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K143R Amino Acid Substitution in 14-α-Demethylase (Erg11p) Changes Plasma Membrane and Cell Wall Structure of Candida albicans. Int J Mol Sci 2022; 23:ijms23031631. [PMID: 35163552 PMCID: PMC8836035 DOI: 10.3390/ijms23031631] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 01/27/2022] [Accepted: 01/28/2022] [Indexed: 02/07/2023] Open
Abstract
The opportunistic pathogen Candida albicans is responsible for life-threating infections in immunocompromised individuals. Azoles and polyenes are two of the most commonly used antifungals and target the ergosterol biosynthesis pathway or ergosterol itself. A limited number of clinically employed antifungals correspond to the development of resistance mechanisms. One resistance mechanism observed in clinical isolates of azole-resistant C. albicans is the introduction of point mutations in the ERG11 gene, which encodes a key enzyme (lanosterol 14-α-demethylase) on the ergosterol biosynthesis pathway. Here, we demonstrate that a point mutation K143R in ERG11 (C. albicans ERG11K143R/K143R) contributes not only to azole resistance, but causes increased gene expression. Overexpression of ERG11 results in increased ergosterol content and a significant reduction in plasma membrane fluidity. Simultaneously, the same point mutation caused cell wall remodeling. This could be facilitated by the unmasking of chitin and β-glucan on the fungal cell surface, which can lead to recognition of the highly immunogenic β-glucan, triggering a stronger immunological reaction. For the first time, we report that a frequently occurring azole-resistance strategy makes C. albicans less susceptible to azole treatment while, at the same time, affects its cell wall architecture, potentially leading to exposure of the pathogen to a more effective host immune response.
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Sitterlé E, Coste AT, Obadia T, Maufrais C, Chauvel M, Sertour N, Sanglard D, Puel A, D'Enfert C, Bougnoux ME. Large-scale genome mining allows identification of neutral polymorphisms and novel resistance mutations in genes involved in Candida albicans resistance to azoles and echinocandins. J Antimicrob Chemother 2021; 75:835-848. [PMID: 31923309 DOI: 10.1093/jac/dkz537] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 11/22/2019] [Accepted: 12/01/2019] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND The genome of Candida albicans displays significant polymorphism. Point mutations in genes involved in resistance to antifungals may either confer phenotypic resistance or be devoid of phenotypic consequences. OBJECTIVES To catalogue polymorphisms in azole and echinocandin resistance genes occurring in susceptible strains in order to rapidly pinpoint relevant mutations in resistant strains. METHODS Genome sequences from 151 unrelated C. albicans strains susceptible to fluconazole and caspofungin were used to create a catalogue of non-synonymous polymorphisms in genes involved in resistance to azoles (ERG11, TAC1, MRR1 and UPC2) or echinocandins (FKS1). The potential of this catalogue to reveal putative resistance mutations was tested in 10 azole-resistant isolates, including 1 intermediate to caspofungin. Selected mutations were analysed by mutagenesis experiments or mutational prediction effect. RESULTS In the susceptible strains, we identified 126 amino acid substitutions constituting the catalogue of phenotypically neutral polymorphisms. By excluding these neutral substitutions, we identified 22 additional substitutions in the 10 resistant strains. Among these substitutions, 10 had already been associated with resistance. The remaining 12 were in Tac1p (n = 6), Upc2p (n = 2) and Erg11p (n = 4). Four out of the six homozygous substitutions in Tac1p (H263Y, A790V, H839Y and P971S) conferred increases in azole MICs, while no effects were observed for those in Upc2p. Additionally, two homozygous substitutions (Y64H and P236S) had a predicted conformation effect on Erg11p. CONCLUSIONS By establishing a catalogue of neutral polymorphisms occurring in genes involved in resistance to antifungal drugs, we provide a useful resource for rapid identification of mutations possibly responsible for phenotypic resistance in C. albicans.
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Affiliation(s)
- Emilie Sitterlé
- Unité Biologie et Pathogénicité Fongiques, Département de Mycologie, Institut Pasteur, USC2019 INRA, Paris, France.,Université Paris Diderot, Sorbonne Paris Cité, Paris, France.,Unité de Parasitologie-Mycologie, Service de Microbiologie clinique, Hôpital Necker-Enfants-Malades, Assistance Publique des Hôpitaux de Paris (APHP), Paris, France
| | - Alix T Coste
- Institut de Microbiologie, Université de Lausanne et Centre Hospitalo-Universitaire, Lausanne, Switzerland
| | - Thomas Obadia
- Hub de Bioinformatique et Biostatistique, Département Biologie Computationnelle, Institut Pasteur, USR 3756 CNRS, Paris, France.,Unité Malaria: parasites et hôtes, Département Parasites et Insectes Vecteurs, Institut Pasteur, Paris, France
| | - Corinne Maufrais
- Hub de Bioinformatique et Biostatistique, Département Biologie Computationnelle, Institut Pasteur, USR 3756 CNRS, Paris, France
| | - Murielle Chauvel
- Unité Biologie et Pathogénicité Fongiques, Département de Mycologie, Institut Pasteur, USC2019 INRA, Paris, France
| | - Natacha Sertour
- Unité Biologie et Pathogénicité Fongiques, Département de Mycologie, Institut Pasteur, USC2019 INRA, Paris, France
| | - Dominique Sanglard
- Institut de Microbiologie, Université de Lausanne et Centre Hospitalo-Universitaire, Lausanne, Switzerland
| | - Anne Puel
- Laboratoire de génétique humaine des maladies infectieuses, Necker, INSERM U1163, Paris, France.,Université Paris Descartes, Institut Imagine, Paris, France
| | - Christophe D'Enfert
- Unité Biologie et Pathogénicité Fongiques, Département de Mycologie, Institut Pasteur, USC2019 INRA, Paris, France
| | - Marie-Elisabeth Bougnoux
- Unité Biologie et Pathogénicité Fongiques, Département de Mycologie, Institut Pasteur, USC2019 INRA, Paris, France.,Unité de Parasitologie-Mycologie, Service de Microbiologie clinique, Hôpital Necker-Enfants-Malades, Assistance Publique des Hôpitaux de Paris (APHP), Paris, France.,Université de Paris, Paris, France
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Nishimoto AT, Sharma C, Rogers PD. Molecular and genetic basis of azole antifungal resistance in the opportunistic pathogenic fungus Candida albicans. J Antimicrob Chemother 2021; 75:257-270. [PMID: 31603213 DOI: 10.1093/jac/dkz400] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Candida albicans is an opportunistic yeast and the major human fungal pathogen in the USA, as well as in many other regions of the world. Infections with C. albicans can range from superficial mucosal and dermatological infections to life-threatening infections of the bloodstream and vital organs. The azole antifungals remain an important mainstay treatment of candidiasis and therefore the investigation and understanding of the evolution, frequency and mechanisms of azole resistance are vital to improving treatment strategies against this organism. Here the organism C. albicans and the genetic changes and molecular bases underlying the currently known resistance mechanisms to the azole antifungal class are reviewed, including up-regulated expression of efflux pumps, changes in the expression and amino acid composition of the azole target Erg11 and alterations to the organism's typical sterol biosynthesis pathways. Additionally, we update what is known about activating mutations in the zinc cluster transcription factor (ZCF) genes regulating many of these resistance mechanisms and review azole import as a potential contributor to azole resistance. Lastly, investigations of azole tolerance in C. albicans and its implicated clinical significance are reviewed.
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Affiliation(s)
- Andrew T Nishimoto
- Department of Clinical Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Cheshta Sharma
- Department of Clinical Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
| | - P David Rogers
- Department of Clinical Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
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4
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Bezerra AR, Oliveira C, Correia I, Guimarães AR, Sousa G, Carvalho MJ, Moura G, Santos MAS. The role of non-standard translation in Candida albicans pathogenesis. FEMS Yeast Res 2021; 21:6280978. [PMID: 34021562 PMCID: PMC8178436 DOI: 10.1093/femsyr/foab032] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 05/20/2021] [Indexed: 12/22/2022] Open
Abstract
Candida albicans typically resides in the human gastrointestinal tract and mucosal membranes as a commensal organism. To adapt and cope with the host immune system, it has evolved a variety of mechanisms of adaptation such as stress-induced mutagenesis and epigenetic regulation. Niche-specific patterns of gene expression also allow the fungus to fine-tune its response to specific microenvironments in the host and switch from harmless commensal to invasive pathogen. Proteome plasticity produced by CUG ambiguity, on the other hand is emerging as a new layer of complexity in C. albicans adaptation, pathogenesis, and drug resistance. Such proteome plasticity is the result of a genetic code alteration where the leucine CUG codon is translated mainly as serine (97%), but maintains some level of leucine (3%) assignment. In this review, we dissect the link between C. albicans non-standard CUG translation, proteome plasticity, host adaptation and pathogenesis. We discuss published work showing how this pathogen uses the fidelity of protein synthesis to spawn novel virulence traits.
