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Albert-Ludwigs-Universität Freiburg Centre for Biological Signalling Studies

Works: 70 works in 70 publications in 1 language and 182 library holdings
Roles: Contributor, his
Publication Timeline
Most widely held works by Albert-Ludwigs-Universität Freiburg
Single molecule imaging of the initial steps of EGFR activation in Mammalian cells by Shima Tahvildar Khazaneh( )

1 edition published in 2017 in English and held by 16 WorldCat member libraries worldwide

Abstract: The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that undergoes ligand mediated dimerization and activation. EGFRs regulate physiological processes such as cell migration, differentiation and proliferation, but their aberrant activation plays a pivotal role in cancer and neurodegenerative disease development. In resting cells, EGFRs are present as a population of inactive monomers and predimers that are laterally mobile and expressed uniformly across the cell surface. Ligand binding rapidly shifts the inactive monomer population to receptor dimers. Besides an increase in dimers, clusters of immobile EGF receptors have been observed shortly after activation. It remains unclear however, to what extent dimerization and clustering depend on one another, their role in receptor phosphorylation, and the intracellular proteins and endocytic compartments involved in facilitating their formation.<br><br>In the present work, the current model for EGFR activation is extended to include the role of EGFR predimers and clusters in receptor signaling. With a highly efficient fluorescent protein labeling approach, we image and track the majority of GFP-labeled EGF receptors at the plasma membrane of a living cell on a single molecule (SM) level. The focus on SM imaging of dynamic EGFR interactions affords in addition to determining diffusion coefficients of receptors, the quantification of their aggregation behavior in real time. The direct observation of EGFR interactions along with the use of several EGFR mutations and pharmacological inhibitors have led to three core findings in this work; (i) EGFR diffusion on the plasma membrane is tightly linked to its activation, where activated receptors have lower diffusion coefficients than unliganded receptors, (ii) EGF induced redistribution of EGFRs into clusters requires an active kinase domain and receptor clustering is non-essential for short-term receptor activation, and (iii) endocytic adaptor proteins provide a scaffold facilitating ligand-induced EGFR clustering. Ultimately, a better understanding of EGFR activation can aid the development of pharmacological targets for down-regulating aberrant EGFR activation
Phytoene Desaturase from Oryza sativa Oligomeric Assembly, Membrane Association and Preliminary 3D-Analysis by Sandra Sina Ellen Gemmecker( )

1 edition published in 2015 in English and held by 4 WorldCat member libraries worldwide

Abstract: Recombinant phytoene desaturase (PDS-His6) from rice was purified to near-homogeneity and shown to be enzymatically active in a biphasic, liposome-based assay system. The protein contains FAD as the sole protein-bound redox-cofactor. Benzoquinones, not replaceable by molecular oxygen, serve as a final electron acceptor defining PDS as a 15-cis-phytoene (donor):plastoquinone oxidoreductase. The herbicidal PDS-inhibitor norflurazon is capable of arresting the reaction by stabilizing the intermediary FADred, while an excess of the quinone acceptor relieves this blockage, indicating competition. The enzyme requires its homo-oligomeric association for activity. The sum of data collected through gel permeation chromatography, non-denaturing polyacrylamide electrophoresis, chemical cross-linking, mass spectrometry and electron microscopy techniques indicate that the high-order oligomers formed in solution are the basis for an active preparation. Of these, a tetramer consisting of dimers represents the active unit. This is corroborated by our preliminary X-ray structural analysis that also revealed similarities of the protein fold with the sequence-inhomologous bacterial phytoene desaturase CRTI and other oxidoreductases of the GR2-family of flavoproteins. This points to an evolutionary relatedness of CRTI and PDS yielding different carotene desaturation sequences based on homologous protein folds
Clinical on-site monitoring of ß-lactam antibiotics for a personalized antibiotherapy by Richard Bruch( )

1 edition published in 2017 in English and held by 4 WorldCat member libraries worldwide

Prevalence of collagen VII-specific autoantibodies in patients with autoimmune and inflammatory diseases by Emilia Licarete( )

1 edition published in 2012 in English and held by 4 WorldCat member libraries worldwide

