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Wu D, Guan YX, Li CH, Zheng Q, Yin ZJ, Wang H, Liu NN. "Nutrient-fungi-host" tripartite interaction in cancer progression. IMETA 2024; 3:e170. [PMID: 38882486 PMCID: PMC11170973 DOI: 10.1002/imt2.170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Revised: 01/04/2024] [Accepted: 01/05/2024] [Indexed: 06/18/2024]
Abstract
The human microbiome exhibits a profound connection with the cancer development, progression, and therapeutic response, with particular emphasis on its components of the mycobiome, which are still in the early stages of research. In this review, we comprehensively summarize cancer-related symbiotic and pathogenic fungal genera. The intricate mechanisms through which fungi impact cancer as an integral member of both gut and tissue-resident microbiomes are further discussed. In addition, we shed light on the pivotal physiological roles of various nutrients, including cholesterol, carbohydrates, proteins and minerals, in facilitating the growth, reproduction, and invasive pathogenesis of the fungi. While our exploration of the interplay between nutrients and cancer, mediated by the mycobiome, is ongoing, the current findings have yet to yield conclusive results. Thus, delving into the relationship between nutrients and fungal pathogenesis in cancer development and progression would provide valuable insights into anticancer therapy and foster precision nutrition and individualized treatments that target fungi from bench to bedside.
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Affiliation(s)
- Di Wu
- State Key Laboratory of Systems Medicine for Cancer, Center for Single-Cell Omics, School of Public Health Shanghai Jiao Tong University School of Medicine Shanghai China
| | - Yun-Xuan Guan
- State Key Laboratory of Systems Medicine for Cancer, Center for Single-Cell Omics, School of Public Health Shanghai Jiao Tong University School of Medicine Shanghai China
| | - Chen-Hao Li
- Institute of Computing Technology Chinese Academy of Sciences Beijing China
| | - Quan Zheng
- State Key Laboratory of Systems Medicine for Cancer, Center for Single-Cell Omics, School of Public Health Shanghai Jiao Tong University School of Medicine Shanghai China
| | - Zuo-Jing Yin
- State Key Laboratory of Systems Medicine for Cancer, Center for Single-Cell Omics, School of Public Health Shanghai Jiao Tong University School of Medicine Shanghai China
| | - Hui Wang
- State Key Laboratory of Systems Medicine for Cancer, Center for Single-Cell Omics, School of Public Health Shanghai Jiao Tong University School of Medicine Shanghai China
| | - Ning-Ning Liu
- State Key Laboratory of Systems Medicine for Cancer, Center for Single-Cell Omics, School of Public Health Shanghai Jiao Tong University School of Medicine Shanghai China
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2
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Touré H, Herrmann JL, Szuplewski S, Girard-Misguich F. Drosophila melanogaster as an organism model for studying cystic fibrosis and its major associated microbial infections. Infect Immun 2023; 91:e0024023. [PMID: 37847031 PMCID: PMC10652941 DOI: 10.1128/iai.00240-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2023] Open
Abstract
Cystic fibrosis (CF) is a human genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator gene that encodes a chloride channel. The most severe clinical manifestation is associated with chronic pulmonary infections by pathogenic and opportunistic microbes. Drosophila melanogaster has become the invertebrate model of choice for modeling microbial infections and studying the induced innate immune response. Here, we review its contribution to the understanding of infections with six major pathogens associated with CF (Staphylococcus aureus, Pseudomonas aeruginosa, Burkholderia cepacia, Mycobacterium abscessus, Streptococcus pneumoniae, and Aspergillus fumigatus) together with the perspectives opened by the recent availability of two CF models in this model organism.
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Affiliation(s)
- Hamadoun Touré
- Université Paris-Saclay, UVSQ, INSERM, Infection et Inflammation, Montigny-le-Bretonneux, France
| | - Jean-Louis Herrmann
- Université Paris-Saclay, UVSQ, INSERM, Infection et Inflammation, Montigny-le-Bretonneux, France
- Assistance Publique-Hôpitaux de Paris, Hôpitaux Universitaires Ile-de-France Ouest, GHU Paris-Saclay, Hôpital Raymond Poincaré, Garches, France
| | - Sébastien Szuplewski
- Université Paris-Saclay, UVSQ, Laboratoire de Génétique et Biologie Cellulaire, Montigny-le-Bretonneux, France
| | - Fabienne Girard-Misguich
- Université Paris-Saclay, UVSQ, INSERM, Infection et Inflammation, Montigny-le-Bretonneux, France
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3
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Silao FGS, Jiang T, Bereczky-Veress B, Kühbacher A, Ryman K, Uwamohoro N, Jenull S, Nogueira F, Ward M, Lion T, Urban CF, Rupp S, Kuchler K, Chen C, Peuckert C, Ljungdahl PO. Proline catabolism is a key factor facilitating Candida albicans pathogenicity. PLoS Pathog 2023; 19:e1011677. [PMID: 37917600 PMCID: PMC10621835 DOI: 10.1371/journal.ppat.1011677] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Accepted: 09/11/2023] [Indexed: 11/04/2023] Open
Abstract
Candida albicans, the primary etiology of human mycoses, is well-adapted to catabolize proline to obtain energy to initiate morphological switching (yeast to hyphal) and for growth. We report that put1-/- and put2-/- strains, carrying defective Proline UTilization genes, display remarkable proline sensitivity with put2-/- mutants being hypersensitive due to the accumulation of the toxic intermediate pyrroline-5-carboxylate (P5C), which inhibits mitochondrial respiration. The put1-/- and put2-/- mutations attenuate virulence in Drosophila and murine candidemia models and decrease survival in human neutrophils and whole blood. Using intravital 2-photon microscopy and label-free non-linear imaging, we visualized the initial stages of C. albicans cells infecting a kidney in real-time, directly deep in the tissue of a living mouse, and observed morphological switching of wildtype but not of put2-/- cells. Multiple members of the Candida species complex, including C. auris, are capable of using proline as a sole energy source. Our results indicate that a tailored proline metabolic network tuned to the mammalian host environment is a key feature of opportunistic fungal pathogens.
