570 Biowissenschaften; Biologie
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Pancreatic ductal adenocarcinoma (PDAC), due to its genomic heterogeneity and lack of development of effective therapies, will become the second leading cause of cancer-related death within 10 years. Therefore, identifying novel targets that can predict response to specific treatments is a key goal to personalize pancreatic cancer therapy and improve survival. Given that the occurrence of oncogenic KRAS mutations is a characteristic event in PDAC leading to genome instability, a better understanding of the role of DNA repair mechanisms in this process is desirable. The aim of our study was to investigate the role of the error-prone DNA double strand breaks (DSBs) repair pathway, alt-EJ in the presence of KRAS G12D mutation in pancreatic cancer formation. Our findings showed that oncogenic KRAS contributes to the activation of the alt-EJ mechanism by increasing the expression of Polθ, Lig3 and Mre11, key components of alt-EJ in both mouse and human PDAC models. In addition, we demonstrated that alt-EJ has increased activity in DNA DSBs repair pathway in a mouse and human model of PDAC bearing KRAS G12D mutation. We further focused on estimating the impact of alt-EJ inactivation by polymerase theta (Polθ) deletion on pancreatic cancer development and survival in genetically engineered mouse models (GEMMs). Here, we described that although deficiency of Polθ resulted in delayed cancer progression and prolonged survival of experimental mice, it can lead to full-blown PDAC. Our study showed that disabling one component of the alt-EJ may be insufficient to fully suppress pancreatic cancer progression and a complete understanding of all alt-EJ factors and their involvement in DSB repair and oncogenesis is required.
Drainage has commonly been a pre-requisite for the productive use of peatlands. The biased focus on agriculture, forestry and peat extraction has long ignored the destructive effects of drainage and the successive degradation of ecosystem functions of wet peatlands. Accelerated by the climate crisis, the finite nature of drainage-based peatland use is increasingly recognised. Consequently, productive land use options for wet or rewetted peatlands (paludiculture) are required as sustainable alternatives. A wide range of paludiculture plants and options of biomass utilisation are identified as suitable and promising. Despite the growing interest, experiences with and research on the economic viability of paludiculture are still rare.
This thesis addresses the lack of knowledge on paludiculture in terms of practical feasibility, costs and benefits at the farm level, market prospects and framework conditions. I selected the two currently most advanced paludicultural practices in Europe: a) Harvesting natural reed beds as a traditional ‘low-input’ paludiculture, i. e. the utilisation of existing ‘wild’ vegetation stands; b) ‘Sphagnum farming’ as a novel ‘high-input’ paludiculture including stand establishment and water management required for the active transformation from drainage-based peatland use to paludiculture. In both cases, I investigate three different biomass utilisation avenues. This thesis adds to the fields of problem-driven sustainability and land-use science. Procedures and costs of paludiculture were studied in transdisciplinary research projects in close cooperation with practitioners. Due to the novelty of the topic, I put special emphasis on the triangulation of methods and data sources: pilot trials, field measurements, semi-structured expert interviews, structured questionnaires, secondary data from trade statistics and literature. To account for uncertainty related to costs and revenues, I conduct stochastic scenario analysis (Monte Carlo simulation) for the extended contribution margin accounting of harvesting reeds and sensitivity analysis for the investment appraisal of Sphagnum farming.
Paludiculture on fens: harvesting reeds
Paper I investigates harvesting procedures for reed-dominated (Phragmites australis) vegetation stands. In many European countries special-purpose tracked machinery is applied for large-scale conservation management and the commercial harvest of thatching reed. Stochastic scenario analysis reveals a wide range of possible economic outcomes (ca. € -1000 to € 1500 ha-1 a-1) and identifies material use of reed superior to its use as a source of energy. Winter harvest of high-quality thatching reed in bundles is the most profitable option. Winter harvest of bales for direct combustion is suitable for low-quality stands and has a limited risk of loss. In the case of summer harvest, revenues for green chaff for biogas production cannot cover harvesting costs but non-market income via subsidies and agri-environmental payments may ensure profitability. While biomass for energy generation is limited to a local market, thatching reed is traded as an international commodity. The market situation for thatching reed is investigated for Europe (Paper II) and Germany (Paper III). The major reed consuming countries in Western Europe (Netherlands, Germany, UK, Denmark) rely on imports of up to 85 % of the national consumption, with reed being imported from Eastern and Southern Europe and since 2005 also from China. The total market volume for reed for thatching in Northern Germany is estimated with 3 ± 0.8 million bundles of reed with a monetary value at sales prices of € 11.6 ± 2.8 million. Most of the thatchers (70 %) did not promote reed of regional origin to their customers due to insufficient availability in the first place and a lack in quality as second reason. The cultivation of reed in paludiculture may improve quantity and quality of domestic thatching reed. An area of 6000 ± 1600 ha with an average yield of 500 bundles per hectare would allow covering the current total demand of 3 million bundles of the German thatching reed market (Paper III).
