scholarly journals Laccases Involved in 1,8-Dihydroxynaphthalene Melanin Biosynthesis in Aspergillus fumigatus Are Regulated by Developmental Factors and Copper Homeostasis

2013 ◽  
Vol 12 (12) ◽  
pp. 1641-1652 ◽  
Author(s):  
Srijana Upadhyay ◽  
Guadalupe Torres ◽  
Xiaorong Lin
Keyword(s):  
Immune Responses ◽  
Aspergillus Fumigatus ◽  
Gene Cluster ◽  
Gene Expression Pattern ◽  
Copper Homeostasis ◽  
Copper Level ◽  
Fungal Virulence ◽  
Copper Transporter ◽  
Melanin Biosynthesis ◽  
Content Type

ABSTRACTAspergillus fumigatusproduces heavily melanized infectious conidia. The conidial melanin is associated with fungal virulence and resistance to various environmental stresses. This 1,8-dihydroxynaphthalene (DHN) melanin is synthesized by enzymes encoded in a gene cluster inA. fumigatus, including two laccases, Abr1 and Abr2. Although this gene cluster is not conserved in all aspergilli, laccases are critical for melanization in all species examined. Here we show that the expression ofA. fumigatuslaccases Abr1/2 is upregulated upon hyphal competency and drastically increased during conidiation. The Abr1 protein is localized at the surface of stalks and conidiophores, but not in young hyphae, consistent with the gene expression pattern and its predicted role. The induction of Abr1/2 upon hyphal competency is controlled by BrlA, the master regulator of conidiophore development, and is responsive to the copper level in the medium. We identified a developmentally regulated putative copper transporter, CtpA, and found that CtpA is critical for conidial melanization under copper-limiting conditions. Accordingly, disruption of CtpA enhanced the induction ofabr1andabr2, a response similar to that induced by copper starvation. Furthermore, nonpigmentedctpAΔ conidia elicited much stronger immune responses from the infected invertebrate hostGalleria mellonellathan the pigmentedctpAΔ or wild-type conidia. Such enhancement in elicitingGalleriaimmune responses was independent of thectpAΔ conidial viability, as previously observed for the DHN melanin mutants. Taken together, our findings indicate that both copper homeostasis and developmental regulators control melanin biosynthesis, which affects conidial surface properties that shape the interaction between this pathogen and its host.

scholarly journals Aspergillus fumigatus and Aspergillosis in 2019

2019 ◽  
Vol 33 (1) ◽  
Author(s):  
Jean-Paul Latgé ◽  
Georgios Chamilos
Keyword(s):  
Aspergillus Fumigatus ◽  
Current Status ◽  
Fungal Virulence ◽  
Content Type ◽  
Nutritional Immunity ◽  
New Concepts ◽  
Clinical Syndromes ◽  
Metabolic Activities ◽  
Primary Habitat ◽  
Hostile Environments

SUMMARY Aspergillus fumigatus is a saprotrophic fungus; its primary habitat is the soil. In its ecological niche, the fungus has learned how to adapt and proliferate in hostile environments. This capacity has helped the fungus to resist and survive against human host defenses and, further, to be responsible for one of the most devastating lung infections in terms of morbidity and mortality. In this review, we will provide (i) a description of the biological cycle of A. fumigatus; (ii) a historical perspective of the spectrum of aspergillus disease and the current epidemiological status of these infections; (iii) an analysis of the modes of immune response against Aspergillus in immunocompetent and immunocompromised patients; (iv) an understanding of the pathways responsible for fungal virulence and their host molecular targets, with a specific focus on the cell wall; (v) the current status of the diagnosis of different clinical syndromes; and (vi) an overview of the available antifungal armamentarium and the therapeutic strategies in the clinical context. In addition, the emergence of new concepts, such as nutritional immunity and the integration and rewiring of multiple fungal metabolic activities occurring during lung invasion, has helped us to redefine the opportunistic pathogenesis of A. fumigatus.

