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MBio Jun 2020The opportunistic fungal pathogen must adapt to the mammalian environment to establish an infection. Proteins facilitating adaptation to novel environments, such as...
The opportunistic fungal pathogen must adapt to the mammalian environment to establish an infection. Proteins facilitating adaptation to novel environments, such as chaperones, may be required for virulence. In this study, we identified a novel mitochondrial co-chaperone, Mrj1 (itochondrial espiration -domain protein ), necessary for virulence in The and J-domain-inactivated mutants had general growth defects at both routine laboratory and human body temperatures and were deficient in the major virulence factor of capsule elaboration. The latter phenotype was associated with cell wall changes and increased capsular polysaccharide shedding. Accordingly, the mutant was avirulent in a murine model of cryptococcosis. Mrj1 has a mitochondrial localization and co-immunoprecipitated with Qcr2, a core component of complex III of the electron transport chain. The mutants were deficient in mitochondrial functions, including growth on alternative carbon sources, growth without iron, and mitochondrial polarization. They were also insensitive to complex III inhibitors and hypersensitive to an alternative oxidase (AOX) inhibitor, suggesting that Mrj1 functions in respiration. In support of this conclusion, mutants also had elevated basal oxygen consumption rates which were completely abolished by the addition of the AOX inhibitor, confirming that Mrj1 is required for mitochondrial respiration through complexes III and IV. Furthermore, inhibition of complex III phenocopied the capsule and cell wall defects of the mutants. Taken together, these results indicate that Mrj1 is required for normal mitochondrial respiration, a key aspect of adaptation to the host environment and virulence. is the causative agent of cryptococcal meningitis, a disease responsible for ∼15% of all HIV-related deaths. Unfortunately, development of antifungal drugs is challenging because potential targets are conserved between humans and In this context, we characterized a unique J-domain protein, Mrj1, which lacks orthologs in humans. We showed that Mrj1 was required for normal mitochondrial respiration and that mutants lacking Mrj1 were deficient in growth, capsule elaboration, and virulence. Furthermore, we were able to phenocopy the defects in growth and capsule elaboration by inhibiting respiration. This result suggests that the role of Mrj1 in mitochondrial function was responsible for the observed virulence defects and reinforces the importance of mitochondria to fungal pathogenesis. Mitochondria are difficult to target, as their function is also key to human cells; however, Mrj1 presents an opportunity to target a unique fungal protein required for mitochondrial function and virulence in .
Topics: Animals; Cryptococcosis; Cryptococcus neoformans; Female; Fungal Proteins; Mice; Mice, Inbred BALB C; Mitochondria; Mutation; Oxidation-Reduction; Virulence
PubMed: 32518190
DOI: 10.1128/mBio.01127-20 -
Metallomics : Integrated Biometal... Mar 2017The devastating infections that fungal pathogens cause in humans are underappreciated relative to viral, bacterial and parasitic diseases. In recent years, the... (Review)
Review
The devastating infections that fungal pathogens cause in humans are underappreciated relative to viral, bacterial and parasitic diseases. In recent years, the contributions to virulence of reductive iron uptake, siderophore-mediated uptake and heme acquisition have been identified in the best studied and most life-threatening fungal pathogens: Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus. In particular, exciting new work illustrates the importance of iron acquisition from heme and hemoglobin in the virulence of pathogenic yeasts. However, the challenge of establishing how these fungi gain access to hemoglobin in blood and to other sources of heme remains to be fully addressed. Recent studies are also expanding our knowledge of iron uptake in less-well studied fungal pathogens, including dimorphic fungi where new information reveals an integration of iron acquisition with morphogenesis and cell-surface properties for adhesion to host cells. Overall, the accumulating information provides opportunities to exploit iron acquisition for antifungal therapy, and new work highlights the development of specific inhibitors of siderophore biosynthesis and metal chelators for therapeutic use alone or in conjunction with existing antifungal drugs. It is clear that iron-related therapies will need to be customized for specific diseases because the emerging view is that fungal pathogens use different combinations of strategies for iron acquisition in the varied niches of vertebrate hosts.
