scholarly journals Endosomal and AP-3-Dependent Vacuolar Trafficking Routes Make Additive Contributions to Candida albicans Hyphal Growth and Pathogenesis

2010 ◽  
Vol 9 (11) ◽  
pp. 1755-1765 ◽  
Author(s):  
Glen E. Palmer
Keyword(s):  
Candida Albicans ◽  
Double Mutant ◽  
Kidney Tissue ◽  
Hyphal Growth ◽  
Endosomal Trafficking ◽  
Transcriptional Responses ◽  
Transport Pathways ◽  
Content Type ◽  
Vacuolar Protein ◽  
Vacuolar Trafficking

ABSTRACT Candida albicans mutants deficient in vacuolar biogenesis are defective in polarized hyphal growth and virulence. However, the specific vacuolar trafficking routes required for hyphal growth and virulence are unknown. In Saccharomyces cerevisiae, two trafficking routes deliver material from the Golgi apparatus to the vacuole. One occurs via the late endosome and is dependent upon Vps21p, while the second bypasses the endosome and requires the AP-3 complex, including Aps3p. To determine the significance of these pathways in C. albicans hyphal growth and virulence, aps3Δ/Δ, vps21Δ/Δ, and aps3Δ/Δ vps21Δ/Δ mutant strains were constructed. Analysis of vacuolar morphology and localization of the vacuolar protein Mlt1p suggests that C. albicans Aps3p and Vps21p mediate two distinct transport pathways. The vps21Δ/Δ mutant has a minor reduction in hyphal elongation, while the aps3Δ/Δ mutant has no defect in hyphal growth. Interestingly, the aps3Δ/Δ vps21Δ/Δ double mutant has dramatically reduced hyphal growth. Overexpression of the Ume6p transcriptional activator resulted in constitutive hyphal growth of wild-type, aps3Δ/Δ, and vps21Δ/Δ strains and formation of highly vacuolated subapical compartments. Thus, Ume6p-dependent transcriptional responses are sufficient to induce subapical vacuolation. However, the aps3Δ/Δ vps21Δ/Δ mutant formed mainly pseudohyphae that lacked vacuolated compartments. The aps3Δ/Δ strain was virulent in a mouse model of disseminated infection; the vps21Δ/Δ mutant failed to kill mice but persisted within kidney tissue, while the double mutant was avirulent and cleared from the kidneys. These results suggest that while the AP-3 pathway alone has little impact on hyphal growth or virulence, it is much more significant when endosomal trafficking is disrupted.

scholarly journals Three Prevacuolar Compartment Rab GTPases Impact Candida albicans Hyphal Growth

2013 ◽  
Vol 12 (7) ◽  
pp. 1039-1050 ◽  
Author(s):  
Douglas A. Johnston ◽  
Arturo Luna Tapia ◽  
Karen E. Eberle ◽  
Glen E. Palmer
Keyword(s):  
Candida Albicans ◽  
Membrane Trafficking ◽  
Gene Deletion ◽  
Hyphal Growth ◽  
Rab Gtpases ◽  
Phenotypic Analysis ◽  
Pathogenic Yeast ◽  
Content Type ◽  
Growth Defects ◽  
Vacuolar Trafficking

ABSTRACTDisruption of vacuolar biogenesis in the pathogenic yeastCandida albicanscauses profound defects in polarized hyphal growth. However, the precise vacuolar pathways involved in yeast-hypha differentiation have not been determined. Previously we focused on Vps21p, a Rab GTPase involved in directing vacuolar trafficking through the late endosomalprevacuolarcompartment (PVC). Herein, we identify two additional Vps21p-related GTPases, Ypt52p and Ypt53p, that colocalize with Vps21p and can suppress the hyphal defects of thevps21Δ/Δ mutant. Phenotypic analysis of gene deletion strains revealed that loss of bothVPS21andYPT52causes synthetic defects in endocytic trafficking to the vacuole, as well as delivery of the virulence-associated vacuolar membrane protein Mlt1p from the Golgi compartment. Transcription of all three GTPase-encoding genes is increased under hyphal growth conditions, and overexpression of the transcription factor Ume6p is sufficient to increase the transcription of these genes. While only thevps21Δ/Δ single mutant has hyphal growth defects, these were greatly exacerbated in avps21Δ/Δypt52Δ/Δ double mutant. On the basis of relative expression levels and phenotypic analysis of gene deletion strains, Vps21p is the most important of the three GTPases, followed by Ypt52p, while Ypt53p has an only marginal impact onC. albicansphysiology. Finally, disruption of a nonendosomal AP-3-dependent vacuolar trafficking pathway in thevps21Δ/Δypt52Δ/Δ mutant, further exacerbated the stress and hyphal growth defects. These findings underscore the importance of membrane trafficking through the PVC in sustaining the invasive hyphal growth form ofC. albicans.

