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Lewis AJ, Richards AC, Mendez AA, Dhakal BK, Jones TA, Sundsbak JL, Eto DS, Rousek AA, Mulvey MA. Plant phenolics inhibit focal adhesion kinase and suppress host cell invasion by uropathogenic Escherichia coli. Infect Immun 2024; 92:e0008024. [PMID: 38534100 PMCID: PMC11075462 DOI: 10.1128/iai.00080-24] [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: 02/18/2024] [Accepted: 03/05/2024] [Indexed: 03/28/2024] Open
Abstract
Traditional folk treatments for the prevention and management of urinary tract infections (UTIs) and other infectious diseases often include plants and plant extracts that are rich in phenolic compounds. These have been ascribed a variety of activities, including inhibition of bacterial interactions with host cells. Here, we tested a panel of four well-studied phenolic compounds-caffeic acid phenethyl ester (CAPE), resveratrol, catechin, and epigallocatechin gallate-for the effects on host cell adherence and invasion by uropathogenic Escherichia coli (UPEC). These bacteria, which are the leading cause of UTIs, can bind and subsequently invade bladder epithelial cells via an actin-dependent process. Intracellular UPEC reservoirs within the bladder are often protected from antibiotics and host defenses and likely contribute to the development of chronic and recurrent infections. In cell culture-based assays, only resveratrol had a notable negative effect on UPEC adherence to bladder cells. However, both CAPE and resveratrol significantly inhibited UPEC entry into the host cells, coordinate with attenuated phosphorylation of the host actin regulator Focal Adhesion Kinase (FAK or PTK2) and marked increases in the numbers of focal adhesion structures. We further show that the intravesical delivery of resveratrol inhibits UPEC infiltration of the bladder mucosa in a murine UTI model and that resveratrol and CAPE can disrupt the ability of other invasive pathogens to enter host cells. Together, these results highlight the therapeutic potential of molecules like CAPE and resveratrol, which could be used to augment antibiotic treatments by restricting pathogen access to protective intracellular niches.IMPORTANCEUrinary tract infections (UTIs) are exceptionally common and increasingly difficult to treat due to the ongoing rise and spread of antibiotic-resistant pathogens. Furthermore, the primary cause of UTIs, uropathogenic Escherichia coli (UPEC), can avoid antibiotic exposure and many host defenses by invading the epithelial cells that line the bladder surface. Here, we identified two plant-derived phenolic compounds that disrupt activation of the host machinery needed for UPEC entry into bladder cells. One of these compounds, resveratrol, effectively inhibited UPEC invasion of the bladder mucosa in a mouse UTI model, and both phenolic compounds significantly reduced host cell entry by other invasive pathogens. These findings suggest that select phenolic compounds could be used to supplement existing antibacterial therapeutics by denying uropathogens shelter within host cells and tissues and help explain some of the benefits attributed to traditional plant-based medicines.
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Affiliation(s)
- Adam J. Lewis
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, Utah, USA
| | - Amanda C. Richards
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, Utah, USA
| | - Alejandra A. Mendez
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, Utah, USA
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, USA
- Henry Eyring Center for Cell & Genome Science, University of Utah, Salt Lake City, Utah, USA
| | - Bijaya K. Dhakal
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, Utah, USA
| | - Tiffani A. Jones
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, Utah, USA
| | - Jamie L. Sundsbak
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, Utah, USA
| | - Danelle S. Eto
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, Utah, USA
| | - Alexis A. Rousek
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, USA
- Henry Eyring Center for Cell & Genome Science, University of Utah, Salt Lake City, Utah, USA
| | - Matthew A. Mulvey
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, Utah, USA
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, USA
- Henry Eyring Center for Cell & Genome Science, University of Utah, Salt Lake City, Utah, USA
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2
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Ernst C, Andreassen PR, Giger GH, Nguyen BD, Gäbelein CG, Guillaume-Gentil O, Fattinger SA, Sellin ME, Hardt WD, Vorholt JA. Direct Salmonella injection into enteroid cells allows the study of host-pathogen interactions in the cytosol with high spatiotemporal resolution. PLoS Biol 2024; 22:e3002597. [PMID: 38684033 PMCID: PMC11057982 DOI: 10.1371/journal.pbio.3002597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 03/21/2024] [Indexed: 05/02/2024] Open
Abstract
Intestinal epithelial cells (IECs) play pivotal roles in nutrient uptake and in the protection against gut microorganisms. However, certain enteric pathogens, such as Salmonella enterica serovar Typhimurium (S. Tm), can invade IECs by employing flagella and type III secretion systems (T3SSs) with cognate effector proteins and exploit IECs as a replicative niche. Detection of flagella or T3SS proteins by IECs results in rapid host cell responses, i.e., the activation of inflammasomes. Here, we introduce a single-cell manipulation technology based on fluidic force microscopy (FluidFM) that enables direct bacteria delivery into the cytosol of single IECs within a murine enteroid monolayer. This approach allows to specifically study pathogen-host cell interactions in the cytosol uncoupled from preceding events such as docking, initiation of uptake, or vacuole escape. Consistent with current understanding, we show using a live-cell inflammasome reporter that exposure of the IEC cytosol to S. Tm induces NAIP/NLRC4 inflammasomes via its known ligands flagellin and T3SS rod and needle. Injected S. Tm mutants devoid of these invasion-relevant ligands were able to grow in the cytosol of IECs despite the absence of T3SS functions, suggesting that, in the absence of NAIP/NLRC4 inflammasome activation and the ensuing cell death, no effector-mediated host cell manipulation is required to render the epithelial cytosol growth-permissive for S. Tm. Overall, the experimental system to introduce S. Tm into single enteroid cells enables investigations into the molecular basis governing host-pathogen interactions in the cytosol with high spatiotemporal resolution.
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Affiliation(s)
- Chantal Ernst
- Institute of Microbiology, Department of Biology, ETH Zurich, Zurich, Switzerland
| | | | - Gabriel H. Giger
- Institute of Microbiology, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Bidong D. Nguyen
- Institute of Microbiology, Department of Biology, ETH Zurich, Zurich, Switzerland
| | | | | | - Stefan A. Fattinger
- Institute of Microbiology, Department of Biology, ETH Zurich, Zurich, Switzerland
- Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Mikael E. Sellin
- Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Wolf-Dietrich Hardt
- Institute of Microbiology, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Julia A. Vorholt
- Institute of Microbiology, Department of Biology, ETH Zurich, Zurich, Switzerland
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3
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von Beek C, Fahlgren A, Geiser P, Di Martino ML, Lindahl O, Prensa GI, Mendez-Enriquez E, Eriksson J, Hallgren J, Fällman M, Pejler G, Sellin ME. A two-step activation mechanism enables mast cells to differentiate their response between extracellular and invasive enterobacterial infection. Nat Commun 2024; 15:904. [PMID: 38291037 PMCID: PMC10828507 DOI: 10.1038/s41467-024-45057-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 01/12/2024] [Indexed: 02/01/2024] Open
Abstract
Mast cells localize to mucosal tissues and contribute to innate immune defense against infection. How mast cells sense, differentiate between, and respond to bacterial pathogens remains a topic of ongoing debate. Using the prototype enteropathogen Salmonella Typhimurium (S.Tm) and other related enterobacteria, here we show that mast cells can regulate their cytokine secretion response to distinguish between extracellular and invasive bacterial infection. Tissue-invasive S.Tm and mast cells colocalize in the mouse gut during acute Salmonella infection. Toll-like Receptor 4 (TLR4) sensing of extracellular S.Tm, or pure lipopolysaccharide, causes a modest induction of cytokine transcripts and proteins, including IL-6, IL-13, and TNF. By contrast, type-III-secretion-system-1 (TTSS-1)-dependent S.Tm invasion of both mouse and human mast cells triggers rapid and potent inflammatory gene expression and >100-fold elevated cytokine secretion. The S.Tm TTSS-1 effectors SopB, SopE, and SopE2 here elicit a second activation signal, including Akt phosphorylation downstream of effector translocation, which combines with TLR activation to drive the full-blown mast cell response. Supernatants from S.Tm-infected mast cells boost macrophage survival and maturation from bone-marrow progenitors. Taken together, this study shows that mast cells can differentiate between extracellular and host-cell invasive enterobacteria via a two-step activation mechanism and tune their inflammatory output accordingly.
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Affiliation(s)
- Christopher von Beek
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Anna Fahlgren
- Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Petra Geiser
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | | | - Otto Lindahl
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Grisna I Prensa
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Erika Mendez-Enriquez
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Jens Eriksson
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Jenny Hallgren
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Maria Fällman
- Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Gunnar Pejler
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
| | - Mikael E Sellin
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
- Science for Life Laboratory, Uppsala, Sweden.
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Kirchenwitz M, Halfen J, von Peinen K, Prettin S, Kollasser J, Zur Lage S, Blankenfeldt W, Brakebusch C, Rottner K, Steffen A, Stradal TEB. RhoB promotes Salmonella survival by regulating autophagy. Eur J Cell Biol 2023; 102:151358. [PMID: 37703749 DOI: 10.1016/j.ejcb.2023.151358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 07/05/2023] [Accepted: 08/29/2023] [Indexed: 09/15/2023] Open
Abstract
Salmonella enterica serovar Typhimurium manipulates cellular Rho GTPases for host cell invasion by effector protein translocation via the Type III Secretion System (T3SS). The two Guanine nucleotide exchange (GEF) mimicking factors SopE and -E2 and the inositol phosphate phosphatase (PiPase) SopB activate the Rho GTPases Rac1, Cdc42 and RhoA, thereby mediating bacterial invasion. S. Typhimurium lacking these three effector proteins are largely invasion-defective. Type III secretion is crucial for both early and later phases of the intracellular life of S. Typhimurium. Here we investigated whether and how the small GTPase RhoB, known to localize on endomembrane vesicles and at the invasion site of S. Typhimurium, contributes to bacterial invasion and to subsequent steps relevant for S. Typhimurium lifestyle. We show that RhoB is significantly upregulated within hours of Salmonella infection. This effect depends on the presence of the bacterial effector SopB, but does not require its phosphatase activity. Our data reveal that SopB and RhoB bind to each other, and that RhoB localizes on early phagosomes of intracellular S. Typhimurium. Whereas both SopB and RhoB promote intracellular survival of Salmonella, RhoB is specifically required for Salmonella-induced upregulation of autophagy. Finally, in the absence of RhoB, vacuolar escape and cytosolic hyper-replication of S. Typhimurium is diminished. Our findings thus uncover a role for RhoB in Salmonella-induced autophagy, which supports intracellular survival of the bacterium and is promoted through a positive feedback loop by the Salmonella effector SopB.
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Affiliation(s)
- Marco Kirchenwitz
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Jessica Halfen
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Kristin von Peinen
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Silvia Prettin
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Jana Kollasser
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Susanne Zur Lage
- Department Structure and Function of Proteins, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Wulf Blankenfeldt
- Department Structure and Function of Proteins, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Cord Brakebusch
- Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Klemens Rottner
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany; Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany
| | - Anika Steffen
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Theresia E B Stradal
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany.
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Lewis AJ, Richards AC, Mendez AA, Dhakal BK, Jones TA, Sundsbak JL, Eto DS, Mulvey MA. Plant Phenolics Inhibit Focal Adhesion Kinase and Suppress Host Cell Invasion by Uropathogenic Escherichia coli. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.23.568486. [PMID: 38045282 PMCID: PMC10690256 DOI: 10.1101/2023.11.23.568486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
Traditional folk treatments for the prevention and management of urinary tract infections (UTIs) and other infectious diseases often include plants and plant extracts that are rich in phenolic and polyphenolic compounds. These have been ascribed a variety of activities, including inhibition of bacterial interactions with host cells. Here we tested a panel of four well-studied phenolic compounds - caffeic acid phenethyl ester (CAPE), resveratrol, catechin, and epigallocatechin gallate - for effects on host cell adherence and invasion by uropathogenic Escherichia coli (UPEC). These bacteria, which are the leading cause of UTIs, can bind and subsequently invade bladder epithelial cells via an actin-dependent process. Intracellular UPEC reservoirs within the bladder are often protected from antibiotics and host defenses, and likely contribute to the development of chronic and recurrent infections. Using cell culture-based assays, we found that only resveratrol had a notable negative effect on UPEC adherence to bladder cells. However, both CAPE and resveratrol significantly inhibited UPEC entry into the host cells, coordinate with attenuated phosphorylation of the host actin regulator Focal Adhesion Kinase (FAK, or PTK2) and marked increases in the numbers of focal adhesion structures. We further show that the intravesical delivery of resveratrol inhibits UPEC infiltration of the bladder mucosa in a murine UTI model, and that resveratrol and CAPE can disrupt the ability of other invasive pathogens to enter host cells. Together, these results highlight the therapeutic potential of molecules like CAPE and resveratrol, which could be used to augment antibiotic treatments by restricting pathogen access to protective intracellular niches.
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Affiliation(s)
- Adam J. Lewis
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, UT 84112, USA
| | - Amanda C. Richards
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, UT 84112, USA
- School of Biological Sciences, 257 S 1400 E, University of Utah, Salt Lake City, UT 84112, USA; Henry Eyring Center for Cell & Genome Science, 1390 Presidents Circle, University of Utah, Salt Lake City, UT 84112, USA
| | - Alejandra A. Mendez
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, UT 84112, USA
- School of Biological Sciences, 257 S 1400 E, University of Utah, Salt Lake City, UT 84112, USA; Henry Eyring Center for Cell & Genome Science, 1390 Presidents Circle, University of Utah, Salt Lake City, UT 84112, USA
| | - Bijaya K. Dhakal
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, UT 84112, USA
| | - Tiffani A. Jones
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, UT 84112, USA
| | - Jamie L. Sundsbak
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, UT 84112, USA
| | - Danelle S. Eto
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, UT 84112, USA
| | - Matthew A. Mulvey
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, UT 84112, USA
- School of Biological Sciences, 257 S 1400 E, University of Utah, Salt Lake City, UT 84112, USA; Henry Eyring Center for Cell & Genome Science, 1390 Presidents Circle, University of Utah, Salt Lake City, UT 84112, USA
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6
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Gioia MD, Poli V, Tan PJ, Spreafico R, Chu A, Cuenca AG, Gordts PL, Pandolfi L, Meloni F, Witztum JL, Chou J, Springstead JR, Zanoni I. Host-derived oxidized phospholipids initiate effector-triggered immunity fostering lethality upon microbial encounter. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.21.568047. [PMID: 38045410 PMCID: PMC10690175 DOI: 10.1101/2023.11.21.568047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
Macrophages detect invading microorganisms via pattern recognition receptors that recognize pathogen-associated molecular patterns, or via sensing the activity of virulence factors that initiates effector-triggered immunity (ETI). Tissue damage that follows pathogen encounter leads to the release of host-derived factors that participate to inflammation. How these self-derived molecules are sensed by macrophages and their impact on immunity remain poorly understood. Here we demonstrate that, in mice and humans, host-derived oxidized phospholipids (oxPLs) are formed upon microbial encounter. oxPL blockade restricts inflammation and prevents the death of the host, without affecting pathogen burden. Mechanistically, oxPLs bind and inhibit AKT, a master regulator of immunity and metabolism. AKT inhibition potentiates the methionine cycle, and epigenetically dampens Il10, a pluripotent anti-inflammatory cytokine. Overall, we found that host-derived inflammatory cues act as "self" virulence factors that initiate ETI and that their activity can be targeted to protect the host against excessive inflammation upon microbial encounter.
