• Mycobiology
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• v.42 no.4
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• pp.427-431
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• 2014

Mitochondrial protein Nfu1 plays an important role in the assembly of mitochondrial Fe-S clusters and intracellular iron homeostasis in the model yeast Saccharomyces cerevisiae. In this study, we identified the Nfu1 ortholog in the human fungal pathogen Cryptococcus neoformans. Our data showed that C. neoformans Nfu1 localized in the mitochondria and influenced homeostasis of essential metals such as iron, copper and manganese. Marked growth defects were observed in the mutant lacking NFU1, which suggests a critical role of Nfu1 in Fe-S cluster biosynthesis and intracellular metal homeostasis in C. neoformans.

• Mycobiology
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• v.31 no.4
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• pp.248-250
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• 2003

Kojic acid was investigated for its antifungal activity against the human pathogenic fungi including Candida albicans, Cryptococcus neoformans and Trichophyton rubrum. For C. albicans, C. neoformans and T. rubrum, the MIC(minimum inhibitory concentration) of kojic acid was 640, 80 and 160 ${\mu}g/ml$, respectively. In C. neoformans, melanin-producing yeast, kojic acid-treated nonmelanized cell was more susceptible to magainin than melanized cell, suggesting melanin give a protective function against microbial peptide.

• Microbiology and Biotechnology Letters
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• v.38 no.1
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• pp.13-18
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• 2010

Past decade systemic mycoses caused by opportunistic human fungal pathogens, including Candida, Aspergillus, and Cryptococcus, have been a growing problem for both immunocompromised and immunocompetent individuals. Particularly, Cryptococcus neoformans has recently emerged as a major fungal pathogen, which can cause fungal pneumonia and meningitis that are lethal if not timely medicated. However, treatment for cryptococcosis has been difficult due to a lack of proper anti-cryptococcal drugs with fungicidal activity and less toxicity. In this review we introduced novel therapeutic methods for treating cryptococcosis by exploring pathogenomic signa1ing networks of C. neoformans with genome-wide transcriptome approaches as well as diverse molecular/genetic tools.

• Mycobiology
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• v.42 no.1
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• pp.73-78
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• 2014

Cryptococcal infection is primarily caused by two species, Cryptococcus neoformans and C. gattii. Between the two species, C. neoformans var. grubii is the major causative agent of cryptococcosis in Asia. We investigated the molecular characteristics of 46 isolates of C. neoformans from patients with cryptococcosis between 2008 and 2012 in Seoul, Korea. All the isolates were determined to be C. neoformans var. grubii (serotype A), mating type $MAT{\alpha}$, and molecular type VNI by PCR-restriction fragment length polymorphism of the URA5 gene. Multilocus sequencing type (MLST) analysis using the International Society of Human and Animal Mycoses (ISHAM) consensus MLST scheme identified two sequence types (ST). Out of the 46 strains, 44 (95.7%) were identified as ST5, and remaining 2 were identified as ST31. Our study revealed that the clinical strains of C. neoformans in Korea are genetically homogeneous with the VNI/ST5 genotypes, and new appearance of VNI/ST31 genotype may serve as an important indicator of global genetic analysis.

• Mycobiology
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• v.37 no.3
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• pp.161-170
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• 2009

Cryptococcus neoformans is a basidiomycete human fungal pathogen that causes meningoencephalitis in both immunocompromised and immunocompetent individuals. The ability to sense and respond to diverse extracellular signals is essential for the pathogen to infect and cause disease in the host. Four major stress-activated signaling (SAS) pathways have been characterized in C. neoformans, including the HOG (high osmolarity glycerol response), PKC/Mpk1 MAPK (mitogen-activated protein kinase), calcium-dependent calcineurin, and RAS signaling pathways. The HOG pathway in C. neoformans not only controls responses to diverse environmental stresses, including osmotic shock, UV irradiation, oxidative stress, heavy metal stress, antifungal drugs, toxic metabolites, and high temperature, but also regulates ergosterol biosynthesis. The PKC(protein kinase C)/Mpk1 pathway in C. neoformans is involved in a variety of stress responses, including osmotic, oxidative, and nitrosative stresses and breaches of cell wall integrity. The $Ca^{2+}$/calmodulin- and Ras-signaling pathways also play critical roles in adaptation to certain environmental stresses, such as high temperature and sexual differentiation. Perturbation of the SAS pathways not only impairs the ability of C. neoformans to resist a variety of environmental stresses during host infection, but also affects production of virulence factors, such as capsule and melanin. A drug(s) capable of targeting signaling components of the SAS pathway will be effective for treatment of cryptococcosis.

• The Journal of the Korean Society for Microbiology
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• v.21 no.1
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• pp.127-131
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• 1986

The mating types and serotypes of 10 clinical isolates of Cryptococcus neoformans have been investigated. Seven isolates were serotype A and three were serotype D and thus they fell in C. neoformans var. neoformans. Mating types of six isolates were found $\alpha$ and two were $\alpha$ but another two isolates were untypable. Enzyme linked immuno-sorbent assay(ELISA) using rabbit hyper-immune serum to cryptococcal polysaccharides was well adapted to the analysis of capsular polysaccharides in sera of the patients with cryptococcal meningitis.

