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Schroeder EA, Toro-Moreno M, Raphemot R, Sylvester K, Colón IC, Derbyshire ER. Toxoplasma and Plasmodium associate with host Arfs during infection. mSphere 2024; 9:e0077023. [PMID: 38349168 PMCID: PMC10964417 DOI: 10.1128/msphere.00770-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 01/17/2024] [Indexed: 03/27/2024] Open
Abstract
The apicomplexans Toxoplasma gondii and Plasmodium are intracellular parasites that reside within a host-derived compartment termed the parasitophorous vacuole (PV). During infection, the parasites must acquire critical host resources and transport them across their PV for development. However, the mechanism by which host resources are trafficked to and across the PV remains uncertain. Here, we investigated host ADP ribosylation factors (Arfs), a class of proteins involved in vesicular trafficking that may be exploited by T. gondii and Plasmodium berghei for nutrient acquisition. Using overexpressed Arf proteins coupled with immunofluorescence microscopy, we found that all Arfs were internalized into the T. gondii PV, with most vacuoles containing at least one punctum of Arf protein by the end of the lytic cycle. We further characterized Arf1, the most abundant Arf inside the T. gondii PV, and observed that active recycling between its GDP/GTP-bound state influenced Arf1 internalization independent of host guanine nucleotide exchange factors (GEFs). In addition, Arf1 colocalized with vesicle coat complexes and exogenous sphingolipids, suggesting a role in nutrient acquisition. While Arf1 and Arf4 were not observed inside the PV during P. berghei infection, our gene depletion studies showed that liver stage development and survival depended on the expression of Arf4 and the host GEF, GBF1. Collectively, these observations indicate that apicomplexans use distinct mechanisms to subvert the host vesicular trafficking network and efficiently replicate. The findings also pave the way for future studies to identify parasite proteins critical to host vesicle recruitment and the components of vesicle cargo. IMPORTANCE The parasites Toxoplasma gondii and Plasmodium live complex intracellular lifestyles where they must acquire essential host nutrients while avoiding recognition. Although previous work has sought to identify the specific nutrients scavenged by apicomplexans, the mechanisms by which host materials are transported to and across the parasite vacuole membrane are largely unknown. Here, we examined members of the host vesicular trafficking network to identify specific pathways subverted by T. gondii and Plasmodium berghei. Our results indicate that T. gondii selectively internalizes host Arfs, a class of proteins involved in intracellular trafficking. For P. berghei, host Arfs were restricted by the parasite's vacuole membrane, but proteins involved in vesicular trafficking were identified as essential for liver stage development. A greater exploration into how and why apicomplexans subvert host vesicular trafficking could help identify targets for host-directed therapeutics.
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Affiliation(s)
- Erin A. Schroeder
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Maria Toro-Moreno
- Department of Chemistry, Duke University, Durham, North Carolina, USA
| | - Rene Raphemot
- Department of Chemistry, Duke University, Durham, North Carolina, USA
| | - Kayla Sylvester
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Isabel C. Colón
- Department of Chemistry, Duke University, Durham, North Carolina, USA
| | - Emily R. Derbyshire
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Chemistry, Duke University, Durham, North Carolina, USA
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2
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Wang Y, Chen X, Xu X, Yang J, Liu X, Sun G, Li Z. Weighted Gene Co-Expression Network Analysis Based on Stimulation by Lipopolysaccharides and Polyinosinic:polycytidylic Acid Provides a Core Set of Genes for Understanding Hemolymph Immune Response Mechanisms of Amphioctopus fangsiao. Animals (Basel) 2023; 14:80. [PMID: 38200810 PMCID: PMC10778463 DOI: 10.3390/ani14010080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 12/05/2023] [Accepted: 12/19/2023] [Indexed: 01/12/2024] Open
Abstract
The primary influencer of aquaculture quality in Amphioctopus fangsiao is pathogen infection. Both lipopolysaccharides (LPS) and polyinosinic:polycytidylic acid (Poly I:C) are recognized by the pattern recognition receptor (PRR) within immune cells, a system that frequently serves to emulate pathogen invasion. Hemolymph, which functions as a transport mechanism for immune cells, offers vital transcriptome information when A. fangsiao is exposed to pathogens, thereby contributing to our comprehension of the species' immune biological mechanisms. In this study, we conducted analyses of transcript profiles under the influence of LPS and Poly I:C within a 24 h period. Concurrently, we developed a Weighted Gene Co-expression Network Analysis (WGCNA) to identify key modules and genes. Further, we carried out Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses to investigate the primary modular functions. Co-expression network analyses unveiled a series of immune response processes following pathogen stress, identifying several key modules and hub genes, including PKMYT1 and NAMPT. The invaluable genetic resources provided by our results aid our understanding of the immune response in A. fangsiao hemolymph and will further our exploration of the molecular mechanisms of pathogen infection in mollusks.
