Characterization and biological activities of polysaccharides extracted from the filamentous fungal cell wall: an updated literature review

Filamentous fungi are eukaryotic organisms with several industrial and pharmaceutical applications. Polysaccharides are the principal components of cell walls from Fungi and other organisms like diatoms, and have been reported in the industrial and medical fields as products with a huge number of different biological activities and applications. The objectives of this narrative review were to assess the characterization methods and and biological activities of polysaccharides extracted from the filamentous fungal cell wall. Glucans, chitin and galactomannans are the most common polysaccharide often found in the cell walls of fungi. These polysaccharides can contain different glycosidic linkage either an α or β-configuration and at various positions, such as (1-3,1-4, 1-6), as well as several molecular sizes. This leads to an almost limitless diversity in their structure and biological activity. There are many methods for polysaccharides characterization, among them; the methods commonly used involve Infrared Spectrometry (FT-IR), Nuclear Magnetic Resonance Spectroscopy (MRS), and gas chromatography-mass spectrometry (CG-MS). Typically, cell wall polysaccharides from filamentous fungi have been shown to possess complex, important and multifaceted biological activities including mainly antioxidant, anti-inflammatory, immunomodulatory, antinociceptive, antitumor and hypoglycemic activities. Due to the large number of filamentous fungi genus and species capable of producing useful polysaccharides, perform scientific researches, and produce novel scientific knowledge and information are particularly interesting in order to identify polysaccharides with potential biological activity and that can be used for medicinal purposes.

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Interactions of proteins with other wall components: a pivotal step in fungal cell wall construction

Canadian Journal of Botany ◽

10.1139/b95-273 ◽

1995 ◽

Vol 73 (S1) ◽

pp. 384-387 ◽

Cited By ~ 3

Author(s):

R. Sentandreu ◽

M. Sentandreu ◽

M. V. Elorza ◽

M. Iranzo ◽

S. Mormeneo

Keyword(s):

Cell Wall ◽

Protein Interactions ◽

Cell Walls ◽

Noncovalent Interactions ◽

Fungal Cell Wall ◽

Fungal Cell ◽

Covalent Bonds ◽

Viscoelastic Composite ◽

Wall Construction ◽

Wall Components

Following synthesis of its individual components, the cell wall of Candida albicans is assembled extracellularly in two steps. First, a viscoelastic composite is formed by noncovalent interactions between mannoproteins and other wall components. Second, the initial network is consolidated by formation of covalent cross-linkages among the wall polymers. In both processes, specific proteins may regulate the final yeast or mycelial morphology. These proteins might carry out part of what could be called a morphogenetic code. Experimental results have shown that some mannoproteins form supramolecular complexes. They are secreted independently, but released together from cell walls by hydrolases. In C. albicans cell walls a transglutaminase activity has been detected that could be responsible for the formation of covalent bonds between structural proteins. Key words: fungal cell wall, construction, morphogenesis, protein interactions, noncovalent linkages, covalent linkages.

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Unconventional Constituents and Shared Molecular Architecture of the Melanized Cell Wall of C. neoformans and Spore Wall of S. cerevisiae

Journal of Fungi ◽

10.3390/jof6040329 ◽

2020 ◽

Vol 6 (4) ◽

pp. 329

Author(s):

Christine Chrissian ◽

Coney Pei-Chen Lin ◽

Emma Camacho ◽

Arturo Casadevall ◽

Aaron M. Neiman ◽

...

Keyword(s):

Cell Wall ◽

Cell Walls ◽

Building Blocks ◽

Cell Types ◽

Resistant Cell ◽

Spore Wall ◽

Fungal Species ◽

Resonance Spectroscopy ◽

Molecular Architecture ◽

Fungal Cell

The fungal cell wall serves as the interface between the cell and the environment. Fungal cell walls are composed largely of polysaccharides, primarily glucans and chitin, though in many fungi stress-resistant cell types elaborate additional cell wall structures. Here, we use solid-state nuclear magnetic resonance spectroscopy to compare the architecture of cell wall fractions isolated from Saccharomyces cerevisiae spores and Cryptococcus neoformans melanized cells. The specialized cell walls of these two divergent fungi are highly similar in composition. Both use chitosan, the deacetylated derivative of chitin, as a scaffold on which a polyaromatic polymer, dityrosine and melanin, respectively, is assembled. Additionally, we demonstrate that a previously identified but uncharacterized component of the S. cerevisiae spore wall is composed of triglycerides, which are also present in the C. neoformans melanized cell wall. Moreover, we identify a tyrosine-derived constituent in the C. neoformans wall that, although it is not dityrosine, is a non-pigment constituent of the cell wall. The similar composition of the walls of these two phylogenetically distant species suggests that triglycerides, polyaromatics, and chitosan are basic building blocks used to assemble highly stress-resistant cell walls and the use of these constituents may be broadly conserved in other fungal species.