Abstract: Background<br>Autoimmunity to collagen VII is typically associated with the skin blistering disease epidermolysis bullosa acquisita (EBA), but also occurs occasionally in patients with systemic lupus erythematosus or inflammatory bowel disease. The aim of our present study was to develop an accurate immunoassay for assessing the presence of autoantibodies against collagen VII in large cohorts of patients and healthy donors.<br><br>Methods<br>Based on in silico antigenic analysis and previous wetlab epitope mapping data, we designed a chimeric collagen VII construct containing all collagen VII epitopes with higher antigenicity. ELISA was performed with sera from patients with EBA (n = 50), Crohn's disease (CD, n = 50), ulcerative colitis (UC, n = 50), bullous pemphigoid (BP, n = 76), and pemphigus vulgaris (PV, n = 42) and healthy donors (n = 245).<br><br>Results<br>By ELISA, the receiver operating characteristics analysis yielded an area under the curve of 0.98 (95% CI: 0.9638-1.005), allowing to set the cut-off at 0.32 OD at a calculated specificity of 98% and a sensitivity of 94%. Running the optimized test showed that serum IgG autoantibodies from 47 EBA (94%; 95% CI: 87.41%-100%), 2 CD (4%; 95% CI: 0%-9.43%), 8 UC (16%; 95% CI: 5.8%-26%), 2 BP (2.63%; 95% CI: 0%-6.23%), and 4 PV (9.52%; 95% CI: 0%-18.4%) patients as well as from 4 (1.63%; 95% CI: 0%-3.21%) healthy donors reacted with the chimeric protein. Further analysis revealed that in 34%, 37%, 16% and 100% of sera autoantibodies of IgG1, IgG2, IgG3, and IgG4 isotype, respectively, recognized the recombinant autoantigen.<br><br>Conclusions<br>Using a chimeric protein, we developed a new sensitive and specific ELISA to detect collagen specific antibodies. Our results show a low prevalence of collagen VII-specific autoantibodies in inflammatory bowel disease, pemphigus and bullous pemphigoid. Furthermore, we show that the autoimmune response against collagen VII is dominated by IgG4 autoantibodies. The new immunoassay should prove a useful tool for clinical and translational research and should improve the routine diagnosis and disease monitoring in diseases associated with collagen VII-specific autoimmunity
Mathematical model of early Reelin-induced Src family kinase-mediated signaling by Helge Haß( )

1 edition published in 2017 in English and held by 3 WorldCat member libraries worldwide

Abstract: Reelin is a large glycoprotein with a dual role in the mammalian brain. It regulates the positioning and differentiation of postmitotic neurons during brain development and modulates neurotransmission and memory formation in the adult brain. Alterations in the Reelin signaling pathway have been described in different psychiatric disorders. Reelin mainly signals by binding to the lipoprotein receptors Vldlr and ApoER2, which induces tyrosine phosphorylation of the adaptor protein Dab1 mediated by Src family kinases (SFKs). In turn, phosphorylated Dab1 activates downstream signaling cascades, including PI3-kinase-dependent signaling. In this work, a mechanistic model based on ordinary differential equations was built to model early dynamics of the Reelin-mediated signaling cascade. Mechanistic models are frequently used to disentangle the highly complex mechanisms underlying cellular processes and obtain new biological insights. The model was calibrated on time-resolved data and a dose-response measurement of protein concentrations measured in cortical neurons treated with Reelin. It focusses on the interplay between Dab1 and SFKs with a special emphasis on the tyrosine phosphorylation of Dab1, and their role for the regulation of Reelin-induced signaling. Model selection was performed on different model structures and a comprehensive mechanistic model of the early Reelin signaling cascade is provided in this work. It emphasizes the importance of Reelin-induced lipoprotein receptor clustering for SFK-mediated Dab1 trans-phosphorylation and does not require co-receptors to describe the measured data. The model is freely available within the open-source framework Data2Dynamics ( It can be used to generate predictions that can be validated experimentally, and provides a platform for model extensions both to downstream targets such as transcription factors and interactions with other transmembrane proteins and neuronal signaling pathways
MICA: multiple interval-based curve alignment by Martin Raden( )

1 edition published in 2018 in English and held by 3 WorldCat member libraries worldwide

