ORAI1 deficiency and lack of store-operated Ca2+ entry cause immunodeficiency, myopathy, and ectodermal dysplasia

TAM-associated CASQ1 mutants diminish intracellular Ca2+ content and interfere with regulation of SOCE

Tubular aggregate myopathy (TAM) is a rare myopathy characterized by muscle weakness and myalgia. Muscle fibers from TAM patients show characteristic accumulation of membrane tubules that contain proteins from the sarcoplasmic reticulum (SR). Gain-of-function mutations in STIM1 and ORAI1, the key proteins participating in the Store-Operated Ca2+ Entry (SOCE) mechanism, were identified in patients with TAM. Recently, the CASQ1 gene was also found to be mutated in patients with TAM. CASQ1 is the main Ca2+ buffer of the SR and a negative regulator of SOCE. Previous characterization of CASQ1 mutants in non-muscle cells revealed that they display altered Ca2+dependent polymerization, reduced Ca2+storage capacity and alteration in SOCE inhibition. We thus aimed to assess how mutations in CASQ1 affect calcium regulation in skeletal muscles, where CASQ1 is naturally expressed. We thus expressed CASQ1 mutants in muscle fibers from Casq1 knockout mice, which provide a valuable model for studying the Ca2+ storage capacity of TAM-associated mutants. Moreover, since Casq1 knockout mice display a constitutively active SOCE, the effect of CASQ1 mutants on SOCE inhibition can be also properly examined in fibers from these mice. Analysis of intracellular Ca2+ confirmed that CASQ1 mutants have impaired ability to store Ca2+and lose their ability to inhibit skeletal muscle SOCE; this is in agreement with the evidence that alterations in Ca2+entry due to mutations in either STIM1, ORAI1 or CASQ1 represents a hallmark of TAM.

Blocking Orai1 constitutive activity inhibits B-cell cancer migration and synergistically acts with drugs to reduce B-CLL cell survival

Orai1 channel capacity to control store-operated Ca2+ entry (SOCE) and B-cell functions is poorly understood and more specifically in B-cell cancers, including human lymphoma and leukemia. As compared to normal B-cells, Orai1 is overexpressed in B-chronic lymphocytic leukemia (B-CLL) and contributes in resting B-CLL to mediate an elevated basal Ca2+ level through a constitutive Ca2+ entry, and in BCR-activated B-cell to regulate the Ca2+ signaling response. Such observations were confirmed in human B-cell lymphoma and leukemia lines, including RAMOS, JOK-1, MEC-1 and JVM-3 cells. Next, the use of pharmacological Orai1 inhibitors (GSK-7975 A and Synta66) blocks constitutive Ca2+ entry and in turn affects B-cell cancer (primary and cell lines) survival and migration, controls cell cycle, and induces apoptosis through a mitochondrial and caspase-3 independent pathway. Finally, the added value of Orai1 inhibitors in combination with B-CLL drugs (ibrutinib, idelalisib, rituximab, and venetoclax) on B-CLL survival was tested, showing an additive/synergistic effect including in the B-cell cancer lines. To conclude, this study highlights the pathophysiological role of the Ca2+ channel Orai1 in B-cell cancers, and pave the way for the use of ORAI1 modulators as a plausible therapeutic strategy.

Impacts of pancreatic exocrine insufficiency on gut microbiota

Pancreatic exocrine insufficiency (PEI) can be induced by various kinds of diseases, including chronic pancreatitis, acute pancreatitis, and post-pancreatectomy. The main pathogenetic mechanism of PEI involves the decline of trypsin synthesis, disorder of pancreatic fluid flow, and imbalance of secretion feedback. Animal studies have shown that PEI could induce gut bacterial overgrowth and dysbiosis, with the abundance of Lactobacillus and Bifidobacterium increasing the most, which could be partially reversed by pancreatic enzyme replacement therapy. Clinical studies have also confirmed the association between PEI and the dysbiosis of gut microbiota. Pancreatic exocrine secretions and changes in duodenal pH as well as bile salt malabsorption brought about by PEI may affect and shape the abundance and composition of gut microbiota. In turn, the gut microbiota may impact the pancreatic exocrine acinus through potential bidirectional crosstalk. Going forward, more and higher-quality studies are needed that focus on the mechanism underlying the impact of PEI on the gut microbiota.

ORAI Ca2+ Channels in Cancers and Therapeutic Interventions

The ORAI proteins serve as crucial pore-forming subunits of calcium-release-activated calcium (CRAC) channels, pivotal in regulating downstream calcium-related signaling pathways. Dysregulated calcium homeostasis arising from mutations and post-translational modifications in ORAI can lead to immune disorders, myopathy, cardiovascular diseases, and even cancers. Small molecules targeting ORAI present an approach for calcium signaling modulation. Moreover, emerging techniques like optogenetics and optochemistry aim to offer more precise regulation of ORAI. This review focuses on the role of ORAI in cancers, providing a concise overview of their significance in the initiation and progression of cancers. Additionally, it highlights state-of-the-art techniques for ORAI channel modulation, including advanced optical tools, potent pharmacological inhibitors, and antibodies. These novel strategies offer promising avenues for the functional regulation of ORAI in research and may inspire innovative approaches to cancer therapy targeting ORAI.

Specific Inhibition of Orai1-mediated Calcium Signalling Resolves Inflammation and Clears Bacteria in an Acute Respiratory Distress Syndrome Model

Rationale: Acute respiratory distress syndrome (ARDS) has an unacceptably high mortality rate (35%) and is without effective therapy. Orai1 is a Ca2+ channel involved in store-operated Ca2+ entry (SOCE), a process that exquisitely regulates inflammation. Orai1 is considered a druggable target, but no Orai1-specific inhibitors exist to date. Objectives: To evaluate whether ELD607, a first-in-class Orai1 antagonist, can treat ARDS caused by bacterial pneumonia in preclinical models. Methods: ELD607 pharmacology was evaluated in HEK293T cells and freshly isolated immune cells from patients with ARDS. A murine acute lung injury model caused by bacterial pneumonia was then used: mice were infected with Pseudomonas aeruginosa, Staphylococcus aureus, methicillin-resistant S. aureus, or multidrug-resistant P. aeruginosa and then treated with ELD607 intranasally. Measurements and Main Results: ELD607 specifically inhibited SOCE in HEK293T cells with a half-maximal inhibitory concentration of 9 nM. ELD607 was stable in ARDS airway secretions and inhibited SOCE in ARDS immune cells. In vivo, inhaled ELD607 significantly reduced neutrophilia and improved survival. Surprisingly, Orai1 inhibition by ELD607 caused a significant reduction in lung bacteria, including methicillin-resistant S. aureus. ELD607 worked as an immunomodulator that reduced cytokine levels, reduced neutrophilia, and promoted macrophage-mediated resolution of inflammation and clearance of bacteria. Indeed, when alveolar macrophages were depleted with inhaled clodronate, ELD607 was no longer able to resolve inflammation or clear bacteria. Conclusions: These data indicate that specific Orai1 inhibition by ELD607 may be a novel approach to reduce multiorgan inflammation and treat antibiotic-resistant bacteria.

Synthetic Biology Meets Ca2+ Release-Activated Ca2+ Channel-Dependent Immunomodulation

Many essential biological processes are triggered by the proximity of molecules. Meanwhile, diverse approaches in synthetic biology, such as new biological parts or engineered cells, have opened up avenues to precisely control the proximity of molecules and eventually downstream signaling processes. This also applies to a main Ca2+ entry pathway into the cell, the so-called Ca2+ release-activated Ca2+ (CRAC) channel. CRAC channels are among other channels are essential in the immune response and are activated by receptor-ligand binding at the cell membrane. The latter initiates a signaling cascade within the cell, which finally triggers the coupling of the two key molecular components of the CRAC channel, namely the stromal interaction molecule, STIM, in the ER membrane and the plasma membrane Ca2+ ion channel, Orai. Ca2+ entry, established via STIM/Orai coupling, is essential for various immune cell functions, including cytokine release, proliferation, and cytotoxicity. In this review, we summarize the tools of synthetic biology that have been used so far to achieve precise control over the CRAC channel pathway and thus over downstream signaling events related to the immune response.

