Regulation of Type IV Secretion Apparatus Genes during
            <i>Ehrlichia chaffeensis</i>
            Intracellular Development by a Previously Unidentified Protein

Cheng, Zhihui; Wang, Xueqi; Rikihisa, Yasuko

doi:10.1128/jb.01813-07

Cited by 51 publications

(94 citation statements)

References 38 publications

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“…Similar to the findings of our previous study (4), when E. chaffeensis was synchronously cultured, bacteria became visually detectable after a long lag phase (ϳ24 to 36 h postinfection [p.i.]). Small (Ͻ1-m) dense morulae were detected in Ͼ80% of host cells at 57 h p.i.…”

Section: Resultssupporting

confidence: 79%

“…We previously reported that an E. chaffeensis transcription factor, EcxR, regulates the expression of genes encoding type IV secretion machinery during the exponential growth stage of E. chaffeensis (4). To examine whether pleC and pleD are coregulated by EcxR, EMSA was performed using rEcxR.…”

Section: Resultsmentioning

confidence: 99%

“…DNA fragments of 453 and 449 bp corresponding to the sequences upstream of the pleC and pleD start codons, respectively, were amplified by PCR. PCR products were biotinylated, and an electrophoretic mobility shift assay (EMSA) using recombinant EcxR (E. chaffeensis expression regulator) (rEcxR) was carried out as previously described (4). Table S1 in the supplemental material for a list of the primers) determined by real-time PCR.…”

Section: Methodsmentioning

confidence: 99%

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Cyclic Dimeric GMP Signaling Regulates Intracellular Aggregation, Sessility, and Growth of Ehrlichia chaffeensis

et al. 2011

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Cyclic dimeric GMP (c-di-GMP), a bacterial second messenger, is known to regulate bacterial biofilm and sessility. Replication of an obligatory intracellular pathogen, Ehrlichia chaffeensis, is characterized by formation of bacterial aggregates called morulae inside membrane-bound inclusions. When E. chaffeensis matures into an infectious form, morulae become loose to allow bacteria to exit from host cells to infect adjacent cells. E. chaffeensis expresses a sensor kinase, PleC, and a cognate response regulator, PleD, which can produce c-di-GMP. A hydrophobic c-di-GMP antagonist, 2-O-di(tert-butyldimethysilyl)-c-di-GMP (CDGA) inhibits E. chaffeensis internalization into host cells by facilitating degradation of some bacterial surface proteins via endogenous serine proteases. In the present study, we found that PleC and PleD were upregulated synchronously during exponential growth of bacteria, concomitant with increased morula size. While CDGA did not affect host cells, when infected cells were treated with CDGA, bacterial proliferation was inhibited, morulae became less compact, and the intracellular movement of bacteria was enhanced. Concurrently, CDGA treatment facilitated the extracellular release of bacteria with lower infectivity than those spontaneously released from sham-treated cells. Addition of CDGA to isolated inclusions induced dispersion of the morulae, degradation of an inclusion matrix protein TRP120, and bacterial intrainclusion movement, all of which were blocked by a serine protease inhibitor. These results suggest that c-di-GMP signaling regulates aggregation and sessility of E. chaffeensis within the inclusion through stabilization of matrix proteins by preventing the serine protease activity, which is associated with bacterial intracellular proliferation and maturation.

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Section: Resultssupporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Cyclic Dimeric GMP Signaling Regulates Intracellular Aggregation, Sessility, and Growth of Ehrlichia chaffeensis

et al. 2011

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“…For example, in A. phagocytophilum and E. chaffeensis (but not Rickettsia spp. ), sodB, encoding an iron superoxide dismutase, is cotranscribed with the virB3-virB6 genes (60,207). A protective oxidative stress response might thus be coupled with T4SS machine assembly in environments, e.g., the eukaryotic cytoplasm or blood-feeding ticks, where both activities are needed for cell survival or proliferation.…”

