Galectin-3, a marker for vacuole lysis by invasive pathogens.
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.
Paz
Irit
I
Unité de Pathogénie Microbienne Moléculaire, Institut Pasteur, 75724 Paris, Cedex 15, France.
Sachse
Martin
M
Dupont
Nicolas
N
Mounier
Joelle
J
Cederfur
Cecilia
C
Enninga
Jost
J
Leffler
Hakon
H
Poirier
Francoise
F
Prevost
Marie-Christine
MC
Lafont
Frank
F
Sansonetti
Philippe
P
D000606:Amino Sugars / Q000378:metabolism; D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004285:Dogs; D037502:Galectin 3 / Q000032:analysis*; D006801:Humans; D007425:Intracellular Membranes / Q000737:chemistry; D008087:Listeria / Q000472:pathogenicity; D051379:Mice; D016253:Microscopy, Immunoelectron; D010588:Phagosomes / Q000737:chemistry* / Q000382:microbiology*; D011134:Polysaccharides / Q000378:metabolism; D011485:Protein Binding; D012475:Salmonella / Q000472:pathogenicity; D012760:Shigella / Q000472:pathogenicity*
D000606:Amino Sugars; D015415:Biomarkers; D037502:Galectin 3; D011134:Polysaccharides; C000458:N-acetyllactosamine