scholarly journals TheCandida albicansDse1 Protein Is Essential and Plays a Role in Cell Wall Rigidity, Biofilm Formation, and Virulence

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Jalil Y. Daher ◽  
Joseph Koussa ◽  
Samer Younes ◽  
Roy A. Khalaf
Keyword(s):  
Cell Wall ◽  
Biofilm Formation ◽  
Essential Gene ◽  
Calcofluor White ◽  
Causative Agents ◽  
A Cell ◽  
Cell Wall Rigidity ◽  
Inducing Factors ◽  
Mouse Model Of Infection ◽  
Increased Susceptibility

The fungal pathogenCandida albicansis one of the leading causative agents of death in immunocompromised individuals. It harbors an arsenal of cell wall anchored factors that are implicated in virulence such as filamentation inducing factors, adhesins, lipases, proteases, and superoxide dismutases. Dse1 is a cell wall protein involved in cell wall metabolism. The purpose of this study is to characterize the role Dse1 plays in virulence. Dse1 appears to be an essential gene as no homozygous null mutant was possible. The heterozygote mutant exhibited increased susceptibility to calcofluor white, a cell wall disrupting agent, with a subsequent reduction in cell wall chitin content, decreased oxidative stress tolerance, a 30% reduction in biofilm formation, and a delay in adhesion that was mirrored by a reduction in virulence in a mouse model of infection. Dse1 thus appears to be an important protein involved in cell wall integrity and rigidity.

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

2007 ◽  
Vol 6 (11) ◽  
pp. 2056-2065 ◽  
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.

scholarly journals Aspergillus fumigatus RasA Regulates Asexual Development and Cell Wall Integrity

2008 ◽  
Vol 7 (9) ◽  
pp. 1530-1539 ◽  
Author(s):  
Jarrod R. Fortwendel ◽  
Kevin K. Fuller ◽  
Timothy J. Stephens ◽  
W. Clark Bacon ◽  
David S. Askew ◽  
...  
Keyword(s):  
Cell Wall ◽  
Hyphal Growth ◽  
Cell Wall Integrity ◽  
Signaling Cascades ◽  
Asexual Development ◽  
Wild Type ◽  
Calcofluor White ◽  
Ras Family ◽  
Type Gene ◽  
Increased Susceptibility

ABSTRACT The Ras family of proteins is a large group of monomeric GTPases. Members of the fungal Ras family act as molecular switches that transduce signals from the outside of the cell to signaling cascades inside the cell. A. fumigatus RasA is 94% identical to the essential RasA gene of Aspergillus nidulans and is the Ras family member sharing the highest identity to Ras homologs studied in many other fungi. In this study, we report that rasA is not essential in A. fumigatus, but its absence is associated with slowed germination and a severe defect in radial growth. The ΔrasA hyphae were more than two times the diameter of wild-type hyphae, and they displayed repeated changes in the axis of polarity during hyphal growth. The deformed hyphae accumulated numerous nuclei within each hyphal compartment. The ΔrasA mutant conidiated poorly, but this phenotype could be ameliorated by growth on osmotically stabilized media. The ΔrasA mutant also showed increased susceptibility to cell wall stressors, stained more intensely with calcofluor white, and was refractory to lysing enzymes used to make protoplasts, suggesting an alteration of the cell wall. All phenotypes associated with deletion of rasA could be corrected by reinsertion of the wild-type gene. These data demonstrate a crucial role for RasA in both hyphal growth and asexual development in A. fumigatus and provide evidence that RasA function is linked to cell wall integrity.

scholarly journals Roles of Calcineurin and Crz1 in Antifungal Susceptibility and Virulence of Candida glabrata

2010 ◽  
Vol 54 (4) ◽  
pp. 1639-1643 ◽  
Author(s):  
Taiga Miyazaki ◽  
Shunsuke Yamauchi ◽  
Tatsuo Inamine ◽  
Yosuke Nagayoshi ◽  
Tomomi Saijo ◽  
...  
Keyword(s):  
Cell Wall ◽  
Transcription Factor ◽  
Candida Glabrata ◽  
Antifungal Susceptibility ◽  
A Cell ◽  
Increased Susceptibility

ABSTRACT A Candida glabrata calcineurin mutant exhibited increased susceptibility to both azole antifungal and cell wall-damaging agents and was also attenuated in virulence. Although a mutant lacking the downstream transcription factor Crz1 displayed a cell wall-associated phenotype intermediate to that of the calcineurin mutant and was modestly attenuated in virulence, it did not show increased azole susceptibility. These results suggest that calcineurin regulates both Crz1-dependent and -independent pathways depending on the type of stress.

scholarly journals The Aspergillus fumigatus sitA Phosphatase Homologue Is Important for Adhesion, Cell Wall Integrity, Biofilm Formation, and Virulence

