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Rybak JM, Xie J, Martin-Vicente A, Guruceaga X, Thorn HI, Nywening AV, Ge W, Souza ACO, Shetty AC, McCracken C, Bruno VM, Parker JE, Kelly SL, Snell HM, Cuomo CA, Rogers PD, Fortwendel JR. A secondary mechanism of action for triazole antifungals in Aspergillus fumigatus mediated by hmg1. Nat Commun 2024; 15:3642. [PMID: 38684680 PMCID: PMC11059170 DOI: 10.1038/s41467-024-48029-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 04/17/2024] [Indexed: 05/02/2024] Open
Abstract
Triazole antifungals function as ergosterol biosynthesis inhibitors and are frontline therapy for invasive fungal infections, such as invasive aspergillosis. The primary mechanism of action of triazoles is through the specific inhibition of a cytochrome P450 14-α-sterol demethylase enzyme, Cyp51A/B, resulting in depletion of cellular ergosterol. Here, we uncover a clinically relevant secondary mechanism of action for triazoles within the ergosterol biosynthesis pathway. We provide evidence that triazole-mediated inhibition of Cyp51A/B activity generates sterol intermediate perturbations that are likely decoded by the sterol sensing functions of HMG-CoA reductase and Insulin-Induced Gene orthologs as increased pathway activity. This, in turn, results in negative feedback regulation of HMG-CoA reductase, the rate-limiting step of sterol biosynthesis. We also provide evidence that HMG-CoA reductase sterol sensing domain mutations previously identified as generating resistance in clinical isolates of Aspergillus fumigatus partially disrupt this triazole-induced feedback. Therefore, our data point to a secondary mechanism of action for the triazoles: induction of HMG-CoA reductase negative feedback for downregulation of ergosterol biosynthesis pathway activity. Abrogation of this feedback through acquired mutations in the HMG-CoA reductase sterol sensing domain diminishes triazole antifungal activity against fungal pathogens and underpins HMG-CoA reductase-mediated resistance.
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Affiliation(s)
- Jeffrey M Rybak
- Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Jinhong Xie
- Graduate Program in Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Adela Martin-Vicente
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Xabier Guruceaga
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Harrison I Thorn
- Graduate Program in Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Ashley V Nywening
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
- Integrated Program in Biomedical Sciences, College of Graduate Health Sciences, University of Tennessee Health Science Center, Memphis, TN, USA
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Wenbo Ge
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Ana C O Souza
- Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Amol C Shetty
- Institute of Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Carrie McCracken
- Institute of Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Vincent M Bruno
- Institute of Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Josie E Parker
- Molecular Biosciences Division, School of Biosciences, Cardiff University, Cardiff, Wales, UK
| | - Steven L Kelly
- Institute of Life Science, Swansea University Medical School, Swansea, Wales, UK
| | - Hannah M Snell
- Infectious Diseases and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Christina A Cuomo
- Infectious Diseases and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - P David Rogers
- Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Jarrod R Fortwendel
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA.
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA.
