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Rastogi SK, van Wijlick L, Ror S, Lee KK, Román E, Agarwal P, Manzoor N, Gow NAR, Pla J, Ernst JF, Panwar SL. Ifu5, a WW domain-containing protein interacts with Efg1 to achieve coordination of normoxic and hypoxic functions to influence pathogenicity traits in Candida albicans. Cell Microbiol 2020; 22:e13140. [PMID: 31736226 PMCID: PMC7614792 DOI: 10.1111/cmi.13140] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 10/03/2019] [Accepted: 10/23/2019] [Indexed: 11/28/2022]
Abstract
Hypoxic adaptation pathways, essential for Candida albicans pathogenesis, are tied to its transition from a commensal to a pathogen. Herein, we identify a WW domain-containing protein, Ifu5, as a determinant of hypoxic adaptation that also impacts normoxic responses in this fungus. Ifu5 activity supports glycosylation homeostasis via the Cek1 mitogen-activated protein kinase-dependent up-regulation of PMT1, under normoxia. Transcriptome analysis of ifu5Δ/Δ under normoxia shows a significant up-regulation of the hypoxic regulator EFG1 and EFG1-dependent genes. We demonstrate physical interaction between Ifu5 by virtue of its WW domain and Efg1 that represses EFG1 expression under normoxia. This interaction is lost under hypoxic growth conditions, relieving EFG1 repression. Hypoxic adaptation processes such as filamentation and biofilm formation are affected in ifu5Δ/Δ cells revealing the role of Ifu5 in hypoxic signalling and modulating pathogenicity traits of C. albicans under varied oxygen conditions. Additionally, the WW domain of Ifu5 facilitates its role in hypoxic adaptation, revealing the importance of this domain in providing a platform to integrate various cellular processes. These data forge a relationship between Efg1 and Ifu5 that fosters the role of Ifu5 in hypoxic adaptation thus illuminating novel strategies to undermine the growth of C. albicans.
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Affiliation(s)
- Sumit K Rastogi
- Yeast Molecular Genetics Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
- Medical Mycology Laboratory, Department of Biosciences, Jamia Millia Islamia University, New Delhi, India
| | - Lasse van Wijlick
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Shivani Ror
- Yeast Molecular Genetics Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Keunsook K Lee
- The Aberdeen Fungal Group, MRC Centre for Medical Mycology, School of Medicine, Medical Sciences & Nutrition, Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Elvira Román
- Departamento de Microbiología y Parasitología-IRYCIS, Facultad de Farmacia, Universidad Complutense de Madrid, Madrid, Spain
| | - Pranjali Agarwal
- Yeast Molecular Genetics Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Nikhat Manzoor
- Medical Mycology Laboratory, Department of Biosciences, Jamia Millia Islamia University, New Delhi, India
| | - Neil A R Gow
- The Aberdeen Fungal Group, MRC Centre for Medical Mycology, School of Medicine, Medical Sciences & Nutrition, Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Jesús Pla
- Departamento de Microbiología y Parasitología-IRYCIS, Facultad de Farmacia, Universidad Complutense de Madrid, Madrid, Spain
| | - Joachim F Ernst
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Sneh L Panwar
- Yeast Molecular Genetics Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
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van Wijlick L, Geissen R, Hilbig JS, Lagadec Q, Cantero PD, Pfeifer E, Juchimiuk M, Kluge S, Wickert S, Alepuz P, Ernst JF. Dom34 Links Translation to Protein O-mannosylation. PLoS Genet 2016; 12:e1006395. [PMID: 27768707 PMCID: PMC5074521 DOI: 10.1371/journal.pgen.1006395] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 09/29/2016] [Indexed: 11/25/2022] Open
Abstract
In eukaryotes, Dom34 upregulates translation by securing levels of activatable ribosomal subunits. We found that in the yeast Saccharomyces cerevisiae and the human fungal pathogen Candida albicans, Dom34 interacts genetically with Pmt1, a major isoform of protein O-mannosyltransferase. In C. albicans, lack of Dom34 exacerbated defective phenotypes of pmt1 mutants, while they were ameliorated by Dom34 overproduction that enhanced Pmt1 protein but not PMT1 transcript levels. Translational effects of Dom34 required the 5′-UTR of the PMT1 transcript, which bound recombinant Dom34 directly at a CA/AC-rich sequence and regulated in vitro translation. Polysomal profiling revealed that Dom34 stimulates general translation moderately, but that it is especially required for translation of transcripts encoding Pmt isoforms 1, 4 and 6. Because defective protein N- or O-glycosylation upregulates transcription of PMT genes, it appears that Dom34-mediated specific translational upregulation of the PMT transcripts optimizes cellular responses to glycostress. Its translational function as an RNA binding protein acting at the 5′-UTR of specific transcripts adds another facet to the known ribosome-releasing functions of Dom34 at the 3′-UTR of transcripts. Fungi respond to damages of their glycostructures in their cell wall by transcriptional upregulation of genes that specify compensatory activities. Upon block of protein N-glycosylation, the human fungal pathogen Candida albicans increases transcription of PMT1 encoding a major isoform of protein O-mannosyltransferase. Here we demonstrate that the Dom34 protein aids in glycostress responses by upregulating the translation of several PMT isoform transcripts. Dom34 has previously been implicated in mechanisms to secure high levels of ribosomal subunits that promote translation in general, e. g. by no-go decay at the 3′-UTR of transcripts. By binding to the 5′-UTR and activating translational initiation of PMT transcripts we add a novel mode of action and suggest a preferred class of targets for the translational activities of the Dom34 protein. The combination of transcriptional and Dom34-mediated translational upregulation of PMT genes optimizes effective recovery and survival of fungal cells upon glycostress.
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Affiliation(s)
- Lasse van Wijlick
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
- Manchot Graduate School Molecules of Infection, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - René Geissen
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Jessica S. Hilbig
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Quentin Lagadec
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Pilar D. Cantero
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Eugen Pfeifer
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Mateusz Juchimiuk
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Sven Kluge
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Stephan Wickert
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Paula Alepuz
- Departamento de Bioquímica y Biología Molecular, Universitat de València, Burjassot Spain
- ERI Biotecmed. Universitat de València, Burjassot Spain
| | - Joachim F. Ernst
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
- Manchot Graduate School Molecules of Infection, Heinrich-Heine-Universität, Düsseldorf, Germany
- * E-mail:
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van Wijlick L, Swidergall M, Brandt P, Ernst JF. Candida albicansresponds to glycostructure damage by Ace2-mediated feedback regulation of Cek1 signaling. Mol Microbiol 2016; 102:827-849. [DOI: 10.1111/mmi.13494] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/30/2016] [Indexed: 11/27/2022]
Affiliation(s)
- Lasse van Wijlick
- Department Biologie; Molekulare Mykologie, Heinrich-Heine-Universität; 40225 Düsseldorf Germany
- Manchot Graduate School Molecules of Infection, Heinrich-Heine-Universität; 40225 Düsseldorf Germany
| | - Marc Swidergall
- Department Biologie; Molekulare Mykologie, Heinrich-Heine-Universität; 40225 Düsseldorf Germany
| | - Philipp Brandt
- Department Biologie; Molekulare Mykologie, Heinrich-Heine-Universität; 40225 Düsseldorf Germany
| | - Joachim F. Ernst
- Department Biologie; Molekulare Mykologie, Heinrich-Heine-Universität; 40225 Düsseldorf Germany
- Manchot Graduate School Molecules of Infection, Heinrich-Heine-Universität; 40225 Düsseldorf Germany
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Eichhof I, Ernst JF. Corrigendum to "Oxygen-independent FbFP: Fluorescent sentinel and oxygen sensor component in Saccharomyces cerevisiae and Candida albicans" [Fungal Genet. Biol. 92 (2016) 14-25]. Fungal Genet Biol 2016; 93:62. [PMID: 27378137 DOI: 10.1016/j.fgb.2016.06.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Isabel Eichhof
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Joachim F Ernst
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany.
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Buerth C, Tielker D, Ernst JF. Candida utilis and Cyberlindnera (Pichia) jadinii: yeast relatives with expanding applications. Appl Microbiol Biotechnol 2016; 100:6981-90. [DOI: 10.1007/s00253-016-7700-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 06/16/2016] [Accepted: 06/20/2016] [Indexed: 11/29/2022]
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Buerth C, Mausberg AK, Heininger MK, Hartung HP, Kieseier BC, Ernst JF. Oral Tolerance Induction in Experimental Autoimmune Encephalomyelitis with Candida utilis Expressing the Immunogenic MOG35-55 Peptide. PLoS One 2016; 11:e0155082. [PMID: 27159446 PMCID: PMC4861260 DOI: 10.1371/journal.pone.0155082] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 04/24/2016] [Indexed: 12/14/2022] Open
Abstract
Multiple sclerosis (MS) is an autoimmune disease that attacks myelinated axons in the central nervous system. Induction of oral tolerance is a potent mechanism to prevent autoimmunity. The food yeast Candida utilis was used to test the therapeutic potential of oral tolerance induction in an animal model of human multiple sclerosis (MS). We constructed a C. utilis strain, which displays a fusion peptide composed of the encephalitogenic MOG35-55 peptide and the C. utilis Gas1 cell wall protein on its surface.By immunizing mice with MOG35-55 peptide experimental autoimmune encephalomyelitis (EAE) was induced in a mouse model. Feeding of mice with C. utilis that expresses MOG35-55 peptide on its surface was started seven days prior to immunization and was continued for ten days. Control animals were treated with wild-type fungus or left untreated. Untreated mice developed first clinical symptoms ten days post immunization (p. i.) with an ascending paralysis reaching maximal clinical disability at day 18 to 20 p. i.. Treatment with the wild-type strain demonstrated comparable clinical symptoms. In contrast, oral gavage of MOG35-55-presenting fungus ameliorated the development of EAE. In addition, incidence as well as maximal clinical disease severity were significantly reduced. Interestingly, reduction of disease severity also occurred in animals treated with heat-inactivated C. utilis cells indicating that tolerance induction was independent of fungal viability. Better disease outcome correlated with reduced demyelination and cellular inflammation in the spinal cord, lower T cell proliferation against rechallenge with MOG35-55 and more regulatory T cells in the lymph nodes. Our data demonstrate successful that using the food approved fungus C. utilis presenting the immunogenic MOG35-55 peptide on its surface induced an oral tolerance against this epitope in EAE. Further studies will reveal the nature and extent of an anti-inflammatory environment established by the treatment that prevents the development of an autoimmune disorder affecting the CNS.