Abstract: MICA enables the automatic synchronization of discrete data curves. To this end, characteristic points of the curves' shapes are identified. These landmarks are used within a heuristic curve registration approach to align profile pairs by mapping similar characteristics onto each other. In combination with a progressive alignment scheme, this enables the computation of multiple curve alignments.<br>Multiple curve alignments are needed to derive meaningful representative consensus data of measured time or data series. MICA was already successfully applied to generate representative profiles of tree growth data based on intra-annual wood density profiles or cell formation data.<br>The MICA package provides a command-line and graphical user interface. The R interface enables the direct embedding of multiple curve alignment computation into larger analyses pipelines. Source code, binaries and documentation are freely available at
Structural and functional analysis of latex clearing protein (Lcp) provides insight into the enzymatic cleavage of rubber by Lorena Ilcu( )

1 edition published in 2017 in English and held by 3 WorldCat member libraries worldwide

Abstract: Latex clearing proteins (Lcps) are rubber oxygenases that catalyse the extracellular cleavage of poly (cis-1,4-isoprene) by Gram-positive rubber degrading bacteria. Lcp of Streptomyces sp. K30 (LcpK30) is a b-type cytochrome and acts as an endo-type dioxygenase producing C20 and higher oligo-isoprenoids that difer in the number of isoprene units but have the same terminal functions, CHO-CH2- and -CH2- COCH3. Our analysis of the LcpK30 structure revealed a 3/3 globin fold with additional domains at the N- and C-termini and similarities to globin-coupled sensor proteins. The haem group of LcpK30 is ligated to the polypeptide by a proximal histidine (His198) and by a lysine residue (Lys167) as the distal axial ligand. The comparison of LcpK30 structures in a closed and in an open state as well as spectroscopic and biochemical analysis of wild type and LcpK30 muteins provided insights into the action of the enzyme during catalysis
From immunologically archaic to neoteric glycovaccines by Marco Cavallari( )

1 edition published in 2017 in English and held by 3 WorldCat member libraries worldwide

Abstract: Polysaccharides (PS) are present in the outermost surface of bacteria and readily come in contact with immune cells. They interact with specific antibodies, which in turn confer protection from infections. Vaccines with PS from pneumococci, meningococci, Haemophilus influenzae type b, and Salmonella typhi may be protective, although with the important constraint of failing to generate permanent immunological memory. This limitation has in part been circumvented by conjugating glycovaccines to proteins that stimulate T helper cells and facilitate the establishment of immunological memory. Currently, protection evoked by conjugated PS vaccines lasts for a few years. The same approach failed with PS from staphylococci, Streptococcus agalactiae, and Klebsiella. All those germs cause severe infections in humans and often develop resistance to antibiotic therapy. Thereby, prevention is of increasing importance to better control outbreaks. As only 23 of more than 90 pneumococcal serotypes and 4 of 13 clinically relevant Neisseria meningitidis serogroups are covered by available vaccines there is still tremendous clinical need for PS vaccines. This review focuses on glycovaccines and the immunological mechanisms for their success or failure. We discuss recent advances that may facilitate generation of high affinity anti-PS antibodies and confer specific immunity and long-lasting protection
Hepatocyte ploidy is a diversity factor for liver homeostasis by Clemens Kreutz( )

1 edition published in 2017 in English and held by 3 WorldCat member libraries worldwide

Abstract: Polyploidy, the existence of cells containing more than one pair of chromosomes, is a well-known feature of mammalian hepatocytes. Polyploid hepatocytes are found either as cells with a single polyploid nucleus or as multinucleated cells with diploid or even polyploid nuclei. In this study, we evaluate the degree of polyploidy in the murine liver by accounting both DNA content and number of nuclei per cell. We demonstrate that mouse hepatocytes with diploid nuclei have distinct metabolic characteristics compared to cells with polyploid nuclei. In addition to strong differential gene expression, comprising metabolic as well as signaling compounds, we found a strongly decreased insulin binding of nuclear polyploid cells. Our observations were associated with nuclear ploidy but not with total ploidy within a cell. We therefore suggest ploidy of the nuclei as an new diversity factor of hepatocytes and hypothesize that hepatocytes with polyploid nuclei may have distinct biological functions than mono-nuclear ones. This diversity is independent from the well-known heterogeneity related to the cells' position along the porto-central liver-axis
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1 edition published in 2015 in English and held by 3 WorldCat member libraries worldwide

