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Binding of the Shigella protein IpaA to vinculin induces F-actin depolymerization
R Bourdet-Sicard1, M Rüdiger, B M Jockusch
1Unité de Pathogénie Microbienne Moléculaire, Institut Pasteur, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France.
Abstract:
Shigella flexneri, the causative agent of bacillary dysentery, enters into epithelial cells by a macropinocytic process. IpaA, a Shigella protein secreted upon cell contact, binds to the focal adhesion protein vinculin and is required for efficient bacterial uptake. IpaA was shown here to bind with high affinity to the N-terminal residues 1-265 of vinculin. Using co-sedimentation and solid-phase assays, we demonstrated that binding of IpaA to vinculin strongly increases the association of vinculin with F-actin. We also characterized a depolymerizing activity on actin filaments associated with the vinculin-IpaA complex both in vitro and in microinjected cells. We propose that the conformational change of vinculin induced by IpaA binding allows interaction of the vinculin-IpaA complex with F-actin and subsequent depolymerization of actin filaments.
Insights
Shigella flexneri uses the IpaA protein to bind vinculin, promoting bacterial entry into host cells. This interaction also affects actin filaments, aiding in bacillary dysentery pathogenesis.
Area of Science:
- Microbiology
- Cell Biology
- Biochemistry
Background:
- Shigella flexneri causes bacillary dysentery by invading epithelial cells.
- Bacterial entry often involves host cell cytoskeletal rearrangements.
- The Shigella protein IpaA is implicated in bacterial invasion.
Purpose of the Study:
- To investigate the interaction between Shigella IpaA and the host cell protein vinculin.
- To elucidate the role of the IpaA-vinculin complex in actin dynamics.
- To understand the mechanism of Shigella entry into epithelial cells.
Main Methods:
- Co-sedimentation assays to study protein binding.
- Solid-phase assays to analyze protein interactions.
- In vitro and in vivo studies using microinjected cells to observe actin dynamics.
Main Results:
- IpaA binds with high affinity to the N-terminal region of vinculin (residues 1-265).
- IpaA binding significantly enhances vinculin's association with F-actin.
- The vinculin-IpaA complex exhibits actin filament depolymerizing activity.
Conclusions:
- IpaA binding induces a conformational change in vinculin.
- This conformational change facilitates the interaction of the vinculin-IpaA complex with F-actin.
- The complex's activity on actin filaments contributes to Shigella's invasion mechanism.