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Affiliation(s)
- Ana Rita Bezerra
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Carla Oliveira
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Inês Correia
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Ana Rita Guimarães
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Gonçalo Sousa
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Maria João Carvalho
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Gabriela Moura
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Manuel A S Santos
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, 3810-193 Aveiro, Portugal
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5
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Costa-de-Oliveira S, Rodrigues AG. Candida albicans Antifungal Resistance and Tolerance in Bloodstream Infections: The Triad Yeast-Host-Antifungal. Microorganisms 2020; 8:microorganisms8020154. [PMID: 31979032 PMCID: PMC7074842 DOI: 10.3390/microorganisms8020154] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Revised: 01/10/2020] [Accepted: 01/16/2020] [Indexed: 01/08/2023] Open
Abstract
Candida albicans represents the most frequent isolated yeast from bloodstream infections. Despite the remarkable progress in diagnostic and therapeutic approaches, these infections continue to be a critical challenge in intensive care units worldwide. The economic cost of bloodstream fungal infections and its associated mortality, especially in debilitated patients, remains unacceptably high. Candida albicans is a highly adaptable microorganism, being able to develop resistance following prolonged exposure to antifungals. Formation of biofilms, which diminish the accessibility of the antifungal, selection of spontaneous mutations that increase expression or decreased susceptibility of the target, altered chromosome abnormalities, overexpression of multidrug efflux pumps and the ability to escape host immune defenses are some of the factors that can contribute to antifungal tolerance and resistance. The knowledge of the antifungal resistance mechanisms can allow the design of alternative therapeutically options in order to modulate or revert the resistance. We have focused this review on the main factors that are involved in antifungal resistance and tolerance in patients with C. albicans bloodstream infections.
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Affiliation(s)
- Sofia Costa-de-Oliveira
- Division of Microbiology, Department of Pathology, Faculty of Medicine, University of Porto, Al. Hernâni Monteiro, 4200-319 Porto, Portugal;
- Center for Research in Health Technologies and Information Systems (CINTESIS), R. Dr. Plácido da Costa, 4200-450 Porto, Portugal
- Correspondence: ; Tel.: +351-220-426-870
| | - Acácio G. Rodrigues
- Division of Microbiology, Department of Pathology, Faculty of Medicine, University of Porto, Al. Hernâni Monteiro, 4200-319 Porto, Portugal;
- Center for Research in Health Technologies and Information Systems (CINTESIS), R. Dr. Plácido da Costa, 4200-450 Porto, Portugal
- Burn Unit, São João Hospital Center, Al. Hernâni Monteiro, 4200-319 Porto, Portugal
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Suchodolski J, Muraszko J, Bernat P, Krasowska A. A Crucial Role for Ergosterol in Plasma Membrane Composition, Localisation, and Activity of Cdr1p and H +-ATPase in Candida albicans. Microorganisms 2019; 7:microorganisms7100378. [PMID: 31546699 PMCID: PMC6843828 DOI: 10.3390/microorganisms7100378] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2019] [Revised: 09/18/2019] [Accepted: 09/20/2019] [Indexed: 12/11/2022] Open
Abstract
Candida albicans is an opportunistic fungal pathogen of humans. Treatment of C. albicans infections relies on azoles, which target the lanosterol 14α-demethylase (Erg11p) encoded by the ERG11 gene. Our results show that targeted gene disruption of ERG11 can result in resistance to ergosterol-dependent drugs (azoles and amphotericin B), auxotrophy and aerobically viable erg11Δ/Δ cells. Abnormal sterol deposition and lack of ergosterol in the erg11Δ/Δ strain leads to reduced plasma membrane (PM) fluidity, as well as dysfunction of the vacuolar and mitochondrial membranes, resulting respectively in defects in vacuole fusion and a reduced intracellular ATP level. The altered PM structure of the erg11Δ/Δ strain contributes to delocalisation of H+-ATPase and the Cdr1 efflux pump from the PM to vacuoles and, resulting in a decrease in PM potential (Δψ) and increased sensitivity to ergosterol-independent xenobiotics. This new insight into intracellular processes under Erg11p inhibition may lead to a better understanding of the indirect effects of azoles on C. albicans cells and the development of new treatment strategies for resistant infections.
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Affiliation(s)
- Jakub Suchodolski
- Department of Biotransformation, Faculty of Biotechnology, University of Wroclaw, 50-383 Wrocław, Poland.
| | - Jakub Muraszko
- Department of Biotransformation, Faculty of Biotechnology, University of Wroclaw, 50-383 Wrocław, Poland.
| | - Przemysław Bernat
- Department of Industrial Microbiology and Biotechnology, Faculty of Biology and Environmental Protection, University of Łódź, 90-237 Łódź, Banacha 12/16, Poland.
| | - Anna Krasowska
- Department of Biotransformation, Faculty of Biotechnology, University of Wroclaw, 50-383 Wrocław, Poland.
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Loss of Upc2p-Inducible ERG3 Transcription Is Sufficient To Confer Niche-Specific Azole Resistance without Compromising Candida albicans Pathogenicity. mBio 2018; 9:mBio.00225-18. [PMID: 29789366 PMCID: PMC5964354 DOI: 10.1128/mbio.00225-18] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Inactivation of sterol Δ5,6-desaturase (Erg3p) in the prevalent fungal pathogen Candida albicans is one of several mechanisms that can confer resistance to the azole antifungal drugs. However, loss of Erg3p activity is also associated with deficiencies in stress tolerance, invasive hyphal growth, and attenuated virulence in a mouse model of disseminated infection. This may explain why relatively few erg3-deficient strains have been reported among azole-resistant clinical isolates. In this study, we examined the consequences of Erg3p inactivation upon C. albicans pathogenicity and azole susceptibility in mouse models of mucosal and disseminated infection. While a C. albicanserg3Δ/Δ mutant was unable to cause lethality in the disseminated model, it induced pathology in a mouse model of vaginal infection. The erg3Δ/Δ mutant was also more resistant to fluconazole treatment than the wild type in both models of infection. Thus, complete loss of Erg3p activity confers azole resistance but also niche-specific virulence deficiencies. Serendipitously, we discovered that loss of azole-inducible ERG3 transcription (rather than complete inactivation) is sufficient to confer in vitro fluconazole resistance, without compromising C. albicans stress tolerance, hyphal growth, or pathogenicity in either mouse model. It is also sufficient to confer fluconazole resistance in the mouse vaginal model, but not in the disseminated model of infection, and thus confers niche-specific azole resistance without compromising C. albicans pathogenicity at either site. Collectively, these results establish that modulating Erg3p expression or activity can have niche-specific consequences on both C. albicans pathogenicity and azole resistance. While conferring resistance to the azole antifungals in vitro, loss of sterol Δ5,6-desaturase (Erg3p) activity has also been shown to reduce C. albicans pathogenicity. Accordingly, it has been presumed that this mechanism may not be significant in the clinical setting. The results presented here challenge this assumption, revealing a more complex relationship between Erg3p activity, azole resistance, C. albicans pathogenicity, and the specific site of infection. Most importantly, we have shown that even modest changes in ERG3 transcription are sufficient to confer azole resistance without compromising C. albicans fitness or pathogenicity. Given that previous efforts to assess the importance of ERG3 as a determinant of clinical azole resistance have focused almost exclusively on detecting null mutants, its role may have been grossly underestimated. On the basis of our results, a more thorough investigation of the contribution of the ERG3 gene to azole resistance in the clinical setting is warranted.
