1
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Gómez-Gaviria M, Contreras-López LM, Aguilera-Domínguez JI, Mora-Montes HM. Strategies of Pharmacological Repositioning for the Treatment of Medically Relevant Mycoses. Infect Drug Resist 2024; 17:2641-2658. [PMID: 38947372 PMCID: PMC11214559 DOI: 10.2147/idr.s466336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Accepted: 06/14/2024] [Indexed: 07/02/2024] Open
Abstract
Fungal infections represent a worldwide concern for public health, due to their prevalence and significant increase in cases each year. Among the most frequent mycoses are those caused by members of the genera Candida, Cryptococcus, Aspergillus, Histoplasma, Pneumocystis, Mucor, and Sporothrix, which have been treated for years with conventional antifungal drugs, such as flucytosine, azoles, polyenes, and echinocandins. However, these microorganisms have acquired the ability to evade the mechanisms of action of these drugs, thus hindering their treatment. Among the most common evasion mechanisms are alterations in sterol biosynthesis, modifications of drug transport through the cell wall and membrane, alterations of drug targets, phenotypic plasticity, horizontal gene transfer, and chromosomal aneuploidies. Taking into account these problems, some research groups have sought new therapeutic alternatives based on drug repositioning. Through repositioning, it is possible to use existing pharmacological compounds for which their mechanism of action is already established for other diseases, and thus exploit their potential antifungal activity. The advantage offered by these drugs is that they may be less prone to resistance. In this article, a comprehensive review was carried out to highlight the most relevant repositioning drugs to treat fungal infections. These include antibiotics, antivirals, anthelmintics, statins, and anti-inflammatory drugs.
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Affiliation(s)
- Manuela Gómez-Gaviria
- Departamento de Biología, División de Ciencias Naturales y Exactas, Universidad de Guanajuato, Guanajuato, Gto, México
| | - Luisa M Contreras-López
- Departamento de Biología, División de Ciencias Naturales y Exactas, Universidad de Guanajuato, Guanajuato, Gto, México
| | - Julieta I Aguilera-Domínguez
- Departamento de Biología, División de Ciencias Naturales y Exactas, Universidad de Guanajuato, Guanajuato, Gto, México
| | - Héctor M Mora-Montes
- Departamento de Biología, División de Ciencias Naturales y Exactas, Universidad de Guanajuato, Guanajuato, Gto, México
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2
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Treerat P, de Mattos C, Burnside M, Zhang H, Zhu Y, Zou Z, Anderson D, Wu H, Merritt J, Kreth J. Ribosomal-processing cysteine protease homolog modulates Streptococcus mutans glucan production and interkingdom interactions. J Bacteriol 2024:e0010424. [PMID: 38899897 DOI: 10.1128/jb.00104-24] [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: 03/25/2024] [Accepted: 06/02/2024] [Indexed: 06/21/2024] Open
Abstract
Glucan-dependent biofilm formation is a crucial process in the establishment of Streptococcus mutans as a cariogenic oral microbe. The process of glucan formation has been investigated in great detail, with glycosyltransferases GtfB, GtfC, and GtfD shown to be indispensable for the synthesis of glucans from sucrose. Glucan production can be visualized during biofilm formation through fluorescent labeling, and its abundance, as well as the effect of glucans on general biofilm architecture, is a common phenotype to study S. mutans virulence regulation. Here, we describe an entirely new phenotype associated with glucan production, caused by a mutation in the open reading frame SMU_848, which is located in an operon encoding ribosome-associated proteins. This mutation led to the excess production and accumulation of glucan-containing droplets on the surface of biofilms formed on agar plates after prolonged incubation. While not characterized in S. mutans, SMU_848 shows homology to the phage-related ribosomal protease Prp, essential in cleaving off the N-terminal extension of ribosomal protein L27 for functional ribosome assembly in Staphylococcus aureus. We present a further characterization of SMU_848/Prp, demonstrating that the deletion of this gene leads to significant changes in S. mutans gtfBC expression. Surprisingly, it also profoundly impacts the interkingdom interaction between S. mutans and Candida albicans, a relevant dual-species interaction implicated in severe early childhood caries. The presented data support a potential broader role for SMU_848/Prp, possibly extending its functionality beyond the ribosomal network to influence important ecological processes. IMPORTANCE Streptococcus mutans is an important member of the oral biofilm and is implicated in the initiation of caries. One of the main virulence mechanisms is the glucan-dependent formation of biofilms. We identified a new player in the regulation of glucan production, SMU_848, which is part of an operon that also encodes for ribosomal proteins L27 and L21. A mutation in SMU_848, which encodes a phage-related ribosomal protease Prp, leads to a significant accumulation of glucan-containing droplets on S. mutans biofilms, a previously unknown phenotype. Further investigations expanded our knowledge about the role of SMU_848 beyond its role in glucan production, including significant involvement in interkingdom interactions, thus potentially playing a global role in the virulence regulation of S. mutans.
