Bimodular effects of D614G mutation on the spike glycoprotein of SARS-CoV-2 enhance protein processing membrane fusion and viral infectivity

摘要

Enhanced infectivity of D614G mutant of SARS-CoV-2 virus. a The mutation profile of SARS-CoV-2 spike glycoprotein. From a set of 9002 SARS-CoV-2 genome sequences, mutations were identified at 82 positions across the gene encoding S glycoprotein with the D614G being the dominant mutation (>62%); for the plot of mutation counts (the left Y axis), only those showing more than 5 counts were displayed. b Three-dimensional structure modeling of the D614 (upper) and G614 (lower) S glycoprotein colored by chain. The α subunit in red is on the left, the neighboring β subunit in green is on the right. The D614, G614, and T859 residues are displayed in the style of scaled ball and stick with simulated surfaces in yellow. c Detection of the expression of the indicated proteins by Western blot. The spike protein was blotted by an antibody against the S2 region. d, e Altered expression of spike trimer in G614 mutant. d Expression of two spike proteins in the absence and presence of ACE2 in 293T cells at the time points of 12 and 48-h post transfection by Western blot. e Quantification of the relative expression of spike trimer and monomer with the respective D614 expression in the absence of ACE2 as the reference. All results were normalized by the expression of β-actin. Data are mean ± SD of triple quantification. f, g Quantification of syncytia formation upon expression of the indicated S glycoprotein in 293T-ACE2 cells (f) and Hela-ACE2 cells (g). Data are the mean ± SD of results from 4–5 fields (20x objective lens). ***p < 0.001; ****p < 0.0001. More than three replicates were done for the experiment. h, i The expression of the luciferase reporter in 293T-ACE2 cells (h) and Hela-ACE2 cells (i) upon infection of viruses pseudotyped with D614 or G614 S glycoproteins as indicated. Data are the mean ± SD of the results of quadruplicate. Fold changes between D614 and G614 genotypes are displayed. More than three replicates were done for the experiment