26 results on '"Jäck, Hans-Martin"'
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2. Metabolic profiling of single cells by exploiting NADH and FAD fluorescence via flow cytometry.
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Abir, Ariful Haque, Weckwerth, Leonie, Wilhelm, Artur, Thomas, Jana, Reichardt, Clara M., Munoz, Luis, Völkl, Simon, Appelt, Uwe, Mroz, Markus, Niesner, Raluca, Hauser, Anja, Sophie Fischer, Rebecca, Pracht, Katharina, Jäck, Hans-Martin, Schett, Georg, Krönke, Gerhard, and Mielenz, Dirk
- Abstract
The metabolism of different cells within the same microenvironment can differ and dictate physiological or pathological adaptions. Current single-cell analysis methods of metabolism are not label-free. The study introduces a label-free, live-cell analysis method assessing endogenous fluorescence of NAD(P)H and FAD in surface-stained cells by flow cytometry. OxPhos inhibition, mitochondrial uncoupling, glucose exposure, genetic inactivation of glucose uptake and mitochondrial respiration alter the optical redox ratios of FAD and NAD(P)H as measured by flow cytometry. Those alterations correlate strongly with measurements obtained by extracellular flux analysis. Consequently, metabolically distinct live B-cell populations can be resolved, showing that human memory B-cells from peripheral blood exhibit a higher glycolytic flexibility than naïve B cells. Moreover, the comparison of blood-derived B- and T-lymphocytes from healthy donors and rheumatoid arthritis patients unleashes rheumatoid arthritis-associated metabolic traits in human naïve and memory B-lymphocytes. Taken together, these data show that the optical redox ratio can depict metabolic differences in distinct cell populations by flow cytometry. • Real-time simultaneous metabolic analysis of different cell populations. • Label-free detection of the optical redox ratio of FAD/NADH fluorescence via flow cytometry. • Correlation with Seahorse extracellular flux analysis and enzymatic NAD(P)H detection. • Applicable to human T cell lymphoma, primary mouse and human lymphocytes. • Distinction of naïve and memory B cell populations in healthy and inflamed background. [ABSTRACT FROM AUTHOR]
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- 2024
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3. IRF4 deficiency vulnerates B-cell progeny for leukemogenesis via somatically acquired Jak3mutations conferring IL-7 hypersensitivity
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Das Gupta, Dennis, Paul, Christoph, Samel, Nadine, Bieringer, Maria, Staudenraus, Daniel, Marini, Federico, Raifer, Hartmann, Menke, Lisa, Hansal, Lea, Camara, Bärbel, Roth, Edith, Daum, Patrick, Wanzel, Michael, Mernberger, Marco, Nist, Andrea, Bauer, Uta-Maria, Helmprobst, Frederik, Buchholz, Malte, Roth, Katrin, Bastian, Lorenz, Hartmann, Alina M., Baldus, Claudia, Ikuta, Koichi, Neubauer, Andreas, Burchert, Andreas, Jäck, Hans-Martin, Klein, Matthias, Bopp, Tobias, Stiewe, Thorsten, Pagenstecher, Axel, and Lohoff, Michael
- Abstract
The processes leading from disturbed B-cell development to adult B-cell progenitor acute lymphoblastic leukemia (BCP-ALL) remain poorly understood. Here, we describe Irf4−/−mice as prone to developing BCP-ALL with age. Irf4−/−preB-I cells exhibited impaired differentiation but enhanced proliferation in response to IL-7, along with reduced retention in the IL-7 providing bone marrow niche due to decreased CXCL12 responsiveness. Thus selected, preB-I cells acquired Jak3mutations, probably following irregular AID activity, resulting in malignant transformation. We demonstrate heightened IL-7 sensitivity due to Jak3mutants, devise a model to explain it, and describe structural and functional similarities to Jak2mutations often occurring in human Ph-like ALL. Finally, targeting JAK signaling with Ruxolitinib in vivo prolonged survival of mice bearing established Irf4−/−leukemia. Intriguingly, organ infiltration including leukemic meningeosis was selectively reduced without affecting blood blast counts. In this work, we present spontaneous leukemogenesis following IRF4 deficiency with potential implications for high-risk BCP-ALL in adult humans.
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- 2022
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4. Krüppel-like factor 2 controls IgA plasma cell compartmentalization and IgA responses
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Wittner, Jens, Schulz, Sebastian R., Steinmetz, Tobit D., Berges, Johannes, Hauke, Manuela, Channell, William M., Cunningham, Adam F., Hauser, Anja E., Hutloff, Andreas, Mielenz, Dirk, Jäck, Hans-Martin, and Schuh, Wolfgang
- Abstract
Krüppel-like factor 2 (KLF2) is a potent regulator of lymphocyte differentiation, activation and migration. However, its functional role in adaptive and humoral immunity remains elusive. Therefore, by using mice with a B cell-specific deletion of KLF2, we investigated plasma cell differentiation and antibody responses. We revealed that the deletion of KLF2 resulted in perturbed IgA plasma cell compartmentalization, characterized by the absence of IgA plasma cells in the bone marrow, their reductions in the spleen, the blood and the lamina propria of the colon and the small intestine, concomitant with their accumulation and retention in mesenteric lymph nodes and Peyer's patches. Most intriguingly, secretory IgA in the intestinal lumen was almost absent, dimeric serum IgA was drastically reduced and antigen-specific IgA responses to soluble Salmonellaflagellin were blunted in KLF2-deficient mice. Perturbance of IgA plasma cell localization was caused by deregulation of CCR9, Integrin chains αM, α4, β7, and sphingosine-1-phosphate receptors. Hence, KLF2 not only orchestrates the localization of IgA plasma cells by fine-tuning chemokine receptors and adhesion molecules but also controls IgA responses to Salmonellaflagellin.
