Loss of Drosha underlies dopaminergic neuron toxicity in models of Parkinson\u2019s disease

Ronglin Wang,Gang Zhu,Lu Huang,Dayun Feng,Zixu Mao,Tiejian Nie,Shaosong Yang,Fangfang Lu,Kai Tao,Jie Lei,Qian Yang

doi:10.1038/s41419-018-0716-5

Abstract

MiRNAs, a group of powerful modulator of gene expression, participate in multiple cellular processes under physiological and pathological conditions. Emerging evidence shows that Drosha, which controls the initial step in canonical miRNA biogenesis, is involved in modulating cell survival and death in models of several diseases. However, the role of Drosha in Parkinson’s disease (PD) has not been well established. Here, we show that the level of Drosha decreases in 6-OHDA-induced cellular and animal models of PD. 6-OHDA induced a p38 MAPK-dependent phosphorylation of Drosha. This triggered Drosha degradation. Enhancing the level of Drosha protected the dopaminergic (DA) neurons from 6-OHDA-induced toxicity in both in vitro and in vivo models of PD and alleviated the motor deficits of PD mice. These findings reveal that Drosha plays a critical role in the survival of DA neurons and suggest that stress-induced destabilization of Drosha may be part of the pathological process in PD.

Highlights

Parkinson’s disease (PD) is the most common neurodegenerative disease affecting the motor system
We show in the current study that 6-hydroxydopamine (6-OHDA), a neurotoxin widely used to model PD in vitro and in vivo, causes a p38 MAPK-dependent phosphorylation of Drosha, leading to its dysfunction
The results showed that 6-OHDA caused a time dependent activation of p38 MAPK in SN4741 cells and p-p38 peaked at about 4 h after treatment, consistent with previous study (Fig. 2a)[20]

Summary

Results

Studies have shown that cellular stress regulates the stability of Drosha[17]. To test whether neurotoxins associated with PD can modulate Drosha in PD, we injected 6OHDA into the SNc to induce stress and the loss of DA neurons, a widely used in vivo model of PD18. The Western blot analysis verified a robust increase of p-p38 in the SNc region at 2 days after neurotoxin injection (Fig. 1e). Together, these results indicate that 6-OHDA activates p38 and reduces the stability of Drosha in the mouse SNc region. To determine the role of p38 MAPK in Drosha phosphorylation, p38 inhibitor SB203580 was added to SN4741 cells half an hour before the 6-OHDA treatment This analysis showed that SB203580 reduced 6-OHDA-induced phosphorylation of Drosha (Fig. 2c and S1b). These data indicate that p38 MAPK is directly involved in phosphorylating Drosha in response to 6-OHDA. These data indicate that augmenting Drosha effectively improves the motor deficits caused by 6-OHDA in mice

Discussion

Findings

Materials and methods