scholarly journals Paradoxical Growth of Candida albicans in the Presence of Caspofungin Is Associated with Multiple Cell Wall Rearrangements and Decreased Virulence

2013 ◽  
Vol 58 (2) ◽  
pp. 1071-1083 ◽  
Author(s):  
Cristina Rueda ◽  
Manuel Cuenca-Estrella ◽  
Oscar Zaragoza
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Galleria Mellonella ◽  
Morphological Changes ◽  
Antifungal Drugs ◽  
Proinflammatory Response ◽  
Content Type ◽  
Multiple Cell ◽  
Fungal Adaptation ◽  
Paradoxical Growth

ABSTRACTIn the last decade, echinocandins have emerged as an important family of antifungal drugs because of their fungicidal activity againstCandidaspp. Echinocandins inhibit the enzyme β-1,3-d-glucan synthase, encoded by theFKSgenes, and resistance to echinocandins is associated with mutations in this gene. In addition, echinocandin exposure can produce paradoxical growth, defined as the ability to grow at high antifungal concentrations but not at intermediate concentrations. In this work, we have demonstrated that paradoxical growth ofCandida albicansin the presence of caspofungin is not due to antifungal degradation or instability. Media with high caspofungin concentrations recovered from wells whereC. albicansshowed paradoxical growth inhibited the growth of aCandida kruseireference strain. Cells exhibiting paradoxical growth at high caspofungin concentrations showed morphological changes such as enlarged size, abnormal septa, and absence of filamentation. Chitin content increased from the MIC to high caspofungin concentrations. Despite the high chitin levels, around 23% of cells died after treatment with caspofungin, indicating that chitin is required but not sufficient to protect the cells from the fungicidal effect of caspofungin. Moreover, we found that after paradoxical growth, β-1,3-glucan was exposed at the cell wall surface. Cells grown at high caspofungin concentrations had decreased virulence in the invertebrate hostGalleria mellonella. Cells grown at high caspofungin concentrations also induced a proinflammatory response in murine macrophages compared to control cells. Our work highlights important aspects about fungal adaptation to caspofungin, and although this adaptation is associated with reduced virulence, the clinical implications remain to be elucidated.

scholarly journals Cell Wall Changes in Amphotericin B-Resistant Strains from Candida tropicalis and Relationship with the Immune Responses Elicited by the Host

2016 ◽  
Vol 60 (4) ◽  
pp. 2326-2335 ◽  
Author(s):  
Ana C. Mesa-Arango ◽  
Cristina Rueda ◽  
Elvira Román ◽  
Jessica Quintin ◽  
María C. Terrón ◽  
...  
Keyword(s):  
Immune Response ◽  
Cell Wall ◽  
Amphotericin B ◽  
Candida Tropicalis ◽  
Galleria Mellonella ◽  
Regular Growth ◽  
Cell Integrity ◽  
Proinflammatory Response ◽  
Content Type ◽  
Resistant Strains

ABSTRACTWe have morphologically characterizedCandida tropicalisisolates resistant to amphotericin B (AmB). These isolates present an enlarged cell wall compared to isolates of regular susceptibility. This correlated with higher levels of β-1,3-glucan in the cell wall but not with detectable changes in chitin content. In line with this, AmB-resistant strains showed reduced susceptibility to Congo red. Moreover, mitogen-activated protein kinases (MAPKs) involved in cell integrity were already activated during regular growth in these strains. Finally, we investigated the response elicited by human blood cells and found that AmB-resistant strains induced a stronger proinflammatory response than susceptible strains. In agreement, AmB-resistant strains also induced stronger melanization ofGalleria mellonellalarvae, indicating that the effect of alterations of the cell wall on the immune response is conserved in different types of hosts. Our results suggest that resistance to AmB is associated with pleiotropic mechanisms that might have important consequences, not only for the efficacy of the treatment but also for the immune response elicited by the host.

scholarly journals Nanoscale Effects of Caspofungin against Two Yeast Species, Saccharomyces cerevisiae and Candida albicans

2013 ◽  
Vol 57 (8) ◽  
pp. 3498-3506 ◽  
Author(s):  
C. Formosa ◽  
M. Schiavone ◽  
H. Martin-Yken ◽  
J. M. François ◽  
R. E. Duval ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Candida Albicans ◽  
Yeast Species ◽  
Young Modulus ◽  
Antifungal Drugs ◽  
Molecular Organization ◽  
Response To Treatment ◽  
Content Type ◽  
High Doses

