Hog1 Regulates Stress Tolerance and Virulence in the Emerging Fungal PathogenCandida auris

ABSTRACTCandida aurishas recently emerged as an important, multidrug-resistant fungal pathogen of humans. Comparative studies indicate that despite high levels of genetic divergence,C. aurisis as virulent as the most pathogenic member of the genus,Candida albicans. However, key virulence attributes ofC. albicans, such as morphogenetic switching, are not utilized byC. auris, indicating that this emerging pathogen employs alternative strategies to infect and colonize the host. An important trait required for the pathogenicity of many fungal pathogens is the ability to adapt to host-imposed stresses encountered during infection. Here, we investigated the relative resistance ofC. aurisand other pathogenicCandidaspecies to physiologically relevant stresses and explored the role of the evolutionarily conserved Hog1 stress-activated protein kinase (SAPK) in promoting stress resistance and virulence. In comparison toC. albicans,C. aurisis relatively resistant to hydrogen peroxide, cationic stress, and cell-wall-damaging agents. However, in contrast to otherCandidaspecies examined,C. auris was unable to grow in an anaerobic environment and was acutely sensitive to organic oxidative-stress-inducing agents. An analysis ofC. aurishog1Δ cells revealed multiple roles for this SAPK in stress resistance, cell morphology, aggregation, and virulence. These data demonstrate thatC. aurishas a unique stress resistance profile compared to those of other pathogenicCandidaspecies and that the Hog1 SAPK has pleiotropic roles that promote the virulence of this emerging pathogen.IMPORTANCEThe rapid global emergence and resistance ofCandidaauristo current antifungal drugs highlight the importance of understanding the virulence traits exploited by this human fungal pathogen to cause disease. Here, we characterize the stress resistance profile ofC. aurisand the role of the Hog1 stress-activated protein kinase (SAPK) in stress resistance and virulence. Our findings thatC. aurisis acutely sensitive to certain stresses may facilitate control measures to prevent persistent colonization in hospital settings. Furthermore, our observation that the Hog1 SAPK promotesC. aurisvirulence akin to that reported for many other pathogenic fungi indicates that antifungals targeting Hog1 signaling would be broad acting and effective, even on emerging drug-resistant pathogens.

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Adenylyl Cyclase and Protein Kinase A Play Redundant and Distinct Roles in Growth, Differentiation, Antifungal Drug Resistance, and Pathogenicity of Candida auris

mBio ◽

10.1128/mbio.02729-21 ◽

2021 ◽

Author(s):

Ji-Seok Kim ◽

Kyung-Tae Lee ◽

Myung Ha Lee ◽

Eunji Cheong ◽

Yong-Sun Bahn

Keyword(s):

Drug Resistance ◽

Protein Kinase ◽

Protein Kinase A ◽

Fungal Pathogen ◽

Fungal Pathogens ◽

Antifungal Drugs ◽

Candida Auris ◽

Content Type ◽

Antifungal Drug Resistance ◽

Kinase A

Despite the recently growing concern of pan-resistant Candida auris infection, the pathogenicity of this ascomycetous fungal pathogen and the signaling circuitries governing its resistance to antifungal drugs are largely unknown. Therefore, we analyzed the pathobiological functions of cyclic AMP (cAMP)/protein kinase A (PKA) signaling pathway in C. auris , which plays conserved roles in the growth and virulence of fungal pathogens.

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Genetic Analysis of Candida auris Implicates Hsp90 in Morphogenesis and Azole Tolerance and Cdr1 in Azole Resistance

mBio ◽

10.1128/mbio.02529-18 ◽

2019 ◽

Vol 10 (1) ◽

pp. e02529-18 ◽

Cited By ~ 17

Author(s):

Sang Hu Kim ◽

Kali R. Iyer ◽

Lakhansing Pardeshi ◽

José F. Muñoz ◽

Nicole Robbins ◽

...

