1
|
Pijuan J, Moreno DF, Yahya G, Moisa M, Ul Haq I, Krukiewicz K, Mosbah R, Metwally K, Cavalu S. Regulatory and pathogenic mechanisms in response to iron deficiency and excess in fungi. Microb Biotechnol 2023; 16:2053-2071. [PMID: 37804207 PMCID: PMC10616654 DOI: 10.1111/1751-7915.14346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 09/14/2023] [Accepted: 09/19/2023] [Indexed: 10/09/2023] Open
Abstract
Iron is an essential element for all eukaryote organisms because of its redox properties, which are important for many biological processes such as DNA synthesis, mitochondrial respiration, oxygen transport, lipid, and carbon metabolism. For this reason, living organisms have developed different strategies and mechanisms to optimally regulate iron acquisition, transport, storage, and uptake in different environmental responses. Moreover, iron plays an essential role during microbial infections. Saccharomyces cerevisiae has been of key importance for decrypting iron homeostasis and regulation mechanisms in eukaryotes. Specifically, the transcription factors Aft1/Aft2 and Yap5 regulate the expression of genes to control iron metabolism in response to its deficiency or excess, adapting to the cell's iron requirements and its availability in the environment. We also review which iron-related virulence factors have the most common fungal human pathogens (Aspergillus fumigatus, Cryptococcus neoformans, and Candida albicans). These factors are essential for adaptation in different host niches during pathogenesis, including different fungal-specific iron-uptake mechanisms. While being necessary for virulence, they provide hope for developing novel antifungal treatments, which are currently scarce and usually toxic for patients. In this review, we provide a compilation of the current knowledge about the metabolic response to iron deficiency and excess in fungi.
Collapse
Affiliation(s)
- Jordi Pijuan
- Laboratory of Neurogenetics and Molecular MedicineInstitut de Recerca Sant Joan de DéuBarcelonaSpain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIIIMadridSpain
| | - David F. Moreno
- Department of Molecular Cellular and Developmental BiologyYale UniversityNew HavenConnecticutUSA
- Systems Biology InstituteYale UniversityWest HavenConnecticutUSA
- Institut de Génétique et de Biologie Moléculaire et CellulaireIllkirchFrance
| | - Galal Yahya
- Department of Microbiology and Immunology, Faculty of PharmacyZagazig UniversityAl SharqiaEgypt
| | - Mihaela Moisa
- Faculty of Medicine and PharmacyUniversity of OradeaOradeaRomania
| | - Ihtisham Ul Haq
- Department of Physical Chemistry and Polymers TechnologySilesian University of TechnologyGliwicePoland
- Programa de Pós‐graduação em Inovação TecnológicaUniversidade Federal de Minas GeraisBelo HorizonteBrazil
| | - Katarzyna Krukiewicz
- Department of Physical Chemistry and Polymers TechnologySilesian University of TechnologyGliwicePoland
- Centre for Organic and Nanohybrid ElectronicsSilesian University of TechnologyGliwicePoland
| | - Rasha Mosbah
- Infection Control UnitHospitals of Zagazig UniversityZagazigEgypt
| | - Kamel Metwally
- Department of Medicinal Chemistry, Faculty of PharmacyUniversity of TabukTabukSaudi Arabia
- Department of Pharmaceutical Medicinal Chemistry, Faculty of PharmacyZagazig UniversityZagazigEgypt
| | - Simona Cavalu
- Faculty of Medicine and PharmacyUniversity of OradeaOradeaRomania
| |
Collapse
|
2
|
Choi Y, Do E, Hu G, Caza M, Horianopoulos LC, Kronstad JW, Jung WH. Involvement of Mrs3/4 in Mitochondrial Iron Transport and Metabolism in Cryptococcus neoformans. J Microbiol Biotechnol 2020; 30:1142-1148. [PMID: 32522963 DOI: 10.4014/jmb.2004.04041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Accepted: 05/18/2020] [Indexed: 11/01/2022]
Abstract
Mitochondria play a vital role in iron uptake and metabolism in pathogenic fungi, and also influence virulence and drug tolerance. However, the regulation of iron transport within the mitochondria of Cryptococcus neoformans, a causative agent of fungal meningoencephalitis in immunocompromised individuals, remains largely uncharacterized. In this study, we identified and functionally characterized Mrs3/4, a homolog of the Saccharomyces cerevisiae mitochondrial iron transporter, in C. neoformans var. grubii. A strain expressing an Mrs3/4-GFP fusion protein was generated, and the mitochondrial localization of the fusion protein was confirmed. Moreover, a mutant lacking the MRS3/4 gene was constructed; this mutant displayed significantly reduced mitochondrial iron and cellular heme accumulation. In addition, impaired mitochondrial iron-sulfur cluster metabolism and altered expression of genes required for iron uptake at the plasma membrane were observed in the mrs3/4 mutant, suggesting that Mrs3/4 is involved in iron import and metabolism in the mitochondria of C. neoformans. Using a murine model of cryptococcosis, we demonstrated that an mrs3/4 mutant is defective in survival and virulence. Taken together, our study suggests that Mrs3/4 is responsible for iron import in mitochondria and reveals a link between mitochondrial iron metabolism and the virulence of C. neoformans.
Collapse
Affiliation(s)
- Yoojeong Choi
- Department of Systems Biotechnology, Chung-Ang University, Anseong 17546, Republic of Korea
| | - Eunsoo Do
- Department of Systems Biotechnology, Chung-Ang University, Anseong 17546, Republic of Korea
| | - Guanggan Hu
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver BC, V6T 1Z4, Canada
| | - Mélissa Caza
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver BC, V6T 1Z4, Canada
| | - Linda C Horianopoulos
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver BC, V6T 1Z4, Canada
| | - James W Kronstad
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver BC, V6T 1Z4, Canada
| | - Won Hee Jung
- Department of Systems Biotechnology, Chung-Ang University, Anseong, 17546, Republic of Korea
| |
Collapse
|
3
|
Connecting iron regulation and mitochondrial function in Cryptococcus neoformans. Curr Opin Microbiol 2019; 52:7-13. [PMID: 31085406 DOI: 10.1016/j.mib.2019.04.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 04/04/2019] [Accepted: 04/05/2019] [Indexed: 12/13/2022]
Abstract
Iron acquisition is essential for the proliferation of microorganisms, and human pathogens such as the fungus Cryptococcus neoformans must use sophisticated uptake mechanisms to overcome host iron sequestration. Iron is of particular interest for C. neoformans because its availability is an important cue for the elaboration of virulence factors. In fungi, extracellular iron is taken up through high affinity, low affinity, siderophore-mediated, and heme uptake pathways, and the details of these mechanisms are under active investigation in C. neoformans. Following uptake, iron is transported to intracellular organelles including mitochondria where it is used in heme biosynthesis and the synthesis of iron-sulfur (Fe-S) cluster precursors. One Fe-S cluster binding protein of note is the monothiol glutaredoxin Grx4 which has emerged as a master regulator of iron sensing in C. neoformans and other fungi through its influence on the expression of proteins for iron uptake or use. The activity of Grx4 likely occurs through interactions with Fe-S clusters and transcription factors known to control expression of the iron-related functions. Although the extent to which Grx4 controls the iron regulatory network is still being investigated in C. neoformans, it is remarkable that it also influences the expression of many genes encoding mitochondrial functions. Coupled with recent studies linking mitochondrial morphology and electron transport to virulence factor elaboration, there is an emerging appreciation of mitochondria as central players in cryptococcal disease.
Collapse
|
4
|
Gerwien F, Skrahina V, Kasper L, Hube B, Brunke S. Metals in fungal virulence. FEMS Microbiol Rev 2018; 42:4562650. [PMID: 29069482 PMCID: PMC5812535 DOI: 10.1093/femsre/fux050] [Citation(s) in RCA: 142] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 10/19/2017] [Indexed: 12/25/2022] Open
Abstract
Metals are essential for life, and they play a central role in the struggle between infecting microbes and their hosts. In fact, an important aspect of microbial pathogenesis is the 'nutritional immunity', in which metals are actively restricted (or, in an extended definition of the term, locally enriched) by the host to hinder microbial growth and virulence. Consequently, fungi have evolved often complex regulatory networks, uptake and detoxification systems for essential metals such as iron, zinc, copper, nickel and manganese. These systems often differ fundamentally from their bacterial counterparts, but even within the fungal pathogens we can find common and unique solutions to maintain metal homeostasis. Thus, we here compare the common and species-specific mechanisms used for different metals among different fungal species-focusing on important human pathogens such as Candida albicans, Aspergillus fumigatus or Cryptococcus neoformans, but also looking at model fungi such as Saccharomyces cerevisiae or A. nidulans as well-studied examples for the underlying principles. These direct comparisons of our current knowledge reveal that we have a good understanding how model fungal pathogens take up iron or zinc, but that much is still to learn about other metals and specific adaptations of individual species-not the least to exploit this knowledge for new antifungal strategies.
Collapse
Affiliation(s)
- Franziska Gerwien
- Department Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology– Hans Knoell Institute, 07745 Jena, Germany
| | - Volha Skrahina
- Department Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology– Hans Knoell Institute, 07745 Jena, Germany
| | - Lydia Kasper
- Department Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology– Hans Knoell Institute, 07745 Jena, Germany
| | - Bernhard Hube
- Department Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology– Hans Knoell Institute, 07745 Jena, Germany
| | - Sascha Brunke
- Department Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology– Hans Knoell Institute, 07745 Jena, Germany
| |
Collapse
|
5
|
Abstract
The devastating infections that fungal pathogens cause in humans are underappreciated relative to viral, bacterial and parasitic diseases. In recent years, the contributions to virulence of reductive iron uptake, siderophore-mediated uptake and heme acquisition have been identified in the best studied and most life-threatening fungal pathogens: Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus. In particular, exciting new work illustrates the importance of iron acquisition from heme and hemoglobin in the virulence of pathogenic yeasts. However, the challenge of establishing how these fungi gain access to hemoglobin in blood and to other sources of heme remains to be fully addressed. Recent studies are also expanding our knowledge of iron uptake in less-well studied fungal pathogens, including dimorphic fungi where new information reveals an integration of iron acquisition with morphogenesis and cell-surface properties for adhesion to host cells. Overall, the accumulating information provides opportunities to exploit iron acquisition for antifungal therapy, and new work highlights the development of specific inhibitors of siderophore biosynthesis and metal chelators for therapeutic use alone or in conjunction with existing antifungal drugs. It is clear that iron-related therapies will need to be customized for specific diseases because the emerging view is that fungal pathogens use different combinations of strategies for iron acquisition in the varied niches of vertebrate hosts.
