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Kim S, Isberg RR. The Sde phosphoribosyl-linked ubiquitin transferases protect the Legionella pneumophila vacuole from degradation by the host. Proc Natl Acad Sci U S A 2023; 120:e2303942120. [PMID: 37549300 PMCID: PMC10437418 DOI: 10.1073/pnas.2303942120] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 07/05/2023] [Indexed: 08/09/2023] Open
Abstract
Legionella pneumophila grows intracellularly within the membrane-bound Legionella-containing vacuole (LCV) established by proteins translocated via the bacterial type IV secretion system (T4SS). The Sde family, one such group of translocated proteins, catalyzes phosphoribosyl-ubiquitin (pR-Ub) modification of target substrates. Mutational loss of the entire Sde family results in small defects in intracellular growth, making it difficult to identify a clear role for this posttranslational modification in supporting the intracellular lifestyle. Therefore, mutations that aggravate the loss of sde genes and caused intracellular growth defects were identified, providing a mechanistic connection between Sde function and vacuole biogenesis. These double mutants drove the formation of LCVs that showed vacuole disintegration within 2 h of bacterial contact. Sde proteins appeared critical for blocking access of membrane-disruptive early endosomal membrane material to the vacuole, as RNAi depletion of endosomal pathway components partially restored LCV integrity. The role of Sde proteins in preventing host degradation of the LCV was limited to the earliest stages of infection. The time that Sde proteins could prevent vacuole disruption, however, was extended by deletion of sidJ, which encodes a translocated protein that inactivates Sde protein active sites. These results indicate that Sde proteins act as temporally regulated vacuole guards during the establishment of the replication niche, possibly by constructing a physical barrier that blocks access of disruptive host compartments during the earliest steps of LCV biogenesis.
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Affiliation(s)
- Seongok Kim
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA02111
| | - Ralph R. Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA02111
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Iyer K, Erkert L, Becker C. Know your neighbors: microbial recognition at the intestinal barrier and its implications for gut homeostasis and inflammatory bowel disease. Front Cell Dev Biol 2023; 11:1228283. [PMID: 37519301 PMCID: PMC10375050 DOI: 10.3389/fcell.2023.1228283] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 07/07/2023] [Indexed: 08/01/2023] Open
Abstract
Intestinal epithelial cells (IECs) perform several physiological and metabolic functions at the epithelial barrier. IECs also play an important role in defining the overall immune functions at the mucosal region. Pattern recognition receptors (PRRs) on the cell surface and in other cellular compartments enable them to sense the presence of microbes and microbial products in the intestinal lumen. IECs are thus at the crossroads of mediating a bidirectional interaction between the microbial population and the immune cells present at the intestinal mucosa. This communication between the microbial population, the IECs and the underlying immune cells has a profound impact on the overall health of the host. In this review, we focus on the various PRRs present in different cellular compartments of IECs and discuss the recent developments in the understanding of their role in microbial recognition. Microbial recognition and signaling at the epithelial barrier have implications in the maintenance of intestinal homeostasis, epithelial barrier function, maintenance of commensals, and the overall tolerogenic function of PRRs in the gut mucosa. We also highlight the role of an aberrant microbial sensing at the epithelial barrier in the pathogenesis of inflammatory bowel disease (IBD) and the development of colorectal cancer.