scholarly journals Cell Wall-Related Bionumbers and Bioestimates of Saccharomyces cerevisiae and Candida albicans

2013 ◽  
Vol 13 (1) ◽  
pp. 2-9 ◽  
Author(s):  
Frans M. Klis ◽  
Chris G. de Koster ◽  
Stanley Brul
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Candida Albicans ◽  
Cell Size ◽  
Pathogenic Fungus ◽  
Turgor Pressure ◽  
Hyphal Growth ◽  
Biological Research ◽  
Content Type ◽  
Starting Point

ABSTRACTBionumbers and bioestimates are valuable tools in biological research. Here we focus on cell wall-related bionumbers and bioestimates of the budding yeastSaccharomyces cerevisiaeand the polymorphic, pathogenic fungusCandida albicans. We discuss the linear relationship between cell size and cell ploidy, the correlation between cell size and specific growth rate, the effect of turgor pressure on cell size, and the reason why using fixed cells for measuring cellular dimensions can result in serious underestimation ofin vivovalues. We further consider the evidence that individual buds and hyphae grow linearly and that exponential growth of the population results from regular formation of new daughter cells and regular hyphal branching. Our calculations show that hyphal growth allowsC. albicansto cover much larger distances per unit of time than the yeast mode of growth and that this is accompanied by strongly increased surface expansion rates. We therefore predict that the transcript levels of genes involved in wall formation increase during hyphal growth. Interestingly, wall proteins and polysaccharides seem barely, if at all, subject to turnover and replacement. A general lesson is how strongly most bionumbers and bioestimates depend on environmental conditions and genetic background, thus reemphasizing the importance of well-defined and carefully chosen culture conditions and experimental approaches. Finally, we propose that the numbers and estimates described here offer a solid starting point for similar studies of other cell compartments and other yeast species.

scholarly journals Role of Retrograde Trafficking in Stress Response, Host Cell Interactions, and Virulence of Candida albicans

2013 ◽  
Vol 13 (2) ◽  
pp. 279-287 ◽  
Author(s):  
Yaoping Liu ◽  
Norma V. Solis ◽  
Clemens J. Heilmann ◽  
Quynh T. Phan ◽  
Aaron P. Mitchell ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Host Cell ◽  
Signaling Pathway ◽  
Stress Resistance ◽  
Cell Interactions ◽  
Content Type ◽  
Retrograde Trafficking ◽  
Host Cell Interactions ◽  
Vacuolar Protein ◽  
Calcineurin Signaling

