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Pourpre R, Lakisic G, Desgranges E, Cossart P, Pagliuso A, Bierne H. A bacterial virulence factor interacts with the splicing factor RBM5 and stimulates formation of nuclear RBM5 granules. Sci Rep 2022; 12:21961. [PMID: 36535993 PMCID: PMC9763339 DOI: 10.1038/s41598-022-26037-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 12/08/2022] [Indexed: 12/23/2022] Open
Abstract
L. monocytogenes causes listeriosis, a foodborne disease that is particularly dangerous for immunocompromised individuals and fetuses. Several virulence factors of this bacterial pathogen belong to a family of leucine-rich repeat (LRR)-containing proteins called internalins. Among these, InlP is known for its role in placental infection. We report here a function of InlP in mammalian cell nucleus organization. We demonstrate that bacteria do not produce InlP under in vitro culture conditions. When ectopically expressed in human cells, InlP translocates into the nucleus and changes the morphology of nuclear speckles, which are membrane-less organelles storing splicing factors. Using yeast two-hybrid screen, immunoprecipitation and pull-down experiments, we identify the tumor suppressor and splicing factor RBM5 as a major nuclear target of InlP. InlP inhibits RBM5-induced cell death and stimulate the formation of RBM5-induced nuclear granules, where the SC35 speckle protein redistributes. Taken together, these results suggest that InlP acts as a nucleomodulin controlling compartmentalization and function of RBM5 in the nucleus and that L. monocytogenes has developed a mechanism to target the host cell splicing machinery.
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Affiliation(s)
- Renaud Pourpre
- grid.462293.80000 0004 0522 0627Université Paris-Saclay, INRAE, Micalis Institute, EpiMic Lab, Jouy-en-Josas, AgroParisTech France
| | - Goran Lakisic
- grid.462293.80000 0004 0522 0627Université Paris-Saclay, INRAE, Micalis Institute, EpiMic Lab, Jouy-en-Josas, AgroParisTech France
| | - Emma Desgranges
- grid.462293.80000 0004 0522 0627Université Paris-Saclay, INRAE, Micalis Institute, EpiMic Lab, Jouy-en-Josas, AgroParisTech France
| | - Pascale Cossart
- grid.428999.70000 0001 2353 6535Institut Pasteur, Paris, France
| | - Alessandro Pagliuso
- grid.462293.80000 0004 0522 0627Université Paris-Saclay, INRAE, Micalis Institute, EpiMic Lab, Jouy-en-Josas, AgroParisTech France
| | - Hélène Bierne
- grid.462293.80000 0004 0522 0627Université Paris-Saclay, INRAE, Micalis Institute, EpiMic Lab, Jouy-en-Josas, AgroParisTech France
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Cohen SK, Aschtgen MS, Lynch JB, Koehler S, Chen F, Escrig S, Daraspe J, Ruby EG, Meibom A, McFall-Ngai M. Tracking the cargo of extracellular symbionts into host tissues with correlated electron microscopy and nanoscale secondary ion mass spectrometry imaging. Cell Microbiol 2021; 22:e13177. [PMID: 32185893 DOI: 10.1111/cmi.13177] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 01/18/2020] [Accepted: 01/23/2020] [Indexed: 12/14/2022]
Abstract
Extracellular bacterial symbionts communicate biochemically with their hosts to establish niches that foster the partnership. Using quantitative ion microprobe isotopic imaging (nanoscale secondary ion mass spectrometry [NanoSIMS]), we surveyed localization of 15 N-labelled molecules produced by the bacterium Vibrio fischeri within the cells of the symbiotic organ of its host, the Hawaiian bobtail squid, and compared that with either labelled non-specific species or amino acids. In all cases, two areas of the organ's epithelia were significantly more 15 N enriched: (a) surface ciliated cells, where environmental symbionts are recruited, and (b) the organ's crypts, where the symbiont population resides in the host. Label enrichment in all cases was strongest inside host cell nuclei, preferentially in the euchromatin regions and the nucleoli. This permissiveness demonstrated that uptake of biomolecules is a general mechanism of the epithelia, but the specific responses to V. fischeri cells recruited to the organ's surface are due to some property exclusive to this species. Similarly, in the organ's deeper crypts, the host responds to common bacterial products that only the specific symbiont can present in that location. The application of NanoSIMS allows the discovery of such distinct modes of downstream signalling dependent on location within the host and provides a unique opportunity to study the microbiogeographical patterns of symbiotic dialogue.
