Expression and role of sugar-recognition molecule galectin in the digestive tract

半乳糖凝集素是一种动物凝集素，可识别糖缀合物的β-半乳糖苷，在肠道和泌尿生殖道中大量存在。本研究通过原位杂交和免疫组织化学方法，揭示了凝集素亚型在小鼠消化道、肾脏和卵巢中的细胞表达。5种亚型（半乳糖凝集素-2、-3、-4/6和-7）的信号仅在消化道上皮中检测到。在腺胃中，半乳糖凝集素2和4/6主要从胃窝到胃腺颈部表达，其中粘膜细胞是主要的细胞来源。小肠显示出与成熟相关的半乳糖凝集素-2、-3和4/6的强烈表达。在大肠中，半乳糖凝集素-4/6占主导地位，隐窝的上半部分同时含有半乳糖凝集素-3的转录本。从唇到前胃和肛门的分层上皮中半乳糖凝集素-7表达强烈，半乳糖凝集素-3表达微弱。在泌尿系统中，主要亚型为半乳糖凝集素-3，从肾脏到尿道远端，半乳糖凝集素-3在集合管和移行上皮中连续表达，提示半乳糖凝集素-3在尿芽和泄殖腔衍生物上皮中有选择性表达。半乳糖凝集素1和3在卵巢中占优势。黄体在消退的特定阶段强烈表达这两种类型的凝集素。半乳糖凝集素-3仅限于黄体的退化，并且总是与一种黄体酮降解酶的表达一致。半乳糖凝集素-1的信号强度首先在回归起点升高，随后半乳糖凝集素-3的表达升高。这表明半乳糖凝集素-1和-3可能通过不同的机制介导黄体细胞中黄体酮的产生和代谢。由于凝集素具有多种功能，有关其细胞/阶段特异性表达的信息有助于更好地理解凝集素的功能和病理参与。

Galectin is an animal lectin that recognizes β-galatosides of glycoconjugates and is abundant in the gut and urogenital tract. This study revealed the cellular expression of galectin subtypes in the digestive tract, kidney and ovary of mice by in situ hybridization and immunohistochemistry. Signals for five subtypes (galectin-2,-3,-4/6, and-7) were detected exclusively in the epithelia of digestive tract. In the glandular stomach, galectin-2 and-4/6 were predominantly expressed from the gastric pits to neck of gastric glands, where mucous cells were the main cellular sources. The small intestine exhibited intense, maturation-associated expressions of galectin-2,-3, and-4/6. In the large intestine, galectin-4/6 were predominated, and the upper half of crypts simultaneously contained transcripts of galectin-3. Stratified epithelium from the lip to forestomach and anus intensely expressed galectin-7 with weak expressions of galectin-3. In the urinary system, the major subtype was galectin-3, which was expressed in the collecting ducts and transitional epithelium continuously from the kidney to the distal end of the urethra, suggesting selective expression of galectin-3 in epithelia of uretic bud and cloaca-derivatives. Galectin-1 and-3 were predominant in the ovary. The corpus luteum at particular stages of regression intensely expressed both types of galectins. Galectin-3 was restricted to regressing corpus luteum and always coincident to the expression of a progesterone degradation enzyme. The signal intensity of galectin-1 first increased at the starting point of regression followed by increasing expression of galectin-3. This finding suggest that galectin-1 and-3 may mediate the progesterone production and metabolism in luteal cells via different mechanisms. Because multi-functions of galectins, information on their cell/stage-specific expression contributes to a better understanding of the functions and pathological involvements of galectins.