Towards understanding the novel adhesin function of Candida albicans phosphoglycerate mutase at the pathogen cell surface: some structural analysis of the interactions with human host extracellular matrix proteins

Although many atypical proteinaceous cell wall components that belong to a group of multitasking, "moonlighting" proteins, have been repeatedly identified in numerous pathogenic microorganisms, their novel extracellular functions and secretion mechanisms remain largely unrecognized. In Candida albicans, one of the most common fungal pathogens in humans, phosphoglycerate mutase (Gpm1) - a cytoplasmic enzyme involved in the glycolysis pathway - has been shown to occur on the cell surface and has been identified as a potentially important virulence factor. In this study, we demonstrated tight binding of C. albicans Gpm1 to the candidal cell surface, thus suggesting that the readsorption of soluble Gpm1 from the external environment could be a likely mechanism leading to the presence of this moonlighting protein on the pathogen surface. Several putative Gpm1-binding receptors on the yeast surface were identified. The affinities of Gpm1 to human vitronectin (VTR) and fibronectin (FN) were characterized with surface plasmon resonance measurements, and the dissociation constants of the complexes formed were determined to be in the order of 10–8 M. The internal Gpm1 sequence motifs, directly interacting with VTR (aa 116-158) and FN (aa 138-175) were mapped using chemical crosslinking and mass spectrometry. Synthetic peptides with matching sequences significantly inhibited formation of the Gpm1-VTR and Gpm1-FN complexes. A molecular model of the Gpm1-VTR complex was developed. These results provide the first structural insights into the adhesin function of candidal surface-exposed Gpm1.

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Structural Insights into the Interactions of Candidal Enolase with Human Vitronectin, Fibronectin and Plasminogen

International Journal of Molecular Sciences ◽

10.3390/ijms21217843 ◽

2020 ◽

Vol 21 (21) ◽

pp. 7843 ◽

Cited By ~ 1

Author(s):

Dorota Satala ◽

Grzegorz Satala ◽

Justyna Karkowska-Kuleta ◽

Michal Bukowski ◽

Anna Kluza ◽

...

Keyword(s):

Protein Interactions ◽

Dissociation Constants ◽

Tight Binding ◽

Protein Protein Interactions ◽

Glycolysis Pathway ◽

Human Proteins ◽

Activity Center ◽

Moonlighting Functions ◽

Structural Insights ◽

Internal Motif

Significant amounts of enolase—a cytosolic enzyme involved in the glycolysis pathway—are exposed on the cell surface of Candida yeast. It has been hypothesized that this exposed enolase form contributes to infection-related phenomena such as fungal adhesion to human tissues, and the activation of fibrinolysis and extracellular matrix degradation. The aim of the present study was to characterize, in structural terms, the protein-protein interactions underlying these moonlighting functions of enolase. The tight binding of human vitronectin, fibronectin and plasminogen by purified C. albicans and C. tropicalis enolases was quantitatively analyzed by surface plasmon resonance measurements, and the dissociation constants of the formed complexes were determined to be in the 10−7–10−8 M range. In contrast, the binding of human proteins by the S.cerevisiae enzyme was much weaker. The chemical cross-linking method was used to map the sites on enolase molecules that come into direct contact with human proteins. An internal motif 235DKAGYKGKVGIAMDVASSEFYKDGK259 in C. albicans enolase was suggested to contribute to the binding of all three human proteins tested. Models for these interactions were developed and revealed the sites on the enolase molecule that bind human proteins, extensively overlap for these ligands, and are well-separated from the catalytic activity center.

