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Oberegger S, Misslinger M, Faserl K, Sarg B, Farhan H, Haas H. The cytosolic form of dual localized BolA family protein Bol3 is important for adaptation to iron starvation in Aspergillus fumigatus. Open Biol 2024; 14:240033. [PMID: 38919062 DOI: 10.1098/rsob.240033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Accepted: 04/23/2024] [Indexed: 06/27/2024] Open
Abstract
Aspergillus fumigatus is the predominant mould pathogen for humans. Adaption to host-imposed iron limitation has previously been demonstrated to be essential for its virulence. [2Fe-2S] clusters are crucial as cofactors of several metabolic pathways and mediate cytosolic/nuclear iron sensing in fungi including A. fumigatus. [2Fe-2S] cluster trafficking has been shown to involve BolA family proteins in both mitochondria and the cytosol/nucleus. Interestingly, both A. fumigatus homologues, termed Bol1 and Bol3, possess mitochondrial targeting sequences, suggesting the lack of cytosolic/nuclear versions. Here, we show by the combination of mutational, proteomic and fluorescence microscopic analyses that expression of the Bol3 encoding gene leads to dual localization of gene products to mitochondria and the cytosol/nucleus via alternative translation initiation downstream of the mitochondrial targeting sequence, which appears to be highly conserved in various Aspergillus species. Lack of either mitochondrial Bol1 or Bol3 was phenotypically inconspicuous while lack of cytosolic/nuclear Bol3 impaired growth during iron limitation but not iron sensing which indicates a particular importance of [2Fe-2S] cluster trafficking during iron limitation. Remarkably, cytosolic/nuclear Bol3 differs from the mitochondrial version only by N-terminal acetylation, a finding that was only possible by mutational hypothesis testing.
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Affiliation(s)
- Simon Oberegger
- Institute of Molecular Biology, Biocenter, Medical University Innsbruck, Innsbruck, Austria
| | - Matthias Misslinger
- Institute of Molecular Biology, Biocenter, Medical University Innsbruck, Innsbruck, Austria
| | - Klaus Faserl
- Institute of Medical Biochemistry, Biocenter, Medical University Innsbruck, Innsbruck, Austria
| | - Bettina Sarg
- Institute of Medical Biochemistry, Biocenter, Medical University Innsbruck, Innsbruck, Austria
| | - Hesso Farhan
- Institute of Pathophysiology, Biocenter, Medical University Innsbruck, Innsbruck, Austria
| | - Hubertus Haas
- Institute of Molecular Biology, Biocenter, Medical University Innsbruck, Innsbruck, Austria
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2
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Kühbacher A, Merschak P, Haas H, Liebl M, Müller C, Gsaller F. The cytochrome P450 reductase CprA is a rate-limiting factor for Cyp51A-mediated azole resistance in Aspergillus fumigatus. Antimicrob Agents Chemother 2023; 67:e0091823. [PMID: 37815358 PMCID: PMC10648939 DOI: 10.1128/aac.00918-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 08/12/2023] [Indexed: 10/11/2023] Open
Abstract
Azole antifungals remain the "gold standard" therapy for invasive aspergillosis. The world-wide emergence of isolates resistant to this drug class, however, developed into a steadily increasing threat to human health over the past years. In Aspergillus fumigatus, major mechanisms of resistance involve increased expression of cyp51A encoding one of two isoenzymes targeted by azoles. Yet, the level of resistance caused by cyp51A upregulation, driven by either clinically relevant tandem repeat mutations within its promoter or the use of high expressing heterologous promoters, is limited. Cytochrome P450 enzymes such as Cyp51A rely on redox partners that provide electrons for their activity. A. fumigatus harbors several genes encoding putative candidate proteins including two paralogous cytochrome P450 reductases, CprA and CprB, and the cytochrome b 5 CybE. In this work, we investigated the contribution of each cprA, cprB, and cybE overexpression to cyp51A-mediated resistance to different medical and agricultural azoles. Using the bidirectional promoter PxylP, we conditionally expressed these genes in combination with cyp51A, revealing cprA as the main limiting factor. Similar to this approach, we overexpressed cprA in an azole-resistant background strain carrying a cyp51A allele with TR34 in its promoter, which led to a further increase in its resistance. Employing sterol measurements, we demonstrate an enhanced eburicol turnover during upregulation of either cprA or cyp51A, which was even more pronounced during their simultaneous overexpression. In summary, our work suggests that mutations leading to increased Cyp51A activity through increased electron supply could be key factors that elevate azole resistance.
