CPS1, a homolog of the Streptococcus pneumoniae type 3 polysaccharide synthase gene, is important for the pathobiology of Cryptococcus neoformans

Infect Immun. 2006 Jul;74(7):3930-8. doi: 10.1128/IAI.00089-06.

Abstract

The polysaccharide capsule is known to be the major factor required for the virulence of Cryptococcus neoformans. We have cloned and characterized a gene, designated CPS1, that encodes a protein containing a glycosyltransferase moiety and shares similarity with the type 3 polysaccharide synthase encoded by the cap3B gene of Streptococcus pneumoniae. Cps1p also shares similarity with hyaluronan synthase of higher eukaryotes. Deletion of the CPS1 gene from a serotype D strain of C. neoformans resulted in a slight reduction of the capsule size as observed by using an India ink preparation. The growth at 37 degrees C was impaired, and the ability to associate with human brain endothelial cells in vitro was also significantly reduced by the deletion of CPS1. Using site-specific mutagenesis, we showed that the conserved glycosyltransferase domains are critical for the ability of the strain to grow at elevated temperatures. A hyaluronan enzyme-linked immunosorbent assay method demonstrated that CPS1 is important for the synthesis of hyaluronan or its related polysaccharides in C. neoformans. Comparisons between the wild-type and the cps1Delta strains, using three different transmission electron microscopic methods, indicated that the CPS1 gene product is involved in the composition or maintenance of an electron-dense layer between the outer cell wall and the capsule. These and the virulence studies in a mouse model suggested that the CPS1 gene is important in the pathobiology of C. neoformans.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Intramural

MeSH terms

  • Animals
  • Bacterial Capsules / chemistry
  • Bacterial Capsules / physiology*
  • Brain / blood supply
  • Brain / enzymology
  • Brain / microbiology
  • Cells, Cultured
  • Cryptococcus neoformans / enzymology*
  • Cryptococcus neoformans / genetics*
  • Cryptococcus neoformans / pathogenicity
  • Cryptococcus neoformans / ultrastructure
  • Disease Models, Animal
  • Endothelium, Vascular / enzymology
  • Endothelium, Vascular / microbiology
  • Female
  • Fungal Proteins / chemistry
  • Fungal Proteins / genetics*
  • Fungal Proteins / physiology
  • Glycosyltransferases / chemistry
  • Glycosyltransferases / genetics
  • Glycosyltransferases / physiology*
  • Humans
  • Mice
  • Mice, Inbred BALB C
  • Microcirculation / enzymology
  • Microcirculation / microbiology
  • Molecular Sequence Data
  • Sepsis / microbiology
  • Sepsis / pathology
  • Streptococcus pneumoniae / enzymology*
  • Streptococcus pneumoniae / genetics
  • Virulence

Substances

  • Fungal Proteins
  • Cap3B protein, Streptococcus pneumoniae
  • Glycosyltransferases
  • CPS1 protein, Cryptococcus neoformans
  • type 3 capsular polysaccharide synthase

Associated data

  • GENBANK/AY063511