Collapse
Affiliation(s)
- Gaurav Bairwa
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
| | - Won Hee Jung
- Department of Systems Biotechnology, Chung-Ang University, Anseong, 456-756, Republic of Korea
| | - James W Kronstad
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
| |
Collapse
|
6
|
Kim E, Kang M, Tschirhart T, Malo M, Dadachova E, Cao G, Yin JJ, Bentley WE, Wang Z, Payne GF. Spectroelectrochemical Reverse Engineering DemonstratesThat Melanin’s Redox and Radical Scavenging Activities Are Linked. Biomacromolecules 2017; 18:4084-4098. [DOI: 10.1021/acs.biomac.7b01166] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Eunkyoung Kim
- Institute
for Bioscience and Biotechnology Research, University of Maryland, 4291 Fieldhouse Drive, 5112 Plant Sciences Building, College Park, Maryland 20742, United States
- Fischell
Department of Bioengineering, University of Maryland, 8228 Paint
Branch Drive, 2330 Jeong H. Kim Engineering Building, College Park, Maryland 20742, United States
| | - Mijeong Kang
- Institute
for Bioscience and Biotechnology Research, University of Maryland, 4291 Fieldhouse Drive, 5112 Plant Sciences Building, College Park, Maryland 20742, United States
- Fischell
Department of Bioengineering, University of Maryland, 8228 Paint
Branch Drive, 2330 Jeong H. Kim Engineering Building, College Park, Maryland 20742, United States
| | - Tanya Tschirhart
- American
Society for Engineering Education, Postdoctoral Fellowship Program, U.S. Naval Research Laboratory, Washington, D.C. 20375, United States
| | - Mackenzie Malo
- College
of Pharmacy and Nutrition, University of Saskatchewan, Saskatchewan, Canada
| | - Ekaterina Dadachova
- College
of Pharmacy and Nutrition, University of Saskatchewan, Saskatchewan, Canada
| | - Gaojuan Cao
- Center for Food
Safety and Applied Nutrition, U.S. Food
and Drug Administration, College Park, Maryland 20740, United States
| | - Jun-Jie Yin
- Center for Food
Safety and Applied Nutrition, U.S. Food
and Drug Administration, College Park, Maryland 20740, United States
| | - William E. Bentley
- Institute
for Bioscience and Biotechnology Research, University of Maryland, 4291 Fieldhouse Drive, 5112 Plant Sciences Building, College Park, Maryland 20742, United States
- Fischell
Department of Bioengineering, University of Maryland, 8228 Paint
Branch Drive, 2330 Jeong H. Kim Engineering Building, College Park, Maryland 20742, United States
| | - Zheng Wang
- Center for
Bio/Molecular Science and Engineering, U.S. Naval Research Laboratory, Washington, DC 20375, United States
| | - Gregory F. Payne
- Institute
for Bioscience and Biotechnology Research, University of Maryland, 4291 Fieldhouse Drive, 5112 Plant Sciences Building, College Park, Maryland 20742, United States
- Fischell
Department of Bioengineering, University of Maryland, 8228 Paint
Branch Drive, 2330 Jeong H. Kim Engineering Building, College Park, Maryland 20742, United States
| |
Collapse
|
7
|
Nutritional Requirements and Their Importance for Virulence of Pathogenic Cryptococcus Species. Microorganisms 2017; 5:microorganisms5040065. [PMID: 28974017 PMCID: PMC5748574 DOI: 10.3390/microorganisms5040065] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 09/27/2017] [Accepted: 09/27/2017] [Indexed: 12/12/2022] Open
Abstract
Cryptococcus sp. are basidiomycete yeasts which can be found widely, free-living in the environment. Interactions with natural predators, such as amoebae in the soil, are thought to have promoted the development of adaptations enabling the organism to survive inside human macrophages. Infection with Cryptococcus in humans occurs following inhalation of desiccated yeast cells or spore particles and may result in fatal meningoencephalitis. Human disease is caused almost exclusively by the Cryptococcus neoformans species complex, which predominantly infects immunocompromised patients, and the Cryptococcus gattii species complex, which is capable of infecting immunocompetent individuals. The nutritional requirements of Cryptococcus are critical for its virulence in animals. Cryptococcus has evolved a broad range of nutrient acquisition strategies, many if not most of which also appear to contribute to its virulence, enabling infection of animal hosts. In this review, we summarise the current understanding of nutritional requirements and acquisition in Cryptococcus and offer perspectives to its evolution as a significant pathogen of humans.
Collapse
|
8
|
Gerwien F, Safyan A, Wisgott S, Brunke S, Kasper L, Hube B. The Fungal Pathogen Candida glabrata Does Not Depend on Surface Ferric Reductases for Iron Acquisition. Front Microbiol 2017. [PMID: 28642757 PMCID: PMC5463049 DOI: 10.3389/fmicb.2017.01055] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Iron acquisition is a crucial virulence determinant for many bacteria and fungi, including the opportunistic fungal pathogens Candida albicans and C. glabrata. While the diverse strategies used by C. albicans for obtaining iron from the host are well-described, much less is known about the acquisition of this micronutrient from host sources by C. glabrata – a distant relative of C. albicans with closer evolutionary ties to Saccharomyces cerevisiae, which nonetheless causes severe clinical symptoms in humans. Here we show that C. glabrata is much more restricted than C. albicans in using host iron sources, lacking, for example, the ability to grow on transferrin and hemin/hemoglobin. Instead, C. glabrata is able to use ferritin and non-protein-bound iron (FeCl3) as iron sources in a pH-dependent manner. As in other fungal pathogens, iron-dependent growth requires the reductive high affinity (HA) iron uptake system. Typically highly conserved, this uptake mechanism normally relies on initial ferric reduction by cell-surface ferric reductases. The C. glabrata genome contains only three such putative ferric reductases, which were found to be dispensable for iron-dependent growth. In addition and in contrast to C. albicans and S. cerevisiae, we also detected no surface ferric reductase activity in C. glabrata. Instead, extracellular ferric reduction was found in this and the two other fungal species, which was largely dependent on an excreted low-molecular weight, non-protein ferric reductant. We therefore propose an iron acquisition strategy of C. glabrata which differs from other pathogenic fungi, such as C. albicans, in that it depends on a limited set of host iron sources and that it lacks the need for surface ferric reductases. Extracellular ferric reduction by a secreted molecule possibly compensates for the loss of surface ferric reductase activity in the HA iron uptake system.
Collapse
Affiliation(s)
- Franziska Gerwien
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell InstituteJena, Germany
| | - Abu Safyan
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell InstituteJena, Germany
| | - Stephanie Wisgott
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell InstituteJena, Germany
| | - Sascha Brunke
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell InstituteJena, Germany
| | - Lydia Kasper
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell InstituteJena, Germany
| | - Bernhard Hube
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell InstituteJena, Germany.,Department of Microbial Pathogenicity Mechanisms, Friedrich Schiller UniversityJena, Germany.,Center for Sepsis Control and Care, University HospitalJena, Germany
| |
Collapse
|
9
|
Kröber A, Scherlach K, Hortschansky P, Shelest E, Staib P, Kniemeyer O, Brakhage AA. HapX Mediates Iron Homeostasis in the Pathogenic Dermatophyte Arthroderma benhamiae but Is Dispensable for Virulence. PLoS One 2016; 11:e0150701. [PMID: 26960149 PMCID: PMC4784894 DOI: 10.1371/journal.pone.0150701] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 02/18/2016] [Indexed: 12/14/2022] Open
Abstract
For many pathogenic fungi, siderophore-mediated iron acquisition is essential for virulence. The process of siderophore production and further mechanisms to adapt to iron limitation are strictly controlled in fungi to maintain iron homeostasis. Here we demonstrate that the human pathogenic dermatophyte Arthroderma benhamiae produces the hydroxamate siderophores ferricrocin and ferrichrome C. Additionally, we show that the iron regulator HapX is crucial for the adaptation to iron starvation and iron excess, but is dispensable for virulence of A. benhamiae. Deletion of hapX caused downregulation of siderophore biosynthesis genes leading to a decreased production of siderophores during iron starvation. Furthermore, HapX was required for transcriptional repression of genes involved in iron-dependent pathways during iron-depleted conditions. Additionally, the ΔhapX mutant of A. benhamiae was sensitive to high-iron concentrations indicating that HapX also contributes to iron detoxification. In contrast to other pathogenic fungi, HapX of A. benhamiae was redundant for virulence and a ΔhapX mutant was still able to infect keratinized host tissues in vitro. Our findings underline the highly conserved role of the transcription factor HapX for maintaining iron homeostasis in ascomycetous fungi but, unlike in many other human and plant pathogenic fungi, HapX of A. benhamiae is not a virulence determinant.
Collapse
Affiliation(s)
- Antje Kröber
- Junior Research Group Fundamental Molecular Biology of Pathogenic Fungi, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute (HKI), Jena, Germany
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Jena, Germany
| | - Kirstin Scherlach
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Jena, Germany
| | - Peter Hortschansky
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Jena, Germany
| | - Ekaterina Shelest
- Systems Biology and Bioinformatics, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Jena, Germany
| | - Peter Staib
- Junior Research Group Fundamental Molecular Biology of Pathogenic Fungi, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute (HKI), Jena, Germany
| | - Olaf Kniemeyer
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Jena, Germany
- Institute of Microbiology, Friedrich Schiller University, Jena, Germany
| | - Axel A. Brakhage
- Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Jena, Germany
- Institute of Microbiology, Friedrich Schiller University, Jena, Germany
- * E-mail:
| |
Collapse
|
10
|
de Paula DAJ, Rosa e Silva LK, Staats CC, Vainstein MH, Joanoni ALP, Nakazato L, Dutra V. Identification of genes expressed by Cryptococcus gattii during iron deprivation. Braz J Microbiol 2014; 45:813-20. [PMID: 25477912 PMCID: PMC4204963 DOI: 10.1590/s1517-83822014000300008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Accepted: 12/13/2013] [Indexed: 11/23/2022] Open
Abstract
Cryptococcus neoformans and C. gattii are pathogenic yeasts that cause life-threatening diseases in humans and animals. Iron is an essential nutrient for virtually every organism as it functions as a cofactor in numerous essential enzymatic reactions. In the literature, the competition for iron between microbes and mammalian hosts during infection is well documented. In this study, we used representational difference analysis (RDA) in order to gain a better understanding of how C. gattii responds to iron starvation. A total of 15 and 29 genes were identified as having altered expression levels due to iron depletion after 3 h and 12 h, respectively. Of these, eight genes were identified in both libraries. The transcripts were related to many biological processes, such as cell cycle, ergosterol metabolism, cell wall organization, transportation, translation, cell respiration and the stress response. These data suggest a remodeling of C. gattii metabolism during conditions of iron deprivation.