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Affiliation(s)
- Puthayalai Treerat
- Biomaterial and Biomedical Sciences, School of Dentistry, Oregon Health & Science University (OHSU), Portland, Oregon, USA
- Division of Infectious Diseases and International Health, Department of Medicine, University of Virginia, Charlottesville, Virginia, USA
| | - Camilla de Mattos
- Biomaterial and Biomedical Sciences, School of Dentistry, Oregon Health & Science University (OHSU), Portland, Oregon, USA
| | - Molly Burnside
- Biomaterial and Biomedical Sciences, School of Dentistry, Oregon Health & Science University (OHSU), Portland, Oregon, USA
| | - Hua Zhang
- Biomaterial and Biomedical Sciences, School of Dentistry, Oregon Health & Science University (OHSU), Portland, Oregon, USA
| | - Yanting Zhu
- Biomaterial and Biomedical Sciences, School of Dentistry, Oregon Health & Science University (OHSU), Portland, Oregon, USA
| | - Zhengzhong Zou
- Biomaterial and Biomedical Sciences, School of Dentistry, Oregon Health & Science University (OHSU), Portland, Oregon, USA
| | - David Anderson
- Biomaterial and Biomedical Sciences, School of Dentistry, Oregon Health & Science University (OHSU), Portland, Oregon, USA
| | - Hui Wu
- Biomaterial and Biomedical Sciences, School of Dentistry, Oregon Health & Science University (OHSU), Portland, Oregon, USA
| | - Justin Merritt
- Biomaterial and Biomedical Sciences, School of Dentistry, Oregon Health & Science University (OHSU), Portland, Oregon, USA
- Department of Molecular Microbiology and Immunology, School of Medicine, Oregon Health & Science University (OHSU), Portland, Oregon, USA
| | - Jens Kreth
- Biomaterial and Biomedical Sciences, School of Dentistry, Oregon Health & Science University (OHSU), Portland, Oregon, USA
- Department of Molecular Microbiology and Immunology, School of Medicine, Oregon Health & Science University (OHSU), Portland, Oregon, USA
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3
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Li SA, Meng XY, Zhang YJ, Chen CL, Jiao YX, Zhu YQ, Liu PP, Sun W. Progress in pH-Sensitive sensors: essential tools for organelle pH detection, spotlighting mitochondrion and diverse applications. Front Pharmacol 2024; 14:1339518. [PMID: 38269286 PMCID: PMC10806205 DOI: 10.3389/fphar.2023.1339518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Accepted: 12/20/2023] [Indexed: 01/26/2024] Open
Abstract
pH-sensitive fluorescent proteins have revolutionized the field of cellular imaging and physiology, offering insight into the dynamic pH changes that underlie fundamental cellular processes. This comprehensive review explores the diverse applications and recent advances in the use of pH-sensitive fluorescent proteins. These remarkable tools enable researchers to visualize and monitor pH variations within subcellular compartments, especially mitochondria, shedding light on organelle-specific pH regulation. They play pivotal roles in visualizing exocytosis and endocytosis events in synaptic transmission, monitoring cell death and apoptosis, and understanding drug effects and disease progression. Recent advancements have led to improved photostability, pH specificity, and subcellular targeting, enhancing their utility. Techniques for multiplexed imaging, three-dimensional visualization, and super-resolution microscopy are expanding the horizon of pH-sensitive protein applications. The future holds promise for their integration into optogenetics and drug discovery. With their ever-evolving capabilities, pH-sensitive fluorescent proteins remain indispensable tools for unravelling cellular dynamics and driving breakthroughs in biological research. This review serves as a comprehensive resource for researchers seeking to harness the potential of pH-sensitive fluorescent proteins.
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Affiliation(s)
- Shu-Ang Li
- Clinical Systems Biology Laboratories, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Xiao-Yan Meng
- Clinical Systems Biology Laboratories, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
- The Academy of Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Ying-Jie Zhang
- Clinical Systems Biology Laboratories, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
- The Academy of Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Cai-Li Chen
- Department of Immunology, School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang, Henan, China
| | - Yu-Xue Jiao
- Clinical Systems Biology Laboratories, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Yong-Qing Zhu
- Clinical Systems Biology Laboratories, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
- The Academy of Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Pei-Pei Liu
- Clinical Systems Biology Laboratories, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Wei Sun
- Department of Burn and Repair Reconstruction, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
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4
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Cao X, Scoffield J, Xie B, Morton DB, Wu H. Drosophila melanogaster as a model to study polymicrobial synergy and dysbiosis. Front Cell Infect Microbiol 2023; 13:1279380. [PMID: 38192401 PMCID: PMC10773677 DOI: 10.3389/fcimb.2023.1279380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 11/01/2023] [Indexed: 01/10/2024] Open
Abstract
The fruit fly Drosophila melanogaster has emerged as a valuable model for investigating human biology, including the role of the microbiome in health and disease. Historically, studies involving the infection of D. melanogaster with single microbial species have yielded critical insights into bacterial colonization and host innate immunity. However, recent evidence has underscored that multiple microbial species can interact in complex ways through physical connections, metabolic cross-feeding, or signaling exchanges, with significant implications for healthy homeostasis and the initiation, progression, and outcomes of disease. As a result, researchers have shifted their focus toward developing more robust and representative in vivo models of co-infection to probe the intricacies of polymicrobial synergy and dysbiosis. This review provides a comprehensive overview of the pioneering work and recent advances in the field, highlighting the utility of Drosophila as an alternative model for studying the multifaceted microbial interactions that occur within the oral cavity and other body sites. We will discuss the factors and mechanisms that drive microbial community dynamics, as well as their impacts on host physiology and immune responses. Furthermore, this review will delve into the emerging evidence that connects oral microbes to systemic conditions in both health and disease. As our understanding of the microbiome continues to evolve, Drosophila offers a powerful and tractable model for unraveling the complex interplay between host and microbes including oral microbes, which has far-reaching implications for human health and the development of targeted therapeutic interventions.
