1
|
Souza ACO, Ge W, Wiederhold NP, Rybak JM, Fortwendel JR, Rogers PD. hapE and hmg1 Mutations Are Drivers of cyp51A-Independent Pan-Triazole Resistance in an Aspergillus fumigatus Clinical Isolate. Microbiol Spectr 2023; 11:e0518822. [PMID: 37140376 PMCID: PMC10269825 DOI: 10.1128/spectrum.05188-22] [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: 01/09/2023] [Accepted: 04/05/2023] [Indexed: 05/05/2023] Open
Abstract
Aspergillus fumigatus is a ubiquitous environmental mold that can cause severe disease in immunocompromised patients and chronic disease in individuals with underlying lung conditions. Triazoles are the most widely used class of antifungal drugs to treat A. fumigatus infections, but their use in the clinic is threatened by the emergence of triazole-resistant isolates worldwide, reinforcing the need for a better understanding of resistance mechanisms. The predominant mechanisms of A. fumigatus triazole resistance involve mutations affecting the promoter region or coding sequence of the target enzyme of the triazoles, Cyp51A. However, triazole-resistant isolates without cyp51A-associated mutations are frequently identified. In this study, we investigate a pan-triazole-resistant clinical isolate, DI15-105, that simultaneously carries the mutations hapEP88L and hmg1F262del, with no mutations in cyp51A. Using a Cas9-mediated gene-editing system, hapEP88L and hmg1F262del mutations were reverted in DI15-105. Here, we show that the combination of these mutations accounts for pan-triazole resistance in DI15-105. To our knowledge, DI15-105 is the first clinical isolate reported to simultaneously carry mutations in hapE and hmg1 and only the second with the hapEP88L mutation. IMPORTANCE Triazole resistance is an important cause of treatment failure and high mortality rates for A. fumigatus human infections. Although Cyp51A-associated mutations are frequently identified as the cause of A. fumigatus triazole resistance, they do not explain the resistance phenotypes for several isolates. In this study, we demonstrate that hapE and hmg1 mutations additively contribute to pan-triazole resistance in an A. fumigatus clinical isolate lacking cyp51-associated mutations. Our results exemplify the importance of and the need for a better understanding of cyp51A-independent triazole resistance mechanisms.
Collapse
Affiliation(s)
- Ana C. O. Souza
- Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, USA
| | - Wenbo Ge
- Department of Clinical Pharmacy and Translational Sciences, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Nathan P. Wiederhold
- Fungus Testing Laboratory, Department of Pathology and Laboratory Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
| | - Jeffrey M. Rybak
- Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, USA
| | - Jarrod R. Fortwendel
- Department of Clinical Pharmacy and Translational Sciences, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - P. David Rogers
- Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, USA
| |
Collapse
|
2
|
Aruanno M, Gozel S, Mouyna I, Parker JE, Bachmann D, Flamant P, Coste AT, Sanglard D, Lamoth F. Insights in the molecular mechanisms of an azole stress adapted laboratory-generated Aspergillus fumigatus strain. Med Mycol 2021; 59:763-772. [PMID: 33550403 DOI: 10.1093/mmy/myaa118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 12/26/2020] [Accepted: 01/18/2021] [Indexed: 12/13/2022] Open
Abstract
Aspergillus fumigatus is the main cause of invasive aspergillosis, for which azole drugs are the first-line therapy. Emergence of pan-azole resistance among A. fumigatus is concerning and has been mainly attributed to mutations in the target gene (cyp51A). However, azole resistance may also result from other mutations (hmg1, hapE) or other adaptive mechanisms. We performed microevolution experiment exposing an A. fumigatus azole-susceptible strain (Ku80) to sub-minimal inhibitory concentration of voriconazole to analyze emergence of azole resistance. We obtained a strain with pan-azole resistance (Ku80R), which was partially reversible after drug relief, and without mutations in cyp51A, hmg1, and hapE. Transcriptomic analyses revealed overexpression of the transcription factor asg1, several ATP-binding cassette (ABC) and major facilitator superfamily transporters and genes of the ergosterol biosynthesis pathway in Ku80R. Sterol analysis showed a significant decrease of the ergosterol mass under voriconazole exposure in Ku80, but not in Ku80R. However, the proportion of the sterol compounds was similar between both strains. To further assess the role of transporters, we used the ABC transporter inhibitor milbemycine oxime (MLB). MLB inhibited transporter activity in both Ku80 and Ku80R and demonstrated some potentiating effect on azole activity. Criteria for synergism were reached for MLB and posaconazole against Ku80. Finally, deletion of asg1 revealed some role of this transcription factor in controlling drug transporter expression, but had no impact on azole susceptibility.This work provides further insight in mechanisms of azole stress adaptation and suggests that drug transporters inhibition may represent a novel therapeutic target. LAY SUMMARY A pan-azole-resistant strain was generated in vitro, in which drug transporter overexpression was a major trait. Analyses suggested a role of the transporter inhibitor milbemycin oxime in inhibiting drug transporters and potentiating azole activity.
Collapse
Affiliation(s)
- Marion Aruanno
- Institute of Microbiology, Lausanne University Hospital and University of Lausanne, 1011 Lausanne, Switzerland.,Infectious Diseases Service, Department of Medicine, Lausanne University Hospital and University of Lausanne, 1011 Lausanne, Switzerland
| | - Samantha Gozel
- Institute of Microbiology, Lausanne University Hospital and University of Lausanne, 1011 Lausanne, Switzerland
| | - Isabelle Mouyna
- Unité des Aspergillus, Institut Pasteur, 75015 Paris, France
| | - Josie E Parker
- Centre for Cytochrome P450 Biodiversity, Institute of Life Science, Swansea University Medical School, Swansea SA2 8PP, UK
| | - Daniel Bachmann
- Institute of Microbiology, Lausanne University Hospital and University of Lausanne, 1011 Lausanne, Switzerland
| | | | - Alix T Coste
- Institute of Microbiology, Lausanne University Hospital and University of Lausanne, 1011 Lausanne, Switzerland
| | - Dominique Sanglard
- Institute of Microbiology, Lausanne University Hospital and University of Lausanne, 1011 Lausanne, Switzerland
| | - Frederic Lamoth
- Institute of Microbiology, Lausanne University Hospital and University of Lausanne, 1011 Lausanne, Switzerland.,Infectious Diseases Service, Department of Medicine, Lausanne University Hospital and University of Lausanne, 1011 Lausanne, Switzerland
| |
Collapse
|
3
|
Ma Y, Ji Y, Yang J, Li W, Li J, Cen W, Wang Y, Feng W. Deletion of bem46 retards spore germination and may be related to the polar growth of Aspergillus fumigatus. Med Mycol 2020; 58:690-697. [PMID: 31711175 DOI: 10.1093/mmy/myz108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 10/08/2019] [Accepted: 10/15/2019] [Indexed: 11/13/2022] Open
Abstract
Bud emergence 46 (BEM46), a member of the α/β hydrolase superfamily, has been reported to be essential for polarized growth in Neurospora crassa. However, the role of BEM46 in aspergillus fumigatus (A. fumigatus) remains unclear. In this study, we constructed an A. fumigatus strain expressing BEM46 fused with enhanced green fluorescent protein, and a Δbem46 mutant, to explore the localization and the role of growth of BEM46 in A. fumigatus, respectively. Confocal laser scanning microscopy revealed that BEM46 was dominantly expressed in the sites where hyphae germinated from conidia in A. fumigatus. When compared with the control strain, the Δbem46 mutant exhibited insignificant morphological changes but delayed germination. No significant changes were found regarding the radial growth of both strains in response to various antifungal agents. These results suggest that BEM46 plays an essential role in timely germination in A. fumigatus. From the observation of fluorescence localization, we infer that that BEM46 might be involved in polarized growth in A. fumigatus.
Collapse
Affiliation(s)
- Yan Ma
- Department of Dermatology, The Second Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Ying Ji
- Department of Dermatology, The Second Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Jing Yang
- Department of Dermatology, The Second Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Wen Li
- Department of Dermatology, The Second Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Jiajuan Li
- Department of Dermatology, The Second Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Wen Cen
- Department of Dermatology, The Second Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Yan Wang
- Department of Dermatology, The Second Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Wenli Feng
- Department of Dermatology, The Second Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| |
Collapse
|
4
|
Abstract
Polymorphonuclear granulocytes (PMNs) are indispensable for controlling life-threatening fungal infections. In addition to various effector mechanisms, PMNs also produce extracellular vesicles (EVs). Their contribution to antifungal defense has remained unexplored. We reveal that the clinically important human-pathogenic fungus Aspergillus fumigatus triggers PMNs to release a distinct set of antifungal EVs (afEVs). Proteome analyses indicated that afEVs are enriched in antimicrobial proteins. The cargo and the release kinetics of EVs are modulated by the fungal strain confronted. Tracking of afEVs indicated that they associated with fungal cells and even entered fungal hyphae, resulting in alterations in the morphology of the fungal cell wall and dose-dependent antifungal effects. To assess as a proof of concept whether the antimicrobial proteins found in afEVs might contribute to growth inhibition of hyphae when present in the fungal cytoplasm, two human proteins enriched in afEVs, cathepsin G and azurocidin, were heterologously expressed in fungal hyphae. This led to reduced fungal growth relative to that of a control strain producing the human retinol binding protein 7. In conclusion, extracellular vesicles produced by neutrophils in response to A. fumigatus infection are able to associate with the fungus, limit growth, and elicit cell damage by delivering antifungal cargo. This finding offers an intriguing, previously overlooked mechanism of antifungal defense against A. fumigatus IMPORTANCE Invasive fungal infections caused by the mold Aspergillus fumigatus are a growing concern in the clinic due to the increasing use of immunosuppressive therapies and increasing antifungal drug resistance. These infections result in high rates of mortality, as treatment and diagnostic options remain limited. In healthy individuals, neutrophilic granulocytes are critical for elimination of A. fumigatus from the host; however, the exact extracellular mechanism of neutrophil-mediated antifungal activity remains unresolved. Here, we present a mode of antifungal defense employed by human neutrophils against A. fumigatus not previously described. We found that extracellular vesicles produced by neutrophils in response to A. fumigatus infection are able to associate with the fungus, limit growth, and elicit cell damage by delivering antifungal cargo. In the end, antifungal extracellular vesicle biology provides a significant step forward in our understanding of A. fumigatus host pathogenesis and opens up novel diagnostic and therapeutic possibilities.
Collapse
|
5
|
Abstract
Aspergilli produce conidia for reproduction or to survive hostile conditions, and they are highly effective in the distribution of conidia through the environment. In immunocompromised individuals, inhaled conidia can germinate inside the respiratory tract, which may result in invasive pulmonary aspergillosis. The management of invasive aspergillosis has become more complex, with new risk groups being identified and the emergence of antifungal resistance. Patient survival is threatened by these developments, stressing the need for alternative therapeutic strategies. As germination is crucial for infection, prevention of this process might be a feasible approach. A broader understanding of conidial germination is important to identify novel antigermination targets. In this review, we describe conidial resistance against various stresses, transition from dormant conidia to hyphal growth, the underlying molecular mechanisms involved in germination of the most common Aspergillus species, and promising antigermination targets. Germination of Aspergillus is characterized by three morphotypes: dormancy, isotropic growth, and polarized growth. Intra- and extracellular proteins play an important role in the protection against unfavorable environmental conditions. Isotropically expanding conidia remodel the cell wall, and biosynthetic machineries are needed for cellular growth. These biosynthetic machineries are also important during polarized growth, together with tip formation and the cell cycle machinery. Genes involved in isotropic and polarized growth could be effective antigermination targets. Transcriptomic and proteomic studies on specific Aspergillus morphotypes will improve our understanding of the germination process and allow discovery of novel antigermination targets and biomarkers for early diagnosis and therapy.
