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Identification of an α-(1 →6)-Mannosyltransferase Contributing To Biosynthesis of the Fungal-Type Galactomannan α-Core-Mannan Structure in Aspergillus fumigatus. mSphere 2022; 7:e0048422. [PMID: 36445154 PMCID: PMC9769593 DOI: 10.1128/msphere.00484-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Fungal-type galactomannan, a cell wall component of Aspergillus fumigatus, is composed of α-(1→2)-/α-(1→6)-linked mannan and β-(1→5)-/β-(1→6)-linked galactofuran side chains. Recently, CmsA and CmsB were identified as the α-(1→2)-mannosyltransferases involved in the biosynthesis of the α-core-mannan. However, the α-(1→6)-mannosyltransferase involved in the biosynthesis of the α-core-mannan has not been identified yet. In this study, we analyzed 9 putative α-(1→6)-mannosyltransferase gene disruption strains of A. fumigatus. The ΔanpA strain resulted in decreased mycelial elongation and reduced conidia formation. Proton nuclear magnetic resonance analysis revealed that the ΔanpA strain failed to produce the α-core-mannan of fungal-type galactomannan. We also found that recombinant AnpA exhibited much stronger α-(1→6)-mannosyltransferase activity toward α-(1→2)-mannobiose than α-(1→6)-mannobiose in vitro. Molecular simulations corroborated the fact that AnpA has a structure that can recognize the donor and acceptor substrates suitable for α-(1→6)-mannoside bond formation and that its catalytic activity would be specific for the elongation of the α-core-mannan structure in vivo. The identified AnpA is similar to Anp1p, which is involved in the elongation of the N-glycan outer chain in budding yeast, but the building sugar chain structure is different. The difference was attributed to the difference in substrate recognition of AnpA, which was clarified by simulations based on protein conformation. Thus, even proteins that seem to be functionally identical due to amino acid sequence similarity may be glycosyltransferase enzymes that make different glycans upon detailed analysis. This study describes an example of such a case. IMPORTANCE Fungal-type galactomannan is a polysaccharide incorporated into the cell wall of filamentous fungi belonging to the subphylum Pezizomycotina. Biosynthetic enzymes of fungal-type galactomannan are potential targets for antifungal drugs and agrochemicals. In this study, we identified an α-(1→6)-mannosyltransferase responsible for the biosynthesis of the α-core-mannan of fungal-type galactomannan, which has not been known for a long time. The findings of this study shed light on processes that shape this cellular structure while identifying a key enzyme essential for the biosynthesis of fungal-type galactomannan.
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Dean N, Jones R, DaSilva J, Chionchio G, Ng H. The Mnn10/Anp1-dependent N-linked outer chain glycan is dispensable for Candida albicans cell wall integrity. Genetics 2022; 221:6554200. [PMID: 35333306 PMCID: PMC9071539 DOI: 10.1093/genetics/iyac048] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 03/11/2022] [Indexed: 11/13/2022] Open
Abstract
Candida albicans cell wall glycoproteins, and in particular their mannose-rich glycans, are important for maintaining cellular integrity as well as host recognition, adhesion, and immunomodulation. The asparagine (N)-linked mannose outer chain of these glycoproteins is produced by Golgi mannosyltransferases (MTases). The outer chain is composed of a linear backbone of ∼50 α1,6-linked mannoses, which acts as a scaffold for addition of ∼150 or more mannoses in other linkages. Here, we describe the characterization of C. albicans OCH1, MNN9, VAN1, ANP1, MNN10, and MNN11, which encode the conserved Golgi MTases that sequentially catalyze the α1,6 mannose outer chain backbone. Candida albicans och1Δ/Δ, mnn9Δ/Δ, and van1Δ/Δ mutants block the earliest steps of backbone synthesis and like their Saccharomyces cerevisiae counterparts, have severe cell wall and growth phenotypes. Unexpectedly, and in stark contrast to S. cerevisiae, loss of Anp1, Mnn10, or Mnn11, which together synthesize most of the backbone, have no obvious deleterious phenotypes. These mutants were unaffected in cell morphology, growth, drug sensitivities, hyphal formation, and macrophage recognition. Analyses of secreted glycosylation reporters demonstrated that anp1Δ/Δ, mnn10Δ/Δ, and mnn11Δ/Δ strains accumulate glycoproteins with severely truncated N-glycan chains. This hypo-mannosylation did not elicit increased chitin deposition in the cell wall, which in other yeast and fungi is a key compensatory response to cell wall integrity breaches. Thus, C. albicans has evolved an alternate mechanism to adapt to cell wall weakness when N-linked mannan levels are reduced.
