Transcriptional activation of heat shock protein 90 mediated via a proximal promoter region as trigger of caspofungin resistance in Aspergillus fumigatus.
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SUBMITTER: Lamoth F
PROVIDER: S-EPMC3883176 | biostudies-literature | 2014 Feb
REPOSITORIES: biostudies-literature
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Transcriptional activation of heat shock protein 90 mediated via a proximal promoter region as trigger of caspofungin resistance in Aspergillus fumigatus.
Lamoth Frédéric F Juvvadi Praveen R PR Gehrke Christopher C Asfaw Yohannes G YG Steinbach William J WJ
The Journal of infectious diseases 20131004 3
Invasive aspergillosis is a deadly infection for which new antifungal therapies are needed. Heat shock protein 90 (Hsp90) is an essential chaperone in Aspergillus fumigatus representing an attractive antifungal target. Using a thiamine-repressible promoter (pthiA), we showed that genetic repression of Hsp90 significantly reduced virulence in a murine model of invasive aspergillosis. Moreover, substituting the A. fumigatus hsp90 promoter with 2 artificial promoters (potef, pthiA) and the Candida ...[more]
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Project description:Aspergillus fumigatus is an opportunistic mold responsible for invasive aspergillosis. Triazoles (e.g., voriconazole) represent the first-line treatment, but emerging resistance is of concern. The echinocandin drug caspofungin is used as second-line treatment but has limited efficacy. The heat shock protein 90 (Hsp90) orchestrates the caspofungin stress response and is the trigger of an adaptive phenomenon called the paradoxical effect (growth recovery at increasing caspofungin concentrations). The aim of this study was to elucidate the Hsp90-dependent mechanisms of the caspofungin stress response. Transcriptomic profiles of the wild-type A. fumigatus strain (KU80) were compared to those of a mutant strain with substitution of the native hsp90 promoter by the thiA promoter (pthiA-hsp90), which lacks the caspofungin paradoxical effect. Caspofungin induced expression of the genes of the mitochondrial respiratory chain (MRC), in particular, NADH-ubiquinone oxidoreductases (complex I), in KU80 but not in the pthiA-hsp90 mutant. The caspofungin paradoxical effect could be abolished by rotenone (MRC complex I inhibitor) in KU80, supporting the role of MRC in the caspofungin stress response. Fluorescent staining of active mitochondria and measurement of oxygen consumption and ATP production confirmed the activation of the MRC in KU80 in response to caspofungin, but this activity was impaired in the pthiA-hsp90 mutant. Using a bioluminescent reporter for the measurement of intracellular calcium, we demonstrated that inhibition of Hsp90 by geldanamycin or MRC complex I by rotenone prevented the increase in intracellular calcium shown to be essential for the caspofungin paradoxical effect. In conclusion, our data support a role of the MRC in the caspofungin stress response which is dependent on Hsp90.
| S-EPMC6591604 | biostudies-literature
Project description:BACKGROUND: Aspergillus fumigatus is a thermotolerant human-pathogenic mold and the most common cause of invasive aspergillosis (IA) in immunocompromised patients. Its predominance is based on several factors most of which are still unknown. The thermotolerance of A. fumigatus is one of the traits which have been assigned to pathogenicity. It allows the fungus to grow at temperatures up to and above that of a fevered human host. To elucidate the mechanisms of heat resistance, we analyzed the change of the A. fumigatus proteome during a temperature shift from 30 degrees C to 48 degrees C by 2D-fluorescence difference gel electrophoresis (DIGE). To improve 2D gel image analysis results, protein spot quantitation was optimized by missing value imputation and normalization. Differentially regulated proteins were compared to previously published transcriptome data of A. fumigatus. The study was augmented by bioinformatical analysis of transcription factor binding sites (TFBSs) in the promoter region of genes whose corresponding proteins were differentially regulated upon heat shock. RESULTS: 91 differentially regulated protein spots, representing 64 different proteins, were identified by mass spectrometry (MS). They showed a continuous up-, down- or an oscillating regulation. Many of the identified proteins were involved in protein folding (chaperones), oxidative stress response, signal transduction, transcription, translation, carbohydrate and nitrogen metabolism. A correlation between alteration of transcript levels and corresponding proteins was detected for half of the differentially regulated proteins. Interestingly, some previously undescribed putative targets for the heat shock regulator Hsf1 were identified. This provides evidence for Hsf1-dependent regulation of mannitol biosynthesis, translation, cytoskeletal dynamics and cell division in A. fumigatus. Furthermore, computational analysis of promoters revealed putative binding sites for an AP-2alpha-like transcription factor upstream of some heat shock induced genes. Until now, this factor has only been found in vertebrates. CONCLUSIONS: Our newly established DIGE data analysis workflow yields improved data quality and is widely applicable for other DIGE datasets. Our findings suggest that the heat shock response in A. fumigatus differs from already well-studied yeasts and other filamentous fungi.
