The Regulatory Function of the Molecular Chaperone Hsp90 in the Cell Wall Integrity of Pathogenic Fungi

2018 ◽  
Vol 16 (1) ◽  
pp. 44-53
Author(s):  
Marina Campos Rocha ◽  
Camilla Alves Santos ◽  
Iran Malavazi
Keyword(s):  
Cell Wall ◽  
Antifungal Therapy ◽  
Molecular Chaperone ◽  
Regulatory Protein ◽  
Pathogenic Fungi ◽  
Antifungal Drugs ◽  
Cell Wall Integrity ◽  
Regulatory Function ◽  
Loss Of Function ◽  
Hsp90 Inhibition

Different signaling cascades including the Cell Wall Integrity (CWI), the High Osmolarity Glycerol (HOG) and the Ca2+/calcineurin pathways control the cell wall biosynthesis and remodeling in fungi. Pathogenic fungi, such as Aspergillus fumigatus and Candida albicans, greatly rely on these signaling circuits to cope with different sources of stress, including the cell wall stress evoked by antifungal drugs and the host’s response during infection. Hsp90 has been proposed as an important regulatory protein and an attractive target for antifungal therapy since it stabilizes major effector proteins that act in the CWI, HOG and Ca2+/calcineurin pathways. Data from the human pathogen C. albicans have provided solid evidence that loss-of-function of Hsp90 impairs the evolution of resistance to azoles and echinocandin drugs. In A. fumigatus, Hsp90 is also required for cell wall integrity maintenance, reinforcing a coordinated function of the CWI pathway and this essential molecular chaperone. In this review, we focus on the current information about how Hsp90 impacts the aforementioned signaling pathways and consequently the homeostasis and maintenance of the cell wall, highlighting this cellular event as a key mechanism underlying antifungal therapy based on Hsp90 inhibition.

scholarly journals Hyperactive TORC1 sensitizes yeast cells to endoplasmic reticulum stress by compromising cell wall integrity

2019 ◽  
Author(s):  
Khadija Ahmed ◽  
David E. Carter ◽  
Patrick Lajoie
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Endoplasmic Reticulum Stress ◽  
Er Stress ◽  
Fungal Infections ◽  
Pathogenic Fungi ◽  
Stress Sensitivity ◽  
Antifungal Drugs ◽  
Cell Wall Integrity ◽  
Yeast Cells

ABSTRACTThe disruption of protein folding homeostasis in the endoplasmic reticulum (ER) results in an accumulation of toxic misfolded proteins and activates a network of signaling events collectively known as the unfolded protein response (UPR). While UPR activation upon ER stress is well characterized, how other signaling pathways integrate into the ER proteostasis network is unclear. Here, we sought to investigate how the target of rapamycin complex 1 (TORC1) signaling cascade acts in parallel with the UPR to regulate ER stress sensitivity. Using S. cerevisiae, we found that TORC1 signaling is attenuated during ER stress and constitutive activation of TORC1 increases sensitivity to ER stressors such as tunicamycin and inositol deprivation. This phenotype is independent of the UPR. Transcriptome analysis revealed that TORC1 hyperactivation results in cell wall remodelling. Conversely, hyperactive TORC1 sensitizes cells to cell wall stressors, including the antifungal caspofungin. Elucidating the crosstalk between the UPR, cell wall integrity, and TORC1 signaling may uncover new paradigms through which the response to protein misfolding is regulated, and thus have crucial implications for the development of novel therapeutics against pathogenic fungal infections.IMPORTANCEThe prevalence of pathogenic fungal infections, coupled with the emergence of new fungal pathogens, has brought these diseases to the forefront of global health problems. While antifungal treatments have advanced over the last decade, patient outcomes have not substantially improved. These shortcomings are largely attributed to the evolutionary similarity between fungi and humans, which limits the scope of drug development. As such, there is a pressing need to understand the unique cellular mechanisms that govern fungal viability. Given that Saccharomyces cerevisiae is evolutionarily related to a number of pathogenic fungi, and in particular to the Candida species, most genes from S. cerevisiae are highly conserved in pathogenic fungal strains. Here we show that hyperactivation of TORC1 signaling sensitizes S. cerevisiae cells to both endoplasmic reticulum stress and cell wall stressors by compromising cell wall integrity. Therefore, targeting TORC1 signaling and endoplasmic reticulum stress pathways may be useful in developing novel targets for antifungal drugs.

scholarly journals Up against the Wall: Is Yeast Cell Wall Integrity Ensured by Mechanosensing in Plasma Membrane Microdomains?