Collapse
|
6
|
Abstract
Aspergillus fumigatus is the predominant pathogen of invasive aspergillosis, a disease state credited with over 200,000 life-threatening infections annually. The triazole class of antifungals are clinically essential to the treatment of invasive aspergillosis. Unfortunately, resistance to the triazoles among A. fumigatus isolates is now increasingly reported worldwide. In this work, we challenge the current paradigm of clinical triazole resistance in A. fumigatus, by first demonstrating that previously characterized mechanisms of resistance have nominal impact on triazole susceptibility and subsequently identifying a novel mechanism of resistance with a profound impact on clinical triazole susceptibility. We demonstrate that mutations in the HMG-CoA reductase gene, hmg1, are common among resistant clinical isolates and that hmg1 mutations confer resistance to all clinically available triazole antifungals. Aspergillus fumigatus is the predominant pathogen of invasive aspergillosis, a disease state credited with over 200,000 life-threatening infections each year. The triazole class of antifungals are clinically essential to the treatment of invasive aspergillosis, both as frontline and as salvage therapy. Unfortunately, resistance to the triazoles among A. fumigatus isolates is now increasingly reported worldwide, and a large proportion of this resistance remains unexplained. In this work, we characterize the contributions of previously identified mechanisms of triazole resistance, including mutations in the sterol-demethylase-encoding gene cyp51A, overexpression of sterol-demethylase genes, and overexpression of the efflux pump-encoding gene abcC, among a large collection of highly triazole-resistant clinical A. fumigatus isolates. Upon revealing that these mechanisms alone cannot substantiate the majority of triazole resistance exhibited by this collection, we subsequently describe the identification and characterization of a novel genetic determinant of triazole resistance. Mutations in the 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase-encoding gene, hmg1, were identified in a majority of triazole-resistant clinical isolates in our collection. Introduction of three different hmg1 mutations, predicted to encode residue alterations in the conserved sterol sensing domain of Hmg1, resulted in significantly increased resistance to the triazole class of agents. Additionally, correction of a hmg1 mutation in a pan-triazole-resistant clinical isolate of A. fumigatus with a novel Cas9-ribonucleoprotein-mediated system was shown to restore clinical susceptibility to all triazole agents. Mutations in hmg1 were also shown to lead to the accumulation of ergosterol precursors, such as eburicol, by sterol profiling, while not altering the expression of sterol-demethylase genes.
Collapse
|
7
|
Renshaw H, Vargas-Muñiz JM, Juvvadi PR, Richards AD, Waitt G, Soderblom EJ, Moseley MA, Steinbach WJ. The tail domain of the Aspergillus fumigatus class V myosin MyoE orchestrates septal localization and hyphal growth. J Cell Sci 2018; 131:jcs.205955. [PMID: 29222113 DOI: 10.1242/jcs.205955] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2017] [Accepted: 12/05/2017] [Indexed: 01/10/2023] Open
Abstract
Myosins are critical motor proteins that contribute to the secretory pathway, polarized growth, and cytokinesis. The globular tail domains of class V myosins have been shown to be important for cargo binding and actin cable organization. Additionally, phosphorylation plays a role in class V myosin cargo choice. Our previous studies on the class V myosin MyoE in the fungal pathogen Aspergillus fumigatus confirmed its requirement for normal morphology and virulence. However, the domains and molecular mechanisms governing the functions of MyoE remain unknown. Here, by analyzing tail mutants, we demonstrate that the tail is required for radial growth, conidiation, septation frequency and MyoE's location at the septum. Furthermore, MyoE is phosphorylated at multiple residues in vivo; however, alanine substitution mutants revealed that no single phosphorylated residue was critical. Importantly, in the absence of the phosphatase calcineurin, an additional residue was phosphorylated in its tail domain. Mutation of this tail residue led to mislocalization of MyoE from the septa. This work reveals the importance of the MyoE tail domain and its phosphorylation/dephosphorylation in the growth and morphology of A. fumigatus.
Collapse
Affiliation(s)
- Hilary Renshaw
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - José M Vargas-Muñiz
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Praveen R Juvvadi
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Duke University Medical Center, Durham, NC 27710, USA
| | - Amber D Richards
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Duke University Medical Center, Durham, NC 27710, USA
| | - Greg Waitt
- Duke Proteomics and Metabolomics Core Facility, Center for Genomic and Computational Biology, Duke University, Durham, NC 27708, USA
| | - Erik J Soderblom
- Duke Proteomics and Metabolomics Core Facility, Center for Genomic and Computational Biology, Duke University, Durham, NC 27708, USA
| | - M Arthur Moseley
- Duke Proteomics and Metabolomics Core Facility, Center for Genomic and Computational Biology, Duke University, Durham, NC 27708, USA
| | - William J Steinbach
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA .,Division of Pediatric Infectious Diseases, Department of Pediatrics, Duke University Medical Center, Durham, NC 27710, USA
| |
Collapse
|
8
|
A Simple and Universal System for Gene Manipulation in Aspergillus fumigatus: In Vitro-Assembled Cas9-Guide RNA Ribonucleoproteins Coupled with Microhomology Repair Templates. mSphere 2017; 2:mSphere00446-17. [PMID: 29202040 PMCID: PMC5700375 DOI: 10.1128/msphere.00446-17] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 11/06/2017] [Indexed: 01/09/2023] Open
Abstract
Tackling the multifactorial nature of virulence and antifungal drug resistance in A. fumigatus requires the mechanistic interrogation of a multitude of genes, sometimes across multiple genetic backgrounds. Classical fungal gene replacement systems can be laborious and time-consuming and, in wild-type isolates, are impeded by low rates of homologous recombination. Our simple and universal CRISPR-Cas9 system for gene manipulation generates efficient gene targeting across different genetic backgrounds of A. fumigatus. We anticipate that our system will simplify genome editing in A. fumigatus, allowing for the generation of single- and multigene knockout libraries. In addition, our system will facilitate the delineation of virulence factors and antifungal drug resistance genes in different genetic backgrounds of A. fumigatus. CRISPR (clustered regularly interspaced short palindromic repeat)-Cas9 is a novel genome-editing system that has been successfully established in Aspergillus fumigatus. However, the current state of the technology relies heavily on DNA-based expression cassettes for delivering Cas9 and the guide RNA (gRNA) to the cell. Therefore, the power of the technology is limited to strains that are engineered to express Cas9 and gRNA. To overcome such limitations, we developed a simple and universal CRISPR-Cas9 system for gene deletion that works across different genetic backgrounds of A. fumigatus. The system employs in vitro assembly of dual Cas9 ribonucleoproteins (RNPs) for targeted gene deletion. Additionally, our CRISPR-Cas9 system utilizes 35 to 50 bp of flanking regions for mediating homologous recombination at Cas9 double-strand breaks (DSBs). As a proof of concept, we first tested our system in the ΔakuB (ΔakuBku80) laboratory strain and generated high rates (97%) of gene deletion using 2 µg of the repair template flanked by homology regions as short as 35 bp. Next, we inspected the portability of our system across other genetic backgrounds of A. fumigatus, namely, the wild-type strain Af293 and a clinical isolate, A. fumigatus DI15-102. In the Af293 strain, 2 µg of the repair template flanked by 35 and 50 bp of homology resulted in highly efficient gene deletion (46% and 74%, respectively) in comparison to classical gene replacement systems. Similar deletion efficiencies were also obtained in the clinical isolate DI15-102. Taken together, our data show that in vitro-assembled Cas9 RNPs coupled with microhomology repair templates are an efficient and universal system for gene manipulation in A. fumigatus. IMPORTANCE Tackling the multifactorial nature of virulence and antifungal drug resistance in A. fumigatus requires the mechanistic interrogation of a multitude of genes, sometimes across multiple genetic backgrounds. Classical fungal gene replacement systems can be laborious and time-consuming and, in wild-type isolates, are impeded by low rates of homologous recombination. Our simple and universal CRISPR-Cas9 system for gene manipulation generates efficient gene targeting across different genetic backgrounds of A. fumigatus. We anticipate that our system will simplify genome editing in A. fumigatus, allowing for the generation of single- and multigene knockout libraries. In addition, our system will facilitate the delineation of virulence factors and antifungal drug resistance genes in different genetic backgrounds of A. fumigatus.
Collapse
|
9
|
Caspofungin-Mediated Growth Inhibition and Paradoxical Growth in Aspergillus fumigatus Involve Fungicidal Hyphal Tip Lysis Coupled with Regenerative Intrahyphal Growth and Dynamic Changes in β-1,3-Glucan Synthase Localization. Antimicrob Agents Chemother 2017; 61:AAC.00710-17. [PMID: 28760907 DOI: 10.1128/aac.00710-17] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 07/13/2017] [Indexed: 12/26/2022] Open
Abstract
Caspofungin targets cell wall β-1,3-glucan synthesis and is the international consensus guideline-recommended salvage therapy for invasive aspergillosis. Although caspofungin is inhibitory at low concentrations, it exhibits a paradoxical effect (reversal of growth inhibition) at high concentrations by an undetermined mechanism. Treatment with caspofungin at either the growth-inhibitory concentration (0.5 μg/ml) or paradoxical growth-inducing concentration (4 μg/ml) for 24 h caused similar abnormalities, including wider, hyperbranched hyphae, increased septation, and repeated hyphal tip lysis, followed by regenerative intrahyphal growth. By 48 h, only hyphae at the colony periphery treated with the high caspofungin concentration displayed paradoxical growth. A similar high concentration of caspofungin also induced the paradoxical growth of Aspergillus fumigatus during human A549 alveolar cell invasion. Localization of the β-1,3-glucan synthase complex (Fks1 and Rho1) revealed significant differences between cells exposed to the growth-inhibitory and paradoxical growth-inducing concentrations of caspofungin. At both concentrations, Fks1 initially mislocalized from the hyphal tips to vacuoles. However, only continuous exposure to 4 μg/ml of caspofungin for 48 h led to recovery of the normal hyphal morphology with renewed localization of Fks1 to hyphal tips. Rho1 remained at the hyphal tip after treatment with both caspofungin concentrations but was required for paradoxical growth. Farnesol blocked paradoxical growth and relocalized Fks1 and Rho1 to vacuoles. Our results highlight the importance of regenerative intrahyphal growth as a rapid adaptation to the fungicidal lytic effects of caspofungin on hyphal tips and the dynamic localization of Fks1 as part of the mechanism for the caspofungin-mediated paradoxical response in A. fumigatus.
Collapse
|
10
|
Abstract
Aspergillus fumigatus is an environmental filamentous fungus that can cause life-threatening disease in immunocompromised individuals. The interactions between A. fumigatus and the host environment are dynamic and complex. The host immune system needs to recognize the distinct morphological forms of A. fumigatus to control fungal growth and prevent tissue invasion, whereas the fungus requires nutrients and needs to adapt to the hostile environment by escaping immune recognition and counteracting host responses. Understanding these highly dynamic interactions is necessary to fully understand the pathogenesis of aspergillosis and to facilitate the design of new therapeutics to overcome the morbidity and mortality caused by A. fumigatus. In this Review, we describe how A. fumigatus adapts to environmental change, the mechanisms of host defence, and our current knowledge of the interplay between the host immune response and the fungus.
Collapse
|
11
|
Dirhamnolipids secreted from Pseudomonas aeruginosa modify anjpegungal susceptibility of Aspergillus fumigatus by inhibiting β1,3 glucan synthase activity. ISME JOURNAL 2017; 11:1578-1591. [PMID: 28338676 PMCID: PMC5584477 DOI: 10.1038/ismej.2017.32] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 01/05/2017] [Accepted: 01/22/2017] [Indexed: 12/16/2022]
Abstract
Pseudomonas aeruginosa and Aspergillus fumigatus are the two microorganisms responsible for most of the chronic infections in cystic fibrosis patients. P. aeruginosa is known to produce quorum-sensing controlled rhamnolipids during chronic infections. Here we show that the dirhamnolipids secreted from P. aeruginosa (i) induce A. fumigatus to produce an extracellular matrix, rich in galactosaminogalactan, 1,8-dihydroxynaphthalene (DHN)- and pyo-melanin, surrounding their hyphae, which facilitates P. aeruginosa binding and (ii) inhibit A. fumigatus growth by blocking β1,3 glucan synthase (GS) activity, thus altering the cell wall architecture. A. fumigatus in the presence of diRhls resulted in a growth phenotype similar to that upon its treatment with anjpegungal echinocandins, showing multibranched hyphae and thicker cell wall rich in chitin. The diRhl structure containing two rhamnose moieties attached to fatty acyl chain is essential for the interaction with β1,3 GS; however, the site of action of diRhls on GS is different from that of echinocandins, and showed synergistic anjpegungal effect with azoles.