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Thorn HI, Guruceaga X, Martin-Vicente A, Nywening AV, Xie J, Ge W, Fortwendel JR. MOB-mediated regulation of septation initiation network (SIN) signaling is required for echinocandin-induced hyperseptation in Aspergillus fumigatus. mSphere 2024; 9:e0069523. [PMID: 38349166 DOI: 10.1128/msphere.00695-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Accepted: 01/17/2024] [Indexed: 03/27/2024] Open
Abstract
Aspergillus fumigatus is a major invasive mold pathogen and the most frequent etiologic agent of invasive aspergillosis. The currently available treatments for invasive aspergillosis are limited in both number and efficacy. Our recent work has uncovered that the β-glucan synthase inhibitors, the echinocandins, are fungicidal against strains of A. fumigatus with defects in septation initiation network (SIN) kinase activity. These drugs are known to be fungistatic against strains with normal septation. Surprisingly, SIN kinase mutant strains also failed to invade lung tissue and were significantly less virulent in immunosuppressed mouse models. Inhibiting septation in filamentous fungi is therefore an exciting therapeutic prospect to both reduce virulence and improve current antifungal therapy. However, the SIN remains understudied in pathogenic fungi. To address this knowledge gap, we characterized the putative regulatory components of the A. fumigatus SIN. These included the GTPase, SpgA, it's two-component GTPase-activating protein, ByrA/BubA, and the kinase activators, SepM and MobA. Deletion of spgA, byrA, or bubA resulted in no overt septation or echinocandin susceptibility phenotypes. In contrast, our data show that deletion of sepM or mobA largely phenocopies disruption of their SIN kinase binding partners, sepL and sidB, respectively. Reduced septum formation, echinocandin hypersusceptibility, and reduced virulence were generated by loss of either gene. These findings provide strong supporting evidence that septa are essential not only for withstanding the cell wall disrupting effects of echinocandins but are also critical for the establishment of invasive disease. Therefore, pharmacological SIN inhibition may be an exciting strategy for future antifungal drug development.IMPORTANCESepta are important structural determinants of echinocandin susceptibility and tissue invasive growth for the ubiquitous fungal pathogen Aspergillus fumigatus. Components of the septation machinery therefore represent promising novel antifungal targets to improve echinocandin activity and reduce virulence. However, little is known about septation regulation in A. fumigatus. Here, we characterize the predicted regulatory components of the A. fumigatus septation initiation network. We show that the kinase activators SepM and MobA are vital for proper septation and echinocandin resistance, with MobA playing an essential role. Null mutants of mobA displayed significantly reduced virulence in a mouse model, underscoring the importance of this pathway for A. fumigatus pathogenesis.
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Affiliation(s)
- Harrison I Thorn
- Graduate Program in Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Xabier Guruceaga
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Adela Martin-Vicente
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Ashley V Nywening
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
- Integrated Program in Biomedical Sciences, College of Graduate Health Sciences, University of Tennessee Health Science Center, Memphis, Tennessee, USA
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Jinhong Xie
- Graduate Program in Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Wenbo Ge
- Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Jarrod R Fortwendel
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
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Guruceaga X, Perez-Cuesta U, Martin-Vicente A, Pelegri-Martinez E, Thorn HI, Cendon-Sanchez S, Xie J, Nywening AV, Ramirez-Garcia A, Fortwendel JR, Rementeria A. The Aspergillus fumigatus maiA gene contributes to cell wall homeostasis and fungal virulence. Front Cell Infect Microbiol 2024; 14:1327299. [PMID: 38343890 PMCID: PMC10853476 DOI: 10.3389/fcimb.2024.1327299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 01/08/2024] [Indexed: 02/15/2024] Open
Abstract
In this study, two distinct in vitro infection models of Aspergillus fumigatus, using murine macrophages (RAW264.7) and human lung epithelial cells (A549), were employed to identify the genes important for fungal adaptation during infection. Transcriptomic analyses of co-incubated A. fumigatus uncovered 140 fungal genes up-regulated in common between both models that, when compared with a previously published in vivo transcriptomic study, allowed the identification of 13 genes consistently up-regulated in all three infection conditions. Among them, the maiA gene, responsible for a critical step in the L-phenylalanine degradation pathway, was identified. Disruption of maiA resulted in a mutant strain unable to complete the Phe degradation pathway, leading to an excessive production of pyomelanin when this amino acid served as the sole carbon source. Moreover, the disruption mutant exhibited noticeable cell wall abnormalities, with reduced levels of β-glucans within the cell wall but did not show lack of chitin or mannans. The maiA-1 mutant strain induced reduced inflammation in primary macrophages and displayed significantly lower virulence in a neutropenic mouse model of infection. This is the first study linking the A. fumigatus maiA gene to fungal cell wall homeostasis and virulence.
