scholarly journals Exploitation of the Endocytic Pathway by Orientia tsutsugamushi in Nonprofessional Phagocytes

2006 ◽  
Vol 74 (7) ◽  
pp. 4246-4253 ◽  
Author(s):  
Hyuk Chu ◽  
Jung-Hee Lee ◽  
Seung-Hoon Han ◽  
Se-Yoon Kim ◽  
Nam-Hyuk Cho ◽  
...  
Keyword(s):  
Host Cell ◽  
Causative Agent ◽  
Scrub Typhus ◽  
Adaptor Protein ◽  
Endocytic Pathway ◽  
Intracellular Bacterium ◽  
Orientia Tsutsugamushi ◽  
Obligate Intracellular Bacterium ◽  
Obligate Intracellular ◽  
Endocytic Vesicles

ABSTRACT Orientia tsutsugamushi, a causative agent of scrub typhus, is an obligate intracellular bacterium that requires the exploitation of the endocytic pathway in the host cell. We observed the localization of O. tsutsugamushi with clathrin or adaptor protein 2 within 30 min after the infection of nonprofessional phagocytes. We have further confirmed that the infectivity of O. tsutsugamushi is significantly reduced by drugs that block clathrin-mediated endocytosis but not by filipin III, an inhibitor that blocks caveola-mediated endocytosis. In the present study, with a confocal microscope, O. tsutsugamushi was sequentially colocalized with the early and late endosomal markers EEA1 and LAMP2, respectively, within 1 h after infection. The colocalization of O. tsutsugamushi organisms with EEA1 and LAMP2 gradually disappeared until 2 h postinfection, and then free O. tsutsugamushi organisms were found in the cytoplasm. When the acidification of endocytic vesicles was blocked by treating the cells with NH4Cl or bafilomycin A, the escape of O. tsutsugamushi organisms from the endocytic pathway was severely impaired, and the infectivity of O. tsutsugamushi was drastically reduced. To our knowledge, this is the first report that the invasion of O. tsutsugamushi is dependent on the clathrin-dependent endocytic pathway and the acidification process of the endocytic vesicles in nonprofessional phagocytes.

scholarly journals Developmental differentiation in a cytoplasm-dwelling obligate intracellular bacterium

2020 ◽  
Author(s):  
Suparat Giengkam ◽  
Jantana Wongsantichon ◽  
Sharanjeet Atwal ◽  
Yanin Jaiyen ◽  
Wah Ing Goh ◽  
...  
Keyword(s):  
Host Cell ◽  
Metabolic Activity ◽  
Model System ◽  
Intracellular Bacterium ◽  
Host Cells ◽  
Orientia Tsutsugamushi ◽  
Obligate Intracellular Bacterium ◽  
New Model ◽  
Obligate Intracellular ◽  
Developmental Differentiation

AbstractDevelopmental differentiation has been described for several vacuole-dwelling obligate intracellular bacteria but never for an obligate intracellular bacterium that resides in the cytoplasm. Here, we show that the cytoplasm-dwelling obligate intracellular bacterium Orientia tsutsugamushi (Ot) exists in five distinct subpopulations. We show that Ot differentiates into a distinct, metabolically inactive, extracellular state upon budding from the surface of host cells and that this stage is preceded by a surface-associated maturation stage. We identify proteins that are differentially expressed in intracellular, replicative bacteria and extracellular, metabolically inactive bacteria. Metabolic activity resumes rapidly upon entry into the cytoplasm and is triggered by the host cell reducing environment. This example of developmental differentiation in a species of Rickettsiaceae provides a new model system for studying synchronized differentiation in a bacterium that has a minimal genome and where the interactions between bacterium and host cell are more direct than they are for bacteria separated from the eukaryote cell host by a vacuolar membrane.Author SummaryScrub typhus is a life-threatening human infection that is caused by the bacterium Orientia tsutsugamushi and spread by mites. Although the disease is estimated to affect at least one million people annually and is often fatal, the infectious agent is much less well understood than many other pathogens. O. tsutsugamushi is an intracellular bacterium that can only grow and divide within eukaryotic cells. During infection, it is found primarily in the cells that make up the lining of blood vessels and in certain immune cell types. O. tsutsugamushi bacteria can remain inside a single infected cell for seven days or more before budding out. The ways in which the bacterium itself changes during the course of an intracellular infection cycle have not been studied. In the current work, we used a range of techniques to show that O. tsutsugamushi differentiates into five distinct subpopulations, and that these are associated with measurable differences in metabolic activity, replication and infectivity. This work opens new avenues of research into the regulation and mechanisms of differentiation of O. tsutsugamushi, which could lead to improved diagnosis and treatments. It also provides a new model system for studying fundamental questions about bacterial development.