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- 2022
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5. Krüppel-like factor 2 controls IgA plasma cell compartmentalization and IgA responses
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Wittner, Jens, Schulz, Sebastian R., Steinmetz, Tobit D., Berges, Johannes, Hauke, Manuela, Channell, William M., Cunningham, Adam F., Hauser, Anja E., Hutloff, Andreas, Mielenz, Dirk, Jäck, Hans-Martin, and Schuh, Wolfgang
- Abstract
Krüppel-like factor 2 (KLF2) is a potent regulator of lymphocyte differentiation, activation and migration. However, its functional role in adaptive and humoral immunity remains elusive. Therefore, by using mice with a B cell-specific deletion of KLF2, we investigated plasma cell differentiation and antibody responses. We revealed that the deletion of KLF2 resulted in perturbed IgA plasma cell compartmentalization, characterized by the absence of IgA plasma cells in the bone marrow, their reductions in the spleen, the blood and the lamina propria of the colon and the small intestine, concomitant with their accumulation and retention in mesenteric lymph nodes and Peyer’s patches. Most intriguingly, secretory IgA in the intestinal lumen was almost absent, dimeric serum IgA was drastically reduced and antigen-specific IgA responses to soluble Salmonellaflagellin were blunted in KLF2-deficient mice. Perturbance of IgA plasma cell localization was caused by deregulation of CCR9, Integrin chains αM, α4, β7, and sphingosine-1-phosphate receptors. Hence, KLF2 not only orchestrates the localization of IgA plasma cells by fine-tuning chemokine receptors and adhesion molecules but also controls IgA responses to Salmonellaflagellin.
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- 2022
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6. TFG is required for autophagy flux and to prevent endoplasmic reticulum stress in CH12 B lymphoma cells
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Steinmetz, Tobit D., Schlötzer-Schrehardt, Ursula, Hearne, Abigail, Schuh, Wolfgang, Wittner, Jens, Schulz, Sebastian R., Winkler, Thomas H., Jäck, Hans-Martin, and Mielenz, Dirk
- Abstract
ABSTRACTPlasma cells depend on quality control of newly synthesized antibodies in the endoplasmic reticulum (ER) via macroautophagy/autophagy and proteasomal degradation. The cytosolic adaptor protein TFG (Trk-fused gene) regulates ER-Golgi transport, the secretory pathway and proteasome activity in non-immune cells. We show here that TFG is upregulated during lipopolysaccharide- and CpG-induced differentiation of B1 and B2 B cells into plasmablasts, with the highest expression of TFG in mature plasma cells. CRISPR-CAS9-mediated gene disruption of tfgin the B lymphoma cell line CH12 revealed increased apoptosis, which was reverted by BCL2 but even more by ectopic TFG expression. Loss of TFG disrupted ER structure, leading to an expanded ER and increased expression of ER stress genes. When compared to wild-type CH12 cells, tfgKO CH12 cells were more sensitive toward ER stress induced by tunicamycin, monensin and proteasome inhibition or by expression of an ER-bound immunoglobulin (Ig) μ heavy (µH) chain. CH12 tfgKO B cells displayed more total LC3, lower LC3-II turnover and increased numbers and size of autophagosomes. Tandem-fluorescent-LC3 revealed less accumulation of GFP-LC3 in starved and chloroquine-treated CH12 tfgKO B cells. The GFP:RFP ratio of tandem-fluorescent-LC3 was higher in tunicamycin-treated CH12 tfgKO B cells, suggesting less autophagy flux during induced ER stress. Based on these data, we suggest that TFG controls autophagy flux in CH12 B cells and propose that TFG is a survival factor that alleviates ER stress through the support of autophagy flux in activated B cells and mature plasma cells.Abbreviations: Ab, antibody; Ag, antigen; ASC, antibody-secreting cells; ATG, autophagy-related; BCR, B cell receptor; COPII, coat protein complex II; CpG, non-methylated CpG oligonucleotide; ER, endoplasmic reticulum; ERAD, ER-associated degradation; FO, follicular; GFP, green fluorescent protein; HC, heavy chain; Ig, immunoglobulin; IRES, internal ribosomal entry site; LC, light chain; MZ, marginal zone; NFKB, nuclear factor of kappa light polypeptide gene enhancer in B cells; TLR, toll-like receptor; UPR, unfolded protein response.
