New Frontiers in Type III Secretion Biology: the Chlamydia Perspective

Mueller, Konrad; Plano, Gregory V.; Fields, Kenneth A.

doi:10.1128/iai.00917-13

Cited by 83 publications

(66 citation statements)

References 101 publications

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“…Numerous Gram-negative bacteria in the genera of Yersinia, Salmonella, Escherichia coli, Salmonella, Shigella, Vibrio, Pseudomonas, and Chlamydia employ a T3S system to inject effectors across host membrane barriers (7)(8)(9)(10)(11). Expression of the T3S system, its assembly into a highly ordered structural apparatus, and its activation are spatiotemporally regulated (12)(13)(14)(15).…”

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confidence: 99%

“…The T3S system is a key pathogenic attribute of Chlamydia spp., in which ϳ80 different T3S effectors are predicted to be secreted into the host cytosol to modulate host function for survival and development (8,20,21). There are three classes of T3S chaperones in Chlamydia spp.…”

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confidence: 99%

“…There are three classes of T3S chaperones in Chlamydia spp. (8,(22)(23)(24)(25)(26)(27). The class I chaperones include class Ia chaperones (Scc1 and Scc4 or CT663), which bind to just one effector, and class Ib chaperones (Slc1, Mcsc, and CT584), which bind to multiple effectors.…”

mentioning

confidence: 99%

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Multipart Chaperone-Effector Recognition in the Type III Secretion System of Chlamydia trachomatis

Shen¹,

Macnaughtan

Frohlich³

et al. 2015

Journal of Biological Chemistry

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Background:The type III secretion (T3S) chaperone Scc4 modulates Chlamydia RNA polymerase holoenzyme activity and is also required for secretion of the gatekeeper CopN. Results: Interactions between the Scc4 and Scc1 chaperones and CopN are characterized. Conclusion: Scc4 forms a ternary complex with Scc1 and CopN to promote CopN secretion during infection. Significance: Scc4 is an important link between the T3S system and transcription.

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Multipart Chaperone-Effector Recognition in the Type III Secretion System of Chlamydia trachomatis

Shen¹,

Macnaughtan

Frohlich³

et al. 2015

Journal of Biological Chemistry

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“…differ in host range and virulence, all species undergo a similar biphasic developmental cycle that involves two morphologically distinct forms, the elementary body (EB) and the reticulate body (RB) (5,6). The environmentally stable and infectious EB attaches to the surface of a mucosal epithelial cell and triggers endocytosis, possibly facilitated by the chlamydial type III secretion system (7). Following internalization, the EB differentiates into the larger metabolically active and replicative RB form within a host-derived membrane vacuole termed the inclusion.…”

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confidence: 99%

CTL0511 from Chlamydia trachomatis Is a Type 2C Protein Phosphatase with Broad Substrate Specificity

Claywell

Fisher

2016

J Bacteriol

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Protein phosphorylation has become increasingly recognized for its role in regulating bacterial physiology and virulence. Chlamydia spp. encode two validated Hanks'-type Ser/Thr protein kinases, which typically function with cognate protein phosphatases and appear capable of global protein phosphorylation. Consequently, we sought to identify a Ser/Thr protein phosphatase partner for the chlamydial kinases. CTL0511 from Chlamydia trachomatis L2 434/Bu, which has homologs in all sequenced Chlamydia spp., is a predicted type 2C Ser/Thr protein phosphatase (PP2C). Recombinant maltose-binding protein (MBP)-tagged CTL0511 (rCTL0511) hydrolyzed p-nitrophenyl phosphate (pNPP), a generic phosphatase substrate, in a MnCl 2 -dependent manner at physiological pH. Assays using phosphopeptide substrates revealed that rCTL0511 can dephosphorylate phosphorylated serine (P-Ser), P-Thr, and P-Tyr residues using either MnCl 2 or MgCl 2 , indicating that metal usage can alter substrate preference. Phosphatase activity was unaffected by PP1, PP2A, and PP3 phosphatase inhibitors, while mutation of conserved PP2C residues significantly inhibited activity. Finally, phosphatase activity was detected in elementary body (EB) and reticulate body (RB) lysates, supporting a role for protein dephosphorylation in chlamydial development. These findings support that CTL0511 is a metal-dependent protein phosphatase with broad substrate specificity, substantiating a reversible phosphorylation network in C. trachomatis. IMPORTANCEChlamydia spp. are obligate intracellular bacterial pathogens responsible for a variety of diseases in humans and economically important animal species. Our work demonstrates that Chlamydia spp. produce a PP2C capable of dephosphorylating P-Thr, P-Ser, and P-Tyr and that Chlamydia trachomatis EBs and RBs possess phosphatase activity. In conjunction with the chlamydial Hanks'-type kinases Pkn1 and PknD, validation of CTL0511 fulfills the enzymatic requirements for a reversible phosphoprotein network. As protein phosphorylation regulates important cellular processes, including metabolism, differentiation, and virulence, in other bacterial pathogens, these results set the stage for elucidating the role of global protein phosphorylation in chlamydial physiology and virulence. C hlamydia spp. are obligate intracellular bacterial pathogens that are widely distributed in nature and are responsible for significant diseases in humans and a variety of animals (1, 2). The human-specific pathogen Chlamydia trachomatis is the leading cause of preventable blindness and the most common reportable bacterial sexually transmitted infection both in the United States and worldwide (3, 4). C. trachomatis infections of the conjunctiva and the urogenital tract may lead to chronic diseases, including trachoma, pelvic inflammatory disease, and infertility (1). Further understanding of the physiology of these highly significant pathogens is critical for developing therapeutics and vaccines.While Chlamydia spp. differ in host range and virul...

