Project description:T cell activation following antigen binding to the T cell receptor (TCR) involves the mobilization of intracellular calcium (Ca2+) to activate the key transcription factors NFAT and NF-κB. The mechanism of NFAT activation by Ca2+ has been determined; however, the role of Ca2+ in controlling NF-κB signaling is poorly understood and the source of Ca2+ required for NF-κB activation is unknown. We demonstrate that TCR- but not TNF- induced NF-κB signaling upstream of IκB kinase (IKK) activation absolutely requires the influx of extracellular Ca2+ via STIM1-dependent CRAC/Orai channels. We further show that Ca2+ influx controls phosphorylation of the NF-κB protein p65 on Ser536 and that this post- translational modification controls its nuclear localization and transcriptional activation. Notably our data reveal that this role for Ca2+ is entirely separate from its upstream control of IκBα degradation, thereby identifying a novel Ca2+- dependent distal step in TCR-induced NF-κB activation. Finally, we demonstrate that this control of distal signaling occurs via Ca2+-dependent PKCk-mediated phosphorylation of p65. Thus, we establish the source of Ca2+ required for TCR induced NF-kB activation and we define a new distal Ca2+-dependent checkpoint in TCR-induced NF-kB signaling that has broad implications for the control of immune cell development and T cell functional specificity. 3 treatments were analyzed, with biological replicates for each treatment. In addition, three timepoints (1 hour, 4 hour, and 8 hour) were examined for each treatment, as well as an untreated control. In total 19 samples were analyzed
Project description:Calcium signals are initiated in immune cells by the process of store-operated calcium entry (SOCE), where receptor activation triggers transient calcium release from the endoplasmic reticulum, followed by opening of plasma membrane calcium-release activated calcium (CRAC) channels. ORAI1, ORAI2 and ORAI3 are known to comprise the CRAC channel, however the contributions of individual isoforms to neutrophil function is not well understood. Here we show that loss of ORAI1 partially decreases calcium influx while loss of both ORAI1 and ORAI2 completely abolishes store-operated calcium entry. In other immune cell types, loss of ORAI2 enhances SOCE. In contrast, we find that ORAI2-deficient neutrophils display decreased calcium influx, which is correlated with measurable differences in regulation of neutrophil membrane potential via KCa3.1. Decreased SOCE in ORAI1-, ORAI2- and ORAI1/2-deficient neutrophils impairs multiple neutrophil functions including phagocytosis, degranulation, leukotriene and ROS production, rendering ORAI1/2-deficient mice highly susceptible to staphylococcal infection. This study demonstrates that ORAI1 and ORAI2 are the primary components of the neutrophil CRAC channel and identifies novel subpopulations of neutrophils where cell membrane potential functions as a rheostat to modulate the SOCE response. These findings have implications for new mechanisms that modulate neutrophil function during infection, acute and chronic inflammatory conditions, and cancer.
Project description:Tween-80 is one of the most important causes resulting in anaphylactoid reaction. However, its mechanism remains unclear. A Label-free LCMS/MS-based proteomics was used to analyze Tween-80-stimulated LAD2 mast cell releasates. Out of a total dataset of 2546 proteins, 882 proteins were found in the supernate samples of Tween-80-treated LAD2 mast cells; 313 proteins were up-expressed and 111 proteins were down-expressed. KEGG pathway analysis showed that endocytosis was the largest class of pathway. A total of 52 proteins were involved in endocytosis, and mainly related to G-protein-coupled receptor (GPCR)-endocytosis and EGFR-endocytosis. Cell adhesion molecules (CAMs) pathway was the most significant differences, with a total of 21 proteins involved. NF-κB signaling activation and calcium signaling pathway play an important role in Tween-80-induced LAD2 cells activation. Proteins, including tyrosine-protein kinase, PLCγ, PKCβ, and p50/p65, were mainly involved in NF-κB pathways. NF-κB signaling activation mainly involved in tyrosine-protein kinase, PLCγ, PKCβ, and NF-κB p50/p65. Calcium signaling pathway mainly related to PLCγ/PKC PLCγ/STIM1 mediated store-operated calcium entry (SOCE) and PLCγ mediated store-operated calcium entry (SOCE)PLCγ/PKC pathway. These results suggest that Tween-80 might be internalized via GPCR-endocytosis, which induces degranulation by SOCE PLCγ/PKC or SOCE PLCγ/PKC pathways mediated calcium influx, and promotes the generation of inflammatory mediators and CAMs via NF-κB signaling pathway finally resulting in anaphylactoid reaction.