The Rogdi knockout mouse is a model for Kohlschütter-Tönz syndrome

Kohlschütter-Tönz syndrome (KTS) is a rare autosomal recessive disorder characterized by severe intellectual disability, early-onset epileptic seizures, and amelogenesis imperfecta. Here, we present a novel Rogdi mutant mouse deleting exons 6-11- a mutation found in KTS patients disabling ROGDI function. This Rogdi-/- mutant model recapitulates most KTS symptoms. Mutants displayed pentylenetetrazol-induced seizures, confirming epilepsy susceptibility. Spontaneous locomotion and circadian activity tests demonstrate Rogdi mutant hyperactivity mirroring patient spasticity. Object recognition impairment indicates memory deficits. Rogdi-/- mutant enamel was markedly less mature. Scanning electron microscopy confirmed its hypomineralized/hypomature crystallization, as well as its low mineral content. Transcriptomic RNA sequencing of postnatal day 5 lower incisors showed downregulated enamel matrix proteins Enam, Amelx, and Ambn. Enamel crystallization appears highly pH-dependent, cycling between an acidic and neutral pH during enamel maturation. Rogdi-/- teeth exhibit no signs of cyclic dental acidification. Additionally, expression changes in Wdr72, Slc9a3r2, and Atp6v0c were identified as potential contributors to these tooth acidification abnormalities. These proteins interact through the acidifying V-ATPase complex. Here, we present the Rogdi-/- mutant as a novel model to partially decipher KTS pathophysiology. Rogdi-/- mutant defects in acidification might explain the unusual combination of enamel and rare neurological disease symptoms.

Regulatory mechanisms controlling store-operated calcium entry

Calcium influx through plasma membrane ion channels is crucial for many events in cellular physiology. Cell surface stimuli lead to the production of inositol 1,4,5-trisphosphate (IP3), which binds to IP3 receptors (IP3R) in the endoplasmic reticulum (ER) to release calcium pools from the ER lumen. This leads to the depletion of ER calcium pools, which has been termed store depletion. Store depletion leads to the dissociation of calcium ions from the EF-hand motif of the ER calcium sensor Stromal Interaction Molecule 1 (STIM1). This leads to a conformational change in STIM1, which helps it to interact with the plasma membrane (PM) at ER:PM junctions. At these ER:PM junctions, STIM1 binds to and activates a calcium channel known as Orai1 to form calcium release-activated calcium (CRAC) channels. Activation of Orai1 leads to calcium influx, known as store-operated calcium entry (SOCE). In addition to Orai1 and STIM1, the homologs of Orai1 and STIM1, such as Orai2/3 and STIM2, also play a crucial role in calcium homeostasis. The influx of calcium through the Orai channel activates a calcium current that has been termed the CRAC current. CRAC channels form multimers and cluster together in large macromolecular assemblies termed "puncta". How CRAC channels form puncta has been contentious since their discovery. In this review, we will outline the history of SOCE, the molecular players involved in this process, as well as the models that have been proposed to explain this critical mechanism in cellular physiology.

Regulatory mechanisms controlling store-operated calcium entry

Calcium influx through plasma membrane ion channels is crucial for many events in cellular physiology. Cell surface stimuli lead to the production of inositol 1,4,5-trisphosphate (IP3), which binds to IP3 receptors (IP3R) in the endoplasmic reticulum (ER) to release calcium pools from the ER lumen. This leads to the depletion of ER calcium pools, which has been termed store depletion. Store depletion leads to the dissociation of calcium ions from the EF-hand motif of the ER calcium sensor Stromal Interaction Molecule 1 (STIM1). This leads to a conformational change in STIM1, which helps it to interact with the plasma membrane (PM) at ER:PM junctions. At these ER:PM junctions, STIM1 binds to and activates a calcium channel known as Orai1 to form calcium-release activated calcium (CRAC) channels. Activation of Orai1 leads to calcium influx, known as store-operated calcium entry (SOCE). In addition to Orai1 and STIM1, the homologs of Orai1 and STIM1, such as Orai2/3 and STIM2, also play a crucial role in calcium homeostasis. The influx of calcium through the Orai channel activates a calcium current that has been termed the CRAC current. CRAC channels form multimers and cluster together in large macromolecular assemblies termed "puncta". How CRAC channels form puncta has been contentious since their discovery. In this review, we will outline the history of SOCE, the molecular players involved in this process, as well as the models that have been proposed to explain this critical mechanism in cellular physiology.

Multifaceted control of T cell differentiation by STIM1

In T cells, stromal interaction molecule (STIM) and Orai are dispensable for conventional T cell development, but critical for activation and differentiation. This review focuses on novel STIM-dependent mechanisms for control of Ca2+ signals during T cell activation and its impact on mitochondrial function and transcriptional activation for control of T cell differentiation and function. We highlight areas that require further work including the roles of plasma membrane Ca2+ ATPase (PMCA) and partner of STIM1 (POST) in controlling Orai function. A major knowledge gap also exists regarding the independence of T cell development from STIM and Orai, despite compelling evidence that it requires Ca2+ signals. Resolving these and other outstanding questions ensures that the field will remain active for many years to come.

Endoplasmic Reticulum Calcium Mediates Drosophila Wing Development

Background

The temporal dynamics of morphogen presentation impacts transcriptional responses and tissue patterning. However, the mechanisms controlling morphogen release are far from clear. We found that inwardly rectifying potassium (Irk) channels regulate endogenous transient increases in intracellular calcium and bone morphogenetic protein (BMP/Dpp) release for Drosophila wing development. Inhibition of Irk channels reduces BMP/Dpp signaling, and ultimately disrupts wing morphology. Ion channels impact development of several tissues and organisms in which BMP signaling is essential. In neurons and pancreatic beta cells, Irk channels modulate membrane potential to affect intracellular Ca++ to control secretion of neurotransmitters and insulin. Based on Irk activity in neurons, we hypothesized that electrical activity controls endoplasmic reticulum (ER) Ca++ release into the cytoplasm to regulate the release of BMP.

Materials and Methods

To test this hypothesis, we reduced expression of four proteins that control ER calcium, Stromal interaction molecule 1 (Stim), Calcium release-activated calcium channel protein 1 (Orai), SarcoEndoplasmic Reticulum Calcium ATPase (SERCA), small conductance calcium-activated potassium channel (SK), and Bestrophin 2 (Best2) using RNAi and documented wing phenotypes. We use live imaging to study calcium and Dpp release within pupal wings and larval wing discs. Additionally, we employed immunohistochemistry to characterize Small Mothers Against Decapentaplegic (SMAD) phosphorylation downstream of the BMP/Dpp pathway following RNAi knockdown.

Results

We found that reduced Stim and SERCA function decreases amplitude and frequency of endogenous calcium transients in the wing disc and reduced BMP/Dpp release.

Conclusion

Our results suggest control of ER calcium homeostasis is required for BMP/Dpp release, and Drosophila wing development.

Cutaneous Findings in Inborn Errors of Immunity: An Immunologist's Perspective

Cutaneous manifestations are common in patients with inborn errors of immunity (IEI)/primary immunodeficiency and could be due to infections, immune dysregulation, or lymphoproliferative/malign diseases. Immunologists accept some as warning signs for underlying IEI. Herein, we include noninfectious/infectious cutaneous manifestations that we come across in rare IEI cases in our clinic and provide a comprehensive literature review. For several skin diseases, the diagnosis is challenging and differential diagnosis is necessary. Detailed disease history and examination play a vital role in reaching a diagnosis, especially if there is a potential underlying IEI. A skin biopsy is sometimes necessary, especially if we need to rule out inflammatory, infectious, lymphoproliferative, and malignant conditions. Specific and immunohistochemical stainings are particularly important when diagnosing granuloma, amyloidosis, malignancies, and infections like human herpes virus-6, human herpes virus-8, human papillomavirus, and orf. Elucidation of mechanisms of IEIs has improved our understanding of their relation to cutaneous findings. In challenging cases, the immunological evaluation may lead the approach when there is a specific primary immunodeficiency diagnosis or at least help to reduce the number of differential diagnoses. Conversely, the response to therapy may provide conclusive evidence for some conditions. This review raises awareness of concomitant lesions and expands the scope of the differential diagnosis of IEI and the spectrum of skin disease therapy by highlighting frequent forms of IEI-associated cutaneous manifestations. The manifestations given here will guide clinicians to plan for alternative use of diverse therapeutics in a multidisciplinary way for skin diseases.

