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Annick Gauthier

Publications and source records attributed to Annick Gauthier.

6 recordsLinked to original sources
PubMed2006

Caminosides B-D, antimicrobial glycolipids isolated from the marine sponge Caminus sphaeroconia.

A screening program aimed at discovering inhibitors of the bacterial type III secretion system identified the MeOH extract of the Caribbean sponge Caminus sphaeroconia as an active hit in the initial assay. Bioassay-guided fractionation of the crude extract led to the isolation of caminosides A (1) to D (4), a family of antimicrobial glycolipids. The structures of the three new caminosides B (2) to D (4) have been elucidated by spectroscopic analysis.

Animals↗
PubMed2005

Transcriptional inhibitor of virulence factors in enteropathogenic Escherichia coli.

The type III secretion system (TTSS) is a key virulence mechanism of many important gram-negative bacterial pathogens. The TTSS is conserved among different bacterial pathogens, and mutations and deletions to the system significantly decrease virulence, making the TTSS an important potential therapeutic target. We have developed a high-throughput assay to search for inhibitors of the TTSS. We screened a commercial library of 20,000 small molecules for their ability to inhibit type III secretion by enteropathogenic Escherichia coli (EPEC). After discarding compounds that had no effect on secretion, inhibited bacterial growth, and/or caused degradation of EPEC-secreted proteins, the search was focused on a class of compounds that, while not direct inhibitors of type III secretion, inhibit expression of TTSS-related genes and other genes involved in virulence. This class of compounds does not affect bacterial viability or motility, indicating that it is not significantly affecting the expression of essential genes and is specific to virulence-associated genes. Transcriptional fusion assays confirmed that virulence-associated promoters were more sensitive to inhibition by this class of compounds. Overall, we have identified a class of compounds that can be used as a tool to probe the mechanism(s) that regulates virulence gene expression in EPEC.

Cell Movement↗
PubMed2003

Secretin of the enteropathogenic Escherichia coli type III secretion system requires components of the type III apparatus for assembly and localization.

At least 16 proteins are thought to be involved in forming the enteropathogenic Escherichia coli (EPEC) type III translocation apparatus which delivers virulence factors into host cells, yet their function and location have not been determined. A biochemical analysis was performed on three components: EscN, a predicted cytoplasmic ATPase; EscV, a predicted inner membrane protein; and EscC, a predicted outer membrane secretin. Wild-type EPEC and mutants constructed in these genes were fractionated by lysozyme treatment, ultracentrifugation, and selective detergent extraction. Fractionation revealed that the type III effectors Tir and EspB required a complete type III apparatus for any degree of export by EPEC, suggesting a continuous channel. Epitope-tagged EscC, EscV, and EscN were localized by fractionation, confirming computer modeling predictions for their location. Transcomplementation experiments revealed that localization of EscV and EscN was unaffected by mutations in other examined type III components. Remarkably, localization of EscC was altered in escV or escN mutants, where EscC accumulated in the periplasm. EscC was correctly localized in the escF needle component mutant, indicating that secretin localization is independent of needle formation. These data indicate that, contrary to previous indications, correct insertion and function of EscC secretin in the outer membrane depends not only on the sec-dependent secretion pathway but also on other type III apparatus components.

Adenosine Triphosphatases↗
PubMed2003

Translocated intimin receptor and its chaperone interact with ATPase of the type III secretion apparatus of enteropathogenic Escherichia coli.

Few interactions have been reported between effectors and components of the type III secretion apparatus, although many interactions have been demonstrated between type III effectors and their cognate chaperones. It is thought that chaperones may play a role in directing effectors to the type III secretion apparatus. The ATPase FliI in the flagellar assembly apparatus plays a pivotal role in interacting with other components of the apparatus and with substrates of the flagellar system. We performed experiments to determine if there were any interactions between the effector Tir and its chaperone CesT and the type III secretion apparatus of enteropathogenic Escherichia coli (EPEC). Specifically, based on analogies with the flagella system, we examined Tir-CesT interactions with the putative ATPase EscN. We showed by affinity chromatography that EscN and Tir bind CesT specifically. Tir is not necessary for CesT and EscN interactions, and EscN binds Tir specifically without its chaperone CesT. Moreover, Tir directly binds EscN, as shown via gel overlay and enzyme-linked immunosorbent assay, and coimmunoprecipitation experiments revealed that Tir interacts with EscN inside EPEC. These data provide evidence for direct interactions between a chaperone, effector, and type III component in the pathogenic type III secretion system and suggest a model for Tir translocation whereby its chaperone, CesT, brings Tir to the type III secretion apparatus by specifically interacting with the type III ATPase EscN.

Adenosine Triphosphatases↗
PubMed2002

Caminoside A, an antimicrobial glycolipid isolated from the marine sponge Caminus sphaeroconia.

Extracts of the marine sponge Caminus sphaeroconia showed potent activity in a screen for bacterial type III secretion inhibitors. Bioassay guided fractionation of the extract led to the isolation of the novel antimicrobial glycolipid caminoside A (1). The structure of caminoside A was elucidated by analysis of spectroscopic data and chemical degradation.[structure: see text]

Animals↗