Localization of the Hypothetical Protein Cpn0797 in the Cytoplasm of
            <i>Chlamydia pneumoniae</i>
            -Infected Host Cells

Dong, Feng; Flores, Rhonda; Chen, Ding; Luo, Jianhua; Zhong, Youmin; Wu, Zhongming; Zhong, Guangming

doi:10.1128/iai.00855-06

Cited by 16 publications

(17 citation statements)

References 26 publications

(29 reference statements)

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“…As a result, Pls1 and Pls2 secretion would be analogous to that observed in two-partner secretion systems (27). A similar transport pathway may be used by the C. pneumoniae protein Cpn0797, which also shares homology to autotransporters but which is considerably shorter than typical autotransporters (11). Whether the cognate outer membrane translocator is provided by recycling a cleaved Pmp transporter or by a gene product encoded elsewhere in the chromosome remains to be determined.…”

Section: Discussionmentioning

confidence: 95%

Pmp-Like Proteins Pls1 and Pls2 Are Secreted into the Lumen of the Chlamydia trachomatis Inclusion

Jørgensen

Valdivia

2008

Infect Immun

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The obligate intracellular pathogen Chlamydia trachomatis secretes effector proteins across the membrane of the pathogen-containing vacuole (inclusion) to modulate host cellular functions. In an immunological screen for secreted chlamydial proteins, we identified CT049 and CT050 as potential inclusion membrane-associated proteins. These acidic, nonglobular proteins are paralogously related to the passenger domain of the polymorphic membrane protein PmpC and, like other Pmp proteins, are highly polymorphic among C. trachomatis ocular and urogenital strains. We generated antibodies to these Pmp-like secreted (Pls) proteins and determined by immunofluorescence microscopy that Pls1 (CT049) and Pls2 (CT050) localized to globular structures within the inclusion lumen and at the inclusion membrane. Fractionation of membranes and cytoplasmic components from infected cells by differential and density gradient centrifugation further indicated that Pls1 and Pls2 associated with membranes distinct from the bulk of bacterial and inclusion membranes. The accumulation of Pls1 and, to a lesser extent, Pls2 in the inclusion lumen was insensitive to the type III secretion inhibitor C1, suggesting that this translocation system is not essential for Pls protein secretion. In contrast, Pls secretion and stability were sensitive to low levels of ␤-lactam antibiotics, suggesting that a functional cell wall is required for Pls secretion from the bacterial cell. Finally, we tested the requirement for these proteins in Chlamydia infection by microinjecting anti-Pls1 and anti-Pls2 antibodies into infected cells. Coinjection of anti-Pls1 and -Pls2 antibodies partially inhibited expansion of the inclusion. Because Pls proteins lack classical sec-dependent secretion signals, we propose that Pls proteins are secreted into the inclusion lumen by a novel mechanism to regulate events important for chlamydial replication and inclusion expansion.

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Section: Discussionmentioning

confidence: 95%

Pmp-Like Proteins Pls1 and Pls2 Are Secreted into the Lumen of the Chlamydia trachomatis Inclusion

Jørgensen

Valdivia

2008

Infect Immun

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“…p111 and p30 were not detected in immunoaffinity-purified oligomers but were observed in the inclusion lumen by confocal microscopy. However, we cannot exclude the possibility that they are secreted into the host cytosol, as shown for other chlamydial proteins (12,26,28,57). Bacterial effectors secreted into host cells at low levels are undetectable by immunofluorescence (27), suggesting that limited quantities of PmpD may exist in the host cytosol.…”

Section: Vol 77 2009mentioning

confidence: 99%

Chlamydia trachomatisPolymorphic Membrane Protein D Is an Oligomeric Autotransporter with a Higher-Order Structure

et al. 2009

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Chlamydia trachomatis is a globally important obligate intracellular bacterial pathogen that is a leading cause of sexually transmitted disease and blinding trachoma. Effective control of these diseases will likely require a preventative vaccine. C. trachomatis polymorphic membrane protein D (PmpD) is an attractive vaccine candidate as it is conserved among C. trachomatis strains and is a target of broadly cross-reactive neutralizing antibodies. We show here that immunoaffinity-purified native PmpD exists as an oligomer with a distinct 23-nm flower-like structure. Two-dimensional blue native-sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses showed that the oligomers were composed of full-length PmpD (p155) and two proteolytically processed fragments, the p73 passenger domain (PD) and the p82 translocator domain. We also show that PmpD undergoes an infection-dependent proteolytic processing step late in the growth cycle that yields a soluble extended PD (p111) that was processed into a p73 PD and a novel p30 fragment. Interestingly, soluble PmpD peptides possess putative eukaryote-interacting functional motifs, implying potential secondary functions within or distal to infected cells. Collectively, our findings show that PmpD exists as two distinct forms, a surface-associated oligomer exhibiting a higher-order flower-like structure and a soluble form restricted to infected cells. We hypothesize that PmpD is a multifunctional virulence factor important in chlamydial pathogenesis and could represent novel vaccine or drug targets for the control of human chlamydial infections.Chlamydia trachomatis is a mucosotropic obligate intracellular gram-negative pathogen that is a leading cause of sexually transmitted and ocular infections. Infection can result in serious sequelae such as infertility and blindness (54, 56) and an increased risk of human immunodeficiency virus infection and transmission (38). The pathophysiology of chlamydial infection is associated with the pathogen's propensities to cause persistent infection and to suppress host immunity (3). A vaccine is needed to control chlamydial diseases; however, progress toward this goal will not be forthcoming until more is known about the virulence factors that mediate persistence and immune evasion.Chlamydiae are characterized by a unique biphasic developmental cycle that modulates between an extracellular, metabolically inactive, infectious elementary body (EB) and an intracellular, metabolically active, noninfectious reticulate body (RB) (34). Their obligate intracellular niche and the lack of a tractable genetic system present unique challenges in the study of chlamydial biology and pathogenesis. To overcome these hurdles, chlamydial genomes from a diverse spectrum of hostspecific strains have been sequenced. Comparative genomics have shown considerable homology among various chlamydial species and have provided important insights into shared and species-specific virulence factors (7,24,41,42,46,49).The type V or autotransporter (AT) secretion p...