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Affiliation(s)
- Yongjie Wang
- School of Agriculture, Ludong University, Yantai 264025, China
| | - Xipan Chen
- School of Agriculture, Ludong University, Yantai 264025, China
| | - Xiaohui Xu
- School of Agriculture, Ludong University, Yantai 264025, China
| | - Jianmin Yang
- School of Agriculture, Ludong University, Yantai 264025, China
| | - Xiumei Liu
- College of Life Sciences, Yantai University, Yantai 264005, China;
| | - Guohua Sun
- School of Agriculture, Ludong University, Yantai 264025, China
| | - Zan Li
- School of Agriculture, Ludong University, Yantai 264025, China
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3
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Cross Talk between ARF1 and RhoA Coordinates the Formation of Cytoskeletal Scaffolds during Chlamydia Infection. mBio 2021; 12:e0239721. [PMID: 34903051 PMCID: PMC8669492 DOI: 10.1128/mbio.02397-21] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Chlamydia trachomatis is an obligate intracellular bacterium that has developed sophisticated mechanisms to survive inside its infectious compartment, the inclusion. Notably, Chlamydia weaves an extensive network of microtubules (MTs) and actin filaments to enable interactions with host organelles and enhance its stability. Despite the global health and economic burden caused by this sexually transmitted pathogen, little is known about how actin and MT scaffolds are integrated into an increasingly complex virulence system. Previously, we established that the chlamydial effector InaC interacts with ARF1 to stabilize MTs. We now demonstrate that InaC regulates RhoA to control actin scaffolds. InaC relies on cross talk between ARF1 and RhoA to coordinate MTs and actin, where the presence of RhoA downregulates stable MT scaffolds and ARF1 activation inhibits actin scaffolds. Understanding how Chlamydia hijacks complex networks will help elucidate how this clinically significant pathogen parasitizes its host and reveal novel cellular signaling pathways.
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Pavišić V, Mahmutefendić Lučin H, Blagojević Zagorac G, Lučin P. Arf GTPases Are Required for the Establishment of the Pre-Assembly Compartment in the Early Phase of Cytomegalovirus Infection. Life (Basel) 2021; 11:867. [PMID: 34440611 PMCID: PMC8399710 DOI: 10.3390/life11080867] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 08/16/2021] [Accepted: 08/18/2021] [Indexed: 12/31/2022] Open
Abstract
Shortly after entering the cells, cytomegaloviruses (CMVs) initiate massive reorganization of cellular endocytic and secretory pathways, which results in the forming of the cytoplasmic virion assembly compartment (AC). We have previously shown that the formation of AC in murine CMV- (MCMV) infected cells begins in the early phase of infection (at 4-6 hpi) with the pre-AC establishment. Pre-AC comprises membranes derived from the endosomal recycling compartment, early endosomes, and the trans-Golgi network, which is surrounded by fragmented Golgi cisterns. To explore the importance of Arf GTPases in the biogenesis of the pre-AC, we infected Balb 3T3 cells with MCMV and analyzed the expression and intracellular localization of Arf proteins in the early phases (up to 16 hpi) of infection and the development of pre-AC in cells with a knockdown of Arf protein expression by small interfering RNAs (siRNAs). Herein, we show that even in the early phase, MCMVs cause massive reorganization of the Arf system of the host cells and induce the over-recruitment of Arf proteins onto the membranes of pre-AC. Knockdown of Arf1, Arf3, Arf4, or Arf6 impaired the establishment of pre-AC. However, the knockdown of Arf1 and Arf6 also abolished the establishment of infection. Our study demonstrates that Arf GTPases are required for different steps of early cytomegalovirus infection, including the establishment of the pre-AC.
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Affiliation(s)
- Valentino Pavišić
- Department of Physiology and Immunology, Faculty of Medicine, University of Rijeka, 51000 Rijeka, Croatia; (V.P.); (H.M.L.); (P.L.)
| | - Hana Mahmutefendić Lučin
- Department of Physiology and Immunology, Faculty of Medicine, University of Rijeka, 51000 Rijeka, Croatia; (V.P.); (H.M.L.); (P.L.)
- Nursing Department, University North, University Center Varaždin, Jurja Križanića 31b, 42000 Varaždin, Croatia
| | - Gordana Blagojević Zagorac
- Department of Physiology and Immunology, Faculty of Medicine, University of Rijeka, 51000 Rijeka, Croatia; (V.P.); (H.M.L.); (P.L.)
- Nursing Department, University North, University Center Varaždin, Jurja Križanića 31b, 42000 Varaždin, Croatia
| | - Pero Lučin
- Department of Physiology and Immunology, Faculty of Medicine, University of Rijeka, 51000 Rijeka, Croatia; (V.P.); (H.M.L.); (P.L.)