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Affiliation(s)
- Krishna Iyer
- Department of Medicine 1, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
- Evergrande Center for Immunologic Diseases, Harvard Medical School and Brigham and Women’s Hospital, Boston, MA, United States
| | - Lena Erkert
- Department of Medicine 1, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Christoph Becker
- Department of Medicine 1, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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Demeter A, Jacomin AC, Gul L, Lister A, Lipscombe J, Invernizzi R, Branchu P, Macaulay I, Nezis IP, Kingsley RA, Korcsmaros T, Hautefort I. Computational prediction and experimental validation of Salmonella Typhimurium SopE-mediated fine-tuning of autophagy in intestinal epithelial cells. Front Cell Infect Microbiol 2022; 12:834895. [PMID: 36061866 PMCID: PMC9428466 DOI: 10.3389/fcimb.2022.834895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 07/28/2022] [Indexed: 11/13/2022] Open
Abstract
Macroautophagy is a ubiquitous homeostasis and health-promoting recycling process of eukaryotic cells, targeting misfolded proteins, damaged organelles and intracellular infectious agents. Some intracellular pathogens such as Salmonella enterica serovar Typhimurium hijack this process during pathogenesis. Here we investigate potential protein-protein interactions between host transcription factors and secreted effector proteins of Salmonella and their effect on host gene transcription. A systems-level analysis identified Salmonella effector proteins that had the potential to affect core autophagy gene regulation. The effect of a SPI-1 effector protein, SopE, that was predicted to interact with regulatory proteins of the autophagy process, was investigated to validate our approach. We then confirmed experimentally that SopE can directly bind to SP1, a host transcription factor, which modulates the expression of the autophagy gene MAP1LC3B. We also revealed that SopE might have a double role in the modulation of autophagy: Following initial increase of MAP1LC3B transcription triggered by Salmonella infection, subsequent decrease in MAP1LC3B transcription at 6h post-infection was SopE-dependent. SopE also played a role in modulation of the autophagy flux machinery, in particular MAP1LC3B and p62 autophagy proteins, depending on the level of autophagy already taking place. Upon typical infection of epithelial cells, the autophagic flux is increased. However, when autophagy was chemically induced prior to infection, SopE dampened the autophagic flux. The same was also observed when most of the intracellular Salmonella cells were not associated with the SCV (strain lacking sifA) regardless of the autophagy induction status before infection. We demonstrated how regulatory network analysis can be used to better characterise the impact of pathogenic effector proteins, in this case, Salmonella. This study complements previous work in which we had demonstrated that specific pathogen effectors can affect the autophagy process through direct interaction with autophagy proteins. Here we show that effector proteins can also influence the upstream regulation of the process. Such interdisciplinary studies can increase our understanding of the infection process and point out targets important in intestinal epithelial cell defense.
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Affiliation(s)
- Amanda Demeter
- Earlham Institute, Norwich Research Park, Norwich, United Kingdom
- Quadram Institute Bioscience, Norwich Research Park, Norwich, United Kingdom
- Department of Genetics, Eotvos Lorand University, Budapest, Hungary
| | | | - Lejla Gul
- Earlham Institute, Norwich Research Park, Norwich, United Kingdom
| | - Ashleigh Lister
- Earlham Institute, Norwich Research Park, Norwich, United Kingdom
| | - James Lipscombe
- Earlham Institute, Norwich Research Park, Norwich, United Kingdom
| | - Rachele Invernizzi
- Quadram Institute Bioscience, Norwich Research Park, Norwich, United Kingdom
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - Priscilla Branchu
- Quadram Institute Bioscience, Norwich Research Park, Norwich, United Kingdom
| | - Iain Macaulay
- Earlham Institute, Norwich Research Park, Norwich, United Kingdom
| | - Ioannis P. Nezis
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Robert A. Kingsley
- Quadram Institute Bioscience, Norwich Research Park, Norwich, United Kingdom
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - Tamas Korcsmaros
- Earlham Institute, Norwich Research Park, Norwich, United Kingdom
- Quadram Institute Bioscience, Norwich Research Park, Norwich, United Kingdom
- Faculty of Medicine, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, United Kingdom
- *Correspondence: Tamas Korcsmaros,
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Kalgudi R, Tamimi R, Kyazze G, Keshavarz T. Quorum quenchers affect the virulence regulation of non-mucoid, mucoid and heavily mucoid biofilms co-cultured on cell lines. Appl Microbiol Biotechnol 2021; 105:8853-8868. [PMID: 34716788 PMCID: PMC8590680 DOI: 10.1007/s00253-021-11638-8] [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: 03/15/2021] [Revised: 09/07/2021] [Accepted: 10/05/2021] [Indexed: 12/04/2022]
Abstract
Biofilm formation conferring pathogenicity is a survival strategy for Pseudomonas aeruginosa. P. aeruginosa’s virulence may differ due to differences in host-microbe interactions and the growth environment. The epithelial cell line within the respiratory system and the keratinocytes on the skin form the first physical barrier of defence. P. aeruginosa spp. biofilm formation and virulence factor secretion with and without quorum quenching (QQ) treatment was studied in co-culture using A549 and HaCaT cell lines; pyocyanin and rhamnolipid productions and elastolytic activity as virulence factors were quantified by independent assays. Biofilm formation was evaluated under dynamic conditions by quantifying total carbohydrates, alginate, proteins and eDNA. A sandwich ELISA was performed to study IL-8 secretion by the epithelial cells. The difference in gene expression of the quorum sensing (QS) and virulence factors between strains during individual and combination treatments was analysed by qPCR. Combination treatment by farnesol and tyrosol was more effective against P. aeruginosa biofilms when grown in co-cultures. The strain RBHi was found to be 3 to 4 times more virulent compared to PAO1 and NCTC 10,662, respectively, and combination treatment was more effective against RBHi strain when grown in co-culture with A549 cell line. The addition of quorum quenchers (QQs) individually and in combination reduced IL-8 secretion by A549 cells. Relative mRNA expression showed upregulation of the QS genes and virulence factors. Co-culture of P. aeruginosa and HaCaT cell line showed a general decrease in gene expression, especially in the case of P. aeruginosa RBHi when treated with farnesol and tyrosol combination. Key points • Differentiating the interactions of biofilm formed by different phenotypes of P. aeruginosa, NCTC 10,662 (non-mucoid), PAO1 (semi mucoid) and RBHi (heavily mucoid). • Biofilm formed by these P. aeruginosa strains on two commonly afflicted tissues represented by A549 (lung) and HaCaT (skin) cell lines. • Anti-biofilm/anti-virulence roles of quorum quenchers, tyrosol and farnesol in co-cultures.
