Type III Secretion: More Systems Than You Think

Physiology ◽  
2005 ◽  
Vol 20 (5) ◽  
pp. 326-339 ◽  
Author(s):  
Paul Troisfontaines ◽  
Guy R. Cornelis
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Type Iii Secretion ◽  
Plant Cells ◽  
Effector Proteins ◽  
Eukaryotic Cells ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Type Iii ◽  
Target Animal

The type III secretion (T3S) pathway allows bacteria to inject effector proteins into the cytosol of target animal or plant cells. T3S systems evolved into seven families that were distributed among Gram-negative bacteria by horizontal gene transfer. There are probably a few hundred effectors interfering with control and signaling in eukaryotic cells and offering a wealth of new tools to cell biologists.

scholarly journals Role of Autocleavage in the Function of a Type III Secretion Specificity Switch Protein in Salmonella enterica Serovar Typhimurium

mBio ◽  
2015 ◽  
Vol 6 (5) ◽  
Author(s):  
Julia V. Monjarás Feria ◽  
Matthew D. Lefebre ◽  
York-Dieter Stierhof ◽  
Jorge E. Galán ◽  
Samuel Wagner
Keyword(s):  
Host Cell ◽  
Type Iii Secretion ◽  
Effector Proteins ◽  
Switching Function ◽  
Gram Negative Bacteria ◽  
Wild Type ◽  
Gram Negative ◽  
Type Iii ◽  
Autocatalytic Cleavage ◽  
Serovar Typhimurium

ABSTRACTType III secretion systems (T3SSs) are multiprotein machines employed by many Gram-negative bacteria to inject bacterial effector proteins into eukaryotic host cells to promote bacterial survival and colonization. The core unit of T3SSs is the needle complex, a supramolecular structure that mediates the passage of the secreted proteins through the bacterial envelope. A distinct feature of the T3SS is that protein export occurs in a strictly hierarchical manner in which proteins destined to form the needle complex filament and associated structures are secreted first, followed by the secretion of effectors and the proteins that will facilitate their translocation through the target host cell membrane. The secretion hierarchy is established by complex mechanisms that involve several T3SS-associated components, including the “switch protein,” a highly conserved, inner membrane protease that undergoes autocatalytic cleavage. It has been proposed that the autocleavage of the switch protein is the trigger for substrate switching. We show here that autocleavage of theSalmonella entericaserovar Typhimurium switch protein SpaS is an unregulated process that occurs after its folding and before its incorporation into the needle complex. Needle complexes assembled with a precleaved form of SpaS function in a manner indistinguishable from that of the wild-type form. Furthermore, an engineered mutant of SpaS that is processed by an external protease also displays wild-type function. These results demonstrate that the cleavage eventper sedoes not provide a signal for substrate switching but support the hypothesis that cleavage allows the proper conformation of SpaS to render it competent for its switching function.IMPORTANCEBacterial interaction with eukaryotic hosts often involves complex molecular machines for targeted delivery of bacterial effector proteins. One such machine, the type III secretion system of some Gram-negative bacteria, serves to inject a multitude of structurally diverse bacterial proteins into the host cell. Critical to the function of these systems is their ability to secrete proteins in a strict hierarchical order, but it is unclear how the mechanism of switching works. Central to the switching mechanism is a highly conserved inner membrane protease that undergoes autocatalytic cleavage. Although it has been suggested previously that the autocleavage event is the trigger for substrate switching, we show here that this is not the case. Rather, our results show that cleavage allows the proper conformation of the protein to render it competent for its switching function. These findings may help develop inhibitors of type III secretion machines that offer novel therapeutic avenues to treat various infectious diseases.

scholarly journals Characterization of the Ruler Protein Interaction Interface on the Substrate Specificity Switch Protein in the Yersinia Type III Secretion System

2016 ◽  
Vol 292 (8) ◽  
pp. 3299-3311 ◽  
Author(s):  
Oanh Ho ◽  
Per Rogne ◽  
Tomas Edgren ◽  
Hans Wolf-Watz ◽  
Frédéric H. Login ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Type Iii ◽  
Binding Interface ◽  
Interaction Interface