- Nursing Department, University North, University Center Varaždin, Jurja Križanića 31b, 42000 Varaždin, Croatia
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5
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De Niz M, Caldelari R, Kaiser G, Zuber B, Heo WD, Heussler VT, Agop-Nersesian C. Hijacking of the host cell Golgi by Plasmodium berghei liver stage parasites. J Cell Sci 2021; 134:jcs252213. [PMID: 34013963 PMCID: PMC8186485 DOI: 10.1242/jcs.252213] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 04/12/2021] [Indexed: 12/28/2022] Open
Abstract
The intracellular lifestyle represents a challenge for the rapidly proliferating liver stage Plasmodium parasite. In order to scavenge host resources, Plasmodium has evolved the ability to target and manipulate host cell organelles. Using dynamic fluorescence-based imaging, we here show an interplay between the pre-erythrocytic stages of Plasmodium berghei and the host cell Golgi during liver stage development. Liver stage schizonts fragment the host cell Golgi into miniaturized stacks, which increases surface interactions with the parasitophorous vacuolar membrane of the parasite. Expression of specific dominant-negative Arf1 and Rab GTPases, which interfere with the host cell Golgi-linked vesicular machinery, results in developmental delay and diminished survival of liver stage parasites. Moreover, functional Rab11a is critical for the ability of the parasites to induce Golgi fragmentation. Altogether, we demonstrate that the structural integrity of the host cell Golgi and Golgi-associated vesicular traffic is important for optimal pre-erythrocytic development of P. berghei. The parasite hijacks the Golgi structure of the hepatocyte to optimize its own intracellular development. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Mariana De Niz
- Institute of Cell Biology, University of Bern, CH-3012 Bern, Switzerland
| | - Reto Caldelari
- Institute of Cell Biology, University of Bern, CH-3012 Bern, Switzerland
| | - Gesine Kaiser
- Institute of Cell Biology, University of Bern, CH-3012 Bern, Switzerland
| | - Benoit Zuber
- Institute for Anatomy, University of Bern, CH-3012 Bern, Switzerland
| | - Won Do Heo
- Dept. of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
| | - Volker T. Heussler
- Institute of Cell Biology, University of Bern, CH-3012 Bern, Switzerland
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6
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Grishin A, Voth K, Gagarinova A, Cygler M. Structural biology of the invasion arsenal of Gram-negative bacterial pathogens. FEBS J 2021; 289:1385-1427. [PMID: 33650300 DOI: 10.1111/febs.15794] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Revised: 02/11/2021] [Accepted: 02/26/2021] [Indexed: 12/20/2022]
Abstract
In the last several years, there has been a tremendous progress in the understanding of host-pathogen interactions and the mechanisms by which bacterial pathogens modulate behavior of the host cell. Pathogens use secretion systems to inject a set of proteins, called effectors, into the cytosol of the host cell. These effectors are secreted in a highly regulated, temporal manner and interact with host proteins to modify a multitude of cellular processes. The number of effectors varies between pathogens from ~ 30 to as many as ~ 350. The functional redundancy of effectors encoded by each pathogen makes it difficult to determine the cellular effects or function of individual effectors, since their individual knockouts frequently produce no easily detectable phenotypes. Structural biology of effector proteins and their interactions with host proteins, in conjunction with cell biology approaches, has provided invaluable information about the cellular function of effectors and underlying molecular mechanisms of their modes of action. Many bacterial effectors are functionally equivalent to host proteins while being structurally divergent from them. Other effector proteins display new, previously unobserved functionalities. Here, we summarize the contribution of the structural characterization of effectors and effector-host protein complexes to our understanding of host subversion mechanisms used by the most commonly investigated Gram-negative bacterial pathogens. We describe in some detail the enzymatic activities discovered among effector proteins and how they affect various cellular processes.
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Affiliation(s)
- Andrey Grishin
- Department of Biochemistry, Microbiology, & Immunology, University of Saskatchewan, Saskatoon, Canada
| | - Kevin Voth
- Department of Biochemistry, Microbiology, & Immunology, University of Saskatchewan, Saskatoon, Canada
| | - Alla Gagarinova
- Department of Biochemistry, Microbiology, & Immunology, University of Saskatchewan, Saskatoon, Canada
| | - Miroslaw Cygler
- Department of Biochemistry, Microbiology, & Immunology, University of Saskatchewan, Saskatoon, Canada
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7
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Herrera A, Satchell KJF. Cross-Kingdom Activation of Vibrio Toxins by ADP-Ribosylation Factor Family GTPases. J Bacteriol 2020; 202:e00278-20. [PMID: 32900828 PMCID: PMC7685564 DOI: 10.1128/jb.00278-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pathogenic Vibrio species use many different approaches to subvert, attack, and undermine the host response. The toxins they produce are often responsible for the devastating effects associated with their diseases. These toxins target a variety of host proteins, which leads to deleterious effects, including dissolution of cell organelle integrity and inhibition of protein secretion. Becoming increasingly prevalent as cofactors for Vibrio toxins are proteins of the small GTPase families. ADP-ribosylation factor small GTPases (ARFs) in particular are emerging as a common host cofactor necessary for full activation of Vibrio toxins. While ARFs are not the direct target of Vibrio cholerae cholera toxin (CT), ARF binding is required for its optimal activity as an ADP-ribosyltransferase. The makes caterpillars floppy (MCF)-like and the domain X (DmX) effectors of the Vibrio vulnificus multifunctional autoprocessing repeats-in-toxin (MARTX) toxin also both require ARFs to initiate autoprocessing and activation as independent effectors. ARFs are ubiquitously expressed in eukaryotes and are key regulators of many cellular processes, and as such they are ideal cofactors for Vibrio pathogens that infect many host species. In this review, we cover in detail the known Vibrio toxins that use ARFs as cross-kingdom activators to both stimulate and optimize their activity. We further discuss how these contrast to toxins and effectors from other bacterial species that coactivate, stimulate, or directly modify host ARFs as their mechanisms of action.
