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Roosen L, Maes D, Musetta L, Himmelreich U. Preclinical Models for Cryptococcosis of the CNS and Their Characterization Using In Vivo Imaging Techniques. J Fungi (Basel) 2024; 10:146. [PMID: 38392818 PMCID: PMC10890286 DOI: 10.3390/jof10020146] [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: 11/30/2023] [Revised: 01/24/2024] [Accepted: 01/30/2024] [Indexed: 02/24/2024] Open
Abstract
Infections caused by Cryptococcus neoformans and Cryptococcus gattii remain a challenge to our healthcare systems as they are still difficult to treat. In order to improve treatment success, in particular for infections that have disseminated to the central nervous system, a better understanding of the disease is needed, addressing questions like how it evolves from a pulmonary to a brain disease and how novel treatment approaches can be developed and validated. This requires not only clinical research and research on the microorganisms in a laboratory environment but also preclinical models in order to study cryptococci in the host. We provide an overview of available preclinical models, with particular emphasis on models of cryptococcosis in rodents. In order to further improve the characterization of rodent models, in particular the dynamic aspects of disease manifestation, development, and ultimate treatment, preclinical in vivo imaging methods are increasingly used, mainly in research for oncological, neurological, and cardiac diseases. In vivo imaging applications for fungal infections are rather sparse. A second aspect of this review is how research on models of cryptococcosis can benefit from in vivo imaging methods that not only provide information on morphology and tissue structure but also on function, metabolism, and cellular properties in a non-invasive way.
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Affiliation(s)
- Lara Roosen
- Biomedical MRI, Department of Imaging and Pathology, KU Leuven, 3000 Leuven, Belgium
| | - Dries Maes
- Biomedical MRI, Department of Imaging and Pathology, KU Leuven, 3000 Leuven, Belgium
| | - Luigi Musetta
- Biomedical MRI, Department of Imaging and Pathology, KU Leuven, 3000 Leuven, Belgium
| | - Uwe Himmelreich
- Biomedical MRI, Department of Imaging and Pathology, KU Leuven, 3000 Leuven, Belgium
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2
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Tugume L, Ssebambulidde K, Kasibante J, Ellis J, Wake RM, Gakuru J, Lawrence DS, Abassi M, Rajasingham R, Meya DB, Boulware DR. Cryptococcal meningitis. Nat Rev Dis Primers 2023; 9:62. [PMID: 37945681 DOI: 10.1038/s41572-023-00472-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/09/2023] [Indexed: 11/12/2023]
Abstract
Cryptococcus neoformans and Cryptococcus gattii species complexes cause meningoencephalitis with high fatality rates and considerable morbidity, particularly in persons with deficient T cell-mediated immunity, most commonly affecting people living with HIV. Whereas the global incidence of HIV-associated cryptococcal meningitis (HIV-CM) has decreased over the past decade, cryptococcosis still accounts for one in five AIDS-related deaths globally due to the persistent burden of advanced HIV disease. Moreover, mortality remains high (~50%) in low-resource settings. The armamentarium to decrease cryptococcosis-associated mortality is expanding: cryptococcal antigen screening in the serum and pre-emptive azole therapy for cryptococcal antigenaemia are well established, whereas enhanced pre-emptive combination treatment regimens to improve survival of persons with cryptococcal antigenaemia are in clinical trials. Short courses (≤7 days) of amphotericin-based therapy combined with flucytosine are currently the preferred options for induction therapy of cryptococcal meningitis. Whether short-course induction regimens improve long-term morbidity such as depression, reduced neurocognitive performance and physical disability among survivors is the subject of further study. Here, we discuss underlying immunology, changing epidemiology, and updates on the management of cryptococcal meningitis with emphasis on HIV-associated disease.
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Affiliation(s)
- Lillian Tugume
- Infectious Diseases Institute, Makerere University, Kampala, Uganda.
| | - Kenneth Ssebambulidde
- Infectious Diseases Institute, Makerere University, Kampala, Uganda
- Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - John Kasibante
- Infectious Diseases Institute, Makerere University, Kampala, Uganda
| | - Jayne Ellis
- Infectious Diseases Institute, Makerere University, Kampala, Uganda
- Clinical Research Department, Faculty of Infectious and Tropical Diseases London School of Hygiene and Tropical Medicine, London, UK
| | - Rachel M Wake
- Institute for Infection and Immunity, St George's University of London, London, UK
| | - Jane Gakuru
- Infectious Diseases Institute, Makerere University, Kampala, Uganda
| | - David S Lawrence
- Clinical Research Department, Faculty of Infectious and Tropical Diseases London School of Hygiene and Tropical Medicine, London, UK
- Botswana Harvard AIDS Institute Partnership, Gaborone, Botswana
| | - Mahsa Abassi
- Department of Medicine, University of Minnesota, Minneapolis, MN, USA
| | - Radha Rajasingham
- Department of Medicine, University of Minnesota, Minneapolis, MN, USA
| | - David B Meya
- Infectious Diseases Institute, Makerere University, Kampala, Uganda
- Department of Medicine, University of Minnesota, Minneapolis, MN, USA
| | - David R Boulware
- Department of Medicine, University of Minnesota, Minneapolis, MN, USA
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3
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Zhao P, Zhuang Z, Guan X, Yang J, Wang W, Kuang Z. Crystal structure of the 3-ketodihydrosphingosine reductase TSC10 from Cryptococcus neoformans. Biochem Biophys Res Commun 2023; 670:73-78. [PMID: 37285720 DOI: 10.1016/j.bbrc.2023.05.109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Accepted: 05/25/2023] [Indexed: 06/09/2023]
Abstract
The second step in the de novo sphingolipid biosynthesis is the reduction of 3-ketodihydrosphingosine by 3-ketodihydrosphingosine reductase (KDSR) to produce dihydrosphingosine (sphinganine). Fungal TSC10 and mammalian KDSR (also named FVT-1) proteins are the enzymes responsible for this process and they belong to the short-chain dehydrogenase/reductase (SDR) superfamily. Albeit that both fungal and mammalian 3-ketodihydrosphingosine reductases were identified more than a decade ago, no structure of these enzymes from any species has been experimentally determined. Here we report the crystal structure of the catalytic domain of TSC10 from Cryptococcus neoformans in complex with NADPH. cnTSC10 adopts a Rossmann fold with a central seven-stranded β-sheet flanked by α-helices on both sides. Several regions are disordered that include the segment connecting the serine and tyrosine residues of the catalytic triad, the so-called 'substrate loop', and the C-terminal region that often participates in homo-tetramerization in other SDRs. In addition, the cofactor NADPH is not fully ordered. These structural features indicate that the catalytic site of cnTSC10 possesses significant flexibility. cnTSC10 is predominantly dimeric in solution while a minor portion of the protein forms homo-tetramer. The crystal structure reveals that the homo-dimer interface involves both hydrophobic and hydrophilic interactions mediated by helices α4 and α5, as well as the loop connecting strand β4 and helix α4. Because residues forming hydrogen bonds and salt bridges in the dimer interface are not conserved between fungal TSC10 and mammalian KDSR proteins, it might be possible to develop inhibitors that selectively target fungal TSC10 dimerization.
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Affiliation(s)
- Panqi Zhao
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China; Guangdong Provincial Key Laboratory of Bioengineering Medicine, Guangzhou, 510632, China; Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou, 510632, China; National Engineering Research Center of Genetic Medicine, Guangzhou, 510632, China
| | - Zewen Zhuang
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China; Guangdong Provincial Key Laboratory of Bioengineering Medicine, Guangzhou, 510632, China; Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou, 510632, China; National Engineering Research Center of Genetic Medicine, Guangzhou, 510632, China
| | - Xueyan Guan
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China; Guangdong Provincial Key Laboratory of Bioengineering Medicine, Guangzhou, 510632, China; Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou, 510632, China; National Engineering Research Center of Genetic Medicine, Guangzhou, 510632, China
| | - Jinjin Yang
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China; Guangdong Provincial Key Laboratory of Bioengineering Medicine, Guangzhou, 510632, China; Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou, 510632, China; National Engineering Research Center of Genetic Medicine, Guangzhou, 510632, China
| | - Weiwei Wang
- Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Zhihe Kuang
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China; Guangdong Provincial Key Laboratory of Bioengineering Medicine, Guangzhou, 510632, China; Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou, 510632, China; National Engineering Research Center of Genetic Medicine, Guangzhou, 510632, China.
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4
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Pereira de Sa N, Del Poeta M. Sterylglucosides in Fungi. J Fungi (Basel) 2022; 8:1130. [PMID: 36354897 PMCID: PMC9698648 DOI: 10.3390/jof8111130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 10/24/2022] [Accepted: 10/24/2022] [Indexed: 11/16/2022] Open
Abstract
Sterylglucosides (SGs) are sterol conjugates widely distributed in nature. Although their universal presence in all living organisms suggests the importance of this kind of glycolipids, they are yet poorly understood. The glycosylation of sterols confers a more hydrophilic character, modifying biophysical properties of cell membranes and altering immunogenicity of the cells. In fungi, SGs regulate different cell pathways to help overcome oxygen and pH challenges, as well as help to accomplish cell recycling and other membrane functions. At the same time, the level of these lipids is highly controlled, especially in wild-type fungi. In addition, modulating SGs metabolism is becoming a novel tool for vaccine and antifungal development. In the present review, we bring together multiple observations to emphasize the underestimated importance of SGs for fungal cell functions.
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Affiliation(s)
- Nivea Pereira de Sa
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, NY 11794, USA
| | - Maurizio Del Poeta
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, NY 11794, USA
- Institute of Chemical Biology and Drug Discovery (ICB&DD), Stony Brook, NY 11794, USA
- Division of Infectious Diseases, School of Medicine, Stony Brook University, Stony Brook, NY 11794, USA
- Veterans Administration Medical Center, Northport, NY 11768, USA
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5
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Rathore SS, Sathiyamoorthy J, Lalitha C, Ramakrishnan J. A holistic review on Cryptococcus neoformans. Microb Pathog 2022; 166:105521. [DOI: 10.1016/j.micpath.2022.105521] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 04/06/2022] [Accepted: 04/06/2022] [Indexed: 12/21/2022]
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6
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Wang J, Chen YL, Li YK, Chen DK, He JF, Yao N. Functions of Sphingolipids in Pathogenesis During Host-Pathogen Interactions. Front Microbiol 2021; 12:701041. [PMID: 34408731 PMCID: PMC8366399 DOI: 10.3389/fmicb.2021.701041] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 06/21/2021] [Indexed: 12/23/2022] Open
Abstract
Sphingolipids are a class of membrane lipids that serve as vital structural and signaling bioactive molecules in organisms ranging from yeast to animals. Recent studies have emphasized the importance of sphingolipids as signaling molecules in the development and pathogenicity of microbial pathogens including bacteria, fungi, and viruses. In particular, sphingolipids play key roles in regulating the delicate balance between microbes and hosts during microbial pathogenesis. Some pathogens, such as bacteria and viruses, harness host sphingolipids to promote development and infection, whereas sphingolipids from both the host and pathogen are involved in fungus-host interactions. Moreover, a regulatory role for sphingolipids has been described, but their effects on host physiology and metabolism remain to be elucidated. Here, we summarize the current state of knowledge about the roles of sphingolipids in pathogenesis and interactions with host factors, including how sphingolipids modify pathogen and host metabolism with a focus on pathogenesis regulators and relevant metabolic enzymes. In addition, we discuss emerging perspectives on targeting sphingolipids that function in host-microbe interactions as new therapeutic strategies for infectious diseases.
