The GPI-modified proteins Pga59 and Pga62 of Candida albicans are required for cell wall integrity

The fungal cell wall is essential in maintaining cellular integrity and plays key roles in the interplay between fungal pathogens and their hosts. The PGA59 and PGA62 genes encode two short and related glycosylphosphatidylinositol-anchored cell wall proteins and their expression has been previously shown to be strongly upregulated when the human pathogen Candida albicans grows as biofilms. Using GFP fusion proteins, we have shown that Pga59 and Pga62 are cell-wall-located, N- and O-glycosylated proteins. The characterization of C. albicans pga59Δ/pga59Δ, pga62Δ/pga62Δ and pga59Δ/pga59Δ pga62Δ/pga62Δ mutants suggested a minor role of these two proteins in hyphal morphogenesis and that they are not critical to biofilm formation. Importantly, the sensitivity to different cell-wall-perturbing agents was altered in these mutants. In particular, simultaneous inactivation of PGA59 and PGA62 resulted in high sensitivity to Calcofluor white, Congo red and nikkomicin Z and in resistance to caspofungin. Furthermore, cell wall composition and observation by transmission electron microscopy indicated an altered cell wall structure in the mutant strains. Collectively, these data suggest that the cell wall proteins Pga59 and Pga62 contribute to cell wall stability and structure.

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Impact of Fungal MAPK Pathway Targets on the Cell Wall

Journal of Fungi ◽

10.3390/jof4030093 ◽

2018 ◽

Vol 4 (3) ◽

pp. 93 ◽

Cited By ~ 8

Author(s):

Jacky Chow ◽

Marysa Notaro ◽

Aditi Prabhakar ◽

Stephen Free ◽

Paul Cullen

Keyword(s):

Cell Wall ◽

Signaling Pathways ◽

Mapk Pathway ◽

Normal Growth ◽

Mitogen Activated Protein Kinase ◽

Cell Wall Proteins ◽

Calcofluor White ◽

Fungal Cell ◽

Mass Spec ◽

Mitogen Activated Protein

The fungal cell wall is an extracellular organelle that provides structure and protection to cells. The cell wall also influences the interactions of cells with each other and surfaces. The cell wall can be reorganized in response to changing environmental conditions and different types of stress. Signaling pathways control the remodeling of the cell wall through target proteins that are in many cases not well defined. The Mitogen Activated Protein Kinase pathway that controls filamentous growth in yeast (fMAPK) was required for normal growth in media containing the cell wall perturbing agent Calcofluor White (CFW). A mass spectrometry (MASS-SPEC) approach and analysis of expression profiling data identified cell wall proteins and modifying enzymes whose levels were influenced by the fMAPK pathway. These include Flo11p, Flo10p, Tip1p, Pry2p and the mannosyltransferase, Och1p. Cells lacking Flo11p or Och1p were sensitive to CFW. The identification of cell wall proteins controlled by a MAPK pathway may provide insights into how signaling pathways regulate the cell wall.

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Analysis of the 3H8 antigen of Candida albicans reveals new aspects of the organization of fungal cell wall proteins

FEMS Yeast Research ◽

10.1093/femsyr/foy035 ◽

2018 ◽

Vol 18 (4) ◽

Author(s):

Rafael Sentandreu ◽

Antonio Caminero ◽

Itzel Rentería ◽

Claudia León-Ramirez ◽

Luis González-de-la-Vara ◽

...

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Fungal Cell Wall ◽

Cell Wall Proteins ◽

Fungal Cell

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Disarming Fungal Pathogens:Bacillus safensisInhibits Virulence Factor Production and Biofilm Formation byCryptococcus neoformansandCandida albicans

mBio ◽

10.1128/mbio.01537-17 ◽

2017 ◽

Vol 8 (5) ◽

Cited By ~ 24

Author(s):

