Fig. 1

Peptides are able to block the interaction between ACE2 and SARS-CoV-2 spike protein, or inhibit the cleavage of spike protein by protease. A Schematic diagram of design strategy for peptides to block SARS-CoV-2 virus from entering cells. B Representative blot image showing that ACE2 can be co-immunoprecipitated by anti-Spike protein (S protein) antibody, but not IgG, in HEK293T cells transfected with S protein and hACE2. C Densitometric analysis of the levels of ACE2 co-immunoprecipitated by anti-S protein antibody in HEK293T cells transfected with S protein and ACE2 shows that TAT-ACE2-1, TAT-ACE2-2 and TAT-ACE2-3 peptides, but not TAT alone, are able to decrease the level of S-ACE2 complex. The level of co-immunoprecipitated ACE2 (ACE2 Co-IP) was normalized to the level of precipitated S protein (S protein IP). Data are shown as mean ± SEM, and presented as the percentage of the control (vehicle) sample. n = 3 independent experiments for each group, one-way ANOVA test followed by Dunnett’s post hoc test. *p < 0.05, **p < 0.01 as compared to control (vehicle) samples. D Western blot shows that TAT-S1/S2 or TAT-S2 peptides are able to inhibit S protein cleavage by TMPRSS2 in HEK293T cells transfected with S protein, ACE2 and TMPRSS2. α-Tubulin was used as a loading control. E Densitometric analysis of the levels of S2 in HEK293T cells transfected with S protein, ACE2 and TMPRSS2, and treated with either vehicle (control), TAT alone, TAT-S1/S2 or TAT-S2 peptides. The level of S2 was normalized to the level of α-Tubulin. Data are shown as mean ± SEM, and presented as the percentage of the control (vehicle) sample. n = 3 independent experiments for each group, one-way ANOVA test followed by Dunnett’s post hoc test. *p < 0.05 as compared to control (vehicle) samples