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Affiliation(s)
- Jian Wang
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resource, School of Agriculture, Sun Yat-sen University, Guangzhou, China
| | - Yi-Li Chen
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resource, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Yong-Kang Li
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resource, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Ding-Kang Chen
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resource, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Jia-Fan He
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resource, School of Agriculture, Sun Yat-sen University, Guangzhou, China
| | - Nan Yao
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resource, School of Agriculture, Sun Yat-sen University, Guangzhou, China
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resource, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
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7
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Strickland AB, Shi M. Mechanisms of fungal dissemination. Cell Mol Life Sci 2021; 78:3219-3238. [PMID: 33449153 PMCID: PMC8044058 DOI: 10.1007/s00018-020-03736-z] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 11/23/2020] [Accepted: 12/08/2020] [Indexed: 12/13/2022]
Abstract
Fungal infections are an increasing threat to global public health. There are more than six million fungal species worldwide, but less than 1% are known to infect humans. Most of these fungal infections are superficial, affecting the hair, skin and nails, but some species are capable of causing life-threatening diseases. The most common of these include Cryptococcus neoformans, Aspergillus fumigatus and Candida albicans. These fungi are typically innocuous and even constitute a part of the human microbiome, but if these pathogens disseminate throughout the body, they can cause fatal infections which account for more than one million deaths worldwide each year. Thus, systemic dissemination of fungi is a critical step in the development of these deadly infections. In this review, we discuss our current understanding of how fungi disseminate from the initial infection sites to the bloodstream, how immune cells eliminate fungi from circulation and how fungi leave the blood and enter distant organs, highlighting some recent advances and offering some perspectives on future directions.
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Affiliation(s)
- Ashley B Strickland
- Division of Immunology, Virginia-Maryland College of Veterinary Medicine and Maryland Pathogen Research Institute, University of Maryland, College Park, MD, USA.
| | - Meiqing Shi
- Division of Immunology, Virginia-Maryland College of Veterinary Medicine and Maryland Pathogen Research Institute, University of Maryland, College Park, MD, USA.
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8
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Normile TG, Bryan AM, Del Poeta M. Animal Models of Cryptococcus neoformans in Identifying Immune Parameters Associated With Primary Infection and Reactivation of Latent Infection. Front Immunol 2020; 11:581750. [PMID: 33042164 PMCID: PMC7522366 DOI: 10.3389/fimmu.2020.581750] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 08/12/2020] [Indexed: 12/13/2022] Open
Abstract
Cryptococcus species are environmental fungal pathogens and the causative agents of cryptococcosis. Infection occurs upon inhalation of infectious particles, which proliferate in the lung causing a primary infection. From this primary lung infection, fungal cells can eventually disseminate to other organs, particularly the brain, causing lethal meningoencephalitis. However, in most cases, the primary infection resolves with the formation of a lung granuloma. Upon severe immunodeficiency, dormant cryptococcal cells will start proliferating in the lung granuloma and eventually will disseminate to the brain. Many investigators have sought to study the protective host immune response to this pathogen in search of host parameters that keep the proliferation of cryptococcal cells under control. The majority of the work assimilates research carried out using the primary infection animal model, mainly because a reactivation model has been available only very recently. This review will focus on anti-cryptococcal immunity in both the primary and reactivation models. An understanding of the differences in host immunity between the primary and reactivation models will help to define the key host parameters that control the infections and are important for the research and development of new therapeutic and vaccine strategies against cryptococcosis.
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Affiliation(s)
- Tyler G Normile
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, NY, United States
| | - Arielle M Bryan
- Ingenious Targeting Laboratory Incorporated, Ronkonkoma, NY, United States
| | - Maurizio Del Poeta
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, NY, United States.,Division of Infectious Diseases, School of Medicine, Stony Brook University, Stony Brook, NY, United States.,Veterans Administration Medical Center, Northport, NY, United States
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9
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Genome-wide functional analysis of phosphatases in the pathogenic fungus Cryptococcus neoformans. Nat Commun 2020; 11:4212. [PMID: 32839469 PMCID: PMC7445287 DOI: 10.1038/s41467-020-18028-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 07/30/2020] [Indexed: 12/13/2022] Open
Abstract
Phosphatases, together with kinases and transcription factors, are key components in cellular signalling networks. Here, we present a systematic functional analysis of the phosphatases in Cryptococcus neoformans, a fungal pathogen that causes life-threatening fungal meningoencephalitis. We analyse 230 signature-tagged mutant strains for 114 putative phosphatases under 30 distinct in vitro growth conditions, revealing at least one function for 60 of these proteins. Large-scale virulence and infectivity assays using insect and mouse models indicate roles in pathogenicity for 31 phosphatases involved in various processes such as thermotolerance, melanin and capsule production, stress responses, O-mannosylation, or retromer function. Notably, phosphatases Xpp1, Ssu72, Siw14, and Sit4 promote blood-brain barrier adhesion and crossing by C. neoformans. Together with our previous systematic studies of transcription factors and kinases, our results provide comprehensive insight into the pathobiological signalling circuitry of C. neoformans. Phosphatases are key components in cellular signalling networks. Here, the authors present a systematic functional analysis of phosphatases of the fungal pathogen Cryptococcus neoformans, revealing roles in virulence, stress responses, O-mannosylation, retromer function and other processes.
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10
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Song J, Liu X, Li R. Sphingolipids: Regulators of azole drug resistance and fungal pathogenicity. Mol Microbiol 2020; 114:891-905. [PMID: 32767804 DOI: 10.1111/mmi.14586] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Revised: 07/29/2020] [Accepted: 08/02/2020] [Indexed: 12/14/2022]
Abstract
In recent years, the role of sphingolipids in pathogenic fungi, in terms of pathogenicity and resistance to azole drugs, has been a rapidly growing field. This review describes evidence about the roles of sphingolipids in azole resistance and fungal virulence. Sphingolipids can serve as signaling molecules that contribute to azole resistance through modulation of the expression of drug efflux pumps. They also contribute to azole resistance by participating in various microbial pathways such as the unfolded protein response (UPR), pH-responsive Rim pathway, and pleiotropic drug resistance (PDR) pathway. In addition, sphingolipid signaling and eisosomes also coordinately regulate sphingolipid biosynthesis in response to azole-induced membrane stress. Sphingolipids are important for fungal virulence, playing roles during growth in hosts under stressful conditions, maintenance of cell wall integrity, biofilm formation, and production of various virulence factors. Finally, we discuss the possibility of exploiting fungal sphingolipids for the development of new therapeutic strategies to treat infections caused by pathogenic fungi.
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Affiliation(s)
- Jinxing Song
- The Key Laboratory of Biotechnology for Medicinal Plants of Jiangsu Province and School of Life Science, Jiangsu Normal University, Xuzhou, PR China
| | - Xiao Liu
- The Key Laboratory of Biotechnology for Medicinal Plants of Jiangsu Province and School of Life Science, Jiangsu Normal University, Xuzhou, PR China
| | - Rongpeng Li
- The Key Laboratory of Biotechnology for Medicinal Plants of Jiangsu Province and School of Life Science, Jiangsu Normal University, Xuzhou, PR China
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Abstract
PURPOSE OF REVIEW Defective cell-mediated immunity is a major risk factor for cryptococcosis, a fatal disease if untreated. Cryptococcal meningitis (CM), the main presentation of disseminated disease, occurs through hematogenous spread to the brain from primary pulmonary foci, facilitated by yeast virulence factors. We revisit remarkable recent improvements in the prevention, diagnosis and management of CM. RECENT FINDINGS Cryptococcal antigen (CrAg), main capsular polysaccharide of Cryptococcus spp. is detectable in blood and cerebrospinal fluid of infected patients with point of care lateral flow assays. Recent World Health Organization guidelines recommend 7-day amphotericin B plus flucytosine, then 7-day high dose (1200 mg/day) fluconazole for induction treatment of HIV-associated CM. Management of raised intracranial pressure, a consequence of CM, should rely mainly on daily therapeutic lumbar punctures until normalisation. In HIV-associated CM, following introduction of antifungal therapy, (re)initiation of antiretroviral therapy should be delayed by 4-6 weeks to prevent immune reconstitution inflammatory syndrome, common in CM. CM is a fatal disease whose diagnosis has recently been simplified. Treatment should always include antifungal combination therapy and management of raised intracranial pressure. Screening for immune deficiency should be mandatory in all patients with cryptococcosis.
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12
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Gerstein AC, Jackson KM, McDonald TR, Wang Y, Lueck BD, Bohjanen S, Smith KD, Akampurira A, Meya DB, Xue C, Boulware DR, Nielsen K. Identification of Pathogen Genomic Differences That Impact Human Immune Response and Disease during Cryptococcus neoformans Infection. mBio 2019; 10:e01440-19. [PMID: 31311883 PMCID: PMC6635531 DOI: 10.1128/mbio.01440-19] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 06/10/2019] [Indexed: 12/18/2022] Open
Abstract
Patient outcomes during infection are due to a complex interplay between the quality of medical care, host immunity factors, and the infecting pathogen's characteristics. To probe the influence of pathogen genotype on human survival, immune response, and other parameters of disease, we examined Cryptococcus neoformans isolates collected during the Cryptococcal Optimal Antiretroviral Therapy (ART) Timing (COAT) Trial in Uganda. We measured human participants' survival, meningitis disease parameters, immunologic phenotypes, and pathogen in vitro growth characteristics. We compared those clinical data to whole-genome sequences from 38 C. neoformans isolates of the most frequently observed sequence type (ST), ST93, in our Ugandan participant population and to sequences from an additional 18 strains of 9 other sequence types representing the known genetic diversity within the Ugandan Cryptococcus clinical isolates. We focused our analyses on 652 polymorphisms that were variable among the ST93 genomes, were not in centromeres or extreme telomeres, and were predicted to have a fitness effect. Logistic regression and principal component analysis identified 40 candidate Cryptococcus genes and 3 hypothetical RNAs associated with human survival, immunologic response, or clinical parameters. We infected mice with 17 available KN99α gene deletion strains for these candidate genes and found that 35% (6/17) directly influenced murine survival. Four of the six gene deletions that impacted murine survival were novel. Such bedside-to-bench translational research identifies important candidate genes for future studies on virulence-associated traits in human Cryptococcus infections.IMPORTANCE Even with the best available care, mortality rates in cryptococcal meningitis range from 20% to 60%. Disease is often due to infection by the fungus Cryptococcus neoformans and involves a complex interaction between the human host and the fungal pathogen. Although previous studies have suggested genetic differences in the pathogen impact human disease, it has proven quite difficult to identify the specific C. neoformans genes that impact the outcome of the human infection. Here, we take advantage of a Ugandan patient cohort infected with closely related C. neoformans strains to examine the role of pathogen genetic variants on several human disease characteristics. Using a pathogen whole-genome sequencing approach, we showed that 40 C. neoformans genes are associated with human disease. Surprisingly, many of these genes are specific to Cryptococcus and have unknown functions. We also show deletion of some of these genes alters disease in a mouse model of infection, confirming their role in disease. These findings are particularly important because they are the first to identify C. neoformans genes associated with human cryptococcal meningitis and lay the foundation for future studies that may lead to new treatment strategies aimed at reducing patient mortality.
