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. 2022 Dec 5;209:105481. doi: 10.1016/j.antiviral.2022.105481

Fig. 2.

Fig. 2

The dopamine receptor D2 (DRD2) antagonists inhibit the SARS-CoV-2 spike protein (SARS2-S)-mediated membrane fusion but not SARS2-S binding to ACE2. (A) Effect of the DRD2 antagonists on SARS2-S-mediated membrane fusion. HEK293T cells transfected with plasmids expressing SARS2-S and ZsGreen (ZsG) were detached with trypsin and overlaid on HEK293T/ACE2 cells that had been pretreated with 0.1% DMSO or one of the DRD2 antagonists (10 μM) for 90 min. DMSO and the DRD2 antagonists were present throughout the experimental period. After a 4-h incubation, the cells were fixed, and their nuclei were stained with Hoechst 33342. Fluorescent images of the cells were captured (left), and the average number (ave. #) of nuclei in each syncytium was determined with a high-content imaging system (right). The presented data are the mean ± SD of the results of four independent experiments. Statistical significance was determined by comparing the average nuclei numbers of the DRD2 antagonist-treated samples with that of the DMSO-treated samples. **p < 0.01. (B) Inhibitory effect of the DRD2 antagonists on the binding of SARS2-S to ACE2. An ELISA-based SARS2-S–ACE2 binding assay was performed in the presence of 0.1% DMSO, the neutralizing antibody anti-SARS2-S S1 domain (anti-S1 Ab, 5 μg/mL), or one of the DRD2 antagonists (10 μM or 100 μM). The mean chemiluminescent signal intensity of DMSO-treated samples was set to 1. The presented data are the mean ± SD of the results of three replicates. ND, not detected.