title: Identification of a new family of genes involved in beta-1,2-mannosylation of glycans in Pichia pastoris and Candida albicans.
abstract: Structural studies of cell wall components of the pathogenic yeast Candida albicans have demonstrated the presence of beta-1,2-linked oligomannosides in phosphopeptidomannan and phospholipomannan. During C. albicans infection, beta-1,2-oligomannosides play an important role in host/pathogen interactions by acting as adhesins and by interfering with the host immune response. Despite the importance of beta-1,2-oligomannosides, the genes responsible for their synthesis have not been identified. The main reason is that the reference species Saccharomyces cerevisiae does not synthesize beta-linked mannoses. On the other hand, the presence of beta-1,2-oligomannosides has been reported in the cell wall of the more genetically tractable C. albicans relative, P. pastoris. Here we present the identification, cloning, and characterization of a novel family of fungal genes involved in beta-mannose transfer. Employing in silico analysis, we identified a family of four related new genes in P. pastoris and subsequently nine homologs in C. albicans. Biochemical, immunological, and structural analyses following deletion of four genes in P. pastoris and deletion of four genes acting specifically on C. albicans mannan demonstrated the involvement of these new genes in beta-1,2-oligomannoside synthesis. Phenotypic characterization of the strains deleted in beta-mannosyltransferase genes (BMTs) allowed us to describe the stepwise activity of Bmtps and acceptor specificity. For C. albicans, despite structural similarities between mannan and phospholipomannan, phospholipomannan beta-mannosylation was not affected by any of the CaBMT1-4 deletions. Surprisingly, depletion in mannan major beta-1,2-oligomannoside epitopes had little impact on cell wall surface beta-1,2-oligomannoside antigenic expression.
authors.affiliation: Unité de Physiopathologie des Candidoses, INSERM U799, Université de Lille 2 EA 2684, Lille 59045, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Mille
authors.forename: Piotr
authors.initials: P
authors.lastname: Bobrowicz
authors.forename: Pierre-André
authors.initials: PA
authors.lastname: Trinel
authors.forename: Huijuan
authors.initials: H
authors.lastname: Li
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Maes
authors.forename: Yann
authors.initials: Y
authors.lastname: Guerardel
authors.forename: Chantal
authors.initials: C
authors.lastname: Fradin
authors.forename: María
authors.initials: M
authors.lastname: Martínez-Esparza
authors.forename: Robert C
authors.initials: RC
authors.lastname: Davidson
authors.forename: Guilhem
authors.initials: G
authors.lastname: Janbon
authors.forename: Daniel
authors.initials: D
authors.lastname: Poulain
authors.forename: Stefan
authors.initials: S
authors.lastname: Wildt
mesh_terms: D002176:Candida albicans / Q000235:genetics* / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000096:biosynthesis / Q000235:genetics; D002473:Cell Wall / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics; D017353:Gene Deletion; D005800:Genes, Fungal / Q000502:physiology*; D006017:Glycolipids / Q000096:biosynthesis / Q000235:genetics; D006031:Glycosylation; D008358:Mannose / Q000235:genetics / Q000378:metabolism; D008364:Mannosyltransferases / Q000235:genetics / Q000378:metabolism; D009844:Oligosaccharides / Q000235:genetics* / Q000378:metabolism; D010843:Pichia / Q000235:genetics* / Q000378:metabolism; D011134:Polysaccharides / Q000096:biosynthesis / Q000235:genetics*
chemical_list: C109455:ALA1 protein, Candida albicans; D015815:Cell Adhesion Molecules; D005656:Fungal Proteins; D006017:Glycolipids; D009844:Oligosaccharides; D011134:Polysaccharides; C028569:oligomannoside; C400188:phospholipomannan; D008364:Mannosyltransferases; D008358:Mannose