2015 ◽  
Vol 14 (8) ◽  
pp. 728-744 ◽  
Author(s):  
Vinícius Leite Pedro Bom ◽  
Patrícia Alves de Castro ◽  
Lizziane K. Winkelströter ◽  
Marçal Marine ◽  
Juliana I. Hori ◽  
...  
Keyword(s):  
Cell Wall ◽  
Aspergillus Fumigatus ◽  
Biofilm Formation ◽  
Essential Gene ◽  
Pathogenic Fungus ◽  
Invasive Pulmonary Aspergillosis ◽  
Cell Wall Integrity ◽  
Necrosis Factor Alpha ◽  
Content Type ◽  
Opportunistic Pathogenic

ABSTRACTAspergillus fumigatusis an opportunistic pathogenic fungus able to infect immunocompromised patients, eventually causing disseminated infections that are difficult to control and lead to high mortality rates. It is important to understand how the signaling pathways that regulate these factors involved in virulence are orchestrated. Protein phosphatases are central to numerous signal transduction pathways. Here, we characterize theA. fumigatusprotein phosphatase 2A SitA, theSaccharomyces cerevisiaeSit4p homologue. ThesitAgene is not an essential gene, and we were able to construct anA. fumigatusnull mutant. The ΔsitAstrain had decreased MpkA phosphorylation levels, was more sensitive to cell wall-damaging agents, had increased β-(1,3)-glucan and chitin, was impaired in biofilm formation, and had decreased protein kinase C activity. The ΔsitAstrain is more sensitive to several metals and ions, such as MnCl2, CaCl2, and LiCl, but it is more resistant to ZnSO4. The ΔsitAstrain was avirulent in a murine model of invasive pulmonary aspergillosis and induces an augmented tumor necrosis factor alpha (TNF-α) response in mouse macrophages. These results stress the importance ofA. fumigatusSitA as a possible modulator of PkcA/MpkA activity and its involvement in the cell wall integrity pathway.

scholarly journals Two Novel, Putatively Cell Wall-Associated and Glycosylphosphatidylinositol-Anchored α-Glucanotransferase Enzymes of Aspergillus niger

2007 ◽  
Vol 6 (7) ◽  
pp. 1178-1188 ◽  
Author(s):  
R. M. van der Kaaij ◽  
X.-L. Yuan ◽  
A. Franken ◽  
A. F. J. Ram ◽  
P. J. Punt ◽  
...  
Keyword(s):  
Cell Wall ◽  
Aspergillus Niger ◽  
Fungal Species ◽  
Degree Of Polymerization ◽  
Reaction Products ◽  
Calcofluor White ◽  
Fungal Cell ◽  
Transglycosylation Activity ◽  
Glycosidic Bonds ◽  
A Cell

ABSTRACT In the genome sequence of Aspergillus niger CBS 513.88, three genes were identified with high similarity to fungal α-amylases. The protein sequences derived from these genes were different in two ways from all described fungal α-amylases: they were predicted to be glycosylphosphatidylinositol anchored, and some highly conserved amino acids of enzymes in the α-amylase family were absent. We expressed two of these enzymes in a suitable A. niger strain and characterized the purified proteins. Both enzymes showed transglycosylation activity on donor substrates with α-(1,4)-glycosidic bonds and at least five anhydroglucose units. The enzymes, designated AgtA and AgtB, produced new α-(1,4)-glycosidic bonds and therefore belong to the group of the 4-α-glucanotransferases (EC 2.4.1.25). Their reaction products reached a degree of polymerization of at least 30. Maltose and larger maltooligosaccharides were the most efficient acceptor substrates, although AgtA also used small nigerooligosaccharides containing α-(1,3)-glycosidic bonds as acceptor substrate. An agtA knockout of A. niger showed an increased susceptibility towards the cell wall-disrupting compound calcofluor white, indicating a cell wall integrity defect in this strain. Homologues of AgtA and AgtB are present in other fungal species with α-glucans in their cell walls, but not in yeast species lacking cell wall α-glucan. Possible roles for these enzymes in the synthesis and/or maintenance of the fungal cell wall are discussed.

scholarly journals CwpFM (EntFM) Is a Bacillus cereus Potential Cell Wall Peptidase Implicated in Adhesion, Biofilm Formation, and Virulence

2010 ◽  
Vol 192 (10) ◽  
pp. 2638-2642 ◽  
Author(s):  
Seav-Ly Tran ◽  
Elisabeth Guillemet ◽  
Michel Gohar ◽  
Didier Lereclus ◽  
Nalini Ramarao
Keyword(s):  
Cell Wall ◽  
Epithelial Cells ◽  
Bacillus Cereus ◽  
Biofilm Formation ◽  
New Information ◽  
A Cell

