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See detailThe recruitment of p47 and Rac2G12V at the phagosome is transient and phosphatidylserine dependent.
Faure, Marie Cecile; Sulpice, Jean-Claude; Delattre, Maud et al

in Biology of the Cell (2013)

BACKGROUND INFORMATION: During phagocytosis, neutrophils internalise pathogens in a phagosome and produce reactive oxygen species (ROS) by the NADPH oxidase to kill the pathogen. The cytosolic NADPH ... [more ▼]

BACKGROUND INFORMATION: During phagocytosis, neutrophils internalise pathogens in a phagosome and produce reactive oxygen species (ROS) by the NADPH oxidase to kill the pathogen. The cytosolic NADPH oxidase subunits p40phox , p47phox , p67phox and Rac2 translocate to the phagosomal membrane to participate in enzyme activation. The kinetics of this recruitment and the underlying signalling pathways are only partially understood. Anionic phospholipids, phosphatidylserine (PS) and phosphoinositides (PPI) provide an important attachment site for numerous proteins, including several oxidase subunits. RESULTS: We investigated the kinetics of p47phox and Rac2 phagosomal membrane recruitment. Both subunits are known to interact with anionic phospholipids; we therefore addressed the role of PS in this recruitment. Phagosomal accumulation of p47phox and Rac2 tagged with fluorescent proteins was analysed by videomicroscopy. We used the C2 domain of lactadherin (lactC2) that interacts strongly and specifically with PS to monitor intracellular PS localisation and to decrease PS accessibility. During phagocytosis of opsonised zymosan, p47phox and constitutively active Rac2G12V briefly translocated to the phagosomal membrane, whereas ROS production continued for a longer period. However, in the presence of lactC2, Rac2G12V recruitment was inhibited and the kinetics of p47phox recruitment and detachment were delayed. A reduced phagosomal ROS production was also observed during the first 7 min following the phagosome closure. CONCLUSIONS: These results suggest that p47phox and Rac2 accumulate only transiently at the phagosome at the onset of NADPH activity and detach from the phagosome before the end of ROS production. Furthermore, lactC2, by masking PS, interfered with the phagosomal recruitment of p47phox and Rac2 and disturbed NADPH oxidase activity. Thus, PS appears as a modulator of NADPH oxidase activation. [less ▲]

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See detailSphingosine kinases regulate NOX2 activity via p38 MAPK-dependent translocation of S100A8/A9
Schenten, Véronique UL; Melchior, Chantal UL; Steinckwich, Nathalie et al

in Journal of Leukocyte Biology (2011), 89(4), 587-596

Neutrophils play a fundamental role in host defense by neutralizing pathogens through the generation of ROS by NOX2. In nonexcitable cells, Ca(2+) influx is essentially mediated via SOCE, a complex ... [more ▼]

Neutrophils play a fundamental role in host defense by neutralizing pathogens through the generation of ROS by NOX2. In nonexcitable cells, Ca(2+) influx is essentially mediated via SOCE, a complex mechanism in which depletion of intracellular Ca(2+) stores from the ER results in Ca(2+) entry through Ca(2+) SOCs at the plasma membrane. In this regard, it is well established that extracellular Ca(2+) entry participates to NOX2 activation. S1P, produced by SphKs, has been involved in Ca(2+) homeostasis and thus, could intervene in NOX2 regulation. The aim of this study was to characterize the importance of SphKs in NOX2 activation and the signaling cascade involved in this mechanism. Treatment of neutrophil-like dHL-60 cells by DHS, a SphK inhibitor, and SphK siRNA inhibited fMLF-induced NOX2 activity. Sequential activation of cells by thapsigargin and the phorbol ester PMA revealed that SphK-regulated NOX2 activity relies on intracellular Ca(2+) store depletion. Confocal microscopy and immunoblot analysis showed that stimulation by thapsigargin and PMA mediated S100A8/A9 recruitment to the plasma membrane and p38 MAPK activation. S100A8/A9 translocation decreased when SphK activity was blocked. This result was confirmed in purified human neutrophils, which were physiologically stimulated by fMLF. In addition, p38 MAPK was found to be regulated by SphKs. These results define a pathway leading to NOX2 activation, in which p38 MAPK-mediated S100A8/A9 translocation is regulated by Ca(2+) store depletion-dependent SphK activation. [less ▲]