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Affiliation(s)
- Stephanie K Cohen
- Laboratory of Biological Geochemistry, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Marie-Stéphanie Aschtgen
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin
| | - Jonathan B Lynch
- Kewalo Marine Laboratory, University of Hawai'i at Mānoa, Honolulu, Hawai'i
| | - Sabrina Koehler
- Kewalo Marine Laboratory, University of Hawai'i at Mānoa, Honolulu, Hawai'i
| | - Fangmin Chen
- Kewalo Marine Laboratory, University of Hawai'i at Mānoa, Honolulu, Hawai'i
| | - Stéphane Escrig
- Laboratory of Biological Geochemistry, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Jean Daraspe
- Electron Microscopy Facility, University of Lausanne, Lausanne, Switzerland
| | - Edward G Ruby
- Kewalo Marine Laboratory, University of Hawai'i at Mānoa, Honolulu, Hawai'i
| | - Anders Meibom
- Laboratory of Biological Geochemistry, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.,Center for Advanced Surface Analysis, Institute of Earth Sciences, University of Lausanne, Lausanne, Switzerland
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Guillonneau R, Baraquet C, Molmeret M. Marine Bacteria Display Different Escape Mechanisms When Facing Their Protozoan Predators. Microorganisms 2020; 8:microorganisms8121982. [PMID: 33322808 PMCID: PMC7763514 DOI: 10.3390/microorganisms8121982] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 11/24/2020] [Accepted: 12/10/2020] [Indexed: 12/20/2022] Open
Abstract
Free-living amoeba are members of microbial communities such as biofilms in terrestrial, fresh, and marine habitats. Although they are known to live in close association with bacteria in many ecosystems such as biofilms, they are considered to be major bacterial predators in many ecosystems. Little is known on the relationship between protozoa and marine bacteria in microbial communities, more precisely on how bacteria are able survive in environmental niches where these bacterial grazers also live. The objective of this work is to study the interaction between the axenized ubiquitous amoeba Acanthamoeba castellanii and four marine bacteria isolated from immersed biofilm, in order to evaluate if they would be all grazed upon by amoeba or if they would be able to survive in the presence of their predator. At a low bacteria-to-amoeba ratio, we show that each bacterium is phagocytized and follows a singular intracellular path within this host cell, which appears to delay or to prevent bacterial digestion. In particular, one of the bacteria was found in the amoeba nucleolar compartment whereas another strain was expelled from the amoeba in vesicles. We then looked at the fate of the bacteria grown in a higher bacteria-to-amoeba ratio, as a preformed mono- or multi-species biofilm in the presence of A. castellanii. We show that all biofilms were subjected to detachment from the surface in the presence of the amoeba or its supernatant. Overall, these results show that bacteria, when facing the same predator, exhibit a variety of escape mechanisms at the cellular and population level, when we could have expected a simple bacterial grazing. Therefore, this study unravels new insights into the survival of environmental bacteria when facing predators that they could encounter in the same microbial communities.
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Affiliation(s)
- Richard Guillonneau
- Laboratoire MAPIEM, EA4323, Université de Toulon, 83130 La Garde, France; (R.G.); (C.B.)
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK
| | - Claudine Baraquet
- Laboratoire MAPIEM, EA4323, Université de Toulon, 83130 La Garde, France; (R.G.); (C.B.)
| | - Maëlle Molmeret
- Laboratoire MAPIEM, EA4323, Université de Toulon, 83130 La Garde, France; (R.G.); (C.B.)
