SUMOylation of Alpha-Synuclein Influences on Alpha-Synuclein Aggregation Induced by Methamphetamine

Abstract

Methamphetamine (METH) is an illegal and widely abused psychoactive stimulant. METH abusers are at high risk of neurodegenerative disorders, including Parkinson’s disease (PD). Previous studies have demonstrated that METH causes alpha-synuclein (α-syn) aggregation in the both laboratory animal and human. In this study, exposure to high METH doses increased the expression of α-syn and the small ubiquitin-related modifier 1 (SUMO-1). Therefore, we hypothesized that SUMOylation of α-syn is involved in high-dose METH-induced α-syn aggregation. We measured the levels of α-syn SUMOylation and these enzymes involved in the SUMOylation cycle in SH-SY5Y human neuroblastoma cells (SH-SY5Y cells), in cultures of C57 BL/6 primary mouse neurons and in brain tissues of mice exposure to METH. We also demonstrated the effect of α-syn SUMOylation on α-syn aggregation after METH exposure by overexpressing the key enzyme of the SUMOylation cycle or silencing SUMO-1 expression in vitro. Then, we make introduced mutations in the major SUMOylation acceptor sites of α-syn by transfecting a lentivirus containing the sequence of WT α-syn or K96/102R α-syn into SH-SY5Y cells and injecting an adenovirus containing the sequence of WT α-syn or K96/102R α-syn into the mouse striatum. Levels of the ubiquitin-proteasome system (UPS)-related makers ubiquitin (Ub) and UbE1, as well as the autophagy-lysosome pathway (ALP)-related markers LC3, P62 and lysosomal associated membrane protein 2A (LAMP2A), were also measured in SH-SY5Y cells transfected with lentivirus and mice injected with adenovirus. The results showed that METH exposure decreases the SUMOylation level of α-syn, although the expression of α-syn and SUMO-1 are increased. One possible cause is the reduction of UBC9 level. The increase in α-syn SUMOylation by UBC9 overexpression relieves METH-induced α-syn overexpression and aggregation, whereas the decrease in α-syn SUMOylation by SUMO-1 silencing exacerbates the same pathology. Furthermore, mutations in the major SUMOylation acceptor sites of α-syn also aggravate α-syn overexpression and aggregation by impairing degradation through the UPS and the ALP in vitro and in vivo. These results suggest that SUMOylation of α-syn plays a fundamental part in α-syn overexpression and aggregation induced by METH and could be a suitable target for the treatment of neurodegenerative diseases.

Effect of Parkin on methamphetamine‐induced α‐synuclein degradation dysfunction in vitro and in vivo

“…Fibrils rapidly aggregate into insoluble macromolecules to form LBs (Auluck, Chan, Trojanowski, Lee, & Bonini, ). In the study, we verified that the level of α‐syn increases with increasing METH concentration and exposure time, which is consistent with previous studies (Qiao et al, ; Zhu et al, ). The accumulation of α‐syn can lead to apoptosis and even death of neurons.…”

“…Therefore, α‐syn is considered to be a protein closely related to neurodegenerative diseases (e.g., Parkinson's disease [PD] and Alzheimer's disease [AD]) (Henderson et al, ; Twohig & Nielsen, ). Previous studies, including studies by our research group, have found that α‐syn expression and the degree of cell injury increase with increasing METH concentrations (Biagioni et al, ; Qiao et al, ; Sun et al, ; Wang et al, ; Zhu et al, ).…”

“…Mice were randomly divided into four groups ( n = 3/group): an LV‐NC group, an LV‐Parkin group, an LV‐NC + METH group, and an LV‐Parkin + METH group. A stereotaxic injection protocol was performed as previously described by our laboratory (Xu et al, ; Zhu et al, ). Mice were anesthetized by 1% pentobarbital and fixed in a stereotaxic frame (Domitor).…”

The SUMO Conjugase Ubc9 Protects Dopaminergic Cells from Cytotoxicity and Enhances the Stability of α-Synuclein in Parkinson’s Disease Models

“…Taken together, our results strongly support the report by Krumova et al (2011) that SUMOylated α-syn promotes its solubility, prevents protein aggregation and further, reduces cytotoxicity in the SNpc. Our findings also support the recent publication that METH exposure reduces the level of SUMOylation on α-syn, and METH-induced α-syn aggregation is relieved by Ubc9 overexpression ( Zhu et al, 2018 ). The study has also demonstrated that mutations in SUMOylation acceptor sites in α-syn enhance α-syn overexpression and aggregation induced by METH, which is mediated by impaired degradation through the UPS and the ALP in vitro and in vivo ( Zhu et al, 2018 ).…”

“…Interestingly, UBC9 overexpression was reported to increase the solubility of α-syn and prevent methamphetamine (METH)-induced protein aggregation. Further, non-SUMO α-syn mutants enhance their aggregation by impairing proteasomal and lysosomal degradation ( Zhu et al, 2018 ). Since SUMOylation of target proteins has been posited as an important factor in the pathogenesis or progression of PD, we assessed the effect of SUMOylation on α-syn for preventing its protein aggregation.…”