scholarly journals Calcineurin Controls Hyphal Growth, Virulence, and Drug Tolerance of Candida tropicalis

2014 ◽  
Vol 13 (7) ◽  
pp. 844-854 ◽  
Author(s):  
Ying-Lien Chen ◽  
Shang-Jie Yu ◽  
Hsin-Yu Huang ◽  
Ya-Lin Chang ◽  
Virginia N. Lehman ◽  
...  
Keyword(s):  
Candida Tropicalis ◽  
Stress Responses ◽  
Hyphal Growth ◽  
Drug Tolerance ◽  
Negative Regulator ◽  
Infection Model ◽  
Positive Role ◽  
Content Type ◽  
Calcium Tolerance ◽  
Independent Functions

ABSTRACTCandida tropicalis, a species closely related toCandida albicans, is an emerging fungal pathogen associated with high mortality rates of 40 to 70%. LikeC. albicansandCandida dubliniensis,C. tropicalisis able to form germ tubes, pseudohyphae, and hyphae, but the genes involved in hyphal growth machinery and virulence remain unclear inC. tropicalis. Recently, echinocandin- and azole-resistantC. tropicalisisolates have frequently been isolated from various patients around the world, making treatment difficult. However, studies of theC. tropicalisgenes involved in drug tolerance are limited. Here, we investigated the roles of calcineurin and its potential target, Crz1, for core stress responses and pathogenesis inC. tropicalis. We demonstrate that calcineurin and Crz1 are required for hyphal growth, micafungin tolerance, and virulence in a murine systemic infection model, while calcineurin but not Crz1 is essential for tolerance of azoles, caspofungin, anidulafungin, and cell wall-perturbing agents, suggesting that calcineurin has both Crz1-dependent and -independent functions inC. tropicalis. In addition, we found that calcineurin and Crz1 have opposite roles in controlling calcium tolerance. Calcineurin serves as a negative regulator, while Crz1 plays a positive role for calcium tolerance inC. tropicalis.

scholarly journals The F-Box Protein Fbp1 Regulates Sexual Reproduction and Virulence in Cryptococcus neoformans

2011 ◽  
Vol 10 (6) ◽  
pp. 791-802 ◽  
Author(s):  
Tong-Bao Liu ◽  
Yina Wang ◽  
Sabriya Stukes ◽  
Qing Chen ◽  
Arturo Casadevall ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Cryptococcus Neoformans ◽  
Stress Responses ◽  
Membrane Integrity ◽  
Infection Model ◽  
Calcofluor White ◽  
Fungal Virulence ◽  
Content Type ◽  
F Box Protein

ABSTRACTCryptococcus neoformansis the leading cause of fungal meningitis in immunocomprised populations. Although extensive studies have been conducted on signal transduction pathways important for fungal sexual reproduction and virulence, how fungal virulence is regulated during infection is still not understood. In this study, we identified the F-box protein Fbp1, which contains a putative F-box domain and 12 leucine-rich repeats (LRR). Althoughfbp1mutants showed normal growth and produced normal major virulence factors, such as melanin and capsule, Fbp1 was found to be essential for fungal virulence, asfbp1mutants were avirulent in a murine systemic-infection model. Fbp1 is also important for fungal sexual reproduction. Basidiospore production was blocked in bilateral mating betweenfbp1mutants, even though normal dikaryotic hyphae were observed during mating.In vitroassays of stress responses revealed thatfbp1mutants are hypersensitive to SDS, but not calcofluor white (CFW) or Congo red, indicating that Fbp1 may regulate cell membrane integrity. Fbp1 physically interacts with Skp1 homologues in bothSaccharomyces cerevisiaeandC. neoformansvia its F-box domain, suggesting it may function as part of an SCF (Skp1, Cullins, F-box proteins) E3 ligase. Overall, our study revealed that the F-box protein Fbp1 is essential for fungal sporulation and virulence inC. neoformans, which likely represents a conserved novel virulence control mechanism that involves the SCF E3 ubiquitin ligase-mediated proteolysis pathway.

