A STUDY FOR PHYSIOLOGICAL FUNCTION OF LUNG GALECTIN-8

半乳糖凝集素-4 （G4）是一种可溶性半乳糖结合凝集素，存在于多种哺乳动物组织中。为了确定该蛋白在结直肠组织中的功能，我们分别制备了大鼠G4的N端和c端半碳水化合物结合域（CBD）作为重组谷胱甘肽s转移酶（GST）融合蛋白（G4-N和G4- c），并通过光镜和电镜（LM和EM）检测了每个CBD的组织结合位点(s)。在LM水平上，这两种融合蛋白都能在结肠粘膜表面上皮细胞的细胞间边界上染色；在EM水平上，两种融合蛋白识别出空间上接近但不同的亚细胞结构。G4-N染色的电子透光絮状物质自由分布在细胞间隙，而G4-C结合在划分细胞间隙的侧细胞膜上。这些发现表明，结肠G4可能参与了表面上皮细胞侧膜的交联，从而增强了上皮细胞的完整性，抵抗来自肠腔的机械应力。

Galectin-4 ( G4 ) is a member of soluble galactoside-binding lectins found in various mammalian tissues. To determine the function of this protein within colorectal tissue, we separately produced N- and C-terminal half carbohydrate-binding domain (CBD) of rat G4 as a recombinant glutathione S-transferase (GST) fusion protein ( G4-N and G4-C ) and examined the tissue-binding site(s) of each CBD by light and electron microscopy (LM and EM). At the LM level both fusion proteins stained the intercellular borders of the surface- lining epithelial cells of colorectal mucosa, At the EM level, two proteins recognized spatially close but distinct subcellular structures. G4-N stained electron-lucent flocculent substances freely located in the intercellular spaces, whereas G4-C bound to the lateral cell membranes demarcating the intercellular spaces. From these findings, it is suggested that colorectal G4 may be involved in cross-linking the lateral cell membranes of the surface-lining epithelial cells, thereby reinforcing the epithelial integrity against mechanical stress coming from the bowel lumen.