scholarly journals Changing calcium: CRAC channel (STIM and Orai) expression, splicing, and posttranslational modifiers

2016 ◽  
Vol 310 (9) ◽  
pp. C701-C709 ◽  
Author(s):  
Barbara A. Niemeyer
Keyword(s):  
Immune Cells ◽  
Posttranslational Modifications ◽  
Splice Variants ◽  
Effector Functions ◽  
Crac Channels ◽  
Intracellular Ca ◽  
Crac Channel ◽  
The Individual ◽  
Sensor Proteins ◽  
Temporal Spread

A wide variety of cellular function depends on the dynamics of intracellular Ca2+ signals. Especially for relatively slow and lasting processes such as gene expression, cell proliferation, and often migration, cells rely on the store-operated Ca2+ entry (SOCE) pathway, which is particularly prominent in immune cells. SOCE is initiated by the sensor proteins (STIM1, STIM2) located within the endoplasmic reticulum (ER) registering the Ca2+ concentration within the ER, and upon its depletion, cluster and trap Orai (Orai1-3) proteins located in the plasma membrane (PM) into ER-PM junctions. These regions become sites of highly selective Ca2+ entry predominantly through Orai1-assembled channels, which, among other effector functions, is necessary for triggering NFAT translocation into the nucleus. What is less clear is how the spatial and temporal spread of intracellular Ca2+ is shaped and regulated by differential expression of the individual SOCE genes and their splice variants, their heteromeric combinations and pre- and posttranslational modifications. This review focuses on principle mechanisms regulating expression, splicing, and targeting of Ca2+ release-activated Ca2+ (CRAC) channels.

Enhanced exocytotic-like insertion of Orai1 into the plasma membrane upon intracellular Ca2+ store depletion

2008 ◽  
Vol 294 (6) ◽  
pp. C1323-C1331 ◽  
Author(s):  
Geoffrey E. Woodard ◽  
Ginés M. Salido ◽  
Juan A. Rosado
Keyword(s):  
Plasma Membrane ◽  
Botulinum Neurotoxin ◽  
Surface Expression ◽  
Membrane Expression ◽  
Botulinum Neurotoxin A ◽  
Crac Channels ◽  
Store Depletion ◽  
Protein Receptor ◽  
Intracellular Ca ◽  
Crac Channel

Ca+ release-activated Ca2+ (CRAC) channels are activated when free Ca2+ concentration in the intracellular stores is substantially reduced and mediate sustained Ca2+ entry. Recent studies have identified Orai1 as a CRAC channel subunit. Here we demonstrate that passive Ca2+ store depletion using the inhibitor of the sarcoendoplasmic reticulum Ca2+-ATPase, thapsigargin (TG), enhances the surface expression of Orai1, a process that depends on rises in cytosolic free Ca2+ concentration, as demonstrated in cells loaded with dimethyl BAPTA, an intracellular Ca2+ chelator that prevented TG-evoked cytosolic free Ca2+ concentration elevation. Similar results were observed with a low concentration of carbachol. Cleavage of the soluble N-ethylmaleimide-sensitive-factor attachment protein receptor, synaptosomal-assiciated protein-25 (SNAP-25), with botulinum neurotoxin A impaired TG-induced increase in the surface expression of Orai1. In addition, SNAP-25 cleaving by botulinum neurotoxin A reduces the maintenance but not the initial stages of store-operated Ca2+ entry. In aggregate, these findings demonstrate that store depletion enhances Orai1 plasma membrane expression in an exocytotic manner that involves SNAP-25, a process that contributes to store-dependent Ca2+ entry.

scholarly journals Molecular mechanisms of STIM/Orai communication

2016 ◽  
Vol 310 (8) ◽  
pp. C643-C662 ◽  
Author(s):  
Isabella Derler ◽  
Isaac Jardin ◽  
Christoph Romanin
Keyword(s):  
Molecular Mechanisms ◽  
Signaling Cascades ◽  
Signaling Cascade ◽  
Cellular Processes ◽  
Crac Channels ◽  
Key Players ◽  
Intracellular Ca ◽  
Crac Channel ◽  
Structural Insights ◽  
Molecular Picture

