Cell wall targeting of laccase of Cryptococcus neoformans during infection of mice

Infect Immun. 2007 Feb;75(2):714-22. doi: 10.1128/IAI.01351-06. Epub 2006 Nov 13.

Abstract

Laccase is a major virulence factor of the pathogenic fungus Cryptococcus neoformans, which afflicts both immunocompetent and immunocompromised individuals. In the present study, laccase was expressed in C. neoformans lac1Delta cells as a fusion protein with an N-terminal green fluorescent protein (GFP) using C. neoformans codon usage. The fusion protein was robustly localized to the cell wall at physiological pH, but it was mislocalized at low pH. Structural analysis of the laccase identified a C-terminal region unique to C. neoformans, and expression studies showed that the region was required for efficient transport to the cell wall both in vitro and during infection of mouse lungs. During infection of mice, adherence to alveolar macrophages was also associated with a partial mislocalization of GFP-laccase within cytosolic vesicles. In addition, recovery of cryptococcal cells from lungs of two strains of mice (CBA/J and Swiss Albino) later in infection was also associated with cytosolic mislocalization, but cells from the brain showed almost exclusive localization to cell walls, suggesting that there was more efficient cell wall targeting during infection of the brain. These data suggest that host cell antifungal defenses may reduce effective cell wall targeting of laccase during infection of the lung but not during infection of the brain, which may contribute to a more predominant role for the enzyme during infection of the brain.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Brain / microbiology
  • Brain Diseases / microbiology
  • Cell Wall / chemistry
  • Cell Wall / enzymology*
  • Central Nervous System Fungal Infections / microbiology*
  • Cryptococcosis / microbiology*
  • Cryptococcosis / physiopathology
  • Cryptococcus neoformans / enzymology*
  • Cryptococcus neoformans / physiology
  • Cytoplasm / enzymology
  • DNA, Fungal / chemistry
  • DNA, Fungal / genetics
  • Green Fluorescent Proteins / analysis
  • Green Fluorescent Proteins / genetics
  • Hydrogen-Ion Concentration
  • Laccase / chemistry
  • Laccase / genetics
  • Laccase / metabolism*
  • Lung / microbiology
  • Lung Diseases, Fungal / microbiology*
  • Macrophages, Alveolar / microbiology
  • Mice
  • Mice, Inbred CBA
  • Molecular Sequence Data
  • Protein Structure, Tertiary
  • Protein Transport
  • Recombinant Fusion Proteins / metabolism
  • Virulence Factors / chemistry
  • Virulence Factors / genetics
  • Virulence Factors / metabolism*

Substances

  • DNA, Fungal
  • Recombinant Fusion Proteins
  • Virulence Factors
  • enhanced green fluorescent protein
  • Green Fluorescent Proteins
  • Laccase

Associated data

  • GENBANK/DQ897640