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Affiliation(s)
- Aleeza C Gerstein
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Katrina M Jackson
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Tami R McDonald
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Yina Wang
- Public Health Research Institute, Rutgers University, Newark, New Jersey, USA
| | - Benjamin D Lueck
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Sara Bohjanen
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Kyle D Smith
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Andrew Akampurira
- Infectious Diseases Institute and School of Medicine, College of Health Sciences, Makerere University, Kampala, Uganda
| | - David B Meya
- Infectious Diseases Institute and School of Medicine, College of Health Sciences, Makerere University, Kampala, Uganda
| | - Chaoyang Xue
- Public Health Research Institute, Rutgers University, Newark, New Jersey, USA
| | - David R Boulware
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota, USA
| | - Kirsten Nielsen
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, Minnesota, USA
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13
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Fabri JHTM, Godoy NL, Rocha MC, Munshi M, Cocio TA, von Zeska Kress MR, Fill TP, da Cunha AF, Del Poeta M, Malavazi I. The AGC Kinase YpkA Regulates Sphingolipids Biosynthesis and Physically Interacts With SakA MAP Kinase in Aspergillus fumigatus. Front Microbiol 2019; 9:3347. [PMID: 30692984 PMCID: PMC6339957 DOI: 10.3389/fmicb.2018.03347] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 12/28/2018] [Indexed: 12/12/2022] Open
Abstract
Sphingolipids (SL) are complex lipids and components of the plasma membrane which are involved in numerous cellular processes, as well as important for virulence of different fungal pathogens. In yeast, SL biosynthesis is regulated by the "AGC kinases" Ypk1 and Ypk2, which also seem to connect the SL biosynthesis with the cell wall integrity (CWI) and the High Osmolarity Glycerol (HOG) pathways. Here, we investigate the role of ypkA Y PK1 in SL biosynthesis and its relationship with the CWI and the HOG pathways in the opportunistic human pathogen Aspergillus fumigatus. We found that ypkA is important for fungal viability, since the ΔypkA strain presented a drastically sick phenotype and complete absence of conidiation. We observed that under repressive condition, the conditional mutant niiA::ypkA exhibited vegetative growth defects, impaired germination and thermosensitivity. In addition, the ypkA loss of function caused a decrease in glycosphingolipid (GSL) levels, especially the metabolic intermediates belonging to the neutral GSL branch including dihydroceramide (DHC), ceramide (Cer), and glucosylceramide (GlcCer), but interestingly a small increase in ergosterol content. Genetic analyzes showed that ypkA genetically interacts with the MAP kinases of CWI and HOG pathways, mpkA and sakA, respectively, while only SakA physically interacts with YpkA. Our results suggest that YpkA is important for fungal survival through the regulation of GSL biosynthesis and cross talks with A. fumigatus MAP kinase pathways.
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Affiliation(s)
| | - Naiane Lima Godoy
- Departamento de Genética e Evolução, Centro de Ciências Biológicas e da Saúde, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Marina Campos Rocha
- Departamento de Genética e Evolução, Centro de Ciências Biológicas e da Saúde, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Mansa Munshi
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, United States
| | - Tiago Alexandre Cocio
- Departamento de Genética e Evolução, Centro de Ciências Biológicas e da Saúde, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Marcia Regina von Zeska Kress
- Departamento de Análises Clínicas Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | | | - Anderson Ferreira da Cunha
- Departamento de Genética e Evolução, Centro de Ciências Biológicas e da Saúde, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Maurizio Del Poeta
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, United States.,Division of Infectious Diseases, School of Medicine, Stony Brook University, Stony Brook, NY, United States.,Institute of Chemical Biology and Drug Discovery, Stony Brook University, Stony Brook, NY, United States.,Veterans Administration Medical Center, Northport, NY, United States
| | - Iran Malavazi
- Departamento de Genética e Evolução, Centro de Ciências Biológicas e da Saúde, Universidade Federal de São Carlos, São Carlos, Brazil
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14
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Casadevall A, Coelho C, Alanio A. Mechanisms of Cryptococcus neoformans-Mediated Host Damage. Front Immunol 2018; 9:855. [PMID: 29760698 PMCID: PMC5936990 DOI: 10.3389/fimmu.2018.00855] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 04/06/2018] [Indexed: 01/22/2023] Open
Abstract
Cryptococcus neoformans is not usually considered a cytotoxic fungal pathogen but there is considerable evidence that this microbe can damage host cells and tissues. In this essay, we review the evidence that C. neoformans damages host cells and note that the mechanisms involved are diverse. We consider C. neoformans-mediated host damage at the molecular, cellular, tissue, and organism level. Direct mechanisms of cytotoxicity include lytic exocytosis, organelle dysfunction, phagolysosomal membrane damage, and cytoskeletal alterations. Cytotoxicity contributes to pathogenesis by interfering with immune effector cell function and disrupting endothelial barriers thus allowing dissemination. When C. neoformans-mediated and immune-mediated host damage is sufficient to affect homeostasis, cryptococcosis occurs at the organism level.
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Affiliation(s)
- Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Johns Hopkins School of Public Health, Baltimore, MD, United States
| | - Carolina Coelho
- Department of Molecular Microbiology and Immunology, Johns Hopkins School of Public Health, Baltimore, MD, United States
| | - Alexandre Alanio
- Department of Molecular Microbiology and Immunology, Johns Hopkins School of Public Health, Baltimore, MD, United States
- Institut Pasteur, Molecular Mycology Unit, 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), Université Paris Diderot, Sorbonne Paris Cité, Paris, France
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15
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Mechanisms of Pulmonary Escape and Dissemination by Cryptococcus neoformans. J Fungi (Basel) 2018; 4:jof4010025. [PMID: 29463005 PMCID: PMC5872328 DOI: 10.3390/jof4010025] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 02/09/2018] [Accepted: 02/16/2018] [Indexed: 12/15/2022] Open
Abstract
Cryptococcus neoformans is a common environmental saprophyte and human fungal pathogen that primarily causes disease in immunocompromised individuals. Similar to many environmentally acquired human fungal pathogens, C. neoformans initiates infection in the lungs. However, the main driver of mortality is invasive cryptococcosis leading to fungal meningitis. After C. neoformans gains a foothold in the lungs, a critical early step in invasion is transversal of the respiratory epithelium. In this review, we summarize current knowledge relating to pulmonary escape. We focus on fungal factors that allow C. neoformans to disseminate from the lungs via intracellular and extracellular routes.
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16
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Squizani ED, Oliveira NK, Reuwsaat JCV, Marques BM, Lopes W, Gerber AL, de Vasconcelos ATR, Lev S, Djordjevic JT, Schrank A, Vainstein MH, Staats CC, Kmetzsch L. Cryptococcal dissemination to the central nervous system requires the vacuolar calcium transporter Pmc1. Cell Microbiol 2017; 20. [PMID: 29113016 DOI: 10.1111/cmi.12803] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 10/27/2017] [Accepted: 10/30/2017] [Indexed: 12/26/2022]
Abstract
Cryptococcus neoformans is a basidiomycetous yeast and the cause of cryptococcosis in immunocompromised individuals. The most severe form of the disease is meningoencephalitis, which is one of the leading causes of death in HIV/AIDS patients. In order to access the central nervous system, C. neoformans relies on the activity of certain virulence factors such as urease, which allows transmigration through the blood-brain barrier. In this study, we demonstrate that the calcium transporter Pmc1 enables C. neoformans to penetrate the central nervous system, because the pmc1 null mutant failed to infect and to survive within the brain parenchyma in a murine systemic infection model. To investigate potential alterations in transmigration pathways in these mutants, global expression profiling of the pmc1 mutant strain was undertaken, and genes associated with urease, the Ca2+ -calcineurin pathway, and capsule assembly were identified as being differentially expressed. Also, a decrease in urease activity was observed in the calcium transporter null mutants. Finally, we demonstrate that the transcription factor Crz1 regulates urease activity and that the Ca2+ -calcineurin signalling pathway positively controls the transcription of calcium transporter genes and factors related to transmigration.
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Affiliation(s)
| | | | | | | | - William Lopes
- Centro de Biotecnologia, UFRGS, Porto Alegre, RS, Brazil
| | - Alexandra L Gerber
- Laboratório Nacional de Computação Científica (LNCC), Petrópolis, RJ, Brazil
| | | | - Sophie Lev
- Fungal Pathogenesis Laboratory, Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, Westmead, NSW, Australia
| | - Julianne T Djordjevic
- Fungal Pathogenesis Laboratory, Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, Westmead, NSW, Australia
| | | | | | | | - Lívia Kmetzsch
- Centro de Biotecnologia, UFRGS, Porto Alegre, RS, Brazil
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17
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Raj S, Nazemidashtarjandi S, Kim J, Joffe L, Zhang X, Singh A, Mor V, Desmarini D, Djordjevic J, Raleigh DP, Rodrigues ML, London E, Del Poeta M, Farnoud AM. Changes in glucosylceramide structure affect virulence and membrane biophysical properties of Cryptococcus neoformans. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:2224-2233. [PMID: 28865794 DOI: 10.1016/j.bbamem.2017.08.017] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 08/03/2017] [Accepted: 08/27/2017] [Indexed: 11/19/2022]
Abstract
Fungal glucosylceramide (GlcCer) is a plasma membrane sphingolipid in which the sphingosine backbone is unsaturated in carbon position 8 (C8) and methylated in carbon position 9 (C9). Studies in the fungal pathogen, Cryptococcus neoformans, have shown that loss of GlcCer synthase activity results in complete loss of virulence in the mouse model. However, whether the loss of virulence is due to the lack of the enzyme or to the loss of the sphingolipid is not known. In this study, we used genetic engineering to alter the chemical structure of fungal GlcCer and studied its effect on fungal growth and pathogenicity. Here we show that unsaturation in C8 and methylation in C9 is required for virulence in the mouse model without affecting fungal growth in vitro or common virulence factors. However, changes in GlcCer structure led to a dramatic susceptibility to membrane stressors resulting in increased cell membrane permeability and rendering the fungal mutant unable to grow within host macrophages. Biophysical studies using synthetic vesicles containing GlcCer revealed that the saturated and unmethylated sphingolipid formed vesicles with higher lipid order that were more likely to phase separate into ordered domains. Taken together, these studies show for the first time that a specific structure of GlcCer is a major regulator of membrane permeability required for fungal pathogenicity.