Topics: Animals; Aspergillosis; Aspergillus fumigatus; Cryptococcosis; Cryptococcus neoformans; Humans; Iron; Virulence
PubMed: 28217776
DOI: 10.1039/c6mt00301j -
Fungal Genetics and Biology : FG & B Dec 2014Opportunistic pathogens like Cryptococcus neoformans are constantly exposed to changing environments, in their natural habitat as well as when encountering a human host....
Opportunistic pathogens like Cryptococcus neoformans are constantly exposed to changing environments, in their natural habitat as well as when encountering a human host. This requires a coordinated program to regulate gene expression that can act at the levels of mRNA synthesis and also mRNA degradation. Here, we find that deletion of the gene encoding the major cytoplasmic 5'→3' exonuclease Xrn1p in C. neoformans has important consequences for virulence associated phenotypes such as growth at 37 °C, capsule and melanin. In an invertebrate model of cryptococcosis the alteration of these virulence properties corresponds to avirulence of the xrn1Δ mutant strains. Additionally, deletion of XRN1 impairs uni- and bisexual mating. On a molecular level, the absence of XRN1 is associated with the upregulation of other major exonuclease encoding genes (i.e. XRN2 and RRP44). Using inducible alleles of RRP44 and XRN2, we show that artificial overexpression of these genes alters LAC1 gene expression and mating. Our data thus suggest the existence of a complex interdependent regulation of exonuclease encoding genes that impact upon virulence and mating in C. neoformans.
Topics: Cryptococcus neoformans; Exoribonucleases; Fungal Proteins; Gene Deletion; Reproduction; Virulence
PubMed: 25267175
DOI: 10.1016/j.fgb.2014.09.007 -
Microbiology (Reading, England) Jan 2006Phenotypic switching has been described in serotype A and D strains of Cryptococcus neoformans. It occurs in vivo during chronic infection and is associated with... (Review)
Review
Phenotypic switching has been described in serotype A and D strains of Cryptococcus neoformans. It occurs in vivo during chronic infection and is associated with differential gene expression and changes in virulence. The switch involves changes in the polysaccharide capsule and cell wall that affect the yeast's ability to resist phagocytosis. In addition, the phenotypic switch variants elicit qualitatively different inflammatory responses in the host. In animal models of chronic cryptococosis, the immune response of the host ultimately determines which of the switch variants are selected and maintained. The importance of phenotypic switching is further underscored by several findings that are relevant in the setting of human disease. These include the ability of the mucoid colony variant of RC-2 (RC-2 MC) but not the smooth variant (RC-2 SM) to promote increased intracerebral pressure in a rat model of cryptococcal meningitis. Furthermore, chemotherapeutic and immunological antifungal interventions can promote the selection of the RC-2 MC variant during chronic murine infection.
Topics: Animals; Bacterial Capsules; Chronic Disease; Cryptococcosis; Cryptococcus neoformans; Genes, Bacterial; Genetic Variation; Humans; Intracranial Pressure; Meningitis, Cryptococcal; Mice; Phagocytosis; Polysaccharides; Rats; Selection, Genetic; Virulence
PubMed: 16385110
DOI: 10.1099/mic.0.28451-0 -
MBio Mar 2017The pathogenic species of are a major cause of mortality owing to severe infections in immunocompromised as well as immunocompetent individuals. Although antifungal...
