1
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Xu D, Wang M, Zhang X, Mao H, Xu H, Zhang B, Zeng X, Li F. The Putative Cytochrome b5 Domain-Containing Protein CaDap1 Homologue Is Involved in Antifungal Drug Tolerance, Cell Wall Chitin Maintenance, and Virulence in Candida albicans. J Fungi (Basel) 2024; 10:316. [PMID: 38786671 PMCID: PMC11122062 DOI: 10.3390/jof10050316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 04/18/2024] [Accepted: 04/19/2024] [Indexed: 05/25/2024] Open
Abstract
Candida albicans (Ca), a prominent opportunistic fungal pathogen in humans, has garnered considerable attention due to its infectious properties. Herein, we have identified and characterized CaCDAP1 (Ca orf19.1034), a homolog of ScDAP1 found in Saccharomyces cerevisiae. CaCDAP1 encodes a 183-amino acid protein with a conserved cytochrome b5-like heme-binding domain. The deletion of CaDAP1 renders Ca cells susceptible to caspofungin and terbinafine. CaDAP1 deletion confers resistance to Congo Red and Calcofluor White, and sensitivity to sodium dodecyl sulfate. The deletion of CaDAP1 results in a 50% reduction in chitin content within the cell wall, the downregulation of phosphorylation levels in CaMkc1, and the upregulation of phosphorylation levels in CaCek1. Notably, CaDAP1 deletion results in the abnormal hyphal development of Ca cells and diminishes virulence in a mouse systemic infection model. Thus, CaDAP1 emerges as a critical regulator governing cellular responses to antifungal drugs, the synthesis of cell wall chitin, and virulence in Ca.
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Affiliation(s)
- Dayong Xu
- College of Life Sciences, Huaibei Normal University, Huaibei 235000, China; (M.W.); (X.Z.); (H.M.); (H.X.); (B.Z.); (X.Z.)
| | | | | | | | | | | | | | - Feng Li
- College of Life Sciences, Huaibei Normal University, Huaibei 235000, China; (M.W.); (X.Z.); (H.M.); (H.X.); (B.Z.); (X.Z.)
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2
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Jin J, Iwama R, Horiuchi H. The N-terminal disordered region of ChsB regulates its efficient transport to the hyphal apical surface in Aspergillus nidulans. Curr Genet 2023; 69:175-188. [PMID: 37071151 PMCID: PMC10163080 DOI: 10.1007/s00294-023-01267-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 03/27/2023] [Accepted: 04/06/2023] [Indexed: 04/19/2023]
Abstract
In fungi, the cell wall plays a crucial role in morphogenesis and response to stress from the external environment. Chitin is one of the main cell wall components in many filamentous fungi. In Aspergillus nidulans, a class III chitin synthase ChsB plays a pivotal role in hyphal extension and morphogenesis. However, little is known about post-translational modifications of ChsB and their functional impacts. In this study, we showed that ChsB is phosphorylated in vivo. We characterized strains that produce ChsB using stepwise truncations of its N-terminal disordered region or deletions of some residues in that region and demonstrated its involvement in ChsB abundance on the hyphal apical surface and in hyphal tip localization. Furthermore, we showed that some deletions in this region affected the phosphorylation states of ChsB, raising the possibility that these states are important for the localization of ChsB to the hyphal surface and the growth of A. nidulans. Our findings indicate that ChsB transport is regulated by its N-terminal disordered region.
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Affiliation(s)
- Jingyun Jin
- Department of Biotechnology, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-8657, Japan
- Peking University Institute of Advanced Agricultural Sciences, Shandong Laboratory of Advanced Agricultural Sciences in Weifang, Shandong, 261325, China
| | - Ryo Iwama
- Department of Biotechnology, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-8657, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Hiroyuki Horiuchi
- Department of Biotechnology, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-8657, Japan.
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-8657, Japan.
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3
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Itani A, Masuo S, Yamamoto R, Serizawa T, Fukasawa Y, Takaya N, Toyota M, Betsuyaku S, Takeshita N. Local calcium signal transmission in mycelial network exhibits decentralized stress responses. PNAS NEXUS 2023; 2:pgad012. [PMID: 36896124 PMCID: PMC9991499 DOI: 10.1093/pnasnexus/pgad012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 01/03/2023] [Accepted: 01/18/2023] [Indexed: 03/09/2023]
Abstract
Many fungi live as mycelia, which are networks of hyphae. Mycelial networks are suited for the widespread distribution of nutrients and water. The logistical capabilities are critical for the extension of fungal survival areas, nutrient cycling in ecosystems, mycorrhizal symbioses, and virulence. In addition, signal transduction in mycelial networks is predicted to be vital for mycelial function and robustness. A lot of cell biological studies have elucidated protein and membrane trafficking and signal transduction in fungal hyphae; however, there are no reports visualizing signal transduction in mycelia. This paper, by using the fluorescent Ca2+ biosensor, visualized for the first time how calcium signaling is conducted inside the mycelial network in response to localized stimuli in the model fungus Aspergillus nidulans. The wavy propagation of the calcium signal inside the mycelium or the signal blinking in the hyphae varies depending on the type of stress and proximity to the stress. The signals, however, only extended around 1,500 μm, suggesting that the mycelium has a localized response. The mycelium showed growth delay only in the stressed areas. Local stress caused arrest and resumption of mycelial growth through reorganization of the actin cytoskeleton and membrane trafficking. To elucidate the downstream of calcium signaling, calmodulin, and calmodulin-dependent protein kinases, the principal intracellular Ca2+ receptors were immunoprecipitated and their downstream targets were identified by mass spectrometry analyses. Our data provide evidence that the mycelial network, which lacks a brain or nervous system, exhibits decentralized response through locally activated calcium signaling in response to local stress.