François L. Mayer ◽

James W. Kronstad

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Cryptococcus Neoformans ◽

Virulence Factors ◽

Virulence Factor ◽

Biofilm Formation ◽

Fungal Pathogens ◽

Soil Bacterium ◽

Fungal Cell ◽

Virulence Factor Production

ABSTRACTBacteria interact with each other in nature and often compete for limited nutrient and space resources. However, it is largely unknown whether and how bacteria also interact with human fungal pathogens naturally found in the environment. Here, we identified a soil bacterium,Bacillus safensis, which potently blocked several keyCryptococcus neoformansvirulence factors, including formation of the antioxidant pigment melanin and production of the antiphagocytic polysaccharide capsule. The bacterium also inhibitedde novocryptococcal biofilm formation but had only modest inhibitory effects on already formed biofilms or planktonic cell growth. The inhibition of fungal melanization was dependent on direct cell contact and live bacteria.B. safensisalso had anti-virulence factor activity against another major human-associated fungal pathogen,Candida albicans. Specifically, dual-species interaction studies revealed that the bacterium strongly inhibitedC. albicansfilamentation and biofilm formation. In particular,B. safensisphysically attached to and degraded candidal filaments. Through genetic and phenotypic analyses, we demonstrated that bacterial chitinase activity against fungal cell wall chitin is a factor contributing to the antipathogen effect ofB. safensis.IMPORTANCEPathogenic fungi are estimated to contribute to as many human deaths as tuberculosis or malaria. Two of the most common fungal pathogens,Cryptococcus neoformansandCandida albicans, account for up to 1.4 million infections per year with very high mortality rates. Few antifungal drugs are available for treatment, and development of novel therapies is complicated by the need for pathogen-specific targets. Therefore, there is an urgent need to identify novel drug targets and new drugs. Pathogens use virulence factors during infection, and it has recently been proposed that targeting these factors instead of the pathogen itself may represent a new approach to develop antimicrobials. Here, we identified a soil bacterium that specifically blocked virulence factor production and biofilm formation byC. neoformansandC. albicans. We demonstrate that the bacterial antipathogen mechanism is based in part on targeting the fungal cell wall, a structure not found in human cells.

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A molecular vision of fungal cell wall organization by functional genomics and solid-state NMR

Nature Communications ◽

10.1038/s41467-021-26749-z ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Arnab Chakraborty ◽

Liyanage D. Fernando ◽

Wenxia Fang ◽

Malitha C. Dickwella Widanage ◽

Pingzhen Wei ◽

...

Keyword(s):

Cell Wall ◽

Solid State ◽

Solid State Nmr ◽

Fungal Pathogens ◽

Spatial Organization ◽

Structural Response ◽

Antifungal Drugs ◽

Wall Structure ◽

Fungal Cell ◽

Intact Cells

AbstractVast efforts have been devoted to the development of antifungal drugs targeting the cell wall, but the supramolecular architecture of this carbohydrate-rich composite remains insufficiently understood. Here we compare the cell wall structure of a fungal pathogen Aspergillus fumigatus and four mutants depleted of major structural polysaccharides. High-resolution solid-state NMR spectroscopy of intact cells reveals a rigid core formed by chitin, β-1,3-glucan, and α-1,3-glucan, with galactosaminogalactan and galactomannan present in the mobile phase. Gene deletion reshuffles the composition and spatial organization of polysaccharides, with significant changes in their dynamics and water accessibility. The distribution of α-1,3-glucan in chemically isolated and dynamically distinct domains supports its functional diversity. Identification of valines in the alkali-insoluble carbohydrate core suggests a putative function in stabilizing macromolecular complexes. We propose a revised model of cell wall architecture which will improve our understanding of the structural response of fungal pathogens to stresses.

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Proteolytic Cleavage of Covalently Linked Cell Wall Proteins by Candida albicans Sap9 and Sap10

Eukaryotic Cell ◽

10.1128/ec.00210-10 ◽

2010 ◽

Vol 10 (1) ◽

pp. 98-109 ◽

Cited By ~ 57

Author(s):

Lydia Schild ◽

Antje Heyken ◽

Piet W. J. de Groot ◽

Ekkehard Hiller ◽

Marlen Mock ◽

...

