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Peng Y, Chen B. Role of cell membrane homeostasis in the pathogenicity of pathogenic filamentous fungi. Virulence 2024; 15:2299183. [PMID: 38156783 PMCID: PMC10761126 DOI: 10.1080/21505594.2023.2299183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Accepted: 12/20/2023] [Indexed: 01/03/2024] Open
Abstract
The cell membrane forms a fundamental part of all living cells and participates in a variety of physiological processes, such as material exchange, stress response, cell recognition, signal transduction, cellular immunity, apoptosis, and pathogenicity. Here, we review the mechanisms and functions of the membrane structure (lipid components of the membrane and the biosynthesis of unsaturated fatty acids), membrane proteins (transmembrane proteins and proteins contributing to membrane curvature), transcriptional regulation, and cell wall components that influence the virulence and pathogenicity of filamentous fungi.
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Affiliation(s)
- Yuejin Peng
- Yunnan State Key Laboratory of Conservation and Utilization of Biological Resources, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Bin Chen
- Yunnan State Key Laboratory of Conservation and Utilization of Biological Resources, Yunnan Agricultural University, Kunming, Yunnan, China
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2
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Lanze CE, Konopka JB. Sur7 mediates a novel pathway for PI 4,5P 2 regulation in C. albicans that promotes stress resistance and cell wall morphogenesis. Mol Biol Cell 2024; 35:ar99. [PMID: 38776129 PMCID: PMC11244165 DOI: 10.1091/mbc.e23-08-0324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 05/01/2024] [Accepted: 05/15/2024] [Indexed: 06/11/2024] Open
Abstract
The human fungal pathogen Candida albicans can cause lethal systemic infections due to its ability to resist stress from the host and to undergo invasive hyphal growth. Previous studies showed that plasma membrane MCC/eisosome domains were important for virulence by promoting the ability of Sur7 to mediate normal cell wall morphogenesis and stress resistance. The sur7Δ mutant displayed abnormal clusters of PI4,5P2, suggesting that misregulation of this lipid underlies the sur7Δ phenotype. To test this, we increased PI4,5P2 levels by deleting combinations of the three PI4,5P2 5' phosphatase genes (INP51, INP52, and INP54) and found that some combinations, such as inp51Δ inp52Δ, gave phenotypes similar the sur7Δ mutant. In contrast, deleting one copy of MSS4, the gene that encodes the 5' kinase needed to create PI4,5P2, reduced the abnormal PI4,5P2 clusters and also decreased the abnormal cell wall and stress sensitive phenotypes of the sur7Δ mutant. Additional studies support a model that the abnormal PI4,5P2 patches recruit septin proteins, which in turn promote aberrant cell wall growth. These results identify Sur7 as a novel regulator of PI4,5P2 and highlight the critical role of PI4,5P2 in the regulation of C. albicans virulence properties.
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Affiliation(s)
- Carla E. Lanze
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, NY 11794-5222
| | - James B. Konopka
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, NY 11794-5222
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Wagner AS, Lumsdaine SW, Mangrum MM, Reynolds TB. Caspofungin-induced β(1,3)-glucan exposure in Candida albicans is driven by increased chitin levels. mBio 2023; 14:e0007423. [PMID: 37377417 PMCID: PMC10470516 DOI: 10.1128/mbio.00074-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 05/04/2023] [Indexed: 06/29/2023] Open
Abstract
To successfully induce disease, Candida albicans must effectively evade the host immune system. One mechanism used by C. albicans to achieve this is to mask immunogenic β(1,3)-glucan epitopes within its cell wall under an outer layer of mannosylated glycoproteins. Consequently, induction of β(1,3)-glucan exposure (unmasking) via genetic or chemical manipulation increases fungal recognition by host immune cells in vitro and attenuates disease during systemic infection in mice. Treatment with the echinocandin caspofungin is one of the most potent drivers of β(1,3)-glucan exposure. Several reports using murine infection models suggest a role for the immune system, and specifically host β(1,3)-glucan receptors, in mediating the efficacy of echinocandin treatment in vivo. However, the mechanism by which caspofungin-induced unmasking occurs is not well understood. In this report, we show that foci of unmasking co-localize with areas of increased chitin within the yeast cell wall in response to caspofungin, and that inhibition of chitin synthesis via nikkomycin Z attenuates caspofungin-induced β(1,3)-glucan exposure. Furthermore, we find that both the calcineurin and Mkc1 mitogen-activated protein kinase pathways work synergistically to regulate β(1,3)-glucan exposure and chitin synthesis in response to drug treatment. When either of these pathways are interrupted, it results in a bimodal population of cells containing either high or low chitin content. Importantly, increased unmasking correlates with increased chitin content within these cells. Microscopy further indicates that caspofungin-induced unmasking correlates with actively growing cells. Collectively, our work presents a model in which chitin synthesis induces unmasking within the cell wall in response to caspofungin in growing cells. IMPORTANCE Systemic candidiasis has reported mortality rates ranging from 20% to 40%. The echinocandins, including caspofungin, are first-line antifungals used to treat systemic candidiasis. However, studies in mice have shown that echinocandin efficacy relies on both its cidal impacts on Candida albicans, as well as a functional immune system to successfully clear invading fungi. In addition to direct C. albicans killing, caspofungin increases exposure (unmasking) of immunogenic β(1,3)-glucan moieties. To evade immune detection, β(1,3)-glucan is normally masked within the C. albicans cell wall. Consequently, unmasked β(1,3)-glucan renders these cells more visible to the host immune system and attenuates disease progression. Therefore, discovery of how caspofungin-induced unmasking occurs is needed to elucidate how the drug facilitates host immune system-mediated clearance in vivo. We report a strong and consistent correlation between chitin deposition and unmasking in response to caspofungin and propose a model in which altered chitin synthesis drives increased unmasking during drug exposure.
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Affiliation(s)
- Andrew S. Wagner
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA
| | | | - Mikayla M. Mangrum
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA
| | - Todd B. Reynolds
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA
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Shekunov EV, Zlodeeva PD, Efimova SS, Muryleva AA, Zarubaev VV, Slita AV, Ostroumova OS. Cyclic lipopeptides as membrane fusion inhibitors against SARS-CoV-2: New tricks for old dogs. Antiviral Res 2023; 212:105575. [PMID: 36868316 PMCID: PMC9977712 DOI: 10.1016/j.antiviral.2023.105575] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 02/25/2023] [Accepted: 02/28/2023] [Indexed: 03/05/2023]
Abstract
With the resurgence of the coronavirus pandemic, the repositioning of FDA-approved drugs against coronovirus and finding alternative strategies for antiviral therapy are both important. We previously identified the viral lipid envelope as a potential target for the prevention and treatment of SARS-CoV-2 infection with plant alkaloids (Shekunov et al., 2021). Here, we investigated the effects of eleven cyclic lipopeptides (CLPs), including well-known antifungal and antibacterial compounds, on the liposome fusion triggered by calcium, polyethylene glycol 8000, and a fragment of SARS-CoV-2 fusion peptide (816-827) by calcein release assays. Differential scanning microcalorimetry of the gel-to-liquid-crystalline and lamellar-to-inverted hexagonal phase transitions and confocal fluorescence microscopy demonstrated the relation of the fusion inhibitory effects of CLPs to alterations in lipid packing, membrane curvature stress and domain organization. The antiviral effects of CLPs were evaluated in an in vitro Vero-based cell model, and aculeacin A, anidulafugin, iturin A, and mycosubtilin attenuated the cytopathogenicity of SARS-CoV-2 without specific toxicity.