Amelogenesis imperfecta: Next-generation sequencing sheds light on Witkop's classification

Amelogenesis imperfecta (AI) is a heterogeneous group of genetic rare diseases disrupting enamel development (Smith et al., Front Physiol, 2017a, 8, 333). The clinical enamel phenotypes can be described as hypoplastic, hypomineralized or hypomature and serve as a basis, together with the mode of inheritance, to Witkop's classification (Witkop, J Oral Pathol, 1988, 17, 547-553). AI can be described in isolation or associated with others symptoms in syndromes. Its occurrence was estimated to range from 1/700 to 1/14,000. More than 70 genes have currently been identified as causative. Objectives: We analyzed using next-generation sequencing (NGS) a heterogeneous cohort of AI patients in order to determine the molecular etiology of AI and to improve diagnosis and disease management. Methods: Individuals presenting with so called "isolated" or syndromic AI were enrolled and examined at the Reference Centre for Rare Oral and Dental Diseases (O-Rares) using D4/phenodent protocol (www.phenodent.org). Families gave written informed consents for both phenotyping and molecular analysis and diagnosis using a dedicated NGS panel named GenoDENT. This panel explores currently simultaneously 567 genes. The study is registered under NCT01746121 and NCT02397824 (https://clinicaltrials.gov/). Results: GenoDENT obtained a 60% diagnostic rate. We reported genetics results for 221 persons divided between 115 AI index cases and their 106 associated relatives from a total of 111 families. From this index cohort, 73% were diagnosed with non-syndromic amelogenesis imperfecta and 27% with syndromic amelogenesis imperfecta. Each individual was classified according to the AI phenotype. Type I hypoplastic AI represented 61 individuals (53%), Type II hypomature AI affected 31 individuals (27%), Type III hypomineralized AI was diagnosed in 18 individuals (16%) and Type IV hypoplastic-hypomature AI with taurodontism concerned 5 individuals (4%). We validated the genetic diagnosis, with class 4 (likely pathogenic) or class 5 (pathogenic) variants, for 81% of the cohort, and identified candidate variants (variant of uncertain significance or VUS) for 19% of index cases. Among the 151 sequenced variants, 47 are newly reported and classified as class 4 or 5. The most frequently discovered genotypes were associated with MMP20 and FAM83H for isolated AI. FAM20A and LTBP3 genes were the most frequent genes identified for syndromic AI. Patients negative to the panel were resolved with exome sequencing elucidating for example the gene involved ie ACP4 or digenic inheritance. Conclusion: NGS GenoDENT panel is a validated and cost-efficient technique offering new perspectives to understand underlying molecular mechanisms of AI. Discovering variants in genes involved in syndromic AI (CNNM4, WDR72, FAM20A … ) transformed patient overall care. Unravelling the genetic basis of AI sheds light on Witkop's AI classification.

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.

Orai3 and Orai1 mediate CRAC channel function and metabolic reprogramming in B cells

The essential role of store-operated Ca2+ entry (SOCE) through Ca2+ release-activated Ca2+ (CRAC) channels in T cells is well established. In contrast, the contribution of individual Orai isoforms to SOCE and their downstream signaling functions in B cells are poorly understood. Here, we demonstrate changes in the expression of Orai isoforms in response to B cell activation. We show that both Orai3 and Orai1 mediate native CRAC channels in B cells. The combined loss of Orai1 and Orai3, but not Orai3 alone, impairs SOCE, proliferation and survival, nuclear factor of activated T cells (NFAT) activation, mitochondrial respiration, glycolysis, and the metabolic reprogramming of primary B cells in response to antigenic stimulation. Nevertheless, the combined deletion of Orai1 and Orai3 in B cells did not compromise humoral immunity to influenza A virus infection in mice, suggesting that other in vivo co-stimulatory signals can overcome the requirement of BCR-mediated CRAC channel function in B cells. Our results shed important new light on the physiological roles of Orai1 and Orai3 proteins in SOCE and the effector functions of B lymphocytes.

Infections in Inborn Errors of Immunity with Combined Immune Deficiency: A Review

Enhanced susceptibility to microbes, often resulting in severe, intractable and frequent infections due to usually innocuous organisms at uncommon sites, is the most striking feature in individuals with an inborn error of immunity. In this narrative review, based on the International Union of Immunological Societies' 2022 (IUIS 2022) Update on phenotypic classification of human inborn errors of immunity, the focus is on commonly encountered Combined Immunodeficiency Disorders (CIDs) with susceptibility to infections. Combined immune deficiency disorders are usually commensurate with survival beyond infancy unlike Severe Combined Immune Deficiency (SCID) and are often associated with clinical features of a syndromic nature. Defective humoral and cellular immune responses result in susceptibility to a broad range of microbial infections. Although disease onset is usually in early childhood, mild defects may present in late childhood or even in adulthood. A precise diagnosis is imperative not only for determining management strategies, but also for providing accurate genetic counseling, including prenatal diagnosis, and also in deciding empiric treatment of infections upfront before investigation reports are available.

Store-operated calcium entry: From physiology to tubular aggregate myopathy

Store-Operated Ca²⁺ entry (SOCE) is recognized as a key mechanism in muscle physiology necessary to refill intracellular Ca²⁺ stores during sustained muscle activity. For many years the cell structures expected to mediate SOCE in skeletal muscle fibres remained unknown. Recently, the identification of Ca²⁺ Entry Units (CEUs) in exercised muscle fibres opened new insights into the role of extracellular Ca²⁺ in muscle contraction and, more generally, in intracellular Ca²⁺ homeostasis. Accordingly, intracellular Ca²⁺ unbalance due to alterations in SOCE strictly correlates with muscle disfunction and disease. Mutations in proteins involved in SOCE (STIM1, ORAI1, and CASQ1) have been linked to tubular aggregate myopathy (TAM), a disease that causes muscle weakness and myalgia and is characterized by a typical accumulation of highly ordered and packed membrane tubules originated from the sarcoplasmic reticulum (SR). Achieving a full understanding of the molecular pathways activated by alterations in Ca²⁺ entry mechanisms is a necessary step to design effective therapies for human SOCE-related disorders.

Hypoparathyroidism-Retardation-Dysmorphism Syndrome due to a Variant in the Tubulin-Specific Chaperone E Gene as a Cause of Combined Immune Deficiency

BACKGROUND

Hypoparathyroidism-retardation-dysmorphism (HRD) syndrome is a disease composed of hypoparathyroidism, growth retardation, severe developmental delay, and typical dysmorphic features caused by the tubulin-specific chaperone E gene variant. Many patients succumb in infancy to HRD due to overwhelming infections mainly caused by Pneumococcus spp. Knowledge related to the immune system in these patients is scarce.

PURPOSE

To define the immune phenotype of a cohort of HRD patients including their cellular, humoral, and neutrophil functions.

METHODS

The study included HRD patients followed at Soroka University Medical Center. Clinical and immunological data were obtained, including immunoglobulin concentrations, specific antibody titers, lymphocyte subpopulations, lymphocyte proliferation, and neutrophil functions.

RESULTS

Nine patients (5 females and 4 males) were enrolled, aged 6 months to 15 years. All received amoxicillin prophylaxis as part of a routine established previously. Three patients had bacteremia with Klebsiella, Shigella spp., and Candida. Three patients had confirmed coronavirus disease 19 (COVID-19), and two of them died from this infection. All patients had normal blood counts. Patients showed high total IgA and IgE levels, low anti-pneumococcal antibodies in spite of a routine vaccination schedule, and reduced frequency of naive B cells with increased frequency of CD21lowCD27- B cells. All patients had abnormal T-cell population distributions, including reduced terminally differentiated effector memory CD8, inverted CD4/CD8 ratios, and impaired phytohemagglutinin (PHA)-induced lymphocyte proliferation. Neutrophil superoxide production and chemotaxis were normal in all patients tested.

CONCLUSION

HRD is a combined immunodeficiency disease with syndromic features, manifesting in severe invasive bacterial and viral infections.