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Affiliation(s)
- Shriya Raj
- Department of Mycology, Institut Pasteur, Paris, France
| | | | - Jihyun Kim
- Department of Chemistry and Biochemistry, Stony Brook University, Stony Brook, NY, USA
| | - Luna Joffe
- Departamento de Microbiologia Geral, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro (UFRJ), Brazil
| | - Xiaoxue Zhang
- Department of Chemistry and Biochemistry, Stony Brook University, Stony Brook, NY, USA
| | - Ashutosh Singh
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA
| | - Visesato Mor
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA
| | - Desmarini Desmarini
- Fungal Pathogenesis Laboratory, Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, Westmead, NSW, Australia
| | - Julianne Djordjevic
- Fungal Pathogenesis Laboratory, Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, Westmead, NSW, Australia; Westmead Clinical School, University of Sydney at Westmead Hospital, Westmead, NSW, Australia; Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney, NSW, Australia
| | - Daniel P Raleigh
- Department of Chemistry and Biochemistry, Stony Brook University, Stony Brook, NY, USA
| | - Marcio L Rodrigues
- Departamento de Microbiologia Geral, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro (UFRJ), Brazil; Centro de Desenvolvimento Tecnológico em Saúde (CDTS) da Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, Brazil
| | - Erwin London
- Department of Chemistry and Biochemistry, Stony Brook University, Stony Brook, NY, USA
| | - Maurizio Del Poeta
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA; Veterans Administration Medical Center, Northport, NY, USA; Division of Infectious Diseases, Stony Brook University, Stony Brook, NY, USA.
| | - Amir M Farnoud
- Department of Chemical and Biomolecular Engineering, Ohio University, Athens, OH, USA.
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18
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Sphingolipids from the human fungal pathogen Aspergillus fumigatus. Biochimie 2017; 141:9-15. [PMID: 28652019 DOI: 10.1016/j.biochi.2017.06.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 06/21/2017] [Indexed: 01/24/2023]
Abstract
Sphingolipids (SPLs) are key components of the plasma membrane in yeast and filamentous fungi. These molecules are involved in a number of cellular processes, and particularly, SGLs are essential components of the highly polarized fungal growth where they are required for the formation of the polarisome organization at the hyphal apex. Aspergillus fumigatus, a human fungal pathogen, produce SGLs that are discriminated into neutral cerebrosides, glycosylinositolphosphoceramides (GIPCs) and glycosylphosphatidylinositol (GPI) anchors. In addition to complex hydrophilic head groups of GIPCs, A. fumigatus is, to date, the sole fungus that produces a GPI-anchored polysaccharide. These SPLs follow three different biosynthetic pathways. Genetics blockage leading to the inhibition of any SPL biosynthesis or to the alteration of the structure of SPL induces growth and virulence defects. The complete lipid moiety of SPLs is essential for the lipid microdomain organization and their biosynthetic pathways are potential antifungal targets but remains understudied.
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19
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Gerstein AC, Nielsen K. It's not all about us: evolution and maintenance of Cryptococcus virulence requires selection outside the human host. Yeast 2017; 34:143-154. [PMID: 27862271 DOI: 10.1002/yea.3222] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 11/02/2016] [Accepted: 11/04/2016] [Indexed: 12/11/2022] Open
Abstract
Cryptococcus is predominantly an AIDS-related pathogen that causes significant morbidity and mortality in immunocompromised patients. Research studies have historically focused on understanding how the organism causes human disease through the use of in vivo and in vitro model systems to identify virulence factors. Cryptococcus is not an obligate pathogen, however, as human-human transmission is either absent or rare. Selection in the environment must thus be invoked to shape the evolution of this taxa, and directly influences genotypic and trait diversity. Importantly, the evolution and maintenance of pathogenicity must also stem directly from environmental selection. To that end, here we examine abiotic and biotic stresses in the environment, and discuss how they could shape the factors that are commonly identified as important virulence traits. We identify a number of important unanswered questions about Cryptococcus diversity and evolution that are critical for understanding this deadly pathogen, and discuss how implementation of modern sampling and genomic tools could be utilized to answer these questions. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Aleeza C Gerstein
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Kirsten Nielsen
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, Minnesota, USA
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20
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Abstract
Cryptococcus neoformans is a human fungal pathogen and a major cause of fungal meningitis in immunocompromised individuals. Treatment options for cryptococcosis are limited. Of the two major antifungal drug classes, azoles are active against C. neoformans but exert a fungistatic effect, necessitating long treatment regimens and leaving open an avenue for emergence of azole resistance. Drugs of the echinocandin class, which target the glucan synthase and are fungicidal against a number of other fungal pathogens, such as Candida species, are ineffective against C. neoformans. Despite the sensitivity of the target enzyme to the drug, the reasons for the innate resistance of C. neoformans to echinocandins remain unknown. To understand the mechanism of echinocandin resistance in C. neoformans, we screened gene disruption and gene deletion libraries for mutants sensitive to the echinocandin-class drug caspofungin and identified a mutation of CDC50, which encodes the β-subunit of membrane lipid flippase. We found that the Cdc50 protein localized to membranes and that its absence led to plasma membrane defects and enhanced caspofungin penetration into the cell, potentially explaining the increased caspofungin sensitivity. Loss of CDC50 also led to hypersensitivity to the azole-class drug fluconazole. Interestingly, in addition to functioning in drug resistance, CDC50 was also essential for fungal resistance to macrophage killing and for virulence in a murine model of cryptococcosis. Furthermore, the surface of cdc50Δ cells contained increased levels of phosphatidylserine, which has been proposed to act as a macrophage recognition signal. Together, these results reveal a previously unappreciated role of membrane lipid flippase in C. neoformans drug resistance and virulence. Cryptococcus neoformans is a fungal pathogen that is the most common cause of fungal meningitis, causing over 620,000 deaths annually. The treatment options for cryptococcosis are very limited. The most commonly used drugs are either fungistatic (azoles) or highly toxic (amphotericin B). Echinocandins are the newest fungicidal drug class that works well in treating candidiasis and aspergillosis, yet they are ineffective in treating cryptococcosis. In this study, we showed that the regulatory subunit of the lipid translocase (flippase), a protein that regulates the asymmetrical orientation of membrane lipids, is required for C. neoformans resistance to caspofungin, as well as for virulence during infection. This discovery identifies lipid flippase as a potential C. neoformans drug target, which plays an important role in the innate resistance of C. neoformans to echinocandins and in fungal virulence.
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21
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Initiation of phospholipomannan β-1,2 mannosylation involves Bmts with redundant activity, influences its cell wall location and regulates β-glucans homeostasis but is dispensable for Candida albicans systemic infection. Biochimie 2016; 120:96-104. [PMID: 26427558 PMCID: PMC7614791 DOI: 10.1016/j.biochi.2015.09.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 09/25/2015] [Indexed: 11/20/2022]
Abstract
Pathogenic and non-pathogenic fungi synthesize glycosphingolipids, which have a crucial role in growth and viability. Glycosphingolipids also contribute to fungal-associated pathogenesis. The opportunistic yeast pathogen Candida albicans synthesizes phospholipomannan (PLM), which is a glycosphingolipid of the mannosylinositol phosphorylceramide family. Through its lipid and glycan moieties, PLM contributes to the initial recognition of the yeast, causing immune system disorder and persistent fungal disease through activation of host signaling pathways. The lipid moiety of PLM activates the deregulation signaling pathway involved in yeast phagocytosis whereas its glycan moiety, composed of β-1,2 mannosides (β-Mans), participates to inflammatory processes through a mechanism involving Galectin-3. Biosynthesis of PLM β-Mans involves two β-1,2 mannosyltransferases (Bmts) that initiate (Bmt5) and elongate (Bmt6) the glycan chains. After generation of double bmtsΔ mutants, we show that Bmt5 has redundant activity with Bmt2, which can replace Bmt5 in bmt5Δ mutant. We also report that PLM is located in the inner layer of the yeast cell wall. PLM seems to be not essential for systemic infection of the yeast. However, defect of PLM β-mannosylation increases resistance of C. albicans to inhibitors of β-glucans and chitin synthesis, highlighting a role of PLM in cell wall homeostasis.
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22
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Singh A, Rella A, Schwacke J, Vacchi-Suzzi C, Luberto C, Del Poeta M. Transmembrane transporter expression regulated by the glucosylceramide pathway in Cryptococcus neoformans. BMC Res Notes 2015; 8:681. [PMID: 26572681 PMCID: PMC4647647 DOI: 10.1186/s13104-015-1613-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 10/20/2015] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND The sphingolipid glucosylceramide (GlcCer) and factors involved in the fungal GlcCer pathways were shown earlier to be an integral part of fungal virulence, especially in fungal replication at 37 °C, in neutral/alkaline pH and 5 % CO2 environments (e.g. alveolar spaces). Two mutants, ∆gcs 1 lacking glucosylceramide synthase 1 gene (GCS1) which catalyzes the formation of sphingolipid GlcCer from the C9-methyl ceramide and ∆smt1 lacking sphingolipid C9 methyltransferase gene (SMT1), which adds a methyl group to position nine of the sphingosine backbone of ceramide, of this pathway were attenuated in virulence and have a growth defect at the above-mentioned conditions. These mutants with either no or structurally modified GlcCer located on the cell-membrane have reduced membrane rigidity, which may have altered not only the physical location of membrane proteins but also their expression, as the pathogen's mode of adaptation to changing need. Importantly, pathogens are known to adapt themselves to the changing host environments by altering their patterns of gene expression. RESULTS By transcriptional analysis of gene expression, we identified six genes whose expression was changed from their wild-type counterpart grown in the same conditions, i.e. they became either down regulated or up regulated in these two mutants. The microarray data was validated by real-time PCR, which confirmed their fold change in gene expression. All the six genes we identified, viz siderochrome-iron transporter (CNAG_02083), monosaccharide transporter (CNAG_05340), glucose transporter (CNAG_03772), membrane protein (CNAG_03912), membrane transport protein (CNAG_00539), and sugar transporter (CNAG_06963), are membrane-localized and have significantly altered gene expression levels. Therefore, we hypothesize that these genes function either independently or in tandem with a structurally modified cell wall/plasma membrane resulting from the modifications of the GlcCer pathway and thus possibly disrupt transmembrane signaling complex, which in turn contributes to cryptococcal osmotic, pH, ion homeostasis and its pathobiology. CONCLUSION Six genes identified from gene expression microarrays by gene set enrichment analysis and validated by RT-PCR, are membrane located and associated with the growth defect at neutral-alkaline pH due to the absence and or presence of a structurally modified GlcCer. They may be involved in the transmembrane signaling network in Cryptococcus neoformans, and therefore the pathobiology of the fungus in these conditions.