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Affiliation(s)
- Ayaka Itani
- Microbiology Research Center for Sustainability (MiCS), Faculty of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, 305-8572, Japan
| | - Shunsuke Masuo
- Microbiology Research Center for Sustainability (MiCS), Faculty of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, 305-8572, Japan
| | - Riho Yamamoto
- Microbiology Research Center for Sustainability (MiCS), Faculty of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, 305-8572, Japan
| | - Tomoko Serizawa
- Microbiology Research Center for Sustainability (MiCS), Faculty of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, 305-8572, Japan
| | - Yu Fukasawa
- Graduate School of Agricultural Science, Tohoku University, 232-3 Yomogida, Naruko, Osaki, Miyagi, 989-6711, Japan
| | - Naoki Takaya
- Microbiology Research Center for Sustainability (MiCS), Faculty of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, 305-8572, Japan
| | - Masatsugu Toyota
- Department of Biochemistry and Molecular Biology, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570, Japan
- Suntory Rising Stars Encouragement Program in Life Sciences (SunRiSE), Kyoto, Japan
- Department of Botany, University of Wisconsin-Madison, 430 Lincoln Drive, Madison, WI 53706, USA
| | - Shigeyuki Betsuyaku
- Department of Plant Life Science, Faculty of Agriculture, Ryukoku University, 1-5 Yokotani, Seta Oe-cho, Otsu, Shiga, 520-2194Japan
| | - Norio Takeshita
- Microbiology Research Center for Sustainability (MiCS), Faculty of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, 305-8572, Japan
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4
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Jenull S, Mair T, Tscherner M, Penninger P, Zwolanek F, Silao FGS, de San Vicente KM, Riedelberger M, Bandari NC, Shivarathri R, Petryshyn A, Chauhan N, Zacchi LF, -Landmann SL, Ljungdahl PO, Kuchler K. The histone chaperone HIR maintains chromatin states to control nitrogen assimilation and fungal virulence. Cell Rep 2021; 36:109406. [PMID: 34289370 PMCID: PMC8493472 DOI: 10.1016/j.celrep.2021.109406] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 03/10/2021] [Accepted: 06/24/2021] [Indexed: 12/13/2022] Open
Abstract
Adaptation to changing environments and immune evasion is pivotal for fitness of pathogens. Yet, the underlying mechanisms remain largely unknown. Adaptation is governed by dynamic transcriptional re-programming, which is tightly connected to chromatin architecture. Here, we report a pivotal role for the HIR histone chaperone complex in modulating virulence of the human fungal pathogen Candida albicans. Genetic ablation of HIR function alters chromatin accessibility linked to aberrant transcriptional responses to protein as nitrogen source. This accelerates metabolic adaptation and increases the release of extracellular proteases, which enables scavenging of alternative nitrogen sources. Furthermore, HIR controls fungal virulence, as HIR1 deletion leads to differential recognition by immune cells and hypervirulence in a mouse model of systemic infection. This work provides mechanistic insights into chromatin-coupled regulatory mechanisms that fine-tune pathogen gene expression and virulence. Furthermore, the data point toward the requirement of refined screening approaches to exploit chromatin modifications as antifungal strategies.
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Affiliation(s)
- Sabrina Jenull
- Department of Medical Biochemistry, Max Perutz Labs Vienna, Medical University of Vienna, Campus Vienna Biocenter, 1030 Vienna, Austria
| | - Theresia Mair
- Department of Medical Biochemistry, Max Perutz Labs Vienna, Medical University of Vienna, Campus Vienna Biocenter, 1030 Vienna, Austria
| | - Michael Tscherner
- Department of Medical Biochemistry, Max Perutz Labs Vienna, Medical University of Vienna, Campus Vienna Biocenter, 1030 Vienna, Austria
| | - Philipp Penninger
- Department of Medical Biochemistry, Max Perutz Labs Vienna, Medical University of Vienna, Campus Vienna Biocenter, 1030 Vienna, Austria
| | - Florian Zwolanek
- Department of Medical Biochemistry, Max Perutz Labs Vienna, Medical University of Vienna, Campus Vienna Biocenter, 1030 Vienna, Austria
| | - Fitz-Gerald S Silao
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91 Stockholm, Sweden
| | - Kontxi Martinez de San Vicente
- Section of Immunology, Vetsuisse Faculty, University of Zürich, 8006 Zürich, Switzerland; Institute of Experimental Immunology, University of Zürich, 8057 Zürich, Switzerland
| | - Michael Riedelberger
- Department of Medical Biochemistry, Max Perutz Labs Vienna, Medical University of Vienna, Campus Vienna Biocenter, 1030 Vienna, Austria
| | - Naga C Bandari
- ARC Training Centre for Biopharmaceutical Innovation, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Raju Shivarathri
- Public Health Research Institute, Rutgers, The State University of New Jersey, Newark, NJ 07102, USA
| | - Andriy Petryshyn
- Department of Medical Biochemistry, Max Perutz Labs Vienna, Medical University of Vienna, Campus Vienna Biocenter, 1030 Vienna, Austria
| | - Neeraj Chauhan
- Public Health Research Institute, Rutgers, The State University of New Jersey, Newark, NJ 07102, USA; Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103, USA
| | - Lucia F Zacchi
- ARC Training Centre for Biopharmaceutical Innovation, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Salomé LeibundGut -Landmann
- Section of Immunology, Vetsuisse Faculty, University of Zürich, 8006 Zürich, Switzerland; Institute of Experimental Immunology, University of Zürich, 8057 Zürich, Switzerland
| | - Per O Ljungdahl
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91 Stockholm, Sweden
| | - Karl Kuchler
- Department of Medical Biochemistry, Max Perutz Labs Vienna, Medical University of Vienna, Campus Vienna Biocenter, 1030 Vienna, Austria.
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5
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Lenardon MD, Sood P, Dorfmueller HC, Brown AJ, Gow NA. Scalar nanostructure of the Candida albicans cell wall; a molecular, cellular and ultrastructural analysis and interpretation. Cell Surf 2020; 6:100047. [PMID: 33294751 PMCID: PMC7691183 DOI: 10.1016/j.tcsw.2020.100047] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 11/02/2020] [Accepted: 11/03/2020] [Indexed: 12/16/2022] Open
Abstract
Despite the importance of fungal cell walls as the principle determinant of fungal morphology and the defining element determining fungal interactions with other cells, few scalar models have been developed that reconcile chemical and microscopic attributes of its structure. The cell wall of the fungal pathogen Candida albicans is comprised of an amorphous inner skeletal layer of β(1,3)- and β(1,6)-glucan and chitin and an outer fibrillar layer thought to be dominated by highly mannosylated cell wall proteins. The architecture of these two layers can be resolved at the electron microscopy level, but the visualised structure of the wall has not yet been defined precisely in chemical terms. We have therefore examined the precise structure, location and molecular sizes of the cell wall components using transmission electron microscopy and tomography and tested predictions of the cell wall models using mutants and agents that perturb the normal cell wall structure. We demonstrate that the fibrils are comprised of a frond of N-linked outer chain mannans linked to a basal layer of GPI-proteins concentrated in the mid-wall region and that the non-elastic chitin microfibrils are cantilevered with sufficient lengths of non-fibrillar chitin and/or β-glucan to enable the chitin-glucan cage to flex, e.g. during morphogenesis and osmotic swelling. We present the first three-dimensional nano-scalar model of the C. albicans cell wall which can be used to test hypotheses relating to the structure-function relationships that underpin the pathobiology of this fungal pathogen.