Collapse
Affiliation(s)
| | - Lívia Kmetzsch Rosa e Silva
- Centro de Biotecnologia Universidade Federal do Rio Grande do Sul Porto AlegreRS Brazil Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Charley Christian Staats
- Centro de Biotecnologia Universidade Federal do Rio Grande do Sul Porto AlegreRS Brazil Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Marilene H Vainstein
- Centro de Biotecnologia Universidade Federal do Rio Grande do Sul Porto AlegreRS Brazil Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Ana Lúcia Pinto Joanoni
- Universidade Federal de Mato Grosso CuiabáMT Brazil Universidade Federal de Mato Grosso, Cuiabá, MT, Brazil
| | - Luciano Nakazato
- Universidade Federal de Mato Grosso CuiabáMT Brazil Universidade Federal de Mato Grosso, Cuiabá, MT, Brazil
| | - Valéria Dutra
- Universidade Federal de Mato Grosso CuiabáMT Brazil Universidade Federal de Mato Grosso, Cuiabá, MT, Brazil
| |
Collapse
|
11
|
Abstract
Fungal pathogens must assimilate local nutrients to establish an infection in their mammalian host. We focus on carbon, nitrogen, and micronutrient assimilation mechanisms, discussing how these influence host-fungus interactions during infection. We highlight several emerging trends based on the available data. First, the perturbation of carbon, nitrogen, or micronutrient assimilation attenuates fungal pathogenicity. Second, the contrasting evolutionary pressures exerted on facultative versus obligatory pathogens have led to contemporary pathogenic fungal species that display differing degrees of metabolic flexibility. The evolutionarily ancient metabolic pathways are conserved in most fungal pathogen, but interesting gaps exist in some species (e.g., Candida glabrata). Third, metabolic flexibility is generally essential for fungal pathogenicity, and in particular, for the adaptation to contrasting host microenvironments such as the gastrointestinal tract, mucosal surfaces, bloodstream, and internal organs. Fourth, this metabolic flexibility relies on complex regulatory networks, some of which are conserved across lineages, whereas others have undergone significant evolutionary rewiring. Fifth, metabolic adaptation affects fungal susceptibility to antifungal drugs and also presents exciting opportunities for the development of novel therapies.
Collapse
Affiliation(s)
- Iuliana V Ene
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Sascha Brunke
- Department of Microbial Pathogenicity Mechanisms, Hans Knoell Institute, 07745 Jena, Germany
| | - Alistair J P Brown
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Bernhard Hube
- Department of Microbial Pathogenicity Mechanisms, Hans Knoell Institute, 07745 Jena, Germany Friedrich Schiller University, 07743 Jena, Germany Center for Sepsis Control and Care, Universitätsklinikum Jena, 07747 Jena, Germany
| |
Collapse
|
12
|
The vacuolar-sorting protein Snf7 is required for export of virulence determinants in members of the Cryptococcus neoformans complex. Sci Rep 2014; 4:6198. [PMID: 25178636 PMCID: PMC4151102 DOI: 10.1038/srep06198] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 08/04/2014] [Indexed: 02/06/2023] Open
Abstract
Fungal pathogenesis requires a number of extracellularly released virulence factors. Recent studies demonstrating that most fungal extracellular molecules lack secretory tags suggest that unconventional secretion mechanisms and fungal virulence are strictly connected. Proteins of the endosomal sorting complex required for transport (ESCRT) have been recently associated with polysaccharide export in the yeast-like human pathogen Cryptococcus neoformans. Snf7 is a key ESCRT operator required for unconventional secretion in Eukaryotes. In this study we generated snf7Δ mutant strains of C. neoformans and its sibling species C. gattii. Lack of Snf7 resulted in important alterations in polysaccharide secretion, capsular formation and pigmentation. This phenotype culminated with loss of virulence in an intranasal model of murine infection in both species. Our data support the notion that Snf7 expression regulates virulence in C. neoformans and C. gattii by ablating polysaccharide and melanin traffic. These results are in agreement with the observation that unconventional secretion is essential for cryptococcal pathogenesis and strongly suggest the occurrence of still obscure mechanisms of exportation of non-protein molecules in Eukaryotes.
Collapse
|
13
|
Jung WH, Do E. Iron acquisition in the human fungal pathogen Cryptococcus neoformans. Curr Opin Microbiol 2013; 16:686-91. [DOI: 10.1016/j.mib.2013.07.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2013] [Revised: 07/11/2013] [Accepted: 07/11/2013] [Indexed: 11/24/2022]
|
14
|
Caza M, Kronstad JW. Shared and distinct mechanisms of iron acquisition by bacterial and fungal pathogens of humans. Front Cell Infect Microbiol 2013; 3:80. [PMID: 24312900 PMCID: PMC3832793 DOI: 10.3389/fcimb.2013.00080] [Citation(s) in RCA: 178] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Accepted: 10/30/2013] [Indexed: 12/12/2022] Open
Abstract
Iron is the most abundant transition metal in the human body and its bioavailability is stringently controlled. In particular, iron is tightly bound to host proteins such as transferrin to maintain homeostasis, to limit potential damage caused by iron toxicity under physiological conditions and to restrict access by pathogens. Therefore, iron acquisition during infection of a human host is a challenge that must be surmounted by every successful pathogenic microorganism. Iron is essential for bacterial and fungal physiological processes such as DNA replication, transcription, metabolism, and energy generation via respiration. Hence, pathogenic bacteria and fungi have developed sophisticated strategies to gain access to iron from host sources. Indeed, siderophore production and transport, iron acquisition from heme and host iron-containing proteins such as hemoglobin and transferrin, and reduction of ferric to ferrous iron with subsequent transport are all strategies found in bacterial and fungal pathogens of humans. This review focuses on a comparison of these strategies between bacterial and fungal pathogens in the context of virulence and the iron limitation that occurs in the human body as a mechanism of innate nutritional defense.
Collapse
Affiliation(s)
| | - James W. Kronstad
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British ColumbiaVancouver, BC, Canada
| |
Collapse
|
15
|
Rabjohns JLA, Park YD, Dehdashti J, Henderson C, Zelazny A, Metallo SJ, Zheng W, Williamson PR. A high-throughput screening assay for fungicidal compounds against Cryptococcus neoformans. ACTA ACUST UNITED AC 2013; 19:270-277. [PMID: 23896686 DOI: 10.1177/1087057113496847] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Cryptococcus neoformans is a pathogenic fungus that causes meningitis worldwide, particularly in human immunodeficiency virus (HIV)-infected individuals. Although amphotericin B is the "gold standard" treatment for cryptococcal meningitis, the toxicity and inconvenience of intravenous injection emphasize a need for development of new anticryptocccal drugs. Recent data from humans and animal studies suggested that a nutrient-deprived host environment may exist in cryptococcal meningitis. Thus, a screening assay for identifying fungicidal compounds under nutrient-deprived conditions may provide an alternative strategy to develop new anticryptococcal drugs for this disease. A high-throughput fungicidal assay was developed using a profluorescent dye, alamarBlue, to detect residual metabolic activity of C. neoformans under nutrient-limiting conditions. Screening the Library of Pharmacologically Active Compounds (LOPAC) with this assay identified a potential chemical scaffold, 10058-F4, that exhibited fungicidal activity in the low micromolar range. These results thus demonstrate the feasibility of this alamarBlue-based assay for high-throughput screening of fungicidal compounds under nutrient-limiting conditions for new anticryptococcal drug development.
Collapse
Affiliation(s)
- Jennifer L A Rabjohns
- Laboratory of Clinical Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Yoon-Dong Park
- Laboratory of Clinical Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Jean Dehdashti
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD, USA
| | - Christina Henderson
- Department of Laboratory Medicine, Clinical Center, National Institutes of Health, Bethesda, MD USA
| | - Adrian Zelazny
- Department of Laboratory Medicine, Clinical Center, National Institutes of Health, Bethesda, MD USA
| | - Steven J Metallo
- Chemistry Department, Georgetown University, Washington D.C., USA
| | - Wei Zheng
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD, USA
| | - Peter R Williamson
- Laboratory of Clinical Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
- Section of Infectious Diseases, Department of Medicine, University of Illinois at Chicago, IL, USA
| |
Collapse
|
16
|
Kronstad JW, Hu G, Jung WH. An encapsulation of iron homeostasis and virulence in Cryptococcus neoformans. Trends Microbiol 2013; 21:457-65. [PMID: 23810126 DOI: 10.1016/j.tim.2013.05.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 05/24/2013] [Accepted: 05/29/2013] [Indexed: 02/07/2023]
Abstract
Vertebrate hosts actively sequester iron, and fungal and other pathogens must therefore adapt to a severe limitation in iron availability to cause disease. Recent studies reveal that the pathogenic fungus Cryptococcus neoformans overcomes iron limitation by multiple mechanisms that target transferrin and heme. The regulation of iron uptake is mediated by an interconnected set of transcription factors that include the master iron regulator Cir1 and the pH-responsive factor Rim101. These factors integrate iron homeostasis with a myriad of other functions including pH sensing, nutrient and stress signaling pathways, virulence factor elaboration, and cell wall biogenesis.