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Affiliation(s)
- Marco Di Gioia
- Harvard Medical School and Boston Children's Hospital, Division of Immunology and Division of Gastroenterology, MA 02115, USA
| | - Valentina Poli
- Harvard Medical School and Boston Children's Hospital, Division of Immunology and Division of Gastroenterology, MA 02115, USA
| | - Piao J Tan
- Department of Chemical and Paper Engineering, Western Michigan University, Kalamazoo, MI, USA
| | - Roberto Spreafico
- Institute for Quantitative and Computational Biosciences, University of California, Los Angeles, Los Angeles, CA, USA
| | - Anne Chu
- Harvard Medical School and Boston Children's Hospital, Division of Immunology and Division of Gastroenterology, MA 02115, USA
| | - Alex G Cuenca
- Department of Surgery, Boston Children's Hospital, Boston, MA 02115, USA; Center for Transplantation Sciences, Department of Surgery, Massachusetts General Hospital, MA 02114, USA
| | - Philip Lsm Gordts
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, CA, USA; Glycobiology Research and Training Center, University of California, San Diego, La Jolla, California, USA
| | - Laura Pandolfi
- Respiratory Disease Unit IRCCS San Matteo Hospital Foundation, and Department of Internal Medicine and Pharmacology, University of Pavia, Pavia, 27100, Italy Pavia, 27100, Italy
| | - Federica Meloni
- Respiratory Disease Unit IRCCS San Matteo Hospital Foundation, and Department of Internal Medicine and Pharmacology, University of Pavia, Pavia, 27100, Italy Pavia, 27100, Italy
| | - Joseph L Witztum
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, CA, USA
| | - Janet Chou
- Harvard Medical School and Boston Children's Hospital, Division of Immunology and Division of Gastroenterology, MA 02115, USA
| | - James R Springstead
- Department of Chemical and Paper Engineering, Western Michigan University, Kalamazoo, MI, USA
| | - Ivan Zanoni
- Harvard Medical School and Boston Children's Hospital, Division of Immunology and Division of Gastroenterology, MA 02115, USA
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7
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Gül E, Fattinger SA, Sellin ME, Hardt WD. Epithelial inflammasomes, gasdermins, and mucosal inflammation - Lessons from Salmonella and Shigella infected mice. Semin Immunol 2023; 70:101812. [PMID: 37562110 DOI: 10.1016/j.smim.2023.101812] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 07/05/2023] [Accepted: 07/15/2023] [Indexed: 08/12/2023]
Abstract
Besides its crucial function in nutrient absorbance and as barrier against the microbiota, the gut epithelium is essential for sensing pathogenic insults and mounting of an appropriate early immune response. In mice, the activation of the canonical NAIP/NLRC4 inflammasome is critical for the defense against enterobacterial infections. Activation of the NAIP/NLRC4 inflammasome triggers the extrusion of infected intestinal epithelial cells (IEC) into the gut lumen, concomitant with inflammasome-mediated lytic cell death. The membrane permeabilization, a hallmark of pyroptosis, is caused by the pore-forming proteins called gasdermins (GSDMs). Recent work has revealed that NAIP/NLRC4-dependent extrusion of infected IECs can, however, also be executed in the absence of GSDMD. In fact, several reports highlighted that various cell death pathways (e.g., pyroptosis or apoptosis) and unique mechanisms specific to particular infection models and stages of gut infection are in action during epithelial inflammasome defense against intestinal pathogens. Here, we summarize the current knowledge regarding the underlying mechanisms and speculate on the putative functions of the epithelial inflammasome activation and cell death, with a particular emphasis on mouse infection models for two prominent enterobacterial pathogens, Salmonella Typhimurium and Shigella flexneri.
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Affiliation(s)
- Ersin Gül
- Institute of Microbiology, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Stefan A Fattinger
- Division of Immunology and Molecular Medicine, Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
| | - Mikael E Sellin
- Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Wolf-Dietrich Hardt
- Institute of Microbiology, Department of Biology, ETH Zurich, Zurich, Switzerland.
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8
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Li W, Ren Q, Ni T, Zhao Y, Sang Z, Luo R, Li Z, Li S. Strategies adopted by Salmonella to survive in host: a review. Arch Microbiol 2023; 205:362. [PMID: 37904066 DOI: 10.1007/s00203-023-03702-w] [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: 09/01/2023] [Revised: 09/30/2023] [Accepted: 10/05/2023] [Indexed: 11/01/2023]
Abstract
Salmonella, a Gram-negative bacterium that infects humans and animals, causes diseases ranging from gastroenteritis to severe systemic infections. Here, we discuss various strategies used by Salmonella against host cell defenses. Epithelial cell invasion largely depends on a Salmonella pathogenicity island (SPI)-1-encoded type 3 secretion system, a molecular syringe for injecting effector proteins directly into host cells. The internalization of Salmonella into macrophages is primarily driven by phagocytosis. After entering the host cell cytoplasm, Salmonella releases many effectors to achieve intracellular survival and replication using several secretion systems, primarily an SPI-2-encoded type 3 secretion system. Salmonella-containing vacuoles protect Salmonella from contacting bactericidal substances in epithelial cells and macrophages. Salmonella modulates the immunity, metabolism, cell cycle, and viability of host cells to expand its survival in the host, and the intracellular environment of Salmonella-infected cells promotes its virulence. This review provides insights into how Salmonella subverts host cell defenses for survival.
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Affiliation(s)
- Wanwu Li
- College of Basic Medicine and Forensic Medicine, Henan University of Science and Technology, Luoyang, China
| | - Qili Ren
- College of Basic Medicine and Forensic Medicine, Henan University of Science and Technology, Luoyang, China
| | - Ting Ni
- College of Basic Medicine and Forensic Medicine, Henan University of Science and Technology, Luoyang, China
| | - Yifei Zhao
- College of Basic Medicine and Forensic Medicine, Henan University of Science and Technology, Luoyang, China
| | - Zichun Sang
- College of Basic Medicine and Forensic Medicine, Henan University of Science and Technology, Luoyang, China
| | - Renli Luo
- College of Basic Medicine and Forensic Medicine, Henan University of Science and Technology, Luoyang, China
| | - Zhongjie Li
- College of Basic Medicine and Forensic Medicine, Henan University of Science and Technology, Luoyang, China.
| | - Sanqiang Li
- College of Basic Medicine and Forensic Medicine, Henan University of Science and Technology, Luoyang, China.
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9
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Suwandi A, Menon MB, Kotlyarov A, Grassl GA, Gaestel M. p38 MAPK/MK2 signaling stimulates host cells autophagy pathways to restrict Salmonella infection. Front Immunol 2023; 14:1245443. [PMID: 37771590 PMCID: PMC10523304 DOI: 10.3389/fimmu.2023.1245443] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 08/28/2023] [Indexed: 09/30/2023] Open
Abstract
Autophagy plays an important role in recognizing and protecting cells from invading intracellular pathogens such as Salmonella. In this work, we investigated the role of p38MAPK/MK2 in modulating the host cell susceptibility to Salmonella infection. Inhibition of p38MAPK or MK2 led to a significant increase of bacterial counts in Salmonella infected mouse embryonic fibroblasts (MEFs), as well as in MK2-deficient (Mk2-/-) cells. Furthermore, western blot analysis showed that Mk2-/- cells have lower level of LC3 lipidation, which is the indicator of general autophagy compared to Mk2-rescued cells. In Mk2-/- cells, we also observed lower activated TANK-binding kinase-1 phosphorylation on Ser172 and p62/SQTM1-Ser403 phosphorylation, which are important to promote the translocation of p62 to ubiquitinated microbes and required for efficient autophagy of bacteria. Furthermore, immunofluorescence analysis revealed reduced colocalization of Salmonella with LC3 and p62 in MEFs. Inhibition of autophagy with bafilomycin A1 showed increased bacterial counts in treated cells compared to control cell. Overall, these results indicate that p38MAPK/MK2-mediated protein phosphorylation modulates the host cell susceptibility to Salmonella infection by affecting the autophagy pathways.
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Affiliation(s)
- Abdulhadi Suwandi
- Institute of Cell Biochemistry, Hannover Medical School, Hannover, Germany
| | - Manoj B. Menon
- Kusuma School of Biological Sciences, Indian Institute of Technology Delhi, New Delhi, India
| | - Alexey Kotlyarov
- Institute of Cell Biochemistry, Hannover Medical School, Hannover, Germany
| | - Guntram A. Grassl
- Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Hannover, Germany
- German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, Hannover, Germany
| | - Matthias Gaestel
- Institute of Cell Biochemistry, Hannover Medical School, Hannover, Germany
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10
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Fels U, Willems P, De Meyer M, Gevaert K, Van Damme P. Shift in vacuolar to cytosolic regime of infecting Salmonella from a dual proteome perspective. PLoS Pathog 2023; 19:e1011183. [PMID: 37535689 PMCID: PMC10426988 DOI: 10.1371/journal.ppat.1011183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 08/15/2023] [Accepted: 06/19/2023] [Indexed: 08/05/2023] Open
Abstract
By applying dual proteome profiling to Salmonella enterica serovar Typhimurium (S. Typhimurium) encounters with its epithelial host (here, S. Typhimurium infected human HeLa cells), a detailed interdependent and holistic proteomic perspective on host-pathogen interactions over the time course of infection was obtained. Data-independent acquisition (DIA)-based proteomics was found to outperform data-dependent acquisition (DDA) workflows, especially in identifying the downregulated bacterial proteome response during infection progression by permitting quantification of low abundant bacterial proteins at early times of infection when bacterial infection load is low. S. Typhimurium invasion and replication specific proteomic signatures in epithelial cells revealed interdependent host/pathogen specific responses besides pointing to putative novel infection markers and signalling responses, including regulated host proteins associated with Salmonella-modified membranes.
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Affiliation(s)
- Ursula Fels
- iRIP unit, Laboratory of Microbiology, Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium
- VIB-UGent Center for Medical Biotechnology, Ghent, Belgium
| | - Patrick Willems
- iRIP unit, Laboratory of Microbiology, Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium
| | - Margaux De Meyer
- iRIP unit, Laboratory of Microbiology, Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium
- VIB-UGent Center for Medical Biotechnology, Ghent, Belgium
| | - Kris Gevaert
- VIB-UGent Center for Medical Biotechnology, Ghent, Belgium
- Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Petra Van Damme
- iRIP unit, Laboratory of Microbiology, Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium
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11
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Chatterjee R, Chowdhury AR, Mukherjee D, Chakravortty D. From Eberthella typhi to Salmonella Typhi: The Fascinating Journey of the Virulence and Pathogenicity of Salmonella Typhi. ACS OMEGA 2023; 8:25674-25697. [PMID: 37521659 PMCID: PMC10373206 DOI: 10.1021/acsomega.3c02386] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/09/2023] [Accepted: 06/30/2023] [Indexed: 08/01/2023]
Abstract
Salmonella Typhi (S. Typhi), the invasive typhoidal serovar of Salmonella enterica that causes typhoid fever in humans, is a severe threat to global health. It is one of the major causes of high morbidity and mortality in developing countries. According to recent WHO estimates, approximately 11-21 million typhoid fever illnesses occur annually worldwide, accounting for 0.12-0.16 million deaths. Salmonella infection can spread to healthy individuals by the consumption of contaminated food and water. Typhoid fever in humans sometimes is accompanied by several other critical extraintestinal complications related to the central nervous system, cardiovascular system, pulmonary system, and hepatobiliary system. Salmonella Pathogenicity Island-1 and Salmonella Pathogenicity Island-2 are the two genomic segments containing genes encoding virulent factors that regulate its invasion and systemic pathogenesis. This Review aims to shed light on a comparative analysis of the virulence and pathogenesis of the typhoidal and nontyphoidal serovars of S. enterica.
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Affiliation(s)
- Ritika Chatterjee
- Department
of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Atish Roy Chowdhury
- Department
of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Debapriya Mukherjee
- Department
of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Dipshikha Chakravortty
- Department
of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, Karnataka 560012, India
- Centre
for Biosystems Science and Engineering, Indian Institute of Science, Bangalore, Karnataka 560012, India
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12
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Chatterjee R, Chaudhuri D, Setty SRG, Chakravortty D. Deceiving the big eaters: Salmonella Typhimurium SopB subverts host cell xenophagy in macrophages via dual mechanisms. Microbes Infect 2023; 25:105128. [PMID: 37019426 DOI: 10.1016/j.micinf.2023.105128] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 03/27/2023] [Accepted: 03/29/2023] [Indexed: 04/05/2023]
Abstract
Salmonella, a stealthy facultative intracellular pathogen, utilises an array of host immune evasion strategies. This facilitates successful survival via replicative niche establishment in otherwise hostile environments such as macrophages. Salmonella survives in and utilises macrophages for effective dissemination, ultimately leading to systemic infection. Bacterial xenophagy or macro-autophagy is an important host defense mechanism in macrophages. Here, we report for the first time that the Salmonella pathogenicity island-1 (SPI-1) effector SopB is involved in subverting host autophagy via dual mechanisms. SopB is a phosphoinositide phosphatase capable of altering the phosphoinositide dynamics of the host cell. Here, we demonstrate that SopB mediates escape from autophagy by inhibiting the terminal fusion of Salmonella-containing vacuoles (SCVs) with lysosomes and/or autophagosomes. We also report that SopB downregulates overall lysosomal biogenesis by modulating the Akt-transcription factor EB (TFEB) axis via restricting the latter's nuclear localisation. TFEB is a master regulator of lysosomal biogenesis and autophagy. This reduces the overall lysosome content inside host macrophages, further facilitating the survival of Salmonella in macrophages and systemic dissemination of Salmonella.