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Function of Candida albicans Adhesin Hwp1 in Biofilm Formation

Eukaryotic Cell ◽

10.1128/ec.00194-06 ◽

2006 ◽

Vol 5 (10) ◽

pp. 1604-1610 ◽

Cited By ~ 212

Author(s):

Clarissa J. Nobile ◽

Jeniel E. Nett ◽

David R. Andes ◽

Aaron P. Mitchell

Keyword(s):

Candida Albicans ◽

Cell Surface ◽

Biofilm Formation ◽

Tight Binding ◽

Surface Protein ◽

Venous Catheter ◽

Cell Surface Protein ◽

Additional Support

ABSTRACT Hwp1 is a well-characterized Candida albicans cell surface protein, expressed only on hyphae, that mediates tight binding to oral epithelial cells. Prior studies indicate that HWP1 expression is dependent upon Bcr1, a key regulator of biofilm formation. Here we test the hypothesis that Hwp1 is required for biofilm formation. In an in vitro model, the hwp1/hwp1 mutant produces a thin biofilm that lacks much of the hyphal mass found in the hwp1/HWP1 reconstituted strain. In a biofilm cell retention assay, we find that the hwp1/hwp1 mutant is defective in retention of nonadherent bcr1/bcr1 mutant cells. In an in vivo rat venous catheter model, the hwp1/hwp1 mutant has a severe biofilm defect, yielding only yeast microcolonies in the catheter lumen. These properties of the hwp1/hwp1 mutant are consistent with its role as a hypha-specific adhesin and indicate that it is required for normal biofilm formation. Overexpression of HWP1 in a bcr1/bcr1 mutant background improves adherence in the in vivo catheter model. This finding provides additional support for the model that Hwp1 is critical for biofilm adhesion. Hwp1 is the first cell surface protein known to be required for C. albicans biofilm formation in vivo and is thus an excellent therapeutic target.

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Scaffold Diversity for Enhanced Activity of Glycosylated Inhibitors of Fungal Adhesion

10.26434/chemrxiv.12295514.v1 ◽

2020 ◽

Author(s):

Tobias Krämer ◽

kevin kavanagh ◽

Trinidad Velasco-Torrijos ◽

Harlei Martin ◽

Tara Somers ◽

...

Keyword(s):

Candida Albicans ◽

Cell Surface ◽

Conformational Analysis ◽

Fungal Pathogens ◽

Yeast Cells ◽

Hospital Acquired Infections ◽

Fungal Adhesion ◽

Buccal Epithelial Cells ◽

Scaffold Diversity ◽

Hospital Acquired

<div>Candida albicans is one of the most prevalent fungal pathogens involved in</div><div>hospital acquired infections. It uses adhesins to bind to glycans at the cell surface of epithelial</div><div>cells and thus initiate infection. These interactions can be blocked by synthetic carbohydrates</div><div>(such as compound 1) that mimics the structure of cell surface glycans. Herein we report the</div><div>synthesis of a new series of divalent galactosides featuring aromatic (benzene, squaramides)</div><div>and aliphatic (norbornenes) central scaffolds, with the latter being the first examples of their</div><div>kind as small molecule anti-adhesion glycoconjugates. The evaluation of these compounds as</div><div>inhibitors of adhesion of C. albicans o exfoliated buccal epithelial cells (BECs) revealed that</div><div>galactosides 1 and 6, built on an aromatic core, were the most efficient inhibitors of adhesion,</div><div>displacing up to 36% and 48%, respectively, of yeast cells already attached to the BECs at</div><div>0.138 μM. Conformational analysis of compound 1 identified the preference for a folded </div><div>presentation in the lowest energy conformers. Remarkably, cis-endo-norbornene 21 performed</div><div>comparably to the benzene-core derivatives, highlighting the potential of norbornenes as a new</div><div>class of aliphatic scaffolds for the synthesis of anti-adhesion compounds.</div>

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Epitope Shaving Promotes Fungal Immune Evasion

mBio ◽

10.1128/mbio.00984-20 ◽

2020 ◽

Vol 11 (4) ◽

Cited By ~ 4

Author(s):

Delma S. Childers ◽

Gabriela Mol Avelar ◽

Judith M. Bain ◽

Arnab Pradhan ◽

Daniel E. Larcombe ◽

...

