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Eukaryotic Cell, January 2008, p. 58-67, Vol. 7, No. 1
1535-9778/08/$08.00+0 doi:10.1128/EC.00370-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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Laboratório de Estudos Integrados em Bioquímica Microbiana, Departamento de Microbiologia Geral, Instituto de Microbiologia Professor Paulo de Góes, Universidade Federal do Rio de Janeiro, CEP 21941590 Rio de Janeiro, Brazil,1 Department of Biological Sciences, The Border Biomedical Research Center, University of Texas at El Paso, El Paso, Texas 79968-0519,2 Department of Microbiology and Immunology,3 Division of Infectious Diseases, Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, New York 104614
Received 8 October 2007/ Accepted 6 November 2007
Cryptococcus neoformans produces vesicles containing its major virulence factor, the capsular polysaccharide glucuronoxylomannan (GXM). These vesicles cross the cell wall to reach the extracellular space, where the polysaccharide is supposedly used for capsule growth or delivered into host tissues. In the present study, we characterized vesicle morphology and protein composition by a combination of techniques including electron microscopy, proteomics, enzymatic activity, and serological reactivity. Secretory vesicles in C. neoformans appear to be correlated with exosome-like compartments derived from multivesicular bodies. Extracellular vesicles manifested various sizes and morphologies, including electron-lucid membrane bodies and electron-dense vesicles. Seventy-six proteins were identified by proteomic analysis, including several related to virulence and protection against oxidative stress. Biochemical tests indicated laccase and urease activities in vesicles. In addition, different vesicle proteins were recognized by sera from patients with cryptococcosis. These results reveal an efficient and general mechanism of secretion of pathogenesis-related molecules in C. neoformans, suggesting that extracellular vesicles function as "virulence bags" that deliver a concentrated payload of fungal products to host effector cells and tissues.
Published ahead of print on 26 November 2007.
Supplemental material for this article may be found at http://ec.asm.org/.
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