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- 2021
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7. Chapter Three: Unraveling the mysteries of plasma cells.
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Schuh, Wolfgang, Mielenz, Dirk, and Jäck, Hans-Martin
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PLASMA cells ,MULTIPLE myeloma ,GENE regulatory networks ,CELL transformation ,HUMORAL immunity - Abstract
Antibody-secreting plasma cells are the central pillars of humoral immunity. They are generated in a fundamental cellular restructuring process from naive B cells upon contact with antigen. This outstanding process is guided and controlled by a complex transcriptional network accompanied by a fascinating morphological metamorphosis, governed by the combined action of Blimp-1, Xbp-1 and IRF-4. The survival of plasma cells requires the intimate interaction with a specific microenvironment, consisting of stromal cells and cells of hematopoietic origin. Cell-cell contacts, cytokines and availability of metabolites such as glucose and amino acids modulate the survival abilities of plasma cells in their niches. Moreover, plasma cells have been shown to regulate immune responses by releasing cytokines. Furthermore, plasma cells are central players in autoimmune diseases and malignant transformation of plasma cells can result in the generation of multiple myeloma. Hence, the development of sophisticated strategies to deplete autoreactive plasma cells and myeloma cells represents a challenge for current and future research. [ABSTRACT FROM AUTHOR]
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- 2020
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8. Unraveling the mysteries of plasma cells
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Schuh, Wolfgang, Mielenz, Dirk, and Jäck, Hans-Martin
- Abstract
Antibody-secreting plasma cells are the central pillars of humoral immunity. They are generated in a fundamental cellular restructuring process from naive B cells upon contact with antigen. This outstanding process is guided and controlled by a complex transcriptional network accompanied by a fascinating morphological metamorphosis, governed by the combined action of Blimp-1, Xbp-1 and IRF-4. The survival of plasma cells requires the intimate interaction with a specific microenvironment, consisting of stromal cells and cells of hematopoietic origin. Cell-cell contacts, cytokines and availability of metabolites such as glucose and amino acids modulate the survival abilities of plasma cells in their niches. Moreover, plasma cells have been shown to regulate immune responses by releasing cytokines. Furthermore, plasma cells are central players in autoimmune diseases and malignant transformation of plasma cells can result in the generation of multiple myeloma. Hence, the development of sophisticated strategies to deplete autoreactive plasma cells and myeloma cells represents a challenge for current and future research.
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- 2020
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9. GLUT1-mediated glucose import in B cells is critical for anaplerotic balance and humoral immunity
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Bierling, Theresa E.H., Gumann, Amelie, Ottmann, Shannon R., Schulz, Sebastian R., Weckwerth, Leonie, Thomas, Jana, Gessner, Arne, Wichert, Magdalena, Kuwert, Frederic, Rost, Franziska, Hauke, Manuela, Freudenreich, Tatjana, Mielenz, Dirk, Jäck, Hans-Martin, and Pracht, Katharina
- Abstract
Glucose uptake increases during B cell activation and antibody-secreting cell (ASC) differentiation, but conflicting findings prevent a clear metabolic profile at different stages of B cell activation. Deletion of the glucose transporter type 1 (GLUT1) gene in mature B cells (GLUT1-cKO) results in normal B cell development, but it reduces germinal center B cells and ASCs. GLUT1-cKO mice show decreased antigen-specific antibody titers after vaccination. In vitro, GLUT1-deficient B cells show impaired activation, whereas established plasmablasts abolish glycolysis, relying on mitochondrial activity and fatty acids. Transcriptomics and metabolomics reveal an altered anaplerotic balance in GLUT1-deficient ASCs. Despite attempts to compensate for glucose deprivation by increasing mitochondrial mass and gene expression associated with glycolysis, the tricarboxylic acid cycle, and hexosamine synthesis, GLUT1-deficient ASCs lack the metabolites for energy production and mitochondrial respiration, limiting protein synthesis. We identify GLUT1 as a critical metabolic player defining the germinal center response and humoral immunity.
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- 2024
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10. A defined metabolic state in pre B cells governs B-cell development and is counterbalanced by Swiprosin-2/EFhd1
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Stein, Merle, Dütting, Sebastian, Mougiakakos, Dimitrios, Bösl, Michael, Fritsch, Kristin, Reimer, Dorothea, Urbanczyk, Sophia, Steinmetz, Tobit, Schuh, Wolfgang, Bozec, Aline, Winkler, Thomas H, Jäck, Hans-Martin, and Mielenz, Dirk
- Abstract
B-cell development in the bone marrow comprises proliferative and resting phases in different niches. We asked whether B-cell metabolism relates to these changes. Compared to pro B and small pre B cells, large pre B cells revealed the highest glucose uptake and ROS but not mitochondrial mass, whereas small pre B cells exhibited the lowest mitochondrial membrane potential. Small pre B cells from Rag1−/−;33.C9 μ heavy chain knock-in mice revealed decreased glycolysis (ECAR) and mitochondrial spare capacity compared to pro B cells from Rag1−/−mice. We were interested in the step regulating this metabolic switch from pro to pre B cells and uncovered that Swiprosin-2/EFhd1, a Ca2+-binding protein of the inner mitochondrial membrane involved in Ca2+-induced mitoflashes, is expressed in pro B cells, but downregulated by surface pre B-cell receptor expression. Knockdown and knockout of EFhd1 in 38B9 pro B cells decreased the oxidative phosphorylation/glycolysis (OCR/ECAR) ratio by increasing glycolysis, glycolytic capacity and reserve. Prolonged expression of EFhd1 in EFhd1 transgenic mice beyond the pro B cell stage increased expression of the mitochondrial co-activator PGC-1α in primary pre B cells, but reduced mitochondrial ATP production at the pro to pre B cell transition in IL-7 cultures. Transgenic EFhd1 expression caused a B-cell intrinsic developmental disadvantage for pro and pre B cells. Hence, coordinated expression of EFhd1 in pro B cells and by the pre BCR regulates metabolic changes and pro/pre B-cell development.
