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. 2022 Mar 4;14(3):531. doi: 10.3390/v14030531

Figure 3.

Figure 3

SARS-CoV-2 S protein palmitoylation is required for cell–cell fusion and syncytia formation. (A) Schematic representation of dual fluorescent syncytia formation assay. HEK293T-EGFP cells were transfected with WT S or its cysteine mutant plasmids. After 24 h, cells were detached and mixed with HEK293T-ACE2 cells labeled with cell tracker red CMPTX dye. After another 24 h, syncytia formation was evaluated by visualizing the yellow fluorescence formed by the fusion of the green and red cells. (B) Dual fluorescent syncytia formation assay with WT S and S∆C and (C) quantification of cell–cell fusion ability by measuring the pixel density of the observed syncytia. (D,E) Same as in B and C, but with cysteine cluster mutants of the S protein. Data shown are averages of the results of at least three independent experiments ± SD. (** p < 0.01; **** p < 0.0001 (t-test)).