ABSTRACTSaccharomyces cerevisiaeandCandida albicansare model yeasts for biotechnology and human health, respectively. We used atomic force microscopy (AFM) to explore the effects of caspofungin, an antifungal drug used in hospitals, on these two species. Our nanoscale investigation revealed similar, but also different, behaviors of the two yeasts in response to treatment with the drug. While administration of caspofungin induced deep cell wall remodeling in both yeast species, as evidenced by a dramatic increase in chitin and decrease in β-glucan content, changes in cell wall composition were more pronounced withC. albicanscells. Notably, the increase of chitin was proportional to the increase in the caspofungin dose. In addition, the Young modulus of the cell was three times lower forC. albicanscells than forS. cerevisiaecells and increased proportionally with the increase of chitin, suggesting differences in the molecular organization of the cell wall between the two yeast species. Also, at a low dose of caspofungin (i.e., 0.5× MIC), the cell surface ofC. albicansexhibited a morphology that was reminiscent of cells expressing adhesion proteins. Interestingly, this morphology was lost at high doses of the drug (i.e., 4× MIC). However, the treatment ofS. cerevisiaecells with high doses of caspofungin resulted in impairment of cytokinesis. Altogether, the use of AFM for investigating the effects of antifungal drugs is relevant in nanomedicine, as it should help in understanding their mechanisms of action on fungal cells, as well as unraveling unexpected effects on cell division and fungal adhesion.

scholarly journals Interface of Candida albicans Biofilm Matrix-Associated Drug Resistance and Cell Wall Integrity Regulation

2011 ◽  
Vol 10 (12) ◽  
pp. 1660-1669 ◽  
Author(s):  
Jeniel E. Nett ◽  
Hiram Sanchez ◽  
Michael T. Cain ◽  
Kelly M. Ross ◽  
David R. Andes
Keyword(s):  
Drug Resistance ◽  
Cell Wall ◽  
Candida Albicans ◽  
Antifungal Drugs ◽  
Cell Wall Integrity ◽  
Candidate Gene Approach ◽  
Content Type ◽  
Resistant Phenotype ◽  
Cell Wall Integrity Pathway ◽  
Biofilm Matrix

ABSTRACTCandida albicansfrequently infects medical devices by growing as a biofilm, i.e., a community of adherent organisms entrenched in an extracellular matrix. During biofilm growth,Candidaspp. acquire the ability to resist high concentrations of antifungal drugs. One recently recognized biofilm resistance mechanism involves drug sequestration by matrix β-1,3 glucan. Using a candidate gene approach, we investigated potentialC. albicansβ-1,3-glucan regulators, based on their homology toSaccharomyces cerevisiae, includingSMI1and protein kinase C (PKC) pathway components. We identified a role for theSMI1in biofilm matrix glucan production and development of the associated drug resistance phenotype. This pathway appears to act through transcription factor Rlmp and glucan synthase Fks1p. The phenotypes of these mutant biofilms mimicked those of thesmi1Δ/smi1Δ biofilm, and overexpression ofFKS1in thesmi1Δ/smi1Δ mutant restored the biofilm resistant phenotype. However, control of this pathway is distinct from that of the upstream PKC pathway because thepkc1Δ/pkc1Δ,bck1Δ/bck1Δ,mkk2Δ/mkk2Δ, andmkc1Δ/mkc1Δ biofilms retained the resistant phenotype of the parent strain. In addition, resistance to cell-perturbing agents and gene expression data do not support a significant role for the cell wall integrity pathway during the biofilm formation. Here we show that Smi1p functions in conjunction with Rlm1p and Fks1p to produce drug-sequestering biofilm β-glucan. Our work provides new insight into how theC. albicansbiofilm matrix production and drug resistance pathways intersect with the planktonic cell wall integrity pathway. This novel connection helps explain how pathogens in a multicellular biofilm community are protected from anti-infective therapy.

scholarly journals Sur7 Promotes Plasma Membrane Organization and Is Needed for Resistance to Stressful Conditions and to the Invasive Growth and Virulence of Candida albicans

mBio ◽  
2011 ◽  
Vol 3 (1) ◽  
Author(s):  
Lois M. Douglas ◽  
Hong X. Wang ◽  
Sabine Keppler-Ross ◽  
Neta Dean ◽  
James B. Konopka
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Plasma Membrane ◽  
Fungal Pathogen ◽  
Antifungal Drugs ◽  
Membrane Organization ◽  
Content Type ◽  
Human Fungal Pathogen ◽  
Membrane Compartment ◽  
Systemic Infections

