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Huber, M.

Publications and source records attributed to Huber, M..

At least 37 records · Page 2Linked to original sources

KIRA6 is an effective and versatile mast cell inhibitor of IgE-mediated activation

Incidents of IgE-mediated, mast cell (MC)-driven allergic diseases are constantly rising and there is an urgent need for the development of novel pharmacological MC stabilizers. Allergen/antigen (Ag)-triggered activation of MCs via crosslinking of the high-affinity receptor for IgE (Fc{varepsilon}RI) is regulated, amongst others, by the coordinated action of various cytosolic tyrosine kinases of the SRC family, e.g. LYN and FYN, which exert positive as well as negative functions. We report that KIRA6, an inhibitor developed for the endoplasmic reticulum (ER) stress sensor IRE1, suppresses IgE-mediated pro-inflammatory MC activation by inhibiting both LYN and FYN. KIRA6 dose-dependently and effectively attenuates Ag-stimulated early signaling (e.g. substrate tyrosine phosphorylation, Ca2+ mobilization, and activation of MAPK pathways) as well as effector functions such as degranulation and pro-inflammatory cytokine production/secretion in murine bone marrow-derived MCs (BMMCs). Moreover, Ag-triggered bronchoconstriction in an ex vivo model of precision-cut lung slices (PCLS), and IgE-mediated stimulation of human MCs were repressed by KIRA6. To get in-depth inside into KIRA6 interaction with three MC-relevant tyrosine kinases, LYN, FYN, and KIT, and to elicit the potential of KIRA6 structure to serve as pharmacophore for the development of respective single-, dual-, or triple-specificity inhibitors, we modeled and evaluated the binding of KIRA6 on the three kinases by applying homology modeling and molecular dynamics simulations, as well as MM GBSA calculations. We found that KIRA6 has a high propensity to bind the inactive state of LYN, FYN, and KIT with comparable affinities. In conclusion, our data suggest the use of novel inhibitors based on the KIRA6 pharmacophore as effective MC stabilizers to improve treatment of pro-inflammatory diseases with MC involvement in need of effective pharmacological interventions.

immunology↗

Full-length structure of the host targeted bacterial effector Bep1 reveals a novel structural domain conserved in FIC effector proteins from Bartonella

Bacterial effector proteins translocated via a type-IV secretion system (T4SS) typically harbor a C-terminal segment required for recognition by the type-IV secretion coupling protein 1. In the -proteobacterial pathogen Bartonella, the signal is bipartite being composed of a BID (Bep intracellular delivery) domain and a positively charged C-terminal tail 2. Here, we show the crystal structure of full length Bartonella effector protein 1 (Bep1), which shows a novel FIC - OB - BAS(BID) domain arrangement conserved in the majority of Beps with the BID domain inserted into the newly discovered BAS parent domain. We propose that the BAS domain is necessary for the overall "boomerang"-like shape of Bep1 and that it plays a role during translocation through the T4SS.

microbiology↗

Enhancer cooperativity can compensate for loss of activity over large genomic distances

Enhancers are short DNA sequences that activate their target promoter from a distance; however, increasing the genomic distance between the enhancer and the promoter decreases expression levels. Many genes are controlled by combinations of multiple enhancers, yet the interaction and cooperation of individual enhancer elements is not well understood. Here, we developed a novel synthetic platform that allows building complex regulatory landscapes from the bottom up. We tested the system by integrating individual enhancers at different distances and revealed that the strength of an enhancer determines how strongly it is affected by increased genomic distance. Furthermore, synergy between two enhancer elements depends on the distance at which the two elements are integrated: introducing a weak enhancer between a strong enhancer and the promoter strongly increases reporter gene expression, allowing enhancers to activate from increased genomic distances.

molecular biology↗

Assessing rapid adaptation through epigenetic inheritance: a new experimental approach

