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

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.

The endosomal sorting complex required for transport machinery influences haem uptake and capsule elaboration in Cryptococcus neoformans

“…We also note that a recent report by Godinho et al . () described an avirulent phenotype for a snf7 mutant of C. neoformans . Overall, we conclude that the ESCRT‐0, ‐I, ‐II and ‐III proteins are required for virulence in mice as well as survival in macrophages.…”

“…However, a role for ESCRT proteins in the secretion of capsular material to influence capsule size is also possible, as suggested by Godinho et al . ().…”

“…We also found that the core ESCRT components play a role in the virulence in C. neoformans . These results confirmed previous virulence assays that revealed that vps23 and snf7 mutants are avirulent in a mouse inhalation model (Hu et al ., ; Godinho et al ., ). Capsule formation and iron acquisition are important for cryptococcal pathogenesis and the defects in these traits may account, in part, for the attenuated virulence of the ESCRT mutants (Kronstad et al ., 2012; 2013; O'Meara and Alspaugh, ).…”

Role of clathrin-mediated endocytosis in the use of heme and hemoglobin by the fungal pathogen Cryptococcus neoformans

“…The ability to use host iron sources, such as heme/hemoglobin and transferrin, is advantageous for the growth and survival of C. neoformans inside a vertebrate host (Jung et al, ). Previous studies have shown key roles for the ESCRT proteins Vps23, Vps22, and Snf7 in the use of heme iron and in the virulence of C. neoformans (Hu et al, ; Godinho et al, ; Hu et al, ). Additionally, a putative hemophore, Cig1, was discovered to be involved in heme binding and uptake and in virulence (Cadieux et al, ).…”

The putative flippase Apt1 is required for intracellular membrane architecture and biosynthesis of polysaccharide and lipids in Cryptococcus neoformans

“…Most of the extracellular molecules in fungi are secreted through non-canonical mechanisms that are regulated at multiple levels. Regulators of non-canonical secretion in fungi include Golgi reassembly and stacking protein (Grasp) [24], sucrose non-fermenting protein 7 (Snf7) [25], and the putative aminophospholipid translocase (flippase) Aptl [26]. …”