scholarly journals The Siderophore Transporters Sit1 and Sit2 Are Essential for Utilization of Ferrichrome-, Ferrioxamine- and Coprogen-Type Siderophores in Aspergillus fumigatus

2021 ◽  
Vol 7 (9) ◽  
pp. 768
Author(s):  
Mario Aguiar ◽  
Thomas Orasch ◽  
Matthias Misslinger ◽  
Anna-Maria Dietl ◽  
Fabio Gsaller ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Filamentous Fungi ◽  
Fungal Pathogens ◽  
Fungal Infections ◽  
The Novel ◽  
Human Pathogen ◽  
Substrate Specificities ◽  
Triacetylfusarinine C ◽  
Opportunistic Human Pathogen ◽  
Siderophore Transporter

Siderophore-mediated acquisition of iron has been shown to be indispensable for the virulence of several fungal pathogens, the siderophore transporter Sit1 was found to mediate uptake of the novel antifungal drug VL-2397, and siderophores were shown to be useful as biomarkers as well as for imaging of fungal infections. However, siderophore uptake in filamentous fungi is poorly characterized. The opportunistic human pathogen Aspergillus fumigatus possesses five putative siderophore transporters. Here, we demonstrate that the siderophore transporters Sit1 and Sit2 have overlapping, as well as unique, substrate specificities. With respect to ferrichrome-type siderophores, the utilization of ferrirhodin and ferrirubin depended exclusively on Sit2, use of ferrichrome A depended mainly on Sit1, and utilization of ferrichrome, ferricrocin, and ferrichrysin was mediated by both transporters. Moreover, both Sit1 and Sit2 mediated use of the coprogen-type siderophores coprogen and coprogen B, while only Sit1 transported the bacterial ferrioxamine-type xenosiderophores ferrioxamines B, G, and E. Neither Sit1 nor Sit2 were important for the utilization of the endogenous siderophores fusarinine C and triacetylfusarinine C. Furthermore, A. fumigatus was found to lack utilization of the xenosiderophores schizokinen, basidiochrome, rhizoferrin, ornibactin, rhodotorulic acid, and enterobactin. Taken together, this study characterized siderophore use by A. fumigatus and substrate characteristics of Sit1 and Sit2.

scholarly journals The Protective Role of 1,8-Dihydroxynaphthalene–Melanin on Conidia of the Opportunistic Human Pathogen Aspergillus fumigatus Revisited: No Role in Protection against Hydrogen Peroxide and Superoxides

mSphere ◽  
2022 ◽  
Author(s):  
E. M. Keizer ◽  
I. D. Valdes ◽  
B. L. McCann ◽  
E. M. Bignell ◽  
H. A. B. Wösten ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Aspergillus Fumigatus ◽  
Protective Role ◽  
Oxygen Species ◽  
Human Pathogen ◽  
Opportunistic Pathogens ◽  
Green Pigment ◽  
Content Type ◽  
Opportunistic Human Pathogen

Opportunistic pathogens like Aspergillus fumigatus have strategies to protect themselves against reactive oxygen species like hydrogen peroxides and superoxides that are produced by immune cells. DHN-melanin is the green pigment on conidia of Aspergillus fumigatus and more than 2 decades ago was reported to protect conidia against hydrogen peroxide.

Analyses of Immune Defense Mechanisms of Human Polymorphonuclear Neutrophils Co-Cultivated with Aspergillus fumigatus Germ Tubes.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3848-3848
Author(s):  
Juergen Loeffler ◽  
Markus Mezger ◽  
Hermann Einsele
Keyword(s):  
Aspergillus Fumigatus ◽  
Defense Mechanisms ◽  
Fungal Pathogens ◽  
Fungal Infections ◽  
Early Stage ◽  
Immune Defense ◽  
Polymorphonuclear Neutrophils ◽  
Number Of Patients ◽  
Human Pmns ◽  
Germ Tubes