• Biomedical Science Letters
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• v.16 no.3
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• pp.139-149
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• 2010

The present study was carried out to elucidate whether an environmental strain of Cryptococcus neoformans (environmental C. neoformans) isolated from an environmental source in a park of Busan has an acute pathophysiological effect in rats. On the second day after peritoneal inoculation of environmental C. neoformans, adverse effects occurred from the viewpoint of hematology and biochemistry. Eosinophil damages and crystal formations were found in the blood. Disturbances in cytokines production were observed in the cerebral and pulmonary tissues. Fungal budding existed in the brain, lung, liver and kidney. Tissue injury findings such as inflammation, leukocyte infiltration, bleeding, or degeneration were found in the brain, lung, liver and kidney. The present data suggest that the environmental C. neoformans can cause systematically harmful effects even for short periods of infection (two days of cryptococcal infection) and the adverse effects are summarized as immune derangements and biochemical and/or histological dysfunction and injury on major organ such as the brain, lung, liver and kidney in the immunocompetent hosts. Further studies should be focused on comparing the differences between environmental and clinical strains of C. neoformans.

• Mycobiology
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• v.51 no.6
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• pp.452-462
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• 2023

Opportunistic infections due to Cryptococcus neoformans and C. gattii species complexes continue to rise unabated among HIV/AIDS patients, despite improved antifungal therapies. Here, we collected a total of 20 environmental and 25 presumptive clinical cryptococcal isolates from cerebrospinal fluid (CSF) samples of 175 patients enrolled in an ongoing clinical trial Ambition 1 Project (Botswana-Harvard Partnership). Identity confirmation of the isolates was done using MALDI-TOF MS and PCR. We describe the diversity of the isolates by PCR fingerprinting and sequencing (Oxford Nanopore Technology) of the intergenic spacer region. Mating types of the isolates were determined by amplification of the MAT locus. We report an unusual prevalence of 42.1% of C. neoformans × C. deneoformans hybrids Serotype AD (n = 16), followed by 39.5% of C. neoformans Serotype A (n = 15), 5.3% of C. deneoformans, Serotype D (n = 2), 7.9% of C. gattii (n = 3), and 5.3% of C. tetragattii (n = 2) in 38 representative isolates that have been characterized. Mating type-specific PCR performed on 38 representative environmental and clinical isolates revealed that 16 (42.1%) were MATa/MAT𝛼 hybrids, 17 (44.7%) were MAT𝛼, and five (13.2%) possessed MATa mating type. We used conventional and NGS platforms to demonstrate a potential link between environmental and clinical isolates and lay a foundation to further describe mating patterns/history in Botswana.

• Biomedical Science Letters
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• v.19 no.3
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• pp.213-223
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• 2013

The objectives of this study are to develop a molecular diagnosis to differentiate serotypes and mating-types of C. neoformans/C. gattii complex isolates from pigeon droppings in Korea and to elucidate molecular epidemiology of the isolates. Phenotypes and genotypes of C. neoformans/C. gattii complex isolates were identified by biochemical properties and PCR using specific CNLAC1 gene, respectively. To classify serotypes and mating-types of C. neoformans/C. gattii complex isolates, the five reference strains and thirty-three isolates in Korea were investigated by restriction fragment length polymorphism (RFLP) analysis using CNLAC1 gene for varieties, by random amplified polymorphic DNA (RAPD) for serotyping, and by PCR using specific primer sets for mating typing. All isolates in Korea were belonged to C. neoformans var. grubii (serotype A) by RFLP and RAPD patterns which showed high sensitivity and specificity. Therefore, RFLP and RFLP were available to differentiate varieties and serotypes of C. neoformans. Amplification patterns of the five reference strains by specific PCR for mating typing were differentiable, and all isolates were classified into $MAT{\alpha}$. All C. neoformans environmental isolates in Korea were Cr. neoformans serotype A and $MAT{\alpha}$ which is a more virulent pathogen. This study suggests that RFLP and RAPD are rapid and correct molecular diagnosis tools for epidemiology of C. neoformans/C. gattii complex isolates.

• Mycobiology
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• v.42 no.1
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• pp.52-58
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• 2014

A nucleoside diphosphate-linked moiety X (Nudix) hydrolase-like gene, YSA1, has been identified as one of the gromwell plant extract-responsive genes in Cryptococcus neoformans. Ysa1 is known to control intracellular concentrations of ADP-ribose or O-acetyl-ADP-ribose, and has diverse biological functions, including the response to oxidative stress in the ascomycete yeast, Saccharomyces cerevisiae. In this study, we characterized the role of YSA1 in the stress response and adaptation of the basidiomycete yeast, C. neoformans. We constructed three independent deletion mutants for YSA1, and analyzed their mutant phenotypes. We found that ysa1 mutants did not show increased sensitivity to reactive oxygen species-producing oxidative damage agents, such as hydrogen peroxide and menadione, but exhibited increased sensitivity to diamide, which is a thiol-specific oxidant. Ysa1 was dispensable for the response to most environmental stresses, such as genotoxic, osmotic, and endoplasmic reticulum stress. In conclusion, modulation of YSA1 may regulate the cellular response and adaptation of C. neoformans to certain oxidative stresses and contribute to the evolution of antifungal drug resistance.