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Wear MP, Jacobs E, Wang S, McConnell S, Bowen A, Strother C, Cordero RJB, Crawford CJ, Casadevall A. Cryptococcus neoformans capsule regrowth experiments reveal dynamics of enlargement and architecture. J Biol Chem 2022; 298:101769. [PMID: 35218774 PMCID: PMC8942833 DOI: 10.1016/j.jbc.2022.101769] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 02/17/2022] [Accepted: 02/18/2022] [Indexed: 11/25/2022] Open
Abstract
The polysaccharide capsule of fungal pathogen Cryptococcus neoformans is a critical virulence factor that has historically evaded complete characterization. Cryptococcal polysaccharides are known to either remain attached to the cell as capsular polysaccharides (CPS) or to be shed into the extracellular space as exopolysaccharides (EPS). While many studies have examined the properties of EPS, far less is known about CPS. In this work, we detail the development of a new physical and enzymatic method for the isolation of CPS which can be used to explore the architecture of the capsule and isolated capsular material. We show that sonication or Glucanex enzyme cocktail digestion yields soluble CPS preparations, while use of a French pressure cell press and Glucanex digestion followed by cell disruption removed the capsule and produced cell wall-associated polysaccharide aggregates that we call 'capsule ghosts', implying an inherent organization that allows the CPS to exist independent of the cell wall surface. Since sonication and Glucanex digestion were non-cytotoxic, it was also possible to observe the cryptococcal cells rebuilding their capsule, revealing the presence of reducing-end glycans throughout the capsule. Finally, analysis of DMSO-extracted and sonicated CPS preparations revealed the conservation of previously identified GXM motifs only in the sonicated CPS. Together, these observations provide new insights into capsule architecture and synthesis, consistent with a model in which the capsule is assembled from the cell wall outwards using smaller polymers, which are then compiled into larger ones.
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Affiliation(s)
- Maggie P Wear
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
| | - Ella Jacobs
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Siqing Wang
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Scott McConnell
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Anthony Bowen
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Camilla Strother
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Radames J B Cordero
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Conor J Crawford
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Arturo Casadevall
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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2
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Crawford CJ, Cordero RJB, Guazzelli L, Wear MP, Bowen A, Oscarson S, Casadevall A. Exploring Cryptococcus neoformans capsule structure and assembly with a hydroxylamine-armed fluorescent probe. J Biol Chem 2020; 295:4327-4340. [PMID: 32005661 PMCID: PMC7105310 DOI: 10.1074/jbc.ra119.012251] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 01/30/2020] [Indexed: 11/06/2022] Open
Abstract
Chemical biology is an emerging field that enables the study and manipulation of biological systems with probes whose reactivities provide structural insights. The opportunistic fungal pathogen Cryptococcus neoformans possesses a polysaccharide capsule that is a major virulence factor, but is challenging to study. We report here the synthesis of a hydroxylamine-armed fluorescent probe that reacts with reducing glycans and its application to study the architecture of the C. neoformans capsule under a variety of conditions. The probe signal localized intracellularly and at the cell wall-membrane interface, implying the presence of reducing-end glycans at this location where the capsule is attached to the cell body. In contrast, no fluorescence signal was detected in the capsule body. We observed vesicle-like structures containing the reducing-end probe, both intra- and extracellularly, consistent with the importance of vesicles in capsular assembly. Disrupting the capsule with DMSO, ultrasound, or mechanical shear stress resulted in capsule alterations that affected the binding of the probe, as reducing ends were exposed and cell membrane integrity was compromised. Unlike the polysaccharides in the assembled capsule, isolated exopolysaccharides contained reducing ends. The reactivity of the hydroxylamine-armed fluorescent probe suggests a model for capsule assembly whereby reducing ends localize to the cell wall surface, supporting previous findings suggesting that this is an initiation point for capsular assembly. We propose that chemical biology is a promising approach for studying the C. neoformans capsule and its associated polysaccharides to unravel their roles in fungal virulence.
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Affiliation(s)
- Conor J Crawford
- Centre for Synthesis and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland; Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland 21205
| | - Radamés J B Cordero
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland 21205
| | - Lorenzo Guazzelli
- Centre for Synthesis and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
| | - Maggie P Wear
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland 21205
| | - Anthony Bowen
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland 21205
| | - Stefan Oscarson
- Centre for Synthesis and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland.
| | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland 21205.
