Alleviating toxic \u03b1-Synuclein accumulation by membrane depolarization: evidence from an in vitro model of Parkinson\u2019s disease

Alysia Ross,Ting Ting Wang,Samantha C Bureau,Shawn Hayley,Giovana A Link,Hui Zhang,Viktoria Xing,Teresa Fortin,Hongyu Sun

doi:10.1186/s13041-020-00648-8

Alysia Ross, Ting Ting Wang + Show 7 more

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https://doi.org/10.1186/s13041-020-00648-8

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Abstract

Parkinson’s disease (PD) is characterized by the formation of toxic, fibrillar form alpha-synuclein (α-Syn) protein aggregates in dopaminergic neurons. Accumulating evidence has shown a multifactorial interplay between the intracellular calcium elevation and α-Syn dynamics. However, whether membrane depolarization regulates toxic α-Syn aggregates remains unclear. To understand this better, we used an in vitro α-Syn preformed fibrils (PFF) model of PD in human neural cells. We demonstrated functional membrane depolarization in differentiated SH-SY5Y cells induced by two independent treatments: high extracellular K+ and the GABAA receptor blocker picrotoxin. We then observed that these treatments significantly alleviated toxic α-Syn aggregation in PFF-treated SH-SY5Y cells. Moreover, clinically relevant direct current stimulation (DCS) also remarkably decreased toxic α-Syn aggregation in PFF-treated SH-SY5Y cells. Taken together, our findings suggest that membrane depolarization plays an important role in alleviating PFF-induced toxic α-Syn aggregates, and that it may represent a novel therapeutic mechanism for PD.

Highlights

Parkinson’s disease (PD) is characterized by the formation of insoluble toxic alpha-synuclein (α-Syn) protein aggregates called amyloid fibrils in dopaminergic neurons [18, 19, 21, 38, 54]. α-Syn is a small soluble protein that concentrates at presynaptic terminals throughout the brain [8, 51]
Cells were cultured for 2 weeks in complete media (DMEM supplemented with 10% fetal bovine serum (FBS) and 1% pen-strep) or reduced media (DMEM supplemented with 1% FBS and 1% penstrep) supplemented with 0.1% retinoic acid (RA)
Preformed fibrils (PFF) treatment induced α-Syn inclusion accumulation in differentiated SH-SY5Y cells In order to test the effects of membrane depolarization on α-Syn accumulation, we first added 0.1% RA to the culture medium for two weeks to differentiate the SHSY5Y neuroblastoma cells

Summary

Introduction

Parkinson’s disease (PD) is characterized by the formation of insoluble toxic alpha-synuclein (α-Syn) protein aggregates called amyloid fibrils in dopaminergic neurons [18, 19, 21, 38, 54]. α-Syn is a small soluble protein that concentrates at presynaptic terminals throughout the brain [8, 51]. Α-Syn monomers facilitate neurotransmitter release through modulating synaptic vesicle maturation and release [6, 19, 44]. In the context of cells overexpressing α-Syn, membrane depolarization leads to an increase in α-Syn aggregation [15, 34] It seems that a multifactorial interplay occurs between the intracellular calcium levels and α-Syn dynamics. How intracellular toxic α-Syn fibril accumulation is affected by membrane depolarization or the disruption of calcium homeostasis under pathological conditions is completely unknown

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