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“…In Chlamydia, T3S is important for a number of steps in the intracellular infection (6). EB entry into the host cell is mediated in part by translocation of the T3S effector protein Tarp, which recruits actin at the site of EB attachment and likely aids in internalization (7).…”

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Chlamydia trachomatis Type III Secretion Proteins Regulate Transcription

et al. 2015

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The Scc4 protein (CT663) of the pathogenic bacterium Chlamydia has been described as a type III secretion (T3S) chaperone as well as an inhibitor of RNA polymerase. To examine if these roles are connected, we first investigated physical interactions between Chlamydia trachomatis Scc4 and the T3S chaperone Scc1 and a T3S substrate, CopN. In a yeast 3-hybrid assay, Scc4, Scc1, and CopN were all required to detect an interaction, which suggests that these proteins form a trimolecular complex. We also detected interactions between any two of these three T3S proteins in a pulldown assay using only recombinant proteins. We next determined whether these interactions affected the function of Scc4 as an inhibitor of RNA transcription. Using Escherichia coli as a heterologous in vivo system, we demonstrated that expression of C. trachomatis Scc4 led to a drastic decrease in transcript levels for multiple genes. However, coexpression of Scc4 with Scc1, CopN, or both alleviated Scc4-mediated inhibition of transcription. Scc4 expression also severely impaired E. coli growth, but this growth defect was reversed by coexpression of Scc4 with Scc1, CopN, or both, suggesting that the inhibitory effect of Scc4 on transcription and growth can be antagonized by interactions between Scc4, Scc1, and CopN. These findings suggest that the dual functions of Scc4 may serve as a bridge to link T3S and the regulation of gene expression in Chlamydia. IMPORTANCEThis study investigates a novel mechanism for regulating gene expression in the pathogenic bacterium Chlamydia. The Chlamydia type III secretion (T3S) chaperone Scc4 has been shown to inhibit transcription by RNA polymerase. This study describes physical interactions between Scc4 and the T3S proteins Scc1 and CopN. Furthermore, Chlamydia Scc1 and CopN antagonized the inhibitory effects of Scc4 on transcription and growth in a heterologous Escherichia coli system. These results provide evidence that transcription in Chlamydia can be regulated by the T3S system through interactions between T3S proteins. C hlamydia trachomatis is the most prevalent cause of bacterial sexually transmitted infections in the United States (1, 2). In addition, it is the most common cause of preventable blindness in the world (3). Chlamydia is an unusual obligate intracellular bacterium that has two distinct forms, the infectious elementary body (EB) and the noninfectious reticulate body (RB) (4). Once the EB attaches and enters a susceptible host cell, it converts into an RB that replicates by binary fission, generating hundreds of progeny within the membrane-bound chlamydial inclusion.Like other pathogenic Gram-negative bacteria, Chlamydia utilizes a type III secretion (T3S) system to deliver effector proteins into a eukaryotic cell (5). In Chlamydia, T3S is important for a number of steps in the intracellular infection (6). EB entry into the host cell is mediated in part by translocation of the T3S effector protein Tarp, which recruits actin at the site of EB attachment and likely aids in internaliz...

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New Frontiers in Type III Secretion Biology: the Chlamydia Perspective

Cited by 83 publications

References 101 publications

Multipart Chaperone-Effector Recognition in the Type III Secretion System of Chlamydia trachomatis

Multipart Chaperone-Effector Recognition in the Type III Secretion System of Chlamydia trachomatis

CTL0511 from Chlamydia trachomatis Is a Type 2C Protein Phosphatase with Broad Substrate Specificity

Chlamydia trachomatis Type III Secretion Proteins Regulate Transcription

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