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8
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Branco J, Ola M, Silva RM, Fonseca E, Gomes NC, Martins-Cruz C, Silva AP, Silva-Dias A, Pina-Vaz C, Erraught C, Brennan L, Rodrigues AG, Butler G, Miranda IM. Impact of ERG3 mutations and expression of ergosterol genes controlled by UPC2 and NDT80 in Candida parapsilosis azole resistance. Clin Microbiol Infect 2017; 23:575.e1-575.e8. [PMID: 28196695 DOI: 10.1016/j.cmi.2017.02.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 02/05/2017] [Accepted: 02/06/2017] [Indexed: 12/22/2022]
Abstract
OBJECTIVES Candida parapsilosis is a healthcare-related fungal pathogen particularly common among immunocompromised patients. Our understanding of antifungal resistance mechanisms in C. parapsilosis remains very limited. We previously described an azole-resistant strain of C. parapsilosis (BC014RPSC), obtained following exposure in vitro to posaconazole. Resistance was associated with overexpression of ergosterol biosynthetic genes (ERG genes), together with the transcription factors UPC2 (CPAR2-207280) and NDT80 (CPAR2-213640). The aim of this study was to identify the mechanisms underlying posaconazole resistance of the BC014RPSC strain. METHODS To identify the causative mutation, we sequenced the genomes of the susceptible (BC014S) and resistant (BC014RPSC) isolates, using Illumina technology. Ergosterol content was assessed in both strains by mass spectrometry. UPC2 and NDT80 genes were deleted in BC014RPSC strain. Mutants were characterized regarding their azole susceptibility profile and ERG gene expression. RESULTS One homozygous missense mutation (R135I) was found in ERG3 (CPAR2-105550) in the azole-resistant isolate. We show that Erg3 activity is completely impaired, resulting in a build up of sterol intermediates and a failure to generate ergosterol. Deleting UPC2 and NDT80 in BC014RPSC reduces the expression of ERG genes and restores susceptibility to azole drugs. CONCLUSIONS A missense mutation in the ERG3 gene results in azole resistance and up-regulation of ERG genes expression. We propose that this mutation prevents the formation of toxic intermediates when cells are treated with azoles. Resistance can be reversed by deleting Upc2 and Ndt80 transcription factors. UPC2 plays a stronger role in C. parapsilosis azole resistance than does NDT80.
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Affiliation(s)
- J Branco
- Division of Microbiology, Department of Pathology, Faculty of Medicine, University of Porto, Porto, Portugal
| | - M Ola
- UCD School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Belfield, Dublin, Ireland
| | - R M Silva
- Department of Medical Sciences, iBiMED & IEETA, University of Aveiro, Aveiro, Portugal
| | - E Fonseca
- Division of Microbiology, Department of Pathology, Faculty of Medicine, University of Porto, Porto, Portugal
| | - N C Gomes
- Division of Microbiology, Department of Pathology, Faculty of Medicine, University of Porto, Porto, Portugal
| | - C Martins-Cruz
- Division of Microbiology, Department of Pathology, Faculty of Medicine, University of Porto, Porto, Portugal
| | - A P Silva
- Division of Microbiology, Department of Pathology, Faculty of Medicine, University of Porto, Porto, Portugal; CINTESIS-Centre for Health Technology and Services Research, Faculty of Medicine, University of Porto, Porto, Portugal
| | - A Silva-Dias
- Division of Microbiology, Department of Pathology, Faculty of Medicine, University of Porto, Porto, Portugal; CINTESIS-Centre for Health Technology and Services Research, Faculty of Medicine, University of Porto, Porto, Portugal
| | - C Pina-Vaz
- Division of Microbiology, Department of Pathology, Faculty of Medicine, University of Porto, Porto, Portugal; CINTESIS-Centre for Health Technology and Services Research, Faculty of Medicine, University of Porto, Porto, Portugal
| | - C Erraught
- Institute of Food and Health, School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - L Brennan
- Institute of Food and Health, School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - A G Rodrigues
- Division of Microbiology, Department of Pathology, Faculty of Medicine, University of Porto, Porto, Portugal; CINTESIS-Centre for Health Technology and Services Research, Faculty of Medicine, University of Porto, Porto, Portugal
| | - G Butler
- UCD School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Belfield, Dublin, Ireland
| | - I M Miranda
- Division of Microbiology, Department of Pathology, Faculty of Medicine, University of Porto, Porto, Portugal; CINTESIS-Centre for Health Technology and Services Research, Faculty of Medicine, University of Porto, Porto, Portugal.
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Jiang C, Ni Q, Dong D, Zhang L, Li Z, Tian Y, Peng Y. The Role of UPC2 Gene in Azole-Resistant Candida tropicalis. Mycopathologia 2016; 181:833-838. [PMID: 27538831 DOI: 10.1007/s11046-016-0050-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 08/04/2016] [Indexed: 01/08/2023]
Abstract
Azole resistance of Candida tropicalis has, in recent years, become a serious issue in hospitals; however, there is limited knowledge of the mechanisms underlying this resistance. We have previously demonstrated that ERG11 plays a vital role in azole resistance in C. tropicalis. Here, we describe the expression and sequence variation of UPC2, which encodes a transcription factor of ERG11. Quantitative real-time RT-PCR showed that 31 azole-resistant C. tropicalis strains significantly overexpressed UPC2. Those isolates resistant to all three azole antifungals upregulated UPC2 expression to a greater degree than those resistant to only fluconazole or itraconazole. The UPC2 promoter contains mutations -118T-G and -155G-A in azole-resistant strains of C. tropicalis. Meanwhile, the mutation G392E was also detected twice in UPC2 gene in azole-resistant C. tropicalis and was demonstrated to mediate azole antifungal susceptibility by using Saccharomyces cerevisiae as an expression host, particularly for fluconazole and itraconazole.
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Affiliation(s)
- Cen Jiang
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, No. 197 Second Ruijin Road, Shanghai, 200025, China
| | - Qi Ni
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, No. 197 Second Ruijin Road, Shanghai, 200025, China
| | - Danfeng Dong
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, No. 197 Second Ruijin Road, Shanghai, 200025, China
| | - Lihua Zhang
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, No. 197 Second Ruijin Road, Shanghai, 200025, China
| | - Zhen Li
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, No. 197 Second Ruijin Road, Shanghai, 200025, China
| | - Yuan Tian
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, No. 197 Second Ruijin Road, Shanghai, 200025, China
| | - Yibing Peng
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, No. 197 Second Ruijin Road, Shanghai, 200025, China.
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10
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Rosana Y, Yasmon A, Lestari DC. Overexpression and mutation as a genetic mechanism of fluconazole resistance in Candida albicans isolated from human immunodeficiency virus patients in Indonesia. J Med Microbiol 2015; 64:1046-1052. [PMID: 26297039 DOI: 10.1099/jmm.0.000123] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Fluconazole is the standard treatment for oropharyngeal candidiasis, which is the third most common opportunistic infection in human immunodeficiency virus (HIV)/AIDS patients in Indonesia. Overuse of this drug could lead to the emergence of resistance. The objective of this study was to analyse the role of ERG11, CDR1, CDR2 and MDR1 gene overexpression and mutations in the ERG11 gene as a genetic mechanism of fluconazole resistance in Candida albicans isolated from HIV patients in Indonesia. Overexpression of ERG11, CDR1, CDR2 and MDR1 was analysed by real-time reverse transcription PCR, while ERG11 gene mutation analysis was performed using sequencing methods. Seventeen isolates out of 92 strains of C. albicans isolated from 108 HIV patients were found to be resistant to azole antifungals. The highest gene overexpression of ERG11 was found in C. albicans resistant to single fluconazole, while the highest gene overexpression of CDR2 was detected in all isolates of C. albicans resistant to multiple azoles. Amino acid substitutions were observed at six positions, i.e. D116E, D153E, I261V, E266D, V437I and V488I. The amino acid substitution I261V was identified in this study and was probably associated with fluconazole resistance. The combination of overexpression of CDR2 and ERG11 and mutation in the ERG11 gene was found to be a genetic mechanism of fluconazole resistance in C. albicans isolated from HIV patients in Indonesia.
