scholarly journals The Pathogenic Fungus Cryptococcus neoformans Expresses Two Functional GDP-Mannose Transporters with Distinct Expression Patterns and Roles in Capsule Synthesis

2007 ◽  
Vol 6 (5) ◽  
pp. 776-785 ◽  
Author(s):  
Tricia R. Cottrell ◽  
Cara L. Griffith ◽  
Hong Liu ◽  
Ashley A. Nenninger ◽  
Tamara L. Doering
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Pathogenic Fungus ◽  
Expression Patterns ◽  
Growth Conditions ◽  
Phosphomannose Isomerase ◽  
Microarray Experiments ◽  
Life Threatening ◽  
Nucleotide Sugars ◽  
Intracellular Organelles

ABSTRACT Cryptococcus neoformans is a fungal pathogen that is responsible for life-threatening disease, particularly in the context of compromised immunity. This organism makes extensive use of mannose in constructing its cell wall, glycoproteins, and glycolipids. Mannose also comprises up to two-thirds of the main cryptococcal virulence factor, a polysaccharide capsule that surrounds the cell. The glycosyltransfer reactions that generate cellular carbohydrate structures usually require activated donors such as nucleotide sugars. GDP-mannose, the mannose donor, is produced in the cytosol by the sequential actions of phosphomannose isomerase, phosphomannomutase, and GDP-mannose pyrophosphorylase. However, most mannose-containing glycoconjugates are synthesized within intracellular organelles. This topological separation necessitates a specific transport mechanism to move this key precursor across biological membranes to the appropriate site for biosynthetic reactions. We have discovered two GDP-mannose transporters in C. neoformans, in contrast to the single such protein reported previously for other fungi. Biochemical studies of each protein expressed in Saccharomyces cerevisiae show that both are functional, with similar kinetics and substrate specificities. Microarray experiments indicate that the two proteins Gmt1 and Gmt2 are transcribed with distinct patterns of expression in response to variations in growth conditions. Additionally, deletion of the GMT1 gene yields cells with small capsules and a defect in capsule induction, while deletion of GMT2 does not alter the capsule. We suggest that C. neoformans produces two GDP-mannose transporters to satisfy its enormous need for mannose utilization in glycan synthesis. Furthermore, we propose that the two proteins have distinct biological roles. This is supported by the different expression patterns of GMT1 and GMT2 in response to environmental stimuli and the dissimilar phenotypes that result when each gene is deleted.

scholarly journals Structural analysis of fungal pathogenicity-related casein kinase α subunit, Cka1, in the human fungal pathogen Cryptococcus neoformans

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Belinda X. Ong ◽  
Youngki Yoo ◽  
Myeong Gil Han ◽  
Jun Bae Park ◽  
Myung Kyung Choi ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Pathogenic Fungus ◽  
Kinase Assay ◽  
Α Subunit ◽  
Dynamic Architecture ◽  
Human Fungal Pathogen ◽  
Life Threatening ◽  
The Difference ◽  
Anti Fungal

Abstract CK2α is a constitutively active and highly conserved serine/threonine protein kinase that is involved in the regulation of key cellular metabolic pathways and associated with a variety of tumours and cancers. The most well-known CK2α inhibitor is the human clinical trial candidate CX-4945, which has recently shown to exhibit not only anti-cancer, but also anti-fungal properties. This prompted us to work on the CK2α orthologue, Cka1, from the pathogenic fungus Cryptococcus neoformans, which causes life-threatening systemic cryptococcosis and meningoencephalitis mainly in immunocompromised individuals. At present, treatment of cryptococcosis remains a challenge due to limited anti-cryptococcal therapeutic strategies. Hence, expanding therapeutic options for the treatment of the disease is highly clinically relevant. Herein, we report the structures of Cka1-AMPPNP-Mg2+ (2.40 Å) and Cka1-CX-4945 (2.09 Å). Structural comparisons of Cka1-AMPPNP-Mg2+ with other orthologues revealed the dynamic architecture of the N-lobe across species. This may explain for the difference in binding affinities and deviations in protein-inhibitor interactions between Cka1-CX-4945 and human CK2α-CX-4945. Supporting it, in vitro kinase assay demonstrated that CX-4945 inhibited human CK2α much more efficiently than Cka1. Our results provide structural insights into the design of more selective inhibitors against Cka1.

scholarly journals Transcription factor Liv4 is required for growth and pathogenesis of Cryptococcus neoformans

