Ability to grow on lipids accounts for the fully virulent phenotype in neutropenic mice of Aspergillus fumigatus null mutants in the key glyoxylate cycle enzymes

Olivas, Israel; Royuela, Mar; Romero, Beatriz; Monteiro, Maria Cândida; Minguez, Jose M.; Laborda, F.; Lucas, J. Ramón De

doi:10.1016/j.fgb.2007.05.002

Cited by 36 publications

(33 citation statements)

References 72 publications

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“…In addition, the glyoxylate cycle is absent in mammals and therefore represents a potential drug target. Whereas this pathway appears to be dispensable for A. fumigatus-induced invasive aspergillosis (26,28), it was found to be virulence associated in infections by other microbial pathogens such as Mycobacterium tuberculosis and the yeast Candida albicans (17,21). In these pathogens, enzymes of the glyoxylate pathway were shown to contribute to the persistence of the microbes in phagocytic immune cells, a function which remains elusive for dermatophytes.…”

Section: Discussionmentioning

confidence: 99%

Gene Expression Profiling in the Human Pathogenic Dermatophyte Trichophyton rubrum during Growth on Proteins

et al. 2009

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Dermatophytes are highly specialized filamentous fungi which cause the majority of superficial mycoses in humans and animals. The high secreted proteolytic activity of these microorganisms during growth on proteins is assumed to be linked to their particular ability to exclusively infect keratinized host structures such as the skin stratum corneum, hair, and nails. Individual secreted dermatophyte proteases were recently described and linked with the in vitro digestion of keratin. However, the overall adaptation and transcriptional response of dermatophytes during protein degradation are largely unknown. To address this question, we constructed a cDNA microarray for the human pathogenic dermatophyte Trichophyton rubrum that was based on transcripts of the fungus grown on proteins. Profiles of gene expression during the growth of T. rubrum on soy and keratin protein displayed the activation of a large set of genes that encode secreted endo-and exoproteases. In addition, other specifically induced factors potentially implicated in protein utilization were identified, including heat shock proteins, transporters, metabolic enzymes, transcription factors, and hypothetical proteins with unknown functions. Of particular interest is the strong upregulation of key enzymes of the glyoxylate cycle in T. rubrum during growth on soy and keratin, namely, isocitrate lyase and malate synthase. This broad-scale transcriptional analysis of dermatophytes during growth on proteins reveals new putative pathogenicityrelated host adaptation mechanisms of these human pathogenic fungi.Dermatophytes are highly specialized fungi which are the most common agents of superficial mycoses in humans and animals (13, 34). Among the human pathogenic dermatophytes, the anthropophilic species Trichophyton rubrum is clinically the most commonly observed. In contrast to most other medically important fungi, dermatophytes are not opportunists but are obligate pathogens, infecting exclusively the skin stratum corneum, nails, or hair. The ability of dermatophytes to degrade and utilize compact hard keratin within such host structures is presumably related to their common secreted keratinolytic activity, which is therefore a major putative virulence attribute of these fungi. Individual endo-and exoproteases secreted by dermatophytes are similar to those of species of the genus Aspergillus. However, in contrast to those of Aspergillus spp., dermatophyte-secreted endoproteases are multiple and members of two large protein families, the subtilisins (Subs) S8 (serine proteases) and the fungalysins M36 (metalloproteases) (see the MEROPS peptidase database, http://merops.sanger.ac.uk) (10, 11). More than 20 genes that encode secreted proteases have been identified in dermatophytes, some of which have been characterized in detail on the molecular level (reviewed in reference 23).In order to better understand the basic mechanisms of protein degradation by dermatophytes, the secretome of different dermatophyte species was previously analyzed during in vitro growt...

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Section: Discussionmentioning

confidence: 99%

Gene Expression Profiling in the Human Pathogenic Dermatophyte Trichophyton rubrum during Growth on Proteins

et al. 2009

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“…This is similar to the situation in Cryptococcus neoformans, where patterns of gene expression and adaptation were tissue specific for lung infection in mice (Hu et al, 2008) or in a rabbit model of experimental meningitis (Lee et al, 2010). Several studies have focused on the pathways of gluconeogenesis, the glyoxylate cycle and b-oxidation of fatty acids, as these pathways are specifically upregulated during contact with host immune cells in a variety of human fungal and bacterial pathogens, such as P. brasiliensis (Derengowski et al, 2008), Cryptococcus neoformans (Fan et al, 2005;Hu et al, 2008;Rude et al, 2002), Candida albicans (Barelle et al, 2006;Fradin et al, 2005;Ramírez & Lorenz, 2009), Aspergillus fumigatus (Ebel et al, 2006;Olivas et al, 2008) and Mycobacterium tuberculosis (McKinney et al, 2000;Muñoz-Elías & McKinney, 2005).…”

Section: R Peres Da Silva and Othersmentioning

confidence: 99%

Differential gene expression analysis of Paracoccidioides brasiliensis during keratinocyte infection