Paludiculture on bogs: Sphagnum farming
Sphagnum farming provides an alternative to peatland degradation in two ways: Firstly, Sphagnum mosses can be cultivated as new agricultural crops on rewetted peatlands. Secondly, the produced Sphagnum biomass is a high-quality raw material suitable to replace peat in horticultural growing media (Paper V). Pilot trials have demonstrated the practical feasibility of establishing Sphagnum cultures on former bog grassland, cut-over bogs and mats floating on acidic waters bodies; Paper IV compares for the three types of production sites the specific procedures, costs and area potential in Germany. Water-based Sphagnum farming is not recommended for large-scale implementation due to highest establishment costs, major cultivation risks and limited area potential. For soil-based Sphagnum farming, the most important cost positions were Sphagnum shoots to set up pilots, investment for water management and regular weed management. Bog grassland has the highest area potential, i. e. 90,000 ha in NW Germany. Paper V assesses the profitability of Sphagnum farming on former bog grassland based on extrapolating five years of field experience data (establishment ņ management ņ harvest) to a total cultivation time of twenty years. Cultivating Sphagnum biomass as founder material for Sphagnum farming or restoration was profitable even in pessimistic scenarios with high costs, high bulk density and low yields. Selling Sphagnum for orchid production was economically viable in the case of medium to high yields with a low bulk density. Cost-covering prices for Sphagnum biomass substituting peat seem achievable if end consumers pay a surcharge of 10 % on the peat-free cultivated horticultural end-product. An area of 35,000 ha of Sphagnum farming suffices to meet the annual demand of the German growing media industry for slightly decomposed Sphagnum peat.
Framework conditions affecting feasibility of paludiculture
The relation of revenues from selling biomass to its production costs is an important piece of the paludiculture feasibility puzzle. Further aspects effecting the economic viability and competitiveness of paludiculture encompass the market demand, the availability of mature technology, legal restrictions, the eligibility for agricultural subsidies, a remuneration of external benefits and the opportunity costs of present farming activities (Paper I, V). Legal and policy regulations are of major importance for land use decisions on peatlands – both for keeping up drainage and for shifting to paludiculture.
Conclusion and Outlook
This thesis provides a first assessment of the costs and profitability of large-scale harvesting of reeds and Sphagnum farming based on real-life data. The paludicultural practices investigated may be a solution for a minor share of the more than 1 million ha of peatlands drained for agriculture in Germany. Future research should also address other biomass utilisation options and other crops. Large-scale pilots are required to improve technical maturity of procedures and machinery, gather reliable data to replace assumptions on costs and revenues and study long-term effects on economics and ecosystem services. The micro-economic perspective needs to be complemented by the societal perspective quantifying and monetising external effects of peatland restoration, paludiculture and drainage-based peatland use. There is a high need for intensified research, large-scale implementation and accelerated adaption of the policy and legal framework to develop paludiculture as an economically viable option for degraded peatlands.
VER155008 konkurriert als ATP-Analogon um die Bindung an HSP70 und agiert hierbei als
spezifischer Inhibitor dieses Hitzeschockproteins. Bisherige Studien konnten einen
zytotoxischen Effekt von VER155008 auf verschiedene Tumorentitäten zeigen, die
vielfältigen Wirkmechanismen bleiben bisher allerdings noch weitgehend ungeklärt.
Hitzeschockproteine (HSPs) sind molekulare Chaperone, sie vermitteln korrekte Faltung,
Stabilisierung, Transport und Abbau von Proteinen, regulieren Transkriptionsfaktoren und
können auf Zellsignalkaskaden Einfluss nehmen. Diverse Tumorentitäten, wie auch das
Prostatakarzinom (PCa) zeigen eine gesteigerte HSP-Expression. HSPs tragen durch
antiapoptotische Effekte zur Proliferation, Invasion und Metastasierung des Tumors bei und
können Resistenzmechanismen gegenüber Therapeutika im PCa vermitteln.