scholarly journals Biotinylated Surfome Profiling Identifies Potential Biomarkers for Diagnosis and Therapy of Aspergillus fumigatus Infection

mSphere ◽  
2020 ◽  
Vol 5 (4) ◽  
Author(s):  
Lei-Jie Jia ◽  
Thomas Krüger ◽  
Matthew G. Blango ◽  
Ferdinand von Eggeling ◽  
Olaf Kniemeyer ◽  
...  
Keyword(s):  
Immune Responses ◽  
Aspergillus Fumigatus ◽  
Dynamic Change ◽  
Invasive Pulmonary Aspergillosis ◽  
Direct Interaction ◽  
Surface Proteins ◽  
Host Cells ◽  
Human Immune System ◽  
Data Set ◽  
Content Type

ABSTRACT Aspergillus fumigatus is one of the most common airborne molds capable of causing mycoses and allergies in humans. During infection, fungal surface proteins mediate the first contact with the human immune system to evade immune responses or to induce hypersensitivity. Several methods have been established for surface proteomics (surfomics). Biotinylation coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) identification of peptides is a particularly efficient method to identify the surface-exposed regions of proteins that potentially mediate interaction with the host. After biotinylation of surface proteins during spore germination, we detected 231 different biotinylated surface proteins (including several well-known proteins such as RodA, CcpA, and DppV; allergens; and heat shock proteins [HSPs]), as well as some previously undescribed surface proteins. The dynamic change of the surface proteome was illustrated by detection of a relatively high number of proteins exclusively at one developmental stage. Using immunofluorescence microscopy, we confirmed the surface localization of several HSPs of the HSP70 family, which may have moonlighting functions. Collectively, by comparing our data with data representative of previously published A. fumigatus surface proteomes, our study generated a comprehensive data set corresponding to the A. fumigatus surfome and uncovered the surface-exposed regions of many proteins on the surface of conidia or hyphae. These surface-exposed regions are candidates for direct interaction with host cells and may represent antigenic epitopes that either induce protective immune responses or mediate immune evasion. Thus, our data sets provided and compiled here represent reasonable immunotherapy and diagnostic targets for future investigations. IMPORTANCE Aspergillus fumigatus is the most important airborne human-pathogenic mold, capable of causing both life-threatening invasive pulmonary aspergillosis in immunocompromised patients and allergy-inducing infections in individuals with atopic allergy. Despite its obvious medical relevance, timely diagnosis and efficient antifungal treatment of A. fumigatus infection remain major challenges. Proteins on the surface of conidia (asexually produced spores) and mycelium directly mediate host-pathogen interaction and also may serve as targets for diagnosis and immunotherapy. However, the similarity of protein sequences between A. fumigatus and other organisms, sometimes even including the human host, makes selection of targets for immunological-based studies difficult. Here, using surface protein biotinylation coupled with LC-MS/MS analysis, we identified hundreds of A. fumigatus surface proteins with exposed regions, further defining putative targets for possible diagnostic and immunotherapeutic design.

scholarly journals Surface Structure Characterization of Aspergillus fumigatus Conidia Mutated in the Melanin Synthesis Pathway and Their Human Cellular Immune Response

2014 ◽  
Vol 82 (8) ◽  
pp. 3141-3153 ◽  
Author(s):  
Jagadeesh Bayry ◽  
Audrey Beaussart ◽  
Yves F. Dufrêne ◽  
Meenu Sharma ◽  
Kushagra Bansal ◽  
...  
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Aspergillus Fumigatus ◽  
Surface Defects ◽  
Structure Characterization ◽  
Inert Material ◽  
Cell Wall Polysaccharides ◽  
Melanin Biosynthesis ◽  
Content Type ◽  
Conidial Surface

ABSTRACTInAspergillus fumigatus, the conidial surface contains dihydroxynaphthalene (DHN)-melanin. Six-clustered gene products have been identified that mediate sequential catalysis of DHN-melanin biosynthesis. Melanin thus produced is known to be a virulence factor, protecting the fungus from the host defense mechanisms. In the present study, individual deletion of the genes involved in the initial three steps of melanin biosynthesis resulted in an altered conidial surface with masked surface rodlet layer, leaky cell wall allowing the deposition of proteins on the cell surface and exposing the otherwise-masked cell wall polysaccharides at the surface. Melanin as such was immunologically inert; however, deletion mutant conidia with modified surfaces could activate human dendritic cells and the subsequent cytokine production in contrast to the wild-type conidia. Cell surface defects were rectified in the conidia mutated in downstream melanin biosynthetic pathway, and maximum immune inertness was observed upon synthesis of vermelone onward. These observations suggest that although melanin as such is an immunologically inert material, it confers virulence by facilitating proper formation of theA. fumigatusconidial surface.

