Annexin 3 is associated with cytoplasmic granules in neutrophils and monocytes and translocates to the plasma membrane in activated cells

Up-Regulation of S100 Gene Family in Brain Samples of a Subgroup of Individuals with Schizophrenia: Meta-analysis

The S100 proteins family is known to affect neuroinflammation and astrocyte activation, which have been suggested to be contributors to the pathogenesis of schizophrenia. We conducted a systematic meta-analysis of S100 genes differential expression in postmortem samples of patients with schizophrenia vs. healthy controls, following the commonly used Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Twelve microarray datasets met the inclusion criteria (overall 511 samples, 253 schizophrenia and 258 controls were analyzed). Nine out of 21 genes were significantly up-regulated or with tendency for up-regulation. A per-sample fold change analysis indicated that the S100 genes' up-regulation was concentrated in a subgroup of the patients. None of the genes have been found to be down-regulated. ANXA3, which encodes Annexin 3 protein and was associated with neuroinflammation, was up-regulated and positively correlated with the S100 genes' expression pattern. In addition, astrocytes and endothelial cell markers were significantly correlated with S100A8 expression. S100 correlation with ANXA3 and endothelial cell markers suggests that the up-regulation we detected reflects increased inflammation. However, it might also reflect astrocytes abundance or activation. The fact that S100 proteins were shown to be up-regulated in blood samples and other body fluids of patients with schizophrenia suggests a potential role as biomarkers, which might help disease subtyping, and the development of etiological treatments for immune dysregulation in schizophrenia.

Citrullination of actin-ligand and nuclear structural proteins, cytoskeleton reorganization and protein redistribution across cellular fractions are early events in ionomycin-induced NETosis

Neutrophil extracellular traps (NETs) are web-like structures of DNA coated with cytotoxic proteins and histones released by activated neutrophils through a process called NETosis. NETs release occurs through a sequence of highly organized events leading to chromatin expansion and rupture of nuclear and cellular membranes. In calcium ionophore-induced NETosis, the enzyme peptidylargine deiminase 4 (PAD4) mediates chromatin decondensation through histone citrullination, but the biochemical pathways involved in this process are not fully understood. Here we use live-imaging microscopy and proteomic studies of the neutrophil cellular fractions to investigate the early events in ionomycin-triggered NETosis. We found that before ionomycin-stimulated neutrophils release NETs, profound biochemical changes occur in and around their nucleus, such as, cytoskeleton reorganization, nuclear redistribution of actin-remodeling related proteins, and citrullination of actin-ligand and nuclear structural proteins. Ionomycin-stimulated neutrophils rapidly lose their characteristic polymorphic nucleus, and these changes are promptly communicated to the extracellular environment through the secretion of proteins related to immune response. Therefore, our findings revealed key biochemical mediators in the early process that subsequently culminates with nuclear and cell membranes rupture, and extracellular DNA release.

Annexin A3 accelerates osteoclast differentiation by promoting the level of RANK and TRAF6

Annexin A3 (ANXA3), a member of Annexin family, is reported to mediate membrane transport and cancer development. However, the effect of ANXA3 on osteoclast formation and bone metabolism is still unclear. In this study, we found that knockdown of ANXA3 can significantly inhibit receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation through NF-κB signaling. ANXA3 downregulation abrogated the expression of osteoclast-specific genes, including Acp5, Mmp9 and Ctsk in osteoclast precursors. Moreover, lentiviral of shRNA against ANXA3 reversed the bone loss in osteoporosis using ovariectomized mice model. Mechanistically, we found that ANXA3 directly bound to RANK and TRAF6 to accelerate osteoclast differentiation by promoting their transcription and limiting degradation. In conclusion, we propose a fundamentally novel RANK-ANXA3-TRAF6 complex to effectively modulate the formation and differentiation of osteoclast to manipulate bone metabolism. The ANXA3-targeted therapeutic strategy may provide new insight for bone degrading-related diseases prevention and treatment.

The role of Annexin A3 in coronary arterial lesions in children with Kawasaki disease

Kawasaki disease (KD) is an acute, self-limited vasculitis, and the etiology is still unclear. Coronary arterial lesions (CALs) are a major complication of KD. Excessive inflammation and immunologic abnormities are involved in the pathogenesis of KD and CALs. Annexin A3 (ANXA3) plays crucial roles in cell migration and differentiation, inflammation, cardiovascular and membrane metabolic diseases. The purpose of this study was to investigate the effect of ANXA3 on the pathogenesis of KD and CALs. There were 109 children with KD in the KD group [which was divided into two groups: 67 patients with CALs in the KD-CAL group, and 42 patients with noncoronary arterial lesions (NCALs) in the KD-NCAL group] and 58 healthy children in the control (HC) group. Clinical and laboratory data were retrospectively collected from all patients with KD. The serum concentration of ANXA3 was measured by enzyme-linked immunosorbent assays (ELISAs). Serum ANXA3 levels were higher in the KD group than in the HC group (P < 0.05). There was a higher concentration of serum ANXA3 in the KD-CAL group than in the KD-NCAL group (P < 0.05). Neutrophil cell counts and serum ANXA3 levels were higher in the KD group than in the HC group (P < 0.05) and quickly decreased when the patients were treated with IVIG after 7 days of illness. Platelet (PLT) counts and ANXA3 levels concurrently exhibited significant increases 7 days after onset. Furthermore, ANXA3 levels were positively correlated with lymphocyte and PLT counts in the KD and KD-CAL groups. ANXA3 may be involved in the pathogenesis of KD and CALs.

Identification of a Four-Gene Signature for Diagnosing Paediatric Sepsis

Aim

Early diagnosis of paediatric sepsis is crucial for the proper treatment of children and reduction of hospitalization and mortality. Biomarkers are a convenient and effective method for diagnosing any disease. However, huge differences among the studies reporting biomarkers for diagnosing sepsis have limited their clinical application. Therefore, in this study, we aimed to evaluate the diagnostic value of key genes involved in paediatric sepsis based on the data of the Gene Expression Omnibus database.

Methods

We used the GSE119217 dataset to identify differentially expressed genes (DEGs) between patients with and without paediatric sepsis. The most relevant gene modules of paediatric sepsis were screened through the weighted gene coexpression network analysis (WGCNA). Common genes (CGs) were found between DEGs and WGCNA. Genes with a potential diagnostic value in paediatric sepsis were selected from the CGs using least absolute shrinkage and selection operator regression and support vector machine recursive feature elimination. The principal component analysis, receiver operating characteristic curves, and C-index were used to verify the diagnostic value of the identified genes in six other independent sepsis datasets. Subsequently, a meta-analysis of the selected genes was performed to evaluate the value of these genes as biomarkers in paediatric sepsis.

Results

A total of 41 CGs were selected from the GSE119217 dataset. A four-gene signature composed of ANXA3, CD177, GRAMD1C, and TIGD3 effectively distinguished patients with paediatric sepsis from those in the control group. The signature was verified using six other independent datasets. In addition, the meta-analysis results showed that the pooled sensitivity, specificity, and area under the curve values were 1.00, 0.98, and 1.00, respectively.

Conclusion

The four-gene signature can be used as new biomarkers to distinguish patients with paediatric sepsis from healthy individuals.