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Key Words
- 2D, two dimensions
- 2°, secondary
- 3D, three dimensions
- 3°, tertiary
- 6xHis, hexahistidine tag
- AFM, atomic force microscopy
- BSA, bovine serum albumin
- CWPs, cell wall proteins
- Cell wall proteins
- ChBD, chitin binding domain
- Chitin
- EndoH, endoglycosidase H
- Fc-dectin-1, soluble chimeric form of dectin-1
- Fungal cell wall ultrastructure
- GPI, glycosylphosphatidylinositol
- HPF/FS, high pressure freezing/freeze substitution
- HuCκ, human kappa light chain
- N-mannan
- NMR, nuclear magnetic resonance
- OD600, optical density at 600 nm
- PAMPs, pathogen associated molecular patterns
- PBS, phosphate buffered saline
- PRRs, pattern recognition receptors
- SEM, scanning electron microscopy
- TEM, transmission electron microscopy
- WGA, wheat germ agglutinin
- rpm, revolutions per minute
- scAb, single chain antibody
- β-glucan
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Affiliation(s)
- Megan D. Lenardon
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
| | - Prashant Sood
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
| | - Helge C. Dorfmueller
- Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
| | - Alistair J.P. Brown
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
| | - Neil A.R. Gow
- Aberdeen Fungal Group, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
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6
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Blatzer M, Beauvais A, Henrissat B, Latgé JP. Revisiting Old Questions and New Approaches to Investigate the Fungal Cell Wall Construction. Curr Top Microbiol Immunol 2020; 425:331-369. [PMID: 32418033 DOI: 10.1007/82_2020_209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The beginning of our understanding of the cell wall construction came from the work of talented biochemists in the 70-80's. Then came the era of sequencing. Paradoxically, the accumulation of fungal genomes complicated rather than solved the mystery of cell wall construction, by revealing the involvement of a much higher number of proteins than originally thought. The situation has become even more complicated since it is now recognized that the cell wall is an organelle whose composition continuously evolves with the changes in the environment or with the age of the fungal cell. The use of new and sophisticated technologies to observe cell wall construction at an almost atomic scale should improve our knowledge of the cell wall construction. This essay will present some of the major and still unresolved questions to understand the fungal cell wall biosynthesis and some of these exciting futurist approaches.
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Affiliation(s)
- Michael Blatzer
- Experimental Neuropathology Unit, Institut Pasteur, 25 rue du Docteur Roux, 75015, Paris, France
| | - Anne Beauvais
- Mycology Department, Institut Pasteur, 25 rue du Docteur Roux, 75015, Paris, France
| | - Bernard Henrissat
- Architecture et Fonction des Macromolécules Biologiques, UMR 7257-CNRS & Aix-Marseille Université, 13288, Marseille cedex 9, France.,Department of Biological Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Jean-Paul Latgé
- Institute of Molecular Biology and Biotechnology of the Foundation for Research and Technology Hellas (IMBB-FORTH), Heraklion, Greece.
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7
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Verdín J, Sánchez-León E, Rico-Ramírez AM, Martínez-Núñez L, Fajardo-Somera RA, Riquelme M. Off the wall: The rhyme and reason of Neurospora crassa hyphal morphogenesis. ACTA ACUST UNITED AC 2019; 5:100020. [PMID: 32743136 PMCID: PMC7389182 DOI: 10.1016/j.tcsw.2019.100020] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 02/07/2019] [Accepted: 02/10/2019] [Indexed: 12/11/2022]
Abstract
Chitin and β-1,3-glucan synthases are transported separately in chitosomes and macrovesicles. Chitin synthases occupy the core of the SPK; β-1,3-glucan synthases the outer layer. CHS-4 arrival to the SPK and septa is CSE-7 dependent. Rabs YPT-1 and YPT-31 localization at the SPK mimics that of chitosomes and macrovesicles. The exocyst acts as a tether between the SPK outer layer vesicles and the apical PM.
The fungal cell wall building processes are the ultimate determinants of hyphal shape. In Neurospora crassa the main cell wall components, β-1,3-glucan and chitin, are synthesized by enzymes conveyed by specialized vesicles to the hyphal tip. These vesicles follow different secretory routes, which are delicately coordinated by cargo-specific Rab GTPases until their accumulation at the Spitzenkörper. From there, the exocyst mediates the docking of secretory vesicles to the plasma membrane, where they ultimately get fused. Although significant progress has been done on the cellular mechanisms that carry cell wall synthesizing enzymes from the endoplasmic reticulum to hyphal tips, a lot of information is still missing. Here, the current knowledge on N. crassa cell wall composition and biosynthesis is presented with an emphasis on the underlying molecular and cellular secretory processes.