- Correspondence:
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Bacterial Factors Targeting the Nucleus: The Growing Family of Nucleomodulins. Toxins (Basel) 2020; 12:toxins12040220. [PMID: 32244550 PMCID: PMC7232420 DOI: 10.3390/toxins12040220] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Revised: 03/23/2020] [Accepted: 03/29/2020] [Indexed: 12/18/2022] Open
Abstract
Pathogenic bacteria secrete a variety of proteins that manipulate host cell function by targeting components of the plasma membrane, cytosol, or organelles. In the last decade, several studies identified bacterial factors acting within the nucleus on gene expression or other nuclear processes, which has led to the emergence of a new family of effectors called “nucleomodulins”. In human and animal pathogens, Listeria monocytogenes for Gram-positive bacteria and Anaplasma phagocytophilum, Ehrlichia chaffeensis, Chlamydia trachomatis, Legionella pneumophila, Shigella flexneri, and Escherichia coli for Gram-negative bacteria, have led to pioneering discoveries. In this review, we present these paradigms and detail various mechanisms and core elements (e.g., DNA, histones, epigenetic regulators, transcription or splicing factors, signaling proteins) targeted by nucleomodulins. We particularly focus on nucleomodulins interacting with epifactors, such as LntA of Listeria and ankyrin repeat- or tandem repeat-containing effectors of Rickettsiales, and nucleomodulins from various bacterial species acting as post-translational modification enzymes. The study of bacterial nucleomodulins not only generates important knowledge about the control of host responses by microbes but also creates new tools to decipher the dynamic regulations that occur in the nucleus. This research also has potential applications in the field of biotechnology. Finally, this raises questions about the epigenetic effects of infectious diseases.
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Frank AC. Molecular host mimicry and manipulation in bacterial symbionts. FEMS Microbiol Lett 2019; 366:5342066. [PMID: 30877310 DOI: 10.1093/femsle/fnz038] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 02/18/2019] [Indexed: 12/17/2022] Open
Abstract
It is common among intracellular bacterial pathogens to use eukaryotic-like proteins that mimic and manipulate host cellular processes to promote colonization and intracellular survival. Eukaryotic-like proteins are bacterial proteins with domains that are rare in bacteria, and known to function in the context of a eukaryotic cell. Such proteins can originate through horizontal gene transfer from eukaryotes or, in the case of simple repeat proteins, through convergent evolution. Recent studies of microbiomes associated with several eukaryotic hosts suggest that similar molecular strategies are deployed by cooperative bacteria that interact closely with eukaryotic cells. Some mimics, like ankyrin repeats, leucine rich repeats and tetratricopeptide repeats are shared across diverse symbiotic systems ranging from amoebae to plants, and may have originated early, or evolved independently in multiple systems. Others, like plant-mimicking domains in members of the plant microbiome are likely to be more recent innovations resulting from horizontal gene transfer from the host, or from microbial eukaryotes occupying the same host. Host protein mimics have only been described in a limited set of symbiotic systems, but are likely to be more widespread. Systematic searches for eukaryote-like proteins in symbiont genomes could lead to the discovery of novel mechanisms underlying host-symbiont interactions.
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Affiliation(s)
- A Carolin Frank
- Life and Environmental Sciences, 5200 North Lake Rd, University of California Merced, Merced, CA 95343, USA.,Sierra Nevada Research Institute, School of Natural Sciences, 5200 North Lake Rd, University of California Merced, Merced, CA 95343, USA
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7
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Vitamin C in Stem Cell Biology: Impact on Extracellular Matrix Homeostasis and Epigenetics. Stem Cells Int 2017; 2017:8936156. [PMID: 28512473 PMCID: PMC5415867 DOI: 10.1155/2017/8936156] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 03/05/2017] [Indexed: 12/30/2022] Open
Abstract
Transcription factors and signaling molecules are well-known regulators of stem cell identity and behavior; however, increasing evidence indicates that environmental cues contribute to this complex network of stimuli, acting as crucial determinants of stem cell fate. l-Ascorbic acid (vitamin C (VitC)) has gained growing interest for its multiple functions and mechanisms of action, contributing to the homeostasis of normal tissues and organs as well as to tissue regeneration. Here, we review the main functions of VitC and its effects on stem cells, focusing on its activity as cofactor of Fe+2/αKG dioxygenases, which regulate the epigenetic signatures, the redox status, and the extracellular matrix (ECM) composition, depending on the enzymes' subcellular localization. Acting as cofactor of collagen prolyl hydroxylases in the endoplasmic reticulum, VitC regulates ECM/collagen homeostasis and plays a key role in the differentiation of mesenchymal stem cells towards osteoblasts, chondrocytes, and tendons. In the nucleus, VitC enhances the activity of DNA and histone demethylases, improving somatic cell reprogramming and pushing embryonic stem cell towards the naive pluripotent state. The broad spectrum of actions of VitC highlights its relevance for stem cell biology in both physiology and disease.
