scholarly journals Structural Insights of Shigella Translocator IpaB and Its Chaperone IpgC in Solution

2021 ◽  
Vol 11 ◽  
Author(s):  
Mariana L. Ferrari ◽  
Spyridoula N. Charova ◽  
Philippe J. Sansonetti ◽  
Efstratios Mylonas ◽  
Anastasia D. Gazi
Keyword(s):  
Host Cell ◽  
Type Iii Secretion ◽  
Secretion Systems ◽  
Host Cell Membrane ◽  
Type Iii ◽  
X Ray Scattering ◽  
Type Iii Secretion Systems ◽  
Key Factor ◽  
Bacterial Cytoplasm ◽  
Structural Insights

Bacterial Type III Secretion Systems (T3SSs) are specialized multicomponent nanomachines that mediate the transport of proteins either to extracellular locations or deliver Type III Secretion effectors directly into eukaryotic host cell cytoplasm. Shigella, the causing agent of bacillary dysentery or shigellosis, bears a set of T3SS proteins termed translocators that form a pore in the host cell membrane. IpaB, the major translocator of the system, is a key factor in promoting Shigella pathogenicity. Prior to secretion, IpaB is maintained inside the bacterial cytoplasm in a secretion competent folding state thanks to its cognate chaperone IpgC. IpgC couples T3SS activation to transcription of effector genes through its binding to MxiE, probably after the delivery of IpaB to the secretion export gate. Small Angle X-ray Scattering experiments and modeling reveal that IpgC is found in different oligomeric states in solution, as it forms a stable heterodimer with full-length IpaB in contrast to an aggregation-prone homodimer in the absence of the translocator. These results support a stoichiometry of interaction 1:1 in the IpgC/IpaB complex and the multi-functional nature of IpgC under different T3SS states.

scholarly journals Tandem Translation Generates a Chaperone for the Salmonella Type III Secretion System Protein SsaQ

2011 ◽  
Vol 286 (41) ◽  
pp. 36098-36107 ◽  
Author(s):  
Xiu-Jun Yu ◽  
Mei Liu ◽  
Steve Matthews ◽  
David W. Holden
Keyword(s):  
Type Iii Secretion ◽  
Ex Vivo ◽  
Eukaryotic Cell ◽  
Effector Proteins ◽  
Secretion Systems ◽  
Type Iii ◽  
Type Iii Secretion Systems ◽  
Function Loss ◽  
Bacterial Cytoplasm

Type III secretion systems (T3SSs) of bacterial pathogens involve the assembly of a surface-localized needle complex, through which translocon proteins are secreted to form a pore in the eukaryotic cell membrane. This enables the transfer of effector proteins from the bacterial cytoplasm to the host cell. A structure known as the C-ring is thought to have a crucial role in secretion by acting as a cytoplasmic sorting platform at the base of the T3SS. Here, we studied SsaQ, an FliN-like putative C-ring protein of the Salmonella pathogenicity island 2 (SPI-2)-encoded T3SS. ssaQ produces two proteins by tandem translation: a long form (SsaQL) composed of 322 amino acids and a shorter protein (SsaQS) comprising the C-terminal 106 residues of SsaQL. SsaQL is essential for SPI-2 T3SS function. Loss of SsaQS impairs the function of the T3SS both ex vivo and in vivo. SsaQS binds to its corresponding region within SsaQL and stabilizes the larger protein. Therefore, SsaQL function is optimized by a novel chaperone-like protein, produced by tandem translation from its own mRNA species.

scholarly journals Type III Protein Secretion Systems in Bacterial Pathogens of Animals and Plants

1998 ◽  
Vol 62 (2) ◽  
pp. 379-433 ◽  
Author(s):  
Christoph J. Hueck
Keyword(s):  
Host Cell ◽  
Protein Secretion ◽  
Type Iii Secretion ◽  
Plant Pathogens ◽  
Host Cells ◽  
Secretion Systems ◽  
Type Iii ◽  
Type Iii Secretion Systems ◽  
Animal Pathogens ◽  
Type Iii Protein Secretion