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Affiliation(s)
- Alexander Kühbacher
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Petra Merschak
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Hubertus Haas
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Maximilian Liebl
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians Universität München, Munich, Germany
| | - Christoph Müller
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians Universität München, Munich, Germany
| | - Fabio Gsaller
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
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3
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Bauer I, Sarikaya Bayram Ö, Bayram Ö. The use of immunoaffinity purification approaches coupled with LC-MS/MS offers a powerful strategy to identify protein complexes in filamentous fungi. Essays Biochem 2023; 67:877-892. [PMID: 37681641 DOI: 10.1042/ebc20220253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 08/23/2023] [Accepted: 08/25/2023] [Indexed: 09/09/2023]
Abstract
Fungi are a diverse group of organisms that can be both beneficial and harmful to mankind. They have advantages such as producing food processing enzymes and antibiotics, but they can also be pathogens and produce mycotoxins that contaminate food. Over the past two decades, there have been significant advancements in methods for studying fungal molecular biology. These advancements have led to important discoveries in fungal development, physiology, pathogenicity, biotechnology, and natural product research. Protein complexes and protein-protein interactions (PPIs) play crucial roles in fungal biology. Various methods, including yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC), are used to investigate PPIs. However, affinity-based PPI methods like co-immunoprecipitation (Co-IP) are highly preferred because they represent the natural conditions of PPIs. In recent years, the integration of liquid chromatography coupled with mass spectrometry (LC-MS/MS) has been used to analyse Co-IPs, leading to the discovery of important protein complexes in filamentous fungi. In this review, we discuss the tandem affinity purification (TAP) method and single affinity purification methods such as GFP, HA, FLAG, and MYC tag purifications. These techniques are used to identify PPIs and protein complexes in filamentous fungi. Additionally, we compare the efficiency, time requirements, and material usage of Sepharose™ and magnetic-based purification systems. Overall, the advancements in fungal molecular biology techniques have provided valuable insights into the complex interactions and functions of proteins in fungi. The methods discussed in this review offer powerful tools for studying fungal biology and will contribute to further discoveries in this field.
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Affiliation(s)
- Ingo Bauer
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | | | - Özgür Bayram
- Department of Biology, Maynooth University, Maynooth, Co. Kildare, Ireland
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Yap A, Volz R, Paul S, Moye-Rowley WS, Haas H. Regulation of High-Affinity Iron Acquisition, Including Acquisition Mediated by the Iron Permease FtrA, Is Coordinated by AtrR, SrbA, and SreA in Aspergillus fumigatus. mBio 2023; 14:e0075723. [PMID: 37093084 PMCID: PMC10294635 DOI: 10.1128/mbio.00757-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 03/29/2023] [Indexed: 04/25/2023] Open
Abstract
Iron acquisition is crucial for virulence of the human pathogen Aspergillus fumigatus. Previous studies indicated that this mold regulates iron uptake via both siderophores and reductive iron assimilation by the GATA factor SreA and the SREBP regulator SrbA. Here, characterization of loss of function as well as hyperactive alleles revealed that transcriptional activation of iron uptake depends additionally on the Zn2Cys6 regulator AtrR, most likely via cooperation with SrbA. Mutational analysis of the promoter of the iron permease-encoding ftrA gene identified a 210-bp sequence, which is both essential and sufficient to impart iron regulation. Further studies located functional sequences, densely packed within 75 bp, that largely resemble binding motifs for SrbA, SreA, and AtrR. The latter, confirmed by chromatin immunoprecipitation (ChIP) analysis, is the first one not fully matching the 5'-CGGN12CCG-3' consensus sequence. The results presented here emphasize for the first time the direct involvement of SrbA, AtrR, and SreA in iron regulation. The essential role of both AtrR and SrbA in activation of iron acquisition underlines the coordination of iron homeostasis with biosynthesis of ergosterol and heme as well as adaptation to hypoxia. The rationale is most likely the iron dependence of these pathways along with the enzymatic link of biosynthesis of ergosterol and siderophores. IMPORTANCE Aspergillus fumigatus is the most common filamentous fungal pathogen infecting humans. Iron acquisition via siderophores has previously been shown to be essential for virulence of this mold species. Here, we demonstrate that AtrR, a transcription factor previously shown to control ergosterol biosynthesis, azole resistance, and adaptation to hypoxia, is essential for activation of iron acquisition, including siderophore biosynthesis and uptake. Dissection of an iron-regulated promoter identified binding motifs for AtrR and the two previously identified regulators of iron acquisition, SrbA and SreA. Altogether, this study identified a new regulator required for maintenance of iron homeostasis, revealed insights into promoter architecture for iron regulation, and emphasized the coordinated regulation of iron homeostasis ergosterol biosynthesis and adaptation to hypoxia.