O_LIEpigenetic inheritance is hypothesized to mediate rapid adaptation to stresses via two fundamentally different routes: first, through spontaneous epimutations that arise in a largely stochastic manner in the presence or absence of stress; if these spontaneous epimutations are heritable and beneficial, they may be selected upon ("stochastic route"); and second, through environment-induced epialleles that arise uniformly among individuals; if heritable, these epialleles may lead to stress adaptation even in the absence of selection ("deterministic route"). Testing and teasing apart these two routes is challenging, largely because a suitable experimental approach is lacking. C_LIO_LIHere, we propose an experimental approach that allows to simultaneously assess the contribution of the stochastic and deterministic route. The essence of the approach is to manipulate the efficacy of selection through the population size and thereby to test whether selection is required for adaptation (stochastic route). To this end, genetically uniform populations are grown under different environments across multiple generations ("pre-treatment") at two different population sizes: in large populations, in which selection is effective; and in small populations, in which drift overcomes the effect of selection. If the deterministic route contributes to adaptation, variation in fitness, phenotypes or epigenetic marks will arise between the small populations of the different pre-treatments. If the stochastic route contributes to adaptation, variation will arise between the small and large population within each pre-treatment. As a proof-of-principle, we tested whether small and large monoclonal populations of the aquatic duckweed Spirodela polyrhiza may adapt to copper excess outdoors. C_LIO_LIAfter five to seven generations of pre-treatment and a subsequent multi-generational growth under control conditions, large populations outperformed small populations under copper excess. Furthermore, small populations pre-treated with copper excess tended to have higher fitness under copper excess than small populations pre-treated under control conditions. These data suggest that both the stochastic and deterministic route may alter plant fitness under recurring stress. C_LIO_LIThe proposed approach will allow to experimentally evaluate whether species may adapt to stresses through either stochastic and deterministic epigenetic changes, which is fundamental to understand whether and how epigenetic inheritance may lead to rapid stress adaptation. C_LI

evolutionary biology↗

Sodium chloride in the tumor microenvironment enhances T-cell metabolic fitness and cytotoxicity

Adoptive T-cell therapy has become a powerful weapon for cancer treatment. The efficacy of antitumor immunity is associated with the metabolic state of cytotoxic T cells, which is highly sensitive to the tumor microenvironment. It is therefore of considerable interest to bypass immunosuppressive signals in the tumor microenvironment and to identify factors that augment cytotoxic effector functions and ultimately tumor killing. Whether ionic signals serve as aberrant immune signals and influence the adaptive human antitumor immune response is still largely unexplored. We therefore investigated the effect of sodium on the phenotype, function and metabolic regulation of human CD8+ T cells using transcriptomic, metabolomic, high-dimensional flow cytometric and functional assays. We demonstrate a significant enrichment of sodium in solid tumors from patients with breast cancer, which leaves a transcriptomic imprint on intratumoral immune cells. Sodium chloride (NaCl) enhanced the activation state and effector functions of human CD8+ memory T cells. These functional alterations were associated with enhanced metabolic fitness, particularly increases in glycolysis, oxidative phosphorylation and overall nutrient uptake. These NaCl-induced effects translated into increased tumor cell killing in vitro and in a tumor mouse model in vivo. We therefore propose NaCl as a positive regulator of acute antitumor immunity that could be harnessed for ex vivo conditioning of adoptively transferred T cells, such as CAR T-cells.

immunology↗

SAMD1 suppresses epithelial-mesenchymal transition (EMT) pathways in pancreatic ductal adenocarcinoma

SAMD1 (SAM-domain containing protein 1), a CpG island-binding protein, plays a pivotal role in the repression of its target genes. Despite its significant correlation with outcomes in various tumor types, the role of SAMD1 in cancer has remained largely unexplored. In this study we focused on pancreatic ductal adenocarcinoma (PDAC) and revealed that SAMD1 acts as a repressor of genes associated with epithelial-mesenchymal transition (EMT). Upon deletion of SAMD1 in PDAC cells, we observed significantly increased migration rates. SAMD1 exerts its effects by binding to specific genomic targets, including CDH2, encoding N-cadherin, which emerged as a driver of enhanced migration upon SAMD1 knockout. Furthermore, we discovered the FBXO11-containing E3 ubiquitin ligase complex as an interactor of SAMD1. FBXO11 ubiquitinates SAMD1 within its DNA-binding winged helix domain and inhibits SAMD1 chromatin binding genome-wide. High FBXO11 expression in PDAC is associated with poor prognosis and increased expression of EMT-related genes, underlining an antagonistic relationship between SAMD1 and FBXO11. In summary, our findings provide new insights into the regulation of EMT-related genes in PDAC, shedding light on the intricate role of SAMD1 and its interplay with FBXO11 in this cancer type.