SUMMARY Various gram-negative animal and plant pathogens use a novel, sec-independent protein secretion system as a basic virulence mechanism. It is becoming increasingly clear that these so-called type III secretion systems inject (translocate) proteins into the cytosol of eukaryotic cells, where the translocated proteins facilitate bacterial pathogenesis by specifically interfering with host cell signal transduction and other cellular processes. Accordingly, some type III secretion systems are activated by bacterial contact with host cell surfaces. Individual type III secretion systems direct the secretion and translocation of a variety of unrelated proteins, which account for species-specific pathogenesis phenotypes. In contrast to the secreted virulence factors, most of the 15 to 20 membrane-associated proteins which constitute the type III secretion apparatus are conserved among different pathogens. Most of the inner membrane components of the type III secretion apparatus show additional homologies to flagellar biosynthetic proteins, while a conserved outer membrane factor is similar to secretins from type II and other secretion pathways. Structurally conserved chaperones which specifically bind to individual secreted proteins play an important role in type III protein secretion, apparently by preventing premature interactions of the secreted factors with other proteins. The genes encoding type III secretion systems are clustered, and various pieces of evidence suggest that these systems have been acquired by horizontal genetic transfer during evolution. Expression of type III secretion systems is coordinately regulated in response to host environmental stimuli by networks of transcription factors. This review comprises a comparison of the structure, function, regulation, and impact on host cells of the type III secretion systems in the animal pathogens Yersinia spp., Pseudomonas aeruginosa, Shigella flexneri, Salmonella typhimurium, enteropathogenic Escherichia coli, and Chlamydia spp. and the plant pathogens Pseudomonas syringae, Erwinia spp., Ralstonia solanacearum, Xanthomonas campestris, and Rhizobium spp.

scholarly journals Type III Secretion Systems and Disease

2007 ◽  
Vol 20 (4) ◽  
pp. 535-549 ◽  
Author(s):  
Bryan Coburn ◽  
Inna Sekirov ◽  
B. Brett Finlay
Keyword(s):  
Host Cell ◽  
Type Iii Secretion ◽  
Human Infection ◽  
Effector Proteins ◽  
Secretion Systems ◽  
Barrier Dysfunction ◽  
Type Iii ◽  
Extracellular Milieu ◽  
Host Cell Cytoplasm ◽  
Type Iii Secretion Systems

SUMMARY Type III secretion systems (T3SSs) are complex bacterial structures that provide gram-negative pathogens with a unique virulence mechanism enabling them to inject bacterial effector proteins directly into the host cell cytoplasm, bypassing the extracellular milieu. Although the effector proteins vary among different T3SS pathogens, common pathogenic mechanisms emerge, including interference with the host cell cytoskeleton to promote attachment and invasion, interference with cellular trafficking processes, cytotoxicity and barrier dysfunction, and immune system subversion. The activity of the T3SSs correlates closely with infection progression and outcome, both in animal models and in human infection. Therefore, to facilitate patient care and improve outcomes, it is important to understand the T3SS-mediated virulence processes and to target T3SSs in therapeutic and prophylactic development efforts.

scholarly journals The Extreme C Terminus of Shigella flexneri IpaB Is Required for Regulation of Type III Secretion, Needle Tip Composition, and Binding

2010 ◽  
Vol 78 (4) ◽  
pp. 1682-1691 ◽  
Author(s):  
A. Dorothea Roehrich ◽  
Isabel Martinez-Argudo ◽  
Steven Johnson ◽  
Ariel J. Blocker ◽  
Andreas K. J. Veenendaal
Keyword(s):  
Host Cell ◽  
Type Iii Secretion ◽  
Physical Contact ◽  
Host Cells ◽  
Cell Contact ◽  
Virulence Determinants ◽  
Secretion Systems ◽  
Host Cell Membrane ◽  
Type Iii ◽  
C Terminus