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- 2017
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11. SARS-CoV-2 Omicron sublineages show comparable cell entry but differential neutralization by therapeutic antibodies.
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Arora, Prerna, Zhang, Lu, Krüger, Nadine, Rocha, Cheila, Sidarovich, Anzhalika, Schulz, Sebastian, Kempf, Amy, Graichen, Luise, Moldenhauer, Anna-Sophie, Cossmann, Anne, Dopfer-Jablonka, Alexandra, Behrens, Georg M.N., Jäck, Hans-Martin, Pöhlmann, Stefan, and Hoffmann, Markus
- Abstract
The Omicron variant of SARS-CoV-2 evades antibody-mediated neutralization with unprecedented efficiency. At least three Omicron sublineages have been identified—BA.1, BA.2, and BA.3—and BA.2 exhibits increased transmissibility. However, it is currently unknown whether BA.2 differs from the other sublineages regarding cell entry and antibody-mediated inhibition. Here, we show that BA.1, BA.2, and BA.3 enter and fuse target cells with similar efficiency and in an ACE2-dependent manner. However, BA.2 was not efficiently neutralized by seven of eight antibodies used for COVID-19 therapy, including Sotrovimab, which robustly neutralized BA.1. In contrast, BA.2 and BA.3 (but not BA.1) were appreciably neutralized by Cilgavimab, which could constitute a treatment option. Finally, all sublineages were comparably and efficiently neutralized by antibodies induced by BNT162b2 booster vaccination after previous two-dose homologous or heterologous vaccination. Collectively, the Omicron sublineages show comparable cell entry and neutralization by vaccine-induced antibodies but differ in susceptibility to therapeutic antibodies. [Display omitted] • SARS-CoV-2 Omicron BA.1, BA.2, and BA.3 harbor shared and unique spike protein mutations • BA.1, BA.2, and BA.3 enter and fuse target cells with similar efficiency • mRNA vaccine boosters comparably increase neutralization of BA.1, BA.2, and BA.3 • BA.1, BA.2, and BA.3 differ regarding neutralization by therapeutic antibodies The SARS-CoV-2 Omicron variant contains at least three main sublineages that harbor shared and unique spike protein mutations. Arora et al. show that sublineages BA.1, BA.2, and BA.3 enter cells with similar efficiency and are comparably neutralized by antibodies induced by BNT162b2 booster vaccination but differ regarding neutralization by therapeutic antibodies. [ABSTRACT FROM AUTHOR]
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- 2022
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12. Essential control of early B-cell development by Mef2 transcription factors
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Herglotz, Julia, Unrau, Ludmilla, Hauschildt, Friderike, Fischer, Meike, Kriebitzsch, Neele, Alawi, Malik, Indenbirken, Daniela, Spohn, Michael, Müller, Ursula, Ziegler, Marion, Schuh, Wolfgang, Jäck, Hans-Martin, and Stocking, Carol
- Abstract
The sequential activation of distinct developmental gene networks governs the ultimate identity of a cell, but the mechanisms involved in initiating downstream programs are incompletely understood. The pre-B-cell receptor (pre-BCR) is an important checkpoint of B-cell development and is essential for a pre-B cell to traverse into an immature B cell. Here, we show that activation of myocyte enhancer factor 2 (Mef2) transcription factors (TFs) by the pre-BCR is necessary for initiating the subsequent genetic network. We demonstrate that B-cell development is blocked at the pre-B-cell stage in mice deficient for Mef2c and Mef2d TFs and that pre-BCR signaling enhances the transcriptional activity of Mef2c/d through phosphorylation by the Erk5 mitogen-activating kinase. This activation is instrumental in inducing Krüppel-like factor 2 and several immediate early genes of the AP1 and Egr family. Finally, we show that Mef2 proteins cooperate with the products of their target genes (Irf4 and Egr2) to induce secondary waves of transcriptional regulation. Our findings uncover a novel role for Mef2c/d in coordinating the transcriptional network that promotes early B-cell development.
