Galectin-3抑制剂体外筛选方法的建立及评价
Establishment and evaluation of in vitro galectin-3 inhibitor screening model
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摘要: 半乳糖凝集素-3 (galectin-3, Gal-3) 属于β半乳糖苷酶结合凝集素家族, 具有特异性结合半乳糖的特性。通过C端糖蛋白结合区(carbohydrate recognition domain, CRD), Gal-3可结合糖基化胰岛素受体(insulin receptor, IR) 的半乳糖苷链, 从而抑制IR信号通路, 导致胰岛素抵抗, 被视为治疗胰岛素抵抗和2型糖尿病的潜在药物作用靶点。本研究根据Gal-3结合糖基化蛋白半乳糖苷链的特性, 设计了一种简便的Gal-3抑制剂筛选模型。在大肠杆菌表达Gal-3蛋白, 经纯化后, 用异硫氰酸荧光素(fluorescein isothiocyanate, FITC) 修饰, 获得Gal-3-FITC。Gal-3-FITC自发绿色荧光, 与表面表达有大量糖蛋白的人胰腺癌细胞(PANC-1) 孵育后, PANC-1细胞带有荧光信号。若待测化合物有Gal-3抑制活性, 则该化合物可降低Gal-3-FITC与细胞的结合, 从而降低PANC-1细胞荧光信号。通过荧光信号变化可评价Gal-3抑制剂的抑制强度。进一步研究表明, 该筛选模型简易稳定, 具有良好重复性, Z'因子在0.7和0.85之间。本研究采用FITC标记Gal-3的方式在PANC-1细胞上用荧光强度反映Gal-3和糖蛋白的结合水平, 构建了Gal-3抑制剂的高通量筛选模型。Abstract: Galectin-3 (Gal-3) belongs to the galectin family and is specific in binding β-galactoside. Through its C-terminal domain, Gal-3 binds to the galactoside group of the glycosylated insulin receptor (IR) and inhibits IR signaling pathway, which leads to the insulin resistance. Thus, Gal-3 is a potential therapeutic target for the treatment of insulin resistance and type 2 diabetes. Here we report a simple Gal-3 screening model based on the property that Gal-3 binds to the galactoside. We expressed and purified human Gal-3 in Escherichia coli (E.coli), and labeled it with fluorescein isothiocyanate (FITC) in vitro. After incubating FITC labeled Gal-3 (Gal-3-FITC) with PANC-1 cells, which express glycosylated membrane protein, PANC-1 cells started to show green fluorescent signal due to the Gal-3-FITC binding to the glycosylated membrane protein. Gal-3 inhibitor disrupts the binding of Gal-3-FITC and PANC1 cells, subsequently leads to the decrease of the fluorescent signal in PANC-1 cells. We can evaluate the inhibitory efficiency of Gal-3 inhibitors through measurement of the fluorescent signal. Further studies show this model is simple, stable, and repeatable with a Z' factor between 0.7 and 0.85. In sum, we have successfully established an in vitro high-throughput screening model for Gal-3 inhibitors.
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