scholarly journals Glycan-Glycan Interaction Determines Shigella Tropism toward Human T Lymphocytes

mBio ◽  
2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Ilia Belotserkovsky ◽  
Katja Brunner ◽  
Laurie Pinaud ◽  
Alexander Rouvinski ◽  
Mariano Dellarole ◽  
...  
Keyword(s):  
T Cells ◽  
Plasma Membrane ◽  
T Lymphocytes ◽  
Immune Cells ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Host Cells ◽  
Gram Negative

ABSTRACT Direct interactions between bacterial and host glycans have been recently reported to be involved in the binding of pathogenic bacteria to host cells. In the case of Shigella, the Gram-negative enteroinvasive bacterium responsible for acute rectocolitis, such interactions contribute to bacterial adherence to epithelial cells. However, the role of glycans in the tropism of Shigella for immune cells whose glycosylation pattern varies depending on their activation state is unknown. We previously reported that Shigella targets activated, but not nonactivated, human CD4+ T lymphocytes. Here, we show that nonactivated CD4+ T lymphocytes can be turned into Shigella-targetable cells upon loading of their plasma membrane with sialylated glycosphingolipids (also termed gangliosides). The Shigella targeting profile of ganglioside-loaded nonactivated T cells is similar to that of activated T cells, with a predominance of injection of effectors from the type III secretion system (T3SS) not resulting in cell invasion. We demonstrate that gangliosides interact with the O-antigen polysaccharide moiety of lipopolysaccharide (LPS), the major bacterial surface antigen, thus promoting Shigella binding to CD4+ T cells. This binding step is critical for the subsequent injection of T3SS effectors, a step which we univocally demonstrate to be dependent on actin polymerization. Altogether, these findings highlight the critical role of glycan-glycan interactions in Shigella pathogenesis. IMPORTANCE Glycosylation of host cell surface varies with species and location in the body, thus contributing to species specificity and tropism of microorganisms. Cross talk by Shigella, the Gram-negative enteroinvasive bacterium responsible for bacillary dysentery, with its exclusively human host has been extensively studied. However, the molecular determinants of the step of binding to host cells are poorly defined. Taking advantage of the observation that human-activated CD4+ T lymphocytes, but not nonactivated cells, are targets of Shigella, we succeeded in rendering the refractory cells susceptible to targeting upon loading of their plasma membrane with sialylated glycosphingolipids (gangliosides) that are abundantly present on activated cells. We show that interactions between the sugar polar part of gangliosides and the polysaccharide moiety of Shigella lipopolysaccharide (LPS) promote bacterial binding, which results in the injection of effectors via the type III secretion system. Whereas LPS interaction with gangliosides was proposed long ago and recently extended to a large variety of glycans, our findings reveal that such glycan-glycan interactions are critical for Shigella pathogenesis by driving selective interactions with host cells, including immune cells.

scholarly journals The Ruler Protein EscP of the Enteropathogenic Escherichia coli Type III Secretion System Is Involved in Calcium Sensing and Secretion Hierarchy Regulation by Interacting with the Gatekeeper Protein SepL

mBio ◽  
2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Lihi Shaulov ◽  
Jenia Gershberg ◽  
Wanyin Deng ◽  
B. Brett Finlay ◽  
Neta Sal-Man
Keyword(s):  
Host Cell ◽  
Type Iii Secretion ◽  
Bacterial Pathogens ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Bacterial Virulence ◽  
Effector Proteins ◽  
Host Cells ◽  
Gram Negative ◽  
Type Iii

ABSTRACT The type III secretion system (T3SS) is a multiprotein complex that plays a central role in the virulence of many Gram-negative bacterial pathogens. To ensure that effector proteins are efficiently translocated into the host cell, bacteria must be able to sense their contact with the host cell. In this study, we found that EscP, which was previously shown to function as the ruler protein of the enteropathogenic Escherichia coli T3SS, is also involved in the switch from the secretion of translocator proteins to the secretion of effector proteins. In addition, we demonstrated that EscP can interact with the gatekeeper protein SepL and that the EscP-SepL complex dissociates upon a calcium concentration drop. We suggest a model in which bacterial contact with the host cell is accompanied by a drop in the calcium concentration that causes SepL-EscP complex dissociation and triggers the secretion of effector proteins. IMPORTANCE The emergence of multidrug-resistant bacterial strains, especially those of pathogenic bacteria, has serious medical and clinical implications. At the same time, the development and approval of new antibiotics have been limited for years. Recently, antivirulence drugs have received considerable attention as a novel antibiotic strategy that specifically targets bacterial virulence rather than growth, an approach that applies milder evolutionary pressure on the bacteria to develop resistance. A highly attractive target for the development of antivirulence compounds is the type III secretion system, a specialized secretory system possessed by many Gram-negative bacterial pathogens for injecting virulence factors (effectors) into host cells. In this study, we shed light on the molecular mechanism that allows bacteria to sense their contact with the host cell and to respond with the timed secretion of effector proteins. Understanding this critical step for bacterial virulence may provide a new therapeutic strategy. IMPORTANCE The emergence of multidrug-resistant bacterial strains, especially those of pathogenic bacteria, has serious medical and clinical implications. At the same time, the development and approval of new antibiotics have been limited for years. Recently, antivirulence drugs have received considerable attention as a novel antibiotic strategy that specifically targets bacterial virulence rather than growth, an approach that applies milder evolutionary pressure on the bacteria to develop resistance. A highly attractive target for the development of antivirulence compounds is the type III secretion system, a specialized secretory system possessed by many Gram-negative bacterial pathogens for injecting virulence factors (effectors) into host cells. In this study, we shed light on the molecular mechanism that allows bacteria to sense their contact with the host cell and to respond with the timed secretion of effector proteins. Understanding this critical step for bacterial virulence may provide a new therapeutic strategy.