molecular biology↗

Dynamic inter-domain transformations mediate the allosteric regulation of human 5, 10-methylenetetrahydrofolate reductase

5,10-methylenetetrahydrofolate reductase (MTHFR) commits folate-derived one-carbon units to generate the methyl-donor S-adenosyl-L-methionine (SAM). Eukaryotic MTHFR appends to the well-conserved catalytic domain (CD) a unique regulatory domain (RD) that confers feedback inhibition by SAM. We determined cryo-electron microscopy structures of human MTHFR bound to SAM and its demethylated product S-adenosyl-L-homocysteine (SAH). In the active state, with the RD bound to a single SAH, the CD is flexible and exposes its active site for catalysis. However, in the inhibited state the RD pocket is remodelled, exposing a second SAM-binding site that was previously occluded. Dual-SAM bound MTHFR demonstrates a substantially rearranged inter-domain linker that reorients the CD, inserts a loop into the active site, positions Tyr404 to bind the cofactor FAD, and blocks substrate access. Our data therefore explain the long-distance regulatory mechanism of MTHFR inhibition, underpinned by the transition between dual-SAM and single-SAH binding in response to cellular methylation status.

biochemistry↗

Population genomics and epigenomics provide insights into the evolution of facultative asexuality in plants

Many organisms, particularly plants, are facultatively asexual. Because asexual reproduction is beneficial for the short term but costly for the long term, during the range expansion, natural selection should act on the genetic controls of asexuality in these facultatively asexual organisms. However, the genomic evidence of natural selection driving asexuality remains scarce, and the evolutionary consequences of facultatively asexuality on the genomic and epigenomic diversity remain controversial. Here, by analyzing population genomes and epigenomes of Spirodela polyrhiza (L.) Schleid., a facultatively asexual plant that flowers rarely, we show that this plant has the lowest genomic diversity and DNA methylation levels among all studied multicellular eukaryotes. Within species, demographic history and the frequency of asexual reproduction jointly determined intra-specific variations of genomic diversity and DNA methylation levels. Genome-wide scans revealed that multiple genes involved in flowering and embryogenesis were under positive selection, consistent with the hypothesis that natural selection drove the evolution of asexuality during the recent habitat expansions in this plant. Together, these results provide new insights into the evolution of plant reproductive systems and suggest that natural selection can drive the evolutionary changes of asexuality, which in turn alters the levels of genomic and epigenomic diversity.

evolutionary biology↗

SR-BI regulates the synergistic mast cell response by modulating the plasma membrane-associated cholesterol pool

The high-affinity IgE receptor Fc{varepsilon}RI is the fundamental mast cell (MC) receptor responsible for the involvement of MCs in IgE-associated allergic disorders. Activation of the Fc{varepsilon}RI is achieved via crosslinking by multivalent antigen (Ag) recognized by IgE, which results in degranulation and pro-inflammatory cytokine production. In comparison to the T and B cell receptor complexes, for which several co-receptors that orchestrate the initial signaling have been described, information is scarce about Fc{varepsilon}RI-associated proteins. Additionally, it is not completely clear how Fc{varepsilon}RI signaling synergizes with input from other receptors and how potential regulators affect this synergistic response. We aimed at identifying new regulators of Fc{varepsilon}RI and found that the HDL receptor SR-BI (gene name: Scarb1/SCARB1) is expressed in MCs, functionally associates with Fc{varepsilon}RI and regulates the local plasma membrane cholesterol content in cholesterol-rich plasma membrane nanodomains as shown by using the cholesterol-sensitive probe GFP-D4. This impacted on the activation of murine MCs upon co-stimulation of the Fc{varepsilon}RI with different receptors known to synergize with Fc{varepsilon}RI-signaling pathways. Amongst them we investigated the co-activation of the Fc{varepsilon}RI with the receptor tyrosine kinase KIT, the IL-33 receptor and GPCRs activated by adenosine or PGE2. Scarb1-deficient bone marrow-derived MCs (BMMCs) showed reduced cytokine secretion in response to these co-stimulation conditions suggesting a role for plasma membrane-associated cholesterol regulating MC-driven inflammation. Mimicking Scarb1 deficiency by membrane cholesterol depletion employing M{beta}CD, we identified PKB and PLC{gamma}1 as cholesterol-sensitive signaling molecules activated downstream of Fc{varepsilon}RI in BMMCs. Specifically, when murine MCs were stimulated with SCF and Ag in combination, PLC{gamma}1 activation appeared to be drastically boosted and this could be mitigated by cholesterol depletion. Inhibiting SR-BI in BMMCs phenocopied this effect. Similarly, SR-BI inhibition also attenuated the synergistic response to PGE2 and anti-IgE in the human ROSAKIT WT mast cell line suggesting that SR-BI is a crucial regulator of synergistic MC activation by regulating the local plasma membrane cholesterol concentration.