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3
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Paes HC, de Oliveira Frazão S, Felipe MSS, Casadevall A, Nicola AM. Imaging Cryptococcus spp. Capsule by Differential Interference Contrast Microscopy Using Percoll ®. Bio Protoc 2019; 9:e3423. [PMID: 33654920 DOI: 10.21769/bioprotoc.3423] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 10/17/2019] [Accepted: 10/22/2019] [Indexed: 11/02/2022] Open
Abstract
The most important virulence factor in the Cryptococcus genus is the polysaccharide capsule. This genus includes several species that cause life-threatening invasive disease. An increase in capsule thickness is important during fungal infection. The capsule is usually imaged using India ink, and crucial insights on the dynamics of its growth have been obtained using capsule-binding proteins such as specific antibodies or complement. We have developed an alternative method that allows both static and time-lapse imaging of the capsule using Percoll®, a suspension of nanometric spheres that do not penetrate the capsule. Given that these particles have a higher refractive index than the capsule, the latter can be imaged by differential interference contrast (DIC) microscopy. Static observation of the capsule with DIC and Percoll® results in capsule thickness measurements that match those made with India ink. Using capsule-inducing media, a glass-bottom incubation chamber and a live-imaging system equipped for DIC microscopy, this method allows time-lapse imaging of capsule growth. In contrast with India ink staining, DIC imaging of Percoll® exclusion halos result in crisp images. The greatest advantage of this method, though, is that unlike India ink, the Percoll® particles are non-toxic and unlike opsonins they do not bind the capsule, resulting in observations of capsule growth that are free from interference of bound proteins on capsule physiology.
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Affiliation(s)
- Hugo Costa Paes
- Faculty of Medicine, University of Brasília, Brasília, Brazil
| | | | - Maria Sueli Soares Felipe
- Department of Cell Biology, University of Brasília, Brasília, Brazil.,Graduate Program in Genomic Sciences and Biotechnology, Catholic University of Brasília, Brasília, Brazil
| | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, USA
| | - André Moraes Nicola
- Faculty of Medicine, University of Brasília, Brasília, Brazil.,Graduate Program in Genomic Sciences and Biotechnology, Catholic University of Brasília, Brasília, Brazil.,Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, USA
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4
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Wang ZA, Li LX, Doering TL. Unraveling synthesis of the cryptococcal cell wall and capsule. Glycobiology 2019; 28:719-730. [PMID: 29648596 DOI: 10.1093/glycob/cwy030] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 03/28/2018] [Indexed: 11/15/2022] Open
Abstract
Fungal pathogens cause devastating infections in millions of individuals each year, representing a huge but underappreciated burden on human health. One of these, the opportunistic fungus Cryptococcus neoformans, kills hundreds of thousands of patients annually, disproportionately affecting people in resource-limited areas. This yeast is distinguished from other pathogenic fungi by a polysaccharide capsule that is displayed on the cell surface. The capsule consists of two complex polysaccharide polymers: a mannan substituted with xylose and glucuronic acid, and a galactan with galactomannan side chains that bear variable amounts of glucuronic acid and xylose. The cell wall, with which the capsule is associated, is a matrix of alpha and beta glucans, chitin, chitosan, and mannoproteins. In this review, we focus on synthesis of the wall and capsule, both of which are critical for the ability of this microbe to cause disease and are distinct from structures found in either model yeasts or the mammals afflicted by this infection. Significant research effort over the last few decades has been applied to defining the synthetic machinery of these two structures, including nucleotide sugar metabolism and transport, glycosyltransferase activities, polysaccharide export, and assembly and association of structural elements. Discoveries in this area have elucidated fundamental biology and may lead to novel targets for antifungal therapy. In this review, we summarize the progress made in this challenging and fascinating area, and outline future research questions.
