1
|
Wickramasinghe HC, Lincoln JN, D'Armond AE, Noble SA, Shen L, Macnaughtan MA. Insights into the association of the Chlamydia trachomatis type III secretion chaperone complex, Scc4:Scc1, from sequential expression in Escherichia coli. Protein Expr Purif 2024; 222:106532. [PMID: 38857716 DOI: 10.1016/j.pep.2024.106532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2024] [Revised: 06/03/2024] [Accepted: 06/08/2024] [Indexed: 06/12/2024]
Abstract
Chlamydia trachomatis (CT) is the bacterial pathogen responsible for causing the most common sexually transmitted disease in the United States. This obligate, intracellular Gram-negative bacterium has a type III secretion system (T3SS) to invade host cells. CopN is an important effector, plug protein that mediates early interactions between the host and Chlamydia. CopN is chaperoned by a heterodimer, T3SS chaperone complex containing Scc4 and Scc1. Scc4 is a unique, bifunctional protein that, in addition to its T3SS chaperone activity, acts as an RNA polymerase (RNAP) binding protein. We hypothesized that the two functions occur at different points in CT's developmental cycle with Scc4 acting alone in the early-to-mid stages and the Scc4:Scc1 complex chaperoning CopN in the mid-to-late stages. To study the Scc4:Scc1 complex by NMR, we previously explored various methods of associating Scc4 and Scc1 in vitro to produce the complex with chain-selective isotopic labeling. Though co-expressed Scc4 and Scc1 form a stable complex, the in vitro association studies suggest that partial protein denaturation and/or components in E. coli lysate are necessary to form the stable complex. In this study Scc4 and Scc1 were sequentially expressed in E. coli under the control of different promoters, allowing separate isotopic labeling of each chain and complex formation in vivo. Sequential expression resulted in no or unstable complex formation depending on the culture medium used. These results, taken together with previous in vitro association studies, suggest that Scc4 and Scc1 assemble co-translationally to form the stable Scc4:Scc1 complex in E. coli.
Collapse
Affiliation(s)
| | - Juliette N Lincoln
- Department of Chemistry, Louisiana State University, Baton Rouge, LA, 70803, United States
| | - Anne E D'Armond
- Department of Chemistry, Louisiana State University, Baton Rouge, LA, 70803, United States
| | - Sadie A Noble
- Department of Chemistry, Louisiana State University, Baton Rouge, LA, 70803, United States
| | - Li Shen
- Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, LA, 70112, United States
| | - Megan A Macnaughtan
- Department of Chemistry, Louisiana State University, Baton Rouge, LA, 70803, United States; Department of Chemistry and Biochemistry, John Carroll University, University Heights, OH, 44118, United States.
| |
Collapse
|
2
|
Jury B, Fleming C, Huston WM, Luu LDW. Molecular pathogenesis of Chlamydia trachomatis. Front Cell Infect Microbiol 2023; 13:1281823. [PMID: 37920447 PMCID: PMC10619736 DOI: 10.3389/fcimb.2023.1281823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 10/03/2023] [Indexed: 11/04/2023] Open
Abstract
Chlamydia trachomatis is a strict intracellular human pathogen. It is the main bacterial cause of sexually transmitted infections and the etiologic agent of trachoma, which is the leading cause of preventable blindness. Despite over 100 years since C. trachomatis was first identified, there is still no vaccine. However in recent years, the advancement of genetic manipulation approaches for C. trachomatis has increased our understanding of the molecular pathogenesis of C. trachomatis and progress towards a vaccine. In this mini-review, we aimed to outline the factors related to the developmental cycle phase and specific pathogenesis activity of C. trachomatis in order to focus priorities for future genetic approaches. We highlight the factors known to be critical for developmental cycle stages, gene expression regulatory factors, type III secretion system and their effectors, and individual virulence factors with known impacts.
Collapse
Affiliation(s)
- Brittany Jury
- School of Life Sciences, Faculty of Science, University of Technology Sydney, Ultimo, NSW, Australia
| | - Charlotte Fleming
- School of Life Sciences, Faculty of Science, University of Technology Sydney, Ultimo, NSW, Australia
| | | | - Laurence Don Wai Luu
- School of Life Sciences, Faculty of Science, University of Technology Sydney, Ultimo, NSW, Australia
| |
Collapse
|
3
|
Navarrete KM, Bumba L, Prudnikova T, Malcova I, Allsop TR, Sebo P, Kamanova J. BopN is a Gatekeeper of the Bordetella Type III Secretion System. Microbiol Spectr 2023; 11:e0411222. [PMID: 37036369 PMCID: PMC10269732 DOI: 10.1128/spectrum.04112-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 03/17/2023] [Indexed: 04/11/2023] Open
Abstract
The classical Bordetella species infect the respiratory tract of mammals. While B. bronchiseptica causes rather chronic respiratory infections in a variety of mammals, the human-adapted species B. pertussis and B. parapertussisHU cause an acute respiratory disease known as whooping cough or pertussis. The virulence factors include a type III secretion system (T3SS) that translocates effectors BteA and BopN into host cells. However, the regulatory mechanisms underlying the secretion and translocation activity of T3SS in bordetellae are largely unknown. We have solved the crystal structure of BopN of B. pertussis and show that it is similar to the structures of gatekeepers that control access to the T3SS channel from the bacterial cytoplasm. We further found that BopN accumulates at the cell periphery at physiological concentrations of calcium ions (2 mM) that inhibit the secretion of BteA and BopN. Deletion of the bopN gene in B. bronchiseptica increased secretion of the BteA effector into calcium-rich medium but had no effect on secretion of the T3SS translocon components BopD and BopB. Moreover, the ΔbopN mutant secreted approximately 10-fold higher amounts of BteA into the medium of infected cells than the wild-type bacteria, but it translocated lower amounts of BteA into the host cell cytoplasm. These data demonstrate that BopN is a Bordetella T3SS gatekeeper required for regulated and targeted translocation of the BteA effector through the T3SS injectisome into host cells. IMPORTANCE The T3SS is utilized by many Gram-negative bacteria to deliver effector proteins from bacterial cytosol directly into infected host cell cytoplasm in a regulated and targeted manner. Pathogenic bordetellae use the T3SS to inject the BteA and BopN proteins into infected cells and upregulate the production of the anti-inflammatory cytokine interleukin-10 (IL-10) to evade host immunity. Previous studies proposed that BopN acted as an effector in host cells. In this study, we report that BopN is a T3SS gatekeeper that regulates the secretion and translocation activity of Bordetella T3SS.
Collapse
Affiliation(s)
- Kevin Munoz Navarrete
- Laboratory of Infection Biology, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Ladislav Bumba
- Laboratory of Molecular Biology of Bacterial Pathogens, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Tatyana Prudnikova
- Faculty of Science, University of South Bohemia in Ceske Budejovice, Ceske Budejovice, Czech Republic
| | - Ivana Malcova
- Laboratory of Infection Biology, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Tania Romero Allsop
- Laboratory of Infection Biology, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Peter Sebo
- Laboratory of Molecular Biology of Bacterial Pathogens, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Jana Kamanova
- Laboratory of Infection Biology, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| |
Collapse
|
4
|
Wevers C, Höhler M, Alcázar-Román AR, Hegemann JH, Fleig U. A Functional Yeast-Based Screen Identifies the Host Microtubule Cytoskeleton as a Target of Numerous Chlamydia pneumoniae Proteins. Int J Mol Sci 2023; 24:ijms24087618. [PMID: 37108781 PMCID: PMC10142024 DOI: 10.3390/ijms24087618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 04/13/2023] [Accepted: 04/14/2023] [Indexed: 04/29/2023] Open
Abstract
Bacterial pathogens have evolved intricate ways to manipulate the host to support infection. Here, we systematically assessed the importance of the microtubule cytoskeleton for infection by Chlamydiae, which are obligate intracellular bacteria that are of great importance for human health. The elimination of microtubules in human HEp-2 cells prior to C. pneumoniae infection profoundly attenuated the infection efficiency, demonstrating the need for microtubules for the early infection processes. To identify microtubule-modulating C. pneumoniae proteins, a screen in the model yeast Schizosaccharomyces pombe was performed. Unexpectedly, among 116 selected chlamydial proteins, more than 10%, namely, 13 proteins, massively altered the yeast interphase microtubule cytoskeleton. With two exceptions, these proteins were predicted to be inclusion membrane proteins. As proof of principle, we selected the conserved CPn0443 protein, which caused massive microtubule instability in yeast, for further analysis. CPn0443 bound and bundled microtubules in vitro and co-localized partially with microtubules in vivo in yeast and human cells. Furthermore, CPn0443-transfected U2OS cells had a significantly reduced infection rate by C. pneumoniae EBs. Thus, our yeast screen identified numerous proteins encoded using the highly reduced C. pneumoniae genome that modulated microtubule dynamics. Hijacking of the host microtubule cytoskeleton must be a vital part of chlamydial infection.
