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Correspondence (2009)
BibTeX
@MISC{Eisenman09correspondence,
author = {Helene C. Eisenman and Susana Frases and Andre ́ M. Nicola and Marcio L. Rodrigues and Arturo Casadevall and Arturo Casadevall},
title = {Correspondence},
year = {2009}
}
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Abstract
Recently, several pathogenic fungi were shown to produce extracellular vesicles that contain various components associated with virulence. In the human pathogenic fungus Cryptococcus neoformans, these components included laccase, an enzyme that catalyses melanin synthesis. Spherical melanin granules have been observed in the cell wall of C. neoformans. Given that melanin granules have dimensions that are comparable to those of extracellular vesicles, and that metazoan organisms produce melanin in vesicular structures known as melanosomes, we investigated the role of vesicles in cryptococcal melanization. Extracellular vesicles melanized when incubated with the melanin precursor L-3,4-dihydroxyphenylalanine (L-DOPA). The kinetics of substrate incorporation into cells and vesicles was analysed using radiolabelled L-DOPA. The results indicated that substrate incorporation was different for cells and isolated vesicles. Acid-generated melanin ghosts stained with lipophilic dyes, implying the presence of associated lipid. A model for C. neoformans melanization is proposed that accounts for these observations and provides a mechanism for the assembly of melanin into relatively uniform spherical particles stacked in an orderly arrangement in the cell wall.
Keyphrases
extracellular vesicle substrate incorporation cell wall uniform spherical particle human pathogenic fungus cryptococcus neoformans metazoan organism vesicular structure melanin precursor l-3 various component spherical melanin granule neoformans melanization orderly arrangement melanin granule several pathogenic fungi isolated vesicle melanin synthesis cryptococcal melanization radiolabelled l-dopa acid-generated melanin ghost associated lipid lipophilic dye
