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Role of the Candida albicans MNN1 gene family in cell wall structure and virulence.

Bates S, Hall RA, Cheetham J, Netea MG, MacCallum DM, Brown AJ, Odds FC, Gow NA - BMC Res Notes (2013)

Bottom Line: However, no gross changes in cell wall composition or N-glycosylation were identified in this mutant, although an extension of phosphomannan chain length was apparent.Although the cell wall defects associated with the mnn14Δ mutant were subtle, this mutant displayed a severe attenuation of virulence in a murine infection model.Mnn14 plays a distinct role from other members of the MNN1 family, demonstrating that specific N-glycan outer chain epitopes are required in the host-pathogen interaction and virulence.

View Article: PubMed Central - HTML - PubMed

Affiliation: College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4QD, UK. s.bates@ex.ac.uk

ABSTRACT

Background: The Candida albicans cell wall is the first point of contact with the host, and its outer surface is heavily enriched in mannoproteins modified through the addition of N- and O-mannan. Previous work, using mutants with gross defects in glycosylation, has clearly identified the importance of mannan in the host-pathogen interaction, immune recognition and virulence. Here we report the first analysis of the MNN1 gene family, which contains six members predicted to act as α-1,3 mannosyltransferases in the terminal stages of glycosylation.

Findings: We generated single mutants in all members of the C. albicans MNN1 gene family, and disruption of MNN14 led to both in vitro and in vivo defects. Null mutants in other members of the family demonstrated no phenotypic defects, suggesting that these members may display functional redundancy. The mnn14Δ mutant displayed hypersensitivity to agents associated with cell wall and glycosylation defects, suggesting an altered cell wall structure. However, no gross changes in cell wall composition or N-glycosylation were identified in this mutant, although an extension of phosphomannan chain length was apparent. Although the cell wall defects associated with the mnn14Δ mutant were subtle, this mutant displayed a severe attenuation of virulence in a murine infection model.

Conclusion: Mnn14 plays a distinct role from other members of the MNN1 family, demonstrating that specific N-glycan outer chain epitopes are required in the host-pathogen interaction and virulence.

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Related in: MedlinePlus

Sensitivity of C. albicans mnn14Δ  mutant to cell wall perturbing agents. The sensitivities of the wild type (closed squares) and Camnn14Δ  mutant (open squares) to cell wall perturbing agents were determined by a broth microdilution method. The agents to which the Camnn14Δ  mutant displayed hypersensitivity are shown (hygromycin B, tunicamycin, and SDS).
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Figure 4: Sensitivity of C. albicans mnn14Δ mutant to cell wall perturbing agents. The sensitivities of the wild type (closed squares) and Camnn14Δ mutant (open squares) to cell wall perturbing agents were determined by a broth microdilution method. The agents to which the Camnn14Δ mutant displayed hypersensitivity are shown (hygromycin B, tunicamycin, and SDS).

Mentions: To examine cell wall integrity we screened the MNN1 family mutants for sensitivity to a range of cell wall perturbing agents. The mnn14Δ mutant was clearly hypersensitive to SDS, tunicamycin, and hygromycin B which is characteristic of glycosylation mutants (Figure 4). However, no increase in sensitivity was seen to the cell wall perturbing agent Calcofluor White, suggesting that the mnn14Δ mutant does not have a defect in the general robustness of the cell wall. No other family members displayed altered sensitivity to any of the compounds tested. Changes in cell wall structure were also assessed through HPLC sugar composition analysis, but no gross alteration in the relative proportions of the three main cell wall polysaccharides (glucan, mannan and chitin) was identified for any of the MNN1 family mutants (data not shown).


Role of the Candida albicans MNN1 gene family in cell wall structure and virulence.

Bates S, Hall RA, Cheetham J, Netea MG, MacCallum DM, Brown AJ, Odds FC, Gow NA - BMC Res Notes (2013)

Sensitivity of C. albicans mnn14Δ  mutant to cell wall perturbing agents. The sensitivities of the wild type (closed squares) and Camnn14Δ  mutant (open squares) to cell wall perturbing agents were determined by a broth microdilution method. The agents to which the Camnn14Δ  mutant displayed hypersensitivity are shown (hygromycin B, tunicamycin, and SDS).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750861&req=5

Figure 4: Sensitivity of C. albicans mnn14Δ mutant to cell wall perturbing agents. The sensitivities of the wild type (closed squares) and Camnn14Δ mutant (open squares) to cell wall perturbing agents were determined by a broth microdilution method. The agents to which the Camnn14Δ mutant displayed hypersensitivity are shown (hygromycin B, tunicamycin, and SDS).
Mentions: To examine cell wall integrity we screened the MNN1 family mutants for sensitivity to a range of cell wall perturbing agents. The mnn14Δ mutant was clearly hypersensitive to SDS, tunicamycin, and hygromycin B which is characteristic of glycosylation mutants (Figure 4). However, no increase in sensitivity was seen to the cell wall perturbing agent Calcofluor White, suggesting that the mnn14Δ mutant does not have a defect in the general robustness of the cell wall. No other family members displayed altered sensitivity to any of the compounds tested. Changes in cell wall structure were also assessed through HPLC sugar composition analysis, but no gross alteration in the relative proportions of the three main cell wall polysaccharides (glucan, mannan and chitin) was identified for any of the MNN1 family mutants (data not shown).

Bottom Line: However, no gross changes in cell wall composition or N-glycosylation were identified in this mutant, although an extension of phosphomannan chain length was apparent.Although the cell wall defects associated with the mnn14Δ mutant were subtle, this mutant displayed a severe attenuation of virulence in a murine infection model.Mnn14 plays a distinct role from other members of the MNN1 family, demonstrating that specific N-glycan outer chain epitopes are required in the host-pathogen interaction and virulence.

View Article: PubMed Central - HTML - PubMed

Affiliation: College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4QD, UK. s.bates@ex.ac.uk

ABSTRACT

Background: The Candida albicans cell wall is the first point of contact with the host, and its outer surface is heavily enriched in mannoproteins modified through the addition of N- and O-mannan. Previous work, using mutants with gross defects in glycosylation, has clearly identified the importance of mannan in the host-pathogen interaction, immune recognition and virulence. Here we report the first analysis of the MNN1 gene family, which contains six members predicted to act as α-1,3 mannosyltransferases in the terminal stages of glycosylation.

Findings: We generated single mutants in all members of the C. albicans MNN1 gene family, and disruption of MNN14 led to both in vitro and in vivo defects. Null mutants in other members of the family demonstrated no phenotypic defects, suggesting that these members may display functional redundancy. The mnn14Δ mutant displayed hypersensitivity to agents associated with cell wall and glycosylation defects, suggesting an altered cell wall structure. However, no gross changes in cell wall composition or N-glycosylation were identified in this mutant, although an extension of phosphomannan chain length was apparent. Although the cell wall defects associated with the mnn14Δ mutant were subtle, this mutant displayed a severe attenuation of virulence in a murine infection model.

Conclusion: Mnn14 plays a distinct role from other members of the MNN1 family, demonstrating that specific N-glycan outer chain epitopes are required in the host-pathogen interaction and virulence.

Show MeSH
Related in: MedlinePlus