| S-EPMC2820008 | biostudies-literature
Project description:Heat shock protein 90 (Hsp90) is an essential chaperone involved in the fungal stress response that can be harnessed as a novel antifungal target for the treatment of invasive aspergillosis. We previously showed that genetic repression of Hsp90 reduced Aspergillus fumigatus virulence and potentiated the effect of the echinocandin caspofungin. In this study, we sought to identify sites of posttranslational modifications (phosphorylation or acetylation) that are important for Hsp90 function in A. fumigatus. Phosphopeptide enrichment and tandem mass spectrometry revealed phosphorylation of three residues in Hsp90 (S49, S288, and T681), but their mutation did not compromise Hsp90 function. Acetylation of lysine residues of Hsp90 was recovered after treatment with deacetylase inhibitors, and acetylation-mimetic mutations (K27A and K271A) resulted in reduced virulence in a murine model of invasive aspergillosis, supporting their role in Hsp90 function. A single deletion of lysine K27 or an acetylation-mimetic mutation (K27A) resulted in increased susceptibility to voriconazole and caspofungin. This effect was attenuated following a deacetylation-mimetic mutation (K27R), suggesting that this site is crucial and should be deacetylated for proper Hsp90 function in antifungal resistance pathways. In contrast to previous reports in Candida albicans, the lysine deacetylase inhibitor trichostatin A (TSA) was active alone against A. fumigatus and potentiated the effect of caspofungin against both the wild type and an echinocandin-resistant strain. Our results indicate that the Hsp90 K27 residue is required for azole and echinocandin resistance in A. fumigatus and that deacetylase inhibition may represent an adjunctive anti-Aspergillus strategy.
| S-EPMC4023766 | biostudies-literature
Project description:The proteomic response of Aspergillus fumigatus to caspofungin was evaluated by gel-free isobaric tagging for relative and absolute quantitation (iTRAQ) as a means to determine potential biomarkers of drug action. A cell fractionation approach yielding 4 subcellular compartment fractions was used to enhance the resolution of proteins for proteomic analysis. Using iTRAQ, a total of 471 unique proteins were identified in soluble and cell wall/plasma membrane fractions at 24 and 48 h of growth in rich media in a wild-type drug-susceptible strain. A total of 122 proteins showed at least a 2-fold change in relative abundance following exposure to caspofungin (CSF) at just below the minimum effective concentration (0.12 ?g/ml). The largest changes were seen in the mitochondrial hypoxia response domain protein (AFUA_1G12250), the level of which decreased >16-fold in the secreted fraction, and ChiA1, the level of which decreased 12.1-fold in the cell wall/plasma membrane fraction. The level of the major allergen and cytotoxin AspF1 was also shown to decrease by 12.1-fold upon the addition of drug. A subsequent iTRAQ analysis of an echinocandin-resistant strain (fks1-S678P) was used to validate proteins specific to drug action. A total of 103 proteins in the 2 fractions tested by iTRAQ were differentially expressed in the wild-type susceptible strain but not significantly changed in the resistant strain. Of these potential biomarkers, 11 had levels that changed at least 12-fold. Microarray analysis of the susceptible strain was performed to evaluate the correlation between proteomics and genomics, with a total of 117 genes found to be changing at least 2-fold. Of these, a total of 22 proteins with significant changes identified by iTRAQ also showed significant gene expression level changes by microarray. Overall, these data have the potential to identify biomarkers that assess the relative efficacy of echinocandin drug therapy.