scholarly journals Antibodies Inhibiting the Type III Secretion System of Gram-Negative Pathogenic Bacteria

Antibodies ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 35
Author(s):  
Julia A. Hotinger ◽  
Aaron E. May
Keyword(s):  
Type Iii Secretion ◽  
Pathogenic Bacteria ◽  
Type Iii Secretion System ◽  
The United States ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Gram Negative ◽  
Type Iii ◽  
Shigella Spp

Pathogenic bacteria are a global health threat, with over 2 million infections caused by Gram-negative bacteria every year in the United States. This problem is exacerbated by the increase in resistance to common antibiotics that are routinely used to treat these infections, creating an urgent need for innovative ways to treat and prevent virulence caused by these pathogens. Many Gram-negative pathogenic bacteria use a type III secretion system (T3SS) to inject toxins and other effector proteins directly into host cells. The T3SS has become a popular anti-virulence target because it is required for pathogenesis and knockouts have attenuated virulence. It is also not required for survival, which should result in less selective pressure for resistance formation against T3SS inhibitors. In this review, we will highlight selected examples of direct antibody immunizations and the use of antibodies in immunotherapy treatments that target the bacterial T3SS. These examples include antibodies targeting the T3SS of Pseudomonas aeruginosa, Yersinia pestis, Escherichia coli, Salmonella enterica, Shigella spp., and Chlamydia trachomatis.

scholarly journals Edwardsiella tarda-Induced Cytotoxicity Depends on Its Type III Secretion System and Flagellin

2014 ◽  
Vol 82 (8) ◽  
pp. 3436-3445 ◽  
Author(s):  
Hai-Xia Xie ◽  
Jin-Fang Lu ◽  
Nathalie Rolhion ◽  
David W. Holden ◽  
Pin Nie ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Host Cells ◽  
Edwardsiella Tarda ◽  
Dependent Manner ◽  
Gram Negative ◽  
Content Type ◽  
Murine Bone Marrow ◽  
Type Iii

ABSTRACTMany Gram-negative bacteria utilize a type III secretion system (T3SS) to translocate virulence proteins into host cells to cause diseases. In responding to infection, macrophages detect some of the translocated proteins to activate caspase-1-mediated cell death, called pyroptosis, and secretion of proinflammatory cytokines to control the infection.Edwardsiella tardais a Gram-negative enteric pathogen that causes hemorrhagic septicemia in fish and both gastrointestinal and extraintestinal infections in humans. In this study, we report that the T3SS ofE. tardafacilitates its survival and replication in murine bone marrow-derived macrophages, andE. tardainfection triggers pyroptosis of infected macrophages from mice and fish and increased secretion of the cytokine interleukin 1β in a T3SS-dependent manner. Deletion of the flagellin genefliCofE. tardaresults in decreased cytotoxicity for infected macrophages and does not attenuate its virulence in a fish model of infection, whereas upregulated expression of FliC in thefliCmutant strain reduces its virulence. We propose that the host controlsE. tardainfection partially by detecting FliC translocated by the T3SS, whereas the bacteria downregulate the expression of FliC to evade innate immunity.

scholarly journals Cloning and Transfer of the Salmonella Pathogenicity Island 2 Type III Secretion System for Studies of a Range of Gram-Negative Genera

2007 ◽  
Vol 73 (18) ◽  
pp. 5911-5918 ◽  
Author(s):  
James W. Wilson ◽  
Clint Coleman ◽  
Cheryl A. Nickerson
Keyword(s):  
Type Iii Secretion ◽  
Vaccine Development ◽  
Type Iii Secretion System ◽  
Pathogenicity Island ◽  
Secretion System ◽  
Host Cells ◽  
Secretion Systems ◽  
Gram Negative ◽  
Type Iii ◽  
Type Iii Secretion Systems