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Cell Surface ◽

Pathogenic Fungus ◽

Proteolytic Cleavage ◽

Cell Wall Proteins ◽

Ph Optimum ◽

Fungal Cell ◽

Content Type ◽

Covalently Linked

ABSTRACT The cell wall of the human-pathogenic fungus Candida albicans is a robust but also dynamic structure which mediates adaptation to changing environmental conditions during infection. Sap9 and Sap10 are cell surface-associated proteases which function in C. albicans cell wall integrity and interaction with human epithelial cells and neutrophils. In this study, we have analyzed the enzymatic properties of Sap9 and Sap10 and investigated whether these proteases cleave proteins on the fungal cell surface. We show that Sap9 and Sap10, in contrast to other aspartic proteases, exhibit a near-neutral pH optimum of proteolytic activity and prefer the processing of peptides containing basic or dibasic residues. However, both proteases also cleaved at nonbasic sites, and not all tested peptides with dibasic residues were processed. By digesting isolated cell walls with Sap9 or Sap10, we identified the covalently linked cell wall proteins (CWPs) Cht2, Ywp1, Als2, Rhd3, Rbt5, Ecm33, and Pga4 as in vitro protease substrates. Proteolytic cleavage of the chitinase Cht2 and the glucan-cross-linking protein Pir1 by Sap9 was verified using hemagglutinin (HA) epitope-tagged versions of both proteins. Deletion of the SAP9 and SAP10 genes resulted in a reduction of cell-associated chitinase activity similar to that upon deletion of CHT2 , suggesting a direct influence of Sap9 and Sap10 on Cht2 function. In contrast, cell surface changes elicited by SAP9 and SAP10 deletion had no major impact on the phagocytosis and killing of C. albicans by human macrophages. We propose that Sap9 and Sap10 influence distinct cell wall functions by proteolytic cleavage of covalently linked cell wall proteins.

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The Candida albicans Sur7 Protein Is Needed for Proper Synthesis of the Fibrillar Component of the Cell Wall That Confers Strength

Eukaryotic Cell ◽

10.1128/ec.00167-10 ◽

2010 ◽

Vol 10 (1) ◽

pp. 72-80 ◽

Cited By ~ 30

Author(s):

Hong X. Wang ◽

Lois M. Douglas ◽

Vishukumar Aimanianda ◽

Jean-Paul Latgé ◽

James B. Konopka

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Plasma Membrane ◽

Wall Structure ◽

Cell Wall Synthesis ◽

Calcofluor White ◽

Content Type ◽

Membrane Compartment ◽

Fibrillar Component ◽

And Function

ABSTRACTTheCandida albicansplasma membrane plays important roles in interfacing with the environment, morphogenesis, and cell wall synthesis. The role of the Sur7 protein in cell wall structure and function was analyzed, since previous studies showed that this plasma membrane protein is needed to prevent abnormal intracellular growth of the cell wall. Sur7 localizes to stable patches in the plasma membrane, known as MCC (membrane compartment occupied by Can1), that are associated with eisosome proteins. Thesur7Δ mutant cells displayed increased sensitivity to factors that exacerbate cell wall defects, such as detergent (SDS) and the chitin-binding agents calcofluor white and Congo red. Thesur7Δ cells were also slightly more sensitive to inhibitors that block the synthesis of cell wall chitin (nikkomycin Z) and β-1,3-glucan (caspofungin). In contrast, Fmp45, a paralog of Sur7 that also localizes to punctate plasma membrane patches, did not have a detectable role in cell wall synthesis. Chemical analysis of cell wall composition demonstrated thatsur7Δ cells contain decreased levels of β-glucan, a glucose polymer that confers rigidity on the cell wall. Consistent with this,sur7Δ cells were more sensitive to lysis, which could be partially rescued by increasing the osmolarity of the medium. Interestingly, Sur7 is present in static patches, whereas β-1,3-glucan synthase is mobile in the plasma membrane and is often associated with actin patches. Thus, Sur7 may influence β-glucan synthesis indirectly, perhaps by altering the functions of the cell signaling components that localize to the MCC and eisosome domains.

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Fungal Cell Wall Proteins and Signaling Pathways Form a Cytoprotective Network to Combat Stresses

Journal of Fungi ◽

10.3390/jof7090739 ◽

2021 ◽

Vol 7 (9) ◽

pp. 739

Author(s):

Chibuike Ibe ◽

Carol A. Munro

Keyword(s):

Cell Wall ◽

Fungal Pathogens ◽

Surface Coat ◽

Cell Wall Proteins ◽

Fungal Cell ◽

Protein Coat ◽

Cell Wall Remodeling ◽

Wall Construction ◽

And Function ◽

Physical And Chemical

Candida species are part of the normal flora of humans, but once the immune system of the host is impaired and they escape from commensal niches, they shift from commensal to pathogen causing candidiasis. Candida albicans remains the primary cause of candidiasis, accounting for about 60% of the global candidiasis burden. The cell wall of C. albicans and related fungal pathogens forms the interface with the host, gives fungal cells their shape, and also provides protection against stresses. The cell wall is a dynamic organelle with great adaptive flexibility that allows remodeling, morphogenesis, and changes in its components in response to the environment. It is mainly composed of the inner polysaccharide rich layer (chitin, and β-glucan) and the outer protein coat (mannoproteins). The highly glycosylated protein coat mediates interactions between C. albicans cells and their environment, including reprograming of wall architecture in response to several conditions, such as carbon source, pH, high temperature, and morphogenesis. The mannoproteins are also associated with C. albicans adherence, drug resistance, and virulence. Vitally, the mannoproteins contribute to cell wall construction and especially cell wall remodeling when cells encounter physical and chemical stresses. This review describes the interconnected cell wall integrity (CWI) and stress-activated pathways (e.g., Hog1, Cek1, and Mkc1 mediated pathways) that regulates cell wall remodeling and the expression of some of the mannoproteins in C. albicans and other species. The mannoproteins of the surface coat is of great importance to pathogen survival, growth, and virulence, thus understanding their structure and function as well as regulatory mechanisms can pave the way for better management of candidiasis.

