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Chen SY, Chang CK, Lan CY. Antimicrobial peptide LL-37 disrupts plasma membrane and calcium homeostasis in Candida albicans via the Rim101 pathway. Microbiol Spectr 2023; 11:e0255123. [PMID: 37888991 PMCID: PMC10715129 DOI: 10.1128/spectrum.02551-23] [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: 06/18/2023] [Accepted: 09/19/2023] [Indexed: 10/28/2023] Open
Abstract
IMPORTANCE Candida albicans is a major human fungal pathogen, and antimicrobial peptides are key components of innate immunity. Studying the interplay between C. albicans and human antimicrobial peptides would enhance a better understanding of pathogen-host interactions. Moreover, potential applications of antimicrobial peptides in antifungal therapy have aroused great interest. This work explores new mechanisms of LL-37 against C. albicans and reveals the complex connection among calcium homeostasis, oxidative stress, signaling, and possibly organelle interaction. Notably, these findings support the possible use of antimicrobial peptides to prevent and treat fungal infections.
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Affiliation(s)
- Sheng-Yuan Chen
- Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsinchu, Taiwan
| | - Che-Kang Chang
- Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsinchu, Taiwan
| | - Chung-Yu Lan
- Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsinchu, Taiwan
- Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan
- School of Medicine, National Tsing Hua University, Hsinchu, Taiwan
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2
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Selnø ATH, Sumbayev VV, Gibbs BF. IgE-dependent human basophil responses are inversely associated with the sarcoplasmic reticulum Ca 2+-ATPase (SERCA). Front Immunol 2023; 13:1052290. [PMID: 36685580 PMCID: PMC9846818 DOI: 10.3389/fimmu.2022.1052290] [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: 09/23/2022] [Accepted: 12/16/2022] [Indexed: 01/06/2023] Open
Abstract
Basophils crucially contribute to allergies and other Th2-driven diseases by rapidly releasing inflammatory and immunomodulatory mediators following high-affinity IgE-receptor crosslinking. Although these basophil-mediated responses depend on sensitization with antigen-specific IgE, this does not necessarily predict clinical symptom severity. It is thought that the balance of early stimulatory (e.g. SYK) and inhibitory (e.g. SHIP-1) intracellular signals are associated with basophil responsiveness, which is also critically dependent on calcium mobilization. Previous studies suggest that the sarcoplasmic reticulum Ca2+-ATPase (SERCA2), which regulates cytosolic calcium levels, may be inversely associated with airway smooth muscle reactivity in asthma. Since basophils are implicated in asthma severity, our aims were to address whether SERCA2 is implicated in human basophil responses, especially following IgE-mediated activation. Human basophils were obtained from buffy coats, following research ethics approval, and further purified by immunomagnetic cell sorting. Expressions of SERCA2, and other isoforms, were determined by Western blotting in parallel to measuring IgE-dependent histamine releases from the same donors. The effects of a SERCA-activator and inhibitor were also assessed on their abilities to modulate basophil histamine release. We observed an inverse correlation between basophil responsiveness to IgE-dependent stimulation and SERCA2 expression. Thapsigargin, a highly-specific SERCA inhibitor, stimulated basophil histamine release and potentiated IgE-dependent secretion of the amine. Conversely, disulfiram, a SERCA activator, inhibited IgE-dependent basophil activation. The results obtained from this exploratory study indicate that SERCA2 may be an additional regulator of basophil reactivity alongside early excitatory or inhibitory signal transduction pathways.
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Affiliation(s)
| | - Vadim V. Sumbayev
- School of Pharmacy, University of Kent, Chatham Maritime, United Kingdom
| | - Bernhard F. Gibbs
- School of Pharmacy, University of Kent, Chatham Maritime, United Kingdom,Department of Human Medicine, University of Oldenburg, Oldenburg, Germany,*Correspondence: Bernhard F. Gibbs,
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A Fungal Transcription Regulator of Vacuolar Function Modulates Candida albicans Interactions with Host Epithelial Cells. mBio 2021; 12:e0302021. [PMID: 34781731 PMCID: PMC8593675 DOI: 10.1128/mbio.03020-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Microorganisms typically maintain cellular homeostasis despite facing large fluctuations in their surroundings. Microbes that reside on human mucosal surfaces may experience significant variations in nutrient and ion availability as well as pH. Whether the mechanisms employed by these microbial cells to sustain homeostasis directly impact on the interplay with the host’s mucosae remains unclear. Here, we report that the previously uncharacterized transcription regulator ZCF8 in the human-associated yeast Candida albicans maintains vacuole homeostasis when the fungus faces fluctuations in nitrogen. Genome-wide identification of genes directly regulated by Zcf8p followed by fluorescence microscopy to define their subcellular localization uncovered the fungal vacuole as a top target of Zcf8p regulation. Deletion and overexpression of ZCF8 resulted in alterations in vacuolar morphology and luminal pH and rendered the fungus resistant or susceptible to nigericin and brefeldin A, two drugs that impair vacuole and associated functions. Furthermore, we establish that the regulator modulates C. albicans attachment to epithelial cells in a manner that depends on the status of the fungal vacuole. Our findings, therefore, suggest that fungal vacuole physiology regulation is intrinsically linked to, and shapes to a significant extent, the physical interactions that Candida cells establish with mammalian mucosal surfaces.
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Akinsola RO, Lee CW, Sim EUH, Narayanan K. Inhibition of lysosomal vacuolar proton pump down-regulates cellular acidification and enhances E. coli bactofection efficiency. Anal Biochem 2020; 616:114088. [PMID: 33358938 DOI: 10.1016/j.ab.2020.114088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 12/04/2020] [Accepted: 12/17/2020] [Indexed: 12/01/2022]
Abstract
Endosomal escape is considered a crucial barrier that needs to be overcome by integrin-mediated E. coli for gene delivery into mammalian cells. Bafilomycin, a potent inhibitor of the H+ proton pump commonly employed to lower endosomal pH, was evaluated as part of the E. coli protocol during delivery. We found an increase in green fluorescent protein expression up 6.9, 3.2, 5.0, 2.8, and 4.5 fold in HeLa, HEK-293, A549, HT1080, and MCF-7 respectively, compared to untreated cells. Our result showed for the first time that Inhibition of lysosomal V-ATPase enhances E. coli efficiency.
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Affiliation(s)
- Rasaq Olajide Akinsola
- School of Science, Monash University Malaysia, Bandar Sunway, 47500, Selangor Darul Ehsan, Malaysia
| | - Choon Weng Lee
- Institute of Biological Sciences, University of Malaya, 50603, Kuala Lumpur, Malaysia
| | - Edmund Ui Hang Sim
- Faculty of Resource Science and Technology, Universiti Malaysia Sarawak, 94300, Sarawak, Malaysia
| | - Kumaran Narayanan
- School of Science, Monash University Malaysia, Bandar Sunway, 47500, Selangor Darul Ehsan, Malaysia.
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5
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Ding M, Baker D. Recent advances in high-throughput flow cytometry for drug discovery. Expert Opin Drug Discov 2020; 16:303-317. [PMID: 33054417 DOI: 10.1080/17460441.2021.1826433] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
INTRODUCTION High-throughput flow cytometry (HTFC) has proven to be an important technology in drug discovery. The use of HTFC enables multi-parametric screening of suspension cells containing heterogenous cell populations and coated particles for screening proteins of interest. Novel targets, novel cell markers and compound clusters for drug development have been identified from HTFC screens. AREAS COVERED In this article, the authors focus on reviewing the recent HTFC applications reported during the last 5-6 years, including drug discovery screens and studies for immune, immune-oncology, infectious and inflammatory diseases. The main HTFC approaches, development of HTFC systems, and automated sample preparation systems for HTFC are also discussed. EXPERT OPINION The advance of HTFC technology coupled with automated sample acquisition and sample preparation has demonstrated its utility in screening large numbers of compounds using suspension cells, facilitated screening of disease-relevant human primary cells, and enabled deep understanding of mechanism of action by analyzing multiple parameters. The authors see HTFC as a very valuable tool in immune, immune-oncology, infectious and inflammatory diseases where immune cells play essential roles.
