The Endoplasmic Reticulum–Mitochondria Encounter Structure (ERMES) is a protein complex that tethers the two organelles and creates the physical basis for communication between them. ERMES functions in lipid and calcium exchange between the ER and mitochondria, mitochondrial protein import and maintenance of mitochondrial morphology and genome. Here we report that ERMES is also required for iron homeostasis. Loss of ERMES components activates an Aft1-dependent iron deficiency response even in iron-replete conditions, leading to accumulation of excess iron inside the cell. This function is independent of ERMES known roles in calcium regulation, phospholipid biosynthesis or mitochondrial biology. A mutation in the vacuolar protein sorting 13 (VPS13) gene that rescues the glycolytic phenotype of ERMES mutants suppresses the iron deficiency response and iron accumulation. Our study reveals that proper communication between the ER and mitochondria is required for appropriate maintenance of cellular iron levels. Overall design: various mutants
Endoplasmic reticulum-mitochondria junction is required for iron homeostasis.
Subject
View SamplesWe expressed a constitutively active mutant of MEK5 (MEK5D) in human primary endothelial cells (EC) to study the transcriptional and functional responses to Erk5 activation under static conditions.
Erk5 activation elicits a vasoprotective endothelial phenotype via induction of Kruppel-like factor 4 (KLF4).
Cell line
View SamplesThe transcription factor NF-E2-related factor 2 (Nrf2) induces cytoprotective genes, but has also been linked to the regulation of hepatic energy metabolism. In order to assess the pharmacological potential of hepatic Nrf2 activation in metabolic disease, Nrf2 was activated over 8 weeks in mice on Western diet using two different siRNAs against kelch-like ECH-associated protein 1 (Keap1), the inhibitory protein of Nrf2. Whole genome expression analysis followed by pathway analysis demonstrated that the suppression of Keap1 expression induced genes that are involved in anti-oxidative stress defense and biotransformation, pathways proving the activation of Nrf2 by the siRNAs against Keap1. The expression of neither fatty acid- nor carbohydrate-handling proteins was regulated by the suppression of Keap1. Metabolic profiling of the animals did also not show effects on plasma and hepatic lipids, energy expenditure or glucose tolerance by the activation of Nrf2. The data indicate that hepatic Nrf2 is not a major regulator of intermediary metabolism in mice.
Chronic Activation of Hepatic Nrf2 Has No Major Effect on Fatty Acid and Glucose Metabolism in Adult Mice.
Specimen part, Treatment
View SamplesTo delineate specific patterns of signaling networks activated by H5N1 we used a comparative systems biology approach analyzing gene expression in endothelial cells infected with three different human and avian influenza strains of high and low pathogenicity.
Essential impact of NF-kappaB signaling on the H5N1 influenza A virus-induced transcriptome.
No sample metadata fields
View SamplesThe activation of the transcription factor NF-E2-related factor 2 (Nrf2) maintains cellular homeostasis in response to oxidative stress by the regulation of multiple cytoprotective genes. Without stressors the activity of Nrf2 is inhibited by its interaction with the kelch-like ECH-associated protein 1 (Keap1). Here, we describe RA839, a small molecule that binds non-covalently to the Nrf2-interacting kelch domain of Keap1 with a Kd of approximately 6 M, as demonstrated by X-ray co-crystallization and isothermal titration calorimetry. Whole-genome DNA arrays showed that at 10 M RA839 significantly regulated 105 genes in bone marrow-derived macrophages. Canonical pathway mapping of these genes revealed an activation of pathways linked with Nrf2 signalling. These pathways were also activated after the activation of Nrf2 by the silencing of Keap1 expression. RA839 regulated only two genes in Nrf2 knockout macrophages. Similar to the activation of Nrf2 by either silencing of Keap1 expression or by the reactive compound CDDO-Me, RA839 prevented the induction of both inducible nitric oxide synthase expression and nitric oxide release in response to lipopolysaccharides in macrophages. In mice RA839 acutely induced Nrf2-target gene expression in liver. RA839 is a selective inhibitor of the Keap1/Nrf2 interaction and a useful tool compound to study the biology of Nrf2.
Characterization of RA839, a Noncovalent Small Molecule Binder to Keap1 and Selective Activator of Nrf2 Signaling.