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Brooks WH, Renaudineau Y. Epigenetics and autoimmune diseases: the X chromosome-nucleolus nexus. Front Genet 2015; 6:22. [PMID: 25763008 PMCID: PMC4329817 DOI: 10.3389/fgene.2015.00022] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Accepted: 01/16/2015] [Indexed: 12/18/2022] Open
Abstract
Autoimmune diseases occur more often in females, suggesting a key role for the X chromosome. X chromosome inactivation, a major epigenetic feature in female cells that provides dosage compensation of X-linked genes to avoid overexpression, presents special vulnerabilities that can contribute to the disease process. Disruption of X inactivation can result in loss of dosage compensation with expression from previously sequestered genes, imbalance of gene products, and altered endogenous material out of normal epigenetic context. In addition, the human X has significant differences compared to other species and these differences can contribute to the frequency and intensity of the autoimmune disease in humans as well as the types of autoantigens encountered. Here a link is demonstrated between autoimmune diseases, such as systemic lupus erythematosus, and the X chromosome by discussing cases in which typically non-autoimmune disorders complicated with X chromosome abnormalities also present lupus-like symptoms. The discussion is then extended to the reported spatial and temporal associations of the inactive X chromosome with the nucleolus. When frequent episodes of cellular stress occur, the inactive X chromosome may be disrupted and inadvertently become involved in the nucleolar stress response. Development of autoantigens, many of which are at least transiently components of the nucleolus, is then described. Polyamines, which aid in nucleoprotein complex assembly in the nucleolus, increase further during cell stress, and appear to have an important role in the autoimmune disease process. Autoantigenic endogenous material can potentially be stabilized by polyamines. This presents a new paradigm for autoimmune diseases: that many are antigen-driven and the autoantigens originate from altered endogenous material due to episodes of cellular stress that disrupt epigenetic control. This suggests that epigenetics and the X chromosome are important aspects of autoimmune diseases.
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Affiliation(s)
- Wesley H Brooks
- Department of Chemistry, University of South Florida Tampa, FL, USA
| | - Yves Renaudineau
- Research Unit INSERM ERI29/EA2216, SFR ScinBios, Labex Igo "Immunotherapy Graft, Oncology", Réseau Épigénétique et Réseau Canaux Ioniques du Cancéropole Grand Ouest, European University of Brittany Brest, France ; Laboratory of Immunology and Immunotherapy, Hôpital Morvan Brest, France
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9
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Michard C, Doublet P. Post-translational modifications are key players of the Legionella pneumophila infection strategy. Front Microbiol 2015; 6:87. [PMID: 25713573 PMCID: PMC4322725 DOI: 10.3389/fmicb.2015.00087] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 01/23/2015] [Indexed: 11/13/2022] Open
Abstract
Post-translational modifications (PTMs) are widely used by eukaryotes to control the enzymatic activity, localization or stability of their proteins. Traditionally, it was believed that the broad biochemical diversity of the PTMs is restricted to eukaryotic cells, which exploit it in extensive networks to fine-tune various and complex cellular functions. During the last decade, the advanced detection methods of PTMs and functional studies of the host-pathogen relationships highlight that bacteria have also developed a large arsenal of PTMs, particularly to subvert host cell pathways to their benefit. Legionella pneumophila, the etiological agent of the severe pneumonia legionellosis, is the paradigm of highly adapted intravacuolar pathogens that have set up sophisticated biochemical strategies. Among them, L. pneumophila has evolved eukaryotic-like and rare/novel PTMs to hijack host cell processes. Here, we review recent progress about the diversity of PTMs catalyzed by Legionella: ubiquitination, prenylation, phosphorylation, glycosylation, methylation, AMPylation, and de-AMPylation, phosphocholination, and de-phosphocholination. We focus on the host cell pathways targeted by the bacteria catalyzed PTMs and we stress the importance of the PTMs in the Legionella infection strategy. Finally, we highlight that the discovery of these PTMs undoubtedly made significant breakthroughs on the molecular basis of Legionella pathogenesis but also lead the way in improving our knowledge of the eukaryotic PTMs and complex cellular processes that are associated to.
