Fig. 4: Overexpression of Drosha protected SN4741 cells from 6-OHDA-induced toxicity.

a The structure of WT and mt5 Drosha. There are five mutations in the RS-rich domain of mt5 Drosha compared to WT Drosha including S220A, S255A, T274A, S300A, and S355A. b mt5 Drosha was more resistant to the phosphorylation induced by 6-OHDA. WT and mt5 Drosha were transfected for 24 h in SN4741 cells before application of 40 μM 6-OHDA for 5 h. The cell lysate was managed as described in Fig. 2(a). (ANOVA test followed by Tukey HSD, **P < 0.01 ***P < 0.001, n = 3). c mt5 Drosha was more resistant to 6-OHDA-induced degradation. After transfection of WT and mt5 Drosha for 24 h, SN4741 cells were treated with 40 μM 6-OHDA for 12 h. (ANOVA test followed by Tukey HSD, **P < 0.01 ***P < 0.001, n = 3). d–f Enhancing Drosha ameliorated the toxicity of 6-OHDA to SN4741 cells and mt5 Drosha offered better protection than WT Drosha. After transfection, SN4741 cells were treated with 40 μM 6-OHDA for 36 h. Clevated caspase3, MTT, and TUNEL assays were used to determine the cellular viability. Densitometric values were normalized using β-actin as an internal control. (ANOVA test followed by Tukey HSD, *P < 0.05, **P < 0.01, ^#P < 0.05, ^##P < 0.01 vs. pcDNA3 treated with 6-OHDA; and ^$$P < 0.01 vs. WT Drosha group treated with 6-OHDA, n = 3)