Collapse
Affiliation(s)
- Carolin Wevers
- Eukaryotic Microbiology, Institute of Functional Microbial Genomics, Heinrich-Heine-University, 40225 Düsseldorf, Germany
| | - Mona Höhler
- Eukaryotic Microbiology, Institute of Functional Microbial Genomics, Heinrich-Heine-University, 40225 Düsseldorf, Germany
| | - Abel R Alcázar-Román
- Eukaryotic Microbiology, Institute of Functional Microbial Genomics, Heinrich-Heine-University, 40225 Düsseldorf, Germany
| | - Johannes H Hegemann
- Institute of Functional Microbial Genomics, Heinrich-Heine-University, 40225 Düsseldorf, Germany
| | - Ursula Fleig
- Eukaryotic Microbiology, Institute of Functional Microbial Genomics, Heinrich-Heine-University, 40225 Düsseldorf, Germany
| |
Collapse
|
5
|
Halter T, Köstlbacher S, Collingro A, Sixt BS, Tönshoff ER, Hendrickx F, Kostanjšek R, Horn M. Ecology and evolution of chlamydial symbionts of arthropods. ISME COMMUNICATIONS 2022; 2:45. [PMID: 37938728 PMCID: PMC9723776 DOI: 10.1038/s43705-022-00124-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 03/31/2022] [Accepted: 04/08/2022] [Indexed: 05/08/2023]
Abstract
The phylum Chlamydiae consists of obligate intracellular bacteria including major human pathogens and diverse environmental representatives. Here we investigated the Rhabdochlamydiaceae, which is predicted to be the largest and most diverse chlamydial family, with the few described members known to infect arthropod hosts. Using published 16 S rRNA gene sequence data we identified at least 388 genus-level lineages containing about 14 051 putative species within this family. We show that rhabdochlamydiae are mainly found in freshwater and soil environments, suggesting the existence of diverse, yet unknown hosts. Next, we used a comprehensive genome dataset including metagenome assembled genomes classified as members of the family Rhabdochlamydiaceae, and we added novel complete genome sequences of Rhabdochlamydia porcellionis infecting the woodlouse Porcellio scaber, and of 'Candidatus R. oedothoracis' associated with the linyphiid dwarf spider Oedothorax gibbosus. Comparative analysis of basic genome features and gene content with reference genomes of well-studied chlamydial families with known host ranges, namely Parachlamydiaceae (protist hosts) and Chlamydiaceae (human and other vertebrate hosts) suggested distinct niches for members of the Rhabdochlamydiaceae. We propose that members of the family represent intermediate stages of adaptation of chlamydiae from protists to vertebrate hosts. Within the genus Rhabdochlamydia, pronounced genome size reduction could be observed (1.49-1.93 Mb). The abundance and genomic distribution of transposases suggests transposable element expansion and subsequent gene inactivation as a mechanism of genome streamlining during adaptation to new hosts. This type of genome reduction has never been described before for any member of the phylum Chlamydiae. This study provides new insights into the molecular ecology, genomic diversity, and evolution of representatives of one of the most divergent chlamydial families.
Collapse
Affiliation(s)
- Tamara Halter
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
- Doctoral School in Microbiology and Environmental Science, University of Vienna, Vienna, Austria
| | - Stephan Köstlbacher
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
- Doctoral School in Microbiology and Environmental Science, University of Vienna, Vienna, Austria
| | - Astrid Collingro
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Barbara S Sixt
- The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Elena R Tönshoff
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule Zürich (ETH), Zurich, Switzerland
| | | | - Rok Kostanjšek
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Matthias Horn
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria.
| |
Collapse
|
6
|
Huang Y, Wurihan W, Lu B, Zou Y, Wang Y, Weldon K, Fondell JD, Lai Z, Wu X, Fan H. Robust Heat Shock Response in Chlamydia Lacking a Typical Heat Shock Sigma Factor. Front Microbiol 2022; 12:812448. [PMID: 35046926 PMCID: PMC8762339 DOI: 10.3389/fmicb.2021.812448] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 12/02/2021] [Indexed: 11/13/2022] Open
Abstract
Cells reprogram their transcriptome in response to stress, such as heat shock. In free-living bacteria, the transcriptomic reprogramming is mediated by increased DNA-binding activity of heat shock sigma factors and activation of genes normally repressed by heat-induced transcription factors. In this study, we performed transcriptomic analyses to investigate heat shock response in the obligate intracellular bacterium Chlamydia trachomatis, whose genome encodes only three sigma factors and a single heat-induced transcription factor. Nearly one-third of C. trachomatis genes showed statistically significant (≥1.5-fold) expression changes 30 min after shifting from 37 to 45°C. Notably, chromosomal genes encoding chaperones, energy metabolism enzymes, type III secretion proteins, as well as most plasmid-encoded genes, were differentially upregulated. In contrast, genes with functions in protein synthesis were disproportionately downregulated. These findings suggest that facilitating protein folding, increasing energy production, manipulating host activities, upregulating plasmid-encoded gene expression, and decreasing general protein synthesis helps facilitate C. trachomatis survival under stress. In addition to relieving negative regulation by the heat-inducible transcriptional repressor HrcA, heat shock upregulated the chlamydial primary sigma factor σ66 and an alternative sigma factor σ28. Interestingly, we show for the first time that heat shock downregulates the other alternative sigma factor σ54 in a bacterium. Downregulation of σ54 was accompanied by increased expression of the σ54 RNA polymerase activator AtoC, thus suggesting a unique regulatory mechanism for reestablishing normal expression of select σ54 target genes. Taken together, our findings reveal that C. trachomatis utilizes multiple novel survival strategies to cope with environmental stress and even to replicate. Future strategies that can specifically target and disrupt Chlamydia’s heat shock response will likely be of therapeutic value.
Collapse
Affiliation(s)
- Yehong Huang
- Department of Parasitology, Xiangya School of Basic Medicine, Central South University, Changsha, China.,Department of Pharmacology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, United States
| | - Wurihan Wurihan
- Department of Pharmacology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, United States
| | - Bin Lu
- Department of Parasitology, Xiangya School of Basic Medicine, Central South University, Changsha, China.,Department of Pharmacology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, United States
| | - Yi Zou
- Greehey Children's Cancer Research Institute, University of Texas Health San Antonio, San Antonio, TX, United States
| | - Yuxuan Wang
- Department of Pharmacology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, United States
| | - Korri Weldon
- Greehey Children's Cancer Research Institute, University of Texas Health San Antonio, San Antonio, TX, United States
| | - Joseph D Fondell
- Department of Pharmacology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, United States
| | - Zhao Lai
- Greehey Children's Cancer Research Institute, University of Texas Health San Antonio, San Antonio, TX, United States.,Department of Molecular Medicine, University of Texas Health San Antonio, San Antonio, TX, United States
| | - Xiang Wu
- Department of Parasitology, Xiangya School of Basic Medicine, Central South University, Changsha, China
| | - Huizhou Fan
- Department of Pharmacology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, United States
| |
Collapse
|
7
|
Köstlbacher S, Collingro A, Halter T, Schulz F, Jungbluth SP, Horn M. Pangenomics reveals alternative environmental lifestyles among chlamydiae. Nat Commun 2021; 12:4021. [PMID: 34188040 PMCID: PMC8242063 DOI: 10.1038/s41467-021-24294-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 06/10/2021] [Indexed: 02/07/2023] Open
Abstract
Chlamydiae are highly successful strictly intracellular bacteria associated with diverse eukaryotic hosts. Here we analyzed metagenome-assembled genomes of the "Genomes from Earth's Microbiomes" initiative from diverse environmental samples, which almost double the known phylogenetic diversity of the phylum and facilitate a highly resolved view at the chlamydial pangenome. Chlamydiae are defined by a relatively large core genome indicative of an intracellular lifestyle, and a highly dynamic accessory genome of environmental lineages. We observe chlamydial lineages that encode enzymes of the reductive tricarboxylic acid cycle and for light-driven ATP synthesis. We show a widespread potential for anaerobic energy generation through pyruvate fermentation or the arginine deiminase pathway, and we add lineages capable of molecular hydrogen production. Genome-informed analysis of environmental distribution revealed lineage-specific niches and a high abundance of chlamydiae in some habitats. Together, our data provide an extended perspective of the variability of chlamydial biology and the ecology of this phylum of intracellular microbes.
Collapse
Affiliation(s)
- Stephan Köstlbacher
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
- Laboratory of Microbiology, Wageningen University and Research, Wageningen, The Netherlands
| | - Astrid Collingro
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Tamara Halter
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | | | | | - Matthias Horn
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria.
| |
Collapse
|
8
|
Ukwaththage TO, Keane SM, Shen L, Macnaughtan MA. Chain-Selective Isotopic Labeling of the Heterodimeric Type III Secretion Chaperone, Scc4:Scc1, Reveals the Total Structural Rearrangement of the Chlamydia trachomatis Bi-Functional Protein, Scc4. Biomolecules 2020; 10:biom10111480. [PMID: 33114427 PMCID: PMC7692554 DOI: 10.3390/biom10111480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 10/09/2020] [Accepted: 10/22/2020] [Indexed: 11/22/2022] Open
Abstract
Scc4 is an unusual bi-functional protein from Chlamydia trachomatis (CT) that functions as a type III secretion system (T3SS) chaperone and an RNA polymerase (RNAP)-binding protein. Both functions require interactions with protein partners during specific stages of the CT developmental cycle. As a T3SS chaperone, Scc4 binds Scc1 during the late stage of development to form a heterodimer complex, which chaperones the essential virulence effector, CopN. During the early-middle stage of development, Scc4 regulates T3SS gene expression by binding the σ66-containing RNAP holoenzyme. In order to study the structure and association mechanism of the Scc4:Scc1 T3SS chaperone complex using nuclear magnetic resonance (NMR) spectroscopy, we developed an approach to selectively label each chain of the Scc4:Scc1 complex with the 15N-isotope. The approach allowed one protein to be visible in the NMR spectrum at a time, which greatly reduced resonance overlap and permitted comparison of the backbone structures of free and bound Scc4. 1H,15N-heteronuclear single quantum coherence spectra of the 15N-Scc4:Scc1 and Scc4:15N-Scc1 complexes showed a total structural rearrangement of Scc4 upon binding Scc1 and a dynamic region isolated to Scc1, respectively. Development of the chain-selective labeling approach revealed that the association of Scc4 and Scc1 requires partial denaturation of Scc1 to form the high affinity complex, while low affinity interactions occurred between the isolated proteins under non-denaturing conditions. These results provide new models for Scc4′s functional switching mechanism and Scc4:Scc1 association in CT.
Collapse
Affiliation(s)
- Thilini O. Ukwaththage
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA; (T.O.U.); (S.M.K.)
| | - Samantha M. Keane
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA; (T.O.U.); (S.M.K.)
| | - Li Shen
- Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA;
| | - Megan A. Macnaughtan
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA; (T.O.U.); (S.M.K.)
