Sterol-response pathways mediate alkaline survival in diverse fungi

AbstractThe ability for cells to maintain homeostasis in the presence of extracellular stress is essential for their survival. Stress adaptations are especially important for microbial pathogens to respond to rapidly changing conditions, such as those encountered during the transition from the environment to the infected host. Many fungal pathogens have acquired the ability to quickly adapt to changes in extracellular pH to promote their survival in the various micro-environments encountered during a host infection. For example, the fungal-specific Rim/Pal alkaline response pathway has been well characterized in many fungal pathogens, including Cryptococcus neoformans. However, alternative mechanisms for sensing and responding to host pH have yet to be extensively studied. Recent observations from a genetic screen suggest that the C. neoformans sterol homeostasis pathway is required for growth at elevated pH. This work explores interactions among mechanisms of membrane homeostasis, alkaline pH tolerance, and Rim pathway activation. We find that the sterol homeostasis pathway is necessary for growth in an alkaline environment, and that an elevated pH is sufficient to induce Sre1 activation. This pH-mediated activation of the Sre1 transcription factor is linked to the biosynthesis of ergosterol, but is not dependent on Rim pathway signaling, suggesting that these two pathways are responding to alkaline pH independently. Furthermore, we discover that C. neoformans is more susceptible to membrane-targeting antifungals in alkaline conditions highlighting the impact of micro-environmental pH on the treatment of invasive fungal infections. Together, these findings further connect membrane integrity and composition with the fungal pH response and pathogenesis.

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Sterol-Response Pathways Mediate Alkaline Survival in Diverse Fungi

mBio ◽

10.1128/mbio.00719-20 ◽

2020 ◽

Vol 11 (3) ◽

Cited By ~ 1

Author(s):

Hannah E. Brown ◽

Calla L. Telzrow ◽

Joseph W. Saelens ◽

Larissa Fernandes ◽

J. Andrew Alspaugh

Keyword(s):

Cryptococcus Neoformans ◽

Fungal Pathogens ◽

Fungal Infections ◽

Membrane Integrity ◽

Extracellular Ph ◽

Alkaline Ph ◽

Content Type ◽

Alkaline Environment ◽

Ph Response ◽

The Impact

ABSTRACT The ability for cells to maintain homeostasis in the presence of extracellular stress is essential for their survival. Stress adaptations are especially important for microbial pathogens to respond to rapidly changing conditions, such as those encountered during the transition from the environment to the infected host. Many fungal pathogens have acquired the ability to quickly adapt to changes in extracellular pH to promote their survival in the various microenvironments encountered during a host infection. For example, the fungus-specific Rim/Pal alkaline response pathway has been well characterized in many fungal pathogens, including Cryptococcus neoformans. However, alternative mechanisms for sensing and responding to host pH have yet to be extensively studied. Recent observations from a genetic screen suggest that the C. neoformans sterol homeostasis pathway is required for growth at elevated pH. This work explores interactions among mechanisms of membrane homeostasis, alkaline pH tolerance, and Rim pathway activation. We find that the sterol homeostasis pathway is necessary for growth in an alkaline environment and that an elevated pH is sufficient to induce Sre1 activation. This pH-mediated activation of the Sre1 transcription factor is linked to the biosynthesis of ergosterol but is not dependent on Rim pathway signaling, suggesting that these two pathways are responding to alkaline pH independently. Furthermore, we discover that C. neoformans is more susceptible to membrane-targeting antifungals under alkaline conditions, highlighting the impact of microenvironmental pH on the treatment of invasive fungal infections. Together, these findings further connect membrane integrity and composition with the fungal pH response and pathogenesis. IMPORTANCE The work described here further elucidates how microorganisms sense and adapt to changes in their environment to establish infections in the human host. Specifically, we uncover a novel mechanism by which an opportunistic human fungal pathogen, Cryptococcus neoformans, responds to increases in extracellular pH in order to survive and thrive within the relatively alkaline environment of the human lung. This mechanism, which is intimately linked with fungal membrane sterol homeostasis, is independent of the previously well-studied alkaline response Rim pathway. Furthermore, this ergosterol-dependent alkaline pH response is present in Candida albicans, indicating that this mechanism spans diverse fungal species. These results are also relevant for novel antimicrobial drug development as we show that currently used ergosterol-targeting antifungals are more active in alkaline environments.