Collapse
|
12
|
Mulvihill ED, Moloney NM, Owens RA, Dolan SK, Russell L, Doyle S. Functional Investigation of Iron-Responsive Microsomal Proteins, including MirC, in Aspergillus fumigatus. Front Microbiol 2017; 8:418. [PMID: 28367141 PMCID: PMC5355445 DOI: 10.3389/fmicb.2017.00418] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 02/27/2017] [Indexed: 11/13/2022] Open
Abstract
The functionality of many microsome-associated proteins which exhibit altered abundance in response to iron limitation in Aspergillus fumigatus is unknown. Here, we generate and characterize eight gene deletion strains, and of most significance reveal that MirC (AFUA_2G05730) contributes to the maintenance of intracellular siderophore [ferricrocin (FC)] levels, augments conidiation, confers protection against oxidative stress, exhibits an intracellular localization and contributes to fungal virulence in the Galleria mellonella animal model system. FC levels were unaffected following deletion of all other genes encoding microsome-associated proteins. MirC does not appear to play a role in either siderophore export from, or uptake into, A. fumigatus. Label-free quantitative proteomic analysis unexpectedly revealed increased abundance of siderophore biosynthetic enzymes. In addition, increased expression of hapX (7.2 and 13.8-fold at 48 and 72 h, respectively; p < 0.001) was observed in ΔmirC compared to wild-type under iron-replete conditions by qRT-PCR. This was complemented by significantly elevated extracellular triacetylfusarinine C (TAFC; p < 0.01) and fusarinine C (FSC; p < 0.05) siderophore secretion. We conclude that MirC plays an important role in FC biosynthesis and contributes to the maintenance of iron homeostasis in A. fumigatus.
Collapse
Affiliation(s)
| | | | | | - Stephen K Dolan
- Department of Biology, Maynooth UniversityKildare, Ireland; Department of Biochemistry, University of CambridgeCambridge, UK
| | - Lauren Russell
- Department of Biology, Maynooth University Kildare, Ireland
| | - Sean Doyle
- Department of Biology, Maynooth University Kildare, Ireland
| |
Collapse
|
13
|
Valiante V, Baldin C, Hortschansky P, Jain R, Thywißen A, Straßburger M, Shelest E, Heinekamp T, Brakhage AA. TheAspergillus fumigatusconidial melanin production is regulated by the bifunctional bHLH DevR and MADS-box RlmA transcription factors. Mol Microbiol 2016; 102:321-335. [DOI: 10.1111/mmi.13462] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/07/2016] [Indexed: 02/02/2023]
Affiliation(s)
- Vito Valiante
- Department of Molecular and Applied Microbiology; Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI); Adolf-Reichwein-Str. 23 Jena 07745 Germany
- Leibniz Research Group - Biobricks of Microbial Natural Product Syntheses, Leibniz Institute for Natural Product Research and Infection Biology (HKI); Jena Germany
| | - Clara Baldin
- Department of Molecular and Applied Microbiology; Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI); Adolf-Reichwein-Str. 23 Jena 07745 Germany
- Department of Microbiology and Molecular Biology; Institute of Microbiology, Friedrich Schiller University Jena; Adolf-Reichwein-Str. 23 Jena 07745 Germany
| | - Peter Hortschansky
- Department of Molecular and Applied Microbiology; Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI); Adolf-Reichwein-Str. 23 Jena 07745 Germany
| | - Radhika Jain
- Department of Molecular and Applied Microbiology; Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI); Adolf-Reichwein-Str. 23 Jena 07745 Germany
- Department of Microbiology and Molecular Biology; Institute of Microbiology, Friedrich Schiller University Jena; Adolf-Reichwein-Str. 23 Jena 07745 Germany
| | - Andreas Thywißen
- Department of Molecular and Applied Microbiology; Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI); Adolf-Reichwein-Str. 23 Jena 07745 Germany
- Department of Microbiology and Molecular Biology; Institute of Microbiology, Friedrich Schiller University Jena; Adolf-Reichwein-Str. 23 Jena 07745 Germany
| | - Maria Straßburger
- Department of Molecular and Applied Microbiology; Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI); Adolf-Reichwein-Str. 23 Jena 07745 Germany
- Transfer Group Anti-Infectives, Leibniz Institute for Natural Product Research and Infection Biology (HKI); Jena Germany
| | - Ekaterina Shelest
- Research Group Bioinformatics/Systems Biology, Leibniz Institute for Natural Product Research and Infection Biology (HKI); Jena Germany
| | - Thorsten Heinekamp
- Department of Molecular and Applied Microbiology; Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI); Adolf-Reichwein-Str. 23 Jena 07745 Germany
- Department of Microbiology and Molecular Biology; Institute of Microbiology, Friedrich Schiller University Jena; Adolf-Reichwein-Str. 23 Jena 07745 Germany
| | - Axel A. Brakhage
- Department of Molecular and Applied Microbiology; Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI); Adolf-Reichwein-Str. 23 Jena 07745 Germany
- Department of Microbiology and Molecular Biology; Institute of Microbiology, Friedrich Schiller University Jena; Adolf-Reichwein-Str. 23 Jena 07745 Germany
| |
Collapse
|
14
|
Distinct Roles of Myosins in Aspergillus fumigatus Hyphal Growth and Pathogenesis. Infect Immun 2016; 84:1556-64. [PMID: 26953327 DOI: 10.1128/iai.01190-15] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 02/24/2016] [Indexed: 11/20/2022] Open
Abstract
Myosins are a family of actin-based motor proteins found in many organisms and are categorized into classes based on their structures. Class II and V myosins are known to be important for critical cellular processes, including cytokinesis, endocytosis, exocytosis, and organelle trafficking, in the model fungi Saccharomyces cerevisiae and Aspergillus nidulans However, the roles of myosins in the growth and virulence of the pathogen Aspergillus fumigatus are unknown. We constructed single- and double-deletion strains of the class II and class V myosins in A. fumigatus and found that while the class II myosin (myoB) is dispensable for growth, the class V myosin (myoE) is required for proper hyphal extension; deletion of myoE resulted in hyperbranching and loss of hyphal polarity. Both myoB and myoE are necessary for proper septation, conidiation, and conidial germination, but only myoB is required for conidial viability. Infection with the ΔmyoE strain in the invertebrate Galleria mellonella model and also in a persistently immunosuppressed murine model of invasive aspergillosis resulted in hypovirulence, while analysis of bronchoalveolar lavage fluid revealed that tumor necrosis factor alpha (TNF-α) release and cellular infiltration were similar compared to those of the wild-type strain. The ΔmyoE strain showed fungal growth in the murine lung, while the ΔmyoB strain exhibited little fungal burden, most likely due to the reduced conidial viability. These results show, for the first time, the important role these cytoskeletal components play in the growth of and disease caused by a known pathogen, prompting future studies to understand their regulation and potential targeting for novel antifungal therapies.
Collapse
|
15
|
Abstract
In vivo, Aspergillus fumigatus grows as a typical biofilm with hyphae covered by an extracellular matrix (ECM) composed of polysaccharides, galactomannan, and galactosaminogalactan. α1,3 glucans and melanin are also constitutive of the ECM in aspergilloma but not in invasive aspergillosis. In vitro, two biofilm models were established to mimic the in vivo situation. The first model (model 1) uses submerged liquid conditions and is characterized by slow growth, while the second model (model 2) uses agar medium and aerial conditions and is characterized by rapid growth. The composition of the ECM was studied only in the second model and has been shown to be composed of galactomannan, galactosaminogalactan (GAG), and α1,3 glucans, melanin, antigens, and hydrophobins. The presence of extracellular DNA was detected in model 1 biofilm but not in model 2. Transcriptomic analysis employing both biofilm models showed upregulation of genes coding for proteins involved in the biosynthesis of secondary metabolites, adhesion, and drug resistance. However, most data on A. fumigatus biofilms have been obtained in vitro and should be confirmed using in vivo animal models. There is a need for new therapeutic antibiofilm strategies that focus on the use of combination therapy, since biofilm formation poses an important clinical problem due to their resistance to antifungal agents. Furthermore, in vivo investigations of A. fumigatus biofilms that incorporate the associated microbiota are needed. Such studies will add another layer of complexity to our understanding of the role of A. fumigatus biofilm during lung invasion.
Collapse
|
16
|
The Aspergillus fumigatus septins play pleiotropic roles in septation, conidiation, and cell wall stress, but are dispensable for virulence. Fungal Genet Biol 2015; 81:41-51. [PMID: 26051489 DOI: 10.1016/j.fgb.2015.05.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 05/13/2015] [Accepted: 05/31/2015] [Indexed: 11/23/2022]
Abstract
Septins are a conserved family of GTPases that regulate important cellular processes such as cell wall integrity, and septation in fungi. The requirement of septins for virulence has been demonstrated in the human pathogenic yeasts Candida albicans and Cryptococcus neoformans, as well as the plant pathogen Magnaporthe oryzae. Aspergillus spp. contains five genes encoding for septins (aspA-E). While the importance of septins AspA, AspB, AspC, and AspE for growth and conidiation has been elucidated in the filamentous fungal model Aspergillus nidulans, nothing is known on the role of septins in growth and virulence in the human pathogen Aspergillus fumigatus. Here we deleted all five A. fumigatus septins, and generated certain double and triple septin deletion strains. Phenotypic analyses revealed that while all the septins are dispensable in normal growth conditions, AspA, AspB, AspC and AspE are required for regular septation. Furthermore, deletion of only the core septin genes significantly reduced conidiation. Concomitant with the absence of an electron-dense outer conidial wall, the ΔaspB strain was also sensitive to anti-cell wall agents. Infection with the ΔaspB strain in a Galleria mellonella model of invasive aspergillosis showed hypervirulence, but no virulence difference was noted when compared to the wild-type strain in a murine model of invasive aspergillosis. Although the deletion of aspB resulted in increased release of TNF-α from the macrophages, no significant inflammation differences in lung histology was noted between the ΔaspB strain and the wild-type strain. Taken together, these results point to the importance of septins in A. fumigatus growth, but not virulence in a murine model.
Collapse
|
17
|
Juvvadi PR, Ma Y, Richards AD, Soderblom EJ, Moseley MA, Lamoth F, Steinbach WJ. Identification and mutational analyses of phosphorylation sites of the calcineurin-binding protein CbpA and the identification of domains required for calcineurin binding in Aspergillus fumigatus. Front Microbiol 2015; 6:175. [PMID: 25821446 PMCID: PMC4358225 DOI: 10.3389/fmicb.2015.00175] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 02/16/2015] [Indexed: 11/26/2022] Open
Abstract
Calcineurin is a key protein phosphatase required for hyphal growth and virulence in Aspergillus fumigatus, making it an attractive antifungal target. However, currently available calcineurin inhibitors, FK506 and cyclosporine A, are immunosuppressive, limiting usage in the treatment of patients with invasive aspergillosis. Therefore, the identification of endogenous inhibitors of calcineurin belonging to the calcipressin family is an important parallel strategy. We previously identified the gene cbpA as the A. fumigatus calcipressin member and showed its involvement in hyphal growth and calcium homeostasis. However, the mechanism of its activation/inhibition through phosphorylation and its interaction with calcineurin remains unknown. Here we show that A. fumigatus CbpA is phosphorylated at three distinct domains, including the conserved SP repeat motif (phosphorylated domain-I; PD-I), a filamentous fungal-specific domain (PD-II), and the C-terminal CIC motif (Calcipressin Inhibitor of Calcineurin; PD-III). While mutation of three phosphorylated residues (Ser208, Ser217, Ser223) in the PD-II did not affect CbpA function in vivo, mutation of the two phosphorylated serines (Ser156, Ser160) in the SP repeat motif caused reduced hyphal growth and sensitivity to oxidative stress. Mutational analysis in the key domains in calcineurin A (CnaA) and proteomic interaction studies confirmed the requirement of PxIxIT motif-binding residues (352-NIR-354) and the calcineurin B (CnaB)-binding helix residue (V371) for the binding of CbpA to CnaA. Additionally, while the calmodulin-binding residues (442-RVF-444) did not affect CbpA binding to CnaA, three mutations (T359P, H361L, and L365S) clustered between the CnaA catalytic and the CnaB-binding helix were also required for CbpA binding. This is the first study to analyze the phosphorylation status of calcipressin in filamentous fungi and identify the domains required for binding to calcineurin.