| S-EPMC3019664 | biostudies-literature
Project description:Aspergillus fumigatus is the leading cause of pulmonary fungal diseases. Azoles have been used for many years as the main antifungal agents to treat and prevent invasive aspergillosis. However, in the last 10 years there have been several reports of azole resistance in A. fumigatus and new strategies are needed to combat invasive aspergillosis. Caspofungin is effective against other human-pathogenic fungal species, but it is fungistatic only against A. fumigatus Resistance to caspofungin in A. fumigatus has been linked to mutations in the fksA gene that encodes the target enzyme of the drug β-1,3-glucan synthase. However, tolerance of high caspofungin concentrations, a phenomenon known as the caspofungin paradoxical effect (CPE), is also important for subsequent adaptation and drug resistance evolution. Here, we identified and characterized the transcription factors involved in the response to CPE by screening an A. fumigatus library of 484 null transcription factors (TFs) in CPE drug concentrations. We identified 11 TFs that had reduced CPE and that encoded proteins involved in the basal modulation of the RNA polymerase II initiation sites, calcium metabolism, and cell wall remodeling. One of these TFs, FhdA, was important for mitochondrial respiratory function and iron metabolism. The ΔfhdA mutant showed decreased growth when exposed to Congo red or to high temperature. Transcriptome sequencing (RNA-seq) analysis and further experimental validation indicated that the ΔfhdA mutant showed diminished respiratory capacity, probably affecting several pathways related to the caspofungin tolerance and resistance. Our results provide the foundation to understand signaling pathways that are important for caspofungin tolerance and resistance.IMPORTANCEAspergillus fumigatus, one of the most important human-pathogenic fungal species, is able to cause aspergillosis, a heterogeneous group of diseases that presents a wide range of clinical manifestations. Invasive pulmonary aspergillosis is the most serious pathology in terms of patient outcome and treatment, with a high mortality rate ranging from 50% to 95% primarily affecting immunocompromised patients. Azoles have been used for many years as the main antifungal agents to treat and prevent invasive aspergillosis. However, there were several reports of evolution of clinical azole resistance in the last decade. Caspofungin, a noncompetitive β-1,3-glucan synthase inhibitor, has been used against A. fumigatus, but it is fungistatic and is recommended as second-line therapy for invasive aspergillosis. More information about caspofungin tolerance and resistance is necessary in order to refine antifungal strategies that target the fungal cell wall. Here, we screened a transcription factor (TF) deletion library for TFs that can mediate caspofungin tolerance and resistance. We have identified 11 TFs that are important for caspofungin sensitivity and/or for the caspofungin paradoxical effect (CPE). These TFs encode proteins involved in the basal modulation of the RNA polymerase II initiation sites, calcium metabolism or cell wall remodeling, and mitochondrial respiratory function. The study of those genes regulated by TFs identified in this work will provide a better understanding of the signaling pathways that are important for caspofungin tolerance and resistance.
