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Nitrogen source-dependent capsule induction in human pathogenic Cryptococcus species.

ABSTRACT: Cryptococcus neoformans causes meningoencephalitis and is an increasing human health threat. C. neoformans is neurotropic, and persists in the cerebrospinal fluid (CSF) of the mammalian host during infection. In order to survive in the host, pathogenic fungi must procure nutrients such as carbon and nitrogen. To enhance our understanding of nutrient acquisition during infection by Cryptococcus species, we examined utilization of nitrogen sources available in CSF. We screened for growth and capsule production of 817 global environmental and clinical isolates on various sources of nitrogen. Capsule production was assessed using ammonium and urea in the presence or absence of benomyl to determine the relationship of urea exposure to capsule production. Since urea is metabolized to ammonia and CO2 (a known signal for capsule induction), we examined urea metabolism mutants for their response to urea regarding capsule production. Non-preferred nitrogen sources were found to greatly affect capsule production in pathogenic species of Cryptococcus. Urea induced the greatest magnitude of capsule production. Capsule induction by urea was greater in Cryptococcus gattii strains than in C. neoformans strains. In addition, both environmental and clinical strains grew robustly on uric acid, casamino acids, creatinine, and asparagine as sole nitrogen sources. While substantial growth on nitrate was not apparent at day 3, growth was apparent by day 6 for all serotypes.

ORGANISM(S): Cryptococcus neoformans

PROVIDER: GSE46829 | GEO | 2013/09/25

SECONDARY ACCESSION(S): PRJNA202429

REPOSITORIES: GEO

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Nitrogen source-dependent capsule induction in human pathogenic Cryptococcus species.

Project description:Cryptococcus neoformans causes meningoencephalitis and is an increasing human health threat. C. neoformans is neurotropic, and persists in the cerebrospinal fluid (CSF) of the mammalian host during infection. In order to survive in the host, pathogenic fungi must procure nutrients such as carbon and nitrogen. To enhance our understanding of nutrient acquisition during infection by Cryptococcus species, we examined utilization of nitrogen sources available in CSF. We screened for growth and capsule production of 817 global environmental and clinical isolates on various sources of nitrogen. Capsule production was assessed using ammonium and urea in the presence or absence of benomyl to determine the relationship of urea exposure to capsule production. Since urea is metabolized to ammonia and CO2 (a known signal for capsule induction), we examined urea metabolism mutants for their response to urea regarding capsule production. Non-preferred nitrogen sources were found to greatly affect capsule production in pathogenic species of Cryptococcus. Urea induced the greatest magnitude of capsule production. Capsule induction by urea was greater in Cryptococcus gattii strains than in C. neoformans strains. In addition, both environmental and clinical strains grew robustly on uric acid, casamino acids, creatinine, and asparagine as sole nitrogen sources. While substantial growth on nitrate was not apparent at day 3, growth was apparent by day 6 for all serotypes. In this study, transcription profiles of urea pathway mutants (ure1 and amt1/2) and WT Cryptococcus neoformans strains were compared in a dye-swap experiment following 1hr exposure to proline or proline + urea (.25g/L).

2013-09-25 | E-GEOD-46829 | biostudies-arrayexpress

Differentiated protein extracts from freshwater and terrestrial mollusks inhibit virulence factor production in Cryptococcus neoformans

Project description:Cryptococcus neoformans is a fungal pathogen responsible for an increased mortality among immunocompromised individuals. Long antifungal therapies to treat cryptococcal infections have compounded the occurrence of resistant strains that threaten the efficacy of current treatments. In this senseDue to resistance mechanisms, discovery of compounds that inhibit virulence factors, rather than kill the fungus, have emerged as potential new strategies to combat infection and reduce the rate of resistance due to lower selective pressure. Invertebrates rely solely on an effective innate immune system to prevent infections, provide providing a potential one health approach for discovery of novel antifungal and antibacterial compounds. Here, we demonstrate a differentiated extraction of proteins from three mollusks (freshwater and terrestrial) and evaluate extract their effects against the growth and virulence factor production (thermotolerance, melanin, capsule, and biofilm) in C. neoformans. We show that clarified extracts of Planorbella pilsbryi have a fungicidal effect on cryptococcal cells in a comparable way to Fluconazolefluconazole. Similarly, crude and clarifiedall extracts of Cipangopaludina chinensis not only affects cryptococcal thermotolerance but also impairs biofilm and capsule production. In addition, incubation of C. neoformans with clarified extracts of Cepaea nemoralis extracts reduced capsule production. Using inhibitory activity of extracts against peptidases related with virulence factors and Quantitative quantitative proteomics arose distinct proteome signatures for each extract and proposed proteins driving the observed anti-virulence properties. Overall, this work demonstratesproves the potential of compounds derived from natural sources to inhibit virulence factor production in a clinically important fungal pathogen.

