scholarly journals Thermotolerance in the pathogen Cryptococcus neoformans is linked to antigen masking via mRNA decay-dependent reprogramming

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Amanda L. M. Bloom ◽  
Richard M. Jin ◽  
Jay Leipheimer ◽  
Jonathan E. Bard ◽  
Donald Yergeau ◽  
...  
Keyword(s):  
Ribosomal Protein ◽  
Cryptococcus Neoformans ◽  
Fungal Pathogens ◽  
Mrna Decay ◽  
Wild Type Strain ◽  
Core Body Temperature ◽  
Temperature Adaptation ◽  
Wild Type ◽  
Transcriptomic Changes ◽  
Core Body

Abstract A common feature shared by systemic fungal pathogens of environmental origin, such as Cryptococcus neoformans, is their ability to adapt to mammalian core body temperature. In C. neoformans, this adaptation is accompanied by Ccr4-mediated decay of ribosomal protein mRNAs. Here we use the related, but thermo-intolerant species Cryptococcus amylolentus to demonstrate that this response contributes to host-temperature adaptation and pathogenicity of cryptococci. In a C. neoformans ccr4Δ mutant, stabilized ribosomal protein mRNAs are retained in the translating pool, and stress-induced transcriptomic changes are reduced in comparison with the wild type strain, likely due to ineffective translation of transcription factors. In addition, the mutant displays increased exposure of cell wall glucans, and recognition by Dectin-1 results in increased phagocytosis by lung macrophages, linking mRNA decay to adaptation and immune evasion.

Reduced recovery of a Cryptococcus neoformans adherence mutant from a rat model of cryptococcosis

1995 ◽  
Vol 41 (4-5) ◽  
pp. 428-432 ◽  
Author(s):  
Glenn J. Merkel ◽  
Barbara A. Scofield ◽  
Frederick J. Rescorla ◽  
Rong Yang ◽  
Jay L. Grosfeld
Keyword(s):  
Cryptococcus Neoformans ◽  
Type Strain ◽  
Wild Type Strain ◽  
Organ Distribution ◽  
Wild Type ◽  
Cell Adherence ◽  
Short Period ◽  
Cyclophosphamide Treatment ◽  
Radiometric Assay ◽  
Reduced Adherence

Stable mutants of Cryptococcus neoformans (strain CSF-1) induced by treatment with ultraviolet light and nitrosoguanidine were isolated that demonstrated reduced adherence to glial cells in culture. Adherence of the mutants, as measured by a radiometric assay, was reduced by 50–70% of that attained for the parent CSF-1 strain. The adherence mutants appeared to be phenotypically similar to the CSF-1 strain. However, all but one mutant (designated as CSF-23) demonstrated slightly slower growth rates than the wild-type strain. The CSF-1 and CSF-23 strains were injected intravenously and intratracheally into normal rats and rats immunosuppressed by cyclophosphamide treatment, and the organ distribution and recovery of viable yeasts determined over 2–96 h. During this relatively short period of observation the majority of the yeasts were localized in the lungs. By either route of injection, the recovery of the CSF-23 adherence mutant was reduced by as much as 90% of that obtained for the wild-type strain. The results indicated that host cell adherence may be important for the persistence of cryptococci in tissue and that further studies with the adherence mutants are warranted.Key words: Cryptococcus, adherence, cryptococcosis, yeast.

scholarly journals Infection Components of Wild-Type and Mutant Strains of Colletotrichum gloeosporioides f. sp. aeschynomene on Northern Jointvetch

Plant Disease ◽  
1997 ◽  
Vol 81 (4) ◽  
pp. 404-409 ◽  
Author(s):  
Y. Luo ◽  
D. O. TeBeest
Keyword(s):  
Fungal Pathogens ◽  
Wild Type Strain ◽  
Colletotrichum Gloeosporioides ◽  
Wild Type ◽  
Biological Control Of Weeds ◽  
Lesion Number ◽  
Mutant Strains ◽  
Controlled Environments ◽  
Resistant Strains ◽  
Type Strains

Colletotrichum gloeosporioides f. sp. aeschynomene causes an anthracnose of northern jointvetch, Aeschynomene virginica. Infection components, including lesion number, latent period, lesion expansion rate, and sporulation, were measured in experiments conducted in controlled environments. Two wild-type strains (3-1-3 and CLA 5A), four benomyl-resistant strains (B13, B15, B18 and B21), and four nitrate nonutilizing mutant strains (Nit A, Nit R, Nit L, and Nit T) of the pathogen were tested. Nitrate nonutilizing strains caused significantly fewer lesions on northern jointvetch than did wild-type and benomyl-resistant strains. Latent periods were significantly shorter for the wild-type strain CLA 5A than for most other strains. Lesion expansion rates of all benomyl-resistant strains were significantly slower than those of the wild- type strains. Large variations in sporulation were observed for most strains, and no differences in sporulation were found between wild-type and mutant strains. The usefulness of infection component analysis for the identification of competitiveness of strains of fungal pathogens for biological control of weeds is discussed.

