Welcome to IMC 2018 International Mycological Congress
Conference Calendar
What are fungal extracellular vesicles and do they impact pathobiology?
- J. Nosanchuk
- D. Zamith-Miranda
- E. Nakayasu
- L. Nimrichter
Abstract
Abstract
Fungal extracellular vesicles (EVs) are lipid-bilayered structures that are released by diverse species. EVs are generated by more than one mechanism and vesicular transport enables the export of large molecules across the complex cell wall of fungi. EVs contain proteins, lipids, and polysaccharides, many of which are linked to virulence. In this session, we will first review current knowledge on fungal EVs. We will then describe the use Histoplasma capsulatum as a model to study EVs and show how host immune molecules can modify fungal responses. Our data demonstrates that cell wall-binding antibody can directly modify protein loading in vesicles as well as fungal metabolism. Moreover, this process is differentially and dynamically regulated by antibody in a concentration dependent manner. EV biology is clearly associated with the homeostatic maintenance of the fungal cell and can be modified in response to external factors, including host-pathogen interactions.
In-depth multi-omics analysis reveal the production of platelet-activating factor by the pathogenic fungus Histoplasma capsulatum
- E. Nakayasu
- H. Heyman
- D. Zamith-Miranda
- M. Burnet
- S. Couvillion
- E. Bredeweg
- X. Zheng
- E. Zink
- J. Kyle
- J. Zucker
- J. Teuton
- S. Baker
- S. Payne
- E. Baker
- J. Nosanchuk
Abstract
Abstract
Lipids are major components of biological membrane, energy storage molecules and cell signaling transducers. Therefore, not surprisingly, lipids play major function in host-pathogen interactions and are frequently targeted for drug development. Seeking to better understand the function of lipids in fungal pathogenesis and identify potential drug targets, we performed a comprehensive analysis of the lipid metabolic pathway of Histoplasma capsulatum yeasts and extracellular vesicles. In-depth proteomic and lipidomic analyses of H. capsulatum yeasts were performed and integrated into a metabolic map, comprising of 5 major lipid metabolic pathways and 19 lipid classes, being 371 lipid species detected in yeasts and 104 in extracellular vesicles. Of notice, the analysis showed that unlike Saccharomyces cerevisiae, H. capsulatum is unable to produce mannosylinositolphosphoceramides, but synthesizes glycosylceramides. The analysis also showed that H. capsulatum produces analogs of platelet-activating factor (PAF), a potent regulator of the human immune response. The structural information of the H. capsulatum PAF was further validated by tandem mass spectrometry, ion mobility and liquid chromatographic analyses. We also tested if the H. capsulatum PAF could stimulate the production of cytokines by treating macrophages with yeast lipids fractionated by liquid chromatography. The lipid fraction potently activated the production of the cytokines interleukin-10 and tumor necrosis factor alpha, which was abolished by the PAF receptor antagonist WEB 2086. Overall, our approach led to the identification of a biologically active lipid in H. capsulatum.
Galectin-3 impacts Cryptococcus neoformans infection through direct antifungal effects
- F. Almeida
- J. Wolf
- M. Rodrigues
- A. Casadevall
Abstract
Abstract
Cryptococcus neoformans is an encapsulated fungal pathogen that causes cryptococcosis, which is a major opportunistic infection in immunosuppressed individuals. Mammalian β-galactoside-binding protein Galectin-3 (Gal-3) modulates the host innate and adaptive immunity, and plays significant roles during microbial infections including some fungal diseases. Here we show that this protein plays a role also in C. neoformans infection. We find augmented Gal-3 serum levels in human and experimental infections, as well as in spleen, lung, and brain tissues of infected mice. Gal-3-deficient mice are more susceptible to cryptococcosis than WT animals, as demonstrated by the higher fungal burden and lower animal survival. In vitro experiments show that Gal-3 inhibits fungal growth and exerts a direct lytic effect on C. neoformans extracellular vesicles (EVs). Our results indicate a direct role for Gal-3 in antifungal immunity whereby this molecule affects the outcome of C. neoformans infection by inhibiting fungal growth and reducing EV stability, which in turn could benefit the host.
Plasma membrane dynamics in the interplay between exocytosis and endocytosis in fungal hyphae.
- S. Bartnicki-Garcia
- R. Mouriño-Pérez
Abstract
Abstract
The apical growth of fungal hyphae is an ideal place to study the relationship between the two primary processes that determine plasma membrane dynamics, its generation by exocytosis and its recycling by endocytosis. Both processes can be neatly imaged by confocal microscopy and fluorescent markers and are located in close proximity, exocytosis in the apex itself and endocytosis in the immediate subapical region. While the role of exocytosis is self-evident, the need for endocytosis is not. In fact, the very existence of endocytosis in mycelial fungi was long questioned but finally proven to exist convincingly. Whereas the amount of exocytosis can be calculated geometrically from values of hyphal diameter and vesicle cycle, estimating endocytosis poses a greater challenge. A mathematical approach led to the prediction that the amount of exocytosis required for plasma membrane growth alone was insufficient to account for cell wall growth and extracellular enzyme secretion, resulting in an excess of plasma membrane formation. To measure this excess, we devised a method to estimate endocytosis experimentally by photobleaching the subapical endocytic collar of hyphae of Neurospora crassa tagged with Lifeact-GFP. Accordingly, we determined that about 4% of the plasma membrane generated by exocytosis was endocytosed. Seemingly, exocytosis and endocytosis operate in tandem. By removing excess plasma membrane, endocytosis allows exocytosis to have the intensity needed to sustain the rapid growth rate and abundant enzyme secretion typical of fungal hyphae.
Insights from Candida auris and Candida albicans extracellular vesicles
- D. Zamith-Miranda
- H. Heyman
- R. Cordero
- A. Casadevall
- E. Nakayasu
- J. Nosanchuk
Abstract
Abstract
Extracellular vesicles (EV) are lipid-bilayered organelles released by many types of cells, including bacteria and mammalian cells and as recently described, by fungi. Pathogenic fungi take advantage of EV release, to secrete virulence factors associated with pathogenesis and immune evasion, thus these organelles can be a target of drug development. Candida auris is an emerging fungal pathogen described in 2009 after being isolated from a patient in Japan. Since its description, some outbreaks have been reported across the globe, and recently in US. C. auris bloodstream infections led to mortality in 30 to 60% of the cases in hospitals, and a common feature among the strains isolated so far, is a remarkable resistance against at least one class of antifungals, and in some cases to the three of them. Our aim was to evaluate if Candida auris releases EV and if these structures could have a role in the pathogenesis. In order to evaluate these points we first addressed the EV release by C. auris, and then these EV were submitted to lipidomic and proteomic analyses to identify novel targets and mechanisms of disease. Our findings to date demonstrate significant differences in the characteristics and content of EVs from C. auris and other pathogens, including C. albicans. C. auris EV secretion may be associated with the pathogenesis of this emerging fungus.
Dissecting the melanin unit in Cryptococcus neoformans
- R. Cordero
- R. Vij
- E. Camacho
- R. Perez-Dulzaides
- A. Casadevall