2014 ◽  
Vol 81 (3) ◽  
pp. 806-811 ◽  
Author(s):  
Christian Kock ◽  
Yves F. Dufrêne ◽  
Jürgen J. Heinisch
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Yeast Cell ◽  
Antifungal Drugs ◽  
Cell Wall Integrity ◽  
Yeast Cell Wall ◽  
Membrane Microdomains ◽  
Wall Structure ◽  
Fungal Cell ◽  
Membrane Spanning

ABSTRACTYeast cell wall integrity (CWI) signaling serves as a model of the regulation of fungal cell wall synthesis and provides the basis for the development of antifungal drugs. A set of five membrane-spanning sensors (Wsc1 to Wsc3, Mid2, and Mtl1) detect cell surface stress and commence the signaling pathway upon perturbations of either the cell wall structure or the plasma membrane. We here summarize the latest advances in the structure/function relationship primarily of the Wsc1 sensor and critically review the evidence that it acts as a mechanosensor. The relevance and physiological significance of the information obtained for the function of the other CWI sensors, as well as expected future developments, are discussed.

scholarly journals Curcumin Targets Cell Wall Integrity via Calcineurin-Mediated Signaling in Candida albicans

2013 ◽  
Vol 58 (1) ◽  
pp. 167-175 ◽  
Author(s):  
Awanish Kumar ◽  
Sanjiveeni Dhamgaye ◽  
Indresh Kumar Maurya ◽  
Ashutosh Singh ◽  
Monika Sharma ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Critical Role ◽  
Pathogenic Fungi ◽  
Cell Wall Integrity ◽  
Ergosterol Biosynthesis ◽  
Ros Generation ◽  
Calcofluor White ◽  
Content Type ◽  
Cell Wall Damage

ABSTRACTCurcumin (CUR) shows antifungal activity against a range of pathogenic fungi, includingCandida albicans. The reported mechanisms of action of CUR include reactive oxygen species (ROS) generation, defects in the ergosterol biosynthesis pathway, decrease in hyphal development, and modulation of multidrug efflux pumps. Reportedly, each of these pathways is independently linked to the cell wall machinery inC. albicans, but surprisingly, CUR has not been previously implicated in cell wall damage. In the present study, we performed transcriptional profiling to identify the yet-unidentified targets of CUR inC. albicans. We found that, among 348 CUR-affected genes, 51 were upregulated and 297 were downregulated. Interestingly, most of the cell wall integrity pathway genes were downregulated. The possibility of the cell wall playing a critical role in the mechanism of CUR required further validation; therefore, we performed specific experiments to establish if there was any link between the two. The fractional inhibitory concentration index values of 0.24 to 0.37 show that CUR interacts synergistically with cell wall-perturbing (CWP) agents (caspofungin, calcofluor white, Congo red, and SDS). Furthermore, we could observe cell wall damage and membrane permeabilization by CUR alone, as well as synergistically with CWP agents. We also found hypersusceptibility in calcineurin and mitogen-activated protein (MAP) kinase pathway mutants against CUR, which confirmed that CUR also targets cell wall biosynthesis inC. albicans. Together, these data provide strong evidence that CUR disrupts cell wall integrity inC. albicans. This new information on the mechanistic action of CUR could be employed in improving treatment strategies and in combinatorial drug therapy.