γ-Aminobutyric Acid Type A Receptor β2 Subunit Mediates the Hypothermic Effect of Etomidate in Mice

2004 ◽  
Vol 100 (6) ◽  
pp. 1438-1445 ◽  
Author(s):  
Jennifer Cirone ◽  
Thomas W. Rosahl ◽  
David S. Reynolds ◽  
Richard J. Newman ◽  
Gillian F. O'Meara ◽  
...  
Keyword(s):  
Gabaa Receptor ◽  
Core Body Temperature ◽  
Mutant Mice ◽  
Aminobutyric Acid ◽  
Wild Type ◽  
Acid Type ◽  
Hypothermic Response ◽  
Beta 2 ◽  
Core Body ◽  
Receptor Beta

Background The authors have previously described that the gamma-aminobutyric acid type A (GABAA) receptor beta 2N265S mutation results in a knock-in mouse with reduced sensitivity to etomidate. After recovery from etomidate anesthesia, these mice have improved motor performance and less slow wave sleep. Because most clinically used anesthetics produce hypothermia, the effect of this mutation on core body temperature was investigated. Methods The effect of etomidate and propofol on core body temperature were measured using radiotelemetry in freely moving GABAA receptor beta 2N265S mutant mice and wild-type controls. Results beta 2N265S mutant mice have a reduced hypothermic response to anesthetic doses of etomidate compared with wild-type controls and after a transient loss of righting reflex regain normothermia more rapidly compared with wild-type controls. Subanesthetic doses of etomidate produce hypothermia, which was not observed in the mutant mice. Vehicle administration resulted in a stress-induced hyperthermic response in both genotypes. Propofol produced a hypothermic response that was similar in both genotypes. Conclusions The GABAA receptor beta 2 subunit mediates a significant proportion of the hypothermic effects of etomidate. As the beta 2 subunit mediates postrecovery ataxia and sedation, anesthetic agents that do not have in vivo potency at beta 2 subunit-containing receptors offer the potential for surgical anesthesia with improved recovery characteristics.

scholarly journals Transcriptional Profiling Identifies a Role for BrlA in the Response to Nitrogen Depletion and for StuA in the Regulation of Secondary Metabolite Clusters in Aspergillus fumigatus

2008 ◽  
Vol 8 (1) ◽  
pp. 104-115 ◽  
Author(s):  
Kwame Twumasi-Boateng ◽  
Yan Yu ◽  
Dan Chen ◽  
Fabrice N. Gravelat ◽  
William C. Nierman ◽  
...  
Keyword(s):  
Gene Expression ◽  
Aspergillus Fumigatus ◽  
Ribosomal Protein ◽  
Secondary Metabolite ◽  
Type Strain ◽  
Wild Type Strain ◽  
Protein Gene ◽  
Ribosomal Protein Gene ◽  
Wild Type ◽  
Tor Pathway

ABSTRACT Conidiation (asexual sporulation) is a key developmental process in filamentous fungi. We examined the gene regulatory roles of the Aspergillus fumigatus developmental transcription factors StuAp and BrlAp during conidiation. Conidiation was completely abrogated in an A. fumigatus ΔbrlA mutant and was severely impaired in a ΔstuA mutant. We determined the full genome conidiation transcriptomes of wild-type and ΔbrlA and ΔstuA mutant A. fumigatus and found that BrlAp and StuAp governed overlapping but distinct transcriptional programs. Six secondary metabolite biosynthetic clusters were found to be regulated by StuAp, while only one cluster exhibited BrlAp-dependent expression. The ΔbrlA mutant, but not the ΔstuA mutant, had impaired downregulation of genes encoding ribosomal proteins under nitrogen-limiting, but not carbon-limiting, conditions. Interestingly, inhibition of the target of rapamycin (TOR) pathway also caused downregulation of ribosomal protein genes in both the wild-type strain and the ΔbrlA mutant. Downregulation of these genes by TOR inhibition was associated with conidiation in the wild-type strain but not in the ΔbrlA mutant. Therefore, BrlAp-mediated repression of ribosomal protein gene expression is not downstream of the TOR pathway. Furthermore, inhibition of ribosomal protein gene expression is not sufficient to induce conidiation in the absence of BrlAp.