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Affiliation(s)
- Céline Michard
- Legionella Pathogenesis Group, International Center for Infectiology Research, Université de Lyon Lyon, France ; INSERM U1111 Lyon, France ; Ecole Normale Supérieure de Lyon Lyon, France ; Centre International de Recherche en Infectiologie, Université Lyon 1 Lyon, France ; Centre National de la Recherche Scientifique, UMR5308 Lyon, France
| | - Patricia Doublet
- Legionella Pathogenesis Group, International Center for Infectiology Research, Université de Lyon Lyon, France ; INSERM U1111 Lyon, France ; Ecole Normale Supérieure de Lyon Lyon, France ; Centre International de Recherche en Infectiologie, Université Lyon 1 Lyon, France ; Centre National de la Recherche Scientifique, UMR5308 Lyon, France
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Stilling RM, Bordenstein SR, Dinan TG, Cryan JF. Friends with social benefits: host-microbe interactions as a driver of brain evolution and development? Front Cell Infect Microbiol 2014; 4:147. [PMID: 25401092 PMCID: PMC4212686 DOI: 10.3389/fcimb.2014.00147] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 10/03/2014] [Indexed: 12/21/2022] Open
Abstract
The tight association of the human body with trillions of colonizing microbes that we observe today is the result of a long evolutionary history. Only very recently have we started to understand how this symbiosis also affects brain function and behavior. In this hypothesis and theory article, we propose how host-microbe associations potentially influenced mammalian brain evolution and development. In particular, we explore the integration of human brain development with evolution, symbiosis, and RNA biology, which together represent a “social triangle” that drives human social behavior and cognition. We argue that, in order to understand how inter-kingdom communication can affect brain adaptation and plasticity, it is inevitable to consider epigenetic mechanisms as important mediators of genome-microbiome interactions on an individual as well as a transgenerational time scale. Finally, we unite these interpretations with the hologenome theory of evolution. Taken together, we propose a tighter integration of neuroscience fields with host-associated microbiology by taking an evolutionary perspective.
