半乳糖凝集素-4與醣配體結合特異性之探討

Abstract

半乳糖凝集素 (Galectin) 是一種醣結合蛋白，與醣分子結合後，調節細胞的增殖、凋亡、黏附或遷移等過程。半乳糖凝集-4 (Galectin-4) 屬於與串聯重複型的半乳糖凝集素，具有兩個醣體辨識區，主要表現在消化道上皮細胞中。文獻中指出，半乳糖凝集-4與發炎性腸道疾病 (Inflammatory Bowel Disease, IBD) 息息相關。本研究聚焦於人類半乳糖凝集素-4 (Galectin-4)，探討其兩個糖體識別區域 (CRDs) 的結合特異性及其在腸道中的潛在配體。利用多醣體微陣列技術篩選出具有高親和力的配體，並通過生物層干涉技術進行定量分析，確定半乳糖凝集-4N及半乳糖凝集-4C與其醣配體的結合親和力。結晶學技術解析了半乳糖凝集-4N的結構，結果表明，半乳糖凝集-4對岩藻糖基化母乳寡糖具有顯著的結合偏好，結合特性受配體結構長短及岩藻糖基化位置的影響。此外，通過結合天然配體和抑制物的分析，本研究展示了不同結合增強效果，提供了更廣泛的視角來探討針對半乳糖凝集-4N及半乳糖凝集-4C的潛在交互作用特性。這些發現深化了對半乳糖凝集-4在生理和病理過程中作用的理解，也可作為開發半乳糖凝集-4抑制物的基礎。

Galectins are a family of carbohydrate-binding proteins that regulate various cellular processes such as proliferation, apoptosis, adhesion, and migration upon binding to glycan molecules. Galectin-4, a tandem-repeat type galectin, contains two carbohydrate recognition domains (CRDs) and is primarily expressed in the epithelial cells of the digestive tract. Previous studies have indicated a strong association between Galectin-4 and inflammatory bowel disease (IBD). This research focuses on human Galectin-4, investigating the binding specificities of its two CRDs and identifying potential ligands in the gut. Using glycan microarray technology, high-affinity ligands were screened, followed by quantitative analysis through biolayer interferometry (BLI) to determine the binding affinities of Galectin-4N and Galectin-4C with their glycan ligands. Crystallography was employed to resolve the structure of Galectin-4N, revealing a significant binding preference for fucosylated human milk oligosaccharides, with binding characteristics influenced by glycan length and fucosylation position. Furthermore, the combined analysis of natural ligands and inhibitors demonstrated varied binding enhancement effects, offering broader insights into the potential interaction properties of Galectin-4N and Galectin-4C. These findings deepen our understanding of Galectin-4's roles in physiological and pathological processes and provide a foundation for developing Galectin-4 inhibitors.