Keyword(s):

Drug Resistance ◽

Fungal Pathogen ◽

Fungal Pathogens ◽

Filamentous Growth ◽

Antifungal Drugs ◽

Clinical Isolates ◽

Azole Resistance ◽

Candida Auris ◽

Content Type ◽

Insight Into

ABSTRACT Candida auris is an emerging fungal pathogen and a serious global health threat as the majority of clinical isolates display elevated resistance to currently available antifungal drugs. Despite the increased prevalence of C. auris infections, the mechanisms governing drug resistance remain largely elusive. In diverse fungi, the evolution of drug resistance is enabled by the essential molecular chaperone Hsp90, which stabilizes key regulators of cellular responses to drug-induced stress. Hsp90 also orchestrates temperature-dependent morphogenesis in Candida albicans, a key virulence trait. However, the role of Hsp90 in the pathobiology of C. auris remains unknown. In order to study regulatory functions of Hsp90 in C. auris, we placed HSP90 under the control of a doxycycline-repressible promoter to enable transcriptional repression. We found that Hsp90 is essential for growth in C. auris and that it enables tolerance of clinical isolates with respect to the azoles, which inhibit biosynthesis of the membrane sterol ergosterol. High-level azole resistance was independent of Hsp90 but dependent on the ABC transporter CDR1, deletion of which resulted in abrogated resistance. Strikingly, we discovered that C. auris undergoes a morphogenetic transition from yeast to filamentous growth in response to HSP90 depletion or cell cycle arrest but not in response to other cues that induce C. albicans filamentation. Finally, we observed that this developmental transition is associated with global transcriptional changes, including the induction of cell wall-related genes. Overall, this report provides a novel insight into mechanisms of drug tolerance and resistance in C. auris and describes a developmental transition in response to perturbation of a core regulator of protein homeostasis. IMPORTANCE Fungal pathogens pose a serious threat to public health. Candida auris is an emerging fungal pathogen that is often resistant to commonly used antifungal drugs. However, the mechanisms governing drug resistance and virulence in this organism remain largely unexplored. In this study, we adapted a conditional expression system to modulate the transcription of an essential gene, HSP90, which regulates antifungal resistance and virulence in diverse fungal pathogens. We showed that Hsp90 is essential for growth in C. auris and is important for tolerance of the clinically important azole antifungals, which block ergosterol biosynthesis. Further, we established that the Cdr1 efflux transporter regulates azole resistance. Finally, we discovered that C. auris transitions from yeast to filamentous growth in response to Hsp90 inhibition, accompanied by global transcriptional remodeling. Overall, this work provides a novel insight into mechanisms regulating azole resistance in C. auris and uncovers a distinct developmental program regulated by Hsp90.

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Transcriptional Profiling of the Candida auris Response to Exogenous Farnesol Exposure

mSphere ◽

10.1128/msphere.00710-21 ◽

2021 ◽

Author(s):

Ágnes Jakab ◽

Noémi Balla ◽

Ágota Ragyák ◽

Fruzsina Nagy ◽

Fruzsina Kovács ◽

...

Keyword(s):

Health Care ◽

Mortality Rate ◽

Fungal Pathogen ◽

Transcriptional Profiling ◽

Health Care Facilities ◽

Antifungal Drugs ◽

Candida Auris ◽

Content Type ◽

Care Facilities ◽

Innovative Therapies

Candida auris is a dangerous fungal pathogen that causes outbreaks in health care facilities, with infections associated with a high mortality rate. As conventional antifungal drugs have limited effects against the majority of clinical isolates, new and innovative therapies are urgently needed.

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The Candida albicans TOR-Activating GTPases Gtr1 and Rhb1 Coregulate Starvation Responses and Biofilm Formation

mSphere ◽

10.1128/msphere.00477-17 ◽

2017 ◽

Vol 2 (6) ◽

Cited By ~ 8

Author(s):

Peter R. Flanagan ◽

Ning-Ning Liu ◽

Darren J. Fitzpatrick ◽

Karsten Hokamp ◽

Julia R. Köhler ◽

...

