TY - JOUR A1 - Raschig, Martina A1 - Ramírez‐Zavala, Bernardo A1 - Wiest, Johannes A1 - Saedtler, Marco A1 - Gutmann, Marcus A1 - Holzgrabe, Ulrike A1 - Morschhäuser, Joachim A1 - Meinel, Lorenz T1 - Azobenzene derivatives with activity against drug‐resistant Candida albicans and Candida auris JF - Archiv der Pharmazie N2 - Increasing resistance against antimycotic drugs challenges anti‐infective therapies today and contributes to the mortality of infections by drug‐resistant Candida species and strains. Therefore, novel antifungal agents are needed. A promising approach in developing new drugs is using naturally occurring molecules as lead structures. In this work, 4,4'‐dihydroxyazobenzene, a compound structurally related to antifungal stilbene derivatives and present in Agaricus xanthodermus (yellow stainer), served as a starting point for the synthesis of five azobenzene derivatives. These compounds prevented the growth of both fluconazole‐susceptible and fluconazole‐resistant Candida albicans and Candida auris strains. Further in vivo studies are required to confirm the potential therapeutic value of these compounds. KW - antifungal drug KW - azobenzenes KW - Candida auris KW - Candida albicans Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312295 VL - 356 IS - 2 ER - TY - JOUR A1 - Ramírez-Zavala, Bernardo A1 - Krüger, Ines A1 - Wollner, Andreas A1 - Schwanfelder, Sonja A1 - Morschhäuser, Joachim T1 - The Ypk1 protein kinase signaling pathway is rewired and not essential for viability in \(Candida\) \(albicans\) JF - PLoS Genetics N2 - Abstract Protein kinases are central components of almost all signaling pathways that control cellular activities. In the model organism Saccharomyces cerevisiae, the paralogous protein kinases Ypk1 and Ypk2, which control membrane lipid homeostasis, are essential for viability, and previous studies strongly indicated that this is also the case for their single ortholog Ypk1 in the pathogenic yeast Candida albicans. Here, using FLP-mediated inducible gene deletion, we reveal that C. albicans ypk1Δ mutants are viable but slow-growing, explaining prior failures to obtain null mutants. Phenotypic analyses of the mutants showed that the functions of Ypk1 in regulating sphingolipid biosynthesis and cell membrane lipid asymmetry are conserved, but the consequences of YPK1 deletion are milder than in S. cerevisiae. Mutational studies demonstrated that the highly conserved PDK1 phosphorylation site T548 in its activation loop is essential for Ypk1 function, whereas the TORC2 phosphorylation sites S687 and T705 at the C-terminus are important for Ypk1-dependent resistance to membrane stress. Unexpectedly, Pkh1, the single C. albicans orthologue of Pkh1/Pkh2, which mediate Ypk1 phosphorylation at the PDK1 site in S. cerevisiae, was not required for normal growth of C. albicans under nonstressed conditions, and Ypk1 phosphorylation at T548 was only slightly reduced in pkh1Δ mutants. We found that another protein kinase, Pkh3, whose ortholog in S. cerevisiae cannot substitute Pkh1/2, acts redundantly with Pkh1 to activate Ypk1 in C. albicans. No phenotypic effects were observed in cells lacking Pkh3 alone, but pkh1Δ pkh3Δ double mutants had a severe growth defect and Ypk1 phosphorylation at T548 was completely abolished. These results establish that Ypk1 is not essential for viability in C. albicans and that, despite its generally conserved function, the Ypk1 signaling pathway is rewired in this pathogenic yeast and includes a novel upstream kinase to activate Ypk1 by phosphorylation at the PDK1 site. Author summary Protein kinases are key components of cellular signaling pathways, and elucidating the specific roles of individual kinases is important to understand how organisms adapt to changes in their environment. The protein kinase Ypk1 is highly conserved in eukaryotic organisms and crucial for the maintenance of cell membrane homeostasis. It was previously thought that Ypk1 is essential for viability in the pathogenic yeast Candida albicans, as in the model organism Saccharomyces cerevisiae. Here, by using forced, inducible gene deletion, we reveal that C. albicans mutants lacking Ypk1 are viable but have a strong growth defect. The phenotypes of the mutants indicate that the known functions of Ypk1 are conserved in C. albicans, but loss of this kinase has less severe consequences than in S. cerevisiae. We also unravel the puzzling previous observation that C. albicans mutants lacking the Ypk1-activating kinase Pkh1, which is essential in S. cerevisiae, have no obvious growth defects. We show that the protein kinase Pkh3, which