scholarly journals Production of Diverse Beauveriolide Analogs in Closely Related Fungi: a Rare Case of Fungal Chemodiversity

mSphere ◽  
2020 ◽  
Vol 5 (5) ◽  
Author(s):  
Ying Yin ◽  
Bo Chen ◽  
Shuangxiu Song ◽  
Bing Li ◽  
Xiuqing Yang ◽  
...  
Keyword(s):  
Gene Cluster ◽  
Growth Condition ◽  
Chain Length ◽  
Rare Case ◽  
Biosynthetic Gene Cluster ◽  
Biosynthetic Gene ◽  
Beauveria Brongniartii ◽  
Fungal Virulence ◽  
Content Type ◽  
A Chain

ABSTRACT Fungal chemodiversity is well known in part due to the production of diverse analogous compounds by a single biosynthetic gene cluster (BGC). Usually, similar or the same metabolites are produced by closely related fungal species under a given condition, the foundation of fungal chemotaxonomy. Here, we report a rare case of the production of the cyclodepsipeptide beauveriolides (BVDs) in three insect-pathogenic fungi. We found that the more closely related fungi Beauveria bassiana and Beauveria brongniartii produced structurally distinct analogs of BVDs, whereas the less-close relatives B. brongniartii and Cordyceps militaris biosynthesized structurally similar congeners under the same growth condition. It was verified that a conserved BGC containing four genes is responsible for BVD biosynthesis in three fungi, including a polyketide synthase (PKS) for the production of 3-hydroxy fatty acids (FAs) with chain length variations. In contrast to BVD production patterns, phylogenetic analysis of the BGC enzymes or enzyme domains largely resulted in the congruence relationship with fungal speciation. Feeding assays demonstrated that an FA with a chain length of eight carbon atoms was preferentially utilized, whereas an FA with a chain longer than 10 carbon atoms could not be used as a substrate for BVD biosynthesis. Insect survival assays suggested that the contribution of BVDs to fungal virulence might be associated with the susceptibility of insect species. The results of this study enrich the knowledge of fungal secondary metabolic diversity that can question the reliability of fungal chemotaxonomy. IMPORTANCE Fungal chemotaxonomy is an approach to classify fungi based on the fungal production profile of metabolites, especially the secondary metabolites. We found an atypical example that could question the reliability of fungal chemical classifications in this study, i.e., the more closely related entomopathogenic species Beauveria bassiana and Beauveria brongniartii produced structurally different congeners of the cyclodepsipeptide beauveriolides, whereas the rather divergent species B. brongniartii and Cordyceps militaris biosynthesized similar analogs under the same growth condition. The conserved biosynthetic gene cluster (BGC) containing four genes present in each species is responsible for beauveriolide production. In contrast to the compound formation profiles, the phylogenies of biosynthetic enzymes or enzymatic domains show associations with fungal speciation. Dependent on the insect species, production of beauveriolides may contribute to fungal virulence against the susceptible insect hosts. The findings in this study augment the diversity of fungal secondary metabolisms.

scholarly journals Aspergillus fumigatus SidJ Mediates Intracellular Siderophore Hydrolysis

2013 ◽  
Vol 79 (23) ◽  
pp. 7534-7536 ◽  
Author(s):  
Mario Gründlinger ◽  
Fabio Gsaller ◽  
Markus Schrettl ◽  
Herbert Lindner ◽  
Hubertus Haas
Keyword(s):  
Aspergillus Fumigatus ◽  
Gene Cluster ◽  
Biosynthetic Gene Cluster ◽  
Protein Family ◽  
Biosynthetic Gene ◽  
Intracellular Accumulation ◽  
Iron Starvation ◽  
Content Type ◽  
Hydrolysis Products ◽  
Encoding Gene