scholarly journals A capsule-associated gene of Cryptococcus neoformans, CAP64, is involved in pH homeostasis

Microbiology ◽  
2021 ◽  
Vol 167 (6) ◽  
Author(s):  
Yumi Imanishi-Shimizu ◽  
Yukina Kamogawa ◽  
Yukino Shimada ◽  
Kiminori Shimizu
Keyword(s):  
Cryptococcus Neoformans ◽  
Type Strain ◽  
Intracellular Transport ◽  
Wild Type Strain ◽  
Intracellular Localization ◽  
Wild Type ◽  
Ph Homeostasis ◽  
Cell Compartments ◽  
In The Wild ◽  
Acidic Organelles

The CAP64 gene is known to be involved in capsule formation in the basidiomycete yeast Cryptococcus neoformans. A null mutant of CAP64, Δcap64, lacks a capsule around the cell wall and its acidic organelles are not stained with quinacrine. In order to clarify whether the Cap64 protein indeed maintains vacuole or vesicle acidification, so that the vesicle containing the capsule polysaccharide or DBB substrate are transported to the cell membrane side, the relationship between CAP64 and intracellular transport genes and between CAP64 and enzyme-secretion activity were analysed. Laccase activity was higher in the Δcap64 strain than in the wild-type strain, and the transcriptional levels of SAV1 and VPH1 were also higher in the Δcap64 strain than in the wild-type strain. The intracellular localization of the Cap64 protein was analysed by overexpressing an mCherry-tagged Cap64 and observing its fluorescence. The Cap64 protein was accumulated within cells in a patch-like manner. The quinacrine-stained cells were observed to analyse the acidified cell compartments; quinacrine was found to be accumulated in a patch-like manner, with the patches overlapping the fluorescence of CAP64-mCherry fusion protein. Quinacrine was thus accumulated in a patch-like fashion in the cells, and the mCherry-tagged Cap64 protein position was consistent with the position of quinacrine accumulation in cells. These results suggest that CAP64 might be involved in intracellular acidification and vesicle secretion via exocytosis.

scholarly journals Calcineurin, Mpk1 and Hog1 MAPK pathways independently control fludioxonil antifungal sensitivity in Cryptococcus neoformans

Microbiology ◽  
2006 ◽  
Vol 152 (3) ◽  
pp. 591-604 ◽  
Author(s):  
Kaihei Kojima ◽  
Yong-Sun Bahn ◽  
Joseph Heitman
Keyword(s):  
Drug Resistance ◽  
Cryptococcus Neoformans ◽  
Type Strain ◽  
Wild Type Strain ◽  
Mapk Pathway ◽  
Control Plant ◽  
Antifungal Drug ◽  
Cell Swelling ◽  
Wild Type ◽  
Mutant Strains

Fludioxonil is employed as an agricultural fungicide to control plant-pathogenic fungi such as Botrytis cinerea. Cryptococcus neoformans is a basidiomycetous human fungal pathogen that causes fatal disease in immunocompromised hosts. This paper demonstrates that three different signalling cascades regulate sensitivity of C. neoformans to fludioxonil. Fludioxonil inhibited growth of the serotype A sequence reference strain H99 but not that of the sequenced serotype D strain JEC21. In the drug-sensitive wild-type strain, fludioxonil exposure activated the Hog1 osmosensing pathway, and hog1Δ mutations conferred fludioxonil resistance. Fludioxonil treatment caused cell growth inhibition following cell swelling and cytokinesis defects in the sensitive wild-type but not in a hog1Δ mutant strain, suggesting that Hog1 activation results in morphological cellular defects. Fludioxonil exerted a fungistatic effect on the wild-type strain H99, but exhibited fungicidal activity against calcineurin mutant strains, indicating that the calcineurin pathway contributes to drug resistance in this fungus. Combination of fludioxonil and the calcineurin inhibitor FK506 synergistically inhibited C. neoformans growth. mpk1Δ MAPK mutant strains exhibited fludioxonil hypersensitivity, indicating that this pathway also contributes to drug resistance. These studies provide evidence that the broad-spectrum antifungal drug fludioxonil exerts its action via activation of the Hog1 MAPK pathway and provide insight into novel targets for synergistic antifungal drug combinations.