ABSTRACT Type III secretion systems (T3SSs) are widely distributed virulence determinants of Gram-negative bacteria. They translocate bacterial proteins into host cells to manipulate them during infection. The Shigella T3SS consists of a cytoplasmic bulb, a transmembrane region, and a hollow needle protruding from the bacterial surface. The distal tip of mature, quiescent needles is composed of IpaD, which is topped by IpaB. Physical contact with host cells initiates secretion and leads to assembly of a pore, formed by IpaB and IpaC, in the host cell membrane, through which other virulence effector proteins may be translocated. IpaB is required for regulation of secretion and may be the host cell sensor. However, its mode of needle association is unknown. Here, we show that deletion of 3 or 9 residues at the C terminus of IpaB leads to fast constitutive secretion of late effectors, as observed in a ΔipaB strain. Like the ΔipaB mutant, mutants with C-terminal mutations also display hyperadhesion. However, unlike the ΔipaB mutant, they are still invasive and able to lyse the internalization vacuole with nearly wild-type efficiency. Finally, the mutant proteins show decreased association with needles and increased recruitment of IpaC. Taken together, these data support the notion that the state of the tip complex regulates secretion. We propose a model where the quiescent needle tip has an “off” conformation that turns “on” upon host cell contact. Our mutants may adopt a partially “on” conformation that activates secretion and is capable of recruiting some IpaC to insert pores into host cell membranes and allow invasion.

scholarly journals Coiled-Coil Domain of Enteropathogenic Escherichia coli Type III Secreted Protein EspD Is Involved in EspA Filament-Mediated Cell Attachment and Hemolysis

2001 ◽  
Vol 69 (6) ◽  
pp. 4055-4064 ◽  
Author(s):  
Sarah J. Daniell ◽  
Robin M. Delahay ◽  
Robert K. Shaw ◽  
Elizabeth L. Hartland ◽  
Mark J. Pallen ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Host Cell ◽  
Type Iii Secretion ◽  
Plant Pathogens ◽  
Cell Attachment ◽  
Coiled Coil ◽  
Secreted Protein ◽  
Secretion Systems ◽  
Host Cell Membrane ◽  
Type Iii

ABSTRACT Many animal and plant pathogens use type III secretion systems to secrete key virulence factors, some directly into the host cell cytosol. However, the basis for such protein translocation has yet to be fully elucidated for any type III secretion system. We have previously shown that in enteropathogenic and enterohemorrhagicEscherichia coli the type III secreted protein EspA is assembled into a filamentous organelle that attaches the bacterium to the plasma membrane of the host cell. Formation of EspA filaments is dependent on expression of another type III secreted protein, EspD. The carboxy terminus of EspD, a protein involved in formation of the translocation pore in the host cell membrane, is predicted to adopt a coiled-coil conformation with 99% probability. Here, we demonstrate EspD-EspD protein interaction using the yeast two-hybrid system and column overlays. Nonconservative triple amino acid substitutions of specific EspD carboxy-terminal residues generated an enteropathogenicE. coli mutant that was attenuated in its ability to induce attaching and effacing lesions on HEp-2 cells. Although the mutation had no effect on EspA filament biosynthesis, it also resulted in reduced binding to and reduced hemolysis of red blood cells. These results segregate, for the first time, functional domains of EspD that control EspA filament length from EspD-mediated cell attachment and pore formation.

scholarly journals The Vibrio parahaemolyticus Type III Secretion Systems manipulate host cell MAPK for critical steps in pathogenesis

2010 ◽  
Vol 10 (1) ◽  
pp. 329 ◽  
Author(s):  
Ksenia Matlawska-Wasowska ◽  
Rebecca Finn ◽  
Ana Mustel ◽  
Conor P O'Byrne ◽  
Alan W Baird ◽  
...  
Keyword(s):  
Host Cell ◽  
Type Iii Secretion ◽  
Vibrio Parahaemolyticus ◽  
Secretion Systems ◽  
Type Iii ◽  
Type Iii Secretion Systems

scholarly journals Domains of the Shigella flexneri Type III Secretion System IpaB Protein Involved in Secretion Regulation