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Affiliation(s)
- Arpita Singh
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, 29425, USA. .,Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, 345 Crispell Dr, Carter Harrison Building, Charlottesville, VA, 22908, USA.
| | - Antonella Rella
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, 29425, USA. .,Department of Molecular Genetics and Microbiology, Stony Brook University, 150 Life Science Building, Stony Brook, NY, 11794, USA.
| | - John Schwacke
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, 29425, USA. .,Integrated Systems and Solutions Division, Scientific Research Corporation, Remount Road, North Charleston, SC, 29406, USA.
| | - Caterina Vacchi-Suzzi
- Department of Preventive Medicine, University of Stony Brook, Stony Brook, NY, 11794, USA.
| | - Chiara Luberto
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, 29425, USA. .,Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, 11794, USA.
| | - Maurizio Del Poeta
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, 29425, USA. .,Department of Molecular Genetics and Microbiology, Stony Brook University, 150 Life Science Building, Stony Brook, NY, 11794, USA. .,Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC, 29425, USA. .,Department of Craniofacial Biology, Medical University of South Carolina, Charleston, SC, 29425, USA. .,Division of Infectious Diseases, Medical University of South Carolina, Charleston, SC, 29425, USA.
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Abstract
Enzymes play key roles in fungal pathogenesis. Manipulation of enzyme expression or activity can significantly alter the infection process, and enzyme expression profiles can be a hallmark of disease. Hence, enzymes are worthy targets for better understanding pathogenesis and identifying new options for combatting fungal infections. Advances in genomics, proteomics, transcriptomics, and mass spectrometry have enabled the identification and characterization of new fungal enzymes. This review focuses on recent developments in the virulence-associated enzymes from Cryptococcus neoformans. The enzymatic suite of C. neoformans has evolved for environmental survival, but several of these enzymes play a dual role in colonizing the mammalian host. We also discuss new therapeutic and diagnostic strategies that could be based on the underlying enzymology.
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Role of Inositol Phosphosphingolipid Phospholipase C1, the Yeast Homolog of Neutral Sphingomyelinases in DNA Damage Response and Diseases. J Lipids 2015; 2015:161392. [PMID: 26346287 PMCID: PMC4544949 DOI: 10.1155/2015/161392] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 07/25/2015] [Accepted: 07/29/2015] [Indexed: 02/06/2023] Open
Abstract
Sphingolipids play a very crucial role in many diseases and are well-known as signaling mediators in many pathways. Sphingolipids are produced during the de novo process in the ER (endoplasmic reticulum) from the nonsphingolipid precursor and comprise both structural and bioactive lipids. Ceramide is the central core of the sphingolipid pathway, and its production has been observed following various treatments that can induce several different cellular effects including growth arrest, DNA damage, apoptosis, differentiation, and senescence. Ceramides are generally produced through the sphingomyelin hydrolysis and catalyzed by the enzyme sphingomyelinase (SMase) in mammals. Presently, there are many known SMases and they are categorized into three groups acid SMases (aSMases), alkaline SMases (alk-SMASES), and neutral SMases (nSMases). The yeast homolog of mammalians neutral SMases is inositol phosphosphingolipid phospholipase C. Yeasts generally have inositol phosphosphingolipids instead of sphingomyelin, which may act as a homolog of mammalian sphingomyelin. In this review, we shall explain the structure and function of inositol phosphosphingolipid phospholipase C1, its localization inside the cells, mechanisms, and its roles in various cell responses during replication stresses and diseases. This review will also give a new basis for our understanding for the mechanisms and nature of the inositol phosphosphingolipid phospholipase C1/nSMase.
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25
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Rella A, Mor V, Farnoud AM, Singh A, Shamseddine AA, Ivanova E, Carpino N, Montagna MT, Luberto C, Del Poeta M. Role of Sterylglucosidase 1 (Sgl1) on the pathogenicity of Cryptococcus neoformans: potential applications for vaccine development. Front Microbiol 2015; 6:836. [PMID: 26322039 PMCID: PMC4531891 DOI: 10.3389/fmicb.2015.00836] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Accepted: 07/29/2015] [Indexed: 01/01/2023] Open
Abstract
Cryptococcosis caused by Cryptococcus neoformans and Cryptococcus gattii affects a large population and is a cause of significant morbidity and mortality. Despite its public health burden, there are currently no vaccines against cryptococcosis and new strategies against such infections are needed. In this study, we demonstrate that C. neoformans has the biochemical ability to metabolize sterylglucosides (SGs), a class of immunomodulatory glycolipids. Genetic manipulations that eliminate cryptococccal sterylglucosidase lead to the accumulation of SGs and generate a mutant strain (Δsgl1) that is non-pathogenic in the mouse models of cryptococcosis. Interestingly, this mutant strain acts as a vaccine strain and protects mice against cryptococcosis following infection with C. neoformans or C. gattii. The immunity induced by the Δsgl1 strain is not CD4+ T-cells dependent. Immunocompromised mice, which lack CD4+ T-cells, are able to control the infection by Δsgl1 and acquire immunity against the challenge by wild-type C. neoformans following vaccination with the Δsgl1 strain. These findings are particularly important in the context of HIV/AIDS immune deficiency and suggest that the Δsgl1 strain might provide a potential vaccination strategy against cryptococcosis.
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Affiliation(s)
- Antonella Rella
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook NY, USA
| | - Visesato Mor
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook NY, USA
| | - Amir M Farnoud
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook NY, USA
| | - Ashutosh Singh
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook NY, USA
| | | | - Elitza Ivanova
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook NY, USA
| | - Nicholas Carpino
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook NY, USA
| | - Maria T Montagna
- Department of Biomedical Science and Human Oncology, Hygiene Section, University of Bari Bari, Italy
| | - Chiara Luberto
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook NY, USA
| | - Maurizio Del Poeta
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook NY, USA
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26
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Farnoud AM, Toledo AM, Konopka JB, Del Poeta M, London E. Raft-like membrane domains in pathogenic microorganisms. CURRENT TOPICS IN MEMBRANES 2015; 75:233-68. [PMID: 26015285 DOI: 10.1016/bs.ctm.2015.03.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The lipid bilayer of the plasma membrane is thought to be compartmentalized by the presence of lipid-protein microdomains. In eukaryotic cells, microdomains composed of sterols and sphingolipids, commonly known as lipid rafts, are believed to exist, and reports on the presence of sterol- or protein-mediated microdomains in bacterial cell membranes are also appearing. Despite increasing attention, little is known about microdomains in the plasma membrane of pathogenic microorganisms. This review attempts to provide an overview of the current state of knowledge of lipid rafts in pathogenic fungi and bacteria. The current literature on characterization of microdomains in pathogens is reviewed, and their potential role in growth, pathogenesis, and drug resistance is discussed. Better insight into the structure and function of membrane microdomains in pathogenic microorganisms might lead to a better understanding of their pathogenesis and development of raft-mediated approaches for therapy.
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Affiliation(s)
- Amir M Farnoud
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA
| | - Alvaro M Toledo
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA
| | - James B Konopka
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA
| | - Maurizio Del Poeta
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, USA
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Farnoud AM, Mor V, Singh A, Del Poeta M. Inositol phosphosphingolipid phospholipase C1 regulates plasma membrane ATPase (Pma1) stability in Cryptococcus neoformans. FEBS Lett 2014; 588:3932-8. [PMID: 25240197 PMCID: PMC4254033 DOI: 10.1016/j.febslet.2014.09.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 09/03/2014] [Accepted: 09/06/2014] [Indexed: 11/24/2022]
Abstract
Cryptococcus neoformans is a facultative intracellular pathogen, which can replicate in the acidic environment inside phagolysosomes. Deletion of the enzyme inositol-phosphosphingolipid-phospholipase-C (Isc1) makes C. neoformans hypersensitive to acidic pH likely by inhibiting the function of the proton pump, plasma membrane ATPase (Pma1). In this work, we examined the role of Isc1 on Pma1 transport and oligomerization. Our studies showed that Isc1 deletion did not affect Pma1 synthesis or transport, but significantly inhibited Pma1 oligomerization. Interestingly, Pma1 oligomerization could be restored by supplementing the medium with phytoceramide. These results offer insight into the mechanism of intracellular survival of C. neoformans.
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Affiliation(s)
- Amir M Farnoud
- Department of Molecular Genetics and Microbiology, Stony Brook University, 145 Life Sciences Building, Stony Brook, NY 11794, USA
| | - Visesato Mor
- Department of Molecular Genetics and Microbiology, Stony Brook University, 145 Life Sciences Building, Stony Brook, NY 11794, USA
| | - Ashutosh Singh
- Department of Molecular Genetics and Microbiology, Stony Brook University, 145 Life Sciences Building, Stony Brook, NY 11794, USA
| | - Maurizio Del Poeta
- Department of Molecular Genetics and Microbiology, Stony Brook University, 145 Life Sciences Building, Stony Brook, NY 11794, USA.
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Coelho C, Bocca AL, Casadevall A. The tools for virulence of Cryptococcus neoformans. ADVANCES IN APPLIED MICROBIOLOGY 2014; 87:1-41. [PMID: 24581388 DOI: 10.1016/b978-0-12-800261-2.00001-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cryptococcus neoformans is a fungal pathogen that causes almost half a million deaths each year. It is believed that most humans are infected with C. neoformans, possibly in a form that survives through latency in the lung and can reactivate to cause disease if the host becomes immunosuppressed. C. neoformans has a remarkably sophisticated intracellular survival capacities yet it is a free-living fungus with no requirement for mammalian virulence whatsoever. In this review, we discuss the tools that C. neoformans possesses to achieve survival, latency and virulence within its host. Some of these tools are mechanisms to withstand starvation and others aim to protect against microbicidal molecules produced by the immune system. Furthermore, we discuss how these tools were acquired through evolutionary pressures and perhaps accidental stochastic events, all of which combined to produce an organism with an unusual and unique intracellular pathogenic strategy.
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Affiliation(s)
- Carolina Coelho
- Department of Microbiology and Immunology, Albert Einstein College of Medicine of Yeshiva University, New York, USA; Centre for Neuroscience and Cell Biology of Coimbra, Institute of Microbiology, Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Anamelia Lorenzetti Bocca
- Department of Cellular Biology, Institute of Biological Sciences, University of Brasília, Brasília, Brazil
| | - Arturo Casadevall
- Department of Microbiology and Immunology, Albert Einstein College of Medicine of Yeshiva University, New York, USA.