has not previously been implicated in the Ypk1 signaling pathway, can substitute Pkh1 and activate Ypk1 in C. albicans. These findings provide novel insights into this conserved signaling pathway and how it is rewired in a human-pathogenic fungus. KW - Ypk1 KW - protein kinase KW - signaling pathway KW - Candida albicans Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-350076 VL - 19 IS - 8 ER - TY - JOUR A1 - Luther, Christian H. A1 - Brandt, Philipp A1 - Vylkova, Slavena A1 - Dandekar, Thomas A1 - Müller, Tobias A1 - Dittrich, Marcus T1 - Integrated analysis of SR-like protein kinases Sky1 and Sky2 links signaling networks with transcriptional regulation in Candida albicans JF - Frontiers in Cellular and Infection Microbiology N2 - Fungal infections are a major global health burden where Candida albicans is among the most common fungal pathogen in humans and is a common cause of invasive candidiasis. Fungal phenotypes, such as those related to morphology, proliferation and virulence are mainly driven by gene expression, which is primarily regulated by kinase signaling cascades. Serine-arginine (SR) protein kinases are highly conserved among eukaryotes and are involved in major transcriptional processes in human and S. cerevisiae. Candida albicans harbors two SR protein kinases, while Sky2 is important for metabolic adaptation, Sky1 has similar functions as in S. cerevisiae. To investigate the role of these SR kinases for the regulation of transcriptional responses in C. albicans, we performed RNA sequencing of sky1Δ and sky2Δ and integrated a comprehensive phosphoproteome dataset of these mutants. Using a Systems Biology approach, we study transcriptional regulation in the context of kinase signaling networks. Transcriptomic enrichment analysis indicates that pathways involved in the regulation of gene expression are downregulated and mitochondrial processes are upregulated in sky1Δ. In sky2Δ, primarily metabolic processes are affected, especially for arginine, and we observed that arginine-induced hyphae formation is impaired in sky2Δ. In addition, our analysis identifies several transcription factors as potential drivers of the transcriptional response. Among these, a core set is shared between both kinase knockouts, but it appears to regulate different subsets of target genes. To elucidate these diverse regulatory patterns, we created network modules by integrating the data of site-specific protein phosphorylation and gene expression with kinase-substrate predictions and protein-protein interactions. These integrated signaling modules reveal shared parts but also highlight specific patterns characteristic for each kinase. Interestingly, the modules contain many proteins involved in fungal morphogenesis and stress response. Accordingly, experimental phenotyping shows a higher resistance to Hygromycin B for sky1Δ. Thus, our study demonstrates that a combination of computational approaches with integration of experimental data can offer a new systems biological perspective on the complex network of signaling and transcription. With that, the investigation of the interface between signaling and transcriptional regulation in C. albicans provides a deeper insight into how cellular mechanisms can shape the phenotype. KW - sky kinases KW - kinase signaling KW - network analysis KW - transcriptome KW - transcriptional regulation KW - phosphoproteome KW - Candida albicans Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-311771 SN - 2235-2988 VL - 13 ER - TY - JOUR A1 - Ramírez-Zavala, Bernardo A1 - Betsova, Darina A1 - Schwanfelder, Sonja A1 - Krüger, Ines A1 - Mottola, Austin A1 - Krüger, Thomas A1 - Kniemeyer, Olaf A1 - Brakhage, Axel A. A1 - Morschhäuser, Joachim T1 - Multiple phosphorylation sites regulate the activity of the repressor Mig1 in \(Candida\) \(albicans\) JF - mSphere N2 - ABSTRACT The highly conserved heterotrimeric protein kinase SNF1 is important for metabolic adaptations in the pathogenic yeast Candida albicans. A key function of SNF1 is to inactivate the repressor protein Mig1 and thereby allow the expression of genes that are required for the utilization of alternative carbon sources when the preferred carbon source, glucose, is absent or becomes limiting. However, how SNF1 controls Mig1 activity in C. albicans has remained elusive. Using a phosphoproteomics approach, we found that Mig1 is phosphorylated at multiple serine residues. Replacement of these serine residues by nonphosphorylatable alanine residues strongly increased the repressor activity of Mig1 in cells lacking a functional SNF1 complex, indicating that additional