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Affiliation(s)
- Mei Ding
- Discovery Biology, Discovery Sciences, R&D, AstraZeneca, Gothenburg, Sweden
| | - David Baker
- Discovery Biology, Discovery Sciences, R&D, AstraZeneca, Cambridge, UK
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Neurodegeneration-related beta-amyloid as autocatabolism-attenuator in a micro-in vivo system. IBRO Rep 2020; 9:319-323. [PMID: 33336107 PMCID: PMC7733039 DOI: 10.1016/j.ibror.2020.10.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 10/02/2020] [Indexed: 11/24/2022] Open
Abstract
Bdelloids are adaptive models for studying aggregate-metabolism interactions. Starvation causes reversible organ shrinkage in bdelloids. The organ shrinkage is in connection with autocatabolic processes. Beta-amyloid attenuates the starvation-induced germovitellaria shrinkage. Human-type amyloid-aggregates are metabolism-regulators in two bdelloid species.
Investigation of human neurodegeneration-related aggregates of beta-amyloid 1–42 (Aβ42) on bdelloid rotifers is a novel interdisciplinary approach in life sciences. We reapplied an organ size-based in vivo monitoring system, exploring the autocatabolism-related alterations evoked by Aβ42, in a glucose-supplemented starvation model. The experientially easy-to-follow size reduction of the bilateral reproductive organ (germovitellaria) in fasted rotifers was rescued by Aβ42, serving as a nutrient source- and peptide sequence-specific attenuator of the organ shrinkage phase and enhancer of the regenerative one including egg reproduction. Recovery of the germovitellaria was significant in comparison with the greatly shrunken form. In contrast to the well-known neurotoxic Aβ42 (except the bdelloids) with specific regulatory roles, the artificially designed scrambled version (random order of amino acids) was inefficient in autocatabolism attenuation, behaving as negative control. This native Aβ42-related modulation of the ‘functionally reversible organ shrinkage’ can be a potential experiential and supramolecular marker of autocatabolism in vivo.
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Key Words
- AO, acridine orange
- AVOs, acidic vesicular organelles
- Acridine orange (PubChem CID: 62344)
- Autocatabolism
- Aβ, beta-amyloid
- Bdelloid rotifer
- Beta-amyloid
- BisANS (PubChem CID: 16213473)
- BisANS, 4,4′-dianilino-1,1′-binaphthyl-5,5′-disulfonic acid dipotassium salt
- ConA, Concanamycin A
- Concanamycin A (PubChem CID: 6438151)
- D0, Day 0
- D20, Day 20
- D25, Day 25
- FROS, functionally reversible organ shrinkage
- FROSi, FROS index
- Invertebrate
- Metabolism
- NFI%, percentage of normalized fluorescence intensity
- NaOH (PubChem CID: 14798)
- Neutral red (PubChem CID: 11105)
- Organ shrinkage
- PI, propidium-iodide
- Propidium-iodide (PubChem CID: 104981)
- S-Aβ42, scrambled isoform of Aβ
- SEM, standard error of the mean
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Translation Inhibition by Rocaglates Activates a Species-Specific Cell Death Program in the Emerging Fungal Pathogen Candida auris. mBio 2020; 11:mBio.03329-19. [PMID: 32156828 PMCID: PMC7064782 DOI: 10.1128/mbio.03329-19] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Emergence of the fungal pathogen Candida auris has ignited intrigue and alarm within the medical community and the public at large. This pathogen is unusually resistant to antifungals, threatening to overwhelm current management options. By screening a library of structurally diverse molecules, we found that C. auris is surprisingly sensitive to translation inhibition by a class of compounds known as rocaglates (also known as flavaglines). Despite the high level of conservation across fungi in their protein synthesis machinery, these compounds inhibited translation initiation and activated a cell death program in C. auris but not in its relative Candida albicans. Our findings highlight a surprising divergence across the cell death programs operating in Candida species and underscore the need to understand the specific biology of a pathogen in attempting to develop more-effective treatments against it. Fungal infections are a major contributor to infectious disease-related deaths worldwide. Recently, global emergence of the fungal pathogen Candida auris has caused considerable concern because most C. auris isolates are resistant to fluconazole, the most commonly administered antifungal, and some isolates are resistant to drugs from all three major antifungal classes. To identify novel agents with bioactivity against C. auris, we screened 2,454 compounds from a diversity-oriented synthesis collection. Of the five hits identified, most shared a common rocaglate core structure and displayed fungicidal activity against C. auris. These rocaglate hits inhibited translation in C. auris but not in its pathogenic relative Candida albicans. Species specificity was contingent on variation at a single amino acid residue in Tif1, a fungal member of the eukaryotic initiation factor 4A (eIF4A) family of translation initiation factors known to be targeted by rocaglates. Rocaglate-mediated inhibition of translation in C. auris activated a cell death program characterized by loss of mitochondrial membrane potential, increased caspase-like activity, and disrupted vacuolar homeostasis. In a rocaglate-sensitized C. albicans mutant engineered to express translation initiation factor 1 (Tif1) with the variant amino acid that we had identified in C. auris, translation was inhibited but no programmed cell death phenotypes were observed. This surprising finding suggests divergence between these related fungal pathogens in their pathways of cellular responses to translation inhibition. From a therapeutic perspective, the chemical biology that we have uncovered reveals species-specific vulnerability in C. auris and identifies a promising target for development of new, mechanistically distinct antifungals in the battle against this emerging pathogen.
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Jia Y, Jiang J, Zhao K, Zhang T, Sun P, Peng J, Yang Q, Qian Y. Disulfiram suppressed ethanol promoted RANKL-induced osteoclastogenesis in vitro and ethanol-induced osteoporosis in vivo via ALDH1A1-NFATc1 axis. Aging (Albany NY) 2019; 11:8103-8119. [PMID: 31596733 PMCID: PMC6814600 DOI: 10.18632/aging.102279] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 09/05/2019] [Indexed: 12/20/2022]
Abstract
Excessive alcohol consumption is positively related to osteoporosis, and its treatment strategies are poorly developed. Disulfiram inhibits receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclastogenesis; however, whether it can be used for ethanol-induced osteoclastogenesis and its underlying mechanism are still unclear. In this study, we demonstrated that ethanol promoted RANKL-induced osteoclast formation and bone resorption, whereas, disulfiram suppressed ethanol-induced osteoclastogenesis by abrogating the expression of nuclear factor of activated T cell c1 (NFATc1) in vitro. Further analysis revealed that aldehyde dehydrogenase 1A1 (ALDH1A1) is important for the expression of NFATc1, the master regulator of osteoclast differentiation. Furthermore, we showed that disulfiram protected ethanol-induced osteoporosis in vivo. Overall, our study provides promising evidence that disulfiram can be used as a treatment strategy for alcohol-related osteoporosis via the ALDH1A1T–NFATc1 axis.