2023-03-06 | PXD038987 | Pride

Transcriptome of ex vivo-sorted and in vitro-grown Cryptococcus neoformans cells

Project description:We compared the transcriptome of subpopulations of Cryptococcus neoformans cells within the lungs and C. neoformans cells cultured in capsule repressing medium, capsule inducing medium, and capsule inducing medium with the addition of 10% conditioned medium from cells grown in capsule repressing medium. The aim of the study was to identify genes that regulate C. neoformans cell body and capsule size reductions.

2022-01-01 | GSE152784 | GEO

Unraveling capsule biosynthesis and signaling networks in Cryptococcus neoformans

Project description:Cryptococcus neoformans is an opportunistic basidiomycete pathogen that is a major etiological agent of fungal meningoencephalitis leading to more than 180,000 deaths worldwide annually. For this pathogen, the polysaccharide capsule is a key virulence factor, which interferes with the phagocytosis by host innate immune cells, but its complex signaling networks remain elusive. In this study, we systematically analyzed capsule biosynthesis and signaling networks by using C. neoformans transcription factor (TF) and kinase mutant libraries under diverse capsule-inducing conditions, such as Dulbecco’s Modified Eagle’s (DME), Littman’s medium (LIT) and fetal bovine serum (FBS) medium. We found that deletion of GAT201, YAP1, BZP4, and ADA2 consistently causes capsule production defects in all tested media, indicating that they are capsule-regulating core TFs. Epistatic and expression analysis showed that Yap1 and Ada2 control Gat201 upstream, whereas Bzp4 and Gat201 regulate capsule production independently. We next searched for potential upstream kinases and found that mutants deleted of PKA1, BUD32, POS5, IRE1 or CDC2801 showed reduced capsule production under all three capsule induction conditions, whereas mutants deleted of HOG1 and IRK5 displayed enhanced capsule production. Notably, Pka1 and Irk5 controls induction of GAT201 and BZP4, respectively, under capsule induction condition. Finally, we monitored transcriptome profiles governed by Bzp4, Gat201, and Ada2 under capsule-inducing condition and demonstrated that these TFs regulate redundant and unique sets of downstream target genes. In conclusion, this study provides further insight into the complex regulatory mechanism of capsule production related signaling pathways in C. neoformans.

2022-10-18 | GSE208163 | GEO

The Cryptococcus transcriptome at the site of human meningitis

Project description:Cryptococcus neoformans is a major cause of fungal meningitis in immunocompromised individuals worldwide. Studies have categorized the transcriptome of Cryptococcus under various stresses, such as temperature, nitric oxide, iron, antifungal drugs and macrophages. However, an accurate and comprehensive transcriptome profiling of C. neoformans in the human host may allow an even better understanding of its survival and disease production. In this study, we isolated RNA from yeast cells taken directly from CSF of two individuals with cryptococcal meningitis. RNA-Seq was used to generate and compare transcriptional profiles from those yeast cells exposed to three environmental conditions. Under same conditions, similar expression patterns were found between the two strains with different genotypes. Yeast cells from in vivo CSF appear to be more metabolically active compared to those exposed to ex vivo CSF. Moreover, genes that were identified as significantly up-regulated in both ex vivo CSF and in vivo CSF conditions compared with growth in YPD appear to be important for the virulence of Cryptococcus. In the central nervous system, differentially expressed genes, single nucleotide variants and novel genes between strains were identified to emphasize that strains have consensus expression patterns but they do have their unique features. Genes with transporter functions were found to be enriched in the regulated transcripts demonstrating this important function of yeasts under host stress. These findings provide the platform for further interrogation into how this yeast survives in humans to provide identification of possible antifungal target(s) and/or genetic signatures to predict outcome. Examination of mRNA expression levels under three different conditions of two different strains with different genotypes

2013-11-10 | E-GEOD-51573 | biostudies-arrayexpress

The Cryptococcus transcriptome at the site of human meningitis

2013-11-10 | GSE51573 | GEO

Usv101 is a key regulator of cryptococcal virulence and determinant of host response

