Participation of Candida albicans Transcription Factor RLM1 in Cell Wall Biogenesis and Virulence

ABSTRACTTheCandida albicanstranscription factor Efg1 is known to be involved in many different cellular processes, including morphogenesis, general metabolism, and virulence. Here we show that besides its manifold roles, Efg1 also has a prominent effect on cell wall structure and composition, strongly affecting the structural glucan part. Deletion of only one allele ofEFG1already results in severe phenotypes for cell wall biogenesis, comparable to those with deletion of both alleles, indicative of a severe haploinsufficiency forEFG1. The observed defects in structural setup of the cell wall, together with previously reported alterations in expression of cell surface proteins, result in altered immunogenic properties of strains with compromised Efg1 function. This is shown by interaction studies with macrophages and primary dendritic cells. The structural changes in the cell wall carbohydrate meshwork presented here, together with the manifold changes in cell wall protein composition and metabolism reported in other studies, contribute to the altered immune response mounted by innate immune cells and to the altered virulence phenotypes observed for strains lackingEFG1.

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The Cek1 and Hog1 Mitogen-Activated Protein Kinases Play Complementary Roles in Cell Wall Biogenesis and Chlamydospore Formation in the Fungal Pathogen Candida albicans

Eukaryotic Cell ◽

10.1128/ec.5.2.347-358.2006 ◽

2006 ◽

Vol 5 (2) ◽

pp. 347-358 ◽

Cited By ~ 109

Author(s):

B. Eisman ◽

R. Alonso-Monge ◽

E. Román ◽

D. Arana ◽

C. Nombela ◽

...

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Map Kinase ◽

Fungal Pathogen ◽

Hog Pathway ◽

Cell Wall Biogenesis ◽

Chlamydospore Formation ◽

Mitogen Activated Protein ◽

Morphological Transitions ◽

Relationship Of

ABSTRACT The Hog1 mitogen-activated protein (MAP) kinase mediates an adaptive response to both osmotic and oxidative stress in the fungal pathogen Candida albicans. This protein also participates in two distinct morphogenetic processes, namely the yeast-to-hypha transition (as a repressor) and chlamydospore formation (as an inducer). We show here that repression of filamentous growth occurs both under serum limitation and under other partially inducing conditions, such as low temperature, low pH, or nitrogen starvation. To understand the relationship of the HOG pathway to other MAP kinase cascades that also play a role in morphological transitions, we have constructed and characterized a set of double mutants in which we deleted both the HOG1 gene and other signaling elements (the CST20, CLA4, and HST7 kinases, the CPH1 and EFG1 transcription factors, and the CPP1 protein phosphatase). We also show that Hog1 prevents the yeast-to-hypha switch independent of all the elements analyzed and that the inability of the hog1 mutants to form chlamydospores is suppressed when additional elements of the CEK1 pathway (CST20 or HST7) are altered. Finally, we report that Hog1 represses the activation of the Cek1 MAP kinase under basal conditions and that Cek1 activation correlates with resistance to certain cell wall inhibitors (such as Congo red), demonstrating a role for this pathway in cell wall biogenesis.

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Candida albicans Sun41p, a Putative Glycosidase, Is Involved in Morphogenesis, Cell Wall Biogenesis, and Biofilm Formation

Eukaryotic Cell ◽

10.1128/ec.00285-07 ◽

2007 ◽

Vol 6 (11) ◽

pp. 2056-2065 ◽

Cited By ~ 58

Author(s):