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Affiliation(s)
- Fitz Gerald S. Silao
- Department of Molecular Biosciences, The Wenner-Gren Institute, Science for Life Laboratory, Stockholm University, Solna, Sweden
| | - Tong Jiang
- Shanghai Institute of Immunity and Infection, Chinese Academy of Sciences, Shanghai, China
| | - Biborka Bereczky-Veress
- Intravital Microscopy Facility, Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Andreas Kühbacher
- Department of Molecular Biotechnology, Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, Stuttgart, Germany
| | - Kicki Ryman
- Department of Molecular Biosciences, The Wenner-Gren Institute, Science for Life Laboratory, Stockholm University, Solna, Sweden
| | - Nathalie Uwamohoro
- Clinical Microbiology and Umeå Centre for Microbial Research (UCMR), Umeå University Umeå, Sweden
| | - Sabrina Jenull
- Medical University of Vienna, Max F. Perutz Laboratories GmbH, Department of Medical Biochemistry, Vienna, Austria
- Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Filomena Nogueira
- Medical University of Vienna, Max F. Perutz Laboratories GmbH, Department of Medical Biochemistry, Vienna, Austria
- St. Anna Kinderkrebsforschung e.V., Children’s Cancer Research Institute, Vienna, Austria
| | - Meliza Ward
- Department of Molecular Biosciences, The Wenner-Gren Institute, Science for Life Laboratory, Stockholm University, Solna, Sweden
| | - Thomas Lion
- St. Anna Kinderkrebsforschung e.V., Children’s Cancer Research Institute, Vienna, Austria
| | - Constantin F. Urban
- Clinical Microbiology and Umeå Centre for Microbial Research (UCMR), Umeå University Umeå, Sweden
| | - Steffen Rupp
- Department of Molecular Biotechnology, Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, Stuttgart, Germany
| | - Karl Kuchler
- Medical University of Vienna, Max F. Perutz Laboratories GmbH, Department of Medical Biochemistry, Vienna, Austria
| | - Changbin Chen
- Shanghai Institute of Immunity and Infection, Chinese Academy of Sciences, Shanghai, China
| | - Christiane Peuckert
- Intravital Microscopy Facility, Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Per O. Ljungdahl
- Department of Molecular Biosciences, The Wenner-Gren Institute, Science for Life Laboratory, Stockholm University, Solna, Sweden
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4
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Cross ST, Brehm AL, Dunham TJ, Rodgers CP, Keene AH, Borlee GI, Stenglein MD. Galbut Virus Infection Minimally Influences Drosophila melanogaster Fitness Traits in a Strain and Sex-Dependent Manner. Viruses 2023; 15:539. [PMID: 36851753 PMCID: PMC9965562 DOI: 10.3390/v15020539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 02/02/2023] [Accepted: 02/07/2023] [Indexed: 02/17/2023] Open
Abstract
Galbut virus (family Partitiviridae) infects Drosophila melanogaster and can be transmitted vertically from infected mothers or infected fathers with near perfect efficiency. This form of super-Mendelian inheritance should drive infection to 100% prevalence, and indeed, galbut virus is ubiquitous in wild D. melanogaster populations. However, on average, only about 60% of individual flies are infected. One possible explanation for this is that a subset of flies are resistant to infection. Although galbut virus-infected flies appear healthy, infection may be sufficiently costly to drive selection for resistant hosts, thereby decreasing overall prevalence. To test this hypothesis, we quantified a variety of fitness-related traits in galbut virus-infected flies from two lines from the Drosophila Genetic Reference Panel (DGRP). Galbut virus-infected flies had no difference in average lifespan and total offspring production compared to their uninfected counterparts. Galbut virus-infected DGRP-517 flies pupated and eclosed faster than their uninfected counterparts. Some galbut virus-infected flies exhibited altered sensitivity to viral, bacterial, and fungal pathogens. The microbiome composition of flies was not measurably perturbed by galbut virus infection. Differences in phenotype attributable to galbut virus infection varied as a function of fly sex and DGRP strain, and differences attributable to infection status were dwarfed by larger differences attributable to strain and sex. Thus, galbut virus infection does produce measurable phenotypic changes, with changes being minor, offsetting, and possibly net-negative.
