title: Sec6-dependent sorting of fungal extracellular exosomes and laccase of Cryptococcus neoformans.
abstract: The cell wall of pathogenic fungi such as Cryptococcus neoformans, provides a formidable barrier to secrete virulence factors that produce host cell damage. To study secretion of virulence factors to the cell periphery, sec6 RNAi mutant strains of C. neoformans were tested for virulence factor expression. The studies reported here show that SEC6 RNAi mutant strains were defective in a number of virulence factors including laccase, urease as well as soluble polysaccharide and demonstrated attenuated virulence in mice. Further analysis by transmission electron microscopy detected the production of abundant extracellular exosomes in wild-type strains containing empty plasmid, but a complete absence in the iSEC6 strain. In addition, a green fluorescent protein-laccase fusion protein demonstrated aberrant localization within cytoplasmic vesicles in iSEC6 strains. In contrast, iSEC6 strains retained normal growth at 37 degrees C, as well as substantially normal capsule formation, phospholipase activity and total secreted protein. These results provide the first molecular evidence for the existence of fungal exosomes and associate these vesicles with the virulence of C. neoformans.
authors.affiliation: Section of Infectious Diseases, Department of Medicine, University of Illinois at Chicago College of Medicine, Chicago, IL, USA.
authors.forename: John
authors.initials: J
authors.lastname: Panepinto
authors.forename: Kazimierz
authors.initials: K
authors.lastname: Komperda
authors.forename: Susana
authors.initials: S
authors.lastname: Frases
authors.forename: Yoon-Dong
authors.initials: YD
authors.lastname: Park
authors.forename: Julianne T
authors.initials: JT
authors.lastname: Djordjevic
authors.forename: Arturo
authors.initials: A
authors.lastname: Casadevall
authors.forename: Peter R
authors.initials: PR
authors.lastname: Williamson
mesh_terms: D000818:Animals; D002473:Cell Wall / Q000378:metabolism; D003455:Cryptococcus neoformans / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D055354:Exosomes / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D005816:Genetic Complementation Test; D042845:Laccase / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D034622:RNA Interference; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D014510:Urease / Q000378:metabolism; D014774:Virulence; D037521:Virulence Factors / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D037521:Virulence Factors; D042845:Laccase; D014510:Urease