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Affiliation(s)
- Yeva Rosana
- Department of Microbiology, Faculty of Medicine, University of Indonesia, Jalan Pegangsaan Timur no. 16, Jakarta 10320, Indonesia
| | - Andi Yasmon
- Department of Microbiology, Faculty of Medicine, University of Indonesia, Jalan Pegangsaan Timur no. 16, Jakarta 10320, Indonesia
| | - Delly Chipta Lestari
- Department of Microbiology, Faculty of Medicine, University of Indonesia, Jalan Pegangsaan Timur no. 16, Jakarta 10320, Indonesia
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11
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Transcription factor ADS-4 regulates adaptive responses and resistance to antifungal azole stress. Antimicrob Agents Chemother 2015; 59:5396-404. [PMID: 26100701 DOI: 10.1128/aac.00542-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 06/13/2015] [Indexed: 11/20/2022] Open
Abstract
Azoles are commonly used as antifungal drugs or pesticides to control fungal infections in medicine and agriculture. Fungi adapt to azole stress by rapidly activating the transcription of a number of genes, and transcriptional increases in some azole-responsive genes can elevate azole resistance. The regulatory mechanisms that control transcriptional responses to azole stress in filamentous fungi are not well understood. This study identified a bZIP transcription factor, ADS-4 (antifungal drug sensitive-4), as a new regulator of adaptive responses and resistance to antifungal azoles. Transcription of ads-4 in Neurospora crassa cells increased when they were subjected to ketoconazole treatment, whereas the deletion of ads-4 resulted in hypersensitivity to ketoconazole and fluconazole. In contrast, the overexpression of ads-4 increased resistance to fluconazole and ketoconazole in N. crassa. Transcriptome sequencing (RNA-seq) analysis, followed by quantitative reverse transcription (qRT)-PCR confirmation, showed that ADS-4 positively regulated the transcriptional responses of at least six genes to ketoconazole stress in N. crassa. The gene products of four ADS-4-regulated genes are known contributors to azole resistance, including the major efflux pump CDR4 (Pdr5p ortholog), an ABC multidrug transporter (NcAbcB), sterol C-22 desaturase (ERG5), and a lipid transporter (NcRTA2) that is involved in calcineurin-mediated azole resistance. Deletion of the ads-4-homologous gene Afads-4 in Aspergillus fumigatus caused hypersensitivity to itraconazole and ketoconazole, which suggested that ADS-4 is a functionally conserved regulator of adaptive responses to azoles. This study provides important information on a new azole resistance factor that could be targeted by a new range of antifungal pesticides and drugs.
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12
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Jensen RH, Astvad KMT, Silva LV, Sanglard D, Jørgensen R, Nielsen KF, Mathiasen EG, Doroudian G, Perlin DS, Arendrup MC. Stepwise emergence of azole, echinocandin and amphotericin B multidrug resistance in vivo in Candida albicans orchestrated by multiple genetic alterations. J Antimicrob Chemother 2015; 70:2551-5. [PMID: 26017038 DOI: 10.1093/jac/dkv140] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 04/24/2015] [Indexed: 01/06/2023] Open
Abstract
OBJECTIVES The objective of this study was to characterize the underlying molecular mechanisms in consecutive clinical Candida albicans isolates from a single patient displaying stepwise-acquired multidrug resistance. METHODS Nine clinical isolates (P-1 to P-9) were susceptibility tested by EUCAST EDef 7.2 and Etest. P-4, P-5, P-7, P-8 and P-9 were available for further studies. Relatedness was evaluated by MLST. Additional genes were analysed by sequencing (including FKS1, ERG11, ERG2 and TAC1) and gene expression by quantitative PCR (CDR1, CDR2 and ERG11). UV-spectrophotometry and GC-MS were used for sterol analyses. In vivo virulence was determined in the insect model Galleria mellonella and evaluated by log-rank Mantel-Cox tests. RESULTS P-1 + P-2 were susceptible, P-3 + P-4 fluconazole resistant, P-5 pan-azole resistant, P-6 + P-7 pan-azole and echinocandin resistant and P-8 + P-9 MDR. MLST supported genetic relatedness among clinical isolates. P-4 harboured four changes in Erg11 (E266D, G307S, G450E and V488I), increased expression of ERG11 and CDR2 and a change in Tac1 (R688Q). P-5, P-7, P-8 and P-9 had an additional change in Erg11 (A61E), increased expression of CDR1, CDR2 and ERG11 (except for P-7) and a different amino acid change in Tac1 (R673L). Echinocandin-resistant isolates harboured the Fks1 S645P alteration. Polyene-resistant P-8 + P-9 lacked ergosterol and harboured a frameshift mutation in ERG2 (F105SfsX23). Virulence was attenuated (but equivalent) in the clinical isolates, but higher than in the azole- and echinocandin-resistant unrelated control strain. CONCLUSIONS C. albicans demonstrates a diverse capacity to adapt to antifungal exposure. Potentially novel resistance-inducing mutations in TAC1, ERG11 and ERG2 require independent validation.
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Affiliation(s)
- Rasmus Hare Jensen
- Microbiology and Infection Control, Statens Serum Institut, Copenhagen, Denmark
| | | | - Luis Vale Silva
- Institute of Microbiology, University of Lausanne and University Hospital Center (CHUV), Lausanne, Switzerland
| | - Dominique Sanglard
- Institute of Microbiology, University of Lausanne and University Hospital Center (CHUV), Lausanne, Switzerland
| | - Rene Jørgensen
- Microbiology and Infection Control, Statens Serum Institut, Copenhagen, Denmark
| | - Kristian Fog Nielsen
- Department of Systems Biology, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Estella Glintborg Mathiasen
- Microbiology and Infection Control, Statens Serum Institut, Copenhagen, Denmark Department of Systems Biology, Technical University of Denmark, Kgs. Lyngby, Denmark
| | | | - David Scott Perlin
- Public Health and Research Institute, New Jersey Medical School-Rutgers Biomedical and Health Sciences, Newark, NJ, USA
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Ford CB, Funt JM, Abbey D, Issi L, Guiducci C, Martinez DA, Delorey T, Li BY, White TC, Cuomo C, Rao RP, Berman J, Thompson DA, Regev A. The evolution of drug resistance in clinical isolates of Candida albicans. eLife 2015; 4:e00662. [PMID: 25646566 PMCID: PMC4383195 DOI: 10.7554/elife.00662] [Citation(s) in RCA: 189] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 12/18/2014] [Indexed: 12/31/2022] Open
Abstract
Candida albicans is both a member of the healthy human microbiome
and a major pathogen in immunocompromised individuals. Infections are typically
treated with azole inhibitors of ergosterol biosynthesis often leading to drug
resistance. Studies in clinical isolates have implicated multiple mechanisms in
resistance, but have focused on large-scale aberrations or candidate genes, and do
not comprehensively chart the genetic basis of adaptation. Here, we leveraged
next-generation sequencing to analyze 43 isolates from 11 oral candidiasis patients.
We detected newly selected mutations, including single-nucleotide polymorphisms
(SNPs), copy-number variations and loss-of-heterozygosity (LOH) events. LOH events
were commonly associated with acquired resistance, and SNPs in 240 genes may be
related to host adaptation. Conversely, most aneuploidies were transient and did not
correlate with drug resistance. Our analysis also shows that isolates also varied in
adherence, filamentation, and virulence. Our work reveals new molecular mechanisms
underlying the evolution of drug resistance and host adaptation. DOI:http://dx.doi.org/10.7554/eLife.00662.001 Nearly all humans are infected with the fungus Candida albicans. In
most people, the infection does not produce any symptoms because their immune system
is able to counteract the fungus' attempts to spread around the body. However, if the
balance between fungal attack and body defence fails, the fungus is able to spread,
which can lead to serious disease that is fatal in 42% of cases. How does C. albicans outcompete the body's defences to cause
disease? This is a pertinent question because the most effective antifungal
medicines—including the drug fluconazole—do not kill the fungus; they
only stop it from growing. This gives the fungus time to develop resistance to the
drug by becoming able to quickly replace the fungal proteins the drug destroys, or to
efficiently remove the drug from its cells. In this study, Ford et al. studied the changes that occur in the DNA of C.
albicans over time in patients who are being treated with fluconazole.
