@phdthesis{MonyNair2021, author = {Mony Nair, Rahul}, title = {Elucidating ubiquitin recognition by the HECT-type ubiquitin ligase HUWE1}, doi = {10.25972/OPUS-22103}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-221030}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {The small protein modifier ubiquitin is at the heart of an immensely versatile posttranslational modification system that orchestrates countless physiological and disease-associated cellular processes. Key to this versatility are the manifold modifications that can be assembled from ubiquitin "building blocks" and are associated with specific functional outcomes for the modified substrates. In particular, ubiquitin molecules can form polymeric chains of distinct lengths and linkage types that give rise to distinct chain conformations, thereby providing recognition sites for specific signaling receptors/effectors. The class of E3 enzymes (ubiquitin ligases) provides critical specificity determinants in ubiquitin linkage formation; it is therefore crucial to unravel precisely how E3 enzymes operate in order to understand the structural basis of ubiquitin signaling and exploit these insights for therapeutic benefit. Overexpression and deregulation of the HECT-type ubiquitin ligase HUWE1 is implicated in several different cancer types and neurodegenerative disorders. It is largely unknown which factors control the ubiquitin modifications formed by HUWE1, how the catalytic HECT domain interacts with functionally distinct ubiquitin molecules (donor, acceptor and regulatory ubiquitin molecules) and which conformational transitions enable these interactions during ubiquitin chain formation. One aim of this study was to structurally elucidate the recognition of donor ubiquitin by the HECT domain of HUWE1. To this end I utilized a ubiquitin activity-based probe to reconstitute a proxy for a donor ubiquitin-linked conjugate of the HECT domain of HUWE1 and determined its structure by X-ray crystallography. This structure reveals that the donor ubiquitin binds to the C-lobe of HUWE1 in the same way as NEDD4-type ligases, corroborating the idea that HECT ligases utilize a conserved mode of donor ubiquitin recognition. independent of their linkage and substrate specificities. With the help of biochemical analyses, I also validated specific features of the structure, in particular the positioning of the C-terminal tail of the ligase, which was known to be critical for activity. In the newly determined structure, which reflects an "L-shaped", active state of the HECT domain, this tail is fully resolved and coordinated at the N-lobe-C-lobe interface. I defined residues that are critical for this coordination and showed that they are also essential for the activity of HUWE1, including auto-ubiquitination, free ubiquitin chain formation, and substrate ubiquitination. Furthermore, I discovered that the N-lobe of HUWE1 harbors a ubiquitin-binding exosite similar to NEDD4-type ligases and E6AP. My in-vitro activity and binding assays show that HUWE1 uses the exosite for isopeptide bond formation, but that it is dispensable for thioester bond formation. The binding assays further show that the donor ubiquitin loaded HECT domain binds an additional ubiquitin molecule at the exosite more tightly than the apo HECT domain, which possibly suggests allosteric communication between the two sites. Finally, I showed that the ubiquitin activity-based probe (ubiquitin-propargylamine) can label the catalytic cysteine of HUWE1 and NEDD4-type with close to quantitative turn- over, while it does not react with the HECT domain of the evolutionarily more divergent E6AP. The determinants underlying these differential reactivities remain to be explored. Taken, together my results significantly enhance our mechanistic understanding of the catalytic domain of HUWE1 and pinpoint linchpins for therapeutic interventions with the activity of this disease-relevant enzyme.}, language = {en} } @article{TruongvanLiMisraetal.2022, author = {Truongvan, Ngoc and Li, Shurong and Misra, Mohit and Kuhn, Monika and Schindelin, Hermann}, title = {Structures of UBA6 explain its dual specificity for ubiquitin and FAT10}, series = {Nature Communications}, volume = {13}, journal = {Nature Communications}, doi = {10.1038/s41467-022-32040-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-301161}, year = {2022}, abstract = {The covalent modification of target proteins with ubiquitin or ubiquitin-like modifiers is initiated by E1 activating enzymes, which typically transfer a single modifier onto cognate conjugating enzymes. UBA6 is an unusual E1 since it activates two highly distinct modifiers, ubiquitin and FAT10. Here, we report crystal structures of UBA6 in complex with either ATP or FAT10. In the UBA6-FAT10 complex, the C-terminal domain of FAT10 binds to where ubiquitin resides in the UBA1-ubiquitin complex, however, a switch element ensures the alternate recruitment of either modifier. Simultaneously, the N-terminal domain of FAT10 interacts with the 3-helix bundle of UBA6. Site-directed mutagenesis identifies residues permitting the selective activation of either ubiquitin or FAT10. These results pave the way for studies investigating the activation of either modifier by UBA6 in physiological and pathophysiological settings.}, language = {en} } @article{PaulsHamaratTrufasuetal.2019, author = {Pauls, Dennis and Hamarat, Yasmin and Trufasu, Luisa and Schendzielorz, Tim M. and Gramlich, Gertrud and Kahnt, J{\"o}rg and Vanselow, Jens and Schlosser, Andreas and Wegener, Christian}, title = {Drosophila carboxypeptidase D (SILVER) is a key enzyme in neuropeptide processing required to maintain locomotor activity levels and survival rate}, series = {European Journal of Neuroscience}, volume = {50}, journal = {European Journal of Neuroscience}, number = {9}, doi = {10.1111/ejn.14516}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204863}, pages = {3502-3519}, year = {2019}, abstract = {Neuropeptides are processed from larger preproproteins by a dedicated set of enzymes. The molecular and biochemical mechanisms underlying preproprotein processing and the functional importance of processing enzymes are well-characterised in mammals, but little studied outside this group. In contrast to mammals, Drosophila melanogaster lacks a gene for carboxypeptidase E (CPE ), a key enzyme for mammalian peptide processing. By combining peptidomics and neurogenetics, we addressed the role of carboxypeptidase D (dCPD ) in global neuropeptide processing and selected peptide-regulated behaviours in Drosophila . We found that a deficiency in dCPD results in C-terminally extended peptides across the peptidome, suggesting that dCPD took over CPE function in the fruit fly. dCPD is widely expressed throughout the nervous system, including peptidergic neurons in the mushroom body and neuroendocrine cells expressing adipokinetic hormone. Conditional hypomorphic mutation in the dCPD -encoding gene silver in the larva causes lethality, and leads to deficits in starvation-induced hyperactivity and appetitive gustatory preference, as well as to reduced viability and activity levels in adults. A phylogenomic analysis suggests that loss of CPE is not common to insects, but only occurred in Hymenoptera and Diptera. Our results show that dCPD is a key enzyme for neuropeptide processing and peptide-regulated behaviour in Drosophila . dCPD thus appears as a suitable target to genetically shut down total neuropeptide production in peptidergic neurons. The persistent occurrence of CPD in insect genomes may point to important further CPD functions beyond neuropeptide processing which cannot be fulfilled by CPE.}, language = {en} } @article{BalakrishnanHemmenChoudhuryetal.2022, author = {Balakrishnan, Ashwin and Hemmen, Katherina and Choudhury, Susobhan and Krohn, Jan-Hagen and Jansen, Kerstin and Friedrich, Mike and Beliu, Gerti and Sauer, Markus and Lohse, Martin J. and Heinze, Katrin G.}, title = {Unraveling the hidden temporal range of fast β2-adrenergic receptor mobility by time-resolved fluorescence}, series = {Communications Biology}, volume = {5}, journal = {Communications Biology}, number = {1}, doi = {10.1038/s42003-022-03106-4}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-301140}, year = {2022}, abstract = {G-protein-coupled receptors (GPCRs) are hypothesized to possess molecular mobility over a wide temporal range. Until now the temporal range has not been fully accessible due to the crucially limited temporal range of available methods. This in turn, may lead relevant dynamic constants to remain masked. Here, we expand this dynamic range by combining fluorescent techniques using a spot confocal setup. We decipher mobility constants of β\(_{2}\)-adrenergic receptor over a wide time range (nanosecond to second). Particularly, a translational mobility (10 µm\(^{2}\)/s), one order of magnitude faster than membrane associated lateral mobility that explains membrane protein turnover and suggests a wider picture of the GPCR availability on the plasma membrane. And a so far elusive rotational mobility (1-200 µs) which depicts a previously overlooked dynamic component that, despite all complexity, behaves largely as predicted by the Saffman-Delbr{\"u}ck model.}, language = {en} } @phdthesis{Balakrishnan2021, author = {Balakrishnan, Ashwin}, title = {Fast molecular mobility of β\(_2\)-adrenergic receptor revealed by time-resolved fluorescence spectroscopy}, doi = {10.25972/OPUS-25085}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-250856}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {G-protein- coupled receptors (GPCRs) are the largest family of membrane confined receptors and they transduce ligand binding to downstream effects. Almost 40\% of the drugs in the world target GPCRs due to their function, albeit knowing less about their activation. Understanding their dynamic behaviour in basal and activated state could prove key to drug development in the future. GPCRs are known to exhibit complex molecular mobility patterns. A plethora of studies have been and are being conducted to understand the mobility of GPCRs. Due to limitations of imaging and spectroscopic techniques commonly used, the relevant timescales are hard to access. The most commonly used techniques are electron paramagnetic resonance or double electronelectron resonance, nuclear magnetic resonance, time-resolved fluorescence, single particle tracking and fluorescence recovery after photobleaching. Among these techniques only fluorescence has the potential to probe live cells. In this thesis, I use different time-resolved fluorescence spectroscopic techniques to quantify diffusion dynamics / molecular mobility of β2-adrenergic receptor (β2-AR) in live cells. The thesis shows that β2-AR exhibits mobility over an exceptionally broad temporal range (nanosecond to second) that can be linked to its respective physiological scenario. I explain how β2-AR possesses surprisingly fast lateral mobility (~10 μm²/s) associated with vesicular transport in contrast to the prior reports of it originating from fluorophore photophysics and free fluorophores in the cytosol. In addition, β2-AR has rotational mobility (~100 μs) that makes it conform to the Saffman-Delbr{\"u}ck model of membrane diffusion unlike earlier studies. These contrasts are due to the limitations of the methodologies used. The limitations are overcome in this thesis by using different time-resolved fluorescence techniques of fluorescence correlation spectroscopy (FCS), time-resolved anisotropy (TRA) and polarisation resolved fullFCS (fullFCS). FCS is limited to microsecond to the second range and TRA is limited to the nanosecond range. fullFCS complements the two techniques by covering the blind spot of FCS and TRA in the microsecond range. Finally, I show how ligand stimulation causes a decrease in lateral mobility which could be a hint at cluster formation due to internalisation and how β2-AR possesses a basal oligomerisation that does not change on activation. Thus, through this thesis, I show how different complementary fluorescence techniques are necessary to overcome limitations of each technique and to thereby elucidate functional dynamics of GPCR activation and how it orchestrates downstream signalling.}, language = {en} } @article{KlenkHommersLohse2022, author = {Klenk, Christoph and Hommers, Leif and Lohse, Martin J.