scholarly journals An antipathogenic compound that targets the OxyR peroxide sensor in Pseudomonas aeruginosa

2021 ◽  
Vol 70 (4) ◽  
Author(s):  
Hyo-Young Oh ◽  
Shivakumar S. Jalde ◽  
In-Young Chung ◽  
Yeon-Ji Yoo ◽  
Hye-Jeong Jang ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Drug Resistance ◽  
Stress Responses ◽  
Type Species ◽  
Reduced Form ◽  
Infection Model ◽  
Redox Cycle ◽  
Content Type ◽  
Link Type ◽  
Computer Based

Introduction. Antipathogenic or antivirulence strategy is to target a virulence pathway that is dispensable for growth, in the hope to mitigate the selection for drug resistance. Hypothesis/Gap Statment. Peroxide stress responses are one of the conserved virulence pathways in bacterial pathogens and thus good targets for antipathogenic strategy. Aim. This study aims to identify a new chemical compound that targets OxyR, the peroxide sensor required for the full virulence of the opportunistic human pathogen, Pseudomonas aeruginosa . Methodology. Computer-based virtual screening under consideration of the ‘eNTRy’ rules and molecular docking were conducted on the reduced form of the OxyR regulatory domain (RD). Selected hits were validated by their ability to phenocopy the oxyR null mutant and modulate the redox cycle of OxyR. Results. We first isolated three robust chemical hits that inhibit OxyR without affecting prototrophic growth or viability. One (compound 1) of those affected the redox cycle of OxyR in response to H2O2 treatment, in a way to impair its function. Compound 1 displayed selective antibacterial efficacy against P. aeruginosa in Drosophila infection model, without antibacterial activity against Staphylococcus aureus . Conclusion. These results suggest that compound 1 could be an antipathogenic hit inhibiting the P. aeruginosa OxyR. More importantly, our study provides an insight into the computer-based discovery of new-paradigm selective antibacterials to treat Gram-negative bacterial infections presumably with few concerns of drug resistance.

scholarly journals In Vitro Antibiofilm Activity of Eucarobustol E against Candida albicans

2017 ◽  
Vol 61 (8) ◽  
Author(s):  
Rui-Huan Liu ◽  
Zhi-Chun Shang ◽  
Tian-Xiao Li ◽  
Ming-Hua Yang ◽  
Ling-Yi Kong
Keyword(s):  
Candida Albicans ◽  
Antifungal Susceptibility ◽  
Hyphal Growth ◽  
Negative Regulator ◽  
Ergosterol Biosynthesis ◽  
Pcr Analysis ◽  
Antibiofilm Activity ◽  
Biofilm Inhibition ◽  
Content Type

ABSTRACT Formyl-phloroglucinol meroterpenoids (FPMs) are important types of natural products with various bioactivities. Our antifungal susceptibility assay showed that one of the Eucalyptus robusta-derived FPMs, eucarobustol E (EE), exerted a strong inhibitory effect against Candida albicans biofilms at a concentration of 16 μg/ml. EE was found to block the yeast-to-hypha transition and reduce the cellular surface hydrophobicity of the biofilm cells. RNA sequencing and real-time reverse transcription-PCR analysis showed that exposure to 16 μg/ml of EE resulted in marked reductions in the levels of expressions of genes involved in hyphal growth (EFG1, CPH1, TEC1, EED1, UME6, and HGC1) and cell surface protein genes (ALS3, HWP1, and SAP5). Interestingly, in response to EE, genes involved in ergosterol biosynthesis were downregulated, while the farnesol-encoding gene (DPP3) was upregulated, and these findings were in agreement with those from the quantification of ergosterol and farnesol. Combined with the obvious elevation of negative regulator genes (TUP1, NRG1), we speculated that EE's inhibition of carbon flow to ergosterol triggered the mechanisms of the negative regulation of hyphal growth and eventually led to biofilm inhibition.

scholarly journals The Heat-Induced Molecular Disaggregase Hsp104 of Candida albicans Plays a Role in Biofilm Formation and Pathogenicity in a Worm Infection Model

