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The vacuolar-sorting protein Snf7 is required for export of virulence determinants in members of the Cryptococcus neoformans complex.

Godinho RM, Crestani J, Kmetzsch L, Araujo Gde S, Frases S, Staats CC, Schrank A, Vainstein MH, Rodrigues ML - Sci Rep (2014)

Bottom Line: Proteins of the endosomal sorting complex required for transport (ESCRT) have been recently associated with polysaccharide export in the yeast-like human pathogen Cryptococcus neoformans.Lack of Snf7 resulted in important alterations in polysaccharide secretion, capsular formation and pigmentation.Our data support the notion that Snf7 expression regulates virulence in C. neoformans and C. gattii by ablating polysaccharide and melanin traffic.

View Article: PubMed Central - PubMed

Affiliation: 1] Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21941-902, Rio de Janeiro, Brazil [2].

ABSTRACT
Fungal pathogenesis requires a number of extracellularly released virulence factors. Recent studies demonstrating that most fungal extracellular molecules lack secretory tags suggest that unconventional secretion mechanisms and fungal virulence are strictly connected. Proteins of the endosomal sorting complex required for transport (ESCRT) have been recently associated with polysaccharide export in the yeast-like human pathogen Cryptococcus neoformans. Snf7 is a key ESCRT operator required for unconventional secretion in Eukaryotes. In this study we generated snf7Δ mutant strains of C. neoformans and its sibling species C. gattii. Lack of Snf7 resulted in important alterations in polysaccharide secretion, capsular formation and pigmentation. This phenotype culminated with loss of virulence in an intranasal model of murine infection in both species. Our data support the notion that Snf7 expression regulates virulence in C. neoformans and C. gattii by ablating polysaccharide and melanin traffic. These results are in agreement with the observation that unconventional secretion is essential for cryptococcal pathogenesis and strongly suggest the occurrence of still obscure mechanisms of exportation of non-protein molecules in Eukaryotes.

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Cryptococcal virulence is affected by SNF7 disruption.Mortality rates of mice lethally infected with wild type (WT), mutant (snf7Δ) and complemented (snf7Δ::SNF7) strains of C. neoformans (A) and C. gattii (B) were monitored daily. SNF7 deletion was associated with a non-virulent phenotype in both cryptococcal species. Determination of GXM concentration (black bars) and lung CFU counts (grey bars) in the lungs of mice infected with wild type (CN-WT) and mutant (CN-snf7Δ) cells (C) revealed defective polysaccharide production and reduced survival of the mutant (**, p = 0.0017; ***, p < 0.0001).
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f6: Cryptococcal virulence is affected by SNF7 disruption.Mortality rates of mice lethally infected with wild type (WT), mutant (snf7Δ) and complemented (snf7Δ::SNF7) strains of C. neoformans (A) and C. gattii (B) were monitored daily. SNF7 deletion was associated with a non-virulent phenotype in both cryptococcal species. Determination of GXM concentration (black bars) and lung CFU counts (grey bars) in the lungs of mice infected with wild type (CN-WT) and mutant (CN-snf7Δ) cells (C) revealed defective polysaccharide production and reduced survival of the mutant (**, p = 0.0017; ***, p < 0.0001).

Mentions: The involvement of Snf7 in melanization, polysaccharide secretion and capsule assembly was in agreement with the possibility that SNF7 deletion could affect pathogenesis. To address this question, mice were infected intranasally with each strain used in this work for mortality assessment. The totality of animals infected with wild type and CN-snf7Δ::SNF7 reconstituted strains died by day 14 post infection (Figure 6A). Infection of mice with the CN-snf7Δ strain, however, resulted in nearly 63% survival at day 40-post infection, when animals were sacrificed. Animals infected with the C. gattiisnf7Δ mutant had a survival rate of 87.5% by day 40 (Figure 6B). Mice infected with parental and complemented strains of C. gattii died by days 18 and 29, respectively. Statistical analysis (Mantel-Cox test) confirmed that C. neoformans (p = 0.0065) and C. gattii (p = 0.0008) cells lacking Snf7 were less efficient than parental and complemented strains in killing mice.