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Affiliation(s)
- Ritika Chatterjee
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bengaluru, India
| | - Debalina Chaudhuri
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bengaluru, India
| | - Subba Rao Gangi Setty
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bengaluru, India
| | - Dipshikha Chakravortty
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bengaluru, India; Indian Institute of Science Research and Education, Thiruvananthapuram, Kerala, India.
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13
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Wang DN, Ni JJ, Li JH, Gao YQ, Ni FJ, Zhang ZZ, Fang JY, Lu J, Yao YF. Bacterial infection promotes tumorigenesis of colorectal cancer via regulating CDC42 acetylation. PLoS Pathog 2023; 19:e1011189. [PMID: 36812247 PMCID: PMC9987831 DOI: 10.1371/journal.ppat.1011189] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 03/06/2023] [Accepted: 02/07/2023] [Indexed: 02/24/2023] Open
Abstract
Increasing evidence highlights the role of bacteria in promoting tumorigenesis. The underlying mechanisms may be diverse and remain poorly understood. Here, we report that Salmonella infection leads to extensive de/acetylation changes in host cell proteins. The acetylation of mammalian cell division cycle 42 (CDC42), a member of the Rho family of GTPases involved in many crucial signaling pathways in cancer cells, is drastically reduced after bacterial infection. CDC42 is deacetylated by SIRT2 and acetylated by p300/CBP. Non-acetylated CDC42 at lysine 153 shows an impaired binding of its downstream effector PAK4 and an attenuated phosphorylation of p38 and JNK, consequently reduces cell apoptosis. The reduction in K153 acetylation also enhances the migration and invasion ability of colon cancer cells. The low level of K153 acetylation in patients with colorectal cancer (CRC) predicts a poor prognosis. Taken together, our findings suggest a new mechanism of bacterial infection-induced promotion of colorectal tumorigenesis by modulation of the CDC42-PAK axis through manipulation of CDC42 acetylation.
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Affiliation(s)
- Dan-Ni Wang
- Laboratory of Bacterial Pathogenesis, Shanghai Institute of Immunology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jin-Jing Ni
- Laboratory of Bacterial Pathogenesis, Shanghai Institute of Immunology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jian-Hui Li
- Laboratory of Bacterial Pathogenesis, Shanghai Institute of Immunology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Institute of Phage, Shanghai Public Health Clinical Center, Fudan University, Shanghai, China
| | - Ya-Qi Gao
- State Key Laboratory for Oncogenes and Related Genes; Division of Gastroenterology and Hepatology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Fang-Jing Ni
- Laboratory of Bacterial Pathogenesis, Shanghai Institute of Immunology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhen-Zhen Zhang
- Department of Pathology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jing-Yuan Fang
- State Key Laboratory for Oncogenes and Related Genes; Division of Gastroenterology and Hepatology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jie Lu
- Department of Infectious Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- * E-mail: (JL); (Y-FY)
| | - Yu-Feng Yao
- Laboratory of Bacterial Pathogenesis, Shanghai Institute of Immunology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Department of Infectious Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Emergency Prevention, Diagnosis and Treatment of Respiratory Infectious Diseases, Shanghai, China
- * E-mail: (JL); (Y-FY)
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14
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Tran Van Nhieu G, Latour-Lambert P, Enninga J. Modification of phosphoinositides by the Shigella effector IpgD during host cell infection. Front Cell Infect Microbiol 2022; 12:1012533. [PMID: 36389142 PMCID: PMC9647168 DOI: 10.3389/fcimb.2022.1012533] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 09/27/2022] [Indexed: 09/15/2023] Open
Abstract
Shigella, the causative agent of bacillary dysentery, subvert cytoskeletal and trafficking processes to invade and replicate in epithelial cells using an arsenal of bacterial effectors translocated through a type III secretion system. Here, we review the various roles of the type III effector IpgD, initially characterized as phosphatidylinositol 4,5 bisphosphate (PI4,5P2) 4-phosphatase. By decreasing PI4,5P2 levels, IpgD triggers the disassembly of cortical actin filaments required for bacterial invasion and cell migration. PI5P produced by IpgD further stimulates signaling pathways regulating cell survival, macropinosome formation, endosomal trafficking and dampening of immune responses. Recently, IpgD was also found to exhibit phosphotransferase activity leading to PI3,4P2 synthesis adding a new flavor to this multipotent bacterial enzyme. The substrate of IpgD, PI4,5P2 is also the main substrate hydrolyzed by endogenous phospholipases C to produce inositoltriphosphate (InsP3), a major Ca2+ second messenger. Hence, beyond the repertoire of effects associated with the direct diversion of phoshoinositides, IpgD indirectly down-regulates InsP3-mediated Ca2+ release by limiting InsP3 production. Furthermore, IpgD controls the intracellular lifestyle of Shigella promoting Rab8/11 -dependent recruitment of the exocyst at macropinosomes to remove damaged vacuolar membrane remnants and promote bacterial cytosolic escape. IpgD thus emerges as a key bacterial effector for the remodeling of host cell membranes.
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Affiliation(s)
- Guy Tran Van Nhieu
- Institute for Integrative Biology of the Cell – Centre National de la Recherche Scientifique (CNRS) UMR9198 - Institut National de la Santé et de la Recherche Médicale (Inserm) U1280, Team Calcium Signaling and Microbial Infections, Gif-sur-Yvette, France
| | - Patricia Latour-Lambert
- Institut Pasteur, Unité Dynamique des interactions hôtes-pathogènes and Centre National de la Recherche Scientifique (CNRS) UMR3691, Université de Paris Cité, Paris, France
| | - Jost Enninga
- Institut Pasteur, Unité Dynamique des interactions hôtes-pathogènes and Centre National de la Recherche Scientifique (CNRS) UMR3691, Université de Paris Cité, Paris, France
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15
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Luk CH, Enninga J, Valenzuela C. Fit to dwell in many places – The growing diversity of intracellular Salmonella niches. Front Cell Infect Microbiol 2022; 12:989451. [PMID: 36061869 PMCID: PMC9433700 DOI: 10.3389/fcimb.2022.989451] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 07/25/2022] [Indexed: 11/21/2022] Open
Abstract
Salmonella enterica is capable of invading different host cell types including epithelial cells and M cells during local infection, and immune cells and fibroblasts during the subsequent systemic spread. The intracellular lifestyles of Salmonella inside different cell types are remarkable for their distinct residential niches, and their varying replication rates. To study this, researchers have employed different cell models, such as various epithelial cells, immune cells, and fibroblasts. In epithelial cells, S. Typhimurium dwells within modified endolysosomes or gains access to the host cytoplasm. In the cytoplasm, the pathogen is exposed to the host autophagy machinery or poised for rapid multiplication, whereas it grows at a slower rate or remains dormant within the endomembrane-bound compartments. The swift bimodal lifestyle is not observed in fibroblasts and immune cells, and it emerges that these cells handle intracellular S. Typhimurium through different clearance machineries. Moreover, in these cell types S. Typhimurium grows withing modified phagosomes of distinct functional composition by adopting targeted molecular countermeasures. The preference for one or the other intracellular niche and the diverse cell type-specific Salmonella lifestyles are determined by the complex interactions between a myriad of bacterial effectors and host factors. It is important to understand how this communication is differentially regulated dependent on the host cell type and on the distinct intracellular growth rate. To support the efforts in deciphering Salmonella invasion across the different infection models, we provide a systematic comparison of the findings yielded from cell culture models. We also outline the future directions towards a better understanding of these differential Salmonella intracellular lifestyles.
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Affiliation(s)
- Chak Hon Luk
- Institut Pasteur, Unité « Dynamique des interactions hôte-pathogène » and CNRS UMR3691, Université de Paris Cité, Paris, France
- Host-Pathogen Interactions in Tuberculosis Laboratory, The Francis Crick Institute, London, United Kingdom
- *Correspondence: Chak Hon Luk, ; Camila Valenzuela,
| | - Jost Enninga
- Institut Pasteur, Unité « Dynamique des interactions hôte-pathogène » and CNRS UMR3691, Université de Paris Cité, Paris, France
| | - Camila Valenzuela
- Institut Pasteur, Unité « Dynamique des interactions hôte-pathogène » and CNRS UMR3691, Université de Paris Cité, Paris, France
- *Correspondence: Chak Hon Luk, ; Camila Valenzuela,
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16
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Luis LB, Ana GT, Carlos GE, Abraham GG, Iris EG, Martha ML, Vianney ON. Salmonella Promotes Its Own Survival in B Cells by Inhibiting Autophagy. Cells 2022; 11:cells11132061. [PMID: 35805144 PMCID: PMC9266210 DOI: 10.3390/cells11132061] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 06/18/2022] [Accepted: 06/27/2022] [Indexed: 02/01/2023] Open
Abstract
Salmonella is a Gram-negative bacterium known to be the major cause of gastrointestinal diseases and systemic infections. During infection of murine B cells, Salmonella activates the PI3K/Akt pathway through its effector, SopB. This signaling pathway induces the downregulation of NLRC4 transcription, resulting in reduced secretion of IL-1β. Thus, Salmonella-infected B cells do not progress to pyroptosis; consequently, the bacteria can survive inside these cells. However, the mechanism by which Salmonella evades the control of B cells has not yet been elucidated. In this study, we found that SopB activates mTORC1, which is necessary for bacterial survival, since B cells cultured with the mTORC1 inhibitor rapamycin and B cells lacking raptor can control Salmonella infection. A similar result was observed in B cells when they were infected with the Salmonella SopB mutant (Δsopb). Salmonella also promoted the phosphorylation of the ULK1 complex at serine 757 (Ser757) by mTORC1, resulting in decreased levels of LC3-II in infected B cells. In this study, we did not observe these results when B cells were infected with Δsopb Salmonella. Our results demonstrated that Salmonella survival within B cells depends on the inhibition of autophagy by mTORC1 activation.
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Affiliation(s)
- Lopez-Bailon Luis
- Departamento y Posgrado en Inmunología, Escuela Nacional de Ciencias Biológicas del Instituto Politécnico Nacional (ENCB-IPN), Mexico 11350, Mexico; (L.-B.L.); (E.-G.I.); (M.-L.M.)
| | - Gonzalez-Telona Ana
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Mexico 07360, Mexico; (G.-T.A.); (G.-E.C.); (G.-G.A.)
| | - Galán-Enríquez Carlos
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Mexico 07360, Mexico; (G.-T.A.); (G.-E.C.); (G.-G.A.)
| | - García-Gil Abraham
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Mexico 07360, Mexico; (G.-T.A.); (G.-E.C.); (G.-G.A.)
| | - Estrada-García Iris
- Departamento y Posgrado en Inmunología, Escuela Nacional de Ciencias Biológicas del Instituto Politécnico Nacional (ENCB-IPN), Mexico 11350, Mexico; (L.-B.L.); (E.-G.I.); (M.-L.M.)
| | - Moreno-Lafont Martha
- Departamento y Posgrado en Inmunología, Escuela Nacional de Ciencias Biológicas del Instituto Politécnico Nacional (ENCB-IPN), Mexico 11350, Mexico; (L.-B.L.); (E.-G.I.); (M.-L.M.)
| | - Ortiz-Navarrete Vianney
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Mexico 07360, Mexico; (G.-T.A.); (G.-E.C.); (G.-G.A.)
- Correspondence:
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17
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Walpole GFW, Pacheco J, Chauhan N, Clark J, Anderson KE, Abbas YM, Brabant-Kirwan D, Montaño-Rendón F, Liu Z, Zhu H, Brumell JH, Deiters A, Stephens LR, Hawkins PT, Hammond GRV, Grinstein S, Fairn GD. Kinase-independent synthesis of 3-phosphorylated phosphoinositides by a phosphotransferase. Nat Cell Biol 2022; 24:708-722. [PMID: 35484249 PMCID: PMC9107517 DOI: 10.1038/s41556-022-00895-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 03/08/2022] [Indexed: 01/10/2023]
Abstract
Despite their low abundance, phosphoinositides play a central role in membrane traffic and signalling. PtdIns(3,4,5)P3 and PtdIns(3,4)P2 are uniquely important, as they promote cell growth, survival and migration. Pathogenic organisms have developed means to subvert phosphoinositide metabolism to promote successful infection and their survival in host organisms. We demonstrate that PtdIns(3,4)P2 is a major product generated in host cells by the effectors of the enteropathogenic bacteria Salmonella and Shigella. Pharmacological, gene silencing and heterologous expression experiments revealed that, remarkably, the biosynthesis of PtdIns(3,4)P2 occurs independently of phosphoinositide 3-kinases. Instead, we found that the Salmonella effector SopB, heretofore believed to be a phosphatase, generates PtdIns(3,4)P2 de novo via a phosphotransferase/phosphoisomerase mechanism. Recombinant SopB is capable of generating PtdIns(3,4,5)P3 and PtdIns(3,4)P2 from PtdIns(4,5)P2 in a cell-free system. Through a remarkable instance of convergent evolution, bacterial effectors acquired the ability to synthesize 3-phosphorylated phosphoinositides by an ATP- and kinase-independent mechanism, thereby subverting host signalling to gain entry and even provoke oncogenic transformation.
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Affiliation(s)
- Glenn F W Walpole
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Jonathan Pacheco
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Neha Chauhan
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada
| | | | | | - Yazan M Abbas
- Molecular Medicine Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | | | - Fernando Montaño-Rendón
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Zetao Liu
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Hongxian Zhu
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - John H Brumell
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Alexander Deiters
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA
| | | | | | - Gerald R V Hammond
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Sergio Grinstein
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada.
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada.
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada.
| | - Gregory D Fairn
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada.
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada.
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, Canada.
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18
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Reprogramming of Cell Death Pathways by Bacterial Effectors as a Widespread Virulence Strategy. Infect Immun 2022; 90:e0061421. [PMID: 35467397 DOI: 10.1128/iai.00614-21] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The modulation of programmed cell death (PCD) processes during bacterial infections is an evolving arms race between pathogens and their hosts. The initiation of apoptosis, necroptosis, and pyroptosis pathways are essential to immunity against many intracellular and extracellular bacteria. These cellular self-destructive mechanisms are used by the infected host to restrict and eliminate bacterial pathogens. Without a tight regulatory control, host cell death can become a double-edged sword. Inflammatory PCDs contribute to an effective immune response against pathogens, but unregulated inflammation aggravates the damage caused by bacterial infections. Thus, fine-tuning of these pathways is required to resolve infection while preserving the host immune homeostasis. In turn, bacterial pathogens have evolved secreted virulence factors or effector proteins that manipulate PCD pathways to promote infection. In this review, we discuss the importance of controlled cell death in immunity to bacterial infection. We also detail the mechanisms employed by type 3 secreted bacterial effectors to bypass these pathways and their importance in bacterial pathogenesis.
