidualizing stromal cells of patients with recurrent pregnancy loss. The present study explored whether Orai1 is expressed in endometrium and sensitive to regulation by SGK1 and/or TGFβ1. To this end, Orai1 protein abundance was determined by western blotting and SOCE by fura-2 fluorescence. As a result, Orai1 was expressed in human endometrium and in human endometrial Ishikawa cells. Orai1 expression and SOCE in Ishikawa cells were increased by transfection with constitutively active (S422D)SGK1 but not by transfection with inactive (K127N)SGK1. The difference of SOCE between (S422D)SGK1 and (K127N)SGK1-transfected cells was virtually abrogated in the presence of Orai1 inhibitor 2-aminoethoxydiphenyl borate (2-APB, 50 µM). Similar to (S422D)SGK1 transfection TGFβ1 treatment up-regulated both Orai1 protein abundance and SOCE. In conclusion, Orai1 is expressed in the human endometrium and is up-regulated by SGK1 and TGFβ1. The present observations thus uncover a novel element in SGK1-sensitive regulation of endometrial cells.

Orai1-NFAT signalling pathway triggered by T cell receptor stimulation

T cell receptor (TCR) stimulation plays a crucial role in development, homeostasis, proliferation, cell death, cytokine production, and differentiation of T cells. Thus, in depth understanding of TCR signalling is crucial for development of therapy targeting inflammatory diseases, improvement of vaccination efficiency, and cancer therapy utilizing T cell-based strategies. TCR activation turns on various signalling pathways, one of the important one being the Ca(2+)-calcineurin-nuclear factor of activated T cells (NFAT) signalling pathway. Stimulation of TCRs triggers depletion of intracellular Ca(2+) store and in turn, initiates store-operated Ca(2+) entry (SOCE), one of the major mechanisms to raise the intracellular Ca(2+) concentrations in T cells. Ca(2+)-release-activated-Ca(2+) (CRAC) channels are a prototype of store-operated Ca(2+) (SOC) channels in immune cells that are very well characterized. Recent identification of STIM1 as the endoplasmic reticulum (ER) Ca(2+) sensor and Orai1 as the pore subunit has dramatically advanced the understanding of CRAC channels and provides a molecular tool to investigate the physiological outcomes of Ca(2+) signalling during immune responses. In this review, we focus on our current understanding of CRAC channel activation, regulation, and downstream calcineurin-NFAT signaling pathway.

The ER Ca²⁺ sensor STIM1 regulates actomyosin contractility of migratory cells

Stromal interaction molecule 1 (STIM1) is an endoplasmic reticulum (ER) Ca(2+) sensor that triggers the store-operated Ca(2+) entry (SOCE). The clinical relevance of STIM1 has been highlighted in breast and cervical cancer, but the molecular mechanism by which STIM1 promotes cancer progression remains unclear. This study explores the regulatory mechanisms by which STIM1-dependent Ca(2+) signaling controls cancer cell migration. Three different SOCE inhibitors, SKF96365, 2-APB and YM-58483, significantly inhibited cervical cancer cell migration to a similar extent to that of STIM1 silencing. In contrast, STIM1 overexpression significantly enhanced cervical cancer cell migration. Live cell confocal images and three-dimensional tomograms showed that STIM1 formed aggregates and translocated towards the plasma membranes of migratory cells, and this was accompanied by increasing cytosolic Ca(2+) spikes. STIM1 silencing also inhibited the recruitment and association of active focal adhesion kinase (pTyr397-FAK) and talin at focal adhesions, indicating the blockade of force transduction from integrin signaling. Epidermal growth factor-induced phosphorylation of myosin II regulatory light chains was abolished by STIM1 knockdown and SOCE inhibition. Dual immunostaining of activated myosin II (pSer19-MLC) and actin revealed that actomyosin formation depended on STIM1-mediated Ca(2+) entry. Most importantly, STIM1 expression levels as well as SOCE activity controlled the generation of cell contractile force, as measured by the microfabricated post-array-detector system. These results highlight the unique role of STIM1-dependent Ca(2+) signaling in controlling cell migration by the regulation of actomyosin reorganization in conjunction with enhanced contractile forces.