| S-EPMC7298710 | biostudies-literature
Project description:Aspergillus fumigatus is an opportunistic and allergenic pathogenic fungus, responsible for fungal infections in humans. A. fumigatus infections are usually treated with polyenes, azoles, or echinocandins. Echinocandins, such as caspofungin, can inhibit the biosynthesis of the β-1,3-glucan polysaccharide, affecting the integrity of the cell wall and leading to fungal death. In some A. fumigatus strains, caspofungin treatment at high concentrations induces an increase of fungal growth, a phenomenon called the caspofungin paradoxical effect (CPE). Here, we analyze the proteome and phosphoproteome of the A. fumigatus wild-type strain and of mitogen-activated protein kinase (MAPK) mpkA and sakA null mutant strains during CPE (2 μg/ml caspofungin for 1 h). The wild-type proteome showed 75 proteins and 814 phosphopeptides (corresponding to 520 proteins) altered in abundance in response to caspofungin treatment. The ΔmpkA (ΔmpkA caspofungin/wild-type caspofungin) and ΔsakA (ΔsakA caspofungin/wild-type caspofungin) strains displayed 626 proteins and 1,236 phosphopeptides (corresponding to 703 proteins) and 101 proteins and 1,217 phosphopeptides (corresponding to 645 proteins), respectively, altered in abundance. Functional characterization of the phosphopeptides from the wild-type strain exposed to caspofungin showed enrichment for transcription factors, protein kinases, and cytoskeleton proteins. Proteomic analysis of the ΔmpkA and ΔsakA mutants indicated that control of proteins involved in metabolism, such as in production of secondary metabolites, was highly represented in both mutants. Results of functional categorization of phosphopeptides from both mutants were very similar and showed a high number of proteins with decreased phosphorylation of proteins involved in transcriptional control, DNA/RNA binding, cell cycle control, and DNA processing. This report reveals novel transcription factors involved in caspofungin tolerance.IMPORTANCEAspergillus fumigatus is an opportunistic human-pathogenic fungus causing allergic reactions or systemic infections, such as invasive pulmonary aspergillosis in immunocompromised patients. Caspofungin is an echinocandin that impacts the construction of the fungal cell wall by inhibiting the biosynthesis of the β-1,3-glucan polysaccharide. Caspofungin is a fungistatic drug and is recommended as a second-line therapy for treatment of aspergillosis. Treatment at high concentrations induces an increase of fungal growth, a phenomenon called the caspofungin paradoxical effect (CPE). Collaboration between the mitogen-activated protein kinases (MAPK) of the cell wall integrity (MapkA) and high-osmolarity glycerol (SakA) pathways is essential for CPE. Here, we investigate the global proteome and phosphoproteome of A. fumigatus wild-type, ΔmpkA, and ΔsakA strains upon CPE. This study showed intense cross talk between the two MAPKs for the CPE and identified novel protein kinases and transcription factors possibly important for CPE. Increased understanding of how the modulation of protein phosphorylation may affect the fungal growth in the presence of caspofungin represents an important step in the development of new strategies and methods to combat the fungus inside the host.
| S-EPMC7253599 | biostudies-literature
Project description:Aspergillus fumigatus, the main etiological agent of invasive aspergillosis, is a leading cause of death in immunocompromised patients. Septins, a conserved family of GTP-binding proteins, serve as scaffolding proteins to recruit enzymes and key regulators to different cellular compartments. Deletion of the A. fumigatus septin aspB increases susceptibility to the echinocandin antifungal caspofungin. However, how AspB mediates this response to caspofungin is unknown. Here, we characterized the AspB interactome under basal conditions and after exposure to a clinically relevant concentration of caspofungin. While A. fumigatus AspB interacted with 334 proteins, including kinases, cell cycle regulators, and cell wall synthesis-related proteins under basal growth conditions, caspofungin exposure altered AspB interactions. A total of 69 of the basal interactants did not interact with AspB after exposure to caspofungin, and 54 new interactants were identified following caspofungin exposure. We generated A. fumigatus deletion strains for 3 proteins (ArpB, Cyp4, and PpoA) that only interacted with AspB following exposure to caspofungin that were previously annotated as induced after exposure to antifungal agents, yet only PpoA was implicated in the response to caspofungin. Taken together, we defined how the septin AspB interactome is altered in the presence of a clinically relevant antifungal.