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Affiliation(s)
- Christoph Buerth
- Institute of Molecular Mycology, Department Biology, Heinrich-Heine-University, Düsseldorf, Germany
- * E-mail: (CB); (AKM)
| | - Anne K. Mausberg
- Research Group for Clinical and Experimental Neuroimmunology, Department of Neurology, Medical Faculty, Heinrich-Heine-University, Düsseldorf, Germany
- * E-mail: (CB); (AKM)
| | - Maximilian K. Heininger
- Research Group for Clinical and Experimental Neuroimmunology, Department of Neurology, Medical Faculty, Heinrich-Heine-University, Düsseldorf, Germany
| | - Hans-Peter Hartung
- Research Group for Clinical and Experimental Neuroimmunology, Department of Neurology, Medical Faculty, Heinrich-Heine-University, Düsseldorf, Germany
| | - Bernd C. Kieseier
- Research Group for Clinical and Experimental Neuroimmunology, Department of Neurology, Medical Faculty, Heinrich-Heine-University, Düsseldorf, Germany
| | - Joachim F. Ernst
- Institute of Molecular Mycology, Department Biology, Heinrich-Heine-University, Düsseldorf, Germany
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Eichhof I, Ernst JF. Oxygen-independent FbFP: Fluorescent sentinel and oxygen sensor component in Saccharomyces cerevisiae and Candida albicans. Fungal Genet Biol 2016; 92:14-25. [PMID: 27126475 DOI: 10.1016/j.fgb.2016.04.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 04/22/2016] [Accepted: 04/23/2016] [Indexed: 02/06/2023]
Abstract
FMN-binding fluorescent proteins (FbFPs) outperform GFP and its derivatives because of their oxygen-independence, small size and rapid maturation. FbFPs have been used successfully as reliable reporters of gene expression in the cytoplasm of pro- and eukaryotes. Here we extend previous findings on the codon-adapted CaFbFP variant, which functions in the apathogenic yeast Saccharomyces cerevisiae and the human fungal pathogen Candida albicans. In both fungal species, CaFbFP could be targeted to the nucleus and the cell wall by endogenous signals (H2B-/Aga2-fusions) demonstrating its use as a fluorescent beacon in these relevant cellular locations. Transformants of both fungal species producing a CaFbFP-YFP fusion (YFOS) showed variable energy transfer from CaFbFP to YFP (FRET) that depended in its extent on external O2 concentrations. Applications as fluorescent sentinel and oxygen biosensor expand the FbFP toolbox to study oxygen-independent cellular processes under hypoxia.
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Affiliation(s)
- Isabel Eichhof
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Joachim F Ernst
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany.
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Desai PR, van Wijlick L, Kurtz D, Juchimiuk M, Ernst JF. Hypoxia and Temperature Regulated Morphogenesis in Candida albicans. PLoS Genet 2015; 11:e1005447. [PMID: 26274602 PMCID: PMC4537295 DOI: 10.1371/journal.pgen.1005447] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2015] [Accepted: 07/15/2015] [Indexed: 01/31/2023] Open
Abstract
Candida albicans is a common commensal in the human gut but in predisposed patients it can become an important human fungal pathogen. As a commensal, C. albicans adapts to low-oxygen conditions and represses its hyphal development by the transcription factor Efg1, which under normoxia activates filamentation. The repressive hypoxic but not the normoxic function of Efg1 required its unmodified N-terminus, was prevented by phosphomimetic residues at normoxic phosphorylation sites T179 and T206 and occurred only at temperatures ≤35°C. Genome-wide binding sites for native Efg1 identified 300 hypoxia-specific target genes, which overlapped partially with hypoxic binding sites for Ace2, a known positive regulator of hypoxic filamentation. Transcriptional analyses revealed that EFG1, ACE2 and their identified targets BCR1 and BRG1 encode an interconnected regulatory hub, in which Efg1/Bcr1 act as negative and Ace2/Brg1 act as positive regulators of gene expression under hypoxia. In this circuit, the hypoxic function of Ace2 was stimulated by elevated CO2 levels. The hyperfilamentous phenotype of efg1 and bcr1 mutants depended on Ace2/Brg1 regulators and required increased expression of genes encoding Cek1 MAP kinase and its downstream target Cph1. The intricate temperature-dependent regulatory mechanisms under hypoxia suggest that C. albicans restricts hyphal morphogenesis in oxygen-poor body niches, possibly to persist as a commensal in the human host.
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Affiliation(s)
- Prashant R. Desai
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Lasse van Wijlick
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
- Manchot Graduate School Molecules of Infection, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Dagmar Kurtz
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Mateusz Juchimiuk
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Joachim F. Ernst
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
- Manchot Graduate School Molecules of Infection, Heinrich-Heine-Universität, Düsseldorf, Germany
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Kunigo M, Buerth C, Ernst JF. Secreted xylanase XynA mediates utilization of xylan as sole carbon source in Candida utilis. Appl Microbiol Biotechnol 2015; 99:8055-64. [PMID: 26051669 DOI: 10.1007/s00253-015-6703-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 05/06/2015] [Accepted: 05/15/2015] [Indexed: 12/30/2022]
Abstract
The fodder yeast Candida utilis is able to use xylose mono- and oligomers as sources of carbon but not the abundant polymer xylan. C. utilis transformants producing the Penicillium simplicissimum xylanase XynA were constructed using expression vectors encoding fusions of the Saccharomyces cerevisiae Mfα1 pre-pro secretion leader to XynA. The Mfα1-XynA fusion was efficiently processed in transformants and XynA was secreted almost quantitatively into the culture medium. Secreted XynA was enzymatically active and allowed transformants to grow on xylan as the sole carbon source. Addition of a second expression unit for the heterologous green fluorescent protein (GFP) generated C. utilis transformants, which showed intracellular GFP fluorescence during growth on xylan. The results suggest that xylanase-producing C. utilis is suited as a cost-effective host organism for heterologous protein production and for other biotechnical applications.
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Affiliation(s)
- Maya Kunigo
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Universitätsstrasse 1/26.12.01, 40225, Düsseldorf, Germany
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Swidergall M, van Wijlick L, Ernst JF. Signaling domains of mucin Msb2 in Candida albicans. Eukaryot Cell 2015; 14:359-70. [PMID: 25636320 PMCID: PMC4385809 DOI: 10.1128/ec.00264-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 01/23/2015] [Indexed: 11/20/2022]
Abstract
Candida albicans adapts to the human host by environmental sensing using the Msb2 signal mucin, which regulates fungal morphogenesis and resistance characteristics. Msb2 is anchored within the cytoplasmic membrane by a single transmembrane (TM) region dividing it into a large N-terminal exodomain, which is shed, and a small cytoplasmic domain. Analyses of strains carrying deleted Msb2 variants revealed an exodomain segment required for cleavage, shedding, and all functions of Msb2. Phosphorylation of the mitogen-activated protein kinase (MAP kinase) Cek1 was regulated by three distinct regions in Msb2: in unstressed cells, N-terminal sequences repressed phosphorylation, while its induction under cell wall stress required the cytoplasmic tail (C-tail) and sequences N-terminally flanking the TM region, downstream of the proposed cleavage site. Within the latter Msb2 region, overlapping but not identical sequences were also required for hyphal morphogenesis, basal resistance to antifungals, and, in unstressed cells, downregulation of the PMT1 transcript, encoding protein O-mannosyltransferase-1. Deletion of two-thirds of the exodomain generated a truncated Msb2 variant with a striking ability to induce hyperfilamentous growth, which depended on the presence of the Msb2-interacting protein Sho1, the MAP kinase Cek1, and the Efg1 transcription factor. Under cell wall stress, the cytoplasmic tail relocalized partially to the nucleus and contributed to regulation of 117 genes, as revealed by transcriptomic analyses. Genes regulated by the C-tail contained binding sites for the Ace2 and Azf1 transcription factors and included the ALS cell wall genes. We concluded that Msb2 fulfills its numerous functions by employing functional domains that are distributed over its entire length.