protein kinases are involved in the regulation of Mig1. Unlike wild-type Mig1, whose levels strongly decreased when the cells were grown on sucrose or glycerol instead of glucose, the levels of a mutant Mig1 protein lacking nine phosphorylation sites remained high under these conditions. Despite the increased protein levels and the absence of multiple phosphorylation sites, cells with a functional SNF1 complex could still sufficiently inhibit the hyperactive Mig1 to enable wild-type growth on alternative carbon sources. In line with this, phosphorylated forms of the mutant Mig1 were still detected in the presence and absence of a functional SNF1, demonstrating that Mig1 contains additional, unidentified phosphorylation sites and that downstream protein kinases are involved in the control of Mig1 activity by SNF1. IMPORTANCE The SNF1 protein kinase signaling pathway, which is highly conserved in eukaryotic cells, is important for metabolic adaptations in the pathogenic yeast Candida albicans. However, so far, it has remained elusive how SNF1 controls the activity of one of its main effectors, the repressor protein Mig1 that inhibits the expression of genes required for the utilization of alternative carbon sources when glucose is available. In this study, we have identified multiple phosphorylation sites in Mig1 that contribute to its inactivation. Mutation of these sites strongly increased Mig1 repressor activity in the absence of SNF1, but SNF1 could still sufficiently inhibit the hyperactive Mig1 to enable growth on alternative carbon sources. These findings reveal features of Mig1 that are important for controlling its repressor activity. Furthermore, they demonstrate that both SNF1 and additional protein kinases regulate Mig1 in this pathogenic yeast. KW - Candida albicans KW - SNF1 KW - Mig1 KW - protein kinase KW - signaling pathway Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-350060 VL - 8 IS - 6 ER - TY - JOUR A1 - Ramírez-Zavala, Bernardo A1 - Krüger, Ines A1 - Dunker, Christine A1 - Jacobsen, Ilse D. A1 - Morschhäuser, Joachim T1 - The protein kinase Ire1 has a Hac1-independent essential role in iron uptake and virulence of Candida albicans JF - PLoS Pathogens N2 - Protein kinases play central roles in virtually all signaling pathways that enable organisms to adapt to their environment. Microbial pathogens must cope with severely restricted iron availability in mammalian hosts to invade and establish themselves within infected tissues. To uncover protein kinase signaling pathways that are involved in the adaptation of the pathogenic yeast Candida albicans to iron limitation, we generated a comprehensive protein kinase deletion mutant library of a wild-type strain. Screening of this library revealed that the protein kinase Ire1, which has a conserved role in the response of eukaryotic cells to endoplasmic reticulum stress, is essential for growth of C. albicans under iron-limiting conditions. Ire1 was not necessary for the activity of the transcription factor Sef1, which regulates the response of the fungus to iron limitation, and Sef1 target genes that are induced by iron depletion were normally upregulated in ire1Δ mutants. Instead, Ire1 was required for proper localization of the high-affinity iron permease Ftr1 to the cell membrane. Intriguingly, iron limitation did not cause increased endoplasmic reticulum stress, and the transcription factor Hac1, which is activated by Ire1-mediated removal of the non-canonical intron in the HAC1 mRNA, was dispensable for Ftr1 localization to the cell membrane and growth under iron-limiting conditions. Nevertheless, expression of a pre-spliced HAC1 copy in ire1Δ mutants restored Ftr1 localization and rescued the growth defects of the mutants. Both ire1Δ and hac1Δ mutants were avirulent in a mouse model of systemic candidiasis, indicating that an appropriate response to endoplasmic reticulum stress is important for the virulence of C. albicans. However, the specific requirement of Ire1 for the functionality of the high-affinity iron permease Ftr1, a well-established virulence factor, even in the absence of endoplasmic reticulum stress uncovers a novel Hac1-independent essential role of Ire1 in iron acquisition and virulence of C. albicans. KW - protein kinase KW - Ire1 KW - Candida albicans Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-300225 VL - 18 IS - 2 ER - TY - THES A1 - Reuter-Weissenberger, Philipp T1 - The role of a fungal-specific transcription regulator on vacuolar biology and host interaction in \(Candida\) \(albicans\) T1 - Die Rolle eines pilzspezifischen Transkriptionsfaktors für