Inhibition Of Store-operated Calcium Entry Research Articles

ELD607 specifically traffics Orai1 to the lysosome leading to inhibition of store operated calcium entry

Orai1 is a plasma membrane Ca2+ channel involved in store operated calcium entry (SOCE). SOCE can regulate cell growth, exocytosis, gene expression and inflammation. We previously found that short palate lung and nasal epithelial clone 1′s (SPLUNC1) sixth α-helix (α6) bound Orai1 to inhibit SOCE. SPLUNC1 was not proteolytically stable, so we developed ELD607, an 11 amino acid peptide based on SPLUNC1’s α6 region which was more stable and more potent than SPLUNC1/α6. Here, we studied ELD607’s mechanism of action. We overexpressed either Orai1-HA or Orai1-YFP in HEK293T cells to probe ELD607-Orai1 interactions by confocal microscopy. We also measured changes in Fluo-4 fluorescence in a multiplate reader as a marker of cytoplasmic Ca2+ levels. ELD607 internalized Orai1 independently of STIM1. Both 15 min and 3 h exposure to ELD607 similarly depleted Orai1 in the plasma membrane. However, 3 h exposure to ELD607 yielded greater inhibition of SOCE. ELD607 continued to colocalize with Orai1 after internalization and this process was dependent on the presence of the ubiquitin ligase NEDD4.2. Similarly, ELD607 increased the colocalization between Orai1 and ubiquitin. ELD607 also increased the colocalization between Orai1 and Rab5 and 7, but not Rab11, suggesting that Orai1 trafficked through early and late but not recycling endosomes. Finally, ELD607 caused Orai1, but not Orai2, Orai3, or STIM1 to traffic to lysosomes. We conclude that ELD607 rapidly binds to Orai1 and works in an identical fashion as full length SPLUNC1 by internalizing Orai1 and sending it to lysosomes, leading to a decrease in SOCE.

Quercetin and Kaempferol inhibit HMC-1 activation via SOCE/NFATc2 signaling and suppress hippocampal mast cell activation in lipopolysaccharide-induced depressive mice.

Mast cells (MCs), as the fastest immune responders, play a critical role in the progression of neuroinflammation-related diseases, especially in depression. Quercetin (Que) and kaempferol (Kae), as two major diet-derived flavonoids, inhibit MC activation and exhibit significant antidepressant effect due to their anti-inflammatory capacity. The study aimed to explore the mechanisms of inhibitory effect of Que and Kae on MC activation, and whether Que and Kae suppress hippocampal mast cell activation in LPS-induced depressive mice. In vitro assays, human mast cells (HMC-1) were pretreated with Que or Kae for 1h, then stimulated by phorbol 12-myristate 13-acetate (PMA) and 2,5-di-t-butyl-1,4-benzohydroquinone (tBHQ) for 3h or 12h. In vivo assays, Que or Kae was administered by oral gavage once daily for 14days and then lipopolysaccharide (LPS) intraperitoneally injection to induce depressive behaviors. The secretion and expression of TNF-α were determined by ELISA and Western blotting. The nuclear factor of activated T cells (NFAT) transcriptional activity was measured in HMC-1 stably expressing NFAT luciferase reporter gene. Nuclear translocation of NFATc2 was detected by nuclear protein extraction and also was fluorescently detected in HMC-1 stably expressing eGFP-NFATc2. We used Ca2+ imaging to evaluate changes of store-operated calcium entry (SOCE) in HMC-1 stably expressing fluorescent Ca2+ indicator jGCamP7s. Molecular docking was used to assess interaction between the Que or Kae and calcium release-activated calcium modulator (ORAI). The hippocampal mast cell accumulation and activation were detected by toluidine blue staining and immunohistochemistry with β-tryptase. In vitro assays of HMC-1 activated by PtBHQ (PMA and tBHQ), Que and Kae significantly decreased expression and secretion of TNF-α. Moreover, NFAT transcriptional activity and nuclear translocation of NFATc2 were remarkably inhibited by Que and Kae. In addition, the Ca2+ influx mediated by SOCE was suppressed by Que, Kae and the YM58483 (ORAI inhibitor), respectively. Importantly, the combination of YM58483 with Que or Kae had no additive effect on the inhibition of SOCE. The molecular docking also showed that Que and Kae both exhibit high binding affinities with ORAI at the same binding site as YM58483. In vivo assays, Que and Kae significantly reversed LPS-induced depression-like behaviors in mice, and inhibited hippocampal mast cellactivation in LPS-induced depressive mice. Our results indicated that suppression of SOCE/NFATc2 pathway-mediated by ORAI channels may be the mechanism of inhibitory effect of Que and Kae on MC activation, and also suggested Que and Kae may exert the antidepressant effect through suppressing hippocampal mast cell activation.