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Affiliation(s)
- Marc Swidergall
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Lasse van Wijlick
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany Manchot Graduate School, Molecules of Infection II, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Joachim F Ernst
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany Manchot Graduate School, Molecules of Infection II, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
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Juchimiuk M, Orłowski J, Gawarecka K, Świeżewska E, Ernst JF, Palamarczyk G. Candida albicans cis-prenyltransferase Rer2 is required for protein glycosylation, cell wall integrity and hypha formation. Fungal Genet Biol 2014; 69:1-12. [DOI: 10.1016/j.fgb.2014.05.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 04/30/2014] [Accepted: 05/04/2014] [Indexed: 11/28/2022]
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Buerth C, Kovacic F, Stock J, Terfrüchte M, Wilhelm S, Jaeger KE, Feldbrügge M, Schipper K, Ernst JF, Tielker D. Uml2 is a novel CalB-type lipase of Ustilago maydis with phospholipase A activity. Appl Microbiol Biotechnol 2014; 98:4963-73. [DOI: 10.1007/s00253-013-5493-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 12/06/2013] [Accepted: 12/24/2013] [Indexed: 10/25/2022]
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Schaekel A, Desai PR, Ernst JF. Morphogenesis-regulated localization of protein kinase A to genomic sites in Candida albicans. BMC Genomics 2013; 14:842. [PMID: 24289325 PMCID: PMC4046665 DOI: 10.1186/1471-2164-14-842] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Accepted: 11/15/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The human fungal pathogen Candida albicans is able to undergo morphogenesis from a yeast to a hyphal growth form. Protein kinase A (PKA) isoforms Tpk1 and Tpk2 promote hyphal growth in a signalling pathway via the transcription factor Efg1. RESULTS C. albicans strains producing epitope-tagged Tpk1 or Tpk2 were used in genome-wide chromatin immunoprecipitation on chip (ChIP chip) to reveal genomic binding sites. During yeast growth, both PKA isoforms were situated primarily within ORFs but moved to promoter regions shortly after hyphal induction. Binding sequences for Tpk2 greatly exceeded Tpk1 sites and did not coincide with binding of the PKA regulatory subunit Bcy1. Consensus binding sequences for Tpk2 within ORFs included ACCAC and CAGCA motifs that appeared to bias codon usage within the binding regions. Promoter residency of Tpk2 correlated with the transcript level of the corresponding gene during hyphal morphogenesis and occurred near Efg1 binding sites, mainly on genes encoding regulators of morphogenesis. CONCLUSIONS PKA isoforms change their genomic binding sites from ORF to promoter regions during yeast-hyphal morphogenesis. Tpk2 binds preferentially to promoters of genes encoding regulators of cellular morphogenesis.
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Affiliation(s)
| | | | - Joachim F Ernst
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany.
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Schmidt SK, Ebel S, Keil E, Woite C, Ernst JF, Benzin AE, Rupp J, Däubener W. Regulation of IDO activity by oxygen supply: inhibitory effects on antimicrobial and immunoregulatory functions. PLoS One 2013; 8:e63301. [PMID: 23675474 PMCID: PMC3652816 DOI: 10.1371/journal.pone.0063301] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 04/02/2013] [Indexed: 01/06/2023] Open
Abstract
Tryptophan is an essential amino acid for human beings as well as for some microorganisms. In human cells the interferon-γ (IFN-γ) inducible enzyme indoleamine 2,3-dioxygenase (IDO) reduces local tryptophan levels and is therefore able to mediate broad-spectrum effector functions: IDO activity restricts the growth of various clinically relevant pathogens such as bacteria, parasites and viruses. On the other hand, it has been observed that IDO has immunoregulatory functions as it efficiently controls the activation and survival of T-cells. Although these important effects have been analysed in much detail, they have been observed in vitro using cells cultured in the presence of 20% O2 (normoxia). Such high oxygen concentrations are not present in vivo especially within infected and inflamed tissues. We therefore analysed IDO-mediated effects under lower oxygen concentrations in vitro and observed that the function of IDO is substantially impaired in tumour cells as well as in native cells. Hypoxia led to reduced IDO expression and as a result to reduced production of kynurenine, the downstream product of tryptophan degradation. Consequently, effector functions of IDO were abrogated under hypoxic conditions: in different human cell lines such as tumour cells (glioblastoma, HeLa) but also in native cells (human foreskin fibroblasts; HFF) IDO lost the capacity to inhibit the growth of bacteria (Staphylococcus aureus), parasites (Toxoplasma gondii) or viruses (herpes simplex virus type 1). Additionally, IDO could no longer efficiently control the proliferation of T-cells that have been co-cultured with IDO expressing HFF cells in vitro. In conclusion, the potent antimicrobial as well as immunoregulatory functions of IDO were substantially impaired under hypoxic conditions that pathophysiologically occurs in vivo.
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Affiliation(s)
- Silvia K. Schmidt
- Institute of Medical Microbiology and Hospital Hygiene, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Sebastian Ebel
- Institute of Medical Microbiology and Hospital Hygiene, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Eric Keil
- Institute of Medical Microbiology and Hospital Hygiene, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Claudia Woite
- Institute of Medical Microbiology and Hospital Hygiene, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Joachim F. Ernst
- Institute for Molecular Mycology, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Anika E. Benzin
- Institute of Medical Microbiology and Hygiene, University of Lübeck, Lübeck, Germany
| | - Jan Rupp
- Institute of Medical Microbiology and Hygiene, University of Lübeck, Lübeck, Germany
- Medical Clinic III/UK-SH, Campus Lübeck, Lübeck, Germany
| | - Walter Däubener
- Institute of Medical Microbiology and Hospital Hygiene, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- * E-mail:
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Kunigo M, Buerth C, Tielker D, Ernst JF. Heterologous protein secretion by Candida utilis. Appl Microbiol Biotechnol 2013; 97:7357-68. [PMID: 23613034 DOI: 10.1007/s00253-013-4890-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 03/26/2013] [Accepted: 03/31/2013] [Indexed: 10/26/2022]
Abstract
The yeast Candida utilis (also referred to as Torula) is used as a whole-cell food additive and as a recombinant host for production of intracellular molecules. Here, we report recombinant C. utilis strains secreting significant amounts of Candida antarctica lipase B (CalB). Native and heterologous secretion signals led to secretion of CalB into the growth medium; CalB was enzymatically active and it carried a short N-glycosyl chain lacking extensive mannosylation. Furthermore, CalB fusions to the C. utilis Gas1 cell wall protein led to effective surface display of enzymatically active CalB and of β-galactosidase. Secretory production in C. utilis was achieved using a novel set of expression vectors containing sat1 conferring nourseothricin resistance, which could be transformed into C. utilis, Pichia jadinii, Candida albicans, and Saccharomyces cerevisiae; C. utilis promoters including the constitutive TDH3 and the highly xylose-inducible GXS1 promoters allowed efficient gene expression. These results establish C. utilis as a promising host for the secretory production of proteins.
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Affiliation(s)
- Maya Kunigo
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Universitätsstrasse 1/26.12.01, 40225 Düsseldorf, Germany
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Szafranski-Schneider E, Swidergall M, Cottier F, Tielker D, Román E, Pla J, Ernst JF. Msb2 shedding protects Candida albicans against antimicrobial peptides. PLoS Pathog 2012; 8:e1002501. [PMID: 22319443 PMCID: PMC3271078 DOI: 10.1371/journal.ppat.1002501] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Accepted: 12/09/2011] [Indexed: 11/30/2022] Open
Abstract
Msb2 is a sensor protein in the plasma membrane of fungi. In the human fungal pathogen C. albicans Msb2 signals via the Cek1 MAP kinase pathway to maintain cell wall integrity and allow filamentous growth. Msb2 doubly epitope-tagged in its large extracellular and small cytoplasmic domain was efficiently cleaved during liquid and surface growth and the extracellular domain was almost quantitatively released into the growth medium. Msb2 cleavage was independent of proteases Sap9, Sap10 and Kex2. Secreted Msb2 was highly O-glycosylated by protein mannosyltransferases including Pmt1 resulting in an apparent molecular mass of >400 kDa. Deletion analyses revealed that the transmembrane region is required for Msb2 function, while the large N-terminal and the small cytoplasmic region function to downregulate Msb2 signaling or, respectively, allow its induction by tunicamycin. Purified extracellular Msb2 domain protected fungal and bacterial cells effectively from antimicrobial peptides (AMPs) histatin-5 and LL-37. AMP inactivation was not due to degradation but depended on the quantity and length of the Msb2 glycofragment. C. albicans msb2 mutants were supersensitive to LL-37 but not histatin-5, suggesting that secreted rather than cell-associated Msb2 determines AMP protection. Thus, in addition to its sensor function Msb2 has a second activity because shedding of its glycofragment generates AMP quorum resistance. Microbial pathogens are attacked by antimicrobial peptides (AMPs) produced by the human host. AMPs kill pathogens and recruit immune cells to the site of infection. In defense, the human fungal pathogen Candida albicans continuously cleaves and secretes a glycoprotein fragment of the surface protein Msb2, which protects against AMPs. The results suggest that shed Msb2 allows fungal colonies to persist and avoid inflammatory responses caused by AMPs. Msb2 shedding and its additional role in stabilizing the fungal cell wall may be considered as novel diagnostic tools and targets for antifungal action.
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Affiliation(s)
| | - Marc Swidergall
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Fabien Cottier
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Denis Tielker
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Elvira Román
- Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
| | - Jesus Pla
- Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
| | - Joachim F. Ernst
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany
- * E-mail:
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17
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Abstract
Efg1 is a central transcriptional regulator of morphogenesis and metabolism in Candida albicans. In vivo genome-wide ChIP chip and in vitro footprint analyses revealed the Efg1 recognition sequence (EGR-box) TATGCATA in the yeast growth form of this human fungal pathogen. Upstream regions of EFG1 and genes encoding transcriptional regulators of hyphal growth including TCC1, CZF1, TEC1, DEF1 and NRG1 contained EGR- and/or EGR-like boxes. Unexpectedly, after brief hyphal induction the genome-wide Efg1 binding pattern was completely altered and new binding sites of yet unknown specificity had appeared. Hyphal induction abolished Efg1 accumulation on EFG1 and TCC1 promoters and led to rapid decline of both transcripts, although the Efg1 protein persisted in cells. While EFG1 promoter activity in the yeast growth form did not depend on bound Efg1, its downregulation under hyphal induction depended on the presence of Efg1 and the protein kinase A isoform Tpk2. Deletion analyses of the EFG1 upstream region revealed that none of its resident EGR-boxes is uniquely responsible for EFG1 promoter downregulation. These results suggest different binding specificities of Efg1 in yeast growth and in hyphal induction and suggest a brief time window following hyphal induction, in which Efg1 exerts its repressive effect on target promoters.
