Fig. 1.

Effect of GB-2 on cell variability of 293 T cells and interaction between ACE2 and SARS-CoV-2 Spike. (A) 293 T cells were measured by XTT assay after indicated hours of culturing in the presence of GB-2. (B) The indicated compounds were tested to evaluate their ability to inhibit the binding of spike protein to immobilized ACE2 by the ACE2/SARS-CoV-2 spike inhibitor screening assay. (C) Flow cytometry analysis of ACE2-Spike protein binding. 293 T cells with pCEP4-MYC-ACE2 plasmid were incubated with RBD (wild type)-sfGFP-containing medium and co-stained with anti-MYC Alexa 647 to detect surface ACE2 by flow cytometry. During analysis, the top population were chosen from the ACE2-positive population. Then, two subsets of the ACE2-positive population were collected: the top population (nCoV-S-High sort, red gate) and the bottom population (nCoV-S-Low sort, green gate) based on the fluorescence of bound RBD-sfGFP relative to ACE2 surface expression. (D) Quantitative results of nCoV-S-High sort and nCoV-S-low sort, which were presented as ratio compared with blank, in the top population or ACE2-positive population. All the results are representative of at least three independent experiments. (Error bars=mean±S.E.M. Asterisks (*) mark samples significantly different from control group with p < 0.05).