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Affiliation(s)
- Alfa Herrera
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Karla J F Satchell
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
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8
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EPEC Recruits a Cdc42-Specific GEF, Frabin, To Facilitate PAK Activation and Host Cell Colonization. mBio 2020; 11:mBio.01423-20. [PMID: 33144373 PMCID: PMC7642674 DOI: 10.1128/mbio.01423-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Enteropathogenic Escherichia coli (EPEC) is a leading cause of diarrhea in children, especially in the developing world. EPEC initiates infection by attaching to cells in the host intestine, triggering the formation of actin-rich “pedestal” structures directly beneath the adherent pathogen. These bacteria inject their own receptor into host cells, which upon binding to a protein on the pathogen surface triggers pedestal formation. Multiple other proteins are also delivered into the cells of the host intestine, which work together to hijack host signaling pathways to drive pedestal production. Here we show how EPEC hijacks a host protein, Frabin, which creates the conditions in the cell necessary for the pathogen to manipulate a specific pathway that promotes pedestal formation. This provides new insights into this essential early stage in disease caused by EPEC. Enteropathogenic Escherichia coli (EPEC) is an extracellular pathogen that tightly adheres to host cells by forming “actin pedestals” beneath the bacteria, a critical step in pathogenesis. EPEC injects effector proteins that manipulate host cell signaling cascades to trigger pedestal assembly. We have recently shown that one such effector, EspG, hijacks p21-activated kinase (PAK) and sustains its activated state to drive the cytoskeletal changes necessary for attachment of the pathogen to target cells. This EspG subversion of PAK required active Rho family small GTPases in the host cell. Here we show that EPEC itself promotes the activation of Rho GTPases by recruiting Frabin, a host guanine nucleotide exchange factor (GEF) for the Rho GTPase Cdc42. Cells devoid of Frabin showed significantly lower EPEC-induced PAK activation, pedestal formation, and bacterial attachment. Frabin recruitment to sites of EPEC attachment was driven by EspG and required localized enrichment of phosphatidylinositol 4,5-bisphosphate (PIP2) and host Arf6. Our findings identify Frabin as a key target for EPEC to ensure the activation status of cellular GTPases required for actin pedestal formation.
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9
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Singh V, Davidson AC, Hume PJ, Humphreys D, Koronakis V. Arf GTPase interplay with Rho GTPases in regulation of the actin cytoskeleton. Small GTPases 2019; 10:411-418. [PMID: 28524754 PMCID: PMC6748364 DOI: 10.1080/21541248.2017.1329691] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 05/08/2017] [Accepted: 05/09/2017] [Indexed: 01/04/2023] Open
Abstract
The Arf and Rho subfamilies of small GTPases are nucleotide-dependent molecular switches that act as master regulators of vesicular trafficking and the actin cytoskeleton organization. Small GTPases control cell processes with high fidelity by acting through distinct repertoires of binding partners called effectors. While we understand a great deal about how these GTPases act individually, relatively little is known about how they cooperate, especially in the control of effectors. This review highlights how Arf GTPases collaborate with Rac1 to regulate actin cytoskeleton dynamics at the membrane via recruiting and activating the Wave Regulatory Complex (WRC), a Rho effector that underpins lamellipodia formation and macropinocytosis. This provides insight into Arf regulation of the actin cytoskeleton, while putting the spotlight on small GTPase cooperation with emerging evidence of its importance in fundamental cell biology and interactions with pathogenic bacteria.
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Affiliation(s)
- Vikash Singh
- Department of Pathology, University of Cambridge, Cambridge, UK
| | | | - Peter J. Hume
- Department of Pathology, University of Cambridge, Cambridge, UK
| | - Daniel Humphreys
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
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10
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Stamm CE, Pasko BL, Chaisavaneeyakorn S, Franco LH, Nair VR, Weigele BA, Alto NM, Shiloh MU. Screening Mycobacterium tuberculosis Secreted Proteins Identifies Mpt64 as a Eukaryotic Membrane-Binding Bacterial Effector. mSphere 2019; 4:e00354-19. [PMID: 31167949 PMCID: PMC6553557 DOI: 10.1128/msphere.00354-19] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 05/19/2019] [Indexed: 02/07/2023] Open
Abstract
Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis, is one of the most successful human pathogens. One reason for its success is that Mtb can reside within host macrophages, a cell type that normally functions to phagocytose and destroy infectious bacteria. However, Mtb is able to evade macrophage defenses in order to survive for prolonged periods of time. Many intracellular pathogens secrete virulence factors targeting host membranes and organelles to remodel their intracellular environmental niche. We hypothesized that Mtb secreted proteins that target host membranes are vital for Mtb to adapt to and manipulate the host environment for survival. Thus, we characterized 200 secreted proteins from Mtb for their ability to associate with eukaryotic membranes using a unique temperature-sensitive yeast screen and to manipulate host trafficking pathways using a modified inducible secretion screen. We identified five Mtb secreted proteins that both associated with eukaryotic membranes and altered the host secretory pathway. One of these secreted proteins, Mpt64, localized to the endoplasmic reticulum during Mtb infection of murine and human macrophages and impaired the unfolded protein response in macrophages. These data highlight the importance of secreted proteins in Mtb pathogenesis and provide a basis for further investigation into their molecular mechanisms.IMPORTANCE Advances have been made to identify secreted proteins of Mycobacterium tuberculosis during animal infections. These data, combined with transposon screens identifying genes important for M. tuberculosis virulence, have generated a vast resource of potential M. tuberculosis virulence proteins. However, the function of many of these proteins in M. tuberculosis pathogenesis remains elusive. We have integrated three cell biological screens to characterize nearly 200 M. tuberculosis secreted proteins for eukaryotic membrane binding, host subcellular localization, and interactions with host vesicular trafficking. In addition, we observed the localization of one secreted protein, Mpt64, to the endoplasmic reticulum (ER) during M. tuberculosis infection of macrophages. Interestingly, although Mpt64 is exported by the Sec pathway, its delivery into host cells was dependent upon the action of the type VII secretion system. Finally, we observed that Mpt64 impairs the ER-mediated unfolded protein response in macrophages.