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Affiliation(s)
- Neta Dean
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, USA
- Corresponding author: Department of Biochemistry and Cell Biology, Life Sciences Bldg Room 310, Stony Brook University, Stony Brook, NY 11794-5215, USA.
| | - Rachel Jones
- Department of Anesthesiology, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY 10467, USA
| | - Justin DaSilva
- Laboratory of Retrovirology, The Rockefeller University, New York, NY 10065, USA
| | - Gregory Chionchio
- Donald and Barbara Zucker School of Medicine, Hofstra/Northwell, Hempstead, NY 11549, USA
| | - Henry Ng
- Department of Physiology, University of California, San Francisco, CA 94143, USA
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Ohashi T, Tanaka T, Tanaka N, Takegawa K. SpMnn9p and SpAnp1p form a protein complex involved in mannan synthesis in the fission yeast Schizosaccharomyces pombe. J Biosci Bioeng 2020; 130:335-340. [DOI: 10.1016/j.jbiosc.2020.06.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 06/02/2020] [Accepted: 06/07/2020] [Indexed: 01/22/2023]
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Golgi localization of glycosyltransferases requires Gpp74p in Schizosaccharomyces pombe. Appl Microbiol Biotechnol 2020; 104:8897-8909. [DOI: 10.1007/s00253-020-10881-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 08/24/2020] [Accepted: 09/02/2020] [Indexed: 12/20/2022]
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Two KTR Mannosyltransferases Are Responsible for the Biosynthesis of Cell Wall Mannans and Control Polarized Growth in Aspergillus fumigatus. mBio 2019; 10:mBio.02647-18. [PMID: 30755510 PMCID: PMC6372797 DOI: 10.1128/mbio.02647-18] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The 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 fumigatus produces 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 of A. fumigatus. Fungal 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. In Aspergillus 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) in A. fumigatus and 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 the KTR4 gene. Biochemical analyses showed that deletion of the KTR4 gene or the KTR7 gene leads to the absence of cell wall galactomannan. In comparison to parental strains, the Δktr4 and Δktr7 mutants 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, in A. fumigatus, cell wall mannans are as important structurally as β-glucans and chitin.
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Henry C, Fontaine T, Heddergott C, Robinet P, Aimanianda V, Beau R, Beauvais A, Mouyna I, Prevost MC, Fekkar A, Zhao Y, Perlin D, Latgé JP. Biosynthesis of cell wall mannan in the conidium and the mycelium ofAspergillusfumigatus. Cell Microbiol 2016; 18:1881-1891. [DOI: 10.1111/cmi.12665] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 09/06/2016] [Indexed: 11/28/2022]
Affiliation(s)
- Christine Henry
- Département de Mycologie; Unité des Aspergillus; Paris Cedex France
| | - Thierry Fontaine
- Département de Mycologie; Unité des Aspergillus; Paris Cedex France
| | | | - Pauline Robinet
- Département de Mycologie; Unité des Aspergillus; Paris Cedex France
| | | | - Remi Beau
- Département de Mycologie; Unité des Aspergillus; Paris Cedex France
| | - Anne Beauvais
- Département de Mycologie; Unité des Aspergillus; Paris Cedex France
| | - Isabelle Mouyna
- Département de Mycologie; Unité des Aspergillus; Paris Cedex France
| | | | - Arnaud Fekkar
- Service de Parasitologie Mycologie; Hôpital de La Pitié-Salpêtrière; Paris France
| | - Yanan Zhao
- Public Health Research Institute, New Jersey Medical School, Rutgers; The State University of New Jersey; Newark New Jersey USA
| | - David Perlin
- Public Health Research Institute, New Jersey Medical School, Rutgers; The State University of New Jersey; Newark New Jersey USA
| | - Jean-Paul Latgé
- Département de Mycologie; Unité des Aspergillus; Paris Cedex France
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Piirainen MA, Boer H, de Ruijter JC, Frey AD. A dual approach for improving homogeneity of a human-type N-glycan structure in Saccharomyces cerevisiae. Glycoconj J 2016; 33:189-99. [PMID: 26983412 DOI: 10.1007/s10719-016-9656-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Revised: 01/26/2016] [Accepted: 02/04/2016] [Indexed: 11/30/2022]
Abstract
N-glycosylation is an important feature of therapeutic and other industrially relevant proteins, and engineering of the N-glycosylation pathway provides opportunities for developing alternative, non-mammalian glycoprotein expression systems. Among yeasts, Saccharomyces cerevisiae is the most established host organism used in therapeutic protein production and therefore an interesting host for glycoengineering. In this work, we present further improvements in the humanization of the N-glycans in a recently developed S. cerevisiae strain. In this strain, a tailored trimannosyl lipid-linked oligosaccharide is formed and transferred to the protein, followed by complex-type glycan formation by Golgi apparatus-targeted human N-acetylglucosamine transferases. We improved the glycan pattern of the glycoengineered strain both in terms of glycoform homogeneity and the efficiency of complex-type glycosylation. Most of the interfering structures present in the glycoengineered strain were eliminated by deletion of the MNN1 gene. The relative abundance of the complex-type target glycan was increased by the expression of a UDP-N-acetylglucosamine transporter from Kluyveromyces lactis, indicating that the import of UDP-N-acetylglucosamine into the Golgi apparatus is a limiting factor for efficient complex-type N-glycosylation in S. cerevisiae. By a combination of the MNN1 deletion and the expression of a UDP-N-acetylglucosamine transporter, a strain forming complex-type glycans with a significantly improved homogeneity was obtained. Our results represent a further step towards obtaining humanized glycoproteins with a high homogeneity in S. cerevisiae.