}, title = {Proteolytic cleavage of the extracellular domain affects signaling of parathyroid hormone 1 receptor}, series = {Frontiers in Endocrinology}, volume = {13}, journal = {Frontiers in Endocrinology}, issn = {1664-2392}, doi = {10.3389/fendo.2022.839351}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-262055}, year = {2022}, abstract = {Parathyroid hormone 1 receptor (PTH1R) is a member of the class B family of G protein-coupled receptors, which are characterized by a large extracellular domain required for ligand binding. We have previously shown that the extracellular domain of PTH1R is subject to metalloproteinase cleavage in vivo that is regulated by ligand-induced receptor trafficking and leads to impaired stability of PTH1R. In this work, we localize the cleavage site in the first loop of the extracellular domain using amino-terminal protein sequencing of purified receptor and by mutagenesis studies. We further show, that a receptor mutant not susceptible to proteolytic cleavage exhibits reduced signaling to G\(_s\) and increased activation of G\(_q\) compared to wild-type PTH1R. These findings indicate that the extracellular domain modulates PTH1R signaling specificity, and that its cleavage affects receptor signaling.}, language = {en} } @phdthesis{Stetter2021, author = {Stetter, Maurice}, title = {LC3-associated phagocytosis seals the fate of the second polar body in \(Caenorhabditis\) \(elegans\)}, doi = {10.25972/OPUS-23198}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-231981}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {This work investigates the death and degradation of the second polar body of the nematode C. elegans in order to improve our understanding how pluripotent undifferentiated cells deal with dying cells. With the use of fluorescence microscopy this work demonstrates that both polar bodies loose membrane integrity early. The second polar body has contact to embryonic cells and gets internalized, dependent on the Rac1-ortholog CED-10. The polar body gets degraded via LC3-associated phagocytosis. While lysosome recruitment depends on RAB-7, LC3 does not improve lysosome recruitment but still accelerates polar body degradation. This work establishes the second polar body as a genetic model to study cell death and LC3-associated phagocytosis and has revealed further aspects of phagosome maturation and degradation.}, subject = {Polk{\"o}rper}, language = {en} } @article{KaiserSauerKisker2017, author = {Kaiser, Sebastian and Sauer, Florian and Kisker, Caroline}, title = {The structural and functional characterization of human RecQ4 reveals insights into its helicase mechanism}, series = {Nature Communications}, volume = {8}, journal = {Nature Communications}, number = {15907}, doi = {10.1038/ncomms15907}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170769}, year = {2017}, abstract = {RecQ4 is a member of the RecQ helicase family, an evolutionarily conserved class of enzymes, dedicated to preserving genomic integrity by operating in telomere maintenance, DNA repair and replication. While reduced RecQ4 activity is associated with cancer predisposition and premature aging, RecQ4 upregulation is related to carcinogenesis and metastasis. Within the RecQ family, RecQ4 assumes an exceptional position, lacking several characteristic RecQ domains. Here we present the crystal structure of human RecQ4, encompassing the conserved ATPase core and a novel C-terminal domain that lacks resemblance to the RQC domain observed in other RecQ helicases. The new domain features a zinc-binding site and two distinct types of winged-helix domains, which are not involved in canonical DNA binding or helicase activity. Based on our structural and functional analysis, we propose that RecQ4 exerts a helicase mechanism, which may be more closely related to bacterial RecQ helicases than to its human family members.}, language = {en} } @article{KronhardtBeitzingerBarthetal.2016, author = {Kronhardt, Angelika and Beitzinger, Christoph and Barth, Holger and Benz, Roland}, title = {Chloroquine Analog Interaction with C2-and Iota-Toxin in Vitro and in Living Cells}, series = {Toxins}, volume = {8}, journal = {Toxins}, number = {8}, doi = {10.3390/toxins8080237}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-168286}, pages = {237}, year = {2016}, abstract = {C2-toxin from Clostridium botulinum and Iota-toxin from Clostridium perfringens belong both to the binary A-B-type of toxins consisting of two separately secreted components, an enzymatic subunit A and a binding component B that facilitates the entry of the corresponding enzymatic subunit into the target cells. The enzymatic subunits are in both cases actin ADP-ribosyltransferases that modify R177 of globular actin finally leading to cell death. Following their binding to host cells' receptors and internalization, the two binding components form heptameric channels in endosomal membranes which mediate the translocation of the enzymatic components Iota a and C2I from endosomes into the cytosol of the target cells. The binding components form ion-permeable channels in artificial and biological membranes. Chloroquine and related 4-aminoquinolines were able to block channel formation in vitro and intoxication of living cells. In this study, we extended our previous work to the use of different chloroquine analogs and demonstrate that positively charged aminoquinolinium salts are able to block channels formed in lipid bilayer membranes by the binding components of C2- and Iota-toxin. Similarly, these molecules protect cultured mammalian cells from intoxication with C2- and Iota-toxin. The aminoquinolinium salts did presumably not interfere with actin ADP-ribosylation or receptor binding but blocked the pores formed by C2IIa and Iota b in living cells and in vitro. The blocking efficiency of pores formed by Iota b and C2IIa by the chloroquine analogs showed interesting differences indicating structural variations between the types of protein-conducting nanochannels formed by Iota b and C2IIa.}, language = {en} } @phdthesis{Beer2021, author = {Beer, Katharina Beate}, title = {Identification and characterization of TAT-5 interactors that regulate extracellular vesicle budding}, doi = {10.25972/OPUS-20672}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206724}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {Cells from bacteria to man release extracellular vesicles (EV) such as microvesicles (MV) that carry signaling molecules like morphogens and miRNAs to control intercellular communication during health and disease. MV release also sculpts membranes, e.g. repairing damaged membranes to avoid cell death. HIV viruses also bud from the plasma membrane in a similar fashion. In order to determine the in vivo functions of MVs and regulate their release, we need to understand the mechanisms of MV release by plasma membrane budding (ectocytosis). The conserved phospholipid flippase TAT-5 maintains the asymmetric localization of phosphatidylethanolamine (PE) in the plasma membrane and was the only known inhibitor of ESCRT-mediated ectocytosis in C. elegans. Loss of TAT-5 lipid flipping activity increased the externalization of PE and accumulation of MVs. However, it was unclear how cells control TAT-5 activity to release the right amount of MVs at the right time, since no upstream regulators of TAT-5 were known. To identify conserved TAT-5 regulators we looked for new proteins that inhibit MV release. To do so, we first developed a degradation-based technique to specifically label MVs. We tagged a plasma membrane reporter with the endogenous ZF1 degradation tag (degron) and expressed it in C. elegans embryos. This reporter is protected from degradation inside MVs, but is degraded inside the cell. Thus, the fluorescence is selectively maintained inside MVs, creating the first MV-specific reporter. We identified four MV release inhibitors associated with retrograde recycling, including the class III PI3Kinase VPS-34, Beclin1 homolog BEC-1, DnaJ protein RME-8, and the uncharacterized Dopey homolog PAD-1. We found that VPS-34, BEC-1, RME-8, and redundant sorting nexins are required for the plasma membrane localization of TAT-5, which is important to maintain PE asymmetry and inhibit MV release. Although we confirmed that PAD-1 and the GEF-like protein MON-2 are required for endosomal recycling, they only traffic TAT-5 in the absence of sorting nexin-mediated recycling. Instead, PAD-1 is specifically required for the lipid flipping activity of TAT-5 that inhibits MV release. Thus, our work pinpoints TAT-5 and PE as key regulators of plasma membrane budding, further supporting the model that PE externalization drives ectocytosis. In addition, we uncovered redundant intracellular trafficking pathways, which affect organelle size and revealed new regulators of TAT-5 flippase activity. These newly identified ectocytosis inhibitors provide a toolkit to test the in vivo roles of MVs. In the long term, our work will help to identify the mechanisms that govern MV budding, furthering our understanding of the mechanisms that regulate disease-mediated EV release, membrane sculpting and viral budding.}, subject = {Caenorhabditis elegans}, language = {en} } @article{GrabarczykBerks2017, author = {Grabarczyk, Daniel B. and Berks, Ben C.}, title = {Intermediates in the Sox sulfur oxidation pathway are bound to a sulfane conjugate of the carrier protein SoxYZ}, series = {PLoS ONE}, volume = {12}, journal = {PLoS ONE}, number = {3}, doi = {10.1371/journal.pone.0173395}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-171147}, pages = {e0173395}, year = {2017}, abstract = {The Sox pathway found in many sulfur bacteria oxidizes thiosulfate to sulfate. Pathway intermediates are covalently bound to a cysteine residue in the carrier protein SoxYZ. We have used biochemical complementation by SoxYZ-conjugates to probe the identity of the intermediates in the Sox pathway. We find that unconjugated SoxYZ and SoxYZ-S-sulfonate are unlikely to be intermediates during normal turnover in disagreement with current models. By contrast, conjugates with multiple sulfane atoms are readily metabolised by the Sox pathway. The most parsimonious interpretation of these data is that the true carrier species in the Sox pathway is a SoxYZ-S-sulfane adduct.}, language = {en} } @phdthesis{Imam2023, author = {Imam, Nasir}, title = {Molecular basis of collybistin conformational activation}, doi = {10.25972/OPUS-31145}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-311458}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {The nervous system relies on an orchestrated assembly of complex cellular entities called neurons, which are specifically committed to information management and transmission. Inter-neuronal communication takes place via synapses, membrane-membrane junctions which ensure efficient signal transfer. Synaptic neurotransmission involves release of presynaptic neurotransmitters and their reception by cognate receptors at postsynaptic terminals. Inhibitory neurotransmission is primarily mediated by the release of neurotransmitters GABA (γ-Aminobutyric acid) and glycine, which are precisely sensed by GABA type-A receptors (GABAARs) and glycine receptors (GlyRs), respectively. GABAAR assembly and maintenance is coordinated by various postsynaptic neuronal factors including the scaffolding protein gephyrin, the neuronal adaptor collybistin (CB) and cell adhesion proteins of the neuroligin (NL) family, specifically NL2 and NL4. At inhibitory postsynaptic specializations, gephyrin has been hypothesized to form extended structures underneath the plasma membrane, where its interaction with the receptors leads to their stabilization and impedes their lateral movement. Gephyrin mutations have been associated with various brain disorders, including autism, schizophrenia, Alzheimer's disease, and epilepsy. Furthermore, gephyrin loss is lethal and causes mice to die within the first post-natal day. Gephyrin recruitment from intracellular deposits to postsynaptic membranes primarily relies on the adaptor protein CB. As a moonlighting protein, CB, a guanine nucleotide exchange factor (GEF), also catalyzes a nucleotide exchange reaction, thereby regenerating the GTP-bound state of the small GTPase Cdc42 from its GDP-bound form. The CB gene undergoes alternative splicing with the majority of CB splice variants featuring an N-terminal SH3 domain followed by tandem Dbl-homology (DH) and pleckstrin-homology (PH) domains. Previous studies demonstrated that the most widely expressed, SH3-domain containing splice variant (CB2SH3+) preferentially adopts a closed conformation, in which the N-terminally located SH3 domain forms intra-molecular interaction with the DH-PH domain tandem. Previous cell-based studies indicated that SH3 domain-encoding CB variants remain untargeted and colocalize with intracellular gephyrin deposits and hence require additional factors which interact with the SH3 domain, thus inducing