Many pathogenic Gram-negative bacteria use the type III secretion system (T3SS) to deliver effector proteins into eukaryotic host cells. In Yersinia, the switch to secretion of effector proteins is induced first after intimate contact between the bacterium and its eukaryotic target cell has been established, and the T3SS proteins YscP and YscU play a central role in this process. Here we identify the molecular details of the YscP binding site on YscU by means of nuclear magnetic resonance (NMR) spectroscopy. The binding interface is centered on the C-terminal domain of YscU. Disrupting the YscU-YscP interaction by introducing point mutations at the interaction interface significantly reduced the secretion of effector proteins and HeLa cell cytotoxicity. Interestingly, the binding of YscP to the slowly self-cleaving YscU variant P264A conferred significant protection against autoproteolysis. The YscP-mediated inhibition of YscU autoproteolysis suggests that the cleavage event may act as a timing switch in the regulation of early versus late T3SS substrates. We also show that YscUC binds to the inner rod protein YscI with a dissociation constant (Kd) of 3.8 μm and with 1:1 stoichiometry. The significant similarity among different members of the YscU, YscP, and YscI families suggests that the protein-protein interactions discussed in this study are also relevant for other T3SS-containing Gram-negative bacteria.

scholarly journals Interactions of the Transmembrane Polymeric Rings of the Salmonella enterica Serovar Typhimurium Type III Secretion System

mBio ◽  
2010 ◽  
Vol 1 (3) ◽  
Author(s):  
Sarah Sanowar ◽  
Pragya Singh ◽  
Richard A. Pfuetzner ◽  
Ingemar André ◽  
Hongjin Zheng ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Effector Proteins ◽  
Carboxyl Terminus ◽  
Gram Negative Bacteria ◽  
Secretion Systems ◽  
Gram Negative ◽  
Type Iii ◽  
Serovar Typhimurium ◽  
Cross Links ◽  
And Function

ABSTRACT The type III secretion system (T3SS) is an interspecies protein transport machine that plays a major role in interactions of Gram-negative bacteria with animals and plants by delivering bacterial effector proteins into host cells. T3SSs span both membranes of Gram-negative bacteria by forming a structure of connected oligomeric rings termed the needle complex (NC). Here, the localization of subunits in the Salmonella enterica serovar Typhimurium T3SS NC were probed via mass spectrometry-assisted identification of chemical cross-links in intact NC preparations. Cross-links between amino acids near the amino terminus of the outer membrane ring component InvG and the carboxyl terminus of the inner membrane ring component PrgH and between the two inner membrane components PrgH and PrgK allowed for spatial localization of the three ring components within the electron density map structures of NCs. Mutational and biochemical analysis demonstrated that the amino terminus of InvG and the carboxyl terminus of PrgH play a critical role in the assembly and function of the T3SS apparatus. Analysis of an InvG mutant indicates that the structure of the InvG oligomer can affect the switching of the T3SS substrate to translocon and effector components. This study provides insights into how structural organization of needle complex base components promotes T3SS assembly and function. IMPORTANCE Many biological macromolecular complexes are composed of symmetrical homomers, which assemble into larger structures. Some complexes, such as secretion systems, span biological membranes, forming hydrophilic domains to move substrates across lipid bilayers. Type III secretion systems (T3SSs) deliver bacterial effector proteins directly to the host cell cytoplasm and allow for critical interactions between many Gram-negative pathogenic bacterial species and their hosts. Progress has been made towards the goal of determining the three-dimensional structure of the secretion apparatus by determination of high-resolution crystal structures of individual protein subunits and low-resolution models of the assembly, using reconstructions of cryoelectron microscopy images. However, a more refined picture of the localization of periplasmic ring structures within the assembly and their interactions has only recently begun to emerge. This work localizes T3SS transmembrane rings and identifies structural elements that affect substrate switching and are essential to the assembly of components that are inserted into host cell membranes.

scholarly journals Pseudomonas syringae Strains Naturally Lacking the Classical P. syringae hrp/hrc Locus Are Common Leaf Colonizers Equipped with an Atypical Type III Secretion System

2010 ◽  
Vol 23 (2) ◽  
pp. 198-210 ◽  
Author(s):  
Christopher R. Clarke ◽  
Rongman Cai ◽  
David J. Studholme ◽  
David S. Guttman ◽  
Boris A. Vinatzer
Keyword(s):  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Plant Cells ◽  
Type Iii Secretion System ◽  
Ice Nucleation ◽  
Secretion System ◽  
Effector Proteins ◽  
Population Densities ◽  
Type Iii ◽  
Effector Genes