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Affiliation(s)
- Yewei Jia
- Department of Orthopaedics, Shaoxing People's Hospital (Shaoxing Hospital, Zhejiang University School of Medicine, Shaoxing), Zhejiang 312000, China.,Department of Orthopaedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 312000, China
| | - Jiawei Jiang
- Department of Urinary Surgery, Jinhua Central Hospital (Jinhua Hospital, Zhejiang University School of Medicine, Jinhua), Zhejiang 321000, China
| | - Kangxian Zhao
- Department of Orthopaedics, Shaoxing People's Hospital (Shaoxing Hospital, Zhejiang University School of Medicine, Shaoxing), Zhejiang 312000, China
| | - Tan Zhang
- Department of Orthopaedics, Shaoxing People's Hospital (Shaoxing Hospital, Zhejiang University School of Medicine, Shaoxing), Zhejiang 312000, China
| | - Peng Sun
- Department of Orthopaedics, Shaoxing People's Hospital (Shaoxing Hospital, Zhejiang University School of Medicine, Shaoxing), Zhejiang 312000, China
| | - Jiaxuan Peng
- Guangxi Key Laboratory of Regenerative Medicine, Guangxi Medical University, Guangxi 530021, China
| | - Qichang Yang
- Department of Orthopaedics, Shaoxing People's Hospital (Shaoxing Hospital, Zhejiang University School of Medicine, Shaoxing), Zhejiang 312000, China
| | - Yu Qian
- Department of Orthopaedics, Shaoxing People's Hospital (Shaoxing Hospital, Zhejiang University School of Medicine, Shaoxing), Zhejiang 312000, China
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9
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Periplanetasin-4, a novel antimicrobial peptide from the cockroach, inhibits communications between mitochondria and vacuoles. Biochem J 2019; 476:1267-1284. [DOI: 10.1042/bcj20180933] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 04/04/2019] [Accepted: 04/08/2019] [Indexed: 12/16/2022]
Abstract
Abstract
Communications between various organelle–organelles play an essential role in cell survival. The cross-talk between mitochondria and vacuoles comes up with the vital roles of the intercompartmental process. In this study, we found a couple of cell death features, membrane damage, and apoptosis using antimicrobial peptide from American Cockroach. Periplanetasin-4 (LRHKVYGYCVLGP-NH2) is a 13-mer peptide derived from Periplaneta americana and exhibits phosphatidylserine exposure and caspase activation without DNA fragmentation. Apoptotic features without DNA damage provide evidence that this peptide did not interact with DNA directly and exhibited dysfunction of mitochondria and vacuoles. Superoxide radicals were generated from mitochondria and converted to hydrogen peroxide. Despite the enhancement of catalase and total glutathione contents, oxidative damage disrupted intracellular contents. Periplanetasin-4 induced cell death associated with the production of superoxide radicals, calcium uptake in mitochondria and disorder of vacuoles, such as increased permeability and alkalization. While calcium movement from vacuoles to the mitochondria occurred, the cross-talk with these organelles proceeded and the inherent functionality was impaired. To sum up, periplanetasin-4 stimulates superoxide signal along with undermining the mitochondrial functions and interfering in communication with vacuoles.
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Minematsu A, Miyazaki T, Shimamura S, Nishikawa H, Nakayama H, Takazono T, Saijo T, Yamamoto K, Imamura Y, Yanagihara K, Kohno S, Mukae H, Izumikawa K. Vacuolar proton-translocating ATPase is required for antifungal resistance and virulence of Candida glabrata. PLoS One 2019; 14:e0210883. [PMID: 30673768 PMCID: PMC6343876 DOI: 10.1371/journal.pone.0210883] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2018] [Accepted: 01/03/2019] [Indexed: 12/04/2022] Open
Abstract
Vacuolar proton-translocating ATPase (V-ATPase) is located in fungal vacuolar membranes. It is involved in multiple cellular processes, including the maintenance of intracellular ion homeostasis by maintaining acidic pH within the cell. The importance of V-ATPase in virulence has been demonstrated in several pathogenic fungi, including Candida albicans. However, it remains to be determined in the clinically important fungal pathogen Candida glabrata. Increasing multidrug resistance of C. glabrata is becoming a critical issue in the clinical setting. In the current study, we demonstrated that the plecomacrolide V-ATPase inhibitor bafilomycin B1 exerts a synergistic effect with azole antifungal agents, including fluconazole and voriconazole, against a C. glabrata wild-type strain. Furthermore, the deletion of the VPH2 gene encoding an assembly factor of V-ATPase was sufficient to interfere with V-ATPase function in C. glabrata, resulting in impaired pH homeostasis in the vacuole and increased sensitivity to a variety of environmental stresses, such as alkaline conditions (pH 7.4), ion stress (Na+, Ca2+, Mn2+, and Zn2+ stress), exposure to the calcineurin inhibitor FK506 and antifungal agents (azoles and amphotericin B), and iron limitation. In addition, virulence of C. glabrata Δvph2 mutant in a mouse model of disseminated candidiasis was reduced in comparison with that of the wild-type and VPH2-reconstituted strains. These findings support the notion that V-ATPase is a potential attractive target for the development of effective antifungal strategies.
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Affiliation(s)
- Asuka Minematsu
- Department of Infectious Diseases, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
- Department of Respiratory Medicine, Nagasaki University Hospital, Nagasaki, Japan
| | - Taiga Miyazaki
- Department of Infectious Diseases, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
- Department of Respiratory Medicine, Nagasaki University Hospital, Nagasaki, Japan
- * E-mail:
| | - Shintaro Shimamura
- Department of Respiratory Medicine, Nagasaki University Hospital, Nagasaki, Japan
| | - Hiroshi Nishikawa
- Department of Respiratory Medicine, Nagasaki University Hospital, Nagasaki, Japan
| | - Hironobu Nakayama
- Faculty of Pharmaceutical Sciences, Suzuka University of Medical Sciences, Mie, Japan
| | - Takahiro Takazono
- Department of Infectious Diseases, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
- Department of Respiratory Medicine, Nagasaki University Hospital, Nagasaki, Japan
| | - Tomomi Saijo
- Department of Respiratory Medicine, Nagasaki University Hospital, Nagasaki, Japan
| | - Kazuko Yamamoto
- Department of Respiratory Medicine, Nagasaki University Hospital, Nagasaki, Japan
| | - Yoshifumi Imamura
- Department of Respiratory Medicine, Nagasaki University Hospital, Nagasaki, Japan
| | - Katsunori Yanagihara
- Department of Laboratory Medicine, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Shigeru Kohno
- Department of Respiratory Medicine, Nagasaki University Hospital, Nagasaki, Japan
| | - Hiroshi Mukae
- Department of Respiratory Medicine, Nagasaki University Hospital, Nagasaki, Japan
| | - Koichi Izumikawa
- Department of Infectious Diseases, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
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Tournu H, Carroll J, Latimer B, Dragoi AM, Dykes S, Cardelli J, Peters TL, Eberle KE, Palmer GE. Identification of small molecules that disrupt vacuolar function in the pathogen Candida albicans. PLoS One 2017; 12:e0171145. [PMID: 28151949 PMCID: PMC5289544 DOI: 10.1371/journal.pone.0171145] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 01/03/2017] [Indexed: 01/01/2023] Open
Abstract
The fungal vacuole is a large acidified organelle that performs a variety of cellular functions. At least a sub-set of these functions are crucial for pathogenic species of fungi, such as Candida albicans, to survive within and invade mammalian tissue as mutants with severe defects in vacuolar biogenesis are avirulent. We therefore sought to identify chemical probes that disrupt the normal function and/or integrity of the fungal vacuole to provide tools for the functional analysis of this organelle as well as potential experimental therapeutics. A convenient indicator of vacuolar integrity based upon the intracellular accumulation of an endogenously produced pigment was adapted to identify Vacuole Disrupting chemical Agents (VDAs). Several chemical libraries were screened and a set of 29 compounds demonstrated to reproducibly cause loss of pigmentation, including 9 azole antifungals, a statin and 3 NSAIDs. Quantitative analysis of vacuolar morphology revealed that (excluding the azoles) a sub-set of 14 VDAs significantly alter vacuolar number, size and/or shape. Many C. albicans mutants with impaired vacuolar function are deficient in the formation of hyphal elements, a process essential for its pathogenicity. Accordingly, all 14 VDAs negatively impact C. albicans hyphal morphogenesis. Fungal selectivity was observed for approximately half of the VDA compounds identified, since they did not alter the morphology of the equivalent mammalian organelle, the lysosome. Collectively, these compounds comprise of a new collection of chemical probes that directly or indirectly perturb normal vacuolar function in C. albicans.
