1
|
Brown JC, Ballou ER. Is Cryptococcus neoformans a pleomorphic fungus? Curr Opin Microbiol 2024; 82:102539. [PMID: 39260180 DOI: 10.1016/j.mib.2024.102539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 05/22/2024] [Accepted: 08/19/2024] [Indexed: 09/13/2024]
Abstract
Improved understanding of the human fungal pathogen Cryptococcus neoformans, classically described as a basidiomycete budding yeast, has revealed new infection-relevant single cell morphologies in vivo and in vitro. Here, we ask whether these morphologies constitute true morphotypes, requiring updated classification of C. neoformans as a pleomorphic fungus. We profile recent discoveries of C. neoformans seed cells and titan cells and provide a framework for determining whether these and other recently described single-cell morphologies constitute true morphotypes. We demonstrate that multiple C. neoformans single-cell morphologies are transcriptionally distinct, stable, heritable, and associated with active growth and therefore should be considered true morphotypes in line with the classification in other well-studied fungi. We conclude that C. neoformans is a pleomorphic fungus with an important capacity for morphotype switching that underpins pathogenesis.
Collapse
Affiliation(s)
- Jessica Cs Brown
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA.
| | - Elizabeth R Ballou
- Medical Research Council Centre for Medical Mycology at the University of Exeter, Exeter EX4 4QD, UK.
| |
Collapse
|
2
|
Winski CJ, Stuckey PV, Marrufo AM, Ross RL, Agyei G, Chapman S, Santiago-Tirado FH. Lack of an atypical PDR transporter generates an immunogenic Cryptococcus neoformans strain that drives a dysregulated and lethal immune response in murine lungs. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.17.599354. [PMID: 38948814 PMCID: PMC11212882 DOI: 10.1101/2024.06.17.599354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Cryptococcus neoformans is an opportunistic fungal pathogen responsible for >150,000 deaths every year with a mortality rate as high as 81%. This high medical burden is due, in part, to an incomplete understanding of its pathogenesis. In a previous study, we identified a cryptococcal atypical pleiotropic drug resistance (PDR) transporter, PDR6, that regulated antifungal resistance and host interactions. Here, we follow-up on the role of PDR6 in cryptococcal virulence. In vivo, mice infected with the pdr6Δ strain display altered symptomatology and disease progression. Specifically, we observed a significant increase in the innate immune cell populations in the pdr6Δ-infected mice when compared to their WT-infected littermates. Furthermore, quantification of pulmonary cytokines/chemokines revealed a robust increase of pro-inflammatory cytokines in mice infected with the pdr6Δ mutant strain. Whereas antifungal treatment of pdr6Δ-infected animals did not affect survival, treatment with a corticosteroid significantly extended survival, highlighting the importance of a balanced/controlled host immune response. We determined that the hyper-inflammatory immune response occurs, in part, because the loss of the Pdr6 transporter indirectly alters the cryptococcal cell wall architecture and results in the increased exposure of chitin, β-glucan, and other cryptococcal-specific pathogen associated molecular patterns. Taken together, this study provides clinical insights regarding cryptococcal pathogenesis while also providing additional functions of PDR-type ATP-binding cassette (ABC) transporters in pathogenic fungi.
Collapse
Affiliation(s)
- Christopher J. Winski
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Peter V. Stuckey
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Armando M. Marrufo
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Robbi L. Ross
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
- Integrated Biomedical Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Georgina Agyei
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Sarah Chapman
- Integrated Imaging Facility, University of Notre Dame, Notre Dame, Indiana, USA
| | - Felipe H. Santiago-Tirado
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
- Integrated Biomedical Sciences, University of Notre Dame, Notre Dame, Indiana, USA
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, USA
- Warren Center for Drug Discovery, University of Notre Dame, Notre Dame, Indiana, USA
| |
Collapse
|
3
|
Hughes ES, Tuck LR, He Z, Ballou ER, Wallace EWJ. A trade-off between proliferation and defense in the fungal pathogen Cryptococcus at alkaline pH is controlled by the transcription factor GAT201. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.06.14.543486. [PMID: 37398450 PMCID: PMC10312749 DOI: 10.1101/2023.06.14.543486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Cryptococcus is a fungal pathogen whose virulence relies on proliferation in and dissemination to host sites, and on synthesis of a defensive yet metabolically costly polysaccharide capsule. Regulatory pathways required for Cryptococcus virulence include a GATA-like transcription factor, Gat201, that regulates Cryptococcal virulence in both capsule-dependent and capsule-independent ways. Here we show that Gat201 is part of a negative regulatory pathway that limits fungal survival at alkaline pH. RNA-seq analysis found strong induction of GAT201 expression within minutes of transfer to RPMI media at alkaline pH. Microscopy, growth curves, and colony forming unit assays show that in RPMI at alkaline pH wild-type Cryptococcus neoformans yeast cells produce capsule but do not bud or maintain viability, while gat201Δ cells make buds and maintain viability, yet fail to produce capsule. GAT201 is required for transcriptional upregulation of a specific set of genes, the majority of which are direct Gat201 targets. Evolutionary analysis shows that Gat201 is in a subfamily of GATA-like transcription factors that is conserved within pathogenic fungi but absent in model yeasts. This work identifies the Gat201 pathway as controlling a trade-off between proliferation and production of defensive capsule. The assays established here will allow characterisation of the mechanisms of action of the Gat201 pathway. Together, our findings urge improved understanding of the regulation of proliferation as a driver of fungal pathogenesis.
Collapse
Affiliation(s)
- Elizabeth S Hughes
- Institute for Cell Biology, and Centre for Engineering Biology, School of Biological Sciences, The University of Edinburgh
| | - Laura R Tuck
- Institute for Cell Biology, and Centre for Engineering Biology, School of Biological Sciences, The University of Edinburgh
| | - Zhenzhen He
- Institute for Cell Biology, and Centre for Engineering Biology, School of Biological Sciences, The University of Edinburgh
| | | | - Edward W J Wallace
- Institute for Cell Biology, and Centre for Engineering Biology, School of Biological Sciences, The University of Edinburgh
| |
Collapse
|
4
|
Kang YS, Jung J, Brown H, Mateusiak C, Doering TL, Brent MR. How host-like signals drive gene expression and capsule expansion in Cryptococcus neoformans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.04.19.537239. [PMID: 37131703 PMCID: PMC10153387 DOI: 10.1101/2023.04.19.537239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Cryptococcus neoformans is an opportunistic fungal pathogen with a polysaccharide capsule that becomes greatly enlarged in the mammalian host and during in vitro growth under host-like conditions. To understand how individual environmental signals affect capsule size and gene expression, we grew cells in all combinations of five signals implicated in capsule size and systematically measured cell and capsule sizes. We also sampled these cultures over time and performed RNA-Seq in quadruplicate, yielding 881 RNA-Seq samples. Analysis of the resulting data sets showed that capsule induction in tissue culture medium, typically used to represent host-like conditions, requires the presence of either CO2 or exogenous cyclic AMP (cAMP). Surprisingly, adding either of these pushes overall gene expression in the opposite direction from tissue culture media alone, even though both are required for capsule development. Another unexpected finding was that rich medium blocks capsule growth completely. Statistical analysis further revealed many genes whose expression is associated with capsule thickness; deletion of one of these significantly reduced capsule size. Beyond illuminating capsule induction, our massive, uniformly collected dataset will be a significant resource for the research community.
Collapse
Affiliation(s)
- Yu Sung Kang
- These authors contributed equally
- Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, MO 63110
- Department of Computer Science and Engineering, Washington University, St. Louis, MO 63108
| | - Jeffery Jung
- These authors contributed equally
- Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, MO 63110
- Department of Computer Science and Engineering, Washington University, St. Louis, MO 63108
| | - Holly Brown
- Department of Computer Science and Engineering, Washington University, St. Louis, MO 63108
| | - Chase Mateusiak
- Department of Computer Science and Engineering, Washington University, St. Louis, MO 63108
| | - Tamara L. Doering
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Michael R. Brent
- Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, MO 63110
- Department of Computer Science and Engineering, Washington University, St. Louis, MO 63108
- Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110
| |
Collapse
|
5
|
Boodwa-Ko D, Doering TL. A Quick reCAP: Discovering Cryptococcus neoformans Capsule Mutants. J Fungi (Basel) 2024; 10:114. [PMID: 38392786 PMCID: PMC10889740 DOI: 10.3390/jof10020114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Revised: 01/25/2024] [Accepted: 01/27/2024] [Indexed: 02/24/2024] Open
Abstract
Cryptococcus neoformans is an opportunistic fungal pathogen that can cause severe meningoencephalitis in immunocompromised hosts and is a leading cause of death in HIV/AIDS patients. This pathogenic yeast is surrounded by a polysaccharide capsule that is critical for virulence and plays important roles in host-pathogen interactions. Understanding capsule biosynthesis is therefore key to defining the biology of C. neoformans and potentially discovering novel therapeutic targets. By exploiting methods to identify mutants deficient in capsule, June Kwon-Chung and other investigators have discovered numerous genes involved in capsule biosynthesis and regulation. Successful approaches have incorporated combinations of techniques including mutagenesis and systematic gene deletion; complementation and genetic screens; morphological examination, physical separation, and antibody binding; and computational modeling based on gene expression analysis. In this review, we discuss these methods and how they have been used to identify capsule mutants.