Cell wall integrity signalling in human pathogenic fungi

2016 ◽  
Vol 18 (9) ◽  
pp. 1228-1238 ◽  
Author(s):  
Karl Dichtl ◽  
Sweta Samantaray ◽  
Johannes Wagener
Keyword(s):  
Cell Wall ◽  
Pathogenic Fungi ◽  
Cell Wall Integrity

scholarly journals Deletion of YLR358C Contributes to Reduce Cell Wall Integrity in Saccharomyces Cerevisiae

2022 ◽  
Author(s):  
Yu Zhang ◽  
Mengyan Li ◽  
Hanying Wang ◽  
Juqing Deng ◽  
Jianxing Liu ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Sodium Dodecyl ◽  
Wall Stress ◽  
Pathogenic Fungi ◽  
Cell Wall Integrity ◽  
Calcofluor White ◽  
Fungal Cell ◽  
Reading Frame ◽  
Stress Signals

Abstract The mechanism of fungal cell wall synthesis and assembly is still unclear. Saccharomyces cerevisiae (S. cerevisiae) and pathogenic fungi are conserved in cell wall construction and response to stress signals, and often respond to cell wall stress through activated cell wall integrity (CWI) pathways. Whether the YLR358C open reading frame regulates CWI remains unclear. This study found that the growth of S. cerevisiae with YLR358C knockout was significantly inhibited on the medium containing different concentrations of cell wall interfering agents Calcofluor White (CFW), Congo Red (CR) and sodium dodecyl sulfate (SDS). CFW staining showed that the cell wall chitin was down-regulated, and transmission electron microscopy also observed a decrease in cell wall thickness. Transcriptome sequencing and analysis showed that YLR358C gene may be involved in the regulation of CWI signaling pathway. It was found by qRT-PCR that WSC3, SWI4 and HSP12 were differentially expressed after YLR358C was knocked out. The above results suggest that YLR358C may regulate the integrity of the yeast cell walls and has some potential for application in fermentation.

scholarly journals Loss-of-function ROX1 mutations suppress the fluconazole susceptibility of upc2AΔ mutation in Candida glabrata, implicating additional positive regulators of ergosterol biosynthesis

2021 ◽  
Author(s):  
Tomye L Ollinger ◽  
Bao Vu ◽  
Daniel Murante ◽  
Josie Parker ◽  
Lucia Simonicova ◽  
...  
Keyword(s):  
Candida Glabrata ◽  
Genetic Interaction ◽  
Pathogenic Fungi ◽  
Antifungal Drugs ◽  
Negative Regulator ◽  
Ergosterol Biosynthesis ◽  
Loss Of Function ◽  
Candida Spp ◽  
Ergosterol Biosynthesis Inhibitors ◽  
Positive Regulators

Two of the major classes of antifungal drugs in clinical use target ergosterol biosynthesis. Despite its importance, our understanding of the transcriptional regulation of ergosterol biosynthesis genes in pathogenic fungi is essentially limited to the role of hypoxia and sterol-stress induced transcription factors such as Upc2 and Upc2A as well as homologs of Sterol Response Element Binding (SREB) factors. To identify additional regulators of ergosterol biosynthesis in Candida glabrata, an important human fungal pathogen with reduced susceptibility to ergosterol biosynthesis inhibitors relative to other Candida spp., we used a serial passaging strategy to isolate suppressors of the fluconazole hypersusceptibility of a upc2AΔ deletion mutant. This led to the identification of loss of function mutants in two genes: ROX1, the homolog of a hypoxia gene transcriptional suppressor in Saccharomyces cerevisiae, and CST6, a transcription factor that is involved in the regulation of carbon dioxide response in C. glabrata. Here, we describe a detailed analysis of the genetic interaction of ROX1 and UPC2A. In the presence of fluconazole, loss of Rox1 function restores ERG11 expression to the upc2AΔ mutant and inhibits the expression of ERG3 and ERG6, leading to increased levels or ergosterol and decreased levels of the toxic sterol, 14α methyl-ergosta-8,24(28)-dien-3β, 6α-diol, relative to upc2AΔ. Our observations establish that Rox1 is a negative regulator of ERG gene biosynthesis and indicate that a least one additional positive transcriptional regulator of ERG gene biosynthesis must be present in C. glabrata.

scholarly journals Global Screening of Genomic and Transcriptomic Factors Associated with Phenotype Differences between Multidrug-Resistant and -Susceptible Candida haemulonii Strains

mSystems ◽  
2019 ◽  
Vol 4 (6) ◽  
Author(s):  
Hao Zhang ◽  
Yifei Niu ◽  
Jingwen Tan ◽  
Weixia Liu ◽  
Ming-an Sun ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Cell Wall ◽  
Multidrug Resistance ◽  
Multidrug Resistant ◽  
Antifungal Drugs ◽  
Cell Wall Integrity ◽  
Close Relative ◽  
Content Type ◽  
Candida Haemulonii ◽  
Resistant Strains