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Affiliation(s)
- Zhuo A Wang
- Department of Molecular Microbiology, Washington University School of Medicine, 660 South Euclid Avenue, Saint Louis, MO, USA
| | - Lucy X Li
- Department of Molecular Microbiology, Washington University School of Medicine, 660 South Euclid Avenue, Saint Louis, MO, USA
| | - Tamara L Doering
- Department of Molecular Microbiology, Washington University School of Medicine, 660 South Euclid Avenue, Saint Louis, MO, USA
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5
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Paes HC, Frazão SDO, Rosa CP, Albuquerque P, Casadevall A, Felipe MSS, Nicola AM. Opsonin-free, real-time imaging of Cryptococcus neoformans capsule during budding. Virulence 2018; 9:1483-1488. [PMID: 30165795 PMCID: PMC6177245 DOI: 10.1080/21505594.2018.1515610] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Affiliation(s)
- Hugo Costa Paes
- Faculty of Medicine, University of Brasília, Brasília, Brazil
| | - Stefânia de Oliveira Frazão
- Graduate Programme in Microbial Biology, Institute of Biological Sciences, University of Brasília, Brasília, Brazil
| | - Camila Pereira Rosa
- Graduate Programme in Genomic Sciences and Biotechnology, Catholic University of Brasília, Brasília, Brazil
| | | | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA
| | - Maria Sueli Soares Felipe
- Graduate Programme in Microbial Biology, Institute of Biological Sciences, University of Brasília, Brasília, Brazil,Graduate Programme in Genomic Sciences and Biotechnology, Catholic University of Brasília, Brasília, Brazil
| | - André Moraes Nicola
- Faculty of Medicine, University of Brasília, Brasília, Brazil,Graduate Programme in Genomic Sciences and Biotechnology, Catholic University of Brasília, Brasília, Brazil,CONTACT André Moraes Nicola
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6
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Casadevall A, Coelho C, Cordero RJB, Dragotakes Q, Jung E, Vij R, Wear MP. The capsule of Cryptococcus neoformans. Virulence 2018; 10:822-831. [PMID: 29436899 PMCID: PMC6779390 DOI: 10.1080/21505594.2018.1431087] [Citation(s) in RCA: 109] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The capsule of Cryptococcus neoformans is its dominant virulence factor and plays a key role in the biology of this fungus. In this essay, we focus on the capsule as a cellular structure and note the limitations inherent in the current methodologies available for its study. Given that no single method can provide the structure of the capsule, our notions of what is the cryptococcal capsule must be arrived at by synthesizing information gathered from very different methodological approaches including microscopy, polysaccharide chemistry and physical chemistry of macromolecules. The emerging picture is one of a carefully regulated dynamic structure that is constantly rearranged as a response to environmental stimulation and cellular replication. In the environment, the capsule protects the fungus against desiccation and phagocytic predators. In animal hosts the capsule functions in both offensive and defensive modes, such that it interferes with immune responses while providing the fungal cell with a defensive shield that is both antiphagocytic and capable of absorbing microbicidal oxidative bursts from phagocytic cells. Finally, we delineate a set of unsolved problems in the cryptococcal capsule field that could provide fertile ground for future investigations.
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Affiliation(s)
- Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA
| | - Carolina Coelho
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA
| | - Radames J B Cordero
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA
| | - Quigly Dragotakes
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA
| | - Eric Jung
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA
| | - Raghav Vij
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA
| | - Maggie P Wear
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA
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7
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Agustinho DP, Miller LC, Li LX, Doering TL. Peeling the onion: the outer layers of Cryptococcus neoformans. Mem Inst Oswaldo Cruz 2018; 113:e180040. [PMID: 29742198 PMCID: PMC5951675 DOI: 10.1590/0074-02760180040] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 02/27/2018] [Indexed: 12/20/2022] Open
Abstract
Cryptococcus neoformans is an opportunistic fungal pathogen
that is ubiquitous in the environment. It causes a deadly meningitis that is
responsible for over 180,000 deaths worldwide each year, including 15% of all
AIDS-related deaths. The high mortality rates for this infection, even with
treatment, suggest a need for improved therapy. Unique characteristics of
C. neoformans may suggest directions for drug discovery.
These include features of three structures that surround the cell: the plasma
membrane, the cell wall around it, and the outermost polysaccharide capsule. We
review current knowledge of the fundamental biology of these fascinating
structures and highlight open questions in the field, with the goal of
stimulating further investigation that will advance basic knowledge and human
health.
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Affiliation(s)
- Daniel P Agustinho
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Liza C Miller
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Lucy X Li
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Tamara L Doering
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
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8
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Guess T, Lai H, Smith SE, Sircy L, Cunningham K, Nelson DE, McClelland EE. Size Matters: Measurement of Capsule Diameter in Cryptococcus neoformans. J Vis Exp 2018. [PMID: 29553511 DOI: 10.3791/57171] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The polysaccharide capsule of Cryptococcus neoformans is the primary virulence factor and one of the most commonly studied aspects of this pathogenic yeast. Capsule size can vary widely between strains, has the ability to grow rapidly when introduced to stressful or low nutrient conditions, and has been positively correlated with strain virulence. For these reasons, the size of the capsule is of great interest to C. neoformans researchers. The growth of the C. neoformans capsule is induced during phenotypic testing to help understand the effects of different treatments on the yeast or size differences between strains. Here we describe one of the standard methods of capsule induction and compare two accepted methods of staining and measuring capsule diameter: (i) India ink, a negative stain, used in conjunction with conventional light microscopy and (ii) co-staining with fluorescent dyes of both the cell wall and capsule followed by confocal microscopy. Finally, we show how measurement of capsule diameter from India ink-stained samples can be automated using computational image analysis.