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Key Words
- BGT, β-1,3-glucan transferases
- CHS, chitin synthase
- CLSM, confocal laser scanning microscopy
- CWI, cell wall integrity
- CWP, cell wall proteins
- Cell wall
- ER, endoplasmic reticulum
- FRAP, fluorescence recovery after photobleaching
- GEF, guanine nucleotide exchange factor
- GFP, green fluorescent protein
- GH, glycosyl hydrolases
- GPI, glycosylphosphatidylinositol
- GSC, β-1,3-glucan synthase complex
- MMD, myosin-like motor domain
- MS, mass spectrometry
- MT, microtubule
- NEC, network of elongated cisternae
- PM, plasma membrane
- SPK, Spitzenkörper
- Spitzenkörper
- TIRFM, total internal reflection fluorescence microscopy
- TM, transmembrane
- Tip growth
- Vesicles
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Affiliation(s)
- Jorge Verdín
- Industrial Biotechnology, CIATEJ-Jalisco State Scientific Research and Technology Assistance Center, Mexico National Council for Science and Technology, Zapopan, Jalisco, Mexico
| | - Eddy Sánchez-León
- Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada
| | - Adriana M Rico-Ramírez
- Department of Microbiology, Centro de Investigación Científica y de Educación Superior de Ensenada, CICESE Ensenada, Baja California, Mexico
| | - Leonora Martínez-Núñez
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Rosa A Fajardo-Somera
- Karlsruhe Institute of Technology (KIT) South Campus, Institute for Applied Biosciences, Department of Microbiology, Karlsruhe, Germany
| | - Meritxell Riquelme
- Department of Microbiology, Centro de Investigación Científica y de Educación Superior de Ensenada, CICESE Ensenada, Baja California, Mexico
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Chen T, Jackson JW, Tams RN, Davis SE, Sparer TE, Reynolds TB. Exposure of Candida albicans β (1,3)-glucan is promoted by activation of the Cek1 pathway. PLoS Genet 2019; 15:e1007892. [PMID: 30703081 PMCID: PMC6372213 DOI: 10.1371/journal.pgen.1007892] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 02/12/2019] [Accepted: 12/12/2018] [Indexed: 01/08/2023] Open
Abstract
Candida albicans is among the most common causes of human fungal infections and is an important source of mortality. C. albicans is able to diminish its detection by innate immune cells through masking of β (1,3)-glucan in the inner cell wall with an outer layer of heavily glycosylated mannoproteins (mannan). However, mutations or drugs that disrupt the cell wall can lead to exposure of β (1,3)-glucan (unmasking) and enhanced detection by innate immune cells through receptors like Dectin-1, the C-type signaling lectin. Previously, our lab showed that the pathway for synthesizing the phospholipid phosphatidylserine (PS) plays a role in β (1,3)-glucan masking. The homozygous PS synthase knockout mutant, cho1Δ/Δ, exhibits increased exposure of β (1,3)-glucan. Several Mitogen Activated Protein Kinase (MAPK) pathways and their upstream Rho-type small GTPases are important for regulating cell wall biogenesis and remodeling. In the cho1Δ/Δ mutant, both the Cek1 and Mkc1 MAPKs are constitutively activated, and they act downstream of the small GTPases Cdc42 and Rho1, respectively. In addition, Cdc42 activity is up-regulated in cho1Δ/Δ. Thus, it was hypothesized that activation of Cdc42 or Rho1 and their downstream kinases cause unmasking. Disruption of MKC1 does not decrease unmasking in cho1Δ/Δ, and hyperactivation of Rho1 in wild-type cells increases unmasking and activation of both Cek1 and Mkc1. Moreover, independent hyperactivation of the MAP kinase kinase kinase Ste11 in wild-type cells leads to Cek1 activation and increased β (1,3)-glucan exposure. Thus, upregulation of the Cek1 MAPK pathway causes unmasking, and may be responsible for unmasking in cho1Δ/Δ. Candida albicans causes fungal infections in the oral cavities and bloodstreams of patients with weakened immune function, such as AIDS or cancer patients. The immune system detects fungal infections, in part, by detecting the antigenic cell wall polysaccharide β (1,3)-glucan. The ability to mask β (1,3)-glucan from immune detection is a virulence factor of C. albicans and a range of fungal pathogens. If synthesis of the phospholipid phosphatidylserine is disrupted in C. albicans (cho1Δ/Δ mutation), then cho1Δ/Δ exhibits significantly increased exposure of β (1,3)-glucan to immune detection compared to wild-type. Intracellular signaling cascades that regulate cell wall synthesis are upregulated in the cho1Δ/Δ mutant. It was hypothesized that upregulation of these pathways might be responsible for unmasking in this mutant. Genetic approaches were used to activate these pathways independently of the cho1Δ/Δ mutation. It was discovered that activation of one pathway, Cdc42-Cek1, leads to β (1,3)-glucan exposure. Thus, this pathway can cause β(1,3)-glucan exposure, and its upregulation may be the cause of unmasking in the cho1Δ/Δ mutant.
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Affiliation(s)
- Tian Chen
- Department of Microbiology, University of Tennessee, Knoxville, TN, United States of America
| | - Joseph W. Jackson
- Department of Microbiology, University of Tennessee, Knoxville, TN, United States of America
| | - Robert N. Tams
- Department of Microbiology, University of Tennessee, Knoxville, TN, United States of America
| | - Sarah E. Davis
- Department of Microbiology, University of Tennessee, Knoxville, TN, United States of America
| | - Timothy E. Sparer
- Department of Microbiology, University of Tennessee, Knoxville, TN, United States of America
| | - Todd B. Reynolds
- Department of Microbiology, University of Tennessee, Knoxville, TN, United States of America
- * E-mail:
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9
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Takeshita N. Control of Actin and Calcium for Chitin Synthase Delivery to the Hyphal Tip of Aspergillus. Curr Top Microbiol Immunol 2019; 425:113-129. [PMID: 31974757 DOI: 10.1007/82_2019_193] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Filamentous fungi are covered by a cell wall consisting mainly of chitin and glucan. The synthesis of chitin, a β-1,4-linked homopolymer of N-acetylglucosamine, is essential for hyphal morphogenesis. Fungal chitin synthases are integral membrane proteins that have been classified into seven classes. ChsB, a class III chitin synthase, is known to play a key role in hyphal tip growth and has been used here as a model to understand the cell biology of cell wall biosynthesis in Aspergillus nidulans. Chitin synthases are transported on secretory vesicles to the plasma membrane for new cell wall synthesis. Super-resolution localization imaging as a powerful biophysical approach indicated dynamics of the Spitzenkörper where spatiotemporally regulated exocytosis and cell extension, whereas high-speed pulse-chase imaging has revealed ChsB transport mechanism mediated by kinesin-1 and myosin-5. In addition, live imaging analysis showed correlations among intracellular Ca2+ levels, actin assembly, and exocytosis in growing hyphal tips. This suggests that pulsed Ca2+ influxes coordinate the temporal control of actin assembly and exocytosis, which results in stepwise cell extension. It is getting clear that turgor pressure and cell wall pressure are involved in the activation of Ca2+ channels for Ca2+ oscillation and cell extension. Here the cell wall synthesis and tip growth meet again.
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Affiliation(s)
- Norio Takeshita
- Microbiology Research Center for Sustainability (MiCS), Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan.