Keyword(s):

Candida Albicans ◽

Fungal Pathogen ◽

Biofilm Formation ◽

Nitrogen Starvation ◽

Antifungal Drugs ◽

Target Of Rapamycin ◽

Content Type ◽

Expression Of Genes ◽

Wide Range

ABSTRACT Candida albicans is the major fungal pathogen of humans and is responsible for a wide range of infections, including life-threatening systemic infections in susceptible hosts. Target of rapamycin complex 1 (TORC1) is an essential regulator of metabolism in this fungus, and components of this complex are under increased investigation as targets for new antifungal drugs. The present study characterized the role of GTR1, encoding a putative GTPase, in TORC1 activation. This study shows that GTR1 encodes a protein required for activation of TORC1 activity in response to amino acids and regulation of nitrogen starvation responses. GTR1 mutants show increased cell-cell adhesion and biofilm formation and increased expression of genes involved in these processes. This study demonstrates that starvation responses and biofilm formation are coregulated by GTR1 and suggests that these responses are linked to compete with the microbiome for space and nutrients. Target of rapamycin complex 1 (TORC1) is an essential regulator of metabolism in eukaryotic cells and in the fungal pathogen Candida albicans regulates morphogenesis and nitrogen acquisition. Gtr1 encodes a highly conserved GTPase that in Saccharomyces cerevisiae regulates nitrogen sensing and TORC1 activation. Here, we characterize the role of C. albicans GTR1 in TORC1 activation and compare it with the previously characterized GTPase Rhb1. A homozygous gtr1/gtr1 mutant exhibited impaired TORC1-mediated phosphorylation of ribosomal protein S6 and increased susceptibility to rapamycin. Overexpression of GTR1 impaired nitrogen starvation-induced filamentous growth, MEP2 expression, and growth in bovine serum albumin as the sole nitrogen source. Both GTR1 and RHB1 were shown to regulate genes involved in ribosome biogenesis, amino acid biosynthesis, and expression of biofilm growth-induced genes. The rhb1/rhb1 mutant exhibited a different pattern of expression of Sko1-regulated genes and increased susceptibility to Congo red and calcofluor white. The homozygous gtr1/gtr1 mutant exhibited enhanced flocculation phenotypes and, similar to the rhb1/rhb1 mutant, exhibited enhanced biofilm formation on plastic surfaces. In summary, Gtr1 and Rhb1 link nutrient sensing and biofilm formation and this connectivity may have evolved to enhance the competitiveness of C. albicans in niches where there is intense competition with other microbes for space and nutrients. IMPORTANCE Candida albicans is the major fungal pathogen of humans and is responsible for a wide range of infections, including life-threatening systemic infections in susceptible hosts. Target of rapamycin complex 1 (TORC1) is an essential regulator of metabolism in this fungus, and components of this complex are under increased investigation as targets for new antifungal drugs. The present study characterized the role of GTR1, encoding a putative GTPase, in TORC1 activation. This study shows that GTR1 encodes a protein required for activation of TORC1 activity in response to amino acids and regulation of nitrogen starvation responses. GTR1 mutants show increased cell-cell adhesion and biofilm formation and increased expression of genes involved in these processes. This study demonstrates that starvation responses and biofilm formation are coregulated by GTR1 and suggests that these responses are linked to compete with the microbiome for space and nutrients.

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Direct evidence for a key role of protein kinase C in the development of vasospasm after subarachnoid hemorrhage

Journal of Neurosurgery ◽

10.3171/jns.1992.76.4.0635 ◽

1992 ◽

Vol 76 (4) ◽

pp. 635-639 ◽

Cited By ~ 68

Author(s):

Shigeru Nishizawa ◽

Nobukazu Nezu ◽

Kenichi Uemura

Keyword(s):

Signal Transduction ◽

Protein Kinase C ◽

Protein Kinase ◽

Direct Evidence ◽

Control Group ◽

Content Type ◽

Kinase C ◽

Protein Kinase C Activity ◽

Fine Print

✓ Vascular contraction is induced by the activation of intracellular contractile proteins mediated through signal transduction from the outside to the inside of cells. Protein kinase C plays a crucial role in this signal transduction. It is hypothesized that protein kinase C plays a causative part in the development of vasospasm after subarachnoid hemorrhage (SAH). To verify this directly, the authors measured protein kinase C activity in canine basilar arteries in an SAH model with (γ-32P)adenosine triphosphate and the data were compared to those in a control group. Protein kinase C is translocated to the membrane from the cytosol when it is activated, and the translocation is an index of the activation; thus, protein kinase C activity was measured both in the cytosol and in the membrane fractions. Protein kinase C activity in the membrane in the SAH model was remarkably enhanced compared to that in the control group. The percentage of membrane activity to the total was also significantly greater in the SAH vessels than in the control group, and the percentage of cytosol activity in the SAH group was decreased compared to that in the control arteries. The results indicate that protein kinase C in the vascular smooth muscle was translocated to the membrane from the cytosol and was activated when SAH occurred. It is concluded that this is direct evidence for a key role of protein kinase C in the development of vasospasm.