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Cell Surface ◽

Immune Evasion ◽

Fungal Pathogen ◽

Fungal Pathogens ◽

Specific Cell ◽

Immune Recognition ◽

Content Type ◽

Evasion Strategy

ABSTRACT The cell wall provides a major physical interface between fungal pathogens and their mammalian host. This extracellular armor is critical for fungal cell homeostasis and survival. Fungus-specific cell wall moieties, such as β-1,3-glucan, are recognized as pathogen-associated molecular patterns (PAMPs) that activate immune-mediated clearance mechanisms. We have reported that the opportunistic human fungal pathogen Candida albicans masks β-1,3-glucan following exposure to lactate, hypoxia, or iron depletion. However, the precise mechanism(s) by which C. albicans masks β-1,3-glucan has remained obscure. Here, we identify a secreted exoglucanase, Xog1, that is induced in response to lactate or hypoxia. Xog1 functions downstream of the lactate-induced β-glucan “masking” pathway to promote β-1,3-glucan “shaving.” Inactivation of XOG1 blocks most but not all β-1,3-glucan masking in response to lactate, suggesting that other activities contribute to this phenomenon. Nevertheless, XOG1 deletion attenuates the lactate-induced reductions in phagocytosis and cytokine stimulation normally observed for wild-type cells. We also demonstrate that the pharmacological inhibition of exoglucanases undermines β-glucan shaving, enhances the immune visibility of the fungus, and attenuates its virulence. Our study establishes a new mechanism underlying environmentally induced PAMP remodeling that can be manipulated pharmacologically to influence immune recognition and infection outcomes. IMPORTANCE The immune system plays a critical role in protecting us against potentially fatal fungal infections. However, some fungal pathogens have evolved evasion strategies that reduce the efficacy of our immune defenses. Previously, we reported that the fungal pathogen Candida albicans exploits specific host-derived signals (such as lactate and hypoxia) to trigger an immune evasion strategy that involves reducing the exposure of β-glucan at its cell surface. Here, we show that this phenomenon is mediated by the induction of a major secreted exoglucanase (Xog1) by the fungus in response to these host signals. Inactivating XOG1-mediated “shaving” of cell surface-exposed β-glucan enhances immune responses against the fungus. Furthermore, inhibiting exoglucanase activity pharmacologically attenuates C. albicans virulence. In addition to revealing the mechanism underlying a key immune evasion strategy in a major fungal pathogen of humans, our work highlights the potential therapeutic value of drugs that block fungal immune evasion.

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Scaffold Diversity for Enhanced Activity of Glycosylated Inhibitors of Fungal Adhesion

10.26434/chemrxiv.12295514 ◽

2020 ◽

Author(s):

Tobias Krämer ◽

kevin kavanagh ◽

Trinidad Velasco-Torrijos ◽

Harlei Martin ◽

Tara Somers ◽

...

Keyword(s):

Candida Albicans ◽

Cell Surface ◽

Conformational Analysis ◽

Fungal Pathogens ◽

Yeast Cells ◽

Hospital Acquired Infections ◽

Fungal Adhesion ◽

Buccal Epithelial Cells ◽

Scaffold Diversity ◽

Hospital Acquired

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Characterization of the interactions between human high-molecular-mass kininogen and cell wall proteins of pathogenic yeasts, Candida tropicalis

Acta Biochimica Polonica ◽

10.18388/abp.2016_1353 ◽

2016 ◽

Vol 63 (3) ◽

Cited By ~ 5

Author(s):

Justyna Karkowska-Kuleta ◽

Dorota Zajac ◽

Grazyna Bras ◽

Oliwia Bochenska ◽

Karolina Seweryn ◽

...