Collapse
Affiliation(s)
- Daphne Boodwa-Ko
- Department of Molecular Microbiology, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Tamara L Doering
- Department of Molecular Microbiology, Washington University in St. Louis, St. Louis, MO 63110, USA
| |
Collapse
|
6
|
Son YE, Han J, Lee KT, Park HS. Pleiotropic functions of SscA on the asexual spore of the human pathogenic fungus Aspergillus fumigatus. Mycology 2023; 15:238-254. [PMID: 38813476 PMCID: PMC11132850 DOI: 10.1080/21501203.2023.2294061] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 12/06/2023] [Indexed: 05/31/2024] Open
Abstract
Asexual spores, called conidia, are key reproductive fungal particles that enable survival in harsh environmental conditions or host systems. The conidia can infect humans, animals, and plants to cause various fungal diseases. Transcription factors, including VosA, WetA, and SscA, have key roles in conidia formation and long-term survival in Aspergillus nidulans. Herein, we report the pleiotropic functions of SscA in the conidia of the human pathogen A. fumigatus. The deletion of sscA increased conidia formation despite decreased fungal growth. Absence of sscA impaired long-term survival and reduced spore resistance to various stresses, including heat, UV, and oxidation. Transcriptomic analyses showed that SscA involved the mRNA expression of cell wall organisation-related genes. Importantly, the sscA deletion mutant conidia contained an increased amount of β-glucan and chitin compared to wild type conidia. In addition, conidial gliotoxin production was decreased in the sscA deletion strain. Overall, SscA has pleiotropic roles in conidia formation, maturation and dormancy and mycotoxin production in A. fumigatus.
Collapse
Affiliation(s)
- Ye-Eun Son
- School of Food Science and Biotechnology, Kyungpook National University, Daegu, Republic of Korea
| | - Jiwoo Han
- Korea Zoonosis Research Institute, Jeonbuk National University, Iksan, Republic of Korea
| | - Kyung-Tae Lee
- Korea Zoonosis Research Institute, Jeonbuk National University, Iksan, Republic of Korea
| | - Hee-Soo Park
- School of Food Science and Biotechnology, Kyungpook National University, Daegu, Republic of Korea
- Department of Integrative Biology, Kyungpook National University, Daegu, Republic of Korea
| |
Collapse
|
7
|
Li C, Meng Y, Li H, Du W, Gao X, Suo C, Gao Y, Ni Y, Sun T, Yang S, Lan T, Xin M, Ding C. Immunization with a heat-killed prm1 deletion strain protects the host from Cryptococcus neoformans infection. Emerg Microbes Infect 2023; 12:2244087. [PMID: 37526401 PMCID: PMC10431737 DOI: 10.1080/22221751.2023.2244087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 07/02/2023] [Accepted: 07/30/2023] [Indexed: 08/02/2023]
Abstract
Systemic infection with Cryptococcus neoformans, a dangerous and contagious pathogen found throughout the world, frequently results in lethal cryptococcal pneumonia and meningoencephalitis, and no effective treatments and vaccination of cryptococcosis are available. Here, we describe Prm1, a novel regulator of C. neoformans virulence. C. neoformans prm1Δ cells exhibit extreme sensitivity to various environmental stress conditions. Furthermore, prm1Δ cells show deficiencies in the biosynthesis of chitosan and mannoprotein, which in turn result in impairment of cell wall integrity. Treatment of mice with heat-killed prm1Δ cells was found to facilitate the host immunological defence against infection with wild-type C. neoformans. Further investigation demonstrated that prm1Δ cells strongly promote pulmonary production of interferon-γ, leading to activation of macrophage M1 differentiation and inhibition of M2 polarization. Therefore, our findings suggest that C. neoformans Prm1 may be a viable target for the development of anti-cryptococcosis medications and, cells lacking Prm1 represent a promising candidate for a vaccine.
Collapse
Affiliation(s)
- Chao Li
- College of Life and Health Sciences, Northeastern University, Shenyang, People’s Republic of China
| | - Yang Meng
- College of Life and Health Sciences, Northeastern University, Shenyang, People’s Republic of China
| | - Hailong Li
- NHC Key Laboratory of AIDS Immunology, National Clinical Research Center for Laboratory Medicine, The First Hospital of China Medical University, Shenyang, People’s Republic of China
| | - Wei Du
- College of Life and Health Sciences, Northeastern University, Shenyang, People’s Republic of China
| | - Xindi Gao
- College of Life and Health Sciences, Northeastern University, Shenyang, People’s Republic of China
| | - Chenhao Suo
- College of Life and Health Sciences, Northeastern University, Shenyang, People’s Republic of China
| | - Yiru Gao
- College of Life and Health Sciences, Northeastern University, Shenyang, People’s Republic of China
| | - Yue Ni
- College of Life and Health Sciences, Northeastern University, Shenyang, People’s Republic of China
| | - Tianshu Sun
- Beijing Key Laboratory for Mechanisms Research and Precision Diagnosis of Invasive Fungal Diseases, Beijing, People’s Republic of China
- Department of Scientific Research, Central Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Science, Beijing, People’s Republic of China
| | - Sheng Yang
- College of Life and Health Sciences, Northeastern University, Shenyang, People’s Republic of China
| | - Tian Lan
- College of Life and Health Sciences, Northeastern University, Shenyang, People’s Republic of China
| | - Meiling Xin
- College of Life and Health Sciences, Northeastern University, Shenyang, People’s Republic of China
| | - Chen Ding
- College of Life and Health Sciences, Northeastern University, Shenyang, People’s Republic of China
| |
Collapse
|
8
|
Francis VI, Liddle C, Camacho E, Kulkarni M, Junior SRS, Harvey JA, Ballou ER, Thomson DD, Hardwick JM, Casadevall A, Witton J, Coelho C. Cryptococcus neoformans rapidly invades the murine brain by sequential breaching of airway and endothelial tissues barriers, followed by engulfment by microglia. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.13.564824. [PMID: 38014111 PMCID: PMC10680653 DOI: 10.1101/2023.11.13.564824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
The fungus Cryptococcus neoformans causes lethal meningitis in humans with weakened immune systems and is estimated to account for 10-15% of AIDS-associated deaths worldwide. There are major gaps in our understanding of how this environmental fungus evades the immune system and invades the mammalian brain before the onset of overt symptoms. To investigate the dynamics of C. neoformans tissue invasion, we mapped early fungal localisation and host cell interactions at early times in infected brain, lung, and upper airways using mouse models of systemic and airway infection. To enable this, we developed an in situ imaging pipeline capable of measuring large volumes of tissue while preserving anatomical and cellular information by combining thick tissue sections, tissue clarification, and confocal imaging. Made possible by these techniques, we confirm high fungal burden in mouse upper airway turbinates after nasal inoculation. Surprisingly, most yeasts in turbinates were titan cells, indicating this microenvironment enables titan cell formation with faster kinetics than reported in mouse lungs. Importantly, we observed one instance of fungal cells enmeshed in lamina propria of upper airways, suggesting penetration of airway mucosa as a possible route of tissue invasion and dissemination to the bloodstream. We extend previous literature positing bloodstream dissemination of C. neoformans, via imaging C. neoformans within blood vessels of mouse lungs and finding viable fungi in the bloodstream of mice a few days after intranasal infection, suggesting that bloodstream access can occur via lung alveoli. In a model of systemic cryptococcosis, we show that as early as 24 h post infection, majority of C. neoformans cells traversed the blood-brain barrier, and are engulfed or in close proximity to microglia. Our work establishes that C. neoformans can breach multiple tissue barriers within the first days of infection. This work presents a new method for investigating cryptococcal invasion mechanisms and demonstrates microglia as the primary cells responding to C. neoformans invasion.
