Protein Glycosylation inAspergillus fumigatusIs Essential for Cell Wall Synthesis and Serves as a Promising Model of Multicellular Eukaryotic Development

Glycosylation is a conserved posttranslational modification that is found in all eukaryotes, which helps generate proteins with multiple functions. Our knowledge of glycosylation mainly comes from the investigation of the yeastSaccharomyces cerevisiaeand mammalian cells. However, during the last decade, glycosylation in the human pathogenic moldAspergillus fumigatushas drawn significant attention. It has been revealed that glycosylation inA. fumigatusis crucial for its growth, cell wall synthesis, and development and that the process is more complicated than that found in the budding yeastS. cerevisiae. The present paper implies that the investigation of glycosylation inA. fumigatusis not only vital for elucidating the mechanism of fungal cell wall synthesis, which will benefit the design of new antifungal therapies, but also helps to understand the role of protein glycosylation in the development of multicellular eukaryotes. This paper describes the advances in functional analysis of protein glycosylation inA. fumigatus.

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Role of Protein Glycosylation in Interactions of Medically Relevant Fungi with the Host

Journal of Fungi ◽

10.3390/jof7100875 ◽

2021 ◽

Vol 7 (10) ◽

pp. 875

Author(s):

Manuela Gómez-Gaviria ◽

Ana P. Vargas-Macías ◽

Laura C. García-Carnero ◽

Iván Martínez-Duncker ◽

Héctor M. Mora-Montes

Keyword(s):

Protein Trafficking ◽

Mammalian Cells ◽

Fungal Infections ◽

Fungal Species ◽

Protein Glycosylation ◽

Amino Acid Side Chain ◽

Post Translational Modification ◽

Fungal Cell ◽

The Relationship

Protein glycosylation is a highly conserved post-translational modification among organisms. It plays fundamental roles in many biological processes, ranging from protein trafficking and cell adhesion to host–pathogen interactions. According to the amino acid side chain atoms to which glycans are linked, protein glycosylation can be divided into two major categories: N-glycosylation and O-glycosylation. However, there are other types of modifications such as the addition of GPI to the C-terminal end of the protein. Besides the importance of glycoproteins in biological functions, they are a major component of the fungal cell wall and plasma membrane and contribute to pathogenicity, virulence, and recognition by the host immunity. Given that this structure is absent in host mammalian cells, it stands as an attractive target for developing selective compounds for the treatment of fungal infections. This review focuses on describing the relationship between protein glycosylation and the host–immune interaction in medically relevant fungal species.

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Contribution of Galactofuranose to the Virulence of the Opportunistic Pathogen Aspergillus fumigatus

Eukaryotic Cell ◽

10.1128/ec.00109-08 ◽

2008 ◽

Vol 7 (8) ◽

pp. 1268-1277 ◽

Cited By ~ 108

Author(s):

Philipp S. Schmalhorst ◽

Sven Krappmann ◽

Wouter Vervecken ◽

Manfred Rohde ◽

Meike Müller ◽

...

Keyword(s):

Cell Wall ◽

Invasive Aspergillosis ◽

Aspergillus Fumigatus ◽

Mammalian Cells ◽

Opportunistic Pathogen ◽

Fungal Cell ◽

Targeted Gene Deletion ◽

Key Enzyme ◽

Glucan Synthesis

ABSTRACT The filamentous fungus Aspergillus fumigatus is responsible for a lethal disease called invasive aspergillosis that affects immunocompromised patients. This disease, like other human fungal diseases, is generally treated by compounds targeting the primary fungal cell membrane sterol. Recently, glucan synthesis inhibitors were added to the limited antifungal arsenal and encouraged the search for novel targets in cell wall biosynthesis. Although galactomannan is a major component of the A. fumigatus cell wall and extracellular matrix, the biosynthesis and role of galactomannan are currently unknown. By a targeted gene deletion approach, we demonstrate that UDP-galactopyranose mutase, a key enzyme of galactofuranose metabolism, controls the biosynthesis of galactomannan and galactofuranose containing glycoconjugates. The glfA deletion mutant generated in this study is devoid of galactofuranose and displays attenuated virulence in a low-dose mouse model of invasive aspergillosis that likely reflects the impaired growth of the mutant at mammalian body temperature. Furthermore, the absence of galactofuranose results in a thinner cell wall that correlates with an increased susceptibility to several antifungal agents. The UDP-galactopyranose mutase thus appears to be an appealing adjunct therapeutic target in combination with other drugs against A. fumigatus. Its absence from mammalian cells indeed offers a considerable advantage to achieve therapeutic selectivity.