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Affiliation(s)
- Shaun T. Cross
- Department of Environmental, Agricultural, and Occupational Health, College of Public Health, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Ali L. Brehm
- Center for Vector-Borne and Infectious Diseases, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Tillie J. Dunham
- Center for Vector-Borne and Infectious Diseases, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Case P. Rodgers
- Center for Vector-Borne and Infectious Diseases, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Alexandra H. Keene
- Center for Vector-Borne and Infectious Diseases, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Grace I. Borlee
- Center for Vector-Borne and Infectious Diseases, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Mark D. Stenglein
- Center for Vector-Borne and Infectious Diseases, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
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5
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Wurster S, Albert ND, Kontoyiannis DP. Drosophila melanogaster as a Rapid and Reliable In Vivo Infection Model to Study the Emerging Yeast Pathogen Candida auris. Methods Mol Biol 2022; 2517:299-316. [PMID: 35674964 DOI: 10.1007/978-1-0716-2417-3_24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
While mammalian models remain the gold standard to study invasive mycoses, mini-host invertebrate models have provided complementary platforms for explorative investigations of fungal pathogenesis, host-pathogen interplay, and antifungal therapy. Specifically, our group has established Toll-deficient Drosophila melanogaster flies as a facile and cost-effective model organism to study candidiasis, and we have recently expanded these studies to the emerging and frequently multidrug-resistant yeast pathogen Candida auris. Our proof-of-concept data suggest that fruit flies could hold a great promise for large-scale applications in antifungal drug discovery and the screening of C. auris (mutant) libraries with disparate pathogenic capacity. This chapter discusses the advantages and limitations of D. melanogaster to study C. auris candidiasis and provides a step-by-step guide for establishing and troubleshooting C. auris infection and antifungal treatment of Toll-deficient flies along with essential downstream readouts.
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Affiliation(s)
- Sebastian Wurster
- Department of Infectious Diseases, Infection Control and Employee Health, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
| | - Nathaniel D Albert
- Department of Infectious Diseases, Infection Control and Employee Health, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Dimitrios P Kontoyiannis
- Department of Infectious Diseases, Infection Control and Employee Health, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
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6
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Burchacka E, Pięta P, Łupicka-Słowik A. Recent advances in fungal serine protease inhibitors. Biomed Pharmacother 2021; 146:112523. [PMID: 34902742 DOI: 10.1016/j.biopha.2021.112523] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 11/30/2021] [Accepted: 12/06/2021] [Indexed: 12/20/2022] Open
Abstract
Four types of antifungal drugs are available that include inhibitors of ergosterol synthesis, of fungal RNA biosynthesis, and of cell wall biosynthesis as well as physiochemical regulators of fungal membrane sterols. Increasing resistance to antifungal drugs can severely limit treatment options of fungal nail infections, vaginal candidiasis, ringworm, blastomycosis, histoplasmosis, and Candida infections of the mouth, throat, and esophagus, among other infections. Development of strategies focused on new fungicides can effectively help tackle troublesome fungal diseases. The virulence and optimal growth of fungi depend on various extracellular secreted factors, among which proteases, such as serine proteases, are of particular interest. A specific extracellular proteolytic system enables fungi to survive and penetrate the tissues. Given the role of fungal proteases in infection, any molecule capable of selectively and specifically inhibiting their activity can lead to the development of potential drugs. Owing to their specific mode of action, fungal protease inhibitors can avoid fungal resistance observed with currently available treatments. Although fungal secreted proteases have been extensively studied as potential virulence factors, our understanding of the substrate specificity of such proteases remains poor. In this review, we summarize the recent advances in the design and development of specific serine protease inhibitors and provide a brief history of the compounds that inhibit fungal serine protease activity.
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Affiliation(s)
- E Burchacka
- Faculty of Chemistry, Department of Organic and Medicinal Chemistry, Wrocław University of Science and Technology, 27 Wybrzeże Wyspiańskiego St, 50-370 Wrocław, Poland.
| | - P Pięta
- Department of Bionic and Medical Experimental Biology, Poznań University of Medical Sciences, Parkowa 2 St, 60-775 Poznań, Poland
| | - A Łupicka-Słowik
- Faculty of Chemistry, Department of Organic and Medicinal Chemistry, Wrocław University of Science and Technology, 27 Wybrzeże Wyspiańskiego St, 50-370 Wrocław, Poland
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Csonka K, Tasi Z, Vedelek V, Vágvölgyi C, Sinka R, Gácser A. Deciphering of Candida parapsilosis induced immune response in Drosophila melanogaster. Virulence 2021; 12:2571-2582. [PMID: 34569900 PMCID: PMC8477938 DOI: 10.1080/21505594.2021.1980989] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Candida infections are the most prevalent cause of serious human mycoses and are the third most common pathogens isolated from bloodstream infections in hospitalized patients. C. parapsilosis is a member of the non-albicans spp., which have a predilection for causing life-threatening disease in neonates and hospitalized pediatric patients. In this study, we utilized a Drosophila melanogaster infection model to analyze the immunological responses to C. parapsilosis. Our results demonstrate that the Toll pathway in Drosophila controls C. parapsilosis proliferation as the Toll signaling mutant MyD88-/- flies are highly susceptible to C. parapsilosis. We also confirmed that the MyD88-/- fly is a convenient invertebrate animal model to analyze virulence properties of different species and strains from the C. parapsilosis sensu lato complex as C. orthopsilosis, C. metapsilosis proved to be less virulent than C. parapsilosis sensu stricto and the N-mannan deficient C. parapsilosis och1Δ/Δ strain showed attenuated pathogenicity in this immunodeficient Drosophila background. We also found that Persephone protease is not required for detection and activation of Toll pathway during C. parapsilosis infection. Furthermore, we observed that Drosophila β-glucan receptor deficient flies where more sensitive to C. parapsilosis compared to wild-type flies; however, we could not find a clear dependence on the recognition of this receptor and the cell wall β-glucan exposure-induced host response. These studies establish this D. melanogaster infection model as an efficient tool in deciphering immune responses to C. parapsilosis as well as for assessing virulence factors produced by this emerging fungal predator.