The pathogenic species of are a major cause of mortality owing to severe infections in immunocompromised as well as immunocompetent individuals. Although antifungal treatment is usually effective, many patients relapse after treatment, and in such cases, comparative analyses of the genomes of incident and relapse isolates may reveal evidence of determinative, microevolutionary changes within the host. Here, we analyzed serial isolates cultured from cerebrospinal fluid specimens of 18 South African patients with recurrent cryptococcal meningitis. The time between collection of the incident isolates and collection of the relapse isolates ranged from 124 days to 290 days, and the analyses revealed that, during this period within the patients, the isolates underwent several genetic and phenotypic changes. Considering the vast genetic diversity of cryptococcal isolates in sub-Saharan Africa, it was not surprising to find that the relapse isolates had acquired different genetic and correlative phenotypic changes. They exhibited various mechanisms for enhancing virulence, such as growth at 39°C, adaptation to stress, and capsule production; a remarkable amplification of at the native and unlinked locus may provide stable resistance to fluconazole. Our data provide a deeper understanding of the microevolution of species under pressure from antifungal chemotherapy and host immune responses. This investigation clearly suggests a promising strategy to identify novel targets for improved diagnosis, therapy, and prognosis. Opportunistic infections caused by species of the pathogenic yeast lead to chronic meningoencephalitis and continue to ravage thousands of patients with HIV/AIDS. Despite receiving antifungal treatment, over 10% of patients develop recurrent disease. In this study, we collected isolates of from cerebrospinal fluid specimens of 18 patients at the time of their diagnosis and when they relapsed several months later. We then sequenced and compared the genomic DNAs of each pair of initial and relapse isolates. We also tested the isolates for several key properties related to cryptococcal virulence as well as for their susceptibility to the antifungal drug fluconazole. These analyses revealed that the relapsing isolates manifested multiple genetic and chromosomal changes that affected a variety of genes implicated in the pathogenicity of or resistance to fluconazole. This application of comparative genomics to serial clinical isolates provides a blueprint for identifying the mechanisms whereby pathogenic microbes adapt within patients to prolong disease.
Topics: Adaptation, Biological; Cerebrospinal Fluid; Cryptococcus gattii; Cryptococcus neoformans; Drug Resistance, Fungal; Evolution, Molecular; Genotype; Humans; Longitudinal Studies; Meningitis, Cryptococcal; Phenotype; Recurrence; South Africa; Temperature; Virulence
PubMed: 28270580
DOI: 10.1128/mBio.00166-17 -
Cellular Microbiology Mar 2009Efficient communication with the environment is critical for all living organisms. Fungi utilize complex signalling systems to sense their environments and control... (Review)
Review
Efficient communication with the environment is critical for all living organisms. Fungi utilize complex signalling systems to sense their environments and control proliferation, development and in some cases virulence. Well-studied signalling pathways include the protein kinase A/cyclic AMP (cAMP), protein kinase C (PKC)/mitogen-activated protein kinase (MAPK), lipid signalling cascades, and the calcium-calcineurin signalling pathway. The human pathogenic basidiomycetous fungus Cryptococcus neoformans deploys sensitive signalling systems to survive in the human host, leading to life-threatening meningoencephalitis. Known virulence traits of this fungus, including the antioxidant melanin production, the antiphagocytic polysaccharide capsule and the ability to grow at 37 degrees C, are orchestrated by complex signalling networks, whose understanding is crucial to better treat, diagnose and prevent cryptococcosis.
Topics: Cryptococcosis; Cryptococcus neoformans; Humans; Signal Transduction; Virulence; Virulence Factors
PubMed: 19170685
DOI: 10.1111/j.1462-5822.2008.01273.x -
International Journal of Molecular... Feb 2020Zinc is one of the essential trace elements in eukaryotes and it is a critical structural component of a large number of proteins. Zinc finger proteins (ZNFs) are... (Review)
Review
Zinc is one of the essential trace elements in eukaryotes and it is a critical structural component of a large number of proteins. Zinc finger proteins (ZNFs) are zinc-finger domain-containing proteins stabilized by bound zinc ions and they form the most abundant proteins, serving extraordinarily diverse biological functions. In recent years, many ZNFs have been identified and characterized in the human fungal pathogen , a fungal pathogen causing fatal meningitis mainly in immunocompromised individuals. It has been shown that ZNFs play important roles in the morphological development, differentiation, and virulence of . In this review, we, first, briefly introduce the ZNFs and their classification. Then, we explain the identification and classification of the ZNFs in . Next, we focus on the biological role of the ZNFs functionally characterized so far in the sexual reproduction, virulence factor production, ion homeostasis, pathogenesis, and stress resistance in . We also discuss the perspectives on future function studies of ZNFs in .