ABSTRACTThe human fungal pathogenCandida albicanscauses lethal systemic infections because of its ability to grow and disseminate in a host. TheC. albicansplasma membrane is essential for virulence by acting as a protective barrier and through its key roles in interfacing with the environment, secretion of virulence factors, morphogenesis, and cell wall synthesis. Difficulties in studying hydrophobic membranes have limited the understanding of how plasma membrane organization contributes to its function and to the actions of antifungal drugs. Therefore, the role of the recently discovered plasma membrane subdomains termed the membrane compartment containing Can1 (MCC) was analyzed by assessing the virulence of asur7Δ mutant. Sur7 is an integral membrane protein component of the MCC that is needed for proper localization of actin, morphogenesis, cell wall synthesis, and responding to cell wall stress. MCC domains are stable 300-nm-sized punctate patches that associate with a complex of cytoplasmic proteins known as an eisosome. Analysis of virulence-related properties of asur7Δ mutant revealed defects in intraphagosomal growth in macrophages that correlate with increased sensitivity to oxidation and copper. Thesur7Δ mutant was also strongly defective in pathogenesis in a mouse model of systemic candidiasis. The mutant cells showed a decreased ability to initiate an infection and greatly diminished invasive growth into kidney tissues. These studies on Sur7 demonstrate that the plasma membrane MCC domains are critical for virulence and represent an important new target for the development of novel therapeutic strategies.IMPORTANCECandida albicans, the most common human fungal pathogen, causes lethal systemic infections by growing and disseminating in a host. The plasma membrane plays key roles in enablingC. albicansto growin vivo, and it is also the target of the most commonly used antifungal drugs. However, plasma membrane organization is poorly understood because of the experimental difficulties in studying hydrophobic components. Interestingly, recent studies have identified a novel type of plasma membrane subdomain in fungi known as the membrane compartment containing Can1 (MCC). Cells lacking the MCC-localized protein Sur7 display broad defects in cellular organization and response to stressin vitro. Consistent with this,C. albicanscells lacking theSUR7gene were more susceptible to attack by macrophages than cells with the gene and showed greatly reduced virulence in a mouse model of systemic infection. Thus, Sur7 and other MCC components represent novel targets for antifungal therapy.

scholarly journals Elevated Chitin Content Reduces the Susceptibility of Candida Species to Caspofungin

2012 ◽  
Vol 57 (1) ◽  
pp. 146-154 ◽  
Author(s):  
Louise A. Walker ◽  
Neil A. R. Gow ◽  
Carol A. Munro
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Point Mutations ◽  
Antifungal Drugs ◽  
Cell Wall Polysaccharide ◽  
Chitin Synthesis ◽  
Fungal Cell ◽  
Content Type ◽  
Chitin Content ◽  
Compensatory Increase

ABSTRACTThe echinocandin antifungal drugs inhibit synthesis of the major fungal cell wall polysaccharide β(1,3)-glucan. Echinocandins have good efficacy againstCandida albicansbut reduced activity against otherCandidaspecies, in particularCandida parapsilosisandCandida guilliermondii. Treatment ofCandida albicanswith a sub-MIC level of caspofungin has been reported to cause a compensatory increase in chitin content and to select for sporadic echinocandin-resistantFKS1point mutants that also have elevated cell wall chitin. Here we show that elevated chitin in response to caspofungin is a common response in variousCandidaspecies. Activation of chitin synthesis was observed in isolates ofC. albicans,Candida tropicalis,C. parapsilosis, andC. guilliermondiiand in some isolates ofCandida kruseiin response to caspofungin treatment. However,Candida glabrataisolates demonstrated no exposure-induced change in chitin content. Furthermore, isolates ofC. albicans,C. krusei,C. parapsilosis, andC. guilliermondiiwhich were stimulated to have higher chitin levels via activation of the calcineurin and protein kinase C (PKC) signaling pathways had reduced susceptibility to caspofungin. Isolates containing point mutations in theFKS1gene generally had higher chitin levels and did not demonstrate a further compensatory increase in chitin content in response to caspofungin treatment. These results highlight the potential of increased chitin synthesis as a potential mechanism of tolerance to caspofungin for the major pathogenicCandidaspecies.