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Affiliation(s)
- Egor V Shekunov
- Institute of Cytology of Russian Academy of Sciences, Tikhoretsky 4, 194064, Saint Petersburg, Russia
| | - Polina D Zlodeeva
- Institute of Cytology of Russian Academy of Sciences, Tikhoretsky 4, 194064, Saint Petersburg, Russia
| | - Svetlana S Efimova
- Institute of Cytology of Russian Academy of Sciences, Tikhoretsky 4, 194064, Saint Petersburg, Russia
| | - Anna A Muryleva
- Institute of Cytology of Russian Academy of Sciences, Tikhoretsky 4, 194064, Saint Petersburg, Russia; Saint-Petersburg Pasteur Institute of Epidemiology and Microbiology, Mira 14, 197101, Saint Petersburg, Russia
| | - Vladimir V Zarubaev
- Saint-Petersburg Pasteur Institute of Epidemiology and Microbiology, Mira 14, 197101, Saint Petersburg, Russia
| | - Alexander V Slita
- Saint-Petersburg Pasteur Institute of Epidemiology and Microbiology, Mira 14, 197101, Saint Petersburg, Russia
| | - Olga S Ostroumova
- Institute of Cytology of Russian Academy of Sciences, Tikhoretsky 4, 194064, Saint Petersburg, Russia.
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Vanzolini T, Di Mambro T, Magnani M, Menotta M. AFM evaluation of a humanized recombinant antibody affecting C. auris cell wall and stability. RSC Adv 2023; 13:6130-6142. [PMID: 36814881 PMCID: PMC9940460 DOI: 10.1039/d2ra07217c] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 02/02/2023] [Indexed: 02/22/2023] Open
Abstract
Fungal infections are increasingly impacting on the health of the population and particularly on subjects with a compromised immune system. The resistance phenomenon and the rise of new species carrying sometimes intrinsic and multi-drug resistance to the most commonly used antifungal drugs are greatly concerning healthcare organizations. As a result of this situation, there is growing interest in the development of therapeutic agents against pathogenic fungi. In particular, the Candida genus is responsible for severe life-threatening infections and among its species, C. auris is considered an urgent threat by the Center for Disease Control and Prevention, and is one of the three leading causes of morbidity and mortality worldwide. H5K1 is a humanized monoclonal antibody (hmAb) that selectively binds to β-1,3-glucans, vital components of the fungal cell wall. It has been previously demonstrated that it is active against Candida species, especially against C. auris, reaching its greatest potential when combined with commercially available antifungal drugs. Here we used atomic force microscopy (AFM) to assess the effects of H5K1, alone and in combination with fluconazole, caspofungin and amphotericin B, on C. auris cells. Through an extensive exploration we found that H5K1 has a significant role in the perturbation and remodeling of the fungal cell wall that is reflected in the loss of whole cell integrity. Moreover, it contributes substantially to the alterations in terms of chemical composition, stiffness and roughness induced specifically by caspofungin and amphotericin B. In addition to this, we demonstrated that AFM is a valuable technique to evaluate drug-microorganism interaction.
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Affiliation(s)
- Tania Vanzolini
- Department of Biomolecular Sciences, University of Urbino Carlo Bo Via Saffi 2 61029 Urbino Italy
| | | | - Mauro Magnani
- Department of Biomolecular Sciences, University of Urbino Carlo Bo Via Saffi 2 61029 Urbino Italy
| | - Michele Menotta
- Department of Biomolecular Sciences, University of Urbino Carlo Bo Via Saffi 2 61029 Urbino Italy
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Chen T, Wagner AS, Reynolds TB. When Is It Appropriate to Take Off the Mask? Signaling Pathways That Regulate ß(1,3)-Glucan Exposure in Candida albicans. FRONTIERS IN FUNGAL BIOLOGY 2022; 3:842501. [PMID: 36908584 PMCID: PMC10003681 DOI: 10.3389/ffunb.2022.842501] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 01/31/2022] [Indexed: 12/21/2022]
Abstract
Candida spp. are an important source of systemic and mucosal infections in immune compromised populations. However, drug resistance or toxicity has put limits on the efficacy of current antifungals. The C. albicans cell wall is considered a good therapeutic target due to its roles in viability and fungal pathogenicity. One potential method for improving antifungal strategies could be to enhance the detection of fungal cell wall antigens by host immune cells. ß(1,3)-glucan, which is an important component of fungal cell walls, is a highly immunogenic epitope. Consequently, multiple host pattern recognition receptors, such as dectin-1, complement receptor 3 (CR3), and the ephrin type A receptor A (EphA2) are capable of recognizing exposed (unmasked) ß(1,3)-glucan moieties on the cell surface to initiate an anti-fungal immune response. However, ß(1,3)-glucan is normally covered (masked) by a layer of glycosylated proteins on the outer surface of the cell wall, hiding it from immune detection. In order to better understand possible mechanisms of unmasking ß(1,3)-glucan, we must develop a deeper comprehension of the pathways driving this phenotype. In this review, we describe the medical importance of ß(1,3)-glucan exposure in anti-fungal immunity, and highlight environmental stimuli and stressors encountered within the host that are capable of inducing changes in the levels of surface exposed ß(1,3)-glucan. Furthermore, particular focus is placed on how signal transduction cascades regulate changes in ß(1,3)-glucan exposure, as understanding the role that these pathways have in mediating this phenotype will be critical for future therapeutic development.
