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Auswirkungen des Einsatzes des Zytokinadsorbers CytoSorb® bei kritisch kranken Patienten mit einer Störung der Mikro- und Makrozirkulation
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Exploring the roles of chloroplast envelope proteins in plant acclimation processes
Get PDFIn vascular plants, the chloroplast not only serves as the cellular site of photosynthesis but also houses the enzymatic machinery essential for numerous interwoven biochemical pathways central to plant metabolism. As the interface between plastid and cytosol, the chloroplast envelopes perform a range of critical functions including the facilitation of ionic and metabolic exchange and acting as a major site for lipid metabolism in plants. Changes in chloroplast metabolism is instrumental in plant acclimation to adverse environmental conditions. Correspondingly, proteins of the chloroplast envelope have been increasingly recognised for their roles in such processes, particularly cold acclimation.
While extensive efforts have illuminated the multifaceted nature of the chloroplast envelope and its potential role in cold acclimation, many of its constituent proteins remain to be characterised on the molecular level. In this work, artificial microRNA-based screens were conducted to probe the chloroplast outer envelope landscape, which led us to investigate the Chloroplast Lipid Remodelling Protein 23 (CLRP23) in more detail. Formerly known in published literature as Outer Envelope Protein 23 (OEP23), CLRP23 was originally identified in the chloroplast envelopes of Pea and assumed to localise to the outer envelope due to the absence of a predicted transit peptide. While subfractionation analysis and protease protection assays suggest an alternative localisation of CLRP23 to the chloroplast inner envelope, characterisation of mutants deficient in CLRP23 reveal significant impairments in photosynthesis and altered galactolipid responses under cold treatment.
This work predominantly explores the alternative function of CLRP23 as component of the chloroplast inner envelope and investigates its role in lipid remodelling processes during cold acclimation. Finally, eight envelope transporter candidates with as yet unknown molecular functions were identified from proteomic analysis of chloroplast envelopes and subjected to preliminary characterisation to provide a basis for future research.In Gefäßpflanzen fungiert der Chloroplast nicht nur als zellulärer Ort der Photosynthese, sondern beherbergt auch die enzymatische Maschinerie, die zahlreiche für den Pflanzenstoffwechsel zentrale biochemische Prozesse ermöglicht. Als Schnittstelle zwischen Plastid und Cytosol übernehmen die Chloroplastenhüllmembranen vielfältige Aufgaben, darunter den Austausch von Ionen und Metaboliten sowie eine zentrale Rolle im Lipidstoffwechsel. Veränderungen im Chloroplastenstoffwechsel sind entscheidend für die Anpassungsfähigkeit von Pflanzen an ungünstige Umweltbedingungen. Entsprechend rückt die Bedeutung der Proteine der Chloroplastenhüllmembran, insbesondere im Kontext der Kälteakklimatisierung, zunehmend in den Fokus der Forschung.
Obwohl die komplexe Beteiligung der Hüllmembranen an der Kälteanpassung bereits Gegenstand früherer Untersuchungen war, sind viele der beteiligten Proteine auf molekularer Ebene noch unzureichend charakterisiert. Im Rahmen dieser Arbeit wurden mikroRNA-basierte Screens eingesetzt, um die Proteinzusammensetzung der äußeren Chloroplastenhülle zu analysieren. Dabei rückte das Chloroplast Lipid Remodelling Protein 23 (CLRP23), früher als OEP23 (Outer Envelope Protein 23) bezeichnet, in den Mittelpunkt. CLRP23 wurde ursprünglich in den Chloroplastenhüllen von Erbsen entdeckt und aufgrund des Fehlens eines Transitpeptids der äußeren Hüllmembran zugeordnet. Subfraktionierungsanalysen und Protease-Assays deuten jedoch auf eine alternative Lokalisation in der inneren Hüllmembran hin. Die Charakterisierung von Mutanten, denen CLRP23 fehlt, zeigt deutliche Beeinträchtigungen der Photosynthese sowie veränderte Galaktolipidreaktionen unter Kälteeinfluss.