Diese Arbeit konnte zunächst einen wachstumshemmenden, konzentrationsabhängigen
Effekt des HSP70-Inhibitors VER155008 auf die PCa-Zelllinien PC-3 und LNCaP nachweisen.
Geeignete Wirkstoffkonzentrationen, um einen halbmaximalen inhibitorischen Effekt (IC50)
zu erzielen wurden in PC-3-Zellen bei 3μM und LNCaP-Zellen bei 10μM VER155008 ermittelt.
Anschließende Proteinanalysen zeigten eine Modulation der Expression verschiedener HSPs,
sowie des Androgenrezeptors (AR), einem zentralen Proliferationsfaktor des PCa, als
Reaktion auf die HSP70-Inhibition. Untersucht wurde die Expression von HSP27, HSP70,
HSP90α/ß, sowie der Co-Chaperone HSP40, HSP60 und HOP und des AR. Die Expression von
HSP90ß, dem Bindungspartner des AR im AR-Multi-Chaperonkomplex, sowie HOP, seinem
Co-Chaperon, wurde in beiden PCa-Zelllinien um bis zu 50% signifikant supprimiert.
Zusätzlich zeigt sich eine um bis zu 70% supprimierte Expression von HSP27 nach
VER155008-Behandlung beider PCa-Zelllinien im Vergleich zur Kontrolle. HSP27 ist ein
wichtiges zytoprotektives Chaperon, dessen vermehrte Expression mit Therapieresistenzen
gegenüber Docetaxel, sowie einer schlechten Prognose des PCa assoziiert wird. Es vermittelt
die Translokation des AR in den Zellkern und reguliert dadurch die proliferative Wirkung der
AR-Aktivierung. Die HSP70-Inhibierung zeigte zusätzlich eine signifikante Reduktion des AR
um 40% in LNCaP-Zellen.
VER155008 zeigt sich als effektiver Wachstumsinhibitor des Prostatakarzinoms, der sowohl
in der hormonsensitiven LNCaP-, als auch in der kastrationsresistenten PC-3-Zelllinie
antiproliferative Wirkung zeigt, die unter anderem durch eine Modulation der Expression
von Hitzeschockproteinen und des Androgenrezeptors vermittelt wird.
Infectious diseases remain a significant threat to the wellbeing of humans and animals
worldwide. Thus, infectious disease outbreaks should be investigated to understand the
emergence of these pathogens, leading to prevention and mitigation strategies for future
outbreaks. High-throughput sequencing (HTS) and bioinformatic analysis tools are reshaping
the surveillance of viral infectious diseases through genome-based outbreak investigations. In
particular, analyzing generic HTS datasets using a metagenomic analysis pipeline enable
simultaneous identification, characterization, and discovery of pathogens.
In this thesis, generic HTS datasets derived from the 2018-19 WNV epidemic and USUV
epizooty in Germany were evaluated using a unified pipeline for outbreak investigation and an
early warning system (EWS). This pipeline obtained 34 West Nile virus (WNV) whole-genome
sequences and detected several sequences of Usutu virus (USUV) and other potential
pathogens. A few WNV and USUV genome sequences were completed using targeted HTS
approaches. Phylogenetic and phylogeographic inferences, reconstructed using WNV wholegenome sequences, revealed that Germany experienced at least six WNV introduction events.
The majority of WNV German variants clustered into the so-called “Eastern German clade
(EGC),” consisting of variants derived from birds, mosquitoes, a horse, and human cases. The
progenitors of the EGC subclade probably circulated within Eastern Europe around 2011. These
flavivirus genome sequences also provided substantial evidence for the first reported cases of
WNV and USUV co-infection in birds. Phylogenetic inferences of USUV genome sequences
showed the further spread of the USUV lineage Africa 3 and might indicate the overwintering
of the USUV lineage Europe 2 in Germany. Among viral sequences reported in the EWS, Hedwig
virus (HEDV; a novel peribunyavirus) and Umatilla virus (UMAV; detected in Europe for the
first time) were investigated using genome characterization, molecular-based screening, and
virus cultivation since these viruses were suspected of causing co-infections in WNV-infected
birds. The EWS detected overall 8 HEDV-positive and 15 UMAV-positive birds in small sets of
samples, and UMAV could be propagated in a mosquito cell culture Future studies are necessary
to investigate the pathogenicity of these viruses and their role in the health of wild and captive
birds.
In conclusion, this study provided a proof-of-concept that the developed unified and
generic pipeline is an effective tool for outbreak investigation and pathogen discovery using the
same generic HTS datasets derived from outbreak and surveillance samples. Therefore, this
thesis recommends incorporating the unified pipeline in the key response to viral outbreaks to
enhance outbreak preparedness and response.