an open or active conformation. The SH3 domain-deficient CB isoform (CB2SH3-), on the contrary, adopts an open conformation, which possess enhanced postsynaptic gephyrin-clustering and also effectively replenishes the GTP-bound small GTPase-Cdc42 from its GDP-bound state. Despite the fundamental role of CB as a neuronal adaptor protein maintaining the proper function of inhibitory GABAergic synapses, its interactions with the neuronal scaffolding protein gephyrin and other post synaptic neuronal factors remain poorly understood. Moreover, CB interaction studies with the small GTPase Cdc42 and TC10, a closely related member of Cdc42 subfamily, remains poorly characterized. Most importantly, the roles of the neuronal factors and small GTPases in CB conformational activation have not been elucidated. This PhD dissertation primarily focuses on delineating the molecular basis of the interactions between CB and postsynaptic neuronal factors. During the course of my PhD dissertation, I engineered a series of CB FRET (F{\"o}rster Resonance Energy Transfer) sensors to characterize the CB interaction with its binding partners along with outlining their role in CB conformational activation. Through the aid of these CB FRET sensors, I analyzed the gephyrin-CB interaction, which, due to technical limitations remained unaddressed for more than two decades (refer Chapter 2 for more details). Subsequently, I also unraveled the molecular basis of the interactions between CB and the neuronal cell adhesion factor neuroligin 2 (refer chapter 2) and the small GTPases Cdc42 and TC10 (refer chapter 3) and describe how these binding partners induce a conformational activation of CB. In summary, this PhD dissertation provides strong evidence of a closely knit CB communication network with gephyrin, neuroligin and the small GTPase TC10, wherein CB activation from closed/inactive to open/active states is effectively triggered by these ligands.}, language = {en} } @article{KuhlemannBeliuJanzenetal.2021, author = {Kuhlemann, Alexander and Beliu, Gerti and Janzen, Dieter and Petrini, Enrica Maria and Taban, Danush and Helmerich, Dominic A. and Doose, S{\"o}ren and Bruno, Martina and Barberis, Andrea and Villmann, Carmen and Sauer, Markus and Werner, Christian}, title = {Genetic Code Expansion and Click-Chemistry Labeling to Visualize GABA-A Receptors by Super-Resolution Microscopy}, series = {Frontiers in Synaptic Neuroscience}, volume = {13}, journal = {Frontiers in Synaptic Neuroscience}, issn = {1663-3563}, doi = {10.3389/fnsyn.2021.727406}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-251035}, year = {2021}, abstract = {Fluorescence labeling of difficult to access protein sites, e.g., in confined compartments, requires small fluorescent labels that can be covalently tethered at well-defined positions with high efficiency. Here, we report site-specific labeling of the extracellular domain of γ-aminobutyric acid type A (GABA-A) receptor subunits by genetic code expansion (GCE) with unnatural amino acids (ncAA) combined with bioorthogonal click-chemistry labeling with tetrazine dyes in HEK-293-T cells and primary cultured neurons. After optimization of GABA-A receptor expression and labeling efficiency, most effective variants were selected for super-resolution microscopy and functionality testing by whole-cell patch clamp. Our results show that GCE with ncAA and bioorthogonal click labeling with small tetrazine dyes represents a versatile method for highly efficient site-specific fluorescence labeling of proteins in a crowded environment, e.g., extracellular protein domains in confined compartments such as the synaptic cleft.}, language = {en} } @article{JeanclosKnoblochHoffmannetal.2020, author = {Jeanclos, Elisabeth and Knobloch, Gunnar and Hoffmann, Axel and Fedorchenko, Oleg and Odersky, Andrea and Lamprecht, Anna-Karina and Schindelin, Hermann and Gohla, Antje}, title = {Ca\(^{2+}\) functions as a molecular switch that controls the mutually exclusive complex formation of pyridoxal phosphatase with CIB1 or calmodulin}, series = {FEBS Letters}, volume = {594}, journal = {FEBS Letters}, number = {13}, doi = {10.1002/1873-3468.13795}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-217963}, pages = {2099 -- 2115}, year = {2020}, abstract = {Pyridoxal 5′-phosphate (PLP) is an essential cofactor for neurotransmitter metabolism. Pyridoxal phosphatase (PDXP) deficiency in mice increases PLP and γ-aminobutyric acid levels in the brain, yet how PDXP is regulated is unclear. Here, we identify the Ca\(^{2+}\)- and integrin-binding protein 1 (CIB1) as a PDXP interactor by yeast two-hybrid screening and find a calmodulin (CaM)-binding motif that overlaps with the PDXP-CIB1 interaction site. Pulldown and crosslinking assays with purified proteins demonstrate that PDXP directly binds to CIB1 or CaM. CIB1 or CaM does not alter PDXP phosphatase activity. However, elevated Ca\(^{2+}\) concentrations promote CaM binding and, thereby, diminish CIB1 binding to PDXP, as both interactors bind in a mutually exclusive way. Hence, the PDXP-CIB1 complex may functionally differ from the PDXP-Ca\(^{2+}\)-CaM complex.}, language = {en} } @article{SchuhmannKraftBieberetal.2019, author = {Schuhmann, Michael K. and Kraft, Peter and Bieber, Michael and Kollikowski, Alexander M. and Schulze, Harald and Nieswandt, Bernhard and Pham, Mirko and Stegner, David and Stoll, Guido}, title = {Targeting platelet GPVI plus rt-PA administration but not α2β1-mediated collagen binding protects against ischemic brain damage in mice}, series = {International Journal of Molecular Science}, volume = {20}, journal = {International Journal of Molecular Science}, number = {8}, issn = {1422-0067}, doi = {10.3390/ijms20082019}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201700}, year = {2019}, abstract = {Platelet collagen interactions at sites of vascular injuries predominantly involve glycoprotein VI (GPVI) and the integrin α2β1. Both proteins are primarily expressed on platelets and megakaryocytes whereas GPVI expression is also shown on endothelial and integrin α2β1 expression on epithelial cells. We recently showed that depletion of GPVI improves stroke outcome without increasing the risk of cerebral hemorrhage. Genetic variants associated with higher platelet surface integrin α2 (ITGA2) receptor levels have frequently been found to correlate with an increased risk of ischemic stroke in patients. However until now, no preclinical stroke study has addressed whether platelet integrin α2β1 contributes to the pathophysiology of ischemia/reperfusion (I/R) injury. Focal cerebral ischemia was induced in C57BL/6 and Itga2\(^{-/-}\) mice by a 60 min transient middle cerebral artery occlusion (tMCAO). Additionally, wild-type animals were pretreated with anti-GPVI antibody (JAQ1) or Fab fragments of a function blocking antibody against integrin α2β1 (LEN/B). In anti-GPVI treated animals, intravenous (IV) recombinant tissue plasminogen activator (rt-PA) treatment was applied immediately prior to reperfusion. Stroke outcome, including infarct size and neurological scoring was determined on day 1 after tMCAO. We demonstrate that targeting the integrin α2β1 (pharmacologic; genetic) did neither reduce stroke size nor improve functional outcome on day 1 after tMCAO. In contrast, depletion of platelet GPVI prior to stroke was safe and effective, even when combined with rt-PA treatment. Our results underscore that GPVI, but not ITGA2, is a promising and safe target in the setting of ischemic stroke.}, language = {en} } @article{MakbulKhayenkoMaricetal.2021, author = {Makbul, Cihan and Khayenko, Vladimir and Maric, Hans Michael and B{\"o}ttcher, Bettina}, title = {Conformational Plasticity of Hepatitis B Core Protein Spikes Promotes Peptide Binding Independent of the Secretion Phenotype}, series = {Microorganisms}, volume = {9}, journal = {Microorganisms}, number = {5}, issn = {2076-2607}, doi = {10.3390/microorganisms9050956}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-236720}, year = {2021}, abstract = {Hepatitis B virus is a major human pathogen, which forms enveloped virus particles. During viral maturation, membrane-bound hepatitis B surface proteins package hepatitis B core protein capsids. This process is intercepted by certain peptides with an "LLGRMKG" motif that binds to the capsids at the tips of dimeric spikes. With microcalorimetry, electron cryo microscopy and peptide microarray-based screens, we have characterized the structural and thermodynamic properties of peptide binding to hepatitis B core protein capsids with different secretion phenotypes. The peptide "GSLLGRMKGA" binds weakly to hepatitis B core protein capsids and mutant capsids with a premature (F97L) or low-secretion phenotype (L60V and P5T). With electron cryo microscopy, we provide novel structures for L60V and P5T and demonstrate that binding occurs at the tips of the spikes at the dimer interface, splaying the helices apart independent of the secretion phenotype. Peptide array screening identifies "SLLGRM" as the core binding motif. This shortened motif binds only to one of the two spikes in the asymmetric unit of the capsid and induces a much smaller conformational change. Altogether, these comprehensive studies suggest that the tips of the spikes act as an autonomous binding platform that is unaffected by mutations that affect secretion phenotypes.}, language = {en} } @article{KitzenmaierSchaeferKasaragodetal.2019, author = {Kitzenmaier, Alexandra and Schaefer, Natascha and Kasaragod, Vikram Babu and Polster, Tilman and Hantschmann, Ralph and Schindelin, Hermann and Villmann, Carmen}, title = {The P429L loss of function mutation of the human glycine transporter 2 associated with hyperekplexia}, series = {European Journal of Neuroscience}, volume = {50}, journal = {European Journal of Neuroscience}, number = {12}, doi = {10.1111/ejn.14533}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206158}, pages = {3906-3920}, year = {2019}, abstract = {Glycine transporter 2 (GlyT2) mutations across the entire sequence have been shown to represent the presynaptic component of the neurological disease hyperekplexia. Dominant, recessive and compound heterozygous mutations have been identified, most of them leading to impaired glycine uptake. Here, we identified a novel loss of function mutation of the GlyT2 resulting from an amino acid exchange of proline 429 to leucine in a family with both parents being heterozygous carriers. A homozygous child suffered from severe neuromotor deficits. We characterised the GlyT2P429L variant at the molecular, cellular and protein level. Functionality was determined by glycine uptake assays. Homology modelling revealed that the mutation localises to α-helix 5, presumably disrupting the integrity of this α-helix. GlyT2P429L shows protein trafficking through various intracellular compartments to the cellular surface. However, the protein expression at the whole cell level was significantly reduced. Although present at the cellular surface, GlyT2P429L demonstrated a loss of protein function. Coexpression of the mutant with the wild-type protein, reflecting the situation in the parents, did not affect transporter function, thus explaining their non-symptomatic phenotype. Nevertheless, when the mutant was expressed in excess compared with the wild-type protein, glycine uptake was significantly reduced. Thus, these data demonstrate that the proline residue at position 429 is structurally important for the correct formation of α-helix 5. The failure in functionality of the mutated GlyT2 is most probably due to structural changes localised in close proximity to the sodium-binding site of the transporter.