101
|
Martínez-Soto D, Robledo-Briones AM, Estrada-Luna AA, Ruiz-Herrera J. Transcriptomic analysis of Ustilago maydis infecting Arabidopsis reveals important aspects of the fungus pathogenic mechanisms. PLANT SIGNALING & BEHAVIOR 2013; 8:e25059. [PMID: 23733054 PMCID: PMC4005800 DOI: 10.4161/psb.25059] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 05/15/2013] [Accepted: 05/16/2013] [Indexed: 05/03/2023]
Abstract
Transcriptomic and biochemical analyses of the experimental pathosystem constituted by Ustilago maydis and Arabidopsis thaliana were performed. Haploid or diploid strains of U. maydis inoculated in A. thaliana plantlets grew on the surface and within the plant tissues in the form of mycelium, inducing chlorosis, anthocyanin formation, malformations, necrosis and adventitious roots development, but not teliospores. Symptoms were more severe in plants inoculated with the haploid strain which grew more vigorously than the diploid strain. RNA extracted at different times post-infection was used for hybridization of one-channel microarrays that were analyzed focusing on the fungal genes involved in the general pathogenic process, biogenesis of the fungal cell wall and the secretome. In total, 3,537 and 3,299 genes were differentially expressed in the haploid and diploid strains, respectively. Differentially expressed genes were related to different functional categories and many of them showed a similar regulation occurring in U. maydis infecting maize. Our data suggest that the haploid strain behaves as a necrotrophic pathogen, whereas the diploid behaves as a biotrophic pathogen. The results obtained are evidence of the usefulness of the U. maydis-A. thaliana pathosystem for the analysis of the pathogenic mechanisms of U. maydis.
Collapse
Affiliation(s)
| | | | - Andrés A. Estrada-Luna
- Departamento de Ingeniería Genética; Unidad Irapuato; Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional; Irapuato, Gto México
| | - José Ruiz-Herrera
- Departamento de Ingeniería Genética; Unidad Irapuato; Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional; Irapuato, Gto México
| |
Collapse
|
102
|
Bates S, Hall RA, Cheetham J, Netea MG, MacCallum DM, Brown AJP, Odds FC, Gow NAR. Role of the Candida albicans MNN1 gene family in cell wall structure and virulence. BMC Res Notes 2013; 6:294. [PMID: 23886038 PMCID: PMC3750861 DOI: 10.1186/1756-0500-6-294] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 07/24/2013] [Indexed: 11/29/2022] Open
Abstract
Background The Candida albicans cell wall is the first point of contact with the host, and its outer surface is heavily enriched in mannoproteins modified through the addition of N- and O-mannan. Previous work, using mutants with gross defects in glycosylation, has clearly identified the importance of mannan in the host-pathogen interaction, immune recognition and virulence. Here we report the first analysis of the MNN1 gene family, which contains six members predicted to act as α-1,3 mannosyltransferases in the terminal stages of glycosylation. Findings We generated single null mutants in all members of the C. albicans MNN1 gene family, and disruption of MNN14 led to both in vitro and in vivo defects. Null mutants in other members of the family demonstrated no phenotypic defects, suggesting that these members may display functional redundancy. The mnn14Δ null mutant displayed hypersensitivity to agents associated with cell wall and glycosylation defects, suggesting an altered cell wall structure. However, no gross changes in cell wall composition or N-glycosylation were identified in this mutant, although an extension of phosphomannan chain length was apparent. Although the cell wall defects associated with the mnn14Δ mutant were subtle, this mutant displayed a severe attenuation of virulence in a murine infection model. Conclusion Mnn14 plays a distinct role from other members of the MNN1 family, demonstrating that specific N-glycan outer chain epitopes are required in the host-pathogen interaction and virulence.
Collapse
Affiliation(s)
- Steven Bates
- College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4QD, UK.
| | | | | | | | | | | | | | | |
Collapse
|
103
|
West L, Lowman DW, Mora-Montes HM, Grubb S, Murdoch C, Thornhill MH, Gow NAR, Williams D, Haynes K. Differential virulence of Candida glabrata glycosylation mutants. J Biol Chem 2013; 288:22006-18. [PMID: 23720756 PMCID: PMC3724654 DOI: 10.1074/jbc.m113.478743] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The fungus Candida glabrata is an important and increasingly common pathogen of humans, particularly in immunocompromised hosts. Despite this, little is known about the attributes that allow this organism to cause disease or its interaction with the host immune system. However, in common with other fungi, the cell wall of C. glabrata is the initial point of contact between the host and pathogen, and as such, it is likely to play an important role in mediating interactions and hence virulence. Here, we show both through genetic complementation and polysaccharide structural analyses that C. glabrata ANP1, MNN2, and MNN11 encode functional orthologues of the respective Saccharomyces cerevisiae mannosyltransferases. Furthermore, we show that deletion of the C. glabrata Anp1, Mnn2, and Mnn11 mannosyltransferases directly affects the structure of the fungal N-linked mannan, in line with their predicted functions, and this has implications for cell wall integrity and consequently virulence. C. glabrata anp1 and mnn2 mutants showed increased virulence, compared with wild-type (and mnn11) cells. This is in contrast to Candida albicans where inactivation of genes involved in mannan biosynthesis has usually been linked to an attenuation of virulence. In the long term, a better understanding of the attributes that allow C. glabrata to cause disease will provide insights that can be adopted for the development of novel therapeutic and diagnostic approaches.
Collapse
Affiliation(s)
- Lara West
- Department of Microbiology, Imperial College London, London, SW7 2AZ, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|
104
|
Hall RA, Bates S, Lenardon MD, MacCallum DM, Wagener J, Lowman DW, Kruppa MD, Williams DL, Odds FC, Brown AJP, Gow NAR. The Mnn2 mannosyltransferase family modulates mannoprotein fibril length, immune recognition and virulence of Candida albicans. PLoS Pathog 2013; 9:e1003276. [PMID: 23633946 PMCID: PMC3636026 DOI: 10.1371/journal.ppat.1003276] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Accepted: 02/06/2013] [Indexed: 11/19/2022] Open
Abstract
The fungal cell wall is the first point of interaction between an invading fungal pathogen and the host immune system. The outer layer of the cell wall is comprised of GPI anchored proteins, which are post-translationally modified by both N- and O-linked glycans. These glycans are important pathogen associated molecular patterns (PAMPs) recognised by the innate immune system. Glycan synthesis is mediated by a series of glycosyl transferases, located in the endoplasmic reticulum and Golgi apparatus. Mnn2 is responsible for the addition of the initial α1,2-mannose residue onto the α1,6-mannose backbone, forming the N-mannan outer chain branches. In Candida albicans, the MNN2 gene family is comprised of six members (MNN2, MNN21, MNN22, MNN23, MNN24 and MNN26). Using a series of single, double, triple, quintuple and sextuple mutants, we show, for the first time, that addition of α1,2-mannose is required for stabilisation of the α1,6-mannose backbone and hence regulates mannan fibril length. Sequential deletion of members of the MNN2 gene family resulted in the synthesis of lower molecular weight, less complex and more uniform N-glycans, with the sextuple mutant displaying only un-substituted α1,6-mannose. TEM images confirmed that the sextuple mutant was completely devoid of the outer mannan fibril layer, while deletion of two MNN2 orthologues resulted in short mannan fibrils. These changes in cell wall architecture correlated with decreased proinflammatory cytokine induction from monocytes and a decrease in fungal virulence in two animal models. Therefore, α1,2-mannose of N-mannan is important for both immune recognition and virulence of C. albicans.
Collapse
Affiliation(s)
- Rebecca A. Hall
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, United Kingdom
| | - Steven Bates
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Megan D. Lenardon
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, United Kingdom
| | - Donna M. MacCallum
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, United Kingdom
| | - Jeanette Wagener
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, United Kingdom
| | - Douglas W. Lowman
- Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee, United States of America
- AppRidge International, LLC, Telford, Tennessee, United States of America
| | - Michael D. Kruppa
- Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee, United States of America
| | - David L. Williams
- Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee, United States of America
| | - Frank C. Odds
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, United Kingdom
| | - Alistair J. P. Brown
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, United Kingdom
| | - Neil A. R. Gow
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, United Kingdom
| |
Collapse
|
105
|
Shahana S, Mora-Montes HM, Castillo L, Bohovych I, Sheth CC, Odds FC, Gow NAR, Brown AJP. Reporters for the analysis of N-glycosylation in Candida albicans. Fungal Genet Biol 2013; 56:107-15. [PMID: 23608318 PMCID: PMC3705205 DOI: 10.1016/j.fgb.2013.03.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2012] [Revised: 03/05/2013] [Accepted: 03/25/2013] [Indexed: 11/27/2022]
Abstract
Reporters for dissection of N-glycosylation in Candida albicans. Detection of glycosylation at the single site on epitope-tagged reporter. Reporter faithfully reflects glycosylation defects in cell wall mutants.
A large proportion of Candida albicans cell surface proteins are decorated post-translationally by glycosylation. Indeed N-glycosylation is critical for cell wall biogenesis in this major fungal pathogen and for its interactions with host cells. A detailed understanding of N-glycosylation will yield deeper insights into host-pathogen interactions. However, the analysis of N-glycosylation is extremely challenging because of the complexity and heterogeneity of these structures. Therefore, in an attempt to reduce this complexity and facilitate the analysis of N-glycosylation, we have developed new synthetic C. albicans reporters that carry a single N-linked glycosylation site derived from Saccharomyces cerevisiae Suc2. These glycosylation reporters, which carry C. albicans Hex1 or Sap2 signal sequences plus carboxy-terminal FLAG3 and His6 tags, were expressed in C. albicans from the ACT1 promoter. The reporter proteins were successfully secreted and hyperglycosylated by C. albicans cells, and their outer chain glycosylation was dependent on Och1 and Pmr1, which are required for N-mannan synthesis, but not on Mnt1 and Mnt2 which are only required for O-mannosylation. These reporters are useful tools for the experimental dissection of N-glycosylation and other related processes in C. albicans, such as secretion.