The soluble blood protein beta2-glycoprotein I (beta2GPI; 326 aa, MW: 48 kDa, 5 domains) is one of the most abundant proteins in human serum and exhibits two main conformational states: the circular or closed conformation, where the first domain (DI) is bound to the last domain (DV) of the protein, and the linear or open conformation. The defined physiological function of beta2GPI is still unknown, though several roles in pro- and anticoagulation as well as oxidative stress protection were discovered. The open form is considered to play a crucial role in the systemic autoimmune disease antiphospholipid syndrome (APS), which is an acquired thrombophilia characterized by recurring thrombotic events and pregnancy morbidity. Beta2GPI constitutes the main antigen for APS autoantibodies which are supposed to bind a cryptic epitope within DI after a conformational change from closed to open form. However, the pathophysiological mechanism of APS is poorly understood. Therefore, investigating the structural dynamics of this protein in relation to its antigenicity is of high interest.
Post-translational modifications (PTM) of a target protein often show an impact on the formation of neoantigens, for instance in the autoimmune-mediated diseases type 1 diabetes mellitus, rheumatoid arthritis, or multiple sclerosis. Such modified antigens may lead to immune tolerance breakdown as they are unknown to the immune system, which therefore could mistakes self for non-self proteins. In this thesis, two frequently occurring PTM were introduced to beta2GPI and their impact on the protein conformation was studied by biophysical tools (i.e. atomic force microscopy (AFM) imaging, transmission electron microscopy (TEM) imaging, dynamic light scattering (DLS), and circular dichroism (CD) spectroscopy). In order to examine immunopathophysiological relevance of these PTM, additional insights were gained from ELISA which was used to examine binding of anti-DI autoantibodies purified from the blood of APS patients to the modified beta2GPI species.
A characteristic feature of beta2GPI is the high content of lysine residues. Previously, opening of beta2GPI was found to be triggered by a drastic shift in pH and salt concentration (pH 11.5 and 1.15 M NaCl), which results in reversible uncharging of the lysine residues. The aim of this study was to investigate the beta2GPI conformation after lysine acetylation as a model system, to elucidate the role of lysine residues on the conformational dynamics of this protein, and to examine anti-DI autoantibody binding to both the untreated as well as acetylated species.
A strategy to permanently open up the closed form under physiological conditions by chemical acetylation of lysine residues utilizing the sensitive acetylation agent acetic acid N-hydroxysuccinimide ester (NHS-Ac) was established. Complete and specific lysine acetylation was verified by quantification of primary amines exerting a fluoraldehyde o-phthaldialdehyde (OPA) reagent assay, as well as by native PAGE and western blot analysis with an anti-acetylated lysine antibody. Beta2GPI acetylation revealed a partial opening of beta2GPI molecules. Compared to untreated, i.e. native beta2GPI which exhibited 93% of the molecules in closed and 7% in open form, complete lysine residue acetylation generated 39% of beta2GPI in closed and 61% in open conformation as shown by AFM high-resolution imaging. pH 11.5-treated beta2GPI was used as a reference in the applied methods and revealed 38% of the protein in closed and 62% in open conformation. Thus, a significant shift in beta2GPI conformation occurred upon lysine residue acetylation as well as basic pH-treatment. The data indicate that lysine residue acetylation destabilizes the closed form, leading to a facilitated opening of the structure. The closed conformation might be predominantly stabilized by electrostatic interactions of lysine residues, which potentially control the conformational dynamics of this glycoprotein. ELISA confirmed that anti-DI autoantibodies do not bind to untreated (closed) beta2GPI. Although acetylated beta2GPI was shown to have a substantial portion of open proteins, no binding of anti-DI autoantibodies to the acetylated species was found either. Hence, acetylated lysine residues may disrupt the immunorelevant epitope in DI which prevents antibody binding. This finding reveals a new hint for epitope organization. However, further detailed epitope mapping has to be performed.
Beta2GPI carries two structural disulfide bonds per domain, whereas an additional disulfide bond Cys288/Cys326 is located at the C-terminus of DV near the putative contact interface of DI and DV in the closed conformation. It was previously shown that beta2GPI is a substrate of thiol oxidoreductases, including human thioredoxin-1 (Trx-1) generating different redox states of disulfide bond Cys288/Cys326, which might serve as a scavenger in oxidative stress protection in the blood stream. In APS patients, anti-DI antibody titers as well as an enhanced risk for thrombotic events are associated with an increase in the oxidized state of the protein. Hitherto, no structural study has been performed in order to prove a correlation of the redox state and the conformation of beta2GPI. Therefore, investigations of beta2GPI conformation in different redox states of disulfide bond Cys288/Cys326 were carried out. In addition, binding of anti-DI autoantibodies to the untreated (native) as well as reduced protein should be explored.