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10
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Orlean P, Funai D. Priming and elongation of chitin chains: Implications for chitin synthase mechanism. ACTA ACUST UNITED AC 2018; 5:100017. [PMID: 32743134 PMCID: PMC7389259 DOI: 10.1016/j.tcsw.2018.100017] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 12/16/2018] [Accepted: 12/18/2018] [Indexed: 11/18/2022]
Abstract
Most fungi have multiple chitin synthases (CSs) that may make chitin at different sites on the cell surface, at different times during growth, and in response to cell wall stress. The structure-based model for CS function is for transfer of GlcNAc from UDP-GlcNAc at the cytoplasmic face of the plasma membrane to the non-reducing end of a growing chitin chain, which is concomitantly translocated through a transmembrane channel formed by the synthase. Two aspects of CS mechanism are investigated: how chains might be initiated, and what governs how long they can get. First, it is shown that CSs incorporate free GlcNAc into di-N-acetylchitobiose and into insoluble chitin in a UDP-GlcNAc-dependent manner, and therefore that GlcNAc primes chitin synthesis. Second, average lengths of insoluble chitin chains were measured by determining the molar ratio of priming GlcNAc to chain-extending, UDP-GlcNAc-derived GlcNAc, and showed dependence on UDP-GlcNAc concentration, approaching a maximum at higher concentrations of substrate. These results, together with previous findings that 2-acylamido GlcN analogues prime formation of chitin oligosaccharides and stimulate chitin synthesis are discussed in the context of the structure-based model, and lead to the following proposals. 1) CSs may "self-prime" by hydrolyzing UDP-GlcNAc to yield GlcNAc. 2) A CS's active site is not continuously occupied by a nascent chitin chain, rather, CSs can release chitin chains, then re-initiate, and therefore synthesize chitin chains in bursts. 3) The length of chitin chains made by a given CS will impact that CS's contribution to construction of the fungal cell wall.
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Affiliation(s)
- Peter Orlean
- Corresponding author at: Department of Microbiology, University of Illinois at Urbana-Champaign, B-213 Chemical and Life Sciences Laboratory, 601 South Goodwin Avenue, Urbana, IL 61801, USA.
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Ghorai P, Irfan M, Narula A, Datta A. A comprehensive analysis of Candida albicans phosphoproteome reveals dynamic changes in phosphoprotein abundance during hyphal morphogenesis. Appl Microbiol Biotechnol 2018; 102:9731-9743. [PMID: 30121747 DOI: 10.1007/s00253-018-9303-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 08/01/2018] [Accepted: 08/02/2018] [Indexed: 12/18/2022]
Abstract
The morphological plasticity of Candida albicans is a virulence determinant as the hyphal form has significant roles in the infection process. Recently, phosphoregulation of proteins through phosphorylation and dephosphorylation events has gained importance in studying the regulation of pathogenicity at the molecular level. To understand the importance of phosphorylation in hyphal morphogenesis, global analysis of the phosphoproteome was performed after hyphal induction with elevated temperature, serum, and N-acetyl-glucosamine (GlcNAc) treatments. The study identified 60, 20, and 53 phosphoproteins unique to elevated temperature-, serum-, and GlcNAc-treated conditions, respectively. Distribution of unique phosphorylation sites sorted by the modified amino acids revealed that predominant phosphorylation occurs in serine, followed by threonine and tyrosine residues in all the datasets. However, the frequency distribution of phosphorylation sites in the proteins varied with treatment conditions. Further, interaction network-based functional annotation of protein kinases of C. albicans as well as identified phosphoproteins was performed, which demonstrated the interaction of kinases with phosphoproteins during filamentous growth. Altogether, the present findings will serve as a base for further functional studies in the aspects of protein kinase-target protein interaction in effectuating phosphorylation of target proteins, and delineating the downstream signaling networks linked to virulence characteristics of C. albicans.
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Affiliation(s)
- Priyanka Ghorai
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India.,Department of Biotechnology, School of Chemical and Life Sciences, Jamia Hamdard, Hamdard Nagar, New Delhi, 110062, India
| | - Mohammad Irfan
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Alka Narula
- Department of Biotechnology, School of Chemical and Life Sciences, Jamia Hamdard, Hamdard Nagar, New Delhi, 110062, India
| | - Asis Datta
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India.
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The Functional Specialization of Exomer as a Cargo Adaptor During the Evolution of Fungi. Genetics 2018; 208:1483-1498. [PMID: 29437703 DOI: 10.1534/genetics.118.300767] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 01/31/2018] [Indexed: 11/18/2022] Open
Abstract
Yeast exomer is a heterotetrameric complex that is assembled at the trans-Golgi network, which is required for the delivery of a distinct set of proteins to the plasma membrane using ChAPs (Chs5-Arf1 binding proteins) Chs6 and Bch2 as dedicated cargo adaptors. However, our results show a significant functional divergence between them, suggesting an evolutionary specialization among the ChAPs. Moreover, the characterization of exomer mutants in several fungi indicates that exomer's function as a cargo adaptor is a late evolutionary acquisition associated with several gene duplications of the fungal ChAPs ancestor. Initial gene duplication led to the formation of the two ChAPs families, Chs6 and Bch1, in the Saccaromycotina group, which have remained functionally redundant based on the characterization of Kluyveromyces lactis mutants. The whole-genome duplication that occurred within the Saccharomyces genus facilitated a further divergence, which allowed Chs6/Bch2 and Bch1/Bud7 pairs to become specialized for specific cellular functions. We also show that the behavior of S. cerevisiae Chs3 as an exomer cargo is associated with the presence of specific cytosolic domains in this protein, which favor its interaction with exomer and AP-1 complexes. However, these domains are not conserved in the Chs3 proteins of other fungi, suggesting that they arose late in the evolution of fungi associated with the specialization of ChAPs as cargo adaptors.