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Susceptible supply limits the role of climate in the COVID-19 pandemic

10.1101/2020.04.03.20052787 ◽

2020 ◽

Cited By ~ 6

Author(s):

Rachel E. Baker ◽

Wenchang Yang ◽

Gabriel A. Vecchi ◽

C. Jessica E. Metcalf ◽

Bryan T. Grenfell

Keyword(s):

Epidemic Model ◽

Preliminary Evidence ◽

Control Measures ◽

Effective Control ◽

High Susceptibility ◽

Emerging Pathogen ◽

Geographic Variations ◽

Summer Temperatures ◽

Endemic Infections

AbstractPreliminary evidence suggests that climate may modulate the transmission of SARS-CoV-2. Yet it remains unclear whether seasonal and geographic variations in climate can substantially alter the pandemic trajectory, given high susceptibility is a core driver. Here, we use a climate-dependent epidemic model to simulate the SARS-CoV-2 pandemic probing different scenarios of climate-dependence based on known coronavirus biology. We find that while variations in humidity may be important for endemic infections, during the pandemic stage of an emerging pathogen such as SARS-CoV-2 climate may drive only modest changes to pandemic size and duration. Our results suggest that, in the absence of effective control measures, significant cases in the coming months are likely to occur in more humid (warmer) climates, irrespective of the climate-dependence of transmission and that summer temperatures will not substantially limit pandemic growth.

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Pleiotropic Effects of the P5-Type ATPase SpfA on Stress Response Networks Contribute to Virulence in the Pathogenic Mold Aspergillus fumigatus

mBio ◽

10.1128/mbio.02735-21 ◽

2021 ◽

Author(s):

José P. Guirao-Abad ◽

Martin Weichert ◽

Ginés Luengo-Gil ◽

Sarah Sze Wah Wong ◽

Vishukumar Aimanianda ◽

...

Keyword(s):

Oxidative Stress ◽

Stress Resistance ◽

Secretory Pathway ◽

Pathogenic Fungi ◽

Antifungal Drugs ◽

Gene Encoding ◽

Content Type ◽

Downstream Target ◽

P Type ◽

Er Homeostasis

The fungal UPR is an adaptive signaling pathway in the ER that buffers fluctuations in ER stress but also serves as a virulence regulatory hub in species of pathogenic fungi that rely on secretory pathway homeostasis for pathogenicity. This study demonstrates that the gene encoding the ER-localized P5-type ATPase SpfA is a downstream target of the UPR in the pathogenic mold A. fumigatus and that it works together with a second ER-localized P-type ATPase, SrcA, to support ER homeostasis, oxidative stress resistance, susceptibility to antifungal drugs, and virulence of A. fumigatus .

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Cryptococcus neoformans Evades Pulmonary Immunity by Modulating Xylose Precursor Transport

Infection and Immunity ◽

10.1128/iai.00288-20 ◽

2020 ◽

Vol 88 (8) ◽

Author(s):

Lucy X. Li ◽

Camaron R. Hole ◽

Javier Rangel-Moreno ◽

Shabaana A. Khader ◽

Tamara L. Doering

Keyword(s):