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Affiliation(s)
- Annie Yap
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Ricarda Volz
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Sanjoy Paul
- Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - W. Scott Moye-Rowley
- Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Hubertus Haas
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
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Baldin C, Kühbacher A, Merschak P, Wagener J, Gsaller F. Modular Inducible Multigene Expression System for Filamentous Fungi. Microbiol Spectr 2022; 10:e0367022. [PMID: 36350143 PMCID: PMC9769661 DOI: 10.1128/spectrum.03670-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Accepted: 10/19/2022] [Indexed: 11/11/2022] Open
Abstract
Inducible promoters are indispensable elements when considering the possibility to modulate gene expression on demand. Desirable traits of conditional expression systems include their capacity for tight downregulation, high overexpression, and in some instances for fine-tuning, to achieve a desired product's stoichiometry. Although the number of inducible systems is slowly increasing, suitable promoters comprising these features are rare. To date, the concomitant use of multiple regulatable promoter platforms for controlled multigene expression has been poorly explored. This work provides pioneer work in the human pathogenic fungus Aspergillus fumigatus, wherein we investigated different inducible systems, elucidated three candidate promoters, and proved for the first time that up to three systems can be used simultaneously without interfering with each other. Proof of concept was obtained by conditionally expressing three antifungal drug targets within the ergosterol biosynthetic pathway under the control of the xylose-inducible PxylP system, the tetracycline-dependent Tet-On system, and the thiamine-repressible PthiA system. IMPORTANCE In recent years, inducible promoters have gained increasing interest for industrial or laboratory use and have become key instruments for protein expression, synthetic biology, and metabolic engineering. Constitutive, high-expressing promoters can be used to achieve high expression yields; however, the continuous overexpression of specific proteins can lead to an unpredictable metabolic burden. To prevent undesirable effects on the expression host's metabolism, the utilization of tunable systems that allow expression of a gene product on demand is indispensable. Here, we elucidated several excellent tunable promoter systems and verified that each can be independently induced in a single strain to ultimately develop a unique conditional multigene expression system. This highly efficient, modular toolbox has the potential to significantly advance applications in fundamental as well as applied research in which regulatable expression of several genes is a key requirement.