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19
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Herod A, Emond-Rheault JG, Tamber S, Goodridge L, Lévesque RC, Rohde J. Genomic and phenotypic analysis of SspH1 identifies a new Salmonella effector, SspH3. Mol Microbiol 2021; 117:770-789. [PMID: 34942035 DOI: 10.1111/mmi.14871] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 12/19/2021] [Accepted: 12/19/2021] [Indexed: 11/28/2022]
Abstract
Salmonella is a major foodborne pathogen and is responsible for a range of diseases. Not all Salmonella contribute to severe health outcomes as there is a large degree of genetic heterogeneity among the 2600 serovars within the genus. This variability across Salmonella serovars is linked to numerous genetic elements that dictate virulence. While several genetic elements encode virulence factors with well documented contributions to pathogenesis, many genetic elements implicated in Salmonella virulence remain uncharacterized. Many pathogens encode a family of E3 ubiquitin ligases that are delivered into the cells that they infect using a Type 3 Secretion System (T3SS). These effectors, known as NEL-domain E3s, were first characterized in Salmonella. Most Salmonella encode the NEL-effectors sspH2 and slrP, whereas only a subset of Salmonella encode sspH1. SspH1 has been shown to ubiquitinate the mammalian protein kinase PKN1, which has been reported to negatively regulate the pro-survival program Akt. We discovered that SspH1 mediates the degradation of PKN1 during infection of a macrophage cell line but that this degradation does not impact Akt signaling. Genomic analysis of a large collection of Salmonella genomes identified a putative new gene, sspH3, with homology to sspH1. SspH3 is a novel NEL-domain effector.
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Affiliation(s)
- Adrian Herod
- Department of Microbiology and Immunology, Dalhousie University Halifax, Halifax, NS, B3H 4R2, Canada
| | | | - Sandeep Tamber
- Microbiology Research Division, Bureau of Microbial Hazards, Health Canada, Ottawa, ON, Canada
| | - Lawrence Goodridge
- Food Science Department, University of Guelph, East Guelph, ON, N1G 2W1, Canada
| | - Roger C Lévesque
- Institute for Integrative and Systems Biology, Université Laval, Québec City, QC, G1V 0A6, Canada
| | - John Rohde
- Department of Microbiology and Immunology, Dalhousie University Halifax, Halifax, NS, B3H 4R2, Canada
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20
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Histone H3 deacetylation promotes host cell viability for efficient infection by Listeria monocytogenes. PLoS Pathog 2021; 17:e1010173. [PMID: 34929015 PMCID: PMC8722725 DOI: 10.1371/journal.ppat.1010173] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 01/03/2022] [Accepted: 12/02/2021] [Indexed: 12/03/2022] Open
Abstract
For many intracellular bacterial pathogens manipulating host cell survival is essential for maintaining their replicative niche, and is a common strategy used to promote infection. The bacterial pathogen Listeria monocytogenes is well known to hijack host machinery for its own benefit, such as targeting the host histone H3 for modification by SIRT2. However, by what means this modification benefits infection, as well as the molecular players involved, were unknown. Here we show that SIRT2 activity supports Listeria intracellular survival by maintaining genome integrity and host cell viability. This protective effect is dependent on H3K18 deacetylation, which safeguards the host genome by counteracting infection-induced DNA damage. Mechanistically, infection causes SIRT2 to interact with the nucleic acid binding protein TDP-43 and localise to genomic R-loops, where H3K18 deacetylation occurs. This work highlights novel functions of TDP-43 and R-loops during bacterial infection and identifies the mechanism through which L. monocytogenes co-opts SIRT2 to allow efficient infection. To cause systemic disease Listeria monocytogenes assumes an intracellular lifestyle which supports its growth and dissemination during infection. In order to maintain the intracellular niche L. monocytogenes manipulates various host cell processes thereby promoting its own survival and infection. One such example is the hijacking of a host deacetylase called SIRT2 which upon infection localises to chromatin, specifically modifies lysine 18 of histone H3 and promotes intracellular bacterial growth. Here we identify how SIRT2 promotes infection. We show that SIRT2-mediated H3K18 deacetylation counteracts infection-induced DNA damage and identify the molecular complex at play. Such SIRT2 activity has a crucial role in promoting host cell viability during infection, allowing for better survival upon heavy intracellular bacterial burden, and resulting in enhanced infection by L. monocytogenes.
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21
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Chu BX, Li YN, Liu N, Yuan LX, Chen SY, Zhu YH, Wang JF. Salmonella Infantis Delays the Death of Infected Epithelial Cells to Aggravate Bacterial Load by Intermittent Phosphorylation of Akt With SopB. Front Immunol 2021; 12:757909. [PMID: 34804044 PMCID: PMC8602575 DOI: 10.3389/fimmu.2021.757909] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 10/19/2021] [Indexed: 11/13/2022] Open
Abstract
Salmonella Infantis has emerged as a major clinical pathogen causing gastroenteritis worldwide in recent years. As an intracellular pathogen, Salmonella has evolved to manipulate and benefit from the cell death signaling pathway. In this study, we discovered that S. Infantis inhibited apoptosis of infected Caco-2 cells by phosphorylating Akt. Notably, Akt phosphorylation was observed in a discontinuous manner: immediately 0.5 h after the invasion, then before peak cytosolic replication. Single-cell analysis revealed that the second phase was only induced by cytosolic hyper-replicating bacteria at 3-4 hpi. Next, Akt-mediated apoptosis inhibition was found to be initiated by Salmonella SopB. Furthermore, Akt phosphorylation increased mitochondrial localization of Bcl-2 to prevent Bax oligomerization on the mitochondrial membrane, maintaining the mitochondrial network homeostasis to resist apoptosis. In addition, S. Infantis induced pyroptosis, as evidenced by increased caspase-1 (p10) and GSDMS-N levels. In contrast, cells infected with the ΔSopB strain displayed faster but less severe pyroptosis and had less bacterial load. The results indicated that S. Infantis SopB-mediated Akt phosphorylation delayed pyroptosis, but aggravated its severity. The wild-type strain also caused more severe diarrhea and intestinal inflammatory damage than the ΔSopB strain in mice. These findings revealed that S. Infantis delayed the cells' death by intermittent activation of Akt, allowing sufficient time for replication, thereby causing more severe inflammation.
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Affiliation(s)
| | | | | | | | | | | | - Jiu-Feng Wang
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, China Agricultural University, Beijing, China
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22
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Chatterjee S, Lekmeechai S, Constantinou N, Grzybowska EA, Kozik Z, Choudhary JS, Berger CN, Frankel G, Clements A. The type III secretion system effector EspO of enterohaemorrhagic Escherichia coli inhibits apoptosis through an interaction with HAX-1. Cell Microbiol 2021; 23:e13366. [PMID: 34021690 PMCID: PMC7613270 DOI: 10.1111/cmi.13366] [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: 12/16/2020] [Revised: 05/13/2021] [Accepted: 05/17/2021] [Indexed: 12/15/2022]
Abstract
Many enteric pathogens employ a type III secretion system (T3SS) to translocate effector proteins directly into the host cell cytoplasm, where they subvert signalling pathways of the intestinal epithelium. Here, we report that the anti-apoptotic regulator HS1-associated protein X1 (HAX-1) is an interaction partner of the T3SS effectors EspO of enterohaemorrhagic Escherichia coli (EHEC) and Citrobacter rodentium, OspE of Shigella flexneri and Osp1STYM of Salmonella enterica serovar Typhimurium. EspO, OspE and Osp1STYM have previously been reported to interact with the focal adhesions protein integrin linked kinase (ILK). We found that EspO localizes both to the focal adhesions (ILK localisation) and mitochondria (HAX-1 localisation), and that increased expression of HAX-1 leads to enhanced mitochondrial localisation of EspO. Ectopic expression of EspO, OspE and Osp1STYM protects cells from apoptosis induced by staurosporine and tunicamycin. Depleting cells of HAX-1 indicates that the anti-apoptotic activity of EspO is HAX-1 dependent. Both HAX-1 and ILK were further confirmed as EspO1-interacting proteins during infection using T3SS-delivered EspO1. Using cell detachment as a proxy for cell death we confirmed that T3SS-delivered EspO1 could inhibit cell death induced during EPEC infection, to a similar extent as the anti-apoptotic effector NleH, or treatment with the pan caspase inhibitor z-VAD. In contrast, in cells lacking HAX-1, EspO1 was no longer able to protect against cell detachment, while NleH1 and z-VAD maintained their protective activity. Therefore, during both infection and ectopic expression EspO protects cells from cell death by interacting with HAX-1. These results suggest that despite the differences between EHEC, C. rodentium, Shigella and S. typhimurium infections, hijacking HAX-1 anti-apoptotic signalling is a common strategy to maintain the viability of infected cells. TAKE AWAY: EspO homologues are found in EHEC, Shigella, S. typhimurium and some EPEC. EspO homologues interact with HAX-1. EspO protects infected cells from apoptosis. EspO joins a growing list of T3SS effectors that manipulate cell death pathways.
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Affiliation(s)
- Sharanya Chatterjee
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College, London, UK
| | - Sujinna Lekmeechai
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College, London, UK
| | - Nicolas Constantinou
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College, London, UK
| | - Ewa A. Grzybowska
- Department of Molecular and Translational Oncology, Maria Sklodowska-Curie National Institute of Oncology, Warsaw, Poland
| | - Zuzanna Kozik
- Functional Proteomics Group, The Institute for Cancer Research, London, UK
| | - Jyoti S. Choudhary
- Functional Proteomics Group, The Institute for Cancer Research, London, UK
| | - Cedric N. Berger
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College, London, UK
| | - Gad Frankel
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College, London, UK
| | - Abigail Clements
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College, London, UK
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23
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Zhuang J, Ji X, Zhu Y, Liu W, Sun J, Jiao X, Xu X. Restriction of intracellular Salmonella typhimurium growth by the small-molecule autophagy inducer A77 1726 through the activation of the AMPK-ULK1 axis. Vet Microbiol 2021; 254:108982. [PMID: 33461007 DOI: 10.1016/j.vetmic.2021.108982] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 01/05/2021] [Indexed: 11/28/2022]
Abstract
Autophagy plays an important role in restricting the growth of invading intracellular microbes. Salmonella (S) Typhimurium, an intracellular pathogen that causes gastroenteritis and food poisoning in humans, evades autophagic detection by multiple mechanisms. There has been growing interest in developing autophagy inducers as novel antimicrobial agents for treating intracellular bacterial infections. We recently reported that A77 1726, the active metabolite of the anti-inflammatory drug leflunomide, induces autophagy by activating AMP-activated protein kinase (AMPK) and Unc-51 like autophagy activating kinase 1 (ULK1). Our present study aims to determine if A77 1726 was able to restrict intracellular Salmonella growth by inducing autophagy. We first confirmed the ability of A77 1726 to induce autophagy by activating the AMPK-ULK1 axis in uninfected RAW264.7 (a murine macrophage cell line) and HeLa cells (a human cervical carcinoma cell line). A77 1726 enhanced autophagy in S. Typhimurium-infected cells, as evidenced by increased levels of LC3 lipidation and increased numbers of autophagosomes and autolysosomes. Confocal microscopy revealed that A77 1726 induced xenophagy in macrophages, as evidenced by an increased number of LC3-coated bacteria in the cytoplasm. A77 1726 significantly decreased the number of intracellular S. Typhimurium in macrophages. Taken together, our study has demonstrated the ability of A77 1726 to restrict intracellular S. Typhimurium growth in vitro by enhancing xenophagy.
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Affiliation(s)
- Jing Zhuang
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu Province, PR China
| | - Xiaoyue Ji
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu Province, PR China
| | - Yue Zhu
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu Province, PR China
| | - Wei Liu
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu Province, PR China
| | - Jing Sun
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu Province, PR China
| | - Xinan Jiao
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, 225009, PR China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, 225009, Jiangsu Province, PR China
| | - Xiulong Xu
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu Province, PR China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, 225009, Jiangsu Province, PR China; Joint International Research Laboratory of Agriculture and Agri-Product Safety, the Ministry of Education of China, Yangzhou University, Yangzhou, 225009, PR China.
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24
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Stévenin V, Chang YY, Le Toquin Y, Duchateau M, Gianetto QG, Luk CH, Salles A, Sohst V, Matondo M, Reiling N, Enninga J. Dynamic Growth and Shrinkage of the Salmonella-Containing Vacuole Determines the Intracellular Pathogen Niche. Cell Rep 2020; 29:3958-3973.e7. [PMID: 31851926 PMCID: PMC6931108 DOI: 10.1016/j.celrep.2019.11.049] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 09/23/2019] [Accepted: 11/12/2019] [Indexed: 12/21/2022] Open
Abstract
Salmonella is a human and animal pathogen that causes gastro-enteric diseases. The key to Salmonella infection is its entry into intestinal epithelial cells, where the bacterium resides within a Salmonella-containing vacuole (SCV). Salmonella entry also induces the formation of empty macropinosomes, distinct from the SCV, in the vicinity of the entering bacteria. A few minutes after its formation, the SCV increases in size through fusions with the surrounding macropinosomes. Salmonella also induces membrane tubules that emanate from the SCV and lead to SCV shrinkage. Here, we show that these antipodal events are utilized by Salmonella to either establish a vacuolar niche or to be released into the cytosol by SCV rupture. We identify the molecular machinery underlying dynamic SCV growth and shrinkage. In particular, the SNARE proteins SNAP25 and STX4 participate in SCV inflation by fusion with macropinosomes. Thus, host compartment size control emerges as a pathogen strategy for intracellular niche regulation. The early SCV simultaneously grows and shrinks through fusion and tubule formation SCV shrinkage promotes vacuolar rupture and cytosolic release IAMs are enriched in the host SNAREs SNAP25 and STX4, enabling IAM-SCV fusion Promoting SNX1-mediated tubule formation, SopB fosters SCV ruptures
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Affiliation(s)
- Virginie Stévenin
- Institut Pasteur, Dynamics of Host-Pathogen Interactions Unit, 25 Rue du Dr. Roux, Paris, France
| | - Yuen-Yan Chang
- Institut Pasteur, Dynamics of Host-Pathogen Interactions Unit, 25 Rue du Dr. Roux, Paris, France
| | - Yoann Le Toquin
- Institut Pasteur, Dynamics of Host-Pathogen Interactions Unit, 25 Rue du Dr. Roux, Paris, France
| | - Magalie Duchateau
- Institut Pasteur, Plateforme Protéomique, Unité de Spectrométrie de Masse pour la Biologie, C2RT, USR 2000 CNRS, Paris, France
| | - Quentin Giai Gianetto
- Institut Pasteur, Plateforme Protéomique, Unité de Spectrométrie de Masse pour la Biologie, C2RT, USR 2000 CNRS, Paris, France; Institut Pasteur, Bioinformatics and Biostatistics HUB, C3BI, USR CNRS 3756, Paris, France
| | - Chak Hon Luk
- Institut Pasteur, Dynamics of Host-Pathogen Interactions Unit, 25 Rue du Dr. Roux, Paris, France
| | - Audrey Salles
- Institut Pasteur, UtechS Photonic BioImaging PBI (Imagopole), Centre de Recherche et de Ressources Technologiques C2RT, Paris, France
| | - Victoria Sohst
- Research Center Borstel, Leibniz Lung Center, RG Microbial Interface Biology, Parkallee 22, 23845 Borstel, Germany
| | - Mariette Matondo
- Institut Pasteur, Plateforme Protéomique, Unité de Spectrométrie de Masse pour la Biologie, C2RT, USR 2000 CNRS, Paris, France
| | - Norbert Reiling
- Research Center Borstel, Leibniz Lung Center, RG Microbial Interface Biology, Parkallee 22, 23845 Borstel, Germany; German Center for Infection Research (DZIF), Partner Site Hamburg-Lübeck-Borstel-Riems, Borstel, Germany
| | - Jost Enninga
- Institut Pasteur, Dynamics of Host-Pathogen Interactions Unit, 25 Rue du Dr. Roux, Paris, France.