STIM1 promotes acquired resistance to sorafenib by attenuating ferroptosis in hepatocellular carcinoma

Dysregulated calcium (Ca2+) signaling pathways are associated with tumor cell death and drug resistance. In non-excitable cells, such as hepatocellular carcinoma (HCC) cells, the primary pathway for Ca2+ influx is through stromal interaction molecule 1 (STIM1)-mediated store-operated calcium entry (SOCE). Previous studies have demonstrated the involvement of STIM1-mediated SOCE in processes such as genesis, metastasis, and stem cell self-renewal of HCC. However, it remains unclear whether STIM1-mediated SOCE plays a role in developing acquired resistance to sorafenib in HCC patients. In this study, we established acquired sorafenib-resistant (SR) HCC cell lines by intermittently exposing them to increasing concentrations of sorafenib. Our results showed higher levels of STIM1 and stronger SOCE in SR cells compared with parental cells. Deleting STIM1 significantly enhanced sensitivity to sorafenib in SR cells, while overexpressing STIM1 promoted SR by activating SOCE. Mechanistically, STIM1 increased the transcription of SLC7A11 through the SOCE-CaN-NFAT pathway. Subsequently, up-regulated SLC7A11 increased glutathione synthesis, resulting in ferroptosis insensitivity and SR. Furthermore, combining the SOCE inhibitor SKF96365 with sorafenib significantly improved the sensitivity of SR cells to sorafenib both in vitro and in vivo. These findings suggest a potential strategy to overcome acquired resistance to sorafenib in HCC cells.

Vulnerability of Store-Operated Calcium Entry to Inhibitors and Microenvironment in Cells of Different Breast Cancer Subtypes.

The incidence and development of cancer are highly dependent on pathological disturbances in calcium homeostasis of the cell. One of the major pathways for calcium entry is store-operated calcium entry (SOCE), which functions in virtually all cell types. Changes in the expression level of the main proteins organizing SOCE are observed during the development of various cancer types, particularly breast cancer (BC). This leads to unique SOCE with characteristics individual for each type of BC and requires particular therapeutic approaches. In this study, we tested the sensitivity of SOCE in various BC cells to selective ORAI channel inhibitors and the less selective compounds Leflunomide and Teriflunomide, approved by the FDA for clinical use. We also analyzed the vulnerability of SOCE to the influence of factors typical of the tumor microenvironment: hypoxia and acidification. We have observed that the SOCE inhibitors Leflunomide and Teriflunomide suppress SOCE in the triple-negative BC cell line MDA-MB-231, but not in the luminal A BC cell line MCF-7. MDA-MB-231 cells also demonstrate higher pH dependence of SOCE compared to MCF-7 cells. In addition, the oxygen scavenger sodium dithionide also affects SOCE, stimulating it in MDA-MB-231 cells but inhibiting in MCF-7 cells. Overall, our data highlight the importance of considering the different sensitivities of various BC cell types to inhibitors and to microenvironmental factors such as hypoxia and acidification when developing targeted drugs.

Development of Chemical Tools Based on GSK-7975A to Study Store-Operated Calcium Entry in Cells

Many physiological functions, such as cell differentiation, proliferation, muscle contraction, neurotransmission and fertilisation, are regulated by changes of Ca2+ levels. The major Ca2+ store in cells is the endoplasmic reticulum (ER). Certain cellular processes induce ER store depletion, e.g. by activating IP3 receptors, that in turn induces a store refilling process known as store-operated calcium entry (SOCE). This refilling process entails protein-protein interactions between Ca2+ sensing stromal interaction molecules (STIM) in the ER membrane and Orai proteins in the plasma membrane. Fully assembled STIM/Orai complexes then form highly selective Ca2+ channels called Ca2+ release activated Ca2+ Channels (CRAC) through which Ca2+ ions flow into the cytosol and subsequently are pumped into the ER by the sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA). Abnormal SOCE has been associated with numerous human diseases and cancers, and therefore key players STIM and Orai have attracted significant therapeutic interest. Several potent experimental and clinical candidate compounds have been developed and have helped to study SOCE in various cell types. We have synthesized multiple novel small-molecule probes based on the known SOCE inhibitor GSK-7975A. Here we present GSK-7975A derivatives, which feature photo-caging, photo-crosslinking, biotin and clickable moieties, and also contain deuterium labels. Evaluation of these GSK-7975A probes using a fluorometric imaging plate reader (FLIPR)-Tetra-based Ca2+ imaging assay showed that most synthetic modifications did not have a detrimental impact on the SOCE inhibitory activity. The photo-caged GSK-7975A was also used in patch-clamp electrophysiology experiments. In summary, we have developed a number of active, GSK-7975A-based molecular probes that have interesting properties and therefore are useful experimental tools to study SOCE in various cells and settings.