}, language = {en} } @article{KalledaAmichArslanetal.2016, author = {Kalleda, Natarajaswamy and Amich, Jorge and Arslan, Berkan and Poreddy, Spoorthi and Mattenheimer, Katharina and Mokhtari, Zeinab and Einsele, Hermann and Brock, Matthias and Heinze, Katrin Gertrud and Beilhack, Andreas}, title = {Dynamic Immune Cell Recruitment After Murine Pulmonary Aspergillus fumigatus Infection under Different Immunosuppressive Regimens}, series = {Frontiers in Microbiology}, volume = {7}, journal = {Frontiers in Microbiology}, number = {1107}, doi = {10.3389/fmicb.2016.01107}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-165368}, year = {2016}, abstract = {Humans are continuously exposed to airborne spores of the saprophytic fungus Aspergillus fumigatus. However, in healthy individuals pulmonary host defense mechanisms efficiently eliminate the fungus. In contrast, A. fumigatus causes devastating infections in immunocompromised patients. Host immune responses against A. fumigatus lung infections in immunocompromised conditions have remained largely elusive. Given the dynamic changes in immune cell subsets within tissues upon immunosuppressive therapy, we dissected the spatiotemporal pulmonary immune response after A. fumigatus infection to reveal basic immunological events that fail to effectively control invasive fungal disease. In different immunocompromised murine models, myeloid, notably neutrophils, and macrophages, but not lymphoid cells were strongly recruited to the lungs upon infection. Other myeloid cells, particularly dendritic cells and monocytes, were only recruited to lungs of corticosteroid treated mice, which developed a strong pulmonary inflammation after infection. Lymphoid cells, particularly CD4\(^+\) or CD8\(^+\) T-cells and NK cells were highly reduced upon immunosuppression and not recruited after A. fumigatus infection. Moreover, adoptive CD11b\(^+\) myeloid cell transfer rescued cyclophosphamide immunosuppressed mice from lethal A. fumigatus infection but not cortisone and cyclophosphamide immunosuppressed mice. Our findings illustrate that CD11b\(^+\) myeloid cells are critical for anti-A. fumigatus defense under cyclophosphamide immunosuppressed conditions.}, language = {en} } @article{KooMatthewsHarrisonetal.2022, author = {Koo, Chek Ziu and Matthews, Alexandra L. and Harrison, Neale and Szyroka, Justyna and Nieswandt, Bernhard and Gardiner, Elizabeth E. and Poulter, Natalie S. and Tomlinson, Michael G.}, title = {The platelet collagen receptor GPVI is cleaved by Tspan15/ADAM10 and Tspan33/ADAM10 molecular scissors}, series = {International Journal of Molecular Sciences}, volume = {23}, journal = {International Journal of Molecular Sciences}, number = {5}, issn = {1422-0067}, doi = {10.3390/ijms23052440}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-284468}, year = {2022}, abstract = {The platelet-activating collagen receptor GPVI represents the focus of clinical trials as an antiplatelet target for arterial thrombosis, and soluble GPVI is a plasma biomarker for several human diseases. A disintegrin and metalloproteinase 10 (ADAM10) acts as a 'molecular scissor' that cleaves the extracellular region from GPVI and many other substrates. ADAM10 interacts with six regulatory tetraspanin membrane proteins, Tspan5, Tspan10, Tspan14, Tspan15, Tspan17 and Tspan33, which are collectively termed the TspanC8s. These are emerging as regulators of ADAM10 substrate specificity. Human platelets express Tspan14, Tspan15 and Tspan33, but which of these regulates GPVI cleavage remains unknown. To address this, CRISPR/Cas9 knockout human cell lines were generated to show that Tspan15 and Tspan33 enact compensatory roles in GPVI cleavage, with Tspan15 bearing the more important role. To investigate this mechanism, a series of Tspan15 and GPVI mutant expression constructs were designed. The Tspan15 extracellular region was found to be critical in promoting GPVI cleavage, and appeared to achieve this by enabling ADAM10 to access the cleavage site at a particular distance above the membrane. These findings bear implications for the regulation of cleavage of other ADAM10 substrates, and provide new insights into post-translational regulation of the clinically relevant GPVI protein.}, language = {en} } @article{StegnerKlausNieswandt2019, author = {Stegner, David and Klaus, Vanessa and Nieswandt, Bernhard}, title = {Platelets as modulators of cerebral ischemia/reperfusion injury}, series = {Frontiers in Immunology}, volume = {10}, journal = {Frontiers in Immunology}, number = {2505}, issn = {1664-3224}, doi = {10.3389/fimmu.2019.02505}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-195748}, year = {2019}, abstract = {Ischemic stroke is among the leading causes of disability and death worldwide. In acute ischemic stroke, the rapid recanalization of occluded cranial vessels is the primary therapeutic aim. However, experimental data (obtained using mostly the transient middle cerebral artery occlusion model) indicates that progressive stroke can still develop despite successful recanalization, a process termed "reperfusion injury." Mounting experimental evidence suggests that platelets and T cells contribute to cerebral ischemia/reperfusion injury, and ischemic stroke is increasingly considered a thrombo-inflammatory disease. The interaction of von Willebrand factor and its receptor on the platelet surface, glycoprotein Ib, as well as many activatory platelet receptors and platelet degranulation contribute to secondary infarct growth in this setting. In contrast, interference with GPIIb/IIIa-dependent platelet aggregation and thrombus formation does not improve the outcome of acute brain ischemia but dramatically increases the susceptibility to intracranial hemorrhage. Here, we summarize the current understanding of the mechanisms and the potential translational impact of platelet contributions to cerebral ischemia/reperfusion injury.}, language = {en} } @article{DuettingGaitsIacovoniStegneretal.2017, author = {D{\"u}tting, Sebastian and Gaits-Iacovoni, Frederique and Stegner, David and Popp, Michael and Antkowiak, Adrien and van Eeuwijk, Judith M.M. and Nurden, Paquita and Stritt, Simon and Heib, Tobias and Aurbach, Katja and Angay, Oguzhan and Cherpokova, Deya and Heinz, Niels and Baig, Ayesha A. and Gorelashvili, Maximilian G. and Gerner, Frank and Heinze, Katrin G. and Ware, Jerry and Krohne, Georg and Ruggeri, Zaverio M. and Nurden, Alan T. and Schulze, Harald and Modlich, Ute and Pleines, Irina and Brakebusch, Cord and Nieswandt, Bernhard}, title = {A Cdc42/RhoA regulatory circuit downstream of glycoprotein Ib guides transendothelial platelet biogenesis}, series = {Nature Communications}, volume = {8}, journal = {Nature Communications}, number = {15838}, doi = {10.1038/ncomms15838}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170797}, year = {2017}, abstract = {Blood platelets are produced by large bone marrow (BM) precursor cells, megakaryocytes (MKs), which extend cytoplasmic protrusions (proplatelets) into BM sinusoids. The molecular cues that control MK polarization towards sinusoids and limit transendothelial crossing to proplatelets remain unknown. Here, we show that the small GTPases Cdc42 and RhoA act as a regulatory circuit downstream of the MK-specific mechanoreceptor GPIb to coordinate polarized transendothelial platelet biogenesis. Functional deficiency of either GPIb or Cdc42 impairs transendothelial proplatelet formation. In the absence of RhoA, increased Cdc42 activity and MK hyperpolarization triggers GPIb-dependent transmigration of entire MKs into BM sinusoids. These findings position Cdc42 (go-signal) and RhoA (stop-signal) at the centre of a molecular checkpoint downstream of GPIb that controls transendothelial platelet biogenesis. Our results may open new avenues for the treatment of platelet production disorders and help to explain the thrombocytopenia in patients with Bernard-Soulier syndrome, a bleeding disorder caused by defects in GPIb-IX-V.}, language = {en} } @article{StegnervanEeuwijkAngayetal.2017, author = {Stegner, David and van Eeuwijk, Judith M.M. and Angay, Oğuzhan and Gorelashvili, Maximilian G. and Semeniak, Daniela and Pinnecker, J{\"u}rgen and Schmithausen, Patrick and Meyer, Imke and Friedrich, Mike and D{\"u}tting, Sebastian and Brede, Christian and Beilhack, Andreas and Schulze, Harald and Nieswandt, Bernhard and Heinze, Katrin G.}, title = {Thrombopoiesis is spatially regulated by the bone marrow vasculature}, series = {Nature Communications}, volume = {8}, journal = {Nature Communications}, number = {127}, doi = {10.1038/s41467-017-00201-7}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170591}, year = {2017}, abstract = {In mammals, megakaryocytes (MKs) in the bone marrow (BM) produce blood platelets, required for hemostasis and thrombosis. MKs originate from hematopoietic stem cells and are thought to migrate from an endosteal niche towards the vascular sinusoids during their maturation. Through imaging of MKs in the intact BM, here we show that MKs can be found within the entire BM, without a bias towards bone-distant regions. By combining in vivo two-photon microscopy and in situ light-sheet fluorescence microscopy with computational simulations, we reveal surprisingly slow MK migration, limited intervascular space, and a vessel-biased MK pool. These data challenge the current thrombopoiesis model of MK migration and support a modified model, where MKs at sinusoids are replenished by sinusoidal precursors rather than cells from a distant periostic niche. As MKs do not need to migrate to reach the vessel, therapies to increase MK numbers might be sufficient to raise platelet counts.}, language = {en} } @article{KollikowskiSchuhmannNieswandtetal.2020, author = {Kollikowski, Alexander M. and Schuhmann, Michael K. and Nieswandt, Bernhard and M{\"u}llges, Wolfgang and Stoll, Guido and Pham, Mirko}, title = {Local Leukocyte Invasion during Hyperacute Human Ischemic Stroke}, series = {Annals of Neurology}, volume = {87}, journal = {Annals of Neurology}, number = {3}, doi = {10.1002/ana.25665}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212168}, pages = {466-479}, year = {2020}, abstract = {Objective Bridging the gap between experimental stroke and patients by ischemic blood probing during the hyperacute stage of vascular occlusion is crucial to assess the role of inflammation in human stroke and for the development of adjunct treatments beyond recanalization. Methods We prospectively observed 151 consecutive ischemic stroke patients with embolic large vessel occlusion of the anterior circulation who underwent mechanical thrombectomy. In all these patients, we attempted microcatheter aspiration of 3 different arterial blood samples: (1) within the core of the occluded vascular compartment and controlled by (2) carotid and (3) femoral samples obtained under physiological flow conditions. Subsequent laboratory analyses comprised leukocyte counting and differentiation, platelet counting, and the quantification of 13 proinflammatory human chemokines/cytokines. Results Forty patients meeting all clinical, imaging, interventional, and laboratory inclusion criteria could be analyzed, showing that the total number of leukocytes significantly increased under the occlusion condition. This increase was predominantly driven by neutrophils. Significant increases were also apparent for lymphocytes and monocytes, accompanied by locally elevated plasma levels of the T-cell chemoattractant CXCL-11. Finally, we found evidence that short-term clinical outcome (National Institute of Health Stroke Scale at 72 hours) was negatively associated with neutrophil accumulation. Interpretation We provide the first direct human evidence that neutrophils, lymphocytes, and monocytes, accompanied by specific chemokine upregulation, accumulate in the ischemic vasculature during hyperacute stroke and may affect outcome. These findings strongly support experimental evidence that immune cells contribute to acute ischemic brain damage and indicate that ischemic inflammation initiates already during vascular occlusion. Ann Neurol 2020;87:466-479}, language = {en} } @article{GoebVollZimmermannetal.2021, author = {G{\"o}b, Vanessa and Voll, Maximilian G. and Zimmermann, Lena and Hemmen, Katharina and Stoll, Guido and Nieswandt, Bernhard and Schuhmann, Michael K. and Heinze, Katrin G. and Stegner, David}, title = {Infarct growth precedes cerebral thrombosis following experimental stroke in mice}, series = {Scientific Reports}, volume = {11}, journal = {Scientific Reports}, number = {1}, doi = {10.1038/s41598-021-02360-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-265791}, year = {2021}, abstract = {Ischemic stroke is among the leading causes of disability and death worldwide. In acute ischemic stroke, successful recanalization of occluded vessels is the primary therapeutic aim, but even if it is achieved, not all patients benefit. Although blockade of platelet aggregation did not prevent infarct progression, cerebral thrombosis as cause of secondary infarct growth has remained a matter of debate. As cerebral thrombi are frequently observed after experimental stroke, a thrombus-induced impairment of the brain microcirculation is considered to contribute to tissue damage. Here, we combine the model of transient middle cerebral artery occlusion (tMCAO) with light sheet fluorescence microscopy and immunohistochemistry of brain slices to investigate the kinetics of thrombus formation and infarct progression. Our data reveal that tissue damage already peaks after 8 h of reperfusion following 60 min MCAO, while cerebral thrombi are only observed at later time points. Thus, cerebral thrombosis is not causative for secondary infarct growth during ischemic stroke.