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Affiliation(s)
- Rachith Kalgudi
- School of Life Sciences, University of Westminster, 115 New Cavendish Street, London, W1W 6UW, UK.
| | - Roya Tamimi
- School of Life Sciences, University of Westminster, 115 New Cavendish Street, London, W1W 6UW, UK
| | - Godfrey Kyazze
- School of Life Sciences, University of Westminster, 115 New Cavendish Street, London, W1W 6UW, UK
| | - Tajalli Keshavarz
- School of Life Sciences, University of Westminster, 115 New Cavendish Street, London, W1W 6UW, UK
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Sheppe AEF, Santelices J, Czyz DM, Edelmann MJ. Yersinia pseudotuberculosis YopJ Limits Macrophage Response by Downregulating COX-2-Mediated Biosynthesis of PGE2 in a MAPK/ERK-Dependent Manner. Microbiol Spectr 2021; 9:e0049621. [PMID: 34319170 PMCID: PMC8552654 DOI: 10.1128/spectrum.00496-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 06/22/2021] [Indexed: 12/23/2022] Open
Abstract
Prostaglandin E2 (PGE2) is an essential immunomodulatory lipid released by cells in response to infection with many bacteria, yet its function in macrophage-mediated bacterial clearance is poorly understood. Yersinia overall inhibits the inflammatory circuit, but its effect on PGE2 production is unknown. We hypothesized that one of the Yersinia effector proteins is responsible for the inhibition of PGE2 biosynthesis. We identified that yopB-deficient Y. enterocolitica and Y. pseudotuberculosis deficient in the secretion of virulence proteins via a type 3 secretion system (T3SS) failed to inhibit PGE2 biosynthesis in macrophages. Consistently, COX-2-mediated PGE2 biosynthesis is upregulated in cells treated with heat-killed or T3SS-deficient Y. pseudotuberculosis but diminished in the presence of a MAPK/ERK inhibitor. Mutants expressing catalytically inactive YopJ induce similar levels of PGE2 as heat-killed or ΔyopB Y. pseudotuberculosis, reversed by YopJ complementation. Shotgun proteomics discovered host pathways regulated in a YopJ-mediated manner, including pathways regulating PGE2 synthesis and oxidative phosphorylation. Consequently, this study identified that YopJ-mediated inhibition of MAPK signal transduction serves as a mechanism targeting PGE2, an alternative means of inflammasome inhibition by Yersinia. Finally, we showed that EP4 signaling supports macrophage function in clearing intracellular bacteria. In summary, our unique contribution was to determine a bacterial virulence factor that targets COX-2 transcription, thereby enhancing the intracellular survival of yersiniae. Future studies should investigate whether PGE2 or its stable synthetic derivatives could serve as a potential therapeutic molecule to improve the outcomes of specific bacterial infections. Since other pathogens encode YopJ homologs, this mechanism is expected to be present in other infections. IMPORTANCE PGE2 is a critical immunomodulatory lipid, but its role in bacterial infection and pathogen clearance is poorly understood. We previously demonstrated that PGE2 leads to macrophage polarization toward the M1 phenotype and stimulates inflammasome activation in infected macrophages. Finally, we also discovered that PGE2 improved the clearance of Y. enterocolitica. The fact that Y. enterocolitica hampers PGE2 secretion in a type 3 secretion system (T3SS)-dependent manner and because PGE2 appears to assist macrophage in the clearance of this bacterium indicates that targeting of the eicosanoid pathway by Yersinia might be an adaption used to counteract host defenses. Our study identified a mechanism used by Yersinia that obstructs PGE2 biosynthesis in human macrophages. We showed that Y. pseudotuberculosis interferes with PGE2 biosynthesis by using one of its T3SS effectors, YopJ. Specifically, YopJ targets the host COX-2 enzyme responsible for PGE2 biosynthesis, which happens in a MAPK/ER-dependent manner. Moreover, in a shotgun proteomics study, we also discovered other pathways that catalytically active YopJ targets in the infected macrophages. YopJ was revealed to play a role in limiting host LPS responses, including repression of EGR1 and JUN proteins, which control transcriptional activation of proinflammatory cytokine production such as interleukin-1β. Since YopJ has homologs in other bacterial species, there are likely other pathogens that target and inhibit PGE2 biosynthesis. In summary, our study's unique contribution was to determine a bacterial virulence factor that targets COX-2 transcription. Future studies should investigate whether PGE2 or its stable synthetic derivatives could serve as a potential therapeutic target.