Collapse
Affiliation(s)
- Shahida Shahana
- Aberdeen Fungal Group, School of Medical Sciences, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen AB25 2ZD, UK
| | | | | | | | | | | | | | | |
Collapse
|
106
|
Ifrim DC, Joosten LAB, Kullberg BJ, Jacobs L, Jansen T, Williams DL, Gow NAR, van der Meer JWM, Netea MG, Quintin J. Candida albicans primes TLR cytokine responses through a Dectin-1/Raf-1-mediated pathway. THE JOURNAL OF IMMUNOLOGY 2013; 190:4129-35. [PMID: 23475217 DOI: 10.4049/jimmunol.1202611] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The immune system is essential to maintain homeostasis with resident microbial populations, ensuring that the symbiotic host-microbial relationship is maintained. In parallel, commensal microbes significantly shape mammalian immunity at the host mucosal surface, as well as systemically. Candida albicans is an opportunistic pathogen that lives as a commensal on skin and mucosa of healthy individuals. Little is known about its capacity to modulate responses toward other microorganisms, such as colonizing bacteria (e.g., intestinal microorganisms). The aim of this study was to assess the cytokine production of PBMCs induced by commensal bacteria when these cells were primed by C. albicans. We show that C. albicans and β-1,3-glucan induce priming of human primary mononuclear cells and this leads to enhanced cytokine production upon in vitro stimulation with TLR ligands and bacterial commensals. This priming requires the β-1,3-glucan receptor dectin-1 and the noncanonical Raf-1 pathway. In addition, although purified mannans cannot solely mediate the priming, the presence of mannosyl residues in the cell wall of C. albicans is nevertheless required. In conclusion, C. albicans is able to modify cytokine responses to TLR ligands and colonizing bacteria, which is likely to impact the inflammatory reaction during mucosal diseases.
Collapse
Affiliation(s)
- Daniela C Ifrim
- Department of Experimental Internal Medicine, Radboud University Nijmegen Medical Centre, Nijmegen 6525 GA, The Netherlands
| | | | | | | | | | | | | | | | | | | |
Collapse
|
107
|
Chen Z, Sun H, Li P, He N, Zhu T, Li Y. Enhancement of the gene targeting efficiency of non-conventional yeasts by increasing genetic redundancy. PLoS One 2013; 8:e57952. [PMID: 23505447 PMCID: PMC3591452 DOI: 10.1371/journal.pone.0057952] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 01/28/2013] [Indexed: 12/19/2022] Open
Abstract
In contrast to model yeasts, gene targeting efficiencies of non-conventional yeasts are usually low, which greatly limits the research and applications of these organisms. In this study, we aimed to enhance the gene targeting efficiency of non-conventional yeasts by improving the fitness of mutant strains, particularly by increasing the genetic redundancy of host cells. To demonstrate this process, OCH1 gene deletion in Pichia pastoris was performed. Extra copies of the OCH1 gene on a helper plasmid were provided for the P. pastoris GS115 strain before the native OCH1 gene in the genomic DNA was knocked out. The redundancy in OCH1 gene significantly eliminated the growth defects of the och1 mutant and increased the deletion efficiency of the OCH1 gene by two orders of magnitude with the same length of homologous flanks. The same strategy was used to delete the KU70 and SGS1 genes. The targeting efficiencies of KU70 and SGS1 were increased by 1- and 23-fold, respectively. Therefore, this study provided an efficient strategy for the deletion of "stubborn" genes in non-conventional yeasts. This study further showed that cellular fitness is potentially an important factor that can limit the efficiency of gene targeting.
Collapse
Affiliation(s)
- Zao Chen
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, People’s Republic of China
| | - Hongbing Sun
- Institute of Microbiology, Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Pengfei Li
- College of Life Science and Agriculture, Hainan University, Haikou, People’s Republic of China
| | - Ning He
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, People’s Republic of China
- * E-mail: (NH); (TZ)
| | - Taicheng Zhu
- Institute of Microbiology, Chinese Academy of Sciences, Beijing, People’s Republic of China
- * E-mail: (NH); (TZ)
| | - Yin Li
- Institute of Microbiology, Chinese Academy of Sciences, Beijing, People’s Republic of China
| |
Collapse
|
108
|
Hsp90 orchestrates transcriptional regulation by Hsf1 and cell wall remodelling by MAPK signalling during thermal adaptation in a pathogenic yeast. PLoS Pathog 2012; 8:e1003069. [PMID: 23300438 PMCID: PMC3531498 DOI: 10.1371/journal.ppat.1003069] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2012] [Accepted: 10/18/2012] [Indexed: 01/30/2023] Open
Abstract
Thermal adaptation is essential in all organisms. In yeasts, the heat shock response is commanded by the heat shock transcription factor Hsf1. Here we have integrated unbiased genetic screens with directed molecular dissection to demonstrate that multiple signalling cascades contribute to thermal adaptation in the pathogenic yeast Candida albicans. We show that the molecular chaperone heat shock protein 90 (Hsp90) interacts with and down-regulates Hsf1 thereby modulating short term thermal adaptation. In the longer term, thermal adaptation depends on key MAP kinase signalling pathways that are associated with cell wall remodelling: the Hog1, Mkc1 and Cek1 pathways. We demonstrate that these pathways are differentially activated and display cross talk during heat shock. As a result ambient temperature significantly affects the resistance of C. albicans cells to cell wall stresses (Calcofluor White and Congo Red), but not osmotic stress (NaCl). We also show that the inactivation of MAP kinase signalling disrupts this cross talk between thermal and cell wall adaptation. Critically, Hsp90 coordinates this cross talk. Genetic and pharmacological inhibition of Hsp90 disrupts the Hsf1-Hsp90 regulatory circuit thereby disturbing HSP gene regulation and reducing the resistance of C. albicans to proteotoxic stresses. Hsp90 depletion also affects cell wall biogenesis by impairing the activation of its client proteins Mkc1 and Hog1, as well as Cek1, which we implicate as a new Hsp90 client in this study. Therefore Hsp90 modulates the short term Hsf1-mediated activation of the classic heat shock response, coordinating this response with long term thermal adaptation via Mkc1- Hog1- and Cek1-mediated cell wall remodelling. Candida albicans is one of the most persistent yeast pathogens known to man, causing frequent mucosal infections (thrush) in otherwise healthy individuals, and potentially fatal bloodstream infections in immunocompromised patients. C. albicans colonises warm-blooded animals and occupies thermally buffered niches. Yet during its evolution this pathogen has retained the classic heat shock response whilst other stress responses have diverged significantly. We have established that the essential, evolutionarily conserved molecular chaperone, Hsp90, coordinates thermal adaptation. Hsp90 interacts with and modulates the activity of the heat shock transcription factor, Hsf1, thereby controlling the expression of heat shock proteins required for the clearance of proteins damaged by proteotoxic stresses. In addition, Hsp90 modulates the activities of key MAP kinase signalling pathways that mediate cell wall remodelling and long term adaptation to heat shock. Loss of any of these factors results in a significant reduction in thermotolerance.
Collapse
|
109
|
Wagener J, Weindl G, de Groot PWJ, de Boer AD, Kaesler S, Thavaraj S, Bader O, Mailänder-Sanchez D, Borelli C, Weig M, Biedermann T, Naglik JR, Korting HC, Schaller M. Glycosylation of Candida albicans cell wall proteins is critical for induction of innate immune responses and apoptosis of epithelial cells. PLoS One 2012; 7:e50518. [PMID: 23226301 PMCID: PMC3511564 DOI: 10.1371/journal.pone.0050518] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 10/23/2012] [Indexed: 12/20/2022] Open
Abstract
C. albicans is one of the most common fungal pathogen of humans, causing local and superficial mucosal infections in immunocompromised individuals. Given that the key structure mediating host-C. albicans interactions is the fungal cell wall, we aimed to identify features of the cell wall inducing epithelial responses and be associated with fungal pathogenesis. We demonstrate here the importance of cell wall protein glycosylation in epithelial immune activation with a predominant role for the highly branched N-glycosylation residues. Moreover, these glycan moieties induce growth arrest and apoptosis of epithelial cells. Using an in vitro model of oral candidosis we demonstrate, that apoptosis induction by C. albicans wild-type occurs in early stage of infection and strongly depends on intact cell wall protein glycosylation. These novel findings demonstrate that glycosylation of the C. albicans cell wall proteins appears essential for modulation of epithelial immunity and apoptosis induction, both of which may promote fungal pathogenesis in vivo.
Collapse
Affiliation(s)
- Jeanette Wagener
- Department of Dermatology, Eberhard Karls University Tübingen, Tübingen, Germany
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Aberdeen, United Kingdom
| | - Günther Weindl
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Freie Universität Berlin, Berlin, Germany
| | - Piet W. J. de Groot
- Regional Center for Biomedical Research, Albacete Science & Technology Park, University of Castilla – La Mancha, Albacete, Spain
| | - Albert D. de Boer
- Regional Center for Biomedical Research, Albacete Science & Technology Park, University of Castilla – La Mancha, Albacete, Spain
- Department of Medical Microbiology and National Reference Center for Systemic Mycoses, University Medical Center Göttingen, Göttingen, Germany
| | - Susanne Kaesler
- Department of Dermatology, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Selvam Thavaraj
- Department of Oral Immunology, King’s College London Dental Institute, King’s College London, London, United Kingdom
| | - Oliver Bader
- Department of Medical Microbiology and National Reference Center for Systemic Mycoses, University Medical Center Göttingen, Göttingen, Germany
| | | | - Claudia Borelli
- Department of Dermatology, Ludwig-Maximilians-University, München, Germany
| | - Michael Weig
- Department of Medical Microbiology and National Reference Center for Systemic Mycoses, University Medical Center Göttingen, Göttingen, Germany
| | - Tilo Biedermann
- Department of Dermatology, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Julian R. Naglik
- Department of Oral Immunology, King’s College London Dental Institute, King’s College London, London, United Kingdom
| | | | - Martin Schaller
- Department of Dermatology, Eberhard Karls University Tübingen, Tübingen, Germany
- * E-mail:
| |
Collapse
|
110
|
|
111
|
Hernández-Cervantes A, Mora-Montes HM, Álvarez-Vargas A, Jiménez DFD, Robledo-Ortiz CI, Flores-Carreón A. Isolation of Sporothrix schenckii MNT1 and the biochemical and functional characterization of the encoded α1,2-mannosyltransferase activity. Microbiology (Reading) 2012; 158:2419-2427. [DOI: 10.1099/mic.0.060392-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Affiliation(s)
- Arturo Hernández-Cervantes
- Departamento de Biología, División de Ciencias Naturales y Exactas, Campus Guanajuato, Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P. 36050, Guanajuato, Gto., Mexico
| | - Héctor M. Mora-Montes
- Departamento de Biología, División de Ciencias Naturales y Exactas, Campus Guanajuato, Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P. 36050, Guanajuato, Gto., Mexico
| | - Aurelio Álvarez-Vargas
- Departamento de Biología, División de Ciencias Naturales y Exactas, Campus Guanajuato, Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P. 36050, Guanajuato, Gto., Mexico
| | - Diana F. Díaz Jiménez
- Departamento de Biología, División de Ciencias Naturales y Exactas, Campus Guanajuato, Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P. 36050, Guanajuato, Gto., Mexico
| | - Claudia I. Robledo-Ortiz
- Departamento de Biología, División de Ciencias Naturales y Exactas, Campus Guanajuato, Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P. 36050, Guanajuato, Gto., Mexico
| | - Arturo Flores-Carreón
- Departamento de Biología, División de Ciencias Naturales y Exactas, Campus Guanajuato, Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P. 36050, Guanajuato, Gto., Mexico
| |
Collapse
|
112
|
Robledo-Ortiz CI, Flores-Carreón A, Hernández-Cervantes A, Álvarez-Vargas A, Lee KK, Díaz-Jiménez DF, Munro CA, Cano-Canchola C, Mora-Montes HM. Isolation and functional characterization of Sporothrix schenckii ROT2, the encoding gene for the endoplasmic reticulum glucosidase II. Fungal Biol 2012; 116:910-8. [DOI: 10.1016/j.funbio.2012.06.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 06/06/2012] [Accepted: 06/15/2012] [Indexed: 12/20/2022]
|
113
|
Lichtheimia species exhibit differences in virulence potential. PLoS One 2012; 7:e40908. [PMID: 22911715 PMCID: PMC3401187 DOI: 10.1371/journal.pone.0040908] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Accepted: 06/14/2012] [Indexed: 11/19/2022] Open
Abstract
Although the number of mucormycosis cases has increased during the last decades, little is known about the pathogenic potential of most mucoralean fungi. Lichtheimia species represent the second and third most common cause of mucormycosis in Europe and worldwide, respectively. To date only three of the five species of the genus have been found to be involved in mucormycosis, namely L. corymbifera, L. ramosa and L. ornata. However, it is not clear whether the clinical situation reflects differences in virulence between the species of Lichtheimia or whether other factors are responsible. In this study the virulence of 46 strains of all five species of Lichtheimia was investigated in chicken embryos. Additionally, strains of the closest-related genus Dichotomocladium were tested. Full virulence was restricted to the clinically relevant species while all strains of L. hyalospora, L. sphaerocystis and Dichotomocladium species were attenuated. Although virulence differences were present in the clinically relevant species, no connection between origin (environmental vs clinical) or phylogenetic position within the species was observed. Physiological studies revealed no clear connection of stress resistance and carbon source utilization with the virulence of the strains. Slower growth at 37°C might explain low virulence of L. hyalospora, L. spaherocystis and Dichotomocladium; however, similarly slow growing strains of L. ornata were fully virulent. Thus, additional factors or a complex interplay of factors determines the virulence of strains. Our data suggest that the clinical situation in fact reflects different virulence potentials in the Lichtheimiaceae.