ABSTRACTSiderophore-mediated iron handling is crucial for the virulence ofAspergillus fumigatus. Here we identified a new component of its siderophore metabolism, termed SidJ, which is encoded by AFUA_3G03390. The encoding gene is localized in a siderophore biosynthetic gene cluster that is conserved in a variety of fungi. During iron starvation, SidJ deficiency resulted in decreased growth and increased intracellular accumulation of hydrolysis products of the siderophore fusarinine C. The implied role in siderophore hydrolysis is consistent with a putative esterase domain in SidJ, which now represents the first functionally characterized member of the DUF1749 (domain ofunknownfunction) protein family, with members found exclusively in fungi and plants.

scholarly journals Genome-Based Cluster Deletion Reveals an Endocrocin Biosynthetic Pathway in Aspergillus fumigatus

2012 ◽  
Vol 78 (12) ◽  
pp. 4117-4125 ◽  
Author(s):  
Fang Yun Lim ◽  
Yanpeng Hou ◽  
Yiming Chen ◽  
Jee-Hwan Oh ◽  
Inhyung Lee ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Gene Cluster ◽  
Biosynthetic Pathway ◽  
Polyketide Synthase ◽  
Wild Type Strain ◽  
Global Regulator ◽  
Content Type ◽  
In The Wild ◽  
Secondary Metabolite Gene Cluster

ABSTRACTEndocrocin is a simple anthraquinone frequently identified in extracts of numerous fungi. Several biosynthetic schemes for endocrocin synthesis have been hypothesized, but to date, no dedicated secondary metabolite gene cluster that produces this polyketide as its major metabolite has been identified. Here we describe our biosynthetic and regulatory characterization of the endocrocin gene cluster inAspergillus fumigatus. This is the first report of this anthraquinone in this species. The biosynthetic genes required for endocrocin production are regulated by the global regulator of secondary metabolism, LaeA, and encode an iterative nonreducing polyketide synthase (encA), a physically discrete metallo-β-lactamase type thioesterase (encB), and a monooxygenase (encC). Interestingly, the deletion of a gene immediately adjacent toencC, termedencDand encoding a putative 2-oxoglutarate-Fe(II) type oxidoreductase, resulted in higher levels of endocrocin production than in the wild-type strain, whereas overexpression ofencDeliminated endocrocin accumulation. We found that overexpression of theencAtranscript resulted in higher transcript levels ofencA-Dand higher production of endocrocin. We discuss a model of theenccluster as one evolutionary origin of fungal anthraquinones derived from a nonreducing polyketide synthase and a discrete metallo-β-lactamase-type thioesterase.

scholarly journals Dsc Orthologs Are Required for Hypoxia Adaptation, Triazole Drug Responses, and Fungal Virulence in Aspergillus fumigatus

2012 ◽  
Vol 11 (12) ◽  
pp. 1557-1567 ◽  
Author(s):  
Sven D. Willger ◽  
E. Jean Cornish ◽  
Dawoon Chung ◽  
Brittany A. Fleming ◽  
Margaret M. Lehmann ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Regulatory Element ◽  
Invasive Pulmonary Aspergillosis ◽  
Fungal Growth ◽  
Drug Susceptibility ◽  
Antifungal Drugs ◽  
Fungal Virulence ◽  
Content Type ◽  
Hypoxia Adaptation ◽  
Element Binding Protein

ABSTRACTHypoxia is an environmental stress encountered byAspergillus fumigatusduring invasive pulmonary aspergillosis (IPA). The ability of this mold to adapt to hypoxia is important for fungal virulence and genetically regulated in part by the sterol regulatory element binding protein (SREBP) SrbA. SrbA is required for fungal growth in the murine lung and to ultimately cause lethal disease in murine models of IPA. Here we identified and partially characterized four genes (dscA,dscB,dscC, anddscD, here referred to asdscA-D) with previously unknown functions inA. fumigatusthat are orthologs of theSchizosaccharomyces pombegenesdsc1,dsc2,dsc3, anddsc4(dsc1-4), which encode a Golgi E3 ligase complex critical for SREBP activation by proteolytic cleavage.A. fumigatusnulldscA-Dmutants displayed remarkable defects in hypoxic growth and increased susceptibility to triazole antifungal drugs. Consistent with the confirmed role of these genes inS. pombe, both ΔdscAand ΔdscCresulted in reduced cleavage of the SrbA precursor protein inA. fumigatus. Inoculation of corticosteroid immunosuppressed mice with ΔdscAand ΔdscCstrains revealed that these genes are critical forA. fumigatusvirulence. Reintroduction of SrbA amino acids 1 to 425, encompassing the N terminus DNA binding domain, into the ΔdscAstrain was able to partially restore virulence, further supporting a mechanistic link between DscA and SrbA function. Thus, we have shown for the first time the importance of a previously uncharacterized group of genes inA. fumigatusthat mediate hypoxia adaptation, fungal virulence, and triazole drug susceptibility and that are likely linked to regulation of SrbA function.