}, language = {en} } @article{BeckStegnerLorochetal.2021, author = {Beck, Sarah and Stegner, David and Loroch, Stefan and Baig, Ayesha A. and G{\"o}b, Vanessa and Schumbutzki, Cornelia and Eilers, Eva and Sickmann, Albert and May, Frauke and Nolte, Marc W. and Panousis, Con and Nieswandt, Bernhard}, title = {Generation of a humanized FXII knock-in mouse-A powerful model system to test novel anti-thrombotic agents}, series = {Journal of Thrombosis and Haemostasis}, volume = {19}, journal = {Journal of Thrombosis and Haemostasis}, number = {11}, doi = {10.1111/jth.15488}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-259567}, pages = {2835-2840}, year = {2021}, abstract = {Background Effective inhibition of thrombosis without generating bleeding risks is a major challenge in medicine. Accumulating evidence suggests that this can be achieved by inhibition of coagulation factor XII (FXII), as either its knock-out or inhibition in animal models efficiently reduced thrombosis without affecting normal hemostasis. Based on these findings, highly specific inhibitors for human FXII(a) are under development. However, currently, in vivo studies on their efficacy and safety are impeded by the lack of an optimized animal model expressing the specific target, that is, human FXII. Objective The primary objective of this study is to develop and functionally characterize a humanized FXII mouse model. Methods A humanized FXII mouse model was generated by replacing the murine with the human F12 gene (genetic knock-in) and tested it in in vitro coagulation assays and in in vivo thrombosis models. Results These hF12\(^{KI}\) mice were indistinguishable from wild-type mice in all tested assays of coagulation and platelet function in vitro and in vivo, except for reduced expression levels of hFXII compared to human plasma. Targeting FXII by the anti-human FXIIa antibody 3F7 increased activated partial thromboplastin time dose-dependently and protected hF12\(^{KI}\) mice in an arterial thrombosis model without affecting bleeding times. Conclusion These data establish the newly generated hF12\(^{KI}\) mouse as a powerful and unique model system for in vivo studies on anti-FXII(a) biologics, supporting the development of efficient and safe human FXII(a) inhibitors.}, language = {en} } @phdthesis{Aigner2023, author = {Aigner, Max}, title = {Establishing successful protocols and imaging pipelines for Expansion Microscopy in murine blood platelets}, doi = {10.25972/OPUS-30900}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-309003}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {Platelets play an important role in the body, since they are part of the hemostasis system, preventing and stopping blood loss. Nevertheless, when platelet or coagulation system function are impaired, uncontrolled bleedings but also irreversible vessel occlusion followed by ischemic tissue damage can occur. Therefore, understanding platelet function and activation, mechanisms which are controlled by a variety of platelet membrane receptors and other factors is important to advance out knowledge of hemostasis and platelet malfunction. For a complete picture of platelet function and their modulating behavior it is desired to be able to quantify receptor distributions and interactions of these densely packed molecular ensembles in the membrane. This challenges scientists for several reasons. Most importantly, platelets are microscopically small objects, challenging the spatial resolution of conventional light microscopy. Moreover, platelet receptors are highly abundant on the membrane so even super-resolution microscopy struggles with quantitative receptor imaging on platelets. With Expansion microscopy (ExM), a new super-resolution technique was introduced, allowing resolutions to achieve super-resolution without using a super-resolution microscope, but by combining a conventional confocal microscopy with a highly processed sample that has been expanded physically. In this doctoral thesis, I evaluated the potential of this technique for super-resolution platelet imaging by optimizing the sample preparation process and establishing an imaging and image processing pipeline for dual-color 3D images of different membrane receptors. The analysis of receptor colocalization using ExM demonstrated a clear superiority compared to conventional microscopy. Furthermore, I identified a library of fluorescently labeled antibodies against different platelet receptors compatible with ExM and showed the possibility of staining membrane receptors and parts of the cytoskeleton at the same time.}, subject = {Mikroskopie}, language = {en} } @article{MammadovaBachBraun2019, author = {Mammadova-Bach, Elmina and Braun, Attila}, title = {Zinc homeostasis in platelet-related diseases}, series = {International Journal of Molecular Sciences}, volume = {20}, journal = {International Journal of Molecular Sciences}, number = {21}, issn = {1422-0067}, doi = {10.3390/ijms20215258}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-285554}, year = {2019}, abstract = {Zn\(^{2+}\) deficiency in the human population is frequent in underdeveloped countries. Worldwide, approximatively 2 billion people consume Zn\(^{2+}\)-deficient diets, accounting for 1-4\% of deaths each year, mainly in infants with a compromised immune system. Depending on the severity of Zn\(^{2+}\) deficiency, clinical symptoms are associated with impaired wound healing, alopecia, diarrhea, poor growth, dysfunction of the immune and nervous system with congenital abnormalities and bleeding disorders. Poor nutritional Zn\(^{2+}\) status in patients with metastatic squamous cell carcinoma or with advanced non-Hodgkin lymphoma, was accompanied by cutaneous bleeding and platelet dysfunction. Forcing Zn\(^{2+}\) uptake in the gut using different nutritional supplementation of Zn\(^{2+}\) could ameliorate many of these pathological symptoms in humans. Feeding adult rodents with a low Zn\(^{2+}\) diet caused poor platelet aggregation and increased bleeding tendency, thereby attracting great scientific interest in investigating the role of Zn\(^{2+}\) in hemostasis. Storage protein metallothionein maintains or releases Zn\(^{2+}\) in the cytoplasm, and the dynamic change of this cytoplasmic Zn\(^{2+}\) pool is regulated by the redox status of the cell. An increase of labile Zn\(^{2+}\) pool can be toxic for the cells, and therefore cytoplasmic Zn\(^{2+}\) levels are tightly regulated by several Zn\(^{2+}\) transporters located on the cell surface and also on the intracellular membrane of Zn\(^{2+}\) storage organelles, such as secretory vesicles, endoplasmic reticulum or Golgi apparatus. Although Zn\(^{2+}\) is a critical cofactor for more than 2000 transcription factors and 300 enzymes, regulating cell differentiation, proliferation, and basic metabolic functions of the cells, the molecular mechanisms of Zn\(^{2+}\) transport and the physiological role of Zn\(^{2+}\) store in megakaryocyte and platelet function remain elusive. In this review, we summarize the contribution of extracellular or intracellular Zn\(^{2+}\) to megakaryocyte and platelet function and discuss the consequences of dysregulated Zn\(^{2+}\) homeostasis in platelet-related diseases by focusing on thrombosis, ischemic stroke and storage pool diseases.}, language = {en} } @article{RiesLiessFeileretal.2020, author = {Ries, Lena K. and Liess, Anna K. L. and Feiler, Christian G. and Spratt, Donald E. and Lowe, Edward D. and Lorenz, Sonja}, title = {Crystal structure of the catalytic C-lobe of the HECT-type ubiquitin ligase E6AP}, series = {Protein Science}, volume = {29}, journal = {Protein Science}, number = {6}, doi = {10.1002/pro.3832}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-214812}, pages = {1550 -- 1554}, year = {2020}, abstract = {The HECT-type ubiquitin ligase E6AP (UBE3A) is critically involved in several neurodevelopmental disorders and human papilloma virus-induced cervical tumorigenesis; the structural mechanisms underlying the activity of this crucial ligase, however, are incompletely understood. Here, we report a crystal structure of the C-terminal lobe ("C-lobe") of the catalytic domain of E6AP that reveals two molecules in a domain-swapped, dimeric arrangement. Interestingly, the molecular hinge that enables this structural reorganization with respect to the monomeric fold coincides with the active-site region. While such dimerization is unlikely to occur in the context of full-length E6AP, we noticed a similar domain swap in a crystal structure of the isolated C-lobe of another HECT-type ubiquitin ligase, HERC6. This may point to conformational strain in the active-site region of HECT-type ligases with possible implications for catalysis. Significance Statement The HECT-type ubiquitin ligase E6AP has key roles in human papilloma virus-induced cervical tumorigenesis and certain neurodevelopmental disorders. Here, we present a crystal structure of the C-terminal, catalytic lobe of E6AP, providing basic insight into the conformational properties of this functionally critical region of HECT-type ligases.}, language = {en} } @article{SchuhmannBieberFrankeetal.2021, author = {Schuhmann, Michael K. and Bieber, Michael and Franke, Maximilian and Kollikowski, Alexander M. and Stegner, David and Heinze, Katrin G. and Nieswandt, Bernhard and Pham, Mirko and Stoll, Guido}, title = {Platelets and lymphocytes drive progressive penumbral tissue loss during middle cerebral artery occlusion in mice}, series = {Journal of Neuroinflammation}, volume = {18}, journal = {Journal of Neuroinflammation}, number = {1}, doi = {10.1186/s12974-021-02095-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-259172}, pages = {46}, year = {2021}, abstract = {Background In acute ischemic stroke, cessation of blood flow causes immediate tissue necrosis within the center of the ischemic brain region accompanied by functional failure in the surrounding brain tissue designated the penumbra. The penumbra can be salvaged by timely thrombolysis/thrombectomy, the only available acute stroke treatment to date, but is progressively destroyed by the expansion of infarction. The underlying mechanisms of progressive infarction are not fully understood. Methods To address mechanisms, mice underwent filament occlusion of the middle cerebral artery (MCAO) for up to 4 h. Infarct development was compared between mice treated with antigen-binding fragments (Fab) against the platelet surface molecules GPIb (p0p/B Fab) or rat immunoglobulin G (IgG) Fab as control treatment. Moreover, Rag1\(^{-/-}\) mice lacking T-cells underwent the same procedures. Infarct volumes as well as the local inflammatory response were determined during vessel occlusion. Results We show that blocking of the platelet adhesion receptor, glycoprotein (GP) Ibα in mice, delays cerebral infarct progression already during occlusion and thus before recanalization/reperfusion. This therapeutic effect was accompanied by decreased T-cell infiltration, particularly at the infarct border zone, which during occlusion is supplied by collateral blood flow. Accordingly, mice lacking T-cells were likewise protected from infarct progression under occlusion. Conclusions Progressive brain infarction can be delayed by blocking detrimental lymphocyte/platelet responses already during occlusion paving the way for ultra-early treatment strategies in hyper-acute stroke before recanalization.