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Multiple functions of Pmt1p-mediated protein O-mannosylation in the fungal pathogen Candida albicans
C Timpel1, S Strahl-Bolsinger, K Ziegelbauer
1Institut für Mikrobiologie und Biologisch-Medizinisches Forschungszentrum, Heinrich-Heine-Universität, D-40225 Düsseldorf, Germany.
Abstract:
Protein mannosylation by Pmt proteins initiates O-glycosylation in fungi. We have identified the PMT1 gene and analyzed the function of Pmt1p in the fungal human pathogen Candida albicans. Mutants defective in PMT1 alleles lacked Pmt in vitro enzymatic activity, showed reduced growth rates, and tended to form cellular aggregates. In addition, multiple specific deficiencies not known in Saccharomyces cerevisiae (including defective hyphal morphogenesis; supersensitivity to the antifungal agents hygromycin B, G418, clotrimazole, and calcofluor white; and reduced adherence to Caco-2 epithelial cells) were observed in pmt1 mutants. PMT1 deficiency also led to faster electrophoretic mobility of the Als1p cell wall protein and to elevated extracellular activities of chitinase. Homozygous pmt1 mutants were avirulent in a mouse model of systemic infection, while heterozygous PMT1/pmt1 strains showed reduced virulence. The results indicate that protein O-mannosylation by Pmt proteins occurs in different fungal species, where PMT1 deficiency can lead to defects in multiple cellular functions.
Insights
The study identifies the PMT1 gene
Area of Science:
- Mycology
- Biochemistry
- Cell Biology
Background:
- Protein O-mannosylation is a key step in fungal glycosylation, initiated by Pmt proteins.
- Understanding the function of Pmt proteins is crucial for fungal pathogenesis research.
Purpose of the Study:
- To identify and analyze the function of the PMT1 gene and its encoded protein, Pmt1p, in the human fungal pathogen Candida albicans.
- To investigate the impact of PMT1 deficiency on cellular functions, antifungal susceptibility, and virulence in C. albicans.
Main Methods:
- Gene identification and allelic analysis of PMT1.
- In vitro enzymatic activity assays for Pmt.
- Phenotypic analysis of pmt1 mutants, including growth rates, cellular aggregation, hyphal morphogenesis, and adherence assays.
- Assessment of antifungal agent susceptibility.
- Analysis of cell wall protein Als1p mobility and chitinase activity.
- Virulence studies in a mouse model of systemic infection.
Main Results:
- pmt1 mutants exhibited defective Pmt enzymatic activity, reduced growth, and cellular aggregation.
- Deficiencies observed included defective hyphal morphogenesis, increased susceptibility to antifungal agents (hygromycin B, G418, clotrimazole, calcofluor white), and reduced adherence to epithelial cells.
- PMT1 deficiency resulted in altered Als1p electrophoretic mobility and increased extracellular chitinase activity.
- Homozygous pmt1 mutants were avirulent, and heterozygous strains showed reduced virulence in a mouse model.
Conclusions:
- Protein O-mannosylation by Pmt proteins is conserved across fungal species, including C. albicans.
- PMT1 is essential for multiple cellular functions in C. albicans, impacting morphogenesis, cell wall integrity, and virulence.
- PMT1 deficiency significantly attenuates the virulence of Candida albicans, highlighting its potential as an antifungal target.