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Affiliation(s)
- Helene Tournu
- Department of Clinical Pharmacy, Division of Clinical and Experimental Therapeutics, College of Pharmacy, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
| | - Jennifer Carroll
- Department of Medicine, Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Brian Latimer
- Department of Medicine, Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Ana-Maria Dragoi
- Department of Medicine, Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Samantha Dykes
- Department of Medicine, Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - James Cardelli
- Department of Medicine, Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Tracy L. Peters
- Department of Clinical Pharmacy, Division of Clinical and Experimental Therapeutics, College of Pharmacy, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
| | - Karen E. Eberle
- Department of Microbiology, Immunology and Parasitology, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - Glen E. Palmer
- Department of Clinical Pharmacy, Division of Clinical and Experimental Therapeutics, College of Pharmacy, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
- * E-mail:
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12
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Couoh-Cardel S, Milgrom E, Wilkens S. Affinity Purification and Structural Features of the Yeast Vacuolar ATPase Vo Membrane Sector. J Biol Chem 2015; 290:27959-71. [PMID: 26416888 DOI: 10.1074/jbc.m115.662494] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Indexed: 12/27/2022] Open
Abstract
The membrane sector (Vo) of the proton pumping vacuolar ATPase (V-ATPase, V1Vo-ATPase) from Saccharomyces cerevisiae was purified to homogeneity, and its structure was characterized by EM of single molecules and two-dimensional crystals. Projection images of negatively stained Vo two-dimensional crystals showed a ring-like structure with a large asymmetric mass at the periphery of the ring. A cryo-EM reconstruction of Vo from single-particle images showed subunits a and d in close contact on the cytoplasmic side of the proton channel. A comparison of three-dimensional reconstructions of free Vo and Vo as part of holo V1Vo revealed that the cytoplasmic N-terminal domain of subunit a (aNT) must undergo a large conformational change upon enzyme disassembly or (re)assembly from Vo, V1, and subunit C. Isothermal titration calorimetry using recombinant subunit d and aNT revealed that the two proteins bind each other with a Kd of ~5 μm. Treatment of the purified Vo sector with 1-palmitoyl-2-hydroxy-sn-glycero-3-[phospho-rac-(1-glycerol)] resulted in selective release of subunit d, allowing purification of a VoΔd complex. Passive proton translocation assays revealed that both Vo and VoΔd are impermeable to protons. We speculate that the structural change in subunit a upon release of V1 from Vo during reversible enzyme dissociation plays a role in blocking passive proton translocation across free Vo and that the interaction between aNT and d seen in free Vo functions to stabilize the Vo sector for efficient reassembly of V1Vo.
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Affiliation(s)
- Sergio Couoh-Cardel
- From the Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210
| | - Elena Milgrom
- From the Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210
| | - Stephan Wilkens
- From the Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210
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13
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Experimental and computational analysis of a large protein network that controls fat storage reveals the design principles of a signaling network. PLoS Comput Biol 2015; 11:e1004264. [PMID: 26020510 PMCID: PMC4447291 DOI: 10.1371/journal.pcbi.1004264] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 04/02/2015] [Indexed: 01/26/2023] Open
Abstract
An approach combining genetic, proteomic, computational, and physiological analysis was used to define a protein network that regulates fat storage in budding yeast (Saccharomyces cerevisiae). A computational analysis of this network shows that it is not scale-free, and is best approximated by the Watts-Strogatz model, which generates “small-world” networks with high clustering and short path lengths. The network is also modular, containing energy level sensing proteins that connect to four output processes: autophagy, fatty acid synthesis, mRNA processing, and MAP kinase signaling. The importance of each protein to network function is dependent on its Katz centrality score, which is related both to the protein’s position within a module and to the module’s relationship to the network as a whole. The network is also divisible into subnetworks that span modular boundaries and regulate different aspects of fat metabolism. We used a combination of genetics and pharmacology to simultaneously block output from multiple network nodes. The phenotypic results of this blockage define patterns of communication among distant network nodes, and these patterns are consistent with the Watts-Strogatz model. We discovered a large protein network that regulates fat storage in budding yeast. This network contains 94 proteins, almost all of which bind to other proteins in the network. To understand the functions of large protein collections such as these, it will be necessary to move away from one-by-one analysis of individual proteins and create computational models of entire networks. This will allow classification of networks into categories and permit researchers to identify key network proteins on theoretical grounds. We show here that the fat regulation network fits a Watts-Strogatz small-world model. This model was devised to explain the clustering phenomena often observed in real networks, but has not been previously applied to signaling networks within cells. The short path length and high clustering coefficients characteristic of the Watts-Strogatz topology allow for rapid communication between distant nodes and for division of the network into modules that perform different functions. The fat regulation network has modules, and it is divisible into subnetworks that span modular boundaries and regulate different aspects of fat metabolism. We experimentally examined communication between nodes within the network using a combination of genetics and pharmacology, and showed that the communication patterns are consistent with the Watts-Strogatz topology.
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Bouchez I, Pouteaux M, Canonge M, Genet M, Chardot T, Guillot A, Froissard M. Regulation of lipid droplet dynamics in Saccharomyces cerevisiae depends on the Rab7-like Ypt7p, HOPS complex and V1-ATPase. Biol Open 2015; 4:764-75. [PMID: 25948753 PMCID: PMC4571102 DOI: 10.1242/bio.20148615] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
It has now been clearly shown that lipid droplets (LDs) play a dynamic role in the cell. This was reinforced by LD proteomics which suggest that a significant number of trafficking proteins are associated with this organelle. Using microscopy, we showed that LDs partly co-localize with the vacuole in S. cerevisiae. Immunoblot experiments confirmed the association of the vacuolar Rab GTPase Rab7-like Ypt7p with LDs. We observed an increase in fatty acid content and LD number in ypt7Δ mutant and also changes in LD morphology and intra LD fusions, revealing a direct role for Ypt7p in LD dynamics. Using co-immunoprecipitation, we isolated potential Ypt7p partners including, Vma13p, the H subunit of the V1 part of the vacuolar (H+) ATPase (V-ATPase). Deletion of the VMA13 gene, as well as deletion of three other subunits of the V1 part of the V-ATPase, also increased the cell fatty acid content and LD number. Mutants of the Homotypic fusion and vacuole protein sorting (HOPS) complex showed similar phenotypes. Here, we demonstrated that LD dynamics and membrane trafficking between the vacuole and LDs are regulated by the Rab7-like Ypt7p and are impaired when the HOPS complex and the V1 domain of the V-ATPase are defective.