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Aspergillus fumigatus Trehalose-Regulatory Subunit Homolog Moonlights To Mediate Cell Wall Homeostasis through Modulation of Chitin Synthase Activity. mBio 2017; 8:mBio.00056-17. [PMID: 28442603 PMCID: PMC5405227 DOI: 10.1128/mbio.00056-17] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Trehalose biosynthesis is found in fungi but not humans. Proteins involved in trehalose biosynthesis are essential for fungal pathogen virulence in humans and plants through multiple mechanisms. Loss of canonical trehalose biosynthesis genes in the human pathogen Aspergillus fumigatus significantly alters cell wall structure and integrity, though the mechanistic link between these virulence-associated pathways remains enigmatic. Here we characterize genes, called tslA and tslB, which encode proteins that contain domains similar to those corresponding to trehalose-6-phosphate phosphatase but lack critical catalytic residues for phosphatase activity. Loss of tslA reduces trehalose content in both conidia and mycelia, impairs cell wall integrity, and significantly alters cell wall structure. To gain mechanistic insights into the role that TslA plays in cell wall homeostasis, immunoprecipitation assays coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to reveal a direct interaction between TslA and CsmA, a type V chitin synthase enzyme. TslA regulates not only chitin synthase activity but also CsmA sub-cellular localization. Loss of TslA impacts the immunopathogenesis of murine invasive pulmonary aspergillosis through altering cytokine production and immune cell recruitment. In conclusion, our data provide a novel model whereby proteins in the trehalose pathway play a direct role in fungal cell wall homeostasis and consequently impact fungus-host interactions. Human fungal infections are increasing globally due to HIV infections and increased use of immunosuppressive therapies for many diseases. Therefore, new antifungal drugs with reduced side effects and increased efficacy are needed to improve treatment outcomes. Trehalose biosynthesis exists in pathogenic fungi and is absent in humans. Components of the trehalose biosynthesis pathway are important for the virulence of human-pathogenic fungi, including Aspergillus fumigatus. Consequently, it has been proposed that components of this pathway are potential targets for antifungal drug development. However, how trehalose biosynthesis influences the fungus-host interaction remains enigmatic. One phenotype associated with fungal trehalose biosynthesis mutants that remains enigmatic is cell wall perturbation. Here we discovered a novel moonlighting role for a regulatory-like subunit of the trehalose biosynthesis pathway in A. fumigatus that regulates cell wall homeostasis through modulation of chitin synthase localization and activity. As the cell wall is a current and promising therapeutic target for fungal infections, understanding the role of trehalose biosynthesis in cell wall homeostasis and virulence is expected to help define new therapeutic opportunities.
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Preechasuth K, Anderson JC, Peck SC, Brown AJP, Gow NAR, Lenardon MD. Cell wall protection by the Candida albicans class I chitin synthases. Fungal Genet Biol 2015; 82:264-76. [PMID: 26257018 PMCID: PMC4557417 DOI: 10.1016/j.fgb.2015.08.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2015] [Revised: 08/05/2015] [Accepted: 08/06/2015] [Indexed: 01/20/2023]
Abstract
Candida albicans has four chitin synthases from three different enzyme classes which deposit chitin in the cell wall, including at the polarized tips of growing buds and hyphae, and sites of septation. The two class I enzymes, Chs2 and Chs8, are responsible for most of the measurable chitin synthase activity in vitro, but their precise biological functions in vivo remain obscure. In this work, detailed phenotypic analyses of a chs2Δchs8Δ mutant have shown that C. albicans class I chitin synthases promote cell integrity during early polarized growth in yeast and hyphal cells. This was supported by live cell imaging of YFP-tagged versions of the class I chitin synthases which revealed that Chs2-YFP was localized at sites of polarized growth. Furthermore, a unique and dynamic pattern of localization of the class I enzymes at septa of yeast and hyphae was revealed. Phosphorylation of Chs2 on the serine at position 222 was shown to regulate the amount of Chs2 that is localized to sites of polarized growth and septation. Independently from this post-translational modification, specific cell wall stresses were also shown to regulate the amount of Chs2 that localizes to specific sites in cells, and this was linked to the ability of the class I enzymes to reinforce cell wall integrity during early polarized growth in the presence of these stresses.
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Affiliation(s)
- Kanya Preechasuth
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom.
| | - Jeffrey C Anderson
- Division of Biochemistry, 271H Bond Life Sciences Center, University of Missouri-Columbia, Columbia, MO 65211, USA.
| | - Scott C Peck
- Division of Biochemistry, 271H Bond Life Sciences Center, University of Missouri-Columbia, Columbia, MO 65211, USA.
| | - Alistair J P Brown
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom.
| | - Neil A R Gow
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom.
| | - Megan D Lenardon
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom.
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Fajardo-Somera RA, Jöhnk B, Bayram Ö, Valerius O, Braus GH, Riquelme M. Dissecting the function of the different chitin synthases in vegetative growth and sexual development in Neurospora crassa. Fungal Genet Biol 2015; 75:30-45. [DOI: 10.1016/j.fgb.2015.01.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 12/17/2014] [Accepted: 01/07/2015] [Indexed: 01/22/2023]
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Identification of Aph1, a phosphate-regulated, secreted, and vacuolar acid phosphatase in Cryptococcus neoformans. mBio 2014; 5:e01649-14. [PMID: 25227465 PMCID: PMC4172073 DOI: 10.1128/mbio.01649-14] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cryptococcus neoformans strains isolated from patients with AIDS secrete acid phosphatase, but the identity and role of the enzyme(s) responsible have not been elucidated. By combining a one-dimensional electrophoresis step with mass spectrometry, a canonically secreted acid phosphatase, CNAG_02944 (Aph1), was identified in the secretome of the highly virulent serotype A strain H99. We created an APH1 deletion mutant (Δaph1) and showed that Δaph1-infected Galleria mellonella and mice survived longer than those infected with the wild type (WT), demonstrating that Aph1 contributes to cryptococcal virulence. Phosphate starvation induced APH1 expression and secretion of catalytically active acid phosphatase in the WT, but not in the Δaph1 mutant, indicating that Aph1 is the major extracellular acid phosphatase in C. neoformans and that it is phosphate repressible. DsRed-tagged Aph1 was transported to the fungal cell periphery and vacuoles via endosome-like structures and was enriched in bud necks. A similar pattern of Aph1 localization was observed in cryptococci cocultured with THP-1 monocytes, suggesting that Aph1 is produced during host infection. In contrast to Aph1, but consistent with our previous biochemical data, green fluorescent protein (GFP)-tagged phospholipase B1 (Plb1) was predominantly localized at the cell periphery, with no evidence of endosome-mediated export. Despite use of different intracellular transport routes by Plb1 and Aph1, secretion of both proteins was compromised in a Δsec14-1 mutant. Secretions from the WT, but not from Δaph1, hydrolyzed a range of physiological substrates, including phosphotyrosine, glucose-1-phosphate, β-glycerol phosphate, AMP, and mannose-6-phosphate, suggesting that the role of Aph1 is to recycle phosphate from macromolecules in cryptococcal vacuoles and to scavenge phosphate from the extracellular environment. Infections with the AIDS-related fungal pathogen Cryptococcus neoformans cause more than 600,000 deaths per year worldwide. Strains of Cryptococcus neoformans isolated from patients with AIDS secrete acid phosphatase; however, the identity and role of the enzyme(s) are unknown. We have analyzed the secretome of the highly virulent serotype A strain H99 and identified Aph1, a canonically secreted acid phosphatase. By creating an APH1 deletion mutant and an Aph1-DsRed-expressing strain, we demonstrate that Aph1 is the major extracellular and vacuolar acid phosphatase in C. neoformans and that it is phosphate repressible. Furthermore, we show that Aph1 is produced in cryptococci during coculture with THP-1 monocytes and contributes to fungal virulence in Galleria mellonella and mouse models of cryptococcosis. Our findings suggest that Aph1 is secreted to the environment to scavenge phosphate from a wide range of physiological substrates and is targeted to vacuoles to recycle phosphate from the expendable macromolecules.