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Affiliation(s)
- Theresia Lassak
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
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Buerth C, Heilmann CJ, Klis FM, de Koster CG, Ernst JF, Tielker D. Growth-dependent secretome of Candida utilis. Microbiology (Reading) 2011; 157:2493-2503. [PMID: 21680638 DOI: 10.1099/mic.0.049320-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Recently, the food yeast Candida utilis has emerged as an excellent host for production of heterologous proteins. Since secretion of the recombinant product is advantageous for its purification, we characterized the secreted proteome of C. utilis. Cells were cultivated to the exponential or stationary growth phase, and the proteins in the medium were identified by MS. In parallel, a draft genome sequence of C. utilis strain DSM 2361 was determined by massively parallel sequencing. Comparisons of protein and coding sequences established that C. utilis is not a member of the CUG clade of Candida species. In total, we identified 37 proteins in the culture solution, 17 of which were exclusively present in the stationary phase, whereas three proteins were specific to the exponential growth phase. Identified proteins represented mostly carbohydrate-active enzymes associated with cell wall organization, while no proteolytic enzymes and only a few cytoplasmic proteins were detected. Remarkably, cultivation in xylose-based medium generated a protein pattern that diverged significantly from glucose-grown cells, containing the invertase Inv1 as the major extracellular protein, particularly in its highly glycosylated S-form (slow-migrating). Furthermore, cultivation without ammonium sulfate induced the secretion of the asparaginase Asp3. Comparisons of the secretome of C. utilis with those of Kluyveromyces lactis and Pichia pastoris, as well as with those of the human fungal pathogens Candida albicans and Candida glabrata, revealed a conserved set of 10 and six secretory proteins, respectively.
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Affiliation(s)
- Christoph Buerth
- Molecular Mycology, Heinrich-Heine-University, Duesseldorf, Universitaetsstraße 1, 40225 Duesseldorf, Germany
| | - Clemens J Heilmann
- Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Frans M Klis
- Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Chris G de Koster
- Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Joachim F Ernst
- Molecular Mycology, Heinrich-Heine-University, Duesseldorf, Universitaetsstraße 1, 40225 Duesseldorf, Germany
| | - Denis Tielker
- Molecular Mycology, Heinrich-Heine-University, Duesseldorf, Universitaetsstraße 1, 40225 Duesseldorf, Germany
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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.
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Affiliation(s)
- Joachim F Ernst
- Institut für Mikrobiologie, Molekulare Mykologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1/26.12, 40225 Düsseldorf, Germany.
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20
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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.
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Affiliation(s)
- Pilar D Cantero
- Institut für Mikrobiologie, Molekulare Mykologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1/26.12, 40225 Düsseldorf, Germany
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Moreno I, Martinez-Esparza M, Laforet LC, Sentandreu R, Ernst JF, Valentin E. Dosage-dependent roles of the Cwt1 transcription factor for cell wall architecture, morphogenesis, drug sensitivity and virulence in Candida albicans. Yeast 2010; 27:77-87. [PMID: 19908200 DOI: 10.1002/yea.1733] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The Cwt1 transcription factor is involved in cell wall architecture of the human fungal pathogen Candida albicans. We demonstrate here that deficiency of Cwt1 leads to decreased beta1,6-glucan in the cell wall, while mannoproteins are increased in the cell wall of exponentially growing cells and are released into the medium of stationary phase cells. Hyphal morphogenesis of cwt1 mutants is reduced on the surfaces of some inducing media. Unexpectedly, the CWT1/cwt1 heterozygous strains shows some stronger in vitro phenotypes compared to the homozygous mutant. The heterozygous but not the homozygous strain is also strongly impaired for its virulence in a mouse model of systemic infection. We suggest that an intermediate dosage of Cwt1 affects phenotypes profoundly, while its complete absence may elicit compensatory responses of C. albicans.
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Affiliation(s)
- Inmaculada Moreno
- GMCA Research Group, Departamento de Microbiología y Ecología, Facultad de Farmacia, Universidad de Valencia, Avenida Vicente Andrés Estellés s/n, 46100 Burjassot, Valencia, Spain
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22
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Wittschier N, Lengsfeld C, Vorthems S, Stratmann U, Ernst JF, Verspohl EJ, Hensel A. Large molecules as anti-adhesive compounds against pathogens. J Pharm Pharmacol 2010; 59:777-86. [PMID: 17637170 DOI: 10.1211/jpp.59.6.0004] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
Anti-adhesive compounds are potential prophylactic tools in alternative treatment regimes against bacterial infection, as bacterial adhesion is commonly mediated by carbohydrate-protein interactions between surface adhesions of microorganisms and the host cell. The use of exogenous polyvalent, high-molecular carbohydrates and tannin-like plant-derived compounds should antagonize the adhesive interaction. A range of carbohydrates and carbohydrate- and proanthocyanidin-enriched plant extracts were screened for potential anti-adhesive effects against Helicobacter pylori, Campylobacter jejuni, Porphyromonas gingivalis and Candida albicans in different in-situ assays on primary tissue. The adhesion of H. pylori on human stomach tissue was effectively blocked by glucuronic acid-enriched polysaccharides from immature okra fruits (Abelmoschus esculentus). These compounds also had strong in-vitro effects against C. jejuni (inhibition up to 80%), but were ineffective in an in-vivo study in infected chicken broilers due to metabolism in the gastrointestinal system. Polysaccharides from Glycyrrhizia glabra, also enriched with glucuronic acid, showed strong anti-adhesive properties against H. pylori and P. gingivalis (inhibition 60–70%). Pelargonium sidoides extract, containing mainly polymeric proanthocyanidins, was effective against H. pylori in a dose-dependent manner. Due to the multifunctional adhesive strategy of C. albicans, no effective compounds were detected against this yeast. Structure-activity relationships are presented and the potential in-vivo use of carbohydrate-based anti-adhesives is discussed.
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Affiliation(s)
- N Wittschier
- University of Münster, Institute for Pharmaceutical Biology and Phytochemistry, Hittorfstrasse 56, D-48149 Münster, Germany
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23
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Abstract
Background Protein-O-mannosyltransferases (Pmt's) catalyze the initial step of protein-O-glycosylation, the addition of mannose residues to serine or threonine residues of target proteins. Methodology/Principal Findings Based on protein similarities, this highly conserved protein family can be divided into three subfamilies: the Pmt1 sub-family, the Pmt2 sub-family and the Pmt4 sub-family. In contrast to Saccharomyces cerevisiae and Candida albicans, but similar to filamentous fungi, three putative PMT genes (PMT1, PMT2, and PMT4) were identified in the genome of the human fungal pathogen Cryptococcus neoformans. Similar to Schizosaccharomyces pombe and C. albicans, C. neoformans PMT2 is an essential gene. In contrast, the pmt1 and pmt4 single mutants are viable; however, the pmt1/pmt4 deletions are synthetically lethal. Mutation of PMT1 and PMT4 resulted in distinct defects in cell morphology and cell integrity. The pmt1 mutant was more susceptible to SDS medium than wild-type strains and the mutant cells were enlarged. The pmt4 mutant grew poorly on high salt medium and demonstrated abnormal septum formation and defects in cell separation. Interestingly, the pmt1 and pmt4 mutants demonstrated variety-specific differences in the levels of susceptibility to osmotic and cell wall stress. Delayed melanin production in the pmt4 mutant was the only alteration of classical virulence-associated phenotypes. However, the pmt1 and pmt4 mutants showed attenuated virulence in a murine inhalation model of cryptococcosis. Conclusion/Significance These findings suggest that C. neoformans protein-O-mannosyltransferases play a crucial role in maintaining cell morphology, and that reduced protein-O-glycosylation leads to alterations in stress resistance, cell wall composition, cell integrity, and survival within the host.
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Affiliation(s)
- Sven D Willger
- Institut für Mikrobiologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany.
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Abstract
Hypoxia is typical for most battlefields of host-pathogen interactions in the human host. While adaptation of human cells to low levels of oxygen has been well established, little information exists on mechanisms of hypoxic adaptation in microbial pathogens. Importantly, the impact of hypoxia on microbial infection, virulence and pathogenesis is rarely investigated. Recent results on the human pathogens Candida albicans and Cryptococcus neoformans indicate that these fungi adapt to hypoxia specifically by altering several morphological phenotypes, metabolic and transcriptomal activities, as well as virulence traits. In this review, novel components and mechanisms involved in hypoxic adaptation of human fungals pathogens are summarized and discussed.
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Affiliation(s)
- Joachim F Ernst
- Institut für Mikrobiologie, Molekulare Mykologie, Heinrich-Heine-Universität Düsseldorf, Germany.