At first, cysteine residues of untreated, i.e. native beta2GPI were confirmed to be completely in oxidized state using Ellman’s reagent assay and the absence of binding of a thiol-specific agent. Statistical analyses of AFM images revealed that untreated beta2GPI was mainly in closed conformation (80% in closed and 20% in open conformation) in the respective system. In this study, an optimized protocol for enzymatic reduction of disulfide bond Cys288/Cys326 was established. The agent TCEP was used to reduce human Trx-1, which in turn enzymatically reduced beta2GPI. To block reoxidation of free thiols and to facilitate product analysis, cysteine residues of reduced beta2GPI were subsequently labeled with the sensitive and thiol-specific reagent 3-(N-maleimidopropionyl) biocytin (MPB), which carries a biotin function. During protocol establishment, complete and specific reduction of disulfide bond Cys288/Cys326 was confirmed utilizing SDS-PAGE, streptavidin western blot, mass spectrometry (MS) analyses, and a biotin quantification assay. Protocol improvements constituted a homogenous system with remarkable decrease of unspecifically reduced beta2GPI. Upon beta2GPI reduction, AFM imaging revealed no significant shift in protein conformation (75% in closed and 25% in open conformation). These results were qualitatively confirmed by TEM imaging. Therefore, reduction of beta2GPI disulfide bond Cys288/Cys326 did not result in a major conformational change of the protein. Upon in vitro reduction, the closed form is still the main conformation and a direct correlation of beta2GPI redox state and conformation must be refused. Furthermore, beta2GPI reduction led to a strong and statistically highly significant increase in anti-DI autoantibody binding compared to untreated beta2GPI. Thus, the reduced form might be the antigenic form of the protein. In contrast to previous knowledge, these findings suggest that anti-DI autoantibodies may also bind to the closed conformation under certain conditions. Hypothetically, reduction of beta2GPI could induce a minor structural change in DV that might facilitate the binding of APS autoantibodies.
Overall, this study reveals that PTM of beta2GPI may lead to a critical level of destabilization of the closed conformation (as in the case of acetylated beta2GPI) or significantly increase the binding of APS autoantibodies (as in the case of reduced beta2GPI), both of which could have a large impact on APS disease. However, further investigations are necessary to put these new findings in the context of APS immunopathophysiology.
Haloalkanes are serious environmental pollutants commonly employed as pesticides, herbicides, and chemical warfare agents. Although haloalkane production is performed mostly in the chemical industry, it also occurs naturally, mostly enzymatically (halide methyltransferases and haloperoxidases). Elimination of toxic haloalkanes is very important and using haloalkane dehalogenases is a promising and environmentally friendly way to achieve this.[53] Therefore, assays are needed for detecting dehalogenase activity either to find new enzymes or to generate laboratory-evolved variants. In this thesis, a new assay for dehalogenase activity was developed based on halide detection. In this assay halides, as dehalogenase products, are oxidized under mild conditions using the vanadium-dependent chloroperoxidase from Curvularia inaequalis, forming hypohalous acids that are detected using aminophenyl fluorescein.[53] This new halide oxidation assay is much more sensitive than previously known assays, with detection limits of 20 nM for bromide and 1 μM for chloride and iodide. Validation of the assay was done by comparison to a well-established GC-MS method in terms of determining the specific activities of two dehalogenases towards five common substrates (Figure 5).
The HOX assay was modified for iodide-specific detection by using two other dyes, o-phenylenediamine (OPD) and 3,3′,5,5′-tetramethylbenzidine (TBM), instead of APF. Also, selective bromide detection in the presence of the common contaminant chloride was achieved by using a bromoperoxidase. Since the assay relies on halide detection, it is possible to use it for other halide-producing enzymes (Section 8.1). For example, the TMB-modified version was used for screening of halide methyltransferase libraries towards various alkyl iodides.[166] Furthermore, the HOX assay was used to identify promiscuous dehalogenase activity of the epoxide hydrolase CorEH from Corynebacterium sp. C12.[105]
Moreover, studies showed that the HOX assay could be used with in-vitro synthesized protein. Selected dehalogenases, DhlA, DhaA, and DmmA, were synthesized in vitro and used in the assay; the product formation was also validated using GC-MS. In conclusion, the HOX assay can be used with purified protein, whole cells, or in vitro synthesized proteins.