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Affiliation(s)
- Tiffany Guess
- Department of Biology, Middle Tennessee State University
| | | | | | - Linda Sircy
- Department of Biology, Middle Tennessee State University
| | | | - David E Nelson
- Department of Biology, Middle Tennessee State University;
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9
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Ballou ER, Johnston SA. The cause and effect of Cryptococcus interactions with the host. Curr Opin Microbiol 2017; 40:88-94. [PMID: 29154043 DOI: 10.1016/j.mib.2017.10.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 10/18/2017] [Indexed: 12/12/2022]
Abstract
Upon Cryptococcus neoformans infection of the host lung, the fungus enters a nutrient poor environment and must adapt to a variety of host-specific stress conditions (temperature, nutrient limitation, pH, CO2). Fungal spores enter this milieu with limited nutritional reserves, germinate, and begin proliferating by budding as yeast. Although relatively little is known about the initial stages of infection, recent work has characterized changes that occur upon germination. This program and subsequent yeast-phase proliferation progress in a dynamic environment as host nutrient immunity responds to the infection via toxic accumulation or sequestration of essential micronutrients and innate immune cells are recruited to the site of infection. Adaptation to the host environment and evasion of the immune response through pathogenicity factor expression allows proliferation and dissemination to multiple sites throughout the body, including, most significantly for human disease, the central nervous system. Here we will discuss recent insights into mechanisms underlying C. neoformans interactions with the host during infection.
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Affiliation(s)
- Elizabeth R Ballou
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Simon A Johnston
- Department of Infection, Immunity and Cardiovascular disease, Medical School, University of Sheffield, UK; Bateson Centre, University of Sheffield, Sheffield, UK.
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10
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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.
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Cordeiro RDA, Evangelista AJDJ, Serpa R, Marques FJDF, Melo CVSD, Oliveira JSD, Franco JDS, Alencar LPD, Bandeira TDJPG, Brilhante RSN, Sidrim JJC, Rocha MFG. Inhibition of heat-shock protein 90 enhances the susceptibility to antifungals and reduces the virulence of Cryptococcus neoformans/Cryptococcus gattii species complex. Microbiology (Reading) 2016; 162:309-317. [DOI: 10.1099/mic.0.000222] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Rossana de Aguiar Cordeiro
- Specialized Medical Mycology Center,Federal University of Ceará,Fortaleza, CE, Brazil
- Postgraduate Program in Medical Sciences,Federal University of Ceará, Fortaleza, CE,Brazil
- Postgraduate Program in Medical Microbiology,Federal University of Ceará, Fortaleza, CE,Brazil
| | - Antonio José de Jesus Evangelista
- Specialized Medical Mycology Center,Federal University of Ceará,Fortaleza, CE, Brazil
- Postgraduate Program in Medical Sciences,Federal University of Ceará, Fortaleza, CE,Brazil
| | - Rosana Serpa
- Specialized Medical Mycology Center,Federal University of Ceará,Fortaleza, CE, Brazil
- Postgraduate Program in Medical Microbiology,Federal University of Ceará, Fortaleza, CE,Brazil
| | - Francisca Jakelyne de Farias Marques
- Specialized Medical Mycology Center,Federal University of Ceará,Fortaleza, CE, Brazil
- Postgraduate Program in Medical Microbiology,Federal University of Ceará, Fortaleza, CE,Brazil
| | - Charlline Vládia Silva de Melo
- Specialized Medical Mycology Center,Federal University of Ceará,Fortaleza, CE, Brazil
- Postgraduate Program in Medical Microbiology,Federal University of Ceará, Fortaleza, CE,Brazil
| | - Jonathas Sales de Oliveira
- Specialized Medical Mycology Center,Federal University of Ceará,Fortaleza, CE, Brazil
- Postgraduate Program in Medical Microbiology,Federal University of Ceará, Fortaleza, CE,Brazil
| | | | - Lucas Pereira de Alencar
- Specialized Medical Mycology Center,Federal University of Ceará,Fortaleza, CE, Brazil
- Postgraduate Program in Veterinary Sciences,State University of Ceará, Fortaleza, CE,Brazil
| | - Tereza de Jesus Pinheiro Gomes Bandeira
- Specialized Medical Mycology Center,Federal University of Ceará,Fortaleza, CE, Brazil
- School of Medicine, Christus College – UNICHRISTUS,Fortaleza, CE,Brazil
| | - Raimunda Sâmia Nogueira Brilhante
- Specialized Medical Mycology Center,Federal University of Ceará,Fortaleza, CE, Brazil