Collapse
Affiliation(s)
- Vanessa I Francis
- MRC Centre for Medical Mycology at University of Exeter, University of Exeter, Exeter, EX4 4QD, UK
- Faculty of Health and Life Sciences, University of Exeter, EX4 4QD, UK
| | - Corin Liddle
- Bioimaging Facility, University of Exeter, Exeter, EX4 4QD, UK
| | - Emma Camacho
- Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Madhura Kulkarni
- Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Samuel R S Junior
- Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Jamie A Harvey
- MRC Centre for Medical Mycology at University of Exeter, University of Exeter, Exeter, EX4 4QD, UK
| | - Elizabeth R Ballou
- MRC Centre for Medical Mycology at University of Exeter, University of Exeter, Exeter, EX4 4QD, UK
| | - Darren D Thomson
- MRC Centre for Medical Mycology at University of Exeter, University of Exeter, Exeter, EX4 4QD, UK
| | - J Marie Hardwick
- Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Arturo Casadevall
- Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Jonathan Witton
- Faculty of Health and Life Sciences, University of Exeter, EX4 4QD, UK
| | - Carolina Coelho
- MRC Centre for Medical Mycology at University of Exeter, University of Exeter, Exeter, EX4 4QD, UK
- Faculty of Health and Life Sciences, University of Exeter, EX4 4QD, UK
| |
Collapse
|
9
|
O’Meara MJ, Rapala JR, Nichols CB, Alexandre C, Billmyre RB, Steenwyk JL, Alspaugh JA, O’Meara TR. CryptoCEN: A Co-Expression Network for Cryptococcus neoformans reveals novel proteins involved in DNA damage repair. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.17.553567. [PMID: 37645941 PMCID: PMC10462067 DOI: 10.1101/2023.08.17.553567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Elucidating gene function is a major goal in biology, especially among non-model organisms. However, doing so is complicated by the fact that molecular conservation does not always mirror functional conservation, and that complex relationships among genes are responsible for encoding pathways and higher-order biological processes. Co-expression, a promising approach for predicting gene function, relies on the general principal that genes with similar expression patterns across multiple conditions will likely be involved in the same biological process. For Cryptococcus neoformans, a prevalent human fungal pathogen greatly diverged from model yeasts, approximately 60% of the predicted genes in the genome lack functional annotations. Here, we leveraged a large amount of publicly available transcriptomic data to generate a C. neoformans Co-Expression Network (CryptoCEN), successfully recapitulating known protein networks, predicting gene function, and enabling insights into the principles influencing co-expression. With 100% predictive accuracy, we used CryptoCEN to identify 13 new DNA damage response genes, underscoring the utility of guilt-by-association for determining gene function. Overall, co-expression is a powerful tool for uncovering gene function, and decreases the experimental tests needed to identify functions for currently under-annotated genes.
Collapse
Affiliation(s)
- Matthew J. O’Meara
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, USA
| | - Jackson R. Rapala
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA
| | - Connie B. Nichols
- Departments of Medicine and Molecular Genetics/Microbiology; and Cell Biology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Christina Alexandre
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA
| | - R. Blake Billmyre
- Departments of Pharmaceutical and Biomedical Sciences/Infectious Disease, College of Pharmacy/College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Jacob L Steenwyk
- Howards Hughes Medical Institute and the Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - J. Andrew Alspaugh
- Departments of Medicine and Molecular Genetics/Microbiology; and Cell Biology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Teresa R. O’Meara
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA
| |
Collapse
|
10
|
Cao C, Wang K, Wang Y, Liu TB, Rivera A, Xue C. Ubiquitin proteolysis of a CDK-related kinase regulates titan cell formation and virulence in the fungal pathogen Cryptococcus neoformans. Nat Commun 2022; 13:6397. [PMID: 36302775 PMCID: PMC9613880 DOI: 10.1038/s41467-022-34151-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 10/17/2022] [Indexed: 12/25/2022] Open
Abstract
Fungal pathogens often undergo morphological switches, including cell size changes, to adapt to the host environment and cause disease. The pathogenic yeast Cryptococcus neoformans forms so-called 'titan cells' during infection. Titan cells are large, polyploid, display alterations in cell wall and capsule, and are more resistant to phagocytosis and various types of stress. Titan cell formation is regulated by the cAMP/PKA signal pathway, which is stimulated by the protein Gpa1. Here, we show that Gpa1 is activated through phosphorylation by a CDK-related kinase (Crk1), which is targeted for degradation by an E3 ubiquitin ligase (Fbp1). Strains overexpressing CRK1 or an allele lacking a PEST domain exhibit increased production of titan cells similarly to the fbp1∆ mutant. Conversely, CRK1 deletion results in reduced titan cell production, indicating that Crk1 stimulates titan cell formation. Crk1 phosphorylates Gpa1, which then localizes to the plasma membrane and activates the cAMP/PKA signal pathway to induce cell enlargement. Furthermore, titan cell-overproducing strains trigger increased Th1 and Th17 cytokine production in CD4+ T cells and show attenuated virulence in a mouse model of systemic cryptococcosis. Overall, our study provides insights into the regulation of titan cell formation and fungal virulence.
Collapse
Affiliation(s)
- Chengjun Cao
- Public Health Research Institute, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA
| | - Keyi Wang
- Center for Immunity and Inflammation, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA
| | - Yina Wang
- Public Health Research Institute, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA
| | - Tong-Bao Liu
- Public Health Research Institute, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA
- Medical Research Institute, Southwest University, Chongqing, 400715, China
| | - Amariliz Rivera
- Center for Immunity and Inflammation, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA
| | - Chaoyang Xue
- Public Health Research Institute, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA.
- Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA.
- Rutgers Center for Lipid Research, Rutgers University, New Brunswick, NJ, 08901, USA.
| |
Collapse
|
11
|
Yu CH, Sephton-Clark P, Tenor JL, Toffaletti DL, Giamberardino C, Haverkamp M, Cuomo CA, Perfect JR. Gene Expression of Diverse Cryptococcus Isolates during Infection of the Human Central Nervous System. mBio 2021; 12:e0231321. [PMID: 34724829 PMCID: PMC8561399 DOI: 10.1128/mbio.02313-21] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Accepted: 09/24/2021] [Indexed: 12/13/2022] Open
Abstract
Cryptococcus neoformans is a major human central nervous system (CNS) fungal pathogen causing considerable morbidity and mortality. In this study, we provide the widest view to date of the yeast transcriptome directly from the human subarachnoid space and within cerebrospinal fluid (CSF). We captured yeast transcriptomes from C. neoformans of various genotypes in 31 patients with cryptococcal meningoencephalitis as well as several Cryptococcus gattii infections. Using transcriptome sequencing (RNA-seq) analyses, we compared the in vivo yeast transcriptomes to those from other environmental conditions, including in vitro growth on nutritious media or artificial CSF as well as samples collected from rabbit CSF at two time points. We ranked gene expressions and identified genetic patterns and networks across these diverse isolates that reveal an emphasis on carbon metabolism, fatty acid synthesis, transport, cell wall structure, and stress-related gene functions during growth in CSF. The most highly expressed yeast genes in human CSF included those known to be associated with survival or virulence and highlighted several genes encoding hypothetical proteins. From that group, a gene encoding the CMP1 putative glycoprotein (CNAG_06000) was selected for functional studies. This gene was found to impact the virulence of Cryptococcus in both mice and the CNS rabbit model, in agreement with a recent study also showing a role in virulence. This transcriptional analysis strategy provides a view of regulated yeast genes across genetic backgrounds important for human CNS infection and a relevant resource for the study of cryptococcal genes, pathways, and networks linked to human disease. IMPORTANCE Cryptococcus is the most common fungus causing high-morbidity and -mortality human meningitis. This encapsulated yeast has a unique propensity to travel to the central nervous system to produce disease. In this study, we captured transcriptomes of yeasts directly out of the human cerebrospinal fluid, the most concerning site of infection. By comparing the RNA transcript levels with other conditions, we gained insights into how the basic machinery involved in metabolism and environmental responses enable this fungus to cause disease at this body site. This approach was applied to clinical isolates with diverse genotypes to begin to establish a genotype-agnostic understanding of how the yeast responds to stress. Based on these results, future studies can focus on how these genes and their pathways and networks can be targeted with new therapeutics and possibly classify yeasts with bad infection outcomes.
