Cell Surface最新文献

The segregation of glycosylphosphatidylinositol-anchored proteins (GPI-APs) to distinct domains on the plasma membrane of eukaryotic cells is important for their correct cellular function, but the mechanisms by which GPI-APs are sorted are yet to be fully resolved. An extreme example of this is in African trypanosomes, where the major surface glycoprotein floods the whole cell surface while most GPI-APs are retained in a specialised domain at the base of the flagellum. One possibility is that anchor attachment signals direct differential sorting of proteins. To investigate this, we fused a monomeric reporter to the GPI-anchor insertion signals of trypanosome proteins that are differentially sorted on the plasma membrane. Fusions were correctly anchored by GPI, post-translationally modified, and routed to the plasma membrane, but this delivery was independent of retained signals upstream of the ω site. Instead, ω−minus signal strength appears key to efficacy of GPI addition and to GPI-AP cellular level. Thus, at least in this system, sorting is not encoded at the time of GPI anchor addition or in the insertion sequence retained in processed proteins. We discuss these findings in the context of previously proposed models for sorting mechanisms in trypanosomes.

Every fungal cell is encapsulated in a cell wall, essential for cell viability, morphogenesis, and pathogenesis. Most knowledge of the cell wall composition in fungi has focused on ascomycetes, especially human pathogens, but considerably less is known about early divergent fungal groups, such as species in the Zoopagomycota and Mucoromycota phyla. To shed light on evolutionary changes in the fungal cell wall, we studied the monosaccharide composition of the cell wall of 18 species including early diverging fungi and species in the Basidiomycota and Ascomycota phyla with a focus on those with pathogenic lifestyles and interactions with plants. Our data revealed that chitin is the most characteristic component of the fungal cell wall, and was found to be in a higher proportion in the early divergent groups. The Mucoromycota species possess few glucans, but instead have other monosaccharides such as fucose and glucuronic acid that are almost exclusively found in their cell walls. Additionally, we observed that hexoses (glucose, mannose and galactose) accumulate in much higher proportions in species belonging to Dikarya. Our data demonstrate a clear relationship between phylogenetic position and fungal cell wall carbohydrate composition and lay the foundation for a better understanding of their evolution and their role in plant interactions.

Host recognition of the pathogen-associated molecular pattern (PAMP), β-1,3-glucan, plays a major role in antifungal immunity. β-1,3-glucan is an essential component of the inner cell wall of the opportunistic pathogen Candida albicans. Most β-1,3-glucan is shielded by the outer cell wall layer of mannan fibrils, but some can become exposed at the cell surface. In response to host signals such as lactate, C. albicans shaves the exposed β-1,3-glucan from its cell surface, thereby reducing the ability of innate immune cells to recognise and kill the fungus. We have used sets of barcoded xog1 and eng1 mutants to compare the impacts of the secreted β-glucanases Xog1 and Eng1 upon C. albicans in vitro and in vivo. Flow cytometry of Fc-dectin-1-stained strains revealed that Eng1 plays the greater role in lactate-induced β-1,3-glucan masking. Transmission electron microscopy and stress assays showed that neither Eng1 nor Xog1 are essential for cell wall maintenance, but the inactivation of either enzyme compromised fungal adhesion to gut and vaginal epithelial cells. Competitive barcode sequencing suggested that neither Eng1 nor Xog1 strongly influence C. albicans fitness during systemic infection or vaginal colonisation in mice. However, the deletion of XOG1 enhanced C. albicans fitness during gut colonisation. We conclude that both Eng1 and Xog1 exert subtle effects on the C. albicans cell surface that influence fungal adhesion to host cells and that affect fungal colonisation in certain host niches.

Cell wall biomass, Earth’s most abundant natural resource, holds significant potential for sustainable biofuel production. Composed of cellulose, hemicellulose, lignin, pectin, and other polymers, the plant cell wall provides essential structural support to diverse organisms in nature. In contrast, non-plant species like insects, crustaceans, and fungi rely on chitin as their primary structural polysaccharide. The saprophytic fungus Aspergillus fumigatus has been widely recognized for its adaptability to various environmental conditions. It achieves this by secreting different cell wall biomass degradation enzymes to obtain essential nutrients. This review compiles a comprehensive collection of cell wall degradation enzymes derived from A. fumigatus, including cellulases, hemicellulases, various chitin degradation enzymes, and other polymer degradation enzymes. Notably, these enzymes exhibit biochemical characteristics such as temperature tolerance or acid adaptability, indicating their potential applications across a spectrum of industries.

