TY - JOUR A1 - Schielmann, Marta A1 - Szweda, Piotr A1 - Gucwa, Katarzyna A1 - Kawczyński, Marcin A1 - Milewska, Maria J. A1 - Martynow, Dorota A1 - Morschhäuser, Joachim A1 - Milewski, Sławomir T1 - Transport deficiency is the molecular basis of \(Candida\) \(albicans\) resistance to antifungal oligopeptides JF - Frontiers in Microbiology N2 - Oligopeptides incorporating \(N3\)-(4-methoxyfumaroyl)-L-2,3-diaminopropanoic acid (FMDP), an inhibitor of glucosamine-6-phosphate synthase, exhibited growth inhibitory activity against \(Candida\) \(albicans\), with minimal inhibitory concentration values in the 0.05–50 μg mL\(^{-1}\) range. Uptake by the peptide permeases was found to be the main factor limiting an anticandidal activity of these compounds. Di- and tripeptide containing FMDP (F2 and F3) were transported by Ptr2p/Ptr22p peptide transporters (PTR) and FMDP-containing hexa-, hepta-, and undecapeptide (F6, F7, and F11) were taken up by the oligopeptide transporters (OPT) oligopeptide permeases, preferably by Opt2p/Opt3p. A phenotypic, apparent resistance of \(C. albicans\) to FMDP-oligopeptides transported by OPT permeases was triggered by the environmental factors, whereas resistance to those taken up by the PTR system had a genetic basis. Anticandidal activity of longer FMDP-oligopeptides was strongly diminished in minimal media containing easily assimilated ammonium sulfate or L-glutamine as the nitrogen source, both known to downregulate expression of the OPT genes. All FMDP-oligopeptides tested were more active at lower pH and this effect was slightly more remarkable for peptides F6, F7, and F11, compared to F2 and F3. Formation of isolated colonies was observed inside the growth inhibitory zones induced by F2 and F3 but not inside those induced by F6, F7, and F11. The vast majority (98%) of those colonies did not originate from truly resistant cells. The true resistance of 2% of isolates was due to the impaired transport of di- and to a lower extent, tripeptides. The resistant cells did not exhibit a lower expression of \(PTR2\), \(PTR22\), or \(OPT1–3\) genes, but mutations in the \(PTR2\) gene resulting in T422H, A320S, D119V, and A320S substitutions in the amino acid sequence of Ptr2p were found. KW - microbiology KW - Candida albicans KW - oligopeptides KW - resistance mechanism KW - permease KW - antifungals Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-173245 VL - 8 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 - 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 - Sasse, Christoph A1 - Schillig, Rebecca A1 - Dierolf, Franziska A1 - Weyler, Michael A1 - Schneider, Sabrina A1 - Mogavero, Selene A1 - Rogers, David P. A1 - Morschhäuser, Joachim T1 - The Transcription Factor Ndt80 Does Not Contribute to Mrr1-, Tac1-, and Upc2-Mediated Fluconazole Resistance in Candida albicans N2 - The pathogenic yeast Candida albicans can develop resistance to the widely used antifungal agent fluconazole, which inhibits ergosterol biosynthesis, by the overexpression of genes encoding multidrug efflux pumps or ergosterol biosynthesis enzymes. Zinc cluster transcription factors play a central role in the transcriptional regulation of drug resistance. Mrr1 regulates the expression of the major facilitator MDR1, Tac1 controls the expression of the ABC transporters CDR1 and CDR2, and Upc2 regulates ergosterol biosynthesis (ERG) genes. Gain-of-function mutations in these transcription factors result in constitutive overexpression of their target genes and are responsible for fluconazole resistance in many clinical C. albicans isolates. The transcription factor Ndt80 contributes to the drug-induced upregulation of CDR1 and ERG genes and also binds to the MDR1 and CDR2 promoters, suggesting that it is an important component of all major transcriptional mechanisms of fluconazole resistance. However, we found that Ndt80 is not required for the induction of MDR1 and CDR2 expression by inducing chemicals. CDR2 was even partially derepressed in ndt80D mutants, indicating that Ndt80 is a repressor of CDR2 expression. Hyperactive forms of Mrr1, Tac1, and Upc2 promoted overexpression of MDR1, CDR1/CDR2, and ERG11, respectively, with the same efficiency in the presence and absence of Ndt80. Mrr1- and Tac1-mediated fluconazole resistance was even slightly enhanced in ndt80D mutants compared to wild-type cells. These results demonstrate that Ndt80 is dispensable for the constitutive overexpression of Mrr1, Tac1, and Upc2 target genes and the increased fluconazole resistance of strains that have acquired activating mutations in these transcription factors. KW - Candida albicans Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-69201 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 - JOUR A1 - Dreschers, Stephan A1 - Saupp, Peter A1 - Hornef, Mathias A1 - Prehn, Andrea A1 - Platen, Christopher A1 - Morschhäuser, Joachim A1 - Orlikowsky, Thorsten W. T1 - Reduced PICD in Monocytes Mounts Altered Neonate Immune Response to Candida albicans JF - PLoS ONE N2 - Background Invasive fungal infections with Candida albicans (C. albicans) occur frequently in extremely low birthweight (ELBW) infants and are associated with poor outcome. Phagocytosis of C.albicans initializes apoptosis in monocytes (phagocytosis induced cell death, PICD). PICD