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Affiliation(s)
- Clara Baldin
- Institute of Molecular Biology, Biocenter Innsbruck, Medical University of Innsbruck, Innsbruck, Austria
| | - Alexander Kühbacher
- Institute of Molecular Biology, Biocenter Innsbruck, Medical University of Innsbruck, Innsbruck, Austria
| | - Petra Merschak
- Institute of Molecular Biology, Biocenter Innsbruck, Medical University of Innsbruck, Innsbruck, Austria
| | - Johannes Wagener
- Department of Clinical Microbiology, School of Medicine, Trinity College Dublin, The University of Dublin, Dublin, Ireland
| | - Fabio Gsaller
- Institute of Molecular Biology, Biocenter Innsbruck, Medical University of Innsbruck, Innsbruck, Austria
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Sastré-Velásquez LE, Dallemulle A, Kühbacher A, Baldin C, Alcazar-Fuoli L, Niedrig A, Müller C, Gsaller F. The fungal expel of 5-fluorocytosine derived fluoropyrimidines mitigates its antifungal activity and generates a cytotoxic environment. PLoS Pathog 2022; 18:e1011066. [PMID: 36574449 PMCID: PMC9829169 DOI: 10.1371/journal.ppat.1011066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 01/09/2023] [Accepted: 12/14/2022] [Indexed: 12/29/2022] Open
Abstract
Invasive aspergillosis remains one of the most devastating fungal diseases and is predominantly linked to infections caused by the opportunistic human mold pathogen Aspergillus fumigatus. Major treatment regimens for the disease comprise the administration of antifungals belonging to the azole, polyene and echinocandin drug class. The prodrug 5-fluorocytosine (5FC), which is the only representative of a fourth class, the nucleobase analogs, shows unsatisfactory in vitro activities and is barely used for the treatment of aspergillosis. The main route of 5FC activation in A. fumigatus comprises its deamination into 5-fluorouracil (5FU) by FcyA, which is followed by Uprt-mediated 5FU phosphoribosylation into 5-fluorouridine monophosphate (5FUMP). In this study, we characterized and examined the role of a metabolic bypass that generates this nucleotide via 5-fluorouridine (5FUR) through uridine phosphorylase and uridine kinase activities. Resistance profiling of mutants lacking distinct pyrimidine salvage activities suggested a minor contribution of the alternative route in 5FUMP formation. We further analyzed the contribution of drug efflux in 5FC tolerance and found that A. fumigatus cells exposed to 5FC reduce intracellular fluoropyrimidine levels through their export into the environment. This release, which was particularly high in mutants lacking Uprt, generates a toxic environment for cytosine deaminase lacking mutants as well as mammalian cells. Employing the broad-spectrum fungal efflux pump inhibitor clorgyline, we demonstrate synergistic properties of this compound in combination with 5FC, 5FU as well as 5FUR.
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Affiliation(s)
| | - Alex Dallemulle
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Alexander Kühbacher
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Clara Baldin
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Laura Alcazar-Fuoli
- Mycology Reference Laboratory, National Centre for Microbiology, Instituto de Salud Carlos III (ISCIII), Madrid, Spain
- Center for Biomedical Research in Network in Infectious Diseases (CIBERINFEC-CB21/13/00105), Instituto de Salud Carlos III, Madrid, Spain
| | - Anna Niedrig
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians University of Munich, Munich, Germany
| | - Christoph Müller
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians University of Munich, Munich, Germany
| | - Fabio Gsaller
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
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7
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Yap A, Glarcher I, Misslinger M, Haas H. Characterization and engineering of the xylose-inducible xylP promoter for use in mold fungal species. Metab Eng Commun 2022; 15:e00214. [DOI: 10.1016/j.mec.2022.e00214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 11/04/2022] [Accepted: 11/14/2022] [Indexed: 11/21/2022] Open
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Aguiar M, Orasch T, Shadkchan Y, Caballero P, Pfister J, Sastré-Velásquez LE, Gsaller F, Decristoforo C, Osherov N, Haas H. Uptake of the Siderophore Triacetylfusarinine C, but Not Fusarinine C, Is Crucial for Virulence of Aspergillus fumigatus. mBio 2022; 13:e0219222. [PMID: 36125294 PMCID: PMC9600649 DOI: 10.1128/mbio.02192-22] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 09/02/2022] [Indexed: 11/20/2022] Open
Abstract