The HOX assay application in microfluidic droplets was investigated since an ultra-high-throughput assay for haloalkane dehalogenases is needed. This investigation showed no leakage of reaction components and products in the short term (~24 h), based on tests done on water-in-oil droplets generated by microfluidic chips. Even though 20 μM droplets were not working, 70 μM droplets were successful for assay implementation. Since the Damborsky group in Brno (CZ) and the deMello group in Zürich (CH), have large dehalogenase libraries and more experience in microfluidics, respectively, we collaborated with these groups to finalize implementation of the assay in an ultrahigh-throughput format. Since the studies are ongoing, final results could not yet be shown in this thesis. However, it can be noted that the issue with 20 μm droplets has been sorted out since our collaborators in Brno noticed that the low fluorescence of the droplets is actually caused by excessive accumulation of fluorescein, which is self-quenching, resulting in low fluorescence once the concentration exceeds 1 μM. By lowering the APF concentration they could optimize the maximum amount of fluorescein formed, and a mutant library has now been successfully screened by our collaborators at the ETH. The last topic of the thesis was an investigation of converting an epoxide hydrolase into a haloalkane dehalogenase. These studies focused on increasing the minor dehalogenase activity of two previously identified epoxide hydrolase (Cif) variants. These Cif variants hardly led to soluble proteins, the PROSS algorithm was used to increase soluble expression. New variants of Cif were generated using a 3DM analysis and the PROSS[164] design. The activities of these variants were determined with the newly developed HOX assay in a whole-cell format. Cif23 E153N-H269D and the PROSS D7 E153N-H269D variant, were found being active against 1,2-dibromoethane. Since the determination of enzyme concentration was hard to measure due to the expression/purification problem, specific activities could not be determined. To solve this problem, a HiBiT-tag was added to the selected variants for determining soluble expression. However, the planned studies could not be completed because of a lack of time and will form the basis for a future study.
Im Rahmen dieser Dissertation wurden die antimikrobiellen Effekte der Phytopharmaka
BNO 101 und Myrtol stand. auf Staphylococcus aureus direkt miteinander verglichen. Für
BNO 101 umfassten die Untersuchungen Wachstumsexperimente mit Messungen der
Optischen Dichte und Experimente zur CFU-Bestimmung. In keinem dieser Experimente
konnten antimikrobielle Effekte auf S. aureus unter Behandlung gezeigt werden. Für Myrtol
stand. wurden Wachstumsexperimente analog durchgeführt. Hierbei konnte ein deutlicher
bakteriostatischer Effekt auf S. aureus und verglichen mit BNO 101 eine höhere Wirksamkeit
nachgewiesen werden.
Unter der Gesamtkonzentration von 0,25% Myrtol stand. liegen die Überlebensraten der
Bakterien 4 h bis 24 h nach Behandlung bei unter 40% im Vergleich zu der Kontrolle. Um
Ursachen für die antibakteriellen Effekte zu finden, wurden die Zellen mittels
Rasterelektronenmikroskopie morphologisch zu verschiedenen Zeitpunkten nach Behandlung
untersucht und eine Myrtol stand.-spezifische Volumenzunahme von bis zu 69% ermittelt.
Zusätzlich wurden Proteinproben der Zellen mittels 2D-DIGE aufgetrennt. Hierbei wurden
separat intrazellulär 1223 sowie extrazellulär 610 Proteinspots detektiert und miteinander
verglichen. Durch Behandlung mit 0,25% Myrtol stand. wurde das S. aureus Proteom über den
gesamten Messzeitraum von 24 h nach Behandlung massiv verändert. Mittels
anschließendem tryptischen Verdau und Massenspektrometrie (LC-MS) signifikant
veränderter Spots, konnte eine Vielzahl von Proteinen identifiziert und davon 54 verschiedene
Proteine einzelnen Stoffwechselwegen durch Datenbankabgleich und Literaturrecherche
zugeordnet werden. Bemerkenswert ist die deutliche Reduktion der Virulenzfaktoren des
Bakteriums durch Myrtol stand. Behandlung. Unter anderem konnten für Superantigen Enterotoxine, Leukotoxine, Hämolysine und Serine-Proteasen und den Genregulator Agr
deutlich verminderte Proteinmengen nach Behandlung gemessen werden. Die veränderten
Proteinmengen sind hierbei sowohl auf eine Umverteilung der Proteine zwischen den
Zellkompartimenten, als auch auf deutliche Regulation in der Proteinbiosynthese
zurückzuführen. Neben den Virulenzfaktoren ließen sich bspw. auch zahlreiche Enzyme der
Zellwand- und Zellmembransynthese sowie des Energiemetabolismus mit deutlich
veränderten Proteinmengen nachweisen, die für das Überleben der Bakterienzellen kritisch
sind. Mittels Direktverdau und nachfolgender LC-MS der Proteinproben wurden die
Ergebnisse bestätigt und weitere regulierte Proteine identifiziert.