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Affiliation(s)
- Austin E. F. Sheppe
- Department of Microbiology and Cell Science, College of Agricultural and Life Sciences, University of Florida, Gainesville, Florida, USA
| | - John Santelices
- Department of Microbiology and Cell Science, College of Agricultural and Life Sciences, University of Florida, Gainesville, Florida, USA
| | - Daniel M. Czyz
- Department of Microbiology and Cell Science, College of Agricultural and Life Sciences, University of Florida, Gainesville, Florida, USA
| | - Mariola J. Edelmann
- Department of Microbiology and Cell Science, College of Agricultural and Life Sciences, University of Florida, Gainesville, Florida, USA
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Roles of Eicosanoids in Regulating Inflammation and Neutrophil Migration as an Innate Host Response to Bacterial Infections. Infect Immun 2021; 89:e0009521. [PMID: 34031130 DOI: 10.1128/iai.00095-21] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Eicosanoids are lipid-based signaling molecules that play a unique role in innate immune responses. The multiple types of eicosanoids, such as prostaglandins (PGs) and leukotrienes (LTs), allow the innate immune cells to respond rapidly to bacterial invaders. Bacterial pathogens alter cyclooxygenase (COX)-derived prostaglandins (PGs) in macrophages, such as PGE2 15d-PGJ2, and lipoxygenase (LOX)-derived leukotriene LTB4, which has chemotactic functions. The PG synthesis and secretion are regulated by substrate availability of arachidonic acid and by the COX-2 enzyme, and the expression of this protein is regulated at multiple levels, both transcriptionally and posttranscriptionally. Bacterial pathogens use virulence strategies such as type three secretion systems (T3SSs) to deliver virulence factors altering the expression of eicosanoid-specific biosynthetic enzymes, thereby modulating the host response to bacterial lipopolysaccharides (LPS). Recent advances have identified a novel role of eicosanoids in inflammasome activation during intracellular infection with bacterial pathogens. Specifically, PGE2 was found to enhance inflammasome activation, driving the formation of pore-induced intracellular traps (PITs), thus trapping bacteria from escaping the dying cell. Finally, eicosanoids and IL-1β released from macrophages are implicated in the efferocytosis of neighboring neutrophils. Neutrophils play an essential role in phagocytosing and degrading PITs and associated bacteria to restore homeostasis. This review focuses on the novel functions of host-derived eicosanoids in the host-pathogen interactions.
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Bacterial virulence mediated by orthogonal post-translational modification. Nat Chem Biol 2020; 16:1043-1051. [PMID: 32943788 DOI: 10.1038/s41589-020-0638-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 07/30/2020] [Indexed: 12/28/2022]
Abstract
Many bacterial pathogens secrete virulence factors, also known as effector proteins, directly into host cells. These effectors suppress pro-inflammatory host signaling while promoting bacterial infection. A particularly interesting subset of effectors post-translationally modify host proteins using novel chemistry that is not otherwise found in the mammalian proteome, which we refer to as 'orthogonal post-translational modification' (oPTM). In this Review, we profile oPTM chemistry for effectors that catalyze serine/threonine acetylation, phosphate β-elimination, phosphoribosyl-linked ubiquitination, glutamine deamidation, phosphocholination, cysteine methylation, arginine N-acetylglucosaminylation, and glutamine ADP-ribosylation on host proteins. AMPylation, a PTM that could be considered orthogonal until only recently, is also discussed. We further highlight known cellular targets of oPTMs and their resulting biological consequences. Developing a complete understanding of oPTMs and the host cell processes they hijack will illuminate critical steps in the infection process, which can be harnessed for a variety of therapeutic, diagnostic, and synthetic applications.
