At the metal-metabolite interface in : towards untangling the intersecting roles of zinc and gliotoxin.

Cryptic links between apparently unrelated metabolic systems represent potential new drug targets in fungi. Evidence of such a link between zinc and gliotoxin (GT) biosynthesis in is emerging. Expression of some genes of the GT biosynthetic gene cluster is influenced by the zinc-dependent transcription activator ZafA, zinc may relieve GT-mediated fungal growth inhibition and, surprisingly, GT biosynthesis is influenced by zinc availability.

Regulation of zinc homeostatic genes by environmental pH in the filamentous fungus Aspergillus fumigatus.

Aspergillus fumigatus can grow over a broad range of pH values even though zinc availability is greatly conditioned by ambient pH. It has been previously shown that regulation of zinc homeostatic genes in this fungus relies on the transcription factor ZafA. In addition, their expression is further modulated by the transcription factor PacC depending on ambient pH, which allows this fungus to grow in diverse types of niches, including soils and the lungs of immunosuppressed hosts.

Involvement of Sulfur in the Biosynthesis of Essential Metabolites in Pathogenic Fungi of Animals, Particularly spp.: Molecular and Therapeutic Implications.

Fungal sulfur uptake is required for incorporation into the sidechains of the amino acids cysteine and methionine, and is also essential for the biosynthesis of the antioxidant glutathione (GSH), -adenosylmethionine (SAM), the key source of methyl groups in cellular transmethylation reactions, and -adenosylhomocysteine (SAH). Biosynthesis of redox-active gliotoxin in the opportunistic fungal pathogen has been elucidated over the past 10 years. Some fungi which produce gliotoxin-like molecular species have undergone unexpected molecular rewiring to accommodate this high-risk biosynthetic process.

The interplay between zinc and iron homeostasis in Aspergillus fumigatus under zinc-replete conditions relies on the iron-mediated regulation of alternative transcription units of zafA and the basal amount of the ZafA zinc-responsiveness transcription factor.

Aspergillus fumigatus is a saprophyte fungus that typically grows on organic decaying matter but can also parasitize immunosuppressed hosts. This is explained, in part, by its great ability to take up Zn ions from living tissues, which is induced by the ZafA transcription factor. This study shows that the ZafA-mediated regulation of fungal growth is also influenced by iron availability and that A.

The Transcription Factor ZafA Regulates the Homeostatic and Adaptive Response to Zinc Starvation in .

One of the most important features that enables to grow within a susceptible individual and to cause disease is its ability to obtain Zn ions from the extremely zinc-limited environment provided by host tissues. Zinc uptake from this source in relies on ZIP transporters encoded by the , and genes. The expression of these genes is tightly regulated by the ZafA transcription factor that regulates zinc homeostasis and is essential for virulence.

A Novel Polyaminocarboxylate Compound To Treat Murine Pulmonary Aspergillosis by Interfering with Zinc Metabolism.

can cause pulmonary aspergillosis in immunocompromised patients and is associated with a high mortality rate due to a lack of reliable treatment options. This opportunistic pathogen requires zinc in order to grow and cause disease. Novel compounds that interfere with fungal zinc metabolism may therefore be of therapeutic interest.

Novel Zinc-Attenuating Compounds as Potent Broad-Spectrum Antifungal Agents with and Efficacy.

An increase in the incidence of rare but hard-to-treat invasive fungal pathogens as well as resistance to the currently available antifungal drugs calls for new broad-spectrum antifungals with a novel mechanism of action. Here we report the identification and characterization of two novel zinc-attenuating compounds, ZAC307 and ZAC989, which exhibit broad-spectrum antifungal activity and efficacy in a fungal kidney burden candidiasis model. The compounds were identified serendipitously as part of a drug discovery process aimed at finding novel inhibitors of the fungal plasma membrane proton ATPase Pma1.

Administration of Zinc Chelators Improves Survival of Mice Infected with Aspergillus fumigatus both in Monotherapy and in Combination with Caspofungin.