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Invasion of the central nervous system by Cryptococcus neoformans requires a secreted fungal metalloprotease. mBio 2014; 5:e01101-14. [PMID: 24895304 PMCID: PMC4049100 DOI: 10.1128/mbio.01101-14] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
UNLABELLED Cryptococcus spp. cause life-threatening fungal infection of the central nervous system (CNS), predominantly in patients with a compromised immune system. Why Cryptococcus neoformans has this remarkable tropism for the CNS is not clear. Recent research on cerebral pathogenesis of C. neoformans revealed a predominantly transcellular migration of cryptococci across the brain endothelium; however, the identities of key fungal virulence factors that function specifically to invade the CNS remain unresolved. Here we found that a novel, secreted metalloprotease (Mpr1) that we identified in the extracellular proteome of C. neoformans (CnMpr1) is required for establishing fungal disease in the CNS. Mpr1 belongs to a poorly characterized M36 class of fungalysins that are expressed in only some fungal species. A strain of C. neoformans lacking the gene encoding Mpr1 (mpr1Δ) failed to breach the endothelium in an in vitro model of the human blood-brain barrier (BBB). A mammalian host infected with the mpr1Δ null strain demonstrated significant improvement in survival due to a reduced brain fungal burden and lacked the brain pathology commonly associated with cryptococcal disease. The in vivo studies further indicate that Mpr1 is not required for fungal dissemination and Mpr1 likely targets the brain endothelium specifically. Remarkably, the sole expression of CnMPR1 in Saccharomyces cerevisiae resulted in a robust migration of yeast cells across the brain endothelium, demonstrating Mpr1's specific activity in breaching the BBB and suggesting that Mpr1 may function independently of the hyaluronic acid-CD44 pathway. This distinct role for Mpr1 may develop into innovative treatment options and facilitate a brain-specific drug delivery platform. IMPORTANCE Cryptococcus neoformans is a medically relevant fungal pathogen causing significant morbidity and mortality, particularly in immunocompromised individuals. An intriguing feature is its strong neurotropism, and consequently the hallmark of cryptococcal disease is a brain infection, cryptococcal meningoencephalitis. For C. neoformans to penetrate the central nervous system (CNS), it first breaches the blood-brain barrier via a transcellular pathway; however, the identities of fungal factors required for this transmigration remain largely unknown. In an effort to identify extracellular fungal proteins that could mediate interactions with the brain endothelium, we undertook a proteomic analysis of the extracellular proteome and identified a secreted metalloprotease (Mpr1) belonging to the M36 class of fungalysins. Here we found that Mpr1 promotes migration of C. neoformans across the brain endothelium and into the CNS by facilitating attachment of cryptococci to the endothelium surface, thus underscoring the critical role of M36 proteases in fungal pathogenesis.
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Del Poeta M, Nimrichter L, Rodrigues ML, Luberto C. Synthesis and biological properties of fungal glucosylceramide. PLoS Pathog 2014; 10:e1003832. [PMID: 24415933 PMCID: PMC3887071 DOI: 10.1371/journal.ppat.1003832] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Affiliation(s)
- Maurizio Del Poeta
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
- * E-mail: (MD); (CL)
| | - Leonardo Nimrichter
- Instituto de Microbiologia Professor Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Marcio L. Rodrigues
- Instituto de Microbiologia Professor Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Fundação Oswaldo Cruz – Fiocruz, Centro de Desenvolvimento Tecnológico em Saúde (CDTS), Rio de Janeiro, Brazil
| | - Chiara Luberto
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, United States of America
- * E-mail: (MD); (CL)
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Fbp1-mediated ubiquitin-proteasome pathway controls Cryptococcus neoformans virulence by regulating fungal intracellular growth in macrophages. Infect Immun 2013; 82:557-68. [PMID: 24478071 DOI: 10.1128/iai.00994-13] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Cryptococcus neoformans is a human fungal pathogen that often causes lung and brain infections in immunocompromised patients, with a high fatality rate. Our previous results showed that an F-box protein, Fbp1, is essential for Cryptococcus virulence independent of the classical virulence factors, suggesting a novel virulence control mechanism. In this study, we show that Fbp1 is part of the ubiquitin-proteasome system, and we further investigated the mechanism of Fbp1 function during infection. Time course studies revealed that the fbp1Δ mutant causes little damage in the infected lung and that the fungal burden in the lung remains at a low but persistent level throughout infection. The fbp1Δ mutant cannot disseminate to other organs following pulmonary infection in the murine inhalation model of cryptococcosis but still causes brain infection in a murine intravenous injection model, suggesting that the block of dissemination of the fbp1Δ mutant is due to its inability to leave the lung. The fbp1Δ mutant showed a defect in intracellular proliferation after phagocytosis in a Cryptococcus-macrophage interaction assay, which likely contributes to its virulence attenuation. To elucidate the molecular basis of the SCF(Fbp1) E3 ligase function, we analyzed potential Fbp1 substrates based on proteomic approaches combined with phenotypic analysis. One substrate, the inositol phosphosphingolipid-phospholipase C1 (Isc1), is required for fungal survival inside macrophage cells, which is consistent with the role of Fbp1 in regulating Cryptococcus-macrophage interaction and fungal virulence. Our results thus reveal a new determinant of fungal virulence that involves the posttranslational regulation of inositol sphingolipid biosynthesis.
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The transcriptional response of Cryptococcus neoformans to ingestion by Acanthamoeba castellanii and macrophages provides insights into the evolutionary adaptation to the mammalian host. EUKARYOTIC CELL 2013; 12:761-74. [PMID: 23524994 DOI: 10.1128/ec.00073-13] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Virulence of Cryptococcus neoformans for mammals, and in particular its intracellular style, was proposed to emerge from evolutionary pressures on its natural environment by protozoan predation, which promoted the selection of strategies that allow intracellular survival in macrophages. In fact, Acanthamoeba castellanii ingests yeast cells, which then can replicate intracellularly. In addition, most fungal factors needed to establish infection in the mammalian host are also important for survival within the amoeba. To better understand the origin of C. neoformans virulence, we compared the transcriptional profile of yeast cells internalized by amoebae and murine macrophages after 6 h of infection. Our results showed 656 and 293 genes whose expression changed at least 2-fold in response to the intracellular environments of amoebae and macrophages, respectively. Among the genes that were found in both groups, we focused on open reading frame (ORF) CNAG_05662, which was potentially related to sugar transport but had no determined biological function. To characterize its function, we constructed a mutant strain and evaluated its ability to grow on various carbon sources. The results showed that this gene, named PTP1 (polyol transporter protein 1), is involved in the transport of 5- and 6-carbon polyols such as mannitol and sorbitol, but its presence or absence had no effect on cryptococcal virulence for mice or moth larvae. Overall, these results are consistent with the hypothesis that the capacity for mammalian virulence originated from fungus-protozoan interactions in the environment and provide a better understanding of how C. neoformans adapts to the mammalian host.
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Johnston SA, May RC. Cryptococcusinteractions with macrophages: evasion and manipulation of the phagosome by a fungal pathogen. Cell Microbiol 2012; 15:403-11. [DOI: 10.1111/cmi.12067] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 10/28/2012] [Accepted: 10/29/2012] [Indexed: 01/19/2023]
Affiliation(s)
| | - Robin C. May
- Institute of Microbiology and Infection; School of Biosciences; University of Birmingham; Birmingham; B15 2TT; UK
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Shi M, Colarusso P, Calaruso P, Mody CH. Real-time in vivo imaging of fungal migration to the central nervous system. Cell Microbiol 2012; 14:1819-27. [PMID: 22966777 DOI: 10.1111/cmi.12027] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Revised: 08/26/2012] [Accepted: 08/29/2012] [Indexed: 01/18/2023]
Abstract
Recent technical advances have afforded valuable new insights into the pathogenesis of fungal infections in the central nervous system (CNS), which continue to cause devastating complications, particularly in immunocompromised individuals. To cause CNS mycosis, organisms such as Cryptococcus neoformans become blood borne and progress through a series of pathogenic checkpoints that culminate in fungal replication in the brain. Critical steps include fungal arrest in the vasculature of the brain, interaction and signalling of the fungal and endothelial cells leading to transmigration with subsequent parenchymal invasion and fungal replication in the CNS. Previous studies that made use of in vitro and ex vivo approaches contributed greatly to our understanding of brain invasion by fungi. However, the knowledge gained from previous studies relied on in vitro models that did not account for vascular haemodynamics. For this reason, more refined approaches that model blood flow and vascular anatomy are required, andultimately studying fungal invasion and dissemination in vivo. Indeed, in vivo imaging (also known as intravital imaging) has emerged as a valuable technique to probe host-pathogen interactions. In this review, with a focus on C. neoformans, we will provide an overview of the applications of the prior techniques and recent advances, their strengths and limitations in characterizing the migration of fungi into the brain, and unanswered questions that may provide new directions for research.
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Affiliation(s)
- Meiqing Shi
- Virginia-Maryland Regional College of Veterinary Medicine, University of Maryland, College Park, MD 20742, USA
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Choi JN, Kim J, Kim J, Jung WH, Lee CH. Influence of iron regulation on the metabolome of Cryptococcus neoformans. PLoS One 2012; 7:e41654. [PMID: 22911836 PMCID: PMC3402442 DOI: 10.1371/journal.pone.0041654] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 06/26/2012] [Indexed: 01/10/2023] Open
Abstract
Iron is an essential nutrient for virtually all organisms and acts as a cofactor for many key enzymes of major metabolic pathways. Furthermore, iron plays a critical role in pathogen-host interactions. In this study, we analyzed metabolomic changes associated with iron availability and the iron regulatory protein Cir1 in a human fungal pathogen Cryptococcus neoformans. Our metabolite analysis revealed that Cir1 influences the glycolytic pathway, ergosterol biosynthesis and inositol metabolism, which require numerous iron-dependent enzymes and play important roles in pathogenesis and antifungal sensitivity of the fungus. Moreover, we demonstrated that increased cellular iron content and altered gene expression in the cir1 mutant contributed to metabolite changes. Our study provides a new insight into iron regulation and the role of Cir1 in metabolome of C. neoformans.