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Affiliation(s)
- Xixi Cao
- Department of Integrative Biomedical & Diagnostic Sciences, Oregon Health and Science University School of Dentistry, Portland, OR, United States
| | - Jessica Scoffield
- Department of Microbiology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Baotong Xie
- Department of Integrative Biomedical & Diagnostic Sciences, Oregon Health and Science University School of Dentistry, Portland, OR, United States
| | - David B. Morton
- Department of Integrative Biomedical & Diagnostic Sciences, Oregon Health and Science University School of Dentistry, Portland, OR, United States
| | - Hui Wu
- Department of Integrative Biomedical & Diagnostic Sciences, Oregon Health and Science University School of Dentistry, Portland, OR, United States
- Department of Microbiology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
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5
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Yang SZ, Peng LT. Significance of the plasma membrane H +-ATPase and V-ATPase for growth and pathogenicity in pathogenic fungi. ADVANCES IN APPLIED MICROBIOLOGY 2023; 124:31-53. [PMID: 37597947 DOI: 10.1016/bs.aambs.2023.07.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/21/2023]
Abstract
Pathogenic fungi are widespread and cause a variety of diseases in human beings and other organisms. At present, limited classes of antifungal agents are available to treat invasive fungal diseases. With the wide use of the commercial antifungal agents, drug resistance of pathogenic fungi are continuously increasing. Therefore, exploring effective antifungal agents with novel drug targets is urgently needed to cope with the challenges that the antifungal area faces. pH homeostasis is vital for multiple cellular processes, revealing the potential for defining novel drug targets. Fungi have evolved a number of strategies to maintain a stable pH internal environment in response to rapid metabolism and a dramatically changing extracellular environment. Among them, plasma membrane H+-ATPase (PMA) and vacuolar H+-ATPase (V-ATPase) play a central role in the regulation of pH homeostasis system. In this chapter, we will summarize the current knowledge about pH homeostasis and its regulation mechanisms in pathogenic fungi, especially for the recent advances in PMA and V-ATPase, which would help in revealing the regulating mechanism of pH on cell growth and pathogenicity, and further designing effective drugs and identify new targets for combating fungal diseases.
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Affiliation(s)
- S Z Yang
- Key Laboratory of Environment Correlative Dietology, Ministry of Education, College of Food Science and Technology, Huazhong Agricultural University, Wuhan, P.R. China.
| | - L T Peng
- Key Laboratory of Environment Correlative Dietology, Ministry of Education, College of Food Science and Technology, Huazhong Agricultural University, Wuhan, P.R. China
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6
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Krysan DJ. The Mystery of Candida albicans Hyphal Morphogenesis in the Macrophage Phagolysosome. Infect Immun 2023; 91:e0010423. [PMID: 37129514 PMCID: PMC10187117 DOI: 10.1128/iai.00104-23] [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] [Indexed: 05/03/2023] Open
Abstract
C. albicans transitions between budding yeast and filamentous hyphal forms in a process that is tightly associated with its virulence. This transition also occurs after the fungus has been phagocytosed by macrophages. A number of somewhat discordant models have been proposed for the environmental characteristics of the phagolysosome that induce this transition. H. B. Wilson and M. C. Lorenz (Infect Immun 91:e00087-23, 2023, https://doi.org/10.1128/iai.00087-23) revisited these models and found that none of them explained morphogenesis in the macrophage.
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Affiliation(s)
- Damian J. Krysan
- Department of Pediatrics, Molecular Physiology and Biophysics and Microbiology/Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
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7
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Wilson HB, Lorenz MC. Candida albicans Hyphal Morphogenesis within Macrophages Does Not Require Carbon Dioxide or pH-Sensing Pathways. Infect Immun 2023; 91:e0008723. [PMID: 37078861 PMCID: PMC10187119 DOI: 10.1128/iai.00087-23] [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: 03/01/2023] [Accepted: 03/29/2023] [Indexed: 04/21/2023] Open
Abstract
The opportunistic fungal pathogen Candida albicans has evolved a variety of mechanisms for surviving inside and escaping macrophages, including the initiation of filamentous growth. Although several distinct models have been proposed to explain this process at the molecular level, the signals driving hyphal morphogenesis in this context have yet to be clarified. Here, we evaluate the following three molecular signals as potential hyphal inducers within macrophage phagosomes: CO2, intracellular pH, and extracellular pH. Additionally, we revisit previous work suggesting that the intracellular pH of C. albicans fluctuates in tandem with morphological changes in vitro. Using time-lapse microscopy, we observed that C. albicans mutants lacking components of the CO2-sensing pathway were able to undergo hyphal morphogenesis within macrophages. Similarly, a rim101Δ strain was competent in hyphal induction, suggesting that neutral/alkaline pH sensing is not necessary for the initiation of morphogenesis within phagosomes either. Contrary to previous findings, single-cell pH-tracking experiments revealed that the cytosolic pH of C. albicans remains tightly regulated both within macrophage phagosomes and under a variety of in vitro conditions throughout the process of morphogenesis. This finding suggests that intracellular pH is not a signal contributing to morphological changes.
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Affiliation(s)
- Hannah B. Wilson
- Graduate School for Biomedical Sciences, University of Texas Science Center at Houston, Houston, Texas, USA
- Department of Microbiology and Molecular Genetics, University of Texas McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Michael C. Lorenz
- Department of Microbiology and Molecular Genetics, University of Texas McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, USA
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8
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XUE P, SÁNCHEZ-LEÓN E, DAMOO D, HU G, JUNG WH, KRONSTAD JW. Heme sensing and trafficking in fungi. FUNGAL BIOL REV 2023; 43:100286. [PMID: 37781717 PMCID: PMC10540271 DOI: 10.1016/j.fbr.2022.09.002] [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] [Indexed: 11/04/2022]
Abstract
Fungal pathogens cause life-threatening diseases in humans, and the increasing prevalence of these diseases emphasizes the need for new targets for therapeutic intervention. Nutrient acquisition during infection is a promising target, and recent studies highlight the contributions of endomembrane trafficking, mitochondria, and vacuoles in the sensing and acquisition of heme by fungi. These studies have been facilitated by genetically encoded biosensors and other tools to quantitate heme in subcellular compartments and to investigate the dynamics of trafficking in living cells. In particular, the applications of biosensors in fungi have been extended beyond the detection of metabolites, cofactors, pH, and redox status to include the detection of heme. Here, we focus on studies that make use of biosensors to examine mechanisms of heme uptake and degradation, with guidance from the model fungus Saccharomyces cerevisiae and an emphasis on the pathogenic fungi Candida albicans and Cryptococcus neoformans that threaten human health. These studies emphasize a role for endocytosis in heme uptake, and highlight membrane contact sites involving mitochondria, the endoplasmic reticulum and vacuoles as mediators of intracellular iron and heme trafficking.