Collapse
Affiliation(s)
- Praveen R Juvvadi
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Duke University Medical Center Durham, NC, USA
| | - Yan Ma
- Department of Dermatology and Venereology, The Second Hospital of Shanxi Medical University Taiyuan, Shanxi, China
| | - Amber D Richards
- Department of Dermatology and Venereology, The Second Hospital of Shanxi Medical University Taiyuan, Shanxi, China
| | - Erik J Soderblom
- Department of Dermatology and Venereology, The Second Hospital of Shanxi Medical University Taiyuan, Shanxi, China
| | - M Arthur Moseley
- Duke Proteomics and Metabolomics Core Facility, Center for Genomic and Computational Biology, Duke University Durham, NC, USA
| | - Frédéric Lamoth
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Duke University Medical Center Durham, NC, USA ; Infectious Diseases Service, Department of Medicine, Lausanne University Hospital Lausanne, Switzerland ; Institute of Microbiology, Lausanne University Hospital Lausanne, Switzerland
| | - William J Steinbach
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Duke University Medical Center Durham, NC, USA ; Department of Molecular Genetics and Microbiology, Duke University Medical Center Durham, NC, USA
| |
Collapse
|
18
|
Islamovic E, García-Pedrajas MD, Chacko N, Andrews DL, Covert SF, Gold SE. Transcriptome Analysis of a Ustilago maydis ust1 Deletion Mutant Uncovers Involvement of Laccase and Polyketide Synthase Genes in Spore Development. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 28:42-54. [PMID: 25226432 DOI: 10.1094/mpmi-05-14-0133-r] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Ustilago maydis, causal agent of corn smut disease, is a dimorphic fungus alternating between a saprobic budding haploid and an obligate pathogenic filamentous dikaryon. Maize responds to U. maydis colonization by producing tumorous structures, and only within these does the fungus sporulate, producing melanized sexual teliospores. Previously we identified Ust1, an APSES (Asm1p, Phd1p, Sok2p, Efg1p, and StuAp) transcription factor, whose deletion led to filamentous haploid growth and the production of highly pigmented teliospore-like structures in culture. In this study, we analyzed the transcriptome of a ust1 deletion mutant and functionally characterized two highly upregulated genes with potential roles in melanin biosynthesis: um05361, encoding a putative laccase (lac1), and um06414, encoding a polyketide synthase (pks1). The Δlac1 mutant strains showed dramatically reduced virulence on maize seedlings and fewer, less-pigmented teliospores in adult plants. The Δpks1 mutant was unaffected in seedling virulence but adult plant tumors generated hyaline, nonmelanized teliospores. Thus, whereas pks1 appeared to be restricted to the synthesis of melanin, lac1 showed a broader role in virulence. In conclusion, the ust1 deletion mutant provided an in vitro model for sporulation in U. maydis, and functional analysis supports the efficacy of this in vitro mutant analysis for identification of genes involved in in planta teliosporogenesis.
Collapse
|
19
|
Cui Q, Zhang Y, Zang Y, Nong X, Wang G, Zhang Z. Screening of high toxic Metarhizium strain against Plutella xylostella and its marking with green fluorescent protein. World J Microbiol Biotechnol 2014; 30:2767-73. [PMID: 25037866 DOI: 10.1007/s11274-014-1700-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 07/03/2014] [Indexed: 11/30/2022]
Abstract
Entomopathogenic fungus is proposed to be one of the best biocontrol agents against the destructive insect pest Plutella xylostella. In this study, we tested the virulence of 11 Metarhizium strain isolates against P. xylostella using a leaf dipping method, and found one strain, named 609, which had displayed the highest pathogenicity. Bioassay results showed that the accumulated corrected mortality rate was 86.7 % on the eighth day after inoculation with a spore concentration 1 × 10(8) conidia/mL, and that the time to 50 % lethality was 5.7-day. The strain was identified as Metarhizium anisopliae var. acridum by internal transcribed spacer (ITS) region sequencing. A green fluorescent protein (GFP) marker containing vector, camben-gfp, was constructed and delivered into strain 609 by Agrobacterium tumefaciens-mediated transformation. Six positive clones expressing GFP were selected and tested for toxicity against P. xylostella, all of which displayed the same toxicity as the parental wild type strain. The survival rate of transformant T1 was investigated by monitoring GFP levels at 4-day intervals after inoculation into soil. We found that the concentration of Metarhizium spores decreased sharply from 1 × 10(7) conidia/g to 1 × 10(6) conidia/g in the first 5 days after inoculation. The decreasing trend then stabilized and the spore count declined to approximately 1 × 10(4)-10(5) conidia/g after 1 month. The results of this study indicate that the expression of gfp gene in strain 609 does not alter the virulence capability of Metarhizium. This strain will therefore be useful for the control of P. xylostella and as a tool to study molecular biology properties and monitor colonization of M. anisopliae in the field.
Collapse
Affiliation(s)
- Qianqian Cui
- State Key Laboratory for Biology of Plant Diseases and Insect Pests/Institute of Plant Protection, Chinese Academy of Agricultural Sciences (CAAS), No. 12, Zhongguancun South Street, Beijing, 100081, China
| | | | | | | | | | | |
Collapse
|
20
|
Identification of a key lysine residue in heat shock protein 90 required for azole and echinocandin resistance in Aspergillus fumigatus. Antimicrob Agents Chemother 2014; 58:1889-96. [PMID: 24395240 DOI: 10.1128/aac.02286-13] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Heat shock protein 90 (Hsp90) is an essential chaperone involved in the fungal stress response that can be harnessed as a novel antifungal target for the treatment of invasive aspergillosis. We previously showed that genetic repression of Hsp90 reduced Aspergillus fumigatus virulence and potentiated the effect of the echinocandin caspofungin. In this study, we sought to identify sites of posttranslational modifications (phosphorylation or acetylation) that are important for Hsp90 function in A. fumigatus. Phosphopeptide enrichment and tandem mass spectrometry revealed phosphorylation of three residues in Hsp90 (S49, S288, and T681), but their mutation did not compromise Hsp90 function. Acetylation of lysine residues of Hsp90 was recovered after treatment with deacetylase inhibitors, and acetylation-mimetic mutations (K27A and K271A) resulted in reduced virulence in a murine model of invasive aspergillosis, supporting their role in Hsp90 function. A single deletion of lysine K27 or an acetylation-mimetic mutation (K27A) resulted in increased susceptibility to voriconazole and caspofungin. This effect was attenuated following a deacetylation-mimetic mutation (K27R), suggesting that this site is crucial and should be deacetylated for proper Hsp90 function in antifungal resistance pathways. In contrast to previous reports in Candida albicans, the lysine deacetylase inhibitor trichostatin A (TSA) was active alone against A. fumigatus and potentiated the effect of caspofungin against both the wild type and an echinocandin-resistant strain. Our results indicate that the Hsp90 K27 residue is required for azole and echinocandin resistance in A. fumigatus and that deacetylase inhibition may represent an adjunctive anti-Aspergillus strategy.
Collapse
|
21
|
Lamoth F, Juvvadi PR, Gehrke C, Asfaw YG, Steinbach WJ. Transcriptional activation of heat shock protein 90 mediated via a proximal promoter region as trigger of caspofungin resistance in Aspergillus fumigatus. J Infect Dis 2013; 209:473-81. [PMID: 24096332 DOI: 10.1093/infdis/jit530] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Invasive aspergillosis is a deadly infection for which new antifungal therapies are needed. Heat shock protein 90 (Hsp90) is an essential chaperone in Aspergillus fumigatus representing an attractive antifungal target. Using a thiamine-repressible promoter (pthiA), we showed that genetic repression of Hsp90 significantly reduced virulence in a murine model of invasive aspergillosis. Moreover, substituting the A. fumigatus hsp90 promoter with 2 artificial promoters (potef, pthiA) and the Candida albicans hsp90 promoter resulted in hypersensitivity to caspofungin and abolition of the paradoxical effect (resistance at high caspofungin concentrations). By inducing truncations in the hsp90 promoter, we identified a 100-base pair proximal sequence that triggers a significant increase of hsp90 expression (≥1.5-fold) and is essential for the paradoxical effect. Preventing this increase of hsp90 expression was sufficient to abolish the paradoxical effect and therefore optimize the antifungal activity of caspofungin.
Collapse
Affiliation(s)
- Frédéric Lamoth
- Division of Pediatric Infectious Diseases, Department of Pediatrics
| | | | | | | | | |
Collapse
|
22
|
Gründlinger M, Yasmin S, Lechner BE, Geley S, Schrettl M, Hynes M, Haas H. Fungal siderophore biosynthesis is partially localized in peroxisomes. Mol Microbiol 2013; 88:862-75. [PMID: 23617799 PMCID: PMC3709128 DOI: 10.1111/mmi.12225] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/03/2013] [Indexed: 11/28/2022]
Abstract
Siderophores play a central role in iron metabolism and virulence of most fungi. Both Aspergillus fumigatus and Aspergillus nidulans excrete the siderophore triacetylfusarinine C (TAFC) for iron acquisition. In A. fumigatus, green fluorescence protein-tagging revealed peroxisomal localization of the TAFC biosynthetic enzymes SidI (mevalonyl-CoA ligase), SidH (mevalonyl-CoA hydratase) and SidF (anhydromevalonyl-CoA transferase), while elimination of the peroxisomal targeting signal (PTS) impaired both, peroxisomal SidH-targeting and TAFC biosynthesis. The analysis of A. nidulans mutants deficient in peroxisomal biogenesis, ATP import or protein import revealed that cytosolic mislocalization of one or two but, interestingly, not all three enzymes impairs TAFC production during iron starvation. The PTS motifs are conserved in fungal orthologues of SidF, SidH and SidI. In agreement with the evolutionary conservation of the partial peroxisomal compartmentalization of fungal siderophore biosynthesis, the SidI orthologue of coprogen-type siderophore-producing Neurospora crassa was confirmed to be peroxisomal. Taken together, this study identified and characterized a novel, evolutionary conserved metabolic function of peroxisomes.
Collapse
Affiliation(s)
- Mario Gründlinger
- Division of Molecular Biology/Biocenter, Innsbruck Medical University, Innrain 80-82, A-6020, Innsbruck, Austria
| | | | | | | | | | | | | |
Collapse
|
23
|
Heinekamp T, Thywißen A, Macheleidt J, Keller S, Valiante V, Brakhage AA. Aspergillus fumigatus melanins: interference with the host endocytosis pathway and impact on virulence. Front Microbiol 2013; 3:440. [PMID: 23346079 PMCID: PMC3548413 DOI: 10.3389/fmicb.2012.00440] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Accepted: 12/19/2012] [Indexed: 11/13/2022] Open
Abstract
The opportunistic human pathogenic fungus Aspergillus fumigatus produces at least two types of melanin, namely pyomelanin and dihydroxynaphthalene (DHN) melanin. Pyomelanin is produced during tyrosine catabolism via accumulation of homogentisic acid. Although pyomelanin protects the fungus against reactive oxygen species (ROS) and acts as a defense compound in response to cell wall stress, mutants deficient for pyomelanin biosynthesis do not differ in virulence when tested in a murine infection model for invasive pulmonary aspergillosis. DHN melanin is responsible for the characteristic gray-greenish color of A. fumigatus conidia. Mutants lacking a functional polyketide synthase PksP, the enzyme responsible for the initial step in DHN-melanin formation, i.e., the synthesis of naphthopyrone, produce white spores and are attenuated in virulence. The activity of PksP was found to be essential not only for inhibition of apoptosis of phagocytes by interfering with the host PI3K/Akt signaling cascade but also for effective inhibition of acidification of conidia-containing phagolysosomes. These features allow A. fumigatus to survive in phagocytes and thereby to escape from human immune effector cells and to become a successful pathogen.