}, language = {en} } @phdthesis{Mietrach2020, author = {Mietrach, Nicole Aline}, title = {Structural and functional elucidation of the Type VIIb secretion system from Staphylococcus aureus}, doi = {10.25972/OPUS-21482}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-214824}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2020}, abstract = {The Type VII secretion system (T7SS) is linked to virulence and long-term pathogenesis in a broad range of Gram-positive bacteria, including the human commensal and pathogen Staphylococcus aureus. The Type VIIb secretion system (T7SSb) is responsible for the export of small toxic proteins, which induce antibacterial immune responses and mediate bacterial persistence in the host. In addition, it is also involved in bacterial competition. The T7SSb requires several proteins to build up the secretion machinery. This work focuses on the structural and functional investigation of the motor ATPase EssC and the putative pore forming, multi-pass membrane component EsaA. Both proteins are indispensable for substrate secretion. EssC belongs to the FtsK/SpoIIIE ATPase family and is conserved among the T7SSs. It contains three C-terminal, cytosolic ATPase domains, designated as EssC- D1, -D2 and -D3, whereby EssC-D3 is the most distal one. In this thesis, I am presenting the crystal structure of the EssC-D3 at 1.7 {\AA} resolution. As the deletion of EssC-D3 abrogates substrate export, I have demonstrated that this domain comprises a hydrophobic, surface-exposed pocket, which is required for substrate secretion. More specifically, I have identified two amino acids involved in the secretion process. In addition, my results indicate that not only EssC-D3 is important for substrate interaction but also EssC-D2 and/or EssC-D1. Unlike in the related Yuk T7SSb of Bacillus subtilis, the ATPase activity of D3 domain contributes to substrate secretion. Mutation of the modified Walker B motif in EssC-D3 diminishes substrate secretion completely. The membrane protein EsaA encompasses an extracellular segment spanning through the cell wall of S. aureus. I was able to reveal that this part folds into a stable domain, which was crystallized and diffracted up to 4 {\AA}. The first attempts to dissolve the structure failed due to a lack of homologues structures. Therefore, crystals for single-wavelength anomalous dispersion, containing selenomethionyl-substitutes, were produced and the structure solution is still in progress. Preliminary experiments addressing the function of the extracellular domain indicate an important role in substrate secretion and bacterial competition.}, subject = {Secretion}, language = {en} } @article{PetrusevaNaumenkoKuperetal.2021, author = {Petruseva, Irina and Naumenko, Natalia and Kuper, Jochen and Anarbaev, Rashid and Kappenberger, Jeannette and Kisker, Caroline and Lavrik, Olga}, title = {The Interaction Efficiency of XPD-p44 With Bulky DNA Damages Depends on the Structure of the Damage}, series = {Frontiers in Cell and Developmental Biology}, volume = {9}, journal = {Frontiers in Cell and Developmental Biology}, issn = {2296-634X}, doi = {10.3389/fcell.2021.617160}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-231806}, year = {2021}, abstract = {The successful elimination of bulky DNA damages via the nucleotide excision repair (NER) system is largely determined by the damage recognition step. This step consists of primary recognition and verification of the damage. The TFIIH helicase XPD plays a key role in the verification step during NER. To date, the mechanism of damage verification is not sufficiently understood and requires further detailed research. This study is a systematic investigation of the interaction of ctXPD (Chaetomium thermophilum) as well as ctXPD-ctp44 with model DNAs, which contain structurally different bulky lesions with previously estimated NER repair efficiencies. We have used ATPase and DNA binding studies to assess the interaction of ctXPD with damaged DNA. The result of the analysis of ctXPD-ctp44 binding to DNA containing fluorescent and photoactivatable lesions demonstrates the relationship between the affinity of XPD for DNAs containing bulky damages and the ability of the NER system to eliminate the damage. Photo-cross-linking of ctXPD with DNA probes containing repairable and unrepairable photoactivatable damages reveals differences in the DNA interaction efficiency in the presence and absence of ctp44. In general, the results obtained indicate the ability of ctXPD-ctp44 to interact with a damage and suggest a significant role for ctp44 subunit in the verification process.}, language = {en} } @article{PeissertSauerGrabarczyketal.2020, author = {Peissert, Stefan and Sauer, Florian and Grabarczyk, Daniel B. and Braun, Cathy and Sander, Gudrun and Poterszman, Arnaud and Egly, Jean-Marc and Kuper, Jochen and Kisker, Caroline}, title = {In TFIIH the Arch domain of XPD is mechanistically essential for transcription and DNA repair}, series = {Nature Communications}, volume = {11}, journal = {Nature Communications}, number = {1}, doi = {10.1038/s41467-020-15241-9}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-229857}, year = {2020}, abstract = {The XPD helicase is a central component of the general transcription factor TFIIH which plays major roles in transcription and nucleotide excision repair (NER). Here we present the high-resolution crystal structure of the Arch domain of XPD with its interaction partner MAT1, a central component of the CDK activating kinase complex. The analysis of the interface led to the identification of amino acid residues that are crucial for the MAT1-XPD interaction. More importantly, mutagenesis of the Arch domain revealed that these residues are essential for the regulation of (i) NER activity by either impairing XPD helicase activity or the interaction of XPD with XPG; (ii) the phosphorylation of the RNA polymerase II and RNA synthesis. Our results reveal how MAT1 shields these functionally important residues thereby providing insights into how XPD is regulated by MAT1 and defining the Arch domain as a major mechanistic player within the XPD scaffold.}, language = {en} } @article{WagnerMottUpcinetal.2021, author = {Wagner, Nicole and Mott, Kristina and Upcin, Berin and Stegner, David and Schulze, Harald and Erg{\"u}n, S{\"u}leyman}, title = {CXCL12-abundant reticular (CAR) cells direct megakaryocyte protrusions across the bone marrow sinusoid wall}, series = {Cells}, volume = {10}, journal = {Cells}, number = {4}, issn = {2073-4409}, doi = {10.3390/cells10040722}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-234180}, year = {2021}, abstract = {Megakaryocytes (MKs) release platelets into the lumen of bone marrow (BM) sinusoids while remaining to reside within the BM. The morphogenetic events of this complex process are still not fully understood. We combined confocal laser scanning microscopy with transmission and serial block-face scanning electron microscopy followed by 3D-reconstruction on mouse BM tissue sections. These analyses revealed that MKs in close vicinity to BM sinusoid (BMS) wall first induce the lateral retraction of CXCL12-abundant reticular (CAR) cells (CAR), followed by basal lamina (BL) degradation enabling direct MK-sinusoidal endothelial cells (SECs) interaction. Subsequently, an endothelial engulfment starts that contains a large MK protrusion. Then, MK protrusions penetrate the SEC, transmigrate into the BMS lumen and form proplatelets that are in direct contact to the SEC surface. Furthermore, such processes are induced on several sites, as observed by 3D reconstructions. Our data demonstrate that MKs in interaction with CAR-cells actively induce BMS wall alterations, including CAR-cell retraction, BL degradation, and SEC engulfment containing a large MK protrusion. This results in SEC penetration enabling the migration of MK protrusion into the BMS lumen where proplatelets that are adherent to the luminal SEC surface are formed and contribute to platelet release into the blood circulation.}, language = {en} } @article{HarnošCanizalJuraseketal.2019, author = {Harnoš, Jakub and Ca{\~n}izal, Maria Consuelo Alonso and Jur{\´a}sek, Miroslav and Kumar, Jitender and Holler, Cornelia and Schambony, Alexandra and Han{\´a}kov{\´a}, Kateřina and Bernat{\´i}k, Ondřej and Zdr{\´a}hal, Zbyn{\^e}k and G{\"o}m{\"o}ryov{\´a}, Krist{\´i}na and Gybeľ, Tom{\´a}š and Radaszkiewicz, Tomasz Witold and Kravec, Marek and Trant{\´i}rek, Luk{\´a}š and Ryneš, Jan and Dave, Zankruti and Fern{\´a}ndez-Llamazares, Ana Iris and V{\´a}cha, Robert and Tripsianes, Konstantinos and Hoffmann, Carsten and Bryja, V{\´i}tězslav}, title = {Dishevelled-3 conformation dynamics analyzed by FRET-based biosensors reveals a key role of casein kinase 1}, series = {Nature Communications}, volume = {10}, journal = {Nature Communications}, doi = {10.1038/s41467-019-09651-7}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-227837}, year = {2019}, abstract = {Dishevelled (DVL) is the key component of the Wnt signaling pathway. Currently, DVL conformational dynamics under native conditions is unknown. To overcome this limitation, we develop the Fluorescein Arsenical Hairpin Binder- (FlAsH-) based FRET in vivo approach to study DVL conformation in living cells. Using this single-cell FRET approach, we demonstrate that (i) Wnt ligands induce open DVL conformation, (ii) DVL variants that are predominantly open, show more even subcellular localization and more efficient membrane recruitment by Frizzled (FZD) and (iii) Casein kinase 1 ɛ (CK1ɛ) has a key regulatory function in DVL conformational dynamics. In silico modeling and in vitro biophysical methods explain how CK1ɛ-specific phosphorylation events control DVL conformations via modulation of the PDZ domain and its interaction with DVL C-terminus. In summary, our study describes an experimental tool for DVL conformational sampling in living cells and elucidates the essential regulatory role of CK1ɛ in DVL conformational dynamics.}, language = {en} } @article{HeilSchreiberGoetzetal.2018, author = {Heil, Hannah S. and Schreiber, Benjamin and G{\"o}tz, Ralph and Emmerling, Monika and Dabauvalle, Marie-Christine and Krohne, Georg and H{\"o}fling, Sven and Kamp, Martin and Sauer, Markus and Heinze, Katrin G.}, title = {Sharpening emitter localization in front of a tuned mirror}, series = {Light: Science \& Applications}, volume = {7}, journal = {Light: Science \& Applications}, doi = {10.1038/s41377-018-0104-z}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-228080}, year = {2018}, abstract = {Single-molecule localization microscopy (SMLM) aims for maximized precision and a high signal-to-noise ratio1. Both features can be provided by placing the emitter in front of a metal-dielectric nanocoating that acts as a tuned mirror2,3,4. Here, we demonstrate that a higher photon yield at a lower background on biocompatible metal-dielectric nanocoatings substantially improves SMLM performance and increases the localization precision by up to a factor of two. The resolution improvement relies solely on easy-to-fabricate nanocoatings on standard glass coverslips and is spectrally and spatially tunable by the layer design and wavelength, as experimentally demonstrated for dual-color SMLM in cells.}, language = {en} } @article{JarickMokhtariSchelleretal.2018, author = {Jarick, Katja J. and Mokhtari, Zeinab and Scheller, Lukas and Hartweg, Julia and Thusek, Sina and Le, Duc-Dung and Ranecky, Maria and Shaikh, Haroon and Qureischi, Musga and Heinze, Katrin G. and Beilhack, Andreas}, title = {Photoconversion of Alloreactive T Cells in Murine Peyer's Patches During Acute Graft-Versus-Host Disease: Tracking the Homing Route of Highly Proliferative Cells In Vivo}, series = {Frontiers in Immunology}, volume = {9}, journal = {Frontiers in Immunology}, doi = {10.3389/fimmu.2018.01468}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-323309}, year = {2018}, abstract = {The regulation of immune cell migration throughout the body is essential to warrant immunosurveillance and to maintain immune homeostasis. Marking and tracking of these cells has proven important to study mechanisms of immune cell trafficking and cell interaction in vivo. Photoconversion is a well-suited technique for intravital application because it enables contactless time- and location-specific marking of cells in the tissue without surgically manipulating the microenvironment of the cells in question. However, in dividing cells the converted fluorescent protein may decline quickly. Here, we provide a detailed description of the photoconversion technique and its applicability to tracking highly proliferating T cells from the priming site of T cell activation to peripheral target organs of effector function in a preclinical model. Dendra2+ T cells were photoconverted in the Peyer's patches during the initiation phase of acute graft-versus-host disease (GvHD) and tracked through the mesenteric lymph nodes and the peripheral blood to the small intestine with flow cytometry and intravital two-photon microscopy. Photoconverted alloreactive T cells preserved the full proliferative capacity, homing, and migration of alloreactive T cells in the intestinal lamina propria. We conclusively proved that photoconversion of highly proliferative alloreactive T cells in the Peyer's patches is an effective tool to study trafficking of alloreactive T cells under physiologic conditions and to GvHD target tissues. This technique can also be applied to the study of immune cell tracking under inflammatory and non-inflammatory conditions.}, language = {en} } @article{HersterBittnerCodreaetal.2019, author = {Herster, Franziska and Bittner, Zsofia and Codrea, Marius Cosmin and Archer, Nathan K. and Heister, Martin and L{\"o}ffler, Markus W. and Heumos, Simon and Wegner, Joanna and Businger, Ramona and Schindler, Michael and Stegner, David and Sch{\"a}kel, Knut and Grabbe, Stephan and Ghoreschi, Kamran and Miller, Lloyd S. and Weber, Alexander N. R.