Cryptococcus Neoformans ◽

Mutant Strain ◽

Fungal Pathogen ◽

Wild Type ◽

Content Type ◽

Helper Cell Type ◽

Lymphoid Structures ◽

Type Infection

ABSTRACT Cryptococcus neoformans is a fungal pathogen that kills almost 200,000 people each year and is distinguished by abundant and unique surface glycan structures that are rich in xylose. A mutant strain of C. neoformans that cannot transport xylose precursors into the secretory compartment is severely attenuated in virulence in mice yet surprisingly is not cleared. We found that this strain failed to induce the nonprotective T helper cell type 2 (Th2) responses characteristic of wild-type infection, instead promoting sustained interleukin 12p40 (IL-12p40) induction and increased IL-17A (IL-17) production. It also stimulated dendritic cells to release high levels of proinflammatory cytokines, a behavior we linked to xylose expression. We further discovered that inducible bronchus-associated lymphoid tissue (iBALT) forms in response to infection with either wild-type cryptococci or the mutant strain with reduced surface xylose; although iBALT formation is slowed in the latter case, the tissue is better organized. Finally, our temporal studies suggest that lymphoid structures in the lung restrict the spread of mutant fungi for at least 18 weeks after infection, which is in contrast to ineffective control of the pathogen after infection with wild-type cells. These studies demonstrate the role of xylose in modulation of host response to a fungal pathogen and show that cryptococcal infection triggers iBALT formation.

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Minocycline-EDTA-Ethanol Antimicrobial Catheter Lock Solution Is Highly Effective In Vitro for Eradication of Candida auris Biofilms

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02146-19 ◽

2020 ◽

Vol 64 (4) ◽

Author(s):

Ruth A. Reitzel ◽

Joel Rosenblatt ◽

Bahgat Z. Gerges ◽

Nylev Vargas-Cruz ◽

Issam I. Raad

Keyword(s):

Therapeutic Option ◽

Bloodstream Infections ◽

Central Line ◽

Emerging Pathogen ◽

Candida Auris ◽

Content Type ◽

Lock Solution ◽

Highly Effective ◽

Catheter Lock

ABSTRACT Candida auris is an emerging pathogen that can cause virulent central-line-associated bloodstream infections. Catheter salvage through the eradication of biofilms is a desirable therapeutic option. We compared taurolidine and minocycline-EDTA-ethanol (MEE) catheter lock solutions in vitro for the eradication of biofilms of 10 C. auris strains. MEE fully eradicated all C. auris biofilms, while taurolidine lock partially eradicated all of the C. auris biofilms. The superiority was significant for all C. auris strains tested (P = 0.002).

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Candida albicans Cek1 Mitogen-Activated Protein Kinase Signaling Enhances Fungicidal Activity of Salivary Histatin 5

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00214-15 ◽

2015 ◽

Vol 59 (6) ◽

pp. 3460-3468 ◽

Cited By ~ 7

Author(s):

Rui Li ◽

Sumant Puri ◽

Swetha Tati ◽

Paul J. Cullen ◽

Mira Edgerton

Keyword(s):

Candida Albicans ◽

Protein Kinase ◽

Antifungal Drugs ◽

Mitogen Activated Protein Kinase ◽

Fungal Cell ◽

Content Type ◽

Histatin 5 ◽

Mitogen Activated Protein ◽

Hyphal Formation ◽

Sensor Proteins

ABSTRACTCandida albicansis a major etiological organism for oropharyngeal candidiasis (OPC), while salivary histatin 5 (Hst 5) is a human fungicidal protein that protects the oral cavity from OPC.C. albicanssenses its environment by mitogen-activated protein kinase (MAPK) activation that can also modulate the activity of some antifungal drugs, including Hst 5. We found that phosphorylation of the MAPK Cek1, induced either byN-acetylglucosamine (GlcNAc) or serum, or its constitutive activation by deletion of its phosphatase Cpp1 elevated the susceptibility ofC. albicanscells to Hst 5. Cek1 phosphorylation but not hyphal formation was needed for increased Hst 5 sensitivity. Interference with the Cek1 pathway by deletion of its head sensor proteins, Msb2 and Sho1, or by addition of secreted aspartyl protease (SAP) cleavage inhibitors, such as pepstatin A, reduced Hst 5 susceptibility under Cek1-inducing conditions. Changes in fungal cell surface glycostructures also modulated Hst 5 sensitivity, and Cek1-inducing conditions resulted in a higher uptake rate of Hst 5. These results show that there is a consistent relationship between activation of Cek1 MAPK and increased Hst 5 susceptibility inC. albicans.

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