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The Shigella type three secretion system effector OspF invades host nucleus by binding host importin α1. World J Microbiol Biotechnol 2019; 35:71. [DOI: 10.1007/s11274-019-2635-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 03/11/2019] [Indexed: 11/26/2022]
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Chambers KA, Abularrage NS, Scheck RA. Selectivity within a Family of Bacterial Phosphothreonine Lyases. Biochemistry 2018; 57:3790-3796. [PMID: 29792689 DOI: 10.1021/acs.biochem.8b00534] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Phosphothreonine lyases are bacterial effector proteins secreted into host cells to facilitate the infection process. This enzyme family catalyzes an irreversible elimination reaction that converts phosphothreonine or phosphoserine to dehydrobutyrine or dehydroalanine, respectively. Herein, we report a study of substrate selectivity for each of the four known phosphothreonine lyases. This was accomplished using a combination of mass spectrometry and enzyme kinetics assays for a series of phosphorylated peptides derived from the mitogen-activated protein kinase (MAPK) activation loop. These studies provide the first experimental evidence that VirA, a putative phosphothreonine lyase identified through homology, is indeed capable of catalyzing phosphate elimination. These studies further demonstrate that OspF is the most promiscuous phosphothreonine lyase, whereas SpvC is the most specific for the MAPK activation loop. Our studies reveal that phospholyases are dramatically more efficient at catalyzing elimination from phosphothreonine than from phosphoserine. Together, our data suggest that each enzyme likely has preferred substrates, either within the MAPK family or beyond. Fully understanding the extent of selectivity is key to understanding the impact of phosphothreonine lyases during bacterial infection and to exploiting their unique chemistry for a range of applications.
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Affiliation(s)
- Kaitlin A Chambers
- Department of Chemistry , Tufts University , 62 Talbot Avenue , Medford , Massachusetts 02155 , United States
| | - Nile S Abularrage
- Department of Chemistry , Tufts University , 62 Talbot Avenue , Medford , Massachusetts 02155 , United States
| | - Rebecca A Scheck
- Department of Chemistry , Tufts University , 62 Talbot Avenue , Medford , Massachusetts 02155 , United States
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Milivojevic M, Dangeard AS, Kasper CA, Tschon T, Emmenlauer M, Pique C, Schnupf P, Guignot J, Arrieumerlou C. ALPK1 controls TIFA/TRAF6-dependent innate immunity against heptose-1,7-bisphosphate of gram-negative bacteria. PLoS Pathog 2017; 13:e1006224. [PMID: 28222186 PMCID: PMC5336308 DOI: 10.1371/journal.ppat.1006224] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Revised: 03/03/2017] [Accepted: 02/07/2017] [Indexed: 12/30/2022] Open
Abstract
During infection by invasive bacteria, epithelial cells contribute to innate immunity via the local secretion of inflammatory cytokines. These are directly produced by infected cells or by uninfected bystanders via connexin-dependent cell-cell communication. However, the cellular pathways underlying this process remain largely unknown. Here we perform a genome-wide RNA interference screen and identify TIFA and TRAF6 as central players of Shigella flexneri and Salmonella typhimurium-induced interleukin-8 expression. We show that threonine 9 and the forkhead-associated domain of TIFA are necessary for the oligomerization of TIFA in both infected and bystander cells. Subsequently, this process triggers TRAF6 oligomerization and NF-κB activation. We demonstrate that TIFA/TRAF6-dependent cytokine expression is induced by the bacterial metabolite heptose-1,7-bisphosphate (HBP). In addition, we identify alpha-kinase 1 (ALPK1) as the critical kinase responsible for TIFA oligomerization and IL-8 expression in response to infection with S. flexneri and S. typhimurium but also to Neisseria meningitidis. Altogether, these results clearly show that ALPK1 is a master regulator of innate immunity against both invasive and extracellular gram-negative bacteria. Epithelial cells line internal body cavities of multicellular organisms. They represent the first line of defense against various pathogens including bacteria and viruses. They can sense the presence of invasive pathogens and initiate the recruitment of immune cells to infected tissues via the local secretion of soluble factors, called chemokines. Although this phenomenon is essential for the development of an efficient immune response, the molecular mechanism underlying this process remains largely unknown. Here we demonstrate that the host proteins ALPK1, TIFA and TRAF6 act sequentially to activate the transcription factor NF-κB and regulate the production of chemokines in response to infection by the pathogens Shigella flexneri, Salmonella typhimurium and Neisseria meningitidis. In addition, we show that the production of chemokines is triggered after detection of the bacterial monosaccharide heptose-1,7-bisphosphate, found in gram-negative bacteria. In conclusion, our study uncovers a new molecular mechanism controlling inflammation during infection by gram-negative bacteria and identifies potential targets for treatments aiming at modulating inflammation during infection.