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Affiliation(s)
- Katalin Csonka
- Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Zsolt Tasi
- Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Viktor Vedelek
- Department of Genetics, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Csaba Vágvölgyi
- Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Rita Sinka
- Department of Genetics, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Attila Gácser
- HCEMM-USZ, Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary.,MTA-SZTE Lendület Mycobiome Research Group, University of Szeged, Szeged, Hungary
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Glutamate dehydrogenase (Gdh2)-dependent alkalization is dispensable for escape from macrophages and virulence of Candida albicans. PLoS Pathog 2020; 16:e1008328. [PMID: 32936835 PMCID: PMC7521896 DOI: 10.1371/journal.ppat.1008328] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 09/28/2020] [Accepted: 08/14/2020] [Indexed: 11/19/2022] Open
Abstract
Candida albicans cells depend on the energy derived from amino acid catabolism to induce and sustain hyphal growth inside phagosomes of engulfing macrophages. The concomitant deamination of amino acids is thought to neutralize the acidic microenvironment of phagosomes, a presumed requisite for survival and initiation of hyphal growth. Here, in contrast to an existing model, we show that mitochondrial-localized NAD+-dependent glutamate dehydrogenase (GDH2) catalyzing the deamination of glutamate to α-ketoglutarate, and not the cytosolic urea amidolyase (DUR1,2), accounts for the observed alkalization of media when amino acids are the sole sources of carbon and nitrogen. C. albicans strains lacking GDH2 (gdh2-/-) are viable and do not extrude ammonia on amino acid-based media. Environmental alkalization does not occur under conditions of high glucose (2%), a finding attributable to glucose-repression of GDH2 expression and mitochondrial function. Consistently, inhibition of oxidative phosphorylation or mitochondrial translation by antimycin A or chloramphenicol, respectively, prevents alkalization. GDH2 expression and mitochondrial function are derepressed as glucose levels are lowered from 2% (~110 mM) to 0.2% (~11 mM), or when glycerol is used as primary carbon source. Using time-lapse microscopy, we document that gdh2-/- cells survive, filament and escape from primary murine macrophages at rates indistinguishable from wildtype. In intact hosts, such as in fly and murine models of systemic candidiasis, gdh2-/- mutants are as virulent as wildtype. Thus, although Gdh2 has a critical role in central nitrogen metabolism, Gdh2-catalyzed deamination of glutamate is surprisingly dispensable for escape from macrophages and virulence. Consistently, using the pH-sensitive dye (pHrodo), we observed no significant difference between wildtype and gdh2-/- mutants in phagosomal pH modulation. Following engulfment of fungal cells, the phagosomal compartment is rapidly acidified and hyphal growth initiates and sustained under consistently acidic conditions within phagosomes. Together, our results demonstrate that amino acid-dependent alkalization is not essential for hyphal growth, survival in macrophages and hosts. An accurate understanding of the microenvironment within macrophage phagosomes and the metabolic events underlying the survival of phagocytized C. albicans cells and their escape are critical to understanding the host-pathogen interactions that ultimately determine the pathogenic outcome. Candida albicans is a commensal component of the human microflora and the most common fungal pathogen. The incidence of candidiasis is low in healthy populations. Consequently, environmental factors, such as interactions with innate immune cells, play critical roles. Macrophages provide the first line of defense and rapidly internalize C. albicans cells within specialized intracellular compartments called phagosomes. The microenvironment within phagosomes is dynamic and ill defined, but has a low pH, and contains potent hydrolytic enzymes and oxidative stressors. Despite the inhospitable conditions, phagocytized C. albicans cells catabolize amino acids to obtain energy to survive and grow. Here, we have critically examined amino acid catabolism and ammonia extrusion in C. albicans, the latter is thought to neutralize the phagosomal pH and induce the switch of morphologies from round “yeast-like” to elongated hyphal cells that can pierce the phagosomal membrane leading to escape from macrophages. We report that Gdh2, which catalyzes the deamination of glutamate to α-ketoglutarate, is responsible for the observed environmental alkalization when C. albicans catabolize amino acids in vitro. However, the phagosomes formed as macrophages engulf wildtype or gdh2-/- cells rapidly become acidified, indicating that Gdh2 has no apparent role in modulating phagosomal pH. Strikingly, and similar to wildtype cells, gdh2-/- cells initiate and sustain hyphal growth enabling them to escape from macrophages. Also, Gdh2 is dispensable for virulent growth in systemic models of infection. These results provide new insights into host-pathogen interactions that determine the pathogenic outcome of C. albicans infections.
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Abstract
We review the mechanisms responsible for amino acid homeostasis in Saccharomyces cerevisiae and other fungi. Amino acid homeostasis is essential for cell growth and survival. Hence, the de novo synthesis reactions, metabolic conversions, and transport of amino acids are tightly regulated. Regulation varies from nitrogen pool sensing to control by individual amino acids and takes place at the gene (transcription), protein (posttranslational modification and allostery), and vesicle (trafficking and endocytosis) levels. The pools of amino acids are controlled via import, export, and compartmentalization. In yeast, the majority of the amino acid transporters belong to the APC (amino acid-polyamine-organocation) superfamily, and the proteins couple the uphill transport of amino acids to the electrochemical proton gradient. Although high-resolution structures of yeast amino acid transporters are not available, homology models have been successfully exploited to determine and engineer the catalytic and regulatory functions of the proteins. This has led to a further understanding of the underlying mechanisms of amino acid sensing and subsequent downregulation of transport. Advances in optical microscopy have revealed a new level of regulation of yeast amino acid transporters, which involves membrane domain partitioning. The significance and the interrelationships of the latest discoveries on amino acid homeostasis are put in context.