Section: More Gram-negative Systemsmentioning

confidence: 99%

Biological Diversity of Prokaryotic Type IV Secretion Systems

Martı́nez

Christie

2009

Microbiol Mol Biol Rev

621

780

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SUMMARY Type IV secretion systems (T4SS) translocate DNA and protein substrates across prokaryotic cell envelopes generally by a mechanism requiring direct contact with a target cell. Three types of T4SS have been described: (i) conjugation systems, operationally defined as machines that translocate DNA substrates intercellularly by a contact-dependent process; (ii) effector translocator systems, functioning to deliver proteins or other macromolecules to eukaryotic target cells; and (iii) DNA release/uptake systems, which translocate DNA to or from the extracellular milieu. Studies of a few paradigmatic systems, notably the conjugation systems of plasmids F, R388, RP4, and pKM101 and the Agrobacterium tumefaciens VirB/VirD4 system, have supplied important insights into the structure, function, and mechanism of action of type IV secretion machines. Information on these systems is updated, with emphasis on recent exciting structural advances. An underappreciated feature of T4SS, most notably of the conjugation subfamily, is that they are widely distributed among many species of gram-negative and -positive bacteria, wall-less bacteria, and the Archaea. Conjugation-mediated lateral gene transfer has shaped the genomes of most if not all prokaryotes over evolutionary time and also contributed in the short term to the dissemination of antibiotic resistance and other virulence traits among medically important pathogens. How have these machines adapted to function across envelopes of distantly related microorganisms? A survey of T4SS functioning in phylogenetically diverse species highlights the biological complexity of these translocation systems and identifies common mechanistic themes as well as novel adaptations for specialized purposes relating to the modulation of the donor-target cell interaction.

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“…T4SSs are encoded by a single polycistronic transfer region in most bacteria, while in others they are encoded as split loci (6). The genes in the transfer region usually have overlapping stop-and-start codons, which allows the expression of a large set of genes from a few promoters and regulation of both transcription and translation.…”

Section: Vol 192 2010 Expression Of Gonococcal T4ss Genes 1917mentioning

confidence: 99%

Increased Expression of the Type IV Secretion System in Piliated Neisseria gonorrhoeae Variants

Salgado-Pabón

Hackett

et al. 2010

J Bacteriol

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Neisseria gonorrhoeae produces a type IV secretion system that secretes chromosomal DNA. The secreted DNA is active in the transformation of other gonococci in the population and may act to transfer antibiotic resistance genes and variant alleles for surface antigens, as well as other genes. We observed that gonococcal variants that produced type IV pili secreted more DNA than variants that were nonpiliated, suggesting that the process may be regulated. Using microarray analysis, we found that a piliated strain showed increased expression of the gene for the putative type IV secretion coupling protein TraD, whereas a nonpiliated variant showed increased expression of genes for transcriptional and translational machinery, consistent with its higher growth rate compared to that of the piliated strain. These results suggested that type IV secretion might be controlled by either traD expression or growth rate. A mutant with a deletion in traD was found to be deficient in DNA secretion. Further mutation and complementation analysis indicated that traD is transcriptionally and translationally coupled to traI, which encodes the type IV secretion relaxase. We were able to increase DNA secretion in a nonpiliated strain by inserting a gene cassette with a strong promoter to drive the expression of the putative operon containing traI and traD. Together, these data suggest a model in which the type IV secretion system apparatus is made constitutively, while its activity is controlled through regulation of traD and traI.

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Regulation of Type IV Secretion Apparatus Genes during Ehrlichia chaffeensis Intracellular Development by a Previously Unidentified Protein

Cited by 51 publications

References 38 publications

Cyclic Dimeric GMP Signaling Regulates Intracellular Aggregation, Sessility, and Growth of Ehrlichia chaffeensis

Cyclic Dimeric GMP Signaling Regulates Intracellular Aggregation, Sessility, and Growth of Ehrlichia chaffeensis

Biological Diversity of Prokaryotic Type IV Secretion Systems

Increased Expression of the Type IV Secretion System in Piliated Neisseria gonorrhoeae Variants

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