scholarly journals Iron Acquisition from Transferrin by Candida albicans Depends on the Reductive Pathway

2005 ◽  
Vol 73 (9) ◽  
pp. 5482-5492 ◽  
Author(s):  
Simon A. B. Knight ◽  
Gaston Vilaire ◽  
Emmanuel Lesuisse ◽  
Andrew Dancis
Keyword(s):  
Candida Albicans ◽  
Iron Uptake ◽  
Iron Reduction ◽  
Reductase Activity ◽  
Iron Acquisition ◽  
Systemic Infection ◽  
Infection Model ◽  
Cell Contact ◽  
Dialysis Bag ◽  
Reductive Pathway

ABSTRACT Host-pathogen interactions that alter virulence are influenced by critical nutrients such as iron. In humans, free iron is unavailable, being present only in high-affinity iron binding proteins such as transferrin. The fungal pathogen Candida albicans grows as a saprophyte on mucosal surfaces. Occasionally it invades systemically, and in this circumstance it will encounter transferrin iron. Here we report that C. albicans is able to acquire iron from transferrin. Iron-loaded transferrin restored growth to cultures arrested by iron deprivation, whereas apotransferrin was unable to promote growth. By using congenic strains, we have been able to show that iron uptake by C. albicans from transferrin was mediated by the reductive pathway (via FTR1). The genetically separate siderophore and heme uptake systems were not involved. FRE10 was required for a surface reductase activity and for efficient transferrin iron uptake activity in unbuffered medium. Other reductase genes were apparently up-regulated in medium buffered at pH 6.3 to 6.4, and the fre10 −/− mutant had no effect under these conditions. Experiments in which transferrin was sequestered in a dialysis bag demonstrated that cell contact with the substrate was required for iron reduction and release. The requirement of FTR1 for virulence in a systemic infection model and its role in transferrin iron uptake raise the possibility that transferrin is a source of iron during systemic C. albicans infections.

scholarly journals Identification and Characterization of TUP1-Regulated Genes in Candida albicans

Genetics ◽  
2000 ◽  
Vol 156 (1) ◽  
pp. 31-44 ◽  
Author(s):  
Burkhard R Braun ◽  
W Steven Head ◽  
Ming X Wang ◽  
Alexander D Johnson
Keyword(s):  
Candida Albicans ◽  
Systemic Infection ◽  
Subtractive Hybridization ◽  
Filamentous Growth ◽  
Surface Proteins ◽  
Infection Model ◽  
Ferric Reductase ◽  
Pathogenesis Related Protein ◽  
Plant Pathogenesis ◽  
Rnase T2

Abstract TUP1 encodes a transcriptional repressor that negatively controls filamentous growth in Candida albicans. Using subtractive hybridization, we identified six genes, termed repressed by TUP1 (RBT), whose expression is regulated by TUP1. One of the genes (HWP1) has previously been characterized, and a seventh TUP1-repressed gene (WAP1) was recovered due to its high similarity to RBT5. These genes all encode secreted or cell surface proteins, and four out of the seven (HWP1, RBT1, RBT5, and WAP1) encode putatively GPI-modified cell wall proteins. The remaining three, RBT2, RBT4, and RBT7, encode, respectively, an apparent ferric reductase, a plant pathogenesis-related protein (PR-1), and a putative secreted RNase T2. The expression of RBT1, RBT4, RBT5, HWP1, and WAP1 was induced in wild-type cells during the switch from the yeast form to filamentous growth, indicating the importance of TUP1 in regulating this process and implicating the RBTs in hyphal-specific functions. We produced knockout strains in C. albicans for RBT1, RBT2, RBT4, RBT5, and WAP1 and detected no phenotypes on several laboratory media. However, two animal models for C. albicans infection, a rabbit cornea model and a mouse systemic infection model, revealed that rbt1Δ and rbt4Δ strains had significantly reduced virulence. TUP1 appears, therefore, to regulate many genes in C. albicans, a significant fraction of which are induced during filamentous growth, and some of which participate in pathogenesis.

scholarly journals The fission yeast ferric reductase gene frp1+ is required for ferric iron uptake and encodes a protein that is homologous to the gp91-phox subunit of the human NADPH phagocyte oxidoreductase