scholarly journals Role of CTR4 in the Virulence of Cryptococcus neoformans

mBio ◽  
2012 ◽  
Vol 3 (5) ◽  
Author(s):  
Scott R. Waterman ◽  
Yoon-Dong Park ◽  
Meera Raja ◽  
Jin Qiu ◽  
Dima A. Hammoud ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Ex Vivo ◽  
Copper Homeostasis ◽  
Fluorescent Imaging ◽  
Microbial Pathogenesis ◽  
Copper Transporter ◽  
Content Type ◽  
Expression Levels ◽  
Patient Cohort

ABSTRACTWhile research has identified an important contribution for metals, such as iron, in microbial pathogenesis, the roles of other transition metals, such as copper, remain mostly unknown. Recent evidence points to a requirement for copper homeostasis in the virulence ofCryptococcus neoformansbased on a role for aCUF1copper regulatory factor in mouse models and in a human patient cohort.C. neoformansis an important fungal pathogen that results in an estimated 600,000 AIDS-related deaths yearly. In the present studies, we found that aC. neoformansmutant lacking theCUF1-dependent copper transporter,CTR4, grows normally in rich medium at 37°C but has reduced survival in macrophages and attenuated virulence in a mouse model. This reduced survival and virulence were traced to a growth defect under nutrient-restricted conditions. Expression studies using a full-lengthCTR4-fluorescent fusion reporter construct demonstrated robust expression in macrophages, brain, and lung, the latter shown byex vivofluorescent imaging. Inductively coupled mass spectroscopy (ICP-MS) was used to probe the copper quota of fungal cells grown in defined medium and recovered from brain, which suggested a role for a copper-protective function ofCTR4in combination with cell metallothioneins under copper-replete conditions. In summary, these data suggest a role forCTR4in copper-related homeostasis and subsequently in fungal virulence.IMPORTANCECrytococcus neoformansis a significant global fungal pathogen, and copper homeostasis is a relatively unexplored aspect of microbial pathogenesis that could lead to novel therapeutics. Previous studies correlated expression levels of a Ctr4 copper transporter to development of meningoencephalitis in a patient cohort of solid-organ transplants, but a direct role for Ctr4 in mammalian pathogenesis has not been demonstrated. The present studies utilize a Δctr4mutant strain which revealed an important role forCTR4inC. neoformansinfections in mice and relate the gene product to homeostatic control of copper and growth under nutrient-restricted conditions. Robust expression levels ofCTR4during fungal infection were exploited to demonstrate expression and lung cryptococcal disease usingex vivofluorescence imaging. In summary, these studies are the first to directly demonstrate a role for a copper transporter in fungal disease and provide anex vivoimaging tool for further study of cryptococcal gene expression and pathogenesis.

scholarly journals Identification and Characterization of a Novel Aspergillus fumigatus Rhomboid Family Putative Protease, RbdA, Involved in Hypoxia Sensing and Virulence

2016 ◽  
Vol 84 (6) ◽  
pp. 1866-1878 ◽  
Author(s):  
Yakir Vaknin ◽  
Falk Hillmann ◽  
Rossana Iannitti ◽  
Netali Ben Baruch ◽  
Hana Sandovsky-Losica ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Regulatory Element ◽  
Invasive Pulmonary Aspergillosis ◽  
Hyphal Growth ◽  
Fungal Virulence ◽  
Th17 Response ◽  
Content Type ◽  
Genes Encoding ◽  
Element Binding Protein