Keyword(s):

Cell Wall ◽

Cell Surface ◽

Molecular Mass ◽

Candida Tropicalis ◽

Dissociation Constants ◽

High Molecular Mass ◽

Biologically Active ◽

Phosphoglycerate Mutase ◽

Cell Wall Proteins ◽

Effective Prevention

Candida tropicalis is one of the most frequent causes of serious, disseminated candidiasis in human patients infected by non-albicans Candida species, but still relatively little is known about its virulence mechanisms. In our current study, the interactions between the cell surface of this species and a multifunctional human protein—high-molecular-mass kininogen (HK), an important component of the plasma contact system involved in the development of the inflammatory state—were characterized at the molecular level. The quick release of biologically active kinins from candidal cell wall-adsorbed HK was presented and the HK-binding ability was assigned to several cell wall-associated proteins. Predicted hyphally regulated cell wall protein (Hyr) and some housekeeping enzymes exposed at the cell surface (known as “moonlighting proteins”) were found to be the major HK binders. Accordingly, after purification of selected proteins, the dissociation constants of the complexes of HK with Hyr, enolase and phosphoglycerate mutase were determined using surface plasmon resonance measurements, giving the values of 2.20 x 10-7 M, 1.42 x 10-7 M and 5.81 x 10-7 M, respectively. Therefore, in this work, for the first time, the interactions between C. tropicalis cell wall proteins and HK were characterized in molecular terms. Our findings may be useful for designing more effective prevention and treatment approaches against infections caused by this dangerous fungal pathogen.

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Characterization of HWP2 a putative GPI anchored candida albicans cell surface protein. (c2007)

10.26756/th.2007.17 ◽

2007 ◽

Author(s):

Peter Jose Hayek

Keyword(s):

Candida Albicans ◽

Cell Surface ◽

Surface Protein ◽

Cell Surface Protein

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Faculty Opinions recommendation of Comparative phenotypic analysis of the major fungal pathogens Candida parapsilosis and Candida albicans.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.718880167.793502175 ◽

2014 ◽

Author(s):

Leah Cowen ◽

Michelle Leach

Keyword(s):

Candida Albicans ◽

Fungal Pathogens ◽

Candida Parapsilosis ◽

Phenotypic Analysis

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Biosynthesis of selenium nanoparticles by Aspergillus flavus and Candida albicans and comparison of their effects with antifungal drugs

10.21203/rs.3.rs-194546/v1 ◽

2021 ◽

Author(s):

Mahdi Hosseini Bafghi ◽

Razieh Nazari ◽

Majid Darroudi ◽

Mohsen Zargar ◽

Hossein Zarrinfar

Keyword(s):

Candida Albicans ◽

Aspergillus Flavus ◽

Fungal Pathogens ◽

Chemical Properties ◽

Cost Effective ◽

Antifungal Drugs ◽

Selenium Nanoparticles ◽

Fungal Strains ◽

Vis Spectroscopy ◽

Physical And Chemical

Abstract Biosynthesis of nanoparticles can stand as a replacement for the available chemical and physical methods by offering new procedures as green syntheses that have proved to be simple, biocompatible, safe, and cost-effective. Considering how nanoparticles with a size of 1 to 100 nanometers contain unique physical and chemical properties, recent reports are indicative of observing the antifungal qualities of selenium nanoparticles (Se-NPs). Recently, the observance of antifungal resistance towards different species of these fungi is often reported. Therefore, due to the antifungal effects of biological nanoparticles, this study aimed to investigate the exertion of these nanoparticles and evaluate their effects on the growth of fungal pathogens. Se-NPs were biosynthesized by the application of wet reduction method, which included specific concentrations of Aspergillus flavus and Candida albicans. The presence of nanoparticles was confirmed by methods such as UV-Vis spectroscopy, FT-IR analysis, and FESEM electron microscope that involved FESEM and EDAX diagram. The fungal strains were cultured in sabouraud dextrose agar medium to perform the sensitivity test based on the minimum inhibitory concentration (MIC) method in duplicate. The utilization of Se-NPs at concentrations of 1 µg/ ml and below resulted in zero growth of fungal agents. However, their growth was inhibited by antifungal drugs at concentrations of 2 µg/ ml and higher. Based on the obtained results, biological nanoparticles produced by fungal agents at different concentrations exhibited favorable inhibitory effects on the growth of fungal strains.

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