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Affiliation(s)
- Chelsea E Stamm
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Breanna L Pasko
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Sujittra Chaisavaneeyakorn
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Luis H Franco
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Center for Autophagy Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Vidhya R Nair
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Bethany A Weigele
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Neal M Alto
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Michael U Shiloh
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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11
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Shenoy AR, Furniss RCD, Goddard PJ, Clements A. Modulation of Host Cell Processes by T3SS Effectors. Curr Top Microbiol Immunol 2018; 416:73-115. [PMID: 30178263 DOI: 10.1007/82_2018_106] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Two of the enteric Escherichia coli pathotypes-enteropathogenic E. coli (EPEC) and enterohaemorrhagic E. coli (EHEC)-have a conserved type 3 secretion system which is essential for virulence. The T3SS is used to translocate between 25 and 50 bacterial proteins directly into the host cytosol where they manipulate a variety of host cell processes to establish a successful infection. In this chapter, we discuss effectors from EPEC/EHEC in the context of the host proteins and processes that they target-the actin cytoskeleton, small guanosine triphosphatases and innate immune signalling pathways that regulate inflammation and cell death. Many of these translocated proteins have been extensively characterised, which has helped obtain insights into the mechanisms of pathogenesis of these bacteria and also understand the host pathways they target in more detail. With increasing knowledge of the positive and negative regulation of host signalling pathways by different effectors, a future challenge is to investigate how the specific effector repertoire of each strain cooperates over the course of an infection.
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Affiliation(s)
- Avinash R Shenoy
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Road, SW7 2AZ, London, UK
| | - R Christopher D Furniss
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Road, SW7 2AZ, London, UK
| | - Philippa J Goddard
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Road, SW7 2AZ, London, UK
| | - Abigail Clements
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Road, SW7 2AZ, London, UK.
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12
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Chlamydia Hijacks ARF GTPases To Coordinate Microtubule Posttranslational Modifications and Golgi Complex Positioning. mBio 2017; 8:mBio.02280-16. [PMID: 28465429 PMCID: PMC5414008 DOI: 10.1128/mbio.02280-16] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The intracellular bacterium Chlamydia trachomatis develops in a parasitic compartment called the inclusion. Posttranslationally modified microtubules encase the inclusion, controlling the positioning of Golgi complex fragments around the inclusion. The molecular mechanisms by which Chlamydia coopts the host cytoskeleton and the Golgi complex to sustain its infectious compartment are unknown. Here, using a genetically modified Chlamydia strain, we discovered that both posttranslationally modified microtubules and Golgi complex positioning around the inclusion are controlled by the chlamydial inclusion protein CT813/CTL0184/InaC and host ARF GTPases. CT813 recruits ARF1 and ARF4 to the inclusion membrane, where they induce posttranslationally modified microtubules. Similarly, both ARF isoforms are required for the repositioning of Golgi complex fragments around the inclusion. We demonstrate that CT813 directly recruits ARF GTPases on the inclusion membrane and plays a pivotal role in their activation. Together, these results reveal that Chlamydia uses CT813 to hijack ARF GTPases to couple posttranslationally modified microtubules and Golgi complex repositioning at the inclusion. Chlamydia trachomatis is an important cause of morbidity and a significant economic burden in the world. However, how Chlamydia develops its intracellular compartment, the so-called inclusion, is poorly understood. Using genetically engineered Chlamydia mutants, we discovered that the effector protein CT813 recruits and activates host ADP-ribosylation factor 1 (ARF1) and ARF4 to regulate microtubules. In this context, CT813 acts as a molecular platform that induces the posttranslational modification of microtubules around the inclusion. These cages are then used to reposition the Golgi complex during infection and promote the development of the inclusion. This study provides the first evidence that ARF1 and ARF4 play critical roles in controlling posttranslationally modified microtubules around the inclusion and that Chlamydia trachomatis hijacks this novel function of ARF to reposition the Golgi complex.
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13
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Tricellular Tight Junction Protein Tricellulin Is Targeted by the Enteropathogenic Escherichia coli Effector EspG1, Leading to Epithelial Barrier Disruption. Infect Immun 2016; 85:IAI.00700-16. [PMID: 27795363 DOI: 10.1128/iai.00700-16] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 10/16/2016] [Indexed: 12/31/2022] Open
Abstract
Enteropathogenic Escherichia coli (EPEC)-induced diarrhea is often associated with disruption of intestinal epithelial tight junctions. Although studies have shown alterations in the expression and localization of bicellular tight junction proteins during EPEC infections, little is known about whether tricellular tight junction proteins (tTJs) are affected. Using Caco-2 cell monolayers, we investigated if EPEC is capable of targeting the tTJ protein tricellulin. Our results demonstrated that at 4 h postinfection, EPEC induced a significant reduction in tricellulin levels, accompanied by a significant loss of transepithelial resistance (TEER) and a corresponding increase in paracellular permeability. Conversely, cells overexpressing tricellulin were highly resistant to EPEC-induced barrier disruption. Confocal microscopy revealed the distribution of tricellulin into the plasma membrane of infected epithelial cells and confirmed the localization of EPEC aggregates in close proximity to tTJs. Moreover, infections with EPEC strains lacking genes encoding specific type III secreted effector proteins demonstrated a crucial role for the effector EspG1 in modulating tricellulin expression. Complementation studies suggest that the EspG-induced depletion of tricellulin is microtubule dependent. Overall, our results show that EPEC-induced epithelial barrier dysfunction is mediated in part by EspG1-induced microtubule-dependent depletion of tricellulin.