Ekkehard Hiller ◽

Sonja Heine ◽

Herwig Brunner ◽

Steffen Rupp

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Biofilm Formation ◽

Cell Monolayer ◽

The Sun ◽

Calcofluor White ◽

Cellular Processes ◽

Cell Wall Biogenesis ◽

Reduced Adherence ◽

Higher Sensitivity

ABSTRACT The SUN gene family has been defined in Saccharomyces cerevisiae and comprises a fungus-specific family of proteins which show high similarity in their C-terminal domains. Genes of this family are involved in different cellular processes, like DNA replication, aging, mitochondrial biogenesis, and cytokinesis. In Candida albicans the SUN family comprises two genes, SUN41 and SIM1. We demonstrate that C. albicans mutants lacking SUN41 show similar defects as found for S. cerevisiae, including defects in cytokinesis. In addition, the SUN41 mutant showed a higher sensitivity towards the cell wall-disturbing agent Congo red, whereas no difference was observed in the presence of calcofluor white. Compared to the wild type, SUN41 deletion strains exhibited a defect in biofilm formation, a reduced adherence on a Caco-2 cell monolayer, and were unable to form hyphae on solid medium under the conditions tested. Interestingly, Sun41p was found to be secreted in the medium of cells growing as blastospores as well as those forming hyphae. Our results support a function of SUN41p as a glycosidase involved in cytokinesis, cell wall biogenesis, adhesion to host tissue, and biofilm formation, indicating an important role in the host-pathogen interaction.

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Msb2 Signaling Mucin Controls Activation of Cek1 Mitogen-Activated Protein Kinase in Candida albicans

Eukaryotic Cell ◽

10.1128/ec.00081-09 ◽

2009 ◽

Vol 8 (8) ◽

pp. 1235-1249 ◽

Cited By ~ 79

Author(s):

Elvira Román ◽

Fabien Cottier ◽

Joachim F. Ernst ◽

Jesús Pla

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Protein Kinase ◽

Osmotic Shock ◽

Mitogen Activated Protein Kinase ◽

Hog Pathway ◽

High Osmolarity ◽

Cell Wall Biogenesis ◽

Solid Media ◽

Mitogen Activated Protein

ABSTRACT We have characterized the role that the Msb2 protein plays in the fungal pathogen Candida albicans by the use of mutants defective in the putative upstream components of the HOG pathway. Msb2, in cooperation with Sho1, controls the activation of the Cek1 mitogen-activated protein kinase under conditions that damage the cell wall, thus defining Msb2 as a signaling element of this pathway in the fungus. msb2 mutants display altered sensitivity to Congo red, caspofungin, zymolyase, or tunicamycin, indicating that this protein is involved in cell wall biogenesis. Msb2 (as well as Sho1 and Hst7) is involved in the transmission of the signal toward Cek1 mediated by the Cdc42 GTPase, as revealed by the use of activated alleles (Cdc42G12V) of this protein. msb2 mutants have a stronger defective invasion phenotype than sho1 mutants when tested on certain solid media that use mannitol or sucrose as a carbon source or under hypoxia. Interestingly, Msb2 contributes to growth under conditions of high osmolarity when both branches of the HOG pathway are altered, as triple ssk1 msb2 sho1 mutants (but not any single or double mutant) are osmosensitive. However, this phenomenon is independent of the presence of Hog1, as Hog1 phosphorylation, Hog1 translocation to the nucleus, and glycerol accumulation are not affected in this mutant following an osmotic shock. These results reveal essential functions in morphogenesis, invasion, cell wall biogenesis, and growth under conditions of high osmolarity for Msb2 in C. albicans and suggest the divergence and specialization of this signaling pathway in filamentous fungi.

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Role of Transcription Factor CaNdt80p in Cell Separation, Hyphal Growth, and Virulence in Candida albicans

Eukaryotic Cell ◽

10.1128/ec.00325-09 ◽

2010 ◽

Vol 9 (4) ◽

pp. 634-644 ◽

Cited By ~ 47

Author(s):

Adnane Sellam ◽

Christopher Askew ◽

Elias Epp ◽

Faiza Tebbji ◽

Alaka Mullick ◽

...