- Correspondence: ; Tel.:+1-225-578-7975
| |
Collapse
|
9
|
Kamanova J. Bordetella Type III Secretion Injectosome and Effector Proteins. Front Cell Infect Microbiol 2020; 10:466. [PMID: 33014891 PMCID: PMC7498569 DOI: 10.3389/fcimb.2020.00466] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 07/29/2020] [Indexed: 01/09/2023] Open
Abstract
Pertussis, also known as whooping cough, is a resurging acute respiratory disease of humans primarily caused by the Gram-negative coccobacilli Bordetella pertussis, and less commonly by the human-adapted lineage of B. parapertussis HU. The ovine-adapted lineage of B. parapertussis OV infects only sheep, while B. bronchiseptica causes chronic and often asymptomatic respiratory infections in a broad range of mammals but rarely in humans. A largely overlapping set of virulence factors inflicts the pathogenicity of these bordetellae. Their genomes also harbor a pathogenicity island, named bsc locus, that encodes components of the type III secretion injectosome, and adjacent btr locus with the type III regulatory proteins. The Bsc injectosome of bordetellae translocates the cytotoxic BteA effector protein, also referred to as BopC, into the cells of the mammalian hosts. While the role of type III secretion activity in the persistent colonization of the lower respiratory tract by B. bronchiseptica is well recognized, the functionality of the type III secretion injectosome in B. pertussis was overlooked for many years due to the adaptation of laboratory-passaged B. pertussis strains. This review highlights the current knowledge of the type III secretion system in the so-called classical Bordetella species, comprising B. pertussis, B. parapertussis, and B. bronchiseptica, and discusses its functional divergence. Comparison with other well-studied bacterial injectosomes, regulation of the type III secretion on the transcriptional and post-transcriptional level, and activities of BteA effector protein and BopN protein, homologous to the type III secretion gatekeepers, are addressed.
Collapse
Affiliation(s)
- Jana Kamanova
- Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| |
Collapse
|
10
|
Ukwaththage TO, Goodwin OY, Songok AC, Tafaro AM, Shen L, Macnaughtan MA. Purification of Tag-Free Chlamydia trachomatis Scc4 for Structural Studies Using Sarkosyl-Assisted on-Column Complex Dissociation. Biochemistry 2019; 58:4284-4292. [PMID: 31545893 DOI: 10.1021/acs.biochem.9b00665] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Chlamydia trachomatis is an obligate intracellular bacterial pathogen that causes the most common sexually transmitted bacterial disease in the world. The bacterium has a unique biphasic developmental cycle with a type III secretion system (T3SS) to invade host cells. Scc4 is a class I T3SS chaperone forming a heterodimer complex with Scc1 to chaperone the essential virulence effector, CopN. Scc4 also functions as an RNA polymerase binding protein to regulate σ66-dependent transcription. Aggregation and low solubility of 6X-histidine-tagged Scc4 and the insolubility of 6X-histidine and FLAG-tagged Scc1 expressed in Escherichia coli have hindered the high-resolution nuclear magnetic resonance (NMR) structure determination of these proteins and motivated the development of an on-column complex dissociation method to produce tag-free Scc4 and soluble FLAG-tagged Scc1. By utilizing a 6X-histidine-tag on one protein, the coexpressed Scc4-Scc1 complex was captured on nickel-charged immobilized metal affinity chromatography resin, and the nondenaturing detergent, sodium N-lauroylsarcosine (sarkosyl), was used to dissociate and elute the non-6X-histidine-tagged protein. Tag-free Scc4 was produced in a higher yield and had better NMR spectral characteristics compared to 6X-histidine-tagged Scc4, and soluble FLAG-tagged Scc1 was purified for the first time in a high yield. The backbone structure of Scc4 after exposure to sarkosyl was validated using NMR spectroscopy, demonstrating the usefulness of the method to produce proteins for structural and functional studies. The sarkosyl-assisted on-column complex dissociation method is generally applicable to protein complexes with high affinity and is particularly useful when affinity tags alter the protein's biophysical properties or when coexpression is necessary for solubility.
Collapse
Affiliation(s)
- Thilini O Ukwaththage
- Department of Chemistry , Louisiana State University , Baton Rouge , Louisiana 70803 , United States
| | - Octavia Y Goodwin
- Department of Chemistry , Louisiana State University , Baton Rouge , Louisiana 70803 , United States
| | - Abigael C Songok
- Department of Chemistry , Louisiana State University , Baton Rouge , Louisiana 70803 , United States
| | - Alexa M Tafaro
- Department of Chemistry , Louisiana State University , Baton Rouge , Louisiana 70803 , United States
| | - Li Shen
- Department of Microbiology, Immunology, and Parasitology , Louisiana State University Health Sciences Center , New Orleans , Louisiana 70112 , United States
| | - Megan A Macnaughtan
- Department of Chemistry , Louisiana State University , Baton Rouge , Louisiana 70803 , United States
| |
Collapse
|
11
|
Bugalhão JN, Mota LJ. The multiple functions of the numerous Chlamydia trachomatis secreted proteins: the tip of the iceberg. MICROBIAL CELL 2019; 6:414-449. [PMID: 31528632 PMCID: PMC6717882 DOI: 10.15698/mic2019.09.691] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Chlamydia trachomatis serovars are obligate intracellular bacterial pathogens mainly causing ocular and urogenital infections that affect millions of people worldwide and which can lead to blindness or sterility. They reside and multiply intracellularly within a membrane-bound vacuolar compartment, known as inclusion, and are characterized by a developmental cycle involving two morphologically and physiologically distinct chlamydial forms. Completion of the developmental cycle involves the secretion of > 70 C. trachomatis proteins that function in the host cell cytoplasm and nucleus, in the inclusion membrane and lumen, and in the extracellular milieu. These proteins can, for example, interfere with the host cell cytoskeleton, vesicular and non-vesicular transport, metabolism, and immune signalling. Generally, this promotes C. trachomatis invasion into, and escape from, host cells, the acquisition of nutrients by the chlamydiae, and evasion of cell-autonomous, humoral and cellular innate immunity. Here, we present an in-depth review on the current knowledge and outstanding questions about these C. trachomatis secreted proteins.
Collapse
Affiliation(s)
- Joana N Bugalhão
- UCIBIO, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Luís Jaime Mota
- UCIBIO, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Caparica, Portugal
| |
Collapse
|
12
|
Abstract
Nucleation is one of the least understood steps of microtubule dynamics. It is a kinetically unfavorable process that is templated in the cell by the γ-tubulin ring complex or by preexisting microtubules; it also occurs in vitro from pure tubulin. Here we study the nucleation inhibition potency of natural or artificial proteins in connection with their binding mode to the longitudinal surface of α- or β-tubulin. The structure of tubulin-bound CopN, a Chlamydia protein that delays nucleation, suggests that this protein may interfere with two protofilaments at the (+) end of a nucleus. Designed ankyrin repeat proteins that share a binding mode similar to that of CopN also impede nucleation, whereas those that target only one protofilament do not. In addition, an αRep protein predicted to target two protofilaments at the (-) end does not delay nucleation, pointing to different behaviors at both ends of the nucleus. Our results link the interference with protofilaments at the (+) end and the inhibition of nucleation.
Collapse
|
13
|
Costa AC, Carvalho F, Cabanes D, Sousa S. Stathmin recruits tubulin to Listeria monocytogenes-induced actin comets and promotes bacterial dissemination. Cell Mol Life Sci 2019; 76:961-975. [PMID: 30506415 PMCID: PMC11105747 DOI: 10.1007/s00018-018-2977-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 10/24/2018] [Accepted: 11/22/2018] [Indexed: 01/18/2023]
Abstract
The tubulin cytoskeleton is one of the main components of the cytoarchitecture and is involved in several cellular functions. Here, we examine the interplay between Listeria monocytogenes (Lm) and the tubulin cytoskeleton upon cellular infection. We show that non-polymeric tubulin is present throughout Lm actin comet tails and, to a less extent, in actin clouds. Moreover, we demonstrate that stathmin, a regulator of microtubule dynamics, is also found in these Lm-associated actin structures and is required for tubulin recruitment. Depletion of host stathmin results in longer comets containing less F-actin, which may be correlated with higher levels of inactive cofilin in the comet, thus suggesting a defect on local F-actin dynamics. In addition, intracellular bacterial speed is significantly reduced in stathmin-depleted cells, revealing the importance of stathmin/tubulin in intracellular Lm motility. In agreement, the area of infection foci and the total bacterial loads are also significantly reduced in stathmin-depleted cells. Collectively, our results demonstrate that stathmin promotes efficient cellular infection, possibly through tubulin recruitment and control of actin dynamics at Lm-polymerized actin structures.
Collapse
Affiliation(s)
- Ana Catarina Costa
- Group of Molecular Microbiology, i3S-Instituto de Investigação e Inovação em Saúde, IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal
| | - Filipe Carvalho
- Group of Molecular Microbiology, i3S-Instituto de Investigação e Inovação em Saúde, IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal
- Unité des Interactions Bactéries-Cellules, Institut Pasteur, 25 Rue du Dr Roux, 75015, Paris, France
| | - Didier Cabanes
- Group of Molecular Microbiology, i3S-Instituto de Investigação e Inovação em Saúde, IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal
| | - Sandra Sousa
- Group of Molecular Microbiology, i3S-Instituto de Investigação e Inovação em Saúde, IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal.
| |
Collapse
|
14
|
Bamyaci S, Nordfelth R, Forsberg Å. Identification of specific sequence motif of YopN of Yersinia pseudotuberculosis required for systemic infection. Virulence 2018; 10:10-25. [PMID: 30488778 PMCID: PMC6298760 DOI: 10.1080/21505594.2018.1551709] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Type III secretion systems (T3SSs) are tightly regulated key virulence mechanisms shared by many Gram-negative pathogens. YopN, one of the substrates, is also crucial in regulation of expression, secretion and activation of the T3SS of pathogenic Yersinia species. Interestingly, YopN itself is also targeted into host cells but so far no activity or direct role for YopN inside host cells has been described. Recently, we were able show that the central region of YopN is required for efficient translocation of YopH and YopE into host cells. This was also shown to impact the ability of Yersinia to block phagocytosis. One difficulty in studying YopN is to generate mutants that are not impaired in regulation of the T3SS. In this study we extended our previous work and were able to generate specific mutants within the central region of YopN. These mutants were predicted to be crucial for formation of a putative coiled-coil domain (CCD). Similar to the previously described deletion mutant of the central region, these mutants were all impaired in translocation of YopE and YopH. Interestingly, these YopN variants were not translocated into host cells. Importantly, when these mutants were introduced in cis on the virulence plasmid, they retained full regulatory function of T3SS expression and secretion. This allowed us to evaluate one of the mutants, yopNGAGA, in the systemic mouse infection model. Using in vivo imaging technology we could verify that the mutant was also attenuated in vivo and highly impaired to establish systemic infection.
