Selection of Mutant Cell Lines Resistant to Infection by<i>Chlamydia trachomatis</i>and<i>Chlamydia pneumoniae</i>

Fudyk, Trevor; Olinger, Lynn; Stephens, Richard S.

doi:10.1128/iai.70.11.6444-6447.2002

Cited by 31 publications

(32 citation statements)

References 24 publications

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“…This would intuitively argue that C. trachomatis and C. caviae utilize different host cell receptors for entry. This hypothesis is supported by studies with chemically mutagenized CHO cells that exhibit different susceptibilities to infection by C. trachomatis and C. pneumoniae (18). Although we did not study C. pneumoniae here, we previously reported that infection with C. pneumoniae, like that with C. caviae, failed to induce Tyr-P of the 70-kDa protein that we have now identified as ezrin.…”

Section: Discussionsupporting

confidence: 55%

“…These mechanistic properties are shared by most chlamydial strains (48), suggesting a shared common chlamydial ligand and host receptor interaction. Work with chemically mutagenized Chinese hamster ovary (CHO) cells has shown that EB entry is phenotypically distinguishable from attachment since it is temperature dependent and irreversible, and the ligands and/or receptors appear to differ among chlamydial strains (7,18). Numerous chlamydial ligands (40,42,47,48) and several host receptors (10,15) have been implicated in attachment, leaving the precise molecular mechanisms largely unresolved and controversial.…”

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confidence: 99%

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Chlamydia trachomatis Species-Specific Induction of Ezrin Tyrosine Phosphorylation Functions in Pathogen Entry

Swanson

Crane

2007

Infect Immun

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Chlamydia trachomatis is an obligate intracellular pathogen of humans that exhibits species-specific biological characteristics in its early interactions with host cells that are likely important to pathogenesis. One such characteristic is the tyrosine phosphorylation (Tyr-P) of an ϳ70-kDa polypeptide that occurs only after infection of mammalian cells by human strains. We sought to identify this protein because of its potential significance to the pathogenesis of human chlamydial infections. Using an immunoproteomic approach we identified the host protein ezrin, a member of the ezrin-radixin-moesin (ERM) protein family that serves as a physical link between host cell receptors and the actin cytoskeleton. Confocal microscopy studies showed colocalization of ezrin and actin at the tips and crypts of microvilli, the site of chlamydial attachment and entry, respectively. To demonstrate a functional role for ezrin we infected cells with a dominant-negative (DN) ezrin phenotype or treated cells with ezrin-specific small interfering RNA (siRNA). We found that both DN and siRNA-treated cells were significantly less susceptible to infection by human chlamydial strains. Moreover, we demonstrated that inhibition of infection in ezrin DN cells occurred at the stage of chlamydial entry. We hypothesize that the C. trachomatis-specific Tyr-P of ezrin might relate to an undefined species-specific mechanism of pathogen entry that involves chlamydial specific ligand(s) and host cell coreceptor usage.Chlamydiae are obligate intracellular prokaryotes that, despite a considerable degree of shared developmental biology and genomic identity, exhibit distinct host infection tropisms and clinical expression of disease (32,33,39). This interesting spectrum in pathogen characteristics is frequently correlated with subtle differences in in vitro infection properties, particularly treatments that affect early chlamydial infection events of cultured mammalian cells (30). Chlamydiae have a biphasic developmental cycle whereby the infectious elementary body (EB) enters the host cell, evades lysosomal fusion, and differentiates into the replicating reticulate body (RB) within a hostderived vacuole (29). Infection of cells by EBs requires both attachment and entry steps. Initial attachment is temperature independent and heparin reversible. These mechanistic properties are shared by most chlamydial strains (48), suggesting a shared common chlamydial ligand and host receptor interaction. Work with chemically mutagenized Chinese hamster ovary (CHO) cells has shown that EB entry is phenotypically distinguishable from attachment since it is temperature dependent and irreversible, and the ligands and/or receptors appear to differ among chlamydial strains (7, 18). Numerous chlamydial ligands (40,42,47,48) and several host receptors (10, 15) have been implicated in attachment, leaving the precise molecular mechanisms largely unresolved and controversial. Despite the apparent species specificity governing chlamydial entry mechanisms, all chlamydiae indu...