| S-EPMC5384791 | biostudies-literature
Project description:BACKGROUND: The thermotolerance of Aspergillus fumigatus plays a critical role in mammalian and avian infections. Thus, the identification of its adaptation mechanism to higher temperature is very important for an efficient anti-fungal drug development as well as fundamental understanding of its pathogenesis. We explored the temporal transcription regulation structure of this pathogenic fungus under heat shock conditions using the time series microarray data reported by Nierman et al. (Nature 2005, 438:1151-1156). RESULTS: The estimated transcription regulation structure of A. fumigatus shows that the heat shock proteins are strongly negatively associated with central metabolic pathway genes such as the tricarboxylic acid cycle (TCA cycle) and carbohydrate metabolism. It was 60 min and 120 min, respectively, after the growth temperature changes from 30 degrees C (corresponding to environments of tropical soil) to 37 degrees C and 48 degrees C (corresponding to temperatures in the human body and compost, respectively) that some of genes in TCA cycle were started to be upregulated. In these points, most of heat shock proteins showed lowest expression level after heat shocks. Among the heat shock proteins, the HSP30 (AFU6G06470), a single integral plasma membrane heat shock protein, presented most active role in transcription regulation structure in both heat shock conditions of 37 degrees C and 48 degrees C. The metabolic genes associated with multiple genes in the gene regulation network showed a tendency to have opposite expression patterns of heat shock proteins. The role of those metabolic genes was second regulator in the coherent feed-forward loop type of regulation structure having heat shock protein as its first regulator. This type of regulation structure might be very advantageous for the thermal adaptation of A. fumigatus under heat shock because a small amount of heat shock proteins can rapidly magnify their regulation effect on target genes. However, the coherent feed-forward loop type of regulation of heat shock proteins with metabolic genes became less frequent with increasing temperature. This might be the reason for dramatic increase in the expression of heat shock proteins and the number of heat shock response genes at heat shock of 48 degrees C. CONCLUSION: We systemically analysed the thermal adaption mechanism of A. fumigatus by state space model with times series microarray data in terms of transcription regulation structure. We suggest for the first time that heat shock proteins might efficiently regulate metabolic genes using the coherent feed-forward loop type of regulation structure. This type of regulation structure would also be efficient for adjustment to the other stresses requiring rapid change of metabolic mode as well as thermal adaptation.
| S-EPMC2714559 | biostudies-literature
Project description:Hsp90 is a dimeric ATP-dependent chaperone involved in the folding, maturation, and activation of diverse target proteins. Extensive in vitro structural analysis has led to a working model of Hsp90's ATP-driven conformational cycle. An implicit assumption is that dilute experimental conditions do not significantly perturb Hsp90 structure and function. However, Hsp90 undergoes a dramatic open/closed conformational change, which raises the possibility that this assumption may not be valid for this chaperone. Indeed, here we show that the ATPase activity of Hsp90 is highly sensitive to molecular crowding, whereas the ATPase activities of Hsp60 and Hsp70 chaperones are insensitive to crowding conditions. Polymer crowders activate Hsp90 in a non-saturable manner, with increasing efficacy at increasing concentration. Crowders exhibit a non-linear relationship between their radius of gyration and the extent to which they activate Hsp90. This experimental relationship can be qualitatively recapitulated with simple structure-based volume calculations comparing open/closed configurations of Hsp90. Thermodynamic analysis indicates that crowding activation of Hsp90 is entropically driven, which is consistent with a model in which excluded volume provides a driving force that favors the closed active state of Hsp90. Multiple Hsp90 homologs are activated by crowders, with the endoplasmic reticulum-specific Hsp90, Grp94, exhibiting the highest sensitivity. Finally, we find that crowding activation works by a different mechanism than co-chaperone activation and that these mechanisms are independent. We hypothesize that Hsp90 has a higher intrinsic activity in the cell than in vitro.
| S-EPMC4813586 | biostudies-literature
Project description:We report the nucleotide sequence of a 2652 bp derived from a chicken 90-kDa heat shock protein (hsp 90) genomic clone. This fragment contains 890 bp of the 5' flanking region and 1762 bp of structural gene sequence encoding the first 85 amino acids of the protein. The start site of transcription was determined by primer extension and RNase mapping. Two introns have been identified. The first intron presents two features in common with the unique intron of the hsp 83 of drosophila: its location just before the ATG initiation codon and its length of approximately 1.3 Kb. The 5' flanking region contains a TATAA element, a CCAAT box and several putative cis-regulatory elements that might account for the basal level of expression and developmental regulation of the gene. Functional analyses show that hsp 90 gene expression is constitutive and heat inducible and that a full heat shock response requires the cooperativity of two distinct blocks of overlapping heat shock response elements.
| S-EPMC318109 | biostudies-other