Unité de Pathogénie Microbienne Moléculaire, Institut Pasteur, 75724 Paris, Cedex 15, France.
Cell Microbiol. 2010 Apr 1;12(4):530-44. doi: 10.1111/j.1462-5822.2009.01415.x. Epub 2009 Nov 27.
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.
志贺氏菌侵入巨噬细胞和上皮细胞，随后在吞噬体中溶解并逃到细胞质中。半乳糖凝集素-3（Galectin-3）是巨噬细胞和上皮细胞中丰富的蛋白质，属于β-半乳糖苷结合蛋白家族中的半乳糖凝集素，在免疫反应、发育、分化、癌症和感染中具有许多功能。半乳糖凝集素最初作为细胞质蛋白合成，然后通过非经典分泌途径与细胞外的β-半乳糖结合。在这里，我们分析了志贺氏菌进入细胞质后半乳糖凝集素-3的定位，并观察到了一个显著的现象。在细菌入侵后很短的时间内，细胞内的半乳糖凝集素-3在靠近内化细菌的结构中积累。通过免疫电子显微镜分析，我们鉴定出在吞噬体中定位的半乳糖凝集素-3以及源自内吞途径的小管和小泡。我们还证明了半乳糖凝集素-3与宿主 N-乙酰乳糖胺结合糖的结合对于形成这些结构是必需的。结构的积累是 III 型分泌系统依赖性的过程。更具体地说，结构的存在严格依赖于吞噬小泡的溶解，并且可以通过革兰氏阳性李斯特菌和沙门氏菌 sifA 突变体来证明。我们提出，含有半乳糖凝集素-3的结构可能成为检测吞噬体溶解的潜在新工具。