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Cantero PD, Lengsfeld C, Prill SKH, Subanović M, Román E, Pla J, Ernst JF. Transcriptional and physiological adaptation to defective protein-O-mannosylation in Candida albicans. Mol Microbiol 2007; 64:1115-28. [PMID: 17501932 DOI: 10.1111/j.1365-2958.2007.05723.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Five Pmt isoforms O-mannosylate secretory proteins in Candida albicans. Comparisons of genome-wide transcript patterns of each pmt mutant revealed commonly downregulated genes involved in glycolysis and glycerol production. Increased phosphorylation of the Cek1p- but not the Mkc1p-MAP kinase, as well as increased transcript levels for some stress-related genes were detected in the pmt1 strain but not in the other pmt mutants. The transcriptomal pattern after short-term inhibition of Pmt1p activity confirmed stress responses, but did not indicate an alteration of glycolytic flow. Short- but not long-term adaptation to Pmt1p inhibition required signalling components Cek1p, Mkc1p, Efg1p and Tpk1p. Cna1p (calcineurin) but not its downstream effectors Crz1p and Crz2p was generally essential to allow growth during Pmt1p inhibition; accordingly, cyclosporin A strongly inhibited growth of the pmt1 mutant. The lack of Pmt isoforms influenced transcript levels for the remaining isoforms both positively and negatively, suggesting complex cross-regulation among PMT genes. These results confirm individual functions of Pmt isoforms but suggest a common biphasic adaptation response to Pmt deficiency. While known signalling pathways modulate adaptation for a short-term, long-term adaptation requires calcineurin, adjustments of remaining Pmt activities and of glycolytic flow.
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Affiliation(s)
- Pilar D Cantero
- Institut für Mikrobiologie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
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Corbucci C, Cenci E, Skrzypek F, Gabrielli E, Mosci P, Ernst JF, Bistoni F, Vecchiarelli A. Immune response toCandida albicansis preserved despite defect inO-mannosylation of secretory proteins. Med Mycol 2007; 45:709-19. [PMID: 17885949 DOI: 10.1080/13693780701537922] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
The PMT gene family in Candida albicans encodes five isoforms of the protein mannosyltransferases that initiate O-mannosylation of secretory proteins. Mutations at the Pmt level have been associated with differences in pathogenicity, e.g. in contrast to pmt5/pmt5, pmt2/PMT2 mutants showed poor virulence. Our objective was to determine whether these differences were related to the capacity of pmt2/PMT2 and pmt5/pmt5 to (i) express differences in selected virulence factors, and (ii) stimulate the natural immune system. The results show that pmt mutants (i) form hyphae in serum, (ii) show defective production of proteases but not of phospholipases with respect to the parental strain, (iii) undergo mycelial transition in the kidneys of hematogenously infected animals, (iv) are phagocytosed and killed by macrophages similar to the parental strain, although neutrophils are unable to destroy pmt5/pmt5, (v) engage TLR4 and stimulate MyD88 leading to NF-kappaB activation, and (vi) stimulate cytokine production by macrophages. Collectively our findings suggest that the defect in protein O-mannosylation in C. albicans cause attenuation of the virulence although the antigenic factors that retain the capacity to stimulate an efficient immune response are preserved.
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Affiliation(s)
- Cristina Corbucci
- Microbiology Section, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy
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Peltroche-Llacsahuanga H, Goyard S, d'Enfert C, Prill SKH, Ernst JF. Protein O-mannosyltransferase isoforms regulate biofilm formation in Candida albicans. Antimicrob Agents Chemother 2006; 50:3488-91. [PMID: 17005840 PMCID: PMC1610076 DOI: 10.1128/aac.00606-06] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Five isoforms of protein mannosyltransferase (Pmt) O-mannosylate secretory proteins in Candida albicans. pmt mutants were differentially defective for biofilm formation on plastic in static and flow-through systems, and a Pmt inhibitor blocked early stages of biofilm formation. Conceptually, Pmt inhibition may prevent surface anchoring and biofilm-dependent resistance of fungal pathogens.
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28
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Setiadi ER, Doedt T, Cottier F, Noffz C, Ernst JF. Transcriptional Response of Candida albicans to Hypoxia: Linkage of Oxygen Sensing and Efg1p-regulatory Networks. J Mol Biol 2006; 361:399-411. [PMID: 16854431 DOI: 10.1016/j.jmb.2006.06.040] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2006] [Revised: 06/14/2006] [Accepted: 06/15/2006] [Indexed: 11/28/2022]
Abstract
The major human fungal pathogen, Candida albicans, colonizes different body sites, differing greatly in oxygen levels. Using whole-genome DNA microarrays, we analysed the transcriptomal response of C. albicans to hypoxia. In this condition, transcripts of genes involved in fermentative metabolism, including glycolytic genes, as well as hypha-specific genes, were up-regulated; in contrast, genes regulating oxidative metabolism were down-regulated. Although the morphogenetic and metabolic regulator Efg1p regulates these genes during normoxia, we found that Efg1p is not involved in their hypoxic regulation. Instead, Efg1p was specifically required for hypoxic expression or repression of subsets of genes. One class of hypoxia-regulated genes, encoding proteins involved in fatty acid biosynthesis, was dependent on Efg1p for maximal hypoxic expression, requiring Efg1p for transcriptional activation. During hypoxia, efg1 mutants contained lower levels of unsaturated fatty acids, while hyphal morphogenesis on solid media was significantly increased at temperatures <37 degrees C. These results suggest that during oxygen-limitation, Efg1p acts as a repressor of filamentation and as a positive regulator of fatty acid desaturation. We discuss that C. albicans responds to hypoxia largely by different mechanisms compared to budding yeast and that hypoxic adaptation requiring Efg1p is crucial for successful infection of human cells and tissues.
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Affiliation(s)
- Eleonora R Setiadi
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
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29
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Rouabhia M, Schaller M, Corbucci C, Vecchiarelli A, Prill SKH, Giasson L, Ernst JF. Virulence of the fungal pathogen Candida albicans requires the five isoforms of protein mannosyltransferases. Infect Immun 2005; 73:4571-80. [PMID: 16040968 PMCID: PMC1201229 DOI: 10.1128/iai.73.8.4571-4580.2005] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The PMT gene family in Candida albicans encodes five isoforms of protein mannosyltransferases (Pmt proteins Pmt1p, Pmt2p, Pmt4p, Pmt5p, and Pmt6p) that initiate O mannosylation of secretory proteins. We compared virulence characteristics of pmt mutants in two complex, three-dimensional models of localized candidiasis, using reconstituted human epithelium (RHE) and engineered human oral mucosa (EHOM); in addition, mutants were tested in a mouse model of hematogenously disseminated candidiasis (HDC). All pmt mutants showed attenuated virulence in the HDC model and at least one model of localized candidiasis. The pmt5 mutant, which lacks in vitro growth phenotypes, was less virulent in the EHOM and HDC assays but had no consistent phenotype in the RHE assay. In contrast, the pmt4 and pmt6 mutants were less virulent in the RHE and HDC assays but not in the EHOM assay. The results stress the contribution of all Pmt isoforms to the virulence of C. albicans and suggest that the importance of individual Pmt isoforms may differ in specific host niches. We propose that Pmt proteins may be suitable targets for future novel classes of antifungal agents.
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Affiliation(s)
- Mahmoud Rouabhia
- Institut for Mikrobiologie, Universitätsstr. 1/26.12, 40225 Düsseldorf, Germany
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Prill SKH, Klinkert B, Timpel C, Gale CA, Schröppel K, Ernst JF. PMT family of Candida albicans: five protein mannosyltransferase isoforms affect growth, morphogenesis and antifungal resistance. Mol Microbiol 2005; 55:546-60. [PMID: 15659169 DOI: 10.1111/j.1365-2958.2004.04401.x] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protein O-mannosyltransferases (Pmt proteins) initiate O-mannosylation of secretory proteins. The PMT gene family of the human fungal pathogen Candida albicans consists of PMT1 and PMT6, as well as three additional PMT genes encoding Pmt2, Pmt4 and Pmt5 isoforms described here. Both PMT2 alleles could not be deleted and growth of conditional strains, containing PMT2 controlled by the MET3- or tetOScHOP1-promoters, was blocked in non-permissive conditions, indicating that PMT2 is essential for growth. A homozygous pmt4 mutant was viable, but synthetic lethality of pmt4 was observed in combination with pmt1 mutations. Hyphal morphogenesis of a pmt4 mutant was defective under aerobic induction conditions, yet increased in embedded or hypoxic conditions, suggesting a role of Pmt4p-mediated O-glycosylation for environment-specific morphogenetic signalling. Although a PMT5 transcript was detected, a homozygous pmt5 mutant was phenotypically silent. All other pmt mutants showed variable degrees of supersensitivity to antifungals and to cell wall-destabilizing agents. Cell wall composition was markedly affected in pmt1 and pmt4 mutants, showing a significant decrease in wall mannoproteins. In a mouse model of haematogenously disseminated infection, PMT4 was required for full virulence of C. albicans. Functional analysis of the first complete PMT gene family in a fungal pathogen indicates that Pmt isoforms have variable and specific roles for in vitro and in vivo growth, morphogenesis and antifungal resistance.
