Computational Analysis Reveals a Key Regulator of Cryptococcal Virulence and Determinant of Host Response

Abstract

Cryptococcus neoformans is a ubiquitous, opportunistic fungal pathogen that kills over 600,000 people annually. Here, we report integrated computational and experimental investigations of the role and mechanisms of transcriptional regulation in cryptococcal infection. Major cryptococcal virulence traits include melanin production and the development of a large polysaccharide capsule upon host entry; shed capsule polysaccharides also impair host defenses. We found that both transcription and translation are required for capsule growth and that Usv101 is a master regulator of pathogenesis, regulating melanin production, capsule growth, and capsule shedding. It does this by directly regulating genes encoding glycoactive enzymes and genes encoding three other transcription factors that are essential for capsule growth: GAT201, RIM101, and SP1. Murine infection with cryptococci lacking Usv101 significantly alters the kinetics and pathogenesis of disease, with extended survival and, unexpectedly, death by pneumonia rather than meningitis. Our approaches and findings will inform studies of other pathogenic microbes.

TheCryptococcus neoformansTitan cell is an inducible and regulated morphotype underlying pathogenesis

“…Usv101 is predicted to act in parallel to the cAMP pathway and downstream of the cell cycle regulator Swi6. The interaction between cell cycle and pathogenicity factor expression is an emerging theme in C. neoformans biology: Recent work has also highlighted cell cycle regulation of pathogenicity factors [33] and the cyclin Cln1 has been shown to regulate capsule and melanin, both of which are regulated by cAMP and negatively regulated by Usv101 [31,32,35,39].…”

“…The C 2 H 2 transcription factor Usv101 is a master regulator of C. neoformans pathogenesis that negatively regulates capsule and acts downstream of Swi6, a regulator of cell cycle progression [31][32][33]. Usv101 is additionally predicted to regulate Gpa1 but is not itself directly influenced by cAMP.…”

“…Usv101 is additionally predicted to regulate Gpa1 but is not itself directly influenced by cAMP. Although USV101 has been shown to be dispensable for virulence, murine infection results in delayed dissemination to the brain, and is characterized by pneumonia rather than meningitis [31]. We therefore investigated the role of Usv101 in in vitro Titanisation.…”

“…The gpr4Δ gpr5Δ [42] was kindly provided by Joseph Heitman, Duke University, NC, USA. Strains ric8Δ and usv101Δ were obtained from the Madhani 2015 collection (NIH funding, R01AI100272) from the Fungal Genetics Stock Centre and were validated by PCR and shown to phenotypically match published strains [30,31]. C. gattii R265 [43] was provided by Neil Gow, University of Aberdeen, UK.…”

The Cell Biology of the Trichosporon-Host Interaction

“…Regardless of the fungal species-specific structural characteristics of this pigment, melanization has been demonstrated as a crucial virulence factor during the interaction with the host immune system (Akoumianaki et al, 2016), to confer protection against antifungals (Fernandes et al, 2015) and to regulate capsule formation (Gish et al, 2016). Accordingly, the production of eumelanin from the phenolic precursor L-dihydroxyphenylalanine was described in T. asahii (Figueiredo-Carvalho et al, 2014).…”