Identifying critical genes associated with aneurysmal subarachnoid hemorrhage by weighted gene co-expression network analysis

Aneurysmal subarachnoid hemorrhage (aSAH) is a life-threatening medical condition with a high mortality and disability rate. aSAH has an unclear pathogenesis, and limited treatment options are available. Here, we aimed to identify critical genes involved in aSAH pathogenesis using peripheral blood gene expression data of 43 patients with aSAH due to ruptured intracranial aneurysms and 18 controls with headache, downloaded from Gene Expression Omnibus. These data were used to construct a co-expression network using weighted gene co-expression network analysis (WGCNA). The biological functions of the hub genes were explored, and critical genes were selected by combining with differentially expressed genes analysis. Fourteen modules were identified by WGCNA. Among those modules, red, blue, brown and cyan modules were closely associated with aSAH. Moreover, 364 hub genes in the significant modules were found to play important roles in aSAH. Biological function analysis suggested that protein biosynthesis-related processes and inflammatory responses-related processes were involved in the pathology of aSAH pathology. Combined with differentially expressed genes analysis and validation in 35 clinical samples, seven gene (CD27, ANXA3, ACSL1, PGLYRP1, ALPL, ARG1, and TPST1) were identified as potential biomarkers for aSAH, and three genes (ANXA3, ALPL, and ARG1) were changed with disease development, that may provide new insights into potential molecular mechanisms for aSAH.

Expression Profile of New Gene Markers and Signaling Pathways Involved in Immunological Processes in Human Cumulus-Oophorus Cells

The function of the immune system extends from defense against external pathogens to the recognition and elimination of mutated or dying cells, aiding elimination of malignant potential and/or maintaining homeostasis. The many cell types of the immune system secrete a broad range of factors to enable cellular signaling that is vital to physiological processes. Additionally, in the ovary, follicular selection and maturation, as well as ovulation, are directly regulated by the nearby immune cells. Additionally, ovulation and rupture of the follicle have been observed to resemble a local inflammatory response. Cells of the cumulus–oocyte complex (COC) show evolving gene expression profiles throughout the oocytes’ lifespan, including genes associated with immunological processes. Analysis of these genes allows the identification of useful molecular markers, as well as highlighting gene functions and interactions in these cells. Cumulus cells were obtained from hormonally stimulated patients undergoing an in vitro fertilization procedure and studied under long-term culture conditions. The microarray technique made it possible to compare the level of CCs’ gene expression on the 1st, 7th, 15th and 30th day of cultivation. Additionally, RNA microarray analysis was performed to map gene expression in these cells, associated with immunological processes and associated cytokine signaling. Subsequently, the use of DAVID software allowed us to identify the “defense response to other organism”, “defense response”, “defense response to virus”, “cytokine secretion”, “cytokine production” and “cytokine-mediated signaling pathway” GO BP terms, as well as allowing further analysis of the most differentially expressed genes associated with these processes. Of the 122 genes involved, 121 were upregulated and only one was downregulated. The seven most upregulated genes related to the abovementioned terms were ANXA3, IFIT1, HLA-DPA1, MX1, KRT8, HLA-DRA and KRT18. Therefore, genes involved in immunological defense processes are upregulated in CC cultures and could serve as useful molecular markers of growth and development in the COC, as well as the proliferation of granulosa and cumulus cells.

Annexin A3, a Calcium-Dependent Phospholipid-Binding Protein: Implication in Cancer

Annexin A3 (ANXA3), also known as lipocortin III and placental anticoagulant protein III, has been reported to be dysregulated in tumor tissues and cancer cell lines, and harbors pronounced diagnostic and prognostic value for certain malignancies, such as breast, prostate, colorectal, lung and liver cancer. Aberrant expression of ANXA3 promotes tumor cell proliferation, invasion, metastasis, angiogenesis, and therapy resistance to multiple chemotherapeutic drugs including platinum-based agents, fluoropyrimidines, cyclophosphamide, doxorubicin, and docetaxel. Genetic alterations on the ANXA3 gene have also been reported to be associated with the propensity to form certain inherited, familial tumors. These diverse functions of ANXA3 in tumors collectively indicate that ANXA3 may serve as an attractive target for novel anticancer therapies and a powerful diagnostic and prognostic biomarker for early tumor detection and population risk screening. In this review, we dissect the role of ANXA3 in cancer in detail.

Annexin A3 in sepsis: novel perspectives from an exploration of public transcriptome data

According to publicly available transcriptome datasets, the abundance of Annexin A3 (ANXA3) is robustly increased during the course of sepsis; however, no studies have examined the biological significance or clinical relevance of ANXA3 in this pathology. Here we explored this interpretation gap and identified possible directions for future research. Based on reference transcriptome datasets, we found that ANXA3 expression is restricted to neutrophils, is upregulated in vitro after exposure to plasma obtained from septic patients, and is associated with adverse clinical outcomes. Secondly, an increase in ANXA3 transcript abundance was also observed in vivo, in the blood of septic patients in multiple independent studies. ANXA3 is known to mediate calcium-dependent granules-phagosome fusion in support of microbicidal activity in neutrophils. More recent work has also shown that ANXA3 enhances proliferation and survival of tumour cells via a Caspase-3-dependent mechanism. And this same molecule is also known to play a critical role in regulation of apoptotic events in neutrophils. Thus, we posit that during sepsis ANXA3 might either play a beneficial role, by facilitating microbial clearance and resolution of the infection; or a detrimental role, by prolonging neutrophil survival, which is known to contribute to sepsis-mediated organ damage.

Expression of S100A Alarmins in Cord Blood Monocytes Is Highly Associated With Chorioamnionitis and Fetal Inflammation in Preterm Infants

Background: Preterm infants exposed to chorioamnionitis and with a fetal inflammatory response are at risk for neonatal morbidity and adverse outcome. Alarmins S100A8, S100A9, and S100A12 are expressed by myeloid cells and have been associated with inflammatory activation and monocyte modulation.

Aim: To study S100A alarmin expression in cord blood monocytes from term healthy and preterm infants and relate results to clinical findings, inflammatory biomarkers and alarmin protein levels, as well as pathways identified by differentially regulated monocyte genes.

Methods: Cord blood CD14+ monocytes were isolated from healthy term (n = 10) and preterm infants (<30 weeks gestational age, n = 33) by MACS technology. Monocyte RNA was sequenced and gene expression was analyzed by Principal Component Analysis and hierarchical clustering. Pathways were identified by Ingenuity Pathway Analysis. Inflammatory proteins were measured by Multiplex ELISA, and plasma S100A proteins by mass spectrometry. Histological chorioamnionitis (HCA) and fetal inflammatory response syndrome (FIRS) were diagnosed by placenta histological examination.

Results: S100A8, S100A9, and S100A12 gene expression was significantly increased and with a wider range in preterm vs. term infants. High S100A8 and S100A9 gene expression (n = 17) within the preterm group was strongly associated with spontaneous onset of delivery, HCA, FIRS and elevated inflammatory proteins in cord blood, while low expression (n = 16) was associated with impaired fetal growth and physician-initiated delivery. S100A8 and S100A9 protein levels were significantly lower in preterm vs. term infants, but within the preterm group high S100A gene expression, spontaneous onset of labor, HCA and FIRS were associated with elevated protein levels. One thousand nine hundred genes were differentially expressed in preterm infants with high vs. low S100A alarmin expression. Analysis of 124 genes differentially expressed in S100A high as well as FIRS and HCA groups identified 18 common pathways and S100A alarmins represented major hubs in network analyses.

