Ca2+ Signaling but Not Store-Operated Ca2+ Entry Is Required for the Function of Macrophages and Dendritic Cells

Vaeth, Martin; Zee, Isabelle; Concepcion, Axel R.; Maus, Máté; Shaw, Patrick J.; Portal-Celhay, Cynthia; Zahra, Aleena; Kozhaya, Lina; Weidinger, Carl; Philips, Jennifer A.; Unutmaz, Derya; Feske, Stefan

doi:10.4049/jimmunol.1403013

Cited by 102 publications

(93 citation statements)

References 88 publications

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“…Surprisingly, preexposure of the THP-1 monocytes to small nonlytic but also lytic concentrations of HlyA did not reduce erythrophagocytosis but showed a slight tendency toward enhancing it. This toxin preconditioning may create readiness for the nonlysed THP-1 monocytes to recognize erythrocytes damaged by HlyA, since an increase in [Ca 2ϩ ] i is known to support the phagocytic function (81,82). This effect was not clear after preexposure to LtxA, presumably because of the larger fraction of lysed phagocytes.…”

Section: Discussionmentioning

confidence: 80%

Inhibition of P2X Receptors Protects Human Monocytes against Damage by Leukotoxin from Aggregatibacter actinomycetemcomitans and α-Hemolysin from Escherichia coli

et al. 2016

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␣-Hemolysin (HlyA) from Escherichia coli and leukotoxin A (LtxA) from Aggregatibacter actinomycetemcomitans are important virulence factors in ascending urinary tract infections and aggressive periodontitis, respectively. The extracellular signaling molecule ATP is released immediately after insertion of the toxins into plasma membranes and, via P2X receptors, is essential for the erythrocyte damage inflicted by these toxins. Moreover, ATP signaling is required for the ensuing recognition and phagocytosis of damaged erythrocytes by the monocytic cell line THP-1. Here, we investigate how these toxins affect THP-1 monocyte function. We demonstrate that both toxins trigger early ATP release and a following increase in the intracellular receptors markedly reduces toxin-induced cytolysis. This pattern is paralleled in freshly isolated human monocytes from healthy volunteers. Interestingly, only a minor fraction of the toxin-damaged THP-1 monocytes eventually lyse. P2X 7 receptor inhibition generally prevents cell damage, except from a distinct cell shrinkage that prevails in response to the toxins. Moreover, we find that preexposure to HlyA preserves the capacity of THP-1 monocytes to phagocytose damaged erythrocytes and may induce readiness to discriminate between damaged and healthy erythrocytes. These findings suggest a new pharmacological target for protecting monocytes during exposure to poreforming cytolysins during infection or injury.␣ -Hemolysin (HlyA) is an important virulence factor frequently produced by strains of pathogenic Escherichia coli (1-3). The frequency with which HlyA-producing E. coli strains are isolated from patients increases with severity of the disease (for a review, see reference 2). HlyA is a pore-forming repeat in toxin (RTX) family member which inserts itself receptor independently into cell membranes (1). The cytotoxic effect of HlyA is massively amplified by ATP release, presumably through the HlyA pore (4) and following P2X receptor activation (5, 6). In erythrocytes, P2X 1 and P2X 7 receptors have been implicated in HlyA-induced hemolysis, and blocking of either of these receptors substantially reduces the hemolysis (5, 6). Interestingly, insertion of a HlyA pore does not cause immediate cell swelling and rupture but initially triggers a significant volume reduction that results from an increase in the intracellular Ca 2ϩ concentration ([Ca 2ϩ ] i ) followed by activation of the Ca 2ϩ -sensitive K ϩ and Cl Ϫ channels K Ca 3.1 and TMEM16A (7). During erythrocyte shrinkage, cells expose phosphatidyl serine (PS) in the outer plasma membrane leaflet (7). Recently, we discovered that THP-1 monocytes are more likely to recognize and phagocytose erythrocytes that have been exposed to HlyA (8). This phagocytosis is prevented if HlyA-induced cell damage is diminished by P2X receptor antagonists or if cell shrinkage and PS exposure are blocked (8).Leukotoxin A (LtxA) is a virulence factor often released from Aggregatibacter actinomycetemcomitans in the periodontal connective tissue (9-11). ...

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Section: Discussionmentioning

confidence: 80%

Inhibition of P2X Receptors Protects Human Monocytes against Damage by Leukotoxin from Aggregatibacter actinomycetemcomitans and α-Hemolysin from Escherichia coli

et al. 2016

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“…Neither Orai1 deletion nor the CRAC channel inhibitor significantly affected the differentiation of murine iTreg cells in vitro or the numbers of Treg cells in the CNS of MOG immunized mice. While it is likely that AMG1 also inhibits CRAC channels in other immune cells such as DC, macrophages and neutrophils, this may not result in a functional impairment of these cells and influence EAE severity because we recently showed that even complete suppression of SOCE in Stim1/Stim2 -deficient DC and macrophages does not significantly impair the function of these cells (52). Given the similar degree of EAE attenuation in mice with genetic deletion of Orai1 in T cells and WT mice treated with AMG1, the main effects of the inhibitor on EAE are likely to result from inhibition of encephalitogenic T cells.…”

Section: Discussionmentioning

confidence: 99%

Selective ORAI1 Inhibition Ameliorates Autoimmune Central Nervous System Inflammation by Suppressing Effector but Not Regulatory T Cell Function