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See detailAn essential role of STIM1, Orai1, and S100A8-A9 proteins for Ca2+ signaling and FcγR-mediated phagosomal oxidative activity
Steinckwich, Natacha; Schenten, Véronique UL; Melchior, Chantal UL et al

in Journal of Immunology (2011), 186(4), 2182-2191

Phagocytosis is a process of innate immunity that allows for the enclosure of pathogens within the phagosome and their subsequent destruction through the production of reactive oxygen species (ROS ... [more ▼]

Phagocytosis is a process of innate immunity that allows for the enclosure of pathogens within the phagosome and their subsequent destruction through the production of reactive oxygen species (ROS). Although these processes have been associated with increases of intracellular Ca(2+) concentrations, the mechanisms by which Ca(2+) could regulate the different phases of phagocytosis remain unknown. The aim of this study was to investigate the Ca(2+) signaling pathways involved in the regulation of FcγRs-induced phagocytosis. Our work focuses on IgG-opsonized zymosan internalization and phagosomal ROS production in DMSO-differentiated HL-60 cells and neutrophils. We found that chelation of intracellular Ca(2+) by BAPTA or emptying of the intracellular Ca(2+) store by thapsigargin reduced the efficiency of zymosan internalization. Using an small interfering RNA strategy, our data establish that the observed Ca(2+) release occurs through two isoforms of inositol 1,4,5-triphosphate receptors, ITPR1 and ITPR3. In addition, we provide evidence that phagosomal ROS production is dependent on extracellular Ca(2+) entry. We demonstrate that the observed Ca(2+) influx is supported by ORAI calcium release-activated calcium modulator 1 (Orai1) and stromal interaction molecule 1 (STIM1). This result suggests that extracellular Ca(2+) entry, which is required for ROS production, is mediated by a store-operated Ca(2+) mechanism. Finally, our data identify the complex formed by S100A8 and S100A9 (S100 calcium-binding protein A8 and A9 complex), two Ca(2+)-binding proteins, as the site of interplay between extracellular Ca(2+) entry and intraphagosomal ROS production. Thus, we demonstrate that FcγR-mediated phagocytosis requires intracellular Ca(2+) store depletion for the internalization phase. Then phagosomal ROS production requires extracellular Ca(2+) entry mediated by Orai1/STIM1 and relayed by S100A8-A9 as Ca(2+) sensor. [less ▲]

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See detailiPLA 2 , a novel determinant in Ca2+ - and phosphorylation-dependent S100A8/A9 regulated NOX2 activity
Schenten, Véronique UL; Bréchard, Sabrina UL; Plançon, Sébastien UL et al

in Biochimica et Biophysica Acta-Molecular Cell Research (2010), 1803(7), 840-847

The neutrophil NADPH oxidase (NOX2) is a key enzyme responsible for host defense against invading pathogens, via the production of reactive oxygen species. Dysfunction of NOX2 can contribute to ... [more ▼]

The neutrophil NADPH oxidase (NOX2) is a key enzyme responsible for host defense against invading pathogens, via the production of reactive oxygen species. Dysfunction of NOX2 can contribute to inflammatory processes, which could lead to the development of diseases such as atherosclerosis. In this paper, we characterize a pathway leading to NOX2 activation in which iPLA(2)-regulated p38 MAPK activity is a key regulator of S100A8/A9 translocation via S100A9 phosphorylation. Studies in cell-free or recombinant systems involved two Ca2+-binding proteins of the S100 family, namely S100A8 and S100A9, in NOX2 activation dependent on intracellular Ca2+ concentration ([Ca2+](i)) elevation. Using differentiated HL-60 cells as a model of neutrophils, we provide evidence that [Ca2+](i)-regulated S100A8/A9 translocation is mediated by an increase in [Ca2+](i) through intracellular Ca2+ store depletion. Moreover, we confirm that p38 MAPK induces S100A9 phosphorylation, a mandatory precondition for S100 translocation. Based on a pharmacological approach and an siRNA strategy, we identify iPLA(2) as a new molecular player aiding S100 translocation and NOX2 activity. Inhibition of p38 MAPK activity and S100A9 phosphorylation by bromoenol lactone, a selective inhibitor of iPLA(2), indicated that p38 MAPK-mediated S100A9 phosphorylation is dependent on iPLA(2). In conclusion, we have characterized a pathway leading to NOX2 activation in which iPLA(2)-regulated p38 MAPK activity is a key regulator of S100A8/A9 translocation via S100A9 phosphorylation. [less ▲]