ABSTRACTInSaccharomyces cerevisiae, the vacuolar protein sorting complexes Vps51/52/53/54 and Vps15/30/34/38 are essential for efficient endosome-to-Golgi complex retrograde transport. Here we investigated the function of Vps15 and Vps51, representative members of these complexes, in the stress resistance, host cell interactions, and virulence ofCandida albicans. We found thatC. albicansvps15Δ/Δ andvps51Δ/Δ mutants had abnormal vacuolar morphology, impaired retrograde protein trafficking, and dramatically increased susceptibility to a variety of stressors. These mutants also had reduced capacity to invade and damage oral epithelial cellsin vitroand attenuated virulence in the mouse model of oropharyngeal candidiasis. Proteomic analysis of the cell wall of thevps51Δ/Δ mutant revealed increased levels of the Crh11 and Utr2 transglycosylases, which are targets of the calcineurin signaling pathway. The transcript levels of the calcineurin pathway membersCHR11,UTR2,CRZ1,CNA1, andCNA2were elevated in thevps15Δ/Δ andvps51Δ/Δ mutants. Furthermore, these strains were highly sensitive to the calcineurin-specific inhibitor FK506. Also, deletion ofCHR11andUTR2further increased the stress susceptibility of these mutants. In contrast, overexpression ofCRH11andUTR2partially rescued their defects in stress resistance, but not host cell interactions. Therefore, intact retrograde trafficking inC. albicansis essential for stress resistance, host cell interactions, and virulence. Aberrant retrograde trafficking stimulates the calcineurin signaling pathway, leading to the increased expression of Chr11 and Utr2, which enablesC. albicansto withstand environmental stress.

scholarly journals Caspofungin Dose Escalation for Invasive Candidiasis Due to Resistant Candida albicans

2011 ◽  
Vol 55 (7) ◽  
pp. 3254-3260 ◽  
Author(s):  
Nathan P. Wiederhold ◽  
Laura K. Najvar ◽  
Rosie A. Bocanegra ◽  
William R. Kirkpatrick ◽  
Thomas F. Patterson
Keyword(s):  
Candida Albicans ◽  
Dose Escalation ◽  
Invasive Candidiasis ◽  
Hot Spot ◽  
Kidney Tissue ◽  
Resistant Isolate ◽  
Content Type ◽  
Tissue Burden ◽  
Higher Doses

ABSTRACTPreviousin vivostudies have reported caspofungin dose escalation to be effective againstCandida glabratawith reduced susceptibility. We hypothesized that higher doses of caspofungin would be effective against invasive candidiasis caused by the more virulent speciesCandida albicans, including isolates resistant to this echinocandin. Immunocompetent mice were inoculated with one of threeC. albicansisolates, including one susceptible and two resistant isolates with differentFKS1hot spot 1 point mutations. Mice received daily caspofungin treatment for 7 days and were then followed off therapy for 2 weeks to assess survival. Kidney tissue and blood were collected, and fungal burden and serum (1→3)-β-d-glucan were measured. Significant differences in virulence were observed among the threeC. albicansisolates, which translated into differences in responses to caspofungin. The most virulent of the resistant isolates studied (isolate 43001; Fks1p F641S) did not respond to caspofungin doses of up to 10 mg/kg of body weight, as there were no differences in survival (survival range, 0 to 12% with treatment), tissue burden, or (1→3)-β-d-glucan concentration compared to those for untreated controls. Higher doses of caspofungin did improve survival against the second resistant isolate (53264; Fks1p S645P) that demonstrated reduced virulence (5 and 10 mg/kg; 80% survival). In contrast, caspofungin doses as low as 1 mg/kg improved survival (85 to 95%) and reduced tissue burden and (1→3)-β-d-glucan concentration against the susceptible isolate (ATCC 90028). These data suggest that caspofungin dose escalation for invasive candidiasis may not be consistently effective against resistantC. albicansisolates, and this may be associated with the virulence of the strain.

scholarly journals Role for Endosomal and Vacuolar GTPases in Candida albicans Pathogenesis

2009 ◽  
Vol 77 (6) ◽  
pp. 2343-2355 ◽  
Author(s):  
Douglas A. Johnston ◽  
Karen E. Eberle ◽  
Joy E. Sturtevant ◽  
Glen E. Palmer
Keyword(s):  
Candida Albicans ◽  
Stress Resistance ◽  
Double Mutant ◽  
Hyphal Growth ◽  
Filamentous Growth ◽  
Rab Gtpases ◽  
Fungal Cell ◽  
Cellular Stresses ◽  
Vacuole Biogenesis