Keyword(s):

Cell Wall ◽

Transcription Factor ◽

Candida Albicans ◽

Cell Separation ◽

Hyphal Growth ◽

Functional Domain ◽

Transcription Factor Family ◽

Content Type ◽

Genes Encoding

ABSTRACT The NDT80/PhoG transcription factor family includes ScNdt80p, a key modulator of the progression of meiotic division in Saccharomyces cerevisiae. In Candida albicans, a member of this family, CaNdt80p, modulates azole sensitivity by controlling the expression of ergosterol biosynthesis genes. We previously demonstrated that CaNdt80p promoter targets, in addition to ERG genes, were significantly enriched in genes related to hyphal growth. Here, we report that CaNdt80p is indeed required for hyphal growth in response to different filament-inducing cues and for the proper expression of genes characterizing the filamentous transcriptional program. These include noteworthy genes encoding cell wall components, such as HWP1, ECE1, RBT4, and ALS3. We also show that CaNdt80p is essential for the completion of cell separation through the direct transcriptional regulation of genes encoding the chitinase Cht3p and the cell wall glucosidase Sun41p. Consistent with their hyphal defect, ndt80 mutants are avirulent in a mouse model of systemic candidiasis. Interestingly, based on functional-domain organization, CaNdt80p seems to be a unique regulator characterizing fungi from the CTG clade within the subphylum Saccharomycotina. Therefore, this study revealed a new role of the novel member of the fungal NDT80 transcription factor family as a regulator of cell separation, hyphal growth, and virulence.

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Deficiencies in the essential Smp3 mannosyltransferase block glycosylphosphatidylinositol assembly and lead to defects in growth and cell wall biogenesis in Candida albicans

Microbiology ◽

10.1099/mic.0.27254-0 ◽

2004 ◽

Vol 150 (10) ◽

pp. 3115-3128 ◽

Cited By ~ 24

Author(s):

S. J. Grimme

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Cell Wall Biogenesis

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Dosage-dependent roles of the Cwt1 transcription factor for cell wall architecture, morphogenesis, drug sensitivity and virulence in Candida albicans

Yeast ◽

10.1002/yea.1733 ◽

2009 ◽

pp. n/a-n/a ◽

Cited By ~ 1

Author(s):

Inmaculada Moreno ◽

Mar��a Martinez-Esparza ◽

Leslie Carolina Laforet ◽

Rafael Sentandreu ◽

Joachim F. Ernst ◽

...

Keyword(s):

Cell Wall ◽

Transcription Factor ◽

Candida Albicans ◽

Drug Sensitivity ◽

Cell Wall Architecture

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Activation of Cph1 causes ß(1,3)-glucan unmasking in Candida albicans and attenuates virulence in mice in a neutrophil-dependent manner

PLoS Pathogens ◽

10.1371/journal.ppat.1009839 ◽

2021 ◽

Vol 17 (8) ◽

pp. e1009839

Author(s):

Andrew S. Wagner ◽

Trevor J. Hancock ◽

Stephen W. Lumsdaine ◽

Sarah J. Kauffman ◽

Mikayla M. Mangrum ◽

...

Keyword(s):