Kaufmann

Shaw

Kozhaya

et al. 2016

The Journal of Immunology

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The function of CD4+ T cells is dependent on Ca2+ influx through Ca2+ release-activated Ca2+ (CRAC) channels formed by ORAI proteins. To investigate the role of ORAI1 in pro-inflammatory Th1 and Th17 cells and autoimmune diseases, we genetically and pharmacologically modulated ORAI1 function. Immunization of mice lacking Orai1 in T cells with MOG peptide resulted in attenuated severity of experimental autoimmune encephalomyelitis (EAE). The numbers of T cells and innate immune cells in the CNS of ORAI1-deficient animals were strongly reduced along with almost completely abolished production of IL-17, IFN-γ and GM-CSF despite only partially reduced Ca2+ influx. In Th1 and Th17 cells differentiated in vitro, ORAI1 was required for cytokine production but not the expression of Th1- and Th17-specific transcription factors T-bet and RORγt. The differentiation and function of induced iTreg cells, by contrast, was independent of ORAI1. Importantly, induced genetic deletion of Orai1 in adoptively transferred, MOG-specific T cells was able to halt EAE progression after disease onset. Likewise, treatment of wild-type mice with a selective CRAC channel inhibitor after EAE onset ameliorated disease. Genetic deletion of Orai1 and pharmacological ORAI1 inhibition reduced the leukocyte numbers in the CNS and attenuated Th1/Th17 cell-mediated cytokine production. In human CD4+ T cells, CRAC channel inhibition reduced the expression of IL-17, IFN-γ and other cytokines in a dose-dependent manner. Taken together, these findings support the conclusion that Th1 and Th17 cell function is particularly dependent on CRAC channels, which could be exploited as a therapeutic approach to T cell-mediated autoimmune diseases.

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“…Maturation of human DCs was inhibited by CRAC channel blockers and siRNA‐mediated knockdown of either STIM1 or ORAI1 mRNA expression . By contrast, genetic deletion of Stim1/Stim2 in mice had no effects on the numbers and phenotype of monocytes and DCs in vivo , or the differentiation of macrophages and DCs from bone marrow stem cells in vitro despite abolished SOCE . Importantly, the function of STIM1/STIM2‐deficient macrophages and DCs was normal; they produced comparable amounts of various cytokines and were able to activate the NLRP3 inflammasome.…”

Section: Lof and Null Mutations In Orai1 And Stim1mentioning

confidence: 99%

“…Importantly, the function of STIM1/STIM2‐deficient macrophages and DCs was normal; they produced comparable amounts of various cytokines and were able to activate the NLRP3 inflammasome. STIM1/STIM2‐deficient macrophages had normal phagocytosis and bone marrow–derived DCs matured normally and activated CD4 + T cells upon coincubation in vitro . SOCE has been suggested to play an important role in neutrophil function on the basis of studies in the promyelocytic HL60 leukemia cell line .…”

Section: Lof and Null Mutations In Orai1 And Stim1mentioning

confidence: 99%

Diseases caused by mutations in ORAI1 and STIM1

Lacruz

Feske

2015

Annals of the New York Academy of Sciences

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384

406

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Ca2+ release-activated Ca2+ (CRAC) channels mediate a specific form of Ca2+ influx called store-operated Ca2+ entry (SOCE) that contributes to the function of many cell types. CRAC channels are formed by ORAI1 proteins located in the plasma membrane, which form its ion-conducting pore. ORAI1 channels are activated by stromal interaction molecule (STIM) 1 and STIM2 located in the endoplasmic reticulum. Loss- and gain-of-function gene mutations in ORAI1 and STIM1 in human patients cause distinct disease syndromes. CRAC channelopathy is caused by loss-of-function mutations in ORAI1 and STIM1 that abolish CRAC channel function and SOCE; it is characterized by severe combined immunodeficiency (SCID)-like disease, autoimmunity, muscular hypotonia, and ectodermal dysplasia, with defects in dental enamel. The latter defect emphasizes an important role of CRAC channels in tooth development. By contrast, autosomal dominant gain-of-function mutations in these genes result in constitutive CRAC channel activation, SOCE, and increased intracellular Ca2+ levels that are associated with an overlapping spectrum of diseases, including non-syndromic tubular aggregate myopathy (TAM) and York platelet and Stormorken syndromes, two syndromes defined, besides myopathy, by thrombocytopenia, thrombopathy, and bleeding diathesis. The fact that myopathy results from loss- and gain-of-function mutations in ORAI1 and STIM1 highlights the importance of CRAC channels for Ca2+ homeostasis in skeletal muscle function. The cellular dysfunction and clinical disease spectrum observed in mutant patients provide important information about the molecular regulation of ORAI1 and STIM1 proteins and the role of CRAC channels in human physiology.

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Ca2+ Signaling but Not Store-Operated Ca2+ Entry Is Required for the Function of Macrophages and Dendritic Cells

Cited by 102 publications

References 88 publications

Inhibition of P2X Receptors Protects Human Monocytes against Damage by Leukotoxin from Aggregatibacter actinomycetemcomitans and α-Hemolysin from Escherichia coli

Inhibition of P2X Receptors Protects Human Monocytes against Damage by Leukotoxin from Aggregatibacter actinomycetemcomitans and α-Hemolysin from Escherichia coli

Selective ORAI1 Inhibition Ameliorates Autoimmune Central Nervous System Inflammation by Suppressing Effector but Not Regulatory T Cell Function

Diseases caused by mutations in ORAI1 and STIM1

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