Diese Arbeit widmet sich daher vorrangig der Erforschung der alternativen Funktion von CLRP23 als Bestandteil der inneren Chloroplastenhülle und beleuchtet dessen Rolle bei Lipidumwandlungsprozessen während der Kälteakklimatisierung. Darüber hinaus wurden acht weitere Transporter-Kandidaten aus der Hüllmembran, deren molekulare Funktionen bislang unbekannt sind, mittels proteomischer Analysen identifiziert und einer ersten Charakterisierung unterzogen, um eine Grundlage für weiterführende Untersuchungen zu schaffen
Untersuchung der Anti-Müller-Hormon Konzentration bei präpubertären und pubertären Hunden und Katzen
Get PDFEvaluierung intramuskulär injizierbarer Anästhesiekombinationen beim Kaninchen unter Verwendung von S-Ketamin, Ketamin, Dexmedetomidin, Medetomidin, Midazolam und Butorphanol
Get PDFImpact of repetitive particle exposure and latent viral infection on lung immunity and diseases
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Transcription-Replication Conflicts and R-loops disrupt the local chromatin landscape in human model cell lines
Get PDFTranscription and DNA replication are fundamental nuclear processes that control the expression of genes and ensure the correct duplication of the genome, respectively. Tight regulation of these molecular machines is of paramount importance as both dysregulated transcription and replication are associated with numerous diseases including cancer. Importantly, both processes require extensive remodeling of the underlying chromatin template to perform their function. Transcription-replication conflicts (TRCs) are nuclear events during which transcription and replication collide on the same DNA template during the S-phase of the cell cycle. Despite their rare occurrence, TRCs are potent inducers of DNA damage, mutations, and genomic instability. Given that transcription and replication extensively remodel chromatin during their progression on the genome, one hypothesis suggests that TRC sites might be particularly vulnerable to chromatin and epigenome alterations that could provoke genome instability. In this work, I engineered an inducible TRC reporter system by genomically integrating an R-loop-prone sequence previously used for conflict induction and characterized the dynamic changes of the local chromatin structure inflicted by TRCs. Importantly, the new reporter system was not only able to induce chromosomal TRCs with high efficiency but also induced drastic local replication impairments, which coincided with an activation of the DNA damage response in a local but also global manner. TRC-inducing cells were also particularly sensitive to inhibition of the Ataxia Telangiectasia and Rad3 related (ATR), a crucial kinase of the replication stress response. Analyzing the impact of TRCs on chromatin organization, I found a striking loss of nucleosome occupancy at the activated TRC reporter that was highly dependent on the stability of the associated R-loops. Furthermore, I investigated numerous histone modifications for an association with TRCs and found an increase in H3K79 methylation specifically at the R-loop forming TRC site. Through inhibition of H3K79 methylation writer enzyme disruptor of telomeric silencing-1-like (DOT1L), I showed that H3K79 methylation is actively deposited at TRC sites. Further, lack of DOT1L activity resulted in reduced transcriptional output and exacerbated DNA damage response, suggesting that deposition of this modification is required for effective transcription recovery and resolution of TRCs. Beyond the work on the reporter system, I characterized the potential of several oncogene overexpression cell lines to induce TRCs and identified CDC25 and CDC6 overexpression as potent disruptors of transcription-replication coordination. Ultimately, my work establishes a powerful new reporter system and cancer model cell lines to study TRC biology, while also uncovering novel chromatin dynamics at TRC sites and revealing a specific epigenetic modifier bookmarking TRCs, that are relevant to cancer and other diseases
Modern-day challenges in electricity markets
Get PDFHigh hopes are placed on the transformation of electricity systems and the electrification of carbon-intensive sectors to reduce greenhouse gas emissions and thereby mitigate climate change. At the same time, electricity prices should remain fair and affordable, as electricity is an omnipresent and essential good. This dissertation contributes to understanding how we can operate electricity markets in a way that prevents excessive pricing, minimizes environmental harm, and ensures resilient supply security in a world affected by climate change. I address these three challenges using simulation, numerical optimization, and econometric methods. The first essay develops improved approaches to approximate firms’ electricity production costs, thereby strengthening regulators’ ability to detect and prevent suspected market power abuse. I simulate how this enables more efficient markets, generating both welfare gains and welfare transfers. The second essay examines long-term trade-offs in jointly reducing carbon emissions and local air pollution from electricity generation. By linking damages and abatement costs of both emission types to specific generation technologies, I show how their mix can be optimized through complementary taxation. Finally, with increased occurrences of extreme weather events due to climate change, the third essay investigates the aftermath of a cold-spell. I demonstrate that experiencing extreme-weather-induced electricity outages induces households to invest in home electricity back-up systems but I also reveal notable socio-economic disparities in how strongly and how quickly communities adapt
Targeting antigens to phosphatidylserine triggers rapid T- and B-cell responses
Get PDFPhosphatidylserine (PS) is a phospholipid that is abundant in cell membranes. In live cells, PS is asymmetrically restrained to the inner leaflet of membrane. In dying cells, activated platelets and extracellular vesicles (EVs), PS is exposed on the membrane surface and it can be bound by PS-binding proteins, such as Milk fat globule epidermal growth factor 8 (Mfge8). In previous studies, we have established use of fluorescent Mfge8 to label and characterize EVs in vivo. Here in this study, we explored the possibility of using Mfge8 as an antigen carrier to load antigens onto PS+ EVs. PS- targeting antigens were created by conjugating antigens to Mfge8 or the tetramerized PS-binding C1 domains of Mfge8. We found that compared with non-targeting conventional antigens, PS-targeting antigens accumulated in the marginal zone of lymphoid follicles soon after injection. Hours later, they were transferred onto the follicular dendritic cell (FDC) network without the need of previous primary immunization. We measured the antigen-specific immune responses elicited by these PS-targeting antigens and found that germinal center (GC) B cell proliferation and somatic hypermutation were significantly enhanced. As a result, serum antigen specific IgG titers were significantly higher than mice immunized with conventional antigens, and antibody isotype switching was greatly accelerated. PS-targeting antigens also induced increased number of T follicular helper cells (Tfh cells) to support GC reaction, as well as more activated CD8 T cells that eliminated target cells more efficiently. Therefore, targeting antigens to PS promoted both B- and T- cell responses, which make it a promising novel vaccination platform