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Affiliation(s)
- Xabier Guruceaga
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Uxue Perez-Cuesta
- Department of Immunology, Microbiology, and Parasitology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Leioa, Spain
| | - Adela Martin-Vicente
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Eduardo Pelegri-Martinez
- Department of Immunology, Microbiology, and Parasitology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Leioa, Spain
| | - Harrison I. Thorn
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, United States
- Graduate Program in Pharmaceutical Science, College of Graduate Health Sciences, University of Tennessee Healths Science Center, Memphis, TN, United States
| | - Saioa Cendon-Sanchez
- Department of Immunology, Microbiology, and Parasitology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Leioa, Spain
| | - Jinhong Xie
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, United States
- Graduate Program in Pharmaceutical Science, College of Graduate Health Sciences, University of Tennessee Healths Science Center, Memphis, TN, United States
| | - Ashley V. Nywening
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, United States
- Integrated Program in Biomedical Sciences, College of Graduate Health Sciences, University of Tennessee Health Science Center, Memphis, TN, United States
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Andoni Ramirez-Garcia
- Department of Immunology, Microbiology, and Parasitology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Leioa, Spain
| | - Jarrod R. Fortwendel
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, United States
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Aitor Rementeria
- Department of Immunology, Microbiology, and Parasitology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Leioa, Spain
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Xie J, Rybak JM, Martin-Vicente A, Guruceaga X, Thorn HI, Nywening AV, Ge W, Parker JE, Kelly SL, Rogers PD, Fortwendel JR. The sterol C-24 methyltransferase encoding gene, erg6, is essential for viability of Aspergillus species. bioRxiv 2023:2023.08.08.552489. [PMID: 37609350 PMCID: PMC10441335 DOI: 10.1101/2023.08.08.552489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Ergosterol is a critical component of fungal plasma membranes. Although many currently available antifungal compounds target the ergosterol biosynthesis pathway for antifungal effect, current knowledge regarding ergosterol synthesis remains incomplete for filamentous fungal pathogens like Aspergillus fumigatus. Here, we show for the first time that the lipid droplet-associated sterol C-24 methyltransferase, Erg6, is essential for A. fumigatus viability. We further show that this essentiality extends to additional Aspergillus species, including A. lentulus, A. terreus, and A. nidulans. Neither the overexpression of a putative erg6 paralog, smt1, nor the exogenous addition of ergosterol could rescue erg6 deficiency. Importantly, Erg6 downregulation results in a dramatic decrease in ergosterol and accumulation in lanosterol and is further characterized by diminished sterol-rich plasma membrane domains (SRDs) at hyphal tips. Unexpectedly, erg6 repressed strains demonstrate wild-type susceptibility against the ergosterol-active triazole and polyene antifungals. Finally, repressing erg6 expression reduced fungal burden accumulation in a murine model of invasive aspergillosis. Taken together, our studies suggest that Erg6, which shows little homology to mammalian proteins, is potentially an attractive antifungal drug target for therapy of Aspergillus infections.
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Affiliation(s)
- Jinhong Xie
- Graduate Program in Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN USA
| | - Jeffrey M. Rybak
- Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children’s Research Hospital, Memphis, TN, USA
| | - Adela Martin-Vicente
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN USA
| | - Xabier Guruceaga
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN USA
| | - Harrison I. Thorn
- Graduate Program in Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN USA
| | - Ashley V. Nywening
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN USA
- Integrated Program in Biomedical Sciences, College of Graduate Health Sciences, University of Tennessee Health Science Center, Memphis, TN, USA
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Wenbo Ge
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN USA
| | - Josie E. Parker
- Molecular Biosciences Division, School of Biosciences, Cardiff University, Cardiff, Wales, UK
| | - Steven L. Kelly
- Institute of Life Science, Swansea University Medical School, Swansea, Wales, UK
| | - P. David Rogers
- Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children’s Research Hospital, Memphis, TN, USA
| | - Jarrod R. Fortwendel
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN USA
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA
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Souza ACO, Martin-Vicente A, Nywening AV, Ge W, Lowes DJ, Peters BM, Fortwendel JR. Loss of Septation Initiation Network (SIN) kinases blocks tissue invasion and unlocks echinocandin cidal activity against Aspergillus fumigatus. PLoS Pathog 2021; 17:e1009806. [PMID: 34370772 PMCID: PMC8376064 DOI: 10.1371/journal.ppat.1009806] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 08/19/2021] [Accepted: 07/16/2021] [Indexed: 11/18/2022] Open
Abstract
Although considered effective treatment for many yeast fungi, the therapeutic efficacy of the echinocandin class of antifungals for invasive aspergillosis (IA) is limited. Recent studies suggest intense kinase- and phosphatase-mediated echinocandin adaptation in A. fumigatus. To identify A. fumigatus protein kinases required for survival under echinocandin stress, we employed CRISPR/Cas9-mediated gene targeting to generate a protein kinase disruption mutant library in a wild type genetic background. Cell wall and echinocandin stress screening of the 118 disruption mutants comprising the library identified only five protein kinase disruption mutants displaying greater than 4-fold decreased echinocandin minimum effective concentrations (MEC) compared to the parental strain. Two of these mutated genes, the previously uncharacterized A. fumigatus sepL and sidB genes, were predicted to encode protein kinases functioning as core components of the Septation Initiation Network (SIN), a tripartite kinase cascade that is necessary for septation in fungi. As the A. fumigatus SIN is completely uncharacterized, we sought to explore these network components as effectors of echinocandin stress survival. Our data show that mutation of any single SIN kinase gene caused complete loss of hyphal septation and increased susceptibility to cell wall stress, as well as widespread hyphal damage and loss of viability in response to echinocandin stress. Strikingly, mutation of each SIN kinase gene also resulted in a profound loss of virulence characterized by lack of tissue invasive growth. Through the deletion of multiple novel regulators of hyphal septation, we show that the non-invasive growth phenotype is not SIN-kinase dependent, but likely due to hyphal septation deficiency. Finally, we also find that echinocandin therapy is highly effective at eliminating residual tissue burden in mice infected with an aseptate strain of A. fumigatus. Together, our findings suggest that inhibitors of septation could enhance echinocandin-mediated killing while simultaneously limiting the invasive potential of A. fumigatus hyphae.
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Affiliation(s)
- Ana Camila Oliveira Souza
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Adela Martin-Vicente
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Ashley V. Nywening
- Integrated Program in Biomedical Sciences, College of Graduate Health Sciences, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Wenbo Ge
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - David J. Lowes
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Brian M. Peters
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Jarrod R. Fortwendel
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
- * E-mail:
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Nywening AV, Rybak JM, Rogers PD, Fortwendel JR. Mechanisms of triazole resistance in Aspergillus fumigatus. Environ Microbiol 2020; 22:4934-4952. [PMID: 33047482 DOI: 10.1111/1462-2920.15274] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 10/07/2020] [Accepted: 10/07/2020] [Indexed: 12/11/2022]
Abstract
The ubiquitous fungal pathogen Aspergillus fumigatus is the primary cause of opportunistic mould infections in humans. Aspergilli disseminate via asexual conidia passively travelling through air currents to germinate within a broad range of environs, wherever suitable nutrients are found. Though the average human inhales hundreds of conidia daily, A. fumigatus invasive infections primarily affect the immunocompromised. At-risk individuals can develop often fatal invasive disease for which therapeutic options are limited. Regrettably, the global insurgence of isolates resistant to the triazoles, the frontline antifungal class used in medicine and agriculture to control A. fumigatus, is complicating the treatment of patients. Triazole antifungal resistance in A. fumigatus has become recognized as a global, yet poorly comprehended, problem. Due to a multitude of factors, the magnitude of resistant infections and their contribution to treatment outcomes are likely underestimated. Current studies suggest that human drug-resistant infections can be either environmentally acquired or de novo host selected during patient therapy. While much concerning development of resistance is yet unknown, recent investigations have revealed assorted underlying mechanisms enabling triazole resistance within individual clinical and environmental isolates. This review will provide an overview of triazole resistance as it is currently understood, as well as highlight some of the prominent biological mechanisms associated with clinical and environmental resistance to triazoles in A. fumigatus.