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Pearson JS, Giogha C, Wong Fok Lung T, Hartland EL. The Genetics of EnteropathogenicEscherichia coliVirulence. Annu Rev Genet 2016; 50:493-513. [DOI: 10.1146/annurev-genet-120215-035138] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jaclyn S. Pearson
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Victoria 3010, Australia; , , ,
| | - Cristina Giogha
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Victoria 3010, Australia; , , ,
| | - Tania Wong Fok Lung
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Victoria 3010, Australia; , , ,
| | - Elizabeth L. Hartland
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Victoria 3010, Australia; , , ,
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15
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Santos JC, Enninga J. At the crossroads: communication of bacteria-containing vacuoles with host organelles. Cell Microbiol 2016; 18:330-9. [PMID: 26762760 DOI: 10.1111/cmi.12567] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 01/08/2016] [Accepted: 01/12/2016] [Indexed: 02/06/2023]
Abstract
Invasive bacterial pathogens are engulfed upon host cell entry in a vacuolar environment called the bacteria-containing vacuole (BCV). BCVs directly contact with numerous host compartments, mainly vesicles of the endocytic pathway, such as endosomes or lysosomes. In addition, they also interact with the endoplasmic reticulum and endomembranes of the secretory pathway. These connections between the pathogen and the host occur either through heterotypic membrane fusions or through membrane contact sites. The precise regulation of BCV contacts with host compartments defines the constitution of the intracellular bacterial niche. It emerges that the associated pathways may control the stability of the BCV resulting either in vacuolar or cytoplasmically growing bacteria. Here, we will portray how the usage of novel proteomics and imaging technologies allows comparison of the communication of different host cell compartments with four relevant intracellular human pathogens, namely Salmonella enterica, Legionella pneumophila, Shigella flexneri and Francisella tularensis. The first two remain mainly within the BCV, and the latter two escape into the cytoplasm.
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Affiliation(s)
- José Carlos Santos
- Unit "Dynamics of Host-Pathogen Interactions", Institut Pasteur, Paris, France
| | - Jost Enninga
- Unit "Dynamics of Host-Pathogen Interactions", Institut Pasteur, Paris, France
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Humphreys D, Singh V, Koronakis V. Inhibition of WAVE Regulatory Complex Activation by a Bacterial Virulence Effector Counteracts Pathogen Phagocytosis. Cell Rep 2016; 17:697-707. [PMID: 27732847 PMCID: PMC5081413 DOI: 10.1016/j.celrep.2016.09.039] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 06/24/2016] [Accepted: 09/14/2016] [Indexed: 02/05/2023] Open
Abstract
To establish pathogenicity, bacteria must evade phagocytosis directed by remodeling of the actin cytoskeleton. We show that macrophages facilitate pathogen phagocytosis through actin polymerization mediated by the WAVE regulatory complex (WRC), small GTPases Arf and Rac1, and the Arf1 activator ARNO. To establish extracellular infections, enteropathogenic (EPEC) and enterohaemorrhagic (EHEC) Escherichia coli hijack the actin cytoskeleton by injecting virulence effectors into the host cell. Here, we find that the virulence effector EspG counteracts WRC-dependent phagocytosis, enabling EPEC and EHEC to remain extracellular. By reconstituting membrane-associated actin polymerization, we find that EspG disabled WRC activation through two mechanisms: EspG interaction with Arf6 blocked signaling to ARNO while EspG binding of Arf1 impeded collaboration with Rac1, thereby inhibiting WRC recruitment and activation. Investigating the mode of EspG interference revealed sites in Arf1 required for WRC activation and a mechanism facilitating pathogen evasion of innate host defenses.
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Affiliation(s)
- Daniel Humphreys
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
| | - Vikash Singh
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
| | - Vassilis Koronakis
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
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17
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Enterohaemorrhagic E. coli modulates an ARF6:Rab35 signaling axis to prevent recycling endosome maturation during infection. J Mol Biol 2016; 428:3399-407. [PMID: 27261256 PMCID: PMC5013874 DOI: 10.1016/j.jmb.2016.05.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 05/19/2016] [Accepted: 05/20/2016] [Indexed: 02/06/2023]
Abstract
Enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC/EHEC) manipulate a plethora of host cell processes to establish infection of the gut mucosa. This manipulation is achieved via the injection of bacterial effector proteins into host cells using a Type III secretion system. We have previously reported that the conserved EHEC and EPEC effector EspG disrupts recycling endosome function, reducing cell surface levels of host receptors through accumulation of recycling cargo within the host cell. Here we report that EspG interacts specifically with the small GTPases ARF6 and Rab35 during infection. These interactions target EspG to endosomes and prevent Rab35-mediated recycling of cargo to the host cell surface. Furthermore, we show that EspG has no effect on Rab35-mediated uncoating of newly formed endosomes, and instead leads to the formation of enlarged EspG/TfR/Rab11 positive, EEA1/Clathrin negative stalled recycling structures. Thus, this paper provides a molecular framework to explain how EspG disrupts recycling whilst also reporting the first known simultaneous targeting of ARF6 and Rab35 by a bacterial pathogen. EHEC delivers effector proteins into host cells to establish infection in the gut The effector EspG interacts with GTP-ARF6 confining EspG to recycling endosomes During infection EspG interacts preferentially with Rab35, not Rab1 Spatial restriction of bacterial effectors during infection determines their function
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Abstract
Bacterial pathogens encode a wide variety of effectors and toxins that hijack host cell structure and function. Of particular importance are virulence factors that target actin cytoskeleton dynamics critical for cell shape, stability, motility, phagocytosis, and division. In addition, many bacteria target organelles of the general secretory pathway (e.g., the endoplasmic reticulum and the Golgi complex) and recycling pathways (e.g., the endolysosomal system) to establish and maintain an intracellular replicative niche. Recent research on the biochemistry and structural biology of bacterial effector proteins and toxins has begun to shed light on the molecular underpinnings of these host-pathogen interactions. This exciting work is revealing how pathogens gain control of the complex and dynamic host cellular environments, which impacts our understanding of microbial infectious disease, immunology, and human cell biology.