scholarly journals Dectin-2-Targeted Antifungal Liposomes Exhibit Enhanced Efficacy

mSphere ◽  
2019 ◽  
Vol 4 (5) ◽  
Author(s):  
Suresh Ambati ◽  
Emma C. Ellis ◽  
Jianfeng Lin ◽  
Xiaorong Lin ◽  
Zachary A. Lewis ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Aspergillus Fumigatus ◽  
Effective Dose ◽  
Cryptococcus Neoformans ◽  
Amphotericin B ◽  
Antifungal Drugs ◽  
Extracellular Matrices ◽  
Content Type ◽  
Order Of Magnitude ◽  
Life Threatening

ABSTRACT Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus cause life-threatening candidiasis, cryptococcosis, and aspergillosis, resulting in several hundred thousand deaths annually. The patients at the greatest risk of developing these life-threatening invasive fungal infections have weakened immune systems. The vulnerable population is increasing due to rising numbers of immunocompromised individuals as a result of HIV infection or immunosuppressed individuals receiving anticancer therapies and/or stem cell or organ transplants. While patients are treated with antifungals such as amphotericin B, all antifungals have serious limitations due to lack of sufficient fungicidal effect and/or host toxicity. Even with treatment, 1-year survival rates are low. We explored methods of increasing drug effectiveness by designing fungicide-loaded liposomes specifically targeted to fungal cells. Most pathogenic fungi are encased in cell walls and exopolysaccharide matrices rich in mannans. Dectin-2 is a mammalian innate immune membrane receptor that binds as a dimer to mannans and signals fungal infection. We coated amphotericin-loaded liposomes with monomers of Dectin-2’s mannan-binding domain, sDectin-2. sDectin monomers were free to float in the lipid membrane and form dimers that bind mannan substrates. sDectin-2-coated liposomes bound orders of magnitude more efficiently to the extracellular matrices of several developmental stages of C. albicans, C. neoformans, and A. fumigatus than untargeted control liposomes. Dectin-2-coated amphotericin B-loaded liposomes reduced the growth and viability of all three species more than an order of magnitude more efficiently than untargeted control liposomes and dramatically decreased the effective dose. Future efforts focus on examining pan-antifungal targeted liposomal drugs in animal models of fungal diseases. IMPORTANCE Invasive fungal diseases caused by Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus have mortality rates ranging from 10 to 95%. Individual patient costs may exceed $100,000 in the United States. All antifungals in current use have serious limitations due to host toxicity and/or insufficient fungal cell killing that results in recurrent infections. Few new antifungal drugs have been introduced in the last 2 decades. Hence, there is a critical need for improved antifungal therapeutics. By targeting antifungal-loaded liposomes to α-mannans in the extracellular matrices secreted by these fungi, we dramatically reduced the effective dose of drug. Dectin-2-coated liposomes loaded with amphotericin B bound 50- to 150-fold more strongly to C. albicans, C. neoformans, and A. fumigatus than untargeted liposomes and killed these fungi more than an order of magnitude more efficiently. Targeting drug-loaded liposomes specifically to fungal cells has the potential to greatly enhance the efficacy of most antifungal drugs.

scholarly journals Masking of β(1-3)-Glucan in the Cell Wall of Candida albicans from Detection by Innate Immune Cells Depends on Phosphatidylserine

2014 ◽  
Vol 82 (10) ◽  
pp. 4405-4413 ◽  
Author(s):  
Sarah E. Davis ◽  
Alex Hopke ◽  
Steven C. Minkin ◽  
Anthony E. Montedonico ◽  
Robert T. Wheeler ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
De Novo ◽  
Invasive Disease ◽  
Innate Immune ◽  
Dependent Manner ◽  
Content Type ◽  
Immune Effector ◽  
Host Interactions ◽  
Innate Immune Effector

ABSTRACTThe virulence ofCandida albicansin a mouse model of invasive candidiasis is dependent on the phospholipids phosphatidylserine (PS) and phosphatidylethanolamine (PE). Disruption of the PS synthase geneCHO1(i.e.,cho1Δ/Δ) eliminates PS and blocks thede novopathway for PE biosynthesis. In addition, thecho1Δ/Δ mutant's ability to cause invasive disease is severely compromised. Thecho1Δ/Δ mutant also exhibits cell wall defects, and in this study, it was determined that loss of PS results in decreased masking of cell wall β(1-3)-glucan from the immune system. In wild-typeC. albicans, the outer mannan layer of the wall masks the inner layer of β(1-3)-glucan from exposure and detection by innate immune effector molecules like the C-type signaling lectin Dectin-1, which is found on macrophages, neutrophils, and dendritic cells. Thecho1Δ/Δ mutant exhibits increases in exposure of β(1-3)-glucan, which leads to greater binding by Dectin-1 in both yeast and hyphal forms. The unmasking of β(1-3)-glucan also results in increased elicitation of TNF-α from macrophages in a Dectin-1-dependent manner. The role of phospholipids in fungal pathogenesis is an emerging field, and this is the first study showing that loss of PS inC. albicansresults in decreased masking of β(1-3)-glucan, which may contribute to our understanding of fungus-host interactions.