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25
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Liu W, Ruan T, Ji X, Ran D, Sun J, Shi H, Prinz RA, Sun J, Pan Z, Jiao X, Xu X. The Gli1-Snail axis contributes to Salmonella Typhimurium-induced disruption of intercellular junctions of intestinal epithelial cells. Cell Microbiol 2020; 22:e13211. [PMID: 32329192 DOI: 10.1111/cmi.13211] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 01/06/2020] [Accepted: 01/07/2020] [Indexed: 12/11/2022]
Abstract
Salmonella enterica serovar Typhimurium (S. Typhimurium) is a facultative intracellular pathogen that damages gastrointestinal tissue and causes severe diarrhoea. The mechanisms by which Salmonella disrupts epithelial barrier and increases the paracellular permeability are incompletely understood. Our present study aims to determine the role of Gli1, a transcription factor activated in the sonic hedgehog (Shh) pathway, in decreasing the levels of apical junction proteins in a Salmonella-infected human colonic epithelial cancer cell line, Caco-2, and in the intestinal tissue of Salmonella-infected mice. Here, we report that S. Typhimurium increased the mRNA and protein levels of Gli1 and Snail, a downstream transcription factor that plays an important role in the epithelial-to-mesenchymal transition (EMT). S. Typhimurium also decreased the levels of E-cadherin and three tight junction proteins (ZO-1, claudin-1, and occludin). Gli1 siRNA and GANT61, a Gli1-specific inhibitor, blocked S. Typhimurium-induced Snail expression, restored the levels of E-cadherin and tight junction proteins, and prevented S. Typhimurium-increased paracellular permeability. Further study showed that Gli1 was cross-activated by the MAP and PI-3 kinase pathways. S. Typhimurium devoid of sopB, an effector of the Type 3 secretion system (T3SS) responsible for AKT activation, was unable to induce Snail expression and to decrease the expression of apical junction proteins. Our study uncovered a novel role of Gli1 in mediating the Salmonella-induced disruption of the intestinal epithelial barrier.
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Affiliation(s)
- Wei Liu
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Tao Ruan
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Xiaoyue Ji
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Di Ran
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Jing Sun
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Huoying Shi
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Richard A Prinz
- Department of Surgery, NorthShore University Health System, Evanston, Illinois, USA
| | - Jun Sun
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Zhiming Pan
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China
| | - Xinan Jiao
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China
| | - Xiulong Xu
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China.,Department of Cell and Molecular Medicine, Rush University Medical Center, Chicago, Illinois, USA
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26
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Yu C, Du F, Zhang C, Li Y, Liao C, He L, Cheng X, Zhang X. Salmonella enterica serovar Typhimurium sseK3 induces apoptosis and enhances glycolysis in macrophages. BMC Microbiol 2020; 20:151. [PMID: 32517648 PMCID: PMC7282050 DOI: 10.1186/s12866-020-01838-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 06/02/2020] [Indexed: 02/07/2023] Open
Abstract
Background Salmonella enterica serovar Typhimurium (S. Typhimurium) is an important infectious disease pathogen that can survive and replicate in macrophages. Glycolysis is essential for immune responses against S. Typhimurium infection in macrophages, and is also associated with apoptosis. S. Typhimurium secreted effector K3 (SseK3) was recently identified as a novel translated and secreted protein. However, there is no study about the role of sseK3 in the relationship between apoptosis and glycolysis in cells infected with S. Typhimurium. It is unclear whether this protein exerts a significant role in the progress of apoptosis and glycolysis in S. Typhimurium-infected macrophages. Results Macrophages were infected with S. Typhimurium SL1344 wild-type (WT), ΔsseK3 mutant or sseK3-complemented strain, and the effects of sseK3 on apoptosis and glycolysis were determined. The adherence and invasion in the ΔsseK3 mutant group were similar to that in the WT and sseK3-complemented groups, indicating that SseK3 was not essential for the adherence and invasion of S. Typhimurium in macrophages. However, the percentage of apoptosis in the ΔsseK3 mutant group was much lower than that in the WT and sseK3-complemented groups. Caspase-3, caspase-8, and caspase-9 enzyme activity in the ΔsseK3 mutant group were significantly lower than in the WT group and sseK3-complemented groups, indicating that sseK3 could improve the caspase-3, caspase-8, and caspase-9 enzyme activity. We also found that there were no significant differences in pyruvic acid levels between the three groups, but the lactic acid level in the ΔsseK3 mutant group was much lower than that in the WT and sseK3-complemented groups. The ATP levels in the ΔsseK3 mutant group were remarkably higher than those in the WT and sseK3-complemented groups. These indicated that the sseK3 enhanced the level of glycolysis in macrophages infected by S. Typhimurium. Conclusions S. Typhimurium sseK3 is likely involved in promoting macrophage apoptosis and modulating glycolysis in macrophages. Our results could improve our understanding of the relationship between apoptosis and glycolysis in macrophages induced by S. Typhimurium sseK3.
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Affiliation(s)
- Chuan Yu
- The Key Lab of Animal Disease and Public Health, Henan University of Science and Technology, 263 Kaiyuan Avenue, Luoyang, 471023, Henan, China.,Luoyang Key Laboratory of Live Carrier Biomaterial and Animal Disease Prevention and Control, Luoyang, 471023, Henan, China.,Luoyang Polytechnic, 6 Airport Road, Luoyang, 471023, Henan, China
| | - Fuyu Du
- The Key Lab of Animal Disease and Public Health, Henan University of Science and Technology, 263 Kaiyuan Avenue, Luoyang, 471023, Henan, China.,Luoyang Key Laboratory of Live Carrier Biomaterial and Animal Disease Prevention and Control, Luoyang, 471023, Henan, China
| | - Chunjie Zhang
- The Key Lab of Animal Disease and Public Health, Henan University of Science and Technology, 263 Kaiyuan Avenue, Luoyang, 471023, Henan, China. .,Luoyang Key Laboratory of Live Carrier Biomaterial and Animal Disease Prevention and Control, Luoyang, 471023, Henan, China.
| | - Yinju Li
- The Key Lab of Animal Disease and Public Health, Henan University of Science and Technology, 263 Kaiyuan Avenue, Luoyang, 471023, Henan, China.,Luoyang Key Laboratory of Live Carrier Biomaterial and Animal Disease Prevention and Control, Luoyang, 471023, Henan, China
| | - Chengshui Liao
- The Key Lab of Animal Disease and Public Health, Henan University of Science and Technology, 263 Kaiyuan Avenue, Luoyang, 471023, Henan, China.,Luoyang Key Laboratory of Live Carrier Biomaterial and Animal Disease Prevention and Control, Luoyang, 471023, Henan, China
| | - Lei He
- The Key Lab of Animal Disease and Public Health, Henan University of Science and Technology, 263 Kaiyuan Avenue, Luoyang, 471023, Henan, China.,Luoyang Key Laboratory of Live Carrier Biomaterial and Animal Disease Prevention and Control, Luoyang, 471023, Henan, China
| | - Xiangchao Cheng
- The Key Lab of Animal Disease and Public Health, Henan University of Science and Technology, 263 Kaiyuan Avenue, Luoyang, 471023, Henan, China.,Luoyang Key Laboratory of Live Carrier Biomaterial and Animal Disease Prevention and Control, Luoyang, 471023, Henan, China.,Luoyang Polytechnic, 6 Airport Road, Luoyang, 471023, Henan, China
| | - Xiaojie Zhang
- The Key Lab of Animal Disease and Public Health, Henan University of Science and Technology, 263 Kaiyuan Avenue, Luoyang, 471023, Henan, China.,Luoyang Key Laboratory of Live Carrier Biomaterial and Animal Disease Prevention and Control, Luoyang, 471023, Henan, China
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27
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Walpole GFW, Grinstein S. Endocytosis and the internalization of pathogenic organisms: focus on phosphoinositides. F1000Res 2020; 9. [PMID: 32494357 PMCID: PMC7233180 DOI: 10.12688/f1000research.22393.1] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/07/2020] [Indexed: 12/18/2022] Open
Abstract
Despite their comparatively low abundance in biological membranes, phosphoinositides are key to the regulation of a diverse array of signaling pathways and direct membrane traffic. The role of phosphoinositides in the initiation and progression of endocytic pathways has been studied in considerable depth. Recent advances have revealed that distinct phosphoinositide species feature prominently in clathrin-dependent and -independent endocytosis as well as in phagocytosis and macropinocytosis. Moreover, a variety of intracellular and cell-associated pathogens have developed strategies to commandeer host cell phosphoinositide metabolism to gain entry and/or metabolic advantage, thereby promoting their survival and proliferation. Here, we briefly survey the current knowledge on the involvement of phosphoinositides in endocytosis, phagocytosis, and macropinocytosis and highlight several examples of molecular mimicry employed by pathogens to either “hitch a ride” on endocytic pathways endogenous to the host or create an entry path of their own.
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Affiliation(s)
- Glenn F W Walpole
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Sergio Grinstein
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada.,Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, ON, Canada
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28
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M Campos JC, Antunes LCM, Ferreira RBR. Global priority pathogens: virulence, antimicrobial resistance and prospective treatment options. Future Microbiol 2020; 15:649-677. [DOI: 10.2217/fmb-2019-0333] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and Salmonella spp. are part of a group of pathogens that pose a major threat to human health due to the emergence of multidrug-resistant strains. Moreover, these bacteria have several virulence factors that allow them to successfully colonize their hosts, such as toxins and the ability to produce biofilms, resulting in an urgent need to develop new strategies to fight these pathogens. In this review, we compile the most up-to-date information on the epidemiology, virulence and resistance of these clinically important microorganisms. Additionally, we address new therapeutic alternatives, with a focus on molecules with antivirulence activity, which are considered promising to combat multidrug-resistant bacteria.
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Affiliation(s)
- Juliana C de M Campos
- Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Luis CM Antunes
- Escola Nacional de Saúde Pública Sergio Arouca, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil
- Instituto Nacional de Ciência e Tecnologia de Inovação em Doenças de Populações Negligenciadas, Centro de Desenvolvimento Tecnológico em Saúde, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil
| | - Rosana BR Ferreira
- Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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29
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He TT, Zhou Y, Liu YL, Li DY, Nie P, Li AH, Xie HX. Edwardsiella piscicida
type III protein EseJ suppresses apoptosis through down regulating type 1 fimbriae, which stimulate the cleavage of caspase‐8. Cell Microbiol 2020; 22:e13193. [DOI: 10.1111/cmi.13193] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 01/24/2020] [Accepted: 02/10/2020] [Indexed: 01/13/2023]
Affiliation(s)
- Tian Tian He
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of HydrobiologyChinese Academy of Sciences Wuhan China
- University of Chinese Academy of Sciences Beijing China
| | - Ying Zhou
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of HydrobiologyChinese Academy of Sciences Wuhan China
- University of Chinese Academy of Sciences Beijing China
| | - Ying Li Liu
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of HydrobiologyChinese Academy of Sciences Wuhan China
- University of Chinese Academy of Sciences Beijing China
| | - Duan You Li
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of HydrobiologyChinese Academy of Sciences Wuhan China
- University of Chinese Academy of Sciences Beijing China
| | - Pin Nie
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of HydrobiologyChinese Academy of Sciences Wuhan China
- Laboratory for Marine Biology and BiotechnologyPilot National Laboratory for Marine Science and Technology (Qingdao) Qingdao China
- School of Marine Science and EngineeringQingdao Agricultural University Qingdao China
| | - Ai Hua Li
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of HydrobiologyChinese Academy of Sciences Wuhan China
| | - Hai Xia Xie
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of HydrobiologyChinese Academy of Sciences Wuhan China
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30
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Azimi T, Zamirnasta M, Sani MA, Soltan Dallal MM, Nasser A. Molecular Mechanisms of Salmonella Effector Proteins: A Comprehensive Review. Infect Drug Resist 2020; 13:11-26. [PMID: 32021316 PMCID: PMC6954085 DOI: 10.2147/idr.s230604] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 12/20/2019] [Indexed: 12/27/2022] Open
Abstract
Salmonella can be categorized into many serotypes, which are specific to known hosts or broadhosts. It makes no difference which one of the serotypes would penetrate the gastrointestinal tract because they all face similar obstacles such as mucus and microbiome. However, following their penetration, some species remain in the gastrointestinal tract; yet, others spread to another organ like gallbladder. Salmonella is required to alter the immune response to sustain its intracellular life. Changing the host response requires particular effector proteins and vehicles to translocate them. To this end, a categorized gene called Salmonella pathogenicity island (SPI) was developed; genes like Salmonella pathogenicity island encode aggressive or modulating proteins. Initially, Salmonella needs to be attached and stabilized via adhesin factor, without which no further steps can be taken. In this review, an attempt has been made to elaborate on each factor attached to the host cell or to modulating and aggressive proteins that evade immune systems. This review includes four sections: (A) attachment factors or T3SS- independent entrance, (B) effector proteins or T3SS-dependent entrance, (c) regulation of invasive genes, and (D) regulation of immune responses.