Collapse
Affiliation(s)
- Chen-Hsin Yu
- Division of Infectious Diseases, Department of Medicine, Duke University School of Medicine, Durham, North Carolina, USA
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Poppy Sephton-Clark
- Infectious Disease and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | - Jennifer L. Tenor
- Division of Infectious Diseases, Department of Medicine, Duke University School of Medicine, Durham, North Carolina, USA
| | - Dena L. Toffaletti
- Division of Infectious Diseases, Department of Medicine, Duke University School of Medicine, Durham, North Carolina, USA
| | - Charles Giamberardino
- Division of Infectious Diseases, Department of Medicine, Duke University School of Medicine, Durham, North Carolina, USA
| | - Miriam Haverkamp
- Department of Infection Control and Infectious Diseases, University Hospital RWTH Aachen, Aachen, Germany
| | - Christina A. Cuomo
- Infectious Disease and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | - John R. Perfect
- Division of Infectious Diseases, Department of Medicine, Duke University School of Medicine, Durham, North Carolina, USA
| |
Collapse
|
12
|
Telzrow CL, Zwack PJ, Esher Righi S, Dietrich FS, Chan C, Owzar K, Alspaugh JA, Granek JA. Comparative analysis of RNA enrichment methods for preparation of Cryptococcus neoformans RNA sequencing libraries. G3 (BETHESDA, MD.) 2021; 11:jkab301. [PMID: 34518880 PMCID: PMC8527493 DOI: 10.1093/g3journal/jkab301] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 08/19/2021] [Indexed: 11/13/2022]
Abstract
RNA sequencing (RNA-Seq) experiments focused on gene expression involve removal of ribosomal RNA (rRNA) because it is the major RNA constituent of cells. This process, called RNA enrichment, is done primarily to reduce cost: without rRNA removal, deeper sequencing must be performed to compensate for the sequencing reads wasted on rRNA. The ideal RNA enrichment method removes all rRNA without affecting other RNA in the sample. We tested the performance of three RNA enrichment methods on RNA isolated from Cryptococcus neoformans, a fungal pathogen of humans. We find that the RNase H depletion method is more efficient in depleting rRNA and more specific in recapitulating non-rRNA levels present in unenriched controls than the commonly-used Poly(A) isolation method. The RNase H depletion method is also more effective than the Ribo-Zero depletion method as measured by rRNA depletion efficiency and recapitulation of protein-coding RNA levels present in unenriched controls, while the Ribo-Zero depletion method more closely recapitulates annotated non-coding RNA (ncRNA) levels. Finally, we leverage these data to accurately map the C. neoformans mitochondrial rRNA genes, and also demonstrate that RNA-Seq data generated with the RNase H and Ribo-Zero depletion methods can be used to explore novel C. neoformans long non-coding RNA genes.
Collapse
Affiliation(s)
- Calla L Telzrow
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710, USA
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Paul J Zwack
- Department of Biology, Duke University, Durham, NC 27710, USA
| | - Shannon Esher Righi
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Fred S Dietrich
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Cliburn Chan
- Department of Biostatistics and Bioinformatics, Duke University Medical Center, Durham, NC 27710, USA
| | - Kouros Owzar
- Department of Biostatistics and Bioinformatics, Duke University Medical Center, Durham, NC 27710, USA
- Duke Cancer Institute, Duke University, Durham, NC 27710, USA
| | - J Andrew Alspaugh
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710, USA
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Joshua A Granek
- Department of Biostatistics and Bioinformatics, Duke University Medical Center, Durham, NC 27710, USA
- Duke Cancer Institute, Duke University, Durham, NC 27710, USA
| |
Collapse
|
13
|
Squizani ED, Reuwsaat JC, Motta H, Tavanti A, Kmetzsch L. Calcium: a central player in Cryptococcus biology. FUNGAL BIOL REV 2021. [DOI: 10.1016/j.fbr.2021.03.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
14
|
The Transcription Factor Pdr802 Regulates Titan Cell Formation and Pathogenicity of Cryptococcus neoformans. mBio 2021; 12:mBio.03457-20. [PMID: 33688010 PMCID: PMC8092302 DOI: 10.1128/mbio.03457-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The pathogenic yeast Cryptococcus neoformans presents a worldwide threat to human health, especially in the context of immunocompromise, and current antifungal therapy is hindered by cost, limited availability, and inadequate efficacy. After the infectious particle is inhaled, C. neoformans initiates a complex transcriptional program that integrates cellular responses and enables adaptation to the host lung environment. Cryptococcus neoformans is a ubiquitous, opportunistic fungal pathogen that kills almost 200,000 people worldwide each year. It is acquired when mammalian hosts inhale the infectious propagules; these are deposited in the lung and, in the context of immunocompromise, may disseminate to the brain and cause lethal meningoencephalitis. Once inside the host, C. neoformans undergoes a variety of adaptive processes, including secretion of virulence factors, expansion of a polysaccharide capsule that impedes phagocytosis, and the production of giant (Titan) cells. The transcription factor Pdr802 is one regulator of these responses to the host environment. Expression of the corresponding gene is highly induced under host-like conditions in vitro and is critical for C. neoformans dissemination and virulence in a mouse model of infection. Direct targets of Pdr802 include the quorum sensing proteins Pqp1, Opt1, and Liv3; the transcription factors Stb4, Zfc3, and Bzp4, which regulate cryptococcal brain infectivity and capsule thickness; the calcineurin targets Had1 and Crz1, important for cell wall remodeling and C. neoformans virulence; and additional genes related to resistance to host temperature and oxidative stress, and to urease activity. Notably, cryptococci engineered to lack Pdr802 showed a dramatic increase in Titan cells, which are not phagocytosed and have diminished ability to directly cross biological barriers. This explains the limited dissemination of pdr802 mutant cells to the central nervous system and the consequently reduced virulence of this strain. The role of Pdr802 as a negative regulator of Titan cell formation is thus critical for cryptococcal pathogenicity.
Collapse
|
15
|
Cryptococcus neoformans Evades Pulmonary Immunity by Modulating Xylose Precursor Transport. Infect Immun 2020; 88:IAI.00288-20. [PMID: 32423915 DOI: 10.1128/iai.00288-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 05/15/2020] [Indexed: 11/20/2022] Open
Abstract
Cryptococcus neoformans is a fungal pathogen that kills almost 200,000 people each year and is distinguished by abundant and unique surface glycan structures that are rich in xylose. A mutant strain of C. neoformans that cannot transport xylose precursors into the secretory compartment is severely attenuated in virulence in mice yet surprisingly is not cleared. We found that this strain failed to induce the nonprotective T helper cell type 2 (Th2) responses characteristic of wild-type infection, instead promoting sustained interleukin 12p40 (IL-12p40) induction and increased IL-17A (IL-17) production. It also stimulated dendritic cells to release high levels of proinflammatory cytokines, a behavior we linked to xylose expression. We further discovered that inducible bronchus-associated lymphoid tissue (iBALT) forms in response to infection with either wild-type cryptococci or the mutant strain with reduced surface xylose; although iBALT formation is slowed in the latter case, the tissue is better organized. Finally, our temporal studies suggest that lymphoid structures in the lung restrict the spread of mutant fungi for at least 18 weeks after infection, which is in contrast to ineffective control of the pathogen after infection with wild-type cells. These studies demonstrate the role of xylose in modulation of host response to a fungal pathogen and show that cryptococcal infection triggers iBALT formation.
Collapse
|
16
|
Billmyre RB, Applen Clancey S, Li LX, Doering TL, Heitman J. 5-fluorocytosine resistance is associated with hypermutation and alterations in capsule biosynthesis in Cryptococcus. Nat Commun 2020; 11:127. [PMID: 31913284 PMCID: PMC6949227 DOI: 10.1038/s41467-019-13890-z] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 11/29/2019] [Indexed: 12/27/2022] Open
Abstract
Patients infected with the fungal pathogen Cryptococcus are most effectively treated with a combination of 5-fluorocytosine (5FC) and amphotericin B. 5FC acts as a prodrug, which is converted into toxic 5-fluorouracil (5FU) upon uptake into fungal cells. However, the pathogen frequently develops resistance through unclear mechanisms. Here we show that resistance to 5FC in Cryptococcus deuterogattii is acquired more frequently in isolates with defects in DNA mismatch repair that confer an elevated mutation rate. We use whole genome sequencing of 16 independent isolates to identify mutations associated with 5FC resistance in vitro. We find mutations in known resistance genes (FUR1 and FCY2) and in a gene UXS1, previously shown to encode an enzyme that converts UDP-glucuronic acid to UDP-xylose for capsule biosynthesis, but not known to play a role in 5FC metabolism. Mutations in UXS1 lead to accumulation of UDP-glucuronic acid and alterations in nucleotide metabolism, which appear to suppress toxicity of both 5FC and its toxic derivative 5FU. The authors show that resistance to the antifungal 5-fluorocytosine in Cryptococcus deuterogattii is acquired more frequently in isolates with elevated mutation rate, and is associated with alterations in capsule biosynthesis and nucleotide metabolism.
Collapse
Affiliation(s)
- R Blake Billmyre
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA.,Stowers Institute for Medical Research, 1000 E 50th St., Kansas City, MO, 64110, USA
| | - Shelly Applen Clancey
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA
| | - Lucy X Li
- Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, MO, 63110, USA
| | - Tamara L Doering
- Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, MO, 63110, USA
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA.
| |
Collapse
|
17
|
Son YE, Fu C, Jung WH, Oh SH, Kwak JH, Cardenas ME, Heitman J, Park HS. Pbp1-Interacting Protein Mkt1 Regulates Virulence and Sexual Reproduction in Cryptococcus neoformans. Front Cell Infect Microbiol 2019; 9:355. [PMID: 31681631 PMCID: PMC6811503 DOI: 10.3389/fcimb.2019.00355] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 10/02/2019] [Indexed: 12/31/2022] Open
Abstract
The Mkt1–Pbp1 complex promotes mating-type switching by regulating the translation of HO mRNA in Saccharomyces cerevisiae. Here, we performed in vivo immunoprecipitation assays and mass spectrometry analyses in the human fungal pathogen Cryptococcus neoformans to show that Pbp1, a poly(A)-binding protein-binding protein, interacts with Mkt1 containing a PIN like-domain. Association of Pbp1 with Mkt1 was confirmed by co-immunoprecipitation assays. Results of spot dilution growth assays showed that unlike pbp1 deletion mutant strains, mkt1 deletion mutant strains were not resistant to heat stress compared with wild-type. However, similar to the pbp1 deletion mutant strains, the mkt1 deletion mutants exhibited both, defective dikaryotic hyphal production and reduced pheromone gene (MFα1) expression during mating. In addition, deletion of mkt1 caused attenuated virulence in a murine intranasal inhalation model. Taken together, our findings reveal that Mkt1 plays a crucial role in sexual reproduction and virulence in C. neoformans.