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Glycoprotein Hypersecretion Alters the Cell Wall in Trichoderma reesei Strains Expressing the Saccharomyces cerevisiae Dolichylphosphate Mannose Synthase Gene

Applied and Environmental Microbiology ◽

10.1128/aem.02375-06 ◽

2006 ◽

Vol 72 (12) ◽

pp. 7778-7784 ◽

Cited By ~ 13

Author(s):

Urszula Perlińska-Lenart ◽

Jacek Orłowski ◽

Agnieszka E. Laudy ◽

Ewa Zdebska ◽

Grażyna Palamarczyk ◽

...

Keyword(s):

Saccharomyces Cerevisiae ◽

Cell Wall ◽

Trichoderma Reesei ◽

Morphological Characterization ◽

Protein Glycosylation ◽

Fungal Cell Wall ◽

Ultrastructural Changes ◽

Calcofluor White ◽

Fungal Cell ◽

Gene Coding

ABSTRACT Expression of the Saccharomyces cerevisiae DPM1 gene (coding for dolichylphosphate mannose synthase) in Trichoderma reesei (Hypocrea jecorina) increases the intensity of protein glycosylation and secretion and causes ultrastructural changes in the fungal cell wall. In the present work, we undertook further biochemical and morphological characterization of the DPM1-expressing T. reesei strains. We established that the carbohydrate composition of the fungal cell wall was altered with an increased amount of N-acetylglucosamine, suggesting an increase in chitin content. Calcofluor white staining followed by fluorescence microscopy indicated changes in chitin distribution. Moreover, we also observed a decreased concentration of mannose and alkali-soluble β-(1,6) glucan. A comparison of protein secretion from protoplasts with that from mycelia showed that the cell wall created a barrier for secretion in the DPM1 transformants. We also discuss the relationships between the observed changes in the cell wall, increased protein glycosylation, and the greater secretory capacity of T. reesei strains expressing the yeast DPM1 gene.

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Fine Structure of Swarmers of Cladophora and Chaetomorpha

Journal of Cell Science ◽

10.1242/jcs.9.3.581 ◽

1971 ◽

Vol 9 (3) ◽

pp. 581-601

Author(s):

D. G. ROBINSON ◽

R. D. PRESTON

Keyword(s):

Cell Wall ◽

Fine Structure ◽

Spatial Arrangement ◽

Cell Wall Synthesis ◽

Fibrous Layer ◽

Etching Technique ◽

Freeze Etching

Naked swarmers of both Cladophora rupestris and Chaetomorpha melagonium have been examined by the freeze-etching technique. The swarmers of Cladophora, collected just after settling, reveal several layers of granules external to the plasmalemma and internal to the so-called ‘fibrous-layer’. Chaetomorpha swarmers collected just before settling show extrusion of vesicles through the plasmalemma. The structures associated with the membranes are discussed in relation to known features of these swarmers already observed by sectioning. The role of granules in the synthesis of cell wall microfibrils is strengthened though the spatial arrangement of the granules seen in this investigation does not completely fulfil the ‘ordered granule’ hypothesis. Description of, and comments on, features related to cell wall synthesis, particularly the Golgi and vacuolar systems, are given.

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The Role of Dimorphism Regulating Histidine Kinase (Drk1) in the Pathogenic Fungus Paracoccidioides brasiliensis Cell Wall

Journal of Fungi ◽

10.3390/jof7121014 ◽

2021 ◽

Vol 7 (12) ◽

pp. 1014

Author(s):

Marina Valente Navarro ◽

Yasmin Nascimento de Barros ◽

Wilson Dias Segura ◽

Alison Felipe Alencar Chaves ◽

Grasielle Pereira Jannuzzi ◽

...