The vacuolar-sorting protein Snf7 is required for export of virulence determinants in members of the Cryptococcus neoformans complex.

Godinho RM, Crestani J, Kmetzsch L, Araujo Gde S, Frases S, Staats CC, Schrank A, Vainstein MH, Rodrigues ML - Sci Rep (2014)

Cryptococcal virulence is affected by SNF7 disruption.Mortality rates of mice lethally infected with wild type (WT), mutant (snf7Δ) and complemented (snf7Δ::SNF7) strains of C. neoformans (A) and C. gattii (B) were monitored daily. SNF7 deletion was associated with a non-virulent phenotype in both cryptococcal species. Determination of GXM concentration (black bars) and lung CFU counts (grey bars) in the lungs of mice infected with wild type (CN-WT) and mutant (CN-snf7Δ) cells (C) revealed defective polysaccharide production and reduced survival of the mutant (**, p = 0.0017; ***, p < 0.0001).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4151102&req=5

f6: Cryptococcal virulence is affected by SNF7 disruption.Mortality rates of mice lethally infected with wild type (WT), mutant (snf7Δ) and complemented (snf7Δ::SNF7) strains of C. neoformans (A) and C. gattii (B) were monitored daily. SNF7 deletion was associated with a non-virulent phenotype in both cryptococcal species. Determination of GXM concentration (black bars) and lung CFU counts (grey bars) in the lungs of mice infected with wild type (CN-WT) and mutant (CN-snf7Δ) cells (C) revealed defective polysaccharide production and reduced survival of the mutant (**, p = 0.0017; ***, p < 0.0001).
Mentions: The involvement of Snf7 in melanization, polysaccharide secretion and capsule assembly was in agreement with the possibility that SNF7 deletion could affect pathogenesis. To address this question, mice were infected intranasally with each strain used in this work for mortality assessment. The totality of animals infected with wild type and CN-snf7Δ::SNF7 reconstituted strains died by day 14 post infection (Figure 6A). Infection of mice with the CN-snf7Δ strain, however, resulted in nearly 63% survival at day 40-post infection, when animals were sacrificed. Animals infected with the C. gattiisnf7Δ mutant had a survival rate of 87.5% by day 40 (Figure 6B). Mice infected with parental and complemented strains of C. gattii died by days 18 and 29, respectively. Statistical analysis (Mantel-Cox test) confirmed that C. neoformans (p = 0.0065) and C. gattii (p = 0.0008) cells lacking Snf7 were less efficient than parental and complemented strains in killing mice.

Bottom Line: Proteins of the endosomal sorting complex required for transport (ESCRT) have been recently associated with polysaccharide export in the yeast-like human pathogen Cryptococcus neoformans.Lack of Snf7 resulted in important alterations in polysaccharide secretion, capsular formation and pigmentation.Our data support the notion that Snf7 expression regulates virulence in C. neoformans and C. gattii by ablating polysaccharide and melanin traffic.

View Article: PubMed Central - PubMed

Affiliation: 1] Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21941-902, Rio de Janeiro, Brazil [2].

ABSTRACT
Fungal pathogenesis requires a number of extracellularly released virulence factors. Recent studies demonstrating that most fungal extracellular molecules lack secretory tags suggest that unconventional secretion mechanisms and fungal virulence are strictly connected. Proteins of the endosomal sorting complex required for transport (ESCRT) have been recently associated with polysaccharide export in the yeast-like human pathogen Cryptococcus neoformans. Snf7 is a key ESCRT operator required for unconventional secretion in Eukaryotes. In this study we generated snf7Δ mutant strains of C. neoformans and its sibling species C. gattii. Lack of Snf7 resulted in important alterations in polysaccharide secretion, capsular formation and pigmentation. This phenotype culminated with loss of virulence in an intranasal model of murine infection in both species. Our data support the notion that Snf7 expression regulates virulence in C. neoformans and C. gattii by ablating polysaccharide and melanin traffic. These results are in agreement with the observation that unconventional secretion is essential for cryptococcal pathogenesis and strongly suggest the occurrence of still obscure mechanisms of exportation of non-protein molecules in Eukaryotes.

Show MeSH
Related in: MedlinePlus