Non-tuberculosis mycobacteria (NTM) can form biofilms on diverse artificial surfaces. In the present study, we induced NTM biofilm formation on materials used in various medical devices, evaluated the total amount of biofilm, and observed the ultrastructure by scanning electron microscopy.

Pattern-Triggered Immunity (PTI) in plants is activated upon recognition by Pattern Recognition Receptors (PRRs) of Damage- and Microbe-Associated Molecular Patterns (DAMPs and MAMPs) from plants or microorganisms, respectively. An increasing number of identified DAMPs/MAMPs are carbohydrates from plant cell walls and microbial extracellular layers, which are perceived by plant PRRs, such as LysM and Leucine Rich Repeat-Malectin (LRR-MAL) receptor kinases (RKs). LysM-RKs (e.g. CERK1, LYK4 and LYK5) are needed for recognition of fungal MAMP chitohexaose (β-1,4-D-(GlcNAc)₆, CHI6), whereas IGP1/CORK1, IGP3 and IGP4 LRR-MAL RKs are required for perception of β-glucans, like cellotriose (β-1,4-D-(Glc)₃, CEL3) and mixed-linked glucans. We have explored the diversity of carbohydrates perceived by Arabidopsis thaliana seedlings by determining PTI responses upon treatment with different oligosaccharides and polysaccharides. These analyses revealed that plant oligosaccharides from xylans [β-1,4-D-(xylose)₄ (XYL4)], glucuronoxylans and α-1,4-glucans, and polysaccharides from plants and seaweeds activate PTI. Cross-elicitation experiments of XYL4 with other glycans showed that the mechanism of recognition of XYL4 and the DAMP 3³-α-L-arabinofuranosyl-xylotetraose (XA₃XX) shares some features with that of CEL3 but differs from that of CHI6. Notably, XYL4 and XA₃XX perception is impaired in igp1/cork1, igp3 and igp4 mutants, and almost not affected in cerk1 lyk4 lyk5 triple mutant. XYL4 perception is conserved in different plant species since XYL4 pre-treatment triggers enhanced disease resistance in tomato to Pseudomonas syringae pv tomato DC3000 and PTI responses in wheat. These results expand the number of glycans triggering plant immunity and support IGP1/CORK1, IGP3 and IGP4 relevance in Arabidopsis thaliana glycans perception and PTI activation.

Significance Statement

The characterization of plant immune mechanisms involved in the perception of carbohydrate-based structures recognized as DAMPs/MAMPs is needed to further understand plant disease resistance modulation. We show here that IGP1/CORK1, IGP3 and IGP4 LRR-MAL RKs are required for the perception of carbohydrate-based DAMPs β-1,4-D-(xylose)₄ (XYL4) and 3³-α-L-arabinofuranosyl-xylotetraose (XA₃XX), further expanding the function of these LRR-MAL RKs in plant glycan perception and immune activation.

Herein, this manuscript explores the significance of the phosphoglucomutase (PGM) enzyme in Pneumocystis spp., focusing on its role in fungal surface mannoprotein formation. Through expression of the Pneumocystis murina Pmpgm2 in a Saccharomyces cerevisiae pgm2Δ strain, we demonstrate restoration of binding to the mannose receptor (MR) and macrophages to wildtype yeast levels in this complemented strain. Gas Chromatography-Mass Spectroscopy (GC-MS) confirmed reduced mannose content in the pgm2Δ yeast strain compared to the wild-type and complemented Pmpgm2 cDNA-expressing strains. This study underscores fungal PGM function in dolichol glucosyl phosphate biosynthesis, crucial for proper cell wall mannoprotein formation. Furthermore, highlighting the conservation of targetable cysteine residues across fungal pathogens, PGM inhibition maybe a potential therapeutic strategy against a broad spectrum of fungal infections.