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Structures of Pathogenic Fungal FKBP12s Reveal Possible Self-Catalysis Function

mBio ◽

10.1128/mbio.00492-16 ◽

2016 ◽

Vol 7 (2) ◽

Cited By ~ 18

Author(s):

Nam K. Tonthat ◽

Praveen Rao Juvvadi ◽

Hengshan Zhang ◽

Soo Chan Lee ◽

Ron Venters ◽

...

Keyword(s):

Active Site ◽

Fungal Pathogens ◽

Active Sites ◽

Fungal Infections ◽

Cellular Protein ◽

Prolyl Isomerase ◽

Peptidyl Prolyl Isomerase ◽

Deep Insertion ◽

The Impact

ABSTRACT Invasive fungal infections remain difficult to treat and require novel targeting strategies. The 12-kDa FK506-binding protein (FKBP12) is a ubiquitously expressed peptidyl-prolyl isomerase with considerable homology between fungal pathogens and is thus a prime candidate for future targeting efforts to generate a panfungal strategy. Despite decades of research on FKBPs, their substrates and mechanisms of action remain unclear. Here we describe structural, biochemical, and in vivo analyses of FKBP12s from the pathogenic fungi Candida albicans , Candida glabrata , and Aspergillus fumigatus . Strikingly, multiple apo A. fumigatus and C. albicans FKBP12 crystal structures revealed a symmetric, intermolecular interaction involving the deep insertion of an active-site loop proline into the active-site pocket of an adjacent subunit. Such interactions have not been observed in previous FKBP structures. This finding indicates the possibility that this is a self-substrate interaction unique to the A. fumigatus and C. albicans fungal proteins that contain this central proline. Structures obtained with the proline in the cis and trans states provide more data in support of self-catalysis. Moreover, cysteine cross-linking experiments captured the interacting dimer, supporting the idea that it forms in solution. Finally, genetic studies exploring the impact of mutations altering the central proline and an adjacent residue provide evidence that any dimeric state formed in vivo , where FKBP12 concentrations are low, is transient. Taken together, these findings suggest a unique mechanism of self-substrate regulation by fungal FKBP12s, lending further novel understanding of this protein for future drug-targeting efforts. IMPORTANCE FKBP12 is a cis-trans peptidyl-prolyl isomerase that plays key roles in cellular protein homeostasis. FKBP12s also bind the immunosuppressive drug FK506 to inhibit the phosphatase calcineurin (CaN). CaN is required for virulence of A. fumigatus , C. albicans , C. glabrata , and other deadly fungal pathogens, marking FKBP12 and CaN as potential broad-spectrum drug targets. Here we describe structures of fungal FKBP12s. Multiple apo A. fumigatus and C. albicans FKBP12 structures reveal the insertion of a proline, conspicuously conserved in these proteins, into the active sites of adjacent molecules. This suggests that these proteins might serve as their own substrates. Cysteine disulfide trapping experiments provide support for this self-interaction and hence possible intermolecular catalysis by these enzymes.

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The Mechanisms of Mating in Pathogenic Fungi—A Plastic Trait

Genes ◽

10.3390/genes10100831 ◽

2019 ◽

Vol 10 (10) ◽

pp. 831

Author(s):

Jane Usher

Keyword(s):

Fungal Pathogens ◽

Crop Yields ◽

Fungal Infections ◽

Pathogenic Fungi ◽

Yeast Saccharomyces Cerevisiae ◽

Closely Related Species ◽

Sexual And Asexual Reproduction ◽

Target Dna ◽

High Degree ◽

The Impact

The impact of fungi on human and plant health is an ever-increasing issue. Recent studies have estimated that human fungal infections result in an excess of one million deaths per year and plant fungal infections resulting in the loss of crop yields worth approximately 200 million per annum. Sexual reproduction in these economically important fungi has evolved in response to the environmental stresses encountered by the pathogens as a method to target DNA damage. Meiosis is integral to this process, through increasing diversity through recombination. Mating and meiosis have been extensively studied in the model yeast Saccharomyces cerevisiae, highlighting that these mechanisms have diverged even between apparently closely related species. To further examine this, this review will inspect these mechanisms in emerging important fungal pathogens, such as Candida, Aspergillus, and Cryptococcus. It shows that both sexual and asexual reproduction in these fungi demonstrate a high degree of plasticity.