1993 ◽  
Vol 13 (7) ◽  
pp. 4342-4350
Author(s):  
D G Roman ◽  
A Dancis ◽  
G J Anderson ◽  
R D Klausner
Keyword(s):  
Fission Yeast ◽  
Iron Uptake ◽  
Ferric Iron ◽  
Reductase Activity ◽  
Iron Acquisition ◽  
Protein A ◽  
Mutant Gene ◽  
Predicted Amino Acid Sequence ◽  
Mrna Levels ◽  
Ferric Reductase

We have identified a cell surface ferric reductase activity in the fission yeast Schizosaccharomyces pombe. A mutant strain deficient in this activity was also deficient in ferric iron uptake, while ferrous iron uptake was not impaired. Therefore, reduction is a required step in cellular ferric iron acquisition. We have cloned frp1+, the wild-type allele of the mutant gene. frp1+ mRNA levels were repressed by iron addition to the growth medium. Fusion of 138 nucleotides of frp1+ promoter sequences to a reporter gene, the bacterial chloramphenicol acetyltransferase gene, conferred iron-dependent regulation upon the latter when introduced into S. pombe. The predicted amino acid sequence of the frp1+ gene exhibits hydrophobic regions compatible with transmembrane domains. It shows similarity to the Saccharomyces cerevisiae FRE1 gene product and the gp91-phox protein, a component of the human NADPH phagocyte oxidoreductase that is deficient in X-linked chronic granulomatous disease.

Role of the high-affinity reductive iron acquisition pathway of Candida albicans in prostaglandin E2 production, virulence, and interaction with Pseudomonas aeruginosa

2021 ◽  
Author(s):  
Bonang M Mochochoko ◽  
Obinna T Ezeokoli ◽  
Olihile Sebolai ◽  
Jacobus Albertyn ◽  
Carolina H Pohl
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Candida Albicans ◽  
Prostaglandin E2 ◽  
Biofilm Formation ◽  
Iron Uptake ◽  
Iron Homeostasis ◽  
Pge2 Production ◽  
Oxidase Gene ◽  
Reductive Pathway

Abstract Components of the iron reductive pathway of Candida albicans have been implicated in the production of prostaglandin E2 (PGE2) and virulence. However, it is unknown whether other components of this pathway influence PGE2. We investigated the role of the iron reductive pathway of C. albicans in biofilm formation, PGE2 production, and virulence in Caenorhabditis elegans. Additionally, as the co-occurrence of C. albicans and Pseudomonas aeruginosa in host tissues is frequent and involves competition for host-associated iron, we examined the effects of this interaction. Deletion of multicopper oxidase gene, FET99, and iron permease genes, FTH1 and FTH2, affected biofilm metabolic activity, and for the FTH2 mutant, also biofilm morphology. Deletion of CCC1 (vacuolar iron transporter) and CCC2 (P-type ATPase copper importer) also influenced biofilm morphology. For PGE2 production, deletion of FET99, FTH1, FTH2, CCC1, and CCC2 caused a significant reduction by monomicrobial biofilms, while FTH2deletion caused the highest reduction in polymicrobial biofilms. URA3 positive mutants of FET99 and FTH2 demonstrated attenuated virulence in C. elegans, potentially due to the inability of mutants to form hyphae in vivo. Deductively, the role of the iron reductive pathway in PGE2 synthesis is indirect, possibly due to their role in iron homeostasis. Lay Summary Iron uptake is vital for disease-causing microbes like Candida albicans. Using strains deficient in some iron-uptake genes, we show that iron-uptake genes, especially FET99 and FTH2, play a role in biofilm formation, prostaglandin production, and virulence in the nematode infection model.

scholarly journals The fission yeast ferric reductase gene frp1+ is required for ferric iron uptake and encodes a protein that is homologous to the gp91-phox subunit of the human NADPH phagocyte oxidoreductase.