Abstract Invasive fungal infections with the opportunistic pathogen Aspergillus fumigatus show an increasing incidence due to a higher number of patients with hematological malignancies. Polymorphonuclear neutrophils (PMNs), as part of the innate immunity, recognize fungal pathogens at an early stage after infiltration. Besides phagocytotic mechanisms, PMNs kill pathogens by the release of reactive oxygen species (ROS). Human PMNs were isolated from blood of healthy donors and co-cultivated with A. fumigatus germ tubes for defined time points. Oxidative burst was determined in a kinetic measurement by the use of dichlorfluorescein. In parallel, PMNs were co-cultivated with A. fumigatus germ tubes, followed by whole genome expression analyses (Affymetrix U133 Plus 2.0 Array). We could demonstrate that A. fumigatus germlings of the clinical relevant strain ATCC 9197 represented a strong stimulus for the release of ROS. PMNs actively tracked germlings and directly attached to fungi as demonstrated by real-time microscopy. In addition, co-cultivation of PMNs with A. fumigatus germ tubes resulted in a strong upregulation of genes involved in self-protection against radicals (hämoxygenase, heat shock 70kDa protein HSPA8, thioredoxin, HSPA1B, HSP90AB1, Ferritin). After 6h of co-cultivation, 195 genes showed an at least 4fold altered gene expression. Therein, 4 genes encoding for cytokines and chemokines (IL-8, CCL3, CXCL2, IL1RN) were significantly upregulated. Luminex ELISA analyses confirmed array data and revealing IL-8 to be strongly released (5fold) by PMNs after fungal co-culturing. In conclusion, A. fumigatus had a substantial effect on the activity of human PMNs. In consequence, various defence strategies were activated, including phagocytosis, ROS release and mobilization of other immune effector cells by secretion of chemoattractant cytokines. A better understanding of innate immune defense mechanisms may provide new directions for antifungal therapies.

scholarly journals Upstream and Downstream Regulation of Asexual Development in Aspergillus fumigatus

2006 ◽  
Vol 5 (10) ◽  
pp. 1585-1595 ◽  
Author(s):  
Jae-Hyung Mah ◽  
Jae-Hyuk Yu
Keyword(s):  
Aspergillus Fumigatus ◽  
G Proteins ◽  
Asexual Development ◽  
Human Pathogen ◽  
Loss Of Function ◽  
Primary Target ◽  
Asexual Sporulation ◽  
Opportunistic Human Pathogen ◽  
Upstream Regulators ◽  
Primary Agent

ABSTRACT The opportunistic human pathogen Aspergillus fumigatus produces a large quantity of asexual spores (conidia), which are the primary agent causing invasive aspergillosis in immunocompromised patients. We investigated the mechanisms controlling asexual sporulation (conidiation) in A. fumigatus via examining functions of four key regulators, GpaA (Gα), AfFlbA (RGS), AfFluG, and AfBrlA, previously studied in Aspergillus nidulans. Expression analyses of gpaA, AfflbA, AffluG, AfbrlA, and AfwetA throughout the life cycle of A. fumigatus revealed that, while transcripts of AfflbA and AffluG accumulate constantly, the latter two downstream developmental regulators are specifically expressed during conidiation. Both loss-of-function AfflbA and dominant activating GpaAQ204L mutations resulted in reduced conidiation with increased hyphal proliferation, indicating that GpaA signaling activates vegetative growth while inhibiting conidiation. As GpaA is the primary target of AfFlbA, the dominant interfering GpaAG203R mutation suppressed reduced conidiation caused by loss of AfflbA function. These results corroborate the hypothesis that functions of G proteins and RGSs are conserved in aspergilli. We then examined functions of the two major developmental activators AfFluG and AfBrlA. While deletion of AfbrlA eliminated conidiation completely, null mutation of AffluG did not cause severe alterations in A. fumigatus sporulation in air-exposed culture, implying that, whereas the two aspergilli may have a common key downstream developmental activator, upstream mechanisms activating brlA may be distinct. Finally, both AffluG and AfflbA mutants showed reduced conidiation and delayed expression of AfbrlA in synchronized developmental induction, indicating that these upstream regulators contribute to the proper progression of conidiation.

scholarly journals Siderophore Scaffold as Carrier for Antifungal Peptides in Therapy of Aspergillus fumigatus Infections