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Troha K, Buchon N. Methods for the study of innate immunity in Drosophila melanogaster. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2019; 8:e344. [PMID: 30993906 DOI: 10.1002/wdev.344] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 02/25/2019] [Accepted: 03/20/2019] [Indexed: 12/12/2022]
Abstract
From flies to humans, many components of the innate immune system have been conserved during metazoan evolution. This foundational observation has allowed us to develop Drosophila melanogaster, the fruit fly, into a powerful model to study innate immunity in animals. Thanks to an ever-growing arsenal of genetic tools, an easily manipulated genome, and its winning disposition, Drosophila is now employed to study not only basic molecular mechanisms of pathogen recognition and immune signaling, but also the nature of physiological responses activated in the host by microbial challenge and how dysregulation of these processes contributes to disease. Here, we present a collection of methods and protocols to challenge the fly with an assortment of microbes, both systemically and orally, and assess its humoral, cellular, and epithelial response to infection. Our review covers techniques for measuring the reaction to microbial infection both qualitatively and quantitatively. Specifically, we describe survival, bacterial load, BLUD (a measure of disease tolerance), phagocytosis, melanization, clotting, and ROS production assays, as well as efficient protocols to collect hemolymph and measure immune gene expression. We also offer an updated catalog of online resources and a collection of popular reporter lines and mutants to facilitate research efforts. This article is categorized under: Technologies > Analysis of Cell, Tissue, and Animal Phenotypes.
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Affiliation(s)
- Katia Troha
- Department of Entomology, Cornell Institute of Host-Microbe Interactions and Disease, Cornell University, Ithaca, New York
| | - Nicolas Buchon
- Department of Entomology, Cornell Institute of Host-Microbe Interactions and Disease, Cornell University, Ithaca, New York
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11
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Silao FGS, Ward M, Ryman K, Wallström A, Brindefalk B, Udekwu K, Ljungdahl PO. Mitochondrial proline catabolism activates Ras1/cAMP/PKA-induced filamentation in Candida albicans. PLoS Genet 2019; 15:e1007976. [PMID: 30742618 PMCID: PMC6386415 DOI: 10.1371/journal.pgen.1007976] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Revised: 02/22/2019] [Accepted: 01/21/2019] [Indexed: 11/18/2022] Open
Abstract
Amino acids are among the earliest identified inducers of yeast-to-hyphal transitions in Candida albicans, an opportunistic fungal pathogen of humans. Here, we show that the morphogenic amino acids arginine, ornithine and proline are internalized and metabolized in mitochondria via a PUT1- and PUT2-dependent pathway that results in enhanced ATP production. Elevated ATP levels correlate with Ras1/cAMP/PKA pathway activation and Efg1-induced gene expression. The magnitude of amino acid-induced filamentation is linked to glucose availability; high levels of glucose repress mitochondrial function thereby dampening filamentation. Furthermore, arginine-induced morphogenesis occurs more rapidly and independently of Dur1,2-catalyzed urea degradation, indicating that mitochondrial-generated ATP, not CO2, is the primary morphogenic signal derived from arginine metabolism. The important role of the SPS-sensor of extracellular amino acids in morphogenesis is the consequence of induced amino acid permease gene expression, i.e., SPS-sensor activation enhances the capacity of cells to take up morphogenic amino acids, a requisite for their catabolism. C. albicans cells engulfed by murine macrophages filament, resulting in macrophage lysis. Phagocytosed put1-/- and put2-/- cells do not filament and exhibit reduced viability, consistent with a critical role of mitochondrial proline metabolism in virulence.
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Affiliation(s)
- Fitz Gerald S. Silao
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Meliza Ward
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Kicki Ryman
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Axel Wallström
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Björn Brindefalk
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Klas Udekwu
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Per O. Ljungdahl
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
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12
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Intersection of phosphate transport, oxidative stress and TOR signalling in Candida albicans virulence. PLoS Pathog 2018; 14:e1007076. [PMID: 30059535 PMCID: PMC6085062 DOI: 10.1371/journal.ppat.1007076] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 08/09/2018] [Accepted: 05/07/2018] [Indexed: 12/11/2022] Open
Abstract
Phosphate is an essential macronutrient required for cell growth and division. Pho84 is the major high-affinity cell-surface phosphate importer of Saccharomyces cerevisiae and a crucial element in the phosphate homeostatic system of this model yeast. We found that loss of Candida albicans Pho84 attenuated virulence in Drosophila and murine oropharyngeal and disseminated models of invasive infection, and conferred hypersensitivity to neutrophil killing. Susceptibility of cells lacking Pho84 to neutrophil attack depended on reactive oxygen species (ROS): pho84-/- cells were no more susceptible than wild type C. albicans to neutrophils from a patient with chronic granulomatous disease, or to those whose oxidative burst was pharmacologically inhibited or neutralized. pho84-/- mutants hyperactivated oxidative stress signalling. They accumulated intracellular ROS in the absence of extrinsic oxidative stress, in high as well as low ambient phosphate conditions. ROS accumulation correlated with diminished levels of the unique superoxide dismutase Sod3 in pho84-/- cells, while SOD3 overexpression from a conditional promoter substantially restored these cells’ oxidative stress resistance in vitro. Repression of SOD3 expression sharply increased their oxidative stress hypersensitivity. Neither of these oxidative stress management effects of manipulating SOD3 transcription was observed in PHO84 wild type cells. Sod3 levels were not the only factor driving oxidative stress effects on pho84-/- cells, though, because overexpressing SOD3 did not ameliorate these cells’ hypersensitivity to neutrophil killing ex vivo, indicating Pho84 has further roles in oxidative stress resistance and virulence. Measurement of cellular metal concentrations demonstrated that diminished Sod3 expression was not due to decreased import of its metal cofactor manganese, as predicted from the function of S. cerevisiae