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Affiliation(s)
- Mari A Piirainen
- Department of Biotechnology and Chemical Technology, Aalto University, Kemistintie 1, 02150, Espoo, Finland
| | - Harry Boer
- VTT Technical research centre of Finland, Espoo, Finland
| | - Jorg C de Ruijter
- Department of Biotechnology and Chemical Technology, Aalto University, Kemistintie 1, 02150, Espoo, Finland
| | - Alexander D Frey
- Department of Biotechnology and Chemical Technology, Aalto University, Kemistintie 1, 02150, Espoo, Finland.
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Comparative Analysis of Protein Glycosylation Pathways in Humans and the Fungal Pathogen Candida albicans. Int J Microbiol 2014; 2014:267497. [PMID: 25104959 PMCID: PMC4106090 DOI: 10.1155/2014/267497] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Accepted: 06/06/2014] [Indexed: 11/30/2022] Open
Abstract
Protein glycosylation pathways are present in all kingdoms of life and are metabolic pathways found in all the life kingdoms. Despite sharing commonalities in their synthesis, glycans attached to glycoproteins have species-specific structures generated by the presence of different sets of enzymes and acceptor substrates in each organism. In this review, we present a comparative analysis of the main glycosylation pathways shared by humans and the fungal pathogen Candida albicans: N-linked glycosylation, O-linked mannosylation and glycosylphosphatidylinositol-anchorage. The knowledge of similarities and divergences between these metabolic pathways could help find new pharmacological targets for C. albicans infection.
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Striebeck A, Robinson DA, Schüttelkopf AW, van Aalten DMF. Yeast Mnn9 is both a priming glycosyltransferase and an allosteric activator of mannan biosynthesis. Open Biol 2013; 3:130022. [PMID: 24026536 PMCID: PMC3787745 DOI: 10.1098/rsob.130022] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The fungal cell possesses an essential carbohydrate cell wall. The outer layer, mannan, is formed by mannoproteins carrying highly mannosylated O- and N-linked glycans. Yeast mannan biosynthesis is initiated by a Golgi-located complex (M-Pol I) of two GT-62 mannosyltransferases, Mnn9p and Van1p, that are conserved in fungal pathogens. Saccharomyces cerevisiae and Candida albicans mnn9 knockouts show an aberrant cell wall and increased antibiotic sensitivity, suggesting the enzyme is a potential drug target. Here, we present the structure of ScMnn9 in complex with GDP and Mn2+, defining the fold and catalytic machinery of the GT-62 family. Compared with distantly related GT-78/GT-15 enzymes, ScMnn9 carries an unusual extension. Using a novel enzyme assay and site-directed mutagenesis, we identify conserved amino acids essential for ScMnn9 ‘priming’ α-1,6-mannosyltransferase activity. Strikingly, both the presence of the ScMnn9 protein and its product, but not ScMnn9 catalytic activity, are required to activate subsequent ScVan1 processive α-1,6-mannosyltransferase activity in the M-Pol I complex. These results reveal the molecular basis of mannan synthesis and will aid development of inhibitors targeting this process.