Collapse
Affiliation(s)
- Sarp Bamyaci
- a Department of Molecular Biology, Umeå Centre for Microbial Research UCMR , Umeå University , Umeå , Sweden.,b Department of Molecular Biology, Laboratory for Molecular Infection Medicine MIMS , Umeå University , Umeå , Sweden
| | - Roland Nordfelth
- a Department of Molecular Biology, Umeå Centre for Microbial Research UCMR , Umeå University , Umeå , Sweden.,b Department of Molecular Biology, Laboratory for Molecular Infection Medicine MIMS , Umeå University , Umeå , Sweden
| | - Åke Forsberg
- a Department of Molecular Biology, Umeå Centre for Microbial Research UCMR , Umeå University , Umeå , Sweden.,b Department of Molecular Biology, Laboratory for Molecular Infection Medicine MIMS , Umeå University , Umeå , Sweden
| |
Collapse
|
15
|
Lindsey ARI, Rice DW, Bordenstein SR, Brooks AW, Bordenstein SR, Newton ILG. Evolutionary Genetics of Cytoplasmic Incompatibility Genes cifA and cifB in Prophage WO of Wolbachia. Genome Biol Evol 2018; 10:434-451. [PMID: 29351633 PMCID: PMC5793819 DOI: 10.1093/gbe/evy012] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/16/2018] [Indexed: 12/20/2022] Open
Abstract
The bacterial endosymbiont Wolbachia manipulates arthropod reproduction to facilitate its maternal spread through host populations. The most common manipulation is cytoplasmic incompatibility (CI): Wolbachia-infected males produce modified sperm that cause embryonic mortality, unless rescued by embryos harboring the same Wolbachia. The genes underlying CI, cifA and cifB, were recently identified in the eukaryotic association module of Wolbachia’s prophage WO. Here, we use transcriptomic and genomic approaches to address three important evolutionary facets of the cif genes. First, we assess whether or not cifA and cifB comprise a classic toxin–antitoxin operon in wMel and show that the two genes exhibit striking, transcriptional differences across host development. They can produce a bicistronic message despite a predicted hairpin termination element in their intergenic region. Second, cifA and cifB strongly coevolve across the diversity of phage WO. Third, we provide new domain and functional predictions across homologs within Wolbachia, and show that amino acid sequences vary substantially across the genus. Finally, we investigate conservation of cifA and cifB and find frequent degradation and loss of the genes in strains that no longer induce CI. Taken together, we demonstrate that cifA and cifB exhibit complex transcriptional regulation in wMel, provide functional annotations that broaden the potential mechanisms of CI induction, and report recurrent erosion of cifA and cifB in non-CI strains, thus expanding our understanding of the most widespread form of reproductive parasitism.
Collapse
Affiliation(s)
| | - Danny W Rice
- Department of Biology, Indiana University, Bloomington
| | | | - Andrew W Brooks
- Department of Biological Sciences, Vanderbilt University.,Vanderbilt Genetics Institute, Vanderbilt University
| | - Seth R Bordenstein
- Department of Biological Sciences, Vanderbilt University.,Vanderbilt Genetics Institute, Vanderbilt University.,Vanderbilt Institute for Infection, Immunology and Inflammation, Vanderbilt University.,Department of Pathology, Microbiology and Immunology, Vanderbilt University
| | | |
Collapse
|
16
|
Wen Y, Chen Y, Li L, Xu M, Tan Y, Li Y, Wang C, Chen Q, Kuang X, Wu Y. Localization and characterization of a putative cysteine desulfurase in Chlamydia psittaci. J Cell Biochem 2018; 120:4409-4422. [PMID: 30260037 DOI: 10.1002/jcb.27727] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Accepted: 08/29/2018] [Indexed: 12/20/2022]
Abstract
Chlamydia psittaci is an obligate intracellular pathogen with a biphasic developmental life cycle. It is auxotrophic for a variety of essential metabolites and obtains amino acids from eukaryotic host cells. Chlamydia can develop inside host cells within chlamydial inclusions. A pathway secreting proteins from inclusions into the host cellular cytoplasm is the type III secretion system (T3SS). The T3SS is universal among several Gram-negative bacteria. Here, we show that CPSIT_0959 of C. psittaci is expressed midcycle and secreted into the infected cellular cytoplasm via the T3SS. Recombinant CPSIT_0959 possesses cysteine desulfurase and PLP-binding activity, which removes sulfur from cysteine to produce alanine, and helps chlamydial replication. Our study shows that CPSIT_0959 improve the infectivity of offspring elementary bodies and seems to promote the replication by its product. This phenomenon has inhibited by the PLP-dependent enzymes inhibitor. Moreover, CPSIT_0959 increased expression of Bim and tBid, and decreased the mitochondrial membrane potential of host mitochondria to induce apoptosis in the latecycle for release of offspring. These results demonstrate that CPSIT_0959 has cysteine desulfurase and PLP-binding activity and is likely to contribute to apoptosis of the infected cells via a mitochondria-mediated pathway to improve the infectivity of progeny.
Collapse
Affiliation(s)
- Yating Wen
- Institute of Pathogenic Biology, Medical College, University of South China, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang, China
| | - Yanbo Chen
- Department of Clinical Laboratory, Jiangmen Wuyi Traditional Chinese Medicine Hospital, Jiangmen, China
| | - Li Li
- Toxicology Laboratory, Hunan Provincial Center for Disease Control and Prevention, Changsha, China
| | - Man Xu
- Institute of Pathogenic Biology, Medical College, University of South China, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang, China
| | - Yuan Tan
- Institute of Pathogenic Biology, Medical College, University of South China, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang, China
| | - Yumeng Li
- Institute of Pathogenic Biology, Medical College, University of South China, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang, China
| | - Chuan Wang
- Institute of Pathogenic Biology, Medical College, University of South China, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang, China
| | - Qian Chen
- Institute of Pathogenic Biology, Medical College, University of South China, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang, China
| | - Xingxing Kuang
- Institute of Pathogenic Biology, Medical College, University of South China, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang, China
| | - Yimou Wu
- Institute of Pathogenic Biology, Medical College, University of South China, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang, China
| |
Collapse
|
17
|
YopN Is Required for Efficient Effector Translocation and Virulence in Yersinia pseudotuberculosis. Infect Immun 2018; 86:IAI.00957-17. [PMID: 29760214 DOI: 10.1128/iai.00957-17] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 05/05/2018] [Indexed: 11/20/2022] Open
Abstract
Type III secretion systems (T3SSs) are used by various Gram-negative pathogens to subvert the host defense by a host cell contact-dependent mechanism to secrete and translocate virulence effectors. While the effectors differ between pathogens and determine the pathogenic life style, the overall mechanism of secretion and translocation is conserved. T3SSs are regulated at multiple levels, and some secreted substrates have also been shown to function in regulation. In Yersinia, one of the substrates, YopN, has long been known to function in the host cell contact-dependent regulation of the T3SS. Prior to contact, through its interaction with TyeA, YopN blocks secretion. Upon cell contact, TyeA dissociates from YopN, which is secreted by the T3SS, resulting in the induction of the system. YopN has also been shown to be translocated into target cells by a T3SS-dependent mechanism. However, no intracellular function has yet been assigned to YopN. The regulatory role of YopN involves the N-terminal and C-terminal parts, while less is known about the role of the central region of YopN. Here, we constructed different in-frame deletion mutants within the central region. The deletion of amino acids 76 to 181 resulted in an unaltered regulation of Yop expression and secretion but triggered reduced YopE and YopH translocation within the first 30 min after infection. As a consequence, this deletion mutant lost its ability to block phagocytosis by macrophages. In conclusion, we were able to differentiate the function of YopN in translocation and virulence from its function in regulation.
Collapse
|
18
|
Roehrich AD, Bordignon E, Mode S, Shen DK, Liu X, Pain M, Murillo I, Martinez-Argudo I, Sessions RB, Blocker AJ. Steps for Shigella Gatekeeper Protein MxiC Function in Hierarchical Type III Secretion Regulation. J Biol Chem 2016; 292:1705-1723. [PMID: 27974466 PMCID: PMC5290946 DOI: 10.1074/jbc.m116.746826] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 12/14/2016] [Indexed: 01/18/2023] Open
Abstract
Type III secretion systems are complex nanomachines used for injection of proteins from Gram-negative bacteria into eukaryotic cells. Although they are assembled when the environmental conditions are appropriate, they only start secreting upon contact with a host cell. Secretion is hierarchical. First, the pore-forming translocators are released. Second, effector proteins are injected. Hierarchy between these protein classes is mediated by a conserved gatekeeper protein, MxiC, in Shigella. As its molecular mechanism of action is still poorly understood, we used its structure to guide site-directed mutagenesis and to dissect its function. We identified mutants predominantly affecting all known features of MxiC regulation as follows: secretion of translocators, MxiC and/or effectors. Using molecular genetics, we then mapped at which point in the regulatory cascade the mutants were affected. Analysis of some of these mutants led us to a set of electron paramagnetic resonance experiments that provide evidence that MxiC interacts directly with IpaD. We suggest how this interaction regulates a switch in its conformation that is key to its functions.