Conclusion: High expression of S100A alarmins in cord blood monocytes identifies a distinct clinical risk group of preterm infants exposed to chorioamnionitis and with a fetal inflammatory response. Gene and pathway analyses suggest that high S100A alarmin expression also affects monocyte function. The connection with monocyte phenotype and inflammation-stimulated S100A expression in other cell types (e.g., neutrophils) warrants further investigation.

Tuberculosis Exacerbates HIV-1 Infection through IL-10/STAT3-Dependent Tunneling Nanotube Formation in Macrophages

The tuberculosis (TB) bacillus, Mycobacterium tuberculosis (Mtb), and HIV-1 act synergistically; however, the mechanisms by which Mtb exacerbates HIV-1 pathogenesis are not well known. Using in vitro and ex vivo cell culture systems, we show that human M(IL-10) anti-inflammatory macrophages, present in TB-associated microenvironment, produce high levels of HIV-1. In vivo, M(IL-10) macrophages are expanded in lungs of co-infected non-human primates, which correlates with disease severity. Furthermore, HIV-1/Mtb co-infected patients display an accumulation of M(IL-10) macrophage markers (soluble CD163 and MerTK). These M(IL-10) macrophages form direct cell-to-cell bridges, which we identified as tunneling nanotubes (TNTs) involved in viral transfer. TNT formation requires the IL-10/STAT3 signaling pathway, and targeted inhibition of TNTs substantially reduces the enhancement of HIV-1 cell-to-cell transfer and overproduction in M(IL-10) macrophages. Our study reveals that TNTs facilitate viral transfer and amplification, thereby promoting TNT formation as a mechanism to be explored in TB/AIDS potential therapeutics.

New markers of human cumulus oophorus cells cultured in vitro – transcriptomic profile

The presence of CCs around the oocyte after ovulation is one of the key elements contributing to oocyte developmental competence. In the presented study, we used CCs from 12 patients aged 18-40 diagnosed with infertility. After harvesting cells on day 1, 7, 15 and 30 of culture, total RNA was isolated and transcriptomic analysis was performed. The DAVID software indicated the following GO BP terms: “cell junction organization”, “cell migration”, “cell morphogenesis involved in differentiation”, “cell morphogenesis” and “cell motility”. Of the genes belonging to all ontological groups, the most downregulated were: SLC7A8, DFNB31, COL1A1, CDC42SE1, TGFBR3, HMGB1, with the most upregulated genes being: ANXA3, KIAA1199, HTR2B, VCAM1, DKK1.

While many studies focus on attempts to obtain fully competent oocytes, scientists still have difficulty attaining adequate results in vitro. Lack of adequate knowledge often results in low in vitro fertilization efficiency. Therefore, our research focuses on CCs cells, thanks to which the oocyte most likely acquires developmental competence. The main purpose of the study was to identify the potential molecular markers responsible for cell junction organization, migration, differentiation, morphogenesis and motility.

Running title: New markers of human cumulus oophorus cells cultured in vitro

PR3 levels are impaired in plasma and PBMCs from Arabs with cardiovascular diseases

Cardiovascular disease (CVD) risks persist in patients despite treatment. CVD susceptibility also varies with sex and ethnicity and is not entirely explained by conventional CVD risk factors. The aim of the present study was to identify novel CVD candidate markers in circulating Peripheral blood mononuclear cells (PBMCs) and plasma from Arab obese subjects with and without CVD using proteomic approaches. Human adults with confirmed CVD (n = 208) and matched non-CVD controls (n = 152) living in Kuwait were examined in the present cross-sectional study. Anthropometric and classical biochemical parameters were determined. We employed a shotgun proteomic profiling approach on PBMCs isolated from a subset of the groups (n = 4, each), and differentially expressed proteins selected between the two groups were validated at the mRNA level using RT-PCR (n = 6, each). Plasma levels of selected proteins from the proteomics profiling: Proteinase-3 (PR3), Annexin-A3 (ANX3), Defensin (DEFA1), and Matrix Metalloproteinase-9 (MMP9), were measured in the entire cohort using human enzyme-linked immunosorbent assay kits and were subsequently correlated with various clinical parameters. Out of the 1407 we identified and quantified from the proteomics profiling, 47 proteins were dysregulated with at least twofold change between the two subject groups. Among the differentially expressed proteins, 11 were confirmed at the mRNA levels. CVD influenced the levels of the shortlisted proteins (MMP9, PR3, ANX3, and DEFA1) in the PBMCs and plasma differentially. Despite the decreased levels of both protein and mRNA in PBMCs, PR3 circulating levels increased significantly in patients with CVD and were influenced by neither diabetes nor statin treatment. No significant changes were; however, observed in the DEFA1, MMP9, and ANX3 levels in plasma. Multivariate logistic regression analysis revealed that only PR3 was independently associated with CVD. Our results suggest that the dysregulation of PR3 levels in plasma and PBMCs reflects underlying residual CVD risks even in the treated population. More prospective and larger studies are required to establish the role of PR3 in CVD progression.

Usefulness of Transcriptional Blood Biomarkers as a Non-invasive Surrogate Marker of Mucosal Healing and Endoscopic Response in Ulcerative Colitis

BACKGROUND AND AIMS

Ulcerative colitis [UC] is a chronic inflammatory disease of the colon. Colonoscopy remains the gold standard for evaluating disease activity, as clinical symptoms are not sufficiently accurate. The aim of this study is to identify new accurate non-invasive biomarkers based on whole-blood transcriptomics that can predict mucosal lesions and response to treatment in UC patients.

METHODS

Whole-blood samples were collected for a total of 152 UC patients at endoscopy. Blood RNA from 25 UC individuals and 20 controls was analysed using microarrays. Genes that correlated with endoscopic activity were validated using real-time polymerase chain reaction in an independent group of 111 UC patients, and a prediction model for mucosal lesions was evaluated. Responsiveness to treatment was assessed in a longitudinal cohort of 16 UC patients who started anti-tumour necrosis factor [TNF] therapy and were followed up for 14 weeks.

RESULTS

Microarray analysis identified 122 genes significantly altered in the blood of endoscopically active UC patients. A significant correlation with the degree of endoscopic activity was observed in several genes, including HP, CD177, GPR84, and S100A12. Using HP as a predictor of endoscopic disease activity, an accuracy of 67.3% was observed, compared with 52.4%, 45.2%, and 30.3% for C-reactive protein, erythrocyte sedimentation rate, and platelet count, respectively. Finally, at 14 weeks of treatment, response to anti-TNF therapy induced alterations in blood HP, CD177, GPR84, and S100A12 transcripts that correlated with changes in endoscopic activity.

CONCLUSIONS

Transcriptional changes in UC patients are sensitive to endoscopic improvement and appear to be an effective tool to monitor patients over time.