ORAI Calcium Channels: Regulation, Function, Pharmacology, and Therapeutic Targets

The changes in intracellular free calcium (Ca2+) levels are one of the most widely regulators of cell function; therefore, calcium as a universal intracellular mediator is involved in very important human diseases and disorders. In many cells, Ca2+ inflow is mediated by store-operated calcium channels, and it is recognized that the store-operated calcium entry (SOCE) is mediated by the two partners: the pore-forming proteins Orai (Orai1-3) and the calcium store sensor, stromal interaction molecule (STIM1-2). Importantly, the Orai/STIM channels are involved in crucial cell signalling processes such as growth factors, neurotransmitters, and cytokines via interaction with protein tyrosine kinase coupled receptors and G protein-coupled receptors. Therefore, in recent years, the issue of Orai/STIM channels as a drug target in human diseases has received considerable attention. This review summarizes and highlights our current knowledge of the Orai/STIM channels in human diseases and disorders, including immunodeficiency, myopathy, tubular aggregate, Stormorken syndrome, York platelet syndrome, cardiovascular and metabolic disorders, and cancers, as well as suggesting these channels as drug targets for pharmacological therapeutic intervention. Moreover, this work will also focus on the pharmacological modulators of Orai/STIM channel complexes. Together, our thoughtful of the biology and physiology of the Orai/STIM channels have grown remarkably during the past three decades, and the next important milestone in the field of store-operated calcium entry will be to identify potent and selective small molecules as a therapeutic agent with the purpose to target human diseases and disorders for patient benefit.

Orai1 as a potential "fits-all approach" therapeutic target for the treatment of DMD

Obliterating skeletal muscle Orai1 expression improves muscle pathology in the mdx mouse model of DMD—could Orai1 emerge as a potential drug target?

PMCA Ca2+ clearance in dental enamel cells depends on the magnitude of cytosolic Ca2

Enamel formation (amelogenesis) is a two-step process whereby crystals partially grow during the secretory stage followed by a significant growth expansion during the maturation stage concurrent with an increase in vectorial Ca2+ transport. This requires tight regulation of cytosolic Ca2+ (c Ca2+ ) concentration in the enamel forming ameloblasts by controlling Ca2+ influx (entry) and Ca2+ extrusion (clearance). Gene and protein expression studies suggest that the plasma membrane Ca2+ -ATPases (PMCA1-4) are likely involved in c Ca2+ extrusion in ameloblasts, yet no functional analysis of these pumps has been reported nor whether their activity changes across amelogenesis. PMCAs have high Ca2+ affinity and low Ca2+ clearance which may be a limiting factor in their contribution to enamel formation as maturation stage ameloblasts handle high Ca2+ loads. We analyzed PMCA function in rat secretory and maturation ameloblasts by blocking or potentiating these pumps. Low/moderate elevations in c Ca2+ measured using the Ca2+ probe Fura-2-AM show that secretory ameloblasts clear Ca2+ faster than maturation stage cells through PMCAs. This process was completely inhibited by an external alkaline (pH 9.0) solution or was significantly delayed by the PMCA blockers vanadate and caloxin 1b1. Eliciting higher c Ca2+ transients via the activation of the ORAI1 Ca2+ channel showed that the PMCAs of maturation ameloblasts were more efficient. Inhibiting PMCAs decreased the rate of Ca2+ influx via ORAI1 but potentiation with forskolin had no effect. Our findings suggest that PMCAs are functional Ca2+ pumps during amelogenesis regulating c Ca2+ upon low and/or moderate Ca2+ stimulus in secretory stage, thus participating in amelogenesis.

Orai1 overexpression improves sepsis-induced T-lymphocyte immunosuppression and acute organ dysfunction in mice

Immune paralysis induced by sepsis, especially dysfunction of CD4⁺ T cells, leads to an increased risk of infection. In sepsis, abnormal differentiation of T lymphocytes is associated with multiorgan dysfunction syndrome. In T lymphocytes, the Orai1/nuclear factor of activated T Cells (NFAT) pathway is a critical mediator of infection, inflammation, and autoimmunity. In this study, we confirmed immunosuppression of splenic CD4⁺ T cells and abnormal differentiation of T lymphocytes in septic mice. Furthermore, we found that the Orai1/NFAT signaling pathway was inhibited in septic mice; however, the overexpression of Orai1 not only improved immune function of T cells in sepsis but also reduced the mortality and organ damage in septic mice. Moreover, the overexpression of Orai1 could reverse the increases in the numbers of T regulatory and T helper 17 cells in septic mice. These data suggest that the Orai1-mediated NFAT signaling pathway can improve sepsis-induced T-lymphocyte immunosuppression and acute organ dysfunction.

The mitochondrial sodium/calcium exchanger NCLX (Slc8b1) in B lymphocytes

Antigen receptor stimulation triggers cytosolic Ca2+ signals, which activate transcriptional and metabolic programs critical for immune function. B-cell receptor (BCR) engagement causes rapid cytosolic Ca2+ rise through the ubiquitous store-operated calcium entry (SOCE) pathway. Slc8b1, which encodes the mitochondrial Na+/Ca2+ exchanger (NCLX), extrudes Ca2+ out of the mitochondria and maintains optimal SOCE activity. Inhibition of NCLX in DT40 and A20 B lymphocyte lines was recently shown to impair cytosolic Ca2+ transients in response to antigen-receptor stimulation, however the downstream functional consequences of this impairment remain unclear. Here, we generated Slc8b1 knockout A20 B-cell lines using CRISPR/Cas9 technology and B-cell specific Slc8b1 knockout mice. Surprisingly, while loss of Slc8b1 in B lymphocytes led to reduction in SOCE, it had a marginal effect on mitochondrial Ca2+ extrusion, suggesting that NCLX is not the major mitochondrial Ca2+ extrusion mechanism in B cells. Furthermore, endoplasmic reticulum (ER) Ca2+ content and rates of ER depletion and refilling remained unaltered in Slc8b1 knockout B cells. Slc8b1 deficiency increased mitochondrial production of oxidants, reduced mitochondrial bioenergetics and altered mitochondrial ultrastructure. B-cell specific Slc8b1 knockout mice showed reduced germinal center B cell responses following foreign antigen and pathogen driven immune responses. Our studies provide novel insights into the function of Slc8b1 in germinal center B cells and its contribution to B-cell signaling and effector function.

Energy metabolic shift contributes to the phenotype modulation of maturation stage ameloblasts

Maturation stage ameloblasts (M-ABs) are responsible for terminal enamel mineralization in teeth and undergo characteristic cyclic changes in both morphology and function between ruffle-ended ameloblasts (RA) and smooth-ended ameloblasts (SA). Energy metabolism has recently emerged as a potential regulator of cell differentiation and fate decisions; however, its implication in M-ABs remains unclear. To elucidate the relationship between M-ABs and energy metabolism, we examined the expression pattern of energy metabolic enzymes in M-ABs of mouse incisors. Further, using the HAT7 cell line with M-AB characteristics, we designed experiments to induce an energy metabolic shift by changes in oxygen concentration. We revealed that RA preferentially utilizes oxidative phosphorylation, whereas SA depends on glycolysis-dominant energy metabolism in mouse incisors. In HAT7 cells, hypoxia induced an energy metabolic shift toward a more glycolytic-dominant state, and the energy metabolic shift reduced alkaline phosphatase (ALP) activity and calcium transport and deposition with a change in calcium-related gene expression, implying a phenotype shift from RA to SA. Taken together, these results indicate that the energy metabolic state is an important determinant of the RA/SA phenotype in M-ABs. This study sheds light on the biological significance of energy metabolism in governing M-ABs, providing a novel molecular basis for understanding enamel mineralization and elucidating the pathogenesis of enamel hypomineralization.

Clinical and genetic characterization of Epstein-Barr virus-associated T/NK-cell lymphoproliferative diseases

BACKGROUND

Epstein-Barr virus (EBV)-associated T-/natural killer (T/NK)-cell lymphoproliferative diseases clinically take on various forms, ranging from an indolent course to an aggressive condition.

OBJECTIVE

Clinically, failure to establish precise diagnosis and provide proper treatment makes it difficult to help patients. We sought to better understand the underlying pathogenesis and to identify genetic prognostic factors to achieve better treatment efficacy.

METHODS

In this study, 119 cases of EBV-associated lymphoproliferative diseases, including EBV-associated hemophagocytic lymphohistiocytosis (n = 46) and chronic active EBV disease of T/NK cell type (n = 73), were retrospectively examined.

RESULTS

Adults aged >20 years at onset accounted for 71.4% of our cohort. About 54.6% patients with unfavorable overall survival developed hemophagocytic lymphohistiocytosis and had higher plasma EBV load. Allogenic hematopoietic stem-cell transplantation was the sole independent favorable factor. We systematically screened germline and somatic aberrations by whole-exome and targeted sequencing. Among 372 antiviral immunity genes, germline variants of 8 genes were significantly enriched. From a panel of 24 driver genes, somatic mutations were frequently identified in dominant EBV-infected T/NK cells. Patients carrying any germline/somatic aberrations in epigenetic modifiers and RIG-I-like receptor (RLR) pathway had worse overall survival than those without 2 type aberrations. Importantly, patients with IFIH1 and/or DDX3X aberrations in the RLR pathway had higher plasma and NK-cell EBV load. Knockdown of DDX3X in NKYS cells downregulated RLR signaling activities and elevated the expression of EBV-encoded oncogenes such as LMP1 and EBNA1.