Auranofin inhibits the enzyme activity of Pasteurella multocida toxin PMT in human cells and protects cells from intoxication by Stefan Carle( )

1 edition published in 2017 in English and held by 3 WorldCat member libraries worldwide

Abstract: The AB-type protein toxin from Pasteurella multocida (PMT) contains a functionally important disulfide bond within its catalytic domain, which must be cleaved in the host cell cytosol to render the catalytic domain of PMT into its active conformation. Here, we found that the reductive potential of the cytosol of target cells, and more specifically, the activity of the thioredoxin reductase (TrxR) is crucial for this process. This was demonstrated by the strong inhibitory effect of the pharmacological TrxR inhibitor auranofin, which inhibited the intoxication of target cells with PMT, as determined by analyzing the PMT-catalyzed deamidation of GTP-binding proteins (G-proteins) in the cytosol of cells. The amount of endogenous substrate levels modified by PMT in cells pretreated with auranofin was reduced compared to cells treated with PMT alone. Auranofin had no inhibitory effect on the activity of the catalytic domain of constitutively active PMT in vitro, demonstrating that auranofin did not directly inhibit PMT activity, but interferes with the mode of action of PMT in cells. In conclusion, the results show that TrxR is crucial for the mode of action of PMT in mammalian cells, and that the drug auranofin can serve as an efficient inhibitor, which might be a starting point for novel therapeutic options against toxin-associated diseases
Plant-type phytoene desaturase: Functional evaluation of structural implications by Julian Koschmieder( )

1 edition published in 2017 in English and held by 3 WorldCat member libraries worldwide

A Chlamydia pneumoniae adhesin induces phosphatidylserine exposure on host cells by Jan-Christoph Galle( )

1 edition published in 2019 in English and held by 3 WorldCat member libraries worldwide

Abstract: In mammalian cells, the internal and external leaflets of the plasma membrane (PM) possess different phospholipids. Phosphatidylserine (PS) is normally confined to the inner (cytoplasmic) membrane leaflet. Here we report that the adhesin CPn0473 of the human pathogenic bacterium Chlamydia pneumoniae (Cpn) binds to the PM of human cells and induces PS externalization but unexpectedly not apoptosis. PS externalization is increased in human cells exposed to infectious Cpn cells expressing increased CPn0473 and reduced in exposure to Cpn expressing decreased CPn0473. CPn0473 binds specifically to synthetic membranes carrying PS and stimulates pore formation. Asymmetric giant unilamellar vesicles (GUVs) in which PS is restricted to the inner leaflet reveal that CPn0473 induces PS externalization in the absence of other proteins. Thus our identification of CPn0473 as a bacterial PS translocator capable of specific and apoptosis-independent PS externalization during infection extends the spectrum of mechanisms intracellular pathogens use to enter host cells
Effect of sodium and chloride binding on a lecithin bilayer : a molecular dynamics study by Maria Reif( )

1 edition published in 2017 in English and held by 3 WorldCat member libraries worldwide

Abstract: The effect of ion binding on the structural, mechanical, dynamic and electrostatic properties of a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer in a 0.5 M aqueous NaCl solution is investigated using classical atomistic molecular dynamics simulation with different force-field descriptions for ion-ion and ion-lipid interactions. Most importantly, the repulsive Lennard-Jones parameters for the latter were modified, such that approximately similar binding of cations and anions to the lipid membrane is achieved. This was done to qualitatively improve the apparent ion-lipid binding constants obtained from simulations with the original force field (Berger lipids and GROMOS87 ions in combination with the SPC water model) in comparison to experimental data. Furthermore, various parameters characterizing membrane structure, elasticity, order and dynamics are analyzed. It is found that ion binding as observed in simulations involving the modified in comparison to the original force-field description leads to: (i) a smaller salt-induced change in the area per lipid, which is in closer agreement with the experiment; (ii) a decrease in the area compressibility and bilayer thickness to values comparable to a bilayer in pure water; (iii) lipid deuterium order parameters and lipid diffusion coefficients on nanosecond timescales that are very similar to the values for a membrane in pure water. In general, salt effects on the structural properties of a POPC bilayer in an aqueous sodium-chloride solution appear to be reproduced reasonably well by the new force-field description. An analysis of membrane-membrane disjoining pressure suggests that the smaller salt-induced change in area per lipid induced by the new force-field description is not due to the alteration of membrane-associated net charge, but must rather be understood as a consequence of ion-specific effects on the arrangement of lipid molecules
Preparation data of the bromodomains BRD3(1), BRD3(2), BRD4(1), and BRPF1B and crystallization of BRD4(1)-inhibitor complexes by Martin Hügle( )