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Affiliation(s)
- Peng XUE
- Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Eddy SÁNCHEZ-LEÓN
- Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Djihane DAMOO
- Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Guanggan HU
- Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Won Hee JUNG
- Department of Systems Biotechnology, Chung-Ang University, Anseong 17546, Korea
| | - James W. KRONSTAD
- Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
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9
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Huang J, Jiang Q, Yang M, Dykes GF, Weetman SL, Xin W, He HL, Liu LN. Probing the Internal pH and Permeability of a Carboxysome Shell. Biomacromolecules 2022; 23:4339-4348. [PMID: 36054822 PMCID: PMC9554877 DOI: 10.1021/acs.biomac.2c00781] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
The carboxysome is a protein-based nanoscale organelle
in cyanobacteria
and many proteobacteria, which encapsulates the key CO2-fixing enzymes ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco)
and carbonic anhydrase (CA) within a polyhedral protein shell. The
intrinsic self-assembly and architectural features of carboxysomes
and the semipermeability of the protein shell provide the foundation
for the accumulation of CO2 within carboxysomes and enhanced
carboxylation. Here, we develop an approach to determine the interior
pH conditions and inorganic carbon accumulation within an α-carboxysome
shell derived from a chemoautotrophic proteobacterium Halothiobacillus neapolitanus and evaluate the shell
permeability. By incorporating a pH reporter, pHluorin2, within empty
α-carboxysome shells produced in Escherichia
coli, we probe the interior pH of the protein shells
with and without CA. Our in vivo and in vitro results demonstrate a lower interior pH of α-carboxysome shells
than the cytoplasmic pH and buffer pH, as well as the modulation of
the interior pH in response to changes in external environments, indicating
the shell permeability to bicarbonate ions and protons. We further
determine the saturated HCO3– concentration
of 15 mM within α-carboxysome shells and show the CA-mediated
increase in the interior CO2 level. Uncovering the interior
physiochemical microenvironment of carboxysomes is crucial for understanding
the mechanisms underlying carboxysomal shell permeability and enhancement
of Rubisco carboxylation within carboxysomes. Such fundamental knowledge
may inform reprogramming carboxysomes to improve metabolism and recruit
foreign enzymes for enhanced catalytical performance.
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Affiliation(s)
- Jiafeng Huang
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, United Kingdom.,School of Life Sciences, Central South University, Changsha 410017, China
| | - Qiuyao Jiang
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, United Kingdom.,Department of Central Laboratory, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan 250021, China
| | - Mengru Yang
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, United Kingdom
| | - Gregory F Dykes
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, United Kingdom
| | - Samantha L Weetman
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, United Kingdom
| | - Wei Xin
- Department of Central Laboratory, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan 250021, China.,Medical Science and Technology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan 271000, China
| | - Hai-Lun He
- School of Life Sciences, Central South University, Changsha 410017, China
| | - Lu-Ning Liu
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, United Kingdom.,College of Marine Life Sciences, and Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao 266003, China
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10
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Van Genechten W, Van Dijck P, Demuyser L. Fluorescent toys 'n' tools lighting the way in fungal research. FEMS Microbiol Rev 2021; 45:fuab013. [PMID: 33595628 PMCID: PMC8498796 DOI: 10.1093/femsre/fuab013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 02/14/2021] [Indexed: 12/13/2022] Open
Abstract
Although largely overlooked compared to bacterial infections, fungal infections pose a significant threat to the health of humans and other organisms. Many pathogenic fungi, especially Candida species, are extremely versatile and flexible in adapting to various host niches and stressful situations. This leads to high pathogenicity and increasing resistance to existing drugs. Due to the high level of conservation between fungi and mammalian cells, it is hard to find fungus-specific drug targets for novel therapy development. In this respect, it is vital to understand how these fungi function on a molecular, cellular as well as organismal level. Fluorescence imaging allows for detailed analysis of molecular mechanisms, cellular structures and interactions on different levels. In this manuscript, we provide researchers with an elaborate and contemporary overview of fluorescence techniques that can be used to study fungal pathogens. We focus on the available fluorescent labelling techniques and guide our readers through the different relevant applications of fluorescent imaging, from subcellular events to multispecies interactions and diagnostics. As well as cautioning researchers for potential challenges and obstacles, we offer hands-on tips and tricks for efficient experimentation and share our expert-view on future developments and possible improvements.
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Affiliation(s)
- Wouter Van Genechten
- VIB-KU Leuven Center for Microbiology, Kasteelpark Arenberg 31, 3001 Leuven-heverlee, Belgium
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Kasteelpark Arenberg 31, 3001 Leuven-Heverlee, Belgium
- Laboratory for Nanobiology, Department of Chemistry, KU Leuven, Celestijnenlaan 200g, 3001 Leuven-Heverlee, Belgium
| | - Patrick Van Dijck
- VIB-KU Leuven Center for Microbiology, Kasteelpark Arenberg 31, 3001 Leuven-heverlee, Belgium
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Kasteelpark Arenberg 31, 3001 Leuven-Heverlee, Belgium
| | - Liesbeth Demuyser
- VIB-KU Leuven Center for Microbiology, Kasteelpark Arenberg 31, 3001 Leuven-heverlee, Belgium
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Kasteelpark Arenberg 31, 3001 Leuven-Heverlee, Belgium
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11
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Baldewijns S, Sillen M, Palmans I, Vandecruys P, Van Dijck P, Demuyser L. The Role of Fatty Acid Metabolites in Vaginal Health and Disease: Application to Candidiasis. Front Microbiol 2021; 12:705779. [PMID: 34276639 PMCID: PMC8282898 DOI: 10.3389/fmicb.2021.705779] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 05/31/2021] [Indexed: 12/28/2022] Open
Abstract
Although the vast majority of women encounters at least one vaginal infection during their life, the amount of microbiome-related research performed in this area lags behind compared to alternative niches such as the intestinal tract. As a result, effective means of diagnosis and treatment, especially of recurrent infections, are limited. The role of the metabolome in vaginal health is largely elusive. It has been shown that lactate produced by the numerous lactobacilli present promotes health by limiting the chance of infection. Short chain fatty acids (SCFA) have been mainly linked to dysbiosis, although the causality of this relationship is still under debate. In this review, we aim to bring together information on the role of the vaginal metabolome and microbiome in infections caused by Candida. Vulvovaginal candidiasis affects near to 70% of all women at least once in their life with a significant proportion of women suffering from the recurrent variant. We assess the role of fatty acid metabolites, mainly SCFA and lactate, in onset of infection and virulence of the fungal pathogen. In addition, we pinpoint where lack of research limits our understanding of the molecular processes involved and restricts the possibility of developing novel treatment strategies.