Ca2+entry into the cell via store-operated Ca2+release-activated Ca2+(CRAC) channels triggers diverse signaling cascades that affect cellular processes like cell growth, gene regulation, secretion, and cell death. These store-operated Ca2+channels open after depletion of intracellular Ca2+stores, and their main features are fully reconstituted by the two molecular key players: the stromal interaction molecule (STIM) and Orai. STIM represents an endoplasmic reticulum-located Ca2+sensor, while Orai forms a highly Ca2+-selective ion channel in the plasma membrane. Functional as well as mutagenesis studies together with structural insights about STIM and Orai proteins provide a molecular picture of the interplay of these two key players in the CRAC signaling cascade. This review focuses on the main experimental advances in the understanding of the STIM1-Orai choreography, thereby establishing a portrait of key mechanistic steps in the CRAC channel signaling cascade. The focus is on the activation of the STIM proteins, the subsequent coupling of STIM1 to Orai1, and the consequent structural rearrangements that gate the Orai channels into the open state to allow Ca2+permeation into the cell.

Abstract 14278: Microglial Calcium Activity During Ischemic Stroke

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Kathryn N Kearns ◽  
Lei Liu ◽  
Khadijeh A Sharifi ◽  
Kenneth A Stauderman ◽  
Min S Park ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Calcium Release ◽  
Therapeutic Benefit ◽  
Artery Occlusion ◽  
Two Photon Microscopy ◽  
Crac Channels ◽  
Intracellular Ca ◽  
Crac Channel ◽  
Cerebral Artery Occlusion

Introduction: Ischemic stroke triggers waves of propagating action potentials followed by a loss of homeostatic ion gradients, known as cortical spreading depolarizations (SD). Our data indicate that microglia respond to SD by raising intracellular Ca 2+ , triggering a release of proinflammatory cytokines that may exacerbate post-stroke morbidity. Hypothesis: Inhibiting calcium release-activated calcium (CRAC) channels may block microglial Ca2+ influx and activation to potentially provide therapeutic benefit in ischemic stroke. Methods: We generated a mouse line expressing the Ca2+ indicator GCaMP5 in cortical microglia. Using two-photon microscopy, we imaged microglia in vivo following physical stroke via middle cerebral artery occlusion (MCAo) or chemical stroke via 1M KCl solution application. Controls were compared to mice treated with lipopolysaccharide (LPS) to mimic the inflammation of ischemic stroke. To study CRAC channels as a therapeutic target, we administered CM-EX-137, a CRAC channel blocker, and compared Ca2+ activity to controls. Results: We identified periodical Ca2+ waves in cortical microglia following MCAo (Fig. 1A), or localized KCl application (Fig. 1B-E). Further, when compared to controls, LPS-exposed mice expressed significantly greater microglial Ca2+ activity during KCl-triggered SD (Fig. 1C). Additionally, administration of CM-EX-137 effectively abolished the Ca2+ signals in the microglia and propagation of SD upon application of KCl (Fig. 1E). Conclusions: Blocking the Ca2+ influx into microglia after ischemic stroke may decrease the frequency of SD and reduce microglial activation, potentially leading to smaller stroke volumes and improved clinical outcomes. Figure 1: Microglial Ca 2+ after SD. (A) Ca 2+ transients in microglia after MCAo. (B) KCl-induced Ca 2+ activity in naïve microglia. (C) KCl-induced Ca 2+ activity after LPS. (D, E) KCl-induced Ca 2+ wave after (D) vehicle or (E) CM-EX-137 administration.