Collapse
|
114
|
Zanni E, Franco M, Nakano M, Iida H, Palleschi C, Uccelletti D. KlMID1, a relevant key player between endoplasmic reticulum homeostasis and mitochondrial dysfunction in Kluyveromyces lactis. Microbiology (Reading) 2012; 158:1694-1701. [DOI: 10.1099/mic.0.056283-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Affiliation(s)
- Elena Zanni
- Department Biology and Biotechnology University of Rome LA SAPIENZA, 00185 Rome, Italy
| | - Milena Franco
- Department Biology and Biotechnology University of Rome LA SAPIENZA, 00185 Rome, Italy
| | - Masataka Nakano
- Department Biology, Tokyo Gakugei University, Koganei-shi, Tokyo 184-8501, Japan
| | - Hidetoshi Iida
- Department Biology, Tokyo Gakugei University, Koganei-shi, Tokyo 184-8501, Japan
| | - Claudio Palleschi
- Department Biology and Biotechnology University of Rome LA SAPIENZA, 00185 Rome, Italy
| | - Daniela Uccelletti
- Department Biology and Biotechnology University of Rome LA SAPIENZA, 00185 Rome, Italy
| |
Collapse
|
115
|
Park JN, Lee DJ, Kwon O, Oh DB, Bahn YS, Kang HA. Unraveling unique structure and biosynthesis pathway of N-linked glycans in human fungal pathogen Cryptococcus neoformans by glycomics analysis. J Biol Chem 2012; 287:19501-15. [PMID: 22500028 DOI: 10.1074/jbc.m112.354209] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The encapsulated fungal pathogen Cryptococcus neoformans causes cryptococcosis in immunocompromised individuals. Although cell surface mannoproteins have been implicated in C. neoformans pathogenicity, the structure of N-linked glycans assembled on mannoproteins has not yet been elucidated. By analyzing oligosaccharide profiles combined with exoglycosidase treatment, we report here that C. neoformans has serotype-specific high mannose-type N-glycans with or without a β1,2-xylose residue, which is attached to the trimannosyl core of N-glycans. Interestingly, the neutral N-glycans of serotypes A and D were shown to contain a xylose residue, whereas those of serotype B appeared to be much shorter and devoid of a xylose residue. Moreover, analysis of the C. neoformans uxs1Δ mutant demonstrated that UDP-xylose is utilized as a donor sugar in N-glycan biosynthesis. We also constructed and analyzed a set of C. neoformans mutant strains lacking genes putatively assigned to the reconstructed N-glycan biosynthesis pathway. It was shown that the outer chain of N-glycan is initiated by CnOch1p with addition of an α1,6-mannose residue and then subsequently extended by CnMnn2p with multiple additions of α1,2-mannose residues. Finally, comparative analysis of acidic N-glycans from wild-type, Cnoch1Δ, Cnmnn2Δ, and Cnuxs1Δ strains strongly indicated the presence of xylose phosphate attached to mannose residues in the core and outer region of N-glycans. Our data present the first report on the unique structure and biosynthesis pathway of N-glycans in C. neoformans.
Collapse
Affiliation(s)
- Jeong-Nam Park
- Department of Life Science, Center for Fungal Pathogenesis, Chung-Ang University, Seoul 156-756, South Korea
| | | | | | | | | | | |
Collapse
|
116
|
Takahashi S, Kudoh A, Okawa Y, Shibata N. Significant differences in the cell-wall mannans from three Candida glabrata strains correlate with antifungal drug sensitivity. FEBS J 2012; 279:1844-56. [PMID: 22404982 DOI: 10.1111/j.1742-4658.2012.08564.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Candida glabrata is often the second or third most common cause of candidiasis after Candida albicans. C. glabrata infections are difficult to treat, often resistant to many azole antifungal agents and are associated with a high mortality rate in compromised patients. We determined the antigenic structure of the cell-wall mannoproteins from three C. glabrata strains, NBRC 0005, NBRC 0622 and NBRC 103857. (1)H NMR and methylation analyses of the acetolysis products of these mannoproteins showed a significant difference in the amount of the β-1,2-linked mannose residue and side-chain structure. The C. glabrata NBRC 103857 strain contained up to the triose side chains and the nonreducing terminal of the triose was predominantly the β-1,2-linked mannose residue. By contrast, the mannans of the two former strains possessed up to the tetraose side chains and the amount of the β-1,2-linked mannose residue was very low. Larger oligosaccharides than tetraose in the acetolysis products of these mannans were identified as incomplete cleavage fragments by analyzing methylation, (1)H NMR spectra and the α1-2,3 mannosidase degradation reaction. Resistance to the antifungal drugs itraconazole and micafungin was significantly different in these strains. Interestingly, the NBRC 103857 strain, which involved a large amount of the β-1,2-linked mannose residues, exhibited significant sensitivity to these antifungal drugs.
Collapse
Affiliation(s)
- Shizuka Takahashi
- Department of Infection and Host Defense, Tohoku Pharmaceutical University, Aoba-ku, Sendai, Japan
| | | | | | | |
Collapse
|
117
|
Lewis LE, Bain JM, Lowes C, Gillespie C, Rudkin FM, Gow NAR, Erwig LP. Stage specific assessment of Candida albicans phagocytosis by macrophages identifies cell wall composition and morphogenesis as key determinants. PLoS Pathog 2012; 8:e1002578. [PMID: 22438806 PMCID: PMC3305454 DOI: 10.1371/journal.ppat.1002578] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Accepted: 01/26/2012] [Indexed: 11/18/2022] Open
Abstract
Candida albicans is a major life-threatening human fungal pathogen. Host defence against systemic Candida infection relies mainly on phagocytosis of fungal cells by cells of the innate immune system. In this study, we have employed video microscopy, coupled with sophisticated image analysis tools, to assess the contribution of distinct C. albicans cell wall components and yeast-hypha morphogenesis to specific stages of phagocytosis by macrophages. We show that macrophage migration towards C. albicans was dependent on the glycosylation status of the fungal cell wall, but not cell viability or morphogenic switching from yeast to hyphal forms. This was not a consequence of differences in maximal macrophage track velocity, but stems from a greater percentage of macrophages pursuing glycosylation deficient C. albicans during the first hour of the phagocytosis assay. The rate of engulfment of C. albicans attached to the macrophage surface was significantly delayed for glycosylation and yeast-locked morphogenetic mutant strains, but enhanced for non-viable cells. Hyphal cells were engulfed at a slower rate than yeast cells, especially those with hyphae in excess of 20 µm, but there was no correlation between hyphal length and the rate of engulfment below this threshold. We show that spatial orientation of the hypha and whether hyphal C. albicans attached to the macrophage via the yeast or hyphal end were also important determinants of the rate of engulfment. Breaking down the overall phagocytic process into its individual components revealed novel insights into what determines the speed and effectiveness of C. albicans phagocytosis by macrophages. Host defence against systemic candidiasis relies mainly on the ingestion and elimination of fungal cells by cells of the innate immune system, especially neutrophils and macrophages. Here we have used live cell video microscopy coupled with sophisticated image analysis to generate a temporal and spatial analysis in unprecedented detail of the specific effects of C. albicans viability, cell wall composition, morphogenesis and spatial orientation on two distinct stages (macrophage migration and engulfment of bound C. albicans) of the phagocytosis process. The novel methods employed here to study phagocytosis of C. albicans could be applied to study other pathogens and uptake of dying host cells. Thus, our studies have direct implications for a much broader community and provide a blueprint for future studies with other phagocytes/microorganisms that would significantly enhance our understanding of the mechanisms that govern effective phagocytosis and ultimately the innate immune response to infection.