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See detailSTIM1 but not STIM2 is an essential regulator of Ca2+ influx-mediated NADPH oxidase activity in neutrophil-like HL-60 cells
Bréchard, Sabrina UL; Plançon, Sébastien UL; Melchior, Chantal UL et al

in Biochemical Pharmacology (2009), 78(5), 504-513

Extracellular Ca2+ entry, primarily mediated through store-operated Ca2+ entry (SOCE), is known to be a critical event for NADPH oxidase (NOX2) regulation in neutrophils. While defective NOX2 activity has ... [more ▼]

Extracellular Ca2+ entry, primarily mediated through store-operated Ca2+ entry (SOCE), is known to be a critical event for NADPH oxidase (NOX2) regulation in neutrophils. While defective NOX2 activity has been linked to various inflammatory diseases, regulatory mechanisms that control Ca2+ influx-induced NOX2 activation are poorly understood in SOCE. The role of STIM1, a Ca2+ sensor that transduces the store depletion signal to the plasma membrane, seems well established and supported by numerous studies in non-phagocytic cells. Here, in neutrophil-like HL-60 cells we used a siRNA approach to delineate the effect of STIM1 knock-down on NOX2 activity regulated by Ca2+ influx. Because the function of the STIM1 homolog, STIM2, is still unclear, we determined the consequence of STIM2 knock-down on Ca2+ and NOX2. STIM1 and STIM2 knock-down was effective and isoform specific when assayed by real-time PCR and Western blotting. Consistent with a unique role of STIM1 in the regulation of SOCE, STIM1, but not STIM2, siRNA significantly decreased Ca2+ influx induced by fMLF or the SERCA pump inhibitor thapsigargin. A redistribution of STIM1, originally localized intracellularly, near the plasma membrane was observed by confocal microscopy upon stimulation by fMLF. Inhibition of STIM1-induced SOCE led to a marked decrease in NOX2 activity while STIM2 siRNA had no effect. Thus, our results provide evidence for a role of STIM1 protein in the control of Ca2+ influx in neutrophils excluding a STIM2 involvement in this process. It also places STIM1 as a key modulator of NOX2 activity with a potential interest for anti-inflammatory pharmacological development. [less ▲]

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See detailStore-operated Ca2+ channels formed by TRPC1, TRPC6 and Orai1 and non-store-operated channels formed by TRPC3 are involved in the regulation of NADPH oxidase in HL-60 granulocytes
Bréchard, Sabrina UL; Melchior, Chantal UL; Plançon, Sébastien UL et al

in Cell Calcium (2008)

Ca(2+) influx has been shown to be essential for NADPH oxidase activity which is involved in the inflammatory process. Ca(2+) conditions underlying the oxidative response are clearly delineated. Here, we ... [more ▼]

Ca(2+) influx has been shown to be essential for NADPH oxidase activity which is involved in the inflammatory process. Ca(2+) conditions underlying the oxidative response are clearly delineated. Here, we show that store-operated Ca(2+) entry (SOCE) is required at the beginning of NADPH oxidase activation in response to fMLF (N-formyl-l-methionyl-l-leucyl-l-phenylalanine ) in neutrophil-like HL-60 cells. When extracellular Ca(2+) is initially removed, early addition of Ca(2+) after stimulation causes a complete restoration of Ca(2+) entry and H(2)O(2) production. Both Ca(2+) entry and H(2)O(2) production are decreased by purported SOCE blockers, 2-aminoethoxydiphenyl borane (2-APB) and SK&F 96365. Endogenously expressed TRPC (transient receptor potential canonical) homologues and Orai1 were investigated for their role in supporting store-operated Ca(2+) channels activity. TRPC1, TRPC6 and Orai1 knock-out by siRNA resulted in the inhibition of Ca(2+) influx and H(2)O(2) production in response to fMLF and thapsigargin while suppression of TRPC3 had no effect on thapsigargin induced-SOCE. 2-APB and SK&F 96365 were able to amplify the reduction of fMLF-stimulated Ca(2+) entry and H(2)O(2) production observed in cells transfected by TRPC3 siRNA. In summary, Ca(2+) influx in HL-60 cells relies on different membrane TRPC channels and Orai1 for allowing NADPH oxidase activation. TRPC3 primarily mediates SOCE-independent pathways and TRPC1, TRPC6 and Orai1 exclusively contribute to SOCE. [less ▲]