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Affiliation(s)
- Meritxell Riquelme
- Departamento de Microbiología, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, Baja California, Mexico 22860;
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Sacristan C, Manzano-Lopez J, Reyes A, Spang A, Muñiz M, Roncero C. Oligomerization of the chitin synthase Chs3 is monitored at the Golgi and affects its endocytic recycling. Mol Microbiol 2013; 90:252-66. [DOI: 10.1111/mmi.12360] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/04/2013] [Indexed: 11/28/2022]
Affiliation(s)
- Carlos Sacristan
- Instituto de Biología Funcional y Genómica and Departamento de Microbiología y Genética; CSIC/Universidad de Salamanca; Salamanca; Spain
| | | | - Abigail Reyes
- Instituto de Biología Funcional y Genómica and Departamento de Microbiología y Genética; CSIC/Universidad de Salamanca; Salamanca; Spain
| | - Anne Spang
- Biozentrum, Growth & Development; University of Basel; Basel; Switzerland
| | - Manuel Muñiz
- Departamento de Biología Celular; Universidad de Sevilla; Sevilla; Spain
| | - Cesar Roncero
- Instituto de Biología Funcional y Genómica and Departamento de Microbiología y Genética; CSIC/Universidad de Salamanca; Salamanca; Spain
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Abstract
The composition and organization of the cell walls from Saccharomyces cerevisiae, Candida albicans, Aspergillus fumigatus, Schizosaccharomyces pombe, Neurospora crassa, and Cryptococcus neoformans are compared and contrasted. These cell walls contain chitin, chitosan, β-1,3-glucan, β-1,6-glucan, mixed β-1,3-/β-1,4-glucan, α-1,3-glucan, melanin, and glycoproteins as major constituents. A comparison of these cell walls shows that there is a great deal of variability in fungal cell wall composition and organization. However, in all cases, the cell wall components are cross-linked together to generate a cell wall matrix. The biosynthesis and properties of each of the major cell wall components are discussed. The chitin and glucans are synthesized and extruded into the cell wall space by plasma membrane-associated chitin synthases and glucan synthases. The glycoproteins are synthesized by ER-associated ribosomes and pass through the canonical secretory pathway. Over half of the major cell wall proteins are modified by the addition of a glycosylphosphatidylinositol anchor. The cell wall glycoproteins are also modified by the addition of O-linked oligosaccharides, and their N-linked oligosaccharides are extensively modified during their passage through the secretory pathway. These cell wall glycoprotein posttranslational modifications are essential for cross-linking the proteins into the cell wall matrix. Cross-linking the cell wall components together is essential for cell wall integrity. The activities of four groups of cross-linking enzymes are discussed. Cell wall proteins function as cross-linking enzymes, structural elements, adhesins, and environmental stress sensors and protect the cell from environmental changes.
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Affiliation(s)
- Stephen J Free
- Department of Biological Sciences, SUNY, University at Buffalo, Buffalo, New York, USA.
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Munro CA. Chitin and glucan, the yin and yang of the fungal cell wall, implications for antifungal drug discovery and therapy. ADVANCES IN APPLIED MICROBIOLOGY 2013; 83:145-72. [PMID: 23651596 DOI: 10.1016/b978-0-12-407678-5.00004-0] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The structural carbohydrate polymers glucan and chitin compliment and reinforce each other in a dynamic process to maintain the integrity and physical strength of the fungal cell wall. The assembly of chitin and glucan in the cell wall of the budding yeast Saccharomyces cerevisiae and the polymorphic human pathogen Candida albicans are essential processes that involve a range of fungal-specific enzymes and regulatory networks. The fungal cell wall is, therefore, an attractive target for novel therapies as host cells lack many cell wall-related proteins. The most recent class of antifungal drug approved for clinical use, the echinocandins, targets the synthesis of cell wall β(1-3)glucan. The echinocandins are effective at treating invasive and bloodstream Candida infections and are now widely used in the clinic. However, there have been sporadic reports of breakthrough infections in patients undergoing echinocandin therapy. The acquisition of point mutations in the FKS genes that encode the catalytic β(1-3)glucan synthase subunits, the target of the echinocandins, has emerged as a dominant resistance mechanism. Cells with elevated chitin levels are also less susceptible to echinocandins and in addition, treatment with sub-MIC echinocandin activates cell wall salvage pathways that increase chitin synthesis to compensate for reduced glucan production. The development of drugs targeting the cell wall has already proven to be beneficial in providing an alternative class of drug for use in the clinic. Other cell wall targets such as chitin synthesis still hold great potential for drug development but careful consideration should be given to the capacity of fungi to manipulate their walls in a dynamic response to cell wall perturbations.
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Affiliation(s)
- Carol A Munro
- School of Medical Sciences, University of Aberdeen, Aberdeen, UK, E-mail:
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21
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Guerriero G. Putative chitin synthases from Branchiostoma floridae show extracellular matrix-related domains and mosaic structures. GENOMICS PROTEOMICS & BIOINFORMATICS 2012; 10:197-207. [PMID: 23084775 PMCID: PMC4937987 DOI: 10.1016/j.gpb.2012.07.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2012] [Revised: 03/27/2012] [Accepted: 04/23/2012] [Indexed: 01/04/2023]
Abstract
The transition from unicellular to multicellular life forms requires the development of a specialized structural component, the extracellular matrix (ECM). In Metazoans, there are two main supportive systems, which are based on chitin and collagen/hyaluronan, respectively. Chitin is the major constituent of fungal cell walls and arthropod exoskeleton. However, presence of chitin/chitooligosaccharides has been reported in lower chordates and during specific stages of vertebrate development. In this study, the occurrence of chitin synthases (CHSs) was investigated with a bioinformatics approach in the cephalochordate Branchiostoma floridae, in which the presence of chitin was initially reported in the skeletal rods of the pharyngeal gill basket. Twelve genes coding for proteins containing conserved amino acid residues of processive glycosyltransferases from GT2 family were found and 10 of them display mosaic structures with novel domains never reported previously in a chitin synthase. In particular, the presence of a discoidin (DS) and a sterile alpha motif (SAM) domain was found in nine identified proteins. Sequence analyses and homology modelling suggest that these domains might interact with the extracellular matrix and mediate protein–protein interaction. The multi-domain putative chitin synthases from B. floridae constitute an emblematic example of the explosion of domain innovation and shuffling which predate Metazoans.