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Affiliation(s)
- Stephan K-H Prill
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
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Pasrija R, Krishnamurthy S, Prasad T, Ernst JF, Prasad R. Squalene epoxidase encoded by ERG1 affects morphogenesis and drug susceptibilities of Candida albicans. J Antimicrob Chemother 2005; 55:905-13. [PMID: 15845783 DOI: 10.1093/jac/dki112] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES Functional characterization of the erg1 mutant of ergosterol biosynthesis of Candida albicans. METHODS We disrupted the ERG1 gene of C. albicans, which encodes squalene epoxidase (EC 1.14.99.7). Since the disruption of both alleles of ERG1 was lethal, the second allele of a heterozygous disruptant was placed under the control of a regulable promoter, MET3p, which is repressed by methionine and cysteine. RESULTS The reverse-phase HPLC analysis of sterol, extracted from the conditional mutant strain, showed a total lack of ergosterol and instead accumulation of squalene. This imbalance in sterol composition led to defects in growth and increased susceptibilities to drugs including fluconazole, ketoconazole, cycloheximide, nystatin, amphotericin B and terbinafine. Reduced drug efflux activity of the erg1 mutant was associated with poor surface localization of Cdr1p, suggesting that enhanced passive diffusion and reduced efflux mediated by the ABC (ATP binding cassette) transporter Cdr1p increases drug susceptibility. Additionally, conditional erg1 mutant strains were unable to form hyphae in various media. CONCLUSIONS Taken together, our results demonstrate that the absence of ergosterol, which is one of the constituents of membrane microdomains (rafts), has a direct effect on drug susceptibility and morphogenesis of C. albicans.
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Affiliation(s)
- Ritu Pasrija
- School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India.
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d'Enfert C, Goyard S, Rodriguez-Arnaveilhe S, Frangeul L, Jones L, Tekaia F, Bader O, Albrecht A, Castillo L, Dominguez A, Ernst JF, Fradin C, Gaillardin C, Garcia-Sanchez S, de Groot P, Hube B, Klis FM, Krishnamurthy S, Kunze D, Lopez MC, Mavor A, Martin N, Moszer I, Onésime D, Perez Martin J, Sentandreu R, Valentin E, Brown AJP. CandidaDB: a genome database for Candida albicans pathogenomics. Nucleic Acids Res 2005; 33:D353-7. [PMID: 15608215 PMCID: PMC540078 DOI: 10.1093/nar/gki124] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
CandidaDB is a database dedicated to the genome of the most prevalent systemic fungal pathogen of humans, Candida albicans. CandidaDB is based on an annotation of the Stanford Genome Technology Center C.albicans genome sequence data by the European Galar Fungail Consortium. CandidaDB Release 2.0 (June 2004) contains information pertaining to Assembly 19 of the genome of C.albicans strain SC5314. The current release contains 6244 annotated entries corresponding to 130 tRNA genes and 5917 protein-coding genes. For these, it provides tentative functional assignments along with numerous pre-run analyses that can assist the researcher in the evaluation of gene function for the purpose of specific or large-scale analysis. CandidaDB is based on GenoList, a generic relational data schema and a World Wide Web interface that has been adapted to the handling of eukaryotic genomes. The interface allows users to browse easily through genome data and retrieve information. CandidaDB also provides more elaborate tools, such as pattern searching, that are tightly connected to the overall browsing system. As the C.albicans genome is diploid and still incompletely assembled, CandidaDB provides tools to browse the genome by individual supercontigs and to examine information about allelic sequences obtained from complementary contigs. CandidaDB is accessible at http://genolist.pasteur.fr/CandidaDB.
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Affiliation(s)
- C d'Enfert
- Unité Postulante Biologie et Pathogénicité Fongiques, INRA USC 2019, Institut Pasteur, Paris, France.
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Weber Y, Prill SKH, Ernst JF. Pmt-mediated O mannosylation stabilizes an essential component of the secretory apparatus, Sec20p, in Candida albicans. Eukaryot Cell 2005; 3:1164-8. [PMID: 15470244 PMCID: PMC522601 DOI: 10.1128/ec.3.5.1164-1168.2004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Sec20p is an essential endoplasmic reticulum (ER) membrane protein in yeasts, functioning as a tSNARE component in retrograde vesicle traffic. We show that Sec20p in the human fungal pathogen Candida albicans is extensively O mannosylated by protein mannosyltransferases (Pmt proteins). Surprisingly, Sec20p occurs at wild-type levels in a pmt6 mutant but at very low levels in pmt1 and pmt4 mutants and also after replacement of specific Ser/Thr residues in the lumenal domain of Sec20p. Pulse-chase experiments revealed rapid degradation of unmodified Sec20p (38.6 kDa) following its biosynthesis, while the stable O-glycosylated form (50 kDa) was not formed in a pmt1 mutant. These results suggest a novel function of O mannosylation in eukaryotes, in that modification by specific Pmt proteins will prevent degradation of ER-resident membrane proteins via ER-associated degradation or a proteasome-independent pathway.
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Affiliation(s)
- Yvonne Weber
- Institut für Mikrobiologie Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1/Geb. 26.12, D-40225 Düsseldorf, Germany
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Doedt T, Krishnamurthy S, Bockmühl DP, Tebarth B, Stempel C, Russell CL, Brown AJ, Ernst JF. APSES proteins regulate morphogenesis and metabolism in Candida albicans. Mol Biol Cell 2005; 15:3167-80. [PMID: 15218092 PMCID: PMC452574 DOI: 10.1091/mbc.e03-11-0782] [Citation(s) in RCA: 193] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Fungal APSES proteins regulate morphogenetic processes, including filamentation and differentiation. The human fungal pathogen Candida albicans contains two APSES proteins: the regulator Efg1p and its homologue Efh1p, described here. Overexpression of EFG1 or EFH1 led to similar phenotypes, including pseudohypha formation and opaque-white switching. An efh1 deletion generated no phenotype under most conditions but caused hyperfilamentation in an efg1 background under embedded or hypoxic conditions. This suggests cooperation of these APSES proteins in the suppression of an alternative morphogenetic signaling pathway. Genome-wide transcriptional profiling revealed that EFG1 and EFH1 regulate partially overlapping sets of genes associated with filament formation. Unexpectedly, Efg1p not only regulates genes involved in morphogenesis but also strongly influences the expression of metabolic genes, inducing glycolytic genes and repressing genes essential for oxidative metabolism. Using one- and two-hybrid assays, we further demonstrate that Efg1p is a repressor, whereas Efh1p is an activator of gene expression. Overall, the results suggest that Efh1p supports the regulatory functions of the primary regulator, Efg1p, and indicate a dual role for these APSES proteins in the regulation of fungal morphogenesis and metabolism.
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Affiliation(s)
- Thomas Doedt
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | | | - Dirk P. Bockmühl
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Bernd Tebarth
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
- Biomedizinisches Forschungszentrum, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Christian Stempel
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Claire L. Russell
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, United Kingdom
| | - Alistair J.P. Brown
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, United Kingdom
| | - Joachim F. Ernst
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
- Biomedizinisches Forschungszentrum, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
- Corresponding author. E-mail address:
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Doedt T, Krishnamurthy S, Bockmühl DP, Tebarth B, Stempel C, Russell CL, Brown AJ, Ernst JF. APSES proteins regulate morphogenesis and metabolism in Candida albicans. Mol Biol Cell 2004. [PMID: 15218092 PMCID: PMC452574 DOI: 10.1091/10.1091/mbc.e03-11-0782] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023] Open
Abstract
Fungal APSES proteins regulate morphogenetic processes, including filamentation and differentiation. The human fungal pathogen Candida albicans contains two APSES proteins: the regulator Efg1p and its homologue Efh1p, described here. Overexpression of EFG1 or EFH1 led to similar phenotypes, including pseudohypha formation and opaque-white switching. An efh1 deletion generated no phenotype under most conditions but caused hyperfilamentation in an efg1 background under embedded or hypoxic conditions. This suggests cooperation of these APSES proteins in the suppression of an alternative morphogenetic signaling pathway. Genome-wide transcriptional profiling revealed that EFG1 and EFH1 regulate partially overlapping sets of genes associated with filament formation. Unexpectedly, Efg1p not only regulates genes involved in morphogenesis but also strongly influences the expression of metabolic genes, inducing glycolytic genes and repressing genes essential for oxidative metabolism. Using one- and two-hybrid assays, we further demonstrate that Efg1p is a repressor, whereas Efh1p is an activator of gene expression. Overall, the results suggest that Efh1p supports the regulatory functions of the primary regulator, Efg1p, and indicate a dual role for these APSES proteins in the regulation of fungal morphogenesis and metabolism.
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Affiliation(s)
- Thomas Doedt
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | | | - Dirk P. Bockmühl
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Bernd Tebarth
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
- Biomedizinisches Forschungszentrum, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Christian Stempel
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Claire L. Russell
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, United Kingdom
| | - Alistair J.P. Brown
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, United Kingdom
| | - Joachim F. Ernst
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
- Biomedizinisches Forschungszentrum, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
- Corresponding author. E-mail address:
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Krishnamurthy S, Plaine A, Albert J, Prasad T, Prasad R, Ernst JF. Dosage-dependent functions of fatty acid desaturase Ole1p in growth and morphogenesis of Candida albicans. Microbiology (Reading) 2004; 150:1991-2003. [PMID: 15184585 DOI: 10.1099/mic.0.27029-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Conditions in the infected human host trigger virulence attributes of the fungal pathogenCandida albicans. Specific inducers and elevated temperatures lead to hyphal development or regulate chlamydospore development. To explore if these processes are affected by membrane lipids, an investigation of the functions of the Ole1 fatty acid desaturase (stearoyl-CoA desaturase) inC. albicans, which synthesizes oleic acid, was undertaken. A conditional strain expressingOLE1from the regulatableMET3promoter was unable to grow in repressing conditions, indicating thatOLE1is an essential gene. In contrast, a mutant lacking both alleles ofOLE2, encoding a Ole1p homologue, was viable and had no apparent phenotypes. Partial repression ofMET3p–OLE1slightly lowered oleic acid levels and decreased membrane fluidity; these conditions permitted growth in the yeast form, but prevented hyphal development in aerobic conditions and blocked the formation of chlamydospores. In contrast, in hypoxic conditions, which trigger an alternative morphogenetic pathway, hyphal morphogenesis was unaffected. Because aerobic morphogenetic signalling and oleic acid biosynthesis require oxygen, it is proposed that oleic acid may function as a sensor activating specific morphogenetic pathways in normoxic conditions.
