Galectin-3, a marker for vacuole lysis by invasive pathogens

Abstract

Shigella bacteria invade macrophages and epithe-lial 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 extra-cellular 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.

The granzyme B-Serpinb9 axis controls the fate of lymphocytes after lysosomal stress

“…Cells were positive for PI staining at times later than that indicated by the white bars normally found within these vesicles and marks the vesicles for removal by autophagy. 35,36 We found that galectin 8 colocalised with GrB-positive vesicles in NK cells on targets, indicating that these LROs have damaged membranes (Figure 7d). Thus, it appears that LMP and release of GrB from LROs occurs as NK cells are working and Sb9 is positioned to oppose cytosolic GrB.…”

Autophagy Induced by Calcium Phosphate Precipitates Targets Damaged Endosomes

“…Intracellular bacteria induced endosomal damage when entering cells by endocytosis/phagocytosis (22,23). It has also been found that osmotic shock triggered endosome damage as indicated by galectin recruitment (23).…”

“…Glycans are normally present only on cell surface and in the lumens of endocytic compartments (24), and would not be accessible to the cytosolic galectins. Glycans on damaged endomembranes become accessible to and bound by the cytosolic galectins, including galectin 3, 8, or 9 (22,23). This galectin-glycan interaction seems to be critical for the anti-bacteria autophagy (23).…”

“…This structure is responsible for the effective clearance of the phagocytosed bacteria through lysosome-mediated degradation. Notably, endosomal vesicles containing phagocytosed bacteria exposed glycans because of vesicle lysis (22,23). Glycans are normally present only on cell surface and in the lumens of endocytic compartments (24), and would not be accessible to the cytosolic galectins.…”

Maintenance of vacuole integrity by bacterial pathogens

“…2). The first assay takes advantage of the observation that cytosolic galectins are specifically recruited to the remnants of ruptured vacuoles [48,49]. Cells expressing GFPGalectin 3 have been successfully used to follow the escape of Shigella into the cytosol in real time [50,51].…”