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Affiliation(s)
- Gea Guerriero
- Fungal Genetics and Genomics Unit, Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Science Vienna, University and Research Center Campus Tulln-Technopol, Tulln, Austria.
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22
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Sacristan C, Reyes A, Roncero C. Neck compartmentalization as the molecular basis for the different endocytic behaviour of Chs3 during budding or hyperpolarized growth in yeast cells. Mol Microbiol 2012; 83:1124-35. [DOI: 10.1111/j.1365-2958.2012.07995.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Rogg LE, Fortwendel JR, Juvvadi PR, Steinbach WJ. Regulation of expression, activity and localization of fungal chitin synthases. Med Mycol 2012; 50:2-17. [PMID: 21526913 PMCID: PMC3660733 DOI: 10.3109/13693786.2011.577104] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The fungal cell wall represents an attractive target for pharmacologic inhibition, as many of the components are fungal-specific. Though targeted inhibition of β-glucan synthesis is effective treatment for certain fungal infections, the ability of the cell wall to dynamically compensate via the cell wall integrity pathway may limit overall efficacy. To date, chitin synthesis inhibitors have not been successfully deployed in the clinical setting. Fungal chitin synthesis is a complex and highly regulated process. Regulation of chitin synthesis occurs on multiple levels, thus targeting of these regulatory pathways may represent an exciting alternative approach. A variety of signaling pathways have been implicated in chitin synthase regulation, at both transcriptional and post-transcriptional levels. Recent research suggests that localization of chitin synthases likely represents a major regulatory mechanism. However, much of the regulatory machinery is not necessarily shared among different chitin synthases. Thus, an in-depth understanding of the precise roles of each protein in cell wall maintenance and repair will be essential to identifying the most likely therapeutic targets.
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Affiliation(s)
- Luise E. Rogg
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Duke University Medical Center, Durham NC, USA
| | - Jarrod R. Fortwendel
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Duke University Medical Center, Durham NC, USA
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham NC, USA
| | - Praveen R. Juvvadi
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Duke University Medical Center, Durham NC, USA
| | - William J. Steinbach
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Duke University Medical Center, Durham NC, USA
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham NC, USA
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25
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The cellular basis of chitin synthesis in fungi and insects: common principles and differences. Eur J Cell Biol 2011; 90:759-69. [PMID: 21700357 DOI: 10.1016/j.ejcb.2011.04.014] [Citation(s) in RCA: 166] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Chitin is a polymer of N-acetylglucosamine, which assembles into microfibrils of about 20 sugar chains. These microfibrils serve as a structural component of natural biocomposites found in cell walls and specialized extracellular matrices such as cuticles and peritrophic membranes. Chitin synthesis is performed by a wide range of organisms including fungi and insects. The underlying biosynthetic machinery is highly conserved and involves several enzymes, of which the chitin synthase is the key enzyme. This membrane integral glycosyltransferase catalyzes the polymerization reaction. Most of what we know about chitin synthesis derives from studies of fungal and insect systems. In this review, common principles and differences will be worked out at the levels of gene organization, enzymatic properties, cellular localization and regulation.
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26
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Kniemeyer O, Schmidt AD, Vödisch M, Wartenberg D, Brakhage AA. Identification of virulence determinants of the human pathogenic fungi Aspergillus fumigatus and Candida albicans by proteomics. Int J Med Microbiol 2011; 301:368-77. [PMID: 21565549 DOI: 10.1016/j.ijmm.2011.04.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Both fungi Candida albicans and Aspergillus fumigatus can cause a number of life-threatening systemic infections in humans. The commensal yeast C. albicans is one of the main causes of nosocomial fungal infectious diseases, whereas the filamentous fungus A. fumigatus has become one of the most prevalent airborne fungal pathogens. Early diagnosis of these fungal infections is challenging, only a limited number of antifungals for treatment are available, and the molecular details of pathogenicity are hardly understood. The completion of both the A. fumigatus and C. albicans genome sequence provides the opportunity to improve diagnosis, to define new drug targets, to understand the functions of many uncharacterised proteins, and to study protein regulation on a global scale. With the application of proteomic tools, particularly two-dimensional gel electrophoresis and LC/MS-based methods, a comprehensive overview about the proteins of A. fumigatus and C. albicans present or induced during environmental changes and stress conditions has been obtained in the past 5 years. However, for the discovery of further putative virulence determinants, more sensitive and targeted proteomic methods have to be applied. Here, we review the recent proteome data generated for A. fumigatus and C. albicans that are related to factors required for pathogenicity.
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Affiliation(s)
- Olaf Kniemeyer
- Dept. of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology - Hans-Knöll-Institute (HKI), Jena, Germany.
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27
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Current awareness on yeast. Yeast 2010. [DOI: 10.1002/yea.1724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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28
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Lenardon MD, Munro CA, Gow NAR. Chitin synthesis and fungal pathogenesis. Curr Opin Microbiol 2010; 13:416-23. [PMID: 20561815 PMCID: PMC2923753 DOI: 10.1016/j.mib.2010.05.002] [Citation(s) in RCA: 286] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Revised: 05/04/2010] [Accepted: 05/06/2010] [Indexed: 11/25/2022]
Abstract
Chitin is an essential part of the carbohydrate skeleton of the fungal cell wall and is a molecule that is not represented in humans and other vertebrates. Complex regulatory mechanisms enable chitin to be positioned at specific sites throughout the cell cycle to maintain the overall strength of the wall and enable rapid, life-saving modifications to be made under cell wall stress conditions. Chitin has also recently emerged as a significant player in the activation and attenuation of immune responses to fungi and other chitin-containing parasites. This review summarises latest advances in the analysis of chitin synthesis regulation in the context of fungal pathogenesis.
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Affiliation(s)
- Megan D Lenardon
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen, AB25 2ZD, UK
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