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Affiliation(s)
| | - Armêl Plaine
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Juliane Albert
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Tulika Prasad
- Jawaharlal Nehru University, New Delhi 110067, India
| | | | - Joachim F Ernst
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
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Ernst JF. H.D. Osiewacz, ed. Molecular Biology of Fungal Development. Mycopathologia 2004. [DOI: 10.1023/b:myco.0000012321.56691.b5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Tebarth B, Doedt T, Krishnamurthy S, Weide M, Monterola F, Dominguez A, Ernst JF. Adaptation of the Efg1p morphogenetic pathway in Candida albicans by negative autoregulation and PKA-dependent repression of the EFG1 gene. J Mol Biol 2003; 329:949-62. [PMID: 12798685 DOI: 10.1016/s0022-2836(03)00505-9] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The Efg1p regulator protein permits hyphal morphogenesis in the human fungal pathogen Candida albicans. We have identified the major promoter of the EFG1 gene as a direct target of Efg1p, resulting in negative autoregulation of EFG1. Enhanced activity of protein kinase A (PKA) isoforms Tpk1p and Tpk2p or exogenous overexpression of EFG1 led to Efg1p-dependent down-regulation of the endogenous EFG1 promoter. Serial deletion analyses of the promoter region revealed that the TATA box region was required for EFG1 autoregulation. By chromatin immunoprecipitation we detected binding of Efg1p to the EFG1 transcriptional initiation region. Furthermore, Sin3p, a component of a specific histone deacetylase complex, was shown to bind to the EFG1 promoter. sin3 mutants grew as budding pseudohyphae and were unable to form true hyphae, similar to strains constitutively expressing EFG1. We propose that the PKA signalling pathway, in addition to its importance in the initial steps of filament formation, is part of a feedback loop that controls EFG1 expression allowing continued hypha formation in inducing conditions. This autoregulation of EFG1 expression is probably mediated through the Sin3p-containing histone deacetylation complex.
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Affiliation(s)
- Bernd Tebarth
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
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39
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Haas H, Schoeser M, Lesuisse E, Ernst JF, Parson W, Abt B, Winkelmann G, Oberegger H. Characterization of the Aspergillus nidulans transporters for the siderophores enterobactin and triacetylfusarinine C. Biochem J 2003; 371:505-13. [PMID: 12487628 PMCID: PMC1223275 DOI: 10.1042/bj20021685] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2002] [Revised: 12/12/2002] [Accepted: 12/17/2002] [Indexed: 11/17/2022]
Abstract
The filamentous ascomycete Aspergillus nidulans produces three major siderophores: fusigen, triacetylfusarinine C, and ferricrocin. Biosynthesis and uptake of iron from these siderophores, as well as from various heterologous siderophores, is repressed by iron and this regulation is mediated in part by the transcriptional repressor SREA. Recently we have characterized a putative siderophore-transporter-encoding gene ( mirA ). Here we present the characterization of two further SREA- and iron-regulated paralogues (mirB and mirC ), including the chromosomal localization and the complete exon/intron structure. Expression of mirA and mirB in a Saccharomyces cerevisiae strain, which lacks high affinity iron transport systems, showed that MIRA transports specifically the heterologous siderophore enterobactin and that MIRB transports exclusively the native siderophore triacetylfusarinine C. Construction and analysis of an A. nidulans mirA deletion mutant confirmed the substrate specificity of MIRA. Phylogenetic analysis of the available sequences suggests that the split of the species A. nidulans and S. cerevisiae predates the divergence of the paralogous Aspergillus siderophore transporters.
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Affiliation(s)
- Hubertus Haas
- Department of Molecular Biology, University of Innsbruck, Austria.
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40
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Weber Y, Swoboda RK, Ernst JF. Sec20p-interacting proteins (Tip20p, Ufe1p) in the retrograde secretory pathway of the fungal pathogen Candida albicans. Mol Genet Genomics 2002; 268:468-76. [PMID: 12471444 DOI: 10.1007/s00438-002-0777-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2002] [Accepted: 10/16/2002] [Indexed: 10/27/2022]
Abstract
Sec20p is an essential Type-II membrane protein of the human fungal pathogen Candida albicans, which is thought to be involved in mediating retrograde vesicle traffic from the Golgi to the endoplasmic reticulum (ER). Using an epitope-tagged Sec20p we obtained evidence for its localization in ER membranes, which is consistent with its proposed role in an ER-tSNARE complex. Two genes encoding potential interaction partners for Sec20p, Tip20p and Ufe1p, were identified in genomic sequences of C. albicans; these show 18% and 27% identity, respectively, to homologues in Saccharomyces cerevisiae. An interaction between the cytoplasmic domain of Sec20p and Tip20p was demonstrated by two-hybrid analysis; in addition, Tip20p was found to form homodimers. Interaction between Sec20p and Tip20p in vivo was verified by co-immunoprecipation experiments. CaUFE1, which encodes a potential ER-tSNARE, was able to complement a thermosensitive ufe1 mutation in S. cerevisiae, suggesting functional conservation between the two fungal proteins. Thus, although the sequences of some components of the ER-tSNARE complex have diverged considerably during evolution, it appears that they have retained similar functions in C. albicans and S. cerevisiae.
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Affiliation(s)
- Y Weber
- Institut für Mikrobiologie, Heinrich-Heine-Universität, Universitätsstrasse 1, Geb. 26.12, 40225 Düsseldorf, Germany
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Heymann P, Gerads M, Schaller M, Dromer F, Winkelmann G, Ernst JF. The siderophore iron transporter of Candida albicans (Sit1p/Arn1p) mediates uptake of ferrichrome-type siderophores and is required for epithelial invasion. Infect Immun 2002; 70:5246-55. [PMID: 12183576 PMCID: PMC128288 DOI: 10.1128/iai.70.9.5246-5255.2002] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The human fungal pathogen Candida albicans contains a close homologue of yeast siderophore transporters, designated Sit1p/Arn1p. We have characterized the function of SIT1 in C. albicans by constructing sit1 deletion strains and testing their virulence and ability to utilize a range of siderophores and other iron complexes. sit1 mutant strains are defective in the uptake of ferrichrome-type siderophores including ferricrocin, ferrichrysin, ferrirubin, coprogen, and triacetylfusarinine C. A mutation of FTR1 did not impair the use of these siderophores but did affect the uptake of ferrioxamines E and B, as well as of ferric citrate, indicating that their utilization was independent of Sit1p. Hemin was a source of iron for both sit1 and ftr1 mutants, suggesting a pathway of hemin uptake distinct from that of siderophores and iron salts. Heterologous expression of SIT1 in the yeast Saccharomyces cerevisiae confirmed the function of Sit1p as a transporter for ferrichrome-type siderophores. The sit1 mutant was defective in infection of a reconstituted human epithelium as a model for human oral mucosa, while the SIT1 strain was invasive. In contrast, both sit1 and SIT1 strains were equally virulent in the mouse model of systemic infection. These results suggest that siderophore uptake by Sit1p/Arn1p is required in a specific process of C. albicans infection, namely epithelial invasion and penetration, while in the blood or within organs other sources of iron, including heme, may be used.
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Affiliation(s)
- Petra Heymann
- Institut für Mikrobiologie, Heinrich-Heine-Universität Düsseldorf, Germany
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42
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Ernst JF, Prill SK. O-glycosylation. Med Mycol 2002; 39 Suppl 1:67-74. [PMID: 11800270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023] Open
Abstract
O-Glycosylation in many fungal species is initiated in the endoplasmic reticulum by protein mannosyltransferases (Pmt-proteins), which transfer mannose to serine or threonine residues, and it is completed by mannosyltransferases (Mnt-proteins) in the Golgi. In this review, some recent results on O-glycosylation in the human fungal pathogen Candida albicans are discussed and compared to the corresponding knowledge in the non-pathogenic yeast Saccharomyces cerevisiae. The Pmt-family in C. albicans comprises five isoforms, of which Pmt1p and Pmt6p have been studied in detail. Surprisingly, O-glycosylation mediated by Pmt-proteins is required not only for the modification of several secreted and cell-wall proteins, but also affects yeast-hyphal morphogenesis (dimorphism) and resistance to several antifungal compounds. Furthermore, Pmt1- and Pmt6p-activities maximize adherence to host cells and determine or contribute to virulence in models of systemic infection. Thus, O-glycosylation processes directly and/or indirectly affect several virulence traits of C. albicans and can be considered as potential antifungal targets.
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Affiliation(s)
- J F Ernst
- Institut für Mikrobiologie, Heinnch-Heine-Universität Düsseldorf, Germany.