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Affiliation(s)
- Silke Baldewijns
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Belgium
- VIB-KU Leuven Center for Microbiology, Leuven, Belgium
| | - Mart Sillen
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Belgium
- VIB-KU Leuven Center for Microbiology, Leuven, Belgium
| | - Ilse Palmans
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Belgium
- VIB-KU Leuven Center for Microbiology, Leuven, Belgium
| | - Paul Vandecruys
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Belgium
- VIB-KU Leuven Center for Microbiology, Leuven, Belgium
| | - Patrick Van Dijck
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Belgium
- VIB-KU Leuven Center for Microbiology, Leuven, Belgium
| | - Liesbeth Demuyser
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Belgium
- VIB-KU Leuven Center for Microbiology, Leuven, Belgium
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Van Genechten W, Demuyser L, Duwé S, Vandenberg W, Van Dijck P, Dedecker P. Photochromic Fluorophores Enable Imaging of Lowly Expressed Proteins in the Autofluorescent Fungus Candida albicans. mSphere 2021; 6:e00146-21. [PMID: 33731469 PMCID: PMC8546692 DOI: 10.1128/msphere.00146-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 02/27/2021] [Indexed: 11/20/2022] Open
Abstract
Fluorescence microscopy is a standard research tool in many fields, although collecting reliable images can be difficult in systems characterized by low expression levels and/or high background fluorescence. We present the combination of a photochromic fluorescent protein and stochastic optical fluctuation imaging (SOFI) to deliver suppression of the background fluorescence. This strategy makes it possible to resolve lowly or endogenously expressed proteins, as we demonstrate for Gcn5, a histone acetyltransferase required for complete virulence, and Erg11, the target of the azole antifungal agents in the fungal pathogen Candida albicans We expect that our method can be readily used for sensitive fluorescence measurements in systems characterized by high background fluorescence.IMPORTANCE Understanding the spatial and temporal organization of proteins of interest is key to unraveling cellular processes and identifying novel possible antifungal targets. Only a few therapeutic targets have been discovered in Candida albicans, and resistance mechanisms against these therapeutic agents are rapidly acquired. Fluorescence microscopy is a valuable tool to investigate molecular processes and assess the localization of possible antifungal targets. Unfortunately, fluorescence microscopy of C. albicans suffers from extensive autofluorescence. In this work, we present the use of a photochromic fluorescent protein and stochastic optical fluctuation imaging to enable the imaging of lowly expressed proteins in C. albicans through the suppression of autofluorescence. This method can be applied in C. albicans research or adapted for other fungal systems, allowing the visualization of intricate processes.
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Affiliation(s)
- Wouter Van Genechten
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven, Belgium
- VIB-KU Leuven Center for Microbiology, KU Leuven, Leuven, Belgium
- Advanced Optical Microscopy Centre, Biomedical Research Institute (BIOMED), Hasselt University, Hasselt, Belgium
| | - Liesbeth Demuyser
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven, Belgium
- VIB-KU Leuven Center for Microbiology, KU Leuven, Leuven, Belgium
| | - Sam Duwé
- Advanced Optical Microscopy Centre, Biomedical Research Institute (BIOMED), Hasselt University, Hasselt, Belgium
| | - Wim Vandenberg
- Lab for Nanobiology, Department of Chemistry, KU Leuven, Leuven, Belgium
| | - Patrick Van Dijck
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven, Belgium
- VIB-KU Leuven Center for Microbiology, KU Leuven, Leuven, Belgium
| | - Peter Dedecker
- Lab for Nanobiology, Department of Chemistry, KU Leuven, Leuven, Belgium
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Exogenous Reproductive Hormones nor Candida albicans Colonization Alter the Near Neutral Mouse Vaginal pH. Infect Immun 2021; 89:IAI.00550-20. [PMID: 33106292 DOI: 10.1128/iai.00550-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 10/16/2020] [Indexed: 12/15/2022] Open
Abstract
While human vaginal pH in childbearing-age women is conclusively acidic, the mouse vaginal pH is reported as being near neutral. However, this information appears to be somewhat anecdotal with respect to vulvovaginal candidiasis, as such claims in the literature frequently lack citations of studies that specifically address this physiological factor. Given the disparate pH between mice and humans, the role of exogenous hormones and colonization by the fungal pathogen Candida albicans in shaping vaginal pH was assessed. Use of a convenient modified vaginal lavage technique with the pH indicator dye phenol red demonstrated that indeed vaginal pH was near neutral (7.2 ± 0.24) and was not altered by delivery of progesterone or estrogen in C57BL/6 mice. These trends were conserved in DBA/2 and CD-1 mouse backgrounds, commonly used in the mouse model of vaginitis. It was also determined that vaginal colonization with C. albicans did not alter the globally neutral vaginal pH over the course of one week. Construction and validation of a C. albicans reporter strain expressing GFPy, driven by the pH-responsive PHR1 promoter, confirmed the murine vaginal pH to be at least ≥6.0. Collectively, our data convincingly demonstrate a stable and conserved near neutrality of the mouse vaginal pH during vulvovaginal candidiasis and should serve as a definitive source for future reference. Implications and rationale for disparate pH in this model system are also discussed.
