Fig. 3

SARS-CoV-2 spike RBD protein binds ACE2. ACE2 plasmid or empty vector was transiently transfected into HEK293T cells for 48 h. A The mRNA expression levels of ACE2 were determined by qPCR analysis (n = 4 for each group). B The protein expression levels of ACE2 were determined by western blot analysis, and the representative images were shown. C HEK293T cells transfected with ACE2 were incubated with Control-Fc protein or SARS-CoV2 Spike RBD-Fc protein, and the binding was detected by FACS using anti-Fc antibody (indicated by gray or pink shadow). Native HEK293T cells incubated with Spike-Fc followed by anti-Fc antibody were shown as controls (indicated by black shadow). The median fluorescence intensity (MFI) for each group was shown. D HEK239T cells were transfected with ACE2 plasmid, SARS-CoV-2 spike RBD-Flag plasmid or both of them for 48 h. The protein expression levels of ACE2 and Flag were determined by western blot analysis, and the representative images were shown. E HEK239T cells were co-transfected with ACE2 plasmid and SARS-CoV-2 spike RBD-Flag plasmid for 48 h. Co-immunoprecipitation analysis using anti-Flag antibody was performed to demonstrate the binding of ACE2 and SARS-CoV-2 spike RBD-Flag, and the representative images were shown. * indicates the light chain of anti-Flag antibody. F The expression level of Fc in the lung tissues of mice followed by injection of Control-Fc or SARS-CoV-2 spike RBD-Fc was determined by IHC, and the representative images were shown. Data are shown as mean ± S.D., **P < 0.01