Proteomic analysis of human cervicovaginal fluid collected before preterm premature rupture of the fetal membranes

A significant obstetric complication facing contemporary materno–fetal medicine is preterm premature rupture of the fetal membranes (preterm PROM), which occurs in 30% of all preterm births. The objective of this study was to identify differentially expressed proteins in the cervicovaginal fluid of asymptomatic women before the clinical manifestation of preterm PROM. The preterm PROM group comprised of women with samples collected 6–23 days before PROM, who subsequently delivered preterm (n=5). Women who spontaneously delivered at term served as gestation-matched controls (n=10). Two-dimensional difference in-gel electrophoresis was used to distinguish differential expression between the pooled groups and fold changes were subsequently confirmed by two-dimensional PAGE of individual samples. Spots of interest were identified by mass spectrometry. Proteins that were significantly reduced with impending preterm PROM included the following: thioredoxin (2.7-fold), interleukin 1 receptor antagonist (1.7-fold), fatty acid-binding protein 5 (2.1-fold), cystatin A (dimer; 1.9-fold), monocyte/neutrophil elastase inhibitor (1.6-fold), squamous cell carcinoma antigen-1 (2.1-fold) and γ-glutamyl cyclotransferase (3.0-fold). By contrast, annexin A3 (3.7-fold) and vitamin D binding protein (3.9-fold) were significantly increased with impending preterm PROM. Western blot analysis was also performed on an independent cohort of preterm PROM and control samples to validate these candidate biomarkers. These proteins have known biological functions in oxidative balance, anti-inflammatory activity, metabolism or protease inhibition that may facilitate membrane rupture.

Blood leukocytes and macrophages of various phenotypes have distinct abilities to form podosomes and to migrate in 3D environments

Leukocytes migrate through most tissues in the body, a process which takes place in 3D environments. We have previously shown that macrophages use the amoeboid migration mode in porous matrices such as fibrillar collagen I and the mesenchymal mode involving podosomes and matrix proteolysis in dense matrices such as Matrigel. Whether such a plasticity may apply to other leukocytes and to all subsets of macrophages is unknown. Here, we therefore provide a comparative analysis of the in vitro 3D migration modes adopted by primary human leukocytes. Blood-derived monocytes, neutrophils and T lymphocytes were found to use the amoeboid mode in a porous fibrillar collagen I matrix but were unable to infiltrate dense Matrigel and to form podosomes. M2-polarized macrophages and elicited peritoneal macrophages formed podosome rosettes, degraded the ECM and infiltrated both matrices. In contrast, M1 macrophages were motionless in 2D and 3D environments, whilst resident macrophages, devoid of podosomes, were only able to use the amoeboid mode. Thus, we conclude that whereas all leukocytes use the amoeboid mode to migrate through porous matrices, it is only certain macrophages that can adopt the mesenchymal mode that permits migration through dense matrices. Interestingly, the acquisition of mesenchymal migration capacity by macrophages correlates with the presence of podosomes and with their capacity to organize those as rosettes, which appears to be modulated by their differentiation and polarization states. As a perspective, specific control of the mesenchymal migration would be a potential target for therapeutic approaches aiming at decreasing macrophage tissue infiltration.

An essential role for phospholipase D in the recruitment of vesicle amine transport protein-1 to membranes in human neutrophils

Although phosphatidic acid (PA) regulates a wide variety of physiological processes, its targets remain poorly characterized in human neutrophils. By co-sedimentation with PA-containing vesicles we identified several PA-binding proteins including vesicle amine transport protein-1 (VAT-1), Annexin A3 (ANXA3), Rac2, Cdc42 and RhoG in neutrophil cytosol. Except for ANXA3, protein binding to PA-containing liposomes was calcium-independent. Cdc42 and RhoG preferentially interacted with PA whereas VAT-1 bound to PA or phosphatidylserine with the same affinity. VAT-1 translocated to neutrophil membranes upon N-formyl-methionyl-leucyl-phenylalanine (fMLF) stimulation. Inhibition of fMLF-induced PLD activity with the Src kinase inhibitor PP2, the selective inhibitor of PLD FIPI, or of PA formation with primary alcohols reduced VAT-1 translocation. In contrast, inhibition of PA hydrolysis with propranolol enhanced fMLF-mediated VAT-1 recruitment to membranes. PMA also redistributed VAT-1 to membranes in a PKC- and PLD-dependent manner. Though fMLF and PMA increased VAT-1 phosphorylation, different kinases appear to be involved. Cell fractionation revealed that a pool of VAT-1 was co-localized with primary, secondary and tertiary granules and plasma membrane markers in resting neutrophils. Stimulation with fMLF enhanced VAT-1 co-localization with CD32a, a plasma membrane marker. Confocal microscopy revealed that VAT-1 decorates granular structures at the cell periphery and double labeling with VAT-1/lactoferrin antibodies showed a partial co-localization with secondary granules in control and fMLF-stimulated cells. Characterization of these putative PA-binding proteins constitutes another step forward for a better understanding of the role of PLD-derived PA in neutrophil physiology.

Proteomic identification of an upregulated isoform of annexin A3 in the rat brain following reversible cerebral ischemia

We used proteomics to identify regulated proteins following cerebral ischemia in a rat model. Young rats were subjected to reversible middle cerebral artery (MCA) occlusion and proteins were extracted from the peri-infarcted and the corresponding contralateral area at days 3 and 14 postischemia. Proteins were analyzed by two-dimensional polyacrylamide gel electrophoresis followed by mass spectrometry. We report for the first time that an isoform of annexin A3 (ANXA3) was among the upregulated proteins in the postischemic rat brain. The results were confirmed by real-time PCR and by western blotting. Double- and triple-immunostaining with neuronal and microglia/macrophagic markers demonstrated that ANXA3 is produced by resting microglia in control tissue and by activated microglial/macrophage cells in the infarcted area. 3D-images of the infarcted area suggest that ANXA3 is associated with a phagocytic phenotype. Our study identifies ANXA3 as a novel marker of brain microglia, which should be of substantial value in future studies of microglial cells and its role in the postischemic brain.

Re-arrangements of podosome structures are observed when Hck is activated in myeloid cells

Podosomes are adhesion structures with an extracellular matrix-degrading capacity mostly found in monocyte-derived cells. We have previously shown that the protein tyrosine kinase Hck, a member of the Src family, triggers the de novo formation of podosome rosettes in a lysosome-dependent manner when expressed in its constitutively active form. Hck is specifically expressed in myeloid cells. In human monocyte-derived macrophages (MDMs) it is present at podosomes. Here we addressed whether its activation by lipopolysaccharide and interferon-gamma has an effect on podosome organization in MDMs. Several structures were observed evolving from individual podosomes to clusters, aggregates and rosettes. In chronic myeloid leukemia cells, Hck is constitutively activated by the fusion protein Bcr-Abl and podosome-like structures were present. Finally, in monocyte-derived osteoclasts, Hck was found to accumulate at podosome belts. In conclusion, in monocyte-derived cells, it is likely that Hck could play a role in podosome re-arrangements.

The human macrophage mannose receptor is not a professional phagocytic receptor

The macrophage mannose receptor (MR) appears to play an important role in the binding and phagocytosis of several human pathogens, but its phagocytic property and signaling pathways have been poorly defined. The general strategy to explore such topics is to express the protein of interest in nonphagocytic cells, but in the case of MR, there are few reports using the full-length MR cDNA. When we searched to clone de novo the human MR (hMR) cDNA, problems were encountered, and full-length hMR cDNA was only obtained after devising a complex cloning strategy. Chinese hamster ovary cells, which have a fully functional phagocytic machinery when expressing professional phagocytic receptors, were stably transfected, and cell clones expressing hMR at quantitatively comparable levels than human macrophages or J774E cells were obtained. They exhibited a functional hMR-mediated endocytic capacity of a soluble ligand but failed to ingest classical particulate ligands of MR such as zymosan, Mycobacterium kansasii, or trimannoside bovine serum albumin-coated latex beads. Transient expression of hMR in two human cell lines did not provide a phagocytic capacity either. In conclusion, we show that MR is not a professional phagocytic receptor, as it does not possess the ability to promote particle ingestion in nonphagocytic cells on its own. We propose that MR is a binding receptor, which requires a partner to trigger phagocytosis in some specialized cells such as macrophages. Our new expression vector could represent a useful tool to study the receptor and its partnership further.

