Molecular Analysis of the Candida albicans Homolog of Saccharomyces cerevisiae MNN9, Required for Glycosylation of Cell Wall Mannoproteins

AUTOR(ES)

Southard, Susan B.

FONTE

American Society for Microbiology

RESUMO

The fungal cell wall has generated interest as a potential target for developing antifungal drugs, and the genes encoding glucan and chitin in fungal pathogens have been studied to this end. Mannoproteins, the third major component of the cell wall, contain mannose in either O- or N-glycosidic linkages. Here we describe the molecular analysis of the Candida albicans homolog of Saccharomyces cerevisiae MNN9, a gene required for the synthesis of N-linked outer-chain mannan in yeast, and the phenotypes associated with its disruption. CaMNN9 has significant homology with S. cerevisiae MNN9, including a putative N-terminal transmembrane domain, and represents a member of a similar gene family in Candida. CaMNN9 resides on chromosome 3 and is expressed at similar levels in both yeast and hyphal cells. Disruption of both copies of CaMNN9 leads to phenotypic effects characteristic of cell wall defects including poor growth in liquid media and on solid media, formation of aggregates in liquid culture, osmotic sensitivity, aberrant hyphal formation, and increased sensitivity to lysis after treatment with β-1,3-glucanase. Like all members of the S. cerevisiae MNN9 gene family the Camnn9Δ strain is resistant to sodium orthovanadate and sensitive to hygromycin B. Analysis of cell wall-associated carbohydrates showed the Camnn9Δ strain to contain half the amount of mannan present in cell walls derived from the wild-type parent strain. Reverse transcription-PCR and Northern analysis of the expression of MNN9 gene family members CaVAN1 and CaANP1 in the Camnn9Δ strain showed that transcription of those genes is not affected in the absence of CaMNN9 transcription. Our results suggest that, while the role MNN9 plays in glycosylation in both Candida and Saccharomyces is conserved, loss of MNN9 function in C. albicans leads to phenotypes that are inconsistent with the pathogenicity of the organism and thus identify CaMnn9p as a potential drug target.

Documentos Relacionados

• Cloning and analysis of the Saccharomyces cerevisiae MNN9 and MNN1 genes required for complex glycosylation of secreted proteins.
• Identification of Two Mannoproteins Released from Cell Walls of a Saccharomyces cerevisiae mnn1 mnn9 Double Mutant by Reducing Agents
• Serologic Response to Cell Wall Mannoproteins and Proteins of Candida albicans
• Identification of three mannoproteins in the cell wall of Saccharomyces cerevisiae.
• Bleomycin affects cell wall anchorage of mannoproteins in Saccharomyces cerevisiae.