}, title = {Platelets Aggregate With Neutrophils and Promote Skin Pathology in Psoriasis}, series = {Frontiers in Immunology}, volume = {10}, journal = {Frontiers in Immunology}, doi = {10.3389/fimmu.2019.01867}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-320175}, year = {2019}, abstract = {Psoriasis is a frequent systemic inflammatory autoimmune disease characterized primarily by skin lesions with massive infiltration of leukocytes, but frequently also presents with cardiovascular comorbidities. Especially polymorphonuclear neutrophils (PMNs) abundantly infiltrate psoriatic skin but the cues that prompt PMNs to home to the skin are not well-defined. To identify PMN surface receptors that may explain PMN skin homing in psoriasis patients, we screened 332 surface antigens on primary human blood PMNs from healthy donors and psoriasis patients. We identified platelet surface antigens as a defining feature of psoriasis PMNs, due to a significantly increased aggregation of neutrophils and platelets in the blood of psoriasis patients. Similarly, in the imiquimod-induced experimental in vivo mouse model of psoriasis, disease induction promoted PMN-platelet aggregate formation. In psoriasis patients, disease incidence directly correlated with blood platelet counts and platelets were detected in direct contact with PMNs in psoriatic but not healthy skin. Importantly, depletion of circulating platelets in mice in vivo ameliorated disease severity significantly, indicating that both PMNs and platelets may be relevant for psoriasis pathology and disease severity.}, language = {en} } @phdthesis{WeigelverhHoffmann2024, author = {Weigel [verh. Hoffmann], Mathis Leonard}, title = {Thrombozytenfunktionsanalyse als potenzielles Instrument zur Fr{\"u}herkennung von Sepsis}, doi = {10.25972/OPUS-35819}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-358193}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2024}, abstract = {Sepsis ist ein h{\"a}ufiges und akut lebensbedrohliches Syndrom, das eine Organfunktionsst{\"o}rung in Folge einer dysregulierten Immunantwort auf eine Infektion beschreibt. Eine fr{\"u}hzeitige Diagnosestellung und Therapieeinleitung sind von zentraler Bedeutung f{\"u}r das {\"U}berleben der Patient:innen. In einer Pilotstudie konnte unsere Forschungsgruppe mittels Durchflusszytometrie eine ausgepr{\"a}gte Hyporeaktivit{\"a}t der Thrombozyten bei Sepsis nachweisen, die einen potenziell neuen Biomarker zur Sepsis-Fr{\"u}herkennung darstellt. Zur Evaluation des Ausmaßes und Entstehungszeitpunktes der detektierten Thrombozytenfunktionsst{\"o}rung wurden im Rahmen der vorliegenden Arbeit zus{\"a}tzlich zu Patient:innen mit Sepsis (SOFA-Score ≥ 2; n=13) auch hospitalisierte Patient:innen mit einer Infektion ohne Sepsis (SOFA-Score < 2; n=12) rekrutiert. Beide Kohorten wurden zu zwei Zeitpunkten (t1: <24h; t2: Tag 5-7) im Krankheitsverlauf mittels Durchflusszytometrie und PFA-200 untersucht und mit einer gesunden Kontrollgruppe (n=28) verglichen. Ph{\"a}notypische Auff{\"a}lligkeiten der Thrombozyten bei Sepsis umfassten: (i) eine ver{\"a}nderte Expression verschiedener Untereinheiten des GPIb-IX-V-Rezeptorkomplexes, die auf ein verst{\"a}rktes Rezeptor-Shedding hindeutet; (ii) ein ausgepr{\"a}gtes Mepacrin-Beladungsdefizit, das auf eine zunehmend reduzierte Anzahl von δ-Granula entlang des Infektion-Sepsis Kontinuums hinweist; (iii) eine Reduktion endst{\"a}ndig gebundener Sialins{\"a}ure im Sinne einer verst{\"a}rkten Desialylierung. Die funktionelle Analyse der Thrombozyten bei Sepsis ergab bei durchflusszytometrischer Messung der Integrin αIIbβ3-Aktivierung (PAC-1-Bindung) eine ausgepr{\"a}gte generalisierte Hyporeaktivit{\"a}t gegen{\"u}ber multiplen Agonisten, die abgeschw{\"a}cht bereits bei Infektion nachweisbar war und gem{\"a}ß ROC-Analysen gut zwischen Infektion und Sepsis diskriminierte (AUC >0.80 f{\"u}r alle Agonisten). Im Gegensatz dazu zeigten Thrombozyten bei Sepsis und Analyse mittels PFA-200 unter Einfluss physiologischer Scherkr{\"a}fte eine normale bis gar beschleunigte Aggregation. Die Reaktivit{\"a}tsmessung von Thrombozyten mittels Durchflusszytometrie stellt weiterhin einen vielversprechenden Biomarker f{\"u}r die Sepsis-Fr{\"u}herkennung dar. F{\"u}r weitere Schlussfolgerungen ist jedoch eine gr{\"o}ßere Kohorte erforderlich. In nachfolgenden Untersuchungen sollten zudem mechanistische Ursachen der beschriebenen ph{\"a}notypischen und funktionellen Auff{\"a}lligkeiten von Thrombozyten bei Infektion und Sepsis z.B. mittels Koinkubationsexperimenten untersucht werden.}, subject = {Sepsis}, language = {de} } @article{GotruvanGeffenNagyetal.2019, author = {Gotru, Sanjeev Kiran and van Geffen, Johanna P. and Nagy, Magdolna and Mammadova-Bach, Elmina and Eilenberger, Julia and Volz, Julia and Manukjan, Georgi and Schulze, Harald and Wagner, Leonard and Eber, Stefan and Schambeck, Christian and Deppermann, Carsten and Brouns, Sanne and Nurden, Paquita and Greinacher, Andreas and Sachs, Ulrich and Nieswandt, Bernhard and Hermanns, Heike M. and Heemskerk, Johan W. M. and Braun, Attila}, title = {Defective Zn2+ homeostasis in mouse and human platelets with α- and δ-storage pool diseases}, series = {Scientific Reports}, volume = {9}, journal = {Scientific Reports}, doi = {10.1038/s41598-019-44751-w}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-227455}, year = {2019}, abstract = {Zinc (Zn2+) can modulate platelet and coagulation activation pathways, including fibrin formation. Here, we studied the (patho)physiological consequences of abnormal platelet Zn2+ storage and release. To visualize Zn2+ storage in human and mouse platelets, the Zn2+ specific fluorescent dye FluoZin3 was used. In resting platelets, the dye transiently accumulated into distinct cytosolic puncta, which were lost upon platelet activation. Platelets isolated from Unc13d-/- mice, characterized by combined defects of α/δ granular release, showed a markedly impaired Zn2+ release upon activation. Platelets from Nbeal2-/- mice mimicking Gray platelet syndrome (GPS), characterized by primarily loss of the α-granule content, had strongly reduced Zn2+ levels, which was also confirmed in primary megakaryocytes. In human platelets isolated from patients with GPS, Hermansky-Pudlak Syndrome (HPS) and Storage Pool Disease (SPD) altered Zn2+ homeostasis was detected. In turbidity and flow based assays, platelet-dependent fibrin formation was impaired in both Nbeal2-/- and Unc13d-/- mice, and the impairment could be partially restored by extracellular Zn2+. Altogether, we conclude that the release of ionic Zn2+ store from secretory granules upon platelet activation contributes to the procoagulant role of Zn2+ in platelet-dependent fibrin formation.}, language = {en} } @article{HinesMaricHinesetal.2018, author = {Hines, Rochelle M. and Maric, Hans Michael and Hines, Dustin J. and Modgil, Amit and Panzanelli, Patrizia and Nakamura, Yasuko and Nathanson, Anna J. and Cross, Alan and Deeb, Tarek and Brandon, Nicholas J. and Davies, Paul and Fritschy, Jean-Marc and Schindelin, Hermann and Moss, Stephen J.}, title = {Developmental seizures and mortality result from reducing GABAA receptor α2-subunit interaction with collybistin}, series = {Nature Communications}, volume = {9}, journal = {Nature Communications}, doi = {10.1038/s41467-018-05481-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-320719}, year = {2018}, abstract = {Fast inhibitory synaptic transmission is mediated by γ-aminobutyric acid type A receptors (GABAARs) that are enriched at functionally diverse synapses via mechanisms that remain unclear. Using isothermal titration calorimetry and complementary methods we demonstrate an exclusive low micromolar binding of collybistin to the α2-subunit of GABAARs. To explore the biological relevance of collybistin-α2-subunit selectivity, we generate mice with a mutation in the α2-subunit-collybistin binding region (Gabra2-1). The mutation results in loss of a distinct subset of inhibitory synapses and decreased amplitude of inhibitory synaptic currents. Gabra2-1 mice have a striking phenotype characterized by increased susceptibility to seizures and early mortality. Surviving Gabra2-1 mice show anxiety and elevations in electroencephalogram δ power, which are ameliorated by treatment with the α2/α3-selective positive modulator, AZD7325. Taken together, our results demonstrate an α2-subunit selective binding of collybistin, which plays a key role in patterned brain activity, particularly during development.}, language = {en} } @article{FazeliStetterLisacketal.2018, author = {Fazeli, Gholamreza and Stetter, Maurice and Lisack, Jaime N. and Wehman, Ann M.}, title = {C. elegans Blastomeres Clear the Corpse of the Second Polar Body by LC3-Associated Phagocytosis}, series = {Cell Reports}, volume = {23}, journal = {Cell Reports}, doi = {10.1016/j.celrep.2018.04.043}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-227651}, pages = {2070-2082}, year = {2018}, abstract = {To understand how undifferentiated pluripotent cells cope with cell corpses, we examined the clearance of polar bodies born during female meiosis. We found that polar bodies lose membrane integrity and expose phosphatidylserine in Caenorhabditis elegans. Polar body signaling recruits engulfment receptors to the plasma membrane of embryonic blastomeres using the PI3K VPS-34, RAB-5 GTPase and the sorting nexin SNX-6. The second polar body is then phagocytosed using receptor-mediated engulfment pathways dependent on the Rac1 ortholog CED-10 but undergoes non-apoptotic programmed cell death independent of engulfment. RAB-7 GTPase is required for lysosome recruitment to the polar body phagosome, while LC3 lipidation is required for degradation of the corpse membrane after lysosome fusion. The polar body phagolysosome vesiculates in an mTOR- and ARL-8-dependent manner, which assists its timely degradation. Thus, we established a genetic model to study clearance by LC3-associated phagocytosis and reveal insights into the mechanisms of phagosome maturation and degradation.}, language = {en} } @phdthesis{Karwen2024, author = {Karwen, Till}, title = {Platelets promote insulin secretion of pancreatic β-cells}, doi = {10.25972/OPUS-31393}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-313933}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2024}, abstract = {The pancreas is the key organ for the maintenance of euglycemia. This is regulated in particular by α-cell-derived glucagon and β-cell-derived insulin, which are released in response to nutrient deficiency and elevated glucose levels, respectively. Although glucose is the main regulator of insulin secretion, it is significantly enhanced by various potentiators. Platelets are anucleate cell fragments in the bloodstream that are essential for hemostasis to prevent and stop bleeding events. Besides their classical role, platelets were implemented to be crucial for other physiological and pathophysiological processes, such as cancer progression, immune defense, and angiogenesis. Platelets from diabetic patients often present increased reactivity and basal activation. Interestingly, platelets store and release several substances that have been reported to potentiate insulin secretion by β-cells. For these reasons, the impact of platelets on β-cell functioning was investigated in this thesis. Here it was shown that both glucose and a β-cell-derived substance/s promote platelet activation and binding to collagen. Additionally, platelet adhesion specifically to the microvasculature of pancreatic islets was revealed, supporting the hypothesis of their influence on glucose homeostasis. Genetic or pharmacological ablation of platelet functioning and platelet depletion consistently resulted in reduced insulin secretion and associated glucose intolerance. Further, the platelet-derived lipid fraction was found to enhance glucose-stimulated insulin secretion, with 20-hydroxyeicosatetraenoic acid (20-HETE) and possibly also lyso-precursor of platelet-activating factor (lysoPAF) being identified as crucial factors. However, the acute platelet-stimulated insulin secretion was found to decline with age, as did the levels of platelet-derived 20-HETE. In addition to their direct stimulatory effect on insulin secretion, specific defects in platelet activation have also been shown to affect glucose homeostasis by potentially influencing islet vascular development. Taking together, the results of this thesis suggest a direct and indirect mechanism of platelets in the regulation of insulin secretion that ensures glucose homeostasis, especially in young individuals.