Store-Operated Calcium Channels

2005 ◽  
Vol 85 (2) ◽  
pp. 757-810 ◽  
Author(s):  
Anant B. Parekh ◽  
James W. Putney
Keyword(s):  
Plasma Membrane ◽  
Molecular Mechanisms ◽  
Excitable Cells ◽  
Entry Pathway ◽  
Crac Channels ◽  
Proliferation And Apoptosis ◽  
Intracellular Ca ◽  
Crac Channel ◽  
Cell Growth And Proliferation ◽  
Insight Into

In electrically nonexcitable cells, Ca2+influx is essential for regulating a host of kinetically distinct processes involving exocytosis, enzyme control, gene regulation, cell growth and proliferation, and apoptosis. The major Ca2+entry pathway in these cells is the store-operated one, in which the emptying of intracellular Ca2+stores activates Ca2+influx (store-operated Ca2+entry, or capacitative Ca2+entry). Several biophysically distinct store-operated currents have been reported, but the best characterized is the Ca2+release-activated Ca2+current, ICRAC. Although it was initially considered to function only in nonexcitable cells, growing evidence now points towards a central role for ICRAC-like currents in excitable cells too. In spite of intense research, the signal that relays the store Ca2+content to CRAC channels in the plasma membrane, as well as the molecular identity of the Ca2+sensor within the stores, remains elusive. Resolution of these issues would be greatly helped by the identification of the CRAC channel gene. In some systems, evidence suggests that store-operated channels might be related to TRP homologs, although no consensus has yet been reached. Better understood are mechanisms that inactivate store-operated entry and hence control the overall duration of Ca2+entry. Recent work has revealed a central role for mitochondria in the regulation of ICRAC, and this is particularly prominent under physiological conditions. ICRACtherefore represents a dynamic interplay between endoplasmic reticulum, mitochondria, and plasma membrane. In this review, we describe the key electrophysiological features of ICRACand other store-operated Ca2+currents and how they are regulated, and we consider recent advances that have shed insight into the molecular mechanisms involved in this ubiquitous and vital Ca2+entry pathway.

scholarly journals Regulation of Store-Operated Ca2+ Entry by SARAF

Cells ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1887
Author(s):  
Inbal Dagan ◽  
Raz Palty
Keyword(s):  
Molecular Mechanisms ◽  
Feedback Mechanism ◽  
Cellular Biology ◽  
Excitable Cells ◽  
Major Pathway ◽  
Negative Feedback Mechanism ◽  
Crac Channels ◽  
Dependent Inactivation ◽  
Crac Channel ◽  
The One

Calcium (Ca2+) signaling plays a dichotomous role in cellular biology, controlling cell survival and proliferation on the one hand and cellular toxicity and cell death on the other. Store-operated Ca2+ entry (SOCE) by CRAC channels represents a major pathway for Ca2+ entry in non-excitable cells. The CRAC channel has two key components, the endoplasmic reticulum Ca2+ sensor stromal interaction molecule (STIM) and the plasma-membrane Ca2+ channel Orai. Physical coupling between STIM and Orai opens the CRAC channel and the resulting Ca2+ flux is regulated by a negative feedback mechanism of slow Ca2+ dependent inactivation (SCDI). The identification of the SOCE-associated regulatory factor (SARAF) and investigations of its role in SCDI have led to new functional and molecular insights into how SOCE is controlled. In this review, we provide an overview of the functional and molecular mechanisms underlying SCDI and discuss how the interaction between SARAF, STIM1, and Orai1 shapes Ca2+ signaling in cells.

scholarly journals Postprenylation CAAX Processing Is Required for Proper Localization of Ras but Not Rho GTPases

2005 ◽  
Vol 16 (4) ◽  
pp. 1606-1616 ◽  
Author(s):  
David Michaelson ◽  
Wasif Ali ◽  
Vi K. Chiu ◽  
Martin Bergo ◽  
Joseph Silletti ◽  
...  
Keyword(s):  
Posttranslational Modifications ◽  
Protein Trafficking ◽  
Rho Gtpases ◽  
Ras Proteins ◽  
Rho Proteins ◽  
Carboxyl Methylation ◽  
C Terminus ◽  
Individual Contributions ◽  
The Individual ◽  
And Function