immunology↗

Transformation of primary murine peritoneal mast cells by constitutive KIT activation as a result of lost Cdkn2a/Arf expression

Mast cells (MCs) are immune cells of the myeloid lineage distributed in tissues throughout the body. Phenotypically, they are a heterogeneous group characterized by different protease repertoires stored in secretory granules and differential presence of receptors. To adequately address aspects of MC biology either primary MCs isolated from human or mouse tissue or different human MC lines, like HMC-1.1 and -1.2, or rodent MC lines like L138.8A or RBL-2H3 are frequently used. Nevertheless, cellular systems to study MC functions are very limited. We have generated a murine connective tissue-like MC line, termed PMC-306, derived from primary peritoneal MCs (PMCs), which spontaneously transformed. We analyzed PMC-306 cells regarding MC surface receptor expression, effector functions and respective signaling pathways, and found that the cells reacted very similar to primary wildtype (WT) PMCs. In this regard, stimulation with MAS-related G-protein-coupled receptor member B2 (MRGPRB2) ligands induced respective signaling and effector functions. Furthermore, PMC-306 cells revealed significantly accelerated cell cycle progression, which however was still dependent on IL-3 and stem cell factor (SCF). Phenotypically, PMC-306 cells adopted an immature connective tissue-like MCs appearance. The reason for immortalization most likely is the loss of the two critical cell cycle regulators Cdkn2a/INK4A and Arf/p19, respectively. The loss of Cdkn2a and Arf expression could be mimicked in primary bone marrow-derived mast cells (BMMCs) by SCF supplementation strongly arguing for an involvement of KIT activation in the transformation process. Hence, this new cell line might be a useful tool to study further aspects of PMC function and to address tumorigenic processes associated with MC leukemia.

immunology↗

Induced responses contribute to rapid plant adaptation to herbivory

Herbivory-induced responses in plants are typical examples of phenotypic plasticity, and their evolution is thought to be driven by herbivory. However, direct evidence of the role of induced responses in plant adaptive evolution to herbivores is scarce. Here, we experimentally evolved populations of an aquatic plant (Spirodela polyrhiza, giant duckweed) and its native herbivore (Lymnaea stagnalis, freshwater snail) testing whether herbivory drives rapid adaptive evolution in plant populations using a combination of bioassays, pool-sequencing, metabolite analyses, and amplicon metagenomics. We found that snail herbivory drove rapid phenotypic changes, increased herbivory resistance, and altered genotype frequencies in the plant populations. Additional bioassays suggested that evolutionary changes of induced responses contributed to the rapid increase of plant resistance to herbivory. This study provides direct evidence that herbivory-induced responses in plants can be subjected to selection and have an adaptive role by increasing resistance to herbivores.

evolutionary biology↗

Schwann cells promote sensory neuron excitability during development

Excitability--the ability to fire action potentials--is a signature feature of neurons. How neurons become excitable during development, and whether excitability is an intrinsic property of neurons or requires signaling from glial cells, remain unclear. Here we demonstrate that Schwann cells, the most abundant glia in the peripheral nervous system, promote somatosensory neuron excitability during development. We find that Schwann cells secrete prostaglandin E2, which is necessary and sufficient to induce developing somatosensory neurons to express normal levels of voltage-gated sodium channels and fire action potential trains. Inactivating this signaling pathway specifically in Schwann cells selectively impairs the maturation of nociceptor and proprioceptor somatosensory neuron subtypes, leading to corresponding sensory defects in thermoception, inflammatory pain, and proprioception. Our studies thus reveal a cell non-autonomous mechanism by which glia regulate neuronal excitability to enable the development of normal sensory functions.