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Affiliation(s)
- Taher Azimi
- Pediatric Infections Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Students Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Maryam Zamirnasta
- Clinical Microbiology Research Center, Ilam University of Medical Science, Ilam, Iran
| | - Mahmood Alizadeh Sani
- Food Safety and Hygiene Division, Environmental health Department, School of Public Health, Tehran University of medical sciences, Tehran, Iran.,Students Research Committee, Department of Food Sciences and Technology, Faculty of Nutrition and Food Sciences, Tabriz University of Medical Sciences, Tabriz, Iran
| | | | - Ahmad Nasser
- Clinical Microbiology Research Center, Ilam University of Medical Science, Ilam, Iran.,Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.,Department of Medical Microbiology, School of Medicine, Ilam University of Medical Science, Ilam, Iran
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31
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Liu W, Zhuang J, Jiang Y, Sun J, Prinz RA, Sun J, Jiao X, Xu X. Toll-like receptor signalling cross-activates the autophagic pathway to restrict Salmonella Typhimurium growth in macrophages. Cell Microbiol 2019; 21:e13095. [PMID: 31392811 DOI: 10.1111/cmi.13095] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 08/05/2019] [Accepted: 08/06/2019] [Indexed: 12/14/2022]
Abstract
It has been long recognised that activation of toll-like receptors (TLRs) induces autophagy to restrict intracellular bacterial growth. However, the mechanisms of TLR-induced autophagy are incompletely understood. Salmonella Typhimurium is an intracellular pathogen that causes food poisoning and gastroenteritis in humans. Whether TLR activation contributes to S. Typhimurium-induced autophagy has not been investigated. Here, we report that S. Typhimurium and TLRs shared a common pathway to induce autophagy in macrophages. We first showed that S. Typhimurium-induced autophagy in a RAW264.7 murine macrophage cell line was mediated by the AMP-activated protein kinase (AMPK) through activation of the TGF-β-activated kinase (TAK1), a kinase activated by multiple TLRs. AMPK activation led to increased phosphorylation of Unc-51-like autophagy activating kinase (ULK1) at S317 and S555. ULK1 phosphorylation at these two sites in S. Typhimurium-infected macrophages overrode the inhibitory effect of mTOR on ULK1 activity due to mTOR-mediated ULK1 phosphorylation at S757. Lipopolysaccharide (LPS), flagellin, and CpG oligodeoxynucleotide, which activate TLR4, TLR5, and TLR9, respectively, increased TAK1 and AMPK phosphorylation and induced autophagy in RAW264.7 cells and in bone marrow-derived macrophages. However, LPS was unable to induce TAK1 and AMPK phosphorylation and autophagy in TLR4-deficient macrophages. TAK1 and AMPK-specific inhibitors blocked S. Typhimurium-induced autophagy and xenophagy and increased the bacterial growth in RAW264.7 cells. These observations collectively suggest that activation of the TAK1-AMPK axis through TLRs is essential for S. Typhimurium-induced autophagy and that TLR signalling cross-activates the autophagic pathway to clear intracellular bacteria.
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Affiliation(s)
- Wei Liu
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Jing Zhuang
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Yuanyuan Jiang
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Jing Sun
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Richard A Prinz
- Department of Surgery, NorthShore University Health System, Evanston, Illinois
| | - Jun Sun
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Xinan Jiao
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China.,Institutes of Agricultural Science and Technology Development, Yangzhou University, Yangzhou, China
| | - Xiulong Xu
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China.,Institutes of Agricultural Science and Technology Development, Yangzhou University, Yangzhou, China.,Department of Cell and Molecular Medicine, Rush University Medical Center, Chicago, Illinois
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32
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Lou L, Zhang P, Piao R, Wang Y. Salmonella Pathogenicity Island 1 (SPI-1) and Its Complex Regulatory Network. Front Cell Infect Microbiol 2019; 9:270. [PMID: 31428589 PMCID: PMC6689963 DOI: 10.3389/fcimb.2019.00270] [Citation(s) in RCA: 153] [Impact Index Per Article: 30.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 07/12/2019] [Indexed: 11/30/2022] Open
Abstract
Salmonella species can infect a diverse range of birds, reptiles, and mammals, including humans. The type III protein secretion system (T3SS) encoded by Salmonella pathogenicity island 1 (SPI-1) delivers effector proteins required for intestinal invasion and the production of enteritis. The T3SS is regarded as the most important virulence factor of Salmonella. SPI-1 encodes transcription factors that regulate the expression of some virulence factors of Salmonella, while other transcription factors encoded outside SPI-1 participate in the expression of SPI-1-encoded genes. SPI-1 genes are responsible for the invasion of host cells, regulation of the host immune response, e.g., the host inflammatory response, immune cell recruitment and apoptosis, and biofilm formation. The regulatory network of SPI-1 is very complex and crucial. Here, we review the function, effectors, and regulation of SPI-1 genes and their contribution to the pathogenicity of Salmonella.
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Affiliation(s)
- Lixin Lou
- Department of Infectious Diseases, First Hospital of Jilin University, Changchun, China
| | - Peng Zhang
- Department of Infectious Diseases, First Hospital of Jilin University, Changchun, China.,Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Rongli Piao
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Department of Gastroenterology, First Hospital of Jilin University, Changchun, China
| | - Yang Wang
- Department of Infectious Diseases, First Hospital of Jilin University, Changchun, China.,Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
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33
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Wemyss MA, Pearson JS. Host Cell Death Responses to Non-typhoidal Salmonella Infection. Front Immunol 2019; 10:1758. [PMID: 31402916 PMCID: PMC6676415 DOI: 10.3389/fimmu.2019.01758] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 07/11/2019] [Indexed: 12/20/2022] Open
Abstract
Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) is a Gram-negative bacterium with a broad host range that causes non-typhoidal salmonellosis in humans. S. Typhimurium infects epithelial cells and macrophages in the small intestine where it replicates in a specialized intracellular niche called the Salmonella-containing vacuole (SCV) and promotes inflammation of the mucosa to induce typically self-limiting gastroenteritis. Virulence and spread of the bacterium is determined in part by the host individual's ability to limit the infection through innate immune responses at the gastrointestinal mucosa, including programmed cell death. S. Typhimurium however, has evolved a myriad of mechanisms to counteract or exploit host responses through the use of Type III Secretion Systems (T3SS), which allow the translocation of virulence (effector) proteins into the host cell for the benefit of optimal bacterial replication and dissemination. T3SS effectors have been found to interact with apoptotic, necroptotic, and pyroptotic cell death cascades, interfering with both efficient clearance of the bacteria and the recruitment of neutrophils or dendritic cells to the area of infection. The interplay of host inflammation, programmed cell death responses, and bacterial defenses in the context of non-typhoidal Salmonella (NTS) infection is a continuing area of interest within the field, and as such has been reviewed here.
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Affiliation(s)
- Madeleine A Wemyss
- Department of Molecular and Translational Research, Monash University, Clayton, VIC, Australia.,Department of Microbiology, Monash University, Clayton, VIC, Australia
| | - Jaclyn S Pearson
- Department of Molecular and Translational Research, Monash University, Clayton, VIC, Australia.,Department of Microbiology, Monash University, Clayton, VIC, Australia
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34
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Behar SM, Briken V. Apoptosis inhibition by intracellular bacteria and its consequence on host immunity. Curr Opin Immunol 2019; 60:103-110. [PMID: 31228759 DOI: 10.1016/j.coi.2019.05.007] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 05/07/2019] [Accepted: 05/11/2019] [Indexed: 02/08/2023]
Abstract
Regulated cell death via apoptosis not only is important for organismal homeostasis but also serves as an innate defense mechanism. The engulfment of apoptotic infected cells, a process known as efferocytosis, is a common pathway for the destruction of many intracellular bacteria. Some pathogens take advantage of efferocytosis to prevent activation of macrophages and thereby facilitate their dissemination. Conversely, many obligate intracellular bacterial pathogens and some facultative-intracellular bacteria inhibit apoptosis, preventing efferocytosis, and evading innate host defenses. The molecular mechanism of bacterial effectors includes secreted proteins that bind to and inhibit apoptosis cell signaling pathways. We provide an overview of the known bacterial effectors, their host cell targets and their importance for the virulence of human pathogens.
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Affiliation(s)
- Samuel M Behar
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA, USA.
| | - Volker Briken
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, USA.
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35
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Wei S, Huang J, Liu Z, Wang M, Zhang B, Lian Z, Guo Y, Han H. Differential immune responses of C57BL/6 mice to infection by Salmonella enterica serovar Typhimurium strain SL1344, CVCC541 and CMCC50115. Virulence 2019; 10:248-259. [PMID: 30898022 PMCID: PMC6527021 DOI: 10.1080/21505594.2019.1597496] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
With a broad range of hosts, Salmonella enterica serovar Typhimurium (S. Typhimurium) is the major cause of gastroenteritis in human beings and systemic disease in susceptible mice strains. However, different S. Typhimurium strains differ in regard to virulence and host adaptation. Here, C57BL/6 mice were infected, respectively, with different S. Typhimurium strains SL1344 (calf), CVCC541 (chicken) and CMCC50115 (mutton) to determine their virulence and host immune responses. It was found that mice were less susceptible to infection by S. Typhimurium CVCC541 and CMCC50115 strains, with lower lethality and decreased bacterial burden in liver and spleen. Besides, S. Typhimurium strains CVCC541 and CMCC50115 enhanced host innate immune responses by increased frequencies of macrophages and neutrophils 3 days after infection. But SL1344 strain evaded immune response by inducing apoptosis of macrophages. Moreover, CVCC541 could elicit adaptive immune responses of host 11 days after infection upon examination of the proliferation and activation of CD4+ T cells. In addition, 125 and 138 unique mutant coding genes, respectively, in S. Typhimurium strains CVCC541 and CMCC50115 and 78 shared mutant coding genes were annotated by genomic alignment to SL1344 genome and the signal pathways involving these genes were further analyzed. The acquired results indicate that different original S. Typhimurium strains show differential virulence and may induce diverse immune responses in the same host infected.
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Affiliation(s)
- Shao Wei
- a State Key Laboratory of Animal Nutrition, College of Animal Science and Technology , China Agricultural University , Beijing , China.,b Beijing Key Laboratory of Animal Genetic Improvement, College of Animal Science and Technology , China Agricultural University , Beijing , China.,c National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology , China Agricultural University , Beijing , China
| | - Jianwei Huang
- b Beijing Key Laboratory of Animal Genetic Improvement, College of Animal Science and Technology , China Agricultural University , Beijing , China.,c National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology , China Agricultural University , Beijing , China.,d Key Laboratory of Animal Genetics, Breeding and Reproduction of the Ministry of Agriculture and Rural Affairs, College of Animal Science and Technology , China Agricultural University , Beijing , China
| | - Zhexi Liu
- b Beijing Key Laboratory of Animal Genetic Improvement, College of Animal Science and Technology , China Agricultural University , Beijing , China.,c National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology , China Agricultural University , Beijing , China.,d Key Laboratory of Animal Genetics, Breeding and Reproduction of the Ministry of Agriculture and Rural Affairs, College of Animal Science and Technology , China Agricultural University , Beijing , China
| | - Mengyao Wang
- b Beijing Key Laboratory of Animal Genetic Improvement, College of Animal Science and Technology , China Agricultural University , Beijing , China.,c National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology , China Agricultural University , Beijing , China.,d Key Laboratory of Animal Genetics, Breeding and Reproduction of the Ministry of Agriculture and Rural Affairs, College of Animal Science and Technology , China Agricultural University , Beijing , China
| | - Bingkun Zhang
- a State Key Laboratory of Animal Nutrition, College of Animal Science and Technology , China Agricultural University , Beijing , China
| | - Zhengxing Lian
- b Beijing Key Laboratory of Animal Genetic Improvement, College of Animal Science and Technology , China Agricultural University , Beijing , China.,c National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology , China Agricultural University , Beijing , China.,d Key Laboratory of Animal Genetics, Breeding and Reproduction of the Ministry of Agriculture and Rural Affairs, College of Animal Science and Technology , China Agricultural University , Beijing , China
| | - Yuming Guo
- a State Key Laboratory of Animal Nutrition, College of Animal Science and Technology , China Agricultural University , Beijing , China
| | - Hongbing Han
- b Beijing Key Laboratory of Animal Genetic Improvement, College of Animal Science and Technology , China Agricultural University , Beijing , China.,c National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology , China Agricultural University , Beijing , China.,d Key Laboratory of Animal Genetics, Breeding and Reproduction of the Ministry of Agriculture and Rural Affairs, College of Animal Science and Technology , China Agricultural University , Beijing , China
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36
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García-Gil A, Galán-Enríquez CS, Pérez-López A, Nava P, Alpuche-Aranda C, Ortiz-Navarrete V. SopB activates the Akt-YAP pathway to promote Salmonella survival within B cells. Virulence 2019; 9:1390-1402. [PMID: 30103648 PMCID: PMC6177241 DOI: 10.1080/21505594.2018.1509664] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
B cells are a target of Salmonella infection, allowing bacteria survival without inducing pyroptosis. This event is due to downregulation of Nlrc4 expression and lack of inflammasome complex activation, which impairs the secretion of IL-1β. YAP phosphorylation is required for downregulation of Nlrc4 in B cells during Salmonella infection; however, the microorganism’s mechanisms underlying the inhibition of the NLRC4 inflammasome in B cells are not fully understood. Our findings demonstrate that the Salmonella effector SopB triggers a signaling cascade involving PI3K, PDK1 and mTORC2 that activates Akt with consequent phosphorylation of YAP. When we deleted sopB in Salmonella, infected B cells that lack Rictor, or inhibited the signaling cascade using a pharmacological approach, we were able to restore the function of the NLRC4 inflammasome in B cells and the ability to control the infection. Furthermore, B cells from infected mice exhibited activation of Akt and YAP phosphorylation, suggesting that Salmonella also triggers this pathway in vivo. In summary, our data demonstrate that the Salmonella effector inositide phosphate phosphatase SopB triggers the PI3K-Akt-YAP pathway to inhibit the NLRC4 inflammasome in B cells. This study provides further evidence that Salmonella triggers cellular mechanisms in B lymphocytes to manipulate the host environment by turning it into a survival niche to establish a successful infection.