ABSTRACT Candida haemulonii, a close relative of Candida auris, is an emerging pathogen which frequently shows multidrug resistance especially to triazoles, the most used antifungal drugs. The mechanisms of drug resistance in C. haemulonii, however, are largely unknown. Here, we sequenced and annotated the genomes of two reference strains from the C. haemulonii complex, compared the phenotypes, genomes, and transcriptomes of a triazole-susceptible and two triazole-resistant C. haemulonii strains, and identified triazole susceptibility, morphology, fitness, and the major genetic and gene expression differences between the strains. A multidrug efflux gene, CDR1, was recurrently found to be upregulated for expression in triazole-resistant strains. Blocking the activity of Cdr1 increased the susceptibility to triazoles strikingly. Comparative transcriptome analysis also demonstrated impaired cell wall integrity, filamentous growth, and iron homeostasis in triazole-resistant strains. Finally, we also identified a zinc-binding MHR family transcription regulator gene that mutated in triazole-resistant strains spontaneously, contributing to the changes of morphology and, possibly, cell wall integrity between the strains. The study provided important clues for future studies exploring the mechanisms of multidrug resistance and related phenotypic differences of C. haemulonii strains. IMPORTANCE A comprehensive, multi-omic survey was performed to disclose the genetic backgrounds and differences between multidrug-resistant and -susceptible C. haemulonii strains. Genes were identified with mutations or significant expression differences in multidrug-resistant compared to multidrug-susceptible strains, which were mainly involved in multidrug resistance, stress fitness, and morphology. The Cdr1-encoding gene, C. haemulonii 2486 (CH_2486), was expressed at a significantly increased level in multidrug-resistant strains. Functional inhibition experiments further implicated potential roles of CH_2486 in drug resistance. A gene spontaneously mutated in resistant strains, CH_4347, was experimentally validated to influence the morphology of spores, possibly by controlling cell wall integrity.

Overview of the Interplay Between Cell Wall Integrity Signaling Pathways and Membrane Lipid Biosynthesis in Fungi: Perspectives forAspergillus fumigatus

2020 ◽  
Vol 21 (3) ◽  
pp. 265-283 ◽  
Author(s):  
João Henrique T.M. Fabri ◽  
Marina C. Rocha ◽  
Iran Malavazi
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Signaling Pathways ◽  
Fungal Infections ◽  
Invasive Pulmonary Aspergillosis ◽  
Pathogenic Fungi ◽  
Cell Wall Integrity ◽  
Immune Recognition ◽  
Fungal Cell ◽  
Low Efficiency

:The cell wall (CW) and plasma membrane are fundamental structures that define cell shape and support different cellular functions. In pathogenic fungi, such as Aspegillus fumigatus, they not only play structural roles but are also important for virulence and immune recognition. Both the CW and the plasma membrane remain as attractive drug targets to treat fungal infections, such as the Invasive Pulmonary Aspergillosis (IPA), a disease associated with high morbimortality in immunocompromised individuals. The low efficiency of echinocandins that target the fungal CW biosynthesis, the occurrence of environmental isolates resistant to azoles such as voriconazole and the known drawbacks associated with amphotericin toxicity foster the urgent need for fungal-specific drugable targets and/or more efficient combinatorial therapeutic strategies. Reverse genetic approaches in fungi unveil that perturbations of the CW also render cells with increased susceptibility to membrane disrupting agents and vice-versa. However, how the fungal cells simultaneously cope with perturbation in CW polysaccharides and cell membrane proteins to allow morphogenesis is scarcely known. Here, we focus on current information on how the main signaling pathways that maintain fungal cell wall integrity, such as the Cell Wall Integrity and the High Osmolarity Glycerol pathways, in different species often cross-talk to regulate the synthesis of molecules that comprise the plasma membrane, especially sphingolipids, ergosterol and phospholipids to promote functioning of both structures concomitantly and thus, cell viability. We propose that the conclusions drawn from other organisms are the foundations to point out experimental lines that can be endeavored in A. fumigatus.

