Galectin‐3, a marker for vacuole lysis by invasive pathogens |
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Authors: | Irit Paz Martin Sachse Nicolas Dupont Joelle Mounier Cecilia Cederfur Jost Enninga Hakon Leffler Francoise Poirier Marie‐Christine Prevost Frank Lafont Philippe Sansonetti |
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Institution: | 1. Unité de Pathogénie Microbienne Moléculaire, Institut Pasteur, 28 Rue du Docteur Roux, 75724 Paris, Cedex 15, France.;2. Unité INSERM 786, Institut Pasteur, 25‐28 rue du Dr Roux, Paris, Cedex 15, France.;3. Platform of Ultrastructural Microscopy, Institut Pasteur, 25‐28 rue du Dr Roux, Paris, Cedex 15, France.;4. Cellular Microbiology and Infectious Pathogeny UMR8161 (CNRS, Lille Pasteur Institute, Universities Lille 1 and Lille 2), Lille Biology Institute, Lille Pasteur Institute, Lille, France.;5. Section MIG (Microbiology Immunology Glycobiology), Institute Laboratory Medicine, Lund University, Lund, Sweden.;6. Institut Pasteur, Groupe ‘Dynamique des interactions h?te‐pathogène’, 25 rue du Dr Roux, 75724, Paris, France.;7. Laboratoire de Genetique et Developpement des Mammiferes, Institut Jacques Monod, UMR CNRS 7592, Universités Paris 6 and Paris 7, Paris, France. |
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Abstract: | Shigella bacteria invade macrophages and epithelial cells and following internalization lyse the phagosome and escape to the cytoplasm. Galectin‐3, an abundant protein in macrophages and epithelial cells, belongs to a family of beta‐galactoside‐binding proteins, the galectins, with many proposed functions in immune response, development, differentiation, cancer and infection. Galectins are synthesized as cytosolic proteins and following non‐classical secretion bind extracellular beta‐galactosides. Here we analysed the localization of galectin‐3 following entry of Shigella into the cytosol and detected a striking phenomenon. Very shortly after bacterial invasion, intracellular galectin‐3 accumulated in structures in vicinity to internalized bacteria. By using immuno‐electron microscopy analysis we identified galectin‐3 in membranes localized in the phagosome and in tubules and vesicles that derive from the endocytic pathway. We also demonstrated that the binding of galectin‐3 to host N‐acetyllactosamine‐containing glycans, was required for forming the structures. Accumulation of the structures was a type three secretion system‐dependent process. More specifically, existence of structures was strictly dependent upon lysis of the phagocytic vacuole and could be shown also by Gram‐positive Listeria and Salmonella sifA mutant. We suggest that galectin‐3‐containing structures may serve as a potential novel tool to spot vacuole lysis. |
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