2020 ◽  
Vol 20 (3) ◽  
Author(s):  
Jiu Yi ◽  
Junjun Sang ◽  
Jingyu Zhao ◽  
Lei Gao ◽  
Yali Yang ◽  
...  
Keyword(s):  
Cell Wall ◽  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Regulatory Mechanisms ◽  
Regulatory Function ◽  
Growth Defect ◽  
Detailed Characterization ◽  
Phenotypic Changes ◽  
Life Threatening

ABSTRACT Cryptococcus neoformans is an important invasive fungal pathogen that causes life-threatening meningoencephalitis in humans. Its biological and pathogenic regulatory mechanisms remain largely unknown, particularly due to the presence of those core transcription factors (TFs). Here, we conducted a detailed characterization of the TF Liv4 in the biology and virulence of C. neoformans. Deletion of TF Liv4 protein resulted in growth defect under both normal and stress conditions (such as high temperature and cell wall/membrane damaging agents), drastic morphological damage and also attenuated virulence in C. neoformans. These phenotypic changes might be contributed to transcriptional abnormality in the liv4Δ mutant, in which several cryptococcal genes involved in energy metabolism and cell wall integrity were downregulated. Furthermore, ChIP-seq and ChIP-qPCR assays suggested TF Liv4 might exert its regulatory function in transcription by its activation of RBP1 in C. neoformans. Taken together, our work highlights the importance of TF Liv4 in the growth and virulence of C. neoformans, and it facilitates a better understanding of cryptococcal pathogenesis mechanisms.

scholarly journals Central Nervous System Vasculitis for Cryptococcosis in an Immunocompetent Patient

Diseases ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 75 ◽  
Author(s):  
Dan Zimelewicz Oberman ◽  
Liliana Patrucco ◽  
Carolina Cuello Oderiz
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Cryptococcus Neoformans ◽  
Cryptococcal Meningitis ◽  
Fungal Pathogen ◽  
Immunocompetent Patient ◽  
Central Nervous System Vasculitis ◽  
Diagnostic Challenge ◽  
Threatening Condition ◽  
Life Threatening

Cryptococcal meningitis is a life-threatening condition caused by a fungal pathogen, Cryptococcus neoformans, that can infect both immunosuppressed and immunocompetent hosts. It is an important cause of morbidity and mortality in severely immunodeficient patients. However, in an immunocompetent patient it represents a diagnostic challenge, mainly because it is extremely rare, but also because of its nonspecific clinical manifestation. Neurovascular involvement in cryptococcal meningitis is rare and not well known and only few reports have described this association. We describe a cryptococcal meningitis in an immunocompetent patient associated with central nervous system vasculitis.

scholarly journals Thioredoxin Reductase Is Essential for Viability in the Fungal Pathogen Cryptococcus neoformans

2005 ◽  
Vol 4 (2) ◽  
pp. 487-489 ◽  
Author(s):  
Tricia A. Missall ◽  
Jennifer K. Lodge
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Nitrosative Stress ◽  
Pathogenic Fungus ◽  
Thioredoxin Reductase ◽  
Mammalian Host ◽  
Low Molecular Weight ◽  
Oxidative And Nitrosative Stress ◽  
Copper Transporter ◽  
Resistance Pathway

ABSTRACT Thioredoxin reductase (TRR1) is an important component of the thioredoxin oxidative stress resistance pathway. Here we show that it is induced during oxidative and nitrosative stress and is preferentially localized to the mitochondria in Cryptococcus neoformans. The C. neoformans TRR1 gene encodes the low-molecular-weight isoform of the thioredoxin reductase enzyme, which shares little homology with that of its mammalian host. By replacing the endogenous TRR1 promoter with an inducible copper transporter promoter, we showed that Trr1 appears to be essential for viability of this pathogenic fungus, making it a potential antifungal target.

scholarly journals Regulation of Cryptococcus neoformans Capsule Size Is Mediated at the Polymer Level

2007 ◽  
Vol 7 (3) ◽  
pp. 546-549 ◽  
Author(s):  
Aki Yoneda ◽  
Tamara L. Doering
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Growth Conditions ◽  
Environmental Stimuli ◽  
Polysaccharide Capsule ◽  
Capsule Size

ABSTRACT The fungal pathogen Cryptococcus neoformans regulates its polysaccharide capsule depending on environmental stimuli. To investigate whether capsule polymers change under different growth conditions, we analyzed shed capsules at physiological concentrations without physical perturbation. Our results indicate that regulation of capsule size is mediated at the level of individual polysaccharide molecules.