is reduced in neonatal cord blood monocytes (CBMO). Hypothesis Phagocytosis of C. albicans causes PICD which differs between neonatal monocytes (CBMO) and adult peripheral blood monocytes (PBMO) due to lower stimulation of TLR-mediated immune responses. Methods The ability to phagocytose C. albicans, expression of TLRs, the induction of apoptosis (assessment of sub-G1 and nick-strand breaks) were analyzed by FACS. TLR signalling was induced by agonists such as lipopolysaccharide (LPS), Pam3Cys, FSL-1 and Zymosan and blocked (neutralizing TLR2 antibodies and MYD88 inhibitor). Results Phagocytic indices of PBMO and CBMO were similar. Following stimulation with agonists and C. albicans induced up-regulation of TLR2 and consecutive phosphorylation of MAP kinase P38 and expression of TNF-α, which were stronger on PBMO compared to CBMO (p < 0.005). Downstream, TLR2 signalling initiated caspase-3-dependent PICD which was found reduced in CBMO (p < 0.05 vs PBMO). Conclusion Our data suggest direct involvement of TLR2-signalling in C. albicans-induced PICD in monocytes and an alteration of this pathway in CBMO. KW - Candida albicans KW - monocytes KW - immune response KW - PICD Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-166778 VL - 11 IS - 11 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 - Mottola, Austin A1 - Schwanfelder, Sonja A1 - Morschhäuser, Joachim T1 - Generation of Viable Candida albicans Mutants Lacking the "Essential" Protein Kinase Snf1 by Inducible Gene Deletion JF - mSphere N2 - The protein kinase Snf1, a member of the highly conserved AMP-activated protein kinase family, is a central regulator of metabolic adaptation. In the pathogenic yeast Candida albicans, Snf1 is considered to be essential, as previous attempts by different research groups to generate homozygous snf1 Delta mutants were unsuccessful. We aimed to elucidate why Snf1 is required for viability in C. albicans by generating snf1 Delta null mutants through forced, inducible gene deletion and observing the terminal phenotype before cell death. Unexpectedly, we found that snf1 Delta mutants were viable and could grow, albeit very slowly, on rich media containing the preferred carbon source glucose. Growth was improved when the cells were incubated at 37 degrees C instead of 30 degrees C, and this phenotype enabled us to isolate homozygous snf1 Delta mutants also by conventional, sequential deletion of both SNF1 alleles in a wild-type C. albicans strain. All snf1 Delta mutants could grow slowly on glucose but were unable to utilize alternative carbon sources. Our results show that, under optimal conditions, C. albicans can live and grow without Snf1. Furthermore, they demonstrate that inducible gene deletion is a powerful method for assessing gene essentiality in C. albicans. IMPORTANCE Essential genes are those that are indispensable for the viability and growth of an organism. Previous studies indicated that the protein kinase Snf1, a central regulator of metabolic adaptation, is essential in the pathogenic yeast Candida albicans, because no homozygous snf1 deletion mutants of C. albicans wild-type strains could be obtained by standard approaches. In order to investigate the lethal consequences of SNF1 deletion, we generated conditional mutants in which SNF1 could be deleted by forced, inducible excision from the genome. Unexpectedly, we found that snf1 null mutants were viable and could grow slowly under optimal conditions. The growth phenotypes of the snf1 Delta mutants explain why such mutants were not recovered in previous attempts. Our study demonstrates that inducible gene deletion is a powerful method for assessing gene essentiality in C. albicans. KW - Candida albicans KW - Snf1 KW - conditional mutants KW - essential genes KW - protein kinases Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230524 VL - 5 IS - 4 ER - TY - JOUR A1 - Popp, Christina A1 - Ramírez-Zavala, Bernardo A1 - Schwanfelder, Sonja A1 - Krüger, Ines A1 - Morschhäuser, Joachim T1 - Evolution of fluconazole-resistant Candida albicans strains by drug-induced mating competence and parasexual recombination JF - mBio N2 - The clonal population structure of Candida albicans suggests that (para)sexual recombination does not play an important role in the lifestyle of this opportunistic fungal pathogen, an assumption that is strengthened by the fact that most C. albicans strains are heterozygous at the mating type locus (MTL) and therefore mating-incompetent. On the other hand, mating might occur within clonal populations and allow the combination of advantageous traits that were acquired by individual cells to adapt to adverse conditions. We have investigated if parasexual recombination may be involved in the evolution of highly drug-resistant strains exhibiting multiple resistance mechanisms against fluconazole, an antifungal drug that is commonly used to treat infections by C. albicans. Growth of strains that were heterozygous for MTL and different fluconazole resistance mutations in the presence of the drug resulted in the emergence of derivatives that had become homozygous for the mutated allele and the mating type locus and exhibited increased drug resistance. When MTLa/a and MTLα/α cells of these strains were mixed in all possible combinations, we could