die Vakuole und Wirtsinteraktion von \(Candida\) \(albicans\) N2 - Microorganisms that colonize the human body face large fluctuations in their surroundings. Therefore, those microbes developed sophisticated mechanisms that allow them to adapt their cell biology and maintain cellular homeostasis. One organelle vital to preserve cell physiology is the vacuole. The vacuole exhibits a wide range of functions and is able to adjust itself in response to both external and internal stimuli. Moreover, it plays an important role in host interaction and virulence in fungi such as Candida albicans. Despite this connection, only a few regulatory proteins have been described to modulate vacuolar biology in fungal pathogens. Furthermore, whether such regulation alters fungus-host interplay remains largely unknown. This thesis focuses on the characterization of ZCF8, a fungus-specific transcription regulator in the human-associated yeast C. albicans. To this end, I combined genome-wide protein-DNA interaction assays and gene expression analysis that identified genes regulated by Zcf8p. Fluorescence microscopy uncovered that several top targets of Zcf8p localize to the fungal vacuole. Moreover, deletion and overexpression of ZCF8 resulted in alterations in vacuolar morphology and in luminal pH and rendered the fungus resistant or susceptible to a vacuole-disturbing drug. Finally, in vitro adherence assays showed that Zcf8p modulates the attachment of C. albicans to human epithelial cells in a vacuole-dependent manner. Given those findings, I posit that the previously uncharacterized transcription regulator Zcf8p modulates fungal attachment to epithelial cells in a manner that depends on the status of the fungal vacuole. Furthermore, the results highlight that vacuolar physiology is a substantial factor influencing the physical interaction between Candida cells and mammalian mucosal surfaces. N2 - Mikroorganismen, die den Menschen besiedeln, sind großen Schwankungen in ihrer Umgebung ausgesetzt. Daher haben sie ausgeklügelte Mechanismen entwickelt, die es ihnen ermöglichen, ihre Zellbiologie anzupassen und die zelluläre Homöostase aufrechtzuerhalten. Eine für die Aufrechterhaltung der Zellphysiologie wichtige Organelle ist die Vakuole. Sie verfügt über ein breites Spektrum an Funktionen und ist in der Lage, auf externe und interne Stimuli zu reagieren. Außerdem spielt dieses Organell eine wichtige Rolle bei der Pilz-Wirt-Interaktion und somit für die Pathogenität von Pilzen wie Candida albicans. Trotz dieses Zusammenhangs wurden bisher nur wenige regulatorische Proteine beschrieben, welche die Biologie der Vakuolen in pathogenen Pilzen modulieren. Zudem ist weitgehend unbekannt, ob eine solche Regulierung das Zusammenspiel von Pilz und Wirt verändert. Diese Arbeit konzentriert sich auf die Charakterisierung von ZCF8, einem pilzspezifischen Transkriptionsregulator in der pathogenen Hefe C. albicans. Zu diesem Zweck wurden Protein-DNA-Interaktionstests und Genexpressionsanalysen kombiniert, um Gene zu identifizieren, die direkt von Zcf8p reguliert werden. Fluoreszenzmikroskopie zeigte zudem, dass mehrere der wichtigsten Ziele von Zcf8p in der Pilzvakuole lokalisiert sind. Darüber hinaus führte die Deletion und Überexpression von ZCF8 zu Veränderungen der Morphologie und des luminalen pH-Werts der Vakuole, und veränderte die Sensitivität des Pilzes gegenüber Stoffen, welche Funktionen der Vakuole beeinträchtigen. Schließlich deuteten In-vitro-Adhärenztests daraufhin, dass Zcf8p die Anheftung von C. albicans an menschliche Epithelzellen auf eine Weise moduliert, die abhängig von der Vakuole ist. Angesichts dieser Ergebnisse kann davon ausgegangen werden, dass der bisher unbekannte Transkriptionsregulator ZCF8 die Interaktion zwischen Pilz- und Epithelzellen des Wirts kontrolliert, und das auf eine Weise, die von der Pilzvakuole abhängig ist. Des Weiteren, unterstreichen die Ergebnisse, dass die Physiologie der Vakuole ein wesentlicher Faktor ist, welcher die Interaktion zwischen C. albicans und dem Wirt beeinflusst. KW - Vakuole KW - Transkriptionsfaktor KW - Candida albicans KW - vacuole KW - host colonization KW - Candida albicans KW - transcription regulator Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-259287 ER - TY - THES A1 - Popp, Christina T1 - Evolution of antifungal drug resistance of the human-pathogenic fungus \(Candida\) \(albicans\) T1 - Evolution der Antimykotikaresistenz im humanpathogenen Pilz \(Candida\) \(albicans\) N2 - Infections with the opportunistic yeast Candida albicans are frequently treated with the first-line drug fluconazole, which inhibits