Mutations of the Ca2+-sensing stromal interaction molecule STIM1 regulate Ca2+ influx by altered oligomerization of STIM1 and by destabilization of the Ca2+ channel Orai1

A drop of endoplasmic reticulum Ca(2+) concentration triggers its Ca(2+) ssensor protein stromal interaction molecule 1 (STIM1) to oligomerize and accumulate within endoplasmic reticulum-plasma membrane junctions where it activates Orai1 channels, providing store-operated Ca(2+) entry. To elucidate the functional significance of N-glycosylation sites of STIM1, we created different mutations of asparagine-131 and asparagine-171. STIM1 NN/DQ resulted in a strong gain of function. Patch clamp, Total Internal Reflection Fluorescent (TIRF) microscopy, and fluorescence recovery after photobleaching (FRAP) analyses revealed that expression of STIM1 DQ mutants increases the number of active Orai1 channels and the rate of STIM1 translocation to endoplasmic reticulum-plasma membrane junctions with a decrease in current latency. Surprisingly, co-expression of STIM1 DQ decreased Orai1 protein, altering the STIM1:Orai1 stoichiometry. We describe a novel mathematical tool to delineate the effects of altered STIM1 or Orai1 diffusion parameters from stoichiometrical changes. The mutant uncovers a novel mechanism whereby "superactive" STIM1 DQ leads to altered oligomerization rate constants and to degradation of Orai1 with a change in stoichiometry of activator (STIM1) to effector (Orai1) ratio leading to altered Ca(2+) homeostasis.

Calcium, cancer and killing: the role of calcium in killing cancer cells by cytotoxic T lymphocytes and natural killer cells

Killing cancer cells by cytotoxic T lymphocytes (CTL) and by natural killer (NK) cells is of vital importance. Cancer cell proliferation and apoptosis depend on the intracellular Ca(2+) concentration, and the expression of numerous ion channels with the ability to control intracellular Ca(2+) concentrations has been correlated with cancer. A rise of intracellular Ca(2+) concentrations is also required for efficient CTL and NK cell function and thus for killing their targets, in this case cancer cells. Here, we review the data on Ca(2+)-dependent killing of cancer cells by CTL and NK cells. In addition, we discuss emerging ideas and present a model how Ca(2+) may be used by CTL and NK cells to optimize their cancer cell killing efficiency. This article is part of a Special Issue entitled: 12th European Symposium on Calcium.

Hypocalcaemia, alcohol drinking and viroimmune responses in ART recipients

Metabolic perturbations associated with HIV and antiretroviral therapies are widespread. Unfortunately, research has predominantly focused in cardiometabolic problems, neglecting other important areas. In fact, the immune-calcium-skeletal interface has been understudied despite its potential relevance in people living with HIV (PLWH). Using a case-control methodology, 200 PLWH receiving medical care were enrolled and stratified according to hazardous vs. non-hazardous alcohol intake (HAU vs. non-HAU) and calcium (Ca) levels by analyzing baseline data. The group was chosen to represent relatively "pure" HAU with minimal drug use and no psychiatric diagnoses. With these narrow parameters in place, we found evidence that HAU significantly increases TNF-α levels compared to Non-HAU (2.8 ± 0.6 vs. 1.9 ± 0.3 pg/ml, p = 0.05) and decreases blood Ca levels (9 ± 0.6 vs. 9.4 ± 0.5, p = 0.03). Our analyses also suggest that chronic inflammation, as indicated by increased TNF-α levels, is associated with hypocalcemia (hypoCa <8.6). Despite the limited prevalence of hypoCa, these findings are clinically significant given that hypoCA PLWH exhibited decreased CD4 (253 ± 224 vs. 417.7 ± 281, p = 0.02), B cells (147 ± 58 vs. 248 ± 151, p = 0.03) and NK cells (146.8 ± 90 vs. 229 ± 148, p = 0.008) and elevated CD8 (902.5 ± 438 vs. 699 ± 510, p = 0.09) compared to those with normal calcium. Furthermore, calcium effects on viral load were also evident with hypoCA exhibiting the highest loads (140,187 ± 111 vs. 35,622 ± 7770 HIV copies, p = 0.01). Multivariate analyses confirmed the significance of hypoCa in predicting viroimmune parameters. This paper provides the first evidence that hypoCa accounts for some of the variation in viroimmune measures in HAART recipients and suggests that hypoCa may be mediating alcohol's deleterious effects.