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Affiliation(s)
- Tian Chen
- Department of Pathogenic Biology, School of Biomedical Sciences, Shandong University, Jinan, China
| | - Andrew S. Wagner
- Department of Microbiology, University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Todd B. Reynolds
- Department of Microbiology, University of Tennessee, Knoxville, Knoxville, TN, United States
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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: 43] [Impact Index Per Article: 10.8] [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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Plasma Membrane MCC/Eisosome Domains Promote Stress Resistance in Fungi. Microbiol Mol Biol Rev 2020; 84:84/4/e00063-19. [PMID: 32938742 DOI: 10.1128/mmbr.00063-19] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
There is growing appreciation that the plasma membrane orchestrates a diverse array of functions by segregating different activities into specialized domains that vary in size, stability, and composition. Studies with the budding yeast Saccharomyces cerevisiae have identified a novel type of plasma membrane domain known as the MCC (membrane compartment of Can1)/eisosomes that correspond to stable furrows in the plasma membrane. MCC/eisosomes maintain proteins at the cell surface, such as nutrient transporters like the Can1 arginine symporter, by protecting them from endocytosis and degradation. Recent studies from several fungal species are now revealing new functional roles for MCC/eisosomes that enable cells to respond to a wide range of stressors, including changes in membrane tension, nutrition, cell wall integrity, oxidation, and copper toxicity. The different MCC/eisosome functions are often intertwined through the roles of these domains in lipid homeostasis, which is important for proper plasma membrane architecture and cell signaling. Therefore, this review will emphasize the emerging models that explain how MCC/eisosomes act as hubs to coordinate cellular responses to stress. The importance of MCC/eisosomes is underscored by their roles in virulence for fungal pathogens of plants, animals, and humans, which also highlights the potential of these domains to act as novel therapeutic targets.
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Transcriptional regulation of the caspofungin-induced cell wall damage response in Candida albicans. Curr Genet 2020; 66:1059-1068. [PMID: 32876716 DOI: 10.1007/s00294-020-01105-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 08/14/2020] [Accepted: 08/25/2020] [Indexed: 12/14/2022]
Abstract
The human fungal pathogen Candida albicans maintains pathogenic and commensal states primarily through cell wall functions. The echinocandin antifungal drug caspofungin inhibits cell wall synthesis and is widely used in treating disseminated candidiasis. Signaling pathways are critical in coordinating the adaptive response to cell wall damage (CWD). C. albicans executes a robust transcriptional program following caspofungin-induced CWD. A comprehensive analysis of signaling pathways at the transcriptional level facilitates the identification of prospective genes for functional characterization and propels the development of novel antifungal interventions. This review article focuses on the molecular functions and signaling crosstalk of the C. albicans transcription factors Sko1, Rlm1, and Cas5 in caspofungin-induced CWD signaling.
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Zhang B, Peng L, Zhu N, Yu Q, Li M. Novel role of the phosphatidylinositol phosphatase Sac1 in membrane homeostasis and polarized growth in Candida albicans. Int J Med Microbiol 2020; 310:151418. [PMID: 32245626 DOI: 10.1016/j.ijmm.2020.151418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 02/16/2020] [Accepted: 03/19/2020] [Indexed: 10/24/2022] Open
Abstract
Phosphoinositides (PIPs) are one kind of membrane components functioning in many intracellular processes, especially in signaling transduction and membrane transport. Phosphatidylinositide phosphatases (PIPases) are specifically important for the PIP homeostasis in cell. In our previous study, we have identified the actin-related protein CaSac1 in Candida albicans, while its functional mechanisms in regulating membrane homeostasis has not been identified. Here, we show that the PIPase CaSac1 is a main membrane-related protein and regulates hyphal polarization by governing phosphoinositide dynamic and plasma membrane (PM) electrostatic field. Deletion of CaSAC1 resulted in large-scale abnormal redistribution of phosphatidylinositide 4-phosphate (PI4P) from the endomembrane to the PM. This abnormality further led to disturbance of the PM's negative electrostatic field and abnormally spotted distribution of phosphatidylinositide 4,5-bisphosphate (PI(4,5)P2). These changes led to a severe defect in polarized hyphal growth, which could be diminished with recovery of the PM's negative electrostatic field by the anionic polymer polyacrylic acid (PAA). This study revealed that the PIPase CaSac1 plays an essential role in regulating membrane homeostasis and membrane traffic, contributing to establishment of polarized hyphal growth.
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Affiliation(s)
- Bing Zhang
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin 300071, China; College of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China
| | - Liping Peng
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Nali Zhu
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Qilin Yu
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin 300071, China.
| | - Mingchun Li
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin 300071, China.
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Colou J, N'Guyen GQ, Dubreu O, Fontaine K, Kwasiborski A, Bastide F, Manero F, Hamon B, Aligon S, Simoneau P, Guillemette T. Role of membrane compartment occupied by Can1 (MCC) and eisosome subdomains in plant pathogenicity of the necrotrophic fungus Alternaria brassicicola. BMC Microbiol 2019; 19:295. [PMID: 31842747 PMCID: PMC6916069 DOI: 10.1186/s12866-019-1667-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 11/28/2019] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND MCC/eisosomes are membrane microdomains that have been proposed to participate in the plasma membrane function in particular by regulating the homeostasis of lipids, promoting the recruitment of specific proteins and acting as provider of membrane reservoirs. RESULTS Here we showed that several potential MCC/eisosomal protein encoding genes in the necrotrophic fungus A. brassicicola were overexpressed when germinated spores were exposed to antimicrobial defence compounds, osmotic and hydric stresses, which are major constraints encountered by the fungus during the plant colonization process. Mutants deficient for key MCC/eisosome components did not exhibit any enhanced susceptibility to phytoalexins and to applied stress conditions compared to the reference strain, except for a slight hypersensitivity of the ∆∆abpil1a-abpil1b strain to 2 M sorbitol. Depending on the considered mutants, we showed that the leaf and silique colonization processes were impaired by comparison to the wild-type, and assumed that these defects in aggressiveness were probably caused by a reduced appressorium formation rate. CONCLUSIONS This is the first study on the role of MCC/eisosomes in the pathogenic process of a plant pathogenic fungus. A link between these membrane domains and the fungus ability to form functional penetration structures was shown, providing new potential directions for plant disease control strategies.