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Candida albicans Iff11, a Secreted Protein Required for Cell Wall Structure and Virulence

Infection and Immunity ◽

10.1128/iai.00102-07 ◽

2007 ◽

Vol 75 (6) ◽

pp. 2922-2928 ◽

Cited By ~ 24

Author(s):

Steven Bates ◽

José M. de la Rosa ◽

Donna M. MacCallum ◽

Alistair J. P. Brown ◽

Neil A. R. Gow ◽

...

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Gene Family ◽

Systemic Infection ◽

Wall Structure ◽

Cell Wall Proteins ◽

Null Mutant ◽

Virulence Analysis ◽

Cell Wall Organization ◽

Related Proteins

ABSTRACT The Candida albicans cell wall is the immediate point of contact with the host and is implicated in the host-fungal interaction and virulence. To date, a number of cell wall proteins have been identified and associated with virulence. Analysis of the C. albicans genome has identified the IFF gene family as encoding the largest family of cell wall-related proteins. This family is also conserved in a range of other Candida species. Iff11 differs from other family members in lacking a GPI anchor, and we have demonstrated it to be O glycosylated and secreted in C. albicans. A null mutant lacking IFF11 was hypersensitive to cell wall-damaging agents, suggesting a role in cell wall organization. In a murine model of systemic infection the null mutant was highly attenuated in virulence, and survival-standardized infections suggest it is required to establish an infection. This work provides the first evidence of the importance of this gene family in the host-fungal interaction and virulence.

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The newly synthesized thiazole derivatives as potential antifungal compounds against Candida albicans

Applied Microbiology and Biotechnology ◽

10.1007/s00253-021-11477-7 ◽

2021 ◽

Author(s):

Anna Biernasiuk ◽

Anna Berecka-Rycerz ◽

Anna Gumieniczek ◽

Maria Malm ◽

Krzysztof Z. Łączkowski ◽

...

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Antifungal Activity ◽

Cell Membrane ◽

Mode Of Action ◽

Thiazole Derivatives ◽

Fungal Cell ◽

Erythrocyte Lysis ◽

Low Cytotoxicity ◽

High Antifungal Activity

Abstract Recently, the occurrence of candidiasis has increased dramatically, especially in immunocompromised patients. Additionally, their treatment is often ineffective due to the resistance of yeasts to antimycotics. Therefore, there is a need to search for new antifungals. A series of nine newly synthesized thiazole derivatives containing the cyclopropane system, showing promising activity against Candida spp., has been further investigated. We decided to verify their antifungal activity towards clinical Candida albicans isolated from the oral cavity of patients with hematological malignancies and investigate the mode of action on fungal cell, the effect of combination with the selected antimycotics, toxicity to erythrocytes, and lipophilicity. These studies were performed by the broth microdilution method, test with sorbitol and ergosterol, checkerboard technique, erythrocyte lysis assay, and reversed phase thin-layer chromatography, respectively. All derivatives showed very strong activity (similar and even higher than nystatin) against all C. albicans isolates with minimal inhibitory concentration (MIC) = 0.008–7.81 µg/mL Their mechanism of action may be related to action within the fungal cell wall structure and/or within the cell membrane. The interactions between the derivatives and the selected antimycotics (nystatin, chlorhexidine, and thymol) showed additive effect only in the case of combination some of them and thymol. The erythrocyte lysis assay confirmed the low cytotoxicity of these compounds as compared to nystatin. The high lipophilicity of the derivatives was related with their high antifungal activity. The present studies confirm that the studied thiazole derivatives containing the cyclopropane system appear to be a very promising group of compounds in treatment of infections caused by C. albicans. However, this requires further studies in vivo. Key points • The newly thiazoles showed high antifungal activity and some of them — additive effect in combination with thymol. • Their mode of action may be related with the influence on the structure of the fungal cell wall and/or the cell membrane. • The low cytotoxicity against erythrocytes and high lipophilicity of these derivatives are their additional good properties. Graphical abstract

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