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See detailCa2+-dependent regulation of NOX2 activity via MRP proteins in HL-60 granulocytes
Schenten, Véronique UL; Bréchard, Sabrina UL; Melchior, Chantal UL et al

in Calcium Binding Proteins (2008), 3(1), 25-30

Recently, two proteins of the S100 protein family, the myeloid-related calcium-binding proteins MRP-8 and MRP-14 have been implicated in the Ca2+-induced activation of the neutrophil NADPH oxidase (NOX2 ... [more ▼]

Recently, two proteins of the S100 protein family, the myeloid-related calcium-binding proteins MRP-8 and MRP-14 have been implicated in the Ca2+-induced activation of the neutrophil NADPH oxidase (NOX2) but the mechanism underlying this process remains unclear. In this study, the role of MRP-8/14 in the Ca2+-dependent regulation of NOX2 activity was characterized in neutrophil-like HL-60 cells using small interfering RNAs (siRNAs) to knock-down endogenous MRP-8 and/or MRP-14 expression. Real-time PCR and Western blot revealed that MRP-8 and MRP-14 expression was 20 times higher in dimethylsulfoxide-differentiated neutrophil-like HL-60 cells compared to quiescent HL-60 cells. Knock-down of MRP-8 and MRP-14 in differentiated HL-60 cells decreased protein levels by 30 and 45% respectively. The impact of the reduced MRP-8/14 protein expression on NOX2 activity was investigated by measuring fMLF-induced H2O2 production. In cells simultaneously transfected with MRP-8 and MRP14 siRNAs, H2O2 production was reduced by 50%, suggesting that both MRP-8 and MRP-14 are required for NOX2 activity; single knock-downs were inefficient. To elucidate the role of Ca2+ in MRP8/14, and consequently in NOX2 activation, siRNA-transfected cells were treated with the Ca2+ ionophore ionomycin prior to stimulation with PMA, a Ca2+-independent protein kinase C activator. PMA-induced H2O2 production was enhanced by ionomycin. This amplification of NOX2 activity was abolished by MRP8/14 knock-down, indicating that both MRP-8 and MRP-14 are necessary to regulate Ca2+-induced NOX2 activation. Taken together, our results suggest that the mechanism of MRPs activation is highly dependent on the increase of intracellular Ca2+ level for a full activation of NOX2. [less ▲]

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See detailCo-cultures of Human Coronary Smooth Muscle Cells and Dimethyl Sulfoxide-differentiated HL60 Cells Upregulate ProMMP9 Activity and Promote Mobility"”Modulation By Reactive Oxygen Species
Bernard, Yohann UL; Melchior, Chantal UL; Tschirhart, Eric UL et al

in Inflammation (2008)

Vascular cells and leukocytes, involved in the development of atherosclerosis, produce cytokines and/or reactive oxygen species (ROS) and matrix metalloproteinases (MMPs) implicated in cell mobility. We ... [more ▼]

Vascular cells and leukocytes, involved in the development of atherosclerosis, produce cytokines and/or reactive oxygen species (ROS) and matrix metalloproteinases (MMPs) implicated in cell mobility. We investigated by co-culture experiments the effects of human coronary smooth muscle cells (HCSMC) on MMPs characteristics and mobility of neutrophil-like dimethyl sulfoxide-differentiated HL60 cells (≠HL60). The effects of superoxide dismutase (SOD) and catalase were also analyzed. All the studied MMP2 characteristics remained unchanged. HCSMC stimulated MMP9 protein level, activity and mobility of ≠HL60 cells and expressed and secreted a variety of cytokines implicated in atherosclerosis. SOD and catalase increased MMP9 expression, protein level and activity of ≠HL60, but migration of ≠HL60 cells was only decreased by catalase, demonstrating that ROS are more efficient in modulating MMP9 activity of ≠HL60 than their mobility. Finally, HCSMC being able to stimulate ≠HL60, their co-cultures may represent an in vitro approach to study cellular interactions occurring in vivo during atherosclerosis. [less ▲]