Aspergillus fumigatusis the most common pathogenic mold infecting humans and a significant cause of morbidity and mortality in immunocompromised patients. In invasive pulmonary aspergillosis,A. fumigatusspores are inhaled into the lungs, undergoing germination and invasive hyphal growth. The fungus occludes and disrupts the blood vessels, leading to hypoxia and eventual tissue necrosis. The ability of this mold to adapt to hypoxia is regulated in part by the sterol regulatory element binding protein (SREBP) SrbA and the DscA to DscD Golgi E3 ligase complex critical for SREBP activation by proteolytic cleavage. Loss of the genes encoding these proteins results in avirulence. To identify novel regulators of hypoxia sensing, we screened theNeurospora crassagene deletion library under hypoxia and identified a novel rhomboid family protease essential for hypoxic growth. Deletion of theA. fumigatusrhomboid homologrbdAresulted in an inability to grow under hypoxia, hypersensitivity to CoCl2, nikkomycin Z, fluconazole, and ferrozine, abnormal swollen tip morphology, and transcriptional dysregulation—accurately phenocopying deletion ofsrbA. In vivo,rbdAdeletion resulted in increased sensitivity to phagocytic killing, a reduced inflammatory Th1 and Th17 response, and strongly attenuated virulence. Phenotypic rescue of the ΔrbdAmutant was achieved by expression and nuclear localization of the N terminus of SrbA, including its HLH domain, further indicating that RbdA and SrbA act in the same signaling pathway. In summary, we have identified RbdA, a novel putative rhomboid family protease inA. fumigatusthat mediates hypoxia adaptation and fungal virulence and that is likely linked to SrbA cleavage and activation.

scholarly journals SidL, an Aspergillus fumigatus Transacetylase Involved in Biosynthesis of the Siderophores Ferricrocin and Hydroxyferricrocin

2011 ◽  
Vol 77 (14) ◽  
pp. 4959-4966 ◽  
Author(s):  
Michael Blatzer ◽  
Markus Schrettl ◽  
Bettina Sarg ◽  
Herbert H. Lindner ◽  
Kristian Pfaller ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Fluorescent Protein ◽  
Iron Starvation ◽  
Fungal Virulence ◽  
Content Type ◽  
Siderophore Biosynthesis ◽  
Opportunistic Fungal Pathogen ◽  
Triacetylfusarinine C ◽  
Green Fluorescent ◽  
Biosynthetic Machinery

ABSTRACTThe opportunistic fungal pathogenAspergillus fumigatusproduces four types of siderophores, low-molecular-mass iron chelators: it excretes fusarinine C (FsC) and triacetylfusarinine C (TAFC) for iron uptake and accumulates ferricrocin (FC) for hyphal and hydroxyferricrocin (HFC) for conidial iron distribution and storage. Siderophore biosynthesis has recently been shown to be crucial for fungal virulence. Here we identified a new component of the fungal siderophore biosynthetic machinery: AFUA_1G04450, termed SidL. SidL is conserved only in siderophore-producing ascomycetes and shows similarity to transacylases involved in bacterial siderophore biosynthesis and theN5-hydroxyornithine:anhydromevalonyl coenzyme A-N5-transacylase SidF, which is essential for TAFC biosynthesis. Inactivation of SidL inA. fumigatusdecreased FC biosynthesis during iron starvation and completely blocked FC biosynthesis during iron-replete growth. In agreement with these findings, SidL deficiency blocked conidial accumulation of FC-derived HFC under iron-replete conditions, which delayed germination and decreased the size of conidia and their resistance to oxidative stress. Remarkably, thesidLgene is not clustered with other siderophore-biosynthetic genes, and its expression is not affected by iron availability. Tagging of SidL with enhanced green fluorescent protein suggested a cytosolic localization of the FC-biosynthetic machinery. Taken together, these data suggest that SidL is a constitutively activeN5-hydroxyornithine-acetylase required for FC biosynthesis, in particular under iron-replete conditions. Moreover, this study revealed the unexpected complexity of siderophore biosynthesis, indicating the existence of an additional, iron-repressedN5-hydroxyornithine-acetylase.

Sign in / Sign up

Export Citation Format

Share Document