title: Cryptococcus neoformans dual GDP-mannose transporters and their role in biology and virulence.
abstract: Cryptococcus neoformans is an opportunistic yeast responsible for lethal meningoencephalitis in humans. This pathogen elaborates a polysaccharide capsule, which is its major virulence factor. Mannose constitutes over one-half of the capsule mass and is also extensively utilized in cell wall synthesis and in glycosylation of proteins and lipids. The activated mannose donor for most biosynthetic reactions, GDP-mannose, is made in the cytosol, although it is primarily consumed in secretory organelles. This compartmentalization necessitates specific transmembrane transporters to make the donor available for glycan synthesis. We previously identified two cryptococcal GDP-mannose transporters, Gmt1 and Gmt2. Biochemical studies of each protein expressed in Saccharomyces cerevisiae showed that both are functional, with similar kinetics and substrate specificities in vitro. We have now examined these proteins in vivo and demonstrate that cells lacking Gmt1 show significant phenotypic differences from those lacking Gmt2 in terms of growth, colony morphology, protein glycosylation, and capsule phenotypes. Some of these observations may be explained by differential expression of the two genes, but others suggest that the two proteins play overlapping but nonidentical roles in cryptococcal biology. Furthermore, gmt1 gmt2 double mutant cells, which are unexpectedly viable, exhibit severe defects in capsule synthesis and protein glycosylation and are avirulent in mouse models of cryptococcosis.
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Zhuo A
authors.initials: ZA
authors.lastname: Wang
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Cara L
authors.initials: CL
authors.lastname: Griffith
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Skowyra
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Nichole
authors.initials: N
authors.lastname: Salinas
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Williams
authors.affiliation: Center for Genome Sciences, Washington University School of Medicine, St. Louis, Missouri, USA Department of Computer Science, Washington University, St. Louis, Missouri, USA.
authors.forename: Ezekiel J
authors.initials: EJ
authors.lastname: Maier
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Stacey R
authors.initials: SR
authors.lastname: Gish
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, USA Center for Genome Sciences, Washington University School of Medicine, St. Louis, Missouri, USA Department of Computer Science, Washington University, St. Louis, Missouri, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Brent
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA doering@wustl.edu.
authors.forename: Tamara L
authors.initials: TL
authors.lastname: Doering
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003455:Cryptococcus neoformans / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000472:pathogenicity; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D014774:Virulence / Q000235:genetics
chemical_list: D002352:Carrier Proteins; D005656:Fungal Proteins; C428326:GDP-mannose transporter
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