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Affiliation(s)
- Isabelle Bouchez
- Institut Jean-Pierre Bourgin IJPB, UMR 1318 INRA, Saclay Plant Sciences, route de St Cyr (RD 10), 78026, Versailles cedex, France Institut Jean-Pierre Bourgin IJPB, UMR 1318 AgroParisTech, route de St Cyr (RD 10), 78026, Versailles cedex, France
| | - Marie Pouteaux
- Institut Jean-Pierre Bourgin IJPB, UMR 1318 INRA, Saclay Plant Sciences, route de St Cyr (RD 10), 78026, Versailles cedex, France Institut Jean-Pierre Bourgin IJPB, UMR 1318 AgroParisTech, route de St Cyr (RD 10), 78026, Versailles cedex, France
| | - Michel Canonge
- Institut Jean-Pierre Bourgin IJPB, UMR 1318 INRA, Saclay Plant Sciences, route de St Cyr (RD 10), 78026, Versailles cedex, France Institut Jean-Pierre Bourgin IJPB, UMR 1318 AgroParisTech, route de St Cyr (RD 10), 78026, Versailles cedex, France
| | - Mélanie Genet
- Institut Jean-Pierre Bourgin IJPB, UMR 1318 INRA, Saclay Plant Sciences, route de St Cyr (RD 10), 78026, Versailles cedex, France Institut Jean-Pierre Bourgin IJPB, UMR 1318 AgroParisTech, route de St Cyr (RD 10), 78026, Versailles cedex, France
| | - Thierry Chardot
- Institut Jean-Pierre Bourgin IJPB, UMR 1318 INRA, Saclay Plant Sciences, route de St Cyr (RD 10), 78026, Versailles cedex, France Institut Jean-Pierre Bourgin IJPB, UMR 1318 AgroParisTech, route de St Cyr (RD 10), 78026, Versailles cedex, France
| | - Alain Guillot
- MICALIS PAPPSO, UMR 1319 INRA, Domaine de Vilvert 78352, Jouy-en-Josas cedex, France MICALIS PAPPSO, UMR 1319 AgroParisTech, Domaine de Vilvert 78352, Jouy-en-Josas cedex, France
| | - Marine Froissard
- Institut Jean-Pierre Bourgin IJPB, UMR 1318 INRA, Saclay Plant Sciences, route de St Cyr (RD 10), 78026, Versailles cedex, France Institut Jean-Pierre Bourgin IJPB, UMR 1318 AgroParisTech, route de St Cyr (RD 10), 78026, Versailles cedex, France
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15
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Ying H, Qin A, Cheng TS, Pavlos NJ, Rea S, Dai K, Zheng MH. Disulfiram attenuates osteoclast differentiation in vitro: a potential antiresorptive agent. PLoS One 2015; 10:e0125696. [PMID: 25928135 PMCID: PMC4416043 DOI: 10.1371/journal.pone.0125696] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 03/19/2015] [Indexed: 01/08/2023] Open
Abstract
Disulfiram (DSF), a cysteine modifying compound, has long been clinically employed for the treatment of alcohol addiction. Mechanistically, DSF acts as a modulator of MAPK and NF-κB pathways signaling pathways. While these pathways are crucial for osteoclast (OC) differentiation, the potential influence of DSF on OC formation and function has not been directly assessed. Here, we explore the pharmacological effects of DSF on OC differentiation, activity and the modulation of osteoclastogenic signaling cascades. We first analyzed cytotoxicity of DSF on bone marrow monocytes isolated from C57BL/6J mice. Upon the establishment of optimal dosage, we conducted osteoclastogenesis and bone resorption assays in the presence or absence of DSF treatment. Luciferase assays in RAW264.7 cells were used to examine the effects of DSF on major transcription factors activation. Western blot, reverse transcription polymerase chain reaction, intracellular acidification and proton influx assays were employed to further dissect the underlying mechanism. DSF treatment dose-dependently inhibited both mouse and human osteoclastogenesis, especially at early stages of differentiation. This inhibition correlated with a decrease in the expression of key osteoclastic marker genes including CtsK, TRAP, DC-STAMP and Atp6v0d2 as well as a reduction in bone resorption in vitro. Suppression of OC differentiation was found to be due, at least in part, to the blockade of several key receptor activators of nuclear factor kappa-B ligand (RANKL)-signaling pathways including ERK, NF-κB and NFATc1. On the other hand, DSF failed to suppress intracellular acidification and proton influx in mouse and human osteoclasts using acridine orange quenching and microsome-based proton transport assays. Our findings indicate that DSF attenuates OC differentiation via the collective suppression of several key RANKL-mediated signaling cascades, thus making it an attractive agent for the treatment of OC-mediated disorders.
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Affiliation(s)
- Hua Ying
- Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Perth, Australia
| | - An Qin
- Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Perth, Australia
- Department of Orthopaedics, The Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Tak S. Cheng
- Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Perth, Australia
| | - Nathan J. Pavlos
- Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Perth, Australia
| | - Sarah Rea
- Harry Perkins Institute of Medical Research, Perth, Australia
- Department of Endocrinology & Diabetes, Sir Charles Gairdner Hospital, Perth, Australia
| | - Kerong Dai
- Department of Orthopaedics, The Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- * E-mail: (MHZ); (KD)
| | - Ming H. Zheng
- Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Perth, Australia
- * E-mail: (MHZ); (KD)
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16
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Tegos GP, Evangelisti AM, Strouse JJ, Ursu O, Bologa C, Sklar LA. A high throughput flow cytometric assay platform targeting transporter inhibition. DRUG DISCOVERY TODAY. TECHNOLOGIES 2015; 12:e95-103. [PMID: 25027381 DOI: 10.1016/j.ddtec.2014.03.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
This review highlights the concepts, recent applications and limitations of High Throughput Screening (HTS) flow cytometry-based efflux inhibitory assays. This platform has been employed in mammalian and yeast efflux systems leading to the identification of small molecules with transporter inhibitory capabilities. This technology offers the possibility of substrate multiplexing and may promote novel strategies targeting microbial efflux systems. This platform can generate a comprehensive dataset that may support efforts to map the interface between chemistry and transporter biology in a variety of pathogenic systems.
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Affiliation(s)
- George P Tegos
- Department of Dermatology, Harvard Medical School, Boston, MA 02114, United States
| | - Annette M Evangelisti
- Center for Molecular Discovery, University of New Mexico, Albuquerque, NM 87131, United States
| | - J Jacob Strouse
- Center for Molecular Discovery, University of New Mexico, Albuquerque, NM 87131, United States
| | - Oleg Ursu
- Division of Translational Informatics, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, United States
| | - Cristian Bologa
- Division of Translational Informatics, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, United States
| | - Larry A Sklar
- Department of Pathology, University of New Mexico, School of Medicine, Albuquerque, NM 87131, United States
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17
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Chan CY, Parra KJ. Yeast phosphofructokinase-1 subunit Pfk2p is necessary for pH homeostasis and glucose-dependent vacuolar ATPase reassembly. J Biol Chem 2014; 289:19448-57. [PMID: 24860096 DOI: 10.1074/jbc.m114.569855] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
V-ATPases are conserved ATP-driven proton pumps that acidify organelles. Yeast V-ATPase assembly and activity are glucose-dependent. Glucose depletion causes V-ATPase disassembly and its inactivation. Glucose readdition triggers reassembly and resumes proton transport and organelle acidification. We investigated the roles of the yeast phosphofructokinase-1 subunits Pfk1p and Pfk2p for V-ATPase function. The pfk1Δ and pfk2Δ mutants grew on glucose and assembled wild-type levels of V-ATPase pumps at the membrane. Both phosphofructokinase-1 subunits co-immunoprecipitated with V-ATPase in wild-type cells; upon deletion of one subunit, the other subunit retained binding to V-ATPase. The pfk2Δ cells exhibited a partial vma growth phenotype. In vitro ATP hydrolysis and proton transport were reduced by 35% in pfk2Δ membrane fractions; they were normal in pfk1Δ. In vivo, the pfk1Δ and pfk2Δ vacuoles were alkalinized and the cytosol acidified, suggestive of impaired V-ATPase proton transport. Overall the pH alterations were more dramatic in pfk2Δ than pfk1Δ at steady state and after readdition of glucose to glucose-deprived cells. Glucose-dependent reassembly was 50% reduced in pfk2Δ, and the vacuolar lumen was not acidified after reassembly. RAVE-assisted glucose-dependent reassembly and/or glucose signals were disturbed in pfk2Δ. Binding of disassembled V-ATPase (V1 domain) to its assembly factor RAVE (subunit Rav1p) was 5-fold enhanced, indicating that Pfk2p is necessary for V-ATPase regulation by glucose. Because Pfk1p and Pfk2p are necessary for V-ATPase proton transport at the vacuole in vivo, a role for glycolysis at regulating V-ATPase proton transport is discussed.