Collapse
Affiliation(s)
- Thorsten Heinekamp
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute Jena, Germany
| | | | | | | | | | | |
Collapse
|
24
|
Abstract
The filamentous fungus Aspergillus fumigatus is an important opportunistic pathogen that can cause high mortality levels in susceptible patient populations. The increasing dependence on antifungal drugs to control A. fumigatus has led to the inevitable acquisition of drug-resistant forms of this pathogen. In other fungal pathogens, drug resistance is often associated with an increase in transcription of genes such as ATP-binding cassette (ABC) transporters that directly lead to tolerance to commonly employed antifungal drugs. In A. fumigatus, tolerance to azole drugs (the major class of antifungal) is often associated with changes in the sequence of the azole target enzyme as well as changes in the transcription level of this gene. The target gene for azole drugs in A. fumigatus is referred to as cyp51A. In order to dissect transcription of cyp51A transcription and other genes of interest, we constructed a set of firefly luciferase reporter genes designed for use in A. fumigatus. These reporter genes can either replicate autonomously or be targeted to the pyrG locus, generating an easily assayable uracil auxotrophy. We fused eight different A. fumigatus promoters to luciferase. Faithful behaviors of these reporter gene fusions compared to their chromosomal equivalents were evaluated by 5' rapid amplification of cDNA ends (RACE) and quantitative reverse transcription-PCR (qRT-PCR) analysis. We used this reporter gene system to study stress-regulated transcription of a Hsp70-encoding gene, map an important promoter element in the cyp51A gene, and correct an annotation error in the actin gene. We anticipate that this luciferase reporter gene system will be broadly applicable in analyses of gene expression in A. fumigatus.
Collapse
|
25
|
Heat shock protein 90 is required for conidiation and cell wall integrity in Aspergillus fumigatus. EUKARYOTIC CELL 2012; 11:1324-32. [PMID: 22822234 DOI: 10.1128/ec.00032-12] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Heat shock protein 90 (Hsp90) is a eukaryotic molecular chaperone. Its involvement in the resistance of Candida albicans to azole and echinocandin antifungals is well established. However, little is known about Hsp90's function in the filamentous fungal pathogen Aspergillus fumigatus. We investigated the role of Hsp90 in A. fumigatus by genetic repression and examined its cellular localization under various stress conditions. Failure to generate a deletion strain of hsp90 suggested that it is essential. Genetic repression of Hsp90 was achieved by an inducible nitrogen-dependent promoter (pniiA-Hsp90) and led to decreased spore viability, decreased hyphal growth, and severe defects in germination and conidiation concomitant with the downregulation of the conidiation-specific transcription factors brlA, wetA, and abaA. Hsp90 repression potentiated the effect of cell wall inhibitors affecting the β-glucan structure of the cell wall (caspofungin, Congo red) and of the calcineurin inhibitor FK506, supporting a role in regulating cell wall integrity pathways. Moreover, compromising Hsp90 abolished the paradoxical effect of caspofungin. Pharmacological inhibition of Hsp90 by geldanamycin and its derivatives (17-AAG and 17-DMAG) resulted in similar effects. C-terminal green fluorescent protein (GFP) tagging of Hsp90 revealed mainly cytosolic distribution under standard growth conditions. However, treatment with caspofungin resulted in Hsp90 accumulation at the cell wall and at sites of septum formation, further highlighting its role in cell wall stress compensatory mechanisms. Targeting Hsp90 with fungal-specific inhibitors to cripple stress response compensatory pathways represents an attractive new antifungal strategy.
Collapse
|
26
|
Priegnitz BE, Wargenau A, Brandt U, Rohde M, Dietrich S, Kwade A, Krull R, Fleißner A. The role of initial spore adhesion in pellet and biofilm formation in Aspergillus niger. Fungal Genet Biol 2012; 49:30-8. [DOI: 10.1016/j.fgb.2011.12.002] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Revised: 10/05/2011] [Accepted: 12/05/2011] [Indexed: 11/30/2022]
|
27
|
Juvvadi PR, Fortwendel JR, Rogg LE, Burns KA, Randell SH, Steinbach WJ. Localization and activity of the calcineurin catalytic and regulatory subunit complex at the septum is essential for hyphal elongation and proper septation in Aspergillus fumigatus. Mol Microbiol 2011; 82:1235-59. [PMID: 22066998 DOI: 10.1111/j.1365-2958.2011.07886.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Calcineurin, a heterodimer composed of the catalytic (CnaA) and regulatory (CnaB) subunits, plays key roles in growth, virulence and stress responses of fungi. To investigate the contribution of CnaA and CnaB to hyphal growth and septation, ΔcnaB and ΔcnaAΔcnaB strains of Aspergillus fumigatus were constructed. CnaA colocalizes to the contractile actin ring early during septation and remains at the centre of the mature septum. While CnaB's septal localization is CnaA-dependent, CnaA's septal localization is CnaB-independent, but CnaB is required for CnaA's function at the septum. Catalytic null mutations in CnaA caused stunted growth despite septal localization of the calcineurin complex, indicating the requirement of calcineurin activity at the septum. Compared to the ΔcnaA and ΔcnaB strains, the ΔcnaAΔcnaB strain displayed more defective growth and aberrant septation. While three Ca(2+) -binding motifs in CnaB were sufficient for its association with CnaA at the septum, the amino-terminal arginine-rich domains (16-RRRR-19 and 44-RLRKR-48) are dispensable for septal localization, yet required for complete functionality. Mutation of the 51-KLDK-54 motif in CnaB causes its mislocalization from the septum to the nucleus, suggesting it is a nuclear export signal sequence. These findings confirm a cooperative role for the calcineurin complex in regulating hyphal growth and septation.
Collapse
Affiliation(s)
- Praveen Rao Juvvadi
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Duke University Medical Center, Durham, NC, USA
| | | | | | | | | | | |
Collapse
|
28
|
Keller S, Macheleidt J, Scherlach K, Schmaler-Ripcke J, Jacobsen ID, Heinekamp T, Brakhage AA. Pyomelanin formation in Aspergillus fumigatus requires HmgX and the transcriptional activator HmgR but is dispensable for virulence. PLoS One 2011; 6:e26604. [PMID: 22046314 PMCID: PMC3203155 DOI: 10.1371/journal.pone.0026604] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 09/29/2011] [Indexed: 01/07/2023] Open
Abstract
The opportunistic human pathogenic fungus Aspergillus fumigatus is able to produce the dark brown pigment pyomelanin by degradation of L-tyrosine. Pyomelanin was shown to protect the fungus against reactive oxygen intermediates as well as cell wall disturbing compounds and is therefore assumed to protect against immune effector cells during the infection process. Several genes for tyrosine degradation and pyomelanin formation are organized in a cluster in the genome of A. fumigatus. Here, we aimed at further analyzing tyrosine degradation and a possible role of pyomelanin in virulence. For this purpose, the function of two not yet characterized genes of the cluster, i.e., hmgX and hmgR, was analyzed. Generation of corresponding gene deletion mutants and reconstituted strains revealed that hmgX and hmgR are essential for tyrosine degradation. Both mutants, ΔhmgX and ΔhmgR, were not able to use tyrosine as sole carbon or nitrogen source and revealed impaired pyomelanin production. HmgR harbors a Zn(II)2Cys6-DNA binding domain. Analyses of the steady state mRNA levels revealed that HmgR acts as a transcriptional activator for the genes of the tyrosine degradation cluster. Consistently, an HmgR-eGFP fusion protein was localized in the nucleus of A. fumigatus cells. By contrast, HmgX was found to be localized in the cytoplasm and does not contribute to regulation of gene transcription. HPLC analyses showed that HmgX is crucial for the conversion of p-hydroxyphenylpyruvate to homogentisic acid, the main intermediate in pyomelanin formation. Thus, HmgX is supposed to function as an accessory factor to mediate specific activity of HppD. Remarkably, the ability to degrade tyrosine and to form pyomelanin is dispensable for virulence of A. fumigatus in a murine infection model.
Collapse
Affiliation(s)
- Sophia Keller
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute (HKI), Jena, Germany
- Department of Microbiology and Molecular Biology, Friedrich Schiller University, Jena, Germany
| | - Juliane Macheleidt
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute (HKI), Jena, Germany
- Department of Microbiology and Molecular Biology, Friedrich Schiller University, Jena, Germany
| | - Kirstin Scherlach
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute (HKI), Jena, Germany
| | - Jeannette Schmaler-Ripcke
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute (HKI), Jena, Germany
| | - Ilse D. Jacobsen
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute (HKI), Jena, Germany
| | - Thorsten Heinekamp
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute (HKI), Jena, Germany
- Department of Microbiology and Molecular Biology, Friedrich Schiller University, Jena, Germany
- * E-mail: (AAB); (TH)
| | - 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 of Microbiology and Molecular Biology, Friedrich Schiller University, Jena, Germany
- * E-mail: (AAB); (TH)
| |
Collapse
|
29
|
Rogg LE, Fortwendel JR, Juvvadi PR, Lilley A, Steinbach WJ. The chitin synthase genes chsA and chsC are not required for cell wall stress responses in the human pathogen Aspergillus fumigatus. Biochem Biophys Res Commun 2011; 411:549-54. [PMID: 21763289 DOI: 10.1016/j.bbrc.2011.06.180] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Accepted: 06/30/2011] [Indexed: 11/30/2022]
Abstract
Invasive aspergillosis is a leading cause of mortality in immunocompromised patients. The fungal cell wall is an attractive antifungal target, but it is dynamic and responsive to external stressors. The existence of multiple chitin synthases within Aspergilli is thought to reflect specialized functions in cell wall damage responses that facilitate continued growth and viability. We previously reported increased transcription of Aspergillus fumigatus chitin synthases chsA and chsC following echinocandin treatment, suggesting important roles for these chitin synthases in cell wall compensation. As only partial disruptions have been made of these genes, we generated deletion mutants of chsA and chsC singly (ΔchsA and ΔchsC) and doubly (ΔchsA ΔchsC). The ΔchsA ΔchsC strain displayed reduced total chitin synthase activity. Interestingly, deletion of these chitin synthase genes did not affect levels of chitin or β-1,3-glucan.The ΔchsA, ΔchsC and ΔchsA ΔchsC strains produced wild-type echinocandin-mediated chitin increases, consistent with unaltered cell wall compensation. Furthermore, transcript levels of the remaining chitin synthase genes were unchanged in the mutant strains. Taken together, these results indicate that chsA and chsC do not play a direct role in the cell wall stress response. Our findings support the existence of complex post-transcriptional regulatory mechanisms controlling chitin biosynthetic machinery in response to cell wall damage.
Collapse
Affiliation(s)
- Luise E Rogg
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Duke University Medical Center, Durham, NC 27710, USA
| | | | | | | | | |
Collapse
|
30
|
Kniemeyer O. Proteomics of eukaryotic microorganisms: The medically and biotechnologically important fungal genus Aspergillus. Proteomics 2011; 11:3232-43. [DOI: 10.1002/pmic.201100087] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Revised: 03/26/2011] [Accepted: 04/05/2011] [Indexed: 11/09/2022]
|
31
|
Bhetariya PJ, Madan T, Basir SF, Varma A, Usha SP. Allergens/Antigens, toxins and polyketides of important Aspergillus species. Indian J Clin Biochem 2011; 26:104-19. [PMID: 22468035 PMCID: PMC3107401 DOI: 10.1007/s12291-011-0131-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Accepted: 04/15/2011] [Indexed: 12/11/2022]
Abstract
The medical, agricultural and biotechnological importance of the primitive eukaryotic microorganisms, the Fungi was recognized way back in 1920. Among various groups of fungi, the Aspergillus species are studied in great detail using advances in genomics and proteomics to unravel biological and molecular mechanisms in these fungi. Aspergillus fumigatus, Aspergillus flavus, Aspergillus niger, Aspergillus parasiticus, Aspergillus nidulans and Aspergillus terreus are some of the important species relevant to human, agricultural and biotechnological applications. The potential of Aspergillus species to produce highly diversified complex biomolecules such as multifunctional proteins (allergens, antigens, enzymes) and polyketides is fascinating and demands greater insight into the understanding of these fungal species for application to human health. Recently a regulator gene for secondary metabolites, LaeA has been identified. Gene mining based on LaeA has facilitated new metabolites with antimicrobial activity such as emericellamides and antitumor activity such as terrequinone A from A. nidulans. Immunoproteomic approach was reported for identification of few novel allergens for A. fumigatus. In this context, the review is focused on recent developments in allergens, antigens, structural and functional diversity of the polyketide synthases that produce polyketides of pharmaceutical and biological importance. Possible antifungal drug targets for development of effective antifungal drugs and new strategies for development of molecular diagnostics are considered.
