Fig. 3.

CTSL knockdown or overexpression affects pseudovirus infection in vitro. a Schematic of the CTSL knockdown and overexpression assay setup. b Dose-dependent knockdown of CTSL by siRNAs without affecting CTSB expression. n = 4. Statistical significance was assessed by the Kruskal–Wallis test with Dunn’s post hoc test. c–e Knockdown of CTSL dose-dependently inhibited SARS-2-S-driven entry, as measured by a luciferase assay and shown as absolute luciferase activity (n = 8) (c) and relative luciferase activity (n = 8) (d) values, and VSV-P mRNA levels (n = 6) (e). Statistical significance was assessed by the Kruskal–Wallis test with Dunn’s post hoc test. f Dose-dependent overexpression of CTSL with a plasmid encoding the CTSL gene without affecting CTSB expression (n = 5). Statistical significance was assessed by the Kruskal–Wallis test with Dunn’s post hoc test. g–i Overexpression of CTSL dose-dependently promoted SARS-2-S-driven entry, as measured by a luciferase assay and shown as absolute luciferase activity (g) and relative luciferase activity h, values, and VSV-P mRNA levels (i) n = 5. Statistical significance was assessed by the Kruskal–Wallis test with Dunn’s post hoc test. The data are expressed as the mean ± s.e.m. values. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001