Selection of reference genes for gene expression studies in human neutrophils by real-time PCR

Background

Reference genes, which are often referred to housekeeping genes, are frequently used to normalize mRNA levels between different samples. However the expression level of these genes may vary among tissues or cells, and may change under certain circumstances. Thus the selection of reference gene(s) is critical for gene expression studies. For this purpose, 10 commonly used housekeeping genes were investigated in isolated human neutrophils.

Results

Initial screening of the expression pattern demonstrated that 3 of the 10 genes were expressed at very low levels in neutrophils and were excluded from further analysis. The range of expression stability of the other 7 genes was (from most stable to least stable): GNB2L1 (Guanine nucleotide binding protein, beta polypeptide 2-like 1), HPRT1 (Hypoxanthine phosphoribosyl transferase 1), RPL32 (ribosomal protein L32), ACTB (beta-actin), B2M (beta-2-microglobulin), GAPD (glyceraldehyde-3-phosphate dehydrogenase) and TBP (TATA-binding protein). Relative expression levels of the genes (from high to low) were: B2M, ACTB, GAPD, RPL32, GNB2L1, TBP, and HPRT1.

Conclusion

Our data suggest that GNB2L1, HPRT1, RPL32, ACTB, and B2M may be suitable reference genes in gene expression studies of neutrophils.

Characterisation and properties of ectosomes released by human polymorphonuclear neutrophils

Human neutrophils release vesicles when activated in vitro and in vivo, in local and systemic inflammation. We have suggested that the presence of these vesicles is due to ectocytosis, defined as the release of rightside-out oriented vesicles expressing a select set of membrane proteins. Herein we have characterised the vesicles released by neutrophils to be ectosomes with specific properties. They contained cytosolic F-actin indicating their outside-out orientation. They bound Annexin V, suggesting that they expose phosphatidylserine, similarly to platelet microparticles. They expressed a subset of cell surface proteins (selectins and integrins, complement regulators, HLA-1, FcgammaRIII, and CD66b, but not CD14, FcgammaRII, and CD87). There was no specificity for transmembrane or glycosyl-phosphatidylinositol-linked proteins and, unexpectedly, L-selectin, known to be cleaved from the surface of activated neutrophils, was present. Ectosomes exposed active enzymes released by neutrophils upon degranulation (matrix metalloproteinase-9, myeloperoxidase, proteinase 3, and elastase). In particular, released myeloperoxidase was able to bind back to ectosomes. The purified complement protein C1q and C1q from serum bound to ectosomes as well. Another aspect of ectosomes was that they became specifically adherent to monocytic and endothelial cells. These observations suggest that neutrophil-derived ectosomes have unique characteristics that make them candidates for playing roles in inflammation and cell signaling.

Mycobacteria-containing phagosomes associate less annexins I, VI, VII and XI, but not II, concomitantly with a diminished phagolysosomal fusion

We have studied the intracellular localization of annexins I,II, VI, VII, and XI in cells containing latex beads or Mycobacterium avium at different times after ingestion in order to establish whether a correlation existed between the association of annexins to phagosomes and phagolysosomal fusion, since the intracellular survival of mycobacteria is linked to an impairment of phagosome maturation. We demonstrate an important decrease in the levels of association of annexins I, VI, VII and XI, but not II to phagosomes containing either live or killed mycobacteria compared with phagosomes containing inert latex particles. The reduced association of annexins observed was detected only on M. avium-containing phagosomes and not in other cell membrane nor in cytosolic fractions from infected cells, and was apparent from 8 hours through to 4 days after phagocytosis. These findings add elements to the present knowledge of the phagosomal modifications that accompany the survival of intracellular pathogens, suggesting that annexins I, VI, VII, and XI play a secondary role in phagosomal fusion events while annexin II does not seem to be related to the mechanism of regulation of endolysosomal fusion.

A genomic and proteomic analysis of activation of the human neutrophil by lipopolysaccharide and its mediation by p38 mitogen-activated protein kinase

Bacterial lipopolysaccharide (LPS) evokes several functional responses in the neutrophil that contribute to innate immunity. Although certain responses, such as adhesion and synthesis of tumor necrosis factor-alpha, are inhibited by pretreatment with an inhibitor of p38 mitogen-activated protein kinase, others, such as actin assembly, are unaffected. The aim of the present study was to investigate the changes in neutrophil gene transcription and protein expression following lipopolysaccharide exposure and to establish their dependence on p38 signaling. Microarray analysis indicated expression of 13% of the 7070 Affymetrix gene set in nonstimulated neutrophils, and LPS up-regulation of 100 distinct genes, including cytokines and chemokines, signaling molecules, and regulators of transcription. Proteomic analysis yielded a separate list of up-regulated modulators of inflammation, signaling molecules, and cytoskeletal proteins. Poor concordance between mRNA transcript and protein expression changes was noted. Pretreatment with the p38 inhibitor SB203580 attenuated 23% of LPS-regulated genes and 18% of LPS-regulated proteins by > or = 40%. This study indicates that p38 plays a selective role in regulation of neutrophil transcripts and proteins following lipopolysaccharide exposure, clarifies that several of the effects of lipopolysaccharide are post-transcriptional and post-translational, and identifies several proteins not previously reported to be involved in the innate immune response.

Complement receptor 3 (CD11b/CD18) mediates type I and type II phagocytosis during nonopsonic and opsonic phagocytosis, respectively

Two types of opsonic phagocytosis have been defined depending on the receptor engaged: FcgammaRs mediate type I phagocytosis of IgG-coated particles; complement receptor 3 (CR3) mediates type II phagocytosis of complement-coated particles. In addition to opsonic phagocytosis, CR3 also mediates nonopsonic phagocytosis of zymosan (Z) and Mycobacterium kansasii through engagement of distinct sites. Using Chinese hamster ovary cells stably expressing human CR3, we studied CR3-mediated ingestion of nonopsonized particles, Z or M. kansasii, compared with opsonized zymosan (OZ). We show that 1) while OZ sinks into cells, Z is engulfed by pseudopodia as visualized by electron microscopy; 2) in contrast to OZ, nonopsonic phagocytosis of Z and M. kansasii depends on Rac and Cdc42 but not on Rho activity; and 3) CR3-mediated phagocytosis of Z depends on the kinase activity of the Src family tyrosine kinase Hck, while OZ internalization does not. Therefore, CR3 mediates type I phagocytosis under nonopsonic conditions and type II under opsonic conditions. This is the first evidence that a single receptor can mediate both types of phagocytosis depending on the ligand used.