Collapse
Affiliation(s)
- Preetida J. Bhetariya
- Division of Plant Pathology, Indian Agricultural Research Institute, Pusa, New Delhi, 110012 India
| | - Taruna Madan
- National Institute for Research in Reproductive Health (NIRRH), Parel, Mumbai, 400012 India
| | - Seemi Farhat Basir
- Department of Biosciences, Jamia Millia Islamia, New Delhi, 110025 India
| | - Anupam Varma
- Division of Plant Pathology, Indian Agricultural Research Institute, Pusa, New Delhi, 110012 India
| | - Sarma P. Usha
- Division of Plant Pathology, Indian Agricultural Research Institute, Pusa, New Delhi, 110012 India
| |
Collapse
|
32
|
Morton CO, Varga JJ, Hornbach A, Mezger M, Sennefelder H, Kneitz S, Kurzai O, Krappmann S, Einsele H, Nierman WC, Rogers TR, Loeffler J. The temporal dynamics of differential gene expression in Aspergillus fumigatus interacting with human immature dendritic cells in vitro. PLoS One 2011; 6:e16016. [PMID: 21264256 PMCID: PMC3021540 DOI: 10.1371/journal.pone.0016016] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Accepted: 12/03/2010] [Indexed: 12/18/2022] Open
Abstract
Dendritic cells (DC) are the most important antigen presenting cells and play a pivotal role in host immunity to infectious agents by acting as a bridge between the innate and adaptive immune systems. Monocyte-derived immature DCs (iDC) were infected with viable resting conidia of Aspergillus fumigatus (Af293) for 12 hours at an MOI of 5; cells were sampled every three hours. RNA was extracted from both organisms at each time point and hybridised to microarrays. iDC cell death increased at 6 h in the presence of A. fumigatus which coincided with fungal germ tube emergence; >80% of conidia were associated with iDC. Over the time course A. fumigatus differentially regulated 210 genes, FunCat analysis indicated significant up-regulation of genes involved in fermentation, drug transport, pathogenesis and response to oxidative stress. Genes related to cytotoxicity were differentially regulated but the gliotoxin biosynthesis genes were down regulated over the time course, while Aspf1 was up-regulated at 9 h and 12 h. There was an up-regulation of genes in the subtelomeric regions of the genome as the interaction progressed. The genes up-regulated by iDC in the presence of A. fumigatus indicated that they were producing a pro-inflammatory response which was consistent with previous transcriptome studies of iDC interacting with A. fumigatus germ tubes. This study shows that A. fumigatus adapts to phagocytosis by iDCs by utilising genes that allow it to survive the interaction rather than just up-regulation of specific virulence genes.
Collapse
Affiliation(s)
- Charles O. Morton
- Department of Clinical Microbiology, Trinity College Dublin, Dublin, Ireland
| | - John J. Varga
- J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Anke Hornbach
- Medizinische Klinik and Poliklinik II, Universitätsklinikum Würzburg, Würzburg, Germany
| | - Markus Mezger
- Medizinische Klinik and Poliklinik II, Universitätsklinikum Würzburg, Würzburg, Germany
| | - Helga Sennefelder
- Medizinische Klinik and Poliklinik II, Universitätsklinikum Würzburg, Würzburg, Germany
| | - Susanne Kneitz
- Labor für Microarray Anwendungen, Interdisziplinäres Zentrum für Klinische Forschung, Würzburg, Germany
| | - Oliver Kurzai
- Septomics Research Centre, Friedrich-Schiller-Universität Jena, Leibniz Institute for Natural Products Research and Infection Biology - Hans-Knöll-Institute, Jena, Germany
| | - Sven Krappmann
- Zentrum für Infektionsforschung, Universität Würzburg, Würzburg, Germany
| | - Hermann Einsele
- Medizinische Klinik and Poliklinik II, Universitätsklinikum Würzburg, Würzburg, Germany
| | - William C. Nierman
- J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Thomas R. Rogers
- Department of Clinical Microbiology, Trinity College Dublin, Dublin, Ireland
| | - Juergen Loeffler
- Medizinische Klinik and Poliklinik II, Universitätsklinikum Würzburg, Würzburg, Germany
| |
Collapse
|
33
|
Differential localization patterns of septins during growth of the human fungal pathogen Aspergillus fumigatus reveal novel functions. Biochem Biophys Res Commun 2011; 405:238-43. [PMID: 21219860 DOI: 10.1016/j.bbrc.2011.01.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Accepted: 01/05/2011] [Indexed: 11/20/2022]
Abstract
Septins, a conserved family of GTPases, are heteropolymeric filament-forming proteins that associate with the cell membrane and cytoskeleton and serve essential functions in cell division and morphogenesis. Their roles in fungal cell wall chitin deposition, septation, cytokinesis, and sporulation have been well established and they have recently been implicated in tissue invasion and virulence in Candida albicans. Septins have never been investigated in the human pathogenic fungus, Aspergillus fumigatus, which is a leading cause of death in immunocompromised patients. Here we localize all the five septins (AspA-E) from A. fumigatus for the first time, and show that each of the five septins exhibit varied patterns of distribution. Interestingly AspE, which is unique to filamentous fungi, and AspD, belonging to the CDC10 class of septins, localized prominently to tubular structures which were dependent on actin and microtubule networks. Localization of AspD and AspE has never been reported in filamentous fungi. Taken together these results suggest that septins in A. fumigatus might have unique functions in morphogenesis and pathogenicity.
Collapse
|
34
|
Schrettl M, Carberry S, Kavanagh K, Haas H, Jones GW, O'Brien J, Nolan A, Stephens J, Fenelon O, Doyle S. Self-protection against gliotoxin--a component of the gliotoxin biosynthetic cluster, GliT, completely protects Aspergillus fumigatus against exogenous gliotoxin. PLoS Pathog 2010; 6:e1000952. [PMID: 20548963 PMCID: PMC2883607 DOI: 10.1371/journal.ppat.1000952] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Accepted: 05/12/2010] [Indexed: 11/29/2022] Open
Abstract
Gliotoxin, and other related molecules, are encoded by multi-gene clusters and biosynthesized by fungi using non-ribosomal biosynthetic mechanisms. Almost universally described in terms of its toxicity towards mammalian cells, gliotoxin has come to be considered as a component of the virulence arsenal of Aspergillus fumigatus. Here we show that deletion of a single gene, gliT, in the gliotoxin biosynthetic cluster of two A. fumigatus strains, rendered the organism highly sensitive to exogenous gliotoxin and completely disrupted gliotoxin secretion. Addition of glutathione to both A. fumigatus ΔgliT strains relieved gliotoxin inhibition. Moreover, expression of gliT appears to be independently regulated compared to all other cluster components and is up-regulated by exogenous gliotoxin presence, at both the transcript and protein level. Upon gliotoxin exposure, gliT is also expressed in A. fumigatus ΔgliZ, which cannot express any other genes in the gliotoxin biosynthetic cluster, indicating that gliT is primarily responsible for protecting this strain against exogenous gliotoxin. GliT exhibits a gliotoxin reductase activity up to 9 µM gliotoxin and appears to prevent irreversible depletion of intracellular glutathione stores by reduction of the oxidized form of gliotoxin. Cross-species resistance to exogenous gliotoxin is acquired by A. nidulans and Saccharomyces cerevisiae, respectively, when transformed with gliT. We hypothesise that the primary role of gliotoxin may be as an antioxidant and that in addition to GliT functionality, gliotoxin secretion may be a component of an auto-protective mechanism, deployed by A. fumigatus to protect itself against this potent biomolecule. The pathogenic fungus Aspergillus fumigatus causes disease in immunocompromised individuals such as cancer patients. The fungus makes a small molecule called gliotoxin which helps A. fumigatus bypass the immune system in ill people, and cause disease. Although a small molecule, gliotoxin biosynthesis is enabled by a complex series of enzymes, one of which is called GliT, in A. fumigatus. Amazingly, nobody has really considered that gliotoxin might be toxic to A. fumigatus itself. Here we show that absence of GliT makes A. fumigatus highly sensitive to added gliotoxin and inhibits fungal growth, both of which can be reversed by restoring GliT. Neither can the fungus make or release its own gliotoxin when GliT is missing. We also show that gliotoxin sensitivity can be totally overcome by adding glutathione, which is an important anti-oxidant within cells. We demonstrate that gliotoxin addition increases the production of GliT, and that GliT breaks the disulphide bond in gliotoxin which may be a step in the pathway for gliotoxin protection or release from A. fumigatus. We conclude that gliotoxin may mainly be involved in protecting A. fumigatus against oxidative stress and that it is an accidental toxin.
Collapse
Affiliation(s)
- Markus Schrettl
- Department of Biology and National Institute for Cellular Biotechnology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
- Biocenter-Division of Molecular Biology, Innsbruck Medical University, Innsbruck, Austria
| | - Stephen Carberry
- Department of Biology and National Institute for Cellular Biotechnology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | - Kevin Kavanagh
- Department of Biology and National Institute for Cellular Biotechnology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | - Hubertus Haas
- Biocenter-Division of Molecular Biology, Innsbruck Medical University, Innsbruck, Austria
| | - Gary W. Jones
- Department of Biology and National Institute for Cellular Biotechnology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | - Jennifer O'Brien
- Department of Biology and National Institute for Cellular Biotechnology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | - Aine Nolan
- Department of Biology and National Institute for Cellular Biotechnology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | - John Stephens
- Department of Chemistry, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | - Orla Fenelon
- Department of Chemistry, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | - Sean Doyle
- Department of Biology and National Institute for Cellular Biotechnology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
- * E-mail:
| |
Collapse
|
35
|
Heptahelical receptors GprC and GprD of Aspergillus fumigatus Are essential regulators of colony growth, hyphal morphogenesis, and virulence. Appl Environ Microbiol 2010; 76:3989-98. [PMID: 20418440 DOI: 10.1128/aem.00052-10] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The filamentous fungus Aspergillus fumigatus normally grows on compost or hay but is also able to colonize environments such as the human lung. In order to survive, this organism needs to react to a multitude of external stimuli. Although extensive work has been carried out to investigate intracellular signal transduction in A. fumigatus, little is known about the specific stimuli and the corresponding receptors activating these signaling cascades. Here, two putative G-protein-coupled receptors, GprC and GprD, were characterized with respect to their cellular functions. Deletion of the corresponding genes resulted in drastic growth defects as hyphal extension was reduced, germination was retarded, and hyphae showed elevated levels of branching. The growth defect was found to be temperature dependent. The higher the temperature the more pronounced was the growth defect. Furthermore, compared with the wild type, the sensitivity of the mutant strains toward environmental stress caused by reactive oxygen intermediates was increased and the mutants displayed an attenuation of virulence in a murine infection model. Both mutants, especially the DeltagprC strain, exhibited increased tolerance toward cyclosporine, an inhibitor of the calcineurin signal transduction pathway. Transcriptome analyses indicated that in both the gprC and gprD deletion mutants, transcripts of primary metabolism genes were less abundant, whereas transcription of several secondary metabolism gene clusters was upregulated. Taken together, our data suggest the receptors are involved in integrating and processing stress signals via modulation of the calcineurin pathway.
Collapse
|
36
|
Féménia F, Huet D, Lair-Fulleringer S, Wagner MC, Sarfati J, Shingarova L, Guillot J, Boireau P, Chermette R, Berkova N. Effects of conidia of various Aspergillus species on apoptosis of human pneumocytes and bronchial epithelial cells. Mycopathologia 2009; 167:249-62. [PMID: 19117118 DOI: 10.1007/s11046-008-9175-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2008] [Accepted: 12/10/2008] [Indexed: 10/21/2022]
Abstract
Aspergillus species can cause mycoses in human and animals. Previously, we demonstrated that A. fumigatus conidia from a human isolate inhibited apoptosis in human pneumocytes and bronchial epithelial cells. In the current study, we studied the effects of A. fumigatus conidia non-human origin and A. flavus, A. nidulans, A. niger and A. oryzae conidia on human cells apoptosis. Human pneumocytes or bronchial epithelial cells were simultaneously exposed to apoptotic inductors and aspergilli conidia. The cell cultures were analyzed by flow cytometry, immunoblotting, and examination of nuclear morphology. Similar to A. fumigatus conidia, A. flavus conidia inhibited cellular apoptosis while A. nidulans, A. niger and A. oryzae conidia did not affect apoptosis. We further studied the species specificity of conidia: there were no differences in the inhibition of apoptosis by A. fumigatus conidia from either human or bird isolates. In order to determine whether the inhibition of apoptosis by conidia is limited to certain strains, the effect on human cell apoptosis of different A. fumigatus human clinical isolates and A. fumigatus of environmental origin was evaluated. All A. fumigatus isolates inhibited apoptosis; an anti-apoptotic factor was released by conidia. For TNF-induced apoptosis, the anti-apoptotic effect of conidia of all isolates was found to be associated with a reduction of caspase-3 in human cells. The results suggest that suppression of apoptosis may play a role in reducing the efficacy of host defense mechanisms during infection with Aspergillus species.