Homoplantaginin attenuates high glucose-induced vascular endothelial dysfunction via inhibiting store-operated calcium entry channel and endoplasmic reticulum stress.

The activation of store-operated calcium entry (SOCE) channel and endoplasmic reticulum stress (ERS) induced by high glucose (HG) is recognized as a major cause of vascular endothelial dysfunction. This study aims to investigate the protective effect of homoplantaginin (Hom) on HG-induced endothelial dysfunction. HG-induced vascular endothelial dysfunction model in human umbilical vein endothelial cells (HUVECs) and rat-isolated thoracic aortas were established to observe the protective effect of Hom, further evaluated the mechanism of SOCE channel and ERS in the pathogenesis. Hom increased the levels of nitric oxide (NO) and phospho-endothelial nitric oxide synthase (p-eNOS) in HUVECs and isolated rat thoracic aortas in a dose-dependent manner, restored acetylcholine-mediated endothelium-dependent vasodilation. Network pharmacology showed that the pathogenesis of diabetic vascular complications may involve calcium (Ca2+) signal pathway. Hom reduced Ca2+ concentration via blocking SOCE channel in HUVECs, and resisted ERS activation by down-regulating ERS-related proteins expression. Importantly, SKF96365 (SOCE inhibitor) intervention experiment showed that Hom inhibited ERS activation by blocking the SOCE channel, further increased the levels of NO and p-eNOS. Hom could alleviate HG-induced vascular endothelial dysfunction by inhibiting SOCE channel and ERS. This provided a potential pharmacological intervention strategy for the treatment of vascular endothelial dysfunction.

Fine tuning calcium dynamics by inhibition of Store-operated Calcium Entry as a novel therapeutic approach for the treatment of chronic pancreatitis

Chronic pancreatitis (CP) is a complex inflammatory disorder characterized by progressive fibrosis, leading to pancreatic dysfunction, reduced quality of life and an elevated pancreatic cancer risk. Current therapeutic options for CP are restricted to symptomatic treatment. Using ex vivo and in vivo preclinical disease models, Szabó et al. now explored for the first time the involvement of Store-operated Ca2+ entry (SOCE) in the progression of CP and propose that a selective pharmacological inhibition of the SOCE signaling component Orai1 might serve as specific treatment option for CP[1,2].

Store-Operated Calcium Entry Inhibition and Plasma Membrane Calcium Pump Upregulation Contribute to the Maintenance of Resting Cytosolic Calcium Concentration in A1-like Astrocytes.

Highly neurotoxic A1-reactive astrocytes have been associated with several human neurodegenerative diseases. Complement protein C3 expression is strongly upregulated in A1 astrocytes, and this protein has been shown to be a specific biomarker of these astrocytes. Several cytokines released in neurodegenerative diseases have been shown to upregulate the production of amyloid β protein precursor (APP) and neurotoxic amyloid β (Aβ) peptides in reactive astrocytes. Also, aberrant Ca2+ signals have been proposed as a hallmark of astrocyte functional remodeling in Alzheimer's disease mouse models. In this work, we induced the generation of A1-like reactive astrocytes after the co-treatment of U251 human astroglioma cells with a cocktail of the cytokines TNF-α, IL1-α and C1q. These A1-like astrocytes show increased production of APP and Aβ peptides compared to untreated U251 cells. Additionally, A1-like astrocytes show a (75 ± 10)% decrease in the Ca2+ stored in the endoplasmic reticulum (ER), (85 ± 10)% attenuation of Ca2+ entry after complete Ca2+ depletion of the ER, and three-fold upregulation of plasma membrane calcium pump expression, with respect to non-treated Control astrocytes. These altered intracellular Ca2+ dynamics allow A1-like astrocytes to efficiently counterbalance the enhanced release of Ca2+ from the ER, preventing a rise in the resting cytosolic Ca2+ concentration.

MAGT1 Deficiency Dysregulates Platelet Cation Homeostasis and Accelerates Arterial Thrombosis and Ischemic Stroke in Mice.