scholarly journals Coxiella burnetiiType 4B Secretion System-dependent manipulation of endolysosomal maturation is required for bacterial growth

2019 ◽  
Author(s):  
Dhritiman Samanta ◽  
Tatiana M. Clemente ◽  
Stacey D. Gilk
Keyword(s):  
Host Cell ◽  
Secretion System ◽  
Intracellular Bacterium ◽  
Host Cells ◽  
Acidic Ph ◽  
Obligate Intracellular Bacterium ◽  
Cell Infection ◽  
Obligate Intracellular ◽  
Endosomal Acidification ◽  
Infected Cells

AbstractUpon host cell infection, the obligate intracellular bacteriumC. burnetiiresides and multiplies within theCoxiella–ContainingVacuole (CCV). The nascent CCV progresses through the endosomal maturation pathway into a phagolysosome, acquiring lysosomal markers as well as acidic pH and active proteases and hydrolases. Approximately 24-48 hours post infection, heterotypic fusion between the CCV and host endosomes/lysosomes leads to CCV expansion and subsequent bacterial replication in the mature CCV. Initial CCV acidification is required to activateC. burnetiimetabolism and the Type 4B Secretion System (T4BSS), which secretes effector proteins required for CCV maturation. However, we recently found that the mature CCV is less acidic (pH~5.2) than lysosomes (pH~4.8). Further, CCV acidification to pH~4.8 causesC. burnetiilysis, suggestingC. burnetiiactively regulates CCV pH. Because heterotypic fusion with host endosomes/lysosomes may influence CCV pH, we investigated endosomal maturation in cells infected with wildtype (WT) or T4BSS mutant (ΔdotA)C. burnetii. We observed significantly fewer LAMP1-positive lysosomes, along with less acidic “mature” endosomes (pH~5.8), in WT-infected cells, compared to mock or ΔdotA-infected cells. Further, while endosomes progressively acidified from the periphery (pH~5.5) to the perinuclear area (pH~4.7) in both mock and ΔdotA-infected cells, endosomes did not acidify beyond pH~5.2 in WT-infected cells, indicating that theC. burnetiiT4BSS inhibits endosomal maturation. Finally, increasing the number of acidic lysosomes by overexpressing the transcription factor EB inhibitedC. burnetiigrowth, indicating lysosomes are detrimental toC. burnetii. Overall, our data suggest thatC. burnetiiregulates CCV pH, possibly by reducing the number of host lysosomes available for heterotypic fusion.Author summaryThe obligate intracellular bacteriumCoxiella burnetiicauses human Q fever, which manifests as a flu-like illness but can develop into a life-threatening and difficult to treat endocarditis.C. burnetii,in contrast to many other intracellular bacteria, thrives within a lysosome-like vacuole in host cells. However, we previously found that theC. burnetiivacuole is not as acidic as lysosomes and increased acidification kills the bacteria, suggesting thatC. burnetiiregulates the pH of its vacuole. Here, we discovered thatC. burnetiiblocks endosomal maturation and acidification during host cell infection, resulting in fewer lysosomes in the host cell. Moreover, increasing lysosomes in the host cells blockedC. burnetiigrowth. Together, our study suggests thatC. burnetiiregulates vacuole acidity and blocks endosomal acidification in order to produce a permissive intracellular niche.