Ford et al. took 43 samples of C. albicans from 11 patients with
weakened immune systems. The experiments show that the fungus samples collected early
on were more sensitive to the drug than the samples collected later. In most cases, the genetic data suggest that the infections begin with a single
fungal cell; the cells in the later samples are its offspring. Despite this, there is
a lot of genetic variation between samples from the same patient, which indicates
that the fungus is under pressure to become more resistant to the drug. There were
240 genes—including those that can alter the surface on the fungus cells to
make it better at evading the host immune system—in which small changes
occurred over time in three or more patients. Laboratory tests revealed that many of
these genes are likely important for the fungus to survive in an animal host in the
presence of the drug. C. albicans cells usually have two genetically distinct copies of
every gene. Ford et al. found that for some genes—including some that make
surface components or are involved in expelling drugs from cells—the loss of
genetic information from one copy, so that both copies become identical, is linked to
resistance to fluconazole. However, the gain of whole or partial
chromosomes—which contain large numbers of genes—is not linked to
resistance, but may provide additional genetic material for generating diversity in
the yeast population that may help the cells to evolve resistance in the future. These experiments have identified many new candidate genes that are important for
drug resistance and evading the host immune system, and which could be used to guide
the development of new therapeutics to treat these life-threatening infections. DOI:http://dx.doi.org/10.7554/eLife.00662.002
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Affiliation(s)
- Christopher B Ford
- Department of Biology, Broad Institute of MIT and Harvard, Cambridge, United States
| | - Jason M Funt
- Department of Biology, Broad Institute of MIT and Harvard, Cambridge, United States
| | - Darren Abbey
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, United States
| | - Luca Issi
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, United States
| | | | | | - Toni Delorey
- Broad Institute of MIT and Harvard, Cambridge, United States
| | - Bi Yu Li
- Broad Institute of MIT and Harvard, Cambridge, United States
| | - Theodore C White
- School of Biological Sciences, University of Missouri at Kansas City, Kansas City, United States
| | - Christina Cuomo
- Broad Institute of MIT and Harvard, Cambridge, United States
| | - Reeta P Rao
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, United States
| | - Judith Berman
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, United States
| | - Dawn A Thompson
- Broad Institute of MIT and Harvard, Cambridge, United States
| | - Aviv Regev
- Department of Biology, Broad Institute of MIT and Harvard, Cambridge, United States
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Ascorbic acid inhibition of Candida albicans Hsp90-mediated morphogenesis occurs via the transcriptional regulator Upc2. EUKARYOTIC CELL 2014; 13:1278-89. [PMID: 25084864 DOI: 10.1128/ec.00096-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Morphogenetic transitions of the opportunistic fungal pathogen Candida albicans are influenced by temperature changes, with induction of filamentation upon a shift from 30 to 37°C. Hsp90 was identified as a major repressor of an elongated cell morphology at low temperatures, as treatment with specific inhibitors of Hsp90 results in elongated growth forms at 30°C. Elongated growth resulting from a compromised Hsp90 is considered neither hyphal nor pseudohyphal growth. It has been reported that ascorbic acid (vitamin C) interferes with the yeast-to-hypha transition in C. albicans. In the present study, we show that ascorbic acid also antagonizes the morphogenetic change caused by hampered Hsp90 function. Further analysis revealed that Upc2, a transcriptional regulator of genes involved in ergosterol biosynthesis, and Erg11, the target of azole antifungals, whose expression is in turn regulated by Upc2, are required for this antagonism. Ergosterol levels correlate with elongated growth and are reduced in cells treated with the Hsp90 inhibitor geldanamycin (GdA) and restored by cotreatment with ascorbic acid. In addition, we show that Upc2 appears to be required for ascorbic acid-mediated inhibition of the antifungal activity of fluconazole. These results identify Upc2 as a major regulator of ascorbic acid-induced effects in C. albicans and suggest an association between ergosterol content and elongated growth upon Hsp90 compromise.
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15
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UPC2A is required for high-level azole antifungal resistance in Candida glabrata. Antimicrob Agents Chemother 2014; 58:4543-54. [PMID: 24867980 DOI: 10.1128/aac.02217-13] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Candida glabrata, the second most common cause of Candida infections, is associated with high rates of mortality and often exhibits resistance to the azole class of antifungal agents. Upc2 and Ecm22 in Saccharomyces cerevisiae and Upc2 in Candida albicans are the transcriptional regulators of ERG11, the gene encoding the target of azoles in the ergosterol biosynthesis pathway. Recently two homologs for these transcription factors, UPC2A and UPC2B, were identified in C. glabrata. One of these, UPC2A, was shown to influence azole susceptibility. We hypothesized that due to the global role for Upc2 in sterol biosynthesis in S. cerevisiae and C. albicans, disruption of UPC2A would enhance the activity of fluconazole in both azole-susceptible dose-dependent (SDD) and -resistant C. glabrata clinical isolates. To test this hypothesis, we constructed mutants with disruptions in UPC2A and UPC2B alone and in combination in a matched pair of clinical azole-SDD and -resistant isolates. Disruption of UPC2A in both the SDD and resistant isolates resulted in increased susceptibility to sterol biosynthesis inhibitors, including a reduction in fluconazole MIC and minimum fungicidal concentration, enhanced azole activity by time-kill analysis, a decrease in ergosterol content, and downregulation of baseline and inducible expression of several sterol biosynthesis genes. Our results indicate that Upc2A is a key regulator of ergosterol biosynthesis and is essential for resistance to sterol biosynthesis inhibitors in C. glabrata. Therefore, the UPC2A pathway may represent a potential cotherapeutic target for enhancing azole activity against this organism.
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16
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UPC2 is universally essential for azole antifungal resistance in Candida albicans. EUKARYOTIC CELL 2014; 13:933-46. [PMID: 24659578 DOI: 10.1128/ec.00221-13] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In Candida albicans, the transcription factor Upc2 is central to the regulation of ergosterol biosynthesis. UPC2-activating mutations contribute to azole resistance, whereas disruption increases azole susceptibility. In the present study, we investigated the relationship of UPC2 to fluconazole susceptibility, particularly in azole-resistant strains. In addition to the reduced fluconazole MIC previously observed with UPC2 disruption, we observed a lower minimum fungicidal concentration (MFC) for a upc2Δ/Δ mutant than for its azole-susceptible parent, SC5314. Moreover, the upc2Δ/Δ mutant was unable to grow on a solid medium containing 10 μg/ml fluconazole and exhibited increased susceptibility and a clear zone of inhibition by Etest. Time-kill analysis showed higher fungistatic activity against the upc2Δ/Δ mutant than against SC5314. UPC2 disruption in strains carrying specific resistance mutations also resulted in reduced MICs and MFCs. UPC2 disruption in a highly azole resistant clinical isolate containing multiple resistance mechanisms likewise resulted in a reduced MIC and MFC. This mutant was unable to grow on a solid medium containing 10 μg/ml fluconazole and exhibited increased susceptibility and a clear zone of inhibition by Etest. Time-kill analysis showed increased fungistatic activity against the upc2Δ/Δ mutant in the resistant background. Microarray analysis showed attenuated induction by fluconazole of genes involved in sterol biosynthesis, iron transport, or iron homeostasis in the absence of UPC2. Taken together, these data demonstrate that the UPC2 transcriptional network is universally essential for azole resistance in C. albicans and represents an attractive target for enhancing azole antifungal activity.
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17
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Christadore LM, Pham L, Kolaczyk ED, Schaus SE. Improvement of experimental testing and network training conditions with genome-wide microarrays for more accurate predictions of drug gene targets. BMC SYSTEMS BIOLOGY 2014; 8:7. [PMID: 24444313 PMCID: PMC3911882 DOI: 10.1186/1752-0509-8-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Accepted: 11/21/2013] [Indexed: 11/10/2022]
Abstract
Background Genome-wide microarrays have been useful for predicting chemical-genetic interactions at the gene level. However, interpreting genome-wide microarray results can be overwhelming due to the vast output of gene expression data combined with off-target transcriptional responses many times induced by a drug treatment. This study demonstrates how experimental and computational methods can interact with each other, to arrive at more accurate predictions of drug-induced perturbations. We present a two-stage strategy that links microarray experimental testing and network training conditions to predict gene perturbations for a drug with a known mechanism of action in a well-studied organism. Results S. cerevisiae cells were treated with the antifungal, fluconazole, and expression profiling was conducted under different biological conditions using Affymetrix genome-wide microarrays. Transcripts were filtered with a formal network-based method, sparse simultaneous equation models and Lasso regression (SSEM-Lasso), under different network training conditions. Gene expression results were evaluated using both gene set and single gene target analyses, and the drug’s transcriptional effects were narrowed first by pathway and then by individual genes. Variables included: (i) Testing conditions – exposure time and concentration and (ii) Network training conditions – training compendium modifications. Two analyses of SSEM-Lasso output – gene set and single gene – were conducted to gain a better understanding of how SSEM-Lasso predicts perturbation targets. Conclusions This study demonstrates that genome-wide microarrays can be optimized using a two-stage strategy for a more in-depth understanding of how a cell manifests biological reactions to a drug treatment at the transcription level. Additionally, a more detailed understanding of how the statistical model, SSEM-Lasso, propagates perturbations through a network of gene regulatory interactions is achieved.
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Affiliation(s)
| | | | | | - Scott E Schaus
- Department of Chemistry, Boston University, Boston, MA, USA.