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- 2016
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13. Essential control of early B-cell development by Mef2 transcription factors
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Herglotz, Julia, Unrau, Ludmilla, Hauschildt, Friderike, Fischer, Meike, Kriebitzsch, Neele, Alawi, Malik, Indenbirken, Daniela, Spohn, Michael, Müller, Ursula, Ziegler, Marion, Schuh, Wolfgang, Jäck, Hans-Martin, and Stocking, Carol
- Abstract
The sequential activation of distinct developmental gene networks governs the ultimate identity of a cell, but the mechanisms involved in initiating downstream programs are incompletely understood. The pre-B-cell receptor (pre-BCR) is an important checkpoint of B-cell development and is essential for a pre-B cell to traverse into an immature B cell. Here, we show that activation of myocyte enhancer factor 2 (Mef2) transcription factors (TFs) by the pre-BCR is necessary for initiating the subsequent genetic network. We demonstrate that B-cell development is blocked at the pre-B-cell stage in mice deficient for Mef2c and Mef2d TFs and that pre-BCR signaling enhances the transcriptional activity of Mef2c/d through phosphorylation by the Erk5 mitogen-activating kinase. This activation is instrumental in inducing Krüppel-like factor 2 and several immediate early genes of the AP1 and Egr family. Finally, we show that Mef2 proteins cooperate with the products of their target genes (Irf4and Egr2) to induce secondary waves of transcriptional regulation. Our findings uncover a novel role for Mef2c/d in coordinating the transcriptional network that promotes early B-cell development.
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- 2016
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14. Chapter 13 Identifying Substrates of mRNA Decay Factors by a Combined RNA Interference and DNA Microarray Approach.
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Wittmann, Jürgen and Jäck, Hans-Martin
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Abstract: The complex control of gene expression has many layers, and the modulation of posttranscriptional events receives more and more attention as a focus of research. In this respect, regulation of mRNA turnover is important, as the differential longevity of an mRNA enables a cell to rapidly alter the abundance of a protein in response to intra- and extracellular signals. While the list of factors known to catalyze or regulate mRNA decay is steadily increasing, the substrate specificities of most of these factors, as well as their precise roles in the degradation of individual mRNAs, have remained elusive. One approach for determining the substrate repertoire of a particular mRNA decay factor involves a genome-wide DNA microarray analysis of mRNAs that accumulate in cells in which the abundance of the respective factor has been reduced by RNA interference. Using the knockdown of the nonsense-mediated mRNA decay factor human UPF2 as a model system, this chapter provides a detailed protocol of how to reduce the abundance of an mRNA decay factor by small interfering RNAs and to determine differential mRNA profiles by a subsequent DNA microarray analysis. Our combined RNA interference/DNA microarray approach, as well as all experimental protocols, can, however, be easily adapted to any mRNA decay factor of interest. [Copyright &y& Elsevier]
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- 2008
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15. BAFFR activates PI3K/AKT signaling in human naive but not in switched memory B cells through direct interactions with B cell antigen receptors
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Sevdali, Eirini, Block, Violeta, Lataretu, Marie, Li, Huiying, Smulski, Cristian R., Briem, Jana-Susann, Heitz, Yannic, Fischer, Beate, Ramirez, Neftali-Jose, Grimbacher, Bodo, Jäck, Hans-Martin, Voll, Reinhard E., Hölzer, Martin, Schneider, Pascal, and Eibel, Hermann
- Abstract
Binding of BAFF to BAFFR activates in mature B cells PI3K/AKT signaling regulating protein synthesis, metabolic fitness, and survival. In humans, naive and memory B cells express the same levels of BAFFR, but only memory B cells seem to survive without BAFF. Here, we show that BAFF activates PI3K/AKT only in naive B cells and changes the expression of genes regulating migration, proliferation, growth, and survival. BAFF-induced PI3K/AKT activation requires direct interactions between BAFFR and the B cell antigen receptor (BCR) components CD79A and CD79B and is enhanced by the AKT coactivator TCL1A. Compared to memory B cells, naive B cells express more surface BCRs, which interact better with BAFFR than IgG or IgA, thus allowing stronger responses to BAFF. As ablation of BAFFR in naive and memory B cells causes cell death independent of BAFF-induced signaling, BAFFR seems to act also as an intrinsic factor for B cell survival.
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- 2022
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16. Inter-domain communication in SARS-CoV-2 spike proteins controls protease-triggered cell entry
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Qing, Enya, Li, Pengfei, Cooper, Laura, Schulz, Sebastian, Jäck, Hans-Martin, Rong, Lijun, Perlman, Stanley, and Gallagher, Tom
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SARS-CoV-2 continues to evolve into variants of concern (VOC), with greatest variability in the multidomain, entry-facilitating spike proteins. To recognize the significance of adaptive spike protein changes, we compare variant SARS-CoV-2 virus particles in several assays reflecting authentic virus-cell entry. Virus particles with adaptive changes in spike amino-terminal domains (NTDs) are hypersensitive to proteolytic activation of membrane fusion, an essential step in virus-cell entry. Proteolysis is within fusion domains (FDs), at sites over 10 nm from the VOC-specific NTD changes, indicating allosteric inter-domain control of fusion activation. In addition, NTD-specific antibodies block FD cleavage, membrane fusion, and virus-cell entry, suggesting restriction of inter-domain communication as a neutralization mechanism. Finally, using structure-guided mutagenesis, we identify an inter-monomer β sheet structure that facilitates NTD-to-FD transmissions and subsequent fusion activation. This NTD-to-FD axis that sensitizes viruses to infection and to NTD-specific antibody neutralization provides new context for understanding selective forces driving SARS-CoV-2 evolution.