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Affiliation(s)
- Roman M Stilling
- Alimentary Pharmabiotic Centre, University College Cork Cork, Ireland ; Department Anatomy and Neuroscience, University College Cork Cork, Ireland
| | - Seth R Bordenstein
- Departments of Biological Sciences and Pathology, Microbiology, and Immunology, Vanderbilt University Nashville, TN, USA
| | - Timothy G Dinan
- Alimentary Pharmabiotic Centre, University College Cork Cork, Ireland ; Department of Psychiatry, University College Cork Cork, Ireland
| | - John F Cryan
- Alimentary Pharmabiotic Centre, University College Cork Cork, Ireland ; Department Anatomy and Neuroscience, University College Cork Cork, Ireland
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Stilling RM, Dinan TG, Cryan JF. Microbial genes, brain & behaviour - epigenetic regulation of the gut-brain axis. GENES BRAIN AND BEHAVIOR 2013; 13:69-86. [PMID: 24286462 DOI: 10.1111/gbb.12109] [Citation(s) in RCA: 406] [Impact Index Per Article: 36.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 11/13/2013] [Accepted: 11/25/2013] [Indexed: 12/12/2022]
Abstract
To date, there is rapidly increasing evidence for host-microbe interaction at virtually all levels of complexity, ranging from direct cell-to-cell communication to extensive systemic signalling, and involving various organs and organ systems, including the central nervous system. As such, the discovery that differential microbial composition is associated with alterations in behaviour and cognition has significantly contributed to establishing the microbiota-gut-brain axis as an extension of the well-accepted gut-brain axis concept. Many efforts have been focused on delineating a role for this axis in health and disease, ranging from stress-related disorders such as depression, anxiety and irritable bowel syndrome to neurodevelopmental disorders such as autism. There is also a growing appreciation of the role of epigenetic mechanisms in shaping brain and behaviour. However, the role of epigenetics in informing host-microbe interactions has received little attention to date. This is despite the fact that there are many plausible routes of interaction between epigenetic mechanisms and the host-microbiota dialogue. From this new perspective we put forward novel, yet testable, hypotheses. Firstly, we suggest that gut-microbial products can affect chromatin plasticity within their host's brain that in turn leads to changes in neuronal transcription and eventually alters host behaviour. Secondly, we argue that the microbiota is an important mediator of gene-environment interactions. Finally, we reason that the microbiota itself may be viewed as an epigenetic entity. In conclusion, the fields of (neuro)epigenetics and microbiology are converging at many levels and more interdisciplinary studies are necessary to unravel the full range of this interaction.
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Su H, Kodiha M, Lee S, Stochaj U. Identification of novel markers that demarcate the nucleolus during severe stress and chemotherapeutic treatment. PLoS One 2013; 8:e80237. [PMID: 24223222 PMCID: PMC3819286 DOI: 10.1371/journal.pone.0080237] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 10/01/2013] [Indexed: 01/08/2023] Open
Abstract
The nucleolus, the ribosomal factory of the cell, has emerged as a key player that regulates many aspects of cell biology. Several thousand proteins associate at least transiently with nucleoli, thereby generating a highly dynamic compartment with a protein profile which is sensitive to changes in cell physiology and pharmacological agents. Powerful tools that reliably demarcate the nucleoli are a prerequisite to measure their composition and activities. Previously, we developed quantitative methods to measure fluorescently labeled molecules in nucleoli. While these tools identify nucleoli under control and mild stress conditions, the accurate detection of nucleolar boundaries under harsh experimental conditions is complicated by the lack of appropriate markers for the nucleolar compartment. Using fluorescence microscopy we have now identified new marker proteins to detect nucleoli upon (a) severe stress and (b) drug treatments that trigger a pronounced reorganization of nucleoli. Our results demonstrate that nucleolin is an ideal marker to delimit nucleoli when cells are exposed to heat or oxidative stress. Furthermore, we show for the first time that cellular apoptosis susceptibility protein (CAS) and human antigen R protein (HuR) are excluded from nucleoli and can be employed to delimit these compartments under severe conditions that redistribute major nucleolar proteins. As proof-of-principle, we used these markers to demarcate nucleoli in cells treated with pharmacological compounds that disrupt the nucleolar organization. Furthermore, to gain new insights into the biology of the nucleolus, we applied our protocols and quantified stress- and drug-induced changes in nucleolar organization and function. Finally, we show that CAS, HuR and nucleolin not only identify nucleoli in optical sections, but are also suitable to demarcate the nucleolar border following 3D reconstruction. Taken together, our studies present novel marker proteins that delimit nucleoli with high confidence under a variety of experimental settings.
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Affiliation(s)
- Haitong Su
- McGill University, Department of Physiology, Montreal, Quebec, Canada
| | - Mohamed Kodiha
- McGill University, Department of Physiology, Montreal, Quebec, Canada
| | - Sunghoon Lee
- McGill University, Department of Physiology, Montreal, Quebec, Canada
| | - Ursula Stochaj
- McGill University, Department of Physiology, Montreal, Quebec, Canada
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