CONCLUSION

Genetic defects were prevalent in adult EBV-associated hemophagocytic lymphohistiocytosis patients and patients with chronic active EBV disease of T/NK cell type; these defects were associated with unfavorable prognosis. These findings can help clinicians work out more precise staging of the condition and provide new insights into these EBV-associated diseases.

Impact of Dentistry Materials on Chemical Remineralisation/Infiltration versus Salivary Remineralisation of Enamel-In Vitro Study

The aim of this study is to evaluate salivary remineralisation versus chemical remineralisation/infiltration of enamel, using different dentistry materials. The enamel changes were studied using confocal laser scanning microscopy (CLSM), and the depth of lesions and demineralisation/remineralisation/infiltration percentage were calculated. Additionally, the macro elemental composition of the teeth was performed using atomic absorption spectroscopy (AAS). Two studies were performed: (i) demineralisation of enamel in 3% citric acid and infiltration treatment with infiltration resin (Icon, DMG), remineralisation with Fluor Protector (Ivoclar Vivadent) and artificial saliva pH 8; and (ii) enamel demineralisation in saliva at pH 3 and remineralisation at salivary pH 8. The results showed that, firstly, for the remineralisation of demineralised enamel samples, Fluor Protector (Ivoclar Vivadent) was very effective for medium demineralised lesions followed by saliva remineralisation. In cases of deep demineralisation lesions where fluoride could not penetrate, low viscosity resin (Icon, DMG, Hamburg) effectively infiltrated to stop the demineralisation process. Secondly, remineralisation in salivary conditions needed supplementary study over a longer period, to analyse the habits, diet and nutrition of patients in detail. Finally, demineralisation/remineralisation processes were found to influence the macro elemental composition of enamel demineralisation, with natural saliva proving to be less aggressive in terms of decreasing Ca and Mg content.

Distinct roles of ORAI1 in T cell-mediated allergic airway inflammation and immunity to influenza A virus infection

T cell activation and function depend on Ca2+ signals mediated by store-operated Ca2+ entry (SOCE) through Ca2+ release-activated Ca2+ (CRAC) channels formed by ORAI1 proteins. We here investigated how SOCE controls T cell function in pulmonary inflammation during a T helper 1 (TH1) cell-mediated response to influenza A virus (IAV) infection and TH2 cell-mediated allergic airway inflammation. T cell-specific deletion of Orai1 did not exacerbate pulmonary inflammation and viral burdens following IAV infection but protected mice from house dust mite-induced allergic airway inflammation. ORAI1 controlled the expression of genes including p53 and E2F transcription factors that regulate the cell cycle in TH2 cells in response to allergen stimulation and the expression of transcription factors and cytokines that regulate TH2 cell function. Systemic application of a CRAC channel blocker suppressed allergic airway inflammation without compromising immunity to IAV infection, suggesting that inhibition of SOCE is a potential treatment for allergic airway disease.

Mutations in proteins involved in E-C coupling and SOCE and congenital myopathies

In skeletal muscle, Ca²⁺ necessary for muscle contraction is stored and released from the sarcoplasmic reticulum (SR), a specialized form of endoplasmic reticulum through the mechanism known as excitation–contraction (E-C) coupling. Following activation of skeletal muscle contraction by the E-C coupling mechanism, replenishment of intracellular stores requires reuptake of cytosolic Ca²⁺ into the SR by the activity of SR Ca²⁺-ATPases, but also Ca²⁺ entry from the extracellular space, through a mechanism called store-operated calcium entry (SOCE). The fine orchestration of these processes requires several proteins, including Ca²⁺ channels, Ca²⁺ sensors, and Ca²⁺ buffers, as well as the active involvement of mitochondria. Mutations in genes coding for proteins participating in E-C coupling and SOCE are causative of several myopathies characterized by a wide spectrum of clinical phenotypes, a variety of histological features, and alterations in intracellular Ca²⁺ balance. This review summarizes current knowledge on these myopathies and discusses available knowledge on the pathogenic mechanisms of disease.

Store-operated calcium entry controls innate and adaptive immune cell function in inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by dysregulated intestinal immune responses. Using mass cytometry (CyTOF) to analyze the immune cell composition in the lamina propria (LP) of patients with ulcerative colitis (UC) and Crohn's disease (CD), we observed an enrichment of CD4⁺ effector T cells producing IL‐17A and TNF, CD8⁺ T cells producing IFNγ, T regulatory (Treg) cells, and innate lymphoid cells (ILC). The function of these immune cells is regulated by store‐operated Ca²⁺ entry (SOCE), which results from the opening of Ca²⁺ release‐activated Ca²⁺ (CRAC) channels formed by ORAI and STIM proteins. We observed that the pharmacologic inhibition of SOCE attenuated the production of proinflammatory cytokines including IL‐2, IL‐4, IL‐6, IL‐17A, TNF, and IFNγ by human colonic T cells and ILCs, reduced the production of IL‐6 by B cells and the production of IFNγ by myeloid cells, but had no effect on the viability, differentiation, and function of intestinal epithelial cells. T cell‐specific deletion of CRAC channel genes in mice showed that Orai1, Stim1, and Stim2‐deficient T cells have quantitatively distinct defects in SOCE, which correlate with gradually more pronounced impairment of cytokine production by Th1 and Th17 cells and the severity of IBD. Moreover, the pharmacologic inhibition of SOCE with a selective CRAC channel inhibitor attenuated IBD severity and colitogenic T cell function in mice. Our data indicate that SOCE inhibition may be a suitable new approach for the treatment of IBD.

Store-Operated Ca2+ Entry Is Up-Regulated in Tumour-Infiltrating Lymphocytes from Metastatic Colorectal Cancer Patients

Simple Summary

Store-operated Ca²⁺ entry (SOCE) has long been known to regulate the differentiation and effector functions of T cells as well as to be instrumental to the ability of cytotoxic T lymphocytes to target cancer cells. Currently, no information is available regarding the expression and function of SOCE in tumour-infiltrating lymphocytes (TILs) that have been expanded in vitro for adoptive cell therapy (ACT). This study provides the first evidence that SOCE is up-regulated in ex vivo-expanded TILs from metastatic colorectal cancer (mCRC) patients. The up-regulation of SOCE mainly depends on diacylglycerol kinase (DGK), which prevents the protein kinase C-dependent inhibition of Ca²⁺ entry in normal T cells. Of note, the pharmacological blockade of SOCE with the selective inhibitor, BTP-2, during target cell killing significantly increases cytotoxic activity at low TIL density, i.e., when TILs-mediated cancer cell death is rarer. This study, albeit preliminary, could lay the foundation to propose an alternative strategy to effect ACT. It has been shown that ex vivo-expanded TILs did not improve the disease-free survival rate in mCRC patients. Our results strongly suggest that pre-treating autologous TILs with a SOCE or DGK inhibitor before being infused into the patient could improve their cytotoxic activity against cancer cells.

Abstract

(1) Background: Store-operated Ca²⁺ entry (SOCE) drives the cytotoxic activity of cytotoxic T lymphocytes (CTLs) against cancer cells. However, SOCE can be enhanced in cancer cells due to an increase in the expression and/or function of its underlying molecular components, i.e., STIM1 and Orai1. Herein, we evaluated the SOCE expression and function in tumour-infiltrating lymphocytes (TILs) from metastatic colorectal cancer (mCRC) patients. (2) Methods: Functional studies were conducted in TILs expanded ex vivo from CRC liver metastases. Peripheral blood T cells from healthy donors (hPBTs) and mCRC patients (cPBTs) were used as controls. (3) Results: SOCE amplitude is enhanced in TILs compared to hPBTs and cPBTs, but the STIM1 protein is only up-regulated in TILs. Pharmacological manipulation showed that the increase in SOCE mainly depends on tonic modulation by diacylglycerol kinase, which prevents the protein kinase C-dependent inhibition of SOCE activity. The larger SOCE caused a stronger Ca²⁺ response to T-cell receptor stimulation by autologous mCRC cells. Reducing Ca²⁺ influx with BTP-2 during target cell killing significantly increases cytotoxic activity at low target:effector ratios. (4) Conclusions: SOCE is enhanced in ex vivo-expanded TILs deriving from mCRC patients but decreasing Ca²⁺ influx with BTP-2 increases cytotoxic activity at a low TIL density.