Pho84 as a low-affinity manganese transporter. Instead of a role of Pho84 in metal transport, we found its role in TORC1 activation to impact oxidative stress management: overexpression of the TORC1-activating GTPase Gtr1 relieved the Sod3 deficit and ROS excess in pho84-/- null mutant cells, though it did not suppress their hypersensitivity to neutrophil killing or hyphal growth defect. Pharmacologic inhibition of Pho84 by small molecules including the FDA-approved drug foscarnet also induced ROS accumulation. Inhibiting Pho84 could hence support host defenses by sensitizing C. albicans to oxidative stress. Candida albicans is the species most often isolated from patients with invasive fungal disease, and is also a common colonizer of healthy people. It is well equipped to compete for nutrients with bacteria co-inhabiting human gastrointestinal mucous membranes, since it possesses multiple transporters to internalize important nutrients like sugars, nitrogen sources, and phosphate. During infection, the fungus needs to withstand human defense cells that attack it with noxious chemicals, among which reactive oxygen species (ROS) are critical. We found that a high-affinity phosphate transporter, Pho84, is required for C. albicans’ ability to successfully invade animal hosts and to eliminate ROS. Levels of a fungal enzyme that breaks down ROS, Sod3, were decreased in cells lacking Pho84. A connection between this phosphate transporter and the ROS-detoxifying enzyme was identified in the Target of Rapamycin (TOR) pathway, to which Pho84 is known to provide activating signals when phosphate is abundant. Small molecules that block Pho84 activity impair the ability of C. albicans to detoxify ROS. Since humans manage phosphate differently than fungi and have no Pho84 homolog, a drug that inhibits Pho84 could disable the defense of the fungus against the host.
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Abstract
To respond to the changing environment, cells must be able to sense external conditions. This is important for many processes including growth, mating, the expression of virulence factors, and several other regulatory effects. Nutrient sensing at the plasma membrane is mediated by different classes of membrane proteins that activate downstream signaling pathways: nontransporting receptors, transceptors, classical and nonclassical G-protein-coupled receptors, and the newly defined extracellular mucin receptors. Nontransporting receptors have the same structure as transport proteins, but have lost the capacity to transport while gaining a receptor function. Transceptors are transporters that also function as a receptor, because they can rapidly activate downstream signaling pathways. In this review, we focus on these four types of fungal membrane proteins. We mainly discuss the sensing mechanisms relating to sugars, ammonium, and amino acids. Mechanisms for other nutrients, such as phosphate and sulfate, are discussed briefly. Because the model yeast Saccharomyces cerevisiae has been the most studied, especially regarding these nutrient-sensing systems, each subsection will commence with what is known in this species.
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Bergman P, Seyedoleslami Esfahani S, Engström Y. Drosophila as a Model for Human Diseases—Focus on Innate Immunity in Barrier Epithelia. Curr Top Dev Biol 2017; 121:29-81. [DOI: 10.1016/bs.ctdb.2016.07.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Dissecting Candida albicans Infection from the Perspective of C. albicans Virulence and Omics Approaches on Host-Pathogen Interaction: A Review. Int J Mol Sci 2016; 17:ijms17101643. [PMID: 27763544 PMCID: PMC5085676 DOI: 10.3390/ijms17101643] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 09/15/2016] [Accepted: 09/19/2016] [Indexed: 02/06/2023] Open
Abstract
Candida bloodstream infections remain the most frequent life-threatening fungal disease, with Candida albicans accounting for 70% to 80% of the Candida isolates recovered from infected patients. In nature, Candida species are part of the normal commensal flora in mammalian hosts. However, they can transform into pathogens once the host immune system is weakened or breached. More recently, mortality attributed to Candida infections has continued to increase due to both inherent and acquired drug resistance in Candida, the inefficacy of the available antifungal drugs, tedious diagnostic procedures, and a rising number of immunocompromised patients. Adoption of animal models, viz. minihosts, mice, and zebrafish, has brought us closer to unraveling the pathogenesis and complexity of Candida infection in human hosts, leading towards the discovery of biomarkers and identification of potential therapeutic agents. In addition, the advancement of omics technologies offers a holistic view of the Candida-host interaction in a non-targeted and non-biased manner. Hence, in this review, we seek to summarize past and present milestone findings on C. albicans virulence, adoption of animal models in the study of C. albicans infection, and the application of omics technologies in the study of Candida–host interaction. A profound understanding of the interaction between host defense and pathogenesis is imperative for better design of novel immunotherapeutic strategies in future.
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Dantoft W, Lundin D, Esfahani SS, Engström Y. The POU/Oct Transcription Factor Pdm1/nub Is Necessary for a Beneficial Gut Microbiota and Normal Lifespan of Drosophila. J Innate Immun 2016; 8:412-26. [PMID: 27231014 DOI: 10.1159/000446368] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 04/23/2016] [Indexed: 01/01/2023] Open
Abstract
Maintenance of a stable gut microbial community relies on a delicate balance between immune defense and immune tolerance. We have used Drosophila to study how the microbial gut flora is affected by changes in host genetic factors and immunity. Flies with a constitutively active gut immune system, due to a mutation in the POU transcriptional regulator Pdm1/nubbin (nub) gene, had higher loads of bacteria and a more diverse taxonomic composition than controls. In addition, the microbial composition shifted considerably during the short lifespan of the nub1 mutants. This shift was characterized by a loss of relatively few OTUs (operational taxonomic units) and a remarkable increase in a large number of Acetobacter spp. and Leuconostoc spp. Treating nub1 mutant flies with antibiotics prolonged their lifetime survival by more than 100%. Immune gene expression was also persistently high in the presence of antibiotics, indicating that the early death was not a direct consequence of an overactive immune defense but rather an indirect consequence of the microbial load and composition. Thus, changes in host genotype and an inability to regulate the normal growth and composition of the gut microbiota leads to a shift in the microbial community, dysbiosis and early death.