Collapse
Affiliation(s)
- A Dorothea Roehrich
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Enrica Bordignon
- the Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Selma Mode
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Da-Kang Shen
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Xia Liu
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Maria Pain
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Isabel Murillo
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Isabel Martinez-Argudo
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom; the Área de Genética, Facultad de Ciencias Ambientales y Bioquímica, Universidad de Castilla-La Mancha, E-45071 Toledo, Spain
| | - Richard B Sessions
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Ariel J Blocker
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom.
| |
Collapse
|
19
|
Menanteau-Ledouble S, Kumar G, Saleh M, El-Matbouli M. Aeromonas salmonicida: updates on an old acquaintance. DISEASES OF AQUATIC ORGANISMS 2016; 120:49-68. [PMID: 27304870 DOI: 10.3354/dao03006] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Aeromonas salmonicida is the oldest known infectious agent to be linked to fish disease and constitutes a major bacterial pathogen of fish, in particular of salmonids. This bacterium can be found almost worldwide in both marine and freshwater environments and has been divided into several sub-species. In this review, we present the most recent developments concerning our understanding of this pathogen, including how the characterization of new isolates from non-salmonid hosts suggests a more nuanced picture of the importance of the so‑called 'atypical isolates'. We also describe the clinical presentation regarding the infection across several fish species and discuss what is known about the virulence of A. salmonicida and, in particular, the role that the type 3 secretion system might play in suppressing the immune response of its hosts. Finally, isolates have displayed varied levels of antibiotic resistance. Hence, we review a number of solutions that have been developed both to prevent outbreaks and to treat them once they occur, including the application of pre- and probiotic supplements.
Collapse
Affiliation(s)
- Simon Menanteau-Ledouble
- Clinical Division of Fish Medicine, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine, Vienna, Austria
| | | | | | | |
Collapse
|
20
|
Ferrell JC, Fields KA. A working model for the type III secretion mechanism in Chlamydia. Microbes Infect 2015; 18:84-92. [PMID: 26515030 DOI: 10.1016/j.micinf.2015.10.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 10/19/2015] [Accepted: 10/19/2015] [Indexed: 01/09/2023]
Abstract
It has been appreciated for almost 20 years that members of the Chlamydiales possess a virulence-associated type III secretion mechanism. Given the obligate intracellular nature of these bacteria, defining exactly how type III secretion functions to promote pathogenesis has been challenging. We present a working model herein that is based on current evidence.
Collapse
Affiliation(s)
- Joshua C Ferrell
- Department of Microbiology, Immunology & Molecular Genetics, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Kenneth A Fields
- Department of Microbiology, Immunology & Molecular Genetics, University of Kentucky College of Medicine, Lexington, KY 40536, USA.
| |
Collapse
|
21
|
Shen L, Macnaughtan MA, Frohlich KM, Cong Y, Goodwin OY, Chou CW, LeCour L, Krup K, Luo M, Worthylake DK. Multipart Chaperone-Effector Recognition in the Type III Secretion System of Chlamydia trachomatis. J Biol Chem 2015; 290:28141-28155. [PMID: 26438824 DOI: 10.1074/jbc.m115.670232] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Indexed: 11/06/2022] Open
Abstract
Secretion of effector proteins into the eukaryotic host cell is required for Chlamydia trachomatis virulence. In the infection process, Scc1 and Scc4, two chaperones of the type III secretion (T3S) system, facilitate secretion of the important effector and plug protein, CopN, but little is known about the details of this event. Here we use biochemistry, mass spectrometry, nuclear magnetic resonance spectroscopy, and genetic analyses to characterize this trimolecular event. We find that Scc4 complexes with Scc1 and CopN in situ at the late developmental cycle of C. trachomatis. We show that Scc4 and Scc1 undergo dynamic interactions as part of the unique bacterial developmental cycle. Using alanine substitutions, we identify several amino acid residues in Scc4 that are critical for the Scc4-Scc1 interaction, which is required for forming the Scc4·Scc1·CopN ternary complex. These results, combined with our previous findings that Scc4 plays a role in transcription (Rao, X., Deighan, P., Hua, Z., Hu, X., Wang, J., Luo, M., Wang, J., Liang, Y., Zhong, G., Hochschild, A., and Shen, L. (2009) Genes Dev. 23, 1818-1829), reveal that the T3S process is linked to bacterial transcriptional events, all of which are mediated by Scc4 and its interacting proteins. A model describing how the T3S process may affect gene expression is proposed.
Collapse
Affiliation(s)
- Li Shen
- Department of Microbiology, Immunology, and Parasitology.
| | - Megan A Macnaughtan
- Department of Chemistry, Louisiana State University, Baton Range, Louisiana 70803
| | | | - Yanguang Cong
- Department of Microbiology, Immunology, and Parasitology
| | - Octavia Y Goodwin
- Department of Chemistry, Louisiana State University, Baton Range, Louisiana 70803
| | - Chau-Wen Chou
- Department of Chemistry, University of Georgia, Athens, Georgia 30602
| | - Louis LeCour
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112
| | - Kristen Krup
- Department of Microbiology, Immunology, and Parasitology
| | - Miao Luo
- Department of Microbiology, Immunology, and Parasitology
| | - David K Worthylake
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112
| |
Collapse
|
22
|
Burkinshaw BJ, Souza SA, Strynadka NCJ. Structural analysis of SepL, an enteropathogenic Escherichia coli type III secretion-system gatekeeper protein. Acta Crystallogr F Struct Biol Commun 2015; 71:1300-8. [PMID: 26457522 PMCID: PMC4601595 DOI: 10.1107/s2053230x15016064] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2015] [Accepted: 08/27/2015] [Indexed: 12/26/2022] Open
Abstract
During infection, enteropathogenic Escherichia coli assembles a complex multi-protein type III secretion system that traverses the bacterial membranes and targets the host cell membrane to directly deliver virulence or effector proteins to the host cytoplasm. As this secretion system is composed of more than 20 proteins, many of which form oligomeric associations, its assembly must be tightly regulated. A protein called the gatekeeper, or SepL, ensures that the secretion of the translocon component, which inserts into the host membrane, occurs before the secretion of effectors. The crystal structure of the gatekeeper SepL was determined and compared with the structures of SepL homologues from other bacterial pathogens in order to identify SepL residues that may be critical for its role in type III secretion-system assembly.
Collapse
Affiliation(s)
- Brianne J. Burkinshaw
- Department of Biochemistry and Molecular Biology, University of British Columbia, Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
- Centre for Blood Research, Life Sciences Centre, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - Sergio A. Souza
- Department of Biochemistry and Molecular Biology, University of British Columbia, Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
- Centre for Blood Research, Life Sciences Centre, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - Natalie C. J. Strynadka
- Department of Biochemistry and Molecular Biology, University of British Columbia, Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
- Centre for Blood Research, Life Sciences Centre, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| |
Collapse
|
23
|
Dumoux M, Menny A, Delacour D, Hayward RD. A Chlamydia effector recruits CEP170 to reprogram host microtubule organization. J Cell Sci 2015. [PMID: 26220855 PMCID: PMC4582400 DOI: 10.1242/jcs.169318] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The obligate intracellular bacterial pathogen Chlamydia trachomatis deploys virulence effectors to subvert host cell functions enabling its replication within a specialized membrane-bound compartment termed an inclusion. The control of the host cytoskeleton is crucial for Chlamydia uptake, inclusion biogenesis and cell exit. Here, we demonstrate how a Chlamydia effector rearranges the microtubule (MT) network by initiating organization of the MTs at the inclusion surface. We identified an inclusion-localized effector that is sufficient to interfere with MT assembly, which we named inclusion protein acting on MTs (IPAM). We established that IPAM recruits and stimulates the centrosomal protein 170 kDa (CEP170) to hijack the MT organizing functions of the host cell. We show that CEP170 is essential for chlamydial control of host MT assembly, and is required for inclusion morphogenesis and bacterial infectivity. Together, we demonstrate how a pathogen effector reprograms the host MT network to support its intracellular development.
Collapse
Affiliation(s)
- Maud Dumoux
- Institute of Structural and Molecular Biology, Birkbeck and University College London, Malet Street, London WC1E 7HX, UK
| | - Anais Menny
- Institute of Structural and Molecular Biology, Birkbeck and University College London, Malet Street, London WC1E 7HX, UK
| | - Delphine Delacour
- Cell Adhesion and Mechanics Group, Institut Jacques Monod, CNRS UMR7592, Université Paris Diderot, 15 rue Helene Brion, Paris 75013, France
| | - Richard D Hayward
- Institute of Structural and Molecular Biology, Birkbeck and University College London, Malet Street, London WC1E 7HX, UK
| |
Collapse
|
24
|
Abstract
UNLABELLED 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. IMPORTANCE This 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.
Collapse
|
25
|
Mojica SA, Hovis KM, Frieman MB, Tran B, Hsia RC, Ravel J, Jenkins-Houk C, Wilson KL, Bavoil PM. SINC, a type III secreted protein of Chlamydia psittaci, targets the inner nuclear membrane of infected cells and uninfected neighbors. Mol Biol Cell 2015; 26:1918-34. [PMID: 25788290 PMCID: PMC4436835 DOI: 10.1091/mbc.e14-11-1530] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 03/06/2015] [Indexed: 12/31/2022] Open
Abstract
SINC, a new type III secreted protein of the avian and human pathogen Chlamydia psittaci, uniquely targets the nuclear envelope of C. psittaci-infected cells and uninfected neighboring cells. Digitonin-permeabilization studies of SINC-GFP-transfected HeLa cells indicate that SINC targets the inner nuclear membrane. SINC localization at the nuclear envelope was blocked by importazole, confirming SINC import into the nucleus. Candidate partners were identified by proximity to biotin ligase-fused SINC in HEK293 cells and mass spectrometry (BioID). This strategy identified 22 candidates with high confidence, including the nucleoporin ELYS, lamin B1, and four proteins (emerin, MAN1, LAP1, and LBR) of the inner nuclear membrane, suggesting that SINC interacts with host proteins that control nuclear structure, signaling, chromatin organization, and gene silencing. GFP-SINC association with the native LEM-domain protein emerin, a conserved component of nuclear "lamina" structure, or with a complex containing emerin was confirmed by GFP pull down. Our findings identify SINC as a novel bacterial protein that targets the nuclear envelope with the capability of globally altering nuclear envelope functions in the infected host cell and neighboring uninfected cells. These properties may contribute to the aggressive virulence of C. psittaci.