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See detailCell passaging rapidly affects expression, secretion and activity of MMP9 as well as mobility of HL60 leukemia cells
Bernard, Yohann UL; Plançon, Sébastien UL; Melchior, Chantal UL et al

in Journal of Cell and Animal Biology (2008), 2(9), 160-165

The HL60 cell line, derived from acute promyelocytic leukemia cells, can differentiate into neutrophil-like cell following DMSO treatment. Mobility of HL60, or DMSO-differentiated HL60 cells (≠HL60 ... [more ▼]

The HL60 cell line, derived from acute promyelocytic leukemia cells, can differentiate into neutrophil-like cell following DMSO treatment. Mobility of HL60, or DMSO-differentiated HL60 cells (≠HL60), requires surface expression of adhesion molecules and production of matrix metalloproteinases (MMPs). The aim of this study was to investigate in HL60 and ≠HL60 the effects of cell passaging (over 5 passages after delivery (P and P+5)) on i) surface expression of adhesion molecule CD11b, which is considered a neutrophil differentiation marker ii) MMP9 mRNA expression, protein release and zymographic activity and iii) cellular mobility. As expected, CD11b expression at both cell passages increased in ≠HL60 relative to undifferentiated HL60, but expression levels of this neutrophils marker did not change over 5 passages. MMP9 mRNA expression however, in basal conditions was increased in HL60 at P+5. At P+5 versus P, MMP9 protein levels, MMP9 zymographic activity and cellular mobility in HL60 and ≠HL60 were elevated. Stimulation by N-formyl-L-Methionyl-L-Leucyl-L-Phenylalanine had no effects on HL60, but raised MMP9 protein concentration and zymographic activity in ≠HL60. Since passage history is likely to also influence cellular functions other than MMP-related effects, it is important to carefully consider passage numbers when designing experiments [less ▲]

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See detailDistinct involvement of beta3 integrin cytoplasmic domain tyrosine residues 747 and 759 in integrin-mediated cytoskeletal assembly and phosphotyrosine signaling.
Schaffner-Reckinger, Elisabeth UL; Gouon, V.; Melchior, Chantal UL et al

in The Journal of biological chemistry (1998), 273(20), 12623-32

We have investigated the structural requirements of the beta3 integrin subunit cytoplasmic domain necessary for tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin during alphav beta3 ... [more ▼]

We have investigated the structural requirements of the beta3 integrin subunit cytoplasmic domain necessary for tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin during alphav beta3-mediated cell spreading. Using CHO cells transfected with various beta3 mutants, we demonstrate a close correlation between alphav beta3-mediated cell spreading and tyrosine phosphorylation of FAK and paxillin, and highlight a distinct involvement of the NPLY747 and NITY759 motifs in these signaling processes. Deletion of the NITY759 motif alone was sufficient to completely prevent alphav beta3-dependent focal contact formation, cell spreading, and FAK/paxillin phosphorylation. The single Y759A substitution induced a strong inhibitory phenotype, while the more conservative, but still phosphorylation-defective, Y759F mutation restored wild type receptor function. Alanine substitution of the highly conserved Tyr747 completely abolished alphav beta3-dependent formation of focal adhesion plaques, cell spreading, and FAK/paxillin phosphorylation, whereas a Y747F substitution only partially restored these events. As none of these mutations affected receptor-ligand interaction, our results suggest that the structural integrity of the NITY759 motif, rather than the phosphorylation status of Tyr759 is important for beta3-mediated cytoskeleton reorganization and tyrosine phosphorylation of FAK and paxillin, while the presence of Tyr at residue 747 within the NPLY747 motif is required for optimal beta3 post-ligand binding events. [less ▲]

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