Topics: Cryptococcus neoformans; Fungal Proteins; Humans; Reproduction; Stress, Physiological; Virulence; Zinc Fingers
PubMed: 32085473
DOI: 10.3390/ijms21041361 -
Frontiers in Cellular and Infection... 2019The Mkt1-Pbp1 complex promotes mating-type switching by regulating the translation of mRNA in . Here, we performed immunoprecipitation assays and mass spectrometry...
The Mkt1-Pbp1 complex promotes mating-type switching by regulating the translation of mRNA in . Here, we performed immunoprecipitation assays and mass spectrometry analyses in the human fungal pathogen to show that Pbp1, a poly(A)-binding protein-binding protein, interacts with Mkt1 containing a PIN like-domain. Association of Pbp1 with Mkt1 was confirmed by co-immunoprecipitation assays. Results of spot dilution growth assays showed that unlike deletion mutant strains, deletion mutant strains were not resistant to heat stress compared with wild-type. However, similar to the deletion mutant strains, the deletion mutants exhibited both, defective dikaryotic hyphal production and reduced pheromone gene (α1) expression during mating. In addition, deletion of caused attenuated virulence in a murine intranasal inhalation model. Taken together, our findings reveal that Mkt1 plays a crucial role in sexual reproduction and virulence in .
Topics: Carrier Proteins; Cryptococcosis; Cryptococcus neoformans; Fungal Proteins; Gene Expression Regulation, Fungal; Genes, Mating Type, Fungal; Mutation; Protein Binding; Virulence
PubMed: 31681631
DOI: 10.3389/fcimb.2019.00355 -
Journal of Microbiology (Seoul, Korea) Mar 2016Lipid modification of proteins is a widespread, essential process whereby fatty acids, cholesterol, isoprenoids, phospholipids, or glycosylphospholipids are attached to... (Review)
Review
Lipid modification of proteins is a widespread, essential process whereby fatty acids, cholesterol, isoprenoids, phospholipids, or glycosylphospholipids are attached to polypeptides. These hydrophobic groups may affect protein structure, function, localization, and/or stability; as a consequence such modifications play critical regulatory roles in cellular systems. Recent advances in chemical biology and proteomics have allowed the profiling of modified proteins, enabling dissection of the functional consequences of lipid addition. The enzymes that mediate lipid modification are specific for both the lipid and protein substrates, and are conserved from fungi to humans. In this article we review these enzymes, their substrates, and the processes involved in eukaryotic lipid modification of proteins. We further focus on its occurrence in the fungal pathogen Cryptococcus neoformans, highlighting unique features that are both relevant for the biology of the organism and potentially important in the search for new therapies.
Topics: Acylation; Cryptococcosis; Cryptococcus neoformans; Fungal Proteins; Humans; Lipid Metabolism; Lipoylation; Models, Molecular; Prenylation; Protein Processing, Post-Translational; Proteomics
PubMed: 26920881
DOI: 10.1007/s12275-016-5626-6 -
ELife Oct 2018In the human fungal pathogen , sex can benefit its pathogenicity through production of meiospores, which are believed to offer both physical and meiosis-created lineage...
In the human fungal pathogen , sex can benefit its pathogenicity through production of meiospores, which are believed to offer both physical and meiosis-created lineage advantages for its infections. sporulation occurs following two parallel events, meiosis and differentiation of the basidium, the characteristic sexual structure of the basidiomycetes. However, the circuit integrating these events to ensure subsequent sporulation is unclear. Here, we show the spatiotemporal coordination of meiosis and basidial maturation by visualizing event-specific molecules in developing basidia defined by a quantitative approach. Monitoring of gene induction timing together with genetic analysis reveals co-regulation of the coordinated events by a shared regulatory program. Two RRM family regulators, Csa1 and Csa2, are crucial components that bridge meiosis and basidial maturation, further determining sporulation. We propose that the regulatory coordination of meiosis and basidial development serves as a determinant underlying the production of infectious meiospores in .
Topics: Cryptococcus neoformans; Fungal Proteins; Gene Expression Regulation, Fungal; Gene Regulatory Networks; Genes, Mating Type, Fungal; Meiosis; Mutation; Phenotype; Phylogeny; Spores, Fungal
PubMed: 30281018
DOI: 10.7554/eLife.38683