ergosterol biosynthesis. An alarming problem in clinics is the development of resistances against this azole, especially during long-term treatment of patients. Well-known resistance mechanisms include mutations in the zinc cluster transcription factors (ZnTFs) Mrr1 and Tac1, which cause an overexpression of efflux pump genes, and Upc2, which results in an overexpression of the drug target. C. albicans strains with such gain-of-function mutations (GOF) have an increased drug resistance conferring a selective advantage in the presence of the drug. It was previously shown that this advantage comes with a fitness defect in the absence of the drug. This was observed in different conditions and is presumably caused by a deregulated gene expression. One aim of the present study was to examine whether C. albicans can overcome the costs of drug resistance by further evolution. Therefore, the relative fitness of clinical isolates with one or a combination of different resistance mutations in Mrr1, Tac1 and/or Upc2 was analyzed in competition with the matched fluconazole-susceptible partner. Most fluconazole-resistant isolates had a decreased fitness in competition with their susceptible partner in vitro in rich medium. In contrast, three fluconazole-resistant strains with Mrr1 resistance mutations did not show a fitness defect in competition with their susceptible partner. In addition, the fitness of four selected clinical isolate pairs was examined in vivo in mouse models of gastrointestinal colonization (GI) and disseminated infection (IV). In the GI model all four fluconazole-resistant strains were outcompeted by their respective susceptible partner. In contrast, in the IV model only one out of four fluconazole-resistant isolates did show a slight fitness defect in competition with its susceptible partner during infection of the kidneys. It can be stated, that in the present work the in vitro fitness did not reflect the in vivo fitness and that the overall fitness was dependent on the tested conditions. In conclusion, C. albicans cannot easily overcome the costs of drug resistance caused by a deregulated gene expression. In addition to GOFs in Mrr1, Tac1 and Upc2, resistance mutations in the drug target Erg11 are a further key fluconazole resistance mechanism of C. albicans. Clinical isolates often harbor several resistance mechanisms, as the fluconazole resistance level is further increased in strains with a combination of different resistance mutations. In this regard, the question arises of how strains with multiple resistance mechanisms evolve. One possibility is that strains acquire mutations successively. In the present study it was examined whether highly drug-resistant C. albicans strains with multiple resistance mechanisms can evolve by parasexual recombination as another possibility. In a clonal population, cells with individually acquired resistance mutations could combine these advantageous traits by mating. Thereupon selection could act on the mating progeny resulting in even better adapted derivatives. Therefore, strains heterozygous for a resistance mutation and the mating type locus (MTL) were grown in the presence of fluconazole. Derivatives were isolated, which had become homozygous for the resistance mutation and at the same time for the MTL. This loss of heterozygosity was accompanied by increased drug resistance. In general, strains which are homozygous for one of both MTL configurations (MTLa and MTLα) can switch to the opaque phenotype, which is the mating-competent form of the yeast, and mate with cells of the opposite MTL. In the following, MTLa and MTLα homozygous strains in the opaque phenotype were mated in all possible combinations. The resulting mating products with combined genetic material from both parents did not show an increased drug resistance. Selected products of each mating cross were passaged with stepwise increasing concentrations of fluconazole. The isolated progeny showed high levels of drug resistance and loss of wild-type alleles of resistance-associated genes. In conclusion, selective pressure caused by fluconazole exposure selects for resistance mutations and at the same time induces genomic rearrangements, resulting in mating competence. Therefore, in a clonal population, cells with individually acquired resistance mutations can mate with each other and generate mating products with combined genetic backgrounds. Selection can act on these mating products and highly drug-resistant und thus highly adapted derivatives can evolve as a result. In summary, the present study contributes to the current understanding of the