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Affiliation(s)
- Chun-Yuan Chan
- From the Department of Biochemistry and Molecular Biology of the School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Karlett J Parra
- From the Department of Biochemistry and Molecular Biology of the School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
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18
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Schlecht U, Suresh S, Xu W, Aparicio AM, Chu A, Proctor MJ, Davis RW, Scharfe C, St Onge RP. A functional screen for copper homeostasis genes identifies a pharmacologically tractable cellular system. BMC Genomics 2014; 15:263. [PMID: 24708151 PMCID: PMC4023593 DOI: 10.1186/1471-2164-15-263] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 03/10/2014] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND Copper is essential for the survival of aerobic organisms. If copper is not properly regulated in the body however, it can be extremely cytotoxic and genetic mutations that compromise copper homeostasis result in severe clinical phenotypes. Understanding how cells maintain optimal copper levels is therefore highly relevant to human health. RESULTS We found that addition of copper (Cu) to culture medium leads to increased respiratory growth of yeast, a phenotype which we then systematically and quantitatively measured in 5050 homozygous diploid deletion strains. Cu's positive effect on respiratory growth was quantitatively reduced in deletion strains representing 73 different genes, the function of which identify increased iron uptake as a cause of the increase in growth rate. Conversely, these effects were enhanced in strains representing 93 genes. Many of these strains exhibited respiratory defects that were specifically rescued by supplementing the growth medium with Cu. Among the genes identified are known and direct regulators of copper homeostasis, genes required to maintain low vacuolar pH, and genes where evidence supporting a functional link with Cu has been heretofore lacking. Roughly half of the genes are conserved in man, and several of these are associated with Mendelian disorders, including the Cu-imbalance syndromes Menkes and Wilson's disease. We additionally demonstrate that pharmacological agents, including the approved drug disulfiram, can rescue Cu-deficiencies of both environmental and genetic origin. CONCLUSIONS A functional screen in yeast has expanded the list of genes required for Cu-dependent fitness, revealing a complex cellular system with implications for human health. Respiratory fitness defects arising from perturbations in this system can be corrected with pharmacological agents that increase intracellular copper concentrations.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Robert P St Onge
- Stanford Genome Technology Center, Department of Biochemistry, Stanford University, 855 S California Avenue, Palo Alto, CA 94304, USA.
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19
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Hayek SR, Lee SA, Parra KJ. Advances in targeting the vacuolar proton-translocating ATPase (V-ATPase) for anti-fungal therapy. Front Pharmacol 2014; 5:4. [PMID: 24478704 PMCID: PMC3902353 DOI: 10.3389/fphar.2014.00004] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2013] [Accepted: 01/06/2014] [Indexed: 11/13/2022] Open
Abstract
Vacuolar proton-translocating ATPase (V-ATPase) is a membrane-bound, multi-subunit enzyme that uses the energy of ATP hydrolysis to pump protons across membranes. V-ATPase activity is critical for pH homeostasis and organelle acidification as well as for generation of the membrane potential that drives secondary transporters and cellular metabolism. V-ATPase is highly conserved across species and is best characterized in the model fungus Saccharomyces cerevisiae. However, recent studies in mammals have identified significant alterations from fungi, particularly in the isoform composition of the 14 subunits and in the regulation of complex disassembly. These differences could be exploited for selectivity between fungi and humans and highlight the potential for V-ATPase as an anti-fungal drug target. Candida albicans is a major human fungal pathogen and causes fatality in 35% of systemic infections, even with anti-fungal treatment. The pathogenicity of C. albicans correlates with environmental, vacuolar, and cytoplasmic pH regulation, and V-ATPase appears to play a fundamental role in each of these processes. Genetic loss of V-ATPase in pathogenic fungi leads to defective virulence, and a comprehensive picture of the mechanisms involved is emerging. Recent studies have explored the practical utility of V-ATPase as an anti-fungal drug target in C. albicans, including pharmacological inhibition, azole therapy, and targeting of downstream pathways. This overview will discuss these studies as well as hypothetical ways to target V-ATPase and novel high-throughput methods for use in future drug discovery screens.
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Affiliation(s)
- Summer R Hayek
- Department of Biochemistry and Molecular Biology, School of Medicine, University of New Mexico Health Sciences Center Albuquerque, NM, USA
| | - Samuel A Lee
- Department of Internal Medicine, School of Medicine, University of New Mexico Health Sciences Center Albuquerque, NM, USA ; Section of Infectious Diseases, New Mexico Veterans Healthcare System Albuquerque, NM, USA
| | - Karlett J Parra
- Department of Biochemistry and Molecular Biology, School of Medicine, University of New Mexico Health Sciences Center Albuquerque, NM, USA
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20
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Patenaude C, Zhang Y, Cormack B, Köhler J, Rao R. Essential role for vacuolar acidification in Candida albicans virulence. J Biol Chem 2013; 288:26256-26264. [PMID: 23884420 DOI: 10.1074/jbc.m113.494815] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fungal infections are on the rise, with mortality above 30% in patients with septic Candida infections. Mutants lacking V-ATPase activity are avirulent and fail to acidify endomembrane compartments, exhibiting pleiotropic defects in secretory, endosomal, and vacuolar pathways. However, the individual contribution of organellar acidification to virulence and its associated traits is not known. To dissect their separate roles in Candida albicans pathogenicity we generated knock-out strains for the V0 subunit a genes VPH1 and STV1, which target the vacuole and secretory pathway, respectively. While the two subunits were redundant in many vma phenotypes, such as alkaline pH sensitivity, calcium homeostasis, respiratory defects, and cell wall integrity, we observed a unique contribution of VPH1. Specifically, vph1Δ was defective in acidification of the vacuole and its dependent functions, such as metal ion sequestration as evidenced by hypersensitivity to Zn(2+) toxicity, whereas stv1Δ resembled wild type. In growth conditions that elicit morphogenic switching, vph1Δ was defective in forming hyphae whereas stv1Δ was normal or only modestly impaired. Host cell interactions were evaluated in vitro using the Caco-2 model of intestinal epithelial cells, and murine macrophages. Like wild type, stv1Δ was able to inflict cellular damage in Caco-2 and macrophage cells, as assayed by LDH release, and escape by filamentation. In contrast, vph1Δ resembled a vma7Δ mutant, with significant attenuation in host cell damage. Finally, we show that VPH1 is required for fungal virulence in a murine model of systemic infection. Our results suggest that vacuolar acidification has an essential function in the ability of C. albicans to form hyphae and establish infection.