scholarly journals Orientia tsutsugamushi Strain Ikeda Ankyrin Repeat-Containing Proteins Recruit SCF1 Ubiquitin Ligase Machinery via Poxvirus-Like F-Box Motifs

2015 ◽  
Vol 197 (19) ◽  
pp. 3097-3109 ◽  
Author(s):  
Andrea R. Beyer ◽  
Lauren VieBrock ◽  
Kyle G. Rodino ◽  
Daniel P. Miller ◽  
Brittney K. Tegels ◽  
...  
Keyword(s):  
Host Cell ◽  
Ubiquitin Ligase ◽  
Scrub Typhus ◽  
Ankyrin Repeat ◽  
Intracellular Bacterium ◽  
Host Cells ◽  
Orientia Tsutsugamushi ◽  
Ligand Interaction ◽  
Content Type ◽  
Cell Functions

ABSTRACTA rising theme among intracellular microbes is the delivery of ankyrin repeat-containing effectors (Anks) that interact with target proteins to co-opt host cell functions.Orientia tsutsugamushi, an obligate intracellular bacterium and the etiologic agent of scrub typhus, encodes one of the largest Ank repertoires of any sequenced microorganism. They have been previously identified as type 1 secretion system substrates. Here,in silicoand manual sequence analyses revealed that a large proportion ofO. tsutsugamushistrain Ikeda Anks bear a eukaryotic/poxvirus-like F-box motif, which is known to recruit host cell SCF1 ubiquitin ligase machinery. We assessed the Anks for the ability to serve as F-box proteins. Coimmunoprecipitation assays demonstrated that F-box-containing Anks interact with overexpressed and/or endogenous SCF1 components. When coexpressed with FLAG-Ank4_01 or FLAG-Ank9, a glutathioneS-transferase (GST)-tagged version of the SCF1 component SKP1 localized to subcellular sites of FLAG-Ank accumulation. The abilities of recombinant Anks to interact and colocalize with SKP1 were F-box dependent. GST-SKP1 precipitatedO. tsutsugamushi-derived Ank9 from infected host cells, verifying both that the pathogen expresses Ank9 during infection and the protein's capability to bind SKP1. AligningO. tsutsugamushi, poxviral, and eukaryotic F-box sequences delineated three F-box residues that are highly conserved and likely to be functionally important. Substitution of these residues ablated the ability of GFP-Ank9 to interact with GST-SKP1. These results demonstrate thatO. tsutsugamushistrain Ikeda Anks can co-opt host cell polyubiquitination machinery, provide the first evidence that anO. tsutsugamushiAnk does so during infection, and advance overall understanding of microbial F-box proteins.IMPORTANCEAnkyrin repeat-containing proteins (Anks) are important virulence factors of intracellular bacteria that mediate protein-protein interactions with host cell targets.Orientia tsutsugamushi, which causes a debilitating infection called scrub typhus in one of the most densely populated regions of the world, encodes one of the largest Ank armamentariums of any sequenced bacterium. This study demonstrates thatO. tsutsugamushistrain Ikeda Anks also bear F-box motifs that interact with host cell polyubiquitination machinery. By proving that anOrientia-derived Ank interacts with SKP1 in infected cells, this evidences the first bona fideOrientiaeffector and the first example of an endogenous F-box-containing Ank–mammalian-host ligand interaction for any intracellular bacterium. Also, importantly, this work identifies key residues that are essential for microbial F-box function.

Host range of obligate intracellular bacterium Parachlamydia acanthamoebae

2010 ◽  
Vol 54 (11) ◽  
pp. 707-713 ◽  
Author(s):  
Yasuhiro Hayashi ◽  
Shinji Nakamura ◽  
Junji Matsuo ◽  
Tatsuya Fukumoto ◽  
Mitsutaka Yoshida ◽  
...  
Keyword(s):  
Host Range ◽  
Intracellular Bacterium ◽  
Obligate Intracellular Bacterium ◽  
Obligate Intracellular

scholarly journals Discovery of Putative Small Non-Coding RNAs from the Obligate Intracellular Bacterium Wolbachia pipientis

