Fig. 3: Plitidepsin reduces the translation of RNAs and the synthesis of de novo proteins without affecting cellular viability.

A Expression of luciferase in Vero E6 cells transfected with lipid nanoparticles (LNP) containing ready-to-express luciferase mRNA ± 50 nM plitidepsin. Vero E6 were assayed by luminometry two days after transfection. B Expression of eGFP in Vero E6 cells transfected with LNP containing ready-to-express eGFP mRNA in the absence or presence of 50 nM plitidepsin. Vero E6 were assayed by FACS two days after transfection. C Expression of eGFP in Vero E6 cells infected with SARS-CoV-2 eGFP reporter in the absence or presence of 50 nM plitidepsin. Vero E6 were assayed by FACS two days after infection. D Relative expression of luciferase in Vero E6 cells pre-treated or not with 50 nM plitidepsin for 48 h before transfection with LNP containing ready-to-express luciferase mRNA, assayed by luminometry one day after transfection. Values were normalized to the mean RLUs of cells transfected without the drug, set at 100 %. A–D show mean and S.D. of n exp = 3 and n rep = 9 (P < 0.0001). E Cellular ATP released by Vero E6 cells exposed for 48 h to the indicated plitidepsin concentrations measured by luminometry. Mean and S.D. of n exp = 4 and n rep = 12. F Cellular viability of Vero E6 cells exposed for 48 h to increasing concentrations of plitidepsin stained with live and dead staining kit by FACS. Cells were incubated with 10 % DMSO to induce mortality (P = 0.0022). G Cellular viability of Vero E6 treated as in F with 0.5, 5, and 50 nM plitidepsin and measured by MTT (P < 0.0001). F and G show mean and S.D. of n exp = 3 and n rep = 9. Statistical differences were assayed with a two-sided one sample t-test in D and with a two-sided Mann–Whitney U test in the rest of the panels. Source Data file provides source data.