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Structure and Biological Activity of Neopeptins A, B and C, Inhibitors of Fungal Cell Wall Glycan Synthesis

Agricultural and Biological Chemistry ◽

10.1080/00021369.1986.10867376 ◽

1986 ◽

Vol 50 (2) ◽

pp. 357-365 ◽

Cited By ~ 1

Author(s):

Makoto Ubukata ◽

Masakasu Uramoto ◽

Jun Uzawa ◽

Kiyoshi Isono

Keyword(s):

Cell Wall ◽

Biological Activity ◽

Fungal Cell Wall ◽

Fungal Cell

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Yeast and fungal cell-wall polysaccharides can self-assemblein vitrointo an ultrastructure resemblingin vivoyeast cell walls

Microscopy ◽

10.1093/jmicro/dfs076 ◽

2012 ◽

Vol 62 (3) ◽

pp. 327-339 ◽

Cited By ~ 2

Author(s):

Marie Kopecká

Keyword(s):

Cell Wall ◽

Cell Walls ◽

Fungal Cell Wall ◽

Cell Wall Polysaccharides ◽

Fungal Cell

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An Assessment of Infrared Spectra as Indicators of Fungal Cell Wall Composition

Australian Journal of Biological Sciences ◽

10.1071/bi9700345 ◽

1970 ◽

Vol 23 (2) ◽

pp. 345 ◽

Cited By ~ 54

Author(s):

A JMichell ◽

G Sourfield

Keyword(s):

Cell Wall ◽

Infrared Spectroscopy ◽

Infrared Spectra ◽

Cell Walls ◽

Cell Wall Composition ◽

Fungal Cell Wall ◽

Fungal Cell ◽

Chemical Treatments ◽

Wall Components ◽

Fungal Cell Walls

Infrared spectroscopy is assessed as a technique for identifying polymers derived from fungal cell walls, both as isolated materials and in mixtures with one another. The technique is then applied to a study of the composition of fungal cell walls and the conclusion reached that infrared spectra provide a rapid and valuable indication of the major components of such walls. They can also be used to follow the effect of chemical treatments designed to separate major wall components.

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Mannan detecting C-type lectin receptor probes recognise immune epitopes with diverse chemical, spatial and phylogenetic heterogeneity in fungal cell walls

10.1101/677104 ◽

2019 ◽

Author(s):

Ingrida Vendele ◽

Janet A. Willment ◽

Lisete M. Silva ◽

Angelina S. Palma ◽

Wengang Chai ◽

...

Keyword(s):