Collapse
Affiliation(s)
- Ye-Eun Son
- School of Food Science and Biotechnology, Institute of Agricultural Science and Technology, Kyungpook National University, Daegu, South Korea
| | - Ci Fu
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, United States
| | - Won-Hee Jung
- School of Food Science and Biotechnology, Institute of Agricultural Science and Technology, Kyungpook National University, Daegu, South Korea
| | - Sang-Hun Oh
- School of Life Science, Handong Global University, Pohang, South Korea
| | - Jin-Hwan Kwak
- School of Life Science, Handong Global University, Pohang, South Korea
| | - Maria E Cardenas
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, United States
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, United States
| | - Hee-Soo Park
- School of Food Science and Biotechnology, Institute of Agricultural Science and Technology, Kyungpook National University, Daegu, South Korea
| |
Collapse
|
18
|
Abstract
Melanins are dark green, brown, or black pigments that serve as antioxidant, reactive oxygen species (ROS) scavengers that protect fungal pathogens from radiation and host immune responses. Cryptococcus neoformans, the major etiological agent of fungal meningoencephalitis, also utilizes melanin as a key virulence factor. In this basidiomycete pathogen, melanin production is regulated by the cAMP and high-osmolarity glycerol response (HOG) pathways, and yet its complex signaling networks remain poorly described. In this study, we uncovered novel melanin synthesis regulatory networks consisting of core transcription factors (TFs), including Bzp4, Usv101, Hob1, and Mbs1, and core kinases Gsk3 and Kic1. These networks were identified through coupling systematic analyses of the expression and epistatic relationships of TF and kinase mutant libraries in the presence of diverse melanin substrates with transcriptome profiling of the core TF mutants. Thus, this report provides comprehensive insight into the melanin-regulating pathways in C. neoformans and other fungal pathogens. Melanin is an antioxidant polyphenol pigment required for the pathogenicity of many fungal pathogens, but comprehensive regulatory mechanisms remain unidentified. In this study, we systematically analyzed melanin-regulating signaling pathways in Cryptococcus neoformans and identified four melanin-regulating core transcription factors (TFs), Bzp4, Usv101, Mbs1, and Hob1, required for induction of the laccase gene (LAC1). Bzp4, Usv101, and Mbs1 independently regulate LAC1 induction, whereas Hob1 controls Bzp4 and Usv101 expression. Both Bzp4 and Usv101 are localized in the cytoplasm under nutrient-rich conditions (i.e., in the presence of yeast extract-peptone-dextrose [YPD] medium) but translocate into the nucleus upon nutrient starvation (i.e., in the presence of yeast nitrogen base [YNB] medium without glucose), and Mbs1 is constitutively localized in the nucleus. Notably, the cAMP pathway is not involved in regulation of the four TFs, but the high-osmolarity glycerol response (HOG) pathway negatively regulates induction of BZP4 and LAC1. Next, we searched for potential kinases upstream of the core TFs and identified nine core kinases; their deletion led to defective melanin production and LAC1 induction. Deletion of GSK3 or KIC1 abolished induction of LAC1 and BZP4 and perturbed nuclear translocation of Bzp4. Notably, Gsk3 also regulated expression of HOB1, USV101, and MBS1, indicating that it is a critical melanin-regulating kinase. Finally, an RNA sequencing-based transcriptome analysis of the wild-type strain and of bzp4Δ, usv101Δ, hob1Δ, and mbs1Δ strains under nutrient-rich and nutrient-starved conditions revealed that the melanin-regulating core TFs govern redundant and distinct classes of genes involved in a variety of biological processes.
Collapse
|
19
|
Caza M, Kronstad JW. The cAMP/Protein Kinase a Pathway Regulates Virulence and Adaptation to Host Conditions in Cryptococcus neoformans. Front Cell Infect Microbiol 2019; 9:212. [PMID: 31275865 PMCID: PMC6592070 DOI: 10.3389/fcimb.2019.00212] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 05/31/2019] [Indexed: 12/28/2022] Open
Abstract
Nutrient sensing is critical for adaptation of fungi to environmental and host conditions. The conserved cAMP/PKA signaling pathway contributes to adaptation by sensing the availability of key nutrients such as glucose and directing changes in gene expression and metabolism. Interestingly, the cAMP/PKA pathway in fungal pathogens also influences the expression of virulence determinants in response to nutritional and host signals. For instance, protein kinase A (PKA) in the human pathogen Cryptococcus neoformans plays a central role in orchestrating phenotypic changes, such as capsule elaboration and melanin production, that directly impact disease development. In this review, we focus first on insights into the role of the cAMP/PKA pathway in nutrient sensing for the model yeast Saccharomyces cerevisiae to provide a foundation for understanding the pathway in C. neoformans. We then discuss key features of cAMP/PKA signaling in C. neoformans including new insights emerging from the analysis of transcriptional and proteomic changes in strains with altered PKA activity and expression. Finally, we highlight recent studies that connect the cAMP/PKA pathway to cell surface remodeling and the formation of titan cells.
Collapse
Affiliation(s)
- Mélissa Caza
- Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - James W Kronstad
- Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
20
|
Abstract
Cryptococcus neoformans is a fungal pathogen that primarily affects severely immunocompromised patients, resulting in 200,000 deaths every year. This yeast occurs in the environment and can establish disease upon inhalation into the lungs of a mammalian host. In this harsh environment it must survive engulfment by host phagocytes, including the oxidative stresses it experiences inside them. To adapt to these challenging conditions, C. neoformans deploys a variety of regulatory proteins to alter gene expression levels and enhance its ability to survive. We have elucidated the role of a protein complex that regulates the cryptococcal response to oxidative stress, survival within phagocytes, and ability to cause disease. These findings are important because they advance our understanding of cryptococcal disease, which we hope will help in the efforts to control this devastating infection. Cryptococcus neoformans kills 200,000 people worldwide each year. After inhalation, this environmental yeast proliferates either extracellularly or within host macrophages. Under conditions of immunocompromise, cryptococci disseminate from the lungs to the brain, causing a deadly meningoencephalitis that is difficult and expensive to treat. Cryptococcal adaptation to the harsh lung environment is a critical first step in its pathogenesis, and consequently a compelling topic of study. This adaptation is mediated by a complex transcriptional program that integrates cellular responses to environmental stimuli. Although several key regulators in this process have been examined, one that remains understudied in C. neoformans is the Mediator complex. In other organisms, this complex promotes transcription of specific genes by increasing assembly of the RNA polymerase II preinitiation complex. We focused on the Kinase Module of Mediator, which consists of cyclin C (Ssn801), cyclin-dependent kinase 8 (Cdk8), Med12, and Med13. This module provides important inhibitory control of Mediator complex assembly and activity. Using transcriptomics, we discovered that Cdk8 and Ssn801 together regulate cryptococcal functions such as the ability to grow on acetate and the response to oxidative stress, both of which were experimentally validated. Deletion of CDK8 yielded altered mitochondrial morphology and the dysregulation of genes involved in oxidation-reduction processes. This strain exhibited increased susceptibility to oxidative stress, resulting in an inability of mutant cells to proliferate within phagocytes, decreased lung burdens, and attenuated virulence in vivo. These findings increase our understanding of cryptococcal adaptation to the host environment and its regulation of oxidative stress resistance and virulence.
Collapse
|
21
|
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.
Collapse
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
| |
Collapse
|
22
|
Birkhead M, Naicker SD, Blasich NP, Rukasha I, Thomas J, Sriruttan C, Abrahams S, Mavuso GS, Govender NP. Cryptococcus neoformans: Diagnostic Dilemmas, Electron Microscopy and Capsular Variants. Trop Med Infect Dis 2018; 4:E1. [PMID: 30577542 PMCID: PMC6473520 DOI: 10.3390/tropicalmed4010001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 12/13/2018] [Accepted: 12/14/2018] [Indexed: 11/16/2022] Open
Abstract
Two cases of cryptococcal meningitis went undetected by a cryptococcal antigen (CrAg) lateral flow assay on blood in a reflex CrAg screen-and-treat programme in South Africa, although Cryptococcus neoformans was identified by culturing the cerebrospinal fluid specimens. Further investigations into these discordant diagnostic results included multilocus sequence typing (which showed no mutations in the CAP59 gene) and transmission electron microscopy using a capsule-staining protocol (which revealed a >50% reduction in capsular material in both cases, relative to a control culture). A multi-disciplinary approach for resolving discordant diagnostic test results is recommended.