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Affiliation(s)
- Abraham García-Gil
- a Departamento de Biomedicina Molecular , Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional , Ciudad de México , México
| | - Carlos Samuel Galán-Enríquez
- a Departamento de Biomedicina Molecular , Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional , Ciudad de México , México
| | - Araceli Pérez-López
- b Department of Pediatrics , University of California San Diego , San Diego , CA , USA
| | - Porfirio Nava
- c Departamento de Fisiología , Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional , Ciudad de México , México
| | - Celia Alpuche-Aranda
- d Centro de Investigación Sobre Enfermedades Infecciosa , Instituto Nacional de Salud Pública, SSA , Cuernavaca , México
| | - Vianney Ortiz-Navarrete
- a Departamento de Biomedicina Molecular , Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional , Ciudad de México , México
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37
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Intracellular Pathogens: Host Immunity and Microbial Persistence Strategies. J Immunol Res 2019; 2019:1356540. [PMID: 31111075 PMCID: PMC6487120 DOI: 10.1155/2019/1356540] [Citation(s) in RCA: 170] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 03/15/2019] [Accepted: 04/02/2019] [Indexed: 01/18/2023] Open
Abstract
Infectious diseases caused by pathogens including viruses, bacteria, fungi, and parasites are ranked as the second leading cause of death worldwide by the World Health Organization. Despite tremendous improvements in global public health since 1950, a number of challenges remain to either prevent or eradicate infectious diseases. Many pathogens can cause acute infections that are effectively cleared by the host immunity, but a subcategory of these pathogens called "intracellular pathogens" can establish persistent and sometimes lifelong infections. Several of these intracellular pathogens manage to evade the host immune monitoring and cause disease by replicating inside the host cells. These pathogens have evolved diverse immune escape strategies and overcome immune responses by residing and multiplying inside host immune cells, primarily macrophages. While these intracellular pathogens that cause persistent infections are phylogenetically diverse and engage in diverse immune evasion and persistence strategies, they share common pathogen type-specific mechanisms during host-pathogen interaction inside host cells. Likewise, the host immune system is also equipped with a diverse range of effector functions to fight against the establishment of pathogen persistence and subsequent host damage. This article provides an overview of the immune effector functions used by the host to counter pathogens and various persistence strategies used by intracellular pathogens to counter host immunity, which enables their extended period of colonization in the host. The improved understanding of persistent intracellular pathogen-derived infections will contribute to develop improved disease diagnostics, therapeutics, and prophylactics.
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38
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Hu GQ, Yang YJ, Qin XX, Qi S, Zhang J, Yu SX, Du CT, Chen W. Salmonella Outer Protein B Suppresses Colitis Development via Protecting Cell From Necroptosis. Front Cell Infect Microbiol 2019; 9:87. [PMID: 31024858 PMCID: PMC6465518 DOI: 10.3389/fcimb.2019.00087] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 03/12/2019] [Indexed: 12/30/2022] Open
Abstract
Salmonella effectors translocated into epithelial cells contribute to the pathogenesis of infection. They mediate epithelial cell invasion and subsequent intracellular replication. However, their functions in vivo have not been well-identified. In this study, we uncovered a role for Salmonella outer protein B (SopB) in modulating necroptosis to facilitate bacteria escape epithelial cell and spread to systemic sites through a Salmonella-induced colitis model. Mice infected with SopB deleted strain ΔsopB displayed increased severity to colitis, reduced mucin expression and increased bacterial translocation. In vitro study, we found there was an increased goblet cell necroptosis following ΔsopB infection. Consistently, mice infected with ΔsopB had a strong upregulation of mixed lineage kinase domain-like (MLKL) phosphorylation. Deletion of MLKL rescued severity of tissue inflammatory, improved mucin2 expression and abolished the increased bacterial translocation in mice infected with ΔsopB. Intriguingly, the expression of sopB in LS174T cells was downregulated. The temporally regulated SopB expression potentially switched the role from epithelial cell invasion to bacterial transmission. Collectively, these results indicated a role for SopB in modulating the onset of necroptosis to increased bacteria pathogenesis and translocated to systemic sites.
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Affiliation(s)
- Gui-Qiu Hu
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Yong-Jun Yang
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Xiao-Xia Qin
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Shuai Qi
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Jie Zhang
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Shui-Xing Yu
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Chong-Tao Du
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Wei Chen
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
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39
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Zha L, Garrett S, Sun J. Salmonella Infection in Chronic Inflammation and Gastrointestinal Cancer. Diseases 2019; 7:E28. [PMID: 30857369 PMCID: PMC6473780 DOI: 10.3390/diseases7010028] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2019] [Revised: 02/16/2019] [Accepted: 03/06/2019] [Indexed: 12/19/2022] Open
Abstract
Salmonella not only causes acute infections, but can also cause patients to become chronic "asymptomatic" carriers. Salmonella has been verified as a pathogenic factor that contributes to chronic inflammation and carcinogenesis. This review summarizes the acute and chronic Salmonella infection and describes the current research progress of Salmonella infection contributing to inflammatory bowel disease and cancer. Furthermore, this review explores the underlying biological mechanism of the host signaling pathways manipulated by Salmonella effector molecules. Using experimental animal models, researchers have shown that Salmonella infection is related to host biological processes, such as host cell transformation, stem cell maintenance, and changes of the gut microbiota (dysbiosis). Finally, this review discusses the current challenges and future directions in studying Salmonella infection and its association with human diseases.
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Affiliation(s)
- Lang Zha
- Division of Gastroenterology and Hepatology, Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
| | - Shari Garrett
- Division of Gastroenterology and Hepatology, Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
| | - Jun Sun
- Division of Gastroenterology and Hepatology, Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
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40
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Transcriptomics analysis of host liver and meta-transcriptome analysis of rumen epimural microbial community in young calves treated with artificial dosing of rumen content from adult donor cow. Sci Rep 2019; 9:790. [PMID: 30692556 PMCID: PMC6349911 DOI: 10.1038/s41598-018-37033-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 11/25/2018] [Indexed: 12/31/2022] Open
Abstract
In mammals, microbial colonization of the digestive tract (GIT) occurs right after birth by several bacterial phyla. Numerous human and mouse studies have reported the importance of early gut microbial inhabitants on host health. However, few attempts have been undertaken to directly interrogate the role of early gut/rumen microbial colonization on GIT development or host health in neonatal ruminants through artificial manipulation of the rumen microbiome. Thus, the molecular changes associated with bacterial colonization are largely unknown in cattle. In this study, we dosed young calves with exogenous rumen fluid obtained from an adult donor cow, starting at birth, and repeated every other week until six weeks of age. Eight Holstein bull calves were included in this study and were separated into two groups of four: the first group was treated with rumen content freshly extracted from an adult cow, and the second group was treated with sterilized rumen content. Using whole-transcriptome RNA-sequencing, we investigated the transcriptional changes in the host liver, which is a major metabolic organ and vital to the calf’s growth performance. Additionally, the comparison of rumen epimural microbial communities between the treatment groups was performed using the rRNA reads generated by sequencing. Liver transcriptome changes were enriched with genes involved in cell signaling and protein phosphorylation. Specifically, up-regulation of SGPL1 suggests a potential increase in the metabolism of sphingolipids, an essential molecular signal for bacterial survival in digestive tracts. Notably, eight genera, belonging to four phyla, had significant increases in abundance in treated calves. Our study provides insight into host liver transcriptome changes associated with early colonization of the microbial communities in neonatal calves. Such knowledge provides a foundation for future probiotics-based research in microbial organism mediated rumen development and nutrition in ruminants.
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41
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Radlinski LC, Brunton J, Steele S, Taft-Benz S, Kawula TH. Defining the Metabolic Pathways and Host-Derived Carbon Substrates Required for Francisella tularensis Intracellular Growth. mBio 2018; 9:e01471-18. [PMID: 30459188 PMCID: PMC6247087 DOI: 10.1128/mbio.01471-18] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 10/05/2018] [Indexed: 12/13/2022] Open
Abstract
Francisella tularensis is a Gram-negative, facultative, intracellular bacterial pathogen and one of the most virulent organisms known. A hallmark of F. tularensis pathogenesis is the bacterium's ability to replicate to high densities within the cytoplasm of infected cells in over 250 known host species, including humans. This demonstrates that F. tularensis is adept at modulating its metabolism to fluctuating concentrations of host-derived nutrients. The precise metabolic pathways and nutrients utilized by F. tularensis during intracellular growth, however, are poorly understood. Here, we use systematic mutational analysis to identify the carbon catabolic pathways and host-derived nutrients required for F. tularensis intracellular replication. We demonstrate that the glycolytic enzyme phosphofructokinase (PfkA), and thus glycolysis, is dispensable for F. tularensis SchuS4 virulence, and we highlight the importance of the gluconeogenic enzyme fructose 1,6-bisphosphatase (GlpX). We found that the specific gluconeogenic enzymes that function upstream of GlpX varied based on infection model, indicating that F. tularensis alters its metabolic flux according to the nutrients available within its replicative niche. Despite this flexibility, we found that glutamate dehydrogenase (GdhA) and glycerol 3-phosphate (G3P) dehydrogenase (GlpA) are essential for F. tularensis intracellular replication in all infection models tested. Finally, we demonstrate that host cell lipolysis is required for F. tularensis intracellular proliferation, suggesting that host triglyceride stores represent a primary source of glycerol during intracellular replication. Altogether, the data presented here reveal common nutritional requirements for a bacterium that exhibits characteristic metabolic flexibility during infection.IMPORTANCE The widespread onset of antibiotic resistance prioritizes the need for novel antimicrobial strategies to prevent the spread of disease. With its low infectious dose, broad host range, and high rate of mortality, F. tularensis poses a severe risk to public health and is considered a potential agent for bioterrorism. F. tularensis reaches extreme densities within the host cell cytosol, often replicating 1,000-fold in a single cell within 24 hours. This remarkable rate of growth demonstrates that F. tularensis is adept at harvesting and utilizing host cell nutrients. However, like most intracellular pathogens, the types of nutrients utilized by F. tularensis and how they are acquired is not fully understood. Identifying the essential pathways for F. tularensis replication may reveal new therapeutic strategies for targeting this highly infectious pathogen and may provide insight for improved targeting of intracellular pathogens in general.
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Affiliation(s)
- Lauren C Radlinski
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Jason Brunton
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Shaun Steele
- Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington, USA
| | - Sharon Taft-Benz
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Thomas H Kawula
- Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington, USA
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42
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Sun H, Kamanova J, Lara-Tejero M, Galán JE. Salmonella stimulates pro-inflammatory signalling through p21-activated kinases bypassing innate immune receptors. Nat Microbiol 2018; 3:1122-1130. [PMID: 30224799 PMCID: PMC6158040 DOI: 10.1038/s41564-018-0246-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 08/13/2018] [Indexed: 01/11/2023]
Abstract
Microbial infections are most often countered by inflammatory responses that are initiated through the recognition of conserved microbial products by innate immune receptors and result in pathogen expulsion1-6. However, inflammation can also lead to pathology. Tissues such as the intestinal epithelium, which are exposed to microbial products, are therefore subject to stringent negative regulatory mechanisms to prevent signalling through innate immune receptors6-11. This presents a challenge to the enteric pathogen Salmonella Typhimurium, which requires intestinal inflammation to compete against the resident microbiota and to acquire the nutrients and electron acceptors that sustain its replication12,13. We show here that S. Typhimurium stimulates pro-inflammatory signalling by a unique mechanism initiated by effector proteins that are delivered by its type III protein secretion system. These effectors activate Cdc42 and the p21-activated kinase 1 (PAK1) leading to the recruitment of TNF receptor-associated factor 6 (TRAF6) and mitogen-activated protein kinase kinase kinase 7 (TAK1), and the stimulation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) inflammatory signalling. The removal of Cdc42, PAK1, TRAF6 or TAK1 prevented S. Typhimurium from stimulating NF-κB signalling in cultured cells. In addition, oral administration of a highly specific PAK inhibitor blocked Salmonella-induced intestinal inflammation and bacterial replication in the mouse intestine, although it resulted in a significant increase in the bacterial loads in systemic tissues. Thus, S. Typhimurium stimulates inflammatory signalling in the intestinal tract by engaging critical downstream signalling components of innate immune receptors. These findings illustrate the unique balance that emerges from host-pathogen co-evolution, in that pathogen-initiated responses that help pathogen replication are also important to prevent pathogen spread to deeper tissues.
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Affiliation(s)
- Hui Sun
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, USA
| | - Jana Kamanova
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, USA
| | - Maria Lara-Tejero
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, USA
| | - Jorge E Galán
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, USA.
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Brink T, Leiss V, Siegert P, Jehle D, Ebner JK, Schwan C, Shymanets A, Wiese S, Nürnberg B, Hensel M, Aktories K, Orth JHC. Salmonella Typhimurium effector SseI inhibits chemotaxis and increases host cell survival by deamidation of heterotrimeric Gi proteins. PLoS Pathog 2018; 14:e1007248. [PMID: 30102745 PMCID: PMC6107295 DOI: 10.1371/journal.ppat.1007248] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 08/23/2018] [Accepted: 07/27/2018] [Indexed: 12/20/2022] Open
Abstract
Salmonella enterica serotype Typhimurium (S. Typhimurium) is one of the most frequent causes of food-borne illness in humans and usually associated with acute self-limiting gastroenteritis. However, in immunocompromised patients, the pathogen can disseminate and lead to severe systemic diseases. S. Typhimurium are facultative intracellular bacteria. For uptake and intracellular life, Salmonella translocate numerous effector proteins into host cells using two type-III secretion systems (T3SS), which are encoded within Salmonella pathogenicity islands 1 (SPI-1) and 2 (SPI-2). While SPI-1 effectors mainly promote initial invasion, SPI-2 effectors control intracellular survival and proliferation. Here, we elucidate the mode of action of Salmonella SPI-2 effector SseI, which is involved in control of systemic dissemination of S. Typhimurium. SseI deamidates a specific glutamine residue of heterotrimeric G proteins of the Gαi family, resulting in persistent activation of the G protein. Gi activation inhibits cAMP production and stimulates PI3-kinase γ by Gαi-released Gβγ subunits, resulting in activation of survival pathways by phosphorylation of Akt and mTOR. Moreover, SseI-induced deamidation leads to non-polarized activation of Gαi and, thereby, to loss of directed migration of dendritic cells. Salmonella Typhimurium is one of the most common causes of gastroenteritis in humans. In immunocompromised patients, the pathogen can cause systemic infections. Crucial virulence factors are encoded on two Salmonella pathogenicity islands SPI-1 and SPI-2. While SPI-1 encodes virulence factors essential for host cell invasion, intracellular proliferation of the pathogen depends mainly on SPI-2 effectors. Here, we elucidate the mode of action of Salmonella SPI-2 effector SseI. SseI activates heterotrimeric G proteins of the Gαi family by deamidation of a specific glutamine residue. Deamidation blocks GTP hydrolysis by Gαi, resulting in a persistently active G protein. Gi activation inhibits cAMP production and stimulates PI3Kγ by Gαi-released Gβγ subunits, resulting in activation of survival pathways by phosphorylation of Akt and mTOR. Moreover, deamidation of Gαi leads to a loss of directed migration in dendritic cells. The data offers a new perspective in the understanding of the actions of SseI.