2010 ◽  
Vol 78 (12) ◽  
pp. 4999-5010 ◽  
Author(s):  
Da-Kang Shen ◽  
Saroj Saurya ◽  
Carolin Wagner ◽  
Hiroaki Nishioka ◽  
Ariel J. Blocker
Keyword(s):  
Host Cell ◽  
Type Iii Secretion ◽  
Effector Proteins ◽  
Physical Contact ◽  
Host Cells ◽  
Cell Contact ◽  
Secretion Systems ◽  
Host Cell Membrane ◽  
Type Iii ◽  
Secretion Regulation

ABSTRACT Type III secretion systems (T3SSs) are key determinants of virulence in many Gram-negative bacterial pathogens. Upon cell contact, they inject effector proteins directly into eukaryotic cells through a needle protruding from the bacterial surface. Host cell sensing occurs through a distal needle “tip complex,” but how this occurs is not understood. The tip complex of quiescent needles is composed of IpaD, which is topped by IpaB. Physical contact with host cells initiates secretion and leads to assembly of a pore, formed by IpaB and IpaC, in the host cell membrane, through which other virulence effector proteins may be translocated. IpaB is required for regulation of secretion and may be the host cell sensor. It binds needles via its extreme C-terminal coiled coil, thereby likely positioning a large domain containing its hydrophobic regions at the distal tips of needles. In this study, we used short deletion mutants within this domain to search for regions of IpaB involved in secretion regulation. This identified two regions, amino acids 227 to 236 and 297 to 306, the presence of which are required for maintenance of IpaB at the needle tip, secretion regulation, and normal pore formation but not invasion. We therefore propose that removal of either of these regions leads to an inability to block secretion prior to reception of the activation signal and/or a defect in host cell sensing.

scholarly journals Type III secretion systems and the evolution of mutualistic endosymbiosis

2002 ◽  
Vol 99 (19) ◽  
pp. 12397-12402 ◽  
Author(s):  
C. Dale ◽  
G. R. Plague ◽  
B. Wang ◽  
H. Ochman ◽  
N. A. Moran
Keyword(s):  
Type Iii Secretion ◽  
Secretion Systems ◽  
Type Iii ◽  
Type Iii Secretion Systems

scholarly journals Small-Molecule Type III Secretion System Inhibitors Block Assembly of the Shigella Type III Secreton

2008 ◽  
Vol 191 (2) ◽  
pp. 563-570 ◽  
Author(s):  
Andreas K. J. Veenendaal ◽  
Charlotta Sundin ◽  
Ariel J. Blocker
Keyword(s):  
Type Iii Secretion ◽  
Bacterial Infections ◽  
Shigella Flexneri ◽  
Effector Proteins ◽  
Host Cells ◽  
Incomplete Penetrance ◽  
Secretion Systems ◽  
Bacterial Surface ◽  
Type Iii ◽  
Type Iii Secretion Systems

ABSTRACT Type III secretion systems (T3SSs) are essential virulence devices for many gram-negative bacteria that are pathogenic for plants, animals, and humans. They serve to translocate virulence effector proteins directly into eukaryotic host cells. T3SSs are composed of a large cytoplasmic bulb and a transmembrane region into which a needle is embedded, protruding above the bacterial surface. The emerging antibiotic resistance of bacterial pathogens urges the development of novel strategies to fight bacterial infections. Therapeutics that rather than kill bacteria only attenuate their virulence may reduce the frequency or progress of resistance emergence. Recently, a group of salicylidene acylhydrazides were identified as inhibitors of T3SSs in Yersinia, Chlamydia, and Salmonella species. Here we show that these are also effective on the T3SS of Shigella flexneri, where they block all related forms of protein secretion so far known, as well as the epithelial cell invasion and induction of macrophage apoptosis usually demonstrated by this bacterium. Furthermore, we show the first evidence for the detrimental effect of these compounds on T3SS needle assembly, as demonstrated by increased numbers of T3S apparatuses without needles or with shorter needles. Therefore, the compounds generate a phenocopy of T3SS export apparatus mutants but with incomplete penetrance. We discuss why this would be sufficient to almost completely block the later secretion of effector proteins and how this begins to narrow the search for the molecular target of these compounds.

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