Siderophores play an important role in fungal virulence, serving as trackers for in vivo imaging and as biomarkers of fungal infections. However, siderophore uptake is only partially characterized. As the major cause of aspergillosis, Aspergillus fumigatus is one of the most common airborne fungal pathogens of humans. Here, we demonstrate that this mold species mediates the uptake of iron chelated by the secreted siderophores triacetylfusarinine C (TAFC) and fusarinine C by the major facilitator-type transporters MirB and MirD, respectively. In a murine aspergillosis model, MirB but not MirD was found to be crucial for virulence, indicating that TAFC-mediated uptake plays a dominant role during infection. In the absence of MirB, TAFC becomes inhibitory by decreasing iron availability because the mutant is not able to recognize iron that is chelated by TAFC. MirB-mediated transport was found to tolerate the conjugation of fluorescein isothiocyanate to triacetylfusarinine C, which might aid in the development of siderophore-based antifungals in a Trojan horse approach, particularly as the role of MirB in pathogenicity restrains its mutational inactivation. Taken together, this study identified the first eukaryotic siderophore transporter that is crucial for virulence and elucidated its translational potential as well as its evolutionary conservation. IMPORTANCE Aspergillus fumigatus is responsible for thousands of cases of invasive fungal disease annually. For iron uptake, A. fumigatus secretes so-called siderophores, which are taken up after the binding of environmental iron. Moreover, A. fumigatus can utilize siderophore types that are produced by other fungi or bacteria. Fungal siderophores raised considerable interest due to their role in virulence and their potential for the diagnosis and treatment of fungal infections. Here, we demonstrate that the siderophore transporter MirB is crucial for the virulence of A. fumigatus, which reveals that its substrate, triacetylfusarinine C, is the most important siderophore during infection. We found that in the absence of MirB, TAFC becomes inhibitory by decreasing the availability of environmental iron and that MirB-mediated transport tolerates the derivatization of its substrate, which might aid in the development of siderophore-based antifungals. This study significantly improved the understanding of fungal iron homeostasis and the role of siderophores in interactions with the host.
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Affiliation(s)
- Mario Aguiar
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Thomas Orasch
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Yana Shadkchan
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine Ramat-Aviv, Tel Aviv, Israel
| | - Patricia Caballero
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Joachim Pfister
- Department of Nuclear Medicine, Medical University Innsbruck, Innsbruck, Austria
| | | | - Fabio Gsaller
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Clemens Decristoforo
- Department of Nuclear Medicine, Medical University Innsbruck, Innsbruck, Austria
| | - Nir Osherov
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine Ramat-Aviv, Tel Aviv, Israel
| | - Hubertus Haas
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
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Delma FZ, Al-Hatmi AMS, Brüggemann RJM, Melchers WJG, de Hoog S, Verweij PE, Buil JB. Molecular Mechanisms of 5-Fluorocytosine Resistance in Yeasts and Filamentous Fungi. J Fungi (Basel) 2021; 7:jof7110909. [PMID: 34829198 PMCID: PMC8623157 DOI: 10.3390/jof7110909] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 10/19/2021] [Accepted: 10/23/2021] [Indexed: 12/30/2022] Open
Abstract
Effective management and treatment of fungal diseases is hampered by poor diagnosis, limited options for antifungal therapy, and the emergence of antifungal drug resistance. An understanding of molecular mechanisms contributing to resistance is essential to optimize the efficacy of currently available antifungals. In this perspective, one of the oldest antifungals, 5-fluorocytosine (5-FC), has been the focus of recent studies applying advanced genomic and transcriptomic techniques to decipher the order of events at the molecular level that lead to resistance. These studies have highlighted the complexity of resistance and provided new insights that are reviewed in the present paper.
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Affiliation(s)
- Fatima Zohra Delma
- Department of Medical Microbiology, Radboud University Medical Centre, 6252 AG Nijmegen, The Netherlands; (F.Z.D.); (W.J.G.M.); (P.E.V.)
| | - Abdullah M. S. Al-Hatmi
- Natural & Medical Sciences Research Center, University of Nizwa, Nizwa 616, Oman;
- Centre of Expertise in Mycology Radboudumc/CWZ, Radboudumc Center for Infectious Diseases (RCI), 6252 AG Nijmegen, The Netherlands; (R.J.M.B.); (S.d.H.)