- Postgraduate Program in Medical Sciences,Federal University of Ceará, Fortaleza, CE,Brazil
- Postgraduate Program in Medical Microbiology,Federal University of Ceará, Fortaleza, CE,Brazil
| | - José Júlio Costa Sidrim
- Specialized Medical Mycology Center,Federal University of Ceará,Fortaleza, CE, Brazil
- Postgraduate Program in Medical Sciences,Federal University of Ceará, Fortaleza, CE,Brazil
- Postgraduate Program in Medical Microbiology,Federal University of Ceará, Fortaleza, CE,Brazil
| | - Marcos Fébio Gadelha Rocha
- Specialized Medical Mycology Center,Federal University of Ceará,Fortaleza, CE, Brazil
- Postgraduate Program in Medical Microbiology,Federal University of Ceará, Fortaleza, CE,Brazil
- Postgraduate Program in Veterinary Sciences,State University of Ceará, Fortaleza, CE,Brazil
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12
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Bouklas T, Fries BC. Aging: an emergent phenotypic trait that contributes to the virulence of Cryptococcus neoformans. Future Microbiol 2015; 10:191-7. [PMID: 25689531 DOI: 10.2217/fmb.14.124] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The pathogenic fungus, Cryptococcus neoformans, is known to undergo phenotypic variation, which affects its virulence in the host. Recent investigations on C. neoformans cells in humans have validated the concept that phenotypic variation is present and relevant for the outcome of chronic cryptococcosis. The C. neoformans capsule is not the only trait that varies among strains. An emerging variant is the "old cell phenotype" generated when C. neoformans undergoes replicative aging. This phenotype, which other than larger size also exhibits a thickened cell wall, inhibits phagocytosis and killing by antifungals in vitro. In concert with the finding that old cells accumulate in vivo, this emergent trait could have significant impact on cryptococcal virulence and infection, and contribute to treatment failure.
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Affiliation(s)
- Tejas Bouklas
- Division of Infectious Diseases, Department of Medicine, Health Sciences Center T15-080, Stony Brook University Medical Center, Stony Brook, NY 11794-8153, USA
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13
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Abstract
The fungal pathogen Cryptococcus neoformans has several virulence factors, among which the most important is a polysaccharide capsule. The size of the capsule is variable and can increase significantly during infection. In this work, we investigated the relationship between capsular enlargement and the cell cycle. Capsule growth occurred primarily during the G1 phase. Real-time visualization of capsule growth demonstrated that this process occurred before the appearance of the bud and that capsule growth arrested during budding. Benomyl, which arrests the cells in G2/M, inhibited capsule growth, while sirolimus (rapamycin) addition, which induces G1 arrest, resulted in cells with larger capsule. Furthermore, we have characterized a mutant strain that lacks a putative G1/S cyclin. This mutant showed an increased capacity to enlarge the capsule, both in vivo (using Galleria mellonella as the host model) and in vitro. In the absence of Cln1, there was a significant increase in the production of extracellular vesicles. Proteomic assays suggest that in the cln1 mutant strain, there is an upregulation of the glyoxylate acid cycle. Besides, this cyclin mutant is avirulent at 37°C, which correlates with growth defects at this temperature in rich medium. In addition, the cln1 mutant showed lower intracellular replication rates in murine macrophages. We conclude that cell cycle regulatory elements are involved in the modulation of the expression of the main virulence factor in C. neoformans. Cryptococcus neoformans is a pathogenic fungus that has significant incidence worldwide. Its main virulence factor is a polysaccharide capsule that can increase in size during infection. In this work, we demonstrate that this process occurs in a specific phase of the cell cycle, in particular, in G1. In agreement, mutants that have an abnormal longer G1 phase show larger capsule sizes. We believe that our findings are relevant because they provide a link between capsule growth, cell cycle progression, and virulence in C. neoformans that reveals new aspects about the pathogenicity of this fungus. Moreover, our findings indicate that cell cycle elements could be used as antifungal targets in C. neoformans by affecting both the growth of the cells and the expression of the main virulence factor of this pathogenic yeast.
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