Specimen part, Treatment
View SamplesTo provide a more detailed survey of adaptive changes in the physiology of P. aeruginosa (PA) during long-term infection of the cystic fibrosis (CF) lung, we performed a comparative proteome and transcriptome analysis of a set of isogenic sequential non-mutator and mutator isolates from three selected CF patients. Recently, we showed that during CF lung persistence PA mutators converge to a virulence-attenuated phenotype. In this study, we demonstrate that besides virulence-associated traits (VATs) the adaptation process of PA predominantly comprises metabolic pathways. In end-stage mutator strains, transcripts of genes encoding VATs, chemotaxis, degradation of aromatic compounds and several two-component regulatory systems were decreased. In contrast, several transcripts of genes or proteins involved in metabolism of fatty acids, nucleotides, amino acids and the generation of energy were increased. Of particular interest is the increased expression level of genes involved in (i) the anaerobic arginine-deiminase pathway, (ii) the anaerobic respiration such as nitrate-uptake protein OprF, redox-active azurin and cytchrome c551 peroxidase, (iii) the micro-aerobic respiration such as high oxygen-affinity cytochrome oxidase cbb3 (iv) the tricarboxylic acid cycle (TCA), glyoxylate shunt and anaplerotic carboxylation reactions to oxaloacetate. Strikingly, an increased transcription of the anaerobic regulator gene anr correlates with the up-regulation of ANR-dependent genes. In conclusion, these changes in transcriptome and proteome indicate an adaptive shift towards constitutive expression of genes of metabolic pathways obviously required for growth under micro-aerobic and nutritional conditions of suppurative CF lung tissue. Finally, these results provide us with new targets for antimicrobial agents and biomarkers reflecting adaptation of PA towards progressive CF lung disease.
Stage-specific adaptation of hypermutable Pseudomonas aeruginosa isolates during chronic pulmonary infection in patients with cystic fibrosis.
No sample metadata fields
View SamplesHighly pathogenic avian influenza viruses (HPAIV) induce severe inflammation in poultry and men. There is still an ongoing threat that these viruses may acquire the capability to freely spread as novel pandemic virus strains that may cause major morbidity and mortality. One characteristic of HPAIV infections is the induction of a cytokine burst that strongly contributes to viral pathogenicity. It has been suggested, that this cytokine overexpression is an intrinsic feature of infected cells and involves hyperinduction of p38 mitogen activated protein kinase (MAPK). Here we investigate the role of MAPK p38 signaling in the antiviral response against HPAIV in mice as well as in endothelial cells, the latter a primary source for cytokines during systemic infections.
Inhibition of p38 mitogen-activated protein kinase impairs influenza virus-induced primary and secondary host gene responses and protects mice from lethal H5N1 infection.
Specimen part
View SamplesInflammation has a causal role in many cancers. In prostate cancers, epidemiological data suggest a link between prostatitis and subsequent cancer development, but a proof for this concept in a tumor model has been lacking. A constitutively active version of the IkappaB kinase 2 (IKK2), the molecule activated by a plethora of inflammatory stimuli, was expressed specifically in the prostate epithelium. Signaling of the IKK2/NF-kappaB axis was insufficient for transformation of prostate tissue. However, while PTEN+/- epithelia exhibited intraepithelial neoplasias only recognizable by nuclear alterations, additional IKK2 activation led to an increase in tumor size and formation of cribriform structures and to a fiber increase in the fibroblastic stroma. This phenotype was coupled with inflammation in the prostate gland characterized by infiltration of granulocytes and macrophages. Molecular characterization of the tissues showed a specific loss of smooth muscle markers as well as expression of chemokines attracting immune cells. Isolation of epithelial and stromal cells showed differential chemokine expression by these cells. Correlation studies showed the inflammatory phenotype coupled to loss of smooth muscle in infiltrated glands, but maintenance of the phenotype in glands where inflammation had decreased. Despite the loss of the smooth muscle barrier, tumors were not invasive in a stable genetic background. Data mining revealed that smooth muscle markers are downregulated in human prostate cancers and literature data show that loss of these markers in primary tumors is associated with subsequent metastasis. Our data show that loss of smooth muscle and invasiveness of the tumor are not coupled. Thus, inflammation during early steps of tumorigenesis can lead to increased tumor size and a potential change in the subsequent metastatic potential, but the tumor requires an additional transformation to become a carcinoma.
Persistent inflammation leads to proliferative neoplasia and loss of smooth muscle cells in a prostate tumor model.
Age, Specimen part
View SamplesThe protease activity of the paracaspase MALT1 plays an important role in antigen receptor-mediated lymphocyte activation by controlling the activity of the transcription factor NF-kB and is thus essential for the expression of inflammatory target genes.
MALT1 Protease Activity Controls the Expression of Inflammatory Genes in Keratinocytes upon Zymosan Stimulation.
Treatment
View SamplesDiffuse large B-cell lymphoma (DLBCL) represents the most common form of lymphoma. We could show that in DLBCL cell lines the transcription factor NFAT is constitutively activated and drives the survival of a DLBCL subset. Aim of the analysis was to identify NFAT target genes in a NFAT-dependent (HBL-1) or -independent (HT) DLBCL cell line. To block NFAT activity, the DLBCL cells were treated with the calcineurin inhibitor cyclosporin A (CsA) up to 48 h. With this approach, we identified several survival-related NFAT target genes in HBL-1 cells that might explain the toxic effects of calcineurin inhibitors.
Targeting chronic NFAT activation with calcineurin inhibitors in diffuse large B-cell lymphoma.
Treatment
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