evolution of antifungal drug resistance by elucidating the effect of resistance mutations on the fitness of the strains in the absence of the drug selection pressure and investigates how highly drug-resistant strains could evolve within a mammalian host. N2 - Infektionen mit dem opportunistischen Hefepilz Candida albicans werden häufig mit dem First-Line-Medikament Fluconazol behandelt, welches die Ergosterol-Biosynthese hemmt. Ein besorgniserregendes Problem in der Klinik, insbesondere bei der Langzeitbehandlung von Patienten, ist die Entwicklung von Resistenzen gegen dieses Azol. Zu den bekannten Resistenzmechanismen gehören Resistenzmutationen in den Zink-Cluster-Transkriptionsfaktoren (ZnTFs) Mrr1 und Tac1, die eine Überexpression von Effluxpumpen-Genen bewirken und Resistenzmutationen in Upc2, die zu einer Überexpression des Wirkstofftargets führen. C. albicans Stämme mit solchen Gain-of-Function-Mutationen (GOF) weisen eine erhöhte Medikamentenresistenz auf, was einen selektiven Vorteil in Gegenwart des Medikaments bedeutet. Es wurde zuvor gezeigt, dass dieser Vorteil mit einem Fitnessdefekt in Abwesenheit des Medikaments einhergeht. Dies wurde in verschiedenen Bedingungen nachgewiesen und wird vermutlich durch eine deregulierte Genexpression verursacht. Ein Ziel der vorliegenden Studie war es zu untersuchen, ob C. albicans die Kosten der Medikamentenresistenz durch Evolution kompensieren kann. Daher wurde die relative Fitness von klinischen Isolaten mit einer oder einer Kombination verschiedener Resistenzmutationen in Mrr1, Tac1 und/oder Upc2 im Wettbewerb mit dem zugehörigen Fluconazol-sensitiven Partner analysiert. Die meisten Fluconazol-resistenten Isolate hatten eine verminderte Fitness im Wettbewerb mit ihrem sensitiven Partner in vitro in vollwertigem Medium. Dennoch zeigten drei Fluconazol-resistente Stämme mit Mrr1-Resistenzmutationen keinen Fitnessdefekt im Wettbewerb mit ihrem jeweiligen Partner. Zusätzlich wurde die Fitness von vier ausgewählten klinischen Isolat-Paaren in vivo in Mausmodellen für gastrointestinale Kolonisation (GI) und disseminierte Infektion (IV) untersucht. Im GI-Modell wurden alle vier Fluconazol-resistenten Stämme von ihren sensitiven Partnern überwachsen. Im Gegensatz dazu zeigte im IV-Modell nur einer der vier Fluconazol-resistenten Isolate einen leichten Fitnessdefekt im Wettbewerb mit dem jeweiligen Fluconazol-sensitiven Partner während der Infektion der Nieren. Es kann festgestellt werden, dass in der vorliegenden Arbeit die in vitro-Fitness nicht die in vivo-Fitness widerspiegelt und dass die Gesamtfitness von den getesteten Bedingungen abhängig ist. Zusammenfassend lässt sich sagen, dass C. albicans die Kosten der Medikamentenresistenz, die durch eine deregulierte Genexpression verursacht werden, nur schwer überwinden kann. Neben GOFs in Mrr1, Tac1 und Upc2 sind Resistenzmutationen im Wirkstofftarget Erg11 ein wichtiger Resistenzmechanismus von C. albicans. Klinische Isolate weißen oft mehrere Resistenzmechanismen auf, da die Kombination verschiedener Resistenzmutationen die Fluconazol-Resistenz potenziert. In diesem Zusammenhang stellt sich die Frage, wie sich Stämme mit mehreren Resistenzmechanismen entwickeln. Eine Möglichkeit ist, dass Stämme Mutationen sequenziell erwerben. In der vorliegenden Studie wurde untersucht, ob als weitere Möglichkeit hochresistente C. albicans Stämme mit multiplen Resistenzmechanismen durch parasexuelle Rekombination evolvieren können. In einer klonalen Population könnten Zellen mit individuell erworbenen Resistenzmutationen diese vorteilhaften Eigenschaften durch Paarung kombinieren. Daraufhin könnte Selektionsdruck auf die Matingprodukte wirken und so die Entstehung von besser angepassten Derivaten begünstigen. Daher wurden Resistenzmutation und Mating Type Locus (MTL) heterozygote Stämme in Gegenwart von Fluconazol kultiviert. So konnten Derivate isoliert werden, die homozygot für die Resistenzmutation und gleichzeitig für den MTL geworden waren. Dieser Verlust der Heterozygotie ging mit einer erhöhten Medikamentenresistenz einher. Generell können Stämme, die homozygot für eine der beiden MTL-Konfigurationen (MTLa und MTLα) sind, in den opaque Phänotyp wechseln, der die paarungskompetente Form der Hefe darstellt, und sich mit Zellen des gegensätzlichen MTL paaren. Im Folgenden wurden MTLa und MTLα homozygote Stämme im opaque Phänotyp in allen möglichen Kombinationen verpaart. Die resultierenden Matingprodukte mit kombiniertem genetischem Material beider Elternteile wiesen keine erhöhte Medikamentenresistenz auf. Ausgewählte Paarungsprodukte jeder Kreuzung wurden mit stufenweise