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Bockmühl DP, Krishnamurthy S, Gerads M, Sonneborn A, Ernst JF. Distinct and redundant roles of the two protein kinase A isoforms Tpk1p and Tpk2p in morphogenesis and growth of Candida albicans. Mol Microbiol 2001; 42:1243-57. [PMID: 11886556 DOI: 10.1046/j.1365-2958.2001.02688.x] [Citation(s) in RCA: 163] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
TPK1 and TPK2 encode both isoforms of protein kinase A (PKA) catalytic subunits in Candida albicans. Mutants lacking both TPK1 alleles showed defective hyphal morphogenesis on solid inducing media, whereas in liquid hypha, formation was affected slightly. In contrast, tpk2 mutants were only partially morphogenesis defective on solid media, whereas a strong block was observed in liquid. In addition, the yeast forms of tpk2-- but not tpk1-- mutants were completely deficient in invading agar. Because Tpk1p and Tpk2p differ in their N-terminal domains of approximately 80--90 amino acids, while the catalytic portions are highly homologous, the functions of hybrid Tpk proteins with exchanged N-terminal domains were tested. The results demonstrate that the catalytic portions mediate Tpk protein specificities with regard to filamentation, whereas agar invasion is mediated by the N-terminal domain of Tpk2p. Homozygous tpk1 and tpk2 mutants grew normally; however, a tpk2 mutant strain containing a single regulatable TPK1 allele (PCK1p-TPK1) at low expression levels was severely growth defective. It was completely blocked in hyphal morphogenesis and was stress resistant to high osmolarities or temperatures. Thus, both Tpk isoforms in C. albicans share growth functions but, unlike Saccharomyces cerevisiae isoforms, they have positive, specific roles in filament formation in different environments.
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Affiliation(s)
- D P Bockmühl
- Institut für Mikrobiologie, Heinrich-Heine-Universität, Universitätsstr. 1/26.12, 40225 Düsseldorf, Germany
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Gruber A, Lell CP, Speth C, Stoiber H, Lass-Flörl C, Sonneborn A, Ernst JF, Dierich MP, Würzner R. Human immunodeficiency virus type 1 Tat binds to Candida albicans, inducing hyphae but augmenting phagocytosis in vitro. Immunology 2001; 104:455-61. [PMID: 11899432 PMCID: PMC1783331 DOI: 10.1046/j.1365-2567.2001.01328.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Tat, the human immunodeficiency virus type 1 (HIV-1) transactivating protein, binds through its RGD-motif to human integrin receptors. Candida albicans, the commonest cause of mucosal candidiasis in subjects infected with HIV-1, also possesses RGD-binding capacity. The present study reveals that Tat binds to C. albicans but not to C. tropicalis. Tat binding was markedly reduced by laminin and to a lesser extent by a complement C3 peptide containing the RGD motif, but not by a control peptide. The outgrowth of C. albicans was accelerated following binding of Tat, but phagocytosis of opsonized C. albicans was also increased after Tat binding. Thus, Tat binding promotes fungal virulence by inducing hyphae but may also reduce it by augmenting phagocytosis. The net effect of Tat in vivo is difficult to judge but in view of the many disease-promoting effects of Tat we propose that accelerating the formation of hyphae dominates over the augmentation of phagocytosis.
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Affiliation(s)
- A Gruber
- Institute for Hygiene and Social Medicine, University of Innsbruck, Ludwig Boltzmann-Institute for AIDS-Research, Innsbruck, Austria.
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Bockmühl DP, Ernst JF. A potential phosphorylation site for an A-type kinase in the Efg1 regulator protein contributes to hyphal morphogenesis of Candida albicans. Genetics 2001; 157:1523-30. [PMID: 11290709 PMCID: PMC1461612 DOI: 10.1093/genetics/157.4.1523] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Efg1p in the human fungal pathogen Candida albicans is a member of the conserved APSES class of proteins regulating morphogenetic processes in fungi. We have analyzed the importance for hyphal morphogenesis of a putative phosphorylation site for protein kinase A (PKA), threonine-206, within an Efg1p domain highly conserved among APSES proteins. Alanine substitution of T206, but not of the adjacent T207 and T208 residues, led to a block of hypha formation on solid and in liquid media, while a T206E exchange caused hyperfilamentation. The extent of the morphogenetic defect caused by the T206A mutation depended on hypha-induction conditions. Extragenous suppression of mutations in signaling components, including tpk2 and cek1 mutations, was achieved by wild-type- and T206E-, but not by the T206A-variant-encoding allele of EFG1. All muteins tested were produced at equal levels and at high production levels supported pseudohyphal formation. The results are consistent with a role of Efg1p as a central downstream component of a PKA-signaling pathway including Tpk2p or other PKA isoforms. Threonine-206 of Efg1p is essential as a putative phosphorylation target to promote hyphal induction by a subset of environmental cues.
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Affiliation(s)
- D P Bockmühl
- Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
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Weber Y, Santore UJ, Ernst JF, Swoboda RK. Divergence of eukaryotic secretory components: the Candida albicans homolog of the Saccharomyces cerevisiae ++Sec20 protein is N terminally truncated, and its levels determine antifungal drug resistance and growth. J Bacteriol 2001; 183:46-54. [PMID: 11114899 PMCID: PMC94848 DOI: 10.1128/jb.183.1.46-54.2001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sec20p is a component of the yeast Saccharomyces cerevisiae secretory pathway that does not have a close homolog in higher eukaryotic cells. To verify the function of Sec20p in other fungal species, we characterized the gene encoding a Sec20p homolog in the human fungal pathogen Candida albicans. The deduced protein has 27% identity with, but is missing about 100 N-terminal residues compared to S. cerevisiae Sec20p, which is part of the cytoplasmic tail interacting with the cytoplasmic protein Tip20p. Because a strain lacking both C. albicans SEC20 alleles could not be constructed, we placed SEC20 under transcriptional control of two regulatable promoters, MET3p and PCK1p. Repression of SEC20 expression in these strains prevented (MET3p-SEC20 allele) or retarded (PCK1p-SEC20 allele) growth and led to the appearance of extensive intracellular membranes, which frequently formed stacks. Reduced SEC20 expression in the PCK1p-SEC20 strain did not affect morphogenesis but led to a series of hypersensitivity phenotypes including supersensitivity to aminoglycoside antibiotics, to nystatin, to sodium dodecyl sulfate, and to cell wall inhibitors. These results demonstrate the occurrence and function of Sec20p in a fungal species other than S. cerevisiae, but the lack of the N-terminal domain and the apparent absence of a close TIP20 homolog in the C. albicans genome also indicate a considerable diversity in mechanisms of retrograde vesicle traffic in eukaryotes.
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Affiliation(s)
- Y Weber
- Institut für Mikrobiologie, Heinrich-Heine-Universität, D-40225 Düsseldorf, Germany
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Affiliation(s)
- J F Ernst
- Institut für Mikrobiologie, Heinrich-Heine-Universität Düsseldorf, Germany.
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Affiliation(s)
- Joachim F Ernst
- Institut für Mikrobiologie, Heinrich-Heine-Universität, Universitätsstr. 1/26.12, D-40225 Düsseldorf, Germany1
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Weide MR, Ernst JF. Caco-2 monolayer as a model for transepithelial migration of the fungal pathogen Candida albicans. Mycoses 2000; 42 Suppl 2:61-7. [PMID: 10865906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
A model for transepithelial migration of human fungal pathogens was established, in which Candida albicans was shown to migrate across a monolayer of Caco-2 intestinal cells in a two-chamber system. Electron microscopy revealed typical stages of epithelial penetration by C. albicans including phagocytosis at the apical side, intra- and intercellular migration and exit on the basolateral side of the monolayer. Hyphal growth forms appeared particularly involved in penetration of the Caco-2 monolayer. The model was examined using defined C. albicans mutants defective in hyphal development (efg1/efg1) or growth (ura3/ura3). Transmigration of the efg1/efg1 mutant strain was reduced, while transmigration of the ura3/ura3 strain was blocked completely in the absence of uridine. Because these results parallel virulence characteristics of the mutants the Caco-2 monolayer system appears a useful model for the study of fungal-human host cell interactions.
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Affiliation(s)
- M R Weide
- Institut für Mikrobiologie, Heinrich-Heine-Universität, Düsseldorf, Germany
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Heymann P, Ernst JF, Winkelmann G. Identification and substrate specificity of a ferrichrome-type siderophore transporter (Arn1p) in Saccharomyces cerevisiae. FEMS Microbiol Lett 2000; 186:221-7. [PMID: 10802175 DOI: 10.1111/j.1574-6968.2000.tb09108.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Genes encoding transporters for heterologous siderophores have been identified in Saccharomyces cerevisiae, of which SIT1, TAF1, and ENB1 encode the transporters for ferrioxamines, ferric triacetylfusarinine C and ferric enterobactin, respectively. In the present communication we have shown that a further gene encoding a member of the major facilitator superfamily, ARN1 (YHL040c), is involved in the transport of a specific class of ferrichromes, possessing anhydromevalonyl residues linked to N(delta)-ornithine (ARN). Ferrirubin and ferrirhodin, which both are produced by filamentous fungi, are the most common representatives of this class of ferrichromes. A strain possessing a disruption in the ARN1 gene was unable to transport ferrirubin, ferrirhodin and also ferrichrome A, indicating that the encoded transporter recognizes anhydromevalonyl and the structurally-related methylglutaconyl side-chains surrounding the iron center. Ferrichromes possessing short-chain ornithine-N(delta)-acetyl residues such as ferrichrome, ferricrocin and ferrichrysin, were excluded by the Arn1 transporter. Substitution of the iron-surrounding N-acyl chains of ferrichromes by propionyl residues had no effect, whereas substitution by butyryl residues led to recognition by the Arn1 transporter. This would indicate that a chain length of four C-atoms is sufficient to allow binding. Using different asperchromes (B1, D1) we also found that a minimal number of two anhydromevalonyl residues is sufficient for recognition by Arn1p. Contrary to the iron-surrounding N-acyl residues, the peptide backbone of ferrichromes was not an important determinant for the Arn1 transporter.
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Affiliation(s)
- P Heymann
- Institut für Mikrobiologie and Biotechnologie, Universität Tübingen, Auf der Morgenstelle 28, D-72076, Tübingen, Germany
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