Collapse
Affiliation(s)
- James W Kronstad
- Department of Microbiology and Immunology, The Michael Smith Laboratories, University of British Columbia, Vancouver BC, V6T 1Z4, Canada.
| | | | | |
Collapse
|
17
|
Álvarez F, Fernández-Ruiz M, Aguado JM. [Iron and invasive fungal infection]. Rev Iberoam Micol 2013; 30:217-25. [PMID: 23684655 DOI: 10.1016/j.riam.2013.04.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 04/08/2013] [Accepted: 04/30/2013] [Indexed: 01/19/2023] Open
Abstract
Iron is an essential factor for both the growth and virulence of most of microorganisms. As a part of the innate (or nutritional) immune system, mammals have developed different mechanisms to store and transport this element in order to limit free iron bioavailability. To survive in this hostile environment, pathogenic fungi have specific uptake systems for host iron sources, one of the most important of which is based on the synthesis of siderophores-soluble, low-molecular-mass, high-affinity iron chelators. The increase in free iron that results from iron-overload conditions is a well-established risk factor for invasive fungal infection (IFI) such as mucormycosis or aspergillosis. Therefore, iron chelation may be an appealing therapeutic option for these infections. Nevertheless, deferoxamine -the first approved iron chelator- paradoxically increases the incidence of IFI, as it serves as a xeno-siderophore to Mucorales. On the contrary, the new oral iron chelators (deferiprone and deferasirox) have shown to exert a deleterious effect on fungal growth both in vitro and in animal models. The present review focuses on the role of iron metabolism in the pathogenesis of IFI and summarises the preclinical data, as well as the limited clinical experience so far, in the use of new iron chelators as treatment for mucormycosis and invasive aspergillosis.
Collapse
Affiliation(s)
- Florencio Álvarez
- Servicio de Medicina Interna, Hospital Universitario 12 de Octubre, Instituto de Investigación Hospital 12 de Octubre (i+12), Universidad Complutense, Madrid, España
| | | | | |
Collapse
|
18
|
Bailão EFLC, Parente AFA, Parente JA, Silva-Bailão MG, de Castro KP, Kmetzsch L, Staats CC, Schrank A, Vainstein MH, Borges CL, Bailão AM, de Almeida Soares CM. Metal Acquisition and Homeostasis in Fungi. CURRENT FUNGAL INFECTION REPORTS 2012. [DOI: 10.1007/s12281-012-0108-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
19
|
Adaptation of Cryptococcus neoformans to mammalian hosts: integrated regulation of metabolism and virulence. EUKARYOTIC CELL 2011; 11:109-18. [PMID: 22140231 DOI: 10.1128/ec.05273-11] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The basidiomycete fungus Cryptococcus neoformans infects humans via inhalation of desiccated yeast cells or spores from the environment. In the absence of effective immune containment, the initial pulmonary infection often spreads to the central nervous system to result in meningoencephalitis. The fungus must therefore make the transition from the environment to different mammalian niches that include the intracellular locale of phagocytic cells and extracellular sites in the lung, bloodstream, and central nervous system. Recent studies provide insights into mechanisms of adaptation during this transition that include the expression of antiphagocytic functions, the remodeling of central carbon metabolism, the expression of specific nutrient acquisition systems, and the response to hypoxia. Specific transcription factors regulate these functions as well as the expression of one or more of the major known virulence factors of C. neoformans. Therefore, virulence factor expression is to a large extent embedded in the regulation of a variety of functions needed for growth in mammalian hosts. In this regard, the complex integration of these processes is reminiscent of the master regulators of virulence in bacterial pathogens.
Collapse
|
20
|
Crestani J, Carvalho PC, Han X, Seixas A, Broetto L, Fischer JDSDG, Staats CC, Schrank A, Yates JR, Vainstein MH. Proteomic profiling of the influence of iron availability on Cryptococcus gattii. J Proteome Res 2011; 11:189-205. [PMID: 21970549 DOI: 10.1021/pr2005296] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Iron is essential and ubiquitous in living organisms. The competition for this micronutrient between the host and its pathogens has been related to disease establishment. Cryptococcus gattii is an encapsulated yeast that causes cryptococcosis mainly in immunocompetent individuals. In this study, we analyzed the proteomic profile of the C. gattii R265 Vancouver Island isolate under iron-depleted and -repleted conditions by multidimensional protein identification technology (MudPIT) and by 2D-GE. Proteins and key mechanisms affected by alteration of iron levels such as capsule production, cAMP-signaling pathway, response to stress, and metabolic pathways related to mitochondrial function were identified. Our results also show both proteomic methodologies employed to be complementary.
Collapse
Affiliation(s)
- Juliana Crestani
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9500, 43421, Caixa Postal 15005, Porto Alegre, RS 91501-970, Brazil
| | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Ziegler L, Terzulli A, Gaur R, McCarthy R, Kosman DJ. Functional characterization of the ferroxidase, permease high-affinity iron transport complex from Candida albicans. Mol Microbiol 2011; 81:473-85. [PMID: 21645130 DOI: 10.1111/j.1365-2958.2011.07704.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Saccharomyces cerevisiae expresses two proteins that together support high-affinity Fe-uptake. These are a multicopper oxidase, Fet3p, with specificity towards Fe²⁺ and a ferric iron permease, Ftr1p, which supports Fe-accumulation. Homologues of the genes encoding these two proteins are found in all fungal genomes including those for the pathogens, Candida albicans and Cryptococcus neoformans. At least one of these loci represents a virulence factor for each pathogen suggesting that this complex would be an appropriate pharmacologic target. However, the mechanism by which this protein pair supports Fe-uptake in any fungal pathogen has not been elucidated. Taking advantage of the robust molecular genetics available in S. cerevisiae, we identify the two of five candidate ferroxidases likely involved in high-affinity Fe-uptake in C. albicans, Fet31 and Fet34. Both localize to the yeast plasma membrane and both support Fe-uptake along with an Ftr1 protein, either from C. albicans or from S. cerevisiae. We express and characterize Fet34, demonstrating that it is functionally homologous to ScFet3p. Using S. cerevisiae as host for the functional expression of the C. albicans Fe-uptake proteins, we demonstrate that they support a mechanism of Fe-trafficking that involves channelling of the CaFet34-generated Fe³⁺ directly to CaFtr1 for transport into the cytoplasm.
Collapse
Affiliation(s)
- Lynn Ziegler
- Department of Biochemistry, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14214, USA
| | | | | | | | | |
Collapse
|
22
|
Silva MG, Schrank A, Bailão EFLC, Bailão AM, Borges CL, Staats CC, Parente JA, Pereira M, Salem-Izacc SM, Mendes-Giannini MJS, Oliveira RMZ, Silva LKRE, Nosanchuk JD, Vainstein MH, de Almeida Soares CM. The homeostasis of iron, copper, and zinc in paracoccidioides brasiliensis, cryptococcus neoformans var. Grubii, and cryptococcus gattii: a comparative analysis. Front Microbiol 2011; 2:49. [PMID: 21833306 PMCID: PMC3153025 DOI: 10.3389/fmicb.2011.00049] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Accepted: 03/03/2011] [Indexed: 01/01/2023] Open
Abstract
Iron, copper, and zinc are essential for all living organisms. Moreover, the homeostasis of these metals is vital to microorganisms during pathogenic interactions with a host. Most pathogens have developed specific mechanisms for the uptake of micronutrients from their hosts in order to counteract the low availability of essential ions in infected tissues. We report here an analysis of genes potentially involved in iron, copper, and zinc uptake and homeostasis in the fungal pathogens Paracoccidioides brasiliensis, Cryptococcus neoformans var. grubii, and Cryptococcus gattii. Although prior studies have identified certain aspects of metal regulation in Cryptococcus species, little is known regarding the regulation of these elements in P. brasiliensis. We also present amino acid sequences analyses of deduced proteins in order to examine possible conserved domains. The genomic data reveals, for the first time, genes associated to iron, copper, and zinc assimilation and homeostasis in P. brasiliensis. Furthermore, analyses of the three fungal species identified homologs to genes associated with high-affinity uptake systems, vacuolar and mitochondrial iron storage, copper uptake and reduction, and zinc assimilation. However, homologs to genes involved in siderophore production were only found in P. brasiliensis. Interestingly, in silico analysis of the genomes of P. brasiliensisPb01, Pb03, and Pb18 revealed significant differences in the presence and/or number of genes involved in metal homeostasis, such as in genes related to iron reduction and oxidation. The broad analyses of the genomes of P. brasiliensis, C. neoformans var. grubii, and C. gattii for genes involved in metal homeostasis provide important groundwork for numerous interesting future areas of investigation that are required in order to validate and explore the function of the identified genes and gene pathways.
Collapse
Affiliation(s)
- Mirelle Garcia Silva
- Laboratório de Biologia Molecular, Instituto de Ciências Biológicas, Universidade Federal de Goiás Goiânia, Goiás, Brazil
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Nevitt T. War-Fe-re: iron at the core of fungal virulence and host immunity. Biometals 2011; 24:547-58. [PMID: 21399939 DOI: 10.1007/s10534-011-9431-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Accepted: 02/22/2011] [Indexed: 12/21/2022]
Abstract
Iron acquisition is a bona fide virulence determinant. The successful colonization of the mammalian host requires that microorganisms overcome the Fe aridity of this milieu in which the levels of circulating Fe are maintained exceedingly low both through the compartmentalization of this nutrient within cells as well as the tight binding of Fe to host circulating proteins and ligands. Microbes notoriously employ multiple strategies for high affinity Fe acquisition from the host that rely either on the expression of receptors for host Fe-binding proteins and ligands, its reduction by cell surface reductases or the utilization of siderophores, small organic molecules with very high affinity for Fe(3+). This review will discuss the multiple mechanisms deployed by fungal pathogens in Fe acquisition focusing on the role of siderophore utilization in virulence as well as host immune strategies of iron withholding and emerging clinical evidence that human disorders of Fe homeostasis can act as modifiers of infectious disease.