Project description:Cryptococcus neoformans is a fungal pathogen responsible for hundreds of thousands of deaths per year. Its critical virulence factor is a polysacharride capsule which grows large upon entry into a mammalian host. We previously identified USV101 as a transcription factor whose deletion results in enlarged capsules. Here, we characterize strains lacking or overexpressing USV101 in terms of their virulence-related phenotypes, the altered course of infection by them and immune response to them in a mouse model, the relationship of Usv101 to other transcription factors involved in capsule regulation, and the changes in Usv101 activity during capsule induction. To study the function of Usv101, a key C. neoformans regulator of virulence, and its interactions with downstream capsule-regulating TFs GAT201 and SP1, expression profiles were generated by RNA-seq of a usv101 deletion mutant, a USV101 overexpression mutant, strains expressing GAT201 under various promoters, various double mutants, and wildtype cells grown in a capsule non-inducing condition, a capsule inducing condition for 90 minutes, or a capsule inducing condition for 24 hours.

2016-03-31 | E-GEOD-69532 | biostudies-arrayexpress

Landscape of gene expression variation of natural isolates of Cryptococcus neoformans in response to biologically relevant stresses

Project description:Cryptococcus neoformans is an opportunistic environmental fungal pathogen that at its peak epidemic levels caused an estimated million cases of cryptococcal meningitis per year worldwide. This yeast can adapt to various external (trees, soil, and/or bird excreta) and internal environments (intracellular microenvironments of phagocytes and/or free-living in host tissues/fluids). The genetic basic for this adaptation is not fully characterized and primarily relies on a single reference C. neoformans strain. To uncover genes important for yeast infection and disease progression we have compared the gene expression from multiple strains of different lineages (VNI and VNBI) and sources (environment and clinic) under diverse conditions. Here, we used RNA sequencing to assess the transcriptional profiles of seven C. neoformans isolates grown in five representative in vitro, environmental, and in vivo conditions. We characterized gene expression differences between isolates from two of the major lineages of this species, VNI and VNBI, between these conditions. Comparing isolates from these two lineages, we find that genes showing lineage specific expression are enriched in sub-telomeric regions and in lineage specific gene clusters. The major gene expression differences common in all conditions are involved in the utilization of different sugar and nitrogen sources. Comparing gene expression in macrophages and cerebrospinal fluid (CSF) also revealed several specific pathways down-regulated in CSF including lipid and carbohydrate metabolism, and valine, leucine and isoleucine degradation, which may reflect the usage of host nutrients during growth in the mammalian subarachnoid space compared to MP. In summary, our study provides the widest view to date of the transcriptome variation of C. neoformans across natural strains and provides insights into genes important for major in vitro and in vivo growth stages.

2019-09-05 | GSE136879 | GEO

Usv101 is a key regulator of cryptococcal virulence and determinant of host response

2016-03-31 | GSE69532 | GEO

Natural compounds from freshwater mussels disrupt fungal virulence and overcome fluconazole resistance in Cryptococcus neoformans

Project description:Cryptococcus neoformans is a human fungal pathogen responsible for fatal infections, especially in patients with a depressed immune system. Overexposure to antifungal drugs due to prolonged treatment regimens and structure-similar applications in agriculture have weakened the efficacy of current antifungals in the clinic. The rapid evolution of antifungal resistance urges the discovery of new compounds that inhibit fungal virulence factors, rather than directly killing the pathogen as alternative strategies to overcome disease and reduce selective pressure towards resistance. Recent studies, including our own, have highlighted the antimicrobial properties of natural sources, such as invertebrates, against human fungal pathogens, including C. neoformans, through virulence factor impairment. Here, we evaluated the efficacy of freshwater mussel extracts (crude and clarified) against virulence factor production (i.e., thermotolerance, melanin, capsule, and biofilm) in C. neoformans. Similarly, we demonstrated the critical potential of these extracts to increase the susceptibility of the pathogen to fluconazole across resistant strains, overcoming a globally devastating problem. Additionally, we measured the inhibitory activity of the extracts against peptidases related to fungal virulence and drug resistance. Furthermore, we integrated these phenotypic findings with quantitative proteomics profiling to define distinct signatures of each treatment and validated a new mechanism of anti-virulence action for a selected extract. By understanding the mechanisms driving the antifungal activity of mussels, we may develop innovative treatments for fungal infections lacking susceptibility to conventional drugs.

2024-01-27 | PXD043643 | Pride

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