Collapse
Affiliation(s)
- Sergio A Mojica
- Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, MD 21201
| | - Kelley M Hovis
- Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, MD 21201
| | - Matthew B Frieman
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD 20201
| | - Bao Tran
- Mass Spectrometry Center, University of Maryland School of Pharmacy, Baltimore, MD 21201
| | - Ru-ching Hsia
- Core Imaging Facility and Department of Neural and Pain Sciences, University of Maryland School of Dentistry, Baltimore, MD 21201
| | - Jacques Ravel
- Institute for Genome Science, University of Maryland School of Medicine, Baltimore, MD 20201
| | - Clifton Jenkins-Houk
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Katherine L Wilson
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Patrik M Bavoil
- Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, MD 21201
| |
Collapse
|
26
|
Ishida K, Matsuo J, Yamamoto Y, Yamaguchi H. Chlamydia pneumoniae effector chlamydial outer protein N sequesters fructose bisphosphate aldolase A, providing a benefit to bacterial growth. BMC Microbiol 2014; 14:330. [PMID: 25528659 PMCID: PMC4302594 DOI: 10.1186/s12866-014-0330-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 12/16/2014] [Indexed: 01/13/2023] Open
Abstract
Background Pathogenic chlamydiae are obligate intracellular pathogens and have adapted successfully to human cells, causing sexually transmitted diseases or pneumonia. Chlamydial outer protein N (CopN) is likely a critical effector protein secreted by the type III secretion system in chlamydiae, which manipulates host cells. However, the mechanisms of its action remain to be clarified. In this work, we aimed to identify previously unidentified CopN effector target in host cells. Results We first performed a pull-down assay with recombinant glutathione S-transferase (GST) fusion CopN proteins (GST–CpCopN: Chlamydia pneumoniae TW183, GST–CtCopN: Chlamydia trachomatis D/UW-3/CX) as “bait” and soluble lysates obtained from human immortal epithelial HEp-2 cells as “prey”, followed by SDS-PAGE with mass spectroscopy (MS). We found that a host cell protein specifically bound to GST–CpCopN, but not GST–CtCopN. MS revealed the host protein to be fructose bisphosphate aldolase A (aldolase A), which plays a key role in glycolytic metabolism. We also confirmed the role of aldolase A in chlamydia-infected HEp-2 cells by using two distinct experiments for gene knockdown with an siRNA specific to aldolase A transcripts, and for assessment of glycolytic enzyme gene expression levels. As a result, both the numbers of chlamydial inclusion-forming units and RpoD transcripts were increased in the chlamydia-infected aldolase A knockdown cells, as compared with the wild-type HEp-2 cells. Meanwhile, chlamydial infection tended to enhance expression of aldolase A. Conclusions We discovered that one of the C. pneumoniae CopN targets is the glycolytic enzyme aldolase A. Sequestering aldolase A may be beneficial to bacterial growth in infected host cells.
Collapse
Affiliation(s)
- Kasumi Ishida
- Department of Medical Laboratory Science, Faculty of Health Sciences, Hokkaido University, Sapporo, Hokkaido, 060-0812, Japan. .,Research Fellow of Japan Society for the Promotion of Science, Tokyo, 102-0083, Japan.
| | - Junji Matsuo
- Department of Medical Laboratory Science, Faculty of Health Sciences, Hokkaido University, Sapporo, Hokkaido, 060-0812, Japan.
| | - Yoshimasa Yamamoto
- Department of Biomedical Informatics, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871, Japan. .,Japan Science and Technology Agency/Japan International Cooperation Agency, Science and Technology Research Partnership for Sustainable Development (JST/JICA, SATREPS), Osaka, Japan. .,Osaka Prefectural Institute of Public Health, Higashinari-ku, Osaka, 537-0025, Japan.
| | - Hiroyuki Yamaguchi
- Department of Medical Laboratory Science, Faculty of Health Sciences, Hokkaido University, Sapporo, Hokkaido, 060-0812, Japan.
| |
Collapse
|
27
|
Archuleta TL, Spiller BW. A gatekeeper chaperone complex directs translocator secretion during type three secretion. PLoS Pathog 2014; 10:e1004498. [PMID: 25375170 PMCID: PMC4222845 DOI: 10.1371/journal.ppat.1004498] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 10/02/2014] [Indexed: 11/18/2022] Open
Abstract
Many Gram-negative bacteria use Type Three Secretion Systems (T3SS) to deliver effector proteins into host cells. These protein delivery machines are composed of cytosolic components that recognize substrates and generate the force needed for translocation, the secretion conduit, formed by a needle complex and associated membrane spanning basal body, and translocators that form the pore in the target cell. A defined order of secretion in which needle component proteins are secreted first, followed by translocators, and finally effectors, is necessary for this system to be effective. While the secreted effectors vary significantly between organisms, the ∼20 individual protein components that form the T3SS are conserved in many pathogenic bacteria. One such conserved protein, referred to as either a plug or gatekeeper, is necessary to prevent unregulated effector release and to allow efficient translocator secretion. The mechanism by which translocator secretion is promoted while effector release is inhibited by gatekeepers is unknown. We present the structure of the Chlamydial gatekeeper, CopN, bound to a translocator-specific chaperone. The structure identifies a previously unknown interface between gatekeepers and translocator chaperones and reveals that in the gatekeeper-chaperone complex the canonical translocator-binding groove is free to bind translocators. Structure-based mutagenesis of the homologous complex in Shigella reveals that the gatekeeper-chaperone-translocator complex is essential for translocator secretion and for the ordered secretion of translocators prior to effectors. Type Three Secretion Systems (T3SS) are essential virulence factors found in many pathogenic Gram-negative bacteria. These machines aid infection by delivering bacterial proteins into host cells where these proteins modulate host processes and help establish a niche for the bacteria. Protein delivery occurs in a highly regulated manner in which proteins involved in early steps in infection, or necessary to build the secretion conduit, are typically secreted before other substrates, a phenomenon termed secretion hierarchy. This study presents the structure of a molecular complex that physically links one class of early substrates, components of the secretion pore termed translocators, to a gatekeeper protein, a protein that has been implicated in the secretion hierarchy. Disruption of this interaction in Shigella disrupts the secretion of translocators, while supporting increased secretion of effectors, resulting in phenotypes indistinguishable from a gatekeeper deletion, and leading to the conclusion that a gatekeeper-chaperone-translocator complex is a critical component of the T3SS.
Collapse
Affiliation(s)
- Tara L. Archuleta
- Chemical and Physical Biology Program, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Benjamin W. Spiller
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- * E-mail:
| |
Collapse
|
28
|
Nawrotek A, Guimarães BG, Velours C, Subtil A, Knossow M, Gigant B. Biochemical and structural insights into microtubule perturbation by CopN from Chlamydia pneumoniae. J Biol Chem 2014; 289:25199-210. [PMID: 25056950 DOI: 10.1074/jbc.m114.568436] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Although the actin network is commonly hijacked by pathogens, there are few reports of parasites targeting microtubules. The proposed member of the LcrE protein family from some Chlamydia species (e.g. pCopN from C. pneumoniae) binds tubulin and inhibits microtubule assembly in vitro. From the pCopN structure and its similarity with that of MxiC from Shigella, we definitively confirm CopN as the Chlamydia homolog of the LcrE family of bacterial proteins involved in the regulation of type III secretion. We have also investigated the molecular basis for the pCopN effect on microtubules. We show that pCopN delays microtubule nucleation and acts as a pure tubulin-sequestering protein at steady state. It targets the β subunit interface involved in the tubulin longitudinal self-association in a way that inhibits nucleotide exchange. pCopN contains three repetitions of a helical motif flanked by disordered N- and C-terminal extensions. We have identified the pCopN minimal tubulin-binding region within the second and third repeats. Together with the intriguing observation that C. trachomatis CopN does not bind tubulin, our data support the notion that, in addition to the shared function of type III secretion regulation, these proteins have evolved different functions in the host cytosol. Our results provide a mechanistic framework for understanding the C. pneumoniae CopN-specific inhibition of microtubule assembly.
Collapse
Affiliation(s)
- Agata Nawrotek
- From the Laboratoire d'Enzymologie et Biochimie Structurales (LEBS), Centre de Recherche de Gif, CNRS, 91198 Gif sur Yvette, France
| | - Beatriz G Guimarães
- the Synchrotron SOLEIL, L'Orme de Merisiers, St Aubin, 91192 Gif sur Yvette, France, and
| | - Christophe Velours
- From the Laboratoire d'Enzymologie et Biochimie Structurales (LEBS), Centre de Recherche de Gif, CNRS, 91198 Gif sur Yvette, France
| | - Agathe Subtil
- the Institut Pasteur, Unité de Biologie des Interactions Cellulaires, 25 Rue du Docteur Roux, 75015 Paris, France
| | - Marcel Knossow
- From the Laboratoire d'Enzymologie et Biochimie Structurales (LEBS), Centre de Recherche de Gif, CNRS, 91198 Gif sur Yvette, France
| | - Benoît Gigant
- From the Laboratoire d'Enzymologie et Biochimie Structurales (LEBS), Centre de Recherche de Gif, CNRS, 91198 Gif sur Yvette, France,
| |
Collapse
|
29
|
Li Y, Hu X, Zhang X, Liu Z, Ding X, Xia L, Hu S. Photorhabdus luminescensPirAB-fusion protein exhibits both cytotoxicity and insecticidal activity. FEMS Microbiol Lett 2014; 356:23-31. [DOI: 10.1111/1574-6968.12474] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 04/29/2014] [Accepted: 05/07/2014] [Indexed: 10/25/2022] Open
Affiliation(s)
- Yusheng Li
- College of Life Sciences; Hunan Provincial Key Laboratory of Microbial Molecular Biology - State Key Laboratory Breeding Base of Microbial Molecular Biology; Hunan Normal University; Changsha China
| | - Xiaofeng Hu
- College of Life Sciences; Hunan Provincial Key Laboratory of Microbial Molecular Biology - State Key Laboratory Breeding Base of Microbial Molecular Biology; Hunan Normal University; Changsha China
| | - Xu Zhang
- College of Life Sciences; Hunan Provincial Key Laboratory of Microbial Molecular Biology - State Key Laboratory Breeding Base of Microbial Molecular Biology; Hunan Normal University; Changsha China
| | - Zhengqiang Liu
- College of Life Sciences; Hunan Provincial Key Laboratory of Microbial Molecular Biology - State Key Laboratory Breeding Base of Microbial Molecular Biology; Hunan Normal University; Changsha China
| | - Xuezhi Ding
- College of Life Sciences; Hunan Provincial Key Laboratory of Microbial Molecular Biology - State Key Laboratory Breeding Base of Microbial Molecular Biology; Hunan Normal University; Changsha China
| | - Liqiu Xia
- College of Life Sciences; Hunan Provincial Key Laboratory of Microbial Molecular Biology - State Key Laboratory Breeding Base of Microbial Molecular Biology; Hunan Normal University; Changsha China
| | - Shengbiao Hu
- College of Life Sciences; Hunan Provincial Key Laboratory of Microbial Molecular Biology - State Key Laboratory Breeding Base of Microbial Molecular Biology; Hunan Normal University; Changsha China
| |
Collapse
|
30
|
Kraft LJ, Nguyen TA, Vogel SS, Kenworthy AK. Size, stoichiometry, and organization of soluble LC3-associated complexes. Autophagy 2014; 10:861-77. [PMID: 24646892 PMCID: PMC4768459 DOI: 10.4161/auto.28175] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
MAP1LC3B, an ortholog of yeast Atg8 and a member of the family of proteins formerly also known as ATG8 in mammals (LC3B henceforth in the text), functions in autophagosome formation and autophagy substrate recruitment. LC3 exists in both a soluble (autophagosome-independent) form as well as a lipid modified form that becomes tightly incorporated into autophagosomal membranes. Although LC3 is known to associate with tens of proteins, relatively little is known about soluble LC3 aside from its interactions with the LC3 lipid conjugation machinery. In previous studies we found autophagosome-independent GFP-LC3B diffuses unusually slowly for a protein of its size, suggesting it may constitutively associate with a high molecular weight complex, form homo-oligomers or aggregates, or reversibly bind microtubules or membranes. To distinguish between these possibilities, we characterized the size, stoichiometry, and organization of autophagosome-independent LC3B in living cells and in cytoplasmic extracts using fluorescence recovery after photobleaching (FRAP) and fluorescence polarization fluctuation analysis (FPFA). We found that the diffusion of LC3B was unaffected by either mutational disruption of its lipid modification or microtubule depolymerization. Brightness and homo-FRET analysis indicate LC3B does not homo-oligomerize. However, mutation of specific residues on LC3B required for binding other proteins and mRNA altered the effective hydrodynamic radius of the protein as well as its stoichiometry. We conclude that when not bound to autophagosomes, LC3B associates with a multicomponent complex with an effective size of ~500 kDa in the cytoplasm. These findings provide new insights into the nature of soluble LC3B and illustrate the power of FRAP and FPFA to investigate the emergent properties of protein complexes in the autophagy pathway.