ABSTRACT The vacuole has crucial roles in stress resistance and adaptation of the fungal cell. Furthermore, in Candida albicans it has been observed to undergo dramatic expansion during the initiation of hyphal growth, to produce highly “vacuolated” subapical compartments. We hypothesized that these functions may be crucial for survival within the host and tissue-invasive hyphal growth. We also considered the role of the late endosome or prevacuole compartment (PVC), a distinct organelle involved in vacuolar and endocytic trafficking. We identified two Rab GTPases, encoded by VPS21 and YPT72, required for trafficking through the PVC and vacuole biogenesis, respectively. Deletion of VPS21 or YPT72 led to mild sensitivities to some cellular stresses. However, deletion of both genes resulted in a synthetic phenotype with severe sensitivity to cellular stress and impaired growth. Both the vps21Δ and ypt72Δ mutants had defects in filamentous growth, while the double mutant was completely deficient in polarized growth. The defects in hyphal growth were not suppressed by an “active” RIM101 allele or loss of the hyphal repressor encoded by TUP1. In addition, both single mutants had significant attenuation in a mouse model of hematogenously disseminated candidiasis, while the double mutant was rapidly cleared. Histological examination confirmed that the vps21Δ and ypt72Δ mutants are deficient in hyphal growth in vivo. We suggest that the PVC and vacuole are required on two levels during C. albicans infection: (i) stress resistance functions required for survival within tissue and (ii) a role in filamentous growth which may aid host tissue invasion.

scholarly journals Adaptations of the Secretome of Candida albicans in Response to Host-Related Environmental Conditions

2015 ◽  
Vol 14 (12) ◽  
pp. 1165-1172 ◽  
Author(s):  
Frans M. Klis ◽  
Stanley Brul
Keyword(s):  
Candida Albicans ◽  
Cell Surface ◽  
Human Body ◽  
Environmental Conditions ◽  
Surface Stress ◽  
Hyphal Growth ◽  
Content Type ◽  
General Response ◽  
Culture Supernatants

ABSTRACTThe wall proteome and the secretome of the fungal pathogenCandida albicanshelp it to thrive in multiple niches of the human body. Mass spectrometry has allowed researchers to study the dynamics of both subproteomes. Here, we discuss some major responses of the secretome to host-related environmental conditions. Three β-1,3-glucan-modifying enzymes, Mp65, Sun41, and Tos1, are consistently found in large amounts in culture supernatants, suggesting that they are needed for construction and expansion of the cell wall β-1,3-glucan layer and thus correlate with growth and might serve as diagnostic biomarkers. The genesENG1,CHT3, andSCW11, which encode an endoglucanase, the major chitinase, and a β-1,3-glucan-modifying enzyme, respectively, are periodically expressed and peak in M/G1. The corresponding protein abundances in the medium correlate with the degree of cell separation during single-yeast-cell, pseudohyphal, and hyphal growth. We also discuss the observation that cells treated with fluconazole, or other agents causing cell surface stress, form pseudohyphal aggregates. Fluconazole-treated cells secrete abundant amounts of the transglucosylase Phr1, which is involved in the accumulation of β-1,3-glucan in biofilms, raising the question whether this is a general response to cell surface stress. Other abundant secretome proteins also contribute to biofilm formation, emphasizing the important role of secretome proteins in this mode of growth. Finally, we discuss the relevance of these observations to therapeutic intervention. Together, these data illustrate thatC. albicansactively adapts its secretome to environmental conditions, thus promoting its survival in widely divergent niches of the human body.

scholarly journals Conjugated Linoleic Acid Inhibits Hyphal Growth in Candida albicans by Modulating Ras1p Cellular Levels and Downregulating TEC1 Expression

2011 ◽  
Vol 10 (4) ◽  
pp. 565-577 ◽  
Author(s):  
Julie Shareck ◽  
André Nantel ◽  
Pierre Belhumeur
Keyword(s):  
Candida Albicans ◽  
Linoleic Acid ◽  
Conjugated Linoleic Acid ◽  
Cellular Localization ◽  
Therapeutic Potential ◽  
Transcriptional Profiling ◽  
Hyphal Growth ◽  
Cellular Growth ◽  
Content Type ◽  
Protein Levels