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Affiliation(s)
- Jung Nam Choi
- Department of Bioscience and Biotechnology, Konkuk University, Seoul, Republic of Korea
| | - Jeongmi Kim
- Department of Biotechnology, Chung-Ang University, Anseong-Si, Gyeonggi-Do, Republic of Korea
| | - Jiyoung Kim
- Department of Bioscience and Biotechnology, Konkuk University, Seoul, Republic of Korea
| | - Won Hee Jung
- Department of Biotechnology, Chung-Ang University, Anseong-Si, Gyeonggi-Do, Republic of Korea
| | - Choong Hwan Lee
- Department of Bioscience and Biotechnology, Konkuk University, Seoul, Republic of Korea
- * E-mail:
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36
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Tripathi K, Mor V, Bairwa NK, Del Poeta M, Mohanty BK. Hydroxyurea treatment inhibits proliferation of Cryptococcus neoformans in mice. Front Microbiol 2012; 3:187. [PMID: 22783238 PMCID: PMC3390589 DOI: 10.3389/fmicb.2012.00187] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 05/08/2012] [Indexed: 01/01/2023] Open
Abstract
The fungal pathogen Cryptococcus neoformans (Cn) is a serious threat to immunocompromised individuals, especially for HIV patients who develop meningoencephalitis. For effective cryptococcal treatment, novel antifungal drugs or innovative combination therapies are needed. Recently, sphingolipids have emerged as important bioactive molecules in the regulation of microbial pathogenesis. Previously we reported that the sphingolipid pathway gene, ISC1, which is responsible for ceramide production, is a major virulence factor in Cn infection. Here we report our studies of the role of ISC1 during genotoxic stress induced by the antineoplastic hydroxyurea (HU) and methyl methanesulfonate (MMS), which affect DNA replication and genome integrity. We observed that Cn cells lacking ISC1 are highly sensitive to HU and MMS in a rich culture medium. HU affected cell division of Cn cells lacking the ISC1 gene, resulting in cell clusters. Cn ISC1, when expressed in a Saccharomyces cerevisiae (Sc) strain lacking its own ISC1 gene, restored HU resistance. In macrophage-like cells, although HU affected the proliferation of wild type (WT) Cn cells by 50% at the concentration tested, HU completely inhibited Cn isc1Δ cell proliferation. Interestingly, our preliminary data show that mice infected with WT or Cn isc1Δ cells and subsequently treated with HU had longer lifespans than untreated, infected control mice. Our work suggests that the sphingolipid pathway gene, ISC1, is a likely target for combination therapy with traditional drugs such as HU.
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Affiliation(s)
- Kaushlendra Tripathi
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA
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37
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Antifungal peptides at membrane interaction. Eur J Med Chem 2012; 51:154-62. [DOI: 10.1016/j.ejmech.2012.02.037] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Revised: 02/02/2012] [Accepted: 02/17/2012] [Indexed: 01/08/2023]
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Abstract
The pathogenic fungus Cryptococcus neoformans exhibits a striking propensity to cause central nervous system (CNS) disease in people with HIV/AIDS. Given that cryptococcal infections are generally initiated by pulmonary colonization, dissemination requires that the fungus withstand phagocytic killing, cross the alveolar-capillary interface in the lung, survive in the circulatory system and breach the blood-brain barrier. We know little about the molecular mechanisms underlying dissemination, but there is a rapidly growing list of mutants that fail to cause CNS disease. These mutants reveal a remarkable diversity of functions and therefore illustrate the complexity of the cryptococcal-host interaction. The challenge now is to extend the analysis of these mutants to acquire a detailed understanding of each step in dissemination.
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Abstract
Fungal meningitis is a serious disease caused by a fungal infection of the central nervous system (CNS) mostly in individuals with immune system deficiencies. Fungal meningitis is often fatal without proper treatment, and the mortality rate remains unacceptably high even with antifungal drug interventions. Currently, cryptococcal meningitis is the most common fungal meningitis in HIV-1/AIDS, and its disease mechanism has been extensively studied. The key steps for fungi to infect brain and cause meningitis after establishment of local infection are the dissemination of fungal cells to the bloodstream and invasion through the blood brain barrier to reach the CNS. In this review, we use cryptococcal CNS infection as an example to describe the current molecular understanding of fungal meningitis, including the establishment of the infection, dissemination, and brain invasion. Host and microbial factors that contribute to these infection steps are also discussed.
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Affiliation(s)
- Tong-Bao Liu
- The Public Health Research Institute, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, NJ, USA
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40
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Bandara HMHN, Lam OLT, Jin LJ, Samaranayake L. Microbial chemical signaling: a current perspective. Crit Rev Microbiol 2012; 38:217-49. [PMID: 22300377 DOI: 10.3109/1040841x.2011.652065] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Communication among microorganisms is mediated through quorum sensing. The latter is defined as cell-density linked, coordinated gene expression in microbial populations as a response to threshold signal concentrations followed by induction of a synchronized population response. This phenomenon is used by a variety of microbes to optimize their survival in a constantly challenging, dynamic milieu, by correlating individual cellular functions to community-based requirements. The synthesis, secretion, and perception of quorum-sensing molecules and their target response play a pivotal role in quorum sensing and are tightly controlled by complex, multilayered and interconnected signal transduction pathways that regulate diverse cellular functions. Quorum sensing exemplifies interactive social behavior innate to the microbial world that controls features such as, virulence, biofilm maturation, antibiotic resistance, swarming motility, and conjugal plasmid transfer. Over the past two decades, studies have been performed to rationalize bacterial cell-to-cell communication mediated by structurally and functionally diverse small molecules. This review describes the theoretical aspects of cellular and quorum-sensing mechanisms that affect microbial physiology and pathobiology.
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Affiliation(s)
- H M H N Bandara
- Oral Biosciences, Prince Philip Dental Hospital, 34, Hospital Road, Sai Ying Pun, Hong Kong
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41
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Zhang O, Xu W, Balakrishna Pillai A, Zhang K. Developmentally regulated sphingolipid degradation in Leishmania major. PLoS One 2012; 7:e31059. [PMID: 22299050 PMCID: PMC3267774 DOI: 10.1371/journal.pone.0031059] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 01/01/2012] [Indexed: 12/22/2022] Open
Abstract
Leishmania parasites alternate between extracellular promastigotes in sandflies and intracellular amastigotes in mammals. These protozoans acquire sphingolipids (SLs) through de novo synthesis (to produce inositol phosphorylceramide) and salvage (to obtain sphingomyelin from the host). A single ISCL (Inositol phosphoSphingolipid phospholipase C-Like) enzyme is responsible for the degradation of both inositol phosphorylceramide (the IPC hydrolase or IPCase activity) and sphingomyelin (the SMase activity). Recent studies of a L. major ISCL-null mutant (iscl−) indicate that SL degradation is required for promastigote survival in stationary phase, especially under acidic pH. ISCL is also essential for L. major proliferation in mammals. To further understand the role of ISCL in Leishmania growth and virulence, we introduced a sole IPCase or a sole SMase into the iscl− mutant. Results showed that restoration of IPCase only complemented the acid resistance defect in iscl− promastigotes and improved their survival in macrophages, but failed to recover virulence in mice. In contrast, a sole SMase fully restored parasite infectivity in mice but was unable to reverse the promastigote defects in iscl−. These findings suggest that SL degradation in Leishmania possesses separate roles in different stages: while the IPCase activity is important for promastigote survival and acid tolerance, the SMase activity is required for amastigote proliferation in mammals. Consistent with these findings, ISCL was preferentially expressed in stationary phase promastigotes and amastigotes. Together, our results indicate that SL degradation by Leishmania is critical for parasites to establish and sustain infection in the mammalian host.
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Affiliation(s)
- Ou Zhang
- Department of Biological Sciences, Texas Tech University, Lubbock, Texas, United States of America
| | - Wei Xu
- Department of Biological Sciences, Texas Tech University, Lubbock, Texas, United States of America
| | | | - Kai Zhang
- Department of Biological Sciences, Texas Tech University, Lubbock, Texas, United States of America
- * E-mail:
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Singh A, Wang H, Silva LC, Na C, Prieto M, Futerman AH, Luberto C, Del Poeta M. Methylation of glycosylated sphingolipid modulates membrane lipid topography and pathogenicity of Cryptococcus neoformans. Cell Microbiol 2012; 14:500-16. [PMID: 22151739 DOI: 10.1111/j.1462-5822.2011.01735.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In previous studies we showed that the replication of Cryptococcus neoformans in the lung environment is controlled by the glucosylceramide (GlcCer) synthase gene (GCS1), which synthesizes the membrane sphingolipid GlcCer from the C9-methyl ceramide. Here, we studied the effect of the mutation of the sphingolipid C9 methyltransferase gene (SMT1), which adds a methyl group to position 9 of the sphingosine backbone of ceramide. The C. neoformans Δsmt1 mutant does not make C9-methyl ceramide and, thus, any methylated GlcCer. However, it accumulates demethylated ceramide and demethylated GlcCer. The Δsmt1 mutant loses more than 80% of its virulence compared with the wild type and the reconstituted strain. Interestingly, growth of C. neoformans Δsmt1 in the lung was decreased and C. neoformans cells were contained in lung granulomas, which significantly reduced the rate of their dissemination to the brain reducing the onset of meningoencephalitis. Thus, using fluorescent spectroscopy and atomic force microscopy we compared the wild type and Δsmt1 mutant and found that the altered membrane composition and GlcCer structure affects fungal membrane rigidity, suggesting that specific sphingolipid structures are required for proper fungal membrane organization and integrity. Therefore, we propose that the physical structure of the plasma membrane imparted by specific classes of sphingolipids represents a critical factor for the ability of the fungus to establish virulence.
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Affiliation(s)
- Arpita Singh
- Biochemistry & Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA
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McQuiston TJ, Williamson PR. Paradoxical roles of alveolar macrophages in the host response to Cryptococcus neoformans. J Infect Chemother 2011; 18:1-9. [PMID: 22045161 DOI: 10.1007/s10156-011-0306-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Indexed: 12/16/2022]
Abstract
Cryptococcus neoformans (Cn) is a fungal pathogen that is a serious health threat to immunocompromised individuals. Upon environmental exposure, infectious fungal propagules are inhaled into the host's lungs. The anticryptococcal actions of alveolar macrophages (AM), the predominant host phagocyte of the innate immune system in the lungs, are fundamental in determining whether containment and clearance of the pathogen occurs by the development of an adapted immune response or whether infection is established and progresses to disease. However, the fungus is also capable of surviving the antimicrobial actions of AM and exploits these host phagocytes to establish infection and exacerbate disease. In addition, there is evidence suggesting that cryptococcosis may occur following reactivation of latent cryptococcal infection. Currently, the role of AM and the fungal factors contributing to latent cryptococcosis are unknown. This review examines the AM-Cn interaction and how it affects the development of pulmonary disease with a focus on host and pathogen factors enabling latency to occur.