Physiological Functions of CRAC Channels

Store-operated Ca2+ entry (SOCE) is a ubiquitous Ca2+ signaling pathway that is evolutionarily conserved across eukaryotes. SOCE is triggered physiologically when the endoplasmic reticulum (ER) Ca2+ stores are emptied through activation of inositol 1,4,5-trisphosphate receptors. SOCE is mediated by the Ca2+ release-activated Ca2+ (CRAC) channels, which are highly Ca2+ selective. Upon store depletion, the ER Ca2+-sensing STIM proteins aggregate and gain extended conformations spanning the ER-plasma membrane junctional space to bind and activate Orai, the pore-forming proteins of hexameric CRAC channels. In recent years, studies on STIM and Orai tissue-specific knockout mice and gain- and loss-of-function mutations in humans have shed light on the physiological functions of SOCE in various tissues. Here, we describe recent findings on the composition of native CRAC channels and their physiological functions in immune, muscle, secretory, and neuronal systems to draw lessons from transgenic mice and human diseases caused by altered CRAC channel activity.

Calcium Signals during SARS-CoV-2 Infection: Assessing the Potential of Emerging Therapies

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a positive-sense single-stranded RNA virus that causes coronavirus disease 2019 (COVID-19). This respiratory illness was declared a pandemic by the world health organization (WHO) in March 2020, just a few weeks after being described for the first time. Since then, global research effort has considerably increased humanity's knowledge about both viruses and disease. It has also spawned several vaccines that have proven to be key tools in attenuating the spread of the pandemic and severity of COVID-19. However, with vaccine-related skepticism being on the rise, as well as breakthrough infections in the vaccinated population and the threat of a complete immune escape variant, alternative strategies in the fight against SARS-CoV-2 are urgently required. Calcium signals have long been known to play an essential role in infection with diverse viruses and thus constitute a promising avenue for further research on therapeutic strategies. In this review, we introduce the pivotal role of calcium signaling in viral infection cascades. Based on this, we discuss prospective calcium-related treatment targets and strategies for the cure of COVID-19 that exploit viral dependence on calcium signals.

Hereditary myopathies associated with hematological abnormalities

The diagnostic evaluation of a patient with suspected hereditary muscle disease can be challenging. Clinicians rely largely on clinical history and examination features, with additional serological, electrodiagnostic, radiologic, histopathologic, and genetic investigations assisting in definitive diagnosis. Hematological testing is inexpensive and widely available, but frequently overlooked in the hereditary myopathy evaluation. Hematological abnormalities are infrequently encountered in this setting; however, their presence provides a valuable clue, helps refine the differential diagnosis, tailors further investigation, and assists interpretation of variants of uncertain significance. A diverse spectrum of hematological abnormalities is associated with hereditary myopathies, including anemias, leukocyte abnormalities, and thrombocytopenia. Recurrent rhabdomyolysis in certain glycolytic enzymopathies co-occurs with hemolytic anemia, often chronic and mild in phosphofructokinase and phosphoglycerate kinase deficiencies, or acute and fever-associated in aldolase-A and triosephosphate isomerase deficiency. Sideroblastic anemia, commonly severe, accompanies congenital-to-childhood onset mitochondrial myopathies including Pearson marrow-pancreas syndrome and mitochondrial myopathy, lactic acidosis, and sideroblastic anemia phenotypes. Congenital megaloblastic macrocytic anemia and mitochondrial dysfunction characterize SFXN4-related myopathy. Neutropenia, chronic or cyclical, with recurrent infections, infantile-to-childhood onset skeletal myopathy and cardiomyopathy are typical of Barth syndrome, while chronic neutropenia without infection occurs rarely in DNM2-centronuclear myopathy. Peripheral eosinophilia may accompany eosinophilic inflammation in recessive calpainopathy. Lipid accumulation in leukocytes on peripheral blood smear (Jordans' anomaly) is pathognomonic for neutral lipid storage diseases. Mild thrombocytopenia occurs in autosomal dominant, childhood-onset STIM1 tubular aggregate myopathy, STIM1 and ORAI1 deficiency syndromes, and GNE myopathy. Herein, we review these hereditary myopathies in which hematological features play a prominent role.

Expression of ORAI1 and STIM1 genes in blood of patients with pulmonary tuberculosis

This study aimed to detect the expression level of ORAI1 and STIM1 genes in blood of patients with bilateral pulmonary tuberculosis (TB) in comparison with the control group. Both genes encode proteins providing store-operated Ca²⁺ entry (SOCE) into the cells, including immune cells, to activate transcriptional factors for producing cytokines and inflammation-restricting proteins. The study included 45 patients with confirmed TB, aged 20 to 86, and 35 volunteers, aged from 21 to 73, without active TB infection. The expression of ORAI1 and STIM1 genes in blood was performed by real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR). Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as the referent gene. Inflammation was assessed by levels of interferon γ (IFN-γ) and interleukin 18 (IL-18) in serum (ELISA method). The results showed lower expression of ORAI1 in blood and higher levels of IFN-γ and IL-18 in serum of TB patients than that of the control group and no differences in expression of the STIM1 gene. It indicates some impairment in the SOCE mechanism of immune cells, which is associated with TB.

Alteration of STIM1/Orai1-Mediated SOCE in Skeletal Muscle: Impact in Genetic Muscle Diseases and Beyond

Intracellular Ca²⁺ ions represent a signaling mediator that plays a critical role in regulating different muscular cellular processes. Ca²⁺ homeostasis preservation is essential for maintaining skeletal muscle structure and function. Store-operated Ca²⁺ entry (SOCE), a Ca²⁺-entry process activated by depletion of intracellular stores contributing to the regulation of various function in many cell types, is pivotal to ensure a proper Ca²⁺ homeostasis in muscle fibers. It is coordinated by STIM1, the main Ca²⁺ sensor located in the sarcoplasmic reticulum, and ORAI1 protein, a Ca²⁺-permeable channel located on transverse tubules. It is commonly accepted that Ca²⁺ entry via SOCE has the crucial role in short- and long-term muscle function, regulating and adapting many cellular processes including muscle contractility, postnatal development, myofiber phenotype and plasticity. Lack or mutations of STIM1 and/or Orai1 and the consequent SOCE alteration have been associated with serious consequences for muscle function. Importantly, evidence suggests that SOCE alteration can trigger a change of intracellular Ca²⁺ signaling in skeletal muscle, participating in the pathogenesis of different progressive muscle diseases such as tubular aggregate myopathy, muscular dystrophy, cachexia, and sarcopenia. This review provides a brief overview of the molecular mechanisms underlying STIM1/Orai1-dependent SOCE in skeletal muscle, focusing on how SOCE alteration could contribute to skeletal muscle wasting disorders and on how SOCE components could represent pharmacological targets with high therapeutic potential.

Identifying digenic disease genes via machine learning in the Undiagnosed Diseases Network

Rare diseases affect millions of people worldwide, and discovering their genetic causes is challenging. More than half of the individuals analyzed by the Undiagnosed Diseases Network (UDN) remain undiagnosed. The central hypothesis of this work is that many of these rare genetic disorders are caused by multiple variants in more than one gene. However, given the large number of variants in each individual genome, experimentally evaluating combinations of variants for potential to cause disease is currently infeasible. To address this challenge, we developed the digenic predictor (DiGePred), a random forest classifier for identifying candidate digenic disease gene pairs by features derived from biological networks, genomics, evolutionary history, and functional annotations. We trained the DiGePred classifier by using DIDA, the largest available database of known digenic-disease-causing gene pairs, and several sets of non-digenic gene pairs, including variant pairs derived from unaffected relatives of UDN individuals. DiGePred achieved high precision and recall in cross-validation and on a held-out test set (PR area under the curve > 77%), and we further demonstrate its utility by using digenic pairs from the recent literature. In contrast to other approaches, DiGePred also appropriately controls the number of false positives when applied in realistic clinical settings. Finally, to enable the rapid screening of variant gene pairs for digenic disease potential, we freely provide the predictions of DiGePred on all human gene pairs. Our work enables the discovery of genetic causes for rare non-monogenic diseases by providing a means to rapidly evaluate variant gene pairs for the potential to cause digenic disease.

Store-Operated Calcium Entry in Skeletal Muscle: What Makes It Different?