- Foundation Atlas of Clinical Fungi, 1214 GP Hilversum, The Netherlands
| | - Roger J. M. Brüggemann
- Centre of Expertise in Mycology Radboudumc/CWZ, Radboudumc Center for Infectious Diseases (RCI), 6252 AG Nijmegen, The Netherlands; (R.J.M.B.); (S.d.H.)
- Department of Pharmacy, Radboud University Medical Center, 6252 AG Nijmegen, The Netherlands
| | - Willem J. G. Melchers
- Department of Medical Microbiology, Radboud University Medical Centre, 6252 AG Nijmegen, The Netherlands; (F.Z.D.); (W.J.G.M.); (P.E.V.)
- Centre of Expertise in Mycology Radboudumc/CWZ, Radboudumc Center for Infectious Diseases (RCI), 6252 AG Nijmegen, The Netherlands; (R.J.M.B.); (S.d.H.)
| | - Sybren de Hoog
- Centre of Expertise in Mycology Radboudumc/CWZ, Radboudumc Center for Infectious Diseases (RCI), 6252 AG Nijmegen, The Netherlands; (R.J.M.B.); (S.d.H.)
- Foundation Atlas of Clinical Fungi, 1214 GP Hilversum, The Netherlands
| | - Paul E. Verweij
- Department of Medical Microbiology, Radboud University Medical Centre, 6252 AG Nijmegen, The Netherlands; (F.Z.D.); (W.J.G.M.); (P.E.V.)
- Centre of Expertise in Mycology Radboudumc/CWZ, Radboudumc Center for Infectious Diseases (RCI), 6252 AG Nijmegen, The Netherlands; (R.J.M.B.); (S.d.H.)
| | - Jochem B. Buil
- Department of Medical Microbiology, Radboud University Medical Centre, 6252 AG Nijmegen, The Netherlands; (F.Z.D.); (W.J.G.M.); (P.E.V.)
- Centre of Expertise in Mycology Radboudumc/CWZ, Radboudumc Center for Infectious Diseases (RCI), 6252 AG Nijmegen, The Netherlands; (R.J.M.B.); (S.d.H.)
- Correspondence: ; Tel.: +31-24-361-4356
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10
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Aguiar M, Orasch T, Misslinger M, Dietl AM, Gsaller F, Haas H. The Siderophore Transporters Sit1 and Sit2 Are Essential for Utilization of Ferrichrome-, Ferrioxamine- and Coprogen-Type Siderophores in Aspergillus fumigatus. J Fungi (Basel) 2021; 7:768. [PMID: 34575806 PMCID: PMC8470733 DOI: 10.3390/jof7090768] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 09/13/2021] [Accepted: 09/14/2021] [Indexed: 11/18/2022] Open
Abstract
Siderophore-mediated acquisition of iron has been shown to be indispensable for the virulence of several fungal pathogens, the siderophore transporter Sit1 was found to mediate uptake of the novel antifungal drug VL-2397, and siderophores were shown to be useful as biomarkers as well as for imaging of fungal infections. However, siderophore uptake in filamentous fungi is poorly characterized. The opportunistic human pathogen Aspergillus fumigatus possesses five putative siderophore transporters. Here, we demonstrate that the siderophore transporters Sit1 and Sit2 have overlapping, as well as unique, substrate specificities. With respect to ferrichrome-type siderophores, the utilization of ferrirhodin and ferrirubin depended exclusively on Sit2, use of ferrichrome A depended mainly on Sit1, and utilization of ferrichrome, ferricrocin, and ferrichrysin was mediated by both transporters. Moreover, both Sit1 and Sit2 mediated use of the coprogen-type siderophores coprogen and coprogen B, while only Sit1 transported the bacterial ferrioxamine-type xenosiderophores ferrioxamines B, G, and E. Neither Sit1 nor Sit2 were important for the utilization of the endogenous siderophores fusarinine C and triacetylfusarinine C. Furthermore, A. fumigatus was found to lack utilization of the xenosiderophores schizokinen, basidiochrome, rhizoferrin, ornibactin, rhodotorulic acid, and enterobactin. Taken together, this study characterized siderophore use by A. fumigatus and substrate characteristics of Sit1 and Sit2.