ABSTRACT Bacillus cereus EntFM displays an NlpC/P60 domain, characteristic of cell wall peptidases. The protein is involved in bacterial shape, motility, adhesion to epithelial cells, biofilm formation, vacuolization of macrophages, and virulence. These data provide new information on this, so far, poorly studied toxin and suggest that this protein is a cell wall peptidase, which we propose to rename CwpFM.

scholarly journals Requirement for Candida albicans Sun41 in Biofilm Formation and Virulence

2007 ◽  
Vol 6 (11) ◽  
pp. 2046-2055 ◽  
Author(s):  
Carmelle T. Norice ◽  
Frank J. Smith ◽  
Norma Solis ◽  
Scott G. Filler ◽  
Aaron P. Mitchell
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Biofilm Formation ◽  
Insertional Mutagenesis ◽  
Surface Protein ◽  
Altered Expression ◽  
Promising Therapeutic Target ◽  
A Cell ◽  
Homozygous Mutations ◽  
Insertion Mutations

ABSTRACT The cell wall of Candida albicans lies at the crossroads of pathogenicity and therapeutics. It contributes to pathogenicity through adherence and invasion; it is the target of both chemical and immunological antifungal strategies. We have initiated a dissection of cell wall function through targeted insertional mutagenesis of cell wall-related genes. Among 25 such genes, we were unable to generate homozygous mutations in 4, and they may be essential for viability. We created homozygous mutations in the remaining 21 genes. Insertion mutations in SUN41, Orf19.5412, Orf19.1277, MSB2, Orf19.3869, and WSC1 caused hypersensitivity to the cell wall inhibitor caspofungin, while two different ecm33 insertions caused mild caspofungin resistance. Insertion mutations in SUN41 and Orf19.5412 caused biofilm defects. Through analysis of homozygous sun41Δ/sun41Δ deletion mutants and sun41Δ/sun41Δ+pSUN41-complemented strains, we verified that Sun41 is required for biofilm formation and normal caspofungin tolerance. The sun41Δ/sun41Δ mutant had altered expression of four cell wall damage response genes, thus suggesting that it suffers a cell wall structural defect. Sun41 is required for inducing disease, because the mutant was severely attenuated in mouse models of disseminated and oropharyngeal candidiasis. Although the mutant produced aberrant hyphae, it had no defect in damaging endothelial or epithelial cells, unlike many other hypha-defective mutants. We suggest that the sun41Δ/sun41Δ cell wall defect is the primary cause of its attenuated virulence. As a small fungal surface protein with predicted glucosidase activity, Sun41 represents a promising therapeutic target.

scholarly journals Emw1p/YNL313cp is essential for maintenance of the cell wall in Saccharomyces cerevisiae

Microbiology ◽  
2011 ◽  
Vol 157 (4) ◽  
pp. 1032-1041 ◽  
Author(s):  
Tatjana Sipling ◽  
Chao Zhai ◽  
Barry Panaretou
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Permissive Temperature ◽  
Loss Of Function ◽  
Chitin Synthesis ◽  
Calcofluor White ◽  
Compensatory Response ◽  
Protein Protein Interaction ◽  
Kinase Cascade ◽  
A Cell

There are six essential genes in the Saccharomyces cerevisiae genome which encode proteins bearing the tetratricopeptide repeat (TPR) domain that mediates protein–protein interaction. Thus far, the function of one of them, YNL313c, remains unknown. Our conditional mutants of YNL313c display osmoremedial temperature sensitivity, hypersensitivity to both Calcofluor White and low concentrations of SDS, and osmoremedial caffeine sensitivity. These are hallmarks of mutants that display cell wall defects. Accordingly we rename the gene as EMW1 (essential for maintenance of the cell wall). Loss of Emw1p function is not associated with abrogation of the cell wall integrity (CWI) MAP kinase cascade. Instead, emw1ts mutants activate this cascade even at permissive temperature, indicating that loss of Emw1p function does not cause a defect in sensors and effectors of cell wall signalling, but leads to a cell wall defect directly. Constitutive activation of the CWI cascade is reflected by the overproduction of chitin by emw1ts mutants, a compensatory response frequently displayed by cell wall mutants. Growth is restored to emw1ts mutants incubated at otherwise non-permissive temperature when GFA1 is overexpressed. GFA1 encodes the hexosephosphate aminotransferase that catalyses the rate-limiting step in the pathway that synthesizes the chitin precursor UDP-GlcNAc. The possibility that Emw1p is required for function of Gfa1p was ruled out, because the emw1ts phenotype persists when the requirement for Gfa1p is bypassed. Furthermore, if loss of Emw1p function leads to loss of function of Gfa1p, then chitin synthesis would be diminished. Instead, a stimulation of the synthesis of this polymer is detected. Consequently, the defect associated with emw1ts mutants may be associated with compromise in one of the remaining processes that depend on UDP-GlcNAc, namely N-glycosylation or glycosylphosphatidylinositol (GPI)-anchor synthesis.

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