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Affiliation(s)
- Alyssa Jimenez
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390;
| | - Didi Chen
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390;
| | - Neal M Alto
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390;
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19
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Abstract
The effector proteins IpaJ and VirA, from the bacterium Shigella flexneri, block the general secretory pathway (GSP) at different stages. In this issue of Cell Host & Microbe, Dobbs et al. (2015) use these proteins as a tool to pinpoint STING trafficking and signaling to the ER-Golgi intermediate compartment (ERGIC).
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Affiliation(s)
- Björn Hiller
- Institute of Molecular Medicine, University Hospital, University of Bonn, Sigmund-Freud-Strasse 25, 53127 Bonn, Germany
| | - Veit Hornung
- Institute of Molecular Medicine, University Hospital, University of Bonn, Sigmund-Freud-Strasse 25, 53127 Bonn, Germany.
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20
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Law RJ, Law HT, Scurll JM, Scholz R, Santos AS, Shames SR, Deng W, Croxen MA, Li Y, de Hoog CL, van der Heijden J, Foster LJ, Guttman JA, Finlay BB. Quantitative Mass Spectrometry Identifies Novel Host Binding Partners for Pathogenic Escherichia coli Type III Secretion System Effectors. J Proteome Res 2016; 15:1613-22. [DOI: 10.1021/acs.jproteome.6b00074] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | - Hong T. Law
- Department
of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | | | | | | | | | | | | | | | | | | | | | - Julian A. Guttman
- Department
of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
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Dobbs N, Burnaevskiy N, Chen D, Gonugunta VK, Alto NM, Yan N. STING Activation by Translocation from the ER Is Associated with Infection and Autoinflammatory Disease. Cell Host Microbe 2015; 18:157-68. [PMID: 26235147 DOI: 10.1016/j.chom.2015.07.001] [Citation(s) in RCA: 459] [Impact Index Per Article: 45.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 06/08/2015] [Accepted: 07/01/2015] [Indexed: 12/30/2022]
Abstract
STING is an ER-associated membrane protein that is critical for innate immune sensing of pathogens. STING-mediated activation of the IFN-I pathway through the TBK1/IRF3 signaling axis involves both cyclic-dinucleotide binding and its translocation from the ER to vesicles. However, how these events are coordinated, and the exact mechanism of STING activation, remain poorly understood. Here, we found that the Shigella effector protein IpaJ potently inhibits STING signaling by blocking its translocation from the ER to ERGIC, even in the context of dinucleotide binding. Reconstitution using purified components revealed STING translocation as the rate-limiting event in maximal signal transduction. Furthermore, STING mutations associated with autoimmunity in humans were found to cause constitutive ER exit and to activate STING independent of cGAMP binding. Together, these data provide compelling evidence for an ER retention and ERGIC/Golgi-trafficking mechanism of STING regulation that is subverted by bacterial pathogens and is deregulated in human genetic disease.
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Affiliation(s)
- Nicole Dobbs
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Nikolay Burnaevskiy
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Didi Chen
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Vijay K Gonugunta
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Neal M Alto
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Nan Yan
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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22
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Singh AP, Aijaz S. Enteropathogenic E. coli: breaking the intestinal tight junction barrier. F1000Res 2015; 4:231. [DOI: 10.12688/f1000research.6778.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/09/2015] [Indexed: 11/20/2022] Open
Abstract
Enteropathogenic E. coli (EPEC) causes acute intestinal infections in infants in the developing world. Infection typically spreads through contaminated food and water and leads to severe, watery diarrhea. EPEC attaches to the intestinal epithelial cells and directly injects virulence factors which modulate multiple signaling pathways leading to host cell dysfunction. However, the molecular mechanisms that regulate the onset of diarrhea are poorly defined. A major target of EPEC is the host cell tight junction complex which acts as a barrier and regulates the passage of water and solutes through the paracellular space. In this review, we focus on the EPEC effectors that target the epithelial barrier, alter its functions and contribute to leakage through the tight junctions.
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23
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Abstract
Enteropathogenic
E. coli (EPEC) causes acute intestinal infections in infants in the developing world. Infection typically spreads through contaminated food and water and leads to severe, watery diarrhea. EPEC attaches to the intestinal epithelial cells and directly injects virulence factors which modulate multiple signaling pathways leading to host cell dysfunction. However, the molecular mechanisms that regulate the onset of diarrhea are poorly defined. A major target of EPEC is the host cell tight junction complex which acts as a barrier and regulates the passage of water and solutes through the paracellular space. In this review, we focus on the EPEC effectors that target the epithelial barrier, alter its functions and contribute to leakage through the tight junctions.