Collapse
Affiliation(s)
- Monica Birkhead
- National Institute for Communicable Diseases-a Division of the National Health Laboratory Service, 1 Modderfontein Road, Sandringham 2192, South Africa.
| | - Serisha D Naicker
- National Institute for Communicable Diseases-a Division of the National Health Laboratory Service, 1 Modderfontein Road, Sandringham 2192, South Africa.
- School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg 2193, South Africa.
| | - Nozuko P Blasich
- National Institute for Communicable Diseases-a Division of the National Health Laboratory Service, 1 Modderfontein Road, Sandringham 2192, South Africa.
| | - Ivy Rukasha
- National Institute for Communicable Diseases-a Division of the National Health Laboratory Service, 1 Modderfontein Road, Sandringham 2192, South Africa.
| | - Juno Thomas
- National Institute for Communicable Diseases-a Division of the National Health Laboratory Service, 1 Modderfontein Road, Sandringham 2192, South Africa.
- School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg 2193, South Africa.
| | - Charlotte Sriruttan
- National Institute for Communicable Diseases-a Division of the National Health Laboratory Service, 1 Modderfontein Road, Sandringham 2192, South Africa.
- School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg 2193, South Africa.
| | - Shareef Abrahams
- National Health Laboratory Service, Port Elizabeth Provincial Hospital, Cnr Buckingham & Eastbourne Road, Port Elizabeth 6001, South Africa.
| | - Grisselda S Mavuso
- National Health Laboratory Service, Tambo Memorial Hospital, Cnr Hospital & Railway Street, Boksburg 1459, South Africa.
| | - Nelesh P Govender
- National Institute for Communicable Diseases-a Division of the National Health Laboratory Service, 1 Modderfontein Road, Sandringham 2192, South Africa.
- School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg 2193, South Africa.
| |
Collapse
|
23
|
Zhou X, Ballou ER. The Cryptococcus neoformans Titan Cell: From In Vivo Phenomenon to In Vitro Model. CURRENT CLINICAL MICROBIOLOGY REPORTS 2018. [DOI: 10.1007/s40588-018-0107-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
|
24
|
Camacho E, Casadevall A. Cryptococcal Traits Mediating Adherence to Biotic and Abiotic Surfaces. J Fungi (Basel) 2018; 4:jof4030088. [PMID: 30060601 PMCID: PMC6162697 DOI: 10.3390/jof4030088] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Revised: 07/25/2018] [Accepted: 07/27/2018] [Indexed: 01/22/2023] Open
Abstract
Several species in the genus Cryptococcus are facultative intracellular pathogens capable of causing disease associated with high mortality and morbidity in humans. These fungi interact with other organisms in the soil, and these interactions may contribute to the development of adaptation mechanisms that function in virulence by promoting fungal survival in animal hosts. Fungal adhesion molecules, also known as adhesins, have been classically considered as cell-surface or secreted proteins that play critical roles in microbial pathogenesis or in biofilm formation as structural components. Pathogenic Cryptococcus spp. differ from other pathogenic yeasts in having a polysaccharide capsule that covers the cell wall surface and precludes interactions of those structures with host cell receptors. Hence, pathogenic Cryptococcus spp. use unconventional tools for surface attachment. In this essay, we review the unique traits and mechanisms favoring adhesion of Cryptococcus spp. to biotic and abiotic surfaces. Knowledge of the traits that mediate adherence could be exploited in the development of therapeutic, biomedical, and/or industrial products.
Collapse
Affiliation(s)
- Emma Camacho
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, 615 N Wolfe St Room E5132, Baltimore, MD 21205, USA.
| | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, 615 N Wolfe St Room E5132, Baltimore, MD 21205, USA.
| |
Collapse
|
25
|
Son YE, Jung WH, Oh SH, Kwak JH, Cardenas ME, Park HS. Mon1 Is Essential for Fungal Virulence and Stress Survival in Cryptococcus neoformans. MYCOBIOLOGY 2018; 46:114-121. [PMID: 29963312 PMCID: PMC6023253 DOI: 10.1080/12298093.2018.1468053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 04/03/2018] [Accepted: 04/04/2018] [Indexed: 06/08/2023]
Abstract
Mon1 is a guanine nucleotide exchange factor subunit that activates the Ypt7 Rab GTPase and is essential for vacuole trafficking and autophagy in eukaryotic organisms. Here, we identified and characterized the function of Mon1, an ortholog of Saccharomyces cerevisiae Mon1, in a human fungal pathogen, Cryptococcus neoformans. Mutation in mon1 resulted in hypersensitivity to thermal stress. The mon1 deletion mutant exhibited increased sensitivity to cell wall and endoplasmic reticulum stress. However, the mon1 deletion mutant showed more resistance to the antifungal agent fluconazole. In vivo studies demonstrated that compared to the wild-type strain, the mon1 deletion mutant attenuated virulence in the Galleria mellonella insect model. Moreover, the mon1 deletion mutant was avirulent in the murine inhalation model. These results demonstrate that Mon1 plays a crucial role in stress survival and pathogenicity in C. neoformans.
Collapse
Affiliation(s)
- Ye-Eun Son
- School of Food Science and Biotechnology, Institute of Agricultural Science and Technology, Kyungpook National University, Daegu, Republic of Korea
| | - Won-Hee Jung
- School of Food Science and Biotechnology, Institute of Agricultural Science and Technology, Kyungpook National University, Daegu, Republic of Korea
| | - Sang-Hun Oh
- School of Life Science, Handong Global University, Pohang, Republic of Korea
| | - Jin-Hwan Kwak
- School of Life Science, Handong Global University, Pohang, Republic of Korea
| | - Maria E. Cardenas
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA
| | - Hee-Soo Park
- School of Food Science and Biotechnology, Institute of Agricultural Science and Technology, Kyungpook National University, Daegu, Republic of Korea
| |
Collapse
|
26
|
Hommel B, Mukaremera L, Cordero RJB, Coelho C, Desjardins CA, Sturny-Leclère A, Janbon G, Perfect JR, Fraser JA, Casadevall A, Cuomo CA, Dromer F, Nielsen K, Alanio A. Titan cells formation in Cryptococcus neoformans is finely tuned by environmental conditions and modulated by positive and negative genetic regulators. PLoS Pathog 2018; 14:e1006982. [PMID: 29775480 PMCID: PMC5959062 DOI: 10.1371/journal.ppat.1006982] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 03/19/2018] [Indexed: 01/06/2023] Open
Abstract
The pathogenic fungus Cryptococcus neoformans exhibits morphological changes in cell size during lung infection, producing both typical size 5 to 7 μm cells and large titan cells (> 10 μm and up to 100 μm). We found and optimized in vitro conditions that produce titan cells in order to identify the ancestry of titan cells, the environmental determinants, and the key gene regulators of titan cell formation. Titan cells generated in vitro harbor the main characteristics of titan cells produced in vivo including their large cell size (>10 μm), polyploidy with a single nucleus, large vacuole, dense capsule, and thick cell wall. Here we show titan cells derived from the enlargement of progenitor cells in the population independent of yeast growth rate. Change in the incubation medium, hypoxia, nutrient starvation and low pH were the main factors that trigger titan cell formation, while quorum sensing factors like the initial inoculum concentration, pantothenic acid, and the quorum sensing peptide Qsp1p also impacted titan cell formation. Inhibition of ergosterol, protein and nucleic acid biosynthesis altered titan cell formation, as did serum, phospholipids and anti-capsular antibodies in our settings. We explored genetic factors important for titan cell formation using three approaches. Using H99-derivative strains with natural genetic differences, we showed that titan cell formation was dependent on LMP1 and SGF29 genes. By screening a gene deletion collection, we also confirmed that GPR4/5-RIM101, and CAC1 genes were required to generate titan cells and that the PKR1, TSP2, USV101 genes negatively regulated titan cell formation. Furthermore, analysis of spontaneous Pkr1 loss-of-function clinical isolates confirmed the important role of the Pkr1 protein as a negative regulator of titan cell formation. Through development of a standardized and robust in vitro assay, our results provide new insights into titan cell biogenesis with the identification of multiple important factors/pathways.