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Candida albicans mutant construction and characterization of selected virulence determinants. J Microbiol Methods 2015; 115:153-65. [DOI: 10.1016/j.mimet.2015.06.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 06/09/2015] [Accepted: 06/10/2015] [Indexed: 11/22/2022]
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Chantranupong L, Wolfson RL, Sabatini DM. Nutrient-sensing mechanisms across evolution. Cell 2015; 161:67-83. [PMID: 25815986 DOI: 10.1016/j.cell.2015.02.041] [Citation(s) in RCA: 229] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Indexed: 12/11/2022]
Abstract
For organisms to coordinate their growth and development with nutrient availability, they must be able to sense nutrient levels in their environment. Here, we review select nutrient-sensing mechanisms in a few diverse organisms. We discuss how these mechanisms reflect the nutrient requirements of specific species and how they have adapted to the emergence of multicellularity in eukaryotes.
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Affiliation(s)
- Lynne Chantranupong
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, 9 Cambridge Center, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Koch Institute for Integrative Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Rachel L Wolfson
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, 9 Cambridge Center, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Koch Institute for Integrative Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - David M Sabatini
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, 9 Cambridge Center, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Koch Institute for Integrative Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
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Diverse nitrogen sources in seminal fluid act in synergy to induce filamentous growth of Candida albicans. Appl Environ Microbiol 2015; 81:2770-80. [PMID: 25662979 DOI: 10.1128/aem.03595-14] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The pathogenic fungus Candida albicans is the leading cause of vulvovaginal candidiasis (VVC). VVC represents a major quality-of-life issue for women during their reproductive years, a stage of life where the vaginal epithelium is subject to periodic hormonally induced changes associated with menstruation and concomitant exposure to serum as well as potential intermittent contact with seminal fluid. Seminal fluid potently triggers Candida albicans to switch from yeastlike to filamentous modes of growth, a developmental response tightly linked to virulence. Conversely, vaginal fluid inhibits filamentation. Here, we used artificial formulations of seminal and vaginal fluids that faithfully mimic genuine fluids to assess the contribution of individual components within these fluids to filamentation. The high levels of albumin, amino acids, and N-acetylglucosamine in seminal fluid act synergistically as potent inducers of filamentous growth, even at atmospheric levels of CO2 and reduced temperatures (30 °C). Using a simplified in vitro model that mimics the natural introduction of seminal fluid into the vulvovaginal environment, a pulse of artificial seminal fluid (ASF) was found to exert an enduring potential to overcome the inhibitory efficacy of artificial vaginal fluid (AVF) on filamentation. These findings suggest that a transient but substantial change in the nutrient levels within the vulvovaginal environment during unprotected coitus can induce resident C. albicans cells to engage developmental programs associated with virulent growth.
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Conrad M, Schothorst J, Kankipati HN, Van Zeebroeck G, Rubio-Texeira M, Thevelein JM. Nutrient sensing and signaling in the yeast Saccharomyces cerevisiae. FEMS Microbiol Rev 2014; 38:254-99. [PMID: 24483210 PMCID: PMC4238866 DOI: 10.1111/1574-6976.12065] [Citation(s) in RCA: 419] [Impact Index Per Article: 41.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 12/23/2013] [Accepted: 01/22/2014] [Indexed: 02/04/2023] Open
Abstract
The yeast Saccharomyces cerevisiae has been a favorite organism for pioneering studies on nutrient-sensing and signaling mechanisms. Many specific nutrient responses have been elucidated in great detail. This has led to important new concepts and insight into nutrient-controlled cellular regulation. Major highlights include the central role of the Snf1 protein kinase in the glucose repression pathway, galactose induction, the discovery of a G-protein-coupled receptor system, and role of Ras in glucose-induced cAMP signaling, the role of the protein synthesis initiation machinery in general control of nitrogen metabolism, the cyclin-controlled protein kinase Pho85 in phosphate regulation, nitrogen catabolite repression and the nitrogen-sensing target of rapamycin pathway, and the discovery of transporter-like proteins acting as nutrient sensors. In addition, a number of cellular targets, like carbohydrate stores, stress tolerance, and ribosomal gene expression, are controlled by the presence of multiple nutrients. The protein kinase A signaling pathway plays a major role in this general nutrient response. It has led to the discovery of nutrient transceptors (transporter receptors) as nutrient sensors. Major shortcomings in our knowledge are the relationship between rapid and steady-state nutrient signaling, the role of metabolic intermediates in intracellular nutrient sensing, and the identity of the nutrient sensors controlling cellular growth.