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Section: Discussionsupporting

confidence: 55%

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confidence: 99%

Chlamydia trachomatis Species-Specific Induction of Ezrin Tyrosine Phosphorylation Functions in Pathogen Entry

Swanson

Crane

2007

Infect Immun

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“…The specific bacterial ligand and host receptor(s) that mediate entry are still unclear. Heparan sulfate acts as a bridging molecule for a relatively weak and reversible interaction (12,38,41,42) that is followed by a stronger, more specific binding to an unidentified secondary receptor (5,11). Internalization is accompanied by induction of a microvillus-like structure over a large portion of the host cell in a process that is dependent upon actin polymerization (3) and is mediated through Rac (4).…”

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confidence: 99%

Lipid Raft-Mediated Entry Is Not Required for Chlamydia trachomatis Infection of Cultured Epithelial Cells

Gabel¹,

Elwell²,

IJzendoorn

et al. 2004

Infect Immun

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Using pharmacologic and biochemical criteria, we evaluated whether uptake of four different Chlamydia trachomatis serovars, D, E, K, and L2, was dependent upon lipid rafts. Our data suggest that lipid raft-mediated entry is not required for C. trachomatis infection of cultured epithelial cells.Microbes often enter into nonphagocytic cells by usurping normal host cell endocytic pathways. In addition to clathrinmediated endocytosis, various nonclathrin endocytic mechanisms have been identified, including uptake through caveolae, macropinosomes, and a separate constitutive pathway (reviewed in reference 24). These non-clathrin-dependent pathways do not use known coat complexes for cargo recruitment and budding of transport intermediates but are heterogeneous in nature. A subset has been identified that utilizes lipid rafts, specialized dynamic, detergent-resistant regions of the plasma membrane enriched in cholesterol, glycosphingolipids, glycosylphosphatidylinositol-anchored proteins, and some membrane proteins, including caveolin (2, 33). A subtype of lipid rafts, caveolae, has a distinct cave-like morphology in the plasma membrane. Whereas caveolin is widely distributed, caveolae are found in only a few cell types and tissues (16).An increasing number of pathogens, including some bacteria, viruses, and even parasites, have been suggested to enter cells through lipid rafts (reviewed in reference 8). These conclusions are based on pharmacologic, biochemical, and cell biological assays. Inhibition of pathogen entry by drugs that are known to extract or bind to membrane cholesterol, such as methyl-␤-cyclodextrin (M␤CD), filipin, and nystatin, has been used as evidence for lipid raft involvement (35). However, M␤CD has pleiotropic effects, including disruption of clathrinmediated endocytosis, and should not be used as the sole criterion for defining lipid raft-dependent processes. Lipid rafts have also been defined by their resistance to extraction with nonionic detergents at 4°C (hence, they are often referred to as detergent-resistant membranes [DRMs]) and their sedimentation in low-density membrane fractions upon sucrose gradient centrifugation. The colocalization of caveolin or GM1 with pathogens is additional evidence that raft-mediated entry may be involved (7). However, the criterion used to define lipid rafts is at best imprecise and still evolving.Chlamydia spp. are obligate intracellular parasites that are associated with many important human diseases and undergo a dimorphic developmental cycle (13). They alternate between an extracellular, spore-like form, the elementary body (EB), and an intracellular form, the metabolically active but noninfectious reticulate body. The specific bacterial ligand and host receptor(s) that mediate entry are still unclear. Heparan sulfate acts as a bridging molecule for a relatively weak and reversible interaction (12,38,41,42) that is followed by a stronger, more specific binding to an unidentified secondary receptor (5, 11). Internalization is accompanied by induction of a...

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“…Recent efforts to understand the chlamydial entry process have employed chemically mutagenized CHO cells to distinguish two distinct stages in the chlamydial entry process (9,17). The identity of the host gene mutated to block this secondary irreversible step was not determined in either study.…”

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confidence: 99%

Tyrosine Phosphorylation of the Chlamydial Effector Protein Tarp Is Species Specific and Not Required for Recruitment of Actin

Clifton¹,

Dooley²,

Grieshaber³

et al. 2005

Infect Immun

105

152

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Selection of Mutant Cell Lines Resistant to Infection byChlamydia trachomatisandChlamydia pneumoniae

Cited by 31 publications

References 24 publications

Chlamydia trachomatis Species-Specific Induction of Ezrin Tyrosine Phosphorylation Functions in Pathogen Entry

Chlamydia trachomatis Species-Specific Induction of Ezrin Tyrosine Phosphorylation Functions in Pathogen Entry

Lipid Raft-Mediated Entry Is Not Required for Chlamydia trachomatis Infection of Cultured Epithelial Cells

Tyrosine Phosphorylation of the Chlamydial Effector Protein Tarp Is Species Specific and Not Required for Recruitment of Actin

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