Collapse
Affiliation(s)
- Benjamin Hommel
- Institut Pasteur, Molecular Mycology Unit, Département de Mycologie, Paris, France
- CNRS UMR2000, Paris, France
- Laboratoire de Parasitologie-Mycologie, Hôpital Saint-Louis, Groupe Hospitalier Lariboisière, Saint-Louis, Fernand Widal, Assistance Publique-Hôpitaux de Paris (AP-HP), Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Liliane Mukaremera
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Radames J. B. Cordero
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD., United States of America
| | - Carolina Coelho
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD., United States of America
| | | | - Aude Sturny-Leclère
- Institut Pasteur, Molecular Mycology Unit, Département de Mycologie, Paris, France
- CNRS UMR2000, Paris, France
| | - Guilhem Janbon
- Institut Pasteur, Unité Biologie des ARN des Pathogènes Fongiques, Département de Mycologie, Paris, France
| | - John R. Perfect
- Division of Infectious Diseases, Department of Medicine, Duke University Medical Center, Durham, North Carolina, United States of America
| | - James A. Fraser
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia
| | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD., United States of America
| | - Christina A. Cuomo
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Françoise Dromer
- Institut Pasteur, Molecular Mycology Unit, Département de Mycologie, Paris, France
- CNRS UMR2000, Paris, France
| | - Kirsten Nielsen
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Alexandre Alanio
- Institut Pasteur, Molecular Mycology Unit, Département de Mycologie, Paris, France
- CNRS UMR2000, Paris, France
- Laboratoire de Parasitologie-Mycologie, Hôpital Saint-Louis, Groupe Hospitalier Lariboisière, Saint-Louis, Fernand Widal, Assistance Publique-Hôpitaux de Paris (AP-HP), Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD., United States of America
- * E-mail:
| |
Collapse
|
27
|
Dambuza IM, Drake T, Chapuis A, Zhou X, Correia J, Taylor-Smith L, LeGrave N, Rasmussen T, Fisher MC, Bicanic T, Harrison TS, Jaspars M, May RC, Brown GD, Yuecel R, MacCallum DM, Ballou ER. The Cryptococcus neoformans Titan cell is an inducible and regulated morphotype underlying pathogenesis. PLoS Pathog 2018; 14:e1006978. [PMID: 29775474 PMCID: PMC5959070 DOI: 10.1371/journal.ppat.1006978] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 03/16/2018] [Indexed: 02/06/2023] Open
Abstract
Fungal cells change shape in response to environmental stimuli, and these morphogenic transitions drive pathogenesis and niche adaptation. For example, dimorphic fungi switch between yeast and hyphae in response to changing temperature. The basidiomycete Cryptococcus neoformans undergoes an unusual morphogenetic transition in the host lung from haploid yeast to large, highly polyploid cells termed Titan cells. Titan cells influence fungal interaction with host cells, including through increased drug resistance, altered cell size, and altered Pathogen Associated Molecular Pattern exposure. Despite the important role these cells play in pathogenesis, understanding the environmental stimuli that drive the morphological transition, and the molecular mechanisms underlying their unique biology, has been hampered by the lack of a reproducible in vitro induction system. Here we demonstrate reproducible in vitro Titan cell induction in response to environmental stimuli consistent with the host lung. In vitro Titan cells exhibit all the properties of in vivo generated Titan cells, the current gold standard, including altered capsule, cell wall, size, high mother cell ploidy, and aneuploid progeny. We identify the bacterial peptidoglycan subunit Muramyl Dipeptide as a serum compound associated with shift in cell size and ploidy, and demonstrate the capacity of bronchial lavage fluid and bacterial co-culture to induce Titanisation. Additionally, we demonstrate the capacity of our assay to identify established (cAMP/PKA) and previously undescribed (USV101) regulators of Titanisation in vitro. Finally, we investigate the Titanisation capacity of clinical isolates and their impact on disease outcome. Together, these findings provide new insight into the environmental stimuli and molecular mechanisms underlying the yeast-to-Titan transition and establish an essential in vitro model for the future characterization of this important morphotype.
Collapse
Affiliation(s)
- Ivy M. Dambuza
- Medical Research Council Centre for Medical Mycology at the University of Aberdeen, Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, Aberdeen, United Kingdom
| | - Thomas Drake
- Medical Research Council Centre for Medical Mycology at the University of Aberdeen, Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, Aberdeen, United Kingdom
| | - Ambre Chapuis
- Medical Research Council Centre for Medical Mycology at the University of Aberdeen, Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, Aberdeen, United Kingdom
| | - Xin Zhou
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Edgbaston, United Kingdom
| | - Joao Correia
- Medical Research Council Centre for Medical Mycology at the University of Aberdeen, Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, Aberdeen, United Kingdom
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Edgbaston, United Kingdom
| | - Leanne Taylor-Smith
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Edgbaston, United Kingdom
| | - Nathalie LeGrave
- Marine Biodiscovery Centre, Department of Chemistry, University of Aberdeen, Aberdeen, United Kingdom
- Francis Crick Institute, London, United Kingdom
| | - Tim Rasmussen
- Marine Biodiscovery Centre, Department of Chemistry, University of Aberdeen, Aberdeen, United Kingdom
- Institut für Biochemie, Universität Würzburg, Wurzburg, Germany
| | - Matthew C. Fisher
- Dpt. Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Tihana Bicanic
- Institute of Infection and Immunity, St George’s University of London, London, United Kingdom
| | - Thomas S. Harrison
- Institute of Infection and Immunity, St George’s University of London, London, United Kingdom
| | - Marcel Jaspars
- Marine Biodiscovery Centre, Department of Chemistry, University of Aberdeen, Aberdeen, United Kingdom
| | - Robin C. May
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Edgbaston, United Kingdom
| | - Gordon D. Brown
- Medical Research Council Centre for Medical Mycology at the University of Aberdeen, Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, Aberdeen, United Kingdom
| | - Raif Yuecel
- Medical Research Council Centre for Medical Mycology at the University of Aberdeen, Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, Aberdeen, United Kingdom
| | - Donna M. MacCallum
- Medical Research Council Centre for Medical Mycology at the University of Aberdeen, Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, Aberdeen, United Kingdom
| | - Elizabeth R. Ballou
- Medical Research Council Centre for Medical Mycology at the University of Aberdeen, Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, Aberdeen, United Kingdom
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Edgbaston, United Kingdom
| |
Collapse
|
28
|
Unintended Side Effects of Transformation Are Very Rare in Cryptococcus neoformans. G3-GENES GENOMES GENETICS 2018; 8:815-822. [PMID: 29305388 PMCID: PMC5844303 DOI: 10.1534/g3.117.300357] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Received wisdom in the field of fungal biology holds that the process of editing a genome by transformation and homologous recombination is inherently mutagenic. However, that belief is based on circumstantial evidence. We provide the first direct measurement of the effects of transformation on a fungal genome by sequencing the genomes of 29 transformants and 30 untransformed controls with high coverage. Contrary to the received wisdom, our results show that transformation of DNA segments flanked by long targeting sequences, followed by homologous recombination and selection for a drug marker, is extremely safe. If a transformation deletes a gene, that may create selective pressure for a few compensatory mutations, but even when we deleted a gene, we found fewer than two point mutations per deletion strain, on average. We also tested these strains for changes in gene expression and found only a few genes that were consistently differentially expressed between the wild type and strains modified by genomic insertion of a drug resistance marker. As part of our report, we provide the assembled genome sequence of the commonly used laboratory strain Cryptococcus neoformans var. grubii strain KN99α.
Collapse
|
29
|
Li LX, Rautengarten C, Heazlewood JL, Doering TL. Xylose donor transport is critical for fungal virulence. PLoS Pathog 2018; 14:e1006765. [PMID: 29346417 PMCID: PMC5773217 DOI: 10.1371/journal.ppat.1006765] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 11/22/2017] [Indexed: 12/22/2022] Open
Abstract
Cryptococcus neoformans, an AIDS-defining opportunistic pathogen, is the leading cause of fungal meningitis worldwide and is responsible for hundreds of thousands of deaths annually. Cryptococcal glycans are required for fungal survival in the host and for pathogenesis. Most glycans are made in the secretory pathway, although the activated precursors for their synthesis, nucleotide sugars, are made primarily in the cytosol. Nucleotide sugar transporters are membrane proteins that solve this topological problem, by exchanging nucleotide sugars for the corresponding nucleoside phosphates. The major virulence factor of C. neoformans is an anti-phagocytic polysaccharide capsule that is displayed on the cell surface; capsule polysaccharides are also shed from the cell and impede the host immune response. Xylose, a neutral monosaccharide that is absent from model yeast, is a significant capsule component. Here we show that Uxt1 and Uxt2 are both transporters specific for the xylose donor, UDP-xylose, although they exhibit distinct subcellular localization, expression patterns, and kinetic parameters. Both proteins also transport the galactofuranose donor, UDP-galactofuranose. We further show that Uxt1 and Uxt2 are required for xylose incorporation into capsule and protein; they are also necessary for C. neoformans to cause disease in mice, although surprisingly not for fungal viability in the context of infection. These findings provide a starting point for deciphering the substrate specificity of an important class of transporters, elucidate a synthetic pathway that may be productively targeted for therapy, and contribute to our understanding of fundamental glycobiology.