MAGT1 (magnesium transporter 1) is a subunit of the oligosaccharide protein complex with thiol-disulfide oxidoreductase activity, supporting the process of N-glycosylation. MAGT1 deficiency was detected in human patients with X-linked immunodeficiency with magnesium defect syndrome and congenital disorders of glycosylation, resulting in decreased cation responses in lymphocytes, thereby inhibiting the immune response against viral infections. Curative hematopoietic stem cell transplantation of patients with X-linked immunodeficiency with magnesium defect causes fatal bleeding and thrombotic complications. We studied the role of MAGT1 deficiency in platelet function in relation to arterial thrombosis and hemostasis using several in vitro experimental settings and in vivo models of arterial thrombosis and transient middle cerebral artery occlusion model of ischemic stroke. MAGT1-deficient mice (Magt1-/y) displayed accelerated occlusive arterial thrombus formation in vivo, a shortened bleeding time, and profound brain damage upon focal cerebral ischemia. These defects resulted in increased calcium influx and enhanced second wave mediator release, which further reinforced platelet reactivity and aggregation responses. Supplementation of MgCl2 or pharmacological blockade of TRPC6 (transient receptor potential cation channel, subfamily C, member 6) channels, but not inhibition of store-operated calcium entry, normalized the aggregation responses of Magt1-/y platelets to the control level. GP (glycoprotein) VI activation of Magt1-/y platelets resulted in hyperphosphorylation of Syk (spleen tyrosine kinase), LAT (linker for activation of T cells), and PLC (phospholipase C) γ2, whereas the inhibitory loop regulated by PKC (protein kinase C) was impaired. A hyperaggregation response to the GP VI agonist was confirmed in human platelets isolated from a MAGT1-deficient (X-linked immunodeficiency with magnesium defect) patient. Haploinsufficiency of TRPC6 in Magt1-/y mice could normalize GP VI signaling, platelet aggregation, and thrombus formation in vivo. These results suggest that MAGT1 and TRPC6 are functionally linked. Therefore, deficiency or impaired functionality of MAGT1 could be a potential risk factor for arterial thrombosis and stroke.

STIM1 signals through NFAT1 independently of Orai1 and SOCE to regulate breast cancer cell migration

Store-operated calcium entry (SOCE) contributes to several physiological and pathological conditions including transcription, secretion, immunodeficiencies, and cancer. SOCE has been shown to be important for breast cancer cell migration where knockdown of SOCE components (STIM1 or Orai1) decreases cancer metastasis. Here we show unexpectedly that complete knockout of STIM1 (STIM1-KO) using gene editing in metastatic MDA-MB-231 breast cancer cells results in faster migration and enhanced invasion capacity. In contrast, Orai1-KO cells, which have similar levels of SOCE inhibition as STIM1-KO, migrate slower than the parental cell line. This shows that the enhanced migration phenotype of STIM1-KO cells is not due to the loss of Ca2+ entry through SOCE, rather it involves transcriptional remodeling as elucidated by RNA-seq analyses. Interestingly, NFAT1 is significantly downregulated in STIM1-KO cells and overexpression of NFAT1 reversed the enhanced migration of STIM1-KO cells. STIM1 knockout in other breast cancer cells, independent of their metastatic potential, also enhanced cell migration while reducing NFAT1 expression. These data argue that in breast cancer cells STIM1 modulates NFAT1 expression and cell migration independently of its role in SOCE.

Identifying 2PHDO as a SOCE inhibitor from Chinese herbal extracts.

STIM- and Orai-mediated store operated calcium entry (SOCE) is a ubiquitous Ca2+ signaling process, crucial for the proper function of immune, muscle and neuronal systems. To treat SOCE-related disorder or diseases of these systems, and to mechanistically dissect activation and function of SOCE, specific SOCE inhibitors are needed. However, strategies for developing new SOCE modifiers are still limited. <P/> Methodology: In this study, we identified a novel SOCE inhibitor named 2PHDO from a small pool of Chinese herbal extracts used for treating psoriasis. It could block SOCE and SOCE-mediated NFAT translocation in multiple types of cells with a half inhibitory concentration around 1 µM. At this concentration, 2PHDO was specific for SOCE. Mechanistically, 2PHDO didn't affect the activation of STIM1 or its physical coupling with Orai1. Rather, 2PHDO inhibited SOCE via its actions on Orai1. <P/> Results: 2PHDO may serve as a good template for developing new medicines aiming to treat SOCE related diseases. <P/> Conclusion: Overall, we proved the feasibility of screening and identification of novel SOCE inhibitors from active monomers of Chinese herbal medicine.

Targeting Store-Operated Calcium Entry Regulates the Inflammation-Induced Proliferation and Migration of Breast Cancer Cells.