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Affiliation(s)
- Ashley V Nywening
- Department of Clinical Pharmacy and Translational Sciences, The University of Tennessee Health Science Center, 881 Madison Avenue, Memphis, TN, USA.,College of Graduate Health Sciences, Integrated Biomedical Sciences Program, The University of Tennessee Health Science Center, Memphis, TN, 38163, USA
| | - Jeffrey M Rybak
- Department of Clinical Pharmacy and Translational Sciences, The University of Tennessee Health Science Center, 881 Madison Avenue, Memphis, TN, USA
| | - Phillip David Rogers
- Department of Clinical Pharmacy and Translational Sciences, The University of Tennessee Health Science Center, 881 Madison Avenue, Memphis, TN, USA
| | - Jarrod R Fortwendel
- Department of Clinical Pharmacy and Translational Sciences, The University of Tennessee Health Science Center, 881 Madison Avenue, Memphis, TN, USA
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Souza ACO, Al Abdallah Q, DeJarnette K, Martin-Vicente A, Nywening AV, DeJarnette C, Sansevere EA, Ge W, Palmer GE, Fortwendel JR. Differential requirements of protein geranylgeranylation for the virulence of human pathogenic fungi. Virulence 2020; 10:511-526. [PMID: 31131706 PMCID: PMC6550545 DOI: 10.1080/21505594.2019.1620063] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Protein prenylation is a crucial post-translational modification largely mediated by two heterodimeric enzyme complexes, farnesyltransferase and geranylgeranyltransferase type-I (GGTase-I), each composed of a shared α-subunit and a unique β-subunit. GGTase-I enzymes are validated drug targets that contribute to virulence in Cryptococcus neoformans and to the yeast-to-hyphal transition in Candida albicans. Therefore, we sought to investigate the importance of the α-subunit, RamB, and the β-subunit, Cdc43, of the A. fumigatus GGTase-I complex to hyphal growth and virulence. Deletion of cdc43 resulted in impaired hyphal morphogenesis and thermo-sensitivity, which was exacerbated during growth in rich media. The Δcdc43 mutant also displayed hypersensitivity to cell wall stress agents and to cell wall synthesis inhibitors, suggesting alterations of cell wall biosynthesis or stress signaling. In support of this, analyses of cell wall content revealed decreased amounts of β-glucan in the Δcdc43 strain. Despite strong in vitro phenotypes, the Δcdc43 mutant was fully virulent in two models of murine invasive aspergillosis, similar to the control strain. We further found that a strain expressing the α-subunit gene, ramB, from a tetracycline-inducible promoter was inviable under non-inducing in vitro growth conditions and was virtually avirulent in both mouse models. Lastly, virulence studies using C. albicans strains with tetracycline-repressible RAM2 or CDC43 expression revealed reduced pathogenicity associated with downregulation of either gene in a murine model of disseminated infection. Together, these findings indicate a differential requirement for protein geranylgeranylation for fungal virulence, and further inform the selection of specific prenyltransferases as promising antifungal drug targets for each pathogen.
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Affiliation(s)
- Ana Camila Oliveira Souza
- a Department of Clinical Pharmacy and Translational Science , College of Pharmacy, University of Tennessee Health Science Center , Memphis , TN , USA
| | - Qusai Al Abdallah
- a Department of Clinical Pharmacy and Translational Science , College of Pharmacy, University of Tennessee Health Science Center , Memphis , TN , USA
| | - Kaci DeJarnette
- a Department of Clinical Pharmacy and Translational Science , College of Pharmacy, University of Tennessee Health Science Center , Memphis , TN , USA
| | - Adela Martin-Vicente
- a Department of Clinical Pharmacy and Translational Science , College of Pharmacy, University of Tennessee Health Science Center , Memphis , TN , USA
| | - Ashley V Nywening
- b Department of Molecular Immunology and Biochemistry , College of Graduate Health Sciences, University of Tennessee Health Science Center , Memphis , TN , USA
| | - Christian DeJarnette
- b Department of Molecular Immunology and Biochemistry , College of Graduate Health Sciences, University of Tennessee Health Science Center , Memphis , TN , USA
| | - Emily A Sansevere
- a Department of Clinical Pharmacy and Translational Science , College of Pharmacy, University of Tennessee Health Science Center , Memphis , TN , USA
| | - Wenbo Ge
- a Department of Clinical Pharmacy and Translational Science , College of Pharmacy, University of Tennessee Health Science Center , Memphis , TN , USA
| | - Glen E Palmer
- a Department of Clinical Pharmacy and Translational Science , College of Pharmacy, University of Tennessee Health Science Center , Memphis , TN , USA
| | - Jarrod R Fortwendel
- a Department of Clinical Pharmacy and Translational Science , College of Pharmacy, University of Tennessee Health Science Center , Memphis , TN , USA
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