Collapse
Affiliation(s)
- Tracy Nevitt
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, USA.
| |
Collapse
|
24
|
Abstract
Cryptococcus gattii recently emerged as the causative agent of cryptococcosis in healthy individuals in western North America, despite previous characterization of the fungus as a pathogen in tropical or subtropical regions. As a foundation to study the genetics of virulence in this pathogen, we sequenced the genomes of a strain (WM276) representing the predominant global molecular type (VGI) and a clinical strain (R265) of the major genotype (VGIIa) causing disease in North America. We compared these C. gattii genomes with each other and with the genomes of representative strains of the two varieties of Cryptococcus neoformans that generally cause disease in immunocompromised people. Our comparisons included chromosome alignments, analysis of gene content and gene family evolution, and comparative genome hybridization (CGH). These studies revealed that the genomes of the two representative C. gattii strains (genotypes VGI and VGIIa) are colinear for the majority of chromosomes, with some minor rearrangements. However, multiortholog phylogenetic analysis and an evaluation of gene/sequence conservation support the existence of speciation within the C. gattii complex. More extensive chromosome rearrangements were observed upon comparison of the C. gattii and the C. neoformans genomes. Finally, CGH revealed considerable variation in clinical and environmental isolates as well as changes in chromosome copy numbers in C. gattii isolates displaying fluconazole heteroresistance. Isolates of Cryptococcus gattii are currently causing an outbreak of cryptococcosis in western North America, and most of the cases occurred in the absence of coinfection with HIV. This pattern is therefore in stark contrast to the current global burden of one million annual cases of cryptococcosis, caused by the related species Cryptococcus neoformans, in the HIV/AIDS population. The genome sequences of two outbreak-associated major genotypes of C. gattii reported here provide insights into genome variation within and between cryptococcal species. These sequences also provide a resource to further evaluate the epidemiology of cryptococcal disease and to evaluate the role of pathogen genes in the differential interactions of C. gattii and C. neoformans with immunocompromised and immunocompetent hosts.
Collapse
|
25
|
Jung WH, Saikia S, Hu G, Wang J, Fung CKY, D'Souza C, White R, Kronstad JW. HapX positively and negatively regulates the transcriptional response to iron deprivation in Cryptococcus neoformans. PLoS Pathog 2010; 6:e1001209. [PMID: 21124817 PMCID: PMC2991262 DOI: 10.1371/journal.ppat.1001209] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Accepted: 10/25/2010] [Indexed: 11/23/2022] Open
Abstract
The fungal pathogen Cryptococcus neoformans is a major cause of illness in immunocompromised individuals such as AIDS patients. The ability of the fungus to acquire nutrients during proliferation in host tissue and the ability to elaborate a polysaccharide capsule are critical determinants of disease outcome. We previously showed that the GATA factor, Cir1, is a major regulator both of the iron uptake functions needed for growth in host tissue and the key virulence factors such as capsule, melanin and growth at 37°C. We are interested in further defining the mechanisms of iron acquisition from inorganic and host-derived iron sources with the goal of understanding the nutritional adaptation of C. neoformans to the host environment. In this study, we investigated the roles of the HAP3 and HAPX genes in iron utilization and virulence. As in other fungi, the C. neoformans Hap proteins negatively influence the expression of genes encoding respiratory and TCA cycle functions under low-iron conditions. However, we also found that HapX plays both positive and negative roles in the regulation of gene expression, including a positive regulatory role in siderophore transporter expression. In addition, HapX also positively regulated the expression of the CIR1 transcript. This situation is in contrast to the negative regulation by HapX of genes encoding GATA iron regulatory factors in Aspergillus nidulans and Schizosaccharomyces pombe. Although both hapX and hap3 mutants were defective in heme utilization in culture, only HapX made a contribution to virulence, and loss of HapX in a strain lacking the high-affinity iron uptake system did not cause further attenuation of disease. Therefore, HapX appears to have a minimal role during infection of mammalian hosts and instead may be an important regulator of environmental iron uptake functions. Overall, these results indicated that C. neoformans employs multiple strategies for iron acquisition during infection. Cryptococcus neoformans causes life-threatening central nervous system infections in immunocompromised people such as AIDS patients. The competition for iron between pathogens such as C. neoformans and mammalian hosts is a key aspect of disease outcome. We previously identified and characterized the major iron regulatory protein Cir1 in C. neoformans, as well as proteins for the transport of iron-binding molecules (siderophores) and for high-affinity iron uptake. In this study, we examined the roles of additional regulatory proteins (Hap proteins) in the response to low-iron conditions and the use of host iron sources such as heme and transferrin. We discovered that the HapX protein has a conserved regulatory function to repress iron-dependent functions during iron deprivation, as well as a positive regulatory role for the expression of putative siderophore transporters. A hapX mutant was defective in the use of heme as an iron source in culture but was only modestly attenuated for virulence in mice. This result suggests that additional mechanisms for iron uptake must be available to support C. neoformans proliferation in the host, and that HapX may play an important role in environmental iron acquisition.
Collapse
Affiliation(s)
- Won Hee Jung
- Department of Biotechnology, Chung-Ang University, Daedeok-Myeon, Anseong-Si, Gyeonggi-Do, Republic of Korea
| | - Sanjay Saikia
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Guanggan Hu
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Joyce Wang
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Carlen Ka-Yin Fung
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Cletus D'Souza
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Rick White
- Department of Statistics, University of British Columbia, Vancouver, British Columbia, Canada
| | - James W. Kronstad
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
| |
Collapse
|
26
|
Kim M, Song E. Iron transport by proteoliposomes containing mitochondrial F(1)F(0) ATP synthase isolated from rat heart. Biochimie 2010; 92:333-42. [PMID: 20100539 DOI: 10.1016/j.biochi.2010.01.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Accepted: 01/17/2010] [Indexed: 01/18/2023]
Abstract
In this work, we present evidence of Fe(2+) transport by rat heart mitochondrial F(1)F(0) ATP synthase. Iron uptake by the vesicles containing the enzyme was concentration- and temperature-dependent, with an optimum temperature of 37 degrees C. Both ATP and ADP stimulated iron uptake in a concentration-dependent manner, whereas AMP, AMPPCP, and mADP did not. Inhibitors of the enzyme, oligomycin, and resveratrol similarly blocked iron transport. The iron uptake was confirmed by inhibition using specific antibodies against the alpha, beta, and c subunits of the enzyme. Interestingly, slight transport of common divalent and trivalent metal ions such as Mg(+2), Ca(+2), Mn(+2), Zn(+2), Cu(+2), Fe(+3), and Al(+3) was observed. Moreover, Cu(+2), even in the nM range, inhibited iron uptake and attained maximum inhibition of approximately 56%. Inorganic phosphate (Pi) in the medium exerted an opposite effect depending on the type of adenosine nucleotide, which was suppressed with ATP, but enhanced with ADP. A similarly stimulating effect of ATP and ADP with an inverse effect of Pi suggests that the activity of ATPase and ATP synthase may be associated with iron uptake in a different manner, probably via antiport of H(+).
Collapse
Affiliation(s)
- Misun Kim
- Department of Biological Science, College of Natural Sciences, Sookmyung Women's University, Seoul, Republic of Korea
| | | |
Collapse
|
27
|
Jung WH, Sham A, Lian T, Singh A, Kosman DJ, Kronstad JW. Iron source preference and regulation of iron uptake in Cryptococcus neoformans. PLoS Pathog 2008; 4:e45. [PMID: 18282105 PMCID: PMC2242830 DOI: 10.1371/journal.ppat.0040045] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2007] [Accepted: 01/07/2008] [Indexed: 01/09/2023] Open
Abstract
The level of available iron in the mammalian host is extremely low, and pathogenic microbes must compete with host proteins such as transferrin for iron. Iron regulation of gene expression, including genes encoding iron uptake functions and virulence factors, is critical for the pathogenesis of the fungus Cryptococcus neoformans. In this study, we characterized the roles of the CFT1 and CFT2 genes that encode C. neoformans orthologs of the Saccharomyces cerevisiae high-affinity iron permease FTR1. Deletion of CFT1 reduced growth and iron uptake with ferric chloride and holo-transferrin as the in vitro iron sources, and the cft1 mutant was attenuated for virulence in a mouse model of infection. A reduction in the fungal burden in the brains of mice infected with the cft1 mutant was observed, thus suggesting a requirement for reductive iron acquisition during cryptococcal meningitis. CFT2 played no apparent role in iron acquisition but did influence virulence. The expression of both CFT1 and CFT2 was influenced by cAMP-dependent protein kinase, and the iron-regulatory transcription factor Cir1 positively regulated CFT1 and negatively regulated CFT2. Overall, these results indicate that C. neoformans utilizes iron sources within the host (e.g., holo-transferrin) that require Cft1 and a reductive iron uptake system. Opportunistic fungal pathogens and other invading microbes must overcome extreme iron limitation to proliferate in the mammalian host. It is not yet known which iron sources are preferred by fungal pathogens of mammals, although the mechanisms of acquisition are beginning to be explored. Some fungi produce iron-chelating siderophores to capture iron from host proteins, while others appear to require a membrane-bound iron permease–ferroxidase system. We describe the ability of the encapsulated yeast Cryptococcus neoformans to use host iron sources including transferrin and heme, and we identify an iron permease that is required for full disease progression in experimental mouse models. The permease is required for iron utilization from transferrin but not heme during growth in laboratory culture. This result when combined with the observed slow growth of the permease mutant during the experimental infections implicates transferrin as an important iron source in the host. However, we find that mutants lacking the permease eventually do cause disease, thus revealing that additional iron sources such as heme and other uptake mechanisms are available to C. neoformans. Finally, we noted that the permease mutant showed particularly poor growth in the brains of infected animals, suggesting that transferrin may be an especially important iron source in this tissue.
Collapse
Affiliation(s)
- Won Hee Jung
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Anita Sham
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Tianshun Lian
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Arvinder Singh
- Department of Biochemistry, School of Medicine and Biomedical Sciences, The University at Buffalo, Buffalo, New York, United States of America
| | - Daniel J Kosman
- Department of Biochemistry, School of Medicine and Biomedical Sciences, The University at Buffalo, Buffalo, New York, United States of America
| | - James W Kronstad
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
- * To whom correspondence should be addressed. E-mail:
| |
Collapse
|
28
|
Jung WH, Kronstad JW. Iron and fungal pathogenesis: a case study with Cryptococcus neoformans. Cell Microbiol 2007; 10:277-84. [PMID: 18042257 DOI: 10.1111/j.1462-5822.2007.01077.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The acquisition of iron from mammalian hosts is an important aspect of infection because microbes must compete with the host for this nutrient and iron perception often regulates virulence factor expression. For example, iron levels are known to influence the elaboration of two major virulence factors, the polysaccharide capsule and melanin, in the pathogenic fungus Cryptococcus neoformans. This pathogen, which causes meningoencephalitis in immunocompromised people, acquires iron through the use of secreted reductants, cell surface reductases, a permease/ferroxidase uptake system and siderophore transporters. In addition, a master regulator, Cir1, integrates iron sensing with the expression of virulence factors, with growth at 37 degrees C and with signalling pathways that also influence virulence. The challenge ahead is to develop mechanistic views of the iron acquisition functions and regulatory schemes that operate when C. neoformans is in host tissue. Achieving these goals may contribute to an understanding of the notable predilection of the fungus for the mammalian central nervous system.