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Presenting a codon-optimized palette of fluorescent proteins for use in Candida albicans. Sci Rep 2020; 10:6158. [PMID: 32273559 PMCID: PMC7145796 DOI: 10.1038/s41598-020-63308-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 03/27/2020] [Indexed: 11/20/2022] Open
Abstract
Fluorescent proteins with varying colors are indispensable tools for the life sciences research community. These fluorophores are often developed for use in mammalian systems, with incremental enhancements or new versions published frequently. However, the successful application of these labels in other organisms in the tree of life, such as the fungus Candida albicans, can be difficult to achieve due to the difficulty in engineering constructs for good expression in these organisms. In this contribution, we present a palette of Candida-optimized fluorescent proteins ranging from cyan to red and assess their application potential. We also compare a range of reported expression optimization techniques, and find that none of these strategies is generally applicable, and that even very closely related proteins require the application of different strategies to achieve good expression. In addition to reporting new fluorescent protein variants for applications in Candida albicans, our work highlights the ongoing challenges in optimizing protein expression in heterologous systems.
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Widiasih Widiyanto T, Chen X, Iwatani S, Chibana H, Kajiwara S. Role of major facilitator superfamily transporter Qdr2p in biofilm formation by Candida glabrata. Mycoses 2019; 62:1154-1163. [PMID: 31519064 DOI: 10.1111/myc.13005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 09/07/2019] [Accepted: 09/09/2019] [Indexed: 11/30/2022]
Abstract
Candida glabrata represents the second-most frequent cause of candidiasis infections of the mucosa, bloodstream and genito-urinary tract in immunocompromised individuals. The incidence of C glabrata infection has increased significantly in the last two decades, mainly due to this species' abilities to resist various antifungal drugs and to form biofilms. We focused on the relationship between biofilm formation and the product of QDR2, a C glabrata member of the major facilitator superfamily (MFS) gene family, given that fungal biofilm formation limits drug penetration and is associated with persistent infection. The fungal cells in biofilms were compared between a C glabrata ∆qdr2 mutant and its wild-type strain. Cells were analysed for metabolism activity and drug susceptibility (using tetrazolium assay), adhesion activity, growth assay and intracellular pH (using flow cytometry). Compared to the wild type, the C glabrata ∆qdr2 showed lower adhesion activity and higher fluconazole susceptibility when assessed as a biofilm. The mutant also showed decreased metabolic activity during biofilm formation. Furthermore, the mutant grew more slowly under neutral-basic pH conditions. The qdr2 deletion in C glabrata resulted in an impaired ability to maintain pH homeostasis, which led in turn to a reduction of cell growth and of adherence to an artificial matrix. These results suggested that the Qdr2p function is needed for proper biofilm formation and biofilm maintenance in C glabrata as well as biofilm drug resistance towards fluconazole. Qdr2p may play an important role in C glabrata's ability to form biofilms on implanted medical devices in human bodies.
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Affiliation(s)
| | - Xinyue Chen
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Shun Iwatani
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Hiroji Chibana
- Medical Mycology Research Center, Chiba University, Chiba, Japan
| | - Susumu Kajiwara
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
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Remasking of Candida albicans β-Glucan in Response to Environmental pH Is Regulated by Quorum Sensing. mBio 2019; 10:mBio.02347-19. [PMID: 31615961 PMCID: PMC6794483 DOI: 10.1128/mbio.02347-19] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Candida albicans is part of the microbiota of the skin and gastrointestinal and reproductive tracts of humans and has coevolved with us for millennia. During that period, C. albicans has developed strategies to modulate the host’s innate immune responses, by regulating the exposure of key epitopes on the fungal cell surface. Here, we report that exposing C. albicans to an acidic environment, similar to the one of the stomach or vagina, increases the detection of the yeast by macrophages. However, this effect is transitory, as C. albicans is able to remask these epitopes (glucan and chitin). We found that glucan remasking is controlled by the production of farnesol, a molecule secreted by C. albicans in response to high cell densities. However, chitin-remasking mechanisms remain to be identified. By understanding the relationship between environmental sensing and modulation of the host-pathogen interaction, new opportunities for the development of innovative antifungal strategies are possible. Candida albicans is a commensal yeast of the human gut which is tolerated by the immune system but has the potential to become an opportunistic pathogen. One way in which C. albicans achieves this duality is through concealing or exposing cell wall pathogen-associated molecular patterns (PAMPs) in response to host-derived environment cues (pH, hypoxia, and lactate). This cell wall remodeling allows C. albicans to evade or hyperactivate the host’s innate immune responses, leading to disease. Previously, we showed that adaptation of C. albicans to acidic environments, conditions encountered during colonization of the female reproductive tract, induces significant cell wall remodeling resulting in the exposure of two key fungal PAMPs (β-glucan and chitin). Here, we report that this pH-dependent cell wall remodeling is time dependent, with the initial change in pH driving cell wall unmasking, which is then remasked at later time points. Remasking of β-glucan was mediated via the cell density-dependent fungal quorum sensing molecule farnesol, while chitin remasking was mediated via a small, heat-stable, nonproteinaceous secreted molecule(s). Transcript profiling identified a core set of 42 genes significantly regulated by pH over time and identified the transcription factor Efg1 as a regulator of chitin exposure through regulation of CHT2. This dynamic cell wall remodeling influenced innate immune recognition of C. albicans, suggesting that during infection, C. albicans can manipulate the host innate immune responses.