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“…At the same time, Chlamydia must communicate with the host cells crossing the inclusion membrane barriers (53,62). It is known that Chlamydia both imports nutrients and metabolic intermediates from host cells into the inclusions (25,62) for maintaining intravacuolar growth and secretes chlamydial genome-encoded factors into either the inclusion membrane (22,26,35,52,54) or the host cell cytosol (14,67,72) for potentially interacting with and/or manipulating host cell signaling pathways. The chlamydial ability to manipulate host cells for promoting chlamydial intracellular survival and intercellular transmission plays a significant role in chlamydial pathogenesis.…”

mentioning

confidence: 99%

The Chlamydial Plasmid-Encoded Protein pgp3 Is Secreted into the Cytosol ofChlamydia-Infected Cells

et al. 2008

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The chlamydial cryptic plasmid encodes eight putative open reading frames (ORFs), designated pORF1 to -8. Antibodies raised against these ORF proteins were used to localize the endogenous proteins during chlamydial infection. We found that the pORF5 protein (also known as pgp3) was detected mainly in the cytosol of Chlamydiainfected cells, while the remaining seven proteins were found inside the chlamydial inclusions only. The pgp3 distribution pattern in the host cell cytosol is similar to but not overlapping with that of chlamydial protease/ proteasome-like activity factor (CPAF), a chlamydial genome-encoded protein known to be secreted from chlamydial inclusions into the host cell cytosol. The anti-pgp3 labeling was removed by preabsorption with pgp3 but not CPAF fusion proteins and vice versa, demonstrating that pgp3 is a unique secretion protein. This conclusion is further supported by the observation that pgp3 was highly enriched in cytosolic fractions and had a minimal presence in the inclusion-containing nuclear fractions prepared from Chlamydia-infected cells. The pgp3 protein was detected as early as 12 h after infection and was secreted by all chlamydial species that carry the cryptic plasmid, suggesting that there is a selection pressure for maintaining pgp3 secretion during chlamydial infection. Although expression of pgp3 in the host cell cytosol via a transgene did not alter the susceptibility of the transfected cells to the subsequent chlamydial infection, purified pgp3 protein stimulated macrophages to release inflammatory cytokines, suggesting that pgp3 may contribute to chlamydial pathogenesis.Chlamydia represents a group of obligate intracellular bacterial pathogens consisting of many different species and causing various health problems in both humans and animals. The species C. trachomatis is composed of more than 15 different serovars (including A to L serovars); some infect the human ocular epithelium, potentially leading to preventable blindness (64), while others infect human urogenital tract tissue, which can potentially cause severe complications such as ectopic pregnancy and infertility (56). C. muridarum, formerly known as the murine biovar of C. trachomatis (designated MoPn, with the single strain Nigg), has been extensively used to study C. trachomatis pathogenesis and immunology in mouse models (32,37,38,42,43). Although most isolates of C. pneumoniae organisms often infect the human respiratory system, causing respiratory pathologies and exacerbating lesions in the vascular wall (3, 28), the C. pneumoniae N16 strain has been isolated from equines (60). Other chlamydial species that mainly infect animals include C. caviae (50), C. psittaci (47), C. abortus (66), and C. felis (1). Despite the apparent differences in tissue tropism, all chlamydial species share similar genome sequences (1,29,49,50,66) and possess a common intracellular growth cycle with distinct biphasic stages (24). The chlamydial intracellular infection-induced inflammation is considered a major cause of Chlamydi...

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Localization of the Hypothetical Protein Cpn0797 in the Cytoplasm of Chlamydia pneumoniae -Infected Host Cells

Cited by 16 publications

References 26 publications

Pmp-Like Proteins Pls1 and Pls2 Are Secreted into the Lumen of the Chlamydia trachomatis Inclusion

Pmp-Like Proteins Pls1 and Pls2 Are Secreted into the Lumen of the Chlamydia trachomatis Inclusion

Chlamydia trachomatisPolymorphic Membrane Protein D Is an Oligomeric Autotransporter with a Higher-Order Structure

The Chlamydial Plasmid-Encoded Protein pgp3 Is Secreted into the Cytosol ofChlamydia-Infected Cells

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