Collapse
Affiliation(s)
- Won Hee Jung
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | | |
Collapse
|
29
|
Jung WH, Sham A, White R, Kronstad JW. Iron regulation of the major virulence factors in the AIDS-associated pathogen Cryptococcus neoformans. PLoS Biol 2007; 4:e410. [PMID: 17121456 PMCID: PMC1637126 DOI: 10.1371/journal.pbio.0040410] [Citation(s) in RCA: 176] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Accepted: 09/22/2006] [Indexed: 11/18/2022] Open
Abstract
Iron overload is known to exacerbate many infectious diseases, and conversely, iron withholding is an important defense strategy for mammalian hosts. Iron is a critical cue for Cryptococcus neoformans because the fungus senses iron to regulate elaboration of the polysaccharide capsule that is the major virulence factor during infection. Excess iron exacerbates experimental cryptococcosis and the prevalence of this disease in Sub-Saharan Africa has been associated with nutritional and genetic aspects of iron loading in the background of the HIV/AIDS epidemic. We demonstrate that the iron-responsive transcription factor Cir1 in Cr. neoformans controls the regulon of genes for iron acquisition such that cir1 mutants are "blind" to changes in external iron levels. Cir1 also controls the known major virulence factors of the pathogen including the capsule, the formation of the anti-oxidant melanin in the cell wall, and the ability to grow at host body temperature. Thus, the fungus is remarkably tuned to perceive iron as part of the disease process, as confirmed by the avirulence of the cir1 mutant; this characteristic of the pathogen may provide opportunities for antifungal treatment.
Collapse
Affiliation(s)
- Won Hee Jung
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Anita Sham
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Rick White
- Department of Statistics, University of British Columbia, Vancouver, British Columbia, Canada
| | - James W Kronstad
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
- * To whom correspondence should be addressed. E-mail:
| |
Collapse
|
30
|
Tangen KL, Jung WH, Sham AP, Lian T, Kronstad JW. The iron- and cAMP-regulated gene SIT1 influences ferrioxamine B utilization, melanization and cell wall structure in Cryptococcus neoformans. MICROBIOLOGY-SGM 2007; 153:29-41. [PMID: 17185532 DOI: 10.1099/mic.0.2006/000927-0] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The mechanisms by which pathogens sense and transport iron are important during infection, because of the low availability of free iron in the mammalian host. Iron is a key nutritional cue for the pathogen Cryptococcus neoformans, because it influences expression of the polysaccharide capsule that is the major virulence factor of the fungus. In this study, C. neoformans mutants were constructed with a defect in the iron-regulated gene SIT1 that encodes a putative siderophore iron transporter. Analysis of mutants in serotype A and D strains demonstrated that SIT1 is required for the use of siderophore-bound iron, and for growth in a low-iron environment. The sit1 mutants also showed changes in melanin formation and cell wall density, and it was found that mutants defective in protein kinase A, which is known to influence melanization and capsule formation, showed elevated SIT1 transcripts in both the serotype A and the serotype D backgrounds. Finally, the mutants were tested for virulence in a murine model of cryptococcosis, and it was found that SIT1 was not required for virulence. Overall, these studies establish links between iron acquisition, melanin formation and cAMP signalling in C. neoformans.
Collapse
Affiliation(s)
- Kristin L Tangen
- Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver BC V6T 1Z4, Canada
| | | | | | | | | |
Collapse
|
31
|
Hissen AHT, Wan ANC, Warwas ML, Pinto LJ, Moore MM. The Aspergillus fumigatus siderophore biosynthetic gene sidA, encoding L-ornithine N5-oxygenase, is required for virulence. Infect Immun 2005; 73:5493-503. [PMID: 16113265 PMCID: PMC1231119 DOI: 10.1128/iai.73.9.5493-5503.2005] [Citation(s) in RCA: 196] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Aspergillus fumigatus is the leading cause of invasive mold infection and is a serious problem in immunocompromised populations worldwide. We have previously shown that survival of A. fumigatus in serum may be related to secretion of siderophores. In this study, we identified and characterized the sidA gene of A. fumigatus, which encodes l-ornithine N(5)-oxygenase, the first committed step in hydroxamate siderophore biosynthesis. A. fumigatus sidA codes for a protein of 501 amino acids with significant homology to other fungal l-ornithine N(5)-oxygenases. A stable DeltasidA strain was created by deletion of A. fumigatus sidA. This strain was unable to synthesize the siderophores N',N",N'''-triacetylfusarinine C (TAF) and ferricrocin. Growth of the DeltasidA strain was the same as that of the wild type in rich media; however, the DeltasidA strain was unable to grow in low-iron defined media or media containing 10% human serum unless supplemented with TAF or ferricrocin. No significant differences in ferric reduction activities were observed between the parental strain and the DeltasidA strain, indicating that blocking siderophore secretion did not result in upregulation of this pathway. Unlike the parental strain, the DeltasidA strain was unable to remove iron from human transferrin. A rescued strain (DeltasidA + sidA) was constructed; it produced siderophores and had the same growth as the wild type on iron-limited media. Unlike the wild-type and rescued strains, the DeltasidA strain was avirulent in a mouse model of invasive aspergillosis, indicating that sidA is necessary for A. fumigatus virulence.
Collapse
Affiliation(s)
- Anna H T Hissen
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada.
| | | | | | | | | |
Collapse
|
32
|
Lian T, Simmer MI, D'Souza CA, Steen BR, Zuyderduyn SD, Jones SJM, Marra MA, Kronstad JW. Iron-regulated transcription and capsule formation in the fungal pathogen Cryptococcus neoformans. Mol Microbiol 2005; 55:1452-72. [PMID: 15720553 DOI: 10.1111/j.1365-2958.2004.04474.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cryptococcus neoformans is the leading cause of fungal meningitis in humans. Production of a polysaccharide capsule is a key virulence property for the fungus and capsule synthesis is regulated by iron levels. Given that iron acquisition is an important aspect of virulence for many pathogens, we employed serial analysis of gene expression (SAGE) to examine the transcriptome under iron-limiting and iron-replete conditions. Initially, we demonstrated by SAGE and Northern analysis that iron limitation results in an elevated transcript level for the CAP60 gene that is required for capsule production. We also identified genes encoding putative components for iron transport and homeostasis, including the FTR1 (iron permease) gene, with higher transcript levels in the low-iron condition. An FTR1 disruption mutant grows more slowly than wild-type cells in low-iron medium, and shows delayed growth and altered capsule regulation in iron-replete medium. Iron deprivation also resulted in elevated SAGE tags for putative extracellular mannoproteins and the GPI8 gene encoding a glycosylphosphatidylinositol (GPI) transamidase. The GPI8 gene appears to be essential while disruption of the CIG1 gene encoding a mannoprotein resulted in impaired growth in low-iron medium and altered capsule response to the iron-replete condition. Additionally, we found that iron-replete conditions led to elevated transcripts for genes for iron storage, nitrogen metabolism, glycolysis, mitochondrial function, lipid metabolism and calmodulin-calcineurin signalling. Overall, these studies provide the first view of the C. neoformans transcriptional response to different iron levels.
Collapse
Affiliation(s)
- Tianshun Lian
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Agricultural Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | | | | | | | | | | | | | | |
Collapse
|
33
|
Jacobson ES, Troy AJ, Nyhus KJ. Mitochondrial functioning of constitutive iron uptake mutations in Cryptococcus neoformans. Mycopathologia 2005; 159:1-6. [PMID: 15750726 DOI: 10.1007/s11046-004-2223-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2004] [Accepted: 06/08/2004] [Indexed: 10/25/2022]
Abstract
Randomly obtained, constitutive plasma membrane ferric reductase/ferrous uptake mutants of Cryptococcus neoformans were mapped to four distinct loci by meiotic analysis. One of those loci, FRR1 , was previously found homologous to MRS3 and MRS4 of Saccharomyces cerevisiae , which determine proteins involved in mitochondrial transport of iron. We were able to complement, clone, sequence and thereby identify two of the three remaining constitutive uptake loci. FRR3 was found to be homologous to ISU1 and ISU2 of S. cerevisiae, which form mitochondrial iron-sulfur complexes; FRR4 was found to be homologous to YFH1, the yeast frataxin homologue, which also participates in iron-sulfur cluster biogenesis. Because of the constitutive iron uptake seen in these mutants, mitochondria appear to have a central role in the cellular iron economy; moreover, as judged by our mutational statistics, the genetic machinery for mitochondrial iron accumulation may be more complex than that of the cytoplasm.
Collapse
Affiliation(s)
- Eric S Jacobson
- Research Service, McGuire Veterans Affairs Medical Center, 1201 Broad Rock Blvd, Richmond, VA 23249, USA.
| | | | | |
Collapse
|
34
|
Giles SS, Czuprynski CJ. Extracellular calcium and magnesium, but not iron, are needed for optimal growth of Blastomyces dermatitidis yeast form cells in vitro. CLINICAL AND DIAGNOSTIC LABORATORY IMMUNOLOGY 2004; 11:426-9. [PMID: 15013999 PMCID: PMC371193 DOI: 10.1128/cdli.11.2.426-429.2004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the present study, we demonstrate that the yeast form of Blastomyces dermatitidis can proliferate for short periods of time in the absence of ferric iron but not in the absence of calcium or magnesium. The results of this study shed light on the resistance of B. dermatitidis to chelating agents, such as deferoxamine, and may explain how B. dermatitidis resists the iron-binding activity of serum transferrin.