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Affiliation(s)
- Michaela Conrad
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU LeuvenLeuven-Heverlee, Flanders, Belgium
- Department of Molecular Microbiology, VIBLeuven-Heverlee, Flanders, Belgium
| | - Joep Schothorst
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU LeuvenLeuven-Heverlee, Flanders, Belgium
- Department of Molecular Microbiology, VIBLeuven-Heverlee, Flanders, Belgium
| | - Harish Nag Kankipati
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU LeuvenLeuven-Heverlee, Flanders, Belgium
- Department of Molecular Microbiology, VIBLeuven-Heverlee, Flanders, Belgium
| | - Griet Van Zeebroeck
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU LeuvenLeuven-Heverlee, Flanders, Belgium
- Department of Molecular Microbiology, VIBLeuven-Heverlee, Flanders, Belgium
| | - Marta Rubio-Texeira
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU LeuvenLeuven-Heverlee, Flanders, Belgium
- Department of Molecular Microbiology, VIBLeuven-Heverlee, Flanders, Belgium
| | - Johan M Thevelein
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU LeuvenLeuven-Heverlee, Flanders, Belgium
- Department of Molecular Microbiology, VIBLeuven-Heverlee, Flanders, Belgium
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Ramírez-Camejo LA, Torres-Ocampo AP, Agosto-Rivera JL, Bayman P. An opportunistic human pathogen on the fly: strains of Aspergillus flavus vary in virulence in Drosophila melanogaster. Med Mycol 2014; 52:211-9. [PMID: 24577003 DOI: 10.1093/mmy/myt008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Aspergilloses are fungal diseases in humans and animals that is caused by members of the genus Aspergillus. Aspergillus flavus is an important opportunistic pathogen, second only to A. fumigatus as a cause of human aspergillosis. Differences in virulence among A. flavus isolates from clinical and other substrates and mating types are not well known. The fruit fly Drosophila melanogaster has become a model organism for investigating virulence of human pathogens due to similarities between its immune system and that of mammals. In this study we used D. melanogaster as a model host to compare virulence among A. flavus strains obtained from clinical sources as compared with other substrates, between isolates of different mating types, and between isolates of A. flavus and A. fumigatus. Anesthetized flies were infected with A. flavus; mortality ranged from 15% to >90%. All strains were virulent, but some were significantly more so than others, which in turn led to the wide mortality range. Clinical strains were significantly less virulent than environmental strains, probably because the clinical strains were from culture collections and the environmental strains were recent isolates. Mean virulence did not differ between MAT1-1 and MAT1-2 mating types and the phylogeny of A. flavus isolates did not predict virulence. A. flavus was on average significantly more virulent than A. fumigatus on two lines of wild-type flies, Canton-S and Oregon-R. D. melanogaster is an attractive model to test pathogenicity and could be useful for identifying genes involved in virulence.
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Perlin MH, Andrews J, San Toh S. Essential Letters in the Fungal Alphabet. ADVANCES IN GENETICS 2014; 85:201-53. [DOI: 10.1016/b978-0-12-800271-1.00004-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Dantoft W, Davis MM, Lindvall JM, Tang X, Uvell H, Junell A, Beskow A, Engström Y. The Oct1 homolog Nubbin is a repressor of NF-κB-dependent immune gene expression that increases the tolerance to gut microbiota. BMC Biol 2013; 11:99. [PMID: 24010524 PMCID: PMC3849502 DOI: 10.1186/1741-7007-11-99] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Accepted: 08/30/2013] [Indexed: 11/10/2022] Open
Abstract
Background Innate immune responses are evolutionarily conserved processes that provide crucial protection against invading organisms. Gene activation by potent NF-κB transcription factors is essential both in mammals and Drosophila during infection and stress challenges. If not strictly controlled, this potent defense system can activate autoimmune and inflammatory stress reactions, with deleterious consequences for the organism. Negative regulation to prevent gene activation in healthy organisms, in the presence of the commensal gut flora, is however not well understood. Results We show that the Drosophila homolog of mammalian Oct1/POU2F1 transcription factor, called Nubbin (Nub), is a repressor of NF-κB/Relish-driven antimicrobial peptide gene expression in flies. In nub1 mutants, which lack Nub-PD protein, excessive expression of antimicrobial peptide genes occurs in the absence of infection, leading to a significant reduction of the numbers of cultivatable gut commensal bacteria. This aberrant immune gene expression was effectively blocked by expression of Nub from a transgene. We have identified an upstream regulatory region, containing a cluster of octamer sites, which is required for repression of antimicrobial peptide gene expression in healthy flies. Chromatin immunoprecipitation experiments demonstrated that Nub binds to octamer-containing promoter fragments of several immune genes. Gene expression profiling revealed that Drosophila Nub negatively regulates many genes that are involved in immune and stress responses, while it is a positive regulator of genes involved in differentiation and metabolism. Conclusions This study demonstrates that a large number of genes that are activated by NF-κB/Relish in response to infection are normally repressed by the evolutionarily conserved Oct/POU transcription factor Nub. This prevents uncontrolled gene activation and supports the existence of a normal gut flora. We suggest that Nub protein plays an ancient role, shared with mammalian Oct/POU transcription factors, to moderate responses to immune challenge, thereby increasing the tolerance to biotic stress.
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Affiliation(s)
- Widad Dantoft
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91, Stockholm, Sweden.
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Utility of insects for studying human pathogens and evaluating new antimicrobial agents. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2013; 135:1-25. [PMID: 23604210 DOI: 10.1007/10_2013_194] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
Abstract
Insect models, such as Galleria mellonella and Drosophila melanogaster have significant ethical, logistical, and economic advantages over mammalian models for the studies of infectious diseases. Using these models, various pathogenic microbes have been studied and many novel virulence genes have been identified. Notably, because insects are susceptible to a wide variety of human pathogens and have immune responses similar to those of mammals, they offer the opportunity to understand innate immune responses against human pathogens better. It is important to note that insect pathosystems have also offered a simple strategy to evaluate the efficacy and toxicity of many antimicrobial agents. Overall, insect models provide a rapid, inexpensive, and reliable way as complementary hosts to conventional vertebrate animal models to study pathogenesis and antimicrobial agents.
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