title: CPS1, a homolog of the Streptococcus pneumoniae type 3 polysaccharide synthase gene, is important for the pathobiology of Cryptococcus neoformans.
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.
authors.affiliation: National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Y C
authors.initials: YC
authors.lastname: Chang
authors.forename: A
authors.initials: A
authors.lastname: Jong
authors.forename: S
authors.initials: S
authors.lastname: Huang
authors.forename: P
authors.initials: P
authors.lastname: Zerfas
authors.forename: K J
authors.initials: KJ
authors.lastname: Kwon-Chung
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000737:chemistry / Q000502:physiology*; D001921:Brain / Q000098:blood supply / Q000201:enzymology / Q000382:microbiology; D002478:Cells, Cultured; D003455:Cryptococcus neoformans / Q000201:enzymology* / Q000235:genetics* / Q000472:pathogenicity / Q000648:ultrastructure; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000201:enzymology / Q000382:microbiology; D005260:Female; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D016695:Glycosyltransferases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008833:Microcirculation / Q000201:enzymology / Q000382:microbiology; D008969:Molecular Sequence Data; D018805:Sepsis / Q000382:microbiology / Q000473:pathology; D013296:Streptococcus pneumoniae / Q000201:enzymology* / Q000235:genetics; D014774:Virulence
chemical_list: D005656:Fungal Proteins; C100944:Cap3B protein, Streptococcus pneumoniae; D016695:Glycosyltransferases; C512598:CPS1 protein, Cryptococcus neoformans; C413445:type 3 capsular polysaccharide synthase