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18
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Mechanisms of Drug Resistance in Fungi and Their Significance in Biofilms. SPRINGER SERIES ON BIOFILMS 2014. [DOI: 10.1007/978-3-642-53833-9_4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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19
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Gallo-Ebert C, Donigan M, Stroke IL, Swanson RN, Manners MT, Francisco J, Toner G, Gallagher D, Huang CY, Gygax SE, Webb M, Nickels JT. Novel antifungal drug discovery based on targeting pathways regulating the fungus-conserved Upc2 transcription factor. Antimicrob Agents Chemother 2013; 58:258-66. [PMID: 24145546 PMCID: PMC3910738 DOI: 10.1128/aac.01677-13] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 10/16/2013] [Indexed: 01/05/2023] Open
Abstract
Infections by Candida albicans and related fungal pathogens pose a serious health problem for immunocompromised patients. Azole drugs, the most common agents used to combat infections, target the sterol biosynthetic pathway. Adaptation to azole therapy develops as drug-stressed cells compensate by upregulating several genes in the pathway, a process mediated in part by the Upc2 transcription factor. We have implemented a cell-based high-throughput screen to identify small-molecule inhibitors of Upc2-dependent induction of sterol gene expression in response to azole drug treatment. The assay is designed to identify not only Upc2 DNA binding inhibitors but also compounds impeding the activation of gene expression by Upc2. An AlphaScreen assay was developed to determine whether the compounds identified interact directly with Upc2 and inhibit DNA binding. Three compounds identified by the cell-based assay inhibited Upc2 protein level and UPC2-LacZ gene expression in response to a block in sterol biosynthesis. The compounds were growth inhibitory and attenuated antifungal-induced sterol gene expression in vivo. They did so by reducing the level of Upc2 protein and Upc2 DNA binding in the presence of drug. The mechanism by which the compounds restrict Upc2 DNA binding is not through a direct interaction, as demonstrated by a lack of DNA binding inhibitory activity using the AlphaScreen assay. Rather, they likely inhibit a novel pathway activating Upc2 in response to a block in sterol biosynthesis. We suggest that the compounds identified represent potential precursors for the synthesis of novel antifungal drugs.
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Affiliation(s)
- Christina Gallo-Ebert
- The Institute of Metabolic Disorders, Genesis Biotechnology Group, Hamilton, New Jersey, USA
| | - Melissa Donigan
- The Institute of Metabolic Disorders, Genesis Biotechnology Group, Hamilton, New Jersey, USA
| | - Ilana L. Stroke
- Venenum Biodesign, Genesis Biotechnology Group, Hamilton, New Jersey, USA
| | - Robert N. Swanson
- Venenum Biodesign, Genesis Biotechnology Group, Hamilton, New Jersey, USA
| | - Melissa T. Manners
- Venenum Biodesign, Genesis Biotechnology Group, Hamilton, New Jersey, USA
| | - Jamie Francisco
- The Institute of Metabolic Disorders, Genesis Biotechnology Group, Hamilton, New Jersey, USA
| | - Geoffrey Toner
- Femeris, Women's Health Research Center, Medical Diagnostic Laboratories, Genesis Biotechnology Group, Hamilton, New Jersey, USA
| | - Denise Gallagher
- Venenum Biodesign, Genesis Biotechnology Group, Hamilton, New Jersey, USA
| | - Chia-Yu Huang
- Venenum Biodesign, Genesis Biotechnology Group, Hamilton, New Jersey, USA
| | - Scott E. Gygax
- Femeris, Women's Health Research Center, Medical Diagnostic Laboratories, Genesis Biotechnology Group, Hamilton, New Jersey, USA
| | - Maria Webb
- Venenum Biodesign, Genesis Biotechnology Group, Hamilton, New Jersey, USA
| | - Joseph T. Nickels
- The Institute of Metabolic Disorders, Genesis Biotechnology Group, Hamilton, New Jersey, USA
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Guida A, Lindstädt C, Maguire SL, Ding C, Higgins DG, Corton NJ, Berriman M, Butler G. Using RNA-seq to determine the transcriptional landscape and the hypoxic response of the pathogenic yeast Candida parapsilosis. BMC Genomics 2011; 12:628. [PMID: 22192698 PMCID: PMC3287387 DOI: 10.1186/1471-2164-12-628] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 12/22/2011] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Candida parapsilosis is one of the most common causes of Candida infection worldwide. However, the genome sequence annotation was made without experimental validation and little is known about the transcriptional landscape. The transcriptional response of C. parapsilosis to hypoxic (low oxygen) conditions, such as those encountered in the host, is also relatively unexplored. RESULTS We used next generation sequencing (RNA-seq) to determine the transcriptional profile of C. parapsilosis growing in several conditions including different media, temperatures and oxygen concentrations. We identified 395 novel protein-coding sequences that had not previously been annotated. We removed > 300 unsupported gene models, and corrected approximately 900. We mapped the 5' and 3' UTR for thousands of genes. We also identified 422 introns, including two introns in the 3' UTR of one gene. This is the first report of 3' UTR introns in the Saccharomycotina. Comparing the introns in coding sequences with other species shows that small numbers have been gained and lost throughout evolution. Our analysis also identified a number of novel transcriptional active regions (nTARs). We used both RNA-seq and microarray analysis to determine the transcriptional profile of cells grown in normoxic and hypoxic conditions in rich media, and we showed that there was a high correlation between the approaches. We also generated a knockout of the UPC2 transcriptional regulator, and we found that similar to C. albicans, Upc2 is required for conferring resistance to azole drugs, and for regulation of expression of the ergosterol pathway in hypoxia. CONCLUSION We provide the first detailed annotation of the C. parapsilosis genome, based on gene predictions and transcriptional analysis. We identified a number of novel ORFs and other transcribed regions, and detected transcripts from approximately 90% of the annotated protein coding genes. We found that the transcription factor Upc2 role has a conserved role as a major regulator of the hypoxic response in C. parapsilosis and C. albicans.
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Affiliation(s)
- Alessandro Guida
- School of Medicine and Medical Science, Conway Institute, UniversityCollege Dublin, Belfield, Dublin 4, Ireland
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21
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Antifungal resistance and new strategies to control fungal infections. Int J Microbiol 2011; 2012:713687. [PMID: 22187560 PMCID: PMC3236459 DOI: 10.1155/2012/713687] [Citation(s) in RCA: 260] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 09/06/2011] [Indexed: 11/28/2022] Open
Abstract
Despite improvement of antifungal therapies over the last 30 years, the phenomenon of antifungal resistance is still of major concern in clinical practice. In the last 10 years the molecular mechanisms underlying this phenomenon were extensively unraveled. In this paper, after a brief overview of currently available antifungals, molecular mechanisms of antifungal resistance will be detailed. It appears that major mechanisms of resistance are essential due to the deregulation of antifungal resistance effector genes. This deregulation is a consequence of point mutations occurring in transcriptional regulators of these effector genes. Resistance can also follow the emergence of point mutations directly in the genes coding antifungal targets. In addition we further describe new strategies currently undertaken to discover alternative therapy targets and antifungals. Identification of new antifungals is essentially achieved by the screening of natural or synthetic chemical compound collections. Discovery of new putative antifungal targets is performed through genome-wide approaches for a better understanding of the human pathogenic fungi biology.
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Shapiro RS, Robbins N, Cowen LE. Regulatory circuitry governing fungal development, drug resistance, and disease. Microbiol Mol Biol Rev 2011; 75:213-67. [PMID: 21646428 PMCID: PMC3122626 DOI: 10.1128/mmbr.00045-10] [Citation(s) in RCA: 384] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Pathogenic fungi have become a leading cause of human mortality due to the increasing frequency of fungal infections in immunocompromised populations and the limited armamentarium of clinically useful antifungal drugs. Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus are the leading causes of opportunistic fungal infections. In these diverse pathogenic fungi, complex signal transduction cascades are critical for sensing environmental changes and mediating appropriate cellular responses. For C. albicans, several environmental cues regulate a morphogenetic switch from yeast to filamentous growth, a reversible transition important for virulence. Many of the signaling cascades regulating morphogenesis are also required for cells to adapt and survive the cellular stresses imposed by antifungal drugs. Many of these signaling networks are conserved in C. neoformans and A. fumigatus, which undergo distinct morphogenetic programs during specific phases of their life cycles. Furthermore, the key mechanisms of fungal drug resistance, including alterations of the drug target, overexpression of drug efflux transporters, and alteration of cellular stress responses, are conserved between these species. This review focuses on the circuitry regulating fungal morphogenesis and drug resistance and the impact of these pathways on virulence. Although the three human-pathogenic fungi highlighted in this review are those most frequently encountered in the clinic, they represent a minute fraction of fungal diversity. Exploration of the conservation and divergence of core signal transduction pathways across C. albicans, C. neoformans, and A. fumigatus provides a foundation for the study of a broader diversity of pathogenic fungi and a platform for the development of new therapeutic strategies for fungal disease.