ABSTRACTThe polymorphic yeastCandida albicansexists in yeast and filamentous forms. Given that the morphogenetic switch coincides with the expression of many virulence factors, the yeast-to-hypha transition constitutes an attractive target for the development of new antifungal agents. Since an untapped therapeutic potential resides in small molecules that hinderC. albicansfilamentation, we characterized the inhibitory effect of conjugated linoleic acid (CLA) on hyphal growth and addressed its mechanism of action. CLA inhibited hyphal growth in a dose-dependent fashion in both liquid and solid hypha-inducing media. The fatty acid blocked germ tube formation without affecting cellular growth rates. Global transcriptional profiling revealed that CLA downregulated the expression of hypha-specific genes and abrogated the induction of several regulators of hyphal growth, includingTEC1,UME6,RFG1, andRAS1. However, neitherUME6norRFG1was necessary for CLA-mediated hyphal growth inhibition. Expression analysis showed that the downregulation ofTEC1expression levels by CLA depended onRAS1. In addition, whileRAS1transcript levels remained constant in CLA-treated cells, its protein levels declined with time. With the use of a strain expressing GFP-Ras1p, CLA treatment was also shown to affect Ras1p localization to the plasma membrane. These findings suggest that CLA inhibits hyphal growth by affecting the cellular localization of Ras1p and blocking the increase inRAS1mRNA and protein levels. Combined, these effects should prevent the induction of the Ras1p signaling pathway. This study provides the biological and molecular explanations that underlie CLA's ability to inhibit hyphal growth inC. albicans.

scholarly journals Candida albicans Ume6, a Filament-Specific Transcriptional Regulator, Directs Hyphal Growth via a Pathway Involving Hgc1 Cyclin-Related Protein

2010 ◽  
Vol 9 (9) ◽  
pp. 1320-1328 ◽  
Author(s):  
Patricia L. Carlisle ◽  
David Kadosh
Keyword(s):  
Candida Albicans ◽  
Molecular Mechanisms ◽  
Constitutive Expression ◽  
Transcriptional Regulator ◽  
Hyphal Growth ◽  
Related Protein ◽  
Content Type ◽  
Epistasis Analysis ◽  
Dependent Inactivation ◽  
Hyphal Formation

ABSTRACT The ability of Candida albicans, the most common human fungal pathogen, to transition from yeast to hyphae is essential for pathogenicity. While a variety of transcription factors important for filamentation have been identified and characterized, links between transcriptional regulators of C. albicans morphogenesis and molecular mechanisms that drive hyphal growth are not well defined. We have previously observed that constitutive expression of UME6, which encodes a filament-specific transcriptional regulator, is sufficient to direct hyphal growth in the absence of filament-inducing conditions. Here we show that HGC1, encoding a cyclin-related protein necessary for hyphal growth under filament-inducing conditions, is specifically important for agar invasion, hyphal extension, and formation of true septa in response to constitutive UME6 expression under non-filament-inducing conditions. HGC1-dependent inactivation of Rga2, a Cdc42 GTPase activating protein (GAP), also appears to be important for these processes. In response to filament-inducing conditions, HGC1 is induced prior to UME6 although UME6 controls the level and duration of HGC1 expression, which are likely to be important for hyphal extension. Interestingly, an epistasis analysis suggests that UME6 and HGC1 play distinct roles during early filament formation. These findings establish a link between a key regulator of filamentation and a downstream mechanism important for hyphal formation. In addition, this study demonstrates that a strain expressing constitutive high levels of UME6 provides a powerful strategy to specifically dissect downstream mechanisms important for hyphal development in the absence of complex filament-inducing conditions.

scholarly journals Linking Sfl1 Regulation of Hyphal Development to Stress Response Kinases in Candida albicans

mSphere ◽  
2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Ohimai Unoje ◽  
Mengli Yang ◽  
Yang Lu ◽  
Chang Su ◽  
Haoping Liu
Keyword(s):  
Candida Albicans ◽  
Stress Response ◽  
Map Kinase ◽  
Hyphal Growth ◽  
Acidic Ph ◽  
Transcriptional Repressors ◽  
Growth Forms ◽  
Content Type ◽  
Hyphal Development ◽  
Study Results