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Affiliation(s)
- Justine Colou
- Institut de Recherche en Horticulture et Semences - UMR 1345, INRA, Université d'Angers, Agrocampus-Ouest, SFR 4207 QuaSaV, 42 rue Georges Morel, 49071 Beaucouzé Cedex, Angers, France
| | - Guillaume Quang N'Guyen
- Institut de Recherche en Horticulture et Semences - UMR 1345, INRA, Université d'Angers, Agrocampus-Ouest, SFR 4207 QuaSaV, 42 rue Georges Morel, 49071 Beaucouzé Cedex, Angers, France.,Institut de Biologie Intégrative et des Systèmes, Département de Biologie, PROTEO, Université Laval, Pavillon Charles-Eugène-Marchand, 1030 Avenue de la Médecine, QC, Québec, G1V 0A6, Canada
| | - Ophélie Dubreu
- Institut de Recherche en Horticulture et Semences - UMR 1345, INRA, Université d'Angers, Agrocampus-Ouest, SFR 4207 QuaSaV, 42 rue Georges Morel, 49071 Beaucouzé Cedex, Angers, France
| | - Kévin Fontaine
- Institut de Recherche en Horticulture et Semences - UMR 1345, INRA, Université d'Angers, Agrocampus-Ouest, SFR 4207 QuaSaV, 42 rue Georges Morel, 49071 Beaucouzé Cedex, Angers, France.,ANSES, Laboratoire de la Santé des Végétaux, Unité de Mycologie, Domaine de Pixérécourt, 54220, Malzéville, France
| | - Anthony Kwasiborski
- Institut de Recherche en Horticulture et Semences - UMR 1345, INRA, Université d'Angers, Agrocampus-Ouest, SFR 4207 QuaSaV, 42 rue Georges Morel, 49071 Beaucouzé Cedex, Angers, France
| | - Franck Bastide
- Institut de Recherche en Horticulture et Semences - UMR 1345, INRA, Université d'Angers, Agrocampus-Ouest, SFR 4207 QuaSaV, 42 rue Georges Morel, 49071 Beaucouzé Cedex, Angers, France
| | - Florence Manero
- Plateforme SCIAM, Institut de Biologie en Santé, CHU, Université d'Angers, 4, Rue Larrey, 49933, Angers Cedex, France
| | - Bruno Hamon
- Institut de Recherche en Horticulture et Semences - UMR 1345, INRA, Université d'Angers, Agrocampus-Ouest, SFR 4207 QuaSaV, 42 rue Georges Morel, 49071 Beaucouzé Cedex, Angers, France
| | - Sophie Aligon
- Institut de Recherche en Horticulture et Semences - UMR 1345, INRA, Université d'Angers, Agrocampus-Ouest, SFR 4207 QuaSaV, 42 rue Georges Morel, 49071 Beaucouzé Cedex, Angers, France
| | - Philippe Simoneau
- Institut de Recherche en Horticulture et Semences - UMR 1345, INRA, Université d'Angers, Agrocampus-Ouest, SFR 4207 QuaSaV, 42 rue Georges Morel, 49071 Beaucouzé Cedex, Angers, France
| | - Thomas Guillemette
- Institut de Recherche en Horticulture et Semences - UMR 1345, INRA, Université d'Angers, Agrocampus-Ouest, SFR 4207 QuaSaV, 42 rue Georges Morel, 49071 Beaucouzé Cedex, Angers, France.
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Caplan T, Polvi EJ, Xie JL, Buckhalter S, Leach MD, Robbins N, Cowen LE. Functional Genomic Screening Reveals Core Modulators of Echinocandin Stress Responses in Candida albicans. Cell Rep 2019; 23:2292-2298. [PMID: 29791841 DOI: 10.1016/j.celrep.2018.04.084] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 03/28/2018] [Accepted: 04/18/2018] [Indexed: 01/28/2023] Open
Abstract
Candida albicans is a leading cause of death due to fungal infection. Treatment of systemic candidiasis often relies on echinocandins, which disrupt cell wall synthesis. Resistance is readily acquired via mutations in the drug target gene, FKS1. Both basal tolerance and resistance to echinocandins require cellular stress responses. We performed a systematic analysis of 3,030 C. albicans mutants to define circuitry governing cellular responses to echinocandins. We identified 16 genes for which deletion or transcriptional repression enhanced echinocandin susceptibility, including components of the Pkc1-MAPK signaling cascade. We discovered that the molecular chaperone Hsp90 is required for the stability of Pkc1 and Bck1, establishing key mechanisms through which Hsp90 mediates echinocandin resistance. We also discovered that perturbation of the CCT chaperonin complex causes enhanced echinocandin sensitivity, altered cell wall architecture, and aberrant septin localization. Thus, we provide insights into the mechanisms by which cellular chaperones enable crucial responses to echinocandin-induced stress.
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Affiliation(s)
- Tavia Caplan
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5G 1M1, Canada
| | - Elizabeth J Polvi
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5G 1M1, Canada
| | - Jinglin L Xie
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5G 1M1, Canada
| | - Shoshana Buckhalter
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5G 1M1, Canada
| | - Michelle D Leach
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5G 1M1, Canada; Aberdeen Fungal Group, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen AB25 2ZD, UK
| | - Nicole Robbins
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5G 1M1, Canada
| | - Leah E Cowen
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5G 1M1, Canada.
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13
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Zahumensky J, Malinsky J. Role of MCC/Eisosome in Fungal Lipid Homeostasis. Biomolecules 2019; 9:E305. [PMID: 31349700 PMCID: PMC6723945 DOI: 10.3390/biom9080305] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 07/19/2019] [Accepted: 07/22/2019] [Indexed: 12/11/2022] Open
Abstract
One of the best characterized fungal membrane microdomains is the MCC/eisosome. The MCC (membrane compartment of Can1) is an evolutionarily conserved ergosterol-rich plasma membrane domain. It is stabilized on its cytosolic face by the eisosome, a hemitubular protein complex composed of Bin/Amphiphysin/Rvs (BAR) domain-containing Pil1 and Lsp1. These two proteins bind directly to phosphatidylinositol 4,5-bisphosphate and promote the typical furrow-like shape of the microdomain, with highly curved edges and bottom. While some proteins display stable localization in the MCC/eisosome, others enter or leave it under particular conditions, such as misbalance in membrane lipid composition, changes in membrane tension, or availability of specific nutrients. These findings reveal that the MCC/eisosome, a plasma membrane microdomain with distinct morphology and lipid composition, acts as a multifaceted regulator of various cellular processes including metabolic pathways, cellular morphogenesis, signalling cascades, and mRNA decay. In this minireview, we focus on the MCC/eisosome's proposed role in the regulation of lipid metabolism. While the molecular mechanisms of the MCC/eisosome function are not completely understood, the idea of intracellular processes being regulated at the plasma membrane, the foremost barrier exposed to environmental challenges, is truly exciting.
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Affiliation(s)
- Jakub Zahumensky
- Department of Microscopy, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, 14220 Prague, Czech Republic
| | - Jan Malinsky
- Department of Microscopy, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, 14220 Prague, Czech Republic.
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14
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MCC/Eisosomes Regulate Cell Wall Synthesis and Stress Responses in Fungi. J Fungi (Basel) 2017; 3:jof3040061. [PMID: 29371577 PMCID: PMC5753163 DOI: 10.3390/jof3040061] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 10/26/2017] [Accepted: 10/31/2017] [Indexed: 12/20/2022] Open
Abstract
The fungal plasma membrane is critical for cell wall synthesis and other important processes including nutrient uptake, secretion, endocytosis, morphogenesis, and response to stress. To coordinate these diverse functions, the plasma membrane is organized into specialized compartments that vary in size, stability, and composition. One recently identified domain known as the Membrane Compartment of Can1 (MCC)/eisosome is distinctive in that it corresponds to a furrow-like invagination in the plasma membrane. MCC/eisosomes have been shown to be formed by the Bin/Amphiphysin/Rvs (BAR) domain proteins Lsp1 and Pil1 in a range of fungi. MCC/eisosome domains influence multiple cellular functions; but a very pronounced defect in cell wall synthesis has been observed for mutants with defects in MCC/eisosomes in some yeast species. For example, Candida albicans MCC/eisosome mutants display abnormal spatial regulation of cell wall synthesis, including large invaginations and altered chemical composition of the walls. Recent studies indicate that MCC/eisosomes affect cell wall synthesis in part by regulating the levels of the key regulatory lipid phosphatidylinositol 4,5-bisphosphate (PI4,5P2) in the plasma membrane. One general way MCC/eisosomes function is by acting as protected islands in the plasma membrane, since these domains are very stable. They also act as scaffolds to recruit >20 proteins. Genetic studies aimed at defining the function of the MCC/eisosome proteins have identified important roles in resistance to stress, such as resistance to oxidative stress mediated by the flavodoxin-like proteins Pst1, Pst2, Pst3 and Ycp4. Thus, MCC/eisosomes play multiple roles in plasma membrane organization that protect fungal cells from the environment.