scholarly journals Chronological Aging Is Associated with Biophysical and Chemical Changes in the Capsule of Cryptococcus neoformans

2011 ◽  
Vol 79 (12) ◽  
pp. 4990-5000 ◽  
Author(s):  
Radames J. B. Cordero ◽  
Bruno Pontes ◽  
Allan J. Guimarães ◽  
Luis R. Martinez ◽  
Johanna Rivera ◽  
...  
Keyword(s):  
Stationary Phase ◽  
Cryptococcus Neoformans ◽  
Pathogenic Fungus ◽  
Growth Conditions ◽  
Cellular Aging ◽  
Phase Growth ◽  
Chronic Infections ◽  
Content Type ◽  
Chronological Aging ◽  
Dynamic Structures

ABSTRACTDoes the age of a microbial cell affect its virulence factors? To our knowledge, this question has not been addressed previously, but the answer is of great relevance for chronic infections where microbial cells persist and age in hosts.Cryptococcus neoformansis an encapsulated human-pathogenic fungus notorious for causing chronic infections where cells of variable age persist in tissue. The major virulence factor forC. neoformansis a polysaccharide (PS) capsule. To understand how chronological age could impact the cryptococcal capsule properties, we compared the elastic properties, permeabilities, zeta potentials, and glycosidic compositions of capsules from young and old cells and found significant differences in all parameters measured. Changes in capsular properties were paralleled by changes in PS molecular mass and density, as well as modified antigenic density and antiphagocytic properties. Remarkably, chronological aging under stationary-phase growth conditions was associated with the expression of α-1,3-glucans in the capsule, indicating a new structural capsular component. Our results establish that cryptococcal capsules are highly dynamic structures that change dramatically with chronological aging under prolonged stationary-phase growth conditions. Changes associated with cellular aging in chronic infections could contribute to the remarkable capacity of this fungus to persist in tissues by generating phenotypically and antigenically different capsules.

scholarly journals The interplay of phenotype and genotype in Cryptococcus neoformans disease

2020 ◽  
Vol 40 (10) ◽  
Author(s):  
Sophie Altamirano ◽  
Katrina M. Jackson ◽  
Kirsten Nielsen
Keyword(s):  
Patient Outcome ◽  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Proper Treatment ◽  
Rapid Adaptation ◽  
Complete Understanding ◽  
Phenotypic Changes ◽  
Life Threatening ◽  
Opportunistic Fungal Pathogen

Abstract Cryptococcus neoformans is an opportunistic fungal pathogen that causes life-threatening meningitis primarily in immunocompromised individuals. In order to survive and proliferate during infection, C. neoformans must adapt to a variety of stresses it encounters within the host. Patient outcome depends on the interaction between the pathogen and the host. Understanding the mechanisms that C. neoformans uses to facilitate adaptation to the host and promote pathogenesis is necessary to better predict disease severity and establish proper treatment. Several virulence phenotypes have been characterized in C. neoformans, but the field still lacks a complete understanding of how genotype and phenotype contribute to clinical outcome. Furthermore, while it is known that C. neoformans genotype impacts patient outcome, the mechanisms remain unknown. This lack of understanding may be due to the genetic heterogeneity of C. neoformans and the extensive phenotypic variation observed between and within isolates during infection. In this review, we summarize the current understanding of how the various genotypes and phenotypes observed in C. neoformans correlate with human disease progression in the context of patient outcome and recurrence. We also postulate the mechanisms underlying the genetic and phenotypic changes that occur in vivo to promote rapid adaptation in the host.

scholarly journals In Vitro Antifungal Activities of Inhibitors of Phospholipases from the Fungal Pathogen Cryptococcus neoformans

2004 ◽  
Vol 48 (5) ◽  
pp. 1561-1569 ◽  
Author(s):  
Ranjini Ganendren ◽  
Fred Widmer ◽  
Vatsala Singhal ◽  
Christabel Wilson ◽  
Tania Sorrell ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Antifungal Agents ◽  
Pathogenic Fungus ◽  
Fungal Enzymes ◽  
Compound A ◽  
Phospholipase B ◽  
The One ◽  
Dioctadecyldimethylammonium Bromide