Keyword(s):

Cell Wall ◽

Histidine Kinase ◽

Mammalian Cells ◽

Paracoccidioides Brasiliensis ◽

Pathogenic Fungus ◽

Fungal Resistance ◽

Phagocytic Index ◽

Mammalian Host ◽

Control Group

Dimorphic fungi of the Paracoccidioides genus are the causative agents of paracoccidioidomycosis (PCM), an endemic disease in Latin America with a high incidence in Brazil. This pathogen presents as infective mycelium at 25 °C in the soil, reverting to its pathogenic form when inhaled by the mammalian host (37 °C). Among these dimorphic fungal species, dimorphism regulating histidine kinase (Drk1) plays an essential role in the morphological transition. These kinases are present in bacteria and fungi but absent in mammalian cells and are important virulence and cellular survival regulators. Hence, the purpose of this study was to investigate the role of PbDrk1 in the cell wall modulation of P. brasiliensis. We observed that PbDrk1 participates in fungal resistance to different cell wall-disturbing agents by reducing viability after treatment with iDrk1. To verify the role of PbDRK1 in cell wall morphogenesis, qPCR results showed that samples previously exposed to iDrk1 presented higher expression levels of several genes related to cell wall modulation. One of them was FKS1, a β-glucan synthase that showed a 3.6-fold increase. Furthermore, confocal microscopy analysis and flow cytometry showed higher β-glucan exposure on the cell surface of P. brasiliensis after incubation with iDrk1. Accordingly, through phagocytosis assays, a significantly higher phagocytic index was observed in yeasts treated with iDrk1 than the control group, demonstrating the role of PbDrk1 in cell wall modulation, which then becomes a relevant target to be investigated. In parallel, the immune response profile showed increased levels of proinflammatory cytokines. Finally, our data strongly suggest that PbDrk1 modulates cell wall component expression, among which we can identify β-glucan. Understanding this signalling pathway may be of great value for identifying targets of antifungal molecular activity since HKs are not present in mammals.

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Editorial: The Role of the Fungal Cell Wall in Host-Fungal Interactions

Frontiers in Cellular and Infection Microbiology ◽

10.3389/fcimb.2020.00392 ◽

2020 ◽

Vol 10 ◽

Author(s):

Laura Alcazar-Fuoli ◽

Jagadeesh Bayry ◽

Vishukumar Aimanianda

Keyword(s):

Cell Wall ◽

Fungal Cell Wall ◽

Fungal Cell ◽

Fungal Interactions

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The Chitin Connection

mBio ◽

10.1128/mbio.00056-12 ◽

2012 ◽

Vol 3 (2) ◽

Cited By ~ 20

Author(s):

David L. Goldman ◽

Alfin G. Vicencio

Keyword(s):

Cell Wall ◽

Cell Membrane ◽

Fungal Infections ◽

Allergic Inflammation ◽

Chitinase Activity ◽

Chitin Deacetylase ◽

Fungal Cell ◽

Content Type ◽

Covalently Linked

ABSTRACTChitin, a polymer ofN-acetylglucosamine, is an essential component of the fungal cell wall. Chitosan, a deacetylated form of chitin, is also important in maintaining cell wall integrity and is essential forCryptococcus neoformansvirulence. In their article, Gilbert et al. [N. M. Gilbert, L. G. Baker, C. A. Specht, and J. K. Lodge, mBio 3(1):e00007-12, 2012] demonstrate that the enzyme responsible for chitosan synthesis, chitin deacetylase (CDA), is differentially attached to the cell membrane and wall. Bioactivity is localized to the cell membrane, where it is covalently linked via a glycosylphosphatidylinositol (GPI) anchor. Findings from this study significantly enhance our understanding of cryptococcal cell wall biology. Besides the role of chitin in supporting structural stability, chitin and host enzymes with chitinase activity have an important role in host defense and modifying the inflammatory response. Thus, chitin appears to provide a link between the fungus and host that involves both innate and adaptive immune responses. Recently, there has been increased attention to the role of chitinases in the pathogenesis of allergic inflammation, especially asthma. We review these findings and explore the possible connection between fungal infections, the induction of chitinases, and asthma.

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