Vam6/Vps39/TRAP1‐domain proteins influence vacuolar morphology, iron acquisition and virulence in Cryptococcus neoformans

2021 ◽  
Author(s):  
Guanggan Hu ◽  
Erik Bakkeren ◽  
Mélissa Caza ◽  
Linda Horianopoulos ◽  
Eddy Sánchez‐León ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Iron Acquisition

scholarly journals Cryptococcus neoformans Requires the ESCRT Protein Vps23 for Iron Acquisition from Heme, for Capsule Formation, and for Virulence

2012 ◽  
Vol 81 (1) ◽  
pp. 292-302 ◽  
Author(s):  
Guanggan Hu ◽  
Mélissa Caza ◽  
Brigitte Cadieux ◽  
Vivienne Chan ◽  
Victor Liu ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Virulence Factor ◽  
Fungal Pathogens ◽  
Capsular Polysaccharide ◽  
Iron Acquisition ◽  
Growth Defect ◽  
Capsule Formation ◽  
Content Type ◽  
Dna Insertion ◽  
Essential Nutrient

Iron availability is a key regulator of virulence factor elaboration inCryptococcus neoformans, the causative agent of fungal meningoencephalitis in HIV/AIDS patients. In addition, iron is an essential nutrient for pathogen proliferation in mammalian hosts but little is known about the mechanisms of iron sensing and uptake in fungal pathogens that attack humans. In this study, we mutagenizedC. neoformansbyAgrobacterium-mediated T-DNA insertion and screened for mutants with reduced growth on heme as the sole iron source. Among 34 mutants, we identified a subset with insertions in the gene for the ESCRT-I (endosomalsortingcomplexrequired fortransport) protein Vps23 that resulted in a growth defect on heme, presumably due to a defect in uptake via endocytosis or misregulation of iron acquisition from heme. Remarkably,vps23mutants were also defective in the elaboration of the cell-associated capsular polysaccharide that is a major virulence factor, while overexpression ofVps23resulted in cells with a slightly enlarged capsule. These phenotypes were mirrored by a virulence defect in thevps23mutant in a mouse model of cryptococcosis and by hypervirulence of the overexpression strain. Overall, these results reveal an important role for trafficking via ESCRT functions in both heme uptake and capsule formation, and they further reinforce the connection between iron and virulence factor deployment inC. neoformans.

scholarly journals The Mannoprotein Cig1 Supports Iron Acquisition From Heme and Virulence in the Pathogenic Fungus Cryptococcus neoformans

2013 ◽  
Vol 207 (8) ◽  
pp. 1339-1347 ◽  
Author(s):  
Brigitte Cadieux ◽  
Tianshun Lian ◽  
Guanggan Hu ◽  
Joyce Wang ◽  
Carmelo Biondo ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Iron Acquisition ◽  
Pathogenic Fungus

scholarly journals Role of Ferric Reductases in Iron Acquisition and Virulence in the Fungal Pathogen Cryptococcus neoformans

2013 ◽  
Vol 82 (2) ◽  
pp. 839-850 ◽  
Author(s):  
Sanjay Saikia ◽  
Debora Oliveira ◽  
Guanggan Hu ◽  
James Kronstad
Keyword(s):  
Cryptococcus Neoformans ◽  
Iron Acquisition ◽  
Antifungal Drugs ◽  
Growth Defect ◽  
Uptake System ◽  
Ferric Reductase ◽  
Pathogenic Yeast ◽  
Content Type ◽  
High Affinity ◽  
Cryptococcal Disease

ABSTRACTIron acquisition is critical for the ability of the pathogenic yeastCryptococcus neoformansto cause disease in vertebrate hosts. In particular, iron overload exacerbates cryptococcal disease in an animal model, defects in iron acquisition attenuate virulence, and iron availability influences the expression of major virulence factors.C. neoformansacquires iron by multiple mechanisms, including a ferroxidase-permease high-affinity system, siderophore uptake, and utilization of both heme and transferrin. In this study, we examined the expression of eight candidate ferric reductase genes and their contributions to iron acquisition as well as to ferric and cupric reductase activities. We found that loss of theFRE4gene resulted in a defect in production of the virulence factor melanin and increased susceptibility to azole antifungal drugs. In addition, theFRE2gene was important for growth on the iron sources heme and transferrin, which are relevant for proliferation in the host. Fre2 may participate with the ferroxidase Cfo1 of the high-affinity uptake system for growth on heme, because a mutant lacking both genes showed a more pronounced growth defect than thefre2single mutant. A role for Fre2 in iron acquisition is consistent with the attenuation of virulence observed for thefre2mutant. This mutant also was defective in accumulation in the brains of infected mice, a phenotype previously observed for mutants with defects in high-affinity iron uptake (e.g., thecfo1mutant). Overall, this study provides a more detailed view of the iron acquisition components required forC. neoformansto cause cryptococcosis.

scholarly journals A Transcriptional Regulatory Map of Iron Homeostasis Reveals a New Control Circuit for Capsule Formation in Cryptococcus neoformans

Genetics ◽  
2020 ◽  
Vol 215 (4) ◽  
pp. 1171-1189
Author(s):  
Eunsoo Do ◽  
Yong-Joon Cho ◽  
Donghyeun Kim ◽  
James W. Kronstad ◽  
Won Hee Jung
Keyword(s):  
Transcription Factors ◽  
Cryptococcus Neoformans ◽  
Regulatory Networks ◽  
Target Genes ◽  
Iron Acquisition ◽  
Transcriptional Networks ◽  
Iron Availability ◽  
Capsule Formation ◽  
Transcriptional Regulatory ◽  
Biochemical Analyses

Iron is essential for the growth of the human fungal pathogen Cryptococcus neoformans within the vertebrate host, and iron sensing contributes to the elaboration of key virulence factors, including the formation of the polysaccharide capsule. C. neoformans employs sophisticated iron acquisition and utilization systems governed by the transcription factors Cir1 and HapX. However, the details of the transcriptional regulatory networks that are governed by these transcription factors and connections to virulence remain to be defined. Here, we used chromatin immunoprecipitation followed by next-generation sequencing (ChIP-seq) and transcriptome analysis (RNA-seq) to identify genes directly regulated by Cir1 and/or HapX in response to iron availability. Overall, 40 and 100 genes were directly regulated by Cir1, and 171 and 12 genes were directly regulated by HapX, under iron-limited and replete conditions, respectively. More specifically, we found that Cir1 directly controls the expression of genes required for iron acquisition and metabolism, and indirectly governs capsule formation by regulating specific protein kinases, a regulatory connection not previously revealed. HapX regulates the genes responsible for iron-dependent pathways, particularly under iron-depleted conditions. By analyzing target genes directly bound by Cir1 and HapX, we predicted the binding motifs for the transcription factors and verified that the purified proteins bind these motifs in vitro. Furthermore, several direct target genes were coordinately and reciprocally regulated by Cir1 and HapX, suggesting that these transcription factors play conserved roles in the response to iron availability. In addition, biochemical analyses revealed that Cir1 and HapX are iron-containing proteins, implying that the regulatory networks of Cir1 and HapX may be influenced by the incorporation of iron into these proteins. Taken together, our identification of the genome-wide transcriptional networks provides a detailed understanding of the iron-related regulatory landscape, establishes a new connection between Cir1 and kinases that regulate capsule, and underpins genetic and biochemical analyses that reveal iron-sensing mechanisms for Cir1 and HapX in C. neoformans.

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