Current knowledge on store-operated Ca²⁺ entry (SOCE) regarding its localization, kinetics, and regulation is mostly derived from studies performed in non-excitable cells. After a long time of relative disinterest in skeletal muscle SOCE, this mechanism is now recognized as an essential contributor to muscle physiology, as highlighted by the muscle pathologies that are associated with mutations in the SOCE molecules STIM1 and Orai1. This review mainly focuses on the peculiar aspects of skeletal muscle SOCE that differentiate it from its counterpart found in non-excitable cells. This includes questions about SOCE localization and the movement of respective proteins in the highly organized skeletal muscle fibers, as well as the diversity of expressed STIM isoforms and their differential expression between muscle fiber types. The emerging evidence of a phasic SOCE, which is activated during EC coupling, and its physiological implication is described as well. The specific issues related to the use of SOCE modulators in skeletal muscles are discussed. This review highlights the complexity of SOCE activation and its regulation in skeletal muscle, with an emphasis on the most recent findings and the aim to reach a current picture of this mesmerizing phenomenon.

Cell-wide mapping of Orai1 channel activity reveals functional heterogeneity in STIM1-Orai1 puncta

Upon Ca²⁺ store depletion, Orai1 channels cluster and open at endoplasmic reticulum–plasma membrane (ER–PM) junctions in signaling complexes called puncta. Little is known about whether and how Orai1 channel activity may vary between individual puncta. Previously, we developed and validated optical recording of Orai channel activity, using genetically encoded Ca²⁺ indicators fused to Orai1 or Orai3 N or C termini. We have now combined total internal reflection fluorescence microscopy with whole-cell recording to map functional properties of channels at individual puncta. After Ca²⁺ store depletion in HEK cells cotransfected with mCherry-STIM1 and Orai1-GCaMP6f, Orai1-GCaMP6f fluorescence increased progressively with increasingly negative test potentials and robust responses could be recorded from individual puncta. Cell-wide fluorescence half-rise and -fall times during steps to −100 mV test potential indicated probe response times of <50 ms. The in situ Orai1-GCaMP6f affinity for Ca²⁺ was 620 nM, assessed by monitoring fluorescence using buffered Ca²⁺ solutions in “unroofed” cells. Channel activity and temporal activation profile were tracked in individual puncta using image maps and automated puncta identification and recording. Simultaneous measurement of mCherry-STIM1 fluorescence uncovered an unexpected gradient in STIM1/Orai1 ratio that extends across the cell surface. Orai1-GCaMP6f channel activity was found to vary across the cell, with inactive channels occurring in the corners of cells where the STIM1/Orai1 ratio was lowest; low-activity channels typically at edges displayed a slow activation phase lasting hundreds of milliseconds. Puncta with high STIM1/Orai1 ratios exhibited a range of channel activity that appeared unrelated to the stoichiometric requirements for gating. These findings demonstrate functional heterogeneity of Orai1 channel activity between individual puncta and establish a new experimental platform that facilitates systematic comparisons between puncta composition and activity.

Calcium Transport in Specialized Dental Epithelia and Its Modulation by Fluoride

Most cells use calcium (Ca2+) as a second messenger to convey signals that affect a multitude of biological processes. The ability of Ca2+ to bind to proteins to alter their charge and conformation is essential to achieve its signaling role. Cytosolic Ca2+ (cCa2+) concentration is maintained low at ~100 nM so that the impact of elevations in cCa2+ is readily sensed and transduced by cells. However, such elevations in cCa2+ must be transient to prevent detrimental effects. Cells have developed a variety of systems to rapidly clear the excess of cCa2+ including Ca2+ pumps, exchangers and sequestering Ca2+ within intracellular organelles. This Ca2+ signaling toolkit is evolutionarily adapted so that each cell, tissue, and organ can fulfill its biological function optimally. One of the most specialized cells in mammals are the enamel forming cells, the ameloblasts, which also handle large quantities of Ca2+. The end goal of ameloblasts is to synthesize, secrete and mineralize a unique proteinaceous matrix without the benefit of remodeling or repair mechanisms. Ca2+ uptake into ameloblasts is mainly regulated by the store operated Ca2+ entry (SOCE) before it is transported across the polarized ameloblasts to reach the insulated enamel space. Here we review the ameloblasts Ca2+ signaling toolkit and address how the common electronegative non-metal fluoride can alter its function, potentially addressing the biology of dental fluorosis.

Isoform-Specific Properties of Orai Homologues in Activation, Downstream Signaling, Physiology and Pathophysiology

Ca2+ ion channels are critical in a variety of physiological events, including cell growth, differentiation, gene transcription and apoptosis. One such essential entry pathway for calcium into the cell is the Ca2+ release-activated Ca2+ (CRAC) channel. It consists of the Ca2+ sensing protein, stromal interaction molecule 1 (STIM1) located in the endoplasmic reticulum (ER) and a Ca2+ ion channel Orai in the plasma membrane. The Orai channel family includes three homologues Orai1, Orai2 and Orai3. While Orai1 is the "classical" Ca2+ ion channel within the CRAC channel complex and plays a universal role in the human body, there is increasing evidence that Orai2 and Orai3 are important in specific physiological and pathophysiological processes. This makes them an attractive target in drug discovery, but requires a detailed understanding of the three Orai channels and, in particular, their differences. Orai channel activation is initiated via Ca2+ store depletion, which is sensed by STIM1 proteins, and induces their conformational change and oligomerization. Upon STIM1 coupling, Orai channels activate to allow Ca2+ permeation into the cell. While this activation mechanism is comparable among the isoforms, they differ by a number of functional and structural properties due to non-conserved regions in their sequences. In this review, we summarize the knowledge as well as open questions in our current understanding of the three isoforms in terms of their structure/function relationship, downstream signaling and physiology as well as pathophysiology.

From Disease Description and Gene Discovery to Functional Cell Pathway: A Decade-Long Journey for TMCO1

A decade has passed since transmembrane coiled-coil domains 1 (TMCO1) defect syndrome was identified in 11 undiagnosed patients within the Old Order Amish of Northeastern Ohio—a disorder characterized by a distinctive craniofacial dysmorphism, skeletal anomalies and global developmental delay. Twenty seven patients, from diverse ethnic groups, have been reported with pathogenic TMCO1 variants now recognized to cause cerebrofaciothoracic dysplasia (CFTD). The implication of previously uncharacterized TMCO1 within disease has instigated a 10-year journey to understand the function of TMCO1 protein in Ca²⁺ homeostasis. TMCO1 is an ER Ca²⁺ leak channel which facilitates Ca²⁺ leak upon ER “overload” through the novel Ca²⁺ load activated Ca²⁺ mechanism. This mini-review brings together the clinical and scientific advances made since the discovery of TMCO1 deficiency in disease, including broadened phenotype, understanding of pathophysiology, and implications to patient management of TMCO1 defect syndrome.

Flos magnoliae constituent fargesin has an anti-allergic effect via ORAI1 channel inhibition

Flos magnoliae (FM), the dry flower buds of Magnolia officinalis or its related species, is a traditional herbal medicine commonly used in Asia for symptomatic relief of and treating allergic rhinitis, headache, and sinusitis. Although several studies have reported the effects of FM on store-operated calcium entry (SOCE) via the ORAI1 channel, which is essential during intracellular calcium signaling cascade generation for T cell activation and mast cell degranulation, the effects of its isolated constituents on SOCE remain unidentified. Therefore, we investigated which of the five major constituents of 30% ethanoic FM (vanillic acid, tiliroside, eudesmin, magnolin, and fargesin) inhibit SOCE and their physiological effects on immune cells. The conventional whole-cell patch clamp results showed that fargesin, magnolin, and eudesmin significantly inhibited SOCE and thus human primary CD4⁺ T lymphocyte proliferation, as well as allergen-induced histamine release in mast cells. Among them, fargesin demonstrated the most potent inhibitory effects not only on ORAI1 (IC50 = 12.46 ± 1.300 μM) but also on T-cell proliferation (by 87.74% ± 1.835%) and mast cell degranulation (by 20.11% ± 5.366%) at 100 μM. Our findings suggest that fargesin can be a promising candidate for the development of therapeutic drugs to treat allergic diseases.