Collapse
Affiliation(s)
- Leanne E. Lewis
- Division of Applied Medicine, University of Aberdeen, Aberdeen, United Kingdom
| | - Judith M. Bain
- Division of Applied Medicine, University of Aberdeen, Aberdeen, United Kingdom
| | - Christina Lowes
- Division of Applied Medicine, University of Aberdeen, Aberdeen, United Kingdom
| | - Collette Gillespie
- Division of Applied Medicine, University of Aberdeen, Aberdeen, United Kingdom
| | - Fiona M. Rudkin
- Division of Applied Medicine, University of Aberdeen, Aberdeen, United Kingdom
- Aberdeen Fungal Group, University of Aberdeen, Aberdeen, United Kingdom
| | - Neil A. R. Gow
- Aberdeen Fungal Group, University of Aberdeen, Aberdeen, United Kingdom
| | - Lars-Peter Erwig
- Division of Applied Medicine, University of Aberdeen, Aberdeen, United Kingdom
- Aberdeen Fungal Group, University of Aberdeen, Aberdeen, United Kingdom
- * E-mail:
| |
Collapse
|
118
|
Biochemical characterization of recombinant Candida albicans mannosyltransferases Mnt1, Mnt2 and Mnt5 reveals new functions in O- and N-mannan biosynthesis. Biochem Biophys Res Commun 2012; 419:77-82. [PMID: 22326920 PMCID: PMC3480643 DOI: 10.1016/j.bbrc.2012.01.131] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Accepted: 01/26/2012] [Indexed: 11/23/2022]
Abstract
The cell surface of Candida albicans is enriched with highly glycosylated mannoproteins that are involved in the interaction with host tissues. N- and O-glycosylation are post-translational modifications that initiate in the endoplasmic reticulum, and finalize in the Golgi. The KRE2/MNT1 family encode a set of multifunctional mannosyltransferases that participate in O-, N- and phosphomannosylation. In order to gain insights into the substrate specificities of these enzymes, recombinant forms of Mnt1, Mnt2, and Mnt5 were expressed in Pichia pastoris and the enzyme activities characterized. Mnt1 and Mnt2 showed a high specificity for α-methylmannoside and α1,2-mannobiose as acceptor substrates. Notably, they also used Saccharomyces cerevisiaeO-mannans as acceptors and generated products with more than three mannose residues, suggesting than Mnt1 and Mnt2 could be the mannosyltransferases adding the fourth and fifth mannose residue to the O-mannans in C. albicans. Mnt5 only recognized α-methylmannoside as acceptor, suggesting that participates in the addition of the second mannose residues to the N-glycan outer chain.
Collapse
|
119
|
Cottier F, Raymond M, Kurzai O, Bolstad M, Leewattanapasuk W, Jiménez-López C, Lorenz MC, Sanglard D, Váchová L, Pavelka N, Palková Z, Mühlschlegel FA. The bZIP transcription factor Rca1p is a central regulator of a novel CO₂ sensing pathway in yeast. PLoS Pathog 2012; 8:e1002485. [PMID: 22253597 PMCID: PMC3257301 DOI: 10.1371/journal.ppat.1002485] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Accepted: 11/29/2011] [Indexed: 11/18/2022] Open
Abstract
Like many organisms the fungal pathogen Candida albicans senses changes in the environmental CO2 concentration. This response involves two major proteins: adenylyl cyclase and carbonic anhydrase (CA). Here, we demonstrate that CA expression is tightly controlled by the availability of CO2 and identify the bZIP transcription factor Rca1p as the first CO2 regulator of CA expression in yeast. We show that Rca1p upregulates CA expression during contact with mammalian phagocytes and demonstrate that serine 124 is critical for Rca1p signaling, which occurs independently of adenylyl cyclase. ChIP-chip analysis and the identification of Rca1p orthologs in the model yeast Saccharomyces cerevisiae (Cst6p) point to the broad significance of this novel pathway in fungi. By using advanced microscopy we visualize for the first time the impact of CO2 build-up on gene expression in entire fungal populations with an exceptional level of detail. Our results present the bZIP protein Rca1p as the first fungal regulator of carbonic anhydrase, and reveal the existence of an adenylyl cyclase independent CO2 sensing pathway in yeast. Rca1p appears to regulate cellular metabolism in response to CO2 availability in environments as diverse as the phagosome, yeast communities or liquid culture. Skin infection, oral and vaginal thrush, or bloodstream candidiasis are some of the diseases caused by the human pathogen Candida albicans. The high versatility of infection niches reflects the capacity of this yeast to respond to strong variations in its environment such as CO2 concentration. This molecule initiates the regulation of an essential protein: carbonic anhydrase, not through the known adenylyl cyclase CO2 sensor but as we discovered via a novel fungal CO2 sensing pathway involving the transcriptional regulator Rca1p. This protein is additionally implicated in growth, yeast-to-hyphae morphological switch and cell wall stability of C. albicans. The ortholog of Rca1p in Saccharomyces cerevisiae demonstrated a conserved function in the induction of the carbonic anhydrase in low CO2 concentration atmospheres pointing to the broad significance of Rca1p in fungal CO2 sensing.
Collapse
Affiliation(s)
- Fabien Cottier
- School of Biosciences, University of Kent, Canterbury, United Kingdom
- Singapore Immunology Network, Agency for Science, Technology and Research, Immunos, Singapore
| | - Martine Raymond
- Institute for Research in Immunology and Cancer and Department of Biochemistry, Université de Montréal, Montréal, Quebec, Canada
| | - Oliver Kurzai
- Septomics Research Centre, Friedrich-Schiller-University and Leibniz-Institute for Natural Products Research and Infection Biology, Hans-Knoell-Institute, Jena, Germany
| | - Marianne Bolstad
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | | | - Claudia Jiménez-López
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, Texas, United States of America
| | - Michael C. Lorenz
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, Texas, United States of America
| | - Dominique Sanglard
- Institute of Microbiology, University of Lausanne and University Hospital Center, Lausanne, Switzerland
| | - Libuše Váchová
- Institute of Microbiology of the ASCR, v.v.i., Prague, Czech Republic
- Department of Genetics and Microbiology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Norman Pavelka
- Singapore Immunology Network, Agency for Science, Technology and Research, Immunos, Singapore
| | - Zdena Palková
- Department of Genetics and Microbiology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Fritz A. Mühlschlegel
- School of Biosciences, University of Kent, Canterbury, United Kingdom
- Clinical Microbiology Service, East Kent Hospitals University NHS Foundation Trust, Ashford, United Kingdom
- * E-mail:
| |
Collapse
|
120
|
Posttranslational modifications of proteins in the pathobiology of medically relevant fungi. EUKARYOTIC CELL 2011; 11:98-108. [PMID: 22158711 DOI: 10.1128/ec.05238-11] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Posttranslational modifications of proteins drive a wide variety of cellular processes in eukaryotes, regulating cell growth and division as well as adaptive and developmental processes. With regard to the fungal kingdom, most information about posttranslational modifications has been generated through studies of the model yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, where, for example, the roles of protein phosphorylation, glycosylation, acetylation, ubiquitination, sumoylation, and neddylation have been dissected. More recently, information has begun to emerge for the medically important fungal pathogens Candida albicans, Aspergillus fumigatus, and Cryptococcus neoformans, highlighting the relevance of posttranslational modifications for virulence. We review the available literature on protein modifications in fungal pathogens, focusing in particular upon the reversible peptide modifications sumoylation, ubiquitination, and neddylation.
Collapse
|
121
|
Sen M, Shah B, Rakshit S, Singh V, Padmanabhan B, Ponnusamy M, Pari K, Vishwakarma R, Nandi D, Sadhale PP. UDP-glucose 4, 6-dehydratase activity plays an important role in maintaining cell wall integrity and virulence of Candida albicans. PLoS Pathog 2011; 7:e1002384. [PMID: 22114559 PMCID: PMC3219719 DOI: 10.1371/journal.ppat.1002384] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Accepted: 10/01/2011] [Indexed: 11/18/2022] Open
Abstract
Candida albicans, a human fungal pathogen, undergoes morphogenetic changes that are associated with virulence. We report here that GAL102 in C. albicans encodes a homolog of dTDP-glucose 4,6-dehydratase, an enzyme that affects cell wall properties as well as virulence of many pathogenic bacteria. We found that GAL102 deletion leads to greater sensitivity to antifungal drugs and cell wall destabilizing agents like Calcofluor white and Congo red. The mutant also formed biofilms consisting mainly of hyphal cells that show less turgor. The NMR analysis of cell wall mannans of gal102 deletion strain revealed that a major constituent of mannan is missing and the phosphomannan component known to affect virulence is greatly reduced. We also observed that there was a substantial reduction in the expression of genes involved in biofilm formation but increase in the expression of genes encoding glycosylphosphatidylinositol-anchored proteins in the mutant. These, along with altered mannosylation of cell wall proteins together might be responsible for multiple phenotypes displayed by the mutant. Finally, the mutant was unable to grow in the presence of resident peritoneal macrophages and elicited a weak pro-inflammatory cytokine response in vitro. Similarly, this mutant elicited a poor serum pro-inflammatory cytokine response as judged by IFNγ and TNFα levels and showed reduced virulence in a mouse model of systemic candidiasis. Importantly, an Ala substitution for a conserved Lys residue in the active site motif YXXXK, that abrogates the enzyme activity also showed reduced virulence and increased filamentation similar to the gal102 deletion strain. Since inactivating the enzyme encoded by GAL102 makes the cells sensitive to antifungal drugs and reduces its virulence, it can serve as a potential drug target in combination therapies for C. albicans and related pathogens.
Collapse
Affiliation(s)
- Manimala Sen
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India
| | - Bhavin Shah
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India
| | - Srabanti Rakshit
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - Vijender Singh
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India
| | - Bhavna Padmanabhan
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India
| | | | | | | | - Dipankar Nandi
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - Parag P. Sadhale
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India
- * E-mail:
| |
Collapse
|
122
|
Candida albicans cell wall glycosylation may be indirectly required for activation of epithelial cell proinflammatory responses. Infect Immun 2011; 79:4902-11. [PMID: 21930756 DOI: 10.1128/iai.05591-11] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Oral epithelial cells discriminate between the yeast and hyphal forms of Candida albicans via the mitogen-activated protein kinase (MAPK) signaling pathway. This occurs through phosphorylation of the MAPK phosphatase MKP1 and activation of the c-Fos transcription factor by the hyphal form. Given that fungal cell wall polysaccharides are critical in host recognition and immune activation in myeloid cells, we sought to determine whether β-glucan and N- or O-glycosylation was important in activating the MAPK/MKP1/c-Fos hypha-mediated response mechanism and proinflammatory cytokines in oral epithelial cells. Using a series of β-glucan and N- and O-mannan mutants, we found that N-mannosylation (via Δoch1 and Δpmr1 mutants) and O-mannosylation (via Δpmt1 and Δmnt1 Δmnt2 mutants), but not phosphomannan (via a Δmnn4 mutant) or β-1,2 mannosylation (via Δbmt1 to Δbmt6 mutants), were required for MKP1/c-Fos activation, proinflammatory cytokine production, and cell damage induction. However, the N- and O-mannan mutants showed reduced adhesion or lack of initial hypha formation at 2 h, resulting in little MKP1/c-Fos activation, or restricted hypha formation/pseudohyphal formation at 24 h, resulting in minimal proinflammatory cytokine production and cell damage. Further, the α-1,6-mannose backbone of the N-linked outer chain (corresponding to a Δmnn9 mutant) may be required for epithelial adhesion, while the α-1,2-mannose component of phospholipomannan (corresponding to a Δmit1 mutant) may contribute to epithelial cell damage. β-Glucan appeared to play no role in adhesion, epithelial activation, or cell damage. In summary, N- and O-mannosylation defects affect the ability of C. albicans to induce proinflammatory cytokines and damage in oral epithelial cells, but this may be due to indirect effects on fungal pathogenicity rather than mannose residues being direct activators of the MAPK/MKP1/c-Fos hypha-mediated immune response.