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15
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Vargas-Muñiz JM, Renshaw H, Waitt G, Soderblom EJ, Moseley MA, Palmer JM, Juvvadi PR, Keller NP, Steinbach WJ. Caspofungin exposure alters the core septin AspB interactome of Aspergillus fumigatus. Biochem Biophys Res Commun 2017; 485:221-226. [PMID: 28238781 PMCID: PMC5384791 DOI: 10.1016/j.bbrc.2017.02.116] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 02/22/2017] [Indexed: 11/24/2022]
Abstract
Aspergillus fumigatus, the main etiological agent of invasive aspergillosis, is a leading cause of death in immunocompromised patients. Septins, a conserved family of GTP-binding proteins, serve as scaffolding proteins to recruit enzymes and key regulators to different cellular compartments. Deletion of the A. fumigatus septin aspB increases susceptibility to the echinocandin antifungal caspofungin. However, how AspB mediates this response to caspofungin is unknown. Here, we characterized the AspB interactome under basal conditions and after exposure to a clinically relevant concentration of caspofungin. While A. fumigatus AspB interacted with 334 proteins, including kinases, cell cycle regulators, and cell wall synthesis-related proteins under basal growth conditions, caspofungin exposure altered AspB interactions. A total of 69 of the basal interactants did not interact with AspB after exposure to caspofungin, and 54 new interactants were identified following caspofungin exposure. We generated A. fumigatus deletion strains for 3 proteins (ArpB, Cyp4, and PpoA) that only interacted with AspB following exposure to caspofungin that were previously annotated as induced after exposure to antifungal agents, yet only PpoA was implicated in the response to caspofungin. Taken together, we defined how the septin AspB interactome is altered in the presence of a clinically relevant antifungal.
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Affiliation(s)
- José M Vargas-Muñiz
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, United States
| | - Hilary Renshaw
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, United States
| | - Greg Waitt
- Duke Proteomics and Metabolomics Core Facility, Center for Genomic and Computational Biology, Duke University, Durham, NC, United States
| | - Erik J Soderblom
- Duke Proteomics and Metabolomics Core Facility, Center for Genomic and Computational Biology, Duke University, Durham, NC, United States
| | - M Arthur Moseley
- Duke Proteomics and Metabolomics Core Facility, Center for Genomic and Computational Biology, Duke University, Durham, NC, United States
| | - Jonathan M Palmer
- U.S. Forest Service, Northern Research Station, Center for Forest Mycology Research, Madison, WI, United States; Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States
| | - Praveen R Juvvadi
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Duke University Medical Center, Durham, NC, United States
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States
| | - William J Steinbach
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, United States; Division of Pediatric Infectious Diseases, Department of Pediatrics, Duke University Medical Center, Durham, NC, United States.
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16
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Feng HQ, Li GH, Du SW, Yang S, Li XQ, de Figueiredo P, Qin QM. The septin protein Sep4 facilitates host infection by plant fungal pathogens via mediating initiation of infection structure formation. Environ Microbiol 2017; 19:1730-1749. [PMID: 27878927 DOI: 10.1111/1462-2920.13613] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 10/17/2016] [Accepted: 11/16/2016] [Indexed: 11/26/2022]
Abstract
Many phytopathogenic fungi use infection structures (IFSs, i.e., appressoria and infection cushions) to penetrate host cuticles. However, the conserved mechanisms that mediate initiation of IFS formation in divergent pathogens upon sensing the presence of host plants remain obscure. Here, we demonstrate that a conserved septin gene SEP4 plays crucial roles in this process. Disruption of SEP4 in the plant grey mould fungus Botrytis cinerea completely blocked IFS formation and abolished the virulence of ΔBcsep4 mutants on unwounded hosts. During IFS formation, mutants lacking SEP4 could produce reactive oxygen species (ROS) normally. Inhibition of ROS production in strains harbouring the SEP4 gene resulted in disordered assembly of Sep4 and the subsequent failure to form infection cushions, suggesting that proper Sep4 assembly regulated by ROS is required for initiation of IFS formation and infection. Moreover, loss of SEP4 severely impaired mutant conidiation, melanin and chitin accumulation in hyphal tips and lesion expansion on wounded hosts, but significantly promoted germ tube elongation and sclerotium production. SEP4-mediated fungal pathogenic development, including IFS formation, was validated in the hemibiotroph Magnaporthe oryzae. Our findings indicate that Sep4 plays pleiotropic roles in B. cinerea development and specifically facilities host infection by mediating initiation of IFS formation in divergent plant fungal pathogens in response to ROS signaling.