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- 2022
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17. SARS-CoV-2 variants C.1.2 and B.1.621 (Mu) partially evade neutralization by antibodies elicited upon infection or vaccination
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Arora, Prerna, Kempf, Amy, Nehlmeier, Inga, Graichen, Luise, Winkler, Martin S., Lier, Martin, Schulz, Sebastian, Jäck, Hans-Martin, Cossmann, Anne, Stankov, Metodi V., Behrens, Georg M.N., Pöhlmann, Stefan, and Hoffmann, Markus
- Abstract
Rapid spread of SARS-CoV-2 variants C.1.2 and B.1.621 (Mu variant) in Africa and the Americas, respectively, as well as a high number of mutations in the viral spike proteins raised concerns that these variants might pose an elevated threat to human health. Here, we show that C.1.2 and B.1.621 spike proteins mediate increased entry into certain cell lines but do not exhibit increased ACE2 binding. Further, we demonstrate that C.1.2 and B.1.621 are resistant to neutralization by bamlanivimab but remain sensitive to inhibition by antibody cocktails used for COVID-19 therapy. Finally, we show that C.1.2 and B.1.621 partially escape neutralization by antibodies induced upon infection and vaccination, with escape of vaccine-induced antibodies being as potent as that measured for B.1.351 (Beta variant), which is known to be highly neutralization resistant. Collectively, C.1.2 and B.1.621 partially evade control by vaccine-induced antibodies, suggesting that close monitoring of these variants is warranted.
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- 2022
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18. Equal transcription rates of productively and nonproductively rearranged immunoglobulin µ heavy chain alleles in a pro-B cell line
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Eberle, Andrea B., Herrmann, Kai, Jäck, Hans-Martin, and Mühlemann, Oliver
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During B cell maturation, immunoglobulin (Ig) genes frequently acquire premature translation-termination codons (PTCs) as a result of the somatic rearrangement of V, D, and J gene segments. However, it is essential for a B lymphocyte to produce only one kind of antibody and therefore to ensure that the heavy and light chain polypeptides are expressed exclusively from the corresponding functional alleles, whereas no protein is made from the nonproductively rearranged alleles. At the post-transcriptional level, a well-studied mRNA quality control mechanism, termed nonsense-mediated mRNA decay (NMD), recognizes and degrades PTC-containing mRNAs in a translation-dependent manner. In addition, transcriptional silencing of PTC-containing Ig-µ and Ig-γ heavy chain reporter genes was observed in HeLa cells. To investigate the silencing of nonproductively rearranged Ig genes in a more physiological context, we analyzed a monoclonal line of immortalized murine pro-B cells harboring one productively (PTC–) and one nonproductively (PTC+) rearranged Ig-µ heavy chain allele. We show that the steady-state abundance of PTC+ mRNA was ∼40-fold lower when compared to that of the PTC– mRNA. However, both the PTC+ and PTC– allele seemed to be equally well transcribed since the abundances of PTC+ and PTC– pre-mRNA were very similar and chromatin immunoprecipitations revealed comparable occupancy of RNA polymerase II and acetylated histone H3 on both alleles. Altogether, we found no evidence for transcriptional silencing of the PTC+ allele in this pro-B cell line; hence, the efficient down-regulation of the PTC+ Ig-µ mRNA results entirely from NMD.
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- 2009
19. The pre-B cell receptor and its ligands – it takes two to tango
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Bradl, Harald, Vettermann, Christian, Schuh, Wolfgang, Meister, Silke, and Jäck, Hans-Martin
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The development of early precursor B cells is governed by the surface-bound pre-B cell receptor consisting of the immunoglobulin μ heavy chain, the surrogate light chain components λ5 and VpreB, and the signal transducing subunits immunglobulin α/immunglobulin β. The pre-B cell receptor controls clonal expansion, survival and efficient differentiation of functional B lymphoid precursors; however, it is still controversial how signals from this receptor are initiated. Recent studies with Abelson murine leukemia virus (Abl-MuLV)-transformed pre-B cell lines suggest that the N-terminal non-immunoglobulin portion of λ5, the so-called unique tail, is required to initiate cell-autonomous signals by mediating self-aggregation of the pre-B cell receptor (pre-BCR). Strikingly however, the λ5 unique tail also controls the interaction with two different groups of stroma cell-derived pre-BCR ligands, namely heparan sulfate glycosaminoglycans and surface-associated galectin-1. Even though these findings are not mutually exclusive, they refresh the discussion about potential modes of pre-BCR signal initiation. In this review, we discuss recent key findings and propose an integrative model for ligand dependent and independent initiation of pre-BCR signals during selection of functional B cell precursors.