neuroscience↗

Natural rubber reduces herbivory and alters the microbiome below ground

O_LILaticifers are hypothesized to mediate both plant-herbivore and plant-microbe interactions. However, there is little evidence for the dual function of these secretory structures. C_LIO_LIWe investigated whether the major constituent of natural rubber, cis-1,4-polyisoprene, a phylogenetically widespread and economically important latex polymer, alters plant resistance and the root microbiome of the Russian dandelion (Taraxacum koksaghyz) under attack of a root herbivore, the larva of the May cockchafer (Melolontha melolontha). C_LIO_LIRubber-depleted transgenic plants lost more shoot and root biomass upon herbivory than normal rubber content near-isogenic lines. M. melolontha preferred to feed on artificial diet supplemented with rubber-depleted rather than normal rubber content latex. Likewise, adding purified cis-1,4-polyisoprene in ecologically relevant concentrations to diet deterred larval feeding and reduced larval weight gain. Metagenomics and metabarcoding revealed that abolishing biosynthesis of natural rubber alters the structure but not the diversity of the rhizosphere and root microbiota in a herbivore-dependent manner. Roots from rubber-depleted plants, however, did not exhibit a higher pathogen load compared to normal rubber content roots. C_LIO_LITaken together, our data demonstrate that natural rubber biosynthesis reduces herbivory and alters the plant microbiota in a herbivore-dependent manner, which highlights the role of plant specialized metabolites and secretory structures in shaping multitrophic interactions. C_LI

plant biology↗

Enhanced methionine cycle suppresses naïve CD8+ T-cell maturation

The metabolic pathways controlling naive CD8+ T (Tn) cell maturation following thymic egress remain mostly undefined. This is important because immature Tn are a major component of peripheral immune tolerance in newborns and under lymphopenia. In this study we demonstrate that TMRM, a mitochondrial membrane potential marker, could be applied to rapidly identify an immature Tn cell population in the periphery. Applying this marker to perform metabolic and proteomic analysis, we show that immature Tn cells maintain accelerated methionine cycle in respect to mature Tn. This unique metabolic state was associated with restricted Tbx21 locus and diminished immune response in vitro and in vivo. Following our findings, we demonstrate that inhibition of methionine cycle leads to rapid functional maturation of Tn and recovery of immune response to stimuli. Our work provides insight into the way the rate of methionine cycling regulates T cell maturation, opening a path for metabolic manipulation of immune tolerance.

immunology↗

Selection of an Ideal Machine Learning Framework for Predicting Perturbation Effects on Network Topology of Bacterial KEGGPathways

Biological networks for bacterial species are used to assign functional information to newly sequenced organisms but network quality can be largely affected by poor gene annotations. Current methods of gene annotation use homologous alignment to determine orthology, and have been shown to degrade network accuracy in non-model bacterial species. To address these issues in the KEGG pathway database, we investigated the ability for machine learning (ML) algorithms to re-annotate bacterial genes based on motif or homology information. The majority of the ensemble, clustering, and deep learning algorithms that we explored showed higher prediction accuracy than CD-hit in predicting EC ID, Map ID, and partial Map ID. Motif-based, machine-learning methods of annotation in new species were more accurate, faster, and had higher precisionrecall than methods of homologous alignment or orthologous gene clustering. Gradient boosted ensemble methods and neural networks also predicted higher connectivity of networks, finding twice as many new pathway interactions than blast alignment. The use of motif-based, machine-learning algorithms in annotation software will allow researchers to develop powerful network tools to interact with bacterial microbiomes in ways previously unachievable through homologous sequence alignment. CCS CONCEPTS* Applied computing [->] Computational biology; Life and medical sciences; Bioinformatics; * Computing methodologies [->] Machine learning algorithms; Machine learning approaches. ACM Reference FormatMichael Robben, Mohammad Sadegh Nasr, Avishek Das, Manfred Huber, Justyn Jaworski, Jon Weidanz, and Jacob Luber. 2022. Selection of an Ideal Machine Learning Framework for Predicting Perturbation Effects on Network Topology of Bacterial KEGG Pathways. In The 13th ACM Conference on Bioinformatics, Computational Biology, and Health Informatics, August 07-10, 2022, Chicago, IL. ACM, New York, NY, USA, 11 pages. https://doi.org/XXXXXXX.XXXXXXX

bioinformatics↗

Effects of sub-lethal single, simultaneous, and sequential abiotic stresses on phenotypic traits of Arabidopsis thaliana