Im Rahmen dieser Dissertation konnten antimikrobielle Effekte von Myrtol stand. auf
Staphylococcus aureus nachgewiesen und deren Ursachen aufgezeigt werden. Die
ausführlichen Proteinanalysen nach Behandlung mit Myrtol stand. lassen auf eine starke
verminderte Virulenz des Bakteriums schließen. Angesichts des Bedarfs an zielgerichteten
Therapieverfahren entsprechend der Phänotypen von CRS und ABRS, bietet die systemische
Gabe von Myrtol stand. hier eine kausale Therapieoption. Die zusätzliche Möglichkeit einer
topischen Anwendungsform kann angesichts der hier gezeigten Wirkungen eine
vielversprechende Behandlungsmaßnahme sein und sollte Ziel klinischer Untersuchungen
werden
The development of the two main types of diabetes mellitus, type 1 and type 2 (T1D, T2D), is closely associated with the formation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in insulin-secreting pancreatic β-cells. In T1D, β-cell death
is triggered by proinflammatory cytokines, which mainly lead to the formation of ROS
in mitochondria and RNS in the cytosol. Pancreatic β-cells are extraordinarily sensitive
to oxidative stress due to their low glutathione peroxidase and catalase expression.
Thus, hydrogen peroxide (H2O2) cannot be detoxified, neither sufficiently, nor rapidly.
H2O2 itself is a rather weakly reactive ROS but can react in the Fenton reaction to form
highly reactive hydroxyl radicals (●OH), that can damage cells in a variety of ways and
induce cell death. The cell and its organelles are bounded by biological membranes
that differ in their permeability to H2O2. Aquaporins (AQPs) are water-transporting
transmembrane proteins, and some isoforms have been shown to facilitate a bidirectional transport of H2O2 across cellular membranes in addition to water. The role of
AQP8 was investigated in an insulin-producing cell model by stably overexpressing
AQP8 (AQP8↑) and by a CRISPR/Cas9-mediated AQP8 knockout. However, AQP8
proved to be an essential protein for the viability of the insulin-producing RINm5F cells, and so we established a tet-on-regulated AQP8 knockdown (AQP8 KD). Our results highlight that AQP8 is involved in H2O2 transport across the plasma and mitochondrial membranes, and that AQP8 expression gets upregulated by proinflammatory cytokines (in vitro) and in an acutely diabetic rat model (in vivo). Furthermore, it was shown that the increased proinflammatory cytokine toxicity is due to enhanced mitochondrial oxidative stress, because H2O2 cannot be efficiently transported in AQP8 KD cells and ●OH
are increasingly generated. Caspase activity then raises, and apoptosis is increasingly
induced coupled with a proportion of ferroptosis-mediated cell death because of a concomitant decrease in nitric oxide (NO●) concentration. In conclusion, AQP8 is localized in the plasma and mitochondrial membrane of insulin-producing RINm5F cells, where it is involved in H2O2 transport. In T1D, AQP8 plays an important role in the transport of H2O2 from the mitochondrial matrix to the cytosol so that the concentration is lowered in the mitochondria. This wider distribution of H2O2 may ease the inactivation of H2O2.
Die akute Pankreatitis ist durch eine vorzeitige Aktivierung von Verdauungsenzymen noch innerhalb der Azinuszellen gekennzeichnet. Die lysosomale Hydrolase Cathepsin B (CTSB) spielt hierbei eine entscheidende Rolle, indem sie Trypsinogen zu Trypsin aktiviert. Für die Trypsinogenaktivierung durch CTSB ist eine Co-Lokalisierung beider Enzyme innerhalb desselben subzellulären Kompartiments erforderlich. Ziel dieser Arbeit war es, die Regulation der CTSB-Aktivität durch den Cysteinprotease-Inhibitor Cystatin C im Verlauf der akuten und chronischen Pankreatitis näher zu untersuchen.