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Affiliation(s)
- Hui-Qiang Feng
- College of Plant Sciences, Jilin University, Changchun, 130062, China
| | - Gui-Hua Li
- College of Plant Sciences, Jilin University, Changchun, 130062, China
| | - Shun-Wen Du
- College of Plant Sciences, Jilin University, Changchun, 130062, China
| | - Song Yang
- College of Plant Sciences, Jilin University, Changchun, 130062, China
| | - Xue-Qian Li
- College of Plant Sciences, Jilin University, Changchun, 130062, China
| | - Paul de Figueiredo
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health Science Center, College Station, TX, 77843, USA.,Norman Borlaug Center, Texas A&M University, College Station, TX, 77843, USA.,Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX, 77843, USA
| | - Qing-Ming Qin
- College of Plant Sciences, Jilin University, Changchun, 130062, China.,Key Laboratory of Zoonosis Research, Ministry of Education, Jilin University, Changchun, 130062, China
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17
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Dyson JM, Conduit SE, Feeney SJ, Hakim S, DiTommaso T, Fulcher AJ, Sriratana A, Ramm G, Horan KA, Gurung R, Wicking C, Smyth I, Mitchell CA. INPP5E regulates phosphoinositide-dependent cilia transition zone function. J Cell Biol 2016; 216:247-263. [PMID: 27998989 PMCID: PMC5223597 DOI: 10.1083/jcb.201511055] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2015] [Revised: 09/19/2016] [Accepted: 12/02/2016] [Indexed: 02/07/2023] Open
Abstract
Dyson et al. demonstrate that the inositol polyphosphate 5-phosphatase INPP5E is essential for Hedgehog-dependent embryonic development. By regulating PI(4,5)P2 and PI(3,4,5)P3 signals at cilia, INPP5E contributes to cilia transition zone function and thereby Smoothened accumulation at cilia. Human ciliopathies, including Joubert syndrome (JBTS), arise from cilia dysfunction. The inositol polyphosphate 5-phosphatase INPP5E localizes to cilia and is mutated in JBTS. Murine Inpp5e ablation is embryonically lethal and recapitulates JBTS, including neural tube defects and polydactyly; however, the underlying defects in cilia signaling and the function of INPP5E at cilia are still emerging. We report Inpp5e−/− embryos exhibit aberrant Hedgehog-dependent patterning with reduced Hedgehog signaling. Using mouse genetics, we show increasing Hedgehog signaling via Smoothened M2 expression rescues some Inpp5e−/− ciliopathy phenotypes and “normalizes” Hedgehog signaling. INPP5E’s phosphoinositide substrates PI(4,5)P2 and PI(3,4,5)P3 accumulated at the transition zone (TZ) in Hedgehog-stimulated Inpp5e−/− cells, which was associated with reduced recruitment of TZ scaffolding proteins and reduced Smoothened levels at cilia. Expression of wild-type, but not 5-phosphatase-dead, INPP5E restored TZ molecular organization and Smoothened accumulation at cilia. Therefore, we identify INPP5E as an essential point of convergence between Hedgehog and phosphoinositide signaling at cilia that maintains TZ function and Hedgehog-dependent embryonic development.
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Affiliation(s)
- Jennifer M Dyson
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Sarah E Conduit
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Sandra J Feeney
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Sandra Hakim
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Tia DiTommaso
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Alex J Fulcher
- Monash Micro Imaging, Monash University, Clayton, Victoria 3800, Australia
| | - Absorn Sriratana
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Georg Ramm
- Monash Micro Imaging, Monash University, Clayton, Victoria 3800, Australia
| | - Kristy A Horan
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Rajendra Gurung
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Carol Wicking
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Ian Smyth
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.,Development and Stem Cells Program, Department of Anatomy and Developmental Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Christina A Mitchell
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
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18
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Vargas-Muñiz JM, Juvvadi PR, Steinbach WJ. Forging the ring: from fungal septins' divergent roles in morphology, septation and virulence to factors contributing to their assembly into higher order structures. MICROBIOLOGY-SGM 2016; 162:1527-1534. [PMID: 27559018 DOI: 10.1099/mic.0.000359] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Septins are a conserved family of GTP-binding proteins that are distributed across different lineages of the eukaryotes, with the exception of plants. Septins perform a myriad of functions in fungal cells, ranging from controlling morphogenetic events to contributing to host tissue invasion and virulence. One key attribute of the septins is their ability to assemble into heterooligomeric complexes that organizse into higher order structures. In addition to the established role of septins in the model budding yeast, Saccharomyces cerevisiae, their importance in other fungi recently emerges. While newer roles for septins are being uncovered in these fungi, the mechanism of how septins assemble into a complex and their regulation is only beginning to be comprehended. In this review, we summarize recent findings on the role of septins in different fungi and focus on how the septin complexes of different fungi are organized in vitro and in vivo. Furthermore, we discuss on how phosphorylation/dephosphorylation can serve as an important mechanism of septin complex assembly and regulation.
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Affiliation(s)
- Jose M Vargas-Muñiz
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA
| | - Praveen R Juvvadi
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - William J Steinbach
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA.,Division of Pediatric Infectious Diseases, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
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19
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Badrane H, Nguyen MH, Clancy CJ. Highly Dynamic and Specific Phosphatidylinositol 4,5-Bisphosphate, Septin, and Cell Wall Integrity Pathway Responses Correlate with Caspofungin Activity against Candida albicans. Antimicrob Agents Chemother 2016; 60:3591-600. [PMID: 27021331 PMCID: PMC4879351 DOI: 10.1128/aac.02711-15] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 03/24/2016] [Indexed: 12/31/2022] Open
Abstract
Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] activates the yeast cell wall integrity pathway. Candida albicans exposure to caspofungin results in the rapid redistribution of PI(4,5)P2 and septins to plasma membrane foci and subsequent fungicidal effects. We studied C. albicans PI(4,5)P2 and septin dynamics and protein kinase C (PKC)-Mkc1 cell wall integrity pathway activation following exposure to caspofungin and other drugs. PI(4,5)P2 and septins were visualized by live imaging of C. albicans cells coexpressing green fluorescent protein (GFP)-pleckstrin homology (PH) domain and red fluorescent protein-Cdc10p, respectively. PI(4,5)P2 was also visualized in GFP-PH domain-expressing C. albicans mkc1 mutants. Mkc1p phosphorylation was measured as a marker of PKC-Mkc1 pathway activation. Fungicidal activity was assessed using 20-h time-kill assays. Caspofungin immediately induced PI(4,5)P2 and Cdc10p colocalization to aberrant foci, a process that was highly dynamic over 3 h. PI(4,5)P2 levels increased in a dose-response manner at caspofungin concentrations of ≤4× MIC and progressively decreased at concentrations of ≥8× MIC. Caspofungin exposure resulted in broad-based mother-daughter bud necks and arrested septum-like structures, in which PI(4,5)P2 and Cdc10 colocalized. PKC-Mkc1 pathway activation was maximal within 10 min, peaked in response to caspofungin at 4× MIC, and declined at higher concentrations. The caspofungin-induced PI(4,5)P2 redistribution remained apparent in mkc1 mutants. Caspofungin exerted dose-dependent killing and paradoxical effects at ≤4× and ≥8× MIC, respectively. Fluconazole, amphotericin B, calcofluor white, and H2O2 did not impact the PI(4,5)P2 or Cdc10p distribution like caspofungin did. Caspofungin exerts rapid PI(4,5)P2-septin and PKC-Mkc1 responses that correlate with the extent of C. albicans killing, and the responses are not induced by other antifungal agents. PI(4,5)P2-septin regulation is crucial in early caspofungin responses and PKC-Mkc1 activation.