Collapse
Affiliation(s)
- F Féménia
- INRA, AFSSA, ENVA, UMR 956; 22 rue Curie, 94700, Maisons Alfort Cedex, France
| | | | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Production of pyomelanin, a second type of melanin, via the tyrosine degradation pathway in Aspergillus fumigatus. Appl Environ Microbiol 2009; 75:493-503. [PMID: 19028908 PMCID: PMC2620705 DOI: 10.1128/aem.02077-08] [Citation(s) in RCA: 173] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Aspergillus fumigatus is the most important airborne fungal pathogen of immunosuppressed humans. A. fumigatus is able to produce dihydroxynaphthalene melanin, which is predominantly present in the conidia. Its biosynthesis is an important virulence determinant. Here, we show that A. fumigatus is able to produce an alternative melanin, i.e., pyomelanin, by a different pathway, starting from L-tyrosine. Proteome analysis indicated that the l-tyrosine degradation enzymes are synthesized when the fungus is grown with L-tyrosine in the medium. To investigate the pathway in detail, we deleted the genes encoding essential enzymes for pigment production, homogentisate dioxygenase (hmgA) and 4-hydroxyphenylpyruvate dioxygenase (hppD). Comparative Fourier transform infrared spectroscopy of synthetic pyomelanin and pigment extracted from A. fumigatus cultures confirmed the identity of the observed pigment as pyomelanin. In the hmgA deletion strain, HmgA activity was abolished and the accumulation of homogentisic acid provoked an increased pigment formation. In contrast, homogentisic acid and pyomelanin were not observed with an hppD deletion mutant. Germlings of the hppD deletion mutant showed an increased sensitivity to reactive oxygen intermediates. The transcription of both studied genes was induced by L-tyrosine. These results confirmed the function of the deleted genes and the predicted pathway in A. fumigatus. Homogentisic acid is the major intermediate, and the L-tyrosine degradation pathway leading to pyomelanin is similar to that in humans leading to alkaptomelanin.
Collapse
|
38
|
Calcineurin localizes to the hyphal septum in Aspergillus fumigatus: implications for septum formation and conidiophore development. EUKARYOTIC CELL 2008; 7:1606-10. [PMID: 18606829 DOI: 10.1128/ec.00200-08] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A functional calcineurin A fusion to enhanced green fluorescent protein (EGFP), CnaA-EGFP, was expressed in the Aspergillus fumigatus DeltacnaA mutant. CnaA-EGFP localized in actively growing hyphal tips, at the septa, and at junctions between the vesicle and phialides in an actin-dependent manner. This is the first study to implicate calcineurin in septum formation and conidiophore development of a filamentous fungus.
Collapse
|
39
|
Protein kinase A regulates growth, sporulation, and pigment formation in Aspergillus fumigatus. Appl Environ Microbiol 2008; 74:4923-33. [PMID: 18539819 DOI: 10.1128/aem.00470-08] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Aspergillus fumigatus is an opportunistic human pathogenic fungus causing severe infections in immunocompromised patients. Cyclic AMP (cAMP) signal transduction plays an important role in virulence. A central component of this signaling cascade is protein kinase A (PKA), which regulates cellular processes by phosphorylation of specific target proteins. Here we describe the generation and analysis of A. fumigatus mutants expressing the gene encoding the catalytic subunit of PKA, pkaC1, under control of an inducible promoter. Strains overexpressing pkaC1 showed high PKA activity, reduced growth, sporulation deficiency, and formation of a dark pigment in the mycelium. These data indicate that cAMP-PKA signaling is involved in the regulation of important processes, such as growth, asexual reproduction, and biosynthesis of secondary metabolites. Furthermore, elevated PKA activity led to increased expression of the pksP gene. The polyketide synthase PksP is an essential enzyme for production of dihydroxynaphthalene-melanin in A. fumigatus and contributes to virulence. Our results suggest that increased pksP expression is responsible for pigment formation in the mycelium. Comparative proteome analysis of the pkaC1-overexpressing strain and the wild-type strain led to the identification of proteins regulated by the cAMP-PKA signal transduction pathway. We showed that elevated PKA activity resulted in activation of stress-associated proteins and of enzymes involved in protein biosynthesis and glucose catabolism. In contrast, proteins which were involved in nucleotide and amino acid biosynthesis were downregulated, as were enzymes involved in catabolism of carbon sources other than glucose.
Collapse
|
40
|
Capilla J, Clemons KV, Stevens DA. Animal models: an important tool in mycology. Med Mycol 2007; 45:657-84. [PMID: 18027253 PMCID: PMC7107685 DOI: 10.1080/13693780701644140] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Accepted: 08/22/2007] [Indexed: 10/29/2022] Open
Abstract
Animal models of fungal infections are, and will remain, a key tool in the advancement of the medical mycology. Many different types of animal models of fungal infection have been developed, with murine models the most frequently used, for studies of pathogenesis, virulence, immunology, diagnosis, and therapy. The ability to control numerous variables in performing the model allows us to mimic human disease states and quantitatively monitor the course of the disease. However, no single model can answer all questions and different animal species or different routes of infection can show somewhat different results. Thus, the choice of which animal model to use must be made carefully, addressing issues of the type of human disease to mimic, the parameters to follow and collection of the appropriate data to answer those questions being asked. This review addresses a variety of uses for animal models in medical mycology. It focuses on the most clinically important diseases affecting humans and cites various examples of the different types of studies that have been performed. Overall, animal models of fungal infection will continue to be valuable tools in addressing questions concerning fungal infections and contribute to our deeper understanding of how these infections occur, progress and can be controlled and eliminated.
Collapse
Affiliation(s)
- Javier Capilla
- California Institute for Medical Research, San Jose, USA
- Department of Medicine, Division of Infectious Diseases, Santa Clara Valley Medical Center, San Jose, USA
- Department of Medicine, Division of Infectious Diseases and Geographic Medicine, Stanford University, Stanford, California, USA
| | - Karl V. Clemons
- California Institute for Medical Research, San Jose, USA
- Department of Medicine, Division of Infectious Diseases, Santa Clara Valley Medical Center, San Jose, USA
- Department of Medicine, Division of Infectious Diseases and Geographic Medicine, Stanford University, Stanford, California, USA
| | - David A. Stevens
- California Institute for Medical Research, San Jose, USA
- Department of Medicine, Division of Infectious Diseases, Santa Clara Valley Medical Center, San Jose, USA
- Department of Medicine, Division of Infectious Diseases and Geographic Medicine, Stanford University, Stanford, California, USA
| |
Collapse
|
41
|
The Aspergillus fumigatus transcriptional regulator AfYap1 represents the major regulator for defense against reactive oxygen intermediates but is dispensable for pathogenicity in an intranasal mouse infection model. EUKARYOTIC CELL 2007; 6:2290-302. [PMID: 17921349 DOI: 10.1128/ec.00267-07] [Citation(s) in RCA: 184] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Macrophages and neutrophils kill the airborne fungal pathogen Aspergillus fumigatus. The dependency of this killing process on reactive oxygen intermediates (ROI) has been strongly suggested. Therefore, we investigated the enzymatic ROI detoxifying system by proteome analysis of A. fumigatus challenged by H(2)O(2). Since many of the identified proteins and genes are apparently regulated by a putative Saccharomyces cerevisiae Yap1 homolog, the corresponding gene of A. fumigatus was identified and designated Afyap1. Nuclear localization of a functional AfYap1-eGFP fusion was stress dependent. Deletion of the Afyap1 gene led to drastically increased sensitivity of the deletion mutant against H(2)O(2) and menadione, but not against diamide and NO radicals. Proteome analysis of the DeltaAfyap1 mutant strain challenged with 2 mM H(2)O(2) indicated that 29 proteins are controlled directly or indirectly by AfYap1, including catalase 2. Despite its importance for defense against reactive agents, the Afyap1 deletion mutant did not show attenuated virulence in a murine model of Aspergillus infection. These data challenge the hypothesis that ROI such as superoxide anions and peroxides play a direct role in killing of A. fumigatus in an immunocompromised host. This conclusion was further supported by the finding that killing of A. fumigatus wild-type and DeltaAfyap1 mutant germlings by human neutrophilic granulocytes worked equally well irrespective of whether the ROI scavenger glutathione or an NADPH-oxidase inhibitor was added to the cells.
Collapse
|
42
|
Hohl TM, Feldmesser M. Aspergillus fumigatus: principles of pathogenesis and host defense. EUKARYOTIC CELL 2007; 6:1953-63. [PMID: 17890370 PMCID: PMC2168400 DOI: 10.1128/ec.00274-07] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Tobias M Hohl
- Infectious Disease Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Ave., New York, NY 10021, USA.
| | | |
Collapse
|
43
|
Sugui JA, Pardo J, Chang YC, Müllbacher A, Zarember KA, Galvez EM, Brinster L, Zerfas P, Gallin JI, Simon MM, Kwon-Chung KJ. Role of laeA in the Regulation of alb1, gliP, Conidial Morphology, and Virulence in Aspergillus fumigatus. EUKARYOTIC CELL 2007; 6:1552-61. [PMID: 17630330 PMCID: PMC2043373 DOI: 10.1128/ec.00140-07] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The alb1 (pksP) gene has been reported as a virulence factor controlling the pigmentation and morphology of conidia in Aspergillus fumigatus. A recent report suggested that laeA regulates alb1 expression and conidial morphology but not pigmentation in the A. fumigatus strain AF293. laeA has also been reported to regulate the synthesis of secondary metabolites, such as gliotoxin. We compared the role of laeA in the regulation of conidial morphology and the expression of alb1 and gliP in strains B-5233 and AF293, which differ in colony morphology and nutritional requirements. Deletion of laeA did not affect conidial morphology or pigmentation in these strains, suggesting that laeA is not involved in alb1 regulation during conidial morphogenesis. Deletion of laeA, however, caused down-regulation of alb1 during mycelial growth in a liquid medium. Transcription of gliP, involved in the synthesis of gliotoxin, was drastically reduced in B-5233laeADelta, and the gliotoxin level found in the culture filtrates was 20% of wild-type concentrations. While up-regulation of gliP in AF293 was comparable to that in B-5233, the relative mRNA level in AF293laeADelta was about fourfold lower than that in B-5233laeADelta. Strain B-5233laeADelta caused slower onset of fatal infection in mice relative to that with B-5233. Histopathology of sections from lungs of infected mice corroborated the survival data. Culture filtrates from B-5233laeADelta caused reduced death in thymoma cells and were less inhibitory to a respiratory burst of neutrophils than culture filtrates from B-5233. Our results suggest that while laeA is not involved in the regulation of alb1 function in conidial morphology, it regulates the synthesis of gliotoxin and the virulence of A. fumigatus.