ansteigenden Konzentrationen von Fluconazol passagiert. Die isolierten Nachkommen zeigten ein hohes Maß an Medikamentenresistenz und den Verlust von Wildtyp-Allelen der resistenzassoziierten Gene. Zusammenfassend lässt sich sagen, dass der selektive Druck, der durch die Fluconazol-Exposition verursacht wird, für Resistenzmutationen selektiert und gleichzeitig genomische Umlagerungen induziert, die eine Paarung ermöglichen. Daher können sich in einer klonalen Population Zellen mit individuell erworbenen Resistenzmutationen miteinander paaren und Matingprodukte mit kombiniertem genetischem Hintergrund generieren. Auf diese Matingprodukte kann die Selektion wirken, woraufhin sich hochresistente und damit stark an ihre Umwelt angepasste Derivate entwickeln können. Zusammenfassend trägt die vorliegende Studie zum aktuellen Verständnis der Evolution der Antimykotika-Resistenz bei, indem sie den Effekt von Resistenzmutationen auf die Fitness der Stämme in Abwesenheit des Medikamenten-Selektionsdrucks untersucht und aufklärt, wie sich hochgradig resistente Stämme in einem Säugetierwirt entwickeln könnten. KW - Evolution KW - Resistenz KW - Fitness KW - Candida albicans KW - Fluconazol KW - Resistance KW - Fluconazole KW - Drug resistance KW - Human-pathogenic KW - Yeast Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-243515 ER - TY - JOUR A1 - Ickrath, Pascal A1 - Sprügel, Lisa A1 - Beyersdorf, Niklas A1 - Scherzad, Agmal A1 - Hagen, Rudolf A1 - Hackenberg, Stephan T1 - Detection of Candida albicans-Specific CD4+ and CD8+ T Cells in the Blood and Nasal Mucosa of Patients with Chronic Rhinosinusitis JF - Journal of Fungi N2 - Candida albicans is ubiquitously present, and colonization in the nose and oral cavity is common. In healthy patients, it usually does not act as a pathogen, but in some cases can cause diseases. The influence of C. albicans as a trigger of T cell activation on the pathogenesis of chronic rhinosinusitis (CRS) is controversial, and its exact role is not clear to date. The aim of the present study was to detect and characterize C. albicans-specific CD4+ and CD8+ T cells in patients with CRS, with and without nasal polyps. Tissue and blood samples were collected from patients suffering from chronic rhinosinusitis with (CRSwNP) and without nasal polyps (CRSsNP), and from healthy controls. A peptide pool derived from C. albicans antigen was added to tissue and blood samples. After 6 days, lymphocytes were analyzed by multicolor flow cytometry. Activation was assessed by the intracellular marker Ki-67, and the cytokine secretion was measured. Tissue CD8+ T cells of CRSsNP patients showed a significantly higher proportion of Ki-67+ cells after activation with C. albicans antigen compared to peripheral blood CD8+ T cells. Cytokine secretion in response to C. albicans antigen was similar for all study groups. In this study, C. albicans-specific CD4+ and CD8+ T cells were detected in peripheral blood and mucosal tissue in all study groups. In patients suffering from CRSsNP, C. albicans-specific CD8+ T cells were relatively enriched in the nasal mucosa, suggesting that they might play a role in the pathogenesis of CRSsNP. KW - Candida albicans KW - chronic rhinosinusitis KW - T cell activation KW - nasal polyps Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-239671 SN - 2309-608X VL - 7 IS - 6 ER - TY - JOUR A1 - Mottola, Austin A1 - Ramírez-Zavala, Bernardo A1 - Hünninger, Kerstin A1 - Kurzai, Oliver A1 - Morschhäuser, Joachim T1 - The zinc cluster transcription factor Czf1 regulates cell wall architecture and integrity in Candida albicans JF - Molecular Microbiology N2 - The fungal cell wall is essential for the maintenance of cellular integrity and mediates interactions of the cells with the environment. It is a highly flexible organelle whose composition and organization is modulated in response to changing growth conditions. In the pathogenic yeast Candida albicans, a network of signaling pathways regulates the structure of the cell wall, and mutants with defects in these pathways are hypersensitive to cell wall stress. By harnessing a library of genetically activated forms of all C. albicans zinc cluster transcription factors, we found that a hyperactive Czf1 rescued the hypersensitivity to cell wall stress of different protein kinase deletion mutants. The hyperactive Czf1 induced the expression of many genes with cell wall-related functions and caused visible changes in the cell wall structure. C. albicans czf1Δ mutants were hypersensitive to the antifungal drug caspofungin, which inhibits cell wall biosynthesis. The changes in cell wall