1 edition published in 2016 in English and held by 3 WorldCat member libraries worldwide

Abstract: This article presents detailed purification procedures for the bromodomains BRD3(1), BRD3(2), BRD4(1), and BRPF1B. In addition we provide crystallization protocols for apo BRD4(1) and BRD4(1) in complex with numerous inhibitors. The protocols described here were successfully applied to obtain affinity data by isothermal titration calorimetry (ITC) and by differential scanning fluorimetry (DSF) as well as structural characterizations of BRD4(1) inhibitor complexes (PDB codes: PDB: 4LYI, PDB: 4LZS, PDB: 4LYW, PDB: 4LZR, PDB: 4LYS, PDB: 5D24, PDB: 5D25, PDB: 5D26, PDB: 5D3H, PDB: 5D3J, PDB: 5D3L, PDB: 5D3N, PDB: 5D3P, PDB: 5D3R, PDB: 5D3S, PDB: 5D3T). These data have been reported previously and are discussed in more detail elsewhere
C. elegans DAF-16/FOXO interacts with TGF-ß/BMP signaling to induce germline tumor formation via mTORC1 activation by Wenjing Qi( )

1 edition published in 2017 in English and held by 3 WorldCat member libraries worldwide

Abstract: Activation of the FOXO transcription factor DAF-16 by reduced insulin/IGF signaling (IIS) is considered to be beneficial in C. elegans due to its ability to extend lifespan and to enhance stress resistance. In the germline, cell-autonomous DAF-16 activity prevents stem cell proliferation, thus acting tumor-suppressive. In contrast, hypodermal DAF-16 causes a tumorous germline phenotype characterized by hyperproliferation of the germline stem cells and rupture of the adjacent basement membrane. Here we show that cross-talk between DAF-16 and the transforming growth factor ß (TGFß)/bone morphogenic protein (BMP) signaling pathway causes germline hyperplasia and results in disruption of the basement membrane. In addition to activating MADM/NRBP/hpo-11 gene alone, DAF-16 also directly interacts with both R-SMAD proteins SMA-2 and SMA-3 in the nucleus to regulate the expression of mTORC1 pathway. Knocking-down of BMP genes or each of the four target genes in the hypodermis was sufficient to inhibit germline proliferation, indicating a cell-non-autonomously controlled regulation of stem cell proliferation by somatic tissues. We propose the existence of two antagonistic DAF-16/FOXO functions, a cell-proliferative somatic and an anti-proliferative germline activity. Whereas germline hyperplasia under reduced IIS is inhibited by DAF-16 cell-autonomously, activation of somatic DAF-16 in the presence of active IIS promotes germline proliferation and eventually induces tumor-like germline growth. In summary, our results suggest a novel pathway crosstalk of DAF-16 and TGF-ß/BMP that can modulate mTORC1 at the transcriptional level to cause stem-cell hyperproliferation. Such cell-type specific differences may help explaining why human FOXO activity is considered to be tumor-suppressive in most contexts, but may become oncogenic, e.g. in chronic and acute myeloid leukemia
Active continuous-flow micromixer using an external Braille pin actuator array by Yawar Abbas( )

1 edition published in 2013 in English and held by 3 WorldCat member libraries worldwide

Matrix-metalloproteinase-9 is cleaved and activated by Cathepsin K by Jon Høj Christensen( )

1 edition published in 2015 in English and held by 3 WorldCat member libraries worldwide