ABSTRACT Secreted phospholipase B is a proven virulence factor for the pathogenic fungus Cryptococcus neoformans and exhibits three phospholipase activities in the one protein. These are phospholipase B (PLB), lysophospholipase (LPL), and lysophospholipase transacylase (LPTA). Our aim was to investigate the feasibility of using this enzyme as a target for antifungal therapy. We determined in C. neoformans var. grubii strain H99 that 82% of PLB activity was secreted but that 64% of LPL activity and 70% of LPTA activity were cell associated. Cell-associated activities (cytosolic and membrane) were further characterized, since it is likely that any fungicidal effect would depend on inhibition of these enzymes. Four commercially available compounds with structural similarities to phospholipid substrates were tested as inhibitors. These were alexidine dihydrochloride (compound A), dioctadecyldimethylammonium bromide (compound O), 1,12 bis-(tributylphosphonium)dodecane dibromide (compound P), and decamethonium dibromide (compound D). The best phospholipase inhibitors (compounds A and P) were also the most potent antifungal agents by the standard broth microdilution test. Compound A was highly selective for secreted and cell-associated PLB activities and showed no inhibition of mammalian phospholipase A 2 at 0.25 μM. Compound O, which was specific for secretory and cytosolic LPL and LPTA and membrane-associated PLB, was not antifungal. We conclude that inhibitors of cryptococcal phospholipases can be selective for fungal enzymes and intrinsically antifungal. They also provide tools for assessing the relative importance of the various enzyme activities in virulence. Our results enable further rational structure-function studies to validate the use of phospholipases as antifungal targets.

scholarly journals Role of clathrin-mediated endocytosis in the use of heme and hemoglobin by the fungal pathogen Cryptococcus neoformans

2018 ◽  
Author(s):  
Gaurav Bairwa ◽  
Mélissa Caza ◽  
Linda Horianopoulos ◽  
Guanggan Hu ◽  
James Kronstad
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Sugar Metabolism ◽  
Heme Iron ◽  
Heme Uptake ◽  
Iron Source ◽  
Life Threatening ◽  
Uptake Process ◽  
Underlying Mechanisms

SummaryHeme is a major source of iron for pathogens of humans, and its use is critical in determining the outcome of infection and disease. Cryptococcus neoformans is an encapsulated fungal pathogen that causes life-threatening infections in immunocompromised individuals. C. neoformans effectively uses heme as an iron source but the underlying mechanisms are poorly defined. Non-iron metalloporphyrins (MPPs) are toxic analogues of heme and are thought to enter microbial cells via endogenous heme acquisition systems. We therefore carried out a mutant screen for susceptibility against manganese metalloporphyrin (Mn MPP) to identify new components for heme uptake in C. neoformans. We identified several genes involved in signaling, DNA repair, sugar metabolism and trafficking that play important roles in susceptibility to Mn MPP and in the use of heme as an iron source. We focused on investigating the role of clathrin-mediated endocytosis (CME) and found that several components of CME including Chc1, Las17, Rvs161 and Rvs167 are required for growth on heme and hemoglobin, and for endocytosis and intracellular trafficking of these molecules. We show that the hemoglobin uptake process in C. neoformans involves clathrin heavy chain, Chc1, which appears to co-localize with hemoglobin containing-vesicles and to potentially assist in proper delivery of hemoglobin to the vacuole. Additionally, C. neoformans strains lacking Chc1, Las17, Rvs161, or Rvs167 were defective in the elaboration of several key virulence factors and a las17 mutant was avirulent in a mouse model of cryptococcosis. Overall, this study unveils crucial functions of CME in the use of heme iron by C. neoformans and reveals a role for CME in fungal pathogenesis.

scholarly journals Networks of fibers and factors: regulation of capsule formation in Cryptococcus neoformans

F1000Research ◽  
2016 ◽  
Vol 5 ◽  
pp. 1786 ◽  
Author(s):  
Hao Ding ◽  
François L. Mayer ◽  
Eddy Sánchez-León ◽  
Glauber R. de S. Araújo ◽  
Susana Frases ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Cryptococcus Neoformans ◽  
Complex Network ◽  
Pathogenic Fungus ◽  
Capsule Formation ◽  
Iron Deprivation ◽  
Life Threatening

The ability of the pathogenic fungus Cryptococcus neoformans to cause life-threatening meningoencephalitis in immunocompromised individuals is due in large part to elaboration of a capsule consisting of polysaccharide fibers. The size of the cell-associated capsule is remarkably responsive to a variety of environmental and host conditions, but the mechanistic details of the regulation, synthesis, trafficking, and attachment of the polysaccharides are poorly understood. Recent studies reveal a complex network of transcription factors that influence capsule elaboration in response to several different signals of relevance to disease (e.g., iron deprivation). The emerging complexity of the network is consistent with the diversity of conditions that influence the capsule and illustrates the responsiveness of the fungus to both the environment and mammalian hosts.

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