Collapse
Affiliation(s)
- Steven S Giles
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | | |
Collapse
|
35
|
Tenney AE, Brown RH, Vaske C, Lodge JK, Doering TL, Brent MR. Gene prediction and verification in a compact genome with numerous small introns. Genome Res 2004; 14:2330-5. [PMID: 15479946 PMCID: PMC525692 DOI: 10.1101/gr.2816704] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The genomes of clusters of related eukaryotes are now being sequenced at an increasing rate, creating a need for accurate, low-cost annotation of exon-intron structures. In this paper, we demonstrate that reverse transcription-polymerase chain reaction (RT-PCR) and direct sequencing based on predicted gene structures satisfy this need, at least for single-celled eukaryotes. The TWINSCAN gene prediction algorithm was adapted for the fungal pathogen Cryptococcus neoformans by using a precise model of intron lengths in combination with ungapped alignments between the genome sequences of the two closely related Cryptococcus varieties. This approach resulted in approximately 60% of known genes being predicted exactly right at every coding base and splice site. When previously unannotated TWINSCAN predictions were tested by RT-PCR and direct sequencing, 75% of targets spanning two predicted introns were amplified and produced high-quality sequence. When targets spanning the complete predicted open reading frame were tested, 72% of them amplified and produced high-quality sequence. We conclude that sequencing a small number of expressed sequence tags (ESTs) to provide training data, running TWINSCAN on an entire genome, and then performing RT-PCR and direct sequencing on all of its predictions would be a cost-effective method for obtaining an experimentally verified genome annotation.
Collapse
Affiliation(s)
- Aaron E Tenney
- Laboratory for Computational Genomics and Department of Computer Science, Washington University, St. Louis, Missouri 63130, USA
| | | | | | | | | | | |
Collapse
|
36
|
Abstract
Iron is a metal required by most microorganisms and is prominently used in the transfer of electrons during metabolism. The gathering of iron is, then, an essential process and its fulfillment becomes a crucial pathogenetic event for zoopathogenic fungi. Iron is rather unavailable because it occurs on the earth's surface in its insoluble ferric form in oxides and hydroxides. In the infected host iron is bound to proteins such as transferrin and ferritin. Solubilization of ferric iron is the major problem confronting microorganisms. This process is achieved by two major mechanisms: ferric reduction and siderophore utilization. Ferric reductase is frequently accompanied by a copper oxidase transport system. There is one example of direct ferric iron transport apparently without prior reduction. Ferric reduction may also be accomplished by low molecular mass compounds. Some fungi have evolved a process of iron acquisition involving the synthesis of iron-gathering compounds called siderophores. Even those fungi that do not synthesize siderophores have developed permeases for transport of such compounds formed by other organisms. Fungi can also reductively release iron from siderophores and transport the ferrous iron often by the copper oxidase transport system. There is a great diversity of iron-gathering mechanisms expressed by pathogenic fungi and such diversity may be found even in a single species.
Collapse
Affiliation(s)
- Dexter H Howard
- Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
| |
Collapse
|
37
|
Hissen AHT, Chow JMT, Pinto LJ, Moore MM. Survival of Aspergillus fumigatus in serum involves removal of iron from transferrin: the role of siderophores. Infect Immun 2004; 72:1402-8. [PMID: 14977945 PMCID: PMC356059 DOI: 10.1128/iai.72.3.1402-1408.2004] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Aspergillus fumigatus is a filamentous fungus which can cause invasive disease in immunocompromised individuals. A. fumigatus can grow in medium containing up to 80% human serum, despite very low concentrations of free iron. The purpose of this study was to determine the mechanism by which A. fumigatus obtains iron from the serum iron-binding protein transferrin. In iron-depleted minimal essential medium (MEM), A. fumigatus growth was supported by the addition of holotransferrin (holoTf) or FeCl(3) but not by the addition of apotransferrin (apoTf). Proteolytic degradation of transferrin by A. fumigatus occurred in MEM-serum; however, transferrin degradation did not occur until late logarithmic phase. Moreover, transferrin was not degraded by A. fumigatus incubated in MEM-holoTf. Urea polyacrylamide gel electrophoresis showed that in MEM-holoTf, holoTf was completely converted to apoTf by A. fumigatus. In human serum, all of the monoferric transferrin was converted to apoTf within 8 h. Siderophores were secreted by A. fumigatus after 8 h of growth in MEM-serum and 12 h in MEM-holoTf. The involvement of small molecules in iron acquisition was confirmed by the fact that transferrin was deferrated by A. fumigatus even when physically separated by a 12-kDa-cutoff membrane. Five siderophores were purified from A. fumigatus culture medium, and the two major siderophores were identified as triacetylfusarinine C and ferricrocin. Both triacetylfusarinine C and ferricrocin removed iron from holoTf with an affinity comparable to that of ferrichrome. These data indicate that A. fumigatus survival in human serum in vitro involves siderophore-mediated removal of iron from transferrin. Proteolytic degradation of transferrin may play a secondary role in iron acquisition.
Collapse
Affiliation(s)
- A H T Hissen
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | | | | | | |
Collapse
|
38
|
Nyhus K, Jacobson ES. Oxy2as a transcriptional activator gene for copper uptake inCryptococcus neoformans. Med Mycol 2004; 42:325-31. [PMID: 15473357 DOI: 10.1080/13693780310001658757] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Cryptococcus neoformans is subject to oxidative attack by host immune cells; consequently, oxidant-resistant mechanisms may be important in pathogenesis. Mutations at the OXY2 locus confer decreased laccase and increased sensitivity to hyperbaric oxygen in the background of the oxyl mutation, but, alone, do not confer sensitivity to oxidants. Because metal deficiency can potentiate or ameliorate sensitivity to oxidants, and because the melanin-synthesizing laccase contains copper, we investigated copper acquisition in an oxy2 mutant. We found that its external Cu/Fe reductase activity was lower than that of wild type, and although copper deprivation induced the reductase in the wild type, it did not do so in oxy2. Oxy2 is sensitive to copper chelation but resistant to high copper, suggesting that copper transport is decreased. The strain expresses large amounts of alternate oxidase in response to Cu-chelation, perhaps in response to defective, Cu-deprived cytochrome oxidase, and is resistant to the oxidant, plumbagin, under this condition, perhaps due to the high alternate oxidase. These phenotypes are similar to those of the mac1- mutant of Saccharomyces cerevisiae and the melanin-deficient grisea mutant of Podospora anserina, in which homologous transcriptional activators for the reductase and copper transporter genes are mutated. They constitute physiologic evidence that oxy2 is mutated in a homologous copper-related transcriptional activator of C. neoformans.
Collapse
Affiliation(s)
- Karin Nyhus
- McGuire VA Medical Center Richmond, VA 23249, USA
| | | |
Collapse
|
39
|
Jacobson ES, Milhausen SM, Manthey MK. 3-Hydroxyanthranilate in Cryptococcus neoformans: a secreted reductant that does not enable wood rot. Med Mycol 2003; 41:309-20. [PMID: 12964724 DOI: 10.1080/13693780310001600831] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Cryptococcus neoformans secretes 3-hydroxyanthranilate (3HAA), but the utility is unknown. Exogenous 3HAA promoted growth of cultures starved for iron with transferrin, presumably by releasing Fe(III) reductively. Exogenous 3HAA protected C. neoformans from strong oxidants, suggesting a role in resistance to killing by immune cells. 3HAA represents an endogenous laccase substrate, in that crude laccase preparations convert 3HAA to cinnabarinic acid, whereas 3HAA concentrations are higher in Lac- mutants. We isolated hypersecreting mutants as highly fluorescent clones. Because C. neoformans has been isolated from rotting wood, we looked for a role in degradation of lignin. Using cyclic voltammetry, we found no electrochemical evidence that organic oxidation products of 3HAA are capable of oxidizing lignin. We found neither cellulose dehydrogenase nor lignin peroxidase enzymic activity, nor did C. neoformans grow on cellulose as carbon source. We found no evidence for production of Fenton reagent by cultures, even in the presence of transition metal ions or of those and 3HAA. The biological utility of 3HAA may be related to its functions as reducing agent and, conceivably, as laccase substrate. It does not appear to attack wood, nor does C. neoformans appear to have a mechanism to rot wood.
Collapse
Affiliation(s)
- E S Jacobson
- Research Service, McGuire Veterans Affairs Medical Center, Richmond, VA 23249, USA.
| | | | | |
Collapse
|
40
|
Nyhus KJ, Ozaki LS, Jacobson ES. Role of mitochondrial carrier protein Mrs3/4 in iron acquisition and oxidative stress resistance of Cryptococcus neoformans. Med Mycol 2002; 40:581-91. [PMID: 12521122 DOI: 10.1080/mmy.40.6.581.591] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Cryptococcus neoformans is a pathogenic basidiomycete that causes meningitis in immunocompromised patients. In this paper, we demonstrate that a previously described oxidant-sensitive mutant, oxy1, has constitutive ferric reductase and iron uptake, similar to a ferric reductase regulatory mutant, frr1. Through meiotic genetic analysis, we show that the two mutations are allelic. By complementation of frr1 with a genomic library, we isolated a gene, MRS3/4. The encoded protein is a putative solute transporter of the inner mitochondrial membrane. Disruption of this gene led to high ferric reductase, iron uptake and iron content, as well as increased sensitivity to hydrogen peroxide and slow growth in low iron medium. The disrupted gene is allelic with oxy1 and frr1. We sequenced the oxy1 and frr1 alleles of MRS3/4 and found that the frr1 mutation results in a premature stop codon, while the oxy1 mutation results in the substitution of a highly conserved glutamate residue with lysine. The Mrs3/4 protein appears to be involved in mitochondrial iron transport in eukaryotes. Resistance to strong oxidants requires stringent control of iron metabolism.