Persistent challenges complicating the treatment of breast cancer remain, despite some recent undeniable successes. Sufficient evidence currently exists demonstrating the crucial role of inflammation, characterized by the enhanced activation of Toll-like receptor 4 (TLR4) and the COX-2/PGE2 pathway, in the migration and proliferation of breast cancer cells. Interestingly, the store-operated calcium entry (SOCE) pathway was shown to be essential for the TLR4 activity and COX-2 expression in immune cells such as macrophages and microglia. However, whether SOCE influences inflammatory signaling and the inflammation-induced proliferation and migration of breast cancer cells is still unknown. Thus, the current study intended to delineate the role of SOCE in the TLR4-induced inflammation, migration, and proliferation of breast cancer cells. To this end, MDA-MB-231 breast cancer cells were treated with lipopolysaccharide (LPS) to activate TLR4, BTP2 to inhibit SOCE, and Thapsigargin to induce SOCE. Following these treatments, several experiments were conducted to evaluate the proliferation and migration rates of the MDA-MB-231 cells and the expression of several inflammatory and oncogenic genes, including COX-2, PGE2, IL-6, IL-8, and VEGF. Different techniques were used to achieve the aims of this study, including qRT-PCR, Western blotting, ELISA, MTT, and wound healing assays. This study shows that SOCE inhibition using BTP2 suppressed the LPS-induced migration and proliferation of breast cancer cells. Additionally, treatment with LPS caused approximately six- and three-fold increases in COX-2 mRNA and protein expression, respectively, compared to the controls. The LPS-induced elevations in the COX-2 mRNA and protein levels were suppressed by BTP2 to the control levels. In addition to its effect on COX-2, BTP2 also suppressed the LPS-induced productions of PGE2, IL-6, IL-8, and VEGF. Conversely, SOCE induction using Thapsigargin enhanced the LPS-induced inflammation, migration, and proliferation of breast cancer cells. Collectively, these results provide evidence for the potentially important role of SOCE in inflammation-induced breast cancer progression processes. Thus, we argue that the current study may provide novel targets for designing new therapeutic approaches for the treatment of breast cancer.

22. The Role of Orai1 in Osteogenic Differentiation Induced by Nanoparticulate Mineralized Collagen Glycosaminoglycan Materials

PURPOSE: Development of synthetic regenerative materials inspired by the extracellular matrix (ECM) has been a topic of significant interest due to the known properties of the ECM to direct cell fate determination via tunable material composition and biomechanical properties. Nanoparticulate mineralized collagen glycosaminoglycan (MC-GAG) is a low density, open-cell foam that has been evaluated in our laboratory to induce osteogenic differentiation of primary osteoprogenitors in vitro as well as regeneration of rabbit skull defects in vivo without pre-seeding with progenitor cells or addition of exogenous growth factors, which was not observed in non-mineralized collagen glycosaminoglycan (Col-GAG) materials. Given that the critical difference between MC-GAG and Col-GAG is the mineral content, the spatial concentration of inorganic ions on MC-GAG may be critical to its osteogenic properties. This is supported by prior research demonstrating that high calcium concentrations in the bone microenvironment stimulate osteoblastic differentiation. How these biochemical cues are transmitted to cells and activate downstream osteogenic signaling pathways should be further elucidated. Orai1 is a critical subunit of store-operated calcium release-activated calcium channels (CRAC) that has been implicated to be involved in bone homeostasis. In this work, we evaluated the contribution of Orai1 to MC-GAG-mediated osteogenesis. METHODS: To examine the role of extracellular calcium signaling through store-operated calcium channels, such as Orai1, on osteogenic differentiation of primary bone marrow-derived human mesenchymal stem cells (hMSCs), we treated 2D cell cultures with a small molecule inhibitor of store-operated calcium entry (SOCE), MRS1845, for 14 days. hMSCs were subsequently seeded on MC-GAG or Col-GAG for 7 days with or without MRS1845. Baseline Orai1 gene and protein expression was evaluated. Next, small interfering RNAs (siRNAs) targeting ORAI1 and a scrambled control were used to specifically knockdown ORAI1 expression in hMSCs cultured on Col-GAG and MC-GAG. Osteogenic gene and protein expression were measured using quantitative RT-PCR and western blot analyses, respectively. Mineralization was evaluated by Alizarin Red staining. RESULTS: To understand whether store-operated calcium entry was essential to osteogenic differentiation, we treated hMSCs in 2D cultures with a small molecule inhibitor of SOCE, MRS1845, and found a reduction in calcium depositions visualized with Alizarin Red staining when compared to untreated hMSCs. In 3D cultures, MRS1845 downregulated the gene expression of early osteogenic marker ALP and protein expression of the intracellular osteogenic mediator Runx2 specifically on MC-GAG compared to controls. As small molecule inhibitors lack channel specificity, we knocked down ORAI1 expression through siRNA transfection. When MC-GAG was compared with Col-GAG, baseline ORAI1 gene expression was 1.8-fold higher (p=0.02) and Orai1 protein expression was upregulated (p=0.003). ORAI1 knockdown reduced the protein expression of Runx2 and gene expression of late osteogenic marker BSP2 specifically on MC-GAG compared to scrambled control siRNA. Mineralization significantly diminished on MC-GAG with ORAI1 knockdown, whereas no effects were evident on Col-GAG as demonstrated by Alizarin Red staining. CONCLUSIONS: ORAI1-mediated calcium ion signaling was required for MC-GAG-induced osteogenic differentiation. Further elucidation of the osteogenic mechanisms and refinement of calcium levels on MC-GAG may facilitate its clinical application in the reconstruction of osseous defects.

