After incubation for 0, 3, 6, … 3.5. Fluorescence Microscopic Observation of the Binding of ESA to OST Cells That Were Pretreated with Glycosidases In a previous study it was shown that ESA is a lectin that specifically binds to high-mannose type (HM) N-glycans [5]. The binding of ESA to OST cells that were pretreated with glycosidases was investigated by labeling cell-bound ESA with rhodamine Inhibitors,research,lifescience,medical 6G (Rh6G), see Section 2.6. First, the OST cells were

pretreated with glycosidases to cleave sugar chains on the cell surface. Incubation was for 2 hours using one of the following three glycosidases, α-mannnosidase, β-mannnosidase, or endoglycosidase H. The method of Rh6G labeling with ESA was Inhibitors,research,lifescience,medical performed by incubating ESA with Rh6G as mentioned in Section 2.6. Then, the ESA labeled with Rh6G was bound

to the cells by incubating the cells for 1 hour, followed by a fluorescence microscopic observation of the labeled cells. As shown in Figure 5, non-treated OST cells (as control) check details displayed Rh6G fluorescence, but other OST cells that were pretreated with a glycosidases showed almost no fluorescence. Inhibitors,research,lifescience,medical This means that ESA could not recognize the molecular structure of the sugar-chains on the surface of OST cell that were cleaved by glycosidases; ESA only recognized the native structure of the sugar-chains of the OST cells. Thus, with these experiments Inhibitors,research,lifescience,medical it could be demonstrated

that ESA specifically binds to OST cells, through recognition of the sugar chains on the surface of the cells. Figure 5 (A) Bright field image of OST cells. The diameter of the OST cells was 19.9μm ± 1.5μm. (B) Fluorescence microscopic observations of the binding of ESA to OST cells. The cells were pretreated Inhibitors,research,lifescience,medical for 2 hours with different … 3.6. Flow Cytometric Analysis of the Specific Binding of ESA to OST Cells Treated with Glycosidases To confirm the specific binding of ESA to OST cells, a flow cytometric examination was also performed in a similar way as described in Sections 3.4 and 3.5. The results are shown in Figure 6(a) for cells treated with α-mannosidase and β-mannosidase, and in Figure 6(b) for cells treated with endoglycosidase H. In both cases, the decreases in fluorescence intensity in those cells that were treated with a glycosidase, if compared to untreated cells, were obvious. The intensity decrease in the case of treatment unless with α-mannosidase seemed to be smaller than in the case of β-mannosidase or endoglycosidase H. This is in good agreement with the images shown in Figure 5 obtained with an independent analysis. Weak Rh6G fluorescence was detectable in glycosidase-treated OST cells—although with rather low intensity—only if the treatment was with α-mannosidase. In the other two cases, there was no detectable fluorescence (Figure 5).