Cardiac-Specific Deletion of Orai3 Leads to Severe Dilated Cardiomyopathy and Heart Failure in Mice

Background Orai3 is a mammalian-specific member of the Orai family (Orai1‒3) and a component of the store-operated Ca2+ entry channels. There is little understanding of the role of Orai channels in cardiomyocytes, and its role in cardiac function remains unexplored. Thus, we developed mice lacking Orai1 and Orai3 to address their role in cardiac homeostasis. Methods and Results We generated constitutive and inducible cardiomyocyte-specific Orai3 knockout (Orai3cKO) mice. Constitutive Orai3-loss led to ventricular dysfunction progressing to dilated cardiomyopathy and heart failure. Orai3cKO mice subjected to pressure overload developed a fulminant dilated cardiomyopathy with rapid heart failure onset, characterized by interstitial fibrosis and apoptosis. Ultrastructural analysis of Orai3-deficient cardiomyocytes showed abnormal M- and Z-line morphology. The greater density of condensed mitochondria in Orai3-deficient cardiomyocytes was associated with the upregulation of DRP1 (dynamin-related protein 1). Cardiomyocytes isolated from Orai3cKO mice exhibited profoundly altered myocardial Ca2+ cycling and changes in the expression of critical proteins involved in the Ca2+ clearance mechanisms. Upregulation of TRPC6 (transient receptor potential canonical type 6) channels was associated with upregulation of the RCAN1 (regulator of calcineurin 1), indicating the activation of the calcineurin signaling pathway in Orai3cKO mice. A more dramatic cardiac phenotype emerged when Orai3 was removed in adult mice using a tamoxifen-inducible Orai3cKO mouse. The removal of Orai1 from adult cardiomyocytes did not change the phenotype of tamoxifen-inducible Orai3cKO mice. Conclusions Our results identify a critical role for Orai3 in the heart. We provide evidence that Orai3-mediated Ca2+ signaling is required for maintaining sarcomere integrity and proper mitochondrial function in adult mammalian cardiomyocytes.

1,2,4-Oxadiazole-Bearing Pyrazoles as Metabolically Stable Modulators of Store-Operated Calcium Entry

Store-operated calcium entry (SOCE) is a pivotal mechanism in calcium homeostasis, and, despite still being under investigation, its dysregulation is known to be associated with severe human disorders. SOCE modulators are therefore needed both as chemical probes and as therapeutic agents. While many small molecules have been described so far, their poor properties in terms of drug-likeness have limited their translation into the clinical practice. In this work, we describe the bioisosteric replacement of the ester moiety in pyrazole derivatives with a 1,2,4-oxadiazole ring as a means to afford a class of modulators with high metabolic stability. Moreover, among our derivatives, a compound able to increase the calcium entry was identified, further enriching the library of available SOCE activators.

ORAI1 Ca2+ Channel as a Therapeutic Target in Pathological Vascular Remodelling

In the adult, vascular smooth muscle cells (VSMC) are normally physiologically quiescent, arranged circumferentially in one or more layers within blood vessel walls. Remodelling of native VSMC to a proliferative state for vascular development, adaptation or repair is driven by platelet-derived growth factor (PDGF). A key effector downstream of PDGF receptors is store-operated calcium entry (SOCE) mediated through the plasma membrane calcium ion channel, ORAI1, which is activated by the endoplasmic reticulum (ER) calcium store sensor, stromal interaction molecule-1 (STIM1). This SOCE was shown to play fundamental roles in the pathological remodelling of VSMC. Exciting transgenic lineage-tracing studies have revealed that the contribution of the phenotypically-modulated VSMC in atherosclerotic plaque formation is more significant than previously appreciated, and growing evidence supports the relevance of ORAI1 signalling in this pathologic remodelling. ORAI1 has also emerged as an attractive potential therapeutic target as it is accessible to extracellular compound inhibition. This is further supported by the progression of several ORAI1 inhibitors into clinical trials. Here we discuss the current knowledge of ORAI1-mediated signalling in pathologic vascular remodelling, particularly in the settings of atherosclerotic cardiovascular diseases (CVDs) and neointimal hyperplasia, and the recent developments in our understanding of the mechanisms by which ORAI1 coordinates VSMC phenotypic remodelling, through the activation of key transcription factor, nuclear factor of activated T-cell (NFAT). In addition, we discuss advances in therapeutic strategies aimed at the ORAI1 target.

A novel bi-allelic loss-of-function mutation in STIM1 expands the phenotype of STIM1-related diseases

STIM1, the stromal interaction molecule 1, is the key protein for maintaining calcium concentration in the endoplasmic reticulum by triggering the Store Operated Calcium Entry (SOCE). Bi-allelic mutations in STIM1 gene are responsible for a loss-of-function in patients affected with a CRAC channelopathy syndrome in which severe combined immunodeficiency syndrome (SCID-like), autoimmunity, ectodermal dysplasia and muscle hypotonia are combined. Here, we studied two siblings from a consanguineous Syrian family, presenting with muscle weakness, hyperlaxity, elastic skin, tooth abnormalities, dysmorphic facies, hypoplastic patellae and history of respiratory infections. Using exome sequencing, we have identified a new homozygous frameshift mutation in STIM1: c.685delT [p.(Phe229Leufs*12)], leading to a complete loss of STIM1 protein. In this study, we describe an unusual phenotype linked to STIM1 mutations, combining clinical signs usually observed in different STIM1-related diseases. In particular, we confirmed that the complete loss of STIM1 function is not always associated with severe immune disorders. Altogether, our results broaden the spectrum of phenotypes associated with mutations in STIM1 and opens new perspectives on the pathological mechanisms associated with a defect in the proteins constituting the SOCE complex.

Effect of MgCl2 and GdCl3 on ORAI1 Expression and Store-Operated Ca2+ Entry in Megakaryocytes

In chronic kidney disease, hyperphosphatemia upregulates the Ca²⁺ channel ORAI and its activating Ca²⁺ sensor STIM in megakaryocytes and platelets. ORAI1 and STIM1 accomplish store-operated Ca²⁺ entry (SOCE) and play a key role in platelet activation. Signaling linking phosphate to upregulation of ORAI1 and STIM1 includes transcription factor NFAT5 and serum and glucocorticoid-inducible kinase SGK1. In vascular smooth muscle cells, the effect of hyperphosphatemia on ORAI1/STIM1 expression and SOCE is suppressed by Mg²⁺ and the calcium-sensing receptor (CaSR) agonist Gd³⁺. The present study explored whether sustained exposure to Mg²⁺ or Gd³⁺ interferes with the phosphate-induced upregulation of NFAT5, SGK1, ORAI1,2,3, STIM1,2 and SOCE in megakaryocytes. To this end, human megakaryocytic Meg-01 cells were treated with 2 mM ß-glycerophosphate for 24 h in the absence and presence of either 1.5 mM MgCl₂ or 50 µM GdCl₃. Transcript levels were estimated utilizing q-RT-PCR, protein abundance by Western blotting, cytosolic Ca²⁺ concentration ([Ca²⁺]_i) by Fura-2 fluorescence and SOCE from the increase in [Ca²⁺]_i following re-addition of extracellular Ca²⁺ after store depletion with thapsigargin (1 µM). As a result, Mg²⁺ and Gd³⁺ upregulated CaSR and blunted or virtually abolished the phosphate-induced upregulation of NFAT5, SGK1, ORAI1,2,3, STIM1,2 and SOCE in megakaryocytes. In conclusion, Mg²⁺ and the CaSR agonist Gd³⁺ interfere with phosphate-induced dysregulation of [Ca²⁺]_i in megakaryocytes.

Inborn errors of immunity associated with characteristic phenotypes

OBJECTIVES

The aim of the report is to describe the main immunodeficiencies with syndromic characteristics according to the new classification of Inborn Errors of Immunity.

DATA SOURCE

The data search was centered on the PubMed platform on review studies, meta-analyses, systematic reviews, case reports and a randomized study published in the last 10 years that allowed the characterization of the several immunological defects included in this group.

DATA SYNTHESIS

Immunodeficiencies with syndromic characteristics include 65 immunological defects in 9 subgroups. The diversity of clinical manifestations is observed in each described disease and may appear early or later, with variable severity. Congenital thrombocytopenia, syndromes with DNA repair defect, immuno-osseous dysplasias, thymic defects, Hyper IgE Syndrome, anhidrotic ectodermal dysplasia with immunodeficiency and purine nucleoside phosphorylase deficiency were addressed.

CONCLUSIONS

Immunological defects can present with very different characteristics; however, the occurrence of infectious processes, autoimmune disorders and progression to malignancy may suggest diagnostic research. In the case of diseases with gene mutations, family history is of utmost importance.