2020 ◽  
Vol 6 (4) ◽  
pp. 367
Author(s):  
Joachim Pfister ◽  
Roland Bata ◽  
Isabella Hubmann ◽  
Anton Amadeus Hörmann ◽  
Fabio Gsaller ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Targeted Delivery ◽  
Fungal Pathogens ◽  
Growth Promotion ◽  
Modern Medicine ◽  
Triacetylfusarinine C ◽  
Gallium 68 ◽  
Conjugated Compounds

Antifungal resistance of human fungal pathogens represents an increasing challenge in modern medicine. Short antimicrobial peptides (AMP) display a promising class of antifungals with a different mode of action, but lack target specificity and metabolic stability. In this study the hexapeptide PAF26 (Ac-dArg-dLys-dLys-dTrp-dPhe-dTrp-NH2) and the three amino acid long peptide NLF (H2N-Asn-Leu-dPhe-COOH) were coupled to diacetylfusarinine C (DAFC), a derivative of the siderophore triacetylfusarinine C (TAFC) of Aspergillus fumigatus, to achieve targeted delivery for treatment of invasive aspergillosis. Conjugated compounds in various modifications were labelled with radioactive gallium-68 to perform in vitro and in vivo characterizations. LogD, serum stability, uptake- growth promotion- and minimal inhibitory concentration assays were performed, as well as in vivo stability tests and biodistribution in BALB/c mice. Uptake and growth assays revealed specific internalization of the siderophore conjugates by A. fumigatus. They showed a high stability in human serum and also in the blood of BALB/c mice but metabolites in urine, probably due to degradation in the kidneys. Only PAF26 showed growth inhibition at 8 µg/ml which was lost after conjugation to DAFC. Despite their lacking antifungal activity conjugates based on a siderophore scaffold have a potential to provide the basis for a new class of antifungals, which allow the combination of imaging by using PET/CT with targeted treatment, thereby opening a theranostic approach for personalized therapy.

scholarly journals An LaeA- and BrlA-Dependent Cellular Network Governs Tissue-Specific Secondary Metabolism in the Human PathogenAspergillus fumigatus

mSphere ◽  
2018 ◽  
Vol 3 (2) ◽  
Author(s):  
Abigail L. Lind ◽  
Fang Yun Lim ◽  
Alexandra A. Soukup ◽  
Nancy P. Keller ◽  
Antonis Rokas
Keyword(s):  
Aspergillus Fumigatus ◽  
Secondary Metabolism ◽  
Filamentous Fungi ◽  
Vegetative Growth ◽  
Cellular Network ◽  
Asexual Development ◽  
Human Pathogen ◽  
Wild Type ◽  
Cellular Processes ◽  
Type Strains

ABSTRACTBiosynthesis of many ecologically important secondary metabolites (SMs) in filamentous fungi is controlled by several global transcriptional regulators, like the chromatin modifier LaeA, and tied to both development and vegetative growth. InAspergillusmolds, asexual development is regulated by the BrlA > AbaA > WetA transcriptional cascade. To elucidate BrlA pathway involvement in SM regulation, we examined the transcriptional and metabolic profiles of ΔbrlA, ΔabaA, and ΔwetAmutant and wild-type strains of the human pathogenAspergillus fumigatus. We find that BrlA, in addition to regulating production of developmental SMs, regulates vegetative SMs and the SrbA-regulated hypoxia stress response in a concordant fashion to LaeA. We further show that the transcriptional and metabolic equivalence of the ΔbrlAand ΔlaeAmutations is mediated by an LaeA requirement preventing heterochromatic marks in thebrlApromoter. These results provide a framework for the cellular network regulating not only fungal SMs but diverse cellular processes linked to virulence of this pathogen.IMPORTANCEFilamentous fungi produce a spectacular variety of small molecules, commonly known as secondary or specialized metabolites (SMs), which are critical to their ecologies and lifestyles (e.g., penicillin, cyclosporine, and aflatoxin). Elucidation of the regulatory network that governs SM production is a major question of both fundamental and applied research relevance. To shed light on the relationship between regulation of development and regulation of secondary metabolism in filamentous fungi, we performed global transcriptomic and metabolomic analyses on mutant and wild-type strains of the human pathogenAspergillus fumigatusunder conditions previously shown to induce the production of both vegetative growth-specific and asexual development-specific SMs. We find that the genebrlA, previously known as a master regulator of asexual development, is also a master regulator of secondary metabolism and other cellular processes. We further show thatbrlAregulation of SM is mediated bylaeA, one of the master regulators of SM, providing a framework for the cellular network regulating not only fungal SMs but diverse cellular processes linked to virulence of this pathogen.