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Arce‐Rodríguez A, Volke DC, Bense S, Häussler S, Nikel PI. Non-invasive, ratiometric determination of intracellular pH in Pseudomonas species using a novel genetically encoded indicator. Microb Biotechnol 2019; 12:799-813. [PMID: 31162835 PMCID: PMC6559197 DOI: 10.1111/1751-7915.13439] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 05/14/2019] [Accepted: 05/15/2019] [Indexed: 11/30/2022] Open
Abstract
The ability of Pseudomonas species to thrive in all major natural environments (i.e. terrestrial, freshwater and marine) is based on its exceptional capability to adapt to physicochemical changes. Thus, environmental bacteria have to tightly control the maintenance of numerous physiological traits across different conditions. The intracellular pH (pHi ) homoeostasis is a particularly important feature, since the pHi influences a large portion of the biochemical processes in the cell. Despite its importance, relatively few reliable, easy-to-implement tools have been designed for quantifying in vivo pHi changes in Gram-negative bacteria with minimal manipulations. Here we describe a convenient, non-invasive protocol for the quantification of the pHi in bacteria, which is based on the ratiometric fluorescent indicator protein PHP (pH indicator for Pseudomonas). The DNA sequence encoding PHP was thoroughly adapted to guarantee optimal transcription and translation of the indicator in Pseudomonas species. Our PHP-based quantification method demonstrated that pHi is tightly regulated over a narrow range of pH values not only in Pseudomonas, but also in other Gram-negative bacterial species such as Escherichia coli. The maintenance of the cytoplasmic pH homoeostasis in vivo could also be observed upon internal (e.g. redirection of glucose consumption pathways in P. putida) and external (e.g. antibiotic exposure in P. aeruginosa) perturbations, and the PHP indicator was also used to follow dynamic changes in the pHi upon external pH shifts. In summary, our work describes a reliable method for measuring pHi in Pseudomonas, allowing for the detailed investigation of bacterial pHi homoeostasis and its regulation.
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Affiliation(s)
- Alejandro Arce‐Rodríguez
- Department of Molecular BacteriologyHelmholtz Centre for Infection Research38124BraunschweigGermany
| | - Daniel C. Volke
- The Novo Nordisk Foundation Center for BiosustainabilityTechnical University of Denmark2800Kongens LyngbyDenmark
| | - Sarina Bense
- Department of Molecular BacteriologyHelmholtz Centre for Infection Research38124BraunschweigGermany
| | - Susanne Häussler
- Department of Molecular BacteriologyHelmholtz Centre for Infection Research38124BraunschweigGermany
| | - Pablo I. Nikel
- The Novo Nordisk Foundation Center for BiosustainabilityTechnical University of Denmark2800Kongens LyngbyDenmark
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Titrating Gene Function in the Human Fungal Pathogen Candida albicans through Poly-Adenosine Tract Insertion. mSphere 2019; 4:4/3/e00192-19. [PMID: 31118301 PMCID: PMC6531883 DOI: 10.1128/msphere.00192-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Investigating a protein’s functional importance at the whole-organism level usually involves altering its expression level or its specific activity and observing the consequences with respect to physiology or phenotype. Several approaches designed to partially or completely abolish the function of a gene, including its deletion from the genome and the use of systems that facilitate conditional expression, have been widely applied. However, each has significant limitations that are especially problematic in pathogenic microbes when it is desirable to determine if a particular gene is required for infection in an animal model. In this study, we sought to determine if an alternative approach—the insertion of poly-A repeats within the coding sequence of the gene—is sufficient to modulate its function in the prevalent human fungal pathogen C. albicans. Our results confirm that this approach enables us to predictably and gradually titrate the expression level of a protein and thus to investigate the phenotypic consequences of various levels of gene/protein function. A recent study demonstrated that the insertion of poly-adenosine (poly-A) tracts into an open reading frame can suppress expression of the encoded protein in both prokaryotic and eukaryotic species. Furthermore, the degree of suppression is proportional to the length of the poly-A insertion, which can therefore provide a reliable and predictable means to titrate a specific protein’s expression. The goal of this study was to determine if this methodology can be applied to modulate the expression of proteins in the prevalent human fungal pathogen, Candida albicans. Insertion of increasing numbers of AAA codons encoding lysine at the N terminus of the C. albicans lanosterol demethylase (Erg11p) progressively diminished expression without significantly reducing the levels of mRNA. This suggests that Erg11p expression was attenuated at the posttranscriptional level. A direct correlation between the number of AAA codons inserted and C. albicans susceptibility to the Erg11p inhibitor fluconazole was also noted, indicating a progressive loss of Erg11p activity. Finally, we constructed a series of C. albicans strains with 3 to 12 AAA codons inserted at the 5′ end of the ARO1 gene, which encodes a pentafunctional enzyme catalyzing five sequential steps of the aromatic amino acid biosynthetic pathway. Increasing numbers of AAA codons progressively reduced the growth rate of C. albicans in standard laboratory medium, indicating a progressive loss of ARO biosynthetic activity. These data unequivocally demonstrate the potential utility of the poly-A insertion method to examine the phenotypic consequences of titrating target protein function in C. albicans. IMPORTANCE Investigating a protein’s functional importance at the whole-organism level usually involves altering its expression level or its specific activity and observing the consequences with respect to physiology or phenotype. Several approaches designed to partially or completely abolish the function of a gene, including its deletion from the genome and the use of systems that facilitate conditional expression, have been widely applied. However, each has significant limitations that are especially problematic in pathogenic microbes when it is desirable to determine if a particular gene is required for infection in an animal model. In this study, we sought to determine if an alternative approach—the insertion of poly-A repeats within the coding sequence of the gene—is sufficient to modulate its function in the prevalent human fungal pathogen C. albicans. Our results confirm that this approach enables us to predictably and gradually titrate the expression level of a protein and thus to investigate the phenotypic consequences of various levels of gene/protein function.