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Affiliation(s)
| | | | - Brendan Cormack
- Molecular Biology and Genetics, The Johns Hopkins School of Medicine, Baltimore, Maryland 21205 and
| | - Julia Köhler
- the Division of Infectious Diseases, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
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21
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Diakov TT, Tarsio M, Kane PM. Measurement of vacuolar and cytosolic pH in vivo in yeast cell suspensions. J Vis Exp 2013. [PMID: 23629151 DOI: 10.3791/50261] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Vacuolar and cytosolic pH are highly regulated in yeast cells and occupy a central role in overall pH homeostasis. We describe protocols for ratiometric measurement of pH in vivo using pH-sensitive fluorophores localized to the vacuole or cytosol. Vacuolar pH is measured using BCECF, which localizes to the vacuole in yeast when introduced into cells in its acetoxymethyl ester form. Cytosolic pH is measured with a pH-sensitive GFP expressed under control of a yeast promoter, yeast pHluorin. Methods for measurement of fluorescence ratios in yeast cell suspensions in a fluorimeter are described. Through these protocols, single time point measurements of pH under different conditions or in different yeast mutants have been compared and changes in pH over time have been monitored. These methods have also been adapted to a fluorescence plate reader format for high-throughput experiments. Advantages of ratiometric pH measurements over other approaches currently in use, potential experimental problems and solutions, and prospects for future use of these techniques are also described.
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Affiliation(s)
- Theodore T Diakov
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, USA
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22
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Ferencz C, Petrovszki P, Kóta Z, Fodor-Ayaydin E, Haracska L, Bóta A, Varga Z, Dér A, Marsh D, Páli T. Estimating the rotation rate in the vacuolar proton-ATPase in native yeast vacuolar membranes. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2012; 42:147-58. [PMID: 23160754 DOI: 10.1007/s00249-012-0871-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Revised: 10/10/2012] [Accepted: 10/25/2012] [Indexed: 11/25/2022]
Abstract
The rate of rotation of the rotor in the yeast vacuolar proton-ATPase (V-ATPase), relative to the stator or steady parts of the enzyme, is estimated in native vacuolar membrane vesicles from Saccharomyces cerevisiae under standardised conditions. Membrane vesicles are formed spontaneously after exposing purified yeast vacuoles to osmotic shock. The fraction of total ATPase activity originating from the V-ATPase is determined by using the potent and specific inhibitor of the enzyme, concanamycin A. Inorganic phosphate liberated from ATP in the vacuolar membrane vesicle system, during ten min of ATPase activity at 20 °C, is assayed spectrophotometrically for different concanamycin A concentrations. A fit of the quadratic binding equation, assuming a single concanamycin A binding site on a monomeric V-ATPase (our data are incompatible with models assuming multiple binding sites), to the inhibitor titration curve determines the concentration of the enzyme. Combining this with the known ATP/rotation stoichiometry of the V-ATPase and the assayed concentration of inorganic phosphate liberated by the V-ATPase, leads to an average rate of ~10 Hz for full 360° rotation (and a range of 6-32 Hz, considering the ± standard deviation of the enzyme concentration), which, from the time-dependence of the activity, extrapolates to ~14 Hz (8-48 Hz) at the beginning of the reaction. These are lower-limit estimates. To our knowledge, this is the first report of the rotation rate in a V-ATPase that is not subjected to genetic or chemical modification and is not fixed to a solid support; instead it is functioning in its native membrane environment.
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Affiliation(s)
- Csilla Ferencz
- Institute of Biophysics, Biological Research Centre, Temesvári krt. 62, 6726, Szeged, Hungary
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23
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Parsons LS, Wilkens S. Probing subunit-subunit interactions in the yeast vacuolar ATPase by peptide arrays. PLoS One 2012; 7:e46960. [PMID: 23071676 PMCID: PMC3470569 DOI: 10.1371/journal.pone.0046960] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Accepted: 09/07/2012] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Vacuolar (H(+))-ATPase (V-ATPase; V(1)V(o)-ATPase) is a large multisubunit enzyme complex found in the endomembrane system of all eukaryotic cells where its proton pumping action serves to acidify subcellular organelles. In the plasma membrane of certain specialized tissues, V-ATPase functions to pump protons from the cytoplasm into the extracellular space. The activity of the V-ATPase is regulated by a reversible dissociation mechanism that involves breaking and re-forming of protein-protein interactions in the V(1)-ATPase - V(o)-proton channel interface. The mechanism responsible for regulated V-ATPase dissociation is poorly understood, largely due to a lack of detailed knowledge of the molecular interactions that are responsible for the structural and functional link between the soluble ATPase and membrane bound proton channel domains. METHODOLOGY/PRINCIPAL FINDINGS To gain insight into where some of the stator subunits of the V-ATPase associate with each other, we have developed peptide arrays from the primary sequences of V-ATPase subunits. By probing the peptide arrays with individually expressed V-ATPase subunits, we have identified several key interactions involving stator subunits E, G, C, H and the N-terminal domain of the membrane bound a subunit. CONCLUSIONS The subunit-peptide interactions identified from the peptide arrays complement low resolution structural models of the eukaryotic vacuolar ATPase obtained from transmission electron microscopy. The subunit-subunit interaction data are discussed in context of our current model of reversible enzyme dissociation.
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Affiliation(s)
- Lee S. Parsons
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, United States of America
| | - Stephan Wilkens
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, United States of America
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24
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Richards A, Gow NAR, Veses V. Identification of vacuole defects in fungi. J Microbiol Methods 2012; 91:155-63. [PMID: 22902527 DOI: 10.1016/j.mimet.2012.08.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2012] [Revised: 07/30/2012] [Accepted: 08/02/2012] [Indexed: 11/25/2022]
Abstract
Fungal vacuoles are involved in a diverse range of cellular functions, participating in cellular homeostasis, degradation of intracellular components, and storage of ions and molecules. In recent years there has been a significant increase in the number of studies linking these organelles with the regulation of growth and control of cellular morphology, particularly in those fungal species able to undergo yeast-hypha morphogenetic transitions. This has contributed to the refinement of previously published protocols and the development of new techniques, particularly in the area of live-cell imaging of membrane trafficking events and vacuolar dynamics. The current review outlines recent advances in the imaging of fungal vacuoles and assays for characterization of trafficking pathways, and other physiological activities of this important cell organelle.
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Affiliation(s)
- Andrea Richards
- The Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, United Kingdom
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25
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Polireddy K, Khan MMT, Chavan H, Young S, Ma X, Waller A, Garcia M, Perez D, Chavez S, Strouse JJ, Haynes MK, Bologa CG, Oprea TI, Tegos GP, Sklar LA, Krishnamurthy P. A novel flow cytometric HTS assay reveals functional modulators of ATP binding cassette transporter ABCB6. PLoS One 2012; 7:e40005. [PMID: 22808084 PMCID: PMC3393737 DOI: 10.1371/journal.pone.0040005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 05/30/2012] [Indexed: 11/18/2022] Open
Abstract
ABCB6 is a member of the adenosine triphosphate (ATP)-binding cassette family of transporter proteins that is increasingly recognized as a relevant physiological and therapeutic target. Evaluation of modulators of ABCB6 activity would pave the way toward a more complete understanding of the significance of this transport process in tumor cell growth, proliferation and therapy-related drug resistance. In addition, this effort would improve our understanding of the function of ABCB6 in normal physiology with respect to heme biosynthesis, and cellular adaptation to metabolic demand and stress responses. To search for modulators of ABCB6, we developed a novel cell-based approach that, in combination with flow cytometric high-throughput screening (HTS), can be used to identify functional modulators of ABCB6. Accumulation of protoporphyrin, a fluorescent molecule, in wild-type ABCB6 expressing K562 cells, forms the basis of the HTS assay. Screening the Prestwick Chemical Library employing the HTS assay identified four compounds, benzethonium chloride, verteporfin, tomatine hydrochloride and piperlongumine, that reduced ABCB6 mediated cellular porphyrin levels. Validation of the identified compounds employing the hemin-agarose affinity chromatography and mitochondrial transport assays demonstrated that three out of the four compounds were capable of inhibiting ABCB6 mediated hemin transport into isolated mitochondria. However, only verteporfin and tomatine hydrochloride inhibited ABCB6's ability to compete with hemin as an ABCB6 substrate. This assay is therefore sensitive, robust, and suitable for automation in a high-throughput environment as demonstrated by our identification of selective functional modulators of ABCB6. Application of this assay to other libraries of synthetic compounds and natural products is expected to identify novel modulators of ABCB6 activity.