The CAAX motif at the C terminus of most monomeric GTPases is required for membrane targeting because it signals for a series of three posttranslational modifications that include isoprenylation, endoproteolytic release of the C-terminal– AAX amino acids, and carboxyl methylation of the newly exposed isoprenylcysteine. The individual contributions of these modifications to protein trafficking and function are unknown. To address this issue, we performed a series of experiments with mouse embryonic fibroblasts (MEFs) lacking Rce1 (responsible for removal of the –AAX sequence) or Icmt (responsible for carboxyl methylation of the isoprenylcysteine). In MEFs lacking Rce1 or Icmt, farnesylated Ras proteins were mislocalized. In contrast, the intracellular localizations of geranylgeranylated Rho GTPases were not perturbed. Consistent with the latter finding, RhoGDI binding and actin remodeling were normal in Rce1- and Icmt-deficient cells. Swapping geranylgeranylation for farnesylation on Ras proteins or vice versa on Rho proteins reversed the differential sensitivities to Rce1 and Icmt deficiency. These results suggest that postprenylation CAAX processing is required for proper localization of farnesylated Ras but not geranygeranylated Rho proteins.

scholarly journals The Epigenome in Atherosclerosis

2020 ◽  
Author(s):  
Sarah Costantino ◽  
Francesco Paneni
Keyword(s):  
Vascular Disease ◽  
Posttranslational Modifications ◽  
Epigenetic Modifications ◽  
Atherosclerotic Vascular Disease ◽  
Biological Regulation ◽  
Genetic Changes ◽  
Epigenetic Biomarkers ◽  
The Individual ◽  
Novel Therapeutic Strategies ◽  
Vascular Oxidative Stress

AbstractEmerging evidence suggests the growing importance of “nongenetic factors” in the pathogenesis of atherosclerotic vascular disease. Indeed, the inherited genome determines only part of the risk profile as genomic approaches do not take into account additional layers of biological regulation by “epi”-genetic changes. Epigenetic modifications are defined as plastic chemical changes of DNA/histone complexes which critically affect gene activity without altering the DNA sequence. These modifications include DNA methylation, histone posttranslational modifications, and non-coding RNAs and have the ability to modulate gene expression at both transcriptional and posttranscriptional level. Notably, epigenetic signals are mainly induced by environmental factors (i.e., pollution, smoking, noise) and, once acquired, may be transmitted to the offspring. The inheritance of adverse epigenetic changes may lead to premature deregulation of pathways involved in vascular damage and endothelial dysfunction. Here, we describe the emerging role of epigenetic modifications as fine-tuners of gene transcription in atherosclerosis. Specifically, the following aspects are described in detail: (1) discovery and impact of the epigenome in cardiovascular disease, (2) the epigenetic landscape in atherosclerosis; (3) inheritance of epigenetic signals and premature vascular disease; (4) epigenetic control of lipid metabolism, vascular oxidative stress, inflammation, autophagy, and apoptosis; (5) epigenetic biomarkers in patients with atherosclerosis; (6) novel therapeutic strategies to modulate epigenetic marks. Understanding the individual epigenetic profile may pave the way for new approaches to determine cardiovascular risk and to develop personalized therapies to treat atherosclerosis and its complications.

PGE2 triggers recovery of transmucosal resistance via EP receptor cross talk in porcine ischemia-injured ileum

2001 ◽  
Vol 281 (2) ◽  
pp. G375-G381 ◽  
Author(s):  
Anthony T. Blikslager ◽  
Susan M. Pell ◽  
Karen M. Young
Keyword(s):  
Cross Talk ◽  
Splice Variants ◽  
Camp Content ◽  
Ep Receptors ◽  
Ussing Chambers ◽  
A 23187 ◽  
Receptor Interactions ◽  
Intracellular Ca ◽  
Ep Receptor ◽  
Receptor Cross Talk