PLoS ONE ◽  
2015 ◽  
Vol 10 (3) ◽  
pp. e0118595 ◽  
Author(s):  
Megan Woolfit ◽  
Manjula Algama ◽  
Jonathan M. Keith ◽  
Elizabeth A. McGraw ◽  
Jean Popovici
Keyword(s):  
Intracellular Bacterium ◽  
Obligate Intracellular Bacterium ◽  
Wolbachia Pipientis ◽  
Obligate Intracellular ◽  
Non Coding Rnas

scholarly journals Cdc42 Couples T Cell Receptor Endocytosis to GRAF1-Mediated Tubular Invaginations of the Plasma Membrane

Cells ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 1388 ◽  
Author(s):  
Rossatti ◽  
Ziegler ◽  
Schregle ◽  
Betzler ◽  
Ecker ◽  
...  
Keyword(s):  
T Cell ◽  
T Cell Receptor ◽  
T Cell Activation ◽  
Cell Activation ◽  
Adaptor Protein ◽  
Cell Receptor ◽  
Small Gtpase ◽  
Endocytic Pathway ◽  
Bar Domain ◽  
Endocytic Vesicles

: T cell activation is immediately followed by internalization of the T cell receptor (TCR). TCR endocytosis is required for T cell activation, but the mechanisms supporting removal of TCR from the cell surface remain incompletely understood. Here we report that TCR endocytosis is linked to the clathrin-independent carrier (CLIC) and GPI-enriched endocytic compartments (GEEC) endocytic pathway. We show that unlike the canonical clathrin cargo transferrin or the adaptor protein Lat, internalized TCR accumulates in tubules shaped by the small GTPase Cdc42 and the Bin/amphiphysin/Rvs (BAR) domain containing protein GRAF1 in T cells. Preventing GRAF1-positive tubules to mature into endocytic vesicles by expressing a constitutively active Cdc42 impairs the endocytosis of TCR, while having no consequence on the uptake of transferrin. Together, our data reveal a link between TCR internalization and the CLIC/GEEC endocytic route supported by Cdc42 and GRAF1.

scholarly journals Antibody-Mediated Elimination of the Obligate Intracellular Bacterial Pathogen Ehrlichia chaffeensisduring Active Infection

2000 ◽  
Vol 68 (4) ◽  
pp. 2187-2195 ◽  
Author(s):  
Gary M. Winslow ◽  
Eric Yager ◽  
Konstantin Shilo ◽  
Erin Volk ◽  
Andrew Reilly ◽  
...  
Keyword(s):  
Bacterial Pathogen ◽  
Immune Serum ◽  
Intracellular Bacterium ◽  
Bacterial Clearance ◽  
Obligate Intracellular Bacterium ◽  
Active Infection ◽  
Obligate Intracellular ◽  
Humoral Responses ◽  
Human Monocytic Ehrlichiosis ◽  
Dose Dependent

ABSTRACT It is generally accepted that cellular, but not humoral immunity, plays an important role in host defense against intracellular bacteria. However, studies of some of these pathogens have provided evidence that antibodies can provide immunity if present during the initiation of infection. Here, we examined immunity against infection byEhrlichia chaffeensis, an obligate intracellular bacterium that causes human monocytic ehrlichiosis. Studies with mice have demonstrated that immunocompetent strains are resistant to persistent infection but that SCID mice become persistently and fatally infected. Transfer of immune serum or antibodies obtained from immunocompetent C57BL/6 mice to C57BL/6 scid mice provided significant although transient protection from infection. Bacterial clearance was observed when administration occurred at the time of inoculation or well after infection was established. The effect was dose dependent, occurred within 2 days, and persisted for as long as 2 weeks. Weekly serum administration prolonged the survival of susceptible mice. Although cellular immunity is required for complete bacterial clearance, the data show that antibodies can play a significant role in the elimination of this obligate intracellular bacterium during active infection and thus challenge the paradigm that humoral responses are unimportant for immunity to such organisms.

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