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Affiliation(s)
- Alexander Striebeck
- Division of Molecular Microbiology, University of Dundee, Dundee DD1 5EH, UK
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Orlean P. Architecture and biosynthesis of the Saccharomyces cerevisiae cell wall. Genetics 2012; 192:775-818. [PMID: 23135325 PMCID: PMC3522159 DOI: 10.1534/genetics.112.144485] [Citation(s) in RCA: 301] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Accepted: 08/06/2012] [Indexed: 01/02/2023] Open
Abstract
The wall gives a Saccharomyces cerevisiae cell its osmotic integrity; defines cell shape during budding growth, mating, sporulation, and pseudohypha formation; and presents adhesive glycoproteins to other yeast cells. The wall consists of β1,3- and β1,6-glucans, a small amount of chitin, and many different proteins that may bear N- and O-linked glycans and a glycolipid anchor. These components become cross-linked in various ways to form higher-order complexes. Wall composition and degree of cross-linking vary during growth and development and change in response to cell wall stress. This article reviews wall biogenesis in vegetative cells, covering the structure of wall components and how they are cross-linked; the biosynthesis of N- and O-linked glycans, glycosylphosphatidylinositol membrane anchors, β1,3- and β1,6-linked glucans, and chitin; the reactions that cross-link wall components; and the possible functions of enzymatic and nonenzymatic cell wall proteins.
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Affiliation(s)
- Peter Orlean
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
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Lambou K, Perkhofer S, Fontaine T, Latge JP. Comparative functional analysis of the OCH1 mannosyltransferase families in Aspergillus fumigatus and Saccharomyces cerevisiae. Yeast 2010; 27:625-36. [PMID: 20586114 DOI: 10.1002/yea.1798] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Alpha1,6-linked mannans are an essential component of the Aspergillus fumigatus galactomannan, which is either GPI-anchored to the plasma membrane or covalently bound to the polysaccharide core of the cell wall. In Saccharomyces cerevisiae, the OCH1 gene encodes an alpha1,6-mannosyltransferase that initiates the synthesis of the alpha1,6 linked-mannan. In the A. fumigatus genome, four orthologous genes of Saccharomyces cerevisiae ScOCH1 gene were identified. Single deletion and the quadruple deletion mutants (Afoch1-4Delta) were constructed in A. fumigatus. No phenotype different from the wild-type strain was observed in all single and the quadruple mutants. The corresponding cDNAs of the AfOCH1-4 A. fumigatus orthologues were expressed in the S. cerevisiae Scoch1Delta mutant. Among the four orthologues, only AfOCH1 complemented the aggregation phenotype, the growth inhibition, the hypersensitivity to hygromycin and the protein glycosylation defects observed in the Scoch1Deltamutant.
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Affiliation(s)
- Karine Lambou
- Unité des Aspergillus, Institut Pasteur, 25 Rue du Docteur Roux, 75724 Paris Cedex 15, France
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Fernández-Alvarez A, Elías-Villalobos A, Ibeas JI. Protein glycosylation in the phytopathogen Ustilago maydis: From core oligosaccharide synthesis to the ER glycoprotein quality control system, a genomic analysis. Fungal Genet Biol 2010; 47:727-35. [PMID: 20554055 DOI: 10.1016/j.fgb.2010.06.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 05/28/2010] [Accepted: 06/01/2010] [Indexed: 01/21/2023]
Abstract
The corn smut fungus Ustilago maydis has, over recent decades, become established as a robust pathogenic model for studying fungi-plant relationships. This use of U. maydis can be attributed to its biotrophic host interaction, easy culture and genetic manipulation in the laboratory, and the severe disease symptoms it induces in infected maize. Recent studies have shown that normal protein glycosylation is essential for pathogenic development, but dispensable for the saprophytic growth or mating. Given the relevance of protein glycosylation for U. maydis virulence, and consequently its role in the plant pathogenesis, here we review the main actors and events implicated in protein glycosylation. Furthermore, we describe the results of an in silico search, where we identify all the conserved members of the N- and O-glycosylation pathways in U. maydis at each stage: core oligosaccharide synthesis, addition of the core oligosaccharide to nascent target proteins, maturation and extension of the core oligosaccharide, and the quality control system used by the cell to avoid the presence of unfolded glycoproteins. Finally, we discuss how these genes could affect U. maydis virulence and their biotechnological implications.
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Affiliation(s)
- Alfonso Fernández-Alvarez
- Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide - Consejo Superior de Investigaciones Científicas, Seville, Spain
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Current awareness on yeast. Yeast 2009. [DOI: 10.1002/yea.1625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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