Collapse
|
123
|
Hopkins D, Gomathinayagam S, Rittenhour AM, Du M, Hoyt E, Karaveg K, Mitchell T, Nett JH, Sharkey NJ, Stadheim TA, Li H, Hamilton SR. Elimination of β-mannose glycan structures in Pichia pastoris. Glycobiology 2011; 21:1616-26. [PMID: 21840970 DOI: 10.1093/glycob/cwr108] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The methylotrophic yeast, Pichia pastoris, is an important organism used for the production of therapeutic proteins. However, the presence of fungal-like glycans, such as those containing β-mannose (Man) linkages, can elicit an immune response or bind to Man receptors, thus reducing their efficacy. Recent studies have confirmed that P. pastoris has four genes from the β-mannosyl transferase (BMT) family and that Bmt2p is responsible for the majority of β-Man linkages on glycans. While expressing recombinant human erythropoietin (rhEPO) in a developmental glycoengineered strain devoid of BMT2 gene expression, cross-reactivity was observed with an antibody raised against host cell antigens. Treatment of the rhEPO with protein N-glycosidase F eliminated cross-reactivity, indicating that the antigen was associated with the glycan. Thorough analysis of the glycan profile of rhEPO demonstrated the presence of low amounts of α-1,2-mannosidase resistant high-Man glycoforms. In an attempt to eliminate the α-mannosidase resistant glycoforms, we used a systemic approach to genetically knock-out the remaining members of the BMT family culminating in a quadruple bmt2,4,1,3 knock-out strain. Data presented here conclude that the additive elimination of Bmt2p, Bmt3p and Bmt1p activities are required for total abolition of β-Man-associated glycans and their related antigenicity. Taken together, the elimination of β-Man containing glycoforms represents an important step forward for the Pichia production platform as a suitable system for the production of therapeutic glycoproteins.
Collapse
Affiliation(s)
- Daniel Hopkins
- GlycoFi Inc., A wholly-Owned Subsidiary of Merck & Co. Inc., 21 Lafayette street, Suite 200, Lebanon, NH 03766, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
124
|
Motteram J, Lovegrove A, Pirie E, Marsh J, Devonshire J, van de Meene A, Hammond-Kosack K, Rudd JJ. Aberrant protein N-glycosylation impacts upon infection-related growth transitions of the haploid plant-pathogenic fungus Mycosphaerella graminicola. Mol Microbiol 2011; 81:415-33. [PMID: 21623954 DOI: 10.1111/j.1365-2958.2011.07701.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The ascomycete fungus Mycosphaerella graminicola is the causal agent of Septoria Tritici Blotch disease of wheat and can grow as yeast-like cells or as hyphae depending on environmental conditions. Hyphal growth is however essential for successful leaf infection. A T-DNA mutagenesis screen performed on haploid spores identified a mutant, which can undergo yeast-like growth but cannot switch to hyphal growth. For this reason the mutant was non-pathogenic towards wheat leaves. The gene affected, MgAlg2, encoded a homologue of Saccharomyces cerevisiae ScAlg2, an alpha-1,2-mannosyltransferase, which functions in the early stages of asparagine-linked protein (N-) glycosylation. Targeted gene deletion and complementation experiments confirmed that loss of MgAlg2 function prevented the developmental growth switch. MgAlg2 was able to functionally complement the S. cerevisiae ScAlg2-1 temperature sensitive growth phenotype. Spores of ΔMgAlg2 mutants were hypersensitive to the cell wall disrupting agent Calcofluor white and produced abnormally hypo-N-glycosylated proteins. Gene expression, proteome and glycoproteome analysis revealed that ΔMgAlg2 mutant spores show responses typically associated with the accumulation of mis-folded proteins. The data presented highlight key roles for protein N-glycosylation in regulating the switch to hyphal growth, possibly as a consequence of maintaining correct folding and localization of key proteins involved in this process.
Collapse
Affiliation(s)
- Juliet Motteram
- Department of Plant Pathology and Microbiology, Rothamsted Research, Harpenden, Herts AL52JQ, UK
| | | | | | | | | | | | | | | |
Collapse
|
125
|
Sandini S, Stringaro A, Arancia S, Colone M, Mondello F, Murtas S, Girolamo A, Mastrangelo N, De Bernardis F. The MP65 gene is required for cell wall integrity, adherence to epithelial cells and biofilm formation in Candida albicans. BMC Microbiol 2011; 11:106. [PMID: 21575184 PMCID: PMC3113926 DOI: 10.1186/1471-2180-11-106] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2010] [Accepted: 05/16/2011] [Indexed: 11/18/2022] Open
Abstract
Background The MP65 gene of Candida albicans (orf19.1779) encodes a putative β-glucanase mannoprotein of 65 kDa, which plays a main role in a host-fungus relationship, morphogenesis and pathogenicity. In this study, we performed an extensive analysis of a mp65Δ mutant to assess the role of this protein in cell wall integrity, adherence to epithelial cells and biofilm formation. Results The mp65Δ mutant showed a high sensitivity to a range of cell wall-perturbing and degrading agents, especially Congo red, which induced morphological changes such as swelling, clumping and formation of hyphae. The mp65Δ mutant showed an activation of two MAPKs (Mkc1p and Cek1p), a high level of expression of two stress-related genes (DDR48 and SOD5), and a modulated expression of β-glucan epitopes, but no gross changes in cell wall polysaccharide composition. Interestingly, the mp65Δ mutant displayed a marked reduction in adhesion to BEC and Caco-2 cells and severe defects in biofilm formation when compared to the wild type. All of the mentioned properties were totally or partially recovered in a revertant strain, demonstrating the specificity of gene deletion. Conclusions We demonstrate that the MP65 gene of Candida albicans plays a significant role in maintaining cell wall integrity, as well as in adherence to epithelia and biofilm formation, which are major virulence attributes of this fungus.
Collapse
Affiliation(s)
- Silvia Sandini
- Department of Infectious, Parasitic and Immuno-mediated Diseases, Istituto Superiore di Sanità, Rome, 00161, Italy.
| | | | | | | | | | | | | | | | | |
Collapse
|
126
|
Ernst JF, Pla J. Signaling the glycoshield: maintenance of the Candida albicans cell wall. Int J Med Microbiol 2011; 301:378-83. [PMID: 21555242 DOI: 10.1016/j.ijmm.2011.04.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
In fungi, the cell wall is a scaffold, an armor and an environmental gate. Sugar polymers including protein-O- or N-linked glycosyl chains or polysaccharides such as glucan or chitin are essential components to maintain cell wall functions. We describe mechanisms in the human fungal pathogen Candida albicans, by which the integrity of glycostructures are sensed and regulated. The results stress the importance of membrane sensors and MAP kinase pathways in the maintenance of cell wall structure and function.
Collapse
Affiliation(s)
- Joachim F Ernst
- Institut für Mikrobiologie, Molekulare Mykologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1/26.12, 40225 Düsseldorf, Germany.
| | | |
Collapse
|
127
|
Cheng SC, van de Veerdonk FL, Lenardon M, Stoffels M, Plantinga T, Smeekens S, Rizzetto L, Mukaremera L, Preechasuth K, Cavalieri D, Kanneganti TD, van der Meer JWM, Kullberg BJ, Joosten LAB, Gow NAR, Netea MG. The dectin-1/inflammasome pathway is responsible for the induction of protective T-helper 17 responses that discriminate between yeasts and hyphae of Candida albicans. J Leukoc Biol 2011; 90:357-66. [PMID: 21531876 PMCID: PMC3513931 DOI: 10.1189/jlb.1210702] [Citation(s) in RCA: 156] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
In the mucosa, the immune pathways discriminating between colonizing and invasive Candida, thus inducing tolerance or inflammation, are poorly understood. Th17 responses induced by Candida albicans hyphae are central for the activation of mucosal antifungal immunity. An essential step for the discrimination between yeasts and hyphae and induction of Th17 responses is the activation of the inflammasome by C. albicans hyphae and the subsequent release of active IL-1β in macrophages. Inflammasome activation in macrophages results from differences in cell-wall architecture between yeasts and hyphae and is partly mediated by the dectin-1/Syk pathway. These results define the dectin-1/inflammasome pathway as the mechanism that enables the host immune system to mount a protective Th17 response and distinguish between colonization and tissue invasion by C. albicans.
Collapse
Affiliation(s)
- Shih-Chin Cheng
- Department of Medicine, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
128
|
Cantero PD, Ernst JF. Damage to the glycoshield activates PMT-directed O-mannosylation via the Msb2-Cek1 pathway in Candida albicans. Mol Microbiol 2011; 80:715-25. [PMID: 21375589 DOI: 10.1111/j.1365-2958.2011.07604.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein-O-mannosyltransferases (Pmt) transfer mannosyl residues to secretory proteins. Five isoforms of Pmt proteins in the human fungal pathogen Candida albicans have distinct functions in growth, morphogenesis and antifungal resistance. We found that PMT genes encoding the major isoforms Pmt1, Pmt2, Pmt4 are regulated differently in response to impaired glycostructures. While the PMT1 transcript level increased in cell wall mutants and under inhibition of N-glycosylation by tunicamycin, PMT2 and PMT4 transcripts were upregulated only by inhibition of Pmt1 activity. Reporter fusions revealed specific promoter sequences to be required for PMT1 repression in undamaged cells, which was de-repressed by tunicamycin. Constitutive PMT1 de-repression was observed in mutants lacking the Cek1 MAP kinase and its upstream sensor Msb2. In contrast, in msb2 and cek1 mutants, upregulation of PMT2/PMT4 by Pmt1 inhibition did not occur and basal expression of both transcripts were decreased. We identified Ace2 as a novel transcription factor, which upregulates PMT basal expression and induction in response to glycostructure damage. Mutants lacking Msb2, Cek1 and Ace2 were supersensitive to glycosylation and cell wall inhibitors. We propose that a Msb2, Cek1 and Ace2 signalling pathway addresses PMT genes as downstream targets and that different modes of regulation have evolved for PMT1 and PMT2/PMT4 genes.
