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

半乳糖凝集素是一种识别糖缀合物的β-半乳糖苷的动物凝集素，在肠道和泌尿生殖道中含量丰富。本研究通过原位杂交和免疫组织化学方法，揭示了半乳糖凝集素亚型在小鼠消化道、肾脏和卵巢中的细胞表达。五个亚型（半乳糖凝集素-2，-3，-4/6，和-7）的信号被检测到专门在消化道上皮。在腺胃中，galectin-2和galectin-4/6主要表达于胃小凹至胃腺颈部，其中粘液细胞是主要的细胞来源。小肠表现出强烈的，成熟相关的半乳糖凝集素-2，3和-4/6的表达。在大肠中，半乳糖凝集素-4/6占主导地位，上半部分的隐窝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强烈表达galectin-7，弱表达galectin-3。在泌尿系统中，主要亚型是半乳糖凝集素-3，其在从肾脏到尿道远端的集合管和移行上皮中连续表达，表明半乳糖凝集素-3在尿芽和泄殖腔衍生物的上皮中选择性表达。半乳糖凝集素-1和-3在卵巢中占优势。黄体在特定阶段的回归强烈表达这两种类型的半乳糖凝集素。半乳凝素-3仅限于退化的黄体，并且总是与孕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的起始点增加，然后增加半乳糖凝集素-3的表达。这一发现表明，galectin-1和galectin-3可能通过不同的机制介导黄体细胞中孕酮的产生和代谢。由于半乳糖凝集素的多功能性，关于其细胞/阶段特异性表达的信息有助于更好地理解半乳糖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.