scholarly journals Comparative Genome Sequence Analyses of Geographic Samples of Aspergillus fumigatus—Relevance for Amphotericin B Resistance

2020 ◽  
Vol 8 (11) ◽  
pp. 1673
Author(s):  
Yuying Fan ◽  
Yue Wang ◽  
Jianping Xu
Keyword(s):  
Aspergillus Fumigatus ◽  
Amphotericin B ◽  
Fungal Pathogens ◽  
Molecular Mechanisms ◽  
Fungal Infections ◽  
High Rate ◽  
Whole Genome ◽  
Nucleotide Polymorphisms ◽  
Genome Sequences ◽  
Resistant Strains

Amphotericin B (AMB) is a major fungicidal polyene agent that has a broad spectrum of action against invasive fungal infections. AMB is typically used as the last-line drug against serious and life-threatening infections when other drugs have failed to eliminate the fungal pathogens. Recently, AMB resistance in Aspergillus fumigatus has become more evident. For example, a high rate of AMB resistance (96%) was noted in the A. fumigatus population in Hamilton, Ontario, Canada. AMB-resistant strains have also been found in other countries. However, the mechanism of AMB resistance remains largely unknown. Here, we investigated the potential genes and mutations associated with AMB resistance using whole-genome sequences and examined AMB resistance distribution among genetic populations. A total of 196 whole-genome sequences representing strains from 11 countries were examined. Analyses of single nucleotide polymorphisms (SNPs) at the whole-genome level revealed that these strains belonged to three divergent genetic clusters, with the majority (90%) of AMB resistant strains located in one of the three clusters, Cluster 2. Our analyses identified over 60 SNPs significantly associated with AMB resistance. Together, these SNPs represent promising candidates from which to investigate the putative molecular mechanisms of AMB resistance and for their potential use in developing rapid diagnostic markers for clinical screening of AMB resistance in A. fumigatus.

scholarly journals Novel Hit Compounds as Putative Antifungals: The Case of Aspergillus fumigatus

Molecules ◽  
2019 ◽  
Vol 24 (21) ◽  
pp. 3853 ◽  
Author(s):  
Eftichia Kritsi ◽  
Minos-Timotheos Matsoukas ◽  
Constantinos Potamitis ◽  
Anastasia Detsi ◽  
Marija Ivanov ◽  
...  
Keyword(s):  
Antifungal Activity ◽  
Aspergillus Fumigatus ◽  
Fungal Pathogens ◽  
Fungal Infections ◽  
Pharmacophore Model ◽  
Antifungal Drugs ◽  
In Vitro Assays ◽  
Minimum Fungicidal Concentration ◽  
Dynamics Simulations

The prevalence of invasive fungal infections has been dramatically increased as the size of the immunocompromised population worldwide has grown. Aspergillus fumigatus is characterized as one of the most widespread and ubiquitous fungal pathogens. Among antifungal drugs, azoles have been the most widely used category for the treatment of fungal infections. However, increasingly, azole-resistant strains constitute a major problem to be faced. Towards this direction, our study focused on the identification of compounds bearing novel structural motifs which may evolve as a new class of antifungals. To fulfil this scope, a combination of in silico techniques and in vitro assays were implemented. Specifically, a ligand-based pharmacophore model was created and served as a 3D search query to screen the ZINC chemical database. Additionally, molecular docking and molecular dynamics simulations were used to improve the reliability and accuracy of virtual screening results. In total, eight compounds, bearing completely different chemical scaffolds from the commercially available azoles, were proposed and their antifungal activity was evaluated using in vitro assays. Results indicated that all tested compounds exhibit antifungal activity, especially compounds 1, 2, and 4, which presented the most promising minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values and, therefore, could be subjected to further hit to lead optimization.

Sign in / Sign up

Export Citation Format

Share Document