Ca(2+) and membrane binding to annexin 3 modulate the structure and dynamics of its N terminus and domain III

Annexin 3 (ANX A3) represents approximately 1% of the total protein of human neutrophils and promotes tight contact between membranes of isolated specific granules in vitro leading to their aggregation. Like for other annexins, the primary molecular events of the action of this protein is likely its binding to negatively charged phospholipid membranes in a Ca(2+)-dependent manner, via Ca(2+)-binding sites located on the convex side of the highly conserved core of the molecule. The conformation and dynamics of domain III can be affected by this process, as it was shown for other members of the family. The 20 amino-acid, N-terminal segment of the protein also could be affected and also might play a role in the modulation of its binding to the membranes. The structure and dynamics of these two regions were investigated by fluorescence of the two tryptophan residues of the protein (respectively, W190 in domain III and W5 in the N-terminal segment) in the wild type and in single-tryptophan mutants. By contrast to ANX A5, which shows a closed conformation and a buried W187 residue in the absence of Ca(2+), domain III of ANX A3 exhibits an open conformation and a widely solvent-accessible W190 residue in the same conditions. This is in agreement with the three-dimensional structure of the ANX A3-E231A mutant lacking the bidentate Ca(2+) ligand in domain III. Ca(2+) in the millimolar concentration range provokes nevertheless a large mobility increase of the W190 residue, while interaction with the membranes reduces it slightly. In the N-terminal region, the W5 residue, inserted in the central pore of the protein, is weakly accessible to the solvent and less mobile than W190. Its amplitude of rotation increases upon binding of Ca(2+) and returns to its original value when interacting with membranes. Ca(2+) concentration for half binding of the W5A mutant to negatively charged membranes is approximately 0.5 mM while it increases to approximately 1 mM for the ANX A3 wild type and to approximately 3 mM for the W190 ANX A3 mutant. In addition to the expected perturbation of the W190 environment at the contact surface between the protein and the membrane bilayer, binding of the protein to Ca(2+) and to membranes modulates the flexibility of the ANX A3 hinge region at the opposite of this interface and might affect its membrane permeabilizing properties.

Lack of fusion of azurophil granules with phagosomes during phagocytosis of Mycobacterium smegmatis by human neutrophils is not actively controlled by the bacterium

Biogenesis of phagolysosomes is a very rapid event in neutrophils which takes place with nascent unclosed phagosomes, leading to the release of lysosomal enzymes such as beta-glucuronidase in the extracellular medium. We have previously shown that, under nonopsonic conditions, both pathogenic and nonpathogenic mycobacteria uncouple phagocytosis from fusion of azurophil granules (specialized secretory lysosomes) with phagosomes. In the present study we questioned whether they actively act on neutrophils to block this process or use phagocytic receptors that negatively control the biogenesis of phagolysosomes. As for live unicellular Mycobacterium smegmatis, we observed that nonopsonic phagocytosis of heat-killed mycobacteria did not induce the release of beta-glucuronidase, indicating that M. smegmatis does not actively act on the fusion process in neutrophils. In contrast, phagocytosis of unicellular M. smegmatis opsonized in immune serum or that of small nonopsonized mycobacterial aggregates restored the biogenesis of phagolysosomes. Aggregates were internalized in a CR3- and cholesterol-dependent manner as unicellular mycobacteria. However, aggregates but not unicellular bacteria triggered F-actin and Hck recruitment at the phagosomes, events that have been associated with lysosome fusion. Thus, we propose that M. smegmatis does not actively control the fusion of azurophil granules at early time points postinfection and that mycobacterial aggregates recruit large clusters of receptors at the neutrophil surface which could trap proteins implicated in the biogenesis of phagolysosomes.

The protein tyrosine kinase Hck is located on lysosomal vesicles that are physically and functionally distinct from CD63-positive lysosomes in human macrophages

In macrophages, lysosomes are suspected to have a heterogenous population of vesicles. This study was thus undertaken to identify and to characterize lysosomal compartments in human macrophages. Hck is a Src-family tyrosine kinase associated with secretory lysosomes in neutrophils and with cytoplasmic vesicles in macrophages that fuse with phagosomes. We identified these Hck-positive vesicles and compared them to CD63-positive, M6PR-negative vesicles known as classical lysosomes. Hck vesicles exhibited lysosomal features. Indeed, Hck-positive vesicles could be loaded with rhodamine-dextran, which has been shown to accumulate in lysosomal compartments. Hck was delivered to zymosan-containing phagosomes at a late stage of the maturation process, which occurs after the fusion with CD63-positive lysosomes. Finally, when mycobacteria were used to prevent phagolysosome biogenesis, Hck was not recruited to phagosomes. Moreover, Hck lysosomes were physically and functionally distinct from CD63-lysosomes. For instance, sucrose induced swelling of CD63-lysosomes without affecting Hck-positive ones. Only CD63-lysosomes fused with phagosomes in a microtubule-dependent manner. Entry of particles through the mannose receptor and Fcγ receptors drove the phagosome towards a fusion with CD63-lysosomes, whereas only Fcγ receptors induced the mobilisation of Hck-lysosomes. This study provides further evidence for the existence of sub-populations of lysosomes in macrophages: one stained by CD63 and another one characterized by the presence of Hck. Therefore, Hck represents a new tool to study the fusion dynamics of lysosomal compartments and their subversion by several intracellular pathogens.

Nuclear gene OPA1, encoding a mitochondrial dynamin-related protein, is mutated in dominant optic atrophy

Optic atrophy type 1 (OPA1, MIM 165500) is a dominantly inherited optic neuropathy occurring in 1 in 50,000 individuals that features progressive loss in visual acuity leading, in many cases, to legal blindness. Phenotypic variations and loss of retinal ganglion cells, as found in Leber hereditary optic neuropathy (LHON), have suggested possible mitochondrial impairment. The OPA1 gene has been localized to 3q28-q29 (refs 13-19). We describe here a nuclear gene, OPA1, that maps within the candidate region and encodes a dynamin-related protein localized to mitochondria. We found four different OPA1 mutations, including frameshift and missense mutations, to segregate with the disease, demonstrating a role for mitochondria in retinal ganglion cell pathophysiology.

Nonopsonic phagocytosis of zymosan and Mycobacterium kansasii by CR3 (CD11b/CD18) involves distinct molecular determinants and is or is not coupled with NADPH oxidase activation

Complement receptor type 3 (CR3) was initially described as an opsonic receptor. Subsequently, CR3-mediated lectin-sugar recognition mechanisms have been shown to play a major role in the nonopsonic phagocytosis of several pathogens, among them Mycobacterium tuberculosis. Little is known about the binding and signal transduction mechanisms operating during nonopsonic ingestion through CR3 of different microorganisms. In the present study, we used CHO cells stably transfected with CR3 to show that CR3 was able to mediate internalization of zymosan and pathogenic mycobacteria (Mycobacterium kansasii and Mycobacterium avium) but not that of nonpathogenic species (Mycobacterium smegmatis and Mycobacterium phlei). A combination of mannan and beta-glucan inhibited the phagocytosis of zymosan but had no effect on M. kansasii ingestion. Among six monoclonal antibodies (MAbs) directed against the CD11b subunit of CR3 that decreased zymosan ingestion, only three inhibited M. kansasii phagocytosis. In particular, MAbs known to block the CR3 lectin site affected only internalization of zymosan. Using U937 macrophages, we observed that zymosan ingestion through CR3 induced superoxide production measured by cytochrome c reduction and by translocation of the NADPH oxidase cytosolic component p47phox to the phagosomal membrane, whereas phagocytosis of viable or heat-killed M. kansasii did not. Furthermore, lack of superoxide anion production during phagocytosis of M. kansasii was not due to inhibition of NADPH oxidase per se or superoxide anion scavenging. Together, our results indicate that (i) nonopsonic phagocytosis of zymosan and M. kansasii by CR3 implicates different molecular mechanisms involving multiple and distinct epitopes of CD11b and (ii) CR3 may transduce different cellular responses depending on the sites mediating nonopsonic phagocytosis.