1993 ◽  
Vol 13 (7) ◽  
pp. 4342-4350 ◽  
Author(s):  
D G Roman ◽  
A Dancis ◽  
G J Anderson ◽  
R D Klausner
Keyword(s):  
Fission Yeast ◽  
Iron Uptake ◽  
Ferric Iron ◽  
Reductase Activity ◽  
Iron Acquisition ◽  
Protein A ◽  
Mutant Gene ◽  
Predicted Amino Acid Sequence ◽  
Mrna Levels ◽  
Ferric Reductase

We have identified a cell surface ferric reductase activity in the fission yeast Schizosaccharomyces pombe. A mutant strain deficient in this activity was also deficient in ferric iron uptake, while ferrous iron uptake was not impaired. Therefore, reduction is a required step in cellular ferric iron acquisition. We have cloned frp1+, the wild-type allele of the mutant gene. frp1+ mRNA levels were repressed by iron addition to the growth medium. Fusion of 138 nucleotides of frp1+ promoter sequences to a reporter gene, the bacterial chloramphenicol acetyltransferase gene, conferred iron-dependent regulation upon the latter when introduced into S. pombe. The predicted amino acid sequence of the frp1+ gene exhibits hydrophobic regions compatible with transmembrane domains. It shows similarity to the Saccharomyces cerevisiae FRE1 gene product and the gp91-phox protein, a component of the human NADPH phagocyte oxidoreductase that is deficient in X-linked chronic granulomatous disease.

scholarly journals Antifungal Activity of Mammalian Serum Amyloid A1 against Candida albicans

2019 ◽  
Vol 64 (1) ◽  
Author(s):  
Jiao Gong ◽  
Jun Wu ◽  
Melanie Ikeh ◽  
Li Tao ◽  
Yulong Zhang ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Antifungal Activity ◽  
Membrane Integrity ◽  
Systemic Infection ◽  
Serum Amyloid ◽  
Infection Model ◽  
Fungal Cell ◽  
Content Type ◽  
Cell Membrane Integrity ◽  
Amyloid A

ABSTRACT Mammalian serum amyloid A (SAA) is a major acute phase protein that shows a massive increase in plasma concentration during inflammation. In the present study, we demonstrate that the expression of mouse SAA1 in serum was increased when infected with Candida albicans, a major human fungal pathogen, in a systemic infection model. We then set out to investigate the antifungal activity of SAA proteins against C. albicans. Recombinant human and mouse SAA1 (rhSAA1 and rmSAA1) were expressed and purified in Escherichia coli. Both rhSAA1 and rmSAA1 exhibited a potent antifungal activity against C. albicans. We further demonstrate that rhSAA1 binds to the cell surface of C. albicans, disrupts cell membrane integrity, and induces rapid fungal cell death in C. albicans. Our finding expands the known functions of SAA1 and provides new insight into host-Candida interactions during fungal infection.

scholarly journals Deletion of the SKO1 Gene in a hog1 Mutant Reverts Virulence in Candida albicans

2019 ◽  
Vol 5 (4) ◽  
pp. 107
Author(s):  
Verónica Urrialde ◽  
Daniel Prieto ◽  
Susana Hidalgo-Vico ◽  
Elvira Román ◽  
Jesús Pla ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Intestinal Tract ◽  
Galleria Mellonella ◽  
Ex Vivo ◽  
Mutant Cell ◽  
Systemic Infection ◽  
Infection Model ◽  
Relevant Role

Candida albicans displays the ability to adapt to a wide variety of environmental conditions, triggering signaling pathways and transcriptional regulation. Sko1 is a transcription factor that was previously involved in early hypoxic response, cell wall remodeling, and stress response. In the present work, the role of sko1 mutant in in vivo and ex vivo studies was explored. The sko1 mutant behaved as its parental wild type strain regarding the ability to colonize murine intestinal tract, ex vivo adhesion to murine gut epithelium, or systemic virulence. These observations suggest that Sko1 is expendable during commensalism or pathogenesis. Nevertheless, the study of the hog1 sko1 double mutant showed unexpected phenotypes. Previous researches reported that the deletion of the HOG1 gene led to avirulent C. albicans mutant cell, which was, therefore, unable to establish as a commensal in a gastrointestinal murine model. Here, we show that the deletion of sko1 in a hog1 background reverted the virulence of the hog1 mutant in a systemic infection model in Galleria mellonella larvae and slightly improved the ability to colonize the murine gut in a commensalism animal model compared to the hog1 mutant. These results indicate that Sko1 acts as a repressor of virulence related genes, concluding that Sko1 plays a relevant role during commensalism and systemic infection.