Collapse
Affiliation(s)
- Karin J Nyhus
- Research Service, McGuire Veterans Affairs Medical Center, 1201 Broad Rock Blvd, Richmond, Virginia 23249, USA
| | | | | |
Collapse
|
41
|
Wilson ME, Lewis TS, Miller MA, McCormick ML, Britigan BE. Leishmania chagasi: uptake of iron bound to lactoferrin or transferrin requires an iron reductase. Exp Parasitol 2002; 100:196-207. [PMID: 12173405 DOI: 10.1016/s0014-4894(02)00018-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Leishmania chagasi can utilize iron bound to transferrin, lactoferrin, or other chelates. We investigated the mechanism of iron uptake. Promastigotes preferentially took up iron in a reduced rather than an oxidized form, suggesting that extracellular iron must be reduced prior to internalization. Similar to literature reports, a 70-kDa protein in promastigote membrane-containing microsomes bound to [125I]-labeled transferrin. However, [125I]lactoferrin and [125I]albumin also bound a similar 70-kDa protein, suggesting that binding might not be specific. Both total and fractionated promastigotes exhibited an NADPH-dependent iron reductase activity. In contrast to trypanosomes, which take up transferrin through a specific receptor, these data support a model in which a parasite-associated or secreted reductase reduces ferric to ferrous iron, decreasing its affinity for the extracellular chelate and allowing it to be readily internalized by the parasite. This could account for the ability of the parasite to utilize iron from multiple sources in diverse host environments. Index Descriptors and Abbreviations. Index descriptors: Cryptococcus neoformans, Histoplasma capsulatum, iron, iron reductase, lactoferrin, L. chagasi, leishmaniasis, nutrient acquisition, protozoan, Saccharomyces cerevisiae, Trypanosoma brucei, Trypanosoma cruzi, transferrin; Abbreviations used: DNA, deoxyribonucleic acid; DTT, dithiothreitol; HBSS, Hanks' balanced salt solution; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; NEM, N-ethylmaleimide; RNA, ribonucleic acid.
Collapse
Affiliation(s)
- Mary E Wilson
- Veterans' Affairs Medical Center, University of Iowa, Iowa City, IA 52242, USA.
| | | | | | | | | |
Collapse
|
42
|
Timmerman MM, Woods JP. Potential role for extracellular glutathione-dependent ferric reductase in utilization of environmental and host ferric compounds by Histoplasma capsulatum. Infect Immun 2001; 69:7671-8. [PMID: 11705947 PMCID: PMC98861 DOI: 10.1128/iai.69.12.7671-7678.2001] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mammalian host specifically limits iron during Histoplasma capsulatum infection, and fungal acquisition of iron is essential for productive infection. H. capsulatum expresses several iron acquisition mechanisms under iron-limited conditions in vitro. These components include hydroxamate siderophores, extracellular glutathione-dependent ferric reductase enzyme, extracellular nonproteinaceous ferric reductant(s), and cell surface ferric reducing agent(s). We examined the relationship between these mechanisms and a potential role for the extracellular ferric reductase in utilization of environmental and host ferric compounds through the production of free, soluble Fe(II). Siderophores and ferric reducing agents were coproduced under conditions of iron limitation. The H. capsulatum siderophore dimerum acid and the structurally similar basidiomycete siderophore rhodotorulic acid acted as substrates for the ferric reductase, and rhodotorulic acid removed Fe(III) bound by transferrin. The mammalian Fe(III)-binding compounds hemin and transferrin served both as substrates for the ferric reductase and as iron sources for yeast-phase growth at neutral pH. In the case of transferrin, there was a correlation between the level of iron saturation and efficacy for both of these functions. Our data are not consistent with an entirely pH-dependent mechanism of iron acquisition from transferrin, as has been suggested to occur in the macrophage phagolysosome. The foreign siderophore ferrioxamine B also acted as a substrate for the ferric reductase, while the foreign siderophore ferrichrome did not. Both ferrioxamine and ferrichrome served as iron sources for yeast- and mold-phase growth, the latter presumably by some other acquisition mechanism(s).
Collapse
Affiliation(s)
- M M Timmerman
- Department of Medical Microbiology and Immunology, Microbiology Doctoral Training Program, University of Wisconsin, Madison 53706, USA
| | | |
Collapse
|
43
|
Sridhar S, Ahluwalia M, Brummer E, Stevens DA. Characterization of an anticryptococcal protein isolated from human serum. Infect Immun 2000; 68:3787-91. [PMID: 10816550 PMCID: PMC97681 DOI: 10.1128/iai.68.6.3787-3791.2000] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human serum at low concentrations inhibits the growth of Cryptococcus neoformans in vitro. Fractionation of serum yielded a purified inhibitory protein with a molecular mass of approximately 81.8 kDa, a pI of approximately 6.2, and an amino acid sequence that matched that of human transferrin. The inhibitory activity and that of apotransferrin and 5% human serum were reversed by 10 microM freshly prepared FeCl(3).
Collapse
Affiliation(s)
- S Sridhar
- Division of Infectious Diseases, Department of Medicine, Santa Clara Valley Medical Center, and California Institute for Medical Research, San Jose, California, USA
| | | | | | | |
Collapse
|
44
|
Taramelli D, Brambilla S, Sala G, Bruccoleri A, Tognazioli C, Riviera-Uzielli L, Boelaert JR. Effects of iron on extracellular and intracellular growth of Penicillium marneffei. Infect Immun 2000; 68:1724-6. [PMID: 10678997 PMCID: PMC97338 DOI: 10.1128/iai.68.3.1724-1726.2000] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Killing of intracellular Penicillium marneffei conidia is demonstrated in gamma interferon-lipopolysaccharide-activated human THP1 and mouse J774 cells. Iron overload significantly reduces the antifungal activity of macrophages. Likewise, exogenous iron enhances and iron chelators inhibit the extracellular growth of P. marneffei. These results suggest that iron availability critically affects immunity to and the pathogenicity of P. marneffei.
Collapse
Affiliation(s)
- D Taramelli
- Istituto di Microbiologia, Università di Milano, Milan, Italy.
| | | | | | | | | | | | | |
Collapse
|
45
|
Timmerman MM, Woods JP. Ferric reduction is a potential iron acquisition mechanism for Histoplasma capsulatum. Infect Immun 1999; 67:6403-8. [PMID: 10569756 PMCID: PMC97048 DOI: 10.1128/iai.67.12.6403-6408.1999] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
For the fungus Histoplasma capsulatum, and for other microbial pathogens, iron is an essential nutrient. Iron sequestration in response to infection is a demonstrated host defense mechanism; thus, iron acquisition may be considered an important pathogenic determinant. H. capsulatum is known to secrete Fe(III)-binding hydroxamate siderophores, which is one common microbial process for acquiring iron. Here, we report H. capsulatum ferric reduction activities in whole yeast cells and in both high- and low-molecular-weight fractions of culture supernatants. Each of these activities was induced or derepressed by growth under iron-limiting conditions, a phenomenon often associated with specific iron acquisition mechanisms. The high-molecular-weight culture supernatant activity was enhanced by the addition of reduced glutathione, was proteinase K sensitive and heat labile, and could utilize ferric chloride, ferric citrate, and human holotransferrin as substrates. The low-molecular-weight culture supernatant activity was resistant to proteinase K digestion. These results are consistent with the expression by H. capsulatum of both enzymatic ferric reductase and nonproteinaceous ferric reductant, both of which are regulated by iron availability. Such components could be involved in fungal acquisition of iron from inorganic or organic ferric salts, from H. capsulatum hydroxamate siderophores, or from host Fe(III)-binding proteins, such as transferrin.
Collapse
Affiliation(s)
- M M Timmerman
- Department of Medical Microbiology and Immunology, Microbiology Doctoral Training Program, University of Wisconsin, Madison, Wisconsin 53706, USA
| | | |
Collapse
|
46
|
Abstract
Iron is required by most living systems. A great variety of means of acquisition, avenues of uptake, and methods of storage are used by pathogenic fungi to ensure a supply of the essential metal. Solubilization of insoluble iron polymers is the first step in iron assimilation. The two methods most commonly used by microorganisms for solubilization of iron are reduction and chelation. Reduction of ferric iron to ferrous iron by enzymatic or nonenzymatic means is a common mechanism among pathogenic yeasts. Under conditions of iron starvation, many fungi synthesize iron chelators known as siderophores. Two classes of compounds that function in iron gathering are commonly observed: hydroxamates and polycarboxylates. Two major responses to iron stress in fungi are a high-affinity ferric iron reductase and siderophore synthesis. Regulation of these two mechanisms at the molecular level has received attention. Uptake of siderophores is a diverse process, which varies among the different classes of compounds. Since free iron is toxic, it must be stored for further metabolic use. Polyphosphates, ferritins, and siderophores themselves have been described as storage molecules. The iron-gathering mechanisms used by a pathogen in an infected host are largely unknown and can only be posited on the basis of in vitro studies at present.
Collapse
Affiliation(s)
- D H Howard
- Department of Microbiology and Immunology, UCLA School of Medicine, Los Angeles, California 90095-1747, USA.
| |
Collapse
|
47
|
Nyhus KJ, Jacobson ES. Genetic and physiologic characterization of ferric/cupric reductase constitutive mutants of Cryptococcus neoformans. Infect Immun 1999; 67:2357-65. [PMID: 10225895 PMCID: PMC115978 DOI: 10.1128/iai.67.5.2357-2365.1999] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cryptococcus neoformans is a pathogenic yeast that causes meningitis in immunocompromised patients. Because iron acquisition is critical for growth of a pathogen in a host, we studied the regulation of the ferric reductase and ferrous uptake system of this organism. We isolated 18 mutants, representing four independent loci, with dysregulated ferric reductase. The mutant strains had >10-fold higher than wild-type WT reductase activity in the presence of iron. Two of the strains also had >7-fold higher than WT iron uptake in the presence of iron but were not markedly iron sensitive. Both were sensitive to the oxidative stresses associated with superoxide and hydrogen peroxide. One strain exhibited only 23% of the WT level of iron uptake in the absence of iron and grew poorly without iron supplementation of the medium, phenotypes consistent with an iron transport deficiency; it was sensitive to superoxide but not to hydrogen peroxide. The fourth strain had high reductase activity but normal iron uptake; it was not very sensitive to oxidative stress. We also demonstrated that the ferric reductase was regulated by copper and could act as a cupric reductase. Sensitivity to oxidants may be related to iron acquisition by a variety of mechanisms and may model the interaction of the yeast with the immune system.
Collapse
Affiliation(s)
- K J Nyhus
- Research Service, McGuire Veterans Affairs Medical Center, Richmond, Virginia 23249, USA.
| | | |
Collapse
|