Project description:T cell activation following antigen binding to the T cell receptor (TCR) involves the mobilization of intracellular calcium (Ca2+) to activate the key transcription factors NFAT and NF-κB. The mechanism of NFAT activation by Ca2+ has been determined; however, the role of Ca2+ in controlling NF-κB signaling is poorly understood and the source of Ca2+ required for NF-κB activation is unknown. We demonstrate that TCR- but not TNF- induced NF-κB signaling upstream of IκB kinase (IKK) activation absolutely requires the influx of extracellular Ca2+ via STIM1-dependent CRAC/Orai channels. We further show that Ca2+ influx controls phosphorylation of the NF-κB protein p65 on Ser536 and that this post- translational modification controls its nuclear localization and transcriptional activation. Notably our data reveal that this role for Ca2+ is entirely separate from its upstream control of IκBα degradation, thereby identifying a novel Ca2+- dependent distal step in TCR-induced NF-κB activation. Finally, we demonstrate that this control of distal signaling occurs via Ca2+-dependent PKCk-mediated phosphorylation of p65. Thus, we establish the source of Ca2+ required for TCR induced NF-kB activation and we define a new distal Ca2+-dependent checkpoint in TCR-induced NF-kB signaling that has broad implications for the control of immune cell development and T cell functional specificity.
Project description:Alternative splicing is a potent modifier of protein function. Stromal interaction molecule 1 (Stim1) is the essential activator of store-operated Ca2+ entry (SOCE) triggering activation of transcription factors. Here, we characterize Stim1A, a splice variant with an additional 31 amino acid domain inserted in frame within its cytosolic domain. Prominent expression of exon A is found in astrocytes, heart, kidney and testes. Full length Stim1A functions as a dominant-negative regulator of SOCE and ICRAC, facilitating sequence specific fast calcium dependent inactivation and destabilizing gating or Orai1. Downregulation or absence of native Stim1A results in increased SOCE. Despite reducing SOCE, Stim1A leads to increased NFAT translocation. Differential proteomics revealed interference of Stim1A with the cAMP-SOCE crosstalk by altered modulation of phosphodiesterase (PDE8B), resulting in reduced cAMP degradation and increased PIP5K activity, facilitating an increased NFAT activation. Our study uncovers a hitherto unknown mechanism regulating NFAT activation and indicates that cell type specific splicing of Stim1 is a potent means to regulate the NFAT signalosome and cAMP-SOCE crosstalk.
Project description:Store operated calcium entry (SOCE) downstream of T cell receptor (TCR) activation in T lymphocytes has been shown to be mediated mainly through the Calcium Release Activated Calcium (CRAC) channel. Here, we compared the effects of a novel, potent and selective CRAC inhibitor, 2,6-Difluoro-N-{5-[4-methyl-1-(5-methyl-thiazol-2-yl)-1,2,5,6-tetrahydro-pyridin-3-yl]-pyrazin-2-yl}-benzamide (RO2959), on T cell effector functions with that of a previously reported CRAC channel inhibitor, YM-58483, and a calcineurin inhibitor Cyclosporin A (CsA). Using both electrophysiological and calcium-based fluorescence measurements, we showed that RO2959 is a potent SOCE inhibitor that blocked an IP3-dependent current in CRAC-expressing RBL-2H3 cells and CHO cells stably expressing human Orai1 and Stim1, as well as SOCE in human primary CD4+ T cells triggered by either TCR stimulation or thapsigargin treatment. Furthermore, we demonstrated that RO2959 completely inhibited cytokine production as well as T cell proliferation mediated by TCR stimulation or MLR (Mixed Lymphocyte Reaction). Lastly, we showed by gene expression array analysis that RO2959 potently blocked TCR triggered gene expression and T cell functional pathways similar to CsA and FK506. Thus, both from a functional and transcriptional level, our data provide evidence that RO2959 is a novel and selective CRAC inhibitor that potently inhibits human T cell functions. PBMC from healthy donors (n=4) were stimulated with anti-CD3/CD28 in the presence or absence of CRAC inhibitor, CsA or FK506 for 24 hrs
Project description:Systemic lupus erythematous (SLE) is a prototype of autoimmune disease. Lupus nephritis (LN) is one of the most serious complications of SLE. The development of autoreactive B cells and the production of autoantibodies have been critical for the initiation and progression of LN. Store-operated Ca2+ entry (SOCE) is the main Ca2+ influx pathway in lymphocytes and is essential for immune response . SOCE is mediated by Ca2+ release-activated Ca2+ (CRAC) channels which are comprised of stromal interaction molecule (STIM) and calcium release-activated calcium modulators (ORAI) . Mutations in genes encoding the CRAC channel abolish SOCE in cells of the immune system and cause severe combined immunodeficiency . Calcium signaling via ORAI1 has been involved in the pathogenesis of autoimmune diseases by driving Th17 differentiation . STIM1 deficiency significantly reduced Th1/Th17 responses and resulted in complete protection from experimental autoimmune encephalomyelitis . Compared to T cells, the roles of CRAC channel in B cells is far less clear. Ca²⁺/calmodulin (CaM)-dependent protein kinase2 (CaMK2) is a serine/threonine-specific protein kinase that is regulated by the Ca²⁺/CaM complex. CaMK2 has been involved in many signaling pathways and is necessary for Ca²⁺ homeostasis, T cell development and activation. CaMK4, another member of the CaMK family, has been shown to compromises podocyte function and promote renal diseases in LN. In the current study, we found that CRAC channel mediated calcium signaling is enhanced in B cells from patients with LN. CRAC channel inhibition by YM-58483 and knocked down of CRAC channel by ORAI1 or STIM2 siRNA led to suppression of CaMK2 signaling and decreased B cell differentiation. Lupus mice treated with CRAC channel inhibitor showed reduced anti-double stranded DNA antibodies (anti-dsDNA), decreased immune deposition in the glomeruli and improved renal function. CRAC channel mediates the development and progression of LN by promoting the differentiation of B cells into plasma cells.