scholarly journals Characterization of MtsR, a New Metal Regulator in Group A Streptococcus, Involved in Iron Acquisition and Virulence

2005 ◽  
Vol 73 (9) ◽  
pp. 5743-5753 ◽  
Author(s):  
Christopher S. Bates ◽  
Chadia Toukoki ◽  
Melody N. Neely ◽  
Zehava Eichenbaum
Keyword(s):  
Iron Uptake ◽  
Iron Homeostasis ◽  
Group A Streptococcus ◽  
Iron Acquisition ◽  
Regulatory Protein ◽  
Infection Model ◽  
Complete Medium ◽  
Dependent Manner ◽  
Metal Levels ◽  
Group A

ABSTRACT Group A streptococcus (GAS) is a common pathogen of the human skin and mucosal surfaces capable of producing a variety of diseases. In this study, we investigated regulation of iron uptake in GAS and the role of a putative transcriptional regulator named MtsR (for Mts repressor) with homology to the DtxR family of metal-dependent regulatory proteins. An mtsR mutant was constructed in NZ131 (M49 serotype) and analyzed. Western blot and RNA analysis showed that mtsR inactivation results in constitutive transcription of the sia (streptococcal iron acquisition) operon, which was negatively regulated by iron in the parent strain. A recombinant MtsR with C-terminal His6 tag fusion (rMtsR) was cloned and purified. Electrophoretic mobility gel shift assays demonstrated that rMtsR specifically binds to the sia promoter region in an iron- and manganese-dependent manner. Together, these observations indicate that MtsR directly represses the sia operon during cell growth under conditions of high metal levels. Consistent with deregulation of iron uptake, the mtsR mutant is hypersensitive to streptonigrin and hydrogen peroxide, and 55Fe uptake assays demonstrate that it accumulates 80% ± 22.5% more iron than the wild-type strain during growth in complete medium. Studies with a zebrafish infection model revealed that the mtsR mutant is attenuated for virulence in both the intramuscular and the intraperitoneal routes. In conclusion, MtsR, a new regulatory protein in GAS, controls iron homeostasis and has a role in disease production.

High stability ferric chelates result in decreased iron uptake by the green alga Chlorella kessleri owing to decreased ferric reductase activity and chelation of ferrous iron

Botany ◽  
2009 ◽  
Vol 87 (10) ◽  
pp. 922-931 ◽  
Author(s):  
Harold G. Weger ◽  
Jackie Lam ◽  
Nikki L. Wirtz ◽  
Crystal N. Walker ◽  
Ron G. Treble
Keyword(s):  
Stability Constant ◽  
Green Alga ◽  
Iron Uptake ◽  
High Stability ◽  
Reductase Activity ◽  
Iron Acquisition ◽  
Free Form ◽  
Ferric Reductase ◽  
Chlorella Kessleri ◽  
Green Alga Chlorella

Cells of the green alga Chlorella kessleri Fott et Nováková use a reductive mechanism for iron acquisition. Iron-limited cells acquired iron more rapidly from a chelator with a lower stability constant for Fe3+ (hydroxyethylethylenediaminetriacetic acid (HEDTA)) than from a chelator with a higher stability constant (N,N′-di[2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid (HBED)). Furthermore, iron uptake rates decreased with increasing chelator concentrations at constant iron concentration. The negative effects of elevated HBED levels on iron uptake could be partly alleviated by the addition of Ga3+, which suggests that iron-free chelator has a negative effect on iron acquisition by competing for Fe2+ with the ferrous transport system. Furthermore, ferric reductase activity progressively decreased with increasing concentrations of both chelators (in the iron-free form). This effect was not alleviated by Ga3+ addition and was apparently caused by the direct inhibition of the reductase. Overall, we conclude that chelators with high stability constants for Fe3+ decrease iron acquisition rates by Strategy I organisms via three separate mechanisms.

