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Sec6‐dependent sorting of fungal extracellular exosomes and laccase of Cryptococcus neoformans
Author(s) -
Panepinto John,
Komperda Kazimierz,
Frases Susana,
Park YoonDong,
Djordjevic Julianne T.,
Casadevall Arturo,
Williamson Peter R.
Publication year - 2009
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2008.06588.x
Subject(s) - virulence , biology , cryptococcus neoformans , virulence factor , secretion , microbiology and biotechnology , laccase , extracellular , mutant , microvesicles , biochemistry , enzyme , gene , microrna
Summary 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 i SEC6 strain. In addition, a green fluorescent protein–laccase fusion protein demonstrated aberrant localization within cytoplasmic vesicles in i SEC6 strains. In contrast, i SEC6 strains retained normal growth at 37°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 .