Collapse
Affiliation(s)
- Lewis J Kraft
- Chemical and Physical Biology Program; Department of Molecular Physiology and Biophysics; Department of Cell and Developmental Biology; Vanderbilt University Medical Center; Nashville, TN USA
| | - Tuan A Nguyen
- Section on Cellular Biophotonics, Laboratory of Molecular Physiology; National Institute on Alcohol Abuse and Alcoholism; National Institutes of Health; Rockville, MD USA
| | - Steven S Vogel
- Section on Cellular Biophotonics, Laboratory of Molecular Physiology; National Institute on Alcohol Abuse and Alcoholism; National Institutes of Health; Rockville, MD USA
| | - Anne K Kenworthy
- Chemical and Physical Biology Program; Department of Molecular Physiology and Biophysics; Department of Cell and Developmental Biology; Vanderbilt University Medical Center; Nashville, TN USA
| |
Collapse
|
31
|
Zhang X, Hu X, Li Y, Ding X, Yang Q, Sun Y, Yu Z, Xia L, Hu S. XaxAB-like binary toxin from Photorhabdus luminescens exhibits both insecticidal activity and cytotoxicity. FEMS Microbiol Lett 2013; 350:48-56. [PMID: 24188660 DOI: 10.1111/1574-6968.12321] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 10/11/2013] [Accepted: 10/30/2013] [Indexed: 11/26/2022] Open
Abstract
The enterobacterium Photorhabdus luminescens produces a number of toxins to kill its insect host. By analyzing the genomic sequence of P. luminescens TT01, we found that amino acid sequences encoded by plu1961 and plu1962 showed high similarity to XaxAB binary toxin of Xenorhabuds nematophila, which has both necrotic and apoptotic activities in both insect and mammalian cells in vitro. To evaluate the biological activity of Plu1961/Plu1962, their coding genes were cloned and expressed in Escherichia coli. Both Plu1961 and Plu1962 were expressed as soluble protein in BL21 (DE3) and their mixture caused insect midgut CF-203 cells death via necrosis. Confocal fluorescence microscopy showed that Plu1961/Plu1962 mixture was able to depolymerize microtubule and induce the increase in plasma membrane permeabilization in CF-203 cells. Moreover, co-expression of Plu1961/Plu1962 in the same cytoplasm exhibited cytotoxic effect against mammalian cells (B16, 4T1, and HeLa cells) and injectable activity against Spodoptera exigua larvae. Until now, two types of binary toxins have been identified in P. luminescens, the first type is PirAB and Plu1961/Plu1962 is the second one. The biological role of Plu1961/Plu1962 binary toxin played in the infection process should attract more attention in future.
Collapse
Affiliation(s)
- Xu Zhang
- College of Life Science, Hunan Normal University, Hunan Provincial Key Laboratory of Microbial Molecular Biology-State Key Laboratory Breeding Base of Microbial Molecular Biology, Changsha, China
| | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Abstract
Members of the order Chlamydiales comprise a group of exquisitely evolved parasites of eukaryotic hosts that extends from single-celled amoeba to mammals. The most notable are human pathogens and include the agent of oculogenital disease Chlamydia trachomatis, the respiratory pathogen C. pneumoniae, and the zoonotic agent C. psittaci. All of these species are obligate intracellular bacteria that develop within parasitophorous vesicles termed inclusions. This demanding lifestyle necessitates orchestrated entry into nonphagocytic cells, creation of a privileged intracellular niche, and subversion of potent host defenses. All chlamydial genomes contain the coding capacity for a nonflagellar type III secretion system, and this mechanism has arisen as an essential contributor to chlamydial virulence. The emergence of tractable approaches to the genetic manipulation of chlamydiae raises the possibility of explosive progress in understanding this important contributor to chlamydial pathogenesis. This minireview considers challenges and recent advances that have revealed how chlamydiae have maintained conserved aspects of T3S while exploiting diversification to yield a system that exerts a fundamental role in the unique biology of Chlamydia species.
Collapse
|
33
|
Vanden Bergh P, Frey J. Aeromonas salmonicida subsp. salmonicida in the light of its type-three secretion system. Microb Biotechnol 2013; 7:381-400. [PMID: 24119189 PMCID: PMC4229320 DOI: 10.1111/1751-7915.12091] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 08/27/2013] [Accepted: 08/28/2013] [Indexed: 11/30/2022] Open
Abstract
Aeromonas salmonicida subsp. salmonicida is an important pathogen in salmonid aquaculture and is responsible for the typical furunculosis. The type-three secretion system (T3SS) is a major virulence system. In this work, we review structure and function of this highly sophisticated nanosyringe in A. salmonicida. Based on the literature as well as personal experimental observations, we document the genetic (re)organization, expression regulation, anatomy, putative functional origin and roles in the infectious process of this T3SS. We propose a model of pathogenesis where A. salmonicida induces a temporary immunosuppression state in fish in order to acquire free access to host tissues. Finally, we highlight putative important therapeutic and vaccine strategies to prevent furunculosis of salmonid fish.
Collapse
Affiliation(s)
- Philippe Vanden Bergh
- Institute of Veterinary Bacteriology, University of Bern, Länggassstrasse 122, Bern, Switzerland
| | | |
Collapse
|
34
|
The Aeromonas salmonicida subsp. salmonicida exoproteome: determination of the complete repertoire of Type-Three Secretion System effectors and identification of other virulence factors. Proteome Sci 2013; 11:42. [PMID: 24073886 PMCID: PMC3852671 DOI: 10.1186/1477-5956-11-42] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 09/23/2013] [Indexed: 01/24/2023] Open
Abstract
Background Aeromonas salmonicida subsp. salmonicida, the etiologic agent of furunculosis, is a major pathogen of fisheries worldwide. Several virulence factors have been described, but the type-three secretion system (T3SS) is recognized as having a major effect on virulence by injecting effectors directly into fish cells. In this study we used high-throughput proteomics to display the differences between in vitro secretome of A. salmonicida wild-type (wt, hypervirulent, JF2267) and T3SS-deficient (isogenic ΔascV, extremely low-virulent, JF2747) strains in exponential and stationary phases of growth. Results Results confirmed the secretion of effectors AopH, AexT, AopP and AopO via T3SS, and for the first time demonstrated the impact of T3SS in secretion of Ati2, AopN and ExsE that are known as effectors in other pathogens. Translocators, needle subunits, Ati1, and AscX were also secreted in supernatants (SNs) dependent on T3SS. AopH, Ati2, AexT, AopB and AopD were in the top seven most abundant excreted proteins. EF-G, EF-Tu, DnaK, HtpG, PNPase, PepN and MdeA were moderately secreted in wt SNs and predicted to be putative T3 effectors by bioinformatics. Pta and ASA_P5G088 were increased in wt SNs and T3-associated in other bacteria. Ten conserved cytoplasmic proteins were more abundant in wt SNs than in the ΔascV mutant, but without any clear association to a secretion system. T1-secreted proteins were predominantly found in wt SNs: OmpAI, OmpK40, DegQ, insulinase ASA_0716, hypothetical ASA_0852 and ASA_3619. Presence of T3SS components in pellets was clearly decreased by ascV deletion, while no impact was observed on T1- and T2SS. Our results demonstrated that the ΔascV mutant strain excreted well-described (VapA, AerA, AerB, GCAT, Pla1, PlaC, TagA, Ahe2, GbpA and enolase) and yet uncharacterized potential toxins, adhesins and enzymes as much as or even more than the wt strain. Other putative important virulence factors were not detected. Conclusions We demonstrated the whole in vitro secretome and T3SS repertoire of hypervirulent A. salmonicida. Several toxins, adhesins and enzymes that are not part of the T3SS secretome were secreted to a higher extent in the extremely low-virulent ΔascV mutant. All together, our results show the high importance of an intact T3SS to initiate the furunculosis and offer new information about the pathogenesis.