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Affiliation(s)
- Travis J McQuiston
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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Bencurova E, Mlynarcik P, Bhide M. An insight into the ligand-receptor interactions involved in the translocation of pathogens across blood-brain barrier. ACTA ACUST UNITED AC 2011; 63:297-318. [PMID: 22092557 DOI: 10.1111/j.1574-695x.2011.00867.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2011] [Revised: 08/09/2011] [Accepted: 09/02/2011] [Indexed: 01/01/2023]
Abstract
Traversal of pathogen across the blood-brain barrier (BBB) is an essential step for central nervous system (CNS) invasion. Pathogen traversal can occur paracellularly, transcellularly, and/or in infected phagocytes (Trojan horse mechanism). To trigger the translocation processes, mainly through paracellular and transcellular ways, interactions between protein molecules of pathogen and BBB are inevitable. Simply, it takes two to tango: both host receptors and pathogen ligands. Underlying molecular basis of BBB translocation of various pathogens has been revealed in the last decade, and a plethora of experimental data on protein-protein interactions has been created. This review compiles these data and should give insights into the ligand-receptor interactions that occur during BBB translocation. Further, it sheds light on cell signaling events triggered in response to ligand-receptor interaction. Understanding of the molecular principles of pathogen-host interactions that are involved in traversal of the BBB should contribute to develop new vaccine and drug strategies to prevent CNS infections.
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Affiliation(s)
- Elena Bencurova
- Laboratory of Biomedical Microbiology and Immunology, Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Kosice, Slovakia
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Qureshi A, Grey A, Rose KL, Schey KL, Del Poeta M. Cryptococcus neoformans modulates extracellular killing by neutrophils. Front Microbiol 2011; 2:193. [PMID: 21960987 PMCID: PMC3177079 DOI: 10.3389/fmicb.2011.00193] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Accepted: 08/31/2011] [Indexed: 01/08/2023] Open
Abstract
We recently established a key role for host sphingomyelin synthase (SMS) in regulating the killing activity of neutrophils against Cryptococcus neoformans. In this paper, we studied the effect of C. neoformans on the killing activity of neutrophils and whether SMS would still be a player against C. neoformans in immunocompromised mice lacking T and natural killer (NK) cells (Tgε26 mice). To this end, we analyzed whether C. neoformans would have any effect on neutrophil survival and killing in vitro and in vivo. We show that unlike Candida albicans, neither the presence nor the capsule size of C. neoformans cells have any effect on neutrophil viability. Interestingly, melanized C. neoformans cells totally abrogated the killing activity of neutrophils. We monitored how exposure of neutrophils to C. neoformans cells would interfere with any further killing activity of the conditioned medium and found that pre-incubation with live but not “heat-killed” fungal cells significantly inhibits further killing activity of the medium. We then studied whether activation of SMS at the site of C. neoformans infection is dependent on T and NK cells. Using matrix-assisted laser desorption–ionization tissue imaging in infected lung we found that similar to previous observations in the isogenic wild-type CBA/J mice, SM 16:0 levels are significantly elevated at the site of infection in mice lacking T and NK cells, but only at early time points. This study highlights that C. neoformans may negatively regulate the killing activity of neutrophils and that SMS activation in neutrophils appears to be partially independent of T and/or NK cells.
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Affiliation(s)
- Asfia Qureshi
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina Charleston, SC, USA
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Chrisman CJ, Albuquerque P, Guimaraes AJ, Nieves E, Casadevall A. Phospholipids trigger Cryptococcus neoformans capsular enlargement during interactions with amoebae and macrophages. PLoS Pathog 2011; 7:e1002047. [PMID: 21637814 PMCID: PMC3102711 DOI: 10.1371/journal.ppat.1002047] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Accepted: 03/11/2011] [Indexed: 11/18/2022] Open
Abstract
A remarkable aspect of the interaction of Cryptococcus
neoformans with mammalian hosts is a consistent increase in capsule
volume. Given that many aspects of the interaction of C.
neoformans with macrophages are also observed with amoebae, we
hypothesized that the capsule enlargement phenomenon also had a protozoan
parallel. Incubation of C. neoformans with Acanthamoeba
castellanii resulted in C. neoformans capsular
enlargement. The phenomenon required contact between fungal and protozoan cells
but did not require amoeba viability. Analysis of amoebae extracts showed that
the likely stimuli for capsule enlargement were protozoan polar lipids. Extracts
from macrophages and mammalian serum also triggered cryptococcal capsular
enlargement. C. neoformans capsule enlargement required
expression of fungal phospholipase B, but not phospholipase C. Purified
phospholipids, in particular, phosphatidylcholine, and derived molecules
triggered capsular enlargement with the subsequent formation of giant cells.
These results implicate phospholipids as a trigger for both C.
neoformans capsule enlargement in vivo and
exopolysaccharide production. The observation that the incubation of C.
neoformans with phospholipids led to the formation of giant cells
provides the means to generate these enigmatic cells in vitro.
Protozoan- or mammalian-derived polar lipids could represent a danger signal for
C. neoformans that triggers capsular enlargement as a
non-specific defense mechanism against potential predatory cells. Hence,
phospholipids are the first host-derived molecules identified to trigger
capsular enlargement. The parallels apparent in the capsular response of
C. neoformans to both amoebae and macrophages provide
additional support for the notion that certain aspects of cryptococcal virulence
emerged as a consequence of environmental interactions with other microorganisms
such as protists. A key event in C. neoformans pathogenesis is capsule enlargement
in mammalian hosts. Historically, this phenomenon was attributed to high
CO2 and iron deprivation but the magnitude of capsular
enlargement observed in vivo cannot be consistently replicated
in vitro. This paper reports that C.
neoformans responds to polar lipid extracts with massive capsule
enlargement, with some cells having dimensions comparable to the giant cells
observed in vivo. Phospholipids are identified in this paper as
the inducers of capsule enlargement. Our work is important because this is the
first host-derived molecule that has been identified as a stimulus of massive
capsule enlargement thus providing a potential mechanism for the capsular
enlargement observed in vivo. Furthermore, the fact that the
signal is common to both macrophages and amoebae suggests that the capsule
enlargement response to phospholipids is a mechanism for fungal sensing of
phagocytic cell predators. This provides another example of a correspondence
between a possible environmental signal and a mechanism of virulence.
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Affiliation(s)
- Cara J. Chrisman
- Department of Microbiology and Immunology,
Albert Einstein College of Medicine, Bronx, New York, United States of
America
| | - Patricia Albuquerque
- Department of Microbiology and Immunology,
Albert Einstein College of Medicine, Bronx, New York, United States of
America
| | - Allan J. Guimaraes
- Department of Microbiology and Immunology,
Albert Einstein College of Medicine, Bronx, New York, United States of
America
| | - Edward Nieves
- Department of Developmental and Molecular
Biology, Albert Einstein College of Medicine, Bronx, New York, United States of
America
- Department of Biochemistry, Albert Einstein
College of Medicine, Bronx, New York, United States of America
| | - Arturo Casadevall
- Department of Microbiology and Immunology,
Albert Einstein College of Medicine, Bronx, New York, United States of
America
- Department of Medicine, Albert Einstein
College of Medicine, Bronx, New York, United States of America
- * E-mail:
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Kronstad JW, Attarian R, Cadieux B, Choi J, D'Souza CA, Griffiths EJ, Geddes JMH, Hu G, Jung WH, Kretschmer M, Saikia S, Wang J. Expanding fungal pathogenesis: Cryptococcus breaks out of the opportunistic box. Nat Rev Microbiol 2011; 9:193-203. [PMID: 21326274 DOI: 10.1038/nrmicro2522] [Citation(s) in RCA: 223] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cryptococcus neoformans is generally considered to be an opportunistic fungal pathogen because of its tendency to infect immunocompromised individuals, particularly those infected with HIV. However, this view has been challenged by the recent discovery of specialized interactions between the fungus and its mammalian hosts, and by the emergence of the related species Cryptococcus gattii as a primary pathogen of immunocompetent populations. In this Review, we highlight features of cryptococcal pathogens that reveal their adaptation to the mammalian environment. These features include not only remarkably sophisticated interactions with phagocytic cells to promote intracellular survival, dissemination to the central nervous system and escape, but also surprising morphological and genomic adaptations such as the formation of polyploid giant cells in the lung.
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Affiliation(s)
- James W Kronstad
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada.
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Two major inositol transporters and their role in cryptococcal virulence. EUKARYOTIC CELL 2011; 10:618-28. [PMID: 21398509 DOI: 10.1128/ec.00327-10] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Cryptococcus neoformans is an AIDS-associated human fungal pathogen and the most common cause of fungal meningitis, with a mortality rate over 40% in AIDS patients. Significant advances have been achieved in understanding its disease mechanisms. Yet the underlying mechanism of a high frequency of cryptococcal meningitis remains unclear. The existence of high inositol concentrations in brain and our earlier discovery of a large inositol transporter (ITR) gene family in C. neoformans led us to investigate the potential role of inositol in Cryptococcus-host interactions. In this study, we focus on functional analyses of two major ITR genes to understand their role in virulence of C. neoformans. Our results show that ITR1A and ITR3C are the only two ITR genes among 10 candidates that can complement the growth defect of a Saccharomyces cerevisiae strain lacking inositol transporters. Both S. cerevisiae strains heterologously expressing ITR1A or ITR3C showed high inositol uptake activity, an indication that they are major inositol transporters. Significantly, itr1a itr3c double mutants showed significant virulence attenuation in murine infection models. Mutating both ITR1A and ITR3C in an ino1 mutant background activates the expression of several remaining ITR candidates and does not show more severe virulence attenuation, suggesting that both inositol uptake and biosynthetic pathways are important for inositol acquisition. Overall, our study provides evidence that host inositol and fungal inositol transporters are important for Cryptococcus pathogenicity.
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De Lederkremer RM, Agusti R, Docampo R. Inositolphosphoceramide metabolism in Trypanosoma cruzi as compared with other trypanosomatids. J Eukaryot Microbiol 2011; 58:79-87. [PMID: 21332877 DOI: 10.1111/j.1550-7408.2011.00533.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Chagas disease is caused by Trypanosoma cruzi and is endemic to North, Central and South American countries. Current therapy against this disease is only partially effective and produces adverse side effects. Studies on the metabolic pathways of T. cruzi, in particular those with no equivalent in mammalian cells, might identify targets for the development of new drugs. Ceramide is metabolized to inositolphosphoceramide (IPC) in T. cruzi and other kinetoplastid protists whereas in mammals it is mainly incorporated into sphingomyelin. In T. cruzi, in contrast to Trypanosoma brucei and Leishmania spp., IPC functions as lipid anchor constituent of glycoproteins and free glycosylinositolphospholipids (GIPLs). Inhibition of IPC and GIPLs biosynthesis impairs differentiation of trypomastigotes into the intracellular amastigote forms. The gene encoding IPC synthase in T. cruzi has been identified and the enzyme has been expressed in a cell-free system. The enzyme involved in IPC degradation and the remodelases responsible for the incorporation of ceramide into free GIPLs or into the glycosylphosphatidylinositols anchoring glycoproteins, and in fatty acid modifications of these molecules of T. cruzi have been understudied. Inositolphosphoceramide metabolism and remodeling could be exploited as targets for Chagas disease chemotherapy.
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Affiliation(s)
- Rosa M De Lederkremer
- CHIDECAR, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
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