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- 2007
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20. Double staining of proteins after separation in SDS gels with Ruthenium Bathophenantroline Disulfonate and Silver is compatible with MALDI-TOF mass spectrometry
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Hampel, Martin, Sehnert, Bettina, Karas, Michael, Jäck, Hans-Martin, and Mielenz, Dirk
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Sensitive peptide mass spectrometry techniques are increasingly used to identify molecular components of intracellular signaling networks. The detection of low abundant, electrophoretically separated proteins requires sensitive SDS gel protein stains, such as silver or fluorescent Ruthenium dyes. Both silver or Ruthenium based fluorescent dyes such as Ruthenium II Tris bathophenanthroline disulfonate (RuBPS) have unique advantages and disadvantages: some proteins stain better with silver whereas others stain better with Ruthenium dyes. Here, we demonstrate that RuBPS-stained stained proteins after separation in SDS gels can be re-stained with silver and that proteins from double-stained gels can still be subjected to MALDI-TOF mass spectrometry without adverse effects. Thus, our new double-staining technique not only produces a permanent record of RuBPS-stained gels, but more importantly, offers also an optimal staining procedure for electrophoretically separated proteins.
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- 2006
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21. SARS-CoV-2 variant B.1.617 is resistant to bamlanivimab and evades antibodies induced by infection and vaccination
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Hoffmann, Markus, Hofmann-Winkler, Heike, Krüger, Nadine, Kempf, Amy, Nehlmeier, Inga, Graichen, Luise, Arora, Prerna, Sidarovich, Anzhalika, Moldenhauer, Anna-Sophie, Winkler, Martin S., Schulz, Sebastian, Jäck, Hans-Martin, Stankov, Metodi V., Behrens, Georg M.N., and Pöhlmann, Stefan
- Abstract
The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants threatens efforts to contain the coronavirus disease 2019 (COVID-19) pandemic. The number of COVID-19 cases and deaths in India has risen steeply, and a SARS-CoV-2 variant, B.1.617, is believed to be responsible for many of these cases. The spike protein of B.1.617 harbors two mutations in the receptor binding domain, which interacts with the angiotensin converting enzyme 2 (ACE2) receptor and constitutes the main target of neutralizing antibodies. Therefore, we analyze whether B.1.617 is more adept in entering cells and/or evades antibody responses. B.1.617 enters two of eight cell lines tested with roughly 50% increased efficiency and is equally inhibited by two entry inhibitors. In contrast, B.1.617 is resistant against bamlanivimab, an antibody used for COVID-19 treatment. B.1.617 evades antibodies induced by infection or vaccination, although less so than the B.1.351 variant. Collectively, our study reveals that antibody evasion of B.1.617 may contribute to the rapid spread of this variant.
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- 2021
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22. Construction and expression of a soluble form of human CD30 ligand with functional activity
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Powell, Isabelle F., Li, Tianhong, Jäck, Hans‐Martin, and Ellis, Thomas M.
- Abstract
CD30 engagement in human lymphoid cells induces pleiotropic cellular responses that affect cellular viability and proliferation, cytokine production, and nuclear factor κB (NF‐κB) nuclear translocation. Studies examining the molecular basis for this pleiotropism thus far have relied on the use of antibodies and cells transfected with CD30L to trigger CD30, two methods of receptor induction that present important limitations: antibodies are not physiological receptor‐triggering molecules and CD30L transfectants induce high background intracellular signaling in the cells under study. We have generated and expressed a functional soluble human CD30L molecule (sCD30L/CD8α) comprised of the extracellular domain ofhuman CD30L fused to the extracellular domain of the human CD8α chain. Immunoprecipitation and Western blot analysis of sCD30L/CD8α revealed the existence of at least two forms of sCD30L/CD8α, which exhibited molecular sizes consistent with the existence of monomeric and trimeric forms of the molecule. Binding analyses performed using a soluble CD30 fusion protein (sCD30/γ1) confirmed the ability of sCD30L/CD8α to bind to CD30. Functionally, immobilized sCD30L/CD8α‐induced cell death in the CD30‐expressing lines Karpas‐299 and HDLM‐2 and reduced proliferative levels in Karpas‐299; these effects were inhibitable by the addition of sCD30/γ1. These studies demonstrate the utility of sCD30L/CD8α in characterizing the normal function of CD30L and CD30 and indicate the natural ability of soluble forms of CD30L to trimerize. J. Leukoc. Biol. 63: 752–757; 1998.