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Monoclonal Antibodies as Tools to Combat Fungal Infections

Journal of Fungi ◽

10.3390/jof6010022 ◽

2020 ◽

Vol 6 (1) ◽

pp. 22 ◽

Cited By ~ 2

Author(s):

Sebastian Ulrich ◽

Frank Ebel

Keyword(s):

Immune Response ◽

Monoclonal Antibodies ◽

Fungal Pathogens ◽

Viral Infections ◽

Fungal Infections ◽

Adaptive Immune Response ◽

Passive Immunization ◽

Microbial Pathogens ◽

Minor Importance ◽

Prophylactic Use

Antibodies represent an important element in the adaptive immune response and a major tool to eliminate microbial pathogens. For many bacterial and viral infections, efficient vaccines exist, but not for fungal pathogens. For a long time, antibodies have been assumed to be of minor importance for a successful clearance of fungal infections; however this perception has been challenged by a large number of studies over the last three decades. In this review, we focus on the potential therapeutic and prophylactic use of monoclonal antibodies. Since systemic mycoses normally occur in severely immunocompromised patients, a passive immunization using monoclonal antibodies is a promising approach to directly attack the fungal pathogen and/or to activate and strengthen the residual antifungal immune response in these patients.

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The Use of Interactions Between Microorganisms in Strawberry Cultivation (Fragaria x ananassa Duch.)

Frontiers in Plant Science ◽

10.3389/fpls.2021.780099 ◽

2021 ◽

Vol 12 ◽

Author(s):

Magdalena Drobek ◽

Justyna Cybulska ◽

Anna Gałązka ◽

Beata Feledyn-Szewczyk ◽

Anna Marzec-Grządziel ◽

...

Keyword(s):

Adverse Effects ◽

Fungal Pathogens ◽

Pathogenic Fungi ◽

Maximum Load ◽

Antagonistic Effect ◽

Solid Content ◽

Microbial Pathogens ◽

Total Phenolic ◽

Soluble Solid Content ◽

The Impact

As the market indicates a growing interest in organically grown fruit, there is a need for biostimulants to counter the adverse effects of pathogenic fungi and fungal-like-pathogens. Four microbial pathogens (Botrytis cinerea, Verticillium sp., Phytophthora sp., and Colletotrichum sp.) which are the most often causes of strawberry diseases were selected. Five kinds of biostimulants (C1, C2, C3, C4, and C5) containing bacterial consortia were developed to combat the pathogens. The antagonistic effect of selected microorganisms against strawberry pathogens was observed. The effectiveness of various beneficial bacteria in combating fungal pathogens of cv. Honeoye strawberries was compared and the impact of their activity on fruit quality was assessed. The most significant effect on the strawberry firmness was found for the C2 consortium, which provided the strawberries infected with the pathogens group (MIX: B. cinerea, Verticillium sp., Phytophthora sp., and Colletotrichum sp.) with a 140% increase in maximum load in a puncture test compared to the positive control (C0). Strawberries contaminated with Phytophthora sp. after the application of Consortium C4 (C4) showed the largest increase (127%) in soluble solid content (SSC) when compared to the C0. Fruit contaminated with Colletotrichum sp. and B. cinerea after the application of C2 and Consortium 5 (C5), respectively, had the highest levels of anthocyanins and total phenolic content, when compared to C0. The largest increase, which reached as high as 25%, in D-galacturonic acid content was observed for the group of pathogens after Consortium 1 (C1) application. The extraction of strawberry pectin allowed for the study of the rheological properties of pectin solutions; on this basis, strawberry pectin from the control (NC) was distinguished as it showed the highest viscosity (0.137–0.415 Pas). Taking into account the individual effects of bacteria on strawberry pathogenic fungi and fungal-like-pathogens, it is possible to reduce the adverse effects of fungal disease and to improve the properties of strawberries by selecting the appropriate bacterial consortium. Interactions between microorganisms are often complex and not fully understood, which suggests the need for further research in this direction.

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ATP13A2 Regulates Cellular α-Synuclein Multimerization, Membrane Association, and Externalization

International Journal of Molecular Sciences ◽

10.3390/ijms22052689 ◽

2021 ◽

Vol 22 (5) ◽

pp. 2689

Author(s):

Jianmin Si ◽

Chris Van den Haute ◽

Evy Lobbestael ◽

Shaun Martin ◽

Sarah van Veen ◽

...