scholarly journals Effects of Mutations in Ribosomal Protein L16 on Susceptibility and Accumulation of Evernimicin

2001 ◽  
Vol 45 (1) ◽  
pp. 79-83 ◽  
Author(s):  
Paul M. McNicholas ◽  
Paul A. Mann ◽  
David J. Najarian ◽  
Lynn Miesel ◽  
Roberta S. Hare ◽  
...  
Keyword(s):  
Ribosomal Protein ◽  
Type Strain ◽  
Wild Type Strain ◽  
Base Change ◽  
Chemical Mutagenesis ◽  
Multicopy Plasmid ◽  
Wild Type ◽  
In Vitro Susceptibility ◽  
Mutant Strains

ABSTRACT Chemical mutagenesis of Staphylococcus aureus RN450 generated two strains that displayed a stable reduction (30- to 60-fold) in susceptibility to evernimicin. Cell-free translation reactions demonstrated that the resistance determinant was located in the ribosomal fraction. Compared to ribosomes isolated from a wild-type strain, ribosomes from the mutant strains displayed an 8- to 10-fold reduction in affinity for [14C]evernimicin. In contrast, the mutants displayed no alteration in either binding affinity or in vitro susceptibility to erythromycin. Exponential cultures of the mutant strains accumulated significantly less [14C]evernimicin than the wild-type strain, suggesting that accumulation is dependent on the high affinity that evernimicin displays for its binding site. Sequencing rplP (encodes ribosomal protein L16) in the mutant strains revealed a single base change in each strain, which resulted in a substitution of either cysteine or histidine for arginine at residue 51. Introduction of a multicopy plasmid carrying wild-type rplP into the mutant strains restored sensitivity to evernimicin, confirming that the alterations in rplP were responsible for the change in susceptibility. Overexpression of the mutant alleles in S. aureus RN450 had no effect on susceptibility to evernimicin, demonstrating that susceptibility is dominant over resistance.

scholarly journals Oxidative Stress Causes Vacuolar Fragmentation in the Human Fungal Pathogen Cryptococcus neoformans

2021 ◽  
Vol 7 (7) ◽  
pp. 523
Author(s):  
Donghyeun Kim ◽  
Moonyong Song ◽  
Eunsoo Do ◽  
Yoojeong Choi ◽  
James W. Kronstad ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Superoxide Dismutase ◽  
Cryptococcus Neoformans ◽  
Fungal Pathogens ◽  
Wild Type ◽  
Human Fungal Pathogen ◽  
Iron Copper ◽  
High Concentrations ◽  
Sod1 Mutant ◽  
Cellular Organelles

Vacuoles are dynamic cellular organelles, and their morphology is altered by various stimuli or stresses. Vacuoles play an important role in the physiology and virulence of many fungal pathogens. For example, a Cryptococcus neoformans mutant deficient in vacuolar functions showed significantly reduced expression of virulence factors such as capsule and melanin synthesis and was avirulent in a mouse model of cryptococcosis. In the current study, we found significantly increased vacuolar fragmentation in the C. neoformans mutants lacking SOD1 or SOD2, which respectively encode Zn, Cu-superoxide dismutase and Mn-superoxide dismutase. The sod2 mutant showed a greater level of vacuole fragmentation than the sod1 mutant. We also observed that the vacuoles were highly fragmented when wild-type cells were grown in a medium containing high concentrations of iron, copper, or zinc. Moreover, elevated temperature and treatment with the antifungal drug fluconazole caused increased vacuolar fragmentation. These conditions also commonly cause an increase in the levels of intracellular reactive oxygen species in the fungus, suggesting that vacuoles are fragmented in response to oxidative stress. Furthermore, we observed that Sod2 is not only localized in mitochondria but also in the cytoplasm within phagocytosed C. neoformans cells, possibly due to copper or iron limitation.

scholarly journals Titan Cell Production Enhances the Virulence of Cryptococcus neoformans

2012 ◽  
Vol 80 (11) ◽  
pp. 3776-3785 ◽  
Author(s):  
Juliet N. Crabtree ◽  
Laura H. Okagaki ◽  
Darin L. Wiesner ◽  
Anna K. Strain ◽  
Judith N. Nielsen ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Mutant Strain ◽  
Type Strain ◽  
Wild Type Strain ◽  
Cell Formation ◽  
Yeast Cells ◽  
Wild Type ◽  
Content Type ◽  
Cell Production