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Affiliation(s)
| | | | | | | | | | - Hubertus Haas
- Institute of Molecular Biology/Biocenter, Medical University of Innsbruck, A-6020 Innsbruck, Austria; (M.A.); (T.O.); (M.M.); (A.-M.D.); (F.G.)
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11
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Baldin C, Kühbacher A, Merschak P, Sastré-Velásquez LE, Abt B, Dietl AM, Haas H, Gsaller F. Inducible Selectable Marker Genes to Improve Aspergillus fumigatus Genetic Manipulation. J Fungi (Basel) 2021; 7:506. [PMID: 34202756 PMCID: PMC8305790 DOI: 10.3390/jof7070506] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 06/17/2021] [Accepted: 06/18/2021] [Indexed: 01/01/2023] Open
Abstract
The hygromycin B phosphotransferase gene from Escherichia coli and the pyrithiamine resistance gene from Aspergillus oryzae are two dominant selectable marker genes widely used to genetically manipulate several fungal species. Despite the recent development of CRISPR/Cas9 and marker-free systems, in vitro molecular tools to study Aspergillus fumigatus, which is a saprophytic fungus causing life-threatening diseases in immunocompromised hosts, still rely extensively on the use of dominant selectable markers. The limited number of drug selectable markers is already a critical aspect, but the possibility that their introduction into a microorganism could induce enhanced virulence or undesired effects on metabolic behavior constitutes another problem. In this context, here, we demonstrate that the use of ptrA in A. fumigatus leads to the secretion of a compound that allows the recovery of thiamine auxotrophy. In this study, we developed a simple modification of the two commonly used dominant markers in which the development of resistance can be controlled by the xylose-inducible promoter PxylP from Penicillium chrysogenum. This strategy provides an easy solution to avoid undesired side effects, since the marker expression can be readily silenced when not required.
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Affiliation(s)
| | | | | | | | | | | | - Hubertus Haas
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria; (C.B.); (A.K.); (P.M.); (L.E.S.-V.); (B.A.); (A.-M.D.)
| | - Fabio Gsaller
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria; (C.B.); (A.K.); (P.M.); (L.E.S.-V.); (B.A.); (A.-M.D.)
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Misslinger M, Hortschansky P, Brakhage AA, Haas H. Fungal iron homeostasis with a focus on Aspergillus fumigatus. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2020; 1868:118885. [PMID: 33045305 DOI: 10.1016/j.bbamcr.2020.118885] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 09/15/2020] [Accepted: 10/01/2020] [Indexed: 02/08/2023]
Abstract
To maintain iron homeostasis, fungi have to balance iron acquisition, storage, and utilization to ensure sufficient supply and to avoid toxic excess of this essential trace element. As pathogens usually encounter iron limitation in the host niche, this metal plays a particular role during virulence. Siderophores are iron-chelators synthesized by most, but not all fungal species to sequester iron extra- and intracellularly. In recent years, the facultative human pathogen Aspergillus fumigatus has become a model for fungal iron homeostasis of siderophore-producing fungal species. This article summarizes the knowledge on fungal iron homeostasis and its links to virulence with a focus on A. fumigatus. It covers mechanisms for iron acquisition, storage, and detoxification, as well as the modes of transcriptional iron regulation and iron sensing in A. fumigatus in comparison to other fungal species. Moreover, potential translational applications of the peculiarities of fungal iron metabolism for treatment and diagnosis of fungal infections is addressed.
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Affiliation(s)
- Matthias Misslinger
- Institute of Molecular Biology - Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Peter Hortschansky
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology-Hans Knöll Institute (HKI), Jena, Germany
| | - Axel A Brakhage
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology-Hans Knöll Institute (HKI), Jena, Germany; Department Microbiology and Molecular Biology, Institute of Microbiology, Friedrich Schiller University Jena, Jena, Germany
| | - Hubertus Haas
- Institute of Molecular Biology - Biocenter, Medical University of Innsbruck, Innsbruck, Austria.
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