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Sec6-dependent sorting of fungal extracellular exosomes and laccase of Cryptococcus neoformans |
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| Authors: | John Panepinto Kazimierz Komperda Susana Frases Yoon-Dong Park Julianne T Djordjevic Arturo Casadevall Peter R Williamson |
| Institution: | Section of Infectious Diseases, Department of Medicine, University of Illinois at Chicago College of Medicine, Chicago, IL, USA.; Department of Microbiology and Immunology and Division of Infectious Diseases of the Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA.; Centre for Infectious Diseases and Microbiology, Westmead Millenium Institute, University of Sydney at Westmead Hospital, NSW 2145, Australia.; Jesse Brown VA Medical Center, Chicago, IL, USA. |
| 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 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 . |
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