2012 ◽  
Vol 11 (8) ◽  
pp. 1012-1020 ◽  
Author(s):  
Alessandro Fiori ◽  
Soňa Kucharíková ◽  
Gilmer Govaert ◽  
Bruno P. A. Cammue ◽  
Karin Thevissen ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Stress Responses ◽  
Biofilm Formation ◽  
Fungal Pathogens ◽  
Elevated Temperatures ◽  
Structural Defects ◽  
Infection Model ◽  
Content Type

ABSTRACT The consequences of deprivation of the molecular chaperone Hsp104 in the fungal pathogen Candida albicans were investigated. Mutants lacking HSP104 became hypersusceptible to lethally high temperatures, similarly to the corresponding mutants of Saccharomyces cerevisiae , whereas normal susceptibility was restored upon reintroduction of the gene. By use of a strain whose only copy of HSP104 is an ectopic gene under the control of a tetracycline-regulated promoter, expression of Hsp104 prior to the administration of heat shock could be demonstrated to be sufficient to confer protection from the subsequent temperature increase. This result points to a key role for Hsp104 in orchestrating the cell response to elevated temperatures. Despite their not showing evident growth or morphological defects, biofilm formation by cells lacking HSP104 proved to be defective in two established in vitro models that use polystyrene and polyurethane as the substrates. Biofilms formed by the wild-type and HSP104 -reconstituted strains showed patterns of intertwined hyphae in the extracellular matrix. In contrast, biofilm formed by the hsp104 Δ/ hsp104 Δ mutant showed structural defects and appeared patchy and loose. Decreased virulence of the hsp104 Δ/ hsp104 Δ mutant was observed in the Caenorhabditis elegans infection model, in which high in vivo temperature does not play a role. In agreement with the view that stress responses in fungal pathogens may have evolved to provide niche-specific adaptation to environmental conditions, these results provide an indication of a temperature-independent role for Hsp104 in support of Candida albicans virulence, in addition to its key role in governing thermotolerance.

scholarly journals Distinct and Redundant Roles of Protein Tyrosine Phosphatases Ptp1 and Ptp2 in Governing the Differentiation and Pathogenicity of Cryptococcus neoformans

2014 ◽  
Vol 13 (6) ◽  
pp. 796-812 ◽  
Author(s):  
Kyung-Tae Lee ◽  
Hyo-Jeong Byun ◽  
Kwang-Woo Jung ◽  
Joohyeon Hong ◽  
Eunji Cheong ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Negative Feedback ◽  
Stress Responses ◽  
Protein Tyrosine Phosphatases ◽  
Mapk Signaling ◽  
Negative Regulator ◽  
Tyrosine Phosphatases ◽  
Hog Pathway ◽  
Content Type ◽  
Protein Tyrosine

ABSTRACTProtein tyrosine phosphatases (PTPs) serve as key negative-feedback regulators of mitogen-activated protein kinase (MAPK) signaling cascades. However, their roles and regulatory mechanisms in human fungal pathogens remain elusive. In this study, we characterized the functions of two PTPs, Ptp1 and Ptp2, inCryptococcus neoformans, which causes fatal meningoencephalitis.PTP1andPTP2were found to be stress-inducible genes, which were controlled by the MAPK Hog1 and the transcription factor Atf1. Ptp2 suppressed the hyperphosphorylation of Hog1 and was involved in mediating vegetative growth, sexual differentiation, stress responses, antifungal drug resistance, and virulence factor regulation through the negative-feedback loop of the HOG pathway. In contrast, Ptp1 was not essential for Hog1 regulation, despite its Hog1-dependent induction. However, in the absence of Ptp2, Ptp1 served as a complementary PTP to control some stress responses. In differentiation, Ptp1 acted as a negative regulator, but in a Hog1- and Cpk1-independent manner. Additionally, Ptp1 and Ptp2 localized to the cytosol but were enriched in the nucleus during the stress response, affecting the transient nuclear localization of Hog1. Finally, Ptp1 and Ptp2 played minor and major roles, respectively, in the virulence ofC. neoformans. Taken together, our data suggested that PTPs could be exploited as novel antifungal targets.