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 Melanin Externalization in Candida albicans Depends on Cell Wall Chitin Structures

2010 ◽  
Vol 9 (9) ◽  
pp. 1329-1342 ◽  
Author(s):  
Claire A. Walker ◽  
Beatriz L. Gómez ◽  
Héctor M. Mora-Montes ◽  
Kevin S. Mackenzie ◽  
Carol A. Munro ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Fungal Pathogen ◽  
Cell Walls ◽  
Chitin Synthesis ◽  
Melanin Production ◽  
Content Type ◽  
Encoding Gene ◽  
Chitinase Genes

ABSTRACT The fungal pathogen Candida albicans produces dark-pigmented melanin after 3 to 4 days of incubation in medium containing l-3,4-dihydroxyphenylalanine (l-DOPA) as a substrate. Expression profiling of C. albicans revealed very few genes significantly up- or downregulated by growth in l-DOPA. We were unable to determine a possible role for melanin in the virulence of C. albicans. However, we showed that melanin was externalized from the fungal cells in the form of electron-dense melanosomes that were free or often loosely bound to the cell wall exterior. Melanin production was boosted by the addition of N-acetylglucosamine to the medium, indicating a possible association between melanin production and chitin synthesis. Melanin externalization was blocked in a mutant specifically disrupted in the chitin synthase-encoding gene CHS2. Melanosomes remained within the outermost cell wall layers in chs3Δ and chs2Δ chs3Δ mutants but were fully externalized in chs8Δ and chs2Δ chs8Δ mutants. All the CHS mutants synthesized dark pigment at equivalent rates from mixed membrane fractions in vitro, suggesting it was the form of chitin structure produced by the enzymes, not the enzymes themselves, that was involved in the melanin externalization process. Mutants with single and double disruptions of the chitinase genes CHT2 and CHT3 and the chitin pathway regulator ECM33 also showed impaired melanin externalization. We hypothesize that the chitin product of Chs3 forms a scaffold essential for normal externalization of melanosomes, while the Chs8 chitin product, probably produced in cell walls in greater quantity in the absence of CHS2, impedes externalization.

scholarly journals Deletion ofADA2Increases Antifungal Drug Susceptibility and Virulence inCandida glabrata

2018 ◽  
Vol 62 (3) ◽  
Author(s):  
Shang-Jie Yu ◽  
Ya-Lin Chang ◽  
Ying-Lien Chen
Keyword(s):  
Cell Wall ◽  
Systemic Infection ◽  
Drug Tolerance ◽  
Drug Susceptibility ◽  
Antifungal Drugs ◽  
Antifungal Drug ◽  
Saga Complex ◽  
Necrosis Factor Alpha ◽  
Content Type ◽  
Downstream Target

ABSTRACTCandida glabrata, the second most frequent cause of candidiasis afterCandida albicans, is an emerging human fungal pathogen that is intrinsically drug tolerant. Currently, studies ofC. glabratagenes involved in drug tolerance are limited. Ada2, a component serving as a transcription adaptor of the Spt-Ada-Gcn5 acetyltransferase (SAGA) complex, is required for antifungal drug tolerance and virulence inC. albicans. However, its roles inC. glabrataremain elusive. In this study, we found thatada2mutants demonstrated severe growth defects at 40°C but only mild defects at 37°C or 25°C. In addition,C. glabrata ada2mutants exhibited pleiotropic phenotypes, including susceptibility to three classes of antifungal drugs (i.e., azoles, echinocandins, and polyenes) and cell wall-perturbing agents but resistance to the endoplasmic reticulum stressor tunicamycin. According to RNA sequence analysis, the expression of 43 genes was downregulated and the expression of 442 genes was upregulated in theada2mutant compared to their expression in the wild type.C. glabrata ADA2, along with its downstream targetERG6, controls antifungal drug tolerance and cell wall integrity. Surprisingly,ada2mutants were hypervirulent in a murine model of systemic infection, possibly due to the upregulation of multiple adhesin-like genes, increased agar invasion, and overstimulation of murine tumor necrosis factor alpha production.

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