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Rane HS, Hayek SR, Frye JE, Abeyta EL, Bernardo SM, Parra KJ, Lee SA. Candida albicans Pma1p Contributes to Growth, pH Homeostasis, and Hyphal Formation. Front Microbiol 2019; 10:1012. [PMID: 31143168 PMCID: PMC6521590 DOI: 10.3389/fmicb.2019.01012] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 04/24/2019] [Indexed: 12/30/2022] Open
Abstract
Candida albicans occupies diverse ecological niches within the host and must tolerate a wide range of environmental pH. The plasma membrane H+-ATPase Pma1p is the major regulator of cytosolic pH in fungi. Pma1p extrudes protons from the cytosol to maintain neutral-to-alkaline pH and is a potential drug target due to its essentiality and fungal specificity. We characterized mutants in which one allele of PMA1 has been deleted and the other truncated by 18–38 amino acids. Increasing C-terminal truncation caused corresponding decreases in plasma membrane ATPase-specific activity and cytosolic pH. Pma1p is regulated by glucose: glucose rapidly activates the ATPase, causing a sharp increase in cytosolic pH. Increasing Pma1p truncation severely impaired this glucose response. Pma1p truncation also altered cation responses, disrupted vacuolar morphology and pH, and reduced filamentation competence. Early studies of cytosolic pH and filamentation have described a rapid, transient alkalinization of the cytosol preceding germ tube formation; Pma1p has been proposed as a regulator of this process. We find Pma1p plays a role in the establishment of cell polarity, and distribution of Pma1p is non-homogenous in emerging hyphae. These findings suggest a role of PMA1 in cytosolic alkalinization and in the specialized form of polarized growth that is filamentation.
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Affiliation(s)
- Hallie S Rane
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Science Center, Albuquerque, NM, United States
| | - Summer R Hayek
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Science Center, Albuquerque, NM, United States
| | - Jillian E Frye
- Section of Infectious Diseases, New Mexico VA Healthcare System, Albuquerque, NM, United States
| | - Esteban L Abeyta
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Science Center, Albuquerque, NM, United States
| | - Stella M Bernardo
- Division of Infectious Diseases, University of New Mexico Health Science Center, Albuquerque, NM, United States
| | - Karlett J Parra
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Science Center, Albuquerque, NM, United States
| | - Samuel A Lee
- Medicine Service, White River Junction VA Medical Center, White River Junction, VT, United States.,Infectious Disease Section, Department of Medicine, Geisel School of Medicine at Dartmouth, Dartmouth College, Hanover, NH, United States
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Granger BL. Accessibility and contribution to glucan masking of natural and genetically tagged versions of yeast wall protein 1 of Candida albicans. PLoS One 2018; 13:e0191194. [PMID: 29329339 PMCID: PMC5766240 DOI: 10.1371/journal.pone.0191194] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 12/30/2017] [Indexed: 02/06/2023] Open
Abstract
Yeast wall protein 1 (Ywp1) is an abundant glycoprotein of the cell wall of the yeast form of Candida albicans, the most prevalent fungal pathogen of humans. Antibodies that bind to the polypeptide backbone of isolated Ywp1 show little binding to intact yeast cells, presumably because the Ywp1 epitopes are masked by the polysaccharides of the mannoproteins that form the outer layer of the cell wall. Rare cells do exhibit much greater anti-Ywp1 binding, however, and one of these was isolated and characterized. No differences were seen in its Ywp1, but it exhibited greater adhesiveness, sensitivity to wall perturbing agents, and exposure of its underlying β-1,3-glucan layer to external antibodies. The molecular basis for this greater epitope accessibility has not been determined, but has facilitated exploration of how these properties change as a function of cell growth and morphology. In addition, previously engineered strains with reduced quantities of Ywp1 in their cell walls were also found to have greater β-1,3-glucan exposure, indicating that Ywp1 itself contributes to the masking of wall epitopes, which may be important for understanding the anti-adhesive effect of Ywp1. Ectopic production of Ywp1 by hyphae, which reduces the adhesivity of these filamentous forms of C. albicans, was similarly found to reduce exposure of the β-1,3-glucan in their walls. To monitor Ywp1 in the cell wall irrespective of its accessibility, green fluorescent protein (Gfp) was genetically inserted into wall-anchored Ywp1 using a bifunctional cassette that also allowed production from a single transfection of a soluble, anchor-free version. The wall-anchored Ywp1-Gfp-Ywp1 accumulated in the wall of the yeast forms but not hyphae, and appeared to have properties similar to native Ywp1, including its adhesion-inhibiting effect. Some pseudohyphal walls also detectably accumulated this probe. Strains of C. albicans with tandem hemagglutinin (HA) epitopes inserted into wall-anchored Ywp1 were previously created by others, and were further explored here. As above, rare cells with much greater accessibility of the HA epitopes were isolated, and also found to exhibit greater exposure of Ywp1 and β-1,3-glucan. The placement of the HA cassette inhibited the normal N-glycosylation and propeptide cleavage of Ywp1, but the wall-anchored Ywp1-HA-Ywp1 still accumulated in the cell wall of yeast forms. Bifunctional transformation cassettes were used to additionally tag these molecules with Gfp, generating soluble Ywp1-HA-Gfp and wall-anchored Ywp1-HA-Gfp-Ywp1 molecules. The former revealed unexpected electrophoretic properties caused by the HA insertion, while the latter further highlighted differences between the presence of a tagged Ywp1 molecule (as revealed by Gfp fluorescence) and its accessibility in the cell wall to externally applied antibodies specific for HA, Gfp and Ywp1, with accessibility being greatest in the rapidly expanding walls of budding daughter cells. These strains and results increase our understanding of cell wall properties and how C. albicans masks itself from recognition by the human immune system.
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Affiliation(s)
- Bruce L. Granger
- Department of Microbiology and Immunology, Montana State University, Bozeman, Montana, United States of America
- * E-mail:
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