Pseudomonas syringae is best known as a plant pathogen that causes disease by translocating immune-suppressing effector proteins into plant cells through a type III secretion system (T3SS). However, P. syringae strains belonging to a newly described phylogenetic subgroup (group 2c) are missing the canonical P. syringae hrp/hrc cluster coding for a T3SS, flanking effector loci, and any close orthologue of known P. syringae effectors. Nonetheless, P. syringae group 2c strains are common leaf colonizers and grow on some tested plant species to population densities higher than those obtained by other P. syringae strains on nonhost species. Moreover, group 2c strains have genes necessary for the production of phytotoxins, have an ice nucleation gene, and, most interestingly, contain a novel hrp/hrc cluster, which is only distantly related to the canonical P. syringae hrp/hrc cluster. This hrp/hrc cluster appears to encode a functional T3SS although the genes hrpK and hrpS, present in the classical P. syringae hrp/hrc cluster, are missing. The genome sequence of a representative group 2c strain also revealed distant orthologues of the P. syringae effector genes avrE1 and hopM1 and the P. aeruginosa effector genes exoU and exoY. A putative life cycle for group 2c P. syringae is discussed.

scholarly journals Developing Cyclic Peptomers as Broad-Spectrum Gram negative Bacterial Type III Secretion System Inhibitors

2020 ◽  
Author(s):  
Hanh N. Lam ◽  
Tannia Lau ◽  
Adam Lentz ◽  
Jessica Sherry ◽  
Alejandro Cabrera-Cortez ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Chlamydia Trachomatis ◽  
Broad Spectrum ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Type Iii ◽  
Bacterial Type

ABSTRACTAntibiotic resistant bacteria are an emerging global health threat. New antimicrobials are urgently needed. The injectisome type III secretion system (T3SS), required by dozens of Gram-negative bacteria for virulence but largely absent from non-pathogenic bacteria, is an attractive antimicrobial target. We previously identified synthetic cyclic peptomers, inspired by the natural product phepropeptin D, that inhibit protein secretion through the Yersinia Ysc and Pseudomonas aeruginosa Psc T3SSs, but do not inhibit bacterial growth. Here we describe identification of an isomer, 4EpDN, that is two-fold more potent (IC50 4 μM) than its parental compound. Furthermore, 4EpDN inhibited the Yersinia Ysa and the Salmonella SPI-1 T3SSs, suggesting that this cyclic peptomer has broad efficacy against evolutionarily distant injectisome T3SSs. Indeed, 4EpDN strongly inhibited intracellular growth of Chlamydia trachomatis in HeLa cells, which requires the T3SS. 4EpDN did not inhibit the unrelated Twin arginine translocation (Tat) system, nor did it impact T3SS gene transcription. Moreover, although the injectisome and flagellar T3SSs are evolutionarily and structurally related, the 4EpDN cyclic peptomer did not inhibit secretion of substrates through the Salmonella flagellar T3SS, indicating that cyclic peptomers broadly but specifically target the injestisome T3SS. 4EpDN reduced the number of T3SS basal bodies detected on the surface of Y. enterocolitica, as visualized using a fluorescent derivative of YscD, an inner membrane ring with low homology to flagellar protein FliG. Collectively, these data suggest that cyclic peptomers specifically inhibit the injectisome T3SS from a variety of Gram-negative bacteria, possibly by preventing complete T3SS assembly.IMPORTANCETraditional antibiotics target both pathogenic and commensal bacteria, resulting in a disruption of the microbiota, which in turn is tied to a number of acute and chronic diseases. The bacterial type III secretion system (T3SS) is an appendage used by many bacterial pathogens to establish infection, but is largely absent from commensal members of the microbiota. In this study, we identify a new derivative of the cyclic peptomer class of T3SS inhibitors. These compounds inhibit the T3SS of the nosocomial ESKAPE pathogen Pseudomonas aeruginosa and enteropathogenic Yersinia and Salmonella. The impact of cyclic peptomers is specific to the T3SS, as other bacterial secretory systems are unaffected. Importantly, cyclic peptomers completely block replication of Chlamydia trachomatis, the causative agent of genital, eye, and lung infections, in human cells, a process that requires the T3SS. Therefore, cyclic peptomers represent promising virulence blockers that can specifically disarm a broad spectrum of Gram-negative pathogens.

scholarly journals Horizontal gene transfer of a genetic island encoding a type III secretion system distributed inVibrio cholerae

2013 ◽  
Vol 57 (5) ◽  
pp. 334-339 ◽  
Author(s):  
Masatomo Morita ◽  
Shouji Yamamoto ◽  
Hirotaka Hiyoshi ◽  
Toshio Kodama ◽  
Masatoshi Okura ◽  
...  
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Type Iii

scholarly journals Pseudomonas syringae HrpP Is a Type III Secretion Substrate Specificity Switch Domain Protein That Is Translocated into Plant Cells but Functions Atypically for a Substrate-Switching Protein

