Critical Role of ASC Inflammasomes and Bacterial Type IV Secretion System in Caspase-1 Activation and Host Innate Resistance toBrucella abortusInfection

ABSTRACT We have previously shown that Legionella pneumophila induces caspase 3-dependent apoptosis in mammalian cells during early stages of infection. In this report, we show that nine L. pneumophila strains with mutations in the dotA, dotDCB, icmT, icmGCD, and icmJB loci are completely defective in the induction of apoptosis, in addition to their severe defects in intracellular replication and pore formation-mediated cytotoxicity. Importantly, all nine dot/icm mutants were complemented for all their defective phenotypes with the respective wild-type loci. We show that the role of the Dot/Icm type IV secretion system in the induction of apoptosis is independent of the RtxA toxin, the dot/icm-regulated pore-forming toxin, and the type II secretion system. However, the pore-forming toxin, which is triggered upon entry into the postexponential growth phase, enhances the ability of L. pneumophila to induce apoptosis. Our data provide the first example of the role of a type IV secretion system of a bacterial pathogen in the induction of apoptosis in the host cell.

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Role of Cal, the colicin A lysis protein, in two steps of colicin A release and in the interaction with colicin A–porin complexes

Microbiology ◽

10.1099/mic.0.27160-0 ◽

2004 ◽

Vol 150 (11) ◽

pp. 3867-3875 ◽

Cited By ~ 6

Author(s):

Danièle Cavard

Keyword(s):

Escherichia Coli ◽

Insoluble Fraction ◽

Cysteine Residue ◽

Secretion System ◽

Type Iv Secretion ◽

Type Iv Secretion System ◽

Temperature Sensitive ◽

Type Iv ◽

Definition Of

Release of colicin A was studied in Escherichia coli cells that differed in expressing the colicin A lysis protein (Cal). Pools of released and unreleased colicin A were harvested throughout colicin A induction. The amount of colicin A in each pool varied with the time of induction, allowing the definition of two sequential steps in colicin A release, one of which was dependent on Cal. Each step of colicin A release was differently affected in cells containing Cal mutants in which the N-terminal cysteine residue was substituted by either proline or threonine, preventing them from being acylated and matured. These Cal mutants were only observed in degP cells, indicating that the DegP protease cleaved the unacylated precursor of Cal. Cal was found in the insoluble fraction of the pools of released and unreleased colicin A together with the hetero-oligomers of colicin A and porins (colicins Au). The biogenesis of colicins Au was studied in temperature-sensitive secA and secY strains and found to be Sec-independent, indicating that they are formed by newly synthesized colicin A binding to mature porins already incorporated in the outer membrane. Cal is a lipoprotein similar to VirB7, a constituent of the type IV secretion system. It would interact with colicins Au to constitute the colicin A export machinery.

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Reassessing the Role of DotF in the Legionella pneumophila Type IV Secretion System

PLoS ONE ◽

10.1371/journal.pone.0065529 ◽

2013 ◽

Vol 8 (6) ◽

pp. e65529 ◽

Cited By ~ 9

Author(s):

Molly C. Sutherland ◽

Kelsey A. Binder ◽

Phillip Y. Cualing ◽

Joseph P. Vogel

Keyword(s):

Legionella Pneumophila ◽

Secretion System ◽

Type Iv Secretion ◽

Type Iv Secretion System ◽

Type Iv

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Host manipulation by bacterial type III and type IV secretion system effector proteases

Cellular Microbiology ◽

10.1111/cmi.13384 ◽

2021 ◽

Author(s):

Flávia Viana ◽

Shruthi Sachidanandan Peringathara ◽

Arshad Rizvi ◽

Gunnar N. Schroeder

Keyword(s):

Secretion System ◽

Type Iv Secretion ◽

Type Iv Secretion System ◽

Host Manipulation ◽

Type Iii ◽

Type Iv ◽

Bacterial Type

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In vivostructures of theHelicobacter pylori cagtype IV secretion system

10.1101/195685 ◽

2017 ◽

Cited By ~ 1

Author(s):

Yi-Wei Chang ◽

Carrie L. Shaffer ◽

Lee A. Rettberg ◽

Debnath Ghosal ◽

Grant J. Jensen

Keyword(s):

Secretion System ◽

Type Iv Secretion ◽

Host Cells ◽

Type Iv Secretion System ◽

Molecular Architecture ◽

Type Iv ◽

H Pylori ◽

Electron Cryotomography ◽

Rod Structures ◽

Bacterial Type

SummaryThe bacterial type IV secretion system (T4SS) is a versatile nanomachine that translocates diverse effector molecules between microbes and into eukaryotic cells. Using electron cryotomography, here we reveal the molecular architecture of the cancer-associatedHelicobacter pylori cagT4SS. Although most components are unique toH. pylori, thecagT4SS exhibits remarkable architectural similarity to previously studied T4SSs. WhenH. pyloriencounters host cells, however, the bacterium elaborates rigid, membranous tubes perforated by lateral ports. Dense, pilus-like rod structures extending from the inner membrane were also observed. We propose that the membrane tubes assemble out of the T4SS and are the delivery system forcagT4SS cargo. These studies reveal the architecture of a dynamic molecular machine that evolved to function in the human gastric niche.

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Implication of the Type IV Secretion System in the Pathogenicity of Vibrio tapetis, the Etiological Agent of Brown Ring Disease Affecting the Manila Clam Ruditapes philippinarum

Frontiers in Cellular and Infection Microbiology ◽

10.3389/fcimb.2021.634427 ◽

2021 ◽

Vol 11 ◽

Author(s):

Alexandra Rahmani ◽

François Delavat ◽

Christophe Lambert ◽

Nelly Le Goic ◽

Eric Dabas ◽

...

Keyword(s):

Ruditapes Philippinarum ◽

Secretion System ◽

Infection Process ◽

Type Iv Secretion ◽

Manila Clam ◽

Type Iv Secretion System ◽

Type Iv ◽

T4ss Gene ◽

Brown Ring Disease

Vibrio tapetis is a Gram-negative bacterium that causes infections of mollusk bivalves and fish. The Brown Ring Disease (BRD) is an infection caused by V. tapetis that primarily affects the Manila clam Ruditapes philippinarum. Recent studies have shown that a type IV secretion system (T4SS) gene cluster is exclusively found in strains of V. tapetis pathogenic to clams. However, whether the T4SS is implicated or not during the infection process remains unknown. The aim of this study was to create and characterize a V. tapetis T4SS null mutant, obtained by a near-complete deletion of the virB4 gene, in order to determine the role of T4SS in the development of BRD. This study demonstrated that the T4SS is neither responsible for the loss of hemocyte adhesion capacities, nor for the decrease of the lysosomal activity during BRD. Nevertheless, we observed a 50% decrease of the BRD prevalence and a decrease of mortality dynamics with the ΔvirB4 mutant. This work demonstrates that the T4SS of V. tapetis plays an important role in the development of BRD in the Manila clam.

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