Aspergillus fumigatus can infect immunocompromised patients, leading to high mortality rates due to the lack of reliable treatment options. This pathogen requires uptake of zinc from host tissues in order to successfully grow and cause virulence. Reducing the availability of that micronutrient could help treat A.

Zinc and Manganese Chelation by Neutrophil S100A8/A9 (Calprotectin) Limits Extracellular Aspergillus fumigatus Hyphal Growth and Corneal Infection.

Calprotectin, a heterodimer of S100A8 and S100A9, is an abundant neutrophil protein that possesses antimicrobial activity primarily because of its ability to chelate zinc and manganese. In the current study, we showed that neutrophils from calprotectin-deficient S100A9(-/-) mice have an impaired ability to inhibit Aspergillus fumigatus hyphal growth in vitro and in infected corneas in a murine model of fungal keratitis; however, the ability to inhibit hyphal growth was restored in S100A9(-/-) mice by injecting recombinant calprotectin. Furthermore, using recombinant calprotectin with mutations in either the Zn and Mn binding sites or the Mn binding site alone, we show that both zinc and manganese binding are necessary for calprotectin's antihyphal activity.

Targeting zinc homeostasis to combat Aspergillus fumigatus infections.

Aspergillus fumigatus is able to invade and grow in the lungs of immunosuppressed individuals and causes invasive pulmonary aspergillosis. The concentration of free zinc in living tissues is much lower than that required for optimal fungal growth in vitro because most of it is tightly bound to proteins. To obtain efficiently zinc from a living host A.

Zinc acquisition: a key aspect in Aspergillus fumigatus virulence.

Zinc is an essential micronutrient required for the growth of all microorganisms. To grow in the lungs of a susceptible patient Aspergillus fumigatus must obtain zinc from the surrounding tissues. The concentration of Zn(2+) ions in living tissues is much lower than that required for optimal fungal growth in vitro because most of them are tightly bound to proteins at the physiological pH.

The ZrfC alkaline zinc transporter is required for Aspergillus fumigatus virulence and its growth in the presence of the Zn/Mn-chelating protein calprotectin.

Aspergillus fumigatus can invade the lungs of immunocompromised individuals causing a life-threatening disease called invasive pulmonary aspergillosis (IPA). To grow in the lungs, A. fumigatus obtains from the host all nutrients, including zinc.

Aspergillus fumigatus survival in alkaline and extreme zinc-limiting environments relies on the induction of a zinc homeostasis system encoded by the zrfC and aspf2 genes.

Aspergillus fumigatus has three zinc transporter-encoding genes whose expression is regulated by both pH and the environmental concentration of zinc. We have previously reported that the zrfA and zrfB genes of A. fumigatus are transcribed at higher levels and are required for fungal growth under acidic zinc-limiting conditions whereas they are dispensable for growth in neutral or alkaline zinc-limiting media.

Repression of the acid ZrfA/ZrfB zinc-uptake system of Aspergillus fumigatus mediated by PacC under neutral, zinc-limiting conditions.

The ZrfA and ZrfB transporters are components of a zinc-uptake system of Aspergillus fumigatus that mainly operates under acidic, zinc-limiting conditions. Expression of the genes zrfA and zrfB is up-regulated by the transcriptional activator ZafA in both acidic and neutral, zinc-limiting media. The transcription of zafA is not influenced by PacC, which is the transcriptional regulator involved in regulating pH homeostasis in Aspergillus.

Culture conditions for zinc- and pH-regulated gene expression studies in Aspergillus fumigatus.

In Aspergillus fumigatus, the regulation of zinc homeostasis is strongly influenced by environmental pH. Thus, the study of zinc-regulated gene expression in A. fumigatus requires controlling variations in culture pH, as this may affect zinc availability.

The regulation of zinc homeostasis by the ZafA transcriptional activator is essential for Aspergillus fumigatus virulence.