Isolation and characterization of monoclonal antibodies directed against novel components of macrophage phagosomes

In order to identify novel proteins associated with various stages of macrophage phagocytosis, we have generated monoclonal antibodies that recognize phagosomes. Purified Fc receptor-mediated phagosomes, isolated by feeding IgG-conjugated magnetic beads to LPS-primed murine peritoneal macrophages, were used as the immunogen. An immunofluorescence screen was used to isolate and single-cell clone approximately 150 monoclonal antibodies that recognize mouse macrophage phagosomes as well as labeling other cellular components in patterns which are frequently distinct from those observed with previously characterized phagosome-associated proteins. Predominant morphological categories (in addition to phagosome labeling) include staining of one or more of the following: cytoskeletal patterns, vesicular patterns and plasma membrane localization. In this paper, we describe the antibody screen, preliminary characterization of the antibodies and our identification of the antigens for three representative monoclonal antibodies. These antibodies identify a plasma membrane associated receptor (Mac-1, a subunit of the complement receptor), an actin binding protein (coronin-2) and a vesicular protein (amphiphysin II). Some of the antibodies recognize many cell types, whereas other antibodies are apparently macrophage specific as assessed by flow cytometry and histology. Remarkably, several of the antibodies cross-react with the phagocytic slime mold, Dictyostelium discoideum, recognizing phagosomes and other cellular elements as assessed by immunofluorescence and immunoblots. These results indicate that macrophage phagocytosis has both conserved ancestral features and unique specialized aspects associated with the role of these phagocytes in immunity.

The mannose receptor mediates uptake of pathogenic and nonpathogenic mycobacteria and bypasses bactericidal responses in human macrophages

The mannose receptor (MR) is involved in the phagocytosis of pathogenic microorganisms. Here we investigated its role in the bactericidal functions of human monocyte-derived macrophages (MDMs), using (i) trimannoside-bovine serum albumin (BSA)-coated latex beads and zymosan as particulate ligands of the MR, and (ii) mannan and mannose-BSA as soluble ligands. We show that phagocytosis of mannosylated latex beads did not elicit the production of O2-. Zymosan, which is composed of alpha-mannan and beta-glucan, was internalized by the MR and a beta-glucan receptor, but the production of O2- was triggered only by phagocytosis through the beta-glucan receptor. Activation and translocation of Hck, a Src family tyrosine kinase located on lysosomes, has previously been used as a marker of fusion between lysosomes and phagosomes in human neutrophils. In MDMs, Hck was activated and recruited to phagosomes containing zymosan later than LAMP-1 and CD63. Phagosomes containing mannosylated latex beads fused with LAMP-1 and CD63 vesicles but not with the Hck compartment, and the kinase was not activated. We also demonstrate that the MR was unable to distinguish between nonpathogenic and pathogenic mycobacteria, as they were internalized at similar rates by this receptor, indicating that this route of entry cannot be considered as a differential determinant of the intracellular fate of mycobacteria. In conclusion, MR-dependent phagocytosis is coupled neither to the activation of NADPH oxidase nor to the maturation of phagosomes until fusion with the Hck compartment and therefore constitutes a safe portal of entry for microorganisms.

Fusion of Azurophil Granules with Phagosomes and Activation of the Tyrosine Kinase Hck Are Specifically Inhibited During Phagocytosis of Mycobacteria by Human Neutrophils

Pathogenic mycobacteria parasitize macrophages and reside within phagosomes, which do not fuse with lysosomal granules. Mycobacteria are also internalized by neutrophils, which possess at least two types of granules, specific and azurophil granules, the latter being specialized lysosomes. Here, we investigated the ability of mycobacteria to inhibit the fusion of these granules with their phagosomes in human neutrophils. It was found that when pathogenic (Mycobacterium kansasii and Mycobacterium avium) or nonpathogenic (Mycobacterium smegmatis and Mycobacterium phlei) mycobacteria were internalized by neutrophils, they induced the inhibition of azurophil granule fusion with phagosomes even when they were serum opsonized. In contrast, secretion of specific granule content and production of O2−, both of which contribute to the neutrophil bactericidal response, were triggered. Hck is a Src family tyrosine kinase associated with azurophil granules. During internalization of zymosan, azurophil granules fused with phagosomes and Hck was activated and translocated to the phagosomal membrane, whereas in neutrophils engulfing mycobacteria, Hck did not translocate and remained unactivated. The activation of the tyrosine kinase Fgr was not affected. These results indicate that 1) pathogenic and nonpathogenic mycobacteria trigger similar bactericidal responses in neutrophils, 2) phagocytosis and fusion of azurophil granules can be uncoupled by mycobacteria, and 3) Hck could be one of the key elements of the azurophil secretory pathway that are altered during phagocytosis of mycobacteria.

Reprogramming the phagocytic pathway--intracellular pathogens and their vacuoles (review)

Phagocytic immune cells (particularly macrophages and neutrophils) take up and digest particles that have invaded our bodies. In doing so, they represent a very early line of defence against a microbial attack. During uptake, the particles are wrapped by a portion of the phagocyte's plasma membrane, and a new endocytic compartment, the phagosome, is formed. The typical fate of a phagosome is its fusion with lysosomes to yield a phagolysosome in which the particle is digested. Recent data show that some 'intracellular microorganisms' that can cause severe illnesses (tuberculosis, leprosy, legionnaire's disease and others) manage to reprogramme the host phagocytes not to deliver them to the lysosomal compartment. This probably results in increased survival of the pathogens. The analysis of the composition of such 'novel' compartments and research on the molecular mechanisms underlying the microbial interference with host cell functions are likely to yield important insights into: (1) which endocytic/phagocytic compartments phagocytes employ to handle ingested material in general; (2) how some pathogenic microorganisms can reprogramme the phagocytic pathway; and possibly (3) how infections caused by these microorganisms can be treated more effectively. Here, some studies are presented analysing which compartments intracellular pathogens inhabit and how microbes might be able to reprogramme their host cells.

Localization of five annexins in J774 macrophages and on isolated phagosomes

Annexins are a family of structurally related proteins which bind phospholipids in a calcium-dependent manner. Although the precise functions of annexins are unknown, there is an accumulating set of data arguing for a role for some of them in vesicular transport and, specifically, in membrane-membrane or membrane-cytoskeletal interactions during these processes. Here we describe our qualitative and quantitative analysis of the localization of annexins I-V in J774 macrophages that had internalized latex beads, both with and without IgG opsonization. Our results show that whereas all these annexins are present on both the plasma membrane and on phagosomes, the localization on other organelles differs. Annexins I, II, III and V were detected on early endosomes, while only annexin V was seen on late endocytic organelles and mitochondria. Annexins I and II distributed along the plasma membrane non-uniformly and co-localized with F-actin at the sites of membrane protrusions. We also investigated by western blot analysis the association of annexins with purified phagosomes isolated at different time-points after latex bead internalization. While the amounts of annexins I, II, III and V associated with phagosomes were similar at all times after their formation, the level of annexin IV was significantly higher on older phagosomes. Whereas annexins I, II, IV and V could be removed from phagosome membranes with a Ca2+ chelator they remained membrane bound under low calcium conditions. In contrast, annexin III was removed under these conditions and needed a relatively high Ca2+ concentration to remain phagosome bound. Because of their purity and ease of preparation we suggest that phagosomes are a powerful system to study the potential role of annexins in membrane traffic.