isolate mating products containing the genetic material from both parents. The initial mating products did not exhibit higher drug resistance than their parental strains, but further propagation under selective pressure resulted in the loss of the wild-type alleles and increased fluconazole resistance. Therefore, fluconazole treatment not only selects for resistance mutations but also promotes genomic alterations that confer mating competence, which allows cells in an originally clonal population to exchange individually acquired resistance mechanisms and generate highly drug-resistant progeny. KW - Candida albicans KW - drug resistance evolution KW - mating KW - parasexual recombination Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-200901 VL - 10 IS - 1 ER - 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 - Mottola, Austin A1 - Morschhäuser, Joachim T1 - An intragenic recombination event generates a Snf4-independent form of the essential protein kinase SNF1 in Candida albicans JF - mSphere N2 - The heterotrimeric protein kinase SNF1 plays a key role in the metabolic adaptation of the pathogenic yeast Candida albicans. It consists of the essential catalytic α-subunit Snf1, the γ-subunit Snf4, and one of the two β-subunits Kis1 and Kis2. Snf4 is required to release the N-terminal catalytic domain of Snf1 from autoinhibition by the C-terminal regulatory domain, and snf4Δ mutants cannot grow on carbon sources other than glucose. In a screen for suppressor mutations that restore growth of a snf4Δ mutant on alternative carbon sources, we isolated a mutant in which six amino acids between the N-terminal kinase domain and the C-terminal regulatory domain of Snf1 were deleted. The deletion was caused by an intragenic recombination event between two 8-bp direct repeats flanking six intervening codons. In contrast to truncated forms of Snf1 that contain only the kinase domain, the Snf4-independent Snf1\(^{Δ311 − 316}\) was fully functional and could replace wild-type Snf1 for normal growth, because it retained the ability to interact with the Kis1 and Kis2 β-subunits via its C-terminal domain. Indeed, the Snf4-independent Snf1\(^{Δ311 − 316}\) still required the β-subunits of the SNF1 complex to perform its functions and did not rescue the growth defects of kis1Δ mutants. Our results demonstrate that a preprogrammed in-frame deletion event within the SNF1 coding region can generate a mutated form of this essential kinase which abolishes autoinhibition and thereby overcomes growth deficiencies caused by a defect in the γ-subunit Snf4. KW - AMP-activated kinases KW - Candida albicans KW - genetic recombination KW - metabolic adaptation KW - suppressor mutation Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-202170 VL - 4 IS - 3 ER - TY - JOUR A1 - Hampe, Irene A. I. A1 - Friedman, Justin A1 - Edgerton, Mira A1 - Morschhäuser, Joachim T1 - An acquired mechanism of antifungal drug resistance simultaneously enables Candida albicans to escape from intrinsic host defenses JF - PLoS Pathogens N2 - The opportunistic fungal pathogen Candida albicans frequently produces genetically altered variants to adapt to environmental changes and new host niches in the course of its life-long association with the human host. Gain-of-function mutations in zinc cluster transcription factors, which result in the constitutive upregulation of their target genes, are a common cause of acquired resistance to the widely used antifungal drug fluconazole, especially during long-term therapy of oropharyngeal candidiasis. In this study, we investigated if C. albicans also can develop resistance to the antimicrobial peptide histatin 5, which is secreted in the saliva of humans to protect the oral mucosa from pathogenic microbes. As histatin 5 has been shown to be transported out of C. albicans cells by the Flu1 efflux pump, we screened a library of C. albicans strains that contain artificially activated forms of all zinc cluster transcription factors of this fungus for increased FLU1 expression. We found that a hyperactive Mrr1, which confers fluconazole resistance by upregulating the multidrug efflux pump MDR1 and other genes, also causes FLU1 overexpression. Similarly to the artificially activated Mrr1, naturally occurring gain-of-function mutations in this transcription factor also caused FLU1 upregulation and increased histatin 5 resistance. Surprisingly, however, Mrr1-mediated histatin 5 resistance was mainly caused by the upregulation of MDR1 instead of FLU1, revealing a previously unrecognized function of the Mdr1 efflux pump. Fluconazole-resistant clinical C. albicans isolates with different Mrr1 gain-of-function mutations were less efficiently killed by histatin 5, and this phenotype was reverted when MRR1 was deleted. Therefore, antimycotic therapy can promote the evolution of strains that, as a consequence of drug resistance mutations, simultaneously have acquired increased resistance against an innate host defense mechanism and are thereby better adapted to certain host niches. KW - antimicrobial resistance KW - transcriptional control KW - Candida albicans KW - transcription factors KW - mutation KW - hyperexpression techniques KW - antifungals KW - point mutation Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-158883 VL - 13 IS - 9 ER -