Keyword(s):

Membrane Integrity ◽

Ubiquitin Proteasome System ◽

Regulatory Function ◽

Membrane Association ◽

Loss Of Function ◽

Atypical Form ◽

Polyamine Transport ◽

Independent Functions ◽

Ubiquitin Proteasome ◽

The Impact

ATP13A2, a late endo-/lysosomal polyamine transporter, is implicated in a variety of neurodegenerative diseases, including Parkinson’s disease and Kufor–Rakeb syndrome, an early-onset atypical form of parkinsonism. Loss-of-function mutations in ATP13A2 result in lysosomal deficiency as a consequence of impaired lysosomal export of the polyamines spermine/spermidine. Furthermore, accumulating evidence suggests the involvement of ATP13A2 in regulating the fate of α-synuclein, such as cytoplasmic accumulation and external release. However, no consensus has yet been reached on the mechanisms underlying these effects. Here, we aimed to gain more insight into how ATP13A2 is linked to α-synuclein biology in cell models with modified ATP13A2 activity. We found that loss of ATP13A2 impairs lysosomal membrane integrity and induces α-synuclein multimerization at the membrane, which is enhanced in conditions of oxidative stress or exposure to spermine. In contrast, overexpression of ATP13A2 wildtype (WT) had a protective effect on α-synuclein multimerization, which corresponded with reduced αsyn membrane association and stimulation of the ubiquitin-proteasome system. We also found that ATP13A2 promoted the secretion of α-synuclein through nanovesicles. Interestingly, the catalytically inactive ATP13A2 D508N mutant also affected polyubiquitination and externalization of α-synuclein multimers, suggesting a regulatory function independent of the ATPase and transport activity. In conclusion, our study demonstrates the impact of ATP13A2 on α-synuclein multimerization via polyamine transport dependent and independent functions.

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The Impact of Gelatin on the Pharmaceutical Characteristics of Fucoidan Microspheres with Posaconazole

Materials ◽

10.3390/ma14154087 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4087

Author(s):

Marta Szekalska ◽

Aleksandra Citkowska ◽

Magdalena Wróblewska ◽

Katarzyna Winnicka

Keyword(s):

Antifungal Activity ◽

Drug Release ◽

Spray Drying ◽

Fungal Infections ◽

Drug Loading ◽

High Surface ◽

Vaginal Fluid ◽

Sustained Drug Release ◽

Candida Spp ◽

The Impact

Fungal infections and invasive mycoses, despite the continuous medicine progress, are an important globally therapeutic problem. Multicompartment dosage formulations (e.g., microparticles) ensure a short drug diffusion way and high surface area of drug release, which as a consequence can provide improvement of therapeutic efficiency compared to the traditional drug dosage forms. As fucoidan is promising component with wide biological activity per se, the aim of this study was to prepare fucospheres (fucoidan microparticles) and fucoidan/gelatin microparticles with posaconazole using the one-step spray-drying technique. Pharmaceutical properties of designed fucospheres and the impact of the gelatin addition on their characteristics were evaluated. An important stage of this research was in vitro evaluation of antifungal activity of developed microparticles using different Candida species. It was observed that gelatin presence in microparticles significantly improved swelling capacity and mucoadhesiveness, and provided a sustained POS release. Furthermore, it was shown that gelatin addition enhanced antifungal activity of microparticles against tested Candida spp. strains. Microparticles formulation GF6, prepared by the spray drying of 20% fucoidan, 5% gelatin and 10% Posaconazole, were characterized by optimal mucoadhesive properties, high drug loading and the most sustained drug release (after 8 h 65.34 ± 4.10% and 33.81 ± 5.58% of posaconazole was dissolved in simulated vaginal fluid pH 4.2 or 0.1 M HCl pH 1.2, respectively).

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A Study of Catechin Photostability Using Photolytic Processing

Processes ◽

10.3390/pr9020293 ◽

2021 ◽

Vol 9 (2) ◽

pp. 293

Author(s):

Jeu-Ming P. Yuann ◽

Shwu-Yuan Lee ◽

Meei-Ju Yang ◽

Shiuh-Tsuen Huang ◽

Chien-Wei Cheng ◽

...