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Affiliation(s)
| | | | - Leah E. Cowen
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
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23
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Abstract
The regulation of the response of Candida albicans to hypoxic (low-oxygen) conditions is poorly understood. We used microarray and other transcriptional analyses to investigate the role of the Upc2 and Bcr1 transcription factors in controlling expression of genes involved in cell wall metabolism, ergosterol synthesis, and glycolysis during adaptation to hypoxia. Hypoxic induction of the ergosterol pathway is mimicked by treatment with sterol-lowering drugs (ketoconazole) and requires UPC2. Expression of three members of the family CFEM (common in several fungal extracellular membranes) of cell wall genes (RBT5, PGA7, and PGA10) is also induced by hypoxia and ketoconazole and requires both UPC2 and BCR1. Expression of glycolytic genes is induced by hypoxia but not by treatment with sterol-lowering drugs, whereas expression of respiratory pathway genes is repressed. However, Upc2 does not play a major role in regulating expression of genes required for central carbon metabolism. Our results indicate that regulation of gene expression in response to hypoxia in C. albicans is complex and is signaled both via lowered sterol levels and other unstudied mechanisms. We also show that induction of filamentation under hypoxic conditions requires the Ras1- and Cdc35-dependent pathway.
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The UPC2 promoter in Candida albicans contains two cis-acting elements that bind directly to Upc2p, resulting in transcriptional autoregulation. EUKARYOTIC CELL 2010; 9:1354-62. [PMID: 20656915 DOI: 10.1128/ec.00130-10] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In Candida albicans, ergosterol biosynthetic genes, including ERG11, which encodes the target of azole antifungal drugs, are regulated by the transcriptional regulator Upc2p. To initially characterize the promoter of the UPC2 gene, 5' rapid amplification of cDNA ends was used to identify two transcriptional initiation sites upstream of the ATG codon. The regions within the UPC2 promoter required for azole regulation of the UPC2 promoter were then identified using nested deletions fused to a luciferase reporter which were tested for azole inducibility in wild-type (WT) and upc2Delta/upc2Delta strains. Two distinct regions important for azole induction were identified: a Upc2p-dependent region (UDR) between bp -450 and -350 upstream of the ATG codon and a Upc2p-independent region (UIR) between bp -350 and -250 upstream of the ATG codon. Within the UDR, loss or mutation of the sterol response element (SRE), so named because of homology to the Saccharomyces cerevisiae Upc2p binding site, resulted in a decrease in both basal and induced expression in the WT strain but did not affect azole inducibility in the upc2Delta/upc2Delta deletion strain. Gel shift analyses using the DNA binding domain of Upc2p confirmed binding of the protein to two SRE-related sequences within the UPC2 promoter, with strongest binding to the UDR SRE. Detailed gel shift analyses of the UDR SRE shows that Upc2p binds to a bipartite element within the UPC2 promoter, including the previously identified SRE and a new, adjacent element, the short direct repeat (SDR), with partial homology to the SRE.
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An A643T mutation in the transcription factor Upc2p causes constitutive ERG11 upregulation and increased fluconazole resistance in Candida albicans. Antimicrob Agents Chemother 2009; 54:353-9. [PMID: 19884367 DOI: 10.1128/aac.01102-09] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The zinc cluster transcription factor Upc2p mediates upregulation of ergosterol biosynthesis genes in response to ergosterol depletion in the fungal pathogen Candida albicans. One mechanism of acquired resistance to the antifungal drug fluconazole, which inhibits ergosterol biosynthesis, is constitutively increased expression of the ERG11 gene encoding the drug target enzyme. A G648D mutation in Upc2p has recently been shown to cause hyperactivity of the transcription factor, resulting in overexpression of ergosterol biosynthesis genes and increased fluconazole resistance. In order to investigate if gain-of-function mutations in Upc2p are a common mechanism of ERG11 upregulation and fluconazole resistance, we sequenced the UPC2 alleles of four ERG11-overexpressing, fluconazole-resistant C. albicans isolates and matched susceptible isolates from the same patients. In three of the isolate pairs, no differences in the UPC2 alleles were found, suggesting that mechanisms other than Upc2p mutations can cause ERG11 overexpression. One resistant isolate had become homozygous for a UPC2 allele containing a G1927A substitution that caused an alanine-to-threonine exchange at amino acid position 643 of Upc2p. Replacement of one of the endogenous UPC2 alleles in a fluconazole-susceptible strain by the UPC2(A643T) allele resulted in ERG11 overexpression and increased fluconazole resistance, which was further elevated when the A643T mutation was also introduced into the second UPC2 allele. These results further establish gain-of-function mutations in UPC2, which can be followed by loss of heterozygosity for the mutated allele, as a mechanism of ERG11 overexpression and increased fluconazole resistance in C. albicans, but other mechanisms of ERG11 upregulation also exist.
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Sanglard D, Coste A, Ferrari S. Antifungal drug resistance mechanisms in fungal pathogens from the perspective of transcriptional gene regulation. FEMS Yeast Res 2009; 9:1029-50. [PMID: 19799636 DOI: 10.1111/j.1567-1364.2009.00578.x] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Fungi are primitive eukaryotes and have adapted to a variety of niches during evolution. Some fungal species may interact with other life forms (plants, insects, mammals), but are considered as pathogens when they cause mild to severe diseases. Chemical control strategies have emerged with the development of several drugs with antifungal activity against pathogenic fungi. Antifungal agents have demonstrated their efficacy by improving patient health in medicine. However, fungi have counteracted antifungal agents in several cases by developing resistance mechanisms. These mechanisms rely on drug resistance genes including multidrug transporters and drug targets. Their regulation is crucial for the development of antifungal drug resistance and therefore transcriptional factors critical for their regulation are being characterized. Recent genome-wide studies have revealed complex regulatory circuits involving these genetic and transcriptional regulators. Here, we review the current understanding of the transcriptional regulation of drug resistance genes from several fungal pathogens including Candida and Aspergillus species.
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Affiliation(s)
- Dominique Sanglard
- Institute of Microbiology, University of Lausanne and University Hospital Center, 1011 Lausanne, Switzerland.
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Abstract
Antifungal resistance caused by mutations of the drug target, overexpression of the drug target, and drug efflux by the upregulation of transporters is increasingly common. Recently our understanding of fungal drug resistance has been advanced by the identification of three key transcriptional regulators of resistance: Tac1p, Upc2p, and Mrr1p. The discovery of hyperactive variants of these regulators in resistant clinical isolates confirms the importance of transcriptional regulation in the development of antifungal resistance. Alternative mechanisms of drug resistance including aneuploidy and biofilm formation have recently been documented in fungi; as well as the phenomenon of drug tolerance. Characterization of the transcriptional regulation of fungal drug resistance and the identification of novel mechanisms of resistance has implications for current therapy and for the development of future antifungal drugs.
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Chen CG, Yang YL, Tseng KY, Shih HI, Liou CH, Lin CC, Lo HJ. Rep1p negatively regulating MDR1 efflux pump involved in drug resistance in Candida albicans. Fungal Genet Biol 2009; 46:714-20. [PMID: 19527793 DOI: 10.1016/j.fgb.2009.06.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2009] [Revised: 06/03/2009] [Accepted: 06/09/2009] [Indexed: 11/28/2022]
Abstract
Overexpression of MDR1 efflux pump is a major mechanism contributing to drug resistance in Candida albicans, the most common human fungal pathogen. To elucidate the regulatory pathway of drug resistance, we have identified a negative regulator of MDR1 and named it Regulator of Efflux Pump 1 (REP1). Overexpression of REP1 in Saccharomyces cerevisiae increased susceptibility to fluconazole. Furthermore, null mutations on REP1 decreased the susceptibility to antifungal drugs in C. albicans resulting from increased expression of MDR1 mRNA. Hence, Rep1p is involved in drug resistance by negatively regulating MDR1 in C. albicans.
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Affiliation(s)
- Chia-Geun Chen
- Institute of Preventive Medicine, National Defense Medical Center, Taiwan, ROC
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Yin Y, Liu X, Li B, Ma Z. Characterization of sterol demethylation inhibitor-resistant isolates of Fusarium asiaticum and F. graminearum collected from wheat in China. PHYTOPATHOLOGY 2009; 99:487-97. [PMID: 19351244 DOI: 10.1094/phyto-99-5-0487] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Fusarium asiaticum and F. graminearum are the primary causal agents of Fusarium head blight (FHB) of wheat in China. In this study, sensitivities of 159 F. asiaticum and F. graminearum isolates to a benzimidazole fungicide carbendazim (MBC) and to sterol demethylation inhibitors (DMIs) tebuconazole and prochloraz were determined. Among the 159 isolates, 9 were resistant to MBC and designated as MBC-R isolates. Three showed resistance to tebuconazole and prochloraz and designated as DMI-R isolates. There was no cross-resistance between MBC and DMI. Genetic analysis by microsatellite-primed polymerase chain reaction (PCR) showed that MBC-R or DMI-R isolates had different genotypes, which indicated that they originated from different wild-type parents. Analysis of two 14alpha-demethylase (cyp51) homologous genes (cyp51A and cyp51B) showed that the F. asiaticum isolates could be distinguished from F. graminearum isolates based on the sequence of cyp51A. Analysis of deduced amino acid sequence of cyp51A and cyp51B suggested that no mutations were associated with DMI resistance. Real-time PCR analysis showed that the DMI resistance was not related to the expression of cyp51A and cyp51B in F. asiaticum and F. graminearum, but expressions of both genes were induced greatly by the tebuconazole. Results of this study indicated that cyp51A would be an informative marker for analysis of population structure of F. asiaticum and F. graminearum, and the existence of homologous cyp51 genes in F. asiaticum and F. graminearum could provide new insights into DMI resistance in phytopathogenic fungi.