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Affiliation(s)
- Hassan Badrane
- Division of Infectious Diseases, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - M Hong Nguyen
- Division of Infectious Diseases, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Cornelius J Clancy
- Division of Infectious Diseases, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA VA Pittsburgh Healthcare System, Pittsburgh, Pennsylvania, USA
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20
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Wang HX, Douglas LM, Veselá P, Rachel R, Malinsky J, Konopka JB. Eisosomes promote the ability of Sur7 to regulate plasma membrane organization in Candida albicans. Mol Biol Cell 2016; 27:1663-75. [PMID: 27009204 PMCID: PMC4865322 DOI: 10.1091/mbc.e16-01-0065] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 03/16/2016] [Indexed: 12/15/2022] Open
Abstract
The plasma membrane of the fungal pathogen Candida albicans forms a protective barrier that also mediates many processes needed for virulence, including cell wall synthesis, invasive hyphal morphogenesis, and nutrient uptake. Because compartmentalization of the plasma membrane is believed to coordinate these diverse activities, we examined plasma membrane microdomains termed eisosomes or membrane compartment of Can1 (MCC), which correspond to ∼200-nm-long furrows in the plasma membrane. A pil1∆ lsp1∆ mutant failed to form eisosomes and displayed strong defects in plasma membrane organization and morphogenesis, including extensive cell wall invaginations. Mutation of eisosome proteins Slm2, Pkh2, and Pkh3 did not cause similar cell wall defects, although pkh2∆ cells formed chains of furrows and pkh3∆ cells formed wider furrows, identifying novel roles for the Pkh protein kinases in regulating furrows. In contrast, the sur7∆ mutant formed cell wall invaginations similar to those for the pil1∆ lsp1∆ mutant even though it could form eisosomes and furrows. A PH-domain probe revealed that the regulatory lipid phosphatidylinositol 4,5-bisphosphate was enriched at sites of cell wall invaginations in both the sur7∆ and pil1∆ lsp1∆ cells, indicating that this contributes to the defects. The sur7∆ and pil1∆ lsp1∆ mutants displayed differential susceptibility to various types of stress, indicating that they affect overlapping but distinct functions. In support of this, many mutant phenotypes of the pil1∆ lsp1∆ cells were rescued by overexpressing SUR7 These results demonstrate that C. albicans eisosomes promote the ability of Sur7 to regulate plasma membrane organization.
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Affiliation(s)
- Hong X Wang
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794-5222
| | - Lois M Douglas
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794-5222
| | - Petra Veselá
- Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, 142 20 Prague, Czech Republic
| | - Reinhard Rachel
- Centre for Electron Microscopy, Faculty of Biology and Preclinical Medicine, University of Regensburg, 93053 Regensburg, Germany
| | - Jan Malinsky
- Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, 142 20 Prague, Czech Republic
| | - James B Konopka
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794-5222
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21
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Douglas LM, Konopka JB. Plasma membrane organization promotes virulence of the human fungal pathogen Candida albicans. J Microbiol 2016; 54:178-91. [PMID: 26920878 DOI: 10.1007/s12275-016-5621-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 01/15/2016] [Accepted: 01/15/2016] [Indexed: 12/21/2022]
Abstract
Candida albicans is a human fungal pathogen capable of causing lethal systemic infections. The plasma membrane plays key roles in virulence because it not only functions as a protective barrier, it also mediates dynamic functions including secretion of virulence factors, cell wall synthesis, invasive hyphal morphogenesis, endocytosis, and nutrient uptake. Consistent with this functional complexity, the plasma membrane is composed of a wide array of lipids and proteins. These components are organized into distinct domains that will be the topic of this review. Some of the plasma membrane domains that will be described are known to act as scaffolds or barriers to diffusion, such as MCC/eisosomes, septins, and sites of contact with the endoplasmic reticulum. Other zones mediate dynamic processes, including secretion, endocytosis, and a special region at hyphal tips that facilitates rapid growth. The highly organized architecture of the plasma membrane facilitates the coordination of diverse functions and promotes the pathogenesis of C. albicans.
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Affiliation(s)
- Lois M Douglas
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, 11794-5222, USA
| | - James B Konopka
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, 11794-5222, USA.
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22
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Merlini L, Bolognesi A, Juanes MA, Vandermoere F, Courtellemont T, Pascolutti R, Séveno M, Barral Y, Piatti S. Rho1- and Pkc1-dependent phosphorylation of the F-BAR protein Syp1 contributes to septin ring assembly. Mol Biol Cell 2015; 26:3245-62. [PMID: 26179915 PMCID: PMC4569315 DOI: 10.1091/mbc.e15-06-0366] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 07/10/2015] [Indexed: 12/20/2022] Open
Abstract
Septins often form filaments and rings at the neck of cellular appendages. Assembly of these structures must be coordinated with membrane remodeling. In budding yeast, the Rho1 GTPase and its effector, Pkc1, play a role in septin ring stabilization during budding at least partly through phosphorylation of the bud neck–associated F-BAR protein Syp1. In many cell types, septins assemble into filaments and rings at the neck of cellular appendages and/or at the cleavage furrow to help compartmentalize the plasma membrane and support cytokinesis. How septin ring assembly is coordinated with membrane remodeling and controlled by mechanical stress at these sites is unclear. Through a genetic screen, we uncovered an unanticipated link between the conserved Rho1 GTPase and its effector protein kinase C (Pkc1) with septin ring stability in yeast. Both Rho1 and Pkc1 stabilize the septin ring, at least partly through phosphorylation of the membrane-associated F-BAR protein Syp1, which colocalizes asymmetrically with the septin ring at the bud neck. Syp1 is displaced from the bud neck upon Pkc1-dependent phosphorylation at two serines, thereby affecting the rigidity of the new-forming septin ring. We propose that Rho1 and Pkc1 coordinate septin ring assembly with membrane and cell wall remodeling partly by controlling Syp1 residence at the bud neck.
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Affiliation(s)
- Laura Merlini
- Centre de Recherche en Biochimie Macromoléculaire, 34293 Montpellier, France
| | | | | | - Franck Vandermoere
- Functional Proteomic Platform, Institut de Génomique Fonctionnelle, 34094 Montpellier, France
| | | | - Roberta Pascolutti
- Centre de Recherche en Biochimie Macromoléculaire, 34293 Montpellier, France
| | - Martial Séveno
- Functional Proteomic Platform, Institut de Génomique Fonctionnelle, 34094 Montpellier, France
| | - Yves Barral
- Institute of Biochemistry, ETH Zurich, 8093 Zurich, Switzerland
| | - Simonetta Piatti
- Centre de Recherche en Biochimie Macromoléculaire, 34293 Montpellier, France
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The Aspergillus fumigatus septins play pleiotropic roles in septation, conidiation, and cell wall stress, but are dispensable for virulence. Fungal Genet Biol 2015; 81:41-51. [PMID: 26051489 DOI: 10.1016/j.fgb.2015.05.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 05/13/2015] [Accepted: 05/31/2015] [Indexed: 11/23/2022]
Abstract
Septins are a conserved family of GTPases that regulate important cellular processes such as cell wall integrity, and septation in fungi. The requirement of septins for virulence has been demonstrated in the human pathogenic yeasts Candida albicans and Cryptococcus neoformans, as well as the plant pathogen Magnaporthe oryzae. Aspergillus spp. contains five genes encoding for septins (aspA-E). While the importance of septins AspA, AspB, AspC, and AspE for growth and conidiation has been elucidated in the filamentous fungal model Aspergillus nidulans, nothing is known on the role of septins in growth and virulence in the human pathogen Aspergillus fumigatus. Here we deleted all five A. fumigatus septins, and generated certain double and triple septin deletion strains. Phenotypic analyses revealed that while all the septins are dispensable in normal growth conditions, AspA, AspB, AspC and AspE are required for regular septation. Furthermore, deletion of only the core septin genes significantly reduced conidiation. Concomitant with the absence of an electron-dense outer conidial wall, the ΔaspB strain was also sensitive to anti-cell wall agents. Infection with the ΔaspB strain in a Galleria mellonella model of invasive aspergillosis showed hypervirulence, but no virulence difference was noted when compared to the wild-type strain in a murine model of invasive aspergillosis. Although the deletion of aspB resulted in increased release of TNF-α from the macrophages, no significant inflammation differences in lung histology was noted between the ΔaspB strain and the wild-type strain. Taken together, these results point to the importance of septins in A. fumigatus growth, but not virulence in a murine model.