ABSTRACTInfection withCryptococcus neoformansbegins when desiccated yeast cells or spores are inhaled and lodge in the alveoli of the lungs. A subset of cryptococcal cells in the lungs differentiate into enlarged cells, referred to as titan cells. Titan cells can be as large as 50 to 100 μm in diameter and exhibit a number of features that may affect interactions with host immune defenses. To characterize the effect of titan cell formation on the host-pathogen interaction, we utilized a previously describedC. neoformansmutant, thegpr4Δgpr5Δ mutant, which has minimal titan cell productionin vivo. Thegpr4Δgpr5Δ mutant strain had attenuated virulence, a lower CFU, and reduced dissemination compared to the wild-type strain. Titan cell production by the wild-type strain also resulted in increased eosinophil accumulation and decreased phagocytosis in the lungs compared to those with thegpr4Δgpr5Δ mutant strain. Phagocytosed cryptococcal cells exhibited less viability than nonphagocytosed cells, which potentially explains the reduced cell survival and overall attenuation of virulence in the absence of titan cells. These data show that titan cell formation is a novel virulence factor inC. neoformansthat promotes establishment of the initial pulmonary infection and plays a key role in disease progression.

scholarly journals Cryptococcus neoformanssecretes small molecules that inhibit IL-1β inflammasome-dependent secretion

2019 ◽  
Author(s):  
Pedro Henrique Bürgel ◽  
Clara Luna Marina ◽  
Pedro H. V. Saavedra ◽  
Patrícia Albuquerque ◽  
Paulo Henrique Holanda ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Cryptococcus Neoformans ◽  
Type Strain ◽  
Wild Type Strain ◽  
Conditioned Media ◽  
Inflammasome Activation ◽  
Wild Type ◽  
Fungal Virulence ◽  
The Impact

AbstractCryptococcus neoformansis an encapsulated yeast that causes disease mainly in immunosuppressed hosts. It is considered a facultative intracellular pathogen because of its capacity to survive and replicate inside phagocytes, especially macrophages. This capacity is heavily dependent on various virulence factors, particularly the glucuronoxylomannan (GXM) component of the polysaccharide capsule, that render the non- or poorly-activated macrophage ineffective against phagocytosed yeast. Strategies utilized by macrophages to prevent this scenario include pyroptosis (a rapid highly inflammatory cell death) and vomocytosis (the expulsion of the pathogen from the intracellular environment without lysis). Inflammasome activation in phagocytes is usually protective against fungal infections, including cryptococcosis. Nevertheless, recognition ofC. neoformansby inflammasome receptors requires specific changes in morphology or the opsonization of the yeast, impairing a proper inflammasome function. In this context, we analyzed the impact of molecules secreted byC. neoformansB3501 strain and its acapsular mutantΔcap67in an inflammasome activationin vitromodel. Our results showed that conditioned media derived from B3501 was capable of inhibiting inflammasome dependent events (i. e. IL-1β secretion and LDH release via pyroptosis) more strongly than conditioned media fromΔcap67, regardless of GXM presence. We also demonstrated that macrophages treated with conditioned media were less responsive against infection with the virulent strain H99, exhibiting lower rates of phagocytosis, increased fungal burdens and enhanced vomocytosis. Moreover, we showed that the aromatic metabolite DL-Indole-3-lactic acid (ILA) was present in B3501’s conditioned media and that this fungal metabolite is involved in the regulation of inflammasome activation byC. neoformans. Overall, the results presented show that conditioned media from a wild-type strain can inhibit an important recognition pathway and subsequent fungicidal functions of macrophages, contributing to fungal survivalin vitroand suggesting that this serves as an important role for secreted molecules during cryptococcal infections.Author’s SummaryCryptococcus neoformansis the agent of cryptococcal meningitis, a disease that can be life-threatening in immunocompromised hosts such as those infected with HIV. The infection thrives in hosts that poorly activate their immune system, mainly because of the yeast’s ability to survive inside macrophages and migrate towards the central nervous system. Emerging data indicate that cryptococci modulate the host immune response, but the underlying mechanisms remain largely uncharacterized. Here we show that secreted molecules from a wild-type strain ofC. neoformansimpair inflammatory responses driven by inflammasome activation, which in turn impact the macrophage antifungal activity. We further show that this inhibition does not involve GXM, the main constituent of the fungal capsule, but rather is partially dependent on DL-Indole-3-lactic acid (ILA), a metabolite not previously implicated in fungal virulence.

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