Collapse
Affiliation(s)
- Janyce A Sugui
- Laboratory of Clinical Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Kragl C, Schrettl M, Abt B, Sarg B, Lindner HH, Haas H. EstB-mediated hydrolysis of the siderophore triacetylfusarinine C optimizes iron uptake of Aspergillus fumigatus. EUKARYOTIC CELL 2007; 6:1278-85. [PMID: 17586718 PMCID: PMC1951140 DOI: 10.1128/ec.00066-07] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Aspergillus fumigatus excretes the fusarinine-type siderophore desferri-triacetylfusarinine C (DF-TafC) to mobilize iron. DF-TafC is a cyclic peptide consisting of three N(5)-cis-anhydromevalonyl-N(5)-hydroxy-N(2)-acetyl-l-ornithine residues linked by ester bonds; these linkages are in contrast to peptide linkages found for ferrichrome-type siderophores. Subsequent to the binding of iron and uptake, triacetylfusarinine C (TafC) is hydrolyzed, the cleavage products are excreted, and the iron is transferred to the metabolism or to the intracellular siderophore desferri-ferricrocin (DF-FC) for iron storage. Here we report the identification and characterization of the TafC esterase EstB, the first eukaryotic siderophore-degrading enzyme to be characterized at the molecular level. The encoding gene, estB, was found to be located in an iron-regulated gene cluster, indicating a role in iron metabolism. Deletion of estB in A. fumigatus eliminated TafC esterase activity of cellular extracts and caused increased intracellular accumulation of TafC and TafC hydrolysis products in vivo. Escherichia coli-expressed EstB displayed specific TafC esterase activity but did not hydrolyze fusarinine C, which has the same core structure as TafC but lacks three N(2)-acetyl residues. Localization of EstB via enhanced green fluorescent protein tagging suggested that TafC hydrolysis takes place in the cytoplasm. EstB abrogation reduced the intracellular transfer rate of iron from TafC to DF-FC and delayed iron sensing. Furthermore, EstB deficiency caused a decreased radial growth rate under iron-depleted but not iron-replete conditions. Taken together, these data suggest that EstB-mediated TafC hydrolysis optimizes but is not essential for TafC-mediated iron uptake in A. fumigatus.
Collapse
Affiliation(s)
- Claudia Kragl
- Division of Molecular Biology, Biocenter, Innsbruck Medical University, Fritz-Pregl-Str. 3, A-6020 Innsbruck, Austria
| | | | | | | | | | | |
Collapse
|
45
|
Behnsen J, Narang P, Hasenberg M, Gunzer F, Bilitewski U, Klippel N, Rohde M, Brock M, Brakhage AA, Gunzer M. Environmental dimensionality controls the interaction of phagocytes with the pathogenic fungi Aspergillus fumigatus and Candida albicans. PLoS Pathog 2007; 3:e13. [PMID: 17274685 PMCID: PMC1790725 DOI: 10.1371/journal.ppat.0030013] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Accepted: 12/19/2006] [Indexed: 11/19/2022] Open
Abstract
The fungal pathogens Aspergillus fumigatus and Candida albicans are major health threats for immune-compromised patients. Normally, macrophages and neutrophil granulocytes phagocytose inhaled Aspergillus conidia in the two-dimensional (2-D) environment of the alveolar lumen or Candida growing in tissue microabscesses, which are composed of a three-dimensional (3-D) extracellular matrix. However, neither the cellular dynamics, the per-cell efficiency, the outcome of this interaction, nor the environmental impact on this process are known. Live imaging shows that the interaction of phagocytes with Aspergillus or Candida in 2-D liquid cultures or 3-D collagen environments is a dynamic process that includes phagocytosis, dragging, or the mere touching of fungal elements. Neutrophils and alveolar macrophages efficiently phagocytosed or dragged Aspergillus conidia in 2-D, while in 3-D their function was severely impaired. The reverse was found for phagocytosis of Candida. The phagocytosis rate was very low in 2-D, while in 3-D most neutrophils internalized multiple yeasts. In competitive assays, neutrophils primarily incorporated Aspergillus conidia in 2-D and Candida yeasts in 3-D despite frequent touching of the other pathogen. Thus, phagocytes show activity best in the environment where a pathogen is naturally encountered. This could explain why "delocalized" Aspergillus infections such as hematogeneous spread are almost uncontrollable diseases, even in immunocompetent individuals.
Collapse
Affiliation(s)
- Judith Behnsen
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute, Jena, Germany
| | - Priyanka Narang
- Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Mike Hasenberg
- Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Frank Gunzer
- Department of Physics, The German University of Cairo, New Cairo City, Egypt
| | | | - Nina Klippel
- Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Manfred Rohde
- Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Matthias Brock
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute, Jena, Germany
| | - Axel A Brakhage
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute, Jena, Germany
| | - Matthias Gunzer
- Helmholtz Centre for Infection Research, Braunschweig, Germany
| |
Collapse
|
46
|
Sugareva V, Härtl A, Brock M, Hübner K, Rohde M, Heinekamp T, Brakhage AA. Characterisation of the laccase-encoding gene abr2 of the dihydroxynaphthalene-like melanin gene cluster of Aspergillus fumigatus. Arch Microbiol 2006; 186:345-55. [PMID: 16988817 DOI: 10.1007/s00203-006-0144-2] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2006] [Revised: 06/07/2006] [Accepted: 06/26/2006] [Indexed: 11/29/2022]
Abstract
Aspergillus fumigatus is an important pathogen of the immunocompromised host. Previously, it was shown that the polyketide synthase encoded by the pksP (alb1) gene represents a virulence determinant. pksP is part of a gene cluster involved in dihydroxynaphthalene (DHN)-like melanin biosynthesis. Because a putative laccase-encoding gene (abr2) is also part of the cluster and a laccase was found to represent a virulence factor in Cryptococcus neoformans, here, the Abr2 laccase was characterised. Deletion of the abr2 gene changed the gray-green conidial pigment to a brown color and the ornamentation of conidia was reduced compared with wild-type conidia. In contrast to the white pksP mutant, the susceptibility of the Deltaabr2 mutant against reactive oxygen species (ROS) was not increased, suggesting that the intermediate of DHN-like melanin produced up to the step catalysed by Abr2 already possesses ROS scavenging activity. In an intranasal mouse infection model, the Deltaabr2 mutant strain showed no reduction in virulence compared with the wild type. In the Deltaabr2 mutant, overall laccase activity was reduced only during sporulation, but not during vegetative growth. An abr2p-lacZ gene fusion was expressed during sporulation, but not during vegetative growth confirming the pattern of laccase activity due to Abr2.
Collapse
Affiliation(s)
- Venelina Sugareva
- Department of Microbiology and Molecular Biology, Friedrich-Schiller-University, Jena, Germany
| | | | | | | | | | | | | |
Collapse
|
47
|
Ronning CM, Fedorova ND, Bowyer P, Coulson R, Goldman G, Kim HS, Turner G, Wortman JR, Yu J, Anderson MJ, Denning DW, Nierman WC. Genomics of Aspergillus fumigatus. Rev Iberoam Micol 2006; 22:223-8. [PMID: 16499415 DOI: 10.1016/s1130-1406(05)70047-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Aspergillus fumigatus is a filamentous fungal saprophyte that is ubiquitous in the environment. It is also a human pathogen and induces allergenic response, negatively impacting health care and associated costs significantly around the world. Much of the basic biology of this organism is only poorly understood, but the recent completion and publication of its genome sequence provides an excellent tool for researchers to gain insight into these processes. In this review we will summarize some of the more salient features revealed by analysis of the genome, including the search for candidate pathogenicity genes and the switch to a pathogenic lifestyle, allergen proteins, DNA repair, secondary metabolite gene clusters that produce compounds both useful and toxic, a theoretical capability of this asexual organism to reproduce sexually, signalling, and transcription. A. fumigatus was compared with the food biotechnology fungus Aspergillus oryzae and sexual fungus Aspergillus nidulans, as well as other fungi, in an attempt to discern key differences between these organisms.
Collapse
Affiliation(s)
- Catherine M Ronning
- The Institute for Genomic Research, 9712 Medical Center Drive, Rockville, MD 20850, USA.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
48
|
Zhang L, Wang M, Li R, Calderone R. Expression of Aspergillus fumigatus virulence-related genes detected in vitro and in vivo with competitive RT-PCR. Mycopathologia 2006; 160:201-6. [PMID: 16205968 DOI: 10.1007/s11046-005-0141-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2005] [Accepted: 06/22/2005] [Indexed: 12/19/2022]
Abstract
We have measured the transcription of several genes that have been implicated as virulence factors in Aspergillus fumigatus, including fos-1, a histidine kinase, two-component signal protein, rhbA, a ras-related protein required for signaling, pksP, a polyketide synthase involved in biosynthesis of melanin, pabA synthetase, an enzyme catalyzing a late step in the biosynthesis of folate, lysF, a homoconitase related to lysine biosynthesis, and cpcA, the transcriptional activator of the cross-pathway control system of amino acid biosynthesis. Transcription levels were determined from in vitro grown organism as well as from lung tissue from mice infected with A. fumigatus. Our data indicate that fos-1 and rhbA transcription increased significantly during the infection in mice, compared to the other genes whose transcription remained the same (pksP, cpcA, pabA) or decreased slightly (lysF). In vitro measurements of transcription compared to transcription in infected lung tissue demonstrated low levels of fos-1 and rhbA, 20-40-fold increases (cpcA, lysF, pabA), while pksP was not detected from cultures. Our data demonstrate that transcription of these genes differs in vitro versus during disease.
Collapse
Affiliation(s)
- Lijuan Zhang
- Department of Dermatology/Research Center of Medical Mycology, Peking University First Hospital, Beijing, China
| | | | | | | |
Collapse
|
49
|
Brakhage AA, Liebmann B. Aspergillus fumigatus conidial pigment and cAMP signal transduction: significance for virulence. Med Mycol 2005; 43 Suppl 1:S75-82. [PMID: 16110796 DOI: 10.1080/13693780400028967] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
The conidial pigment of Aspergillus fumigatus contains 1,8-dihydroxynaphthalene (DHN)-like pentaketide melanin. It plays a major role in the protection of the fungus against immune effector cells; for example, it is able to scavenge reactive oxygen species generated by alveolar macrophages and neutrophiles. The polyketide synthase PKSP (ALB1) is a key-enzyme of the biosynthesis pathway; its structural gene is part of a gene cluster. Furthermore, the presence of a functional pksP (albl) gene in A. fumigatus conidia is associated with an inhibition of phagolysosome fusion in human monocyte-derived macrophages. Moreover, the analysis of mutants that are defective in elements of the cAMP signaling pathway found that they are almost avirulent in an optimized low dose murine inhalation model. Taken together, our results indicate that the cAMP/PKA signal transduction pathway is required for A. fumigatus pathogenicity. In addition, we showed that the expression of the pksP gene is, at least in part, controlled by the cAMP/ PKA signal transduction pathway. Currently, we hypothesize that pentaketide melanin is important for defence against ROS. However, besides its contribution to the biosynthesis of DHN-like melanin, PKSP also appears to be involved in the formation of another compound which is immunosuppressive.
Collapse
Affiliation(s)
- A A Brakhage
- Leibniz-lnstitute for Natural Products Research and Infection Biology-Hans-Knoell-lnstitute, Department of Molecular and Applied Microbiology, Jena, Germany.
| | | |
Collapse
|
50
|
Maerker C, Rohde M, Brakhage AA, Brock M. Methylcitrate synthase from Aspergillus fumigatus. Propionyl-CoA affects polyketide synthesis, growth and morphology of conidia. FEBS J 2005; 272:3615-30. [PMID: 16008561 DOI: 10.1111/j.1742-4658.2005.04784.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Methylcitrate synthase is a key enzyme of the methylcitrate cycle and required for fungal propionate degradation. Propionate not only serves as a carbon source, but also acts as a food preservative (E280-283) and possesses a negative effect on polyketide synthesis. To investigate propionate metabolism from the opportunistic human pathogenic fungus Aspergillus fumigatus, methylcitrate synthase was purified to homogeneity and characterized. The purified enzyme displayed both, citrate and methylcitrate synthase activity and showed similar characteristics to the corresponding enzyme from Aspergillus nidulans. The coding region of the A. fumigatus enzyme was identified and a deletion strain was constructed for phenotypic analysis. The deletion resulted in an inability to grow on propionate as the sole carbon source. A strong reduction of growth rate and spore colour formation on media containing both, glucose and propionate was observed, which was coincident with an accumulation of propionyl-CoA. Similarly, the use of valine, isoleucine and methionine as nitrogen sources, which yield propionyl-CoA upon degradation, inhibited growth and polyketide production. These effects are due to a direct inhibition of the pyruvate dehydrogenase complex and blockage of polyketide synthesis by propionyl-CoA. The surface of conidia was studied by electron scanning microscopy and revealed a correlation between spore colour and ornamentation of the conidial surface. In addition, a methylcitrate synthase deletion led to an attenuation of virulence, when tested in an insect infection model and attenuation was even more pronounced, when whitish conidia from glucose/propionate medium were applied. Therefore, an impact of methylcitrate synthase in the infection process is discussed.
Collapse
|