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Affiliation(s)
- Anand Prakash Singh
- Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Saima Aijaz
- Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, 110067, India
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24
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Burnaevskiy N, Peng T, Reddick LE, Hang HC, Alto NM. Myristoylome profiling reveals a concerted mechanism of ARF GTPase deacylation by the bacterial protease IpaJ. Mol Cell 2015; 58:110-22. [PMID: 25773595 DOI: 10.1016/j.molcel.2015.01.040] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Revised: 01/02/2015] [Accepted: 01/27/2015] [Indexed: 10/23/2022]
Abstract
N-myristoylation is an essential fatty acid modification that governs the localization and activity of cell signaling enzymes, architectural proteins, and immune regulatory factors. Despite its importance in health and disease, there are currently no methods for reversing protein myristoylation in vivo. Recently, the Shigella flexneri protease IpaJ was found to cleave myristoylated glycine of eukaryotic proteins, yet the discriminatory mechanisms of substrate selection required for targeted demyristoylation have not yet been evaluated. Here, we performed global myristoylome profiling of cells treated with IpaJ under distinct physiological conditions. The protease is highly promiscuous among diverse N-myristoylated proteins in vitro but is remarkably specific to Golgi-associated ARF/ARL family GTPases during Shigella infection. Reconstitution studies revealed a mechanistic framework for substrate discrimination based on IpaJ's function as a GTPase "effector" of bacterial origin. We now propose a concerted model for IpaJ function that highlights its potential for programmable demyristoylation in vivo.
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Affiliation(s)
- Nikolay Burnaevskiy
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-8816, USA
| | - Tao Peng
- Laboratory of Chemical Biology and Microbial Pathogenesis, The Rockefeller University, New York, NY 10065, USA
| | - L Evan Reddick
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-8816, USA
| | - Howard C Hang
- Laboratory of Chemical Biology and Microbial Pathogenesis, The Rockefeller University, New York, NY 10065, USA
| | - Neal M Alto
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-8816, USA.
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25
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Santos AS, Finlay BB. Bringing down the host: enteropathogenic and enterohaemorrhagic Escherichia coli effector-mediated subversion of host innate immune pathways. Cell Microbiol 2015; 17:318-32. [PMID: 25588886 DOI: 10.1111/cmi.12412] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 12/17/2014] [Accepted: 12/22/2014] [Indexed: 12/14/2022]
Abstract
Enteric bacterial pathogens commonly use a type III secretion system (T3SS) to successfully infect intestinal epithelial cells and survive and proliferate in the host. Enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC; EHEC) colonize the human intestinal mucosa, form characteristic histological lesions on the infected epithelium and require the T3SS for full virulence. T3SS effectors injected into host cells subvert cellular pathways to execute a variety of functions within infected host cells. The EPEC and EHEC effectors that subvert innate immune pathways--specifically those involved in phagocytosis, host cell survival, apoptotic cell death and inflammatory signalling--are all required to cause disease. These processes are reviewed within, with a focus on recent work that has provided insights into the functions and host cell targets of these effectors.
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Affiliation(s)
- Andrew S Santos
- Department of Microbiology and Immunology, The University of British Columbia, Vancouver, BC, Canada; Michael Smith Laboratories, The University of British Columbia, Vancouver, BC, Canada
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26
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Abstract
Citrobacter rodentium is a mucosal pathogen of mice that shares several pathogenic mechanisms with enteropathogenic Escherichia coli (EPEC) and enterohaemorrhagic E. coli (EHEC), which are two clinically important human gastrointestinal pathogens. Thus, C. rodentium has long been used as a model to understand the molecular basis of EPEC and EHEC infection in vivo. In this Review, we discuss recent studies in which C. rodentium has been used to study mucosal immunology, including the deregulation of intestinal inflammatory responses during bacteria-induced colitis and the role of the intestinal microbiota in mediating resistance to colonization by enteric pathogens. These insights should help to elucidate the roles of mucosal inflammatory responses and the microbiota in the virulence of enteric pathogens.
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Clements A, Stoneham CA, Furniss RCD, Frankel G. Enterohaemorrhagic Escherichia coli inhibits recycling endosome function and trafficking of surface receptors. Cell Microbiol 2014; 16:1693-705. [PMID: 24898821 PMCID: PMC4336558 DOI: 10.1111/cmi.12319] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 05/23/2014] [Accepted: 05/28/2014] [Indexed: 01/26/2023]
Abstract
Enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC/EHEC) manipulate many cell processes by injecting effector proteins from the bacteria into the host cell via a Type III secretion system. In this paper we report that the effector protein EspG disrupts recycling endosome function. In particular, we found that following transferrin binding and endocytosis EspG reduces recycling of the transferrin receptor (TfR), the prototypical recycling protein, from an intracellular location to the cell surface, resulting in an accumulation of TfR within the cell. The surface levels of three receptors [TfR, epidermal growth factor receptor (EGFR) and β1 integrin] were tested and found to be reduced dependent on EspG translocation. Furthermore, disruption of recycling endosome function and the reduced surface presentation of receptors was dependent on the previously reported RabGAP activity and ARF binding ability of EspG. This paper therefore supports the previous hypothesis that EspG acts as an enzyme scaffold perturbing cell signalling events, in this case altering recycling endosome function and cell surface receptor levels during infection.
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Affiliation(s)
- Abigail Clements
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College, London, UK
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28
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Abstract
The innate immune system has evolved under selective pressure since the radiation of multicellular life approximately 600 million years ago. Because of this long history, innate immune mechanisms found in modern eukaryotic organisms today are highly complex but yet built from common molecular strategies. It is now clear that evolution has selected a conserved set of antimicrobial peptides as well as pattern-recognition receptors (PRRs) that initiate cellular-based signals as a first line of defense against invading pathogens. Conversely, microbial pathogens employ their own strategies in order to evade, inhibit, or otherwise manipulate the innate immune response. Here, we discuss recent discoveries that have changed our view of immune modulatory mechanisms employed by bacterial pathogens, focusing specifically on the initial sites of microbial recognition and extending to host cellular signal transduction, proinflammatory cytokine production, and alteration of protein trafficking and secretion.
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