Cell Wall ◽

Transcription Factor ◽

Candida Albicans ◽

Immune System ◽

Mapk Pathway ◽

Host Immune System ◽

Dependent Manner ◽

Antibody Treatment ◽

Fungal Burden ◽

Upstream Kinase

Masking the immunogenic cell wall epitope ß(1,3)-glucan under an outer layer of mannosylated glycoproteins is an important virulence factor deployed by Candida albicans during infection. Consequently, increased ß(1,3)-glucan exposure (unmasking) reveals C. albicans to the host’s immune system and attenuates its virulence. We have previously shown that activation of the Cek1 MAPK pathway via expression of a hyperactive allele of an upstream kinase (STE11ΔN467) induces unmasking. It also increased survival of mice in a murine disseminated candidiasis model and attenuated kidney fungal burden by ≥33 fold. In this communication, we utilized cyclophosphamide-induced immunosuppression to test if the clearance of the unmasked STE11ΔN467 mutant was dependent on the host immune system. Suppression of the immune response by cyclophosphamide reduced the attenuation in fungal burden caused by the STE11ΔN467 allele. Moreover, specific depletion of neutrophils via 1A8 antibody treatment also reduced STE11ΔN467-dependent fungal burden attenuation, but to a lesser extent than cyclophosphamide, demonstrating an important role for neutrophils in mediating fungal clearance of unmasked STE11ΔN467 cells. In an effort to understand the mechanism by which Ste11ΔN467 causes unmasking, transcriptomics were used to reveal that several components in the Cek1 MAPK pathway were upregulated, including the transcription factor CPH1 and the cell wall sensor DFI1. In this report we show that a cph1ΔΔ mutation restored ß(1,3)-glucan exposure to wild-type levels in the STE11ΔN467 strain, confirming that Cph1 is the transcription factor mediating Ste11ΔN467-induced unmasking. Furthermore, Cph1 is shown to induce a positive feedback loop that increases Cek1 activation. In addition, full unmasking by STE11ΔN467 is dependent on the upstream cell wall sensor DFI1. However, while deletion of DFI1 significantly reduced Ste11ΔN467-induced unmasking, it did not impact activation of the downstream kinase Cek1. Thus, it appears that once stimulated by Ste11ΔN467, Dfi1 activates a parallel signaling pathway that is involved in Ste11ΔN467-induced unmasking.

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The Candida albicans homologue of PIG-P, CaGpi19p: gene dosage and role in growth and filamentation

Microbiology ◽

10.1099/mic.0.039628-0 ◽

2010 ◽

Vol 156 (10) ◽

pp. 3041-3051 ◽

Cited By ~ 20

Author(s):

Guiliana Soraya Victoria ◽

Pravin Kumar ◽

Sneha Sudha Komath

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Gene Dosage ◽

Gene Dosage Effect ◽

Growth Defects ◽

Cell Wall Biogenesis ◽

Truncation Mutant ◽

Range Of Functions ◽

Functional Equivalent ◽

Glycosylphosphatidyl Inositol

Glycosylphosphatidyl inositol (GPI)-anchored proteins in Candida albicans are responsible for a vast range of functions, and deletions in certain GPI-anchored proteins severely reduce adhesion and virulence of this organism. In addition, completely modified GPIs are necessary for virulence. GPI anchor biosynthesis is essential for viability and starts with the transfer of N-acetylglucosamine to phosphatidylinositol. This step is catalysed by a multi-subunit complex, GPI–N-acetylglucosaminyltransferase (GPI–GnT). In this, the first report to our knowledge on a subunit of the Candida GPI–GnT complex, we show that CaGpi19p is the functional equivalent of the Saccharomyces cerevisiae Gpi19p. An N-terminal truncation mutant of CaGpi19p functionally complements a conditionally lethal S. cerevisiae gpi19 mutant. Further, we constructed a conditional null mutant of CaGPI19 by disrupting one allele and placing the remaining copy under the control of the MET3 promoter. Repression leads to growth defects, cell wall biogenesis aberrations, azole sensitivity and hyperfilamention. In addition, there is a noticeable gene dosage effect, with the heterozygote also displaying intermediate degrees of most phenotypes. The mutants also displayed a reduced susceptibility to the antifungal agent amphotericin B. Collectively, the results suggest that CaGPI19 is required for normal morphology and cell wall architecture.

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The zinc cluster transcription factor Czf1 regulates cell wall architecture and integrity in Candida albicans

Molecular Microbiology ◽

10.1111/mmi.14727 ◽

2021 ◽

Author(s):

Austin Mottola ◽

Bernardo Ramírez‐Zavala ◽

Kerstin Hünniger ◽

Oliver Kurzai ◽

Joachim Morschhäuser

Keyword(s):

Cell Wall ◽

Transcription Factor ◽

Candida Albicans ◽

Zinc Cluster ◽

Cell Wall Architecture

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