scholarly journals The pH of the Host Niche Controls Gene Expression in and Virulence of Candida albicans

1998 ◽  
Vol 66 (7) ◽  
pp. 3317-3325 ◽  
Author(s):  
Flavia De Bernardis ◽  
Fritz A. Mühlschlegel ◽  
Antonio Cassone ◽  
William A. Fonzi
Keyword(s):  
Candida Albicans ◽  
Gene Dosage ◽  
Systemic Infection ◽  
Infection Model ◽  
Null Mutant ◽  
Vaginal Infection ◽  
Pathogenic Potential ◽  
Hyphal Development ◽  
Virulence Phenotype

ABSTRACT Little is known of the biological attributes conferring pathogenicity on the opportunistic fungal pathogen Candida albicans. Infection by this pathogen, as for bacterial pathogens, may rely upon environmental signals within the host niche to regulate the expression of virulence determinants. To determine if C. albicans responds to the pH of the host niche, we tested the virulence of strains with mutations in either of two pH-regulated genes, PHR1 and PHR2. In vitro,PHR1 is expressed when the ambient pH is at 5.5 or higher and deletion of the gene results in growth and morphological defects at neutral to alkaline pHs. Conversely, PHR2 is expressed at an ambient pH below 5.5, and the growth and morphology of the null mutant is compromised below this pH. A PHR1 null mutant was avirulent in a mouse model of systemic infection but uncompromised in its ability to cause vaginal infection in rats. Since systemic pH is near neutrality and vaginal pH is around 4.5, the virulence phenotype paralleled the pH dependence of the in vitro phenotypes. The virulence phenotype of a PHR2 null mutant was the inverse. The mutant was virulent in a systemic-infection model but avirulent in a vaginal-infection model. Heterozygous mutants exhibited partial reductions in their pathogenic potential, suggesting a gene dosage effect. Unexpectedly, deletion of PHR2 did not prevent hyphal development in vaginal tissue, suggesting that it is not essential for hyphal development in this host niche. The results suggest that the pH of the infection site regulates the expression of genes essential to survival within that niche. This implies that the study of environmentally regulated genes may provide a rationale for understanding the pathobiology of C. albicans.

scholarly journals Inactivation of Sterol Δ5,6-Desaturase Attenuates Virulence in Candida albicans

2005 ◽  
Vol 49 (9) ◽  
pp. 3646-3651 ◽  
Author(s):  
Andrew S. Chau ◽  
Maya Gurnani ◽  
Robyn Hawkinson ◽  
Michel Laverdiere ◽  
Anthony Cacciapuoti ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Deletion Mutant ◽  
Desaturase Activity ◽  
Systemic Infection ◽  
Homozygous Deletion ◽  
Infection Model ◽  
Wild Type ◽  
Competitive Disadvantage ◽  
Ergosterol Synthesis ◽  
High Level

ABSTRACT Two clinical Candida albicans isolates that exhibited high-level resistance to azoles and modest decreases in susceptibility to amphotericin B were cultured from unrelated patients. Both isolates harbored homozygous nonsense mutations in ERG3, which encodes an enzyme, sterol Δ5,6-desaturase, involved in ergosterol synthesis. Extraction and analysis of the sterols from both isolates confirmed the absence of sterol Δ5,6-desaturase activity. Although the loss of sterol Δ5,6-desaturase activity is known to confer resistance to azoles, this mechanism of resistance has rarely been seen in clinical isolates, suggesting that such mutants are at a competitive disadvantage. To test this hypothesis, the virulence of the erg3 mutants was assayed by using a mouse systemic infection model. The mutants were significantly less virulent than the wild-type comparator strains. However, the kidney fungal burdens in mice infected with the erg3 mutants were similar to those in mice infected with the wild-type strains. Similar results were obtained by using a laboratory-generated homozygous erg3 deletion mutant (D. Sanglard et al., Antimicrob. Agents Chemother. 47:2404-2412, 2003). Reintroduction of a wild-type ERG3 allele into the homozygous deletion mutant restored virulence, ergosterol synthesis, and susceptibility to azoles, confirming that these phenotypic changes were solely due to the inactivation of Erg3p.

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