scholarly journals Protein Phosphatase 2A (PP2A) Regulatory Subunits ParA and PabA Orchestrate Septation and Conidiation and Are Essential for PP2A Activity in Aspergillus nidulans

2014 ◽  
Vol 13 (12) ◽  
pp. 1494-1506 ◽  
Author(s):  
Guo-wei Zhong ◽  
Ping Jiang ◽  
Wei-ran Qiao ◽  
Yuan-wei Zhang ◽  
Wen-fan Wei ◽  
...  
Keyword(s):  
Aspergillus Nidulans ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Hyphal Growth ◽  
Negative Regulator ◽  
Regulatory Subunit ◽  
Content Type ◽  
Regulatory Subunits ◽  
Pp2a Activity ◽  
Phosphatase 2A

ABSTRACTProtein phosphatase 2A (PP2A) is a major intracellular protein phosphatase that regulates multiple aspects of cell growth and metabolism. Different activities of PP2A and subcellular localization are determined by its regulatory subunits. Here we identified and characterized the functions of two protein phosphatase regulatory subunit homologs, ParA and PabA, inAspergillus nidulans. Our results demonstrate that ParA localizes to the septum site and that deletion ofparAcauses hyperseptation, while overexpression ofparAabolishes septum formation; this suggests that ParA may function as a negative regulator of septation. In comparison, PabA displays a clear colocalization pattern with 4′,6-diamidino-2-phenylindole (DAPI)-stained nuclei, and deletion ofpabAinduces a remarkable delayed-septation phenotype. BothparAandpabAare required for hyphal growth, conidiation, and self-fertilization, likely to maintain normal levels of PP2A activity. Most interestingly,parAdeletion is capable of suppressing septation defects inpabAmutants, suggesting that ParA counteracts PabA during the septation process. In contrast, double mutants ofparAandpabAled to synthetic defects in colony growth, indicating that ParA functions synthetically with PabA during hyphal growth. Moreover, unlike the case for PP2A-Par1 and PP2A-Pab1 in yeast (which are negative regulators that inactivate the septation initiation network [SIN]), loss of ParA or PabA fails to suppress defects of temperature-sensitive mutants of the SEPH kinase of the SIN. Thus, our findings support the previously unrealized evidence that the B-family subunits of PP2A have comprehensive functions as partners of heterotrimeric enzyme complexes of PP2A, both spatially and temporally, inA. nidulans.

scholarly journals c-di-AMP-Regulated K+ Importer KtrAB Affects Biofilm Formation, Stress Response, and SpeB Expression in Streptococcus pyogenes

2021 ◽  
Vol 89 (4) ◽  
Author(s):  
Sabrina Faozia ◽  
Tazin Fahmi ◽  
Gary C. Port ◽  
Kyu Hong Cho
Keyword(s):  
Stress Response ◽  
Streptococcus Pyogenes ◽  
Stress Responses ◽  
Biofilm Formation ◽  
Growth Conditions ◽  
Infection Model ◽  
Wild Type ◽  
Content Type ◽  
Double Deletion ◽  
A Subunit

ABSTRACT The second messenger cyclic di-AMP (c-di-AMP) controls biofilm formation, stress response, and virulence in Streptococcus pyogenes. The deletion of the c-di-AMP synthase gene, dacA, results in pleiotropic effects including reduced expression of the secreted protease SpeB. Here, we report a role for K+ transport in c-di-AMP-mediated SpeB expression. The deletion of ktrB in the ΔdacA mutant restores SpeB expression. KtrB is a subunit of the K+ transport system KtrAB that forms a putative high-affinity K+ importer. KtrB forms a membrane K+ channel, and KtrA acts as a cytosolic gating protein that controls the transport capacity of the system by binding ligands including c-di-AMP. SpeB induction in the ΔdacA mutant by K+ specific ionophore treatment also supports the importance of cellular K+ balance in SpeB production. The ΔdacA ΔktrB double deletion mutant not only produces wild-type levels of SpeB but also partially or fully reverts the defective ΔdacA phenotypes of biofilm formation and stress responses, suggesting that many ΔdacA phenotypes are due to cellular K+ imbalance. However, the null pathogenicity of the ΔdacA mutant in a murine subcutaneous infection model is not restored by ktrB deletion, suggesting that c-di-AMP controls not only cellular K+ balance but also other metabolic and/or virulence pathways. The deletion of other putative K+ importer genes, kup and kimA, does not phenocopy the deletion of ktrB regarding SpeB induction in the ΔdacA mutant, suggesting that KtrAB is the primary K+ importer that is responsible for controlling cellular K+ levels under laboratory growth conditions.