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Affiliation(s)
- Milica Milivojevic
- INSERM, U1016, Institut Cochin, Paris, France, CNRS, UMR8104, Paris, France, Université Paris Descartes, Sorbonne Paris Cité, France
| | - Anne-Sophie Dangeard
- INSERM, U1016, Institut Cochin, Paris, France, CNRS, UMR8104, Paris, France, Université Paris Descartes, Sorbonne Paris Cité, France
| | | | | | | | - Claudine Pique
- INSERM, U1016, Institut Cochin, Paris, France, CNRS, UMR8104, Paris, France, Université Paris Descartes, Sorbonne Paris Cité, France
| | | | - Julie Guignot
- INSERM, U1016, Institut Cochin, Paris, France, CNRS, UMR8104, Paris, France, Université Paris Descartes, Sorbonne Paris Cité, France
| | - Cécile Arrieumerlou
- INSERM, U1016, Institut Cochin, Paris, France, CNRS, UMR8104, Paris, France, Université Paris Descartes, Sorbonne Paris Cité, France
- * E-mail:
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Friedrich A, Pechstein J, Berens C, Lührmann A. Modulation of host cell apoptotic pathways by intracellular pathogens. Curr Opin Microbiol 2017; 35:88-99. [DOI: 10.1016/j.mib.2017.03.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 12/03/2016] [Accepted: 03/01/2017] [Indexed: 12/13/2022]
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Campbell-Valois FX, Pontier SM. Implications of Spatiotemporal Regulation of Shigella flexneri Type Three Secretion Activity on Effector Functions: Think Globally, Act Locally. Front Cell Infect Microbiol 2016; 6:28. [PMID: 27014638 PMCID: PMC4783576 DOI: 10.3389/fcimb.2016.00028] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 02/23/2016] [Indexed: 11/13/2022] Open
Abstract
Shigella spp. are Gram-negative bacterial pathogens that infect human colonic epithelia and cause bacterial dysentery. These bacteria express multiple copies of a syringe-like protein complex, the Type Three Secretion apparatus (T3SA), which is instrumental in the etiology of the disease. The T3SA triggers the plasma membrane (PM) engulfment of the bacteria by host cells during the initial entry process. It then enables bacteria to escape the resulting phagocytic-like vacuole. Freed bacteria form actin comets to move in the cytoplasm, which provokes bacterial collision with the inner leaflet of the PM. This phenomenon culminates in T3SA-dependent secondary uptake and vacuolar rupture in neighboring cells in a process akin to what is observed during entry and named cell-to-cell spread. The activity of the T3SA of Shigella flexneri was recently demonstrated to display an on/off regulation during the infection. While the T3SA is active when bacteria are in contact with PM-derived compartments, it switches to an inactive state when bacteria are released within the cytosol. These observations indicate that effector proteins transiting through the T3SA are therefore translocated in a highly time and space constrained fashion, likely impacting on their cellular distribution. Herein, we present what is currently known about the composition, the assembly and the regulation of the T3SA activity and discuss the consequences of the on/off regulation of T3SA on Shigella effector properties and functions during the infection. Specific examples that will be developed include the role of effectors IcsB and VirA in the escape from LC3/ATG8-positive vacuoles formed during cell-to-cell spread and of IpaJ protease activity against N-miristoylated proteins. The conservation of a similar regulation of T3SA activity in other pathogens such as Salmonella or Enteropathogenic Escherichia coli will also be briefly discussed.
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Affiliation(s)
- F-X Campbell-Valois
- Department of Chemistry and Biomolecular Sciences, University of Ottawa Ottawa, ON, Canada
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