scholarly journals Cell wall integrity is compromised under temperature stress in Schizosaccharomyces pombe expressing a valproic acid-sensitive vas4 mutant

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sen Qiao ◽  
Xiaofang Luo ◽  
Hui Wang ◽  
Yue Fang ◽  
Lili Zhang
Keyword(s):  
Valproic Acid ◽  
Cell Wall ◽  
Temperature Stress ◽  
Histone Deacetylases ◽  
Target Genes ◽  
Trichostatin A ◽  
Anticonvulsant Drug ◽  
Cell Wall Integrity ◽  
Loss Of Function ◽  
Copii Vesicles

AbstractValproic acid (VPA) is widely used as a eutherapeutic and safe anticonvulsant drug, but the mechanism is not well elucidated. Histone deacetylases (HDACs) were first identified as direct targets of VPA. Many loss-of function mutants in S. pombe have been shown to be VPA sensitive but not sensitive to other HDAC inhibitors, such as sodium butyrate or trichostatin A (TSA). This difference suggests that there are multiple VPA target genes. In the current study, we isolated a VPA-sensitive (vas) mutant, vas4-1, and cloned the VPA target gene vas4+/vrg4+ by performing complementation experiments. The vas4+/vrg4+ gene encodes a putative Golgi GDP-mannose transporter, Vrg4, which is highly homologous with ScVrg4p. Physiological experiments indicated that SpVrg4p is involved in maintaining cell wall integrity (CWI) under high- or low-temperature stress. The results of a coimmunoprecipitation assay suggested that SpVrg4p may be transferred from the ER to the Golgi through SpGot1p loaded COPII vesicles, and both single and double mutations (S263C and A271V) in SpVrg4p compromised this transfer. Our results suggested that CWI in S. pombe is compromised under temperature stress by the VPA-sensitive vas4 mutant.

scholarly journals Defects in Protein Glycosylation Cause SHO1-Dependent Activation of a STE12 Signaling Pathway in Yeast

Genetics ◽  
2000 ◽  
Vol 155 (3) ◽  
pp. 1005-1018 ◽  
Author(s):  
Paul J Cullen ◽  
Janet Schultz ◽  
Joe Horecka ◽  
Brian J Stevenson ◽  
Yoshifumi Jigami ◽  
...  
Keyword(s):  
Cell Wall ◽  
Genetic Selection ◽  
Protein Glycosylation ◽  
Cell Wall Integrity ◽  
Growth Defect ◽  
Loss Of Function ◽  
Pheromone Response ◽  
Pheromone Response Pathway ◽  
Pathway Activation ◽  
Synthetic Growth

Abstract In haploid Saccharomyces cerevisiae, mating occurs by activation of the pheromone response pathway. A genetic selection for mutants that activate this pathway uncovered a class of mutants defective in cell wall integrity. Partial loss-of-function alleles of PGI1, PMI40, PSA1, DPM1, ALG1, MNN10, SPT14, and OCH1, genes required for mannose utilization and protein glycosylation, activated a pheromone-response-pathway-dependent reporter (FUS1) in cells lacking a basal signal (ste4). Pathway activation was suppressed by the addition of mannose to hexose isomerase mutants pgi1-101 and pmi40-101, which bypassed the requirement for mannose biosynthesis in these mutants. Pathway activation was also suppressed in dpm1-101 mutants by plasmids that contained RER2 or PSA1, which produce the substrates for Dpm1. Activation of FUS1 transcription in the mannose utilization/protein glycosylation mutants required some but not all proteins from three different signaling pathways: the pheromone response, invasive growth, and HOG pathways. We specifically suggest that a Sho1 → Ste20/Ste50 → Ste11 → Ste7 → Kss1 → Ste12 pathway is responsible for activation of FUS1 transcription in these mutants. Because loss of pheromone response pathway components leads to a synthetic growth defect in mannose utilization/protein glycosylation mutants, we suggest that the Sho1 → Ste12 pathway contributes to maintenance of cell wall integrity in vegetative cells.

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