Identification and characterization of the Cryptococcus neoformans phosphomannose isomerase-encoding gene, MAN1, and its impact on pathogenicity

Elizabeth A. Wills, Ian S. Roberts, Maurizio Del Poeta, Johanna Rivera, Arturo Casadevall, Gary M. Cox, John R. Perfect

Research output: Contribution to journalArticle

74 Scopus citations

Abstract

The polysaccharide capsule surrounding Cryptococcus neoformans comprises manose, xylose and glucuronic acid, of which mannose is the major constituent. The GDP-mannose biosynthesis pathway is highly conserved in fungi and consists of three key enzymes: phosphomannose isomerase (PMI), phosphomannomutase (PMM) and GDP-mannose pyrophosphorylase (GMP). The MAN1 gene, encoding for the PMI enzyme, was isolated and sequenced from C. neoformans, and a disruption of the MAN1 gene was generated. One MAN1 disruption mutant, man1, which showed poor capsule formation, reduced polysaccharide secretion and morphological abnormalities, was chosen for virulence studies. In both the rabbit and the mouse models of invasive cryptococcosis, man1 was shown to be severely impaired in its virulence, with complete elimination of the yeast from the host. A reconstituted strain of man1 was constructed using gene replacement at the native locus. The wild-type and reconstituted strains were significantly more virulent than the knock-out mutant in both animal models. Our findings reveal that PMI activity is essential for the survival of C. neoformans in the host. The fact that the man1 mutant was not pathogenic suggests that blocking mannose synthesis could be fungicidal in the mammalian host and thus an excellent target for antifungal drug development.

Original languageEnglish (US)
Pages (from-to)610-620
Number of pages11
JournalMolecular Microbiology
Volume40
Issue number3
DOIs
StatePublished - 2001

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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