16,16-Dimethyl-PGE2 (PGE2) may interact with one of four prostaglandin type E (EP) receptors, which signal via cAMP (via EP2 or EP4 receptors) or intracellular Ca2+ (via EP1 receptors). Furthermore, EP3 receptors have several splice variants, which may signal via cAMP or intracellular Ca2+. We sought to determine the PGE2 receptor interactions that mediate recovery of transmucosal resistance ( R) in ischemia-injured porcine ileum. Porcine ileum was subjected to 45 min of ischemia, after which the mucosa was mounted in Ussing chambers. Tissues were pretreated with indomethacin (5 μM). Treatment with the EP1, EP2, EP3, and EP4 agonist PGE2 (1 μM) elevated R twofold and significantly increased tissue cAMP content, whereas the EP2 and EP4 agonist deoxy-PGE1 (1 μM) or the EP1 and EP3 agonist sulprostone (1 μM) had no effect. However, a combination of deoxy-PGE1 and sulprostone stimulated synergistic elevations in R and tissue cAMP content. Furthermore, treatment of tissues with deoxy-PGE1 and the Ca2+ ionophore A-23187 stimulated synergistic increases in R and cAMP, indicating that PGE2 triggers recovery of R via EP receptor cross talk mechanisms involving cAMP and intracellular Ca2+.

Tumor-associated immune cells and progression-free survival in advanced endometrial cancer (EC), results from the PHAEDRA trial (ANZGOG 1601).

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. 5584-5584
Author(s):  
Deborah Smith ◽  
Kristy Robledo ◽  
Sonia Yip ◽  
Michelle Cummins ◽  
Peey-Sei Kok ◽  
...  
Keyword(s):  
Immune Cells ◽  
Predictive Value ◽  
Tumor Response ◽  
External Validation ◽  
Prognostic Significance ◽  
Progression Free Survival ◽  
Immune Biomarkers ◽  
Formalin Fixed Paraffin ◽  
Formalin Fixed Paraffin Embedded ◽  
The Individual

5584 Background: Activity of durvalumab in patients with deficient mismatch repair (dMMR) advanced endometrial carcinoma (EC) was confirmed in the PHAEDRA trial (ANZGOG 1601). This study investigated the association between immune biomarkers and clinical outcomes in PHAEDRA. Methods: Formalin-fixed paraffin embedded sections immunohistochemically stained for PD-L1 using the Ventana platform, were with matched H&E slides scored independently by two pathologists according to the Ventana PD-L1 (SP263) algorithm for urothelial carcinoma (UC). Immune biomarkers assessed were PD-L1 staining of tumor cells (TCP) and immune cells (IC), and presence of tumor-associated immune cells (ICP). Results: Sixty-seven of the 71 patients had sufficient tumor for PD-L1 testing. AUC were 0.667, 0.726 and 0.644 for TCP, ICP and IC, respectively for predicting tumor response. Optimal cutpoints were TCP≥1%, ICP≥10% and IC≥35%. ICP≥10% achieved the highest sensitivity (53%) and specificity (82%) of the individual cutpoints. The optimal cutpoint algorithm was able to identify patients who would not respond, (sensitivity 88%, negative predictive value 92%), but had low specificity (48%) and positive predictive value (37%). Differences in PFS were found using ICP≥10% (logrank p = 0.01), compared to TCP (p = 0.25), IC (p = 0.48) and the UC algorithm (p = 0.08) (Figure 1). PFS was shorter in patients with pMMR than dMMR after adjusting for ICP (HR 2.99, 95%CI: 1.61-5.57, p < 0.001). Adjustment for MMR reduced the prognostic significance of ICP≥10% for PFS (HR 0.59, 95% CI: 0.28-1.23, p = 0.16). For OS, differences were seen for the UC algorithm (p = 0.02), but not ICP (p = 0.07), TCP (p = 0.18) or IC (p = 0.23). Similarly to PFS, adjustment for MMR reduced the prognostic significance of the UC algorithm for OS (HR: 0.53, 95% CI: 0.25-1.12, p = 0.10). Conclusions: In this exploratory analysis, ICP was more closely associated with tumor response and PFS than TCP or IC. ICP alone was better than the UC algorithm for predicting PFS. The optimum cutpoint algorithm was promising for identifying non-responders, but requires external validation. Clinical trial information: ACTRN12617000106336.

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