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- 1998
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23. B.1.617.2 enters and fuses lung cells with increased efficiency and evades antibodies induced by infection and vaccination
- Author
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Arora, Prerna, Sidarovich, Anzhalika, Krüger, Nadine, Kempf, Amy, Nehlmeier, Inga, Graichen, Luise, Moldenhauer, Anna-Sophie, Winkler, Martin S., Schulz, Sebastian, Jäck, Hans-Martin, Stankov, Metodi V., Behrens, Georg M.N., Pöhlmann, Stefan, and Hoffmann, Markus
- Abstract
The Delta variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), B.1.617.2, emerged in India and has spread to over 80 countries. B.1.617.2 replaced B.1.1.7 as the dominant virus in the United Kingdom, resulting in a steep increase in new infections, and a similar development is expected for other countries. Effective countermeasures require information on susceptibility of B.1.617.2 to control by antibodies elicited by vaccines and used for coronavirus disease 2019 (COVID-19) therapy. We show, using pseudotyping, that B.1.617.2 evades control by antibodies induced upon infection and BNT162b2 vaccination, although to a lesser extent as compared to B.1.351. We find that B.1.617.2 is resistant against bamlanivimab, a monoclonal antibody with emergency use authorization for COVID-19 therapy. Finally, we show increased Calu-3 lung cell entry and enhanced cell-to-cell fusion of B.1.617.2, which may contribute to augmented transmissibility and pathogenicity of this variant. These results identify B.1.617.2 as an immune evasion variant with increased capacity to enter and fuse lung cells.
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- 2021
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24. SARS-CoV-2 mutations acquired in mink reduce antibody-mediated neutralization
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Hoffmann, Markus, Zhang, Lu, Krüger, Nadine, Graichen, Luise, Kleine-Weber, Hannah, Hofmann-Winkler, Heike, Kempf, Amy, Nessler, Stefan, Riggert, Joachim, Winkler, Martin Sebastian, Schulz, Sebastian, Jäck, Hans-Martin, and Pöhlmann, Stefan
- Abstract
Transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from humans to farmed mink has been observed in Europe and the US. In the infected animals, viral variants arose that harbored mutations in the spike (S) protein, the target of neutralizing antibodies, and these variants were transmitted back to humans. This raised concerns that mink might become a constant source of human infection with SARS-CoV-2 variants associated with an increased threat to human health and resulted in mass culling of mink. Here, we report that mutations frequently found in the S proteins of SARS-CoV-2 from mink are mostly compatible with efficient entry into human cells and its inhibition by soluble angiotensin-converting enzyme 2 (ACE2). In contrast, mutation Y453F reduces neutralization by an antibody with emergency use authorization for coronavirus disease 2019 (COVID-19) therapy and sera/plasma from COVID-19 patients. These results suggest that antibody responses induced upon infection or certain antibodies used for treatment might offer insufficient protection against SARS-CoV-2 variants from mink.
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- 2021
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25. Immunoglobulin ? Gene Rearrangement Can Precede ? Gene Rearrangement
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Berg, Jörg, Mcdowell, Mindy, Jäck, Hans-Martin, and Wabl, Matthias
- Abstract
Immunoglobulin genes are generated during differentiation of B lymphocytes by joining gene segments. A mouse pre-B cell contains a functional immunoglobulin heavy-chain gene, but no light-chain gene. Although there is only one heavy-chain locus, there are two lightchain loci: ? and ?.It has been reported that ? loci in the germ-line configuration are never (in man) or very rarely (in the mouse) present in cells with functionally rearranged ?-chain genes. Two explanations have been proposed to explain this: (a) the ordered rearrangement theory, which postulates that light-chain gene rearrangement in the pre-B cell is first attempted at the ? locus, and that only upon failure to produce a functional ? chain is there an attempt to rearrange the ? locus; and (b) the stochastic theory, which postulates that rearrangement at the ? locus proceeds at a rate that is intrinsically much slower than that at the ? locus. We show here that ?-chain genes are generated whether or not the ? locus has lost its germ-line arrangement, a result that is compatible only with the stochastic theory.
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- 1990
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26. Cloning and characterization of HUPF1, a human homolog of the Saccharomyces cerevisiae nonsense mRNA-reducing UPF1 protein
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Applequist, Steven E., Selg, Manuel, Raman, Chander, and Jäck, Hans-Martin
- Abstract
Levels of most nonsense mRNAs are normally reduced in prokaryotes and eukaryotes when compared with that of corresponding functional mRNAs. Genes encoding polypeptides that selectively reduce levels of nonsense mRNA have so far only been identified in simple eukaryotes. We have now cloned a human cDNA whose deduced amino acid sequence shows the highest degree of homology to that of UPF1, a bona fide Saccharomyces cerevisiae group I RNA helicase required for accelerated degradation of nonsense mRNA. Based on the total sequence of the shorter yeast UPF1 protein, the overall identity between the human protein and UPF1 is 51%. Besides NTPase and other RNA helicase consensus motifs, UPF1 and its human homolog also share similar putative zinc finger motifs that are absent in other group I RNA helicases. Northern blot analysis with the human cDNA probe revealed two transcripts in several human cell lines. Further, antibodies raised against a synthetic peptide of the human polypeptide detected a single 130 kDa polypeptide on Western blots from human and mouse cells. Finally, immunofluorescence and Western blot analyses revealed that the human and mouse polypeptides, like yeast UPF1, are expressed in the cytoplasm, but not in the nucleus. We have thus identified the first mammalian homolog of yeast UPF1, a protein that regulates levels of nonsense mRNA, and we tentatively name this protein human HUPF1 (for human homolog of UPF1).
- Published
- 1997
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