Cell Wall ◽

Immune Responses ◽

Cell Walls ◽

Fungal Pathogens ◽

Fungal Species ◽

Fungal Cell Wall ◽

Immune Recognition ◽

Cell Surfaces ◽

Fungal Cell ◽

Wall Components

AbstractDuring the course of fungal infection, pathogen recognition by the innate immune system is critical to initiate efficient protective immune responses. The primary event that triggers immune responses is the binding of Pattern Recognition Receptors (PRRs), which are expressed at the surface of host immune cells, to Pathogen-Associated Molecular Patterns (PAMPs) located predominantly in the fungal cell wall. Most fungi have mannosylated PAMPs in their cell walls and these are recognized by a range of C-type lectin receptors (CTLs). However, the precise spatial distribution of the ligands that induce immune responses within the cell walls of fungi are not well defined. We used recombinant IgG Fc-CTLs fusions of three murine mannan detecting CTLs, including dectin-2, the mannose receptor (MR) carbohydrate recognition domains (CRDs) 4-7 (CRD4-7), and human DC-SIGN (hDC-SIGN) and the β-1,3 glucan-binding lectin dectin-1 to map PRR ligands in the fungal cell wall. We show that epitopes of mannan-specific CTL receptors can be clustered or diffuse, superficial or buried in the inner cell wall. We demonstrate that PRR ligands do not correlate well with phylogenetic relationships between fungi, and that Fc-lectin binding discriminated between mannosides expressed on different cell morphologies of the same fungus. We also demonstrate CTL epitope differentiation during different phases of the growth cycle ofCandida albicansand that MR and DC-SIGN labelled outer chainN-mannans whilst dectin-2 labelled coreN-mannans displayed deeper in the cell wall. These immune receptor maps of fungal walls therefore reveal remarkable spatial, temporal and chemical diversity, indicating that the triggering of immune recognition events originates from multiple physical origins at the fungal cell surface.Author SummaryInvasive fungal infections remain an important health problem in immunocompromised patients. Immune recognition of fungal pathogens involves binding of specific cell wall components by pathogen recognition receptors (PRRs) and subsequent activation of immune defences. Some cell wall components are conserved among fungal species while other components are species-specific and phenotypically diverse. The fungal cell wall is dynamic and capable of changing its composition and organization when adapting to different growth niches and environmental stresses. Differences in the composition of the cell wall lead to differential immune recognition by the host. Understanding how changes in the cell wall composition affect recognition by PRRs is likely to be of major diagnostic and clinical relevance. Here we address this fundamental question using four soluble immune receptor-probes which recognize mannans and β-glucan in the cell wall. We use this novel methodology to demonstrate that mannan epitopes are differentially distributed in the inner and outer layers of fungal cell wall in a clustered or diffuse manner. Immune reactivity of fungal cell surfaces did not correlate with relatedness of different fungal species, and mannan-detecting receptor-probes discriminated between cell surface mannans generated by the same fungus growing under different conditions. These studies demonstrate that mannan-epitopes on fungal cell surfaces are differentially distributed within and between the cell walls of fungal pathogens.

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Two KTR Mannosyltransferases Are Responsible for the Biosynthesis of Cell Wall Mannans and Control Polarized Growth inAspergillus fumigatus

mBio ◽

10.1128/mbio.02647-18 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 13

Author(s):

Christine Henry ◽

Jizhou Li ◽

François Danion ◽

Laura Alcazar-Fuoli ◽

Emilia Mellado ◽

...

Keyword(s):

Cell Wall ◽

Invasive Aspergillosis ◽

Aspergillus Fumigatus ◽

Filamentous Fungi ◽

Biosynthetic Pathway ◽

Fungal Cell Wall ◽

Polarized Growth ◽

Biological Functions ◽

Fungal Cell ◽

Content Type

ABSTRACTFungal cell wall mannans are complex carbohydrate polysaccharides with different structures in yeasts and molds. In contrast to yeasts, their biosynthetic pathway has been poorly investigated in filamentous fungi. InAspergillus fumigatus, the major mannan structure is a galactomannan that is cross-linked to the β-1,3-glucan-chitin cell wall core. This polymer is composed of a linear mannan with a repeating unit composed of four α1,6-linked and α1,2-linked mannoses with side chains of galactofuran. Despite its use as a biomarker to diagnose invasive aspergillosis, its biosynthesis and biological function were unknown. Here, we have investigated the function of three members of the Ktr (also named Kre2/Mnt1) family (Ktr1, Ktr4, and Ktr7) inA. fumigatusand show that two of them are required for the biosynthesis of galactomannan. In particular, we describe a newly discovered form of α-1,2-mannosyltransferase activity encoded by theKTR4gene. Biochemical analyses showed that deletion of theKTR4gene or theKTR7gene leads to the absence of cell wall galactomannan. In comparison to parental strains, theΔktr4andΔktr7mutants showed a severe growth phenotype with defects in polarized growth and in conidiation, marked alteration of the conidial viability, and reduced virulence in a mouse model of invasive aspergillosis. In yeast, the KTR proteins are involved in protein 0- and N-glycosylation. This study provided another confirmation that orthologous genes can code for proteins that have very different biological functions in yeasts and filamentous fungi. Moreover, inA. fumigatus, cell wall mannans are as important structurally as β-glucans and chitin.IMPORTANCEThe fungal cell wall is a complex and dynamic entity essential for the development of fungi. It allows fungal pathogens to survive environmental challenge posed by nutrient stress and host defenses, and it also is central to polarized growth. The cell wall is mainly composed of polysaccharides organized in a three-dimensional network.Aspergillus fumigatusproduces a cell wall galactomannan whose biosynthetic pathway and biological functions remain poorly defined. Here, we described two new mannosyltransferases essential to the synthesis of the cell wall galactomannan. Their absence leads to a growth defect with misregulation of polarization and altered conidiation, with conidia which are bigger and more permeable than the conidia of the parental strain. This study showed that in spite of its low concentration in the cell wall, this polysaccharide is absolutely required for cell wall stability, for apical growth, and for the full virulence ofA. fumigatus.

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