ABSTRACT The engineering of bacterial strains with specific phenotypes frequently requires the use of blocks or “cassettes” of genes that act together to perform a desired function. The potential benefits of utilizing type III secretion systems in this regard are becoming increasingly realized since these systems can be used to direct interactions with host cells for beneficial purposes such as vaccine development, anticancer therapies, and targeted protein delivery. However, convenient methods to clone and transfer type III secretion systems for studies of a range of different types of bacteria are lacking. In addition to functional applications, such methods would also reveal important information about the evolution of a given type III secretion system, such as its ability to be expressed and functional outside of the strain of origin. We describe here the cloning of the Salmonella enterica serovar Typhimurium pathogenicity island 2 (SPI-2) type III secretion system onto a vector that can be easily transferred to a range of gram-negative bacterial genera. We found that expression of the cloned SPI-2 system in different Gammaproteobacteria and Alphaproteobacteria (as monitored by SseB protein levels) is dependent on the bacterial strain and growth medium. We also demonstrate that the cloned system is functional for secretion, can direct interactions with macrophages, and can be used as a novel tool to analyze the predicted interaction of SseB with host cells. This work provides a foundation for future applications where the cloned SPI-2 region (or other cloned type III systems) can provide a desired function to an engineered gram-negative strain.

scholarly journals Characterization of the Ruler Protein Interaction Interface on the Substrate Specificity Switch Protein in the Yersinia Type III Secretion System

2016 ◽  
Vol 292 (8) ◽  
pp. 3299-3311 ◽  
Author(s):  
Oanh Ho ◽  
Per Rogne ◽  
Tomas Edgren ◽  
Hans Wolf-Watz ◽  
Frédéric H. Login ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Type Iii ◽  
Binding Interface ◽  
Interaction Interface

Many pathogenic Gram-negative bacteria use the type III secretion system (T3SS) to deliver effector proteins into eukaryotic host cells. In Yersinia, the switch to secretion of effector proteins is induced first after intimate contact between the bacterium and its eukaryotic target cell has been established, and the T3SS proteins YscP and YscU play a central role in this process. Here we identify the molecular details of the YscP binding site on YscU by means of nuclear magnetic resonance (NMR) spectroscopy. The binding interface is centered on the C-terminal domain of YscU. Disrupting the YscU-YscP interaction by introducing point mutations at the interaction interface significantly reduced the secretion of effector proteins and HeLa cell cytotoxicity. Interestingly, the binding of YscP to the slowly self-cleaving YscU variant P264A conferred significant protection against autoproteolysis. The YscP-mediated inhibition of YscU autoproteolysis suggests that the cleavage event may act as a timing switch in the regulation of early versus late T3SS substrates. We also show that YscUC binds to the inner rod protein YscI with a dissociation constant (Kd) of 3.8 μm and with 1:1 stoichiometry. The significant similarity among different members of the YscU, YscP, and YscI families suggests that the protein-protein interactions discussed in this study are also relevant for other T3SS-containing Gram-negative bacteria.

scholarly journals Chlamydial Lytic Exit from Host Cells Is Plasmid Regulated

mBio ◽  
2015 ◽  
Vol 6 (6) ◽  
Author(s):  
Chunfu Yang ◽  
Tregei Starr ◽  
Lihua Song ◽  
John H. Carlson ◽  
Gail L. Sturdevant ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Actin Polymerization ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Cytoskeletal Proteins ◽  
Host Cells ◽  
Genetic Mechanism ◽  
Developmental Cycle ◽  
Obligate Intracellular ◽  
Type Iii

ABSTRACTChlamydia trachomatisis an obligate intracellular bacterium that is a globally important human pathogen. The chlamydial plasmid is an attenuating virulence factor, but the molecular basis for attenuation is not understood. Chlamydiae replicate within a membrane-bound vacuole termed an inclusion, where they undergo a biphasic developmental growth cycle and differentiate from noninfectious into infectious organisms. Late in the developmental cycle, the fragile chlamydia-laden inclusion retains its integrity by surrounding itself with scaffolds of host cytoskeletal proteins. The ability of chlamydiae to developmentally free themselves from this cytoskeleton network is a fundamental virulence trait of the pathogen. Here, we show that plasmidless chlamydiae are incapable of disrupting their cytoskeletal entrapment and remain intracellular as stable mature inclusions that support high numbers of infectious organisms. By using deletion mutants of the eight plasmid-carried genes (Δpgp1to Δpgp8), we show that Pgp4, a transcriptional regulator of multiple chromosomal genes, is required for exit. Exit of chlamydiae is dependent on protein synthesis and is inhibited by the compound C1, an inhibitor of the type III secretion system (T3S). Exit of plasmid-free and Δpgp4organisms, which failed to lyse infected cells, was rescued by latrunculin B, an inhibitor of actin polymerization. Our findings describe a genetic mechanism of chlamydial exit from host cells that is dependent on an unknownpgp4-regulated chromosomal T3S effector gene.IMPORTANCEChlamydia's obligate intracellular life style requires both entry into and exit from host cells. Virulence factors that function in exiting are unknown. The chlamydial inclusion is stabilized late in the infection cycle by F-actin. A prerequisite of chlamydial exit is its ability to disassemble actin from the inclusion. We show that chlamydial plasmid-free organisms, and also a plasmid gene protein 4 (pgp4) null mutant, do not disassociate actin from the inclusion and fail to exit cells. We further provide evidence that Pgp4-regulated exit is dependent on the chlamydial type III secretion system. This study is the first to define a genetic mechanism that functions in chlamydial lytic exit from host cells. The findings also have practical implications for understanding why plasmid-free chlamydiae are highly attenuated and have the ability to elicit robust protective immune responses.

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