Collapse
Affiliation(s)
- Pilar D Cantero
- Institut für Mikrobiologie, Molekulare Mykologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1/26.12, 40225 Düsseldorf, Germany
| | | |
Collapse
|
129
|
Sheth CC, Hall R, Lewis L, Brown AJP, Odds FC, Erwig LP, Gow NAR. Glycosylation status of the C. albicans cell wall affects the efficiency of neutrophil phagocytosis and killing but not cytokine signaling. Med Mycol 2011; 49:513-24. [PMID: 21254968 PMCID: PMC3119872 DOI: 10.3109/13693786.2010.551425] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The cell wall of the opportunistic human fungal pathogen, Candida albicans is a complex, layered network of rigid structural polysaccharides composed of β-glucans and chitin that is covered with a fibrillar matrix of highly glycosylated mannoproteins. Polymorphonuclear cells (PMNs, neutrophils) are the most prevalent circulating phagocytic leukocyte in peripheral blood and they are pivotal in the clearance of invading fungal cells from tissues. The importance of cell-wall mannans for the recognition and uptake of C. albicans by human PMNs was therefore investigated. N- and O-glycosylation-deficient mutants were attenuated in binding and phagocytosis by PMNs and this was associated with reduced killing of C. albicans yeast cells. No differences were found in the production of the respiratory burst enzyme myeloperoxidase (MPO) and the neutrophil chemokine IL-8 in PMNs exposed to control and glycosylation-deficient C. albicans strains. Thus, the significant decrease in killing of glycan-deficient C. albicans strains by PMNs is a consequence of a marked reduction in phagocytosis rather than changes in the release of inflammatory mediators by PMNs.
Collapse
Affiliation(s)
- Chirag C Sheth
- The Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | | | | | | | | | | | | |
Collapse
|
130
|
Gene Expression in Leaves of Susceptible Glycine max during Infection with Phakopsora pachyrhizi Using Next Generation Sequencing. ACTA ACUST UNITED AC 2011. [DOI: 10.1155/2011/827250] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Soybean rust is caused by the obligate biotrophic fungus Phakopsora pachyrhizi, an exotic pathogen causing important yield losses in soybean production. We used an mRNA-Seq strategy to analyze the expression pattern of soybean genes and better understand molecular events occurring in soybean following the infection. cDNA libraries were constructed from RNA isolated from whole infected soybean leaves 10 days after inoculation with P. pachyrhizi and sequenced using an Illumina platform to identify soybean genes that are affected by pathogen growth. We obtained 15 million sequences corresponding to soybean genes. Forty-two percent of the genes were downregulated including genes encoding proteins involved in amino acid metabolism, carbohydrate metabolism, and transport facilitation; 31% were upregulated including genes encoding proteins involved in lipid metabolism, glycan biosynthesis, and signal transduction. Candidate host genes identified in this study will be manipulated to assay their potential to control soybean rust disease.
Collapse
|
131
|
López-Romero E, Reyes-Montes MDR, Pérez-Torres A, Ruiz-Baca E, Villagómez-Castro JC, Mora-Montes HM, Flores-Carreón A, Toriello C. Sporothrix schenckii complex and sporotrichosis, an emerging health problem. Future Microbiol 2011; 6:85-102. [DOI: 10.2217/fmb.10.157] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Sporothrix schenckii, now named the S. schenckii species complex, has largely been known as the etiological agent of sporotrichosis, which is an acute or chronic subcutaneous mycosis of humans and other mammals. Gene sequencing has revealed the following species in the S. schenckii complex: Sporothrix albicans, Sporothrix brasiliensis, Sporothrix globosa, Sporothrix luriei, Sporothrix mexicana and S. schenckii. The increasing number of reports of Sporothrix infection in immunocompromised patients, mainly the HIV-infected population, suggests sporotrichosis as an emerging global health problem concomitant with the AIDS pandemic. Molecular studies have demonstrated a high level of intraspecific variability. Components of the S. schenckii cell wall that act as adhesins and immunogenic inducers, such as a 70-kDa glycoprotein, are apparently specific to this fungus. The main glycan peptidorhamnomannan cell wall component is the only O-linked glycan structure known in S. schenckii. It contains an α-mannobiose core followed by one α-glucuronic acid unit, which may be mono- or di-rhamnosylated. The oligomeric structure of glucosamine-6-P synthase has led to a significant advance in the development of antifungals targeted to the enzyme’s catalytic domain in S. schenckii.
Collapse
|
132
|
Kotz A, Wagener J, Engel J, Routier FH, Echtenacher B, Jacobsen I, Heesemann J, Ebel F. Approaching the secrets of N-glycosylation in Aspergillus fumigatus: characterization of the AfOch1 protein. PLoS One 2010; 5:e15729. [PMID: 21206755 PMCID: PMC3012087 DOI: 10.1371/journal.pone.0015729] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Accepted: 11/22/2010] [Indexed: 11/21/2022] Open
Abstract
The mannosyltransferase Och1 is the key enzyme for synthesis of elaborated protein N-glycans in yeast. In filamentous fungi genes implicated in outer chain formation are present, but their function is unclear. In this study we have analyzed the Och1 protein of Aspergillus fumigatus. We provide first evidence that poly-mannosylated N-glycans exist in A. fumigatus and that their synthesis requires AfOch1 activity. This implies that AfOch1 plays a similar role as S. cerevisiae ScOch1 in the initiation of an N-glycan outer chain. A Δafoch1 mutant showed normal growth under standard and various stress conditions including elevated temperature, cell wall and oxidative stress. However, sporulation of this mutant was dramatically reduced in the presence of high calcium concentrations, suggesting that certain proteins engaged in sporulation require N-glycan outer chains to be fully functional. A characteristic feature of AfOch1 and Och1 homologues from other filamentous fungi is a signal peptide that clearly distinguishes them from their yeast counterparts. However, this difference does not appear to have consequences for its localization in the Golgi. Replacing the signal peptide of AfOch1 by a membrane anchor had no impact on its ability to complement the sporulation defect of the Δafoch1 strain. The mutant triggered a normal cytokine response in infected murine macrophages, arguing against a role of outer chains as relevant Aspergillus pathogen associated molecular patterns. Infection experiments provided no evidence for attenuation in virulence; in fact, according to our data the Δafoch1 mutant may even be slightly more virulent than the control strains.
Collapse
Affiliation(s)
- Andrea Kotz
- Max-von-Pettenkofer-Institute, Ludwig-Maximilians-University, Munich, Germany
| | - Johannes Wagener
- Max-von-Pettenkofer-Institute, Ludwig-Maximilians-University, Munich, Germany
| | - Jakob Engel
- Department of Cellular Chemistry, Hanover Medical School, Hanover, Germany
| | | | - Bernd Echtenacher
- Institute for Immunology, University of Regensburg, Regensburg, Germany
| | - Ilse Jacobsen
- Department for Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany
| | - Jürgen Heesemann
- Max-von-Pettenkofer-Institute, Ludwig-Maximilians-University, Munich, Germany
- Faculty of Medicine, Center of Integrated Protein Science Munich, Ludwig-Maximilians-University, Munich, Germany
| | - Frank Ebel
- Max-von-Pettenkofer-Institute, Ludwig-Maximilians-University, Munich, Germany
| |
Collapse
|
133
|
Lambou K, Perkhofer S, Fontaine T, Latge JP. Comparative functional analysis of the OCH1 mannosyltransferase families in Aspergillus fumigatus and Saccharomyces cerevisiae. Yeast 2010; 27:625-36. [PMID: 20586114 DOI: 10.1002/yea.1798] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Alpha1,6-linked mannans are an essential component of the Aspergillus fumigatus galactomannan, which is either GPI-anchored to the plasma membrane or covalently bound to the polysaccharide core of the cell wall. In Saccharomyces cerevisiae, the OCH1 gene encodes an alpha1,6-mannosyltransferase that initiates the synthesis of the alpha1,6 linked-mannan. In the A. fumigatus genome, four orthologous genes of Saccharomyces cerevisiae ScOCH1 gene were identified. Single deletion and the quadruple deletion mutants (Afoch1-4Delta) were constructed in A. fumigatus. No phenotype different from the wild-type strain was observed in all single and the quadruple mutants. The corresponding cDNAs of the AfOCH1-4 A. fumigatus orthologues were expressed in the S. cerevisiae Scoch1Delta mutant. Among the four orthologues, only AfOCH1 complemented the aggregation phenotype, the growth inhibition, the hypersensitivity to hygromycin and the protein glycosylation defects observed in the Scoch1Deltamutant.
Collapse
Affiliation(s)
- Karine Lambou
- Unité des Aspergillus, Institut Pasteur, 25 Rue du Docteur Roux, 75724 Paris Cedex 15, France
| | | | | | | |
Collapse
|
134
|
Sandoval-Bernal G, Barbosa-Sabanero G, Shibayama M, Perez-Torres A, Tsutsumi V, Sabanero M. Cell wall glycoproteins participate in the adhesion of Sporothrix schenckii to epithelial cells. Mycopathologia 2010; 171:251-9. [PMID: 21082256 DOI: 10.1007/s11046-010-9372-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Accepted: 10/02/2010] [Indexed: 11/29/2022]
Abstract
Sporothrix schenckii is the etiologic agent of sporotrichosis. This fungal infection is an emerging disease potentially fatal in immunocompromised patients. The adhesion to host cells is a crucial early event related with the dissemination of pathogens. In order to clarify the mechanisms of adhesion of S. schenckii yeast cell to epithelial cells, we studied the biochemical basis of this process. The electrophoretic analysis of cell wall protein from S. schenckii coupled at ConA and stained with HRP, revealed nine different proteins with MW ≥ 180, 115, 90, 80, 58, 40, 36, 22 and 18 kDa. Using ligand-like assay with biotinylated S. schenckii surface proteins, five proteins with MW ≥ 190, 180, 115, 90 and 80 kDa which have affinity to epithelial cells were identified. The adhesion of yeast to epithelial monolayer was significantly inhibited when S. schenckii was pretreated with concanavalinA (ConA) and wheat germ agglutinin (WGA) lectins, alkali, periodate, trypsin, endoglycosidase H (EndoH), salt solutions and detergents. The ability of adhesion of S. schenckii yeast was recovered by blocking the lectin with sugar complementary. These data suggest that surface glycoprotein with mannose and glucose residue could be participate in the process of fungal adhesion to epithelial cells.