scholarly journals SpoVG Modulates Cell Aggregation in Staphylococcus aureus by Regulating sasC Expression and Extracellular DNA Release

2020 ◽  
Vol 86 (15) ◽  
Author(s):  
Qing Zhu ◽  
Banghui Liu ◽  
Baolin Sun
Keyword(s):  
Staphylococcus Aureus ◽  
Biofilm Formation ◽  
Cell Aggregation ◽  
Drug Tolerance ◽  
Negative Regulator ◽  
Extracellular Dna ◽  
Deletion Strain ◽  
Content Type ◽  
Oxacillin Resistance ◽  
Biofilm Development

ABSTRACT Biofilm formation is involved in numerous Staphylococcus aureus infections such as endocarditis, septic arthritis, osteomyelitis, and infections of indwelling medical devices. In these diseases, S. aureus forms biofilms as cell aggregates interspersed in host matrix material. Here, we have observed that the level of cell aggregation was significantly higher in the isogenic spoVG-deletion strain than in the wild-type strain. Reverse transcription-quantitative PCR data indicated that SpoVG could repress the expression of sasC, which codes for S. aureus surface protein C and is involved in cell aggregation and biofilm accumulation. Electromagnetic mobility shift assay demonstrated that SpoVG could specifically bind to the promoter region of sasC, indicating that SpoVG is a negative regulator and directly represses the expression of sasC. In addition, deletion of the SasC aggregation domain in the spoVG-deletion strain indicated that high-level expression of sasC could be the underlying cause of significantly increased cell aggregation formation. Our previous study showed that SpoVG is involved in oxacillin resistance of methicillin-resistant S. aureus by regulating the expression of genes involved in cell wall synthesis and degradation. In this study, we also found that SpoVG was able to negatively modulate the S. aureus drug tolerance under conditions of a high concentration of oxacillin treatment. These findings can broaden our understanding of the regulation of biofilm formation and drug tolerance in S. aureus. IMPORTANCE This study revealed that SpoVG can modulate cell aggregation by repressing sasC expression and extracellular DNA (eDNA) release. Furthermore, we have demonstrated the potential linkage between cell aggregation and antibiotic resistance. Our findings provide novel insights into the regulatory mechanisms of SpoVG involved in cell aggregation and in biofilm development and formation in Staphylococcus aureus.

scholarly journals Interplay of Toll-Like Receptor 9, Myeloid Cells, and Deubiquitinase A20 in Periodontal Inflammation

2016 ◽  
Vol 85 (1) ◽  
Author(s):  
Katie E. Crump ◽  
Jennifer C. Oakley ◽  
Xia Xia-Juan ◽  
Theandra C. Madu ◽  
Swathi Devaki ◽  
...  
Keyword(s):  
Alveolar Bone ◽  
Ex Vivo ◽  
Negative Regulator ◽  
Gingival Tissue ◽  
Infection Model ◽  
Limiting Factor ◽  
Toll Like Receptor ◽  
Necrosis Factor Alpha ◽  
Content Type ◽  
Periodontal Inflammation