Plant responses to abiotic stresses are complex and dynamic, and involve changes in different traits, either as the direct consequence of the stress, or as an active acclimatory response. Abiotic stresses frequently occur simultaneously or in succession, rather than in isolation. Despite this, most studies have focused on a single stress and single or few plant traits. To address this gap, our study comprehensively and categorically quantified the individual and combined effects of three major abiotic stresses associated with climate change (flooding, progressive drought and high temperature) on 12 phenotypic traits related to morphology, development, growth and fitness, at different developmental stages in four Arabidopsis thaliana accessions. Combined sub-lethal stresses were applied either simultaneously (high temperature and drought) or sequentially (flooding followed by drought). In total, we analyzed the phenotypic responses of 1782 individuals across these stresses and different developmental stages. Overall, abiotic stresses and their combinations resulted in distinct patterns of effects across the traits analyzed, with both quantitative and qualitative differences across accessions. Stress combinations had additive effects on some traits, whereas clear positive and negative interactions were observed for other traits: 9 out of 12 traits for high temperature and drought, 6 out of 12 traits for post-submergence and drought showed significant interactions. In many cases where the stresses interacted, the strength of interactions varied across accessions. Hence, our results indicated a general pattern of response in most phenotypic traits to the different stresses and stress combinations, but it also indicated a natural genetic variation in the strength of these responses. Overall, our study provides a rich characterization of trait responses of Arabidopsis plants to sub-lethal abiotic stresses at the phenotypic level and can serve as starting point for further in-depth physiological research and plant modelling efforts.

plant biology↗

Stem cell specific interferon stimulated gene expression is regulated by the formative pluripotency network through IRF1

Stem cells intrinsically express a subset of genes which are normally associated with interferon stimulation, and thus the innate immunity response. Expression of these interferon stimulated genes (ISG) in stem cells is independent of external stimuli such as viral infection. Here we show that the interferon regulatory factor 1, Irf1, is directly controlled by the murine formative pluripotency gene regulatory network and therefore upregulated in the transition from naive to formative pluripotency. IRF1 in turn binds to regulatory regions of a conserved set of ISGs and is required for their faithful expression in formative pluripotent cells. IRF1 also binds to an enhancer of the formative pluripotency transcription factor Oct6 and is partially required for upregulation of Oct6. IRF1 therefore acts as a link between the formative pluripotency network and the regulation of innate immunity genes in formative pluripotency.

developmental biology↗

TRAIP regulates DNA double-strand break-induced ATM activation

DNA double-strand breaks (DSBs) affect cell survival and genomic integrity. They are repaired by a highly coordinated process called the DNA damage response. Here, we report that the ubiquitously expressed nucleolar E3 ubiquitin ligase TRAF-interacting protein (TRAIP), previously shown to regulate the spindle assembly checkpoint, has an essential role during the DNA damage response. A biotinylation proximity screening assay (BioID) identified Ku80, Ku70, SMARCA5 (SNF2H) and DNA-PKcs as novel TRAIP interactors. Co-immunoprecipitations demonstrated that the interaction of TRAIP with Ku80 was transiently increased while the one with SMARCA5 was strongly decreased after treatment of HeLa cells with neocarzinostatin (NCS). Treatment of fibroblasts from a microcephalic primordial dwarfism patient carrying a hypomorphic TRAIP mutation or shRNA-mediated knockdown of TRAIP in HeLa cells with NCS impaired the activation of ataxia-telangiectasia mutated (ATM), a protein kinase crucial for the DNA damage response. As consequence, the maintenance of {gamma}H2AX and Chk2-T68 phosphorylation, two downstream targets of ATM, was significantly abrogated after NCS-inflicted DSBs. DNA repair assays showed that TRAIP inhibits incorrect end utilization during non-homologous end joining. These observations highlight TRAIP as novel regulator of ATM activity in DNA damage signaling.

cell biology↗