Collapse
Affiliation(s)
- Gerardo Sandoval-Bernal
- División de Ciencias Naturales y Exactas Campus Guanajuato, Departamento de Biología, Universidad de Guanajuato, Noria Alta S/N, Col. Noria Alta, 36000, Guanajuato, Guanajuato, México
| | | | | | | | | | | |
Collapse
|
135
|
Leal JA, Prieto A, Bernabé M, Hawksworth DL. An assessment of fungal wall heteromannans as a phylogenetically informative character in ascomycetes. FEMS Microbiol Rev 2010; 34:986-1014. [DOI: 10.1111/j.1574-6976.2010.00225.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
|
136
|
Keppler-Ross S, Douglas L, Konopka JB, Dean N. Recognition of yeast by murine macrophages requires mannan but not glucan. EUKARYOTIC CELL 2010; 9:1776-87. [PMID: 20833894 PMCID: PMC2976302 DOI: 10.1128/ec.00156-10] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Accepted: 09/02/2010] [Indexed: 11/20/2022]
Abstract
The first barrier against infection by Candida albicans involves fungal recognition and destruction by phagocytic cells of the innate immune system. It is well established that interactions between different phagocyte receptors and components of the fungal cell wall trigger phagocytosis and subsequent immune responses, but the fungal ligands mediating the initial stage of recognition have not been identified. Here, we describe a novel assay for fungal recognition and uptake by macrophages which monitors this early recognition step independently of other downstream events of phagocytosis. To analyze infection in live macrophages, we validated the neutrality of a codon-optimized red fluorescent protein (yEmRFP) biomarker in C. albicans; growth, hyphal formation, and virulence in infected mice and macrophages were unaffected by yEmRFP production. This permitted a new approach for studying phagocytosis by carrying out competition assays between red and green fluorescent yeast cells to measure the efficiency of yeast uptake by murine macrophages as a function of dimorphism or cell wall defects. These competition experiments demonstrate that, given a choice, macrophages display strong preferences for phagocytosis based on genus, species, and morphology. Candida glabrata and Saccharomyces cerevisiae are taken up by J774 macrophage cells more rapidly than C. albicans, and C. albicans yeast cells are favored over hyphal cells. Significantly, these preferences are mannan dependent. Mutations that affect mannan, but not those that affect glucan or chitin, reduce the uptake of yeast challenged with wild-type competitors by both J774 and primary murine macrophages. These results suggest that mannose side chains or mannosylated proteins are the ligands recognized by murine macrophages prior to fungal uptake.
Collapse
Affiliation(s)
| | - Lois Douglas
- Department of Microbiology, Stony Brook University, Stony Brook, New York 11794-5215
| | - James B. Konopka
- Department of Microbiology, Stony Brook University, Stony Brook, New York 11794-5215
| | - Neta Dean
- Department of Biochemistry and Cell Biology
| |
Collapse
|
137
|
α-1,6-Mannosylation of N-linked oligosaccharide present on cell wall proteins is required for their incorporation into the cell wall in the filamentous fungus Neurospora crassa. EUKARYOTIC CELL 2010; 9:1766-75. [PMID: 20870880 DOI: 10.1128/ec.00134-10] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The enzyme α-1,6-mannosyltransferase (OCH-1) is required for the synthesis of galactomannans attached to the N-linked oligosaccharides of Neurospora crassa cell wall proteins. The Neurospora crassa och-1 mutant has a tight colonial phenotype and a defective cell wall. A carbohydrate analysis of the och-1 mutant cell wall revealed a 10-fold reduction in the levels of mannose and galactose and a total lack of 1,6-linked mannose residues. Analysis of the integral cell wall protein from wild-type and och-1 mutant cells showed that the mutant cell wall had reduced protein content. The och-1 mutant was found to secrete 18-fold more protein than wild-type cells. Proteomic analysis of the proteins released by the mutant into the growth medium identified seven of the major cell wall proteins. Western blot analysis of ACW-1 and GEL-1 (two glycosylphosphatidylinositol [GPI]-anchored proteins that are covalently integrated into the wild-type cell wall) showed that high levels of these proteins were being released into the medium by the och-1 mutant. High levels of ACW-1 and GEL-1 were also released from the och-1 mutant cell wall by subjecting the wall to boiling in a 1% SDS solution, indicating that these proteins are not being covalently integrated into the mutant cell wall. From these results, we conclude that N-linked mannosylation of cell wall proteins by OCH-1 is required for their efficient covalent incorporation into the cell wall.
Collapse
|
138
|
Mora-Montes HM, Bates S, Netea MG, Castillo L, Brand A, Buurman ET, Díaz-Jiménez DF, Jan Kullberg B, Brown AJP, Odds FC, Gow NAR. A multifunctional mannosyltransferase family in Candida albicans determines cell wall mannan structure and host-fungus interactions. J Biol Chem 2010; 285:12087-95. [PMID: 20164191 PMCID: PMC2852947 DOI: 10.1074/jbc.m109.081513] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cell wall proteins of fungi are modified by N- and O-linked mannosylation and phosphomannosylation, resulting in changes to the physical and immunological properties of the cell. Glycosylation of cell wall proteins involves the activities of families of endoplasmic reticulum and Golgi-located glycosyl transferases whose activities are difficult to infer through bioinformatics. The Candida albicans MNT1/KRE2 mannosyl transferase family is represented by five members. We showed previously that Mnt1 and Mnt2 are involved in O-linked mannosylation and are required for virulence. Here, the role of C. albicans MNT3, MNT4, and MNT5 was determined by generating single and multiple MnTDelta null mutants and by functional complementation experiments in Saccharomyces cerevisiae. CaMnt3, CaMnt4, and CaMnt5 did not participate in O-linked mannosylation, but CaMnt3 and CaMnt5 had redundant activities in phosphomannosylation and were responsible for attachment of approximately half of the phosphomannan attached to N-linked mannans. CaMnt4 and CaMnt5 participated in N-mannan branching. Deletion of CaMNT3, CaMNT4, and CaMNT5 affected the growth rate and virulence of C. albicans, affected the recognition of the yeast by human monocytes and cytokine stimulation, and led to increased cell wall chitin content and exposure of beta-glucan at the cell wall surface. Therefore, the MNT1/KRE2 gene family participates in three types of protein mannosylation in C. albicans, and these modifications play vital roles in fungal cell wall structure and cell surface recognition by the innate immune system.
Collapse
Affiliation(s)
- Héctor M Mora-Montes
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, Scotland, UK
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
139
|
Chen YL, Montedonico AE, Kauffman S, Dunlap JR, Menn FM, Reynolds TB. Phosphatidylserine synthase and phosphatidylserine decarboxylase are essential for cell wall integrity and virulence in Candida albicans. Mol Microbiol 2010; 75:1112-32. [PMID: 20132453 DOI: 10.1111/j.1365-2958.2009.07018.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Phospholipid biosynthetic pathways play crucial roles in the virulence of several pathogens; however, little is known about how phospholipid synthesis affects pathogenesis in fungi such as Candida albicans. A C. albicans phosphatidylserine (PS) synthase mutant, cho1 Delta/Delta, lacks PS, has decreased phosphatidylethanolamine (PE), and is avirulent in a mouse model of systemic candidiasis. The cho1 Delta/Delta mutant exhibits defects in cell wall integrity, mitochondrial function, filamentous growth, and is auxotrophic for ethanolamine. PS is a precursor for de novo PE biosynthesis. A psd1 Delta/Delta psd2 Delta/Delta double mutant, which lacks the PS decarboxylase enzymes that convert PS to PE in the de novo pathway, has diminished PE levels like those of the cho1 Delta/Delta mutant. The psd1 Delta/Delta psd2 Delta/Delta mutant exhibits phenotypes similar to those of the cho1 Delta/Delta mutant; however, it is slightly more virulent and has less of a cell wall defect. The virulence losses exhibited by the cho1 Delta/Delta and psd1 Delta/Delta psd2 Delta/Delta mutants appear to be related to their cell wall defects which are due to loss of de novo PE biosynthesis, but are exacerbated by loss of PS itself. Cho1p is conserved in fungi, but not mammals, so fungal PS synthase is a potential novel antifungal drug target.
Collapse
Affiliation(s)
- Ying-Lien Chen
- Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA
| | | | | | | | | | | |
Collapse
|
140
|
Contribution of Candida albicans cell wall components to recognition by and escape from murine macrophages. Infect Immun 2010; 78:1650-8. [PMID: 20123707 DOI: 10.1128/iai.00001-10] [Citation(s) in RCA: 178] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The pathogenicity of the opportunistic human fungal pathogen Candida albicans depends on its ability to escape destruction by the host immune system. Using mutant strains that are defective in cell surface glycosylation, cell wall protein synthesis, and yeast-hypha morphogenesis, we have investigated three important aspects of C. albicans innate immune interactions: phagocytosis by primary macrophages and macrophage cell lines, hyphal formation within macrophage phagosomes, and the ability to escape from and kill macrophages. We show that cell wall glycosylation is critically important for the recognition and ingestion of C. albicans by macrophages. Phagocytosis was significantly reduced for mutants deficient in phosphomannan biosynthesis (mmn4Delta, pmr1Delta, and mnt3 mnt5Delta), whereas O- and N-linked mannan defects (mnt1Delta mnt2Delta and mns1Delta) were associated with increased ingestion, compared to the parent wild-type strains and genetically complemented controls. In contrast, macrophage uptake of mutants deficient in cell wall proteins such as adhesins (ece1Delta, hwp1Delta, and als3Delta) and yeast-locked mutants (clb2Delta, hgc1Delta, cph1Delta, efg1Delta, and efg1Delta cph1Delta), was similar to that observed for wild-type C. albicans. Killing of macrophages was abrogated in hypha-deficient strains, significantly reduced in all glycosylation mutants, and comparable to wild type in cell wall protein mutants. The diminished ability of glycosylation mutants to kill macrophages was not a consequence of impaired hyphal formation within macrophage phagosomes. Therefore, cell wall composition and the ability to undergo yeast-hypha morphogenesis are critical determinants of the macrophage's ability to ingest and process C. albicans.
Collapse
|
141
|
Mora-Montes HM, Ponce-Noyola P, Villagómez-Castro JC, Gow NA, Flores-Carreón A, López-Romero E. Protein glycosylation in Candida. Future Microbiol 2010; 4:1167-83. [PMID: 19895219 DOI: 10.2217/fmb.09.88] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Candidiasis is a significant cause of invasive human mycosis with associated mortality rates that are equivalent to, or worse than, those cited for most cases of bacterial septicemia. As a result, considerable efforts are being made to understand how the fungus invades host cells and to identify new targets for fungal chemotherapy. This has led to an increasing interest in Candida glycobiology, with an emphasis on the identification of enzymes essential for glycoprotein and adhesion metabolism, and the role of N- and O-linked glycans in host recognition and virulence. Here, we refer to studies dealing with the identification and characterization of enzymes such as dolichol phosphate mannose synthase, dolichol phosphate glucose synthase and processing glycosidases and synthesis, structure and recognition of mannans and discuss recent findings in the context of Candida albicans pathogenesis.