Collapse
|
35
|
Romano JD, Coppens I. Host Organelle Hijackers: a similar modus operandi for Toxoplasma gondii and Chlamydia trachomatis: co-infection model as a tool to investigate pathogenesis. Pathog Dis 2013; 69:72-86. [PMID: 23821471 DOI: 10.1111/2049-632x.12057] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 06/11/2013] [Accepted: 06/11/2013] [Indexed: 12/27/2022] Open
Abstract
The bacterium Chlamydia trachomatis and the protozoan parasite Toxoplasma gondii are the causative agents of chlamydiosis and toxoplasmosis in humans, respectively. Both microorganisms are obligate intracellular pathogens and notorious for extensively modifying the cytoskeletal architecture and the endomembrane system of their host cells to establish productive infections. This review highlights the similar tactics developed by these two pathogens to manipulate their host cell despite their genetic unrelatedness. Using an in vitro cell culture model whereby single fibroblasts are infected by C. trachomatis and T. gondii simultaneously, thus setting up an intracellular competition, we demonstrate that the solutions to the problem of intracellular survival deployed by the parasite and the bacterium may represent an example of convergent evolution, driven by the necessity to acquire nutrients in a hostile environment.
Collapse
Affiliation(s)
- Julia D Romano
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, USA
| | | |
Collapse
|
36
|
Cherradi Y, Schiavolin L, Moussa S, Meghraoui A, Meksem A, Biskri L, Azarkan M, Allaoui A, Botteaux A. Interplay between predicted inner-rod and gatekeeper in controlling substrate specificity of the type III secretion system. Mol Microbiol 2013; 87:1183-99. [PMID: 23336839 DOI: 10.1111/mmi.12158] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/15/2013] [Indexed: 11/30/2022]
Abstract
The type III secretion apparatus (T3SA) is a multi-protein complex central to the virulence of many Gram-negative pathogens. Currently, the mechanisms controlling the hierarchical addressing of needle subunits, translocators and effectors to the T3SA are still poorly understood. In Shigella, MxiC is known to sequester effectors within the cytoplasm prior to receiving the activation signal from the needle. However, molecules involved in linking the needle and MxiC are unknown. Here, we demonstrate a molecular interaction between MxiC and the predicted inner-rod component MxiI suggesting that this complex plugs the T3SA entry gate. Our results suggest that MxiI-MxiC complex dissociation facilitates the switch in secretion from translocators to effectors. We identified MxiC(F)(206)(S) variant, unable to interact with MxiI, which exhibits a constitutive secretion phenotype although it remains responsive to induction. Moreover, we identified the mxiI(Q67A) mutant that only secretes translocators, a phenotype that was suppressed by coexpression of the MxiC(F)(206)(S) variant. We demonstrated the interaction between MxiI and MxiC homologues in Yersinia and Salmonella. Lastly, we identified an interaction between MxiC and chaperone IpgC which contributes to understanding how translocators secretion is regulated. In summary, this study suggests the existence of a widely conserved T3S mechanism that regulates effectors secretion.
Collapse
Affiliation(s)
- Youness Cherradi
- Laboratoire de Bactériologie Moléculaire, Université Libre de Bruxelles, Route de Lennik, 808, 1070, Bruxelles, Belgium
| | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Kim JS, Jang JI, Eom JS, Oh CH, Kim HG, Kim BH, Bang IS, Bang SH, Park YK. Molecular characterization of the InvE regulator in the secretion of type III secretion translocases in Salmonella enterica serovar Typhimurium. MICROBIOLOGY-SGM 2013; 159:446-461. [PMID: 23288540 DOI: 10.1099/mic.0.061689-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The type III secretion systems (T3SSs) are exploited by many Gram-negative pathogenic bacteria to deliver a set of effector proteins into the host cytosol during cell entry. The T3SS of Salmonella enterica serovar Typhimurium is composed of more than 20 proteins that constitute the membrane-associated base, the needle and the tip complex at the distal end of the T3SS needle. Membrane docking and piercing between the T3SS and host cells is followed by the secretion of effector proteins. Therefore, a secretion hierarchy among the substrates of the T3SS is required. The secretion of the pore-forming translocase proteins SipB, SipC and SipD is controlled by the T3SS regulator protein, InvE. During an attempt to identify the regions of InvE that are involved in T3SS regulation, it was observed that the secretion of SipB, SipC and SipD was inhibited when the C-terminal 52 amino acids were removed from InvE. In addition, InvE derivatives lacking the N-terminal 30 and 100 residues were unable to secrete translocases into the culture medium. Interestingly, in the absence of the N-terminal 180 residues of InvE, SipD is unstable, resulting in the hypersecretion of SipB. We also found that both the type III secretion signals of SipB and SptP were functionally interchangeable with the first 30 amino acids of InvE, which could allow the secretion of a reporter protein. These results indicate that InvE may have two functional domains responsible for regulating the secretion of translocases: an N-terminal secretion signal and a C-terminal regulatory domain.
Collapse
Affiliation(s)
- Jin Seok Kim
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
| | - Jung Im Jang
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
| | - Jeong Seon Eom
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
| | - Chang Heon Oh
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
| | - Hyeon Guk Kim
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
| | - Bae Hoon Kim
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
| | - Iel Soo Bang
- Department of Microbiology and Immunology, Chosun University School of Dentistry, Gwang ju 501-759, Republic of Korea
| | - Seong Ho Bang
- Department of Biological Science, Hanseo University, Chungcheongnam-do 356-706, Republic of Korea
| | - Yong Keun Park
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
| |
Collapse
|
38
|
Radhakrishnan GK, Splitter GA. Modulation of host microtubule dynamics by pathogenic bacteria. Biomol Concepts 2012; 3:571-580. [PMID: 23585820 DOI: 10.1515/bmc-2012-0030] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The eukaryotic cytoskeleton is a vulnerable target of many microbial pathogens during the course of infection. Rearrangements of host cytoskeleton benefit microbes in various stages of their infection cycle such as invasion, motility, and persistence. Bacterial pathogens deliver a number of effector proteins into host cells for modulating the dynamics of actin and microtubule cytoskeleton. Alteration of the actin cytoskeleton is generally achieved by bacterial effectors that target the small GTPases of the host. Modulation of microtubule dynamics involves direct interaction of effector proteins with the subunits of microtubules or recruiting cellular proteins that affect microtubule dynamics. This review will discuss effector proteins from animal and human bacterial pathogens that either destabilize or stabilize host micro-tubules to advance the infectious process. A compilation of these research findings will provide an overview of known and unknown strategies used by various bacterial effectors to modulate the host microtubule dynamics. The present review will undoubtedly help direct future research to determine the mechanisms of action of many bacterial effector proteins and contribute to understanding the survival strategies of diverse adherent and invasive bacterial pathogens.
Collapse
Affiliation(s)
- Girish K Radhakrishnan
- Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA
| | | |
Collapse
|
39
|
Wei HL, Collmer A. Multiple lessons from the multiple functions of a regulator of type III secretion system assembly in the plant pathogen Pseudomonas syringae. Mol Microbiol 2012; 85:195-200. [PMID: 22646515 DOI: 10.1111/j.1365-2958.2012.08119.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The assembly of type III secretion systems (T3SSs), which inject bacterial effector proteins into the cytosol of animal and plant hosts, is a highly regulated process. Animal pathogens use a length-control protein to produce T3SS needles of fixed length and then a second regulator, such as YopN in Yersinia spp, to mediate host contact-dependent effector delivery. For Pseudomonas syringae and other plant pathogens, regulation of the assembly process differs because the T3SS pilus must grow through variably thick plant cell walls before contacting the host plasma membrane. In this issue of Molecular Microbiology, Crabill et al. (2012) report evidence that the YopN homologue HrpJ is a multifunctional regulator of T3SS assembly in DC3000. A hrpJ mutant hyper-secretes pilus protein and no longer secretes four translocator proteins in culture, and it fails to inject effectors in planta. As with other proteins in this class, HrpJ is itself a T3SS substrate, but secretion-incompetent forms retain regulatory function. However, HrpJ is unusual in suppressing innate immune responses within host cells, as demonstrated with transgenic plants. The multiple capabilities of HrpJ appear to couple host contact sensing with pilus length control and translocator secretion while also contributing to immunity suppression early in the interaction.
Collapse
Affiliation(s)
- Hai-Lei Wei
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY 14853, USA
| | | |
Collapse
|
40
|
Crabill E, Karpisek A, Alfano JR. The Pseudomonas syringae HrpJ protein controls the secretion of type III translocator proteins and has a virulence role inside plant cells. Mol Microbiol 2012; 85:225-38. [PMID: 22607547 DOI: 10.1111/j.1365-2958.2012.08097.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The bacterial plant pathogen Pseudomonas syringae injects effector proteins into plant cells via a type III secretion system (T3SS), which is required for pathogenesis. The protein HrpJ is secreted by P. syringae and is required for a fully functional T3SS. A hrpJ mutant is non-pathogenic and cannot inject effectors into plant cells or secrete the harpin HrpZ1. Here we show that the hrpJ mutant also cannot secrete the harpins HrpW1 and HopAK1 or the translocator HrpK1, suggesting that these proteins are required in the translocation (injection) of effectors into plant cells. Complementation of the hrpJ mutant with secretion incompetent HrpJ derivatives restores the secretion of HrpZ1 and HrpW1 and the ability to elicit a hypersensitive response, a measure of translocation. However, growth in planta and disease symptom production is only partially restored, suggesting that secreted HrpJ may have a direct role in virulence. Transgenic Arabidopsis plants expressing HrpJ-HA complemented the virulence phenotype of the hrpJ mutant expressing a secretion incompetent HrpJ derivative and were reduced in their immune responses. Collectively, these data indicate that HrpJ has a dual role in P. syringae: inside bacterial cells HrpJ controls the secretion of translocator proteins and inside plant cells it suppresses plant immunity.
Collapse
Affiliation(s)
- Emerson Crabill
- Center for Plant Science Innovation, University of Nebraska, Lincoln, NE 68588-0660, USA
| | | | | |
Collapse
|