ABSTRACT Toll-like receptor 9 (TLR9)-deficient (TLR9−/−) mice are resistant to periodontitis, a disease characterized by a dysbiotic microbiota and deregulated immune response and resulting in tooth loss and various systemic conditions. However, the mechanisms and biological pathways by which TLR9 instigates periodontal inflammation are yet to be identified. In a ligature-induced model of periodontitis, we demonstrate that TLR9−/− mice exhibited significantly less alveolar bone loss than their wild-type (WT) counterparts. Consistent with the disease phenotype, gingival tissues showed significantly more inflammatory cell infiltration in the WT ligated but not in the TLR9−/− ligated mice compared to the unligated controls. The peritoneal infection model using Porphyromonas gingivalis, a keystone pathogen for periodontitis, revealed reduced neutrophils in TLR9−/− mice on day 1 postinfection compared to the levels in WT mice. Transcriptomics analyses showed increased expression of A20 (tumor necrosis factor alpha [TNF-α]-induced protein 3 [TNFAIP3]), an inhibitor of the NF-κB pathway and a negative regulator of TLR signaling, in ligated TLR9−/− mouse gingival tissues compared to its expression in the WT. Ex vivo, TLR9−/− bone marrow-derived macrophages produced more A20 than WT cells following P. gingivalis challenge. Clinically, A20 was modestly upregulated in human gingival tissue specimens from chronic periodontitis patients, further confirming the biological relevance of A20 in periodontal inflammation. We conclude that TLR9 modulates periodontal disease progression at both the cellular and molecular level and identify A20 as a novel downstream signaling molecule in the course of periodontal inflammation. Understanding the regulation of the TLR9 signaling pathway and the involvement of A20 as a limiting factor of inflammation will uncover alternative therapeutic targets to treat periodontitis and other chronic inflammatory diseases.

scholarly journals Calcineurin Controls Drug Tolerance, Hyphal Growth, and Virulence in Candida dubliniensis

2011 ◽  
Vol 10 (6) ◽  
pp. 803-819 ◽  
Author(s):  
Ying-Lien Chen ◽  
Alexandra Brand ◽  
Emma L. Morrison ◽  
Fitz Gerald S. Silao ◽  
Ursela G. Bigol ◽  
...  
Keyword(s):  
Cell Wall ◽  
Combination Therapy ◽  
Calcineurin Inhibitors ◽  
Hyphal Growth ◽  
Drug Tolerance ◽  
Candida Dubliniensis ◽  
Cell Wall Integrity ◽  
Ocular Infection ◽  
Pathogenic Yeast ◽  
Content Type

ABSTRACTCandida dubliniensisis an emerging pathogenic yeast species closely related toCandida albicansand frequently found colonizing or infecting the oral cavities of HIV/AIDS patients. Drug resistance duringC. dubliniensisinfection is common and constitutes a significant therapeutic challenge. The calcineurin inhibitor FK506 exhibits synergistic fungicidal activity with azoles or echinocandins in the fungal pathogensC. albicans,Cryptococcus neoformans, andAspergillus fumigatus. In this study, we show that calcineurin is required for cell wall integrity and wild-type tolerance ofC. dubliniensisto azoles and echinocandins; hence, these drugs are candidates for combination therapy with calcineurin inhibitors. In contrast toC. albicans, in which the roles of calcineurin and Crz1 in hyphal growth are unclear, here we show that calcineurin and Crz1 play a clearly demonstrable role in hyphal growth in response to nutrient limitation inC. dubliniensis. We further demonstrate that thigmotropism is controlled by Crz1, but not calcineurin, inC. dubliniensis. Similar toC. albicans,C. dubliniensiscalcineurin enhances survival in serum.C. dubliniensiscalcineurin andcrz1/crz1mutants exhibit attenuated virulence in a murine systemic infection model, likely attributable to defects in cell wall integrity, hyphal growth, and serum survival. Furthermore, we show thatC. dubliniensiscalcineurin mutants are unable to establish murine ocular infection or form biofilms in a rat denture model. That calcineurin is required for drug tolerance and virulence makes fungus-specific calcineurin inhibitors attractive candidates for combination therapy with azoles or echinocandins against emergingC. dubliniensisinfections.

Sign in / Sign up

Export Citation Format

Share Document