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Affiliation(s)
- Thorsten Brink
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Veronika Leiss
- Abteilung für Pharmakologie und Experimentelle Therapie, Medizinische Fakultät und ICePhA, Eberhard-Karls-Universität Tübingen, Germany
| | - Peter Siegert
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Doris Jehle
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Julia K. Ebner
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- Spemann Graduate School of Biology and Medicine (SGBM), Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- Fakultät für Biologie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Carsten Schwan
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Aliaksei Shymanets
- Abteilung für Pharmakologie und Experimentelle Therapie, Medizinische Fakultät und ICePhA, Eberhard-Karls-Universität Tübingen, Germany
| | - Sebastian Wiese
- Zentrum für Biosystemanalyse, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Bernd Nürnberg
- Abteilung für Pharmakologie und Experimentelle Therapie, Medizinische Fakultät und ICePhA, Eberhard-Karls-Universität Tübingen, Germany
| | - Michael Hensel
- Abteilung Mikrobiologie, Fachbereich Biologie/Chemie, Universität Osnabrück, Osnabrück, Germany
| | - Klaus Aktories
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- * E-mail:
| | - Joachim H. C. Orth
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
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Johnson R, Mylona E, Frankel G. TyphoidalSalmonella: Distinctive virulence factors and pathogenesis. Cell Microbiol 2018; 20:e12939. [DOI: 10.1111/cmi.12939] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 07/06/2018] [Accepted: 07/13/2018] [Indexed: 01/13/2023]
Affiliation(s)
- Rebecca Johnson
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences; Imperial College London; London UK
| | - Elli Mylona
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences; Imperial College London; London UK
| | - Gad Frankel
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences; Imperial College London; London UK
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Truong D, Boddy KC, Canadien V, Brabant D, Fairn GD, D'Costa VM, Coyaud E, Raught B, Pérez-Sala D, Park WS, Heo WD, Grinstein S, Brumell JH. Salmonella
exploits host Rho GTPase signalling pathways through the phosphatase activity of SopB. Cell Microbiol 2018; 20:e12938. [DOI: 10.1111/cmi.12938] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 06/11/2018] [Accepted: 07/06/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Dorothy Truong
- Cell Biology Program; Hospital for Sick Children; Toronto ON Canada
- Department of Molecular Genetics; University of Toronto; Toronto ON Canada
| | - Kirsten C. Boddy
- Cell Biology Program; Hospital for Sick Children; Toronto ON Canada
- Institute of Medical Science; University of Toronto; Toronto ON Canada
| | | | - Danielle Brabant
- Cell Biology Program; Hospital for Sick Children; Toronto ON Canada
| | - Gregory D. Fairn
- Institute of Medical Science; University of Toronto; Toronto ON Canada
- Keenan Research Centre for Biomedical Science; St. Michael's Hospital; Toronto ON Canada
| | | | - Etienne Coyaud
- Princess Margaret Cancer Centre; University Health Network; Toronto Ontario Canada
| | - Brian Raught
- Princess Margaret Cancer Centre; University Health Network; Toronto Ontario Canada
- Department of Medical Biophysics; University of Toronto; Toronto Ontario Canada
| | - Dolores Pérez-Sala
- Department of Structural and Chemical Biology; Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas; Madrid Spain
| | - Wei Sun Park
- Department of Biological Sciences; Korea Advanced Institute of Science and Technology (KAIST); Daejeon Republic of Korea
| | - Won Do Heo
- Department of Biological Sciences; Korea Advanced Institute of Science and Technology (KAIST); Daejeon Republic of Korea
- Center for Cognition and Sociality; Institute of Basic Science (IBS); Daejeon Republic of Korea
| | - Sergio Grinstein
- Cell Biology Program; Hospital for Sick Children; Toronto ON Canada
- Institute of Medical Science; University of Toronto; Toronto ON Canada
- Keenan Research Centre for Biomedical Science; St. Michael's Hospital; Toronto ON Canada
- Department of Biochemistry; University of Toronto; Toronto ON Canada
| | - John H. Brumell
- Cell Biology Program; Hospital for Sick Children; Toronto ON Canada
- Department of Molecular Genetics; University of Toronto; Toronto ON Canada
- Institute of Medical Science; University of Toronto; Toronto ON Canada
- Sickkids IBD Centre; Hospital for Sick Children; Toronto ON Canada
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46
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dos Santos AMP, Ferrari RG, Conte-Junior CA. Virulence Factors in Salmonella Typhimurium: The Sagacity of a Bacterium. Curr Microbiol 2018; 76:762-773. [DOI: 10.1007/s00284-018-1510-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 05/16/2018] [Indexed: 12/20/2022]
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47
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Liu W, Jiang Y, Sun J, Geng S, Pan Z, Prinz RA, Wang C, Sun J, Jiao X, Xu X. Activation of TGF-β-activated kinase 1 (TAK1) restricts Salmonella Typhimurium growth by inducing AMPK activation and autophagy. Cell Death Dis 2018; 9:570. [PMID: 29752434 PMCID: PMC5948208 DOI: 10.1038/s41419-018-0612-z] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 04/07/2018] [Accepted: 04/10/2018] [Indexed: 01/24/2023]
Abstract
Autophagy is a conserved cellular process that functions as a first-line defense to restrict the growth of invading parasitic bacteria. As an intracellular pathogen, Salmonella (S) Typhimurium invades host cells through two Type III secretion systems (T3SS) and resides in the Salmonella-containing vacuole (SCV). When the SCV membrane is perforated and ruptured by T3SS-1, a small portion of the Salmonella egresses from the SCV and replicates rapidly in the nutrient-rich cytosol. Cytosolic Salmonella and those residing in the membrane-damaged SCV are tagged by ubiquitination and marked for autophagy through the ubiquitin-binding adaptor proteins such as p62, NDP52, and optineurin. Prior studies suggest that transient intracellular amino-acid starvation and subsequent inactivation of the mechanistic target of rapamycin (mTOR), a key molecule that phosphorylates Unc-51 like autophagy activating kinase (ULK1) and inhibits its activity, can trigger autophagy in S. Typhimurium-infected cells. Other studies suggest that energy stress in S. Typhimurium-infected cells leads to AMP-activated protein kinase (AMPK) activation and autophagy. In the present study, we report that autophagy was rapidly induced in S. Typhimurium-infected cells, as evidenced by increased LC3 lipidation and decreased p62 levels. However, S. Typhimurium infection drastically increased AKT phosphorylation but decreased S6K1T389, 4E-BPT37/46, and ULK1S757 phosphorylation, suggesting that mTOR activation by AKT is subverted. Further studies showed that AMPK was activated in S. Typhimurium-infected cells, as evidenced by increased ULK1S317 and ACCS79 phosphorylation. AMPK activation was mediated by Toll-like receptor-activated TAK1. Functional studies revealed that AMPK and TAK1 inhibitors accelerated S. Typhimurium growth in HeLa cells. Our results strongly suggest that TAK1 activation leads to AMPK activation, which activates ULK1 by phosphorylating ULK1S317 and suppressing mTOR activity and ULK1S757 phosphorylation. Our study has unveiled a previously unrecognized pathway for S. Typhimurium-induced autophagy.
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Affiliation(s)
- Wei Liu
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu Province, 225009, P. R. China
| | - Yuanyuan Jiang
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu Province, 225009, P. R. China
| | - Jing Sun
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu Province, 225009, P. R. China
| | - Shizhong Geng
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, 225009, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu Province, 225009, China
| | - Zhiming Pan
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, 225009, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu Province, 225009, China
| | - Richard A Prinz
- Department of Surgery, NorthShore University Health System, Evanston, IL, 60201, USA
| | - Chengming Wang
- Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL, 36849, USA
| | - Jun Sun
- Department of Medicine, University of Illinois at Chicago, Chicago, IL, 60612, USA
| | - Xinan Jiao
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, 225009, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu Province, 225009, China
| | - Xiulong Xu
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu Province, 225009, P. R. China.
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu Province, 225009, China.
- Department of Cell and Molecular Medicine, Rush University Medical Center, Chicago, IL, 60612, USA.
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48
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Pinaud L, Sansonetti PJ, Phalipon A. Host Cell Targeting by Enteropathogenic Bacteria T3SS Effectors. Trends Microbiol 2018; 26:266-283. [DOI: 10.1016/j.tim.2018.01.010] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 01/29/2018] [Accepted: 01/29/2018] [Indexed: 12/23/2022]
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Zhang K, Riba A, Nietschke M, Torow N, Repnik U, Pütz A, Fulde M, Dupont A, Hensel M, Hornef M. Minimal SPI1-T3SS effector requirement for Salmonella enterocyte invasion and intracellular proliferation in vivo. PLoS Pathog 2018. [PMID: 29522566 PMCID: PMC5862521 DOI: 10.1371/journal.ppat.1006925] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Effector molecules translocated by the Salmonella pathogenicity island (SPI)1-encoded type 3 secretion system (T3SS) critically contribute to the pathogenesis of human Salmonella infection. They facilitate internalization by non-phagocytic enterocytes rendering the intestinal epithelium an entry site for infection. Their function in vivo has remained ill-defined due to the lack of a suitable animal model that allows visualization of intraepithelial Salmonella. Here, we took advantage of our novel neonatal mouse model and analyzed various bacterial mutants and reporter strains as well as gene deficient mice. Our results demonstrate the critical but redundant role of SopE2 and SipA for enterocyte invasion, prerequisite for transcriptional stimulation and mucosal translocation in vivo. In contrast, the generation of a replicative intraepithelial endosomal compartment required the cooperative action of SipA and SopE2 or SipA and SopB but was independent of SopA or host MyD88 signaling. Intraepithelial growth had no critical influence on systemic spread. Our results define the role of SPI1-T3SS effector molecules during enterocyte invasion and intraepithelial proliferation in vivo providing novel insight in the early course of Salmonella infection. Non-typhoidal Salmonella represent a major causative agent of gastroenteritis worldwide. Hallmark of the pathogenesis is their ability to actively invade the intestinal epithelium by virtue of their type 3 secretion system that delivers bacterial virulence factors directly into the host cell cytosol. The role of these virulence factors during enterocyte entry and intraepithelial growth has only been investigated in vitro since the previously established in vivo models in small animals did not allow visualization of intraepithelial Salmonella. However, immortalized cell lines lack the overlaying mucus layer, final cell lineage differentiation, apical-basolateral polarization as well as continuous migration along the crypt villus axis and thus the role of virulence factors during the Salmonella infection in vivo has remained largely undefined. Here, we took advantage of our novel neonatal mouse infection model and for the first time systematically analyzed the importance of Salmonella virulence factors for enterocyte invasion and intraepithelial growth.
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Affiliation(s)
- Kaiyi Zhang
- Institute of Medical Microbiology, RWTH University Hospital, Aachen, Germany
| | - Ambre Riba
- Institute of Medical Microbiology, RWTH University Hospital, Aachen, Germany
| | - Monika Nietschke
- Division of Microbiology, University of Osnabrück, Osnabrück, Germany
| | - Natalia Torow
- Institute of Medical Microbiology, RWTH University Hospital, Aachen, Germany
| | - Urska Repnik
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Andreas Pütz
- Institute of Medical Microbiology, RWTH University Hospital, Aachen, Germany
| | - Marcus Fulde
- Institute of Microbiology and Epizootics, Freie Universität Berlin, Berlin, Germany
| | - Aline Dupont
- Institute of Medical Microbiology, RWTH University Hospital, Aachen, Germany
| | - Michael Hensel
- Division of Microbiology, University of Osnabrück, Osnabrück, Germany
| | - Mathias Hornef
- Institute of Medical Microbiology, RWTH University Hospital, Aachen, Germany
- * E-mail:
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50
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Controlled Activity of the Salmonella Invasion-Associated Injectisome Reveals Its Intracellular Role in the Cytosolic Population. mBio 2017; 8:mBio.01931-17. [PMID: 29208746 PMCID: PMC5717391 DOI: 10.1128/mbio.01931-17] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The Salmonella invasion-associated type III secretion system (T3SS1) is an essential virulence factor required for entry into nonphagocytic cells and consequent uptake into a Salmonella-containing vacuole (SCV). While Salmonella is typically regarded as a vacuolar pathogen, a subset of bacteria escape from the SCV in epithelial cells and eventually hyperreplicate in the cytosol. T3SS1 is downregulated following bacterial entry into mammalian cells, but cytosolic Salmonella cells are T3SS1 induced, suggesting prolonged or resurgent activity of T3SS1 in this population. In order to investigate the postinternalization contributions of T3SS1 to the Salmonella infectious cycle in epithelial cells, we bypassed its requirement for bacterial entry by tagging the T3SS1-energizing ATPase InvC at the C terminus with peptides that are recognized by bacterial tail-specific proteases. This caused a dramatic increase in InvC turnover which rendered even assembled injectisomes inactive. Bacterial strains conditionally expressing these unstable InvC variants were proficient for invasion but underwent rapid and sustained intracellular inactivation of T3SS1 activity when InvC expression ceased. This allowed us to directly implicate T3SS1 activity in cytosolic colonization and bacterial egress. We subsequently identified two T3SS1-delivered effectors, SopB and SipA, that are required for efficient colonization of the epithelial cell cytosol. Overall, our findings support a multifaceted, postinvasion role for T3SS1 and its effectors in defining the cytosolic population of intracellular Salmonella. A needle-like apparatus, the type III secretion system (T3SS) injectisome, is absolutely required for Salmonella enterica to enter epithelial cells; this requirement has hampered the analysis of its postentry contributions. To identify T3SS1-dependent intracellular activities, in this study we overcame this limitation by developing a conditional inactivation in the T3SS whereby T3SS activity is chemically induced during culture in liquid broth, permitting bacterial entry into epithelial cells, but is quickly and perpetually inactivated in the absence of inducer. In this sense, the mutant acts like wild-type bacteria when extracellular and as a T3SS mutant once it enters a host cell. This “conditional” mutant allowed us to directly link activity of this T3SS with nascent vacuole lysis, cytosolic proliferation, and cellular egress, demonstrating that the invasion-associated T3SS also contributes to essential intracellular stages of the S. enterica infectious cycle.
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