2009 ◽  
Vol 191 (9) ◽  
pp. 3120-3131 ◽  
Author(s):  
Joanne E. Morello ◽  
Alan Collmer
Keyword(s):  
Substrate Specificity ◽  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Fluorescent Protein ◽  
Plant Cells ◽  
Effector Proteins ◽  
Type Iii ◽  
Native Promoter ◽  
C Terminus ◽  
Green Fluorescent

ABSTRACT Pseudomonas syringae delivers virulence effector proteins into plant cells via an Hrp1 type III secretion system (T3SS). P. syringae pv. tomato DC3000 HrpP has a C-terminal, putative T3SS substrate specificity switch domain, like Yersinia YscP. A ΔhrpP DC3000 mutant could not cause disease in tomato or elicit a hypersensitive response (HR) in tobacco, but the HR could be restored by expression of HrpP in trans. Though HrpP is a relatively divergent protein in the T3SS of different P. syringae pathovars, hrpP from P. syringae pv. syringae 61 and P. syringae pv. phaseolicola 1448A restored HR elicitation and pathogenicity to DC3000 ΔhrpP. HrpP was translocated into Nicotiana benthamiana cells via the DC3000 T3SS when expressed from its native promoter, but it was not secreted in culture. N- and C-terminal truncations of HrpP were tested for their ability to be translocated and to restore HR elicitation activity to the ΔhrpP mutant. No N-terminal truncation completely abolished translocation, implying that HrpP has an atypical T3SS translocation signal. Deleting more than 20 amino acids from the C terminus abolished the ability to restore HR elicitation. HrpP fused to green fluorescent protein was no longer translocated but could restore HR elicitation activity to the ΔhrpP mutant, suggesting that translocation is not essential for the function of HrpP. No T3SS substrates were detectably secreted by DC3000 ΔhrpP except the pilin subunit HrpA, which unexpectedly was secreted poorly. HrpP may function somewhat differently than YscP because the P. syringae T3SS pilus likely varies in length due to differing plant cell walls.

scholarly journals Genome-Wide Identification of a Large Repertoire of Ralstonia solanacearum Type III Effector Proteins by a New Functional Screen

2010 ◽  
Vol 23 (3) ◽  
pp. 251-262 ◽  
Author(s):  
Takafumi Mukaihara ◽  
Naoyuki Tamura ◽  
Masaki Iwabuchi
Keyword(s):  
Ralstonia Solanacearum ◽  
Type Iii Secretion ◽  
Plant Cells ◽  
Amino Acid Sequences ◽  
Effector Proteins ◽  
Type Iii ◽  
Functional Screen ◽  
Genome Wide ◽  
Large Repertoire ◽  
Insertion Mutants

The gram-negative plant-pathogenic bacterium Ralstonia solanacearum utilizes the hypersensitive response and pathogenicity (Hrp) type III secretion system (T3SS) to cause disease in plants. To determine the entire repertoire of effector proteins possessed by R. solanacearum RS1000, we constructed a transposon carrying a calmodulin-dependent adenylate cyclase reporter that can be used to specifically detect rip (Ralstonia protein injected into plant cells) genes by monitoring the cAMP level in plant leaves inoculated with insertion mutants. From the new functional screen using this transposon, we identified 38 new Rip proteins translocated into plant cells via the Hrp T3SS. In addition, most of the 34 known effectors of RS1000 could be detected by the screen, except for three effectors that appear to be small in size or only weakly expressed. Finally, we identified 72 Rips in RS1000, which include 68 effector proteins classified into over 50 families and four extracellular components of the Hrp T3SS. Interestingly, one-third of the effectors are specific to R. solanacearum. Many effector proteins contain various repeated amino acid sequences or known enzyme motifs. We also show that most of the R. solanacearum effector proteins, but not Hrp extracellular components, require an Hrp-associated protein, HpaB, for their effective translocation into plant cells.

scholarly journals Identification of Pseudomonas syringae pv. syringae 61 Type III Secretion System Hrp Proteins That Can Travel the Type III Pathway and Contribute to the Translocation of Effector Proteins into Plant Cells

2007 ◽  
Vol 189 (15) ◽  
pp. 5773-5778 ◽  
Author(s):  
Adela R. Ramos ◽  
Joanne E. Morello ◽  
Sandeep Ravindran ◽  
Wen-Ling Deng ◽  
Hsiou-Chen Huang ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Hypersensitive Response ◽  
Type Iii Secretion ◽  
Plant Cells ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Type Iii

ABSTRACT Pseudomonas syringae translocates effector proteins into plant cells via an Hrp1 type III secretion system (T3SS). T3SS components HrpB, HrpD, HrpF, and HrpP were shown to be pathway substrates and to contribute to elicitation of the plant hypersensitive response and to translocation and secretion of the model effector AvrPto1.

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