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Mol Microbiol. 2011 Jul;81(1):206-18. doi: 10.1111/j.1365-2958.2011.07686.x. Epub 2011 May 18.

Role for Golgi reassembly and stacking protein (GRASP) in polysaccharide secretion and fungal virulence.

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Centro de Biotecnologia Departamento de Biologia Molecular e Biotecnologia, Universidade Federal do Rio Grande do Sul, Av Bento Gonçalves 9500, 43421, Caixa Postal 15005, Porto Alegre, RS 91501-970, Brazil.


Secretion of virulence factors is a critical mechanism for the establishment of cryptococcosis, a disease caused by the yeast pathogen Cryptococcus neoformans. One key virulence strategy of C. neoformans is the release of glucuronoxylomannan (GXM), a capsule-associated immune-modulatory polysaccharide that reaches the extracellular space through secretory vesicles. Golgi reassembly and stacking protein (GRASP) is required for unconventional protein secretion mechanisms in different eukaryotic cells, but its role in polysaccharide secretion is unknown. This study demonstrates that a C. neoformans functional mutant of a GRASP orthologue had attenuated virulence in an animal model of cryptococcosis, in comparison with wild-type (WT) and reconstituted cells. Mutant cells manifested altered Golgi morphology, failed to produce typical polysaccharide capsules and showed a reduced ability to secrete GXM both in vitro and during animal infection. Isolation of GXM from cultures of WT, reconstituted or mutant strains revealed that the GRASP orthologue mutant produced polysaccharides with reduced dimensions. The mutant was also more efficiently associated to and killed by macrophages than WT and reconstituted cells. These results demonstrate that GRASP, a protein involved in unconventional protein secretion, is also required for polysaccharide secretion and virulence in C. neoformans.

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