Subzelluläre Fraktionierungsexperimente zeigten eine deutliche Lokalisation von Cystatin C und aktiven Cathepsin B im sekretorischen Kompartiment muriner Azinuszellen. Immunofluoreszenzfärbungen zeigten ebenfalls, dass Cystatin C zusammen mit der pankreatischen Amylase im sekretorischen Kompartiment von Azinuszellen lokalisiert ist. Auch in humanen Probenmaterial konnten wir zeigen, dass Cystatin C im sekretorischen Kompartiment lokalisiert ist und auch sekretiert wird. Experimente mit rekombinanten Proteinen zeigten eine deutliche pH-abhängige inhibitorische Wirkung von Cystatin C auf Cathepsin B. Unter sauren pH Bedingungen dimerisiert Cystatin C und ist somit nicht mehr in der Lage die Aktivität von CTSB zu inhibieren. Weiterhin konnten wir zeigen, dass aktives Trypsin Cystatin C prozessiert. Bei dieser Spaltung entsteht ein Cystatin C-Fragment, welches nicht mehr in der Lage ist, CTSB zu inhibieren, sondern vielmehr die auto-inhibitorische Kapazität von Cathepsin B unterbindet und somit die Aktivität stabilisiert. Neben Cystatin C wird in Azinuszellen auch Cystatin B exprimiert, ein weiterer Inhibitor der Cystein-Proteasen. Im Gegensatz zu Cystatin C ist Cystatin B exklusiv im cytosolischen Kompartiment der Azinuszelle lokalisiert. Dies ist wahrscheinlich ein Schutzmechanismus, welcher die Zelle vor einer cytosolischen Cathepsin-Aktivität schützen soll. Die genetische Deletion von Cystatin C im Mausmodell der akuten Pankreatitis führte zu einer erhöhten Aktivität sekretorischer Proteasen in Azinuszellen, sowie im Gesamthomogenat und in subzellulären Fraktionen. Dementsprechend zeigte sich auch ein deutlich erhöhter Schweregrad in der akuten und chronischen Pankreatitis.
Unsere Experimente lassen vermuten, dass die Aktivität von Cathepsin B unter physiologischen Bedingungen durch Cystatin C unterbunden wird, um so eine verfrühte Aktivierung des Trypsinogens zu verhindern. Im Verlauf der Pankreatitis wird dieser protektive Mechanismus jedoch überwunden. Die Aktivität von Cathepsin B steigt deutlich in der schweren Zymogengranula-Fraktion an, trotz der Präsenz von Cystatin C.
Zusammenfassend lassen unsere Ergebnisse vermuten, dass prozessiertes (aktives) Cathepsin B selbst unter physiologischen Bedingungen im sekretorischen Kompartiment von Azinuszellen bereits vorhanden ist. Seine Aktivität wird dort durch Cystatin C inhibiert, wodurch eine vorzeitige, durch CTSB induzierte Trypsinogenaktivierung verhindert wird. Die Ansäuerung der sekretorischen Vesikel, wie bei der Pankreatitis, verringert die CTSB-Hemmung durch Cystatin C, während es gleichzeitig zu einer Cystatin C-Degradation durch Trypsin kommt. Dies ermöglicht eine verlängerte und pH-unempfindliche Protease-Aktivierung über CTSB in der Anfangsphase der Pankreatitis. Cystatin C spielt somit eine wesentliche Rolle für die Regulation der CTSB-Aktivität im sekretorischen Kompartiment von Azinuszellen und stellt damit einen entscheidenden pathophysiologisch relevanten Mechanismus für die akute und chronische Pankreatitis dar.
Analysis and Reduction of Cellular Heterogeneity in Strain Optimization of Bacillus licheniformis
(2021)
Bacillus species invest substantial resources in inherent cellular processes for pre-adaptation to environmental changes, many of which are dispensable in the controlled environment of industrial bioprocesses. The underlying physiological mechanisms are well characterized in B. subtilis, but only little is known about these processes in the closely related B. licheniformis. Moreover, experimental conditions in previous studies differ from industrial settings in most parameters, foremost in batch cultures or plate-based analysis over fed-batch processes. In this thesis, cellular heterogeneity was analyzed in B. licheniformis in optimized, nutrient-rich media in batch and fed-batch cultivations. Systematic inactivation of genes involved in biofilm formation and synthesis of the flagellar apparatus or global regulators thereof resulted in higher protein production and provided new insights into biofilm formation and cellular heterogeneity in this strain.