Abstract: Background: Matrix-metalloproteinases 9 (MMP-9) belongs to the class of matrix metalloproteinases whose main function is to degrade and remodel the extracellular matrix (ECM). MMP-9 has been shown to be an integral part of many diseases where modulation of the ECM is a key step such as cancer, osteoporosis and fibrosis. MMP-9 is secreted as a latent pro-enzyme that requires activation in the extracellular space. Therefore, identifying physiological and molecular contexts, which can activate MMP-9 is important.<br>Results: Acidification of osteoclast-conditioned media to pH 5 resulted in a fragment with a size corresponding to active MMP-9. Also, treatment of recombinant proMMP-9 with recombinant cathepsin K (CTSK) at pH 5 yielded a fragment that corresponded to the molecular weight of active MMP-9, and showed MMP-9 activity. This activation was abrogated in the presence of CTSK inhibitor indicating that CTSK was responsible for the activation of pro-MMP-9. Knocking down CTSK in MDA-MB-231 cells also diminished MMP-9 activity compared to wild type control.<br>Conclusions: Here we provide the first evidence that CTSK can cleave and activate MMP-9 in acidic environments such as seen in tumors and during bone resorption. This finding provides a key link between CTSK expression in tumors and bone and ECM remodeling, through MMP-9 activation. This novel mechanism to activate MMP-9 through extracellular physiological changes elucidated in this study reveals a protease-signaling network involving CTSK and MMP-9 and provides the impetus to explore ECM proteases as physiological markers and pharmacological targets
The Fe-V cofactor of vanadium nitrogenase contains an interstitial carbon atom by Julian A Rees( )

1 edition published in 2015 in English and held by 3 WorldCat member libraries worldwide

Reproducible proteomics sample preparation for single FFPE tissue slices using acid-labile surfactant and direct trypsinization by Melanie Christine Föll( )

1 edition published in 2018 in English and held by 3 WorldCat member libraries worldwide

Abstract: Background<br>Proteomic analyses of clinical specimens often rely on human tissues preserved through formalin-fixation and paraffin embedding (FFPE). Minimal sample consumption is the key to preserve the integrity of pathological archives but also to deal with minimal invasive core biopsies. This has been achieved by using the acid-labile surfactant RapiGest in combination with a direct trypsinization (DTR) strategy. A critical comparison of the DTR protocol with the most commonly used filter aided sample preparation (FASP) protocol is lacking. Furthermore, it is unknown how common histological stainings influence the outcome of the DTR protocol.<br><br>Methods<br>Four single consecutive murine kidney tissue specimens were prepared with the DTR approach or with the FASP protocol using both 10 and 30 k filter devices and analyzed by label-free, quantitative liquid chromatography-tandem mass spectrometry (LC-MS/MS). We compared the different protocols in terms of proteome coverage, relative label-free quantitation, missed cleavages, physicochemical properties and gene ontology term annotations of the proteins. Additionally, we probed compatibility of the DTR protocol for the analysis of common used histological stainings, namely hematoxylin & eosin (H&E), hematoxylin and hemalaun. These were proteomically compared to an unstained control by analyzing four human tonsil FFPE tissue specimens per condition.<br><br>Results<br>On average, the DTR protocol identified 1841 ± 22 proteins in a single, non-fractionated LC-MS/MS analysis, whereas these numbers were 1857 ± 120 and 1970 ± 28 proteins for the FASP 10 and 30 k protocol. The DTR protocol showed 15% more missed cleavages, which did not adversely affect quantitation and intersample comparability. Hematoxylin or hemalaun staining did not adversely impact the performance of the DTR protocol. A minor perturbation was observed for H&E staining, decreasing overall protein identification by 13%.<br><br>Conclusions<br>In essence, the DTR protocol can keep up with the FASP protocol in terms of qualitative and quantitative reproducibility and performed almost as well in terms of proteome coverage and missed cleavages. We highlight the suitability of the DTR protocol as a viable and straightforward alternative to the FASP protocol for proteomics-based clinical research
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Audience level: 0.94 (from 0.92 for Phytoene D ... to 0.95 for Prevalence ...)

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Albert-Ludwigs-Universität Freiburg Zentrum für Biologische Signalstudien


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