The cAMP/Protein Kinase A Pathway Regulates Virulence and Adaptation to Host Conditions in Cryptococcus neoformans

Caza, Mélissa; Kronstad, James W.

doi:10.3389/fcimb.2019.00212

Cited by 68 publications

(60 citation statements)

References 163 publications

(225 reference statements)

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“…The target of rapamycin (TOR) TORC1 effector, which is widely known to activate anabolism and growth ( 61 – 63 ), has been described to activate the PPP in mammalian cells ( 64 , 65 ) and has been functionally connected with energy production and nucleotide metabolism in A. fumigatus ( 66 ). In addition, the cAMP/PKA (cyclic AMP/protein kinase A) pathway is known to be paramount for sensing of nutrients and the correspondent adaptation of gene expression and metabolism ( 67 ) and was found to be implicated in the regulation of nucleotide biosynthesis in A. fumigatus ( 68 ). Consequently, we explored whether a partial block of TOR with low concentrations of rapamycin or of PKA with H-89 could prevent the imbalanced activation of the PPP in the absence of MetH activity.…”

Section: Resultsmentioning

confidence: 99%

Targeting Methionine Synthase in a Fungal Pathogen Causes a Metabolic Imbalance That Impacts Cell Energetics, Growth, and Virulence

Scott

Sueiro-Olivares

Thornton

et al. 2020

mBio

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There is an urgent need to develop novel antifungals to tackle the threat fungal pathogens pose to human health. Here, we have performed a comprehensive characterization and validation of the promising target methionine synthase (MetH). We show that in Aspergillus fumigatus the absence of this enzymatic activity triggers a metabolic imbalance that causes a reduction in intracellular ATP, which prevents fungal growth even in the presence of methionine. Interestingly, growth can be recovered in the presence of certain metabolites, which shows that metH is a conditionally essential gene and consequently should be targeted in established infections for a more comprehensive validation. Accordingly, we have validated the use of the tetOFF genetic model in fungal research and improved its performance in vivo to achieve initial validation of targets in models of established infection. We show that repression of metH in growing hyphae halts growth in vitro, which translates into a beneficial effect when targeting established infections using this model in vivo. Finally, a structure-based virtual screening of methionine synthases reveals key differences between the human and fungal structures and unravels features in the fungal enzyme that can guide the design of novel specific inhibitors. Therefore, methionine synthase is a valuable target for the development of new antifungals. IMPORTANCE Fungal pathogens are responsible for millions of life-threatening infections on an annual basis worldwide. The current repertoire of antifungal drugs is very limited and, worryingly, resistance has emerged and already become a serious threat to our capacity to treat fungal diseases. The first step to develop new drugs is often to identify molecular targets in the pathogen whose inhibition during infection can prevent its growth. However, the current models are not suitable to validate targets in established infections. Here, we have characterized the promising antifungal target methionine synthase in great detail, using the prominent fungal pathogen Aspergillus fumigatus as a model. We have uncovered the underlying reason for its essentiality and confirmed its druggability. Furthermore, we have optimized the use of a genetic system to show a beneficial effect of targeting methionine synthase in established infections. Therefore, we believe that antifungal drugs to target methionine synthase should be pursued and additionally, we provide a model that permits gaining information about the validity of antifungal targets in established infections.

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Section: Resultsmentioning

confidence: 99%

Targeting Methionine Synthase in a Fungal Pathogen Causes a Metabolic Imbalance That Impacts Cell Energetics, Growth, and Virulence

Scott

Sueiro-Olivares

Thornton

et al. 2020

mBio

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“…By exploiting the detailed SNP information that whole-genome sequence data provides, we subsequently identified specific genes (Quantitative Trait Genes; QTG) and nucleotide variants (Quantitative Trait Nucleotide; QTN) that are likely to underlie those QTL. Of particular note is the fact that the three QTG we identified are regulators of signaling pathways -the cAMP-PKA pathway and the HOG pathway -that are important for fungal adaptation to extracellular stresses (Hohmann et al, 2007;Brewster and Gustin, 2014) and have been shown to be integral to virulence in Cryptococcus (Bahn and Jung, 2013;Caza and Kronstad, 2019). Both of these pathways regulate multiple physiological and morphological traits in Cryptococcus as well as other fungi including S. cerevisiae (Granek et al, 2011), Candida albicans (Brown et al, 2014;Lin and Chen, 2018), and Candida auris (Day et al, 2018).…”

Section: Discussionmentioning

confidence: 96%

Pleiotropy and epistasis within and between signaling pathways defines the genetic architecture of fungal virulence

Roth

Murray

Scott

et al. 2020

Preprint

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Cryptococcal disease is estimated to affect nearly a quarter of a million people annually. Environmental isolates of Cryptococcus deneoformans, which make up 15 to 30% of clinical infections in temperate climates such as Europe, vary in their pathogenicity, ranging from benign to hyper-virulent. Key traits that contribute to virulence, such as the production of the pigment melanin, an extracellular polysaccharide capsule, and the ability to grow at human body temperature have been identified, yet little is known about the genetic basis of variation in such traits. Here we investigate the genetic basis of melanization, capsule size, thermal tolerance, oxidative stress resistance, and antifungal drug sensitivity using quantitative trait locus (QTL) mapping in progeny derived from a cross between two divergent C. deneoformans strains. Using a "function-valued" QTL analysis framework that exploits both time-series information and growth differences across multiple environments, we identified QTL for each of these virulence traits and drug susceptibility. For three QTL we identified the underlying genes and nucleotide differences that govern variation in virulence traits. One of these genes, RIC8, which encodes a regulator of cAMP-PKA signaling, contributes to variation in four virulence traits: melanization, capsule size, thermal tolerance, and resistance to oxidative stress. Two major effect QTL for amphotericin B resistance map to the genes SSK1 and SSK2, which encode key components of the HOG pathway, a fungal-specific signal transduction network that orchestrates cellular responses to osmotic and other stresses. We also discovered complex epistatic interactions within and between genes in the HOG and cAMP-PKA pathways that regulate antifungal drug resistance and resistance to oxdiative stress. Our findings advance the understanding of virulence traits among diverse lineages of Cryptococcus, and highlight the role of genetic variation in key stress-responsive signaling pathways as a major contributor to phenotypic variation.

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“…During bisexual reproduction opposite mating type cells secrete pheromones under nutrient-limiting conditions, and a compatible mating type would sense these molecules (secreted by the opposite mating type) via the pheromone MAPK signalling circuit [118], initiating the formation of conjugation tubes leading to cell-cell fusion. The two cells form a diploid heterokaryon and initiate filamentous growth.…”

Section: Tolerance To the Limitation Of Nutrients And Watermentioning

confidence: 99%

Environmental Factors That Contribute to the Maintenance of Cryptococcus neoformans Pathogenesis

et al. 2020

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The ability of microorganisms to colonise and display an intracellular lifestyle within a host body increases their fitness to survive and avoid extinction. This host–pathogen association drives microbial evolution, as such organisms are under selective pressure and can become more pathogenic. Some of these microorganisms can quickly spread through the environment via transmission. The non-transmittable fungal pathogens, such as Cryptococcus, probably return into the environment upon decomposition of the infected host. This review analyses whether re-entry of the pathogen into the environment causes restoration of its non-pathogenic state or whether environmental factors and parameters assist them in maintaining pathogenesis. Cryptococcus (C.) neoformans is therefore used as a model organism to evaluate the impact of environmental stress factors that aid the survival and pathogenesis of C. neoformans intracellularly and extracellularly.

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The cAMP/Protein Kinase A Pathway Regulates Virulence and Adaptation to Host Conditions in Cryptococcus neoformans

Cited by 68 publications

References 163 publications

Targeting Methionine Synthase in a Fungal Pathogen Causes a Metabolic Imbalance That Impacts Cell Energetics, Growth, and Virulence

Targeting Methionine Synthase in a Fungal Pathogen Causes a Metabolic Imbalance That Impacts Cell Energetics, Growth, and Virulence

Pleiotropy and epistasis within and between signaling pathways defines the genetic architecture of fungal virulence

Environmental Factors That Contribute to the Maintenance of Cryptococcus neoformans Pathogenesis

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