Collapse
Affiliation(s)
- Lucy X. Li
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | | | | | - Tamara L. Doering
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
- * E-mail:
| |
Collapse
|
30
|
Abstract
Cryptococcus neoformans is a human pathogenic yeast that causes hundreds of thousands of deaths worldwide among susceptible individuals, in particular, HIV+ patients. This yeast has developed several adaptation mechanisms that allow replication within the host. During decades, this yeast has been well known for a very peculiar and unique structure that contributes to virulence, a complex polysaccharide capsule that surrounds the cell wall. In contrast to other fungal pathogens, such as Candida albicans or Aspergillus fumigatus, the role of morphological transitions has not been studied in the virulence of Cryptococcus neoformans since this yeast does not form hyphae during infection. However, in the last years, different groups have described the ability of this fungus to change its size during infection. In particular, Cryptococcus can form "titan cells," which are blastoconidia of an abnormal large size. Since their discovery, there is increasing evidence that these cells contribute, not only to long-term persistence in the host, but they can also actively participate in the development of the disease. Recently, several groups have simultaneously described different media that induce the appearance of titan cells in laboratory conditions. Using these conditions, new inducing factors and signaling pathways involved in this transition have been described. In this article, we will review the main phenotypic features of these cells, factors, and transduction pathways that induce cell growth, and how titan cells contribute to the disease caused by this pathogen.
Collapse
|
31
|
Song Y, Laureijssen-van de Sande WWJ, Moreno LF, Gerrits van den Ende B, Li R, de Hoog S. Comparative Ecology of Capsular Exophiala Species Causing Disseminated Infection in Humans. Front Microbiol 2017; 8:2514. [PMID: 29312215 PMCID: PMC5742258 DOI: 10.3389/fmicb.2017.02514] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 12/04/2017] [Indexed: 12/15/2022] Open
Abstract
Exophiala spinifera and Exophiala dermatitidis (Fungi: Chaetothyriales) are black yeast agents potentially causing disseminated infection in apparently healthy humans. They are the only Exophiala species producing extracellular polysaccharides around yeast cells. In order to gain understanding of eventual differences in intrinsic virulence of the species, their clinical profiles were compared and found to be different, suggesting pathogenic strategies rather than coincidental opportunism. Ecologically relevant factors were compared in a model set of strains of both species, and significant differences were found in clinical and environmental preferences, but virulence, tested in Galleria mellonella larvae, yielded nearly identical results. Virulence factors, i.e., melanin, capsule and muriform cells responded in opposite direction under hydrogen peroxide and temperature stress and thus were inconsistent with their hypothesized role in survival of phagocytosis. On the basis of physiological profiles, possible natural habitats of both species were extrapolated, which proved to be environmental rather than animal-associated. Using comparative genomic analyses we found differences in gene content related to lipid metabolism, cell wall modification and polysaccharide capsule production. Despite the fact that both species cause disseminated infections in apparently healthy humans, it is concluded that they are opportunists rather than pathogens.
Collapse
Affiliation(s)
- Yinggai Song
- Department of Dermatology, Peking University First Hospital, Beijing, China.,Research Center for Medical Mycology, Peking University, Beijing, China.,Beijing Key Laboratory of Molecular Diagnosis of Dermatoses, Peking University First Hospital, Beijing, China.,Westerdijk Fungal Biodiversity Institute, Utrecht, Netherlands
| | | | | | | | - Ruoyu Li
- Department of Dermatology, Peking University First Hospital, Beijing, China.,Research Center for Medical Mycology, Peking University, Beijing, China.,Beijing Key Laboratory of Molecular Diagnosis of Dermatoses, Peking University First Hospital, Beijing, China
| | - Sybren de Hoog
- Westerdijk Fungal Biodiversity Institute, Utrecht, Netherlands.,Center of Expertise in Mycology Radboudumc/CWZ, Radboud University Nijmegen Medical Center, Nijmegen, Netherlands
| |
Collapse
|
32
|
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.
Collapse
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.
| |
Collapse
|
33
|
Duarte-Oliveira C, Rodrigues F, Gonçalves SM, Goldman GH, Carvalho A, Cunha C. The Cell Biology of the Trichosporon-Host Interaction. Front Cell Infect Microbiol 2017; 7:118. [PMID: 28439501 PMCID: PMC5383668 DOI: 10.3389/fcimb.2017.00118] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 03/23/2017] [Indexed: 11/13/2022] Open
Abstract
Fungi of the genus Trichosporon are increasingly recognized as causative agents of superficial and invasive fungal disease in humans. Although most species are considered commensals of the human skin and gastrointestinal tract, these basidiomycetes are an increasing cause of fungal disease among immunocompromised hosts, such as hematological patients and solid organ transplant recipients. The initiation of commensal or pathogenic programs by Trichosporon spp. involves the adaptation to the host microenvironment and its immune system. However, the exact virulence factors activated upon the transition to a pathogenic lifestyle, including the intricate biology of the cell wall, and how these interact with and subvert the host immune responses remain largely unknown. Here, we revisit our current understanding of the virulence attributes of Trichosporon spp., particularly T. asahii, and their interaction with the host immune system, and accommodate this knowledge within novel perspectives on fungal diagnostics and therapeutics.
Collapse
Affiliation(s)
- Cláudio Duarte-Oliveira
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of MinhoBraga, Portugal.,ICVS/3B's - PT Government Associate LaboratoryBraga/Guimarães, Portugal
| | - Fernando Rodrigues
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of MinhoBraga, Portugal.,ICVS/3B's - PT Government Associate LaboratoryBraga/Guimarães, Portugal
| | - Samuel M Gonçalves
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of MinhoBraga, Portugal.,ICVS/3B's - PT Government Associate LaboratoryBraga/Guimarães, Portugal
| | - Gustavo H Goldman
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São PauloSão Paulo, Brazil
| | - Agostinho Carvalho
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of MinhoBraga, Portugal.,ICVS/3B's - PT Government Associate LaboratoryBraga/Guimarães, Portugal
| | - Cristina Cunha
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of MinhoBraga, Portugal.,ICVS/3B's - PT Government Associate LaboratoryBraga/Guimarães, Portugal
| |
Collapse
|
34
|
Taylor-Smith LM, May RC. New weapons in the Cryptococcus infection toolkit. Curr Opin Microbiol 2016; 34:67-74. [PMID: 27522351 DOI: 10.1016/j.mib.2016.07.018] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2016] [Accepted: 07/12/2016] [Indexed: 12/30/2022]
Abstract
The global burden of fungal infections is unacceptably high. The human fungal pathogen Cryptococcus neoformans causes cryptococcosis and accounts for a significant proportion of this burden. Cryptococci undergo a number of elaborate interactions with their hosts, including survival and proliferation within phagocytes as well as dissemination to the central nervous system and other tissues. In this review we highlight a number of exciting recent advances in the field of cryptococcal biology. In particular we discuss new insights into cryptococcal morphology and its impact on virulence, as well as describing novel findings revealing how cryptoccoci may 'talk' to each other.
Collapse
Affiliation(s)
- Leanne M Taylor-Smith
- Institute of Microbiology and Infection and School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Robin C May
- Institute of Microbiology and Infection and School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
| |
Collapse
|
35
|
Ding H, Mayer FL, Sánchez-León E, de S Araújo GR, Frases S, Kronstad JW. Networks of fibers and factors: regulation of capsule formation in Cryptococcus neoformans. F1000Res 2016; 5. [PMID: 27516877 PMCID: PMC4979528 DOI: 10.12688/f1000research.8854.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/12/2016] [Indexed: 12/15/2022] Open
Abstract
The ability of the pathogenic fungus
Cryptococcus neoformans to cause life-threatening meningoencephalitis in immunocompromised individuals is due in large part to elaboration of a capsule consisting of polysaccharide fibers. The size of the cell-associated capsule is remarkably responsive to a variety of environmental and host conditions, but the mechanistic details of the regulation, synthesis, trafficking, and attachment of the polysaccharides are poorly understood. Recent studies reveal a complex network of transcription factors that influence capsule elaboration in response to several different signals of relevance to disease (e.g., iron deprivation). The emerging complexity of the network is consistent with the diversity of conditions that influence the capsule and illustrates the responsiveness of the fungus to both the environment and mammalian hosts.
Collapse
Affiliation(s)
- Hao Ding
- Michael Smith Laboratories, University of British Columbia, Vancouver, Canada
| | - François L Mayer
- Michael Smith Laboratories, University of British Columbia, Vancouver, Canada
| | - Eddy Sánchez-León
- Michael Smith Laboratories, University of British Columbia, Vancouver, Canada
| | - Glauber R de S Araújo
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Susana Frases
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - James W Kronstad
- Michael Smith Laboratories, University of British Columbia, Vancouver, Canada.,Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
| |
Collapse
|