architecture caused by hyperactivity or absence of Czf1 resulted in an increased recognition of C. albicans by human neutrophils. Our results show that Czf1, which is known as a regulator of filamentous growth and white-opaque switching, controls the expression of cell wall genes and modulates the architecture of the cell wall. KW - cell wall KW - zinc cluster transcription factor KW - Candida albicans KW - protein kinases Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-259583 VL - 116 IS - 2 ER - TY - THES A1 - Böhm, Lena T1 - Dissecting Mechanisms of Host Colonization by C. albicans T1 - Untersuchungen zur Wirtskoloniserung durch C. albicans N2 - The human body is laden with trillions of microorganisms that belong to all three domains of life. Some species of this microbiota subsist as harmless commensals in healthy adults, but under certain circumstances, they can cause mucosal disease or even systemic, life-threatening infections. While the bacterial members of our microbiota are heavily studied today, much less attention is afforded to eukaryotic species that colonize different mucocutaneous surfaces of the human body. This dissertation focuses on identifying regulatory circuits that enable a prominent member of these eukaryotes, C. albicans, to, on the one hand, live on a specific mammalian mucosal surface as a harmless commensal and, on the other hand, proliferate as a pathogen. Since the ultimate source of many fatal Candida infections is the gastrointestinal (GI) tract of the infected individual, this organism is particularly suited to distinguishing traits essential for the gut colonization of commensal fungi and their ability to cause disease. Sequence-specific DNA-binding proteins that regulate transcription are important to most biological processes; I thus used these proteins as starting points to gain insights into 1) how a specific transcription regulator promotes virulence in C. albicans; 2) which traits C. albicans requires to inhabit the GI tract of a specific, well-defined mouse model as a harmless commensal; and 3) how three previously undescribed transcriptional regulators contribute to the commensal colonization of the digestive tract of this mouse model. Altogether, this work advances the knowledge concerning the biology of commensal fungi in the mammalian gut and genetic determinants of fungal commensalism, as well as pathogenicity. N2 - Der menschliche Körper wird von unzähligen Mikroorganismen aus allen drei Domänen des Lebens besiedelt. Einige Spezies dieser so genannten Mikrobiota leben mit gesunden Menschen als harmlose Kommensale, können jedoch unter bestimmten Umständen auch Erkrankungen der Schleimhäute oder sogar systemische, lebensbedrohliche Krankheiten verursachen. Der bakterielle Anteil unserer Mikrobiota wurde bereits ausgiebig untersucht. Sehr viel weniger Aufmerksamkeit haben bisher eukaryotische Organismen erlangt, die unterschiedliche Schleimhäute des menschlichen Körpers besiedeln. Ziel dieser Dissertation ist es regulatorische Kreisläufe zu identifizieren, die es einem prominenten eukaryotischen Mitglied unserer Mikrobiota, Candida albicans, ermöglichen auf der einen Seite eine spezielle mukokutane Oberfläche von Säugern zu besiedeln, und sich auf der anderen Seite als Pathogen zu verbreiten. Da man annimmt, dass viele bedrohliche Candida Infektionen ihren Ursprung im Gastrointestinaltrakt desselben Individuums haben, eignet sich dieser Organismus im speziellen um Eigenschaften zu identifizieren, die es kommensalen Pilzen ermöglicht den Darm zu besiedeln aber auch Krankheiten zu verursachen. Sequenz-spezifische DNA Bindeproteine, die die Transkription regulieren sind zentrale Akteure in den meisten biologischen Prozessen; aus diesem Grund verwende ich diese Proteine als Startpunkte um Einblicke in Folgendes zu erlangen: Zuerst, wie ein spezieller Transkriptionsregulator C. albicans‘ Virulenz beeinflusst. Dann welche Eigenschaften von C. albicans Voraussetzung für die Kolonisierung des Gastrointestinaltrakts eines klar definierten Mausmodells sind. Und zuletzt wie drei bisher nicht beschriebene Transkriptionsregulatoren zu der kommensale Kolonisierung des Verdauungstrakts dieses Mausmodells beitragen. Zusammenfassend trägt diese Arbeit dazu bei, das Wissen über die Biologie kommensaler Pilze im Säugertrakt und über genetische Determinanten zu erweitern, die zum Kommensalismus aber auch zur Pathogenität von Pilzen beitragen. KW - Candida albicans KW - Host Colonization KW - Microbiota KW - Pathogenicity KW - Commensalism KW - Transcription Factor Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-192303 ER -