We have previously shown that Aspergillus fumigatus is able to grow in zinc-limiting media and that this ability is regulated at transcriptional level by both the availability of zinc and pH. When A. fumigatus grows as a pathogen, it must necessarily obtain zinc from the zinc-limiting environment provided by host tissue.

The zrfA and zrfB genes of Aspergillus fumigatus encode the zinc transporter proteins of a zinc uptake system induced in an acid, zinc-depleted environment.

Zinc is an essential micronutrient that cells must obtain from the environment in order to develop their normal growth. Previous work performed at our laboratory showed that the synthesis of immunodominant antigens from Aspergillus spp., including A.

Candida albicans response regulator gene SSK1 regulates a subset of genes whose functions are associated with cell wall biosynthesis and adaptation to oxidative stress.

Ssk1p of Candida albicans is a putative response regulator protein of the Hog1 two-component signal transduction system. In Saccharomyces cerevisiae, the phosphorylation state of Ssk1p determines whether genes that promote the adaptation of cells to osmotic stress are activated. We have previously shown that C.

Deletion of the two-component histidine kinase gene (CHK1) of Candida albicans contributes to enhanced growth inhibition and killing by human neutrophils in vitro.

We have observed that human neutrophils (polymorphonuclear leukocytes [PMNs]) have an increased growth-inhibitory and killing effect on a strain of Candida albicans with a deletion of CHK1, a gene encoding a putative histidine kinase. The PMN effect was not due to increased phagocytosis of the null strain. This observation may partially explain the reduced virulence in a hematogenously disseminated murine model of candidiasis.

Candida albicans: adherence, signaling and virulence.

The focus of this symposium was to present new information on the morphogenesis of Candida albicans, particularly how it relates to signal transduction pathways and other genes involved in the regulation of morphogenesis. In addition, we discuss the role of adherence and colonization of the oral cavity by the organism and discuss the role of mannan as an adhesin that recognizes the human red blood cell. C.

Identification of YPD1, a gene of Candida albicans which encodes a two-component phosphohistidine intermediate protein.

We have identified the YPD1 phosphohistidine intermediate two-component gene of Candida albicans. YPD1 has an open reading frame of 552 bp. It is located on chromosome 1 and an mRNA specific for YPD1 is detected under both yeast and hyphal growth.

Histidine kinase, two-component signal transduction proteins of Candida albicans and the pathogenesis of candidosis.

Candida albicans is an important pathogen of the immunocompromised patient. Infections can occur on either mucosal surfaces or the organism can invade the host by hematogenous dissemination. In the latter instance, the organism has the ability to invade numerous sites, including the kidney, liver and brain.

Distinctive properties of the catalase B of Aspergillus nidulans.

Aspergillus nidulans catalase B (CatB) was purified to homogeneity and characterized as a hydroperoxidase which resembles typical catalases in some physicochemical characteristics: (1) it has an apparent molecular weight of 360000 and is composed of four glycosylated subunits, (2) it has hydrophobic properties as revealed by extractability in ethanol/chloroform and binding to phenyl-Superose, and (3) it has an acidic isoelectric point at pH 3. 5. Also CatB exhibits some distinctive properties, e.

Defective hyphal development and avirulence caused by a deletion of the SSK1 response regulator gene in Candida albicans.

In a previous study, we reported the isolation and characterization of the two-component response regulator SSK1 gene of Candida albicans. This gene is a structural but not a functional homolog of the SSK1 and mcs4(+) genes of Saccharomyces cerevisiae and Schizosaccharomyces pombe, respectively. In the present study, we have constructed and phenotypically characterized Deltassk1 mutants of C.

Histidine kinase, two-component signal transduction proteins of Candida albicans and the pathogenesis of candidosis.

Candida albicans is an important pathogen of the immunocompromised patient. Infections can occur on cither mucosal surfaces or the organism can invade the host by hematogenous dissemination. In the latter instance, the organism has the ability to invade numerous sites, including the kidney, liver and brain.