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Mutational analysis of essential septins reveals a role for septin-mediated signaling in filamentation. EUKARYOTIC CELL 2014; 13:1403-10. [PMID: 25217462 DOI: 10.1128/ec.00127-14] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Septin proteins are conserved structural proteins that often demarcate regions of cell division. The essential nature of the septin ring, composed of several septin proteins, complicates investigation of the functions of the ring, although careful analysis in the model yeast Saccharomyces cerevisiae has elucidated the role that septins play in the cell cycle. Mutation analysis of nonessential septins in the pathogenic fungus Candida albicans has shown that septins also have vital roles in cell wall regulation (CWR), hyphal formation, and pathogenesis. While mutations in nonessential septins have been useful in establishing phenotypes, the septin defect is so slight that identifying causative associations between septins and downstream effectors has been difficult. In this work, we describe decreased abundance by mRNA perturbation (DAmP) alleles of essential septins, which display a septin defect more severe than the defect observed in deletions of nonessential septins. The septin DAmP alleles have allowed us to genetically separate the roles of septins in hyphal growth and CWR and to identify the cyclic AMP pathway as a pathway that likely acts in a parallel manner with septins in hyphal morphogenesis.
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Affiliation(s)
- Lois M. Douglas
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York 11794; ,
| | - James B. Konopka
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York 11794; ,
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Rho GTPase-phosphatidylinositol phosphate interplay in fungal cell polarity. Biochem Soc Trans 2014; 42:206-11. [PMID: 24450653 DOI: 10.1042/bst20130226] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Rho G-proteins and phosphatidylinositol phosphates, which are important for exocytosis, endocytosis and cytoskeleton organization, are key regulators of polarized growth in a range of organisms. The aim of the present brief review is to highlight recent findings and their implications with respect to the functions and interplay between Rho G-proteins and phosphatidylinositol phosphates in highly polarized fungal filamentous growth.
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Candida Biofilm: Clinical Implications of Recent Advances in Research. CURRENT FUNGAL INFECTION REPORTS 2014. [DOI: 10.1007/s12281-014-0176-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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A competitive infection model of hematogenously disseminated candidiasis in mice redefines the role of Candida albicans IRS4 in pathogenesis. Infect Immun 2013; 81:1430-8. [PMID: 23429534 DOI: 10.1128/iai.00743-12] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Candida albicans IRS4 encodes a protein that regulates phosphatidylinositol-(4,5)-bisphosphate, which was shown to contribute to hematogenously disseminated candidiasis (DC) after several days in the standard mouse model. Our objective was to more accurately define the temporal contributions of IRS4 to pathogenesis. During competition assays in vitro, an irs4-null (Δirs4) mutant exhibited wild-type fitness. In DC experiments, mice were infected intravenously with the Δirs4 mutant, strain CAI-12 (1 × 10(5) CFU), or a mixture of the strains (0.5 × 10(5) CFU each). In single-strain infections, quantitative PCR revealed reduced Δirs4 mutant burdens within kidneys at days 1, 4, and 7 but not 6 h. In competitive infections, the Δirs4 mutant was outcompeted by CAI-12 in each mouse at ≥6 h (competitive indices, P ≤ 0.0001). At 4 and 7 days, the Δirs4 mutant burdens during competitive infections were significantly lower than those during single-strain infections (P = 0.01 and P < 0.001, respectively), suggesting increased susceptibility to inflammatory responses. Phagocytic infiltration of kidneys in response to CAI-12 or competitive infections was significantly greater than that in response to Δirs4 mutant infection at days 1 and 4 (P < 0.001), and the Δirs4 mutant was more susceptible to phagocytosis and killing by human polymorphonuclear cells (P = 0.01 and P = 0.006, respectively) and mouse macrophages in vitro (P = 0.04 and P = 0.01, respectively). Therefore, IRS4 contributes to tissue invasion at early stages of DC and mediates resistance to phagocytosis as DC progresses. Microarray analysis revealed remarkably similar gene expression by the Δirs4 mutant and reference strain CAI-12 within blood, suggesting that IRS4 is not significantly involved in the hematogenous stage of disease. A competitive DC model detects attenuated virulence that is not evident with the standard model.
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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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A Candida albicans temperature-sensitive cdc12-6 mutant identifies roles for septins in selection of sites of germ tube formation and hyphal morphogenesis. EUKARYOTIC CELL 2012; 11:1210-8. [PMID: 22886998 DOI: 10.1128/ec.00216-12] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Septins were identified for their role in septation in Saccharomyces cerevisiae and were subsequently implicated in other morphogenic processes. To study septins in Candida albicans hyphal morphogenesis, a temperature-sensitive mutation was created that altered the C terminus of the essential Cdc12 septin. The cdc12-6 cells grew well at room temperature, but at 37°C they displayed expected defects in septation, nuclear localization, and bud morphogenesis. Although serum stimulated the cdc12-6 cells at 37°C to form germ tube outgrowths, the mutant could not maintain polarized hyphal growth and instead formed chains of elongated cell compartments. Serum also stimulated the cdc12-6 mutant to induce a hyphal reporter gene (HWP1-GFP) and a characteristic zone of filipin staining at the leading edge of growth. Interestingly, cdc12-6 cells shifted to 37°C in the absence of serum gradually displayed enriched filipin staining at the tip, which may be due to the altered cell cycle regulation. A striking difference from the wild type was that the cdc12-6 cells frequently formed a second germ tube in close proximity to the first. The mutant cells also failed to form the diffuse band of septins at the base of germ tubes and hyphae, indicating that this septin band plays a role in preventing proximal formation of germ tubes in a manner analogous to bud site selection. These studies demonstrate that not only are septins important for cytokinesis, but they also promote polarized morphogenesis and selection of germ tube sites that may help disseminate an infection in host tissues.
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