Identification of a new family of genes involved in beta-1,2-mannosylation of glycans in Pichia pastoris and Candida albicans.
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.
Mille
Céline
C
Unité de Physiopathologie des Candidoses, INSERM U799, Université de Lille 2 EA 2684, Lille 59045, France.
Bobrowicz
Piotr
P
Trinel
Pierre-André
PA
Li
Huijuan
H
Maes
Emmanuel
E
Guerardel
Yann
Y
Fradin
Chantal
C
Martínez-Esparza
María
M
Davidson
Robert C
RC
Janbon
Guilhem
G
Poulain
Daniel
D
Wildt
Stefan
S
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*
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