Store-operated calcium entry inhibition ameliorates Ang II induced podocyte apoptosis and mitochondria respiratory dysfunction

Purpose and hypothesis: Podocyte injury induced by Angiotensin II (Ang II) is the key factor contributing to proteinuria and glomerulopathy in many kidney diseases including diabetic nephropathy and hypertensive kidney disease. Recent studies suggest that mitochondria dysfunction mediates Ang II-induced podocyte injury. However, the mechanism for Ang II-induced podocyte mitochondria damage is poorly understood. Store-operated Ca2+ entry (SOCE) has multiple functions in both excitable and non-excitable cells. Ang II can activate SOCE by releasing endoplasmic reticulum Ca2+ through generation of IP3. In addition, Ang II also activates Transient Receptor Potential Conventional Member 6 (TRPC6) channel through diacylglycerol (DAG). Our previous study demonstrated that enhanced SOCE mediated high glucose-induced podocyte cytoskeleton remodeling. However, the role of SOCE in podocyte injury by Ang II is not clear. The present study was carried out to test the hypothesis that enhanced SOCE contributed to Ang II-induced podocyte apoptosis and mitochondria respiration dysfunction. Methods: All experiments were carried out using cultured immortalized human podocytes. BTP2 (4 μM) was used to inhibit SOCE. SAR 7334 (100 nM) was used to block TRPC6 channel. Podocyte apoptosis was determined by flow cytometry using Annexin V/Propidium iodide (PI) staining. The conventional whole-cell patch-clamp was performed to measure store-operated Ca2+ channel (SOC) currents. Mitochondrial respiration function and mitochondria ATP production were evaluated by oxygen consumption rate (OCR) using seahorse analysis. Results: Ang II (1 μM) evoked inward currents, which were significantly blunted by BTP2 (10 μM), an SOC channel blocker. Ang II (1 μM) treatments for 24 hours significantly increased podocyte apoptosis and reduced podocyte basal OCR, maximal OCR, spare capacity and mitochondria ATP production. All these responses were significantly blunted by BTP2. However, Ang II treatment for 30 min did not induce a significant response of OCR, but significantly reduced maximal respiration and spare capacity. These responses were also significantly inhibited by BTP2 (10 μM), but not by SAR 7334 (100 nM). Conclusion: SOCE contributed to Ang II-induced podocyte apoptosis and mitochondria respiratory dysfunction. Translational Project Award from American Heart Association (20TPA35500045, to RM); National Institute of Diabetes and Digestive and Kidney Disease (DK115424-01, to RM); Predoctoral Fellowship from American Heart Association (903925, to YT). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Reduction of TRPC1/TRPC3 mediated Ca2+-signaling protects oxidative stress-induced COPD