ABSTRACT Candida albicans is an important human pathogen responsible for causing both superficial and systemic infections. Its ability to switch from the yeast form to the hyphal growth form is required for its pathogenicity. Acidic pH inhibits hyphal initiation, but the nature of the mechanism for this inhibition is not completely clear. We show that acidic pH represses hyphal initiation independently of the temperature- and farnesol-mediated Nrg1 downregulation. Using a collection of transcription factor deletion mutants, we observed that the sfl1 mutant induced hyphae in acidic pH but not in farnesol at 37°C. Furthermore, transcription of hyphal regulators BRG1 and UME6 was not induced in wild-type (WT) cells but was induced in the sfl1 mutant during hyphal induction in acidic pH. Using the same screening conditions with the collection of kinase mutants, we found that deletions of the core stress response mitogen-activated protein (MAP) kinase HOG1 and its kinase PBS2, the cell wall stress MAP kinase MKC1, and the calcium/calmodulin-dependent kinase CMK1 allowed hyphal initiation in acidic pH. Furthermore, Hog1 phosphorylation induced by high osmotic stress also retarded hyphal initiation, and the effect was abolished in the sfl1 and three kinase mutants but was enhanced in the phosphatase mutant ptp2 ptp3. We also found functional associations among Cmk1, Hog1, and Sfl1 for cation stress. Our study results suggest that robust hyphal initiation requires downregulation of both Nrg1 and Sfl1 transcriptional repressors as well as timely BRG1 expression. Acidic pH and cationic stress retard hyphal initiation via the stress-responsive kinases and Sfl1. IMPORTANCE Candida albicans is a commensal as well as a pathogen of humans. C. albicans is able to mount a cellular response to a diverse range of external stimuli in the host and switch reversibly between the yeast and hyphal growth forms. Hyphal development is a key virulence determinant. Here, we studied how C. albicans senses different environmental signals to control its growth forms. Our study results suggest that robust hyphal development requires downregulation of two transcriptional repressors, Nrg1 and Sfl1. Acidic pH or cationic stress inhibits hyphal formation via stress-responsive kinases and Sfl1.

scholarly journals In Vitro Antibiofilm Activity of Eucarobustol E against Candida albicans

2017 ◽  
Vol 61 (8) ◽  
Author(s):  
Rui-Huan Liu ◽  
Zhi-Chun Shang ◽  
Tian-Xiao Li ◽  
Ming-Hua Yang ◽  
Ling-Yi Kong
Keyword(s):  
Candida Albicans ◽  
Antifungal Susceptibility ◽  
Hyphal Growth ◽  
Negative Regulator ◽  
Ergosterol Biosynthesis ◽  
Pcr Analysis ◽  
Antibiofilm Activity ◽  
Biofilm Inhibition ◽  
Content Type

ABSTRACT Formyl-phloroglucinol meroterpenoids (FPMs) are important types of natural products with various bioactivities. Our antifungal susceptibility assay showed that one of the Eucalyptus robusta-derived FPMs, eucarobustol E (EE), exerted a strong inhibitory effect against Candida albicans biofilms at a concentration of 16 μg/ml. EE was found to block the yeast-to-hypha transition and reduce the cellular surface hydrophobicity of the biofilm cells. RNA sequencing and real-time reverse transcription-PCR analysis showed that exposure to 16 μg/ml of EE resulted in marked reductions in the levels of expressions of genes involved in hyphal growth (EFG1, CPH1, TEC1, EED1, UME6, and HGC1) and cell surface protein genes (ALS3, HWP1, and SAP5). Interestingly, in response to EE, genes involved in ergosterol biosynthesis were downregulated, while the farnesol-encoding gene (DPP3) was upregulated, and these findings were in agreement with those from the quantification of ergosterol and farnesol. Combined with the obvious elevation of negative regulator genes (TUP1, NRG1), we speculated that EE's inhibition of carbon flow to ergosterol triggered the mechanisms of the negative regulation of hyphal growth and eventually led to biofilm inhibition.

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