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Affiliation(s)
- Y Yin
- Institute of Biotechnology, Zhejiang University, Hangzhou, China
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Eckert SE, Mühlschlegel FA. Promoter regulation inCandida albicansand related species. FEMS Yeast Res 2009; 9:2-15. [DOI: 10.1111/j.1567-1364.2008.00455.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
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Abc1p is a multidrug efflux transporter that tips the balance in favor of innate azole resistance in Candida krusei. Antimicrob Agents Chemother 2008; 53:354-69. [PMID: 19015352 DOI: 10.1128/aac.01095-08] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Most Candida krusei strains are innately resistant to fluconazole (FLC) and can cause breakthrough candidemia in immunocompromised individuals receiving long-term prophylactic FLC treatment. Although the azole drug target, Erg11p, of C. krusei has a relatively low affinity for FLC, drug efflux pumps are also believed to be involved in its innate FLC resistance. We describe here the isolation and characterization of Abc1p, a constitutively expressed multidrug efflux pump, and investigate ERG11 and ABC1 expression in C. krusei. Examination of the ERG11 promoter revealed a conserved azole responsive element that has been shown to be necessary for the transcription factor Upc2p mediated upregulation by azoles in related yeast. Extensive cloning and sequencing identified three distinct ERG11 alleles in one of two C. krusei strains. Functional overexpression of ERG11 and ABC1 in Saccharomyces cerevisiae conferred high levels of resistance to azoles and a range of unrelated Abc1p pump substrates, while small molecule inhibitors of Abc1p chemosensitized C. krusei to azole antifungals. Our data show that despite the presence of multiple alleles of ERG11 in some, likely aneuploid, C. krusei strains, it is mainly the low affinity of Erg11p for FLC, together with the constitutive but low level of expression of the multidrug efflux pump Abc1p, that are responsible for the innate FLC resistance of C. krusei.
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Hoot SJ, Oliver BG, White TC. Candida albicans UPC2 is transcriptionally induced in response to antifungal drugs and anaerobicity through Upc2p-dependent and -independent mechanisms. MICROBIOLOGY-SGM 2008; 154:2748-2756. [PMID: 18757808 DOI: 10.1099/mic.0.2008/017475-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Many genes in the Candida albicans ergosterol biosynthetic pathway are controlled by the transcriptional activator Upc2p, which is upregulated in the presence of azole drugs and has been suggested to regulate its own transcription by an autoregulatory mechanism. The UPC2 promoter was cloned upstream of a luciferase reporter gene (RLUC). UPC2-RLUC activity was induced in response to ergosterol biosynthesis inhibitors and in response to anaerobicity. Under both conditions, induction correlates with the magnitude of sterol depletion. Azole inducibility in the parental strain was approximately 100-fold, and in a UPC2 homozygous deletion strain was 17-fold, suggesting that, in addition to autoregulation, UPC2 transcription is controlled by a novel, Upc2p-independent mechanism(s). Curiously, basal UPC2-RLUC activity was fivefold higher in the deletion strain, which may be an indirect consequence of the lower sterol level in this strain, or a direct consequence of repression by an autoregulatory mechanism. These results suggest that transcriptional regulation of UPC2 expression is important in the response to antifungal drugs, and that this regulation occurs through Upc2p-dependent as well as novel Upc2p-independent mechanisms.
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Affiliation(s)
- Samantha J Hoot
- Seattle Biomedical Research Institute, Seattle, WA, USA.,Department of Pathobiology, School of Public Health and Community Medicine, University of Washington, Seattle, WA, USA
| | | | - Theodore C White
- Seattle Biomedical Research Institute, Seattle, WA, USA.,Department of Pathobiology, School of Public Health and Community Medicine, University of Washington, Seattle, WA, USA
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Current awareness on yeast. Yeast 2008. [DOI: 10.1002/yea.1563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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A gain-of-function mutation in the transcription factor Upc2p causes upregulation of ergosterol biosynthesis genes and increased fluconazole resistance in a clinical Candida albicans isolate. EUKARYOTIC CELL 2008; 7:1180-90. [PMID: 18487346 DOI: 10.1128/ec.00103-08] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the pathogenic yeast Candida albicans, the zinc cluster transcription factor Upc2p has been shown to regulate the expression of ERG11 and other genes involved in ergosterol biosynthesis upon exposure to azole antifungals. ERG11 encodes lanosterol demethylase, the target enzyme of this antifungal class. Overexpression of UPC2 reduces azole susceptibility, whereas its disruption results in hypersusceptibility to azoles and reduced accumulation of exogenous sterols. Overexpression of ERG11 leads to the increased production of lanosterol demethylase, which contributes to azole resistance in clinical isolates of C. albicans, but the mechanism for this has yet to be determined. Using genome-wide gene expression profiling, we found UPC2 and other genes involved in ergosterol biosynthesis to be coordinately upregulated with ERG11 in a fluconazole-resistant clinical isolate compared with a matched susceptible isolate from the same patient. Sequence analysis of the UPC2 alleles of these isolates revealed that the resistant isolate contained a single-nucleotide substitution in one UPC2 allele that resulted in a G648D exchange in the encoded protein. Introduction of the mutated allele into a drug-susceptible strain resulted in constitutive upregulation of ERG11 and increased resistance to fluconazole. By comparing the gene expression profiles of the fluconazole-resistant isolate and of strains carrying wild-type and mutated UPC2 alleles, we identified target genes that are controlled by Upc2p. Here we show for the first time that a gain-of-function mutation in UPC2 leads to the increased expression of ERG11 and imparts resistance to fluconazole in clinical isolates of C. albicans.
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Genomewide location analysis of Candida albicans Upc2p, a regulator of sterol metabolism and azole drug resistance. EUKARYOTIC CELL 2008; 7:836-47. [PMID: 18390649 DOI: 10.1128/ec.00070-08] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Upc2p, a transcription factor of the zinc cluster family, is an important regulator of sterol biosynthesis and azole drug resistance in Candida albicans. To better understand Upc2p function in C. albicans, we used genomewide location profiling to identify the transcriptional targets of Upc2p in vivo. A triple hemagglutinin epitope, introduced at the C terminus of Upc2p, conferred a gain-of-function effect on the fusion protein. Location profiling identified 202 bound promoters (P < 0.05). Overrepresented functional groups of genes whose promoters were bound by Upc2p included 12 genes involved in ergosterol biosynthesis (NCP1, ERG11, ERG2, and others), 18 genes encoding ribosomal subunits (RPS30, RPL32, RPL12, and others), 3 genes encoding drug transporters (CDR1, MDR1, and YOR1), 4 genes encoding transcription factors (INO2, ACE2, SUT1, and UPC2), and 6 genes involved in sulfur amino acid metabolism (MET6, SAM2, SAH1, and others). Bioinformatic analyses suggested that Upc2p binds to the DNA motif 5'-VNCGBDTR that includes the previously characterized Upc2p binding site 5'-TCGTATA. Northern blot analysis showed that increased binding correlates with increased expression for the analyzed Upc2p targets (ERG11, MDR1, CDR1, YOR1, SUT1, SMF12, and CBP1). The analysis of ERG11, MDR1, and CDR1 transcripts in wild-type and upc2Delta/upc2Delta strains grown under Upc2p-activating conditions (lovastatin treatment and hypoxia) showed that Upc2p regulates its targets in a complex manner, acting as an activator or as a repressor depending upon the target and the activating condition. Taken together, our results indicate that Upc2p is a key regulator of ergosterol metabolism. They also suggest that Upc2p may contribute to azole resistance by regulating the expression of drug efflux pump-encoding genes in addition to ergosterol biosynthesis genes.
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