Annexin II binds to the membrane of A549 cells in a calcium-dependent and calcium-independent manner

We investigated the nature of annexin II binding to the biological membranes using a lung epithelium-derived cell line A549. The cytosolic and membrane fractions of A549 cells were separated in the presence of 5 mM EGTA. Both fractions contain annexin II monomer and tetramer as evaluated by western blots using specific monoclonal antibodies against p36 and p11 subunits of annexin II. A substantial amount of annexin II was associated with the membrane fraction even after extensive washing with EGTA buffer, indicating the presence of two pools of annexin II. The EGTA-resistant membrane-bound annexin II could be partially extracted by 1% Triton X-100 or 60 mM n-octyl-beta-D-glucopyranoside, and completely by 30 mM CHAPS or 0.1% deoxycholate. This fraction of annexin II was also extracted by 0.1 M Na2CO3, pH 11 and partitioned into the aqueous phase after being treated with Triton X-114, demonstrating that the EGTA-resistant annexin II is a peripheral membrane protein. When the cells were lysed in varying concentrations of Ca2+, annexin II translocated from cytosolic fraction to membrane fraction at 4-25 microM Ca2+. To identify proteins closely associated with annexin II the membrane fraction was treated with the bifunctional chemical cross-linker disulfosuccinimidyl tartarate, followed by western blot analysis using anti-p36 or anti-p11 antibodies. We find that both p36 and p11 were cross-linked to a 51 kDa protein. In addition, p11 also binds to several proteins with molecular mass of 91, 65, 40 and 36 kDa. Our results suggest that annexin II may bind to the A549 cell membranes via specific membrane-associated proteins.

Can enzymatic activity, or otherwise, be inferred from structural studies of annexin III?

Annexin III, a putative inositol (1,2)-phosphohydrolase, was co-crystallized with inositol 2-phosphate, the inhibitor of the reaction, and its structure was solved to 1.95 A resolution. No enzyme active site was observed in the structure. Assays for enzymatic activity were also negative. Search for annexin III-inositol phosphate interactions using the BIAcoreTM system revealed an affinity for inositol cyclic (1,2)-phosphate, suggesting annexin III may sequester the molecule in the cell. The BIAcoreTM system used with different phospholipids showed that annexin III displays specificity for phosphatidylethanolamine, but not for phosphatidylinositols. Interestingly, a molecule of ethanolamine was found bound to the protein in the crystal structure. Coupled with the fact that this is a particularly abundant phospholipid in granules specific to neutrophils, cells where annexin III is highly expressed, our finding could be pointing to a physiological role of annexin III.

Neutrophil-associated inflammatory responses in rats are inhibited by phenylarsine oxide

NADPH oxidase is a phagocyte-specific enzyme which produces O2- and so initiates a cascade of reactive oxygen species formation. Inflammatory diseases involve overproduction of reactive oxygen species which induce tissue damage. Phenylarsine oxide has been described previously as a complete and direct inhibitor of NADPH oxidase in vitro that acts by covalently binding to vicinal thiol groups of a membrane-associated component of the enzyme. In the present work, the potential anti-inflammatory effect of phenylarsine oxide was tested on two experimental models in rats, carrageenan-induced paw oedema and lipopolysaccharide-mediated lung inflammation. Intraperitoneal injection of phenylarsine oxide reduced (i) reactive oxygen species production by rat phagocytes, (ii) neutrophil infiltration into the lung after inhalation of lipopolysaccharide and (iii) neutrophil-dependent oedema induced by carrageenan in hindpaws. We conclude that phenylarsine oxide has anti-inflammatory properties which are probably exerted by its ability to inhibit neutrophil NADPH oxidase-dependent reactive oxygen species production. The present work provides the basis for the development of new anti-inflammatory, arsenic-free agents reacting at the phenylarsine oxide site, which seems to be the Achilles' heel of NADPH oxidase.

Hck is activated by opsonized zymosan and A23187 in distinct subcellular fractions of human granulocytes

Regulation of neutrophil responses is known to involve tyrosine phosphorylation. Hck, a major neutrophil protein-tyrosine kinase, becomes expressed during differentiation of human promyelocytic NB4 cells into neutrophil-like cells. Hck is mainly localized in a secretory granule-enriched cell fraction, but it is also present in a granule-free membrane fraction and the cytosol. Hck is rapidly and transiently activated upon stimulation of differentiated NB4 cells or human neutrophils with serum-opsonized zymosan or the calcium ionophore A23187, but not by phorbol 12-myristate 13-acetate. In NB4 cells, Hck is also weakly activated by fMet-Leu-Phe. Cell fractionation showed that opsonized zymosan and A23187 induce Hck activation in distinct subcellular fractions. Both stimuli activate Hck in the secretory granule-enriched fraction, but only A23187 activates the kinase in the granule-free membrane fraction. Our results suggest that Hck might regulate early signal transduction events induced by opsonized zymosan and A23187, and that the different subcellular fractions of Hck might serve discrete functions, one of which could be regulation of the degranulation response.

Annexin II in exocytosis: catecholamine secretion requires the translocation of p36 to the subplasmalemmal region in chromaffin cells

Annexin II is a Ca(2+)-dependent membrane-binding protein present in a wide variety of cells and tissues. Within cells, annexin II is found either as a 36-kD monomer (p36) or as a heterotetrameric complex (p90) coupled with the S-100-related protein, p11. Annexin II has been suggested to be involved in exocytosis as it can restore the secretory responsiveness of permeabilized chromaffin cells. By quantitative confocal immunofluorescence, immunoreplica analysis and immunoprecipitation, we show here the translocation of p36 from the cytosol to a subplasmalemmal Triton X-100 insoluble fraction in chromaffin cells following nicotinic stimulation. A synthetic peptide corresponding to the NH2-terminal domain of p36 which contains the phosphorylation sites was microinjected into individual chromaffin cells and catecholamine secretion was monitored by amperometry. This peptide blocked completely the nicotine-induced recruitment of p36 to the cell periphery and strongly inhibited exocytosis evoked by either nicotine or high K+. The light chain of annexin II, p11, was selectively expressed by adrenergic chromaffin cells, and was only present in the subplasmalemmal Triton X-100 insoluble protein fraction of both resting and stimulated cells. p11 can modify the Ca(2+)- and/or the phospholipid-binding properties of p36. We found that loss Ca2+ was required to stimulate the translocation of p36 and to trigger exocytosis in adrenergic chromaffin cells. Our findings suggest that the translocation of p36 to the subplasmalemmal region is an essential event in regulated exocytosis and support the idea that the presence of p11 in adrenergic cells may confer a higher Ca2+ affinity to the exocytotic pathway in these cells.