Keyword(s):

Ascorbic Acid ◽

Superoxide Anion ◽

Anion Radical ◽

Alkaline Solutions ◽

Light Illumination ◽

Drug Resistant ◽

Alkaline Ph ◽

Radical Species ◽

Alkaline Conditions ◽

Photolytic Reaction

Catechin exhibits numerous physiological characteristics. In this study, we determined the photosensitivity of catechin to various lights under alkaline conditions, and the mechanisms by which catechin generates free radical species and polymerizes via a photoreaction. In addition to this, the application of catechin photolysis was investigated. A solution of catechin is transparent, but turns yellowish under blue light illumination (BLI) in neutral or weak alkaline solutions. When catechin is subjected to BLI, a dimeric catechin (proanthocyanidin) and a superoxide anion radical (O2•−) are generated in a photolytic reaction. When ascorbic acid or gallic acid is added to catechin and the mixture is subjected to BLI at alkaline pH, fewer catechin dimers and less O2•− are produced, because both acids inhibit the photosensitive oxidation of catechin. When AlCl3 is added to catechin and the mixture is subjected to BLI at pH 8, a photolytic reaction is suppressed by AlCl3, and AlCl3 acts as a catalyst for the disconnection of proanthocyanidin during photolysis. Under alkaline conditions, catechin generates O2•− via photosensitive oxidation, which suppresses the growth of Acinetobacter baumannii (A. baumannii) by at least 4 logs, and deactivates its multi-drug-resistant strain. This study shows that catechin photolysis is a process of oxidation, and that it can be safely applied as a tool for environmental applications.

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Post-Translational Modifications Drive Success and Failure of Fungal–Host Interactions

Journal of Fungi ◽

10.3390/jof7020124 ◽

2021 ◽

Vol 7 (2) ◽

pp. 124

Author(s):

Charmaine Retanal ◽

Brianna Ball ◽

Jennifer Geddes-McAlister

Keyword(s):

Fungal Pathogens ◽

Fungal Infections ◽

Treatment Options ◽

Global Scale ◽

Host Cells ◽

Candida Spp ◽

Post Translational Modifications ◽

Fungal Host ◽

Resistant Species

Post-translational modifications (PTMs) change the structure and function of proteins and regulate a diverse array of biological processes. Fungal pathogens rely on PTMs to modulate protein production and activity during infection, manipulate the host response, and ultimately, promote fungal survival. Given the high mortality rates of fungal infections on a global scale, along with the emergence of antifungal-resistant species, identifying new treatment options is critical. In this review, we focus on the role of PTMs (e.g., phosphorylation, acetylation, ubiquitination, glycosylation, and methylation) among the highly prevalent and medically relevant fungal pathogens, Candida spp., Aspergillus spp., and Cryptococcus spp. We explore the role of PTMs in fungal stress response and host adaptation, the use of PTMs to manipulate host cells and the immune system upon fungal invasion, and the importance of PTMs in conferring antifungal resistance. We also provide a critical view on the current knowledgebase, pose questions key to our understanding of the intricate roles of PTMs within fungal pathogens, and provide research opportunities to uncover new therapeutic strategies.

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Plasma membrane integrity: implications for health and disease

BMC Biology ◽

10.1186/s12915-021-00972-y ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Dustin A. Ammendolia ◽

William M. Bement ◽

John H. Brumell

Keyword(s):

Plasma Membrane ◽

Membrane Damage ◽

Membrane Integrity ◽

Whole Body ◽

Plasma Membrane Integrity ◽

Plasma Membrane Damage ◽

Cellular Environment ◽

Health And Disease ◽

Repair Pathways ◽

The Impact

AbstractPlasma membrane integrity is essential for cellular homeostasis. In vivo, cells experience plasma membrane damage from a multitude of stressors in the extra- and intra-cellular environment. To avoid lethal consequences, cells are equipped with repair pathways to restore membrane integrity. Here, we assess plasma membrane damage and repair from a whole-body perspective. We highlight the role of tissue-specific stressors in health and disease and examine membrane repair pathways across diverse cell types. Furthermore, we outline the impact of genetic and environmental factors on plasma membrane integrity and how these contribute to disease pathogenesis in different tissues.

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