Collapse
|
142
|
Ramage G, Mowat E, Jones B, Williams C, Lopez-Ribot J. Our current understanding of fungal biofilms. Crit Rev Microbiol 2010; 35:340-55. [PMID: 19863383 DOI: 10.3109/10408410903241436] [Citation(s) in RCA: 326] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Fungal biofilms are an escalating clinical problem associated with significant rates of mortality. Candida albicans is the most notorious of all fungal biofilm formers. However, non-Candida species, yeasts such as Cryptococcus neoformans, and filamentous moulds such as Aspergillus fumigatus, have been shown to be implicated in biofilm-associated infections. Fungal biofilms have distinct developmental phases, including adhesion, colonisation, maturation and dispersal, which are governed by complex molecular events. Recalcitrance to antifungal therapy remains the greatest threat to patients with fungal biofilms. This review discusses our current understanding of the basic biology and clinical implications associated with fungal biofilms.
Collapse
Affiliation(s)
- Gordon Ramage
- Section of Infection and Immunity, Glasgow Dental School and Hospital, Faculty of Medicine, University of Glasgow, UK.
| | | | | | | | | |
Collapse
|
143
|
Goto K, Suzuki A, Shibata N, Okawa Y. Some properties of beta-1,2-mannosyltransferases related to the biosynthesis of the acid-labile oligomannosyl side chains in Candida albicans NIH B-792 strain cells. Biol Pharm Bull 2009; 32:1921-3. [PMID: 19881309 DOI: 10.1248/bpb.32.1921] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We detected the beta-1,2-mannosyltransferases (beta-1,2-MTs), which participate in the biosynthesis of oligomannosyl side chains in the mannan acid-labile fraction, in a particulate insoluble fractions prepared from Candida albicans NIH B-792 strain cells grown at 27 degrees C and at 37 degrees C in a yeast extract-added Sabouraud liquid medium (YSLM). The beta-1,2-MT VI-6 prepared from the cells grown at 27 degrees C exhibited the maximum activity at pH 7.0 and at 30 degrees C. The beta-1,2-MT VI-6 activity was only slightly affected by Mn2+, Mg2+, Ca2+, and ethylenediaminetetraacetic acid, but completely inhibited by Zn2+ and Ni2+. The beta-1,2-MT activities from the cells grown at 37 degrees C were lower than that from the cells grown at 27 degrees C, especially on the longer beta-1,2-mannooligosaccharides than tetraose.
Collapse
Affiliation(s)
- Kouji Goto
- Department of Infection and Host Defense, Tohoku Pharmaceutical University, Komatsushima, Aoba-ku, Sendai, Miyagi 981-8558, Japan
| | | | | | | |
Collapse
|
144
|
Ohashi T, Takegawa K. N- and O-linked oligosaccharides completely lack galactose residues in the gms1och1 mutant of Schizosaccharomyces pombe. Appl Microbiol Biotechnol 2009; 86:263-72. [DOI: 10.1007/s00253-009-2297-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Revised: 10/03/2009] [Accepted: 10/04/2009] [Indexed: 10/20/2022]
|
145
|
Shibata N, Saitoh T, Tadokoro Y, Okawa Y. The cell wall galactomannan antigen from Malassezia furfur and Malassezia pachydermatis contains β-1,6-linked linear galactofuranosyl residues and its detection has diagnostic potential. Microbiology (Reading) 2009; 155:3420-3429. [DOI: 10.1099/mic.0.029967-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Lipophilic yeasts of the genus Malassezia are associated with several skin diseases, such as pityriasis versicolor, Malassezia folliculitis, seborrhoeic dermatitis and atopic dermatitis, and are also increasingly associated with catheter-related fungaemia. The cell wall components of pathogenic micro-organisms behave as an antigen and/or ligand of the innate immune response. Live cells of Malassezia furfur and Malassezia pachydermatis did not react with an anti-α-1,2-mannoside antibody. However, they showed a strong hydrophobicity and reactivity with an anti-β-1,3-glucan antibody compared to those of C. albicans. The cell wall polysaccharides of M. furfur and M. pachydermatis were isolated and their structures analysed by 1H and 13C NMR experiments. Both polysaccharides were shown to be β-1,6-linked linear galactofuranosyl polymers with a small amount of mannan. The presence of galactomannan on cells of Malassezia species has not been described previously. The galactomannan did not react with an anti-Aspergillus fumigatus monoclonal antibody which has specificity for β-1,5-linked galactofuranosyl residues. An anti-M. furfur antibody strongly reacted with the galactomannans of M. furfur and M. pachydermatis, but did not react with the galactomannans of Trichophyton rubrum, A. fumigatus or Fonsecaea pedrosoi. The characteristics of the anti-M. furfur antibody suggest that there is potential for diagnosis of Malassezia infections by antigen detection.
Collapse
Affiliation(s)
- Nobuyuki Shibata
- Department of Infection and Host Defense, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai, Miyagi 981-8558, Japan
| | - Tomomi Saitoh
- Department of Infection and Host Defense, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai, Miyagi 981-8558, Japan
| | - Yukari Tadokoro
- Department of Infection and Host Defense, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai, Miyagi 981-8558, Japan
| | - Yoshio Okawa
- Department of Infection and Host Defense, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai, Miyagi 981-8558, Japan
| |
Collapse
|
146
|
Expression and purification of recombinant M-Pol I from Saccharomyces cerevisiae with α-1,6 mannosylpolymerase activity. Protein Expr Purif 2009; 66:1-6. [DOI: 10.1016/j.pep.2009.02.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Revised: 02/17/2009] [Accepted: 02/18/2009] [Indexed: 11/17/2022]
|
147
|
|
148
|
Production of heterologous proteins using the fission-yeast (Schizosaccharomyces pombe) expression system. Biotechnol Appl Biochem 2009; 53:227-35. [PMID: 19531030 DOI: 10.1042/ba20090048] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The fission yeast Schizosaccharomyces pombe is a particularly useful model for studying the function and regulation of genes from higher eukaryotes. The genome of Sc. pombe has been sequenced, and DNA microarray, proteome and transcriptome analyses have been carried out. Among the well-characterized yeast species, Sc. pombe is considered an attractive host for the production of heterologous proteins. Expression vectors for high-level expression in Sc. pombe have been developed and many foreign proteins have been successfully expressed. However, further improvements in the protein-expressing host systems are still required for the production of heterologous proteins involved in post-translational modification, metabolism and intracellular trafficking. This minireview focuses on recent advances in heterologous protein production by use of engineered fission-yeast strains.
Collapse
|
149
|
Harris M, Mora-Montes HM, Gow NAR, Coote PJ. Loss of mannosylphosphate from Candida albicans cell wall proteins results in enhanced resistance to the inhibitory effect of a cationic antimicrobial peptide via reduced peptide binding to the cell surface. MICROBIOLOGY-SGM 2009; 155:1058-1070. [PMID: 19332808 DOI: 10.1099/mic.0.026120-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The outermost layer of the Candida albicans cell wall is enriched with mannosylated glycoproteins. We have used a range of isogenic glycosylation mutants of C. albicans, which are defective to varying degrees in cell wall protein mannosylation, to investigate the role of the outermost layer of the yeast cell wall in mediating the fungicidal action of the cationic, alpha-helical antimicrobial peptide dermaseptin S3(1-16) [DsS3(1-16)]. The degree of phosphomannan loss, and concomitant reduction in surface negative charge, from the series of glycosylation mutants correlated with reduced levels of peptide binding to the cells. In turn, the reduced peptide binding correlated with enhanced resistance to DsS3(1-16). To ascertain whether DsS3(1-16) binds to negatively charged phosphate, we studied the effect of exogenous glucosamine 6-phosphate, and glucosamine hydrochloride as a negative control, on the antifungal efficacy of DsS3(1-16). Glucosamine 6-phosphate retarded the efficacy of DsS3(1-16), and this was attributed to the presence of phosphate, because addition of identical concentrations of glucosamine hydrochloride had little detrimental effect on peptide efficacy. Fluorescence microscopy with DsS3(1-16) tagged with fluorescein revealed that the peptide binds to the outer surface of the yeast cell, supporting our previous conclusion that the presence of exterior phosphomannan is a major determinant of the antifungal potency of DsS3(1-16). The binding of the peptide to the cell surface was a transient event that was followed by apparent localization of DsS3(1-16) in the vacuole or dissemination throughout the entire cytosol. The presence of glucosamine 6-phosphate clearly reduced the proportion of cells in the population that showed complete cytosolic staining, implying that the binding and entry of the peptide into the cytosol is significantly reduced due to the exogenous phosphate sequestering the peptide and reducing the amount of peptide able to bind to the surface phosphomannan. In conclusion, we present evidence that an antimicrobial peptide, similar to those employed by cells of the human immune system, has evolved to recognize molecular patterns on the surface of pathogens in order to maximize efficacy.
Collapse
Affiliation(s)
- Mark Harris
- Centre for Biomolecular Sciences, School of Biology, University of St Andrews, The North Haugh, St Andrews KY16 9ST, UK
| | - Héctor M Mora-Montes
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK
| | - Neil A R Gow
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK
| | - Peter J Coote
- Centre for Biomolecular Sciences, School of Biology, University of St Andrews, The North Haugh, St Andrews KY16 9ST, UK
| |
Collapse
|
150
|
Hypoxic adaptation by Efg1 regulates biofilm formation by Candida albicans. Appl Environ Microbiol 2009; 75:3663-72. [PMID: 19346360 DOI: 10.1128/aem.00098-09] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Hypoxia is encountered frequently by Candida albicans during systemic infection of the human host. We tested if hypoxia allows biofilm formation by C. albicans, which is a major cause of perseverance and antifungal resistance in C. albicans infections. Using an in vitro biofilm system, we unexpectedly discovered that several positive regulators of biofilm formation during normoxia, including Tec1, Ace2, Czf1, Och1, and Als3, had little or no influence on biofilm development during hypoxia, irrespective of the carbon dioxide level, indicating that C. albicans biofilm pathways differ depending on the oxygen level. In contrast, the Efg1 and Flo8 regulators were required for both normoxic and hypoxic biofilm formation. To explore the role of Efg1 during hypoxic and/or biofilm growth, we determined transcriptome kinetics following release of EFG1 expression by a system under transcriptional control of a doxycycline-inducible promoter. During hypoxia, Efg1 rapidly induced expression of all major classes of genes known to be associated with normoxic biofilm formation, including genes involved in glycolysis, sulfur metabolism, and antioxidative and peroxisome activities, as well as genes for iron uptake. The results suggest that hypoxic adaptation mediated by the Efg1 and Flo8 regulators is required even during normoxic biofilm development, while hypoxic biofilm formation in deep tissues or in organs may generate foci of C. albicans infections.
Collapse
|