}, subject = {Thrombozyt}, language = {en} } @article{SchurrSpindlerKurzetal.2019, author = {Schurr, Yvonne and Spindler, Markus and Kurz, Hendrikje and Bender, Markus}, title = {The cytoskeletal crosslinking protein MACF1 is dispensable for thrombus formation and hemostasis}, series = {Scientific Reports}, volume = {9}, journal = {Scientific Reports}, doi = {10.1038/s41598-019-44183-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-234966}, year = {2019}, abstract = {Coordinated reorganization of cytoskeletal structures is critical for key aspects of platelet physiology. While several studies have addressed the role of microtubules and filamentous actin in platelet production and function, the significance of their crosstalk in these processes has been poorly investigated. The microtubule-actin cross-linking factor 1 (MACF1; synonym: Actin cross-linking factor 7, ACF7) is a member of the spectraplakin family, and one of the few proteins expressed in platelets, which possess actin and microtubule binding domains thereby facilitating actin-microtubule interaction and regulation. We used megakaryocyte- and platelet-specific Macf1 knockout (Macf1fl/fl, Pf4-Cre) mice to study the role of MACF1 in platelet production and function. MACF1 deficient mice displayed comparable platelet counts to control mice. Analysis of the platelet cytoskeletal ultrastructure revealed a normal marginal band and actin network. Platelet spreading on fibrinogen was slightly delayed but platelet activation and clot traction was unaffected. Ex vivo thrombus formation and mouse tail bleeding responses were similar between control and mutant mice. These results suggest that MACF1 is dispensable for thrombopoiesis, platelet activation, thrombus formation and the hemostatic function in mice.}, language = {en} } @article{LeeLiRuanetal.2019, author = {Lee, Hong-Jen and Li, Chien-Feng and Ruan, Diane and He, Jiabei and Montal, Emily D. and Lorenz, Sonja and Girnun, Geoffrey D. and Chan, Chia-Hsin}, title = {Non-proteolytic ubiquitination of Hexokinase 2 by HectH9 controls tumor metabolism and cancer stem cell expansion}, series = {Nature Communications}, volume = {10}, journal = {Nature Communications}, doi = {10.1038/s41467-019-10374-y}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-236445}, year = {2019}, abstract = {Enormous efforts have been made to target metabolic dependencies of cancer cells for developing new therapies. However, the therapeutic efficacy of glycolysis inhibitors is limited due to their inability to elicit cell death. Hexokinase 2 (HK2), via its mitochondrial localization, functions as a central nexus integrating glycolysis activation and apoptosis resilience. Here we identify that K63-linked ubiquitination by HectH9 regulates the mitochondrial localization and function of HK2. Through stable isotope tracer approach and functional metabolic analyses, we show that HectH9 deficiency impedes tumor glucose metabolism and growth by HK2 inhibition. The HectH9/HK2 pathway regulates cancer stem cell (CSC) expansion and CSC-associated chemoresistance. Histological analyses show that HectH9 expression is upregulated and correlated with disease progression in prostate cancer. This work uncovers that HectH9 is a novel regulator of HK2 and cancer metabolism. Targeting HectH9 represents an effective strategy to achieve long-term tumor remission by concomitantly disrupting glycolysis and inducing apoptosis.}, language = {en} } @article{BaluapuriHofstetterDudvarskiStankovicetal.2019, author = {Baluapuri, Apoorva and Hofstetter, Julia and Dudvarski Stankovic, Nevenka and Endres, Theresa and Bhandare, Pranjali and Vos, Seychelle Monique and Adhikari, Bikash and Schwarz, Jessica Denise and Narain, Ashwin and Vogt, Markus and Wang, Shuang-Yan and D{\"u}ster, Robert and Jung, Lisa Anna and Vanselow, Jens Thorsten and Wiegering, Armin and Geyer, Matthias and Maric, Hans Michael and Gallant, Peter and Walz, Susanne and Schlosser, Andreas and Cramer, Patrick and Eilers, Martin and Wolf, Elmar}, title = {MYC Recruits SPT5 to RNA Polymerase II to Promote Processive Transcription Elongation}, series = {Molecular Cell}, volume = {74}, journal = {Molecular Cell}, doi = {10.1016/j.molcel.2019.02.031}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-221438}, pages = {674-687}, year = {2019}, abstract = {The MYC oncoprotein binds to promoter-proximal regions of virtually all transcribed genes and enhances RNA polymerase II (Pol II) function, but its precise mode of action is poorly understood. Using mass spectrometry of both MYC and Pol II complexes, we show here that MYC controls the assembly of Pol II with a small set of transcription elongation factors that includes SPT5, a subunit of the elongation factor DSIF. MYC directly binds SPT5, recruits SPT5 to promoters, and enables the CDK7-dependent transfer of SPT5 onto Pol II. Consistent with known functions of SPT5, MYC is required for fast and processive transcription elongation. Intriguingly, the high levels of MYC that are expressed in tumors sequester SPT5 into non-functional complexes, thereby decreasing the expression of growth-suppressive genes. Altogether, these results argue that MYC controls the productive assembly of processive Pol II elongation complexes and provide insight into how oncogenic levels of MYC permit uncontrolled cellular growth.}, language = {en} } @article{ChenGehringerLorenz2018, author = {Chen, Dan and Gehringer, Matthias and Lorenz, Sonja}, title = {Developing Small-Molecule Inhibitors of HECT-Type Ubiquitin Ligases for Therapeutic Applications: Challenges and Opportunities}, series = {ChemBioChem}, volume = {19}, journal = {ChemBioChem}, doi = {10.1002/cbic.201800321}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-222412}, pages = {2123-2135}, year = {2018}, abstract = {The ubiquitin system regulates countless physiological and disease-associated processes and has emerged as an attractive entryway for therapeutic efforts. With over 600 members in the human proteome, ubiquitin ligases are the most diverse class of ubiquitylation enzymes and pivotal in encoding specificity in ubiquitin signaling. Although considerable progress has been made in the identification of small molecules targeting RING ligases, relatively little is known about the "druggability" of HECT (homologous to E6AP C terminus) ligases, many of which are critically implicated in human pathologies. A major obstacle to optimizing the few available ligands is our incomplete understanding of their inhibitory mechanisms and the structural basis of catalysis in HECT ligases. Here, we survey recent approaches to manipulate the activities of HECT ligases with small molecules to showcase the particular challenges and opportunities these enzymes hold as therapeutic targets.}, language = {en} } @phdthesis{Nair2024, author = {Nair, Radhika Karal}, title = {Structural and biochemical characterization of USP28 inhibition by small molecule inhibitors}, doi = {10.25972/OPUS-28174}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-281742}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2024}, abstract = {Ubiquitination is an important post-translational modification that maintains cellular homeostasis by regulating various biological processes. Deubiquitinases (DUBs) are enzymes that reverse the ubiquitination process by catalyzing the removal of ubiquitin from a substrate. Abnormal expression or function of DUBs is often associated with the onset and progression of various diseases, including cancer. Ubiquitin specific proteases (USPs), which constitute the largest family of DUBs in humans, have become the center of interest as potential targets in cancer therapy as many of them display increased activity or are overexpressed in a range of malignant tumors or the tumor microenvironment. Two related members of the USP family, USP28 and USP25, share high sequence identities but play diverse biological roles. USP28 regulates cell proliferation, oncogenesis, DNA damage repair and apoptosis, whereas USP25 is involved in the anti-viral response, innate immunity and ER-associated degradation in addition to carcinogenesis. USP28 and USP25 also exhibit different oligomeric states - while USP28 is a constitutively active dimer, USP25 assumes an auto-inhibited tetrameric structure. The catalytic domains of both USP28 and USP25 comprise the canonical, globular USP-domain but contain an additional, extended insertion site called USP25/28 catalytic domain inserted domain (UCID) that mediates oligomerization of the proteins. Disruption of the USP25 tetramer leads to the formation of an activated dimeric protein. However, it is still not clear what triggers its activation. Due to their role in maintaining and stabilizing numerous oncoproteins, USP28 and USP25 have emerged as interesting candidates for anti-cancer therapy. Recent advances in small-molecular inhibitor development have led to the discovery of relatively potent inhibitors of USP28 and USP25. This thesis focuses on the structural elucidation of USP28 and the biochemical characterization of USP28/USP25, both in complex with representatives of three out of the eight compound classes reported as USP28/USP25-specific inhibitors. The crystal structures of USP28 in complex with the AZ compounds, Vismodegib and FT206 reveal that all three inhibitor classes bind into the same allosteric pocket distant from the catalytic center, located between the palm and the thumb subdomains (the S1-site). Intriguingly, this binding pocket is identical to the UCID-tip binding interface in the USP25 tetramer, rendering the protein in a locked, inactive conformation. Formation of the binding pocket in USP28 requires a shift in the helix α5, which induces conformational changes and local distortion of the binding channel that typically accommodates the C-terminal tail of Ubiquitin, thus preventing catalysis and abrogating USP28 activity. The key residues of the USP28-inhibitor binding pocket are highly conserved in USP25. Mutagenesis studies of these residues accompanied by biochemical and biophysical assays confirm the proposed mechanism of inhibition and similar binding to USP25. This work provides valuable insights into the inhibition mechanism of the small molecule compounds specifically for the DUBs USP28 and USP25. The USP28-inhibitor complex structures offer a framework to develop more specific and potent inhibitors.}, subject = {Unique Selling Proposition}, language = {en} } @article{AngayFriedrichPinneckeretal.2018, author = {Angay, Oguzhan and Friedrich, Mike and Pinnecker, J{\"u}rgen and Hintzsche, Henning and Stopper, Helga and Hempel, Klaus and Heinze, Katrin G.}, title = {Image-based modeling and scoring of Howell-Jolly Bodies in human erythrocytes}, series = {Cytometry Part A}, volume = {93}, journal = {Cytometry Part A}, doi = {10.1002/cyto.a.23123}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-221140}, pages = {305-313}, year = {2018}, abstract = {The spleen selectively removes cells with intracellular inclusions, for example, detached nuclear fragments in circulating erythrocytes, called Howell-Jolly Bodies (HJBs). With absent or deficient splenic function HJBs appear in the peripheral blood and can be used as a simple and non-invasive risk-indicator for fulminant potentially life-threatening infection after spleenectomy. However, it is still under debate whether counting of the rare HJBs is a reliable measure of splenic function. Investigating HJBs in premature erythrocytes from patients during radioiodine therapy gives about 10 thousand times higher HJB counts than in blood smears. However, we show that there is still the risk of false-positive results by unspecific nuclear remnants in the prepared samples that do not originate from HJBs, but from cell debris residing above or below the cell. Therefore, we present a method to improve accuracy of image-based tests that can be performed even in non-specialized medical institutions. We show how to selectively label HJB-like clusters in human blood samples and how to only count those that are undoubtedly inside the cell. We found a "critical distance" dcrit referring to a relative HJB-Cell distance that true HJBs do not exceed. To rule out false-positive counts we present a simple inside-outside-rule based on dcrit—a robust threshold that can be easily assessed by combining conventional 2D imaging and straight-forward image analysis. Besides data based on fluorescence imaging, simulations of randomly distributed HJB-like objects on realistically modelled cell objects demonstrate the risk and impact of biased counting in conventional analysis. © 2017 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of ISAC.}, language = {en} }