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Affiliation(s)
- Kishore Polireddy
- Department of Pharmacology, Toxicology, and Therapeutics, The University of Kansas Medical Center, Kansas City, Kansas, United States of America
| | - Mohiuddin Md. Taimur Khan
- Center for Molecular Discovery, University of New Mexico, Albuquerque, New Mexico, United States of America
- Division of Biocomputing, University of New Mexico Health Sciences Center, Albuquerque, New Mexico, United States of America
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, New Mexico, United States of America
| | - Hemantkumar Chavan
- Department of Pharmacology, Toxicology, and Therapeutics, The University of Kansas Medical Center, Kansas City, Kansas, United States of America
| | - Susan Young
- Center for Molecular Discovery, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Xiaochao Ma
- Department of Pharmacology, Toxicology, and Therapeutics, The University of Kansas Medical Center, Kansas City, Kansas, United States of America
| | - Anna Waller
- Center for Molecular Discovery, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Matthew Garcia
- Center for Molecular Discovery, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Dominique Perez
- Center for Molecular Discovery, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Stephanie Chavez
- Center for Molecular Discovery, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Jacob J. Strouse
- Center for Molecular Discovery, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Mark K. Haynes
- Center for Molecular Discovery, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Cristian G. Bologa
- Center for Molecular Discovery, University of New Mexico, Albuquerque, New Mexico, United States of America
- Division of Biocomputing, University of New Mexico Health Sciences Center, Albuquerque, New Mexico, United States of America
| | - Tudor I. Oprea
- Center for Molecular Discovery, University of New Mexico, Albuquerque, New Mexico, United States of America
- Division of Biocomputing, University of New Mexico Health Sciences Center, Albuquerque, New Mexico, United States of America
| | - George P. Tegos
- Center for Molecular Discovery, University of New Mexico, Albuquerque, New Mexico, United States of America
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, New Mexico, United States of America
- Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Dermatology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Larry A. Sklar
- Center for Molecular Discovery, University of New Mexico, Albuquerque, New Mexico, United States of America
- Division of Biocomputing, University of New Mexico Health Sciences Center, Albuquerque, New Mexico, United States of America
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, New Mexico, United States of America
| | - Partha Krishnamurthy
- Department of Pharmacology, Toxicology, and Therapeutics, The University of Kansas Medical Center, Kansas City, Kansas, United States of America
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Chan CY, Prudom C, Raines SM, Charkhzarrin S, Melman SD, De Haro LP, Allen C, Lee SA, Sklar LA, Parra KJ. Inhibitors of V-ATPase proton transport reveal uncoupling functions of tether linking cytosolic and membrane domains of V0 subunit a (Vph1p). J Biol Chem 2012; 287:10236-10250. [PMID: 22215674 DOI: 10.1074/jbc.m111.321133] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Vacuolar ATPases (V-ATPases) are important for many cellular processes, as they regulate pH by pumping cytosolic protons into intracellular organelles. The cytoplasm is acidified when V-ATPase is inhibited; thus we conducted a high-throughput screen of a chemical library to search for compounds that acidify the yeast cytosol in vivo using pHluorin-based flow cytometry. Two inhibitors, alexidine dihydrochloride (EC(50) = 39 μM) and thonzonium bromide (EC(50) = 69 μM), prevented ATP-dependent proton transport in purified vacuolar membranes. They acidified the yeast cytosol and caused pH-sensitive growth defects typical of V-ATPase mutants (vma phenotype). At concentrations greater than 10 μM the inhibitors were cytotoxic, even at the permissive pH (pH 5.0). Membrane fractions treated with alexidine dihydrochloride and thonzonium bromide fully retained concanamycin A-sensitive ATPase activity despite the fact that proton translocation was inhibited by 80-90%, indicating that V-ATPases were uncoupled. Mutant V-ATPase membranes lacking residues 362-407 of the tether of Vph1p subunit a of V(0) were resistant to thonzonium bromide but not to alexidine dihydrochloride, suggesting that this conserved sequence confers uncoupling potential to V(1)V(0) complexes and that alexidine dihydrochloride uncouples the enzyme by a different mechanism. The inhibitors also uncoupled the Candida albicans enzyme and prevented cell growth, showing further specificity for V-ATPases. Thus, a new class of V-ATPase inhibitors (uncouplers), which are not simply ionophores, provided new insights into the enzyme mechanism and original evidence supporting the hypothesis that V-ATPases may not be optimally coupled in vivo. The consequences of uncoupling V-ATPases in vivo as potential drug targets are discussed.
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Affiliation(s)
- Chun-Yuan Chan
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Catherine Prudom
- Center for Molecular Discovery, School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Summer M Raines
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Sahba Charkhzarrin
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Sandra D Melman
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Leyma P De Haro
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Chris Allen
- Center for Molecular Discovery, School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Samuel A Lee
- Department of Internal Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Larry A Sklar
- Center for Molecular Discovery, School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131; Department of Pathology and Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Karlett J Parra
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131.
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Tegos GP, Haynes M, Strouse JJ, Khan MMT, Bologa CG, Oprea TI, Sklar LA. Microbial efflux pump inhibition: tactics and strategies. Curr Pharm Des 2011; 17:1291-302. [PMID: 21470111 DOI: 10.2174/138161211795703726] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Accepted: 03/21/2011] [Indexed: 11/22/2022]
Abstract
Traditional antimicrobials are increasingly suffering from the emergence of multidrug resistance among pathogenic microorganisms. To overcome these deficiencies, a range of novel approaches to control microbial infections are under investigation as potential alternative treatments. Multidrug efflux is a key target of these efforts. Efflux mechanisms are broadly recognized as major components of resistance to many classes of chemotherapeutic agents as well as antimicrobials. Efflux occurs due to the activity of membrane transporter proteins widely known as Multidrug Efflux Systems (MES). They are implicated in a variety of physiological roles other than efflux and identifying natural substrates and inhibitors is an active and expanding research discipline. One plausible alternative is the combination of conventional antimicrobial agents/antibiotics with small molecules that block MES known as multidrug efflux pump inhibitors (EPIs). An array of approaches in academic and industrial research settings, varying from high-throughput screening (HTS) ventures to bioassay guided purification and determination, have yielded a number of promising EPIs in a series of pathogenic systems. This synergistic discovery platform has been exploited in translational directions beyond the potentiation of conventional antimicrobial treatments. This venture attempts to highlight different tactical elements of this platform, identifying the need for highly informative and comprehensive EPI-discovery strategies. Advances in assay development genomics, proteomics as well as the accumulation of bioactivity and structural information regarding MES facilitates the basis for a new discovery era. This platform is expanding drastically. A combination of chemogenomics and chemoinformatics approaches will integrate data mining with virtual and physical HTS ventures and populate the chemical-biological interface with a plethora of novel chemotypes. This comprehensive step will expedite the preclinical development of lead EPIs.
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Affiliation(s)
- George P Tegos
- Center for Molecular Discovery, University of New Mexico, Albuquerque, NM 87131, USA.
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Ding J, Zhang L, Qu F, Ren X, Zhao X, Liu Q. Cell activity analysis by capillary zone electrophoresis combined with specific cell staining. Electrophoresis 2010; 32:455-63. [DOI: 10.1002/elps.201000324] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2010] [Revised: 10/12/2010] [Accepted: 10/28/2010] [Indexed: 11/08/2022]
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29
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Current awareness on yeast. Yeast 2010. [DOI: 10.1002/yea.1719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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