Establishment and evaluation of in vitro galectin-3 inhibitor screening model

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.