Project description:STIM1 is an endoplasmic reticulum (ER) calcium (Ca2+) sensor that serves to replenish ER Ca2+ stores in response to ER Ca2+ depletion through gating of plasmalemmal Orai1 channels in a process known as store operated calcium entry (SOCE). Previously, we have shown that SOCE is impaired in the diabetic pancreatic β cell; however, the consequences of reduced β cell SOCE have not been well studied. To test this, we generated mice with pancreatic β cell specific deletion of STIM1 (STIM1Δβ). Our results revealed a striking sexual dimorphism in metabolic phenotypes when STIM1Δβ mice were challenged with high fat diet for 8 weeks. Male STIM1Δβ mice showed no differences in total weight, lean or fat mass, or glucose tolerance compared to WT littermate controls. In contrast, female STIM1Δβ mice displayed significantly increased total body weight, fat mass, and reduced glucose tolerance, in vivo glucose-stimulated insulin secretion and β cell mass compared to WT littermate controls, while insulin sensitivity, food intake, and energy expenditure were unchanged. To investigate mechanisms underlying these findings, RNA sequencing was performed in isolated islets and revealed altered 17-beta estradiol (E2) signaling, lipid metabolism, epithelial cell differentiation and decreased noncanonical estradiol receptor GPER. Consistent with this, alpha cell mass was increased in female STIM1Δβ, while proteomics and immunoblot analysis of STIM1 knockout (STIM1KO) INS-1 beta cells revealed reduce insulin expression and increased glucagon expression, suggesting STIM1 may be required for the maintenance of β cell identity. To this end, we show that a reduction of a noncanonical estradiol receptor GPER in STIM1 deficient islets contributes to the marked sexual dimorphism observed during beta cell dysfunction in female STIM1Δβ mice. This present study delineates a sexually dimorphic regulation of STIM1 in the maintenance of pancreatic beta cell identity through GPER and may expand the field of therapeutic approaches to diabetes. Our findings demonstrate the importance of STIM1 and GPER expression stability in the anti-diabetogenic response from estradiol.
Project description:Store operated calcium entry (SOCE) downstream of T cell receptor (TCR) activation in T lymphocytes has been shown to be mediated mainly through the Calcium Release Activated Calcium (CRAC) channel. Here, we compared the effects of a novel, potent and selective CRAC inhibitor, 2,6-Difluoro-N-{5-[4-methyl-1-(5-methyl-thiazol-2-yl)-1,2,5,6-tetrahydro-pyridin-3-yl]-pyrazin-2-yl}-benzamide (RO2959), on T cell effector functions with that of a previously reported CRAC channel inhibitor, YM-58483, and a calcineurin inhibitor Cyclosporin A (CsA). Using both electrophysiological and calcium-based fluorescence measurements, we showed that RO2959 is a potent SOCE inhibitor that blocked an IP3-dependent current in CRAC-expressing RBL-2H3 cells and CHO cells stably expressing human Orai1 and Stim1, as well as SOCE in human primary CD4+ T cells triggered by either TCR stimulation or thapsigargin treatment. Furthermore, we demonstrated that RO2959 completely inhibited cytokine production as well as T cell proliferation mediated by TCR stimulation or MLR (Mixed Lymphocyte Reaction). Lastly, we showed by gene expression array analysis that RO2959 potently blocked TCR triggered gene expression and T cell functional pathways similar to CsA and FK506. Thus, both from a functional and transcriptional level, our data provide evidence that RO2959 is a novel and selective CRAC inhibitor that potently inhibits human T cell functions.
Project description:Platelet-derived growth factor (PDGF) signalling and the subsequent activation of the calcium ion channel, ORAI1 are critical drivers of pathological remodelling of native vascular smooth muscle cells to proliferative state, which is a process associated with various vascular diseases. This study aims to reveal transcriptional networks altered following ORAI1 inhibition in vascular smooth muscle cells. To study the effect of ORAI1 inhibition on VSMC biology, we performed RNA-Seq analysis of PDGF-stimulated primary human aortic smooth muscle cells treated with either ORAI1 inhibitor, (n=4) or with vehicle (n=4), and investigated the effect of ORAI1 inhibition on the transcriptional response of cells.