Oxidative stress is a predisposing factor in Chronic Obstructive Pulmonary Disease (COPD). Specifically, pulmonary epithelial (PE) cells reduce antioxidant capacity during COPD because of the continuous production of reactive oxygen species (ROS). However, the molecular pathogenesis that governs such ROS activity is unclear. Here we show that the dysregulation of intracellular calcium concentration ([Ca2+]i) in PE cells from COPD patients, compared to the healthy PE cells, is associated with the robust functional expressions of Transient Receptor Potential Canonical (TRPC)1 and TRPC3 channels, and Ca2+ entry (SOCE) components, Stromal Interaction Molecule 1 (STIM1) and ORAI1 channels. Additionally, the elevated expression levels of fibrotic, inflammatory, oxidative, and apoptotic markers in cells from COPD patients suggest detrimental pathway activation, thereby reducing the ability of lung remodeling. To further delineate the mechanism, we used human lung epithelial cell line, A549, since the behavior of SOCE and the expression patterns of TRPC1/C3, STIM1, and ORAI1 were much like PE cells. Notably, the knockdown of TRPC1/C3 in A549 cells substantially reduced the SOCE-induced [Ca2+]i rise, and reversed the ROS-mediated oxidative, fibrotic, inflammatory, and apoptotic responses, thus confirming the role of TRPC1/C3 in SOCE driven COPD-like condition. Higher TRPC1/C3, STIM1, and ORAI1 expressions, along with a greater Ca2+ entry, via SOCE in ROS-induced A549 cells, led to the rise in oxidative, fibrotic, inflammatory, and apoptotic gene expression, specifically through the extracellular signal-regulated kinase (ERK) pathway. Abatement of TRPC1 and/or TRPC3 reduced the mobilization of [Ca2+]i and reversed apoptotic gene expression and ERK activation, signifying the involvement of TRPC1/C3. Together these data suggest that TRPC1/C3 and SOCE facilitate the COPD condition through ROS-mediated cell death, thus implicating their likely roles as potential therapeutic targets for COPD. SummaryAlterations in Ca2+ signaling modalities in normal pulmonary epithelial cells exhibit COPD through oxidative stress and cellular injury, compromising repair, which was alleviated through inhibition of store-operated calcium entry. Subject areaCalcium, ROS, Cellular signaling, lung disease.

Pregnancy-Specific Glycoprotein 9 Enhances Store-Operated Calcium Entry and Nitric Oxide Release in Human Umbilical Vein Endothelial Cells

We explored changes in pregnancy-specific glycoprotein 9 (PSG9) levels in the serum of patients with preeclampsia and the effects and underlying mechanisms of PSG9 effects on calcium (Ca2+) homeostasis and nitric oxide (NO) release in human umbilical vein endothelial cells (HUVECs). Western blotting was used to detect protein expression levels, and an NO fluorescence probe was used to examine NO production. Intracellular Ca2+ concentrations were measured using a Ca2+-sensitive fluorescent dye under a fluorescence microscope. Compared with those in healthy pregnant women, serum PSG9 levels were significantly decreased in patients with preeclampsia. PSG9 (0.1 μg/mL) treatment of HUVECs significantly enhanced the expression levels of store-operated calcium entry (SOCE) channel proteins Orai1 and Orai2, but not Orai3, and of endothelial nitric oxide synthase (eNOS) and NO production. Pretreatment with an inhibitor of SOCE (BTP2) abolished PSG9-enhanced Orai1, Orai2, and eNOS expression levels and NO production in HUVECs. The mechanisms underlying SOCE that were PSG9 enhanced in HUVECs appear to involve the Ca2+/eNOS/NO signaling pathway. These findings suggest that serum PSG9 levels may be a potential biomarker for monitoring the occurrence or development of preeclampsia in pregnancy and that PSG9 may be a potential therapeutic target for the treatment of preeclampsia.

Blockade of store-operated calcium entry sensitizes breast cancer cells to cisplatin therapy via modulating inflammatory response

Store-operated calcium entry (SOCE) is an important pathway for calcium signaling that regulates calcium influx across the plasma membrane upon the depletion of calcium stores in the endoplasmic reticulum. SOCE participates in regulating a number of physiological processes including cell proliferation and migration while SOCE dysregulation has been linked with pathophysiological conditions such as inflammation and cancer. The crosslink between cancer and inflammation has been well-established where abundant evidence demonstrate that inflammation plays a role in cancer pathophysiology and the response of cancer cells to chemotherapeutic agents including cisplatin. Indeed, the efficacy of cisplatin against cancer cells is reduced by inflammation. Interestingly, it was shown that SOCE enhances inflammatory signaling in immune cells. Therefore, the main objectives of this study are to examine the impact of SOCE inhibition on the cisplatin sensitivity of breast cancer cells and to explore its related mechanism in modulating the inflammatory response in breast cancer cells. Our findings showed that SOCE inhibitor (BTP2) enhanced cisplatin cytotoxicity against resistant breast cancer cells via inhibition of cell proliferation and migration as well as induction of apoptosis. We also found an upregulation in the gene expression of two major components of SOCE, STIM1 and ORAI1, in cisplatin-resistant breast cancer cells compared to cisplatin-sensitive breast cancer cells. In addition, cisplatin treatment increased the gene expression of STIM1 and ORAI1 in cisplatin-resistant breast cancer cells. Finally, this study also demonstrated that cisplatin therapy caused an increase in the gene expression of inflammatory mediators COX2, IL-8, and TNF-α as well as COX2 protein and upon SOCE inhibition using BTP2, the effect of cisplatin on the inflammatory mediators was reversed. Altogether, this study has proven the pivotal role of SOCE in cisplatin resistance of breast cancer cells and showed the importance of targeting this pathway in improving breast cancer therapy.

Pharmacological inhibitors of the cystic fibrosis transmembrane conductance regulator exert off-target effects on epithelial cation channels

The cystic fibrosis transmembrane conductance regulator (CFTR) anion channel and the epithelial Na+ channel (ENaC) play essential roles in transepithelial ion and fluid transport in numerous epithelial tissues. Inhibitors of both channels have been important tools for defining their physiological role in vitro. However, two commonly used CFTR inhibitors, CFTRinh-172 and GlyH-101, also inhibit non-CFTR anion channels, indicating they are not CFTR specific. However, the potential off-target effects of these inhibitors on epithelial cation channels has to date not been addressed. Here, we show that both CFTR blockers, at concentrations routinely employed by many researchers, caused a significant inhibition of store-operated calcium entry (SOCE) that was time-dependent, poorly reversible and independent of CFTR. Patch clamp experiments showed that both CFTRinh-172 and GlyH-101 caused a significant block of Orai1-mediated whole cell currents, establishing that they likely reduce SOCE via modulation of this Ca2+ release-activated Ca2+ (CRAC) channel. In addition to off-target effects on calcium channels, both inhibitors significantly reduced human αβγ-ENaC-mediated currents after heterologous expression in Xenopus oocytes, but had differential effects on δβγ-ENaC function. Molecular docking identified two putative binding sites in the extracellular domain of ENaC for both CFTR blockers. Together, our results indicate that caution is needed when using these two CFTR inhibitors to dissect the role of CFTR, and potentially ENaC, in physiological processes.

Dithiadiazole derivative 3-(4-nitrophenyl)-5-phenyl-3H-1,2,3,4-dithiadiazole-2-oxide – Novel modulator of store-operated calcium entry

Pathological calcium homeostasis accompanies the development of a large number of different diseases, therefore, the search for new modulators of calcium signaling remains highly actual. Last decades store-operated calcium channels have been repeatedly postulated as a therapeutic target, so the compounds acting on them can be considered promising drug prototypes. Here, we tested several derivatives of 1,2,3,4-dithiadiazole, 1,3-thiazine, pyrazolopyrimidine and thiohydrazides for the ability to affect the thapsigargin-induced calcium response. Using calcium imaging and the patch-clamp technique we found that dithiadiazole derivative3-(4-nitrophenyl)-5-phenyl-3H-1,2,3,4-dithiadiazole-2-oxidehad a strong inhibitory effect on store-operated calcium entry at the micromolar concentration in HEK293 cells. Moreover, incubation of the cells with this compound also resulted in the decrease of ER calcium content. Thus, we have postulated 3-(4-nitrophenyl)-5-phenyl-3H-1,2,3,4-dithiadiazole-2-oxide as a novel inhibitor of store-operated calcium entry and suggested the derivatives of 1,2,3,4-dithiadiazole as a prospective class of compounds for searching new calcium modulators.

STIM1-Orai1 interaction mediated calcium influx activation contributes to cardiac contractility of insulin-resistant rats

PurposeMetabolic syndrome (MetS) became a tremendous public health burden in the last decades. Store-operated calcium entry (SOCE) is a unique mechanism that causes a calcium influx, which is triggered by calcium store depletion. MetS-induced alterations in cardiac calcium signaling, especially in SOCE are still unclear. Therefore, we aim to examine the possible role of SOCE and its components (STIM1 and Orai1) in the MetS-induced cardiac remodeling.MethodsWe used male, adult (12 weeks) Wistar albino rats (n = 20). Animals were randomly divided into two groups which were: control (C) and MetS. We gave 33% sucrose solution to animals instead of water for 24 weeks to establish MetS model. In the end, papillary muscle function was evaluated, and various electrophysiological analyses were made in isolated cardiomyocytes. Additionally, STIM1 and Orai1 protein and mRNA expressions were analyzed.ResultsWe observed a deterioration in contractility in MetS animals and demonstrated the contribution of SOCE by applying a SOCE inhibitor (BTP2). Calcium spark frequency was increased while its amplitude was decreasing in MetS hearts, which was reversed after SOCE inhibition. The amplitude of transient calcium changes in the MetS group was decreased, and it decreased further BTP2 application. Both protein and mRNA levels of STIM1 and Orai1 were increased significantly in MetS hearts.ConclusionCurrent data indicate the significant contribution of SOCE to cardiac calcium handling in the MetS model. We think MetS-induced SOCE activation is a compensation mechanism that is required for the continuum of proper cardiac functioning, although the activation can also cause cardiac hypertrophy.