Silva

Matsumoto

Braz

et al. 2011

Journal of Medical Microbiology

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Paracoccidioides brasiliensis is the agent of paracoccidioidomycosis, one of the most important systemic fungal diseases in Latin America. This initiates in lung tissue and can subsequently disseminate to other tissues. Clinical manifestations range from localized forms to disseminated disease that can progress to lethality, probably depending on the relationships among the virulence of the fungus, the immune response and the ability to interact with the surface structures and invade epithelial cells and mononuclear cells of the host. It is generally regarded as a multifocal disease, with oral lesions as the prominent feature. The aim of this study was to evaluate P. brasiliensis yeast infection in normal oral keratinocytes (NOKs). The differential expression of mRNAs and proteins was also determined when the fungus was placed in contact with the cell in order to characterize differentially expressed genes and proteins during P. brasiliensis infection. After contact with NOKs, the fungus appeared to induce alterations in the cells, which showed cellular extensions and cavitations, probably resulting from changes in the actin cytoskeleton seen at 5 and 8 h after infection. Levels of protein expression were higher after reisolation of the fungus from infected NOK culture compared with culture of the fungus in medium. The analysis identified transcripts related to 19 proteins involved in different biological processes. Transcripts were found with multiple functions including induction of cytokines, protein metabolism, alternative carbon metabolism, zinc transport and the stress response during contact with NOKs. The proteins found suggested that the yeast was in a stress situation, as indicated by the presence of RDS1. Nevertheless, the yeast seemed to be proliferating and metabolically active, as shown by the presence of a proteasome, short-chain acetylator, glucosamine-6-phosphate isomerase and ADP/ATP carrier transcripts. Additionally, metabolic pathways may have been activated in order to eliminate toxic substances from the cell as a zinc transporter was detected, which is a potential target for the development of future drugs. INTRODUCTIONParacoccidioides brasiliensis is a thermodimorphic pathogenic fungus, the aetiological agent of paracoccidioidomycosis (PCM), an endemic disease geographically limited to Latin America and one of the most prevalent human deep systemic mycoses found in Brazil, Colombia and Venezuela (San-Blas et al., 2002). The transition from mycelium at 25 u C to yeast at 37 u C is essential for P. brasiliensis to establish the disease (Franco et al., 1997). P. brasiliensis may be inhaled and, once in the lungs, the fungus initiates a process of morphological transition into the pathogenic yeast form (San-Blas et al., 2002).PCM has a multiplicity of clinical presentations, from cutaneous to systemic forms, and can attack various tissues, especially the lungs (Benard & Franco, 2007). Oral mucosal lesions are commonly multiple, with a granular, mulberry-like surface and microulcerations, and ...

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“…Interestingly, it has been shown that the glyoxylate bypass is essential for full virulence of Candida albicans (5,34,45) but is dispensable for virulence of Cryptococcus neoformans (51) and A. fumigatus (41,53). In contrast, the methylcitrate cycle, which is essential for the removal of toxic propionyl-coenzyme A (propionyl-CoA), has been shown to be important for full virulence of A. fumigatus (24), but unfortunately, no genes coding for enzymes of this cycle can be detected in the genome of C. albicans.…”

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confidence: 99%

Evaluation of Lysine Biosynthesis as an Antifungal Drug Target: Biochemical Characterization of Aspergillus fumigatus Homocitrate Synthase and Virulence Studies

2010

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Aspergillus fumigatus is the main cause of severe invasive aspergillosis. To combat this life-threatening infection, only limited numbers of antifungals are available. The fungal ␣-aminoadipate pathway, which is essential for lysine biosynthesis, has been suggested as a potential antifungal drug target. Here we reanalyzed the role of this pathway for establishment of invasive aspergillosis in murine models. We selected the first pathway-specific enzyme, homocitrate synthase (HcsA), for biochemical characterization and for study of its role in virulence. A. fumigatus HcsA was specific for the substrates acetyl-coenzyme A (acetyl-CoA) and ␣-ketoglutarate, and its activity was independent of any metal ions. In contrast to the case for other homocitrate synthases, enzymatic activity was hardly affected by lysine and gene expression increased under conditions of lysine supplementation. An hcsA deletion mutant was lysine auxotrophic and unable to germinate on unhydrolyzed proteins given as a sole nutrient source. However, the addition of partially purified A. fumigatus proteases restored growth, confirming the importance of free lysine to complement auxotrophy. In contrast to lysine-auxotrophic mutants from other fungal species, the mutant grew on blood and serum, indicating the existence of high-affinity lysine uptake systems. In agreement, although the virulence of the mutant was strongly attenuated in murine models of bronchopulmonary aspergillosis, virulence was partially restored by lysine supplementation via the drinking water. Additionally, in contrast to the case for attenuated pulmonary infections, the mutant retained full virulence when injected intravenously. Therefore, we concluded that inhibition of fungal lysine biosynthesis, at least for disseminating invasive aspergillosis, does not appear to provide a suitable target for new antifungals.

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Ability to grow on lipids accounts for the fully virulent phenotype in neutropenic mice of Aspergillus fumigatus null mutants in the key glyoxylate cycle enzymes

Cited by 36 publications

References 72 publications

Gene Expression Profiling in the Human Pathogenic Dermatophyte Trichophyton rubrum during Growth on Proteins

Gene Expression Profiling in the Human Pathogenic Dermatophyte Trichophyton rubrum during Growth on Proteins